Reduced VOC emission alkenyl aromatic polymer foams and processes

1. A method for producing an alkenyl aromatic polymer foam structure comprising:

melting at least one alkenyl aromatic polymer resin;

dissolving a blowing agent mixture in the at least one alkenyl aromatic polymer resin, wherein the blowing agent mixture is less than about 4.5 wt. % based on a total mixture of the at least one alkenyl aromatic polymer resin and the blowing agent mixture and wherein the blowing agent mixture comprises at least one volatile organic compound (VOC) blowing agent and acetone, the VOC blowing agent being selected from the group consisting of n-butane, propane and combinations thereof;

forming an extrudate comprising the at least one alkenyl aromatic polymer resin, the at least one VOC blowing agent, and acetone, the extrudate comprising less than about 2.7 wt. % of the at least one VOC blowing agent; and

permitting the extrudate to expand to produce the alkenyl aromatic polymer foam structure, the alkenyl aromatic polymer foam structure having an extruded density less than about 7 lbs/ft 3 and a basis weight of less than about 20 grams per 100 in 2 .

2. The method of claim 1 , wherein the extrudate comprises less than about 2.4 wt. % VOC blowing agent.

3. The method of claim 2 , wherein the extrudate comprises from about 2.0 to about 2.4 wt. % VOC blowing agent.

4. The method of claim 1 , wherein the extrudate comprises from about 0.5 to about 2.0 wt. % acetone.

5. The method of claim 4 , wherein the extrudate comprises from about 0.8 to about 1.8 wt. % acetone.

6. The method of claim 1 , wherein the extrudate comprises from about 3 to about 4.5 wt. % of the blowing agent mixture.

7. The method of claim 1 , wherein the alkenyl aromatic polymer foam structure has an extruded density of from about 3 to about 7 lbs/ft 3 .

8. The method of claim 1 , wherein the at least one alkenyl aromatic polymer foam structure is a homopolymer of styrene, copolymers of styrene, or rubber-toughened polystyrene.

9. The method of claim 1 , wherein the polystyrene foam structure has a basis weight of less than about 15 grams per 100 in 2 .

10. The method of claim 1 further including thermoforming the alkenyl aromatic polymer foam structure into an article, the thermoformed density of the article being less than 6 lbs/ft 3 .

11. The method of claim 10 , wherein the thermoformed article is a homopolymer of styrene, copolymers of styrene, or rubber-toughened polystyrene.

12. The method of claim 1 , wherein the blowing agent mixture is from about 3.6 wt. % to about 4.3 wt. % based the total mixture of the at least one alkenyl aromatic polymer and the blowing agent mixture.

13. The method of claim 12 , wherein the blowing agent mixture is less than about 4.0 wt. % based the total mixture of the at least one alkenyl aromatic polymer and the blowing agent mixture.

14. The method of claim 1 , wherein the blowing agent mixture further comprises carbon dioxide.

15. The method of claim 1 , wherein the blowing agent mixture further comprises methyl acetate and/or water.

16. The method of claim 14 , wherein the extrudate further comprises from about 0.3 to about 1.0 wt. % carbon dioxide.

17. The method of claim 7 , wherein the alkenyl aromatic polymer foam structure has an extruded density of at least 3.8 lbs/ft 3 .

18. A method for producing an alkenyl aromatic polymer foam structure comprising:

melting at least one alkenyl aromatic polymer resin;

dissolving a blowing agent mixture in the at least one alkenyl aromatic polymer resin, wherein the blowing agent mixture is less than about 4.5 wt. % based on a total mixture of the at least one alkenyl aromatic polymer resin and the blowing agent mixture and wherein the blowing agent mixture consists essentially of at least one volatile organic compound (VOC) blowing agent, acetone, and at least one non-VOC blowing agent, the VOC blowing agent being selected from the group consisting of n-butane, propane and combinations thereof and the non-VOC blowing agent being selected from the group consisting of carbon dioxide, methyl acetate, water and combinations thereof;

forming an extrudate comprising the at least one alkenyl aromatic polymer resin, the at least one VOC blowing agent, and acetone, the extrudate comprising less than about 2.7 wt. % of the at least one VOC blowing agent; and

permitting the extrudate to expand to produce the alkenyl aromatic polymer foam structure, the alkenyl aromatic polymer foam structure having an extruded density less than about 7 lbs/ft 3 and a basis weight of less than about 20 grams per 100 in 2 .

19. The method of claim 18 , wherein the extrudate comprises less than about 2.4 wt. % VOC blowing agent.

20. The method of claim 18 , wherein the extrudate comprises from about 2.0 to about 2.4 wt. % VOC blowing agent.

21. The method of claim 18 , wherein the extrudate comprises from about 0.5 to about 2.0 wt. % acetone.

22. The method of claim 18 , wherein the at least one alkenyl aromatic polymer foam structure is a homopolymer of styrene, copolymers of styrene, or rubber-toughened polystyrene.

23. The method of claim 18 , further including thermoforming the alkenyl aromatic polymer foam structure into an article, the thermoformed density of the article being less than 6 lbs/ft 3 .

24. The method of claim 23 , wherein the thermoformed article is a homopolymer of styrene, copolymers of styrene, or rubber-toughened polystyrene.

25. The method of claim 18 , wherein the blowing agent mixture is from about 3.6 wt. % to about 4.3 wt. % based on the total mixture of the at least one alkenyl aromatic polymer and the blowing agent mixture.

26. The method of claim 25 , wherein the blowing agent mixture is less than about 4.0 wt. % based the total mixture of the at least one alkenyl aromatic polymer and the blowing agent mixture.

27. A method for producing an alkenyl aromatic polymer foam structure comprising:

melting at least one alkenyl aromatic polymer resin;

dissolving a blowing agent mixture in the at least one alkenyl aromatic polymer resin, wherein the blowing agent mixture is less than about 4.5 wt. % based on a total mixture of the at least one alkenyl aromatic polymer resin and the blowing agent mixture and wherein the blowing agent mixture consists essentially of at least one volatile organic compound (VOC) blowing agent, acetone and carbon dioxide, the VOC blowing agent being selected from the group consisting of n-butane, propane and combinations thereof;

forming an extrudate comprising the at least one alkenyl aromatic polymer resin, the at least one VOC blowing agent, acetone and carbon dioxide, the extrudate comprising less than about 2.7 wt. % of the at least one VOC blowing agent; and

permitting the extrudate to expand to produce the alkenyl aromatic polymer foam structure, the alkenyl aromatic polymer foam structure having an extruded density less than about 7 lbs/ft 3 and a basis weight of less than about 20 grams per 100 in 2 .

28. The method of claim 27 , wherein the extrudate comprises less than about 2.4 wt. % VOC blowing agent.

29. The method of claim 27 , wherein the extrudate comprises from about 2.0 to about 2.4 wt. % VOC blowing agent.

30. The method of claim 27 , wherein the extrudate comprises from about 0.5 to about 2.0 wt. % acetone.

31. The method of claim 27 , wherein the at least one alkenyl aromatic polymer foam structure is a homopolymer of styrene, copolymers of styrene, or rubber-toughened polystyrene.

32. The method of claim 27 , further including thermoforming the alkenyl aromatic polymer foam structure into an article, the thermoformed density of the article being less than 6 lbs/ft 3 .

33. The method of claim 32 , wherein the thermoformed article is a homopolymer of styrene, copolymers of styrene, or rubber-toughened polystyrene.

34. The method of claim 27 , wherein the extrudate consists essentially of from about 2.0 to about 2.4 wt. % VOC blowing agent, from about 0.5 to about 2.0 wt. % acetone, and from about 0.3 to about 1.0 wt. % carbon dioxide.

35. The method of claim 27 , wherein the blowing agent mixture is from about 3.6 wt. % to about 4.3 wt. % based on the total mixture of the at least one alkenyl aromatic polymer and the blowing agent mixture.

36. A method for producing an alkenyl aromatic polymer foam structure comprising:

melting at least one alkenyl aromatic polymer resin;

dissolving an effective amount of a blowing agent mixture in the at least one alkenyl aromatic polymer, wherein the blowing agent mixture consists essentially of at least one volatile organic compound (VOC) blowing agent and acetone, the VOC blowing agent being selected from the group consisting of n-butane, propane and combinations thereof;

forming an extrudate comprising the at least one alkenyl aromatic polymer resin, the at least one VOC blowing agent and acetone, the extrudate comprising less than about 2.7 wt. % of the at least one VOC blowing agent; and

permitting the extrudate to expand to produce the alkenyl aromatic polymer foam structure, the alkenyl aromatic polymer foam structure having an extruded density less than about 7 lbs/ft 3 and a basis weight of less than about 20 grams per 100 in 2 .

37. The method of claim 36 , wherein the extrudate comprises from about 2.0 to about 2.4 wt. % VOC blowing agent.

38. The method of claim 36 , wherein the extrudate comprises from about 0.5 to about 2.0 wt. % acetone.

39. The method of claim 36 , wherein the at least one alkenyl aromatic polymer foam structure is a homopolymer of styrene, copolymers of styrene, or rubber-toughened polystyrene.

40. The method of claim 36 , further including thermoforming the alkenyl aromatic polymer foam structure into an article, the thermoformed density of the article being less than 6 lbs/ft 3 .

41. The method of claim 40 , wherein the thermoformed article is a homopolymer of styrene, copolymers of styrene, or rubber-toughened polystyrene.

42. The method of claim 36 , wherein the extrudate comprises less than about 2.4 wt. % VOC blowing agent.