Patent GB-1081144-A (GB)
Title: Improvements relating to the manufacture of polyester films
IPC: C09D5/46
Filed: 1965-04-09
Abstract: A copolyester film is made by melt extruding a copolyester of ethylene glycol, terephthalic acid and an aliphatic dibasic carboxylic acid of the formula HOOC-CH2XCH2-COOH wherein X is a chain containing 3 to 30 atoms, of which not more than 3 (all in the main chain) may be oxygen and the remainder are hydrocarbon carbon atoms, any two such oxygen atoms being separated by at least two carbon atoms, all the carbon atoms being saturated and not more than three of them being present in side chain substituents, the proportion by weight of the aliphatic acid (based on the total weight of the acid components) being 11 to 22%, and biaxially orienting and heat-setting the film.  The copolyesters are preferably prepared by reacting first under ester interchange conditions and then under polymerization conditions, ethylene glycol, a dialkyl ester of terephthalic acid in which the esterifying alkyl groups contain 1 to 7 carbon atoms, and a dialkyl ester of an aliphatic dicarboxylic acid having the formula HOOC-(CH2)n-COOH, where n is 5-10, in which the esterifying alkyl groups contain 1-7 carbon atoms.  The preferred copolyester is prepared from ethylene glycol, dimethyl terephthalate and dimethyl sebacate.ALSO:A copolyester film is made by melt extruding a copolyester of ethylene glycol, terephthalic acid and an aliphatic dibasic carboxylic acid of the formula HOOC-CH2XCH2-COOH wherein X is a chain containing 3 to 30 atoms, of which not more than 3 (all in the main chain) may be oxygen and the remainder are hydrocarbon carbon atoms, any two such oxygen atoms being separated by at least two carbon atoms, all the carbon atoms being saturated and not more than three of them being present in side chain substituents, the proportion by weight of the aliphatic acid (based on the total weight of the acid components) being 11% to 22%, and biaxially orienting and heat-setting the film.  The film may be biaxially oriented by stretching it to 2.6 to 4.0 times its initial dimension in the machine direction and the transverse direction at a temperature of 65 to 90 DEG C.  The film may then be heat-set at a temperature of 130 to 160 DEG C.  The aliphatic acid may have the formula HOOC-(CH2)n-COOH in which n is 5 to 10.  The aliphatic acid may be sebacic acid.  The film may be coated on one or both sides with a copolymer of at least 80% by weight of vinylidene chloride and at most 20% by weight of an ethylenically unsaturated monomer copolymerizable therewith.  The coated film may be given on one or both sides a top coating of a polymer of an alpha-olefine such as polyethylene or a copolymer of ethylene with propylene or the butylenes.  The copolyesters of the invention may be prepared by any conventional method, e.g. as described in Specification No. 578,079. They are preferably prepared by reacting first under ester interchange conditions and then under polymerization conditions, ethylene glycol, a dialkyl ester of terephthalic acid in which the esterifying alkyl groups contain 1 to 7 carbon atoms, and a dialkyl ester of an aliphatic dicarboxylic acid having the formula HOOC-(CH2)n-COOH where n is 5-10, in which the esterifying alkyl groups contain 1-7 carbon atoms.  The preferred copolyester is prepared from ethylene glycol, dimethyl terephthalate and dimethyl sebacate.