Slip additive composition in thermoplastic polymer processing
The present invention relates to the use of a fatty acid ester as a slip additive in the production of molded polyethylene terephthalate articles, to a thermoplastic molding composition comprising a polyethylene terephthalate and a fatty acid ester selected to be effective for reducing the co-efficient of friction of molded articles formed from the composition, to a molded polyethylene terephthalate article comprising a fatty acid ester selected to be effective in reducing the co-efficient of friction of the molded article, and to a process for producing a molded thermoplastic article comprising providing a thermoplastic molding composition comprising polyethylene terephthalate, admixing with the thermoplastic molding composition at least one fatty acid ester selected to be effective in reducing the co-efficient of friction of the molded article, heating the composition and molding the hot composition so as to form a molded article.
1. A method of using a fatty acid ester as a slip additive in a thermoplastic moulding composition in the production of colourless moulded polyethylene terephthalate articles in the form of bottle preforms, the method comprising incorporating said fatty acid ester into a bottle preform moulded from polyethylene terephthalate, said slip additive reducing the coefficient of friction of the preform, wherein the fatty acid ester is selected from the group consisting of:
(a) acetylated glycerol fatty acid esters;
(b) sorbitan fatty acid esters; and
(c) refined rapeseed oil, montanic acid triglyceride, PEG-400 dilaurate, PEG-200 dioleate, acetylated triglyceride, and mixtures of two or more thereof;
wherein the moulded polyethylene terephthalate articles in the form of bottle preforms are colourless; and
wherein the thermoplastic moulding composition does not comprise a fatty amide.
2. A method according to claim 1 , wherein the fatty acid ester is colourless.
3. A method according to claim 1 wherein the fatty acid ester is selected from acetylated glycerol fatty acid esters.
4. A method according to claim 3 , wherein the acetylated glycerol fatty acid ester is ethoxylated glycerol monostearate.
5. A method according to claim 1 , wherein the fatty acid ester is selected from sorbitan fatty acid esters.
6. A method according to claim 5 , wherein the sorbitan fatty acid ester is selected from sorbitan monolaurate, sorbitan monooleate, sorbitan monopalmitate, sorbitan monostearate, and mixtures of two or more thereof.
7. A method according to claim 1 , wherein the fatty acid ester is selected from refined rapeseed oil, montanic acid triglyceride, PEG-400dilaurate, PEG-200 dioleate, acetylated triglyceride, and mixtures of two or more thereof.
8. A method according to claim 1 wherein the fatty acid ester is present in the moulding composition in an amount effective to reduce the coefficient of friction of a moulded article formed from the moulding composition by at least 25% relative to the coefficient of friction of a corresponding moulded article formed from the moulding composition in the absence of the slip additive.
9. The method according to claim 1 , wherein said fatty acid ester is a long chain fatty acid ester wherein the chain length is at least 12.
10. The method according to claim 1 , wherein said fatty acid ester is a long chain fatty acid ester wherein the chain length is twelve to eighteen.
11. The method according to claim 1 , wherein the amount of slip additive included in the thermoplastic moulding composition from which a said moulded article is produced is at least 0.1% w/w.
12. The method according to claim 11 , wherein the amount of slip additive is at least 0.3% w/w.
13. The method according to claim 12 , wherein the amount of slip additive is at least 0.4% w/w.
14. The method according to claim 13 wherein the amount of slip additive is no more than 0.5% w/w.
15. The method according to claim 1 , wherein said slip additive is able to withstand injection moulding at a temperature in the range 260° C. to 310° C.
16. The method of claim 1 , wherein the thermoplastic moulding composition does not comprise an oxygen scavenger.
17. The method according to claim 1 , wherein said fatty acid ester is admixed with said polyethylene terephthalate.
18. A method of using a slip additive in a thermoplastic moulding composition in the production of moulded polyethylene terephthalate articles in the form of bottle preforms, the method comprising incorporating said slip additive into a bottle preform moulded from polyethylene terephthalate, said slip additive reducing the coefficient of friction of the preform, wherein the slip additive comprises a fatty acid ester and a further slip agent, wherein said fatty acid ester is selected from the group consisting of:
(a) acetylated glycerol fatty acid esters;
(b) sorbitan fatty acid esters; and
(c) refined rapeseed oil, montanic acid triglyceride, PEG-400 dilaurate, PEG-200dioleate, acetylated triglyceride, and mixtures of two or more thereof; and
wherein said further slip agent is a mineral oil.