Catalyst for polyester production, process for producing polyester using the catalyst, polyester obtained by the process, and uses of the polyester

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was separated from the supernatant liquid by centrifugation of 2500 revolutions for 15 minutes. Then, the resulting titanium hydroxide precipitate was washed five times with deionized water. After the washing, solid-liquid separation was carried out by centrifugation of 2500 revolutions for 15 minutes. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compound was pulverized into particles of about 10μ.

The absorbed water content in the solid titanium compound thus obtained was measured by a Karl Fischer's water content meter. As a result, the absorbed water content was 6.73% by weight. Further, the weight loss on heating was measured by thermogravimetry. As a result, the weight of the compound was reduced by 7.50% by weight on heating up to 280° C. and was further reduced by 2.17% by weight on heating from 280° C. to 600° C., based on the initial weight, and this weight loss proved to be due to desoprtion of water content and a nitrogen compound. In the catalyst, nitrogen was contained in an amount of 1.3% by weight and chlorine was contained in an amount of only 14 ppm. Therefore, it is presumed that nitrogen is derived from not ammonium chloride but ammonia. The titanium content in the solid titanium compound, as measured by a high-frequency plasma emission analyzer, was 46% by weight.

From the above, the molar ratio between titanium and hydroxyl group in the solid titanium compound was found to be 1:0.157. Nitrogen and chlorine was analyzed by an all nitrogen microanalyzer (chemiluminescence method) and a chromatography, respectively, and for the calculation of the contents, they were considered to be desorbed as ammonia and hydrogen chloride, respectively.

Example 495-2

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. To the deionized water, 0.15 g of anhydrous magnesium hydroxide was added to give a dispersion. The dispersion in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. The liquid became acidic, and the magnesium hydroxide was dissolved. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium-containing complex hydroxide produced was separated from the supernatant liquid by centrifugation of 2500 revolutions for 15 minutes. Then, the precipitate of titanium-containing complex hydroxide was washed five times with deionized water. After the washing, solid-liquid separation was carried out by centrifugation of 2500 revolutions for 15 minutes. The washed titanium-containing complex hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a titanium-containing solid compound was obtained.

In the titanium-containing solid compound, the ratio between titanium atom and magnesium atom was 91:9 by mol. By thermogravimetry, the molar ratio between titanium and hydroxyl group in the titanium-containing solid compound proved to be 1:0.31. Prior to use as a polycondensation catalyst, the titanium-containing solid compound was pulverized in particles of about 10μ.

Example 495-3

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. To the deionized water, 0.16 g of colloidal silica (trade name: Snowtex OXS) was added to give a dispersion. The dispersion in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. The liquid became acidic, and the colloidal silica was dissolved. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium-containing complex hydroxide produced was separated from the supernatant liquid by centrifugation of 2500 revolutions for 15 minutes. Then, the precipitate of titanium-containing complex hydroxide was washed five times with deionized water. After the washing, solid-liquid separation was carried out by centrifugation of 2500 revolutions for 15 minutes. The washed titanium-containing complex hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a titanium-containing solid compound was obtained.

In the titanium-containing solid compound, the ratio between titanium atom and silicon atom was 94:6 by mol. By thermogravimetry, the molar ratio between titanium and hydroxyl group in the titanium-containing solid compound proved to be 1:0.60. Prior to use as a polycondensation catalyst, the titanium-containing solid compound was pulverized into particles of about 10μ.

Example 495-4

Comparative Example 495-1

The esterification reaction product (low condensate) was continuously drawn out of the system so that the average residence time was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Using the solid titanium compound prepared in Example 495-1 as a polycondensation catalyst, liquid phase polycondensation reaction of the low condensate was conducted.

The amount of the solid titanium compound added as the catalyst was 0.005% by mol in terms of titanium atom, based on the terephthalic acid unit in the low condensate. The polycondensation reaction was carried out under the conditions of a temperature of 285° C. and a pressure of 1 Torr.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was 95 minutes.

Example 495-5

Polycondensation reaction was carried out in the same manner as in Example 495-4, except that the titanium-containing solid compound prepared in Example 495-2 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was 76 minutes.

Example 495-6

Polycondensation reaction was carried out in the same manner as in Example 495-4, except that the titanium-containing solid compound prepared in Example 495-3 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was 85 minutes.

Example 495-7

Polycondensation reaction was carried out in the same manner as in Example 495-4, except that magnesium carbonate was used as the polycondensation catalyst in addition to the solid titanium compound prepared in Example 495-1. The amount of magnesium carbonate added was 0.005% by mol in terms of magnesium atom, based on the terephthalic acid unit in the low condensate.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was 75 minutes.

Example 495-8

Polycondensation reaction was carried out in the same manner as in Example 495-4, except that magnesium acetate was used as the polycondensation catalyst in addition to the solid titanium compound prepared in Example 495-1. The amount of magnesium acetate added was 0.005% by mol in terms of magnesium atom, based on the terephthalic acid unit in the low condensate.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was 70 minutes.

Example 495-9

Polycondensation reaction was carried out in the same manner as in Example 495-4, except that the solid titanium compound prepared in Example 495-1 was stored in a closed container at room temperature for 2 months prior to use as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was 101 minutes.

It can be seen from this example that the solid titanium compound according to the invention is free from deterioration with time and had good storage properties. For reference, it is shown in a comparative example of Japanese Patent Publication No. 26597/1972 that orthotitanic acid is deteriorated with time and lowered in the polycondensation activity.

Polycondensation reaction was carried out in the same manner as in Example 495-4, except that antimony acetate that was industrially used was used as the polycondensation catalyst. The amount of antimony acetate added was 0.025% by mol in terms of antimony, abased on the terephthalic acid unit in the low condensate.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was 120 minutes.

Comparative Example 495-2

Preparation of Titanium Compound

The titanium hydroxide obtained after washing with deionized water in Example 495-1 was boiled at 100° C. for 2 hours and then dried, to obtain a titanium compound.

Examples 496-8 to 495-13 Example 491-2C

Polycondensation reaction was carried out in the same manner as in Example 495-4, except that the titanium compound obtained above was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.58 dl/g of polyethylene terephthalate was 185 minutes.

It is known that titanium hydroxide is converted into metatitanic aced when heated in water, and the titanium compound obtained by way of metatitanic acid has beer found to have low polycondensation activity.

Example 496-7

To an esteriafion reactor, 76.81 mol of high-purity terephthalic acid and 86.03 mol of ethylene glycol were fed at 100° C. at atmospheric pressure. Then, 0.0045 mol of the titanium-containing solid compound prepared in Example 495-2 was further added as a catalyst. Thereafter, the temperature of the reactor was raised to 260° C., and the reaction was conducted for 340 minutes under a pressure of 1.7 kg/cm²-G in a nitrogen atmosphere. Water produced by the reaction was continually distilled off from the system.

The total amount of the reaction solution in the esterification reactor was transferred into a polycondensation reactor beforehand set at 260° C. Then, a solution of 0.0073 mol of tributyl phosphate in 6.44 mol of ethylene glycol was further added to the reactor at atmospheric pressure, and the temperature of the reactor was raised to 280° C. from 260° C., while the pressure was reduced down to 2 Torr from atmospheric pressure.

The reaction in the polycondensation reactor was further conducted for 108 minutes. Then, the reaction product was drawn out of the polycondensation reactor in the form of strands. The strands were immersed in water, cooled and cut into particles by a strand cutter to obtain polyethylene terephthalate. The intrinsic viscosity of the polyethylene terephthalate was 0.65 dl/g, the titanium content and the magnesium content as measured by atomic absorption analysis were 25 ppm and 2 ppm, respectively, and the Mg/Ti weight ratio was 0.08.

The polyethylene terephthalate obtained by the liquid phase polymerization was then transferred into a solid phase polymerization tower, crystallized at 170° C. for 2 hours in a nitrogen atmosphere, and then subjected to solid phase polymerization at 210° C. for 13 hours to obtain particulate polyethylene terephthalate. The intrinsic viscosity of the polyethylene terephthalate was 0.825 dl/g. Using the polyethylene terephthalate, a stepped square plate molded product was produced in the same method as described above. The haze of part C of the stepped square plate molded product was 17.8%.

Polyethylene terephthalate was produced in the same manner as in Example 496-7, except that the catalyst and the polymerization conditions were changed as shown in Table 496-1. The results are set forth in Table 496-1.

Comparative Example 496-1

Preparation of Titanium Compound

The titanium hydroxide obtained after washing with deionized water in Example 495-1 was boiled at 100° C. for 2 hours and then dried, to obtained a titanium compound.

Preparation of solid Titanium Compound

Polycondensation reaction was carried out in the same manner as in Example 496-7, except that the titanium compound obtained above was used as the polycondensation catalyst.

The time (liquid chase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was 263 minutes.

It is known that titanium hydroxide is converted into metatitanic acid when heated in water, and the titanium compound obtained by way of metatitanic acid has been found to have low polycondensation activity.

The titanium content and the magnesium content in the polyethylene terephthalate were 25 ppm and 16 ppm, respectively, the Mg/Ti ratio (by weight) was 0.64, and the chlorine content in the polyethylene terephthalate was not more than 1 ppm.

	TABLE 496-1

			Liquid phase	Solid phase
	Polycondensation catalyst (I)	Co-catalyst component (II)	polymerization	polymerization
		Amount added *3	Residue *4		Amount added *3	Residue *4	Time	IV	Time	IV	Haze
	Type	(% by mol)	(ppm)	Type	(% by mol)	(ppm)	(hr)	(dl/g)	(hr)	(dl/g)	(%)


Ex.496-8	*1	0.013	31	—	—	—	2.62	0.643	23.0	0.816	16.5
Ex.496-9	*2	0.013	27	Mg(OAc)₂	0.020	22	0.93	0.657	10.0	0.803	1.5
Ex.496-10	*2	0.013	13	Mg(OAc)₂	0.020	25	1.03	0.660	17.0	0.843	0.4
Ex.496-11	*2	0.013	25	Mg(OAc)₂	0.020	16	1.70	0.651	12.5	0.820	13.7
Ex.496-12	*2	0.013	30	Ca(OAc)₂	0.020	36	2.53	0.644	21.0	0.814	22.4
Ex.496-13	*2	0.013	29	Zn(OAc)₂	0.020	59	1.12	0.665	10.5	0.807	13.7
Ex.496-2C	*2	0.013	29	—	—	—	3.63	0.653	26.0	0.834	19.4

*1: titanium-containing solid compound prepared in Example 495-3
*2: solid titanium compound prepared in Example 495-1
*3: in terms of metal atom based on terephthalic acid unit
*4: contents of metal atom based on particulate polyethylene terephthalate
Mg(OAc)₂: magnesium acetate
Ca(OAc)₂: calcium acetate
Zn(OAc)₂: zinc acetate

Example 473-1

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added at room temperature with stirring, to adjust pH of the solution to 9. To the solution, a 15% acetic acid aqueous solution was dropwise added at room temperature with stirring, to adjust pH of the solution to 5. The resulting precipitate was separated by flirtation and washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by filtration similarly to the above. The washed titanium compound was vacuum dried at 70° C. udner a pressure of 10 Torr for 18 hours to remove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compound was pulverized into particles of about 10μ.

The absorbed water content in the solid titanium compound thus obtained was measured by a Karl Fischer's water content meter. As a result, the absorbed water content was 11.29% by weight. Further, the weight loss on heating was measured by thermogravimetry. As a result, the weight loss on heating up to 600° C. was 13.65% by weight. Measurements of titanium content, nitrogen content and chlorine content in the solid titanium compound resulted in 43% by weight, 510 ppm and 76 ppm, respectively. From these results, the molar ratio between titanium and hydroxyl group in the solid titanium compound was found to be 1:0.28. The titanium content was measured by atomic absorption analysis. Nitrogen and chlorine were analyzed by an all nitrogen microanlayzer (chemiluminescence method) and chromatography, respectively, and for the calculation of the contents, they were considered to be desorbed as ammonia and hydrogen chloride, respectively.

Example 473-2

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added at room temperature with stirring, to adjust pH of the solution to 5. The resulting precipitate was separated by filtration and washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by filtration similarly to the above. The washed titanium compound was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compound was pulverized into particles of about 10μ.

With respect to the solid titanium compound obtained above, absorbed water content, weight loss on heating up to 600° C., titanium content, nitrogen content and chlorine content were measured in the same manner as in Example 473-1. As a result, the water content measured by a Karl Fischer's water content meter was 14.35% by weight, the weight loss on heating up to 600° C. was 16.82% by weight, the titanium content was 40% by weight, the nitrogen content was 950 ppm, and the chlorine content was 54 ppm. From these results, the molar ratio between titanium and hydroxyl group in the solid titanium compound was found to be 1:0.31.

Example 473-3

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added at room temperature with stirring, to adjust pH o0 to solution to 3.5. The resulting precipitate was separated by filtration and washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by filtration similarly to the above. The washed titanium compound was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyze, the solid titanium compound was pulverized into particles of about 10μ.

With respect to the solid titanium compound obtained above, absorbed water content, weight loss on heating up to 600° C., titanium content, nitrogen content and chlorine content were measured in the same manner as in Example 473-1. As a result, the water content measured by a Karl Fischer's water content meter was 12.24% by weight, the weight loss on heating up to 600° C. was 14.36% by weight, the titanium content was 41% by weight, the nitrogen content was 150 ppm, and the chloride content was 26 ppm. From these results, the molar ratio between titanium and hydroxyl gruop in the solid titanium compound was found to be 1:0.27.

Example 473-4

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and a 5% sodium hydroxide aqueous solution was dropwise added at room temperature with stirring, to adjust pH of the solution to 5. The resulting precipitate was separated by filtration and washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by filtration similarly to the above. The washed titanium compound was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compound was pulverized into particles of about 10μ.

With respect to the solid titanium compound obtained above, absorbed water content, weight loss on heating up to 600° C., metallic titanium content, metallic sodium content and chlorine content were measured in the same manner as in Example 473-1. As a result, the water content measured by a Karl Fischer's water content meter was 12.37% by weight, the weight loss on heating up to 600° C. was 10.12% by weight, the titanium content was 40% by weight, and the chlorine content was 54 ppm. Sodium was not detected. From these results, the molar ratio between titanium and hydroxyl group in the solid titanium compound was found to be 1:0.30.

Example 473-5

Comparative Example 473-1

The esterification reaction product (low condensate) was continuously drawn out of the system so that the average residence time was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Using the solid titanium compound prepared in Example 473-1 and magnesium acetate as polycondensation catalysts, liquid phase polycondensation reaction of the low condensate was conducted.

The amount of the solid titanium compound added as the catalyst was 0.01% by mol in terms of titanium atom and the around of magnesium acetate added as the catalyst was 0.02% by mol in terms of magnesium atom, each amount being based on the terephthalic acid unit in the low condensate.

The polycondensation reaction was conducted under the conditions of a temperature of 280° C. and a pressure of 1 Torr. As a result, the time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was 58 minutes.

Example 473-6

Polycondensation reaction was carried out in the same manner as in Example 473-5, except that the solid titanium compound prepared in Example 473-2 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was 60 minutes.

Example 473-7

Polycondensation reaction was carried out in the same manner as in Example 473-5, except that the solid titanium compound prepared in Example 473-3 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was 67 minutes.

Example 473-8

Polycondensation reaction was carried out in the same manner as in Example 473-5, except that the solid titanium compound prepared in Example 473-4 was used as the polycondensation catalyst.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was 65 minutes.

Polycondensation reaction was carried out in the same manner as in Example 473-5, except that antimony acetate that was industrially used was used as the polycondensation catalyst. The amount of antimony acetate added was 0.025% by mol in terms of antimony, based on the terephthalic acid unit in the low condensate.

The time (liquid phase polycondensation time) required to attain an intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was 120 minutes.

Example 510-1

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. At this time, the temperature or the solution was 0 to 5° C. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. At this time, the temperature of the solution was 0 to 10° C. The precipitate of titanium hydroxide produced was filtered under a pressure of 4 kg/cm²-G through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 4 kg/cm²-G similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compound was pulverized into particles of about 50μ.

As a result of analysis of the sol-d titanium compound, the titanium content was 40% by weight, the nitrogen content was 950 ppm, the chlorine content was 54 ppm, the weigh: loss on heating up to 600° C. was 16.8% by weight, and the absorbed water content was 15.25% by weight. The OH/Ti ratio calculated from these results was 0.193. Measurement of crystallinity resulted in 0%, and this solid titanium compound was completely amorphous.

In Examples 510-1 and 510-2 and Comparative Examples 510-1 and 510-2, X-ray diffraction intensity was measured under the following conditions.

- X-ray: Cu K-ALPHA1/50 kV/300 mA
- Goniometer: RINT2000 wide angle goniometer
- Attachment: standard sample holder
- Filter: none
- Counter monochrometer: fully automatic monochrometer
- Divergence slit: ½ deg.
- Scattering slit: ½ deg.
- Light receiving slit: 0.15 mm
- Counter: scintillation counter
- Scanning mode: continuous
- Scanning speed: 4°/min
- Scanning step: 0.02°
- Scanning axis: 2θ/θ
- Scanning range: 1.5-70°
- θ Offset: 0°
- Fixed angle: 0°

To a reactor in which 33500 parts of weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid (6458 parts by weight/hr) and ethylene glycol (2615 parts by weight/hr) was continuously fed with stirring under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere, to perform esterification reaction. In the esterification reaction, a mixture of water and ethylene glycol was distilled off.

The esterification reaction product (low condensate) was continuously drawn out of the system so that the average residence time was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Using the solid titanium compound prepared above and magnesium acetate as polycondensation catalysts, polycondensation reaction of the low condensate was conducted.

The amount of the solid titanium compound added as the catalyst was 0.0105% by mol in terms of titanium atom, based on the terephthalic-c acid unit in the low condensate, and the amount of magnesium acetate added as the catalyst was 0.021% by mol in terms of magnesium atom, based on the terephthalic acid unit in the low condensate. In the polycondensation, tributyl phosphate was further added in an amount of 0.0105% by mol in terms of phosphorus atom. The polycondensation reaction was conducted under the conditions of a temperature of 285° C. and a pressure of 1 Torr, to obtain polyethylene terephthalate (liquid phase polycondensation product) having an intrinsic viscosity of 0.65 dl/g. The polycondensation time was 65 minutes.

Example 510-2

A solid titanium compound was obtained in the same manner as in Example 510-1, except that the drying temperature is changed to 100° C. from 70° C.

Prior to use as a polycondensation catalyst, the solid titanium compound was pulverized into particles of about 50μ.

As a result of analysis of the solid titanium compound, the titanium content was 43% by weight, the nitrogen content was 510 ppm, the chlorine content was 71 ppm, the weight loss on heating up to 600° C. was 13.65% by weight, and the absorbed water contend was 12.11% by weight. The OH/Ti ratio calculated from these results was 0.182. Measurement of crystallinity resulted in 7%, and this solid titanium compound was slightly crystallized.

Comparative Example 510-1

Polycondensation reaction was carried out in the same manner as in Example 510-1, except that the solid titanium compound prepared above was used. As a result, polyethylene terephthalate (liquid phase polycondensation product) having an intrinsic viscosity of 0.65 dl/g was obtained. The polycondensation time was 68 minutes.

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. At this time, the temperature of the solution was about 25° C. After production of hydrogen chloride stopped, the temperature of the solution was kept at 80° C., and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 4 kg/cm²-G through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 4 kg/cm²-G similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compound was pulverized into particles of about 50μ.

As a result of analysis of the solid titanium compound, the titanium content was 50% by weight, the nitrogen content was 530 ppm, the chlorine content was 41 ppm, the weight loss on heating up to 600° C. was 16.63% by weight, and the absorbed water content was 14.68% by weight. The OH/Ti ratio calculated from these results was 0.200. Measurement of crystallinity resulted in 64%, and this solid titanium compound was considerably crystallized.

Comparative Example 510-2

Polycondensation reaction was carried out in the same manner as in Example 510-1, except that the solid titanium compound prepared above was used. However, an intrinsic viscosity of 0.65 dl/g could not be obtained by the polycondensation for a period up to 240 minutes.

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The temperature of the deionized water was kept at 60° C., and 5 g of titanium tetrachloride was dropwise added with stirring. After production of hydrogen chloride stopped, the temperature of the solution was kept at 80° C., and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 4 kg/cm²-G through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times wish deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 4 kg/cm²-G similarly to the above. The washed titanium hydroxide was vacuum dried at 100° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a solid titanium compound was obtained.

Prior to use as a polycondensation catalyst, the solid titanium compound was pulverized into particles of about 50μ.

As a result of analysis of the solid titanium compound, the titanium content was 47% by weight, the nitrogen content was 840 ppm, the chlorine content was 1050 ppm, the weight loss on heating up to 600° C. was 15.95% by weight, and the absorbed water content was 13.62% by weight. The OH/Ti ratio calculated from these results was 0.240. Measurement of crystallinity resulted in 71%, and this solid titanium compound was considerably crystallized.

Preparation of Titanium-containing Hydrolyzate

Example 198-1 498-1

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 3 kg/cm²through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water contend, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containing solid compound was pulverized into particles of about 10 μm.

Preparation of Catalyst For Polyester Production

A mixture of 10 g of the titanium-containing hydrolyzate, 65 g of ethylene glycol and 25 g of tetraethylammonium hydroxide was heated at 190° C. for 3 hours to obtain a catalyst for polyester production.

Comparative Example 498-2

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid and ethylene glycol was continuously fed, and esterification reaction was conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. The slurry of high-purity terephthalic acid and ethylene glycol was prepared by mixing high-purity terephthalic acid and ethylene glycol at rate of 6458 parts by weight/hr and 2615 parts by eeight/hr, respectively.

In the esterification reaction, a mixture of water and ethylene glycol was distilled off. The esterification reaction product (low condensate) wad continuously drawn out of the system so that the average residence time was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

To the low condensate, the catalyst for polyester production was added in an amount of 0.021% by mol in terms of titanium atom, based on 1 mol of the terephthalic acid unit in the low condensate, and liquid phase polycondensation reaction was conducted under the conditions of a temperature of 285° C. and a pressure of 1 Torr. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 57 minutes.

Example 498-1C

Polycondensation reaction was carried out in he same manner as in Example 498-1, except that the titanium-containing hydrolyzate was used in an amount of 0.021% by mol in terms of titanium atom, based on 1 mol of the terephthalic acid unit in low condensate, instead of the catalyst for polyester production. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 3 hours and 55 minutes. The acetaldehyde content in the polyethylene terephthalate was 52 ppm.

Preparation of Polycondensation Catalyst (1)

A mixture of 10 g of the titanium-containing hydrolyzate, 65 g of ethylene glycol and 25 g of acetic acid was heated at 190° C. for 3 hours to obtain a polycondensation catalyst (1).

Comparative Example 498-3

Polycondensation reaction was carried out in the same manner as in Example 498-1, except that the polycondensation catalyst (1) was used in an amount of 0.021% by mol in terms of titanium atom, based on 1 mol of the terephthalic acid unit in low condensate, instead of the catalyst for polyester production. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 146 minutes. The acetaldehyde content in the polyethylene terephthalate was 58 ppm.

Preparation of Polycondensation Catalyst (2)

A mixture of 10 g of the titanium-containing hydrolyzate and 90 g of ethylene glycol was heated at 190° C. for 3 hours to obtain a polycondensation catalyst (2).

Polycondensation reaction was carried out in the same manner as in Example 498-1, except that the polycondensation catalyst (2) was used in an amount of 0.021% by mol in terms of titanium atom, based on 1 mol of the terephthalic acid unit in low condensate, instead of the catalyst for polyester production. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 1 hour and 50 minutes.

Example 501-1

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 3 kg/cm²through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containing solid compound was pulverized into particles of about 10 μm.

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid and ethylene glycol was continuously fed, and esterification reaction was conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. The slurry of high-purity terephthalic acid and ethylene glycol was prepared by mixing high-purity terephthalic acid and ethylene glycol at races of 6458 parts by weight/hr and 2615 parts by weight/hr, respectively.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer)

To the low condensate, the titanium-containing solid compound was added in an amount of 0.021% by mol in terms of titanium atom, based on the terephthalic acid unit in the low condensate, magnesium hydrogenphosphate was added in an amount of 0.021% by mol in terms of magnesium atom, based on the terephthalic acid unit in the low condensate, and phosphoric acid was added in an amount of 0.0105% by mol in terms of phosphorus atom, and liquid phase polycondensation reaction was conducted under the conditions of a temperature of 285° C. and a pressure of 1 Torr. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 57 minutes. The acetaldehyde content in the resulting polyethylene terephthalate was 60 ppm.

Example 501-2

Polycondensation reaction was carried out in the same manner as in Example 501-1, except that trimagnesium diphosphate was used instead of magnesium hydrogenphosphate. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 67 minutes. The acetaldehyde content in the resulting polyethylene terephthalate was 57 ppm.

Example 501-1C

Polycondensation reaction was carried out in the same manner as in Example 501-1, except that magnesium acetate was used instead of magnesium hydrogenphosphate. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 100 minutes. The acetaldehyde content in the resulting polyethylene terephthalate was 70 ppm.

Example 497-1

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 3 kg/cm²through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containing solid compound was pulverized into particles of about 10 μm.

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid and ethylene glycol was continuously fed, and esterification reaction was conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. The slurry of high-purity terephthalic acid and ethylene glycol was prepared by mixing high-purity terephthalic acid and ethylene glycol at rates of 6458 parts by weight/hr and 2615 parts by weight/hr, respectively.

Before the beginning of the esterification reaction, the titanium-containing solid compound, magnesium acetate and tributyl phosphate were added. The amount of the titanium-containing solid compound added was 0.021% by mol in terms of titanium atom, based on terephthalic acid (unit), the amount of magnesium acetate added was 0.021% by mol in terms of magnesium atom, based on the terephthalic acid (unit), and the amount of tributyl phosphate added was 0.0105% by mol in terms of phosphate atom, based on the terephthalic aced (unit).

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer)

The low condensate thus obtained was subjected to liquid phase polycondensation reaction under the conditions of a temperature of 285° C. and a pressure of 1 Torr. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 56 minutes.

Example 497-1C

Polyethylene terephthalate was produced in the same manner as in Example 497-1, except that the titanium-containing solid compound was not added in the esterification reaction step but added to the reactor of the first step in the liquid phase polycondensation step. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 4 hours.

Example 499-1

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 3 kg/cm²through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containing solid compound was pulverized into particles of about 10 μm.

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid and ethylene glycol was continuously fed, and esterification reaction was conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. The slurry of high-purity terephthalic acid and ethylene glycol was prepared by mixing high-purity terephthalic acid and ethylene glycol at rates of 6458 parts by weight/hr and 2615 parts by weight/hr, respectively.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer)

To the low condensate, the titanium-containing solid compound and tributyl phosphate were added, and liquid phase polycondensation reaction was conducted under the conditions of a temperature of 285° C. and a pressure of 1 Torr. The amount of the titanium-containing solid compound added was 0.021% by mol in terms of titanium atom, based on 1 mol of the terephthalic acid unit in the low condensate, and the amount of tributyl phosphate added was 0.0105% by mol in terms of phosphorus atom, based on 1 mol of the terephthalic acid unit. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalic was 60 minutes.

Example 499-2

Polycondensation reaction was carried out in the same manner as in Example 499-1, except that trioctyl phosphate was used instead of tributyl phosphate. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 60 minutes.

Example 499-3

Polycondensation reaction was carried out in the same manner as in Example 499-1, except that triphenyl phosphate was used instead of tributyl phosphate. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 60 minutes.

Example 499-4

Polycondensation reaction was carried out in the same manner as in Example 499-1, except that trimethyl phosphate was used instead of tributyl phosphate. The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 75 minutes.

Example 500-1

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 3 kg/cm²through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containing solid compound was pulverized into particles of about 10 μm.

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid and ethylene glycol was continuously fed, and esterification reaction was conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. The slurry of high-purity terephthalic acid and ethylene glycol was prepared by mixing high-purity terephthalic acid and ethylene glycol at rates of 6458 parts by weight/hr and 2615 parts by weight/hr, respectively.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

To the low condensate, the titanium-containing solid compound, magnesium acetate and tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane were added, and liquid phase polycondensation reaction was conducted under the conditions of a temperature of 285° C. and a pressure of 1 Torr. The amount of the titanium-containing solid compound added was 0.021% by mol in terms of titanium atom, based on the terephthalic acid unit in the low condensate, the amount of magnesium acetate added was 0.021% by mol in terms of magnesium atom, based on the terephthalic acid unit in the low condensate, and the amount of tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane added was 600 ppm based on the low condensate.

The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 50 minutes. The acetaldehyde content in the resulting polyethylene terephthalate was 60 ppm.

Example 500-2

Polycondensation reaction was carried out in the same manner as in Example 500-1, except that bis(2,6-di-t-butyl-4-phenylmethyl)pentaerythritol diphosphite was used in an amount of 300 ppm based on the low condensate instead of tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 48 minutes. The acetaldehyde content in the resulting polyethylene terephthalate was 52 ppm.

Example 500-3

Polycondensation reaction was carried out in the same manner as in Example 500-1, except that 3,5-di-t-butyl-4-hydroxybenzylphosphoric acid distearyl easter was used in an amount of 400 ppm based on the low condensate instead of tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 dl/g of Polyethylene terephthalate was 46 minutes. The acetaldehyde content in the resulting polyethylene terephthalate was 58 ppm.

Example 500-4

Polycondensation reaction was carried out in the same manner as in Example 500-1, except that a mixture of tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane, 5,7-di-t-butyl-3-(3,4-dimethylphenyl)-3H-benzofuran-2-one and tris(2,4-di-t-butylphenly)phosphite (mixing ratio=42.5:15:42.5) was used in an amount of 500 ppm based on the low condensate instead of tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 49 minutes. The acetaldehyde content in the resulting polyethylene terephthalate was 55 ppm.

Example 500-5

Polycondensation reaction was carried out in the same manner as in example 500-1, except that tributyl phosphate was used in an amount of 0.0105% by mol in terms or phosphorus atom, based on the terephthalic acid in the low condensate, in addition to tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 dl/g of polyethylene terephthalate was 50 minutes. The acetaldehyde content in the resulting polyethylene terephthalate was 50 ppm.

Example 500-1C

Polycondensation reaction was carried out in the same manner as in Example 500-1, except that phosphoric acid was used in an amount of 0.0105% by mol in terms of phosphorus atom, based on the terephthalic acid unit in the low condensate, instead of tetrakis(methylene-3(3,5-di-t-butyl-4-hydroxyphenyl)propionate)methane.

The time required to attain an intrinsic viscosity of 0.65 gl/g of polyethylene terephthalate was 70 minutes. The acetaldehyde content in the resulting polyethylene terephthalate was 70 ppm.

Example 502-1

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 3 kg/cm²through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a titanium-containing solid compound was obtained.

Prior to use as a polycondensation catalyst, the titanium-containing solid compound was pulverized into particles of about 10 μm.

Examples 502-2 to 502-5. Examples 502-1C

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid and ethylene glycol was continuously fed, and esterification reaction wad conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. The slurry of high-purity terephthalic acid and ethylene glycol was prepared by mixing high-purity terephthalic acid and ethylene glycol at rates of 6458 parts by weight/hr and 2615 parts by weight/hr, respectively.

Before the beginning of the esterification reaction, the titanium-containing solid compound, magnesium acetate, tributyl phosphate and a tint adjusting agent were added to the reactor. The amount of the titanium-containing solid compound added was 12 ppm in terms of titanium atom, based on the polyethylene terephthalate, the amount of magnesium acetate added was 25 ppm in terms of magnesium atom, based on the polyethylene terephthalate, the amount of tributyl phosphate added was 15 ppm in berms of phosphorus atom, based on the polyethylene terephthalate, and the amount of the tint adjusting agent (Solvent Blue 104) added was 5.0 ppm based on the polyethylene terephthalate.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

The low condensate thus obtained was subjected to liquid phase polycondensation reaction under the conditions of a temperature of 285° C. and a pressure of 1 Torr.

The tint of the polyester chips obtained above was measured by a 45° diffusion type color difference meter (Nippon Denshoku SQ 300H Model). The result is set forth in Table 502-1.

A polyester was produced in the same manner as in Example 502-1, except that the type and the amount of the tint adjusting agent were changed as shown in Table 502-1. The tint of the polyester chips was measured. The result is set forth in Table 502-1.

Examples 502-6 to 502-11. Examples 502-2C to 502-4C

A polyester was produced in the same manner as in Example 502-1, except that the amounts of the titanium-containing solid compound, magnesium acetate and the phosphorus compound were changed as shown in Table 502-1 and the type and the amount of the tint adjusting agent were changed as shown in Table 502-1. The tint of the polyester chips was measured. The result is set froth in Table 502-1.

	TABLE 502-1

	Titanium-
	containing
	solid	Magnesium	Phosphorus	Tint adjusting agent (ppm)	Tint
	compound	acetate	compound	Solvent	Pigment	Solvent	L	a	b
	(ppm)	(ppm)	(ppm)	Blue 104	Red 263	Red 135	value	value	value


Ex. 502-1	12	25	15	5.0	—	—	51.2	−7.4	−5.0
Ex. 502-2	″	″	″	5.0	3.0	—	45.4	0.0	−7.0
Ex. 502-3	″	″	″	3.0	1.8	—	51.4	−0.7	−2.4
Ex. 502-4	″	″	″	1.0	0.6	—	58.8	−2.1	4.0
Ex. 502-5	″	″	″	—	5.0	—	55.7	14.0	5.1
Ex. 502-1C	″	″	″	—	—	—	65.9	−2.8	10.5
Ex. 502-6	18	18	30	2.0	1.5	—	71.5	−0.2	−1.1
Ex. 502-7	″	″	″	2.5	—	2.5	53.4	−1.6	−0.4
Ex. 502-2C	″	″	″	—	—	—	65.4	−2.5	8.8
Ex. 502-8	25	25	15	—	—	5.0	56.7	10.2	10.7
Ex. 502-9	″	″	″	—	—	2.0	61.0	3.6	10.1
Ex. 502-3C	″	″	″	—	—	—	64.8	−3.0	11.9
Ex. 502-10	18	18	15	1.5	—	1.0	55.9	−2.8	1.5
Ex. 502-11	″	″	″	2.5	—	2.0	52.4	−2.0	−0.5
Ex. 502-4C	″	″	″	—	—	—	65.8	−2.4	9.1

Example 46a-1

In a stainless steel container, 2.5 kg of particulate polyethylene terephthalate having an intrinsic viscosity of 0.85 dl/g, a density of 1.40 g/cm³and an acetaldehyde content of 1.5 ppm was immersed in 4 kg of a trimethyl phosphate aqueous solution of 0.0695% by weight (161 ppm in terms of phosphorus atom), and they were kept at room temperature for 4 hours. Thereafter, the particulate polyethylene terephthalate was separated from the trimethyl phosphate aqueous solution, hydro-extracted and then dried at 160° C. for 5 hours in a stream of nitrogen. Using the resulting polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The stepped square plate molded product has an acetaldehyde content of 7.7 ppm and an intrinsic viscosity of 0.821 dl/g.

Example 464-2

In a stainless steel container, 2.5 kg of the same particulate polyethylene terephthalate as used in Example 464-1 was immersed in 4 kg of a trimethyl phosphate aqueous solution of 0.0595% by weight (161 ppm in terms of phosphorus atom). Then, the stainless steel container containing the polyethylene terephthalate and the trimethyl phosphate aqueous solution was externally heated to control the internal temperature to 95° C. and kept for 4 hours to perform heat treatment. Thereafter, the particulate polyethylene terephthalate was separated from the trimethyl phosphate aqueous solution, hydro-extracted and then dried at 160° C. for 5 hours in a stream of nitrogen. Using the resulting polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The stepped square plate molded product had an acetaldehyde content of 8.5 ppm and an intrinsic viscosity of 0.802 dl/g.

Example 46d-1C

The same particulate polyethylene terephthalate as used in Example 464-1 was molded into a stepped square plate molded product by the aforesaid method, without performing a contact treatment with a phosphorus-containing aqueous solution. The stepped square plate molded product had an acetaldehyde content of 11 ppm and an intrinsic viscosity of 0.833 dl/g.

Example a64-2C

Treatment of particulate polyethylene terephthalate was carried out in the same manner as in Example 464-1, except that a phosphoric acid aqueous solution having the same concentration (0.0508% by weight, 161 ppm in terms of phosphorus atom) was used instead of the trimethyl phosphate aqueous solution. Using the resulting polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The stepped square plate molded product had an acetaldehyde content of 8.3 ppm and an intrinsic viscosity of 0.814 dl/g.

Comparative Example 464-3

Treatment of particulate polyethylene terephthalate was carried out in the same manner as in Example 464-2, except that a phosphoric acid aqueous solution was used instead of the trimethyl phosphate aqueous solution. Using the resulting polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The stepped square plate molded product had an acetaldehyde content of 10.0 ppm and an intrinsic viscosity of 0.788 dl/g.

Example 465-1

Production of Polyethylene Terephthalate

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 3 kg/cm²through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a titanium-containing solid compound was obtained.

Prior to use, the titanium-containing solid compound was pulverized into particles of about 10 μm.

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid and ethylene glycol was continuously fed, and esterification reaction was conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. The slurry of high-purity terephthalic acid and ethylene glycol was prepared by mixing high-purity terephthalic acid and ethylene glycol at rates of 6458 parts by weight/hr and 2615 parts by weight/hr, respectively.

In the esterification reaction, a mixture of water and ethylene glycol was distilled off. The esterification reaction product (low condensate) was continuously drawn out of the system so that the average residence time was controlled to 3.5 hours. The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

To the low condensate, the titanium-containing solid compound, magnesium acetate and tributyl phosphate were added, and liquid phase polycondensation reaction was conducted under the conditions of a temperature of 285° C. and a pressure of 1 Torr to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65 dl/g. The amount of the titanium-containing solid compound added was 0.021% by mol in terms of titanium atom, based on the terephthalic acid unit in the low condensate, the amount of magnesium acetate added was 0.021% by mol in terms of magnesium atom, based on the terephthalic acid unit in the low condensate, and the amount of tributyl phosphate added was 0.0105% by mol in terms of phosphorus atom, based on the terephthalic acid unit in the low condensate.

The polyethylene terephthalate in which the liquid phase polycondensation had been completed was subjected to solid phase polycondensation, to obtain particulate polyethylene terephthalate having an intrinsic viscosity of 0.81 dl/g, a density of 1.40 g/cm³and an acetaldehyde content of 1.0 ppm.

Treatment of Polyethylene Terephthalate

Into a 100 ml flask, 10 g of the particulate polyethylene terephthalate and 40 g of isopropanol were introduced, and they were heated for 4 hours under reflux. The mixture was dried at 70° C. for 16 hours, melted by heating at 270° C. for 6 minutes and then cooled to room temperature to give a sample. Measurement of acetaldehyde content in the sample resulted in 5.2 ppm.

Example 465-2

Contact of particulate polyethylene terephthalate with an organic solvent was carried out in the same manner as in Example 465-1, except that methanol was used instead of isopropanol. Then, the acetaldehyde content was measured in the same manner as in Example 465-1. As a result, the acetaldehyde content was 6.4 ppm.

Example 465-3

Contact of particulate polyethylene terephthalate with an organic solvent was carried out in the same manner as in Example 465-1, except that acetone was used instead of isopropanol. Then, the acetaldehyde content was measured in the same manner as in Example 465-1. As a result, the acetaldehyde content was 6.7 ppm.

Example 465-4

Contact of particulate polyethylene terephthalate with an organic solvent was carried out in the same manner as in Example 465-1, except that hexane was used instead of isopropanol. Then, the acetaldehyde content was measured in the same manner as in Example 465-1. As a result, the acetaldehyde content was 6.8 ppm.

Example 465-1C

The same particulate polyethylene terephthalate as used in Example 465-1 was dried at 70° C. for 16 hours, melted by heating at 270° C. for 6 minutes and cooled to room temperature, without performing a contact treatment with an organic solvent, to give a sample. Measurement of acetaldehyde content in the sample resulted in 7.3 ppm.

Example 466-1

Production of Polyethylene Terephthalate

Deionized water of 500 ml was weighed out and introduced into a 1000 ml glass beaker. The deionized water in the beaker was cooled in an ice bath, and thereto was dropwise added 5 g of titanium tetrachloride with stirring. When production of hydrogen chloride stopped, the beaker containing the reaction solution was taken out of the ice bath, and 25% aqueous ammonia was dropwise added with stirring, to adjust pH of the solution to 8. The precipitate of titanium hydroxide produced was filtered under a pressure of 3 kg/cm²through a pressure filter and separated. Thereafter, the precipitate of titanium hydroxide was washed 5 times with deionized water. After the washing, solid-liquid separation was carried out by pressure filtration under a pressure of 3 kg/cm²similarly to the above. The washed titanium hydroxide was vacuum dried at 70° C. under a pressure of 10 Torr for 18 hours to remove water content, whereby a titanium-containing solid compound was obtained.

Prior to use, the titanium-containing solid compound was pulverized into particles of about 10 μm.

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid and ethylene glycol was continuously fed, and esterification reaction was conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. The slurry of high-purity terephthalic acid and ethylene glycol was prepared by mixing high-purity terephthalic acid and ethylene glycol at rates of 6458 parts by weight/hr and 2615 parts by weight/hr, respectively.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

To the low condensate, the titanium-containing solid compound, magnesium acetate and tributyl phosphate were added, and liquid phase polycondensation reaction was conducted under the conditions of a temperature 285° C. and a pressure of 1 Torr to obtain polyethylene terephthalate having an intrinsic viscosity of 0.65 dl/g. The amount of the titanium-containing solid compound added was 0.021% by mol in terms of titanium atom, based on the terephthalic acid unit in the low condensate, the amount of magnesium acetate added was 0.021% by mol in terms of magnesium atom, based on the terephthalic acid unit in the low condensate, and the amount of tributyl phosphate added was 0.0105% by mol in terms of phosphorus atom, based on the terephthalic acid unit in the low condensate.

Treatment of Polyethylene Terephthalate

Into a 200 ml flask, 30 g of the particulate polyethylene terephthalate, 60 g of isopropanol and 10.3 of tributyl phosphate (2% by weight in terms of phosphorus atom based on isopropanol) were introduced, and they were heated for 4 hours under reflux. Thereafter, he mixture was washed three times with 60 g of isopropanol, dried at 70° C. for 16 hours, melted by heating at 285° C. for 10 minutes an then cooled to room temperature to give a sample. Measurement of an acetaldehyde content in the sample resulted in 30 ppm.

Example 466-2

Contact of particulate polyethylene terephthalate with a phosphorus-containing organic solvent solution was carried out in the same manner as in Example 466-1, except that methanol was used instead of isopropanol and 5.4 g (2% by weight in terms of phosphorus atom based on methanol) of trimethyl phosphate was used instead of 10.3 g of tributyl phosphate. Then, the acetaldehyde content was measured in the same manner as in Example 466-1. As a result, the acetaldehyde content was 28 ppm.

Example 466-3

Contact of particulate polyethylene terephthalate with a phosphorus-containing organic solvent solution was carried out in the same manner as in Example 466-1, except that acetone was used instead of isopropanol. Then, the acetaldehyde content was measured in the same manner as in Example 466-1. As a result, the acetaldehyde content was 40 ppm.

Example 466-4

Contact of particulate polyethylene terephthalate with a phosphorus-containing organic solvent solution was carried out in the same manner as in Example 466-1, except that hexane was used instead of isopropanol. Then, the acetaldehyde content was measured in the same manner as in Example 466-1. As a result, the acetaldehyde content was 35 ppm.

Example 466-5

Contact of particulate polyethylene terephthalate with a phosphorus-containing organic solvent solution was carried out in the same manner as in Example 466-1, except that 3.8 g (2% by weight in terms of phosphorus atom based on isopropanol) of phosphoric acid was used instead of 10.3 g of tributyl phosphate. Then, the acetaldehyde content was measured in the same manner as in Example 466-1. As a result, the acetaldehyde content was 36 ppm.

Example 466-1C

The same particulate polyethylene terephthalate as used in Example 466-1 was dried at 70° C. for 16 hours, melted by heating at 285° C. for 10 minutes and cooled to room temperature, without performing a contact treatment with a phosphorus-containing organic solvent solution, to give a sample. Measurement of an acetaldehyde content in the sample resulted in 50 ppm.

Comparative Example 466-2

Contact of particulate polyethylene terephthalate with a phosphoric acid aqueous solution was carried out in the same manner as in Example 466-1, except that water was used instead of isopropanol and 3.8 g (2% by weight in terms of phosphorus atom based on water) of phosphoric acid was used instead of 10.3 g of tributyl phosphate. Then, the acetaldehyde content was measured in the same manner as in Example 466-1. As a result, the acetaldehyde content was 45 ppm.

Example 462-1

Comparative Example 462-2

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid (6458 parts by weight/hr) and ethylene glycol (261 parts by weigh/hr) was continuously fed, and esterification reaction was conducted under the condition of a temperature or 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. In the esterification reaction, the solid titanium compound prepared in Example 495-1 was fed at a rate of 0.187 part by weight/hr in terms of titanium atom, and magnesium acetate was fed at a rate of 0.187 part by weight/hr in terms of magnesium atom. In the esterification reaction, a mixture of water and ethylene glycol was distilled off.

The esterification reaction product (low condensate) was continuously drawn out of the system so that the average residence time was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Then, liquid phase polycondensation reaction of the low condensate was conducted under the conditions of a temperature of 280° C. and a pressure of 1 Torr, with feeding tributyl phosphate at a race of 0.831 part by weight/hr.

The residence time (liquid phase polymerization time) required to attain an intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was 95 minutes.

The polyethylene terephthalate obtained by the liquid phase polymerization was crystallized at about 170° C. for 2 hours in a nitrogen atmosphere and then filled in a tower type solid phase polymerization reactor to perform solid phase polymerization at 210° C. for 14 hours in a nitrogen atmosphere.

In the resulting polyethylene terephthalate, the titanium atom content was 25 ppm, the magnesium atom content was 25 ppm, the titanium atom/magnesium atom molar ratio was 0.5, the intrinsic viscosity was 0.85 dl/g, the density was 1.40 g/cm³, and the acetaldehyde content was 1.0 ppm.

In a stainless steel container, 2.5 kg of the polyethylene terephthalate was immersed in 4 kg of a trimethyl phosphate aqueous solution of 0.0695% by weight, and they were kept at room temperature for 4 hours. Thereafter, the particulate polyethylene terephthalate was separated from the trimethyl phosphate aqueous solution, hydro-extracted and then dried at 160° C. for 5 hours in a stream of nitrogen. The acetaldehyde content in the resulting polyethylene terephthalate was 1.0 ppm. Using the polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The acetaldehyde content in the stepped square plate molded product was 9.0 ppm, and a difference in the acetaldehyde content between before and after the molding was 8.0 ppm. The intrinsic viscosity of the stepped square plate molded product was 0.821 dl/g.

Example 462-2

In a stainless steel container, 2.5 kg of the same particulate polyethylene terephthalate as used in Example 462-1 was immersed in 4 kg of a trimethyl phosphate aqueous solution of 0.0695% by weight. Then, the stainless steel container containing the polyethylene terephthalate and the trimethyl phosphate aqueous solution was externally heated to control the internal temperature to 95° C. and kept for 4 hours to perform heat treatment. Thereafter, the particulate polyethylene terephthalate was separated from the trimethyl phosphate aqueous solution, hydro-extracted and then dried at 160° C. for 5 hours in a stream of nitrogen. Using the resulting polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The acetaldehyde content in the stepped square plate molded product was 9.5 ppm, and a difference in the acetaldehyde content between before and after the molding was 8.5 ppm. The intrinsic viscosity of the stepped square plate molded product was 0.802 dl/g.

Example 462-1C

The same particulate polyethylene terephthalate as used in Example 462-1 was molded into a stepped square plate molded product by the aforesaid method, without performing a contact treatment with a phosphorus-containing aqueous solution. The acetaldehyde content in the stepped square plate molded product was 20 ppm, and a difference in the acetaldehyde content between before and after the molding was 19 ppm. The intrinsic viscosity of the stepped square plate molded product was 0.833 dl/g.

Treatment of particulate polyethylene terephthalate was carried out in the same manner as in Example 402-1, except that a phosphoric acid aqueous solution having the same concentration was used instead of the trimethyl phosphate aqueous solution. Using the resulting polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The acetaldehyde content in the stepped square plate molded product was 13 ppm, and a difference in the acetaldehyde content between before and after the molding was 12 ppm. The intrinsic viscosity of the stepped square plate molded product was 0.814 dl/g.

Example 462-3

In the esterification reaction, a solid titanium compound prepared in the same manner as in Example 462-1 was fed at a rate of 0.112 part by weight/hr in terms of titanium atom, and magnesium acetate was fed at a rate of 0.187 part by weight/hr in terms of magnesium atom. In the esterification reaction, a mixture of water and ethylene glycol was distilled off.

The esterification reaction product (low condensate) was continuously drawn out of the system so that the average residence time was controlled co 3.5 hours.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

The residence time (liquid phase polymerization time) required to attain an intrinsic viscosity (IV) of 0.65 dl/g of polyethylene terephthalate was 115 minutes.

In the resulting polyethylene terephthalate, the titanium atom content was 15 ppm, the magnesium atom content was 25 ppm, the titanium atom/magnesium atom molar ratio was 0.3, the intrinsic viscosity was 0.83 dl/g, the density was 1.40 g/cm³, and the acetaldehyde content was 0.9 ppm.

In a stainless steel container, 2.5 kg of the polyethylene terephthalate was immersed in 4 kg of a trimethyl phosphate aqueous solution of 0.0695% by weight, and they were kept at room temperature for 4 hours. Thereafter, the particulate polyethylene terephthalate was separated from the trimethyl phosphate aqueous solution, hydro-extracted and then dried at 160° C. for 5 hours in a stream of nitrogen. The acetaldehyde content in the resulting polyethylene terephthalate was 0.8 ppm. Using the polyethylene terephthalate, a stepped square plate molded product as produced by the aforesaid method. The acetaldehyde content in the stepped square plate molded product was 8.2 ppm, and a difference in the acetaldehyde content between before and after the molding was 7.4 ppm. The intrinsic viscosity of the stepped square plate molded product was 0.819 dl/g.

Example 462-4

In a stainless steel container, the polyethylene terephthalate obtained after the solid phase polymerization in Example 462-3 was immersed in isopropanol at 95° C. and kept for 4 hours under heating.

Then, the polyethylene terephthalate was separated from isopropanol and dried at 160° C. for 5 hours in a stream of nitrogen. The acetaldehyde content in the resulting polyethylene terephthalate was 0.9 ppm. Using the polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The acetaldehyde content in the stepped square plate molded product was 9.5 ppm, and a difference in the acetaldehyde content between before and after the molding was 8.6 ppm. The intrinsic viscosity of the stepped square plate molded product was 0.810 dl/g.

Example 462-5

In a stainless steel container, the polyethylene terephthalate obtained after the solid phase polymerization in Example 462-3 was immersed in an isopropanol solution of tributyl phosphate (tributyl phosphate: 0.0695% by weight) and kept for 2 hours under heating.

Then, the polyethylene terephthalate was separated from the isopropanol solution and dried at 160° C. for 5 hours in a stream of nitrogen. The acetaldehyde content in the resulting polyethylene terephthalate was 0.7 ppm. Using the polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The acetaldehyde content in the stepped square plate molded product was 8.2 ppm, and a difference in the acetaldehyde content between before and after the molding was 7.5 ppm. The intrinsic viscosity of the stepped square plate molded product was 0.808 dl/g.

Example 463-1

Comparative Example 469-1

To a reactor in which 33500 parts by weigh of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid (6458 parts by weight/hr) and ethylene glycol (2909 parts by weight/hr) was continuously fed, and esterification reaction was conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. In the esterification reaction, the solid titanium compound prepared in Example 495-1 was fed at a rate of 0.187 part by weight/hr in terms of titanium atom, and magnesium acetate was fed at a rate of 0.187 part by weight/hr in terms of magnesium atom. In the esterification reaction, a mixture of water and ethylene glycol was distilled off.

The esterification reaction product (low condensate) was continuously drawn out of the system so that the average residence time was controlled to 3.5 hours.

The number-average molecular weight of he low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer).

Then, liquid phase polycondensation reaction or the low condensate was conducted under the conditions of a temperature of 280° C. and a pressure of 1 Torr, with Feeding tributyl phosphate at a rate of 0.831 part by weight/hr.

The residence time (liquid chase polymerization time) required to attain an intrinsic viscosity (IV) of 0.55 dl/g of polyethylene terephthalate was 87 minutes.

In the resulting polyethylene terephthalate, the titanium atom content was 24 ppm, the magnesium atom content was 24 ppm, the titanium atom/magnesium molar ratio was 0.5, the intrinsic viscosity was 0.760 dl/g, the density was 1.40 g/cm³, and the cyclic trimer content was 0.3% by weight.

In a stainless steel container, 2.5 kg of the polyethylene terephthalate was immersed in 4 kg of a trimethyl phosphate aqueous solution of 0.0695% by weight, and they were kept at room temperature for 4 hours. Thereafter, the particulate polyethylene terephthalate was separated from the trimethyl phosphate aqueous solution, hydro-extracted and then dried at 160° C. for 5 hours in a stream of nitrogen. The cyclic trimer content in the resulting polyethylene terephthalate was 0.30% by weight (x % by weight). Using the polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The cyclic trimer content in the stepped square plate molded product was 0.35% by weight, a difference in the cyclic trimer content between before and after the molding was 0.05% by weight (y % by weight), and the value of −0.2+0.2 was 0.14. The intrinsic viscosity of the stepped square plate molded product was 0.825 dl/g.

Example 463-2

In a stainless steel container, 2.5 kg of the same particulate polyethylene terephthalate as used in Example 463-1 was immersed in 4 kg of a trimethyl phosphate aqueous solution of 0.0695% by weight. Then, the stainless steel container containing the polyethylene terephthalate and the trimethyl phosphate aqueous solution was externally heated to control the internal temperature to 95° C. and kept for 4 hours at perform heat treatment. Thereafter, the particulate polyethylene terephthalate was separated from the trimethyl phosphate aqueous solution, hydro-extracted and then dried at 160° C. for 5 hours in a stream of nitrogen. The cyclic trimer content in the resulting polyethylene terephthalate was 0.30% by weight (x % by weight). Using the polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The cyclic trimer content in the stepped square plate molded product was 0.33% by weight (x % by weight), a difference in the cyclic trimer content between before and after the molding was 0.03% by weight (y % by weight), and the value of −0.20+0.2 was 0.134. The intrinsic viscosity of the stepped square plate molded product was 0.811 dl/g.

Example 463-1C

The same particulate polyethylene terephthalate as used in Example 463-1 was molded into a stepped square plate molded product by the aforesaid method, without performing a constant treatment with a phosphorus-containing aqueous solution. The cyclic trimer content in the stepped square plate molded product was 0.52% by weight (x % by weight), a difference in the cyclic trimer content between before and after the molding was 0.22% by weight (y % by weight), and the value of −0.2+0.2 was 0.096. The intrinsic viscosity of the stepped square plate molded product was 0.833 dl/g.

Example 463-3

To a reactor in which 33500 parts by weight of a reaction solution was resident during the steady operation, a slurry prepared by mixing high-purity terephthalic acid (6329 parts by weight/hr), isophthalic acid (129 parts by weight) and ethylene glycol (2615 parts by weight/hr) was continuously fed, and esterification reaction was conducted under the conditions of a temperature of 260° C. and a pressure of 0.9 kg/cm²-G in a nitrogen atmosphere with stirring. In the esterification reaction, a solid titanium compound prepared in the same manner as in Example 463-1 was fed at a rate of 0.112 part by weight/hr in terms of titanium atom, and magnesium acetate was fed at a rate of 0.187 part by weight/hr in terms of magnesium atom. In the esterification reaction, a mixture of water and ethylene glycol was distilled off.

The esterification reaction product (low condensate) was continuously drawn out of the system so that than average residence time was controlled to 3.5 hours.

The number-average molecular weight of the low condensate of ethylene glycol and terephthalic acid was 600 to 1300 (trimer to pentamer)

The residence time (liquid phase polymerization time) required to attain an intrinsic viscosity (IV) of 058 dl/g of polyethylene terephthalate was 100 minutes.

In the resulting polyethylene terephthalate, the titanium atom content was 15 ppm, the magnesium atom content was 25 ppm, the titanium atom/magnesium atom molar ratio was 0.3, the intrinsic viscosity was 0.82 dl/g, the density was 1.40 g/cm³, and the cyclic trimer content was 0.40% by weight.

In a stainless steel container, 2.5 kg of the polyethylene terephthalate was immersed in 4 kg of a trimethyl phosphate aqueous solution of 00695% by weight, and they were kept at room temperature for 4 hours. Thereafter, the particulate polyethylene terephthalate was separated from the trimethyl phosphate aqueous solution, hydro-extracted and then dried at 160° C. for 5 hours in a scream of nitrogen. The cyclic trimer content in the resulting polyethylene terephthalate was 0.40% by weight (x % by weight). Using the polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The cyclic trimer content in the stepped square plate molded product was 0.48% by weight, a difference in the cyclic trimer content between before and after the molding was 0.08% by weight (y % by weight), and the value of −0.2+0.2 was 0.104. The intrinsic viscosity of the stepped square plate molded product was 0.805 dl/g.

Example 463-4

In a stainless steel container, the polyethylene terephthalate obtained after the solid phase polymerization in Example 463-3 was immersed in isopropanol at 95° C. and kept for 4 hours under heating.

Then, the polyethylene terephthalate was separated from the isopropanol and dried at 160° C. for 5 hours in a stream of nitrogen. The cyclic trimer content in the resulting polyethylene terephthalate was 0.40% by weight (x % by weight). Using the polyethylene terephthalate, a stepped square plate molded product was produced by the aforesaid method. The cyclic trimer content in the stepped square plate molded product was 0.46% by weight, a difference in the cyclic trimer content between before and after the molding was 0.06% by weight (y % by weight), and the value of −0.2+0.2 was 0.12. The intrinsic viscosity of the stepped square plate molded product was 0.810 dl/g.

Example 463-2C

The same particulate polyethylene terephthalate as used in Example 463-2 was molded into a stepped square plate molded product by the aforesaid method, without performing a contact treatment with a trimethyl phosphate aqueous solution. The cyclic trimer content in the stepped square plate molded product was 0.57% by weight (x % by weight), a difference in the cyclic trimer content between before and after the molding was 0.17% by weight (y % by weight), and the value of −0.2+0.2 was 0.086. The intrinsic viscosity of the stepped square plate molded product was 0.811 dl/g.

Example 469-1

To an esterification reactor, 76.81 mol of high-purity terephthalic acid and 86.03 mol of ethylene glycol were fed at 100° C. at atmospheric pressure, and 0.0045 mol of the titanium-containing solid compound prepared in Example 495-1 was further added as a catalyst. Then, the temperature of the reactor was raised to 260° C., and the reaction was conducted for 340 minutes under a pressure of 1.7 kg/cm²-G in a nitrogen atmosphere. Water produced by the reaction was continually distilled off from the system.

Then, the total amount of the solution in the esterification reactor was transferred into a polycondensation reactor beforehand set at 260° C. To he reactor, a solution of 0.0073 mol of tributyl phosphate in 6.44 mol of ethylene glycol was further added at atmospheric pressure, and the temperature of the reactor was raised to 280° C. from 260° C. over a period of 60 minutes, while the pressure was reduced to 2 Torr from atmospheric pressure.

The reaction in the polycondensation reactor was further conducted for 108 minutes, and the reaction product was drawn out of the polycondensation reactor in the form of strands. The strands were immersed in water, cooled and cut into particles by a strand cutter to obtain polyethylene terephthalate. The polyethylene terephthalate has an intrinsic viscosity of 0.65 dl/g and a titanium content, as measured by atomic absorption analysis, of 28 ppm.

The haze of the part C of the stepped square molded product was 17.8%. Then, the polyethylene terephthalate was molded into a blow molded article in the following manner.

A preform having a diameter of 28 mm was produced by an injection molding machine M-100A (manufactured by Meiki Seisakusho) under the conditions of a cylinder preset temperature of 260° C. and a mold temperature of 10° C. In the molding, the injection molding temperature was 276° C. and the molding cycle was 54 seconds.

The preform was then subjected to stretch blow molding by the use of a blow molding machine (model No. LB01, manufactured by CORPOPLAST Co.) under the conditions of a stretch temperature of 110° C. and a blow mold temperature of 30° C., to obtain a 1.5 liter blow molded article.

The appearance of the blow molded article was evaluated in the following manner.

Further, flowability (L/T) of the polyethylene terephthalate was evaluated in the following manner using an injection molding machine of M-70B model manufactured by Meiki Seisakusho. Moreover, an intrinsic viscosity of the resulting L/T specimen was measured. The results are set forth in Table 469-1.

In Examples 469-1 to 469-6 and Comparative Examples 469-1 to 469-4, each property was evaluated in the following manner.

Intrinsic Viscosity (IV)

The intrinsic viscosity of the molded product was determined as follows. Using a mixed solvent of phenol and 1,1,2,2-tetrachloroethane (50/50 by weight), 10 a sample solution having a concentration of 0.5 g/dl was prepared, and the solution viscosity was measured at 25° C. From the solution viscosity, the intrinsic viscosity was calculated. The intrinsic viscosity of the particulate polyethylene terephthalate was determined as follows. 1.2 Grams of the polyethylene terephthalate was dissolved in 15 cc of o-chlorophenol under heating, then cooled, and the solution viscosity was measured at 25° C. From the solution viscosity, the intrinsic viscosity was calculated.

Haze

In a tray dryer, 2 kg of particulate polyethylene terephthalate as a starting material was dried at 140° C. under a pressure of 10 Torr for 1 hours or more, to allow the particulate polyethylene terephthalate to have a water content of not more than 50 ppm.

Then, the dried particulate polyethylene terephthalate was injection molded by a M-70A injection molding machine manufactured by Meiki Seisakusho K.K. under the conditions of a cylinder temperature of 275° C. and a mold cooling water temperature of 15° C., to produce a stepped square plate molded product.

In detail, the stepped square plate molded product was produced by feeding the dried particulate polyethylene terephthalate to an injection molding machine adjusted to have molding conditions of metering of 12 seconds and injection of 60 seconds through a hopper. The residence time of the molter, resin in the molding machine was about 72 seconds. The weight of the resin used per stepped square plate molded product was 75 g. As a specimen for measuring a haze, any one of the eleventh to fifteenth stepped square molded products from the beginning of the injection molding was adopted.

The stepped square plate molded product has a shape shown in FIG. 1, and the thicknesses of the parts A, B and C are about 6.5 mm, about 5 mm and about 4 mm, respectively. In the present invention, the haze of the part C of the stepped square plate molded product was measured using a haze meter (Suga tester) HGM-2DP.

Appearance of Blow Molded Article

A haze value (irregular reflectance of white light) at the almost central portion of a sidewall of the hollow container was measured. Based on the haze value (%), appearance of the blow molded article was evaluated as follows.

- AA: 0≦haze value<5
- BB: 5≦haze value
  Flowability (L/T) Measuring Method

The flowability was measured by the method described in the specification.

Examples 469-2 to 469-5

Polyethylene terephthalate was produced in the same manner as in Example 469-1, except that the polycondensation catalyst and the polymerization conditions were changed as shown in Table 409-1.

Using the polyethylene terephthalate, a blow molded article was produced in the same manner as in Example 469-1, and appearance thereof was evaluated. Further, flowability (L/T) and an intrinsic viscosity of the L/T specimen were measured in the same manner as in Example 469-1. The results are set forth in Table 469-1.

Polyethylene terephthalate (intrinsic viscosity: 0.825 dl/g; type of a catalyst determined by atomic absorption analysis: antimony compound; and the antimony content: 235 ppm) was used.

Using the polyethylene terephthalate, a blow molded article was produced in the same manner as in Example 469-1, and appearance thereof was evaluated. Further, flowability (L/T) and an intrinsic viscosity of the L/T specimen were measured In the same manner as in Example 469-1. The results are set forth in Table 469-1.

Comparative Example 469-2

Polyethylene terephthalate (intrinsic viscosity: 0.843 dl/g; the type of a catalyst determined by atomic absorption analysis: antimony compound; and the antimony content: 232 ppm) was used.

Using the polyethylene terephthalate, a blow molded article was produced in the same manner as in Example 469-1, the appearance thereof was evaluated. Further, flowability (L/T) and an intrinsic viscosity of the L/T specimen were measured in the same manner as in Example 469-1. The result are set forth in Table 469-1.

Comparative Example 469-3

Polyethylene terephthalate (intrinsic viscosity: 0.778 dl/g; the type of a catalyst determined by atomic absorption analysis: germanium compound; and the germanium content: 56 ppm.) was used.

Comparative Example 469-4

Polyethylene terephthalate (intrinsic viscosity: 0.823 dl/g; type of catalyst determined by atomic absorption analysis; germanium compound; and the germanium content: 42 ppm) was used.

Example 469-6