METHOD OF FORMULATING LOW GRAVITY SPONGE RUBBER FOR AUTOMOTIVE WEATHERSTRIPS
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.