A process for chlorinating solid, finely-divided ethylene polymers is disclosed, wherein the resulting chloropolyethylene has a statistical or hybridical distribution of chlorine in the polymer. The polymer is mixed with 10 - 100% by weight of water, based on the weight of the ethylene polymer, and the polymer is chlorinated with chlorine at a temperature which is above the crystalline melting point of the ethylene polymer during at least 70% a portion of the chorination period. The chlorination pressure is such that the boiling point of water at that pressure is at least equal to the chlorination temperature. The amount of water in the ethylene polymer is maintained at a level of at least 10% by weight based on starting ethylene polymer until the chlorination has proceeded at least to the point where the chlorine content of the polymer is 15% by weight.
The resulting chloropolyethylenes are useful in applications wherein previous chloropolyethylenes have been used, such as for mixing with synthetic polymers to improve the properties thereof.
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1. Process for chlorinating a solid, finely divided ethylene polymer to produce statistical or hybridical chloropolyethylene, said process comprising
a. mixing said polymer with 10 to 100% by weight of water, based on the weight of ethylene polymer, and b. chlorinating the polymer with gaseous chlorine at a temperature which is below the ethylene polymer decomposition temperature and above the crystalline melting point of the ethylene polymer during at least about 70% a part of the chlorination period and at a pressure such that the boiling point of water at said pressure is at least equal to the said chlorination temperature while maintaining the amount of water in the ethylene polymer at a level of at least 10% by weight, based on the weight of starting ethylene polymer, until the chlorination has proceeded to a polymer chlorine content of at least 15% by weight and maintaining the water substantially uniformly distributed in the polymer.
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The present invention relates to a process for chlorinating ethylene polymers. By the term ethylene polymers', the present application refers to both homopolymers of ethylene and copolymers containing at least 50 mol percent of ethylene units, and at least one other ethylinically unsaturated comonomer of 3 - 8 carbon atoms, such as, for instance, propylene, butylene, pentene-1, hexene-1, 4-methylpentene-1, heptene-1 and octene-1.
The halogenation of polyolefins, and especially the chlorination of polyethylene, has been known for a considerable period of time, especially for low-density polyethylenes. Note, for instance, U.S. Pat. No. 2,183,556, indicating that this process was known in 1939.
Chlorinated polyethylene has been commercially available since the eary '40s. However, the initial product was expensive and involved difficult methods of preparation, with the resulting polymers exhibiting physical properties which were not as high as desired.
Shortly after the low-pressure polyethylene processes were developed, there was a revival of interest in chlorinated polyethylene, especially the chlorinated polyethylene prepared from so-called high-density polyethylene. Since then, development has continued in the field of chlorination methods for polyethylene, both of the high density and low density types. The methods previously utilized can be catagorized as of three types, the chlorination of polyethylene in solution, in suspension or in bulk.
The chlorination of polyethylene by the solution method is disclosed in, for instance, U.S. Pat. Nos. 2,398,803, 2,748,105, 2,920,064 and 3,060,164. U.S. Pat. No. 2,592,763 discloses the chlorination of polyethylene in an aqueous suspension. The chlorination of polyethylene in a fluidized bed is disclosed in U.S. Pat. No. 2,890,283, and the chlorination of free-flowing polyethylene is disclosed in British Pat. No. 834,905. These two latter processes involve the absence of a liquid dispersing agent or solvent.
The chlorinated polyethylenes which are obtained by the various prior art chlorination methods differ in properties, even if the same starting polyethylene is utilized, and even if the chlorination is effected to the same polymer chlorine content. This difference in properties appears to depend upon whether or not statistical distribution of the chlorine occurs in the chlorinated polyethylene, as explained in French Pat. No. 1,316,044 and British Pat. No. 843,209.
Each of the three prior art chlorination mentioned above, that is, suspension chlorination, solution chlorination and bulk chlorination, involves a number of disadvantages. For instance, solution chlorination is expensive. The solubility of polyethylene in the organic solvents which are inert to chlorine is quite low, so that relatively large quantities of solvent are required. As a rule, expensive halogenated hydrocarbons are used as the chlorination solvent. The chlorinated polyethylene must be freed from the solvent, and freeing the polymer from the last traces of solvent is difficult. The separation is generally cumbersome and expensive. An advantage of the solution chlorination process, however, is that the chlorination reaction proceeds statistically.
At temperatures below the crystalline melting point of the polymer, the chlorination of polyethylene in suspension or in bulk proceeds on a non-statistical basis. A type of block polymer, having chlorinated and unchlorinated segments in the molecule, is obtained unless chlorination is continued until high chlorine contents are achieved. Block copolymers of this type are hard and brittle, whereas in general it is desired to obtain soft and flexible chloropolyethylene, generally having a crystallinity of less than 2% -- that is, the chloropolyethylene should be amorphous or substantially amorphous. In some applications, however, chloropolyethylenes having a higher crystallinity, such as a crystallinity of less than 10%, preferably between 5 and 10%, are desired. A two-stage process for obtaining a more statistical chlorination is described in French Pat. No. 1,216,044. In the process of that patent, the second stage is conducted at a rather high temperature, above the crystalline melting point of the polyethylene (the crystalline melting point, as used herein, is the temperature at which the (comparative example) Test 14 has been included for comparative purposes and shows that while the chlorination proceeded at a satisfactory rate, the product was unsatisfactory due to discolorations.
The procedure of Example II was repeated for a series of linear polyethylene chlorinations, with a degree of suspension of 66.7% used for all runs. However, the chlorinations were conducted for different periods of time, and at oil bath temperatures of 100°C and 130°C (chlorination temperatures of 95°C and 125°C, respectively), with the results indicated in Table 5 below.
| Table 5 |
| ______________________________________ |
| chlorination time |
| at a reaction |
| temperature in the |
| test reactor of % b.w. of Cl in |
| No. 95° C |
| 125° C |
| end-product |
| % of crystallinity |
| ______________________________________ |
| 0 min. 0 min. 0 68.0 starting product |
| 15 15 min. -- 17.9 27.3 |
| 16 30 min. -- 22.0 21.4 |
| 17 45 min. -- 26.7 19.0 |
| 18 60 min. -- 31.5 14.0 |
| 19 15 min. 15 min. 30.4 13.6 |
| 20 15 min. 30 min. 37.4 <1 |
| 21 15 min. 45 min. 41.9 <1 |
| 22 15 min. 60 min. 43.3 <1 |
| 23 45 min. 15 min. 35.9 <1 |
| 24 45 min. 30 min. 39.8 <1 |
| 25 45 min. 45 min. 40.5 <1 |
| 26 45 min. 60 min. 42.5 <1 |
| 27 60 min. 60 min. 43.7 <1 |
| 28 90 min. 30 min. 40.5 <1 |
| ______________________________________ |
A series of polyethylene chlorinations were conducted in a manner analogous to that of Example V. In this case, however, different polyethylenes were used as the starting polymer, with 0.125 g of α,α' -axo-di-isobutronitrile, 7.5 g of NaCl, and 12.5 g of deionized water (degree of suspension of 66.7) added to 25 g of the ethylene polymer. In all cases, the ethylene polymer particle size was <500 μ. The chlorination results are summarized in Table 6 below.
| Table 6 |
| __________________________________________________________________________ |
| test data of the starting polyethylene |
| Vicat % b.w. |
| softening |
| chlorination |
| of Cl |
| kind of poly- melt |
| point |
| time at in end- |
| crystal- |
| ethylene density |
| index |
| ° C |
| 95° C |
| 125° C |
| product |
| linity |
| __________________________________________________________________________ |
| 30 |
| low-density |
| 0.917 |
| 22 88 60 min. |
| -- 31.0 5.4 |
| 31 |
| low-density |
| 0.918 |
| 1.7 88 15 min. |
| 45 min. |
| 43.7 <1 |
| 32 |
| low-density |
| 0.920 |
| 0.3 90 60 min. |
| -- 39.5 5.4 |
| 33 |
| low-density |
| 0.923 |
| 4.4 95 60 min. |
| -- 36.0 5.2 |
| 34 |
| high-density |
| 0.953 |
| 19 124 15 min. |
| 45 min. |
| 44.3 <1 |
| __________________________________________________________________________ |
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| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Jun 08 1976 | Stamicarbon, B.V. | (assignment on the face of the patent) | / |
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