Composite foam product
A composite foam product comprising a foam core surrounded by a gas-impermeable film. The gas-impermeable film retains the gas formed from the blowing agent so that the pressure inside the foam core is above ambient pressures.
1. A process for forming a composite foam product comprising:
forming a foam core from a foamable material and a blowing agent, said foam core having a plurality of cells therein, said plurality of cells retaining a gas from said blowing agent therein at a pressure above an ambient pressure, and said foam core having an exterior surface; and then
placing a first gas impermeable film in a molding cavity;
placing said foam core in said molding cavity;
placing a second gas impermeable film over said foam core in said molding cavity;
adhering the first and second gas impermeable films to said exterior surface of said foam core by heating the first and second gas impermeable films to their softening temperatures, wherein the first and second gas impermeable films are adhered to substantially all of the exterior surface of the foam core such that said gas from said blowing agent is retained in said cells of said foam core at said pressure above said ambient pressure;
wherein the process further comprises applying a first adhesive between said foam core and said first gas impermeable film and applying a second adhesive between said foam core and said second gas impermeable film.
2. The process of claim 1 wherein said foamable material is selected from the group consisting of polyethylene resins, polypropylene resins, thermoplastic resins, or mixtures thereof.
3. The process of claim 1 wherein said foamable material is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic ester-maleic anhydride terpolymer, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-methacrylateterpolymer, ethylene-glycidyl methacrylate-vinyl acetate terpolymer, ethylene-alpha-olefin copolymer, modified polyolefin, and chlorinated polyethylene.
4. The process of claim 1 wherein said foamable material is selected from the group consisting of propylene homopolymer, propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-butene random copolymer, and propylene-ethylene-butene terpolymer.
5. The process of claim 1 wherein said foamable material is selected from the group consisting of polyvinyl chloride, polyvinyl chloride-vinyl acetate copolymer, chlorinated polyvinyl chloride, polyvinyl chloride-ethylene-vinyl acetate copolymer, polyvinyl chloride-urethane copolymer, acrylonitrile-butadiene-styrene copolymer, methyl methacrylate-butadiene-styrene copolymer, styrene-butadiene-styrene block copolymer, acrylonitrile-styrene copolymer, and PVC-nitrile rubber.
6. The process of claim 1 wherein said blowing agent is selected from the group consisting of N-nitroso compounds, sulfonyl hydrazines, sulfonyl semicarbazides, ammonium, and azo type compounds.
7. The process of claim 1 wherein said gas from said blowing agent is substantially an inert gas.
8. The process of claim 1 wherein each of said first and second gas impermeable films is selected from the group consisting of one or more polyolefins, polyurethanes, polyvinyls, polyethers, and polyesters.
9. The process of claim 1 wherein each of said first and second gas impermeable films is selected from the group consisting of polyethylene/vinyl alcohol copolymers, poly(vinylidine chloride) copolymer, polyethylene terephthalate, polyamides, nylon, and thermoplastic polyurethane.
10. The process of claim 1 wherein said step of forming said foam core comprises the step of:
applying an alternating radio frequency dielectric field to heat said foamable material and said blowing agent.
11. The process of claim 10 wherein said alternating radio frequency dielectric field is generated between a first top electrode and a second bottom electrode.
12. The process of claim 11 wherein said first top electrode is a high voltage electrode having a voltage between 1000 and 10,000 V.
13. A process for forming a composite foam product comprising:
providing a flow molding apparatus having an upper mold and a bottom mold that define a molding cavity therebetween and also having a movable diaphragm disposed in said molding cavity;
positioning a first gas impermeable film on said bottom mold in said molding cavity;
placing a foaming mixture comprising a foamable material and a blowing agent on said gas impermeable film in said molding cavity;
placing a second gas impermeable film over said foaming mixture in said molding cavity; and
deflecting said moveable diaphragm downwards so as to expel air from said molding cavity;
heating said foaming mixture and said first and second gas-impermeable films in said molding cavity, whereby said moveable diaphragm is deflected upwards as said foaming mixture expands to form a foam core having an exterior surface and a plurality of cells therein, said plurality of cells having a gas from said blowing agent therein at a pressure above an ambient pressure; and whereby said first and second gas-impermeable films are adhered to said exterior surface of said foam core.
14. The process of claim 13 wherein said foamable material is selected from the group consisting of polyethylene resins, polypropylene resins, thermoplastic resins, or mixtures thereof.
15. The process of claim 13 wherein said foamable material is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic ester-maleic anhydride terpolymer, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-methacrylateterpolymer, ethylene-glycidyl methacrylate-vinyl acetate terpolymer, ethylene-alpha-olefin copolymer, modified polyolefin, and chlorinated polyethylene.
16. The process of claim 13 wherein said foamable material is selected from the group consisting of propylene homopolymer, propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-butene random copolymer, and propylene-ethylene-butene terpolymer.
17. The process of claim 13 wherein said foamable material is selected from the group consisting of polyvinyl chloride, polyvinyl chloride-vinyl acetate copolymer, chlorinated polyvinyl chloride, polyvinyl chloride-ethylene-vinyl acetate copolymer, polyvinyl chloride-urethane copolymer, acrylonitrile-butadiene-styrene copolymer, methyl methacrylate-butadiene-styrene copolymer, styrene-butadiene-styrene block copolymer, acrylonitrile-styrene copolymer, and PVC-nitrile rubber.
18. The process of claim 13 wherein said blowing agent is selected from the group consisting of N-nitroso compounds, sulfonyl hydrazines, sulfonyl semicarbazides, ammonium, and azo type compounds.
19. The process of claim 13 wherein said gas from said blowing agent is substantially an inert gas.
20. The process of claim 13 wherein each of said first and second gas impermeable films is selected from the group consisting of one or more polyolefins, polyurethanes, polyvinyls, polyethers, and polyesters.
21. The process of claim 13 wherein each of said first and second gas impermeable films is selected from the group consisting of polyethylene/vinyl alcohol copolymers, poly(vinylidine chloride) copolymer, polyethylene terephthalate, polyamides, nylon, and thermoplastic polyurethane.
22. The process of claim 13 further comprising the step of applying an adhesive film between said foam core and each of said first and second gas impermeable films.
23. The process of claim 13 wherein said heating occurs by applying an alternating radio frequency dielectric field across said molding cavity.
24. The process of claim 23 wherein said alternating radio frequency dielectric field has a frequency between about 1 MHz to 100 MHz, and a voltage of between about 1000 V to 10,000 V.
25. A process for forming a composite foam product comprising:
providing a flow molding apparatus having a first mold and a second mold that define a molding cavity and also having a movable diaphragm disposed in said molding cavity;
positioning a gas impermeable film in said molding cavity;
placing a foaming mixture comprising a foamable material and a blowing agent in said molding cavity;
deflecting said moveable diaphragm downwards so as to expel air from said molding cavity;
heating said foaming mixture and said gas impermeable film in said molding cavity, whereby said moveable diaphragm is deflected upwards as said foaming mixture expands to form a foam core having an exterior surface and a plurality of cells therein, said plurality of cells having a gas from said blowing agent therein at a pressure above an ambient pressure; and
whereby said gas impermeable film is adhered to said foam core.
26. The process of claim 25 wherein said foamable material is selected from the group consisting of polyethylene resins, polypropylene resins, thermoplastic resins, or mixtures thereof.
27. The process of claim 25 wherein said foamable material is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic ester-maleic anhydride terpolymer, ethylene-glycidyl methacrylate copolymer, ethylene-glycidyl methacrylate-methacrylateterpolymer, ethylene-glycidyl methacrylate-vinyl acetate terpolymer, ethylene-alpha-olefin copolymer, modified polyolefin, and chlorinated polyethylene.
28. The process of claim 25 wherein said foamable material is selected from the group consisting of propylene homopolymer, propylene-ethylene random copolymer, propylene-ethylene block copolymer, propylene-butene random copolymer, and propylene-ethylene-butene terpolymer.
29. The process of claim 25 wherein said foamable material is selected from the group consisting of polyvinyl chloride, polyvinyl chloride-vinyl acetate copolymer, chlorinated polyvinyl chloride, polyvinyl chloride-ethylene-vinyl acetate copolymer, polyvinyl chloride-urethane copolymer, acrylonitrile-butadiene-styrene copolymer, methyl methacrylate-butadiene-styrene copolymer, styrene-butadiene-styrene block copolymer, acrylonitrile-styrene copolymer, and PVC-nitrile rubber.
30. The process of claim 25 wherein said blowing agent is selected from the group consisting of N-nitroso compounds, sulfonyl hydrazines, sulfonyl semicarbazides, ammonium, and azo type compounds.
31. The process of claim 25 wherein said gas from said blowing agent is substantially an inert gas.
32. The process of claim 25 wherein said gas impermeable film is selected from the group consisting of one or more polyolefins, polyurethanes, polyvinyls, polyethers, and polyesters.
33. The process of claim 25 wherein said gas impermeable film is selected from the group consisting of polyethylene/vinyl alcohol copolymers, poly(vinylidine chloride) copolymer, polyethylene terephthalate, polyamides, nylon, and thermoplastic polyurethane.
34. The process of claim 25 further comprising the step of applying an adhesive film between said foam core and said gas impermeable film.
35. The process of claim 25 wherein said heating occurs by applying an alternating radio frequency electric field across said molding cavity.
36. The process of claim 35 wherein said heating occurs by applying an alternating radio frequency dielectric field having a frequency between about 1 MHz to 100 MHz and a voltage between about 1000 V to 10,000 V.