Claims
- 1. A method for producing a shaped resin article, which comprises:
- filling a first storage cavity having an inner volume with a molten core-layer resin which contains a foaming agent while applying pressure to a screw in the first storage cavity in such a manner as not to foam said molten core-layer resin,
- filling a second storage cavity with a molten skin-layer resin which does not contain a foaming agent,
- increasing the inner volume of the first storage cavity by retracting the screw of the first storage cavity to reduce the pressure exerted on the core-layer resin, thereby foaming said core-layer resin within the first storage cavity, and
- injecting the skin-layer resin from the second storage cavity and subsequently or simultaneously therewith injecting the foamed core-layer resin from the first storage cavity into a molding cavity to thereby form a shaped resin article.
- 2. The method according to claim 1, wherein said core-layer resin is foamed sufficiently by the increasing of the inner volume of the first storage cavity that the core-layer of the shaped resin article has a void ratio in the range of from 50 to 80%.
- 3. The method according to claim 1, wherein said foaming agent is selected from the group consisting of pentane, heptane, azodicarbonamide, sodium bicarbonate, and sodium citrate.
- 4. The method according to claim 1, wherein said skin-layer resin is injected into said molding cavity simultaneously with said core-layer resin.
- 5. A method for producing a shaped resin article, which comprises:
- filling a first storage cavity having an inner volume with a molten core-layer resin which contains a foaming agent while applying pressure to a screw in the first storage cavity in such a manner as not to foam said molten core-layer resin,
- filling a second storage cavity with a molten skin-layer resin which contains a foaming agent,
- increasing the inner volume of the first storage cavity by retracting the screw of the first storage cavity to reduce the pressure exerted on the core-layer resin, thereby foaming said core-layer resin within the first storage cavity,
- injecting the skin-layer resin from the second storage cavity and subsequently or simultaneously therewith injecting the foamed core-layer resin from the first storage cavity into a gas pressurized molding cavity, and
- releasing the gas pressure from said molding cavity after injecting the skin-layer resin and the core-layer resin into the molding cavity to thereby form a shaped resin article.
- 6. The method according to claim 5, wherein said core-layer resin is foamed sufficiently by the increasing of the inner volume of the first storage cavity that the core-layer of the shaped resin article has a void ratio in the range of from 50 to 80%.
- 7. The method according to claim 5, wherein said foaming agent is selected from the group consisting of pentane, heptane, azodicarbonamide, sodium bicarbonate, and sodium citrate.
- 8. The method according to claim 5, wherein said skin-layer resin is injected into said molding cavity simultaneously with said core-layer resin.
Parent Case Info
This application is a continuation of application Ser. No. 07/838,256 filed as PCT/JP90/01661 on Dec. 20, 1990, now abandoned.
US Referenced Citations (16)
Foreign Referenced Citations (8)
Number |
Date |
Country |
2256021 |
Jul 1975 |
FRX |
50-17476 |
Feb 1975 |
JPX |
51-68675 |
Jun 1976 |
JPX |
57-14968 |
Mar 1982 |
JPX |
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JPX |
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JPX |
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JPX |
2132932 |
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GBX |
Non-Patent Literature Citations (1)
Entry |
Machine Design, vol. 44, No. 6, 29 Jun. 1972, pp. 69-71, Ogorkiewicz R. M. "Sandwich Molding". |
Continuations (1)
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Number |
Date |
Country |
Parent |
838256 |
Apr 1992 |
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