Aromatic polyamide resin moldings, production methods thereof, and magnetic recording medium produced therefrom

Abstract

The present invention provides aromatic polyamide resin moldings comprising at least one surface that is 1.0 nm or more in root-mean-square roughness and is 80 nm or less in 10-point average roughness, both of the roughness being as determined by atomic force microscopy, and that is 9.8 GPa or more in tensile young's modulus at least in one direction. Such aromatic polyamide resin moldings serve effectively as material for film, film for magnetic recording medium in particular, that is highly resistant to scraping and has highly uniform surface protrusions.

Description

TECHNICAL FIELD

The present invention relates to Adis
General Formula (II)
NH—Ar₃—CO
where Ar₁, Ar₂, and Ar₃ may be, for instance: ##STR00001##
and X and Y may be selected from, but not limited to, the group of —O—, —CH₂—, —CO—, —SO₂—, —S—, and C(CH₃)₂—. One or more of the hydrogen atoms on their aromatic ring may be replaced with a halogen atom such as fluorine, chlorine, and bromine (preferably chlorine), an alkyl group such as nitro, methyl, ethyl, and propyl (preferably methyl), or an alkoxy group such as methoxy, ethoxy, propoxy, and isopropoxy. In addition, one or more hydrogen atoms in the amide bond that forms the polymer may be replaced by a substituent. For enhanced characteristics,
2(MJ/m³)^1/2≦|δa−δb|≦20(MJ/m³)^1/2
The solubility parameter used herein is calculated from the method proposed by Fedors (calculation process is shown, for instance, in Properties of Polymers, chapter 7, written by D. W. VanKreveren, 1976, Elsevier). For aromatic polyamides and dissimilar polymers of some special structures, the parameter cannot be calculated by the Fedors' method because the parameter concerning a chemical species contained is not known. In such a case, the parameter of a similar chemical species is used (for instance, the parameter for
more preferably,
2 (MJ/m³)½≦|δa−δb|≦12(MJ/m³)^1/2

To allow the aromatic polyamide to fully show its inherent high heat resistance and good mechanical properties, it is preferred that the dissimilar polymers are also high in heat resistance, and their glass-transition temperature, or thermal deformation temperature as defined in JIS-D648 when the glass-transition temperature is not apparent, should preferably be 150° C. or more, preferably 200° C. or more.

Such dissimilar polymers include polysulfone, polyethersulfone, polysulfide sulfone, polyphenylene sulfide, polyetherimide,

If Ta−Tb is less than 20° C., the temperature difference is not sufficiently large to generate a required convection current to produce sufficient protrusions. The difference should more preferably be 40° C. or more, further more preferably 50° C. or more. The upper limit of Ta−Tb is about 100° C. as long as excessive drying stain is produced. If an endless belt is used as support, a required temperature difference can be produced effectively during the polymer casting by adjusting the heating temperature above and below the endless belt or by cooling the film after the peeling of film. It is further preferred that the solvent is evaporated from the cast film which is then dried at a desolvating rate of 3-20%/min, more preferably 5-15%/min. If the desolvating rate is less than 3%/min,
Equipment: field emission-type scanning electron microscope S-800, manufactured by Hitachi, Ltd.

energy dispersive X-ray analyzer EMAX-3770, manufactured by Horiba, Ltd.

Measuring conditions

Desolvating ratio=(P₁−P₀)/t
(8) Electromagnetic Conversion Properties
a) Initial Output Properties

Vacuum deposition is performed to form a magnetic layer on the surface of the film that is not in contact with the metal belt during the film product ion production process. A specimen 6.35 mm wide and 150 m long is cut off from the film, and set in a cassette. A sine wave is recorded with the optimum recording current, and the reproduction output from the film minus that from the reference tape is determined.

b) Dropout

The above tape cassette is placed on a video player, and signals of 4.4 MHz are recorded. The tape is then reproduced and the dropout at 15 μsec-20dB is measured for 20 minutes with a dropout USA counter manufactured by Okura Industries, Ltd., followed by calculation of the dropout per minute.

(9) Durability

In an environment of 25° C. and 55 %RH, the tape produced in paragraph 4-a 4a is allowed to run 100 times at 1,000 m/min on a 6 mm diameter guide pin with an angle, θ, of π/2 (rad) and tape-feed tension, T1, of 200 g, followed by measurement of the output and evaluation according to the following criteria.

• • ∘:difference from initial output less than 1 dB
  • Δ: difference from initial output 1 dB or more and less than 3 dB
  • X: difference from initial output more than 3 dB
    Examples are given below, not by way of limitations, to further illustrate the present invention.

EXAMPLE 1

In N-methyl-2-pyrrolidone (hereinafter denoted by NMP), 2-chloroparaphenylendiamin 2-chloroparaphenylendiamine, as an aromatic diamine component, and 4,4′-diamino diphenyl ether were dissolved up to a content equivalent to 80 mol % and 20 mol %, respectively, and 2-chloroterephthaloyl chloride was then added up to a content equivalent to 100 mol %, followed by stirring for 2 hours to complete the polymerization. The solution was neutralized with lithium hydroxide to provide an aromatic polyamide solution with a polymer content of 10wt % and viscosity of 3,000 poise (hereinafter referred to as solution A).

A 10 wt % amount of polyethersulfone (PES-E2010, hereinafter referred to as PES, manufactured by Mitsui Toatsu Chemicals, Inc.) was dissolved in NMP, and blended with solution A to provide a mixed solution in which PES accounted for 3 wt % of the total amount of aromatic polyamide and PES, followed by adequate mixing at 50° C. for 3 hours.

The mixed solution thus obtained was filtered through filters with filtering accuracy of 5,000 nm and 1,000 nm, and, while being kept at a temperature of 60° C., cast onto an endless belt that had surface defects of 30 μm or more in diameter at a rate of 0.005/mm². At the time of casting, the temperature of the support, Tb, and the temperature of hot air, Ta, were 140° C. and 170° C., respectively. The desolvating rate was 10.2%/min. After being peeled off from the belt, the film was then immersed in a water bath at 140° C. for 5 minutes, dried at 160° C. for 30 seconds, and heat-treated in 280° C. hot air of a flow speed of 5 m/sec to produce aromatic polyamide film of 4.3 μm in thickness. During the film production process, the film was stretched up to the ratio, 1.2 and 1.3 in the machine direction and the transverse direction, respectively.

The film had a Rq of 2.9 nm, Rz of 23.2 nm, Ra of 1.9 nm, Rt of 28.0 nm, non-particle index of 100%, HD of 0.07, and number of not less than 5 nm protrusions of 14,000,000/mm². Its tensile Young's modulus and elongation in the machine direction and the transverse direction, were 13.1 GPa and 13.2 GPa, respectively, and 45% and 46 %, respectively. Its resistance to scraping, film dust/particle removal, and resistance to scratch were evaluated as ⊚, ⊚, and ∘. respectively. Production conditions and film properties are shown in Tables 1 to 5.

EXAMPLE 2

Polyetherimide (“Ultem-1000”, hereinafter PEI, manufactured by Japan GE Plastics) is dissolved in NMP up to 10 wt %, and blended with solution A prepared in Example 1 to provide a mixed solution in which PEI accounted for 1.5 wt % of the total. amount of aromatic polyamide and PEI, followed by adequate mixing at 70° C 70° C. for 3 hours.

The mixed solution thus obtained was filtered through filters with filtering accuracy of 5,000 nm and 1,000 nm, and, while being kept at a temperature of 120° C., cast onto an endless belt that had surface defects of 30μm or more in diameter at a rate of 0.005/mm². At the time of casting, the temperature of the support, Tb, and the temperature of hot air, Ta, were 140° C. and 170° C., respectively. The desolvating rate was 10.2%/min. After being peeled off from the belt, the film was then immersed in a water bath at 40° C. for 5 minutes, dried at 160° C. for 30 seconds, and heat-treated in 280° C. hot air of a flow speed of 5 m/sec to produce aromatic polyamide film of 4.3 μm in thickness. During the film production process, the film was stretched up to the ratio, 1.2 and 1.3 in the machine direction and the transverse direction, respectively.

Production conditions and film properties are shown in Tables 1 to 5.

EXAMPLE 3

Polycarbonate (“Taflon”, hereinafter PC, manufactured by Idemitsu Petrochemical Co., Ltd.) is dissolved in NMP up to 10 wt %, and blended with solution. A prepared in Example 1 to provide a mixed solution in which PC accounted for 2.0 wt % of the total amount of aromatic polyamide and PC, followed by adequate mixing at 50° C. for 3 hours.

The mixed solution thus obtained was filtered through filters with filtering accuracy of 5,000 nm and 1,000 nm, and, while being kept at a temperature of 50° C., cast onto an endless belt that had 2 surface defects of 30 μm or more in diameter at a rate of 0.005/mm². At the time of casting, the temperature of the support, Tb, and the temperature of hot air, Ta, were 110° C. and 140° C., respectively. The desolvating rate was 7.2%/min. After being peeled off from the belt, the film was the immersed in a water bath at 40° C. for 5 minutes, dried at 160° C. for 30 seconds, and heat-treated in 280° C. hot air of a flow speed of 5 m/sec to produce aromatic polyamide film of 4.3 μm in thickness. During the film production process, the film was stretched up to the ratio, 1.2 and 1.3 in the machine direction and the transverse direction, respectively.

Production conditions and film properties are shown in Tables 1 to 5.

EXAMPLE 4

Polycarbonate (“U-100”, hereinafter PAR, manufactured by Untika Ltd.) is dissolved in NUP NMP up to 10 wt %, and blended with solution A prepared in Example 1 to provide a mixed solution in which PAR accounted for 8.0 wt % of the total amount of aromatic polyamide and PAR, followed by adequate mixing at 50° C. for 3 hours.

The mixed solution thus obtained was filtered through filters with filtering accuracy of 5,000 nm and 1,000 nm, and, while being kept at a temperature of 50° C., cast onto an endless belt that had 2 surface defects of 30 μm or more in diameter at a rate of 0.005/mm 0.005/mm². At the time of casting, the temperature of the support, Tb, and the temperature of hot air, Ta, were 140° C. and 170° C., respectively. The desolvating rate was 10.3%/min. After being off from the belt, the film was then immersed in a water bath at 40° C. for 5 minutes, dried at 160° C. for 30 seconds, and heat-treated in 280° C. hot air of a flow speed of 5 m/sec to produce aromatic polyamide film of 4.3 μm in thickness. During the film production process, the film was stretched up to the ratio, 1.2 and 1.3 in the machine direction and the transverse direction, respectively.

Production conditions and film properties are shown in Tables 1 to 5.

EXAMPLE 5

Paraphenylendiamine and terephthaloyl chloride were subjected to a known polymerization method, washed, and dried to produce polyparaphenylene terephthalamide (hereinafter referred as PPTA) with a n inh η inh of 5.5 (intrinsic viscosity measured in concentrated sulfuric acid solution with a polymer content of 0.5 g/10 m 0.5 g/10 ml), which was dissolved in 99.5% concentrated sulfuric acid up to a polymer content of 12 wt %.

Elsewhere, 100 mol % of diamino diphenyl either and 93 mol % of pyromellitic anhydride were subjected to polymerization for 2 hours while being kept at not more than 50° C. After the completion of polymerization, large amounts of water was used to ensure reprecipitation, followed by repeated washing in water and acetone and vacuum drying at 50° C. to provide polyamic acid which is a precursor of polyamide (hereinafter referred to as PI).

Powder of this polyamic acid was added to the PPTA solution prepared earlier so that the weight fraction of Pi PI becomes 4%, followed by stirring at 50° C. for 3 hours to ensure complete dissolution.

The stock solution for film production thus obtained, while being kept at 60° C., was cast onto an tantalum endless belt with a Tb of 60° C., and moistened air of temperature of 90° C. and relative humidity of 70% was blown against it (Ta=90° C.). The cast polymer film, together with the belt, was put in a 40% sulfuric acid solution of 0° C. to ensure coagulation. After being peeled off from the belt, the film was washed in a water bath of 10° C., neutralized in a 1% sodium hydroxide bath, washed in a hot water bath of 50° C., set to a tenter, dried at 160° C. for 30 seconds, and heat-treated in hot air of temperature of 350° C. and flow rate of 5 m/sec to produce aromatic polyamide film of 4.3 μm in thickness. During the film production process, the film was stretched up to the ratio, 1.1 and 1.25 in the machine direction and the transverse direction, respectively.

Production conditions and film properties are shown in Tables 1 to 5.

EXAMPLE 6

Colloidal silica with a primary particle diameter of 20 nm was dispersed adequately in NMP and added to aromatic polyamide up to 0.1 wt %, followed by polymerization by the same procedure as in Example 1. The resultant solution was blended with a PES solution as in Example 1 to produce a stock solution for film production, from which film was produced by the same procedure as in Example 1. Production conditions and film properties are shown in Tables 1 to 5.

Comparative Example 1

Only solution A prepared in Example 1 was subjected to the same film production process as in Example 1 to produce film.

Production conditions and film properties are shown in Tables 1 to 5.

Comparative Example 2

Except that blending with solution A was performed up to a PEI content of 12 wt %, the same procedure as in Example 2 was carried out to produce film. Production conditions and film properties are shown in Tables 1 to 5.

Comparative Example 3

Except that blending with solution A was performed up to a PES content of 0.3 wt % and that drying was performed at both Ta and Tb of 170° C., the same procedure as in Example 1 was carried out to procedure film.

Production conditions and film properties are shown in Tables 1 to 5.

Comparative Example 4

Colloidal silica with a primary particle diameter of 30 nm was dispersed in NMP using ultrasonic wave, and added to solution A prepared in Example 1 up to 2 wt % relative to aromatic polyamide, followed by stirring at 60° C. for 3 hours. The resultant solution, without adding a dissimilar polymer, was used as stock solution to produce film by the same procedure as in Example 1.

Product ion Production conditions and film properties are shown in Tables 1 to 5.

	TABLE 1
						Polymer
	Dissimilar					temp. at	Hot	Support
	polymer or	Content	δa	δb	δa-δb|	discharge	air temp.	temp.
	particle	(wt %)	(MJ/m3)1/2	(MJ/m3)1/2	(MJ/m3)1/2	casting (° C.)	Ta (° C.)	tb Tb (° C.)
Example 1	PES	3	56.6	53.6	3.0	60	170	140
Example 2	PEI	1.5	56.6	55.7	0.9	120	170	140
Example 3	PC	2	56.6	49.2	7.4	50	140	110
Example 4	PAR	8	56.6	51.1	5.5	50	140	110
Example 5	PI	4	59.9	58.9	1.0	60	90	60
	(polyamic acid)						(70 RH %)
Example 6	PES	3	56.6	53.6	3.0	60	170	140
	colloidal silica	0.1
Comparative	none	none	56.6	—	—	60	170	140
example 1
Comparative	PEI	12	56.6	55.7	0.9	120	170	140
example 2
Comparative	PFS PES	0.3	56.6	53.6	3.0	60	170	170
example 3
Comparative	colloidal silica	2	56.6	—	—	60	170	140
example 4

	TABLE 2
					Stretching ratio	Stretching ratio
	Desolvating rate	Drying temp.	Heat treatment	Heat treatment	in machine	in transverse
	(%/min)	(° C.)	temp. (° C.)	air speed (m/sec)	direction	direction
Example 1	10.2	160	280	5	1.2	1.3
Example 2	10.2	160	280	5	1.2	1.3
Example 3	7.2	160	280	5	1.2	1.3
Example 4	10.3	160	280	5	1.2	1.3
Example 5	3.2	160	350	5	1.1	1.25
Example 6	9.9	160	280	5	1.2	1.3
Comparative	10.1	160	280	5	1.2	1.3
example 1
Comparative	10.3	160	280	5	1.2	1.3
example 2
Comparative	20.5	160	280	5	1.2	1.3
example 3
Comparative	10.5	160	280	5	1.2	1.3
example 4
	45 5

	TABLE 3
								Average
						Non-particle		protrusion
	Rq (nm)	Rz (nm)	Ra (nm)	Rt (nm)	Rt/Ra	index (%)	HD (nm)	diameter (nm)
Example 1	2.9	23.2	1.9	28.0	14.7	100	0.07	190
Example 2	4.8	57.2	3.7	66.2	17.9	100	0.13	420
Example 3	1.5	12.0	0.9	13.5	15.0	100	0.06	60
Example 4	2.8	30.2	2.2	44.0	20.0	100	0.15	350
Example 5	3.1	28.4	2.3	32.4	14.1	100	0.10	210
Example 6	3.7	33.5	2.3	40.7	17.7	99	0.12	180
Comparative	0.9	11.3	0.8	17.5	21.8	100	0.02	20
example 1
Comparative	12.5	120	10.8	250	23.1	100	0.16	560
example 2
Comparative	0.9	10.5	0.7	13.5	19.3	100	0.06	30
example 3
Comparative	8.4	88.0	6.7	105	15.7	3	0.66	40
example 4

	TABLE 4
				Young's
	No. of protrusions		Particle protrusions	modulus	Elongation
	(×10,000/mm2)	Cross-section (%)	Number	Height	(GPa)	(%)
	5 nm≦	10 nm≦	15 nm≦	50 nm≦	5 nm	10 nm	15 nm	(×10,000/mm2)	(nm)	MD/TD	MD/TD
Example 1	1400	250	70	0	7.8	2.3	0.03	—	—	13.1/13.2	45/46
Example 2	580	80	40	20	15.5	6.2	1.3	—	—	13.5/13.3	36/35
Example 3	250	4	0	0	0.9	0	0	—	—	12.0/11.7	52/36
Example 4	130	100	60	40	4.3	1.6	0.9	—	—	11.0/10.8	46/39
Example 5	720	280	160	0	7.3	1.8	0.04	—	—	14.2/13.5	28/29
Example 6	1450	300	100	2	8.0	2.4	0.3	10.0	42	13.1/13.1	42/44
Comparative	18	0	0	0	0.02	0	0	—	—	13.2/13.1	46/48
example 1
Comparative	275	120	100	80	22.0	11.3	6	—	—	9.5/9.6	27/25
example 2
Comparative	65	8	0	0	0.4	0	0	—	—	13.3/13.2	46/45
example 3
Comparative	780	420	210	80	2.2	1.0	0.7	750	38	13.0/13.0	45/40
example 4
MD: machine direction
TD: transverse direction

	TABLE 5
					Dropout
	Resistance to	Film dust/	Resistance to		number/min)
	scraping	particle removal	scratch	Output (dB)	(number/min)	Durability
Example 1	⊚	⊚	◯	2.3	0.3	◯
Example 2	◯	◯	◯	−0.3	1.1	Δ
Example 3	⊚	◯	Δ	2.0	1.5	Δ
Example 4	◯	◯	Δ	1.9	0.8	Δ
Example 5	⊚	⊚	◯	2.0	0.5	◯
Example 6	⊚	⊚	◯	1.5	1.1	◯
Comparative	⊚	X	X	2.7	0.3	X
example 1
Comparative	X	X	Δ	−2.3	3.2	Δ
example 2
Comparative	Δ	X	X	1.4	0.3	X
example 3
Comparative	X	X	Δ	−1.3	3.7	X
example 4

EXAMPLE 7

In dehydrated NMP, CPA and DPE were dissolved up to a content equivalent to 90 mol % and 10 mol %, respectively, and CTPC was then added up to a content equivalent to 98.5 mol % followed by stirring for 2 hours to complete the polymerization. The solution was neutralized with lithium carbonate to provide an aromatic polyamide solution with a polymer content of 10.5 wt % (hereinafter referred to as solution A).

Elsewhere, a 15 wt % amount of dried polyethersulfone PES-E2010 (hereinafter referred to as PES), manufactured by Mitsui Toatsu Chemicals, Inc., was dissolved in NMP, ancl and this PES solution was added to solution A to provide a mixed solution in which PES accounted for 3 wt % relative to aromatic polyamide. This solution is hereinafter referred to as solution B.

Solution B thus obtained was filtered through a 5 μm-cut filter, cast onto a stainless steel endless belt with a mirror finished surface, and heated at 150° C. for 5 minutes to evaporate the solvent until the film acquired self-sustain self-sustaining property. The film was then peeled off from the belt continuously. At this point, the polymer content in the get film was 39.8 wt %, and the desolvating rate was 5.9%/min. The film was then immersed in a water bath for 2 minutes for aqueous extraction of the remaining solvent and inorganic salts that had resulted from neutralization. During this process, the film was stretched up to the ratio of 1.2 in the machine direction. Subsequently, while being dried and heat-treated in 280° C. hot air of a flow speed of 3 m/sec, the film was stretched up to the ratio of 1.3 in the transverse direction. The film was further heat-treated at 250° C. for 1.5 minutes, followed by slow cooling at 20° C./sec to produce aromatic polyamide film of 4.2 μm in thickness.

EXAMPLE 8

Spherical silica with an average particle diameter of 20 nm was added to polymer solution B prepared in Example 1 7 up to 0.2 wt % relative to polyamide, followed by film production by the same procedure as in Example 7.

Production conditions and film properties are shown in Tables 6 to 10.

EXAMPLE 9

PES was added to polymer solution A prepared in Example 7 up to 4 wt % relative to aromatic polyamide by the same procedure as in Example 6, followed by film production by the same procedure as in Example 7.

Production conditions and film properties are shown in Tables 6 to 10.

EXAMPLE 10

Using polymer solution B prepared in Example 7, film was produced by the same procedure as in Example 7 except that drying was performed at 220° C. for 1.5 minutes.

Production conditions and film properties are shown in Tables 6 to 10.

Comparative Example 5

PES was added to polymer solution A prepared in Example 6 up to 0.05 wt % relative to aromatic polyamide by the same procedure as in Example 7, followed by film production by the same procedure as in Example 7.

Production conditions and film properties are shown in Tables 6 to 10.

Comparative Example 6

PES was added to polymer solution A prepared in Example 7 up to 20 wt % relative to aromatic polyamide by the same procedure as in Example 7, followed by film production by the same procedure as in Example 7 except that drying was performed at 150° C. for 6 minutes.

Production conditions and film properties are shown in Tables 6 to 10.

	TABLE 6
	Dissimilar polymer		Hot air temp.	Support temp.	Desolvating rate
	or particle	Content (wt %)	Ta (° C.)	Tb (° C.)	(%/min)
Example 7	PES	3	150	95	5.9
Example 8	PES	3	150	95	6.1
	colloidal silica	0.2
Example 9	PES	4	150	95	5.8
Example 10	PES	3	220	95	17.0
Comparative	PES	0.05	150	95	5.7
example 5
Comparative	PES	20	150	95	5.5
example 6

	TABLE 7
				Stretching ratio	Stretching ratio
	Heat treatment	Heat treatment	Re-heat treatment	in machine	in transverse
	temp. (° C.)	air speed (m/sec)	temp. (° C.)	direction	direction
Example 7	280	3	250	1.2	1.3
Example 8	280	3	250	1.2	1.3
Example 9	280	3	250	1.2	1.3
Example 10	280	3	250	1.2	1.3
Comparative	280	3	250	1.2	1.3
example 5
Comparative	280	3	250	1.2	1.3
example 6

	TABLE 8
								Average
						Non-particle		protrusion
	Rq (nm)	Rz (nm)	Ra (nm)	Rt (nm)	Rt/Ra	index (%)	HD (nm)	diameter (nm)
Example 7	2.5	21.3	1.8	26.3	14.6	100	0.06	220
Example 8	2.7	27.5	1.9	30.4	16.0	99	0.06	210
Example 9	3.3	29.2	2.5	32.3	12.9	100	0.05	280
Example 10	4.1	33.6	3.2	44.0	13.8	100	0.11	330
Comparative	0.9	11.0	0.8	16.3	20.4	100	0.03	30
example 5
Comparative	8.4	81.5	8.1	97.0	12.0	100	0.10	380
example 6

	TABLE 9
	No. of protrusions		Particle protrusions	Young's
	(×10,000/mm2)	Cross-section (%)	Number	Height	modulus
	5 nm≦	10 nm≦	15 nm≦	50 nm≦	5 nm	10 nm	15 nm	(×10,000/mm2)	(nm)	(GPa)
Example 7	860	280	44	0	8.2	2.2	0.3	—	—	13.2
Example 8	1200	400	62	1	7.9	2.5	0.4	17	65	13.1
Example 9	520	400	220	0	13.5	7.6	2.7	—	—	13.1
Example 10	430	380	270	15	5.2	3.2	2.3	—	—	12.7
Comparative	54	4	0	0	0.5	0	0	—	—	13.2
example 5
Comparative	940	690	430	30	26.2	13.4	5.3	—	—	10.8
example 6

	TABLE 10
	Resistance	Film dust/	Resistance		Dropout
	to	particle	to	Output	(number/
	scraping	removal	scratch	(dB)	min)	Durability
Example 7	⊚	⊚	◯	2.2	0.3	◯
Example 8	⊚	⊚	◯	1.7	0.6	◯
Example 9	◯	◯	Δ	1.9	0.3	◯
Example 10	◯	◯	Δ	−0.7	1.3	Δ
Comparative	Δ	X	X	0.8	0.4	X
example 5
Comparative	X	X	X	−2.4	4.2	X
example 6

EXAMPLE 11

Colloidal silica with a primary particle diameter of 30 80 nm was dispersed adequately in NMP and added to aromatic polyamide up to 0.02 wt %, followed by polymerization by the same procedure as in Example 1. The resultant solution was blended with a PES solution as in Example 1 to produce a mixed solution, which was filtered through filters with filtering accuracy of 5,000 nm and 1,000 nm, and, while being kept at 60° C., cast onto an endless belt that had surface defects of 30 cm μm or more in diameter at a rate of 0.005/mm². At the time of casting, the temperature of the support, Tb, and the temperature of hot air, Ta, were 120° C. and 150° C., respectively. The desolvating rate was 8.5%/min. After being peeled off from the belt, the film was then immersed in a water bath at 40° C. for 5 minutes, dried at 160° C. for 30 seconds, and heat-treated in 250° C. hot air of a flow speed of 3 m/sec to produce aromatic polyamide film of 4.3 μm in thickness. During the film production process, the film was stretched up to the ratio, 1.2 and 1.3 in the machine direction and the transverse direction, respectively.

Production conditions and film properties are shown in Tables 11 to 15.

EXAMPLE 12

Polymerization was performed to produce a mixed solution by the same procedure as in Example 11 except that colloidal silica with a primary particle diameter of 50 nm was added up to 0.005 wt % relative to aromatic polyamide and that PES was added up to 6 wt % relative to aromatic polyamide. The mixed solution thus obtained was filtered through filters with filtering accuracy of 5,000 nm and 1,000 nm, and, while being kept at 60° C., cast onto an endless belt that had surface defects of 30 cm μm or more in diameter at a rate of 0.005/mm². At the time of casting, the temperature of the support, Tb, and the temperature of hot air, Ta, were 120° C. and 150° C. 170° C., respectively. The desolvating rate was 8.5%/min 7.2%/min. After being peeled off from the belt, the film was then immersed in a water bath at 40° C. for 5 minutes, dried at 160° C. for 30 seconds, and heat-treated in 250° C. hot air of a flow speed of 6 m/sec to produce aromatic polyamide film of 4.3 μm in thickness. During the film production process, the film was stretched up to the ratio, 1.2 and 1.3 in the machine direction and the transverse direction, respectively.

Production conditions and film properties are shown in Tables a 11 to 15.

Comparative example 7

Using the mixed solution prepared in Example 1, aromatic polyamide film of 4.3 μm in thickness was produced by the same procedure as in Example 1 except that heat treatment was performed at a flow speed of 35 m/sec. The surface of this film was so rough with numerous crater-like irregularities that is was impossible to count the number of protrusions.

Production conditions and film properties are shown in Tables 10 11 to 15.

	TABLE 11
						Content (wt
	Dissimilar		δa			%) Polymer	Hot	Support
	polymer or	Content	(MJ/mm3)1/2	δb	|δa-δb|	temp. at	air temp.	temp.
	particle	(wt %)	(MJ/m3)1/2	(MJ/m3)1/2	(MJ/m3)1/2	casting (° C.)	Ta (° C.)	Tb (° C.)
Example 1	PES	3	56.6	53.6	3.0	60	150	120
11
	colloidal silica	0.02
Example 12	PES	6	56.6	53.6	3.0	60	170	120
	colloidal silica	0.005
Comparative	PES	3	56.6	53.6	3.0	60	170	140
example 7

	TABLE 12
					Stretching	Stretching
				Heat treatment	ratio in	ratio in
	Desolvating	Drying temp.	Heat treatment	air speed	machine	transverse
	rate (%/min)	(° C.)	temp. (° C.)	(m/sec)	direction	direction
Example 11	8.5	220	250	3	1.1	1.4
Example 12	7.2	220	250	6	1.1	1.4
Comparative	11.5	220	280	35	1.2	1.3
example 7

	TABLE 13
								Average
						Non-particle		protrusion
	Rq (nm)	Rz (nm)	Ra (nm)	Rt (nm)	Rt/Ra	index (%)	HD (nm)	diameter (nm)
Example 11	1.7	18.5	1.2	17.8	14.8	99	0.03	70
Example 12	2.7	24.2	1.8	30.4	16.9	99	0.10	140
Comparative	1.2	12.1	1.0	12.5	12.5	100	—	—
example 7
*Comparative example 7: Heavy roughness due to crater-like dents was seen all over the surface.

	TABLE 14
				Young's
	No. of protrusions		Particle protrusions	modulus	Elongation
	(×10,000/mm2)	Cross-section (%)	Number	Height	(GPa)	(%)
	5 nm≦	10 nm≦	15 nm≦	50 nm≦	5 nm	10 nm	15 nm	(×10,000/mm2)	(nm)	MD/TD	MD/TD
Example 11	800	170	12	0	2.4	0.3	0.01	2.2	38	11.3/18.2	50/38
Example 12	690	280	20	0	6.5	1.8	0.02	0.7	31	11.6/17.3	55/31
Comparative	—	—	—	—	—	—	—	—	—	12.7/12.8	48/50
example 7
MD: machine direction
TD: transverse direction

	TABLE 15
	Resistance	Film dust/	Resistance		Dropout
	to	particle	to	Output	(number/
	scraping	removal	scratch	(dB)	min)	Durability
Example 11	⊚	⊚	◯	3.1	0.1	◯
Example 12	⊚	⊚	◯	2.9	0.3	◯
Comparative	X	Δ	X	−0.8	2.5	X
example 1

INDUSTRIAL APPLICABILITY

The invention provides aromatic polyamide resin moldings whose surface have protrusions that are virtually uniform, fine, and so high in affinity with aromatic polyamide that they are hard to be destroyed resist destruction.

Further, the invention provides aromatic polyamide film that, when used as base film for a magnetic recording medium, are excel lent excellent in electromagnetic conversion properties and durability.

Claims

1. aromatic polyamide resin molding comprising at least one surface that has an R_q root-mean-square roughness of 1.0 nm or more and a 10-point average roughness of 80 nm or less, both of said roughness being as determined by atomic force microscopy, and said molding having a tensile young's modulus of at least 9.8 Gpa or more in at least one direction,

in which said aromatic polyamide layer that comprises said surface consist essentially of an aromatic polyamide plus a dissimilar polymer that is not an aromatic polyamide, and wherein said dissimilar polymer comprises 0.1 wt % to 10 wt %,

where H/D is the value given by dividing the average height of the protrusions on the surface by the average diameter of the protrusions and wherein H/D is in the range of 1/40 to ½, and

wherein the average diameter of the protrusions on the surface is 30 nm to 300 nm.

2. aromatic polyamide resin molding as defined in claim 1, wherein the height of highest non-particle protrusion on the surface of said molding is 20 times or less the average roughness of said surface.

3. aromatic polyamide resin molding as defined in claim 1, which number of protrusions that are 5 nm or more in height that are formed on said surface is 2×10⁵/mm² or more.

4. aromatic polyamide resin molding as defined in claim 3, which the number of protrusions that are 50 nm or more in height is 2×10⁵/mm² or less, and cross section of said protrusions taken in a horizontal plane at a height of 5 nm above said surface comprises 1-20% of the total area of said surface.

5. aromatic polyamide resin molding defined in claim 1, in which number of particle protrusions on said surface is 0.1×10⁴/mm² to 20×10^4/mm² 20×10⁴/mm².

6. aromatic polyamide resin molding defined in claim 5, in which average height of said particle protrusions on the surface of said molding is 10 nm to 75 nm.

7. aromatic polyamide resin molding as defined in claim 6, in which said particle protrusions comprise an inorganic substance.

8. aromatic polyamide resin molding as defined in claim 1, including said dissimilar polymer that is not an aromatic polyamide, and in which the solubility parameter of said aromatic polyamide, 6a, and the solubility parameter of said dissimilar polymer, 6b, satisfy the following formulae:

50(MJ/m³)^1/2≦δa≦70(MJ/m³)^1/2

|δa−δb|≦(MJ/m³)^1/2 |δa−δb|≦20(MJ/m³)^1/2.

9. aromatic polyamide resin molding as defined in claim 1, in which said aromatic polyamide layer that comprises said surface consists essentially of an aromatic polyamide plus a dissimilar polymer that is not an aromatic polyamide. and wherein said dissimilar polymer comprises 0.1 wt % to 10 wt % of the total of the aromatic and the dissimilar polymer, in which said dissimilar polymer is selected from the group consisting of at least one of the following polymers: polysulfone, polyetherimide, polyphenylene oxide, polyketone, polycarbonate, polyester, and polyimide.

10. aromatic polyamide resin molding as defined in claim 9, in which said dissimilar polymer is polysulfone.

11. aromatic polyamide resin molding as defined in claim 1, further comprising a plurality of particles in an amount of 0.0001 wt % to 1.0 wt %.

12. aromatic polyamide resin molding as defined in claim 1, in which said moldings are in the form of a film.

13. Method for producing a magnetic recording medium as defined in claim 12, in which an aprotic organic polar solution of an aromatic polyamide and a dissimilar polymer is cast onto the form of support, dried at a desolvating rate of 3-15 %/min, and immersed in a water bath, followed by drying and/or heat treatment in a temperature range whose maximum is not less than the glass transition temperature of said dissimilar polymer and not more than said glass transition temperature plus 100° C., with the flow speed of air at said film surface being 1 m/sec to 30 m/sec.

14. Magnetic recording medium that is produced by forming a magnetic layer over at least one surface of said aromatic polyamide resin molding as defined in claim 1.

15. Magnetic recording medium as defined in claim 14, in which said magnetic layer is a thin metal magnetic layer.

16. Magnetic recording medium as defined in claim 14, in the form of a magnetic tape of 2, 3-13 mm in width, 6.5 μm or less in support thickness, 100 m/roll or more in length, and 8 KB/mm² or more in recording density.

17. An aromatic polyamide resin molding comprising at least one surface that has a root-mean-square roughness of 1.0 nm or more and a 10-point roughness of 80 nm or less, both of said roughness being as determined by atomic force microscopy, and said molding having a tensile young's modulus of at least 9.8 Gpa or more in at least one direction wherein said molding further has a non-particle index of 80% or more for protrusions 5 nm or more in height on its surface, and wherein said molding has a value of 1/40 to ½ obtained by dividing the average height of the protrusions on the molding surface by the average diameter of the protrusions.

18. An aromatic polyamide resin molding comprising at least one surface that has an R_q root-mean-square roughness of 1.0 nm or more and a 10-point average roughness of 80 nm or less, both of said roughness being as determined by atomic force microscopy, and said molding having a tensile young's modulus of at least 9.8 GPa or more in at least one direction wherein said molding further has a non-particle index of 80% or more for protusions protrusions 5 nm or more in height, on its surface,

and wherein the average diameter of the protrusions on said surface is 30 nm to 300 nm, and wherein the height of the highest non-particle protusion protrusion on the surface of said molding is 20 times or less of the average roughness of said surface, and wherein the number of protrusions that are 5 nm or more in height that are formed on said surface is 2×10⁵/mm² or more, and the cross sections of said protrusions, taken in a horizontal plane at a height of 5 nm above said surface comprises 1 to 20% of the total area of said surface, and wherein the average height of said particle protrusions on the surface of said moldings is 10 nm to 75 nm, said protrusions having an H/D ratio in the range of 1/40 to ½ herein H represents the average height and D represents the average diameter of said protrusions, and wherein said aromatic polyamide layer that comprises said surface consists essentially of an aromatic polyamide plus a dissimilar polymer that is not an aromatic polyamide, and wherein said dissimilar polymer comprises 0.1 wt % to 10 wt % of the total of the aromatic and the dissimilar polymers.

19. An aromatic polyamide resin molding comprising at least one surface that has an rq root-mean-square roughness of 1.0 nm or more and a 10-point average roughness of 80 nm or less, both of said roughnesses being as determined by atomic force microscopy and said molding having a tensile young's modulus of at least 9.8 Gpa or more in at least on direction,

in which said aromatic polyamide layer that comprises said surface contains an aromatic polyamide plus a dissimilar polymer that is not an aromatic polyamide,

where H/D is the value given by dividing the average height of the protrusions on the surface by the average diameter of the protrusions and wherein H/D in the range of 1/40 to ½,

wherein the average diameter of the protrusions on the surface is 30 nm to 300 nm.

20. aromatic polyamide resin molding as defined in claim 1 or in claim 19, wherein said dissimilar polymer is an aromatic polysulfon polymer which comprises one or more repeating units represented by a formula selected from the following group: ##STR00004##