JPS6111197B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a three-layer structure by covering a core material with a thermoplastic resin foam and then covering it with a non-foaming resin. However, the object of the present invention is to provide a manufacturing method in which a three-layer structure can be continuously obtained by winding a linear foam around a core material and bringing it into close contact with the core material.

The gist of the present invention is to extrude and foam a foamable thermoplastic resin into a low-pressure zone through at least one discharge port provided in a mold that is rotatable with the axis of the core material moving in a straight line as the rotation axis, and to form a spiral onto the core material. After wrapping it into a shape,
The present invention relates to a method for manufacturing a three-layer structure, characterized in that the outer peripheral surface of the three-layer structure is covered with a non-foamable resin extruded from an annular extrusion port surrounding the outer peripheral surface thereof.

The core material used in the present invention is metal, synthetic resin,
It is a long body made of glass, rubber, wood, fiber, etc., and its forms include round rods, hollow tubes, rectangular rods,
Ropes etc. are used.

In addition, the foamable thermoplastic resin in the present invention is
It refers to a resin that is mixed with a blowing agent and can be foamed in a low pressure zone, and examples of the thermoplastic resin include polyethylene, polypropylene, polystyrene, vinylidene chloride, and ethylene-vinyl acetate copolymer. As a foaming agent for foaming such a thermoplastic resin, a gas or a volatile liquid under normal pressure, or a foaming agent that decomposes by heating can be used. Examples include gases such as nitrogen, carbon dioxide, and air, low-boiling aliphatic hydrocarbons such as propane, butane, and pentane, low-boiling organic compounds such as alcohols, ketones, and esters, monochlorodifluoromethane, dichlorodifluoromethane, and dichlorotetra. Examples include halogenated hydrocarbons such as fluoroethane, azodicarbonamide, dinitrosopentamethylenetetramine, and thermally decomposable blowing agents such as sodium bicarbonate.

The blowing agent may be mixed into the thermoplastic resin by feeding a mixture of the resin and the blowing agent into the extruder in advance, or by injecting the blowing agent into the middle of the cylinder of the extruder and heating and melting the resin. It may also be kneaded into a resin.

The type of non-foamable resin used in the present invention is not limited, and may be, for example, a foamable thermoplastic resin or other resins.

Next, the method of the present invention will be explained with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of the device used to carry out the method of the present invention together with an example of its use. For convenience of illustrating the structure of each part, some parts are not filled with resin. The condition is shown.

Reference numeral 1 denotes an outer mold having a discharge port 3 for a foamable thermoplastic resin 2, which is made rotatable via a bevel gear 4 about the axis of a core material 5, which will be described later, by a drive device such as an electric motor (not shown). ing. 7, the inner mold 6 is inserted into the hole drilled in the center, and the bolt 8 is inserted.
It is an annular flange fixed to the outer mold by.
The inner mold 6 has a built-in resin passage 9 that communicates with the discharge port 3 of the outer mold 1, and a flange 14 is fixed to the right end of the resin passage 9 by bolts 16.
4, the lower end of an L-shaped resin supply pipe 10 whose upper end is connected and fixed to an extruder (not shown) is fixed by welding.

A plurality of discharge ports 3 of the outer mold 1 may be provided,
Further, any shape such as circular, semicircular, rectangular, etc. can be adopted.

Reference numeral 11 denotes an annular member that presses and supports the outer peripheral portion of the outer mold 1, and is supported by bolts 13 via bearings 12.

Reference numeral 5 denotes a pipe-shaped core material that is supplied to a hole passing through the center of the inner mold 6 and sent out in the direction of arrow A by a feeder (not shown). The core material 5 may be cut into predetermined lengths, or may be continuously supplied by an extruder (not shown).

17 is connected to an extruder (not shown), and the core material 5
It is an extrusion mold provided so as to surround the foam 15 wound around the core material, and an annular extrusion port 19 is provided so that the non-foamable resin 18 is extruded in the same direction as the feeding direction of the core material. .

Next, when manufacturing a three-layer structure by the method of the present invention using the above-mentioned apparatus, the core material 5 is first moved in the direction of arrow A at a constant speed by a feeder (not shown).

On the other hand, a gaseous or liquid blowing agent is injected into the kneaded and melted resin by the extruder, and the molten resin containing the blowing agent further reaches the resin passage 9 through the resin supply pipe 10 connected to the extruder. do. Prior to or at the same time, the bevel gear 4 starts rotating by a drive device (not shown), and the outer mold 1 rotates about the axis of the core material as the rotation axis. Thereafter, the molten foamable thermoplastic resin 2 containing the foaming agent is further discharged into the atmosphere from the discharge port 3 through the resin passage 9 to become a foamed body 15. If the rotational speed of the outer mold 1, the viscosity of the foam immediately after discharge, the discharge angle of the discharge port, etc. are appropriately set, the foam 15 immediately after discharge will hang down on the outer surface of the core material due to its own weight.
As the outer mold adheres and rotates, it is wound helically around the core material 5 as shown in FIG.

Immediately after the foam is discharged, the foam can be attached to the core material using an adhesive tape, etc., if necessary, and the shape of the foam, that is, the shape of the discharge port, the discharge speed of the foam, and the movement of the core material can be freely attached. By appropriately adjusting the speed and the like, the foams can be uniformly fused and coated on the outer peripheral surface of the core material, or they can be overlapped or coated at appropriate intervals. Thereafter, the melt-kneaded non-foaming resin 18 is extruded from an annular extrusion port 19 using an extruder (not shown) to obtain a three-layer structure in which the outermost layer is a non-foaming resin.

In the method of the present invention, a foamable thermoplastic resin is extruded into a low-pressure zone through at least one discharge port provided in a mold that is rotatable with the axis of the core material moving in a straight line as the rotation axis, and the resin is foamed into the core material in a spiral manner. After wrapping it into a shape,
Since the outer circumferential surface is covered with non-foamable resin extruded from an annular extrusion port surrounding the outer circumferential surface, compared to the method of rotating the core material itself, even when using a very long core material, there is no wire attached to the core material. This results in a three-layer structure in which the thermoplastic resin foams are in close contact with each other, and the foams are also in close contact with each other, and the outermost layer is made of a non-foamable resin.

Next, examples of the method of the present invention will be shown.

EXAMPLE An apparatus shown in FIG. 1 was used in which the discharge port 3 had a rectangular shape of 1 mm x 30 mm with a small radius. 10 parts by weight of dichlorotetrafluoroethane and fine calcium carbonate powder per 100 parts by weight of polyethylene
A foamable thermoplastic resin 2 mixed with 0.5 parts by weight is introduced from the resin supply pipe 10 into the inner diameter 6, and the outer mold 1 is heated every minute.
While rotating at a rate of 53 times, it was discharged into the atmosphere at a rate of 18 g per minute. Resin 2 immediately foams to form a foam 15 with a thickness of 3 mm, width of 40 mm, and density of 0.05 g/cc.
was obtained at a speed of 3 m/min. On the other hand, prior to this, a steel pipe with an outer diameter of 30 mm was passed inside the inner mold 6 as the core material 5, and was moved toward the front of the inner mold 6 at a rate of 2.1 m/min. The foam 15 was tightly wound spirally around the surface of the steel pipe, and the foams were also fused adjacent to each other without overlapping each other.

Further, the polyethylene foam layer was covered with an ethylene-vinyl acetate copolymer extruded from the annular extrusion port 19 at a rate of 100 g per minute to form a three-layer structure.

Adhesion between the foamed layer and the non-foamed layer was also good.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of an apparatus used to carry out the method of the present invention, together with an example of its use. DESCRIPTION OF SYMBOLS 1... Outer mold, 2... Foamable thermoplastic resin, 3... Discharge port, 5... Core material, 15... Foam, 18... Annular extrusion port, 19... Non-foamable resin.

Claims (1)

[Claims] 1. Foamable thermoplastic resin is extruded into a low-pressure zone through at least one discharge port provided in a mold that is rotatable with the axis of the core material moving in a straight line as the rotation axis, and the core material is foamed. 1. A method for manufacturing a three-layer structure, which comprises wrapping the three-layer structure in a spiral manner, and then covering the outer circumferential surface of the structure with a non-foamable resin extruded from an annular extrusion port. 2. The manufacturing method according to claim 1, wherein the expandable thermoplastic resin is expandable polyethylene and the non-expandable resin is an ethylene-vinyl acetate copolymer.