Claims
- 1. A process for producing an improved polyoxymethylene molding composition comprising heating a mixture of:
- (1) a polyoxymethylene polymer which exhibits a propensity to form mold deposits upon molding, and
- (2) about 1 to about 4 percent by weight based on the weight of the polyoxymethylene polymer of an aromatic polycarbonate having an intrinsic viscosity of about 0.35 to 0.75 in methylene chloride at 25.degree. C. which is derived from a non-hindered non-halogenated dihydric phenol,
- for at least about 2 minutes at a temperature at which the polyoxymethylene polymer is molten to yield a molding composition which forms a reduced quantity of mold deposits upon molding.
- 2. The process for producing an improved polyoxymethylene molding composition of claim 1 wherein the mixture is heated at a temperature above about 160.degree. C.
- 3. The process for producing an improved polyoxymethylene molding composition of claim 1 wherein the polymer mixture is heated at a temperature between about 180.degree. C. and about 240.degree. C. for a time period of from about 2 to about 20 minutes.
- 4. The process for producing an improved polyoxymethylene molding composition of claim 1 wherein the polyoxymethylene polymer has an inherent viscosity of at least 0.8 (measured at 60.degree. C. in a 0.1 weight percent solution in p-chlorophenol containing 2 weight percent of alpha-pinene), a weight average molecular weight of at least 35,000, and a melting point of at least 150.degree. C.
- 5. The process for producing an improved polyoxymethylene molding composition of claim 4 wherein the polyoxymethylene polymer is a copolymer comprising about 60 to about 99.6 percent recurring --OCH.sub.2 -- groups.
- 6. The process for producing an improved polyoxymethylene molding composition of claim 5 wherein the polyoxymethylene polymer has been pre-stabilized by melt hydrolysis prior to mixture with component (2).
- 7. The process for producing an improved polyoxymethylene molding composition of claim 5 wherein the polyoxymethylene polymer is a mixture of melt hydrolyzed and solution hydrolyzed polymer prior to mixture with component (2).
- 8. The process for producing an improved polyoxymethylene molding composition of claim 5 wherein the polyoxymethylene polymer has been pre-stabilized by the addition of an antioxidant and an acid scavenger prior to heating.
- 9. The process for producing an improved polyoxymethylene molding composition of claim 1 wherein the aromatic polycarbonate has an intrinsic viscosity of about 0.35 to 0.6 in methylene chloride at 25.degree. C.
- 10. The process for producing an improved polyoxymethylene molding composition of claim 1 wherein the dihydric phenol from which the aromatic polycarbonate is derived is 2,2-bis(4-hydroxyphenyl)propane.
- 11. The process for producing an improved polyoxymethylene molding composition of claim 1 wherein a minor quantity of malonamide is admixed with components (1) and (2) during said heating.
- 12. The process for producing an improved polyoxymethylene molding composition of claim 1 wherein the resulting molding composition is free of fibrous reinforcement.
- 13. A process for producing an improved polyoxymethylene, molding composition which is free of fibrous reinforcement comprising heating a mixture of:
- (1) a polyoxymethylene polymer which exhibits a propensity to form mold deposits upon molding,
- (2) about 1 to about 2 percent by weight based on the weight of the polyoxymethylene polymer of an aromatic polycarbonate having an intrinsic viscosity of about 0.35 to 0.75 in methylene chloride at 25.degree. C. which is derived from a non-hindered non-halogenated dihydric phenol, and
- (3) about 0.1 to about 1 percent by weight based on the weight of the polyoxymethylene polymer of malonamide,
- at a temperature between about 180.degree. C. and about 240.degree. C. for a time period of from about 2 to about 20 minutes to yield an improved molding composition which forms a reduced quantity of mold deposits upon molding.
- 14. The process for producing an improved polyoxymethylene molding composition of claim 13 wherein the polyoxymethylene polymer has an inherent viscosity of at least 0.8 (measured at 60.degree. C. in a 0.1 weight percent solution in p-chlorophenol containing 2 weight percent of alpha-pinene), a weight average molecular weight of at least 35,000, and a melting point of at least 150.degree. C.
- 15. The process for producing an improved polyoxymethylene molding composition of claim 13 wherein the polyoxymethylene polymer is a copolymer comprising about 60 to about 99.6 percent recurring --OCH.sub.2 -- groups.
- 16. The process for producing an improved polyoxymethylene molding composition of claim 15 wherein the polyoxymethylene polymer has been pre-stabilized by melt hydrolysis prior to mixture with component (2).
- 17. The process for producing an improved polyoxymethylene molding composition of claim 15 wherein the polyoxymethylene polymer is a mixture of melt hydrolyzed and solution hydrolyzed polymer prior to mixture with components (2) and (3).
- 18. The process for producing an improved polyoxymethylene molding composition of claim 15 wherein said polyoxymethylene polymer is pre-stabilized by the addition of an antioxidant and an acid scavenger prior to heating.
- 19. The process for producing an improved polyoxymethylene molding composition of claim 18 wherein said antioxidant is 2,2'-methylene -bis-(4-methyl-6-tertiary butyl phenol) and said acid scavenger is cyanoguanidine.
- 20. The process for producing an improved polyoxymethylene molding composition of claim 13 wherein the aromatic polycarbonate has an intrinsic viscosity of about 0.35 to 0.6 in methylene chloride at 25.degree. C.
- 21. The process for producing an improved polyoxymethylene molding composition of claim 13 wherein the dihydric phenol from which the aromatic polycarbonate is derived is 2,2-bis(4-hydroxyphenyl)propane.
- 22. The process for producing an improved polyoxymethylene molding composition of claim 13 wherein component (3) is present in a concentration of about 0.1 to about 0.5 percent by weight based upon the weight of the oxymethylene polymer.
- 23. The process for producing an improved polyoxymethylene molding composition of claim 1 which includes the additional step of injection molding the resulting improved polyoxymethylene molding composition.
- 24. The improved polyoxymethylene molding composition which is produced by the process of claim 1.
- 25. The improved polyoxymethylene molding composition which is produced by the process of claim 13.
CROSS REFERENCE TO RELATED APPLICATION
This is a continuation-in-part of U.S. Ser. No. 751,849, filed Dec. 17, 1976 and now abandoned.
US Referenced Citations (5)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
751849 |
Dec 1976 |
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