Method and device for producing a pipe member
An object of the present invention is to provide a method for producing a pipe, which is capable of reducing the amount of thermoplastic material, without complicating an device for producing a pipe. The present invention provides a method for producing a pipe, comprising a thermoplastic material filling process for filling a die with a thermoplastic material, and a thermoplastic material discharging process for pushing out an unsolidified part of the thermoplastic material in the molding die using pressurized fluid, wherein the thermoplastic material is mixed with a foaming agent, the method further comprises a process for foaming the thermoplastic material filling the molding die, and the thermoplastic material discharging process is a process for pushing out a inner part of the thermoplastic material foamed in the molding die, by using the pressurized fluid prior to solidification of the inner part.
1. A method for producing a pipe member, comprising:
filling a molding die with a thermoplastic material containing a foaming agent;
foaming the thermoplastic material in the molding die while controlling pressure and temperature conditions inside the molding die to provide a foamed core layer and a non-foamed skin layer; and
discharging an unsolidified part of the thermoplastic material from the molding die by introducing or flowing pressurized fluid into the thermoplastic material in the molding die prior to a solidification of the core layer and using the pressurized fluid directly contacting the unsolidified thermoplastic material to push the unsolidified thermoplastic material out of the molding die and out of the skin layer.
2. The method for producing a pipe member according to claim 1 , wherein the thermoplastic material is thermoplastic or thermoplastic elastomer, and the foaming agent is carbon dioxide and/or nitrogen and is mixed with the thermoplastic material at a temperature and a pressure at which the carbon dioxide and/or the nitrogen can be kept in a supercritical fluid state.
3. The method for producing a pipe member according to claim 1 , wherein the pressurized fluid is made of nitrogen gas and/or water.
4. The method for producing a pipe member according to claim 1 , wherein the pressurized fluid is made of air and/or water.
5. The method for producing a pipe member according to claim 1 , wherein the thermoplastic material is further mixed with a melt tension modifier.
6. The method for producing a pipe member according to claim 1 , wherein the thermoplastic material is further mixed with reinforced fibers.
7. An device for producing a pipe member, comprising:
a molding die for molding a pipe member;
thermoplastic material filling means for filling the molding die with a thermoplastic material; and
thermoplastic material discharging means for introducing or flowing pressurized fluid into direct contact with the thermoplastic material in said molding die to thereby push out an unsolidified part of the thermoplastic material in the molding die,
wherein the molding die is provided with a controller which controls temperature and pressure conditions of thermoplastic material in said molding die,
wherein the thermoplastic material filling means has thermoplastic material supply means, foaming agent supply means, and a thermoplastic material injection machine that mixes the thermoplastic material supplied by the thermoplastic material supply means with a foaming agent supplied by the foaming agent supply means and injects the mixture,
the thermoplastic material discharging means has a fluid tank, pressurizing means for pressurizing fluid stored in the fluid tank, and a fluid control valve for controlling flow of the pressurized fluid from the fluid tank into thermoplastic material in said molding die, and
after the molding die is filled with the thermoplastic material mixed with the foaming agent by using the thermoplastic material injection machine, and the thermoplastic material in said molding die is foamed under temperature and pressure control by said controller, the fluid control valve is opened to push out an unsolidified and foamed thermoplastic material in the molding die by using the fluid pressurized by the pressurizing means.
8. The device for producing a pipe member according to claim 7 , wherein the foaming agent is carbon dioxide and/or nitrogen and is supplied by the foaming agent supply means into the thermoplastic material injection molding machine in which a temperature and a pressure are equal to or greater than those at which the carbon dioxide and/or the nitrogen become supercritical fluid.
9. The device for producing a pipe member according to claim 7 , wherein the foaming agent is carbon dioxide and/or nitrogen, and the carbon dioxide and/or the nitrogen, which is in a supercritical fluid state beforehand, is supplied from the foaming agent supply means to the thermoplastic material injection molding machine.
10. The device for producing a pipe member according to claim 7 , wherein the thermoplastic material filling means is configured to fill the molding die with the thermoplastic material mixed with a melt tension modifier.
11. The device for producing a pipe member according to claim 7 , wherein the thermoplastic material filling means further has melt tension modifier supply means, and
the thermoplastic material injection machine mixes the thermoplastic material supplied by the thermoplastic material supply means with the foaming agent supplied by the foaming agent supply means and a melt tension modifier supplied by the melt tension modifier supply means, and injects the mixture.
12. The device for producing a pipe member according to claim 7 , wherein the thermoplastic material filling means is configured to fill the molding die with the thermoplastic material mixed with reinforced fibers.