Expanded pellets and method for manufacturing molded components using them
The invention refers to a method for producing expanded polymer pellets, which comprises the following steps: melting a polymer comprising a polyamide; adding at least one blowing agent; expanding the melt through at least one die for producing an expanded polymer; and pelletizing the expanded polymer. The invention further concerns polymer pellets produced with the method as well as their use, e.g. for the production of cushioning elements for sports apparel, such as for producing soles or parts of soles of sports shoes. A further aspect of the invention concerns a method for the manufacture of molded components, comprising loading pellets of an expanded polymer material into a mold, and connecting the pellets by providing heat energy, wherein the expanded polymer material of the pellets or beads comprises a chain extender. The molded components may be used in broad ranges of application.
1. Method for the manufacture of molded components, comprising
a. forming pellets of a foamed, expanded polymer material comprising:
melting a polymer to form a melt,
adding at least one blowing agent and a chain extender to the melt,
expanding the melt through at least one die to produce a foamed, expanded polymer, and
pelletizing the foamed, expanded polymer;
b. loading the pellets of the foamed, expanded polymer material into a mold, wherein the foamed, expanded polymer material is selected from at least one of polyamide, polyester, polyetherketone, and polyolefin;
wherein the polyamide is at least one of homopolyamide, copolyamide, polyetherblockamide, and polyphthalamide;
wherein the polyester is at least one of polybutylene terephthalate (PBT), thermoplastic polyester ether elastomer (TPEE), and polyethylene terephthalate (PET);
wherein the polyetherketone is at least one of polyether ketone (PEK), polyether ether ketone (PEEK), and polyetherketoneketone (PEKK); and/or
wherein the polyolefin is at least one of polypropylene (PP), polyethylene (PE), olefin co-block polymer (OBC), polyolefin elastomer (POE), polyethylene co-vinyl acetate (EVA), polybutene (PB), and polyisobutylene (PIB); and
c. connecting the pellets by providing heat energy; wherein the pellets are connected to one another at their surfaces while substantially retaining their individual pellet shapes.
2. Method according to claim 1 , wherein the foamed expanded polymer material comprises a semi-crystalline polymer.
3. Method according to claim 1 , wherein the heat energy is provided by means of at least one of the following: pressurized steam, electromagnetic radiation, radio frequency radiation, microwave radiation, infrared radiation, ultraviolet radiation, electromagnetic induction.
4. Method according to claim 1 , wherein during step c., the pellets are heated to a temperature between a glass transition temperature and below the onset of melting of the foamed, expanded polymer material.
5. Method according to claim 4 , wherein during step c., the pellets are heated up to a range of from 100° C. to 5° C. below the melting point of the foamed, expanded polymer material.
6. Method according to claim 1 , wherein the chain extender comprises at least one selected from a polymeric material containing epoxy groups, pyromellitic dianhydride, and styrene maleic anhydride, or combinations of one or more thereof.
7. Method according to claim 6 , wherein the chain extender is a styrene-acrylate copolymer containing reactive epoxy groups.
8. Method according to claim 6 , wherein the chain extender is a styrene-acrylate copolymer containing reactive epoxy groups having the following formula:
wherein R 1 to R 5 are H, CH 3 , a higher alkyl group, or combinations of them; R 6 is an alkyl group, and x, y, and z are each between 1 and 20.
9. Method according to claim 1 , wherein the chain extender is selected from one or more of a tri-epoxide or tetra-epoxide.
10. Method according to claim 1 , wherein the chain extender is selected from one or more of styrene maleic anhydride.
11. Method according to claim 1 , wherein the chain extender is pyromellitic dianhydride.
12. Method according to claim 1 , wherein the chain extender is added in an amount from 0.1 to 20% by weight based on 100% by weight of the base polymer material to provide amorphous regions in the expanded polymer material allowing interdiffusion of polymer chains across the interfaces of the pellet boundaries.
13. Method according to claim 1 , wherein the chain extender is added in an amount from 1 to 10% by weight based on 100% by weight of the polymer material.
14. Method according to claim 1 , wherein the chain extender is added in an amount from 1 to 5% by weight based on 100% by weight of the polymer material.
15. Method according to claim 1 , wherein the blowing agent is added in an amount from 1 to 20% by weight based on 100% by weight of the polymer material.
16. Method for the manufacture of molded components, comprising
a. forming pellets of a foamed, expanded polymer material comprising:
melting a polymer to form a melt,
adding at least one blowing agent and a chain extender to the melt,
expanding the melt through at least one die to produce a foamed, expanded polymer, and
pelletizing the foamed, expanded polymer to form a spherical, ellipsoid, or triangular shape;
b. loading pellets of the foamed, expanded polymer material into a mold, wherein the foamed, expanded polymer material is selected from at least one of polyoxymethylene (POM), polyvinylidene chloride (PVCD), polyvinylalcohol (PVAL), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene (FEP), ethylene-tetrafluoroethylene (ETFE), polyvinylfluoride (PVF), perfluoroalkoxy (PFA), and thermoplastic polyurethanes (TPU); and
c. connecting the pellets by providing heat energy; wherein the pellets are connected to one another at their surfaces while substantially retaining their individual pellet shapes.
17. Method according to claim 16 , wherein the chain extender comprises at least one selected from a polymeric material containing epoxy groups, pyromellitic dianhydride, styrene maleic anhydride, or combinations of one or more thereof.
18. Method according to claim 16 , wherein the chain extender is added in an amount from 1 to 10% by weight based on 100% by weight of the polymer material.
19. Method according to claim 16 , wherein the chain extender is added in an amount from 1 to 5% by weight based on 100% by weight of the polymer material.
20. Method according to claim 16 , wherein the blowing agent is added in an amount from 1 to 20% by weight based on 100% by weight of the polymer material.