Method of manufacturing a boot seal
View Patent ↗The present invention resides in a boot seal for use in sealing a joint. The joint comprises first and second relatively movable parts. The boot seal is configured in the form of a sleeve to extend between and around the vehicle relatively movable parts. The sleeve has a laminate wall which comprises at least two layers of thermoplastic elastomeric material which are bonded together. At least one of the layers is a stretch-toughenable polyester thermoplastic elastomer which has been diametrically stretched in an amount effective to increase the toughness of said one layer. The laminate wall has a percent elongation to rupture of at least 100, and a flexural modulus which is less than 100,000 psi. The laminate wall preferably has a puncture resistance of at least 50 Newtons/mm wall thickness.
1. A process for making a boot seal comprising the steps of:
(a) obtaining two plastics, at least one being a polyester resin;
(b) feeding said plastics separately into an extruder die;
(c) separately extruding said plastics from said extruder die as coaxial tubular molten streams, into a mold cavity having a corrugated inner wall;
(d) vacuum expanding the coaxial tubular molten streams against said mold cavity inner wall;
(e) cooling the molten streams while vacuum held against the mold cavity inner wall; and
(f) stretching said polyester resin to cause a molecular orientation for increasing the strength of said polyester resin, said polyester resin, when cooled, being stretch toughened to have a percent elongation to rupture of at least 100 and a flexural modulus less than 100,000 psi.
2. The process of claim 1 wherein the second of said two plastics is a polyolefin, and an adhesive bonding layer is co-extruded with and between said two molten streams.
3. The process of claim 1 wherein the two plastics are the same polyester resin and the plastic for the innermost molten stream of the coaxial molten streams contains a blowing agent.
4. The process of claim 1 wherein the polyester resin is a polyester material which is stretch toughenable to a puncture resistance of at least 50 Newtons/mm wall thickness.
5. The process of claim 1 wherein said vacuum expansion is at least 200%.
6. The process of claim 1 wherein said extrusion is continuous forming a continuous series of boot seals which are separable by cutting subsequent to cooling.
7. A boot seal made by the process of claim 1 .
8. A process of making a flexible part comprising the steps of:
(a) obtaining two plastics, at least one being a polyester resin;
(b) feeding said plastics separately into an extruder die;
(c) separately extruding said plastics from said extruder die as molten streams into a mold cavity having an inner wall of a desired shape;
(d) vacuum expanding the molten streams against said mold cavity inner wall;
(e) cooling the molten streams while vacuum holds the molten streams against the mold cavity inner wall; and
(f) stretching said polyester resin to cause molecular orientation for increasing the strength of said polyester resin, said polyester resin, when cooled, being stretch toughened to have a percent elongation to rupture of at least 100 and a flexural modulus less than 100,000 psi.
9. A process as set forth in claim 8 wherein, said polyester resin is a material which is stretch toughenable and said flexible part when cooled has a percent elongation to rupture of at least 100 and a flexural modulus less than 100,000 psi.
10. The process of claim 9 wherein another of said plastics is a thermoplastic elastomer which when expanded and cooled has a higher degree of flexibility and softness than said polyester resin, said polyester resin when expanded and cooled being tougher and having a greater resistance to hydrocarbon chemicals than said thermoplastic elastomer.
11. The process of claim 10 wherein said thermoplastic elastomer is a polyolefin.
12. The process of claim 8 wherein said plastics are extruded as coaxial tubular molten streams.