Method of formulating low gravity sponge rubber for automotive weatherstrips

Abstract

The invention relates to automotive weatherstrip material. More specifically, the invention utilizes thermo-expand-able microspheres in the sponge bulb member of the weatherstrip to produce a microcellular structure which provides a lower weight weatherstrip material with improved surface appearance and comparable stiffness to known materials for use in the auto-motive industry, and exhibiting a blown specific gravity of less than about 0.60 g/cc.

1 - 7 . (canceled) 
     
     
         8 . A method of making a weatherstrip material comprising:
 a) providing a main body member dense rubber composition and processing the same to form a main body member of the weatherstrip;   b) providing a sponge bulb member less dense rubber composition as compared to the dense rubber composition in step (a) and processing the same to form a sponge bulb member;   c) prior to forming the sponge bulb member, mixing a microsphere physical blowing agent having a shell and core structure with the sponge bulb member composition of step (b);   d) heating the mixture of step (c) to volatilize the core and rupture the microsphere shells; and   e) extruding the material of steps (a) and (b) such that the main body member and the sponge bulb member are combined to form a weatherstrip having a main body member and a contiguous sponge bulb member, wherein the sponge bulb member exhibits a uniform pore structure having pores with a diameter of less than about 110μ and a blown specific gravity of up to about 0.60 g/cc.   
     
     
         9 . The method of  claim 8  wherein the main body member comprises at least a thermoplastic component. 
     
     
         10 . The method of  claim 8  wherein steps (b) and (c) are performed simultaneously. 
     
     
         11 . The method of  claim 8  wherein step (b) and step (c) are performed in sequence. 
     
     
         12 . The method of  claim 8  wherein step (a) and step (b) each include the addition of additives to the rubber composition. 
     
     
         13 . The method of  claim 8  wherein the composition of step (b) includes additives selected from the group consisting of accelerators, activators, chemical blowing agents, and physical blowing agents. 
     
     
         14 . The method of  claim 8  wherein the sponge bulb member exhibits a blown specific gravity of up to about 0.40 g/cc. 
     
     
         15 . A method of making a weatherstrip material comprising:
 a) providing a main body member dense rubber composition and processing the same to form a main body member of the weatherstrip;   b) providing a sponge bulb member less dense rubber composition as compared to the dense rubber composition in step (a) and processing the same to form a sponge bulb member;   c) prior to forming the sponge bulb member, mixing a microsphere physical blowing agent having a shell and core structure with the sponge bulb member composition of step (b);   d) heating the mixture of step (c) to volatilize the core and rupture the microsphere shells; and   e) extruding the material of steps (a) and (b) such that the main body member and the sponge bulb member are combined to form a weatherstrip having a main body member and a contiguous sponge bulb member, wherein the sponge bulb member comprises a uniform pore structure comprising open pores having a cross-sectional diameter of less than about 110μ and a blown specific gravity of up to about 0.60 g/cc;   wherein the sponge bulb member comprises an ethylene propylene diene terpolymer (EPDM);   wherein the EPDM of the sponge bulb member is a thermoset material; and   wherein the main body member comprises a thermoset EPDM.   
     
     
         16 . The method of  claim 15  wherein the main body member comprises at least a thermoplastic component. 
     
     
         17 . The method of  claim 15  wherein steps (b) and (c) are performed simultaneously. 
     
     
         18 . The method of  claim 15  wherein step (b) and step (c) are performed in sequence. 
     
     
         19 . The method of  claim 15  wherein step (a) and step (b) each include the addition of additives to the rubber composition. 
     
     
         20 . The method of  claim 15  wherein the composition of step (b) includes additives selected from the group consisting of accelerators, activators, chemical blowing agents, and physical blowing agents. 
     
     
         21 . The method of  claim 15  wherein the sponge bulb member exhibits a blown specific gravity of up to about 0.40 g/cc. 
     
     
         22 . A method of making a weatherstrip material comprising:
 a) providing a main body member dense rubber composition and processing the same to form a main body member of the weatherstrip;   b) providing a sponge bulb member less dense rubber composition as compared to the dense rubber composition in step (a) and processing the same to form a sponge bulb member;   c) prior to forming the sponge bulb member, mixing a microsphere physical blowing agent having a shell and core structure with the sponge bulb member composition of step (b);   d) heating the mixture of step (c) to volatilize the core and rupture the microsphere shells; and   e) extruding the material of steps (a) and (b) such that the main body member and the sponge bulb member are combined to form a weatherstrip having a main body member and a contiguous sponge bulb member, wherein the sponge bulb member comprises a uniform pore structure comprising open pores having a cross-sectional diameter of less than about 110μ and a blown specific gravity of up to about 0.40 g/cc;   wherein the sponge bulb member does not comprise thermoplastic vulcanizates;   wherein the sponge bulb member comprises an ethylene propylene diene terpolymer (EPDM);   wherein the EPDM of the sponge bulb member is a thermoset material; and   wherein the main body member comprises a thermoset EPDM.   
     
     
         23 . The method of  claim 22  wherein the main body member comprises at least a thermoplastic component. 
     
     
         24 . The method of  claim 22  wherein steps (b) and (c) are performed simultaneously. 
     
     
         25 . The method of  claim 22  wherein step (b) and step (c) are performed in sequence. 
     
     
         26 . The method of  claim 22  wherein step (a) and step (b) each include the addition of additives to the rubber composition. 
     
     
         27 . The method of  claim 22  wherein the composition of step (b) includes additives selected from the group consisting of accelerators, activators, chemical blowing agents, and physical blowing agents.