Method of thermoforming
View Patent ↗A method of thermoforming comprises the steps of providing a film, heating the film, and forming the heated film onto a mold. The film comprises a propylene/ethylene copolymer skin layer having a melting point of from about 130° C. to about 150° C. and a interior polyamide layer having a melting point of from about 125° C. to about 230° C.
1. A method of thermoforming comprising the steps of:
(1) providing a film comprising:
(i) a skin layer forming an outer surface of the film, wherein:
the skin layer has a melting point of at least about 130° C. and at most about 150° C.; and
the skin layer comprises one or more propylene/ethylene copolymers; and
(ii) a first polyamide layer forming an interior layer of the film, wherein:
the first polyamide layer has a melting point of at least about 125° C. and at most about 230° C.; and
the first polyamide layer comprises one or more polyamides;
(iii) an intermediate layer between the skin layer and the first polyamide layer, wherein:
the intermediate layer has a melting point of at least about 105° C. and at most about 150° C.; and
the intermediate layer comprises one or more propylene/ethylene copolymers;
(iv) a sealant layer forming an outer layer of the film, wherein the sealant layer has a melting point of at most about 130° C.;
(v) a barrier layer comprising ethylene/vinyl alcohol copolymer, wherein the barrier layer is directly adjacent the first polyamide layer;
(vi) a second polyamide layer directly adjacent the barrier layer and comprising one or more polyamides; and
(vii) a tie layer between the intermediate layer and the first polyamide layer, the tie layer comprising one or more tie polymers;
(2) heating the film; and
(3) thermoforming the heated film onto a mold having a mold depth of at least about 2 inches.
2. The method of claim 1 wherein the skin layer has a melting point of at most about 145° C.
3. The method of claim 1 wherein the skin layer has a melting point of at most about 140° C.
4. The method of claim 1 wherein the skin layer comprises at least about 50%, by weight of the layer, of propylene/ethylene copolymer having an ethylene comonomer content of at least about 1 wt % and at most about 10 wt %.
5. The method of claim 1 wherein the skin layer comprises at least about 50%, by weight of the layer, of propylene/ethylene copolymer having an ethylene comonomer content of at least about 3 wt % and at most about 8 wt %.
6. The method of claim 1 wherein the skin layer comprises at least about 50%, by weight of the layer, of propylene/ethylene copolymer having a melting point of at least about 130° C. and at most about 145° C.
7. The method of claim 1 wherein the skin layer comprises one or more homogeneous propylene/ethylene copolymers.
8. The method of claim 1 wherein the skin layer comprises one or more random propylene/ethylene copolymers.
9. The method of claim 1 wherein the thickness of the skin layer is at least about 5% and at most about 25% of the total thickness of the film of the providing step.
10. The method of claim 1 wherein the first polyamide layer has a melting point of at most about 210° C.
11. The method of claim 1 wherein the first polyamide layer has a melting point of at most about 200° C.
12. The method of claim 1 wherein the first polyamide layer has a melting point of at least about 170° C.
13. The method of claim 1 wherein the first polyamide layer comprises at least about 20%, by weight of the layer, of nylon-6/6,6.
14. The method of claim 1 wherein the first polyamide layer comprises at least about 90%, by weight of the layer, of nylon-6/6,6.
15. The method of claim 1 wherein the first polyamide layer comprises at least about 30%, by weight of the layer, of nylon-6/6,6 having a melting point of at least about 180° C. and at most about 195° C.
16. The method of claim 1 wherein the first polyamide layer comprises at least about 50%, by weight of the layer, of nylon-6/6,6 having a caprolactam comonomer content range selected from: 1) at least about 30 mole % to at most about 35 mole % and 2) at least about 85 mole % to at most about 90 mole %.
17. The method of claim 1 wherein the first polyamide layer comprises from about 1 to about 80%, by weight of the layer, of one or more amorphous polyamides.
18. The method of claim 1 wherein the first polyamide layer comprises at most about 5%, by weight of the layer, of amorphous polyamide.
19. The method of claim 1 wherein the first polyamide layer is substantially free of amorphous polyamide.
20. The method of claim 1 wherein the thickness of the first polyamide layer is at least about 5% and at most about 25% of the total thickness of the film of the providing step.
21. The method of claim 1 wherein the barrier layer comprises at least about 80%, by weight of the layer, of ethylene/vinyl alcohol copolymer.
22. The method of claim 1 wherein the barrier layer has a thickness that is at least about 5% and at most about 20% of the total thickness of the film of the providing step.
23. The method of claim 1 wherein the second polyamide layer has a melting point of at most about 210° C.
24. The method of claim 1 wherein the second polyamide layer has a melting point of at most about 200° C.
25. The method of claim 1 wherein the second polyamide layer has a melting point of at least about 170° C.
26. The method of claim 1 wherein the second polyamide layer comprises at least about 20%, by weight of the layer, of nylon-6/6,6.
27. The method of claim 1 wherein the second polyamide layer comprises at least about 90%, by weight of the layer, of nylon-6/6,6.
28. The method of claim 1 wherein the second polyamide layer comprises at least about 50%, by weight of the layer, of nylon-6/6,6 having a melting point of at least about 180° C. and at most about 195° C.
29. The method of claim 1 wherein the second polyamide layer comprises at least about 50%, by weight of the layer, of nylon-6/6,6 having a nylon-6 comonomer content range selected from: 1) at least about 30 mole % to at most about 35 mole % and 2) at least about 85 mole % to at most about 90 mole %.
30. The method of claim 1 wherein the second polyamide layer comprises from about 1 to about 80%, by weight of the layer, of one or more amorphous polyamides.
31. The method of claim 1 wherein the second polyamide layer comprises at most about 5%, by weight of the layer, of amorphous polyamide.
32. The method of claim 1 wherein the second polyamide layer is substantially free of amorphous polyamide.
33. The method of claim 1 wherein the thickness of the second polyamide layer is at least about 10% and at most about 20% of the total thickness of the film of the providing step.
34. The method of claim 1 wherein:
the first polyamide layer comprises at least about 50%, by weight of the layer, of Nylon-6/6,6; and
the second polyamide layer comprises at least about 50%, by weight of the layer, of nylon-6/6,6.
35. The method of claim 34 wherein the nylon-6/6,6 of the first and second polyamide layers are substantially the same.
36. The method of claim 1 wherein the intermediate layer is directly adjacent the skin layer.
37. The method of claim 36 wherein the intermediate layer has a melting point of at most about 130° C.
38. The method of claim 36 wherein the intermediate layer has a melting point of at most about 120° C.
39. The method of claim 36 wherein the intermediate layer has a melting point of at most about 115° C.
40. The method of claim 36 wherein the intermediate layer comprises at least about 50%, by weight of the layer, of propylene/ethylene copolymer having an ethylene content of at least about 1 wt % and at most about 10 wt %.
41. The method of claim 36 wherein the intermediate layer comprises at least about 50%, by weight of the layer, of propylene/ethylene copolymer having an ethylene content of at least about 3 wt % and at most about 8 wt %.
42. The method of claim 36 wherein the intermediate layer comprises at least about 50%, by weight of the layer, of propylene/ethylene copolymer having a melting point of at least about 105° C. and at most about 130° C.
43. The method of claim 36 wherein the intermediate layer comprises at least about 50%, by weight of the layer, of propylene/ethylene copolymer having a melting point of at least about 105° C. and at most about 120° C.
44. The method of claim 36 wherein the intermediate layer comprises one or more homogenous propylene/ethylene copolymers.
45. The method of claim 36 wherein the intermediate layer comprises one or more random propylene/ethylene copolymers.
46. The method of claim 36 wherein the intermediate layer comprises:
at least about 40%, by weight of the layer, of a first propylene/ethylene copolymer having a melting point of at least about 110° C.; and
at least about 10%, by weight of the layer, of a second propylene/ethylene copolymer having a melting point of at most about 110° C.
47. The method of claim 46 wherein the first propylene/ethylene copolymer has a melting point of at least about 115° C. and the second propylene/ethylene copolymer has a melting point of at most about 100° C.
48. The method of claim 46 wherein at least one of the first and second propylene/ethylene copolymers is a homogeneous propylene/ethylene copolymer.
49. The method of claim 1 wherein the intermediate layer comprises at least about 50 weight %, by weight of the intermediate layer, of propylene/ethylene copolymer having a density of at least about 0.860 and at most about 0.905.
50. The method of claim 1 wherein the film of the providing step has not been oriented and the film has a thickness of at most about 10 mils.
51. The method of claim 1 wherein the film of the providing step has not been oriented and the film has a thickness of at most about 6 mils.
52. The method of claim 1 wherein the film is substantially free of polyester.
53. The method of claim 1 wherein the film of the providing step has a Young's modulus of at most about 120,000 psi at 50° C., measured according to ASTM D882.
54. The method of claim 1 wherein the total luminous transmittance of the film of the providing step is at least about 95%, measured according to ASTM D1003.
55. The method of claim 1 wherein the heating step heats the film to a temperature of at least about 45° C.
56. The method of claim 1 wherein the heating step heats the film to a temperature of at most about 105° C.
57. The method of claim 1 wherein the heating step heats the film to a temperature of at most about 60° C.
58. The method of claim 1 wherein the thermoforming step comprises vacuum forming.
59. The method of claim 1 wherein the thermoforming step comprises plug assist vacuum forming.
60. The method of claim 1 wherein the thermoforming step comprises air assist vacuum forming.
61. The method of claim 1 wherein:
the film of the providing step is non-oriented and has a thickness of at most about 12 mils;
the skin layer comprises at least about 50%, by weight of the layer, of one or more propylene/ethylene copolymers having a melting point of at least about 130° C. and at most about 150° C.; and
the first polyamide layer comprises at least about 50%, by weight of the layer, of one or more polyamides having a melting point of at least about 125° C. and at most about 230° C.; and
the intermediate layer is directly adjacent the skin layer, wherein the intermediate layer comprises at least about 50%, by weight of the layer, of one or more propylene/ethylene copolymers having a melting point of at least about 105° C. and at most about 150° C.;
the second polyamide layer comprises at least about 50%, by weight of the layer, of one or more polyamides having a melting point of at least about 125° C. and at most about 230° C.; and
the heating step heats the film to a temperature of at least about 45° C. and at most about 105° C.
62. The method of claim 61 wherein the first polyamide layer comprises at least about 50%, by weight of the layer, of nylon-6/6,6 and the second polyamide layer comprises at least about 50%, by weight of the layer, of nylon-6/6,6.
63. The method of claim 61 wherein the film further comprises a tie layer directly adjacent to both the intermediate layer and the first polyamide layer, wherein the tie layer comprises at least about 50%, by weight of the layer, of a modified polyethylene polymer.
64. The method of claim 1 wherein the sealant layer has a melting point of at most about 125° C.
65. The method of claim 1 wherein in the tie layer comprises at least 40% by weight of the tie layer of one or more tie polymers selected from ethylene/vinyl acetate copolymer, ethylene/(meth)acrylic acid copolymers, ethylene/C 1 -C 12 alkyl (meth)acrylate copolymers, and anhydride-modified polymers.