Reactive injection molding process for manufacturing a two-colored molded product of polyurethanes

Claim 2

A reactive injection molding process for manufacturing a two-colored molded product of polyurethanes which is characterized by comprising the steps of: creating a reduced pressure in a mold cavity; injecting a surface-forming polyurethane material into said reduced pressure cavity; and injecting an inner-forming polyurethane material into said reduced pressure cavity, wherein said surface-forming polyurethane material injected into said cavity is cured to the extent that it may not be reduced in thickness by the streams of said inner-forming polyurethane material by the time when said inner-forming polyurethane material is subsequently injected.

Claim 3

A process as set forth in claim 2, wherein the curing of said surface-forming polyurethane material is achieved by forming said surface-forming polyurethane material with a higher rate of urethane reaction than said inner-forming polyurethane material.

Claim 4

A process as set forth in claim 2, wherein the curing of said surface-forming polyurethane material is achieved by adding an additional intervening step of allowing time for said surface-forming polyurethane material injected during said step of injecting a surface-forming polyurethane material to cure between said steps of injecting a surface-forming polyurethane material and injecting an inner-forming polyurethane material.

Claim 5

A process as set forth in claim 2, wherein the curing of said surface-forming polyurethane material is achieved by dividing said step of injecting a surface-forming polyurethane material into a first injection step and a second injection step, adding an additional step of time delay for allowing said surface-forming polyurethane material injected during said first injection step to cure intervening between said first and second injection steps.

Claim 6

A reactive injection molding process for manufacturing a two-colored molded product of polyurethanes which is characterized by comprising the steps of: placing in a mold cavity a metal core having a hollow portion and at least one open hole connected with said hollow portion, and locating said open hole in a final material filling portion of said cavity; creating a reduced pressure in said cavity, and in said hollow portion by evacuating it through said open hole; injecting a surface-forming polyurethane material into said reduced pressure cavity; and injecting an inner-forming polyurethane material into said reduced pressure cavity, wherein leading ends of streams of said inner-forming polyurethane material reach said final material filling portion and flow into said hollow portion through said open hole during said step of injecting inner-forming polyurethane material.

Claim 7

A process as set forth in claim 1, wherein said surface-forming polyurethane material contains a mold release agent while said inner-forming polyurethane material does not contain a mold release agent.

Claim 8

A process as set forth in claim 1, wherein said surface-forming polyurethane material has a higher rate of urethane reaction than said inner-forming polyurethane material.

Claim 9

A process as set forth in claim 2, wherein said surface-forming polyurethane material contains coloring matter while said inner-forming polyurethane material does not contain coloring matter.

Claim 10

A process as set forth in claim 2, wherein said surface-forming polyurethane material contains a mold release agent while said inner-forming polyurethane material does not contain a mold release agent.

Claim 11

A process as set forth in claim 4, wherein said step of injecting an inner-forming polyurethane material is divided into a first injection step and a second injection step, wherein an inner-forming polyurethane material free of any coloring matter is injected during said first injection step, and an inner-forming polyurethane material containing coloring matter is injected during said second injection step.

Claim 12

A process as set forth in claim 4, wherein said surface-forming polyurethane material has a higher rate of urethane reaction than said inner-forming polyurethane material.

Claim 13

A process as set forth in claim 5, wherein said step of injecting an inner-forming polyurethane material is divided into a first injection step and a second injection step, wherein an inner-forming polyurethane material free of any coloring matter is injected during said first injection step, and an inner-forming polyurethane material containing coloring matter is injected during said second injection step.

Claim 14

A process as set forth in claim 5, wherein said surface-forming polyurethane material has a higher rate of urethane reaction than said inner-forming polyurethane material.

Claim 15

A process as set forth in claim 6, wherein said metal core is supported by at least one support pin having a communicating passage and has a suction hole other than said open hole in which said pin can be connected to connect said passage with said hollow portion, and said hollow portion is evacuated through said suction hole and said passage, as well as through said open hole.

Claim 16

A process as set forth in claim 6, wherein said product is a polyurethane covering for a steering wheel, and said metal core has a hollow tubular ring connected to outer ends of a plurality of spokes extending from a central boss, said ring having said open hole.

Claim 17

A process as set forth in claim 16, wherein said open hole is located adjacent an end of one of said spokes.

Claim 18

A process as set forth in claim 6, wherein said surface-forming polyurethane material has a higher rate of urethane reaction than said inner-forming polyurethane material.