Method of manufacturing polystyrene foam with polymer processing additives
View Patent ↗Disclosed is a method for making polystyrene foam which utilizes one or more atmospheric gases, particularly combinations of HFCs and CO 2 , as the blowing system in combination with a polymer processing aid (PPA), typically an ester that is relatively non-volatile at the extrusion temperature range. The blowing system and the PPA may both be introduced into the molten thermoplastic polystyrene resin or the PPA may be incorporated in the solid source polystyrene resins. The resulting foams will typically exhibit improved dimensional stability at ambient temperatures.
1. A method of manufacturing extruded polymeric foam, comprising:
preparing a polymeric melt from a major amount of a polymer composition having a melt flow index of at least about 2.0 wherein the polymer composition includes a major portion of polystyrene by weight and a minor amount of an adipate having the formula
injecting a blowing system into the polymeric melt to form a foamable mixture, the blowing system comprising CO 2 , one or more blowing agent, and optionally water, said one or more blowing agent being selected from HCFC-22, HCFC-123, HCFC142b, HFC-134a, HFC-152a, HCFC-141b and mixtures thereof; and
extruding the foamable mixture through a die at a die pressure into a region of reduced pressure to form said extruded polymeric foam.
2. The method of manufacturing extruded polymeric foam according to claim 1 , wherein: the polymer composition has a melt flow index of at least about 10.0.
3. The method of manufacturing extruded polymeric foam according to claim 1 , wherein: the polymer composition is substantially all polystyrene.
4. The method of manufacturing extruded polymeric foam according to claim 1 , wherein the adipate represents no more than about 1.5% by weight of the foamable mixture.
5. The method of manufacturing extruded polymeric foam according to claim 1 , wherein: the adipate represents from about 0.5% to about 3.0% by weight of the foamable mixture.
6. The method of manufacturing extruded polymeric foam according to claim 1 , wherein:
the polymer composition includes a major portion of polystyrene;
the CO 2 represents about 3.7% by weight of the foamable mixture;
the reduced pressure is between about 101.3 kPa and about 47.3 kPa; and
the resulting expanded foam has an average cell size of less than about 0.3 mm and a density of from about 1.7 to about 2.3 pcf.
7. The method of manufacturing extruded polymeric foam according to claim 1 , wherein:
the polymer composition includes a major portion of polystyrene;
the reduced pressure is between about 202.7 kPa and about 25.3 kPa; and
the resulting expanded foam has an average cell size of less than about 0.3 mm and a density of from about 1.7 to about 2.3 pcf.
8. The method of manufacturing extruded polymeric foam according to claim 1 , wherein:
the polymer composition includes a major portion of polystyrene;
the reduced pressure is between about 101.3 kPa and about 47.3 kPa; and
the resulting expanded foam has an average cell size of less than about 0.3 mm and a density from about 1.7 to about 2.3 pcf.
9. The method of manufacturing extruded polymeric foam according to claim 1 , wherein said polymer melt further includes methyl methacrylate in an amount less than 10% by weight.
10. A method of manufacturing extruded polymeric foam comprising:
Preparing a polymeric melt from a major amount of a polymer composition having a melt flow index of at least about 2.0 wherein the polymer composition includes a major portion of polystyrene by weight and a minor amount of at least one adipate having the formula
injecting a blowing system into the polymeric melt to form a foamable mixture, the blowing system comprising less than 4 wt % CO 2 , one or more HFC, and optionally water; and extruding the foamable mixture through a die at a die pressure into a region of reduced pressure to form said extruded polymeric foam,
wherein said adipate represents no more than about 3 wt % of said foamable mixture, and
wherein said adipate is present in said foamable mixture in combination with a similar or greater amount of said blowing system.
11. The method according to claim 10 wherein:
said one or more HFC is selected from HCFC-22, HCFC-123, HCFC-142b, HFC-134a, HFC-152a, HCFC-141b and mixtures thereof; and
the polymer composition has a melt flow index of at least about 10.0.
12. The method according to claim 10 , wherein said adipate represents no more than about 1.5% by weight of said foamable mixture.
13. The method according to claim 10 , wherein said adipate represents from about 0.5% to about 3.0% by weight of said foamable mixture.
14. A method of manufacturing an extruded polymeric foam, comprising:
preparing a polymeric melt from
(1) a major amount of a polymer composition having a melt flow index at least about 2.0 wherein the polymer composition includes a major portion of polystyrene by weight; and
(2) a minor portion of at least one compound according to Formula V;
wherein R 1 is selected from C 8 -C 13 aliphatic and C 6 -C 16 aromatic groups;
injecting a blowing system into the polymeric melt to form a foamable mixture, the compound according to formula V increasing the solubility of the blowing system, said blowing system including CO 2 , one or more blowing agent selected from HCFC-22, HCFC-123, HCFC-142b, HFC-134a, HFC-152a, HCFC-141b and mixtures thereof, and optionally water; and
extruding the foamable mixture through a die into a region of reduced pressure to form said polymeric foam.
15. The method of manufacturing extruded polymeric foam according to claim 14 , wherein: the polymer composition has melt flow index of at least about 10.0.
16. The method of manufacturing extruded polymeric foam according to claim 14 , wherein: the polymer composition is substantially all polystyrene.
17. The method of manufacturing extruded polymeric foam according to claim 14 , wherein: the blowing system includes CO 2 in an amount of at least about 3.5% by weight of the foamable mixture.
18. The method of manufacturing extruded polymeric foam according to claim 14 , wherein: the blowing system includes CO 2 in an amount of at least about 3.5% by weight of the foamable mixture.
19. The method of manufacturing extruded polymeric foam according to claim 14 , wherein: the region of reduced pressure is between about 101.3 kPa and about 47.3 kPa.
20. The method of manufacturing extruded polymeric foam according to claim 14 , wherein; the region of reduced pressure is between about 202.7 kPa and about 25.3 kPa.
21. The method of manufacturing extruded polymeric foam according to claim 14 , wherein said polymer melt further included methyl methacrylate in an amount less than 10% by weight.
22. The method of manufacturing extruded polymeric foam according to claim 14 , wherein R 1 is selected from C 6 -C 16 aromatic groups.
23. The method of manufacturing extruded polymeric foam according to claim 15 , wherein R 1 is selected from C 8 -C 13 aromatic groups.