JP3661913B2 - Method for producing plastic cylindrical molded body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a plastic cylindrical molded body having a pseudo-wood pattern or the like formed on its surface.
[0002]
[Prior art]
For buildings such as parks, fences such as walkways, retaining walls, etc., tubular composite molded bodies are used in which metal pipes are used as the core material and the surface is covered with plastic with a pseudo-wood pattern. It was.
[0003]
Since this type of pseudo-tree-shaped cylindrical composite molded body has a large difference in thermal expansion coefficient between the core metal tube and the coating resin layer, thermal expansion and thermal contraction are repeated during use, and the coating resin layer There is a drawback that cracks are likely to occur.
[0004]
In order to improve such drawbacks, Japanese Patent Application Laid-Open No. 8-216276 discloses that a hollow portion of a plastic hollow molded body having a thickness of 10 to 50 mm and a length of 1 m or more is provided with the hollow portion wall body. There has been proposed a plastic hollow molded body having a void and filled with a metal tube as a core material.
[0005]
The plastic hollow molded body uses an upper and lower mold having a pseudo-tree-like pattern on the inner surface, the upper and lower molds are opened, a cooling core is inserted therein, the upper and lower molds are then closed, and the upper and lower molds and the cooling mold are cooled. Cooling water is passed through the core and molten resin is poured into the upper and lower molds. The cooling core is pulled out from the cooled and solidified resin, and the upper and lower molds are opened to form a hollow molded body. A metal tube is used as a core material in the hollow molded body. It is manufactured by filling.
[0006]
[Problems to be solved by the invention]
The proposed plastic hollow molded body has a relatively thick plastic layer and uses a metal tube as the core material, so it is heavy and difficult to carry during construction. There is a problem in that a certain metal pipe slips out of the plastic layer and construction workability is poor. Also, cutting is not easy.
[0007]
In addition, since the plastic hollow molded body is obtained by a so-called cast molding method using an upper and lower mold, an upper and lower mold and a cooling core having the corresponding dimensions are required to obtain long products having different lengths. There is a problem that the equipment cost becomes high because it is necessary and the plastic layer is thick and the use of a metal tube as the core increases the manufacturing cost.
[0008]
The present invention solves the above-described problems, and the object of the present invention is to prevent cracks during use, and to be lightweight, have good workability, can be manufactured at low cost, and is further cut and halved. It is an object of the present invention to provide a method for manufacturing a plastic cylindrical molded body that can be easily post-processed into a flat shape or a flat plate shape, and has a pattern such as a pseudo-wood shape formed on the surface.
[0009]
[Means for Solving the Problems]
The method for producing a plastic cylindrical molded body of the present invention uses a screw extruder provided with a crosshead mold and introduces a cylindrical core made of a metal tube into the crosshead mold while screw extrusion. The plastic is melt extruded from the machine to the crosshead mold, the plastic is melt coated on the surface of the cylindrical core in the crosshead mold, and a coating resin layer is formed on the cylindrical core, The cylindrical core body on which the coating resin layer is formed is cooled by a cooling device until the coating resin layer is in a softened state, and a pair of mold rolls having a pattern such as a pseudo-tree shape while the coating resin layer is in a softened state The mold pattern is continuously molded on the surface of the coating resin layer, and then the cylindrical core body is pulled out from the coating resin layer. 5-10mm It characterized by producing a cylindrical molded body made of sticks, thereby to achieve the above object.
[0010]
[Action]
The plastic cylindrical molded body obtained according to the present invention has a thickness of 5 to 10 mm and is relatively thin, and does not use a core material such as a metal tube. Therefore, thermal expansion and contraction are repeated during use. Even if this occurs, the plastic does not crack, and it is lightweight and does not cause any trouble that the core material is displaced. Moreover, since it is relatively thick and has no core material, the material cost is low, and it becomes easy to post-process into half- and flat-plate products by cutting or the like.
[0011]
Furthermore, the method for producing a plastic cylindrical molded body of the present invention is obtained by a process of extrusion-coating plastic onto a cylindrical core body, a molding process using a molding roll, and a cylindrical core body drawing process. Compared with what is obtained by the casting method to be used, it is possible to obtain long products having different lengths with the same equipment, and the equipment cost is reduced. Further, since the wall thickness is 5 to 10 mm and the wall thickness is relatively thin, the molding distortion is small, and the cylindrical core can be easily pulled out from the coating resin layer.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. FIG. 1 is a partially cutaway perspective view showing an example of a plastic cylindrical molded body obtained by the present invention, and FIG. 2 is an explanatory view showing an example of a method for producing a plastic cylindrical molded body of the present invention.
[0013]
In FIG. 1, 10 is a plastic cylindrical molded body obtained by the present invention, and 11 is a pattern such as a pseudo-tree formed on the surface thereof. Here, as the plastic, thermoplastic resins such as polyethylene, ethylene-vinyl acetate copolymer, and vinyl chloride resin are used. Moreover, wood powder, a short fiber, an inorganic filler, a coloring agent, a foaming agent, a weather resistance improving agent, and other compounding agents may be added to these thermoplastic resins.
[0014]
As the pattern formed on the surface, various patterns having three-dimensional effects that can be molded, such as pseudo-wood, bamboo, stone, mosaic, and screw, are employed. Further, the cylindrical molded body 10 may have an elliptical shape or a rectangular shape as well as a circular cross section.
[0015]
And the thickness of the plastic cylindrical molded object 10 shall be 5-10 mm. When the wall thickness is less than 5 mm, the mechanical strength is reduced. Conversely, when the wall thickness exceeds 10 mm, not only the material cost is increased, but also the molding distortion is increased, and the resin coating layer is formed when the plastic cylindrical molded body 10 is molded. It becomes difficult to pull out the cylindrical core from the core, and it becomes difficult to post-process into a half-cut or flat product by cutting. Here, the said thickness refers to the whole thickness including a pattern.
[0016]
As shown in FIG. 2, the plastic cylindrical molded body 10 of the present invention uses a screw extruder 20 provided with a crosshead mold 21 and the crosshead mold 21 is like a metal tube. While introducing the cylindrical core 30, the plastic is melt-extruded from the screw extruder 20 to the crosshead mold 21, and the plastic is melt coated on the surface of the cylindrical core 30 in the crosshead mold 21. The covering resin layer 10a is formed.
[0017]
Next, the cylindrical core body 30 coated with the plastic is cooled by the cooling device 40 so that the temperature of the coating resin layer 10a is adjusted to the softening temperature of the resin, and while the coating resin layer 10a is in the softened state, A pair of mold rolls 50 having a pattern is passed between them, and a pattern 11 such as a pseudo-tree is continuously molded on the surface of the coating resin layer 10a. Since each of the pair of mold rolls 50 has a drum shape and the coating resin layer 10a is supported by the cylindrical core body 30, the mold is easy to mold.
[0018]
Thereafter, the cylindrical core body 30 is pulled out from the coating resin layer 10a, thereby forming a cylindrical shape. In order to pull out the cylindrical core body 30 from the coating resin layer 10a, the surface of the cylindrical core body 30 is previously treated with a silicon-based release agent or a fluorine-based release agent, and further, a lubricating oil is applied and coated. The surface of the resin layer 10a is fixed with a fixing tool fitted with rubber having a good anti-slip property, and the cylindrical core body 30 is easily pulled by pulling only the cylindrical core body 30 with an appropriate tension instrument. Is pulled out.
[0019]
In addition, the cylindrical core 30 may be configured by a split mold that can be reduced, and the split core may be reduced to pull out the cylindrical core 30. In this way, a plastic cylindrical molded body 10 having a pseudo-wood pattern 11 formed on the surface is obtained.
[0020]
The plastic cylindrical molded body 10 obtained by the present invention is cut into an appropriate length, and a large number of them are arranged or combined, and used for, for example, a structure such as a park, a fence such as a promenade, and a retaining wall. The In this case, the upper end or both ends of the plastic cylindrical molded body 10 are usually covered with a cap.
[0021]
Further, the plastic cylindrical molded body 10 obtained by the present invention is relatively thin and does not have a core material such as a metal tube, so it is easy to process, and is cut into a half or flat product. It can be post-processed and used for wall materials and roofing materials.
[0022]
【The invention's effect】
Since the method for producing a plastic cylindrical molded body of the present invention is configured as described above, the plastic cylindrical molded body obtained according to the present invention does not generate cracks during use, and is light in construction. Workability is good and can be manufactured at low cost. Further, it is easy to post-process in half or flat, and the surface is formed with a pattern such as a pseudo-tree, so structures such as parks, fences such as walkways, It can be used for a wide range of applications such as retaining walls, wall materials and roofing materials.
[Brief description of the drawings]
FIG. 1 is a partially cutaway perspective view showing an example of a plastic cylindrical molded body obtained by the present invention.
FIG. 2 is an explanatory view showing an example of a method for producing a plastic cylindrical molded body of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Plastic cylindrical molded body 10a Covering resin layer 11 Pseudo-woody pattern 20 Screw extruder 21 Crosshead mold 30 Cylindrical core 40 Cooling device 50 Molding roll

Claims (1)

Using a screw extruder equipped with a crosshead mold, a plastic core is melt-extruded from the screw extruder to the crosshead mold while a cylindrical core made of a metal tube is introduced into the crosshead mold. A plastic is melt-coated on the surface of the cylindrical core body in a head mold, a coating resin layer is formed on the cylindrical core body, and then the cylindrical core body on which the coating resin layer is formed is cooled. The coating resin layer is cooled until it becomes softened, and is passed between a pair of mold rolls having a pattern such as a pseudo-tree while the coating resin layer is in the softened state, and the pattern is formed on the surface of the coating resin layer. And then pulling out the cylindrical core body from the coating resin layer, so that a mold pattern such as a pseudo-wood shape is formed on the surface, and a cylindrical molded body made of plastic having a thickness of 5 to 10 mm is manufactured. Specially Method for producing a plastic cylindrical molded bodies to.

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