JPH0127848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for integrally molding a pipe cover made of foamed synthetic resin to serve as a heat insulating layer on the outer peripheral surface of a plastic pipe.

(Prior Art) When insulating piping for air conditioning equipment, etc., it is common to cover the pipe with a separately molded insulating pipe cover made of foamed synthetic resin. However, this method of adhesion requires the first step of adhering the pipe cover to the pipe, which is difficult to work with, and also requires creating a crack in the longitudinal direction of the pipe cover during adhesion. The cracks had to be taped, and it was not always possible to achieve a finish that was desirable not only in terms of workability but also in terms of appearance. Moreover, since the pipe cover is a foam molded product, when it is molded, it is extruded from the extrusion head H with an inner diameter r' that is approximately one-fifth of the inner diameter r of the product, as shown in Figure 3. After extrusion, the product is foam-molded to the desired size, but due to variations in foaming conditions, it is not always possible to obtain the desired pipe cover C. In particular, the dimensions of the inner diameter of the pipe cover and the outer diameter of the pipe This left a serious problem in that there were often cases where they did not match.

In response, an attempt was made to use the pipe as an insert and extrude cover material resin around the outer periphery of the pipe and mold it integrally, but as mentioned above, if the cover material resin foams in its natural state after extrusion, it will expand by about 5 times. Due to its size, it cannot be attached integrally to the pipe. On the other hand, the cover material resin is about one-fifth of the product.
If you try to extrude with a size of , you will not be able to insert the pipe into the die.

(Problems to be solved by the invention) However, as a result of various researches, the present inventor has found that
The cover material resin, which is a foamed resin, is not foamed in the molten state in the die, and if this state is maintained, welded with the pipe material resin and extruded, and foam molded after extrusion, the desired purpose can be achieved. They discovered this. Therefore, the object of the present invention is to provide a method for integrally and simultaneously extruding a pipe and a pipe cover, and in particular, to extrude a pipe cover made of a foamable synthetic resin around the outer periphery of a pipe made of a non-foaming synthetic resin. The present invention aims to provide a method for integrally and simultaneously extrusion molding.

(Means for solving the problem) A pipe material molten resin made of a non-foaming synthetic resin is fed from one extruder into a single die, and a pipe material molten resin made of a non-foaming synthetic resin is fed from another extruder into a single die. Supplying molten resin for the cover material made of a certain foamable synthetic resin,
A pipe is molded from the pipe material molten resin in the die, and the cover material molten resin is welded to the outer peripheral surface of the pipe in a non-foamed state, and after the molded product is extruded from the die, its outer periphery is The present invention relates to a method of integrally molding a pipe cover made of a foamed synthetic resin around the outer periphery of a synthetic resin pipe, which is characterized by foaming a foamed synthetic resin layer of the surface cover material.

(Example) The details will be explained below.

First, as shown in FIG. 2, a product P1 obtained by the present invention is one in which a pipe cover 9 made of foamed synthetic resin is integrally molded around the outer periphery of a synthetic resin pipe 8. The most important point in this invention is that the synthetic resin 8a constituting the pipe 8 and the foamed synthetic resin 9a constituting the pipe cover 9 are the same type of synthetic resin or are compatible. To give a typical example, when the cover material resin 9a is a foamed polyethylene resin, a non-foamed polyethylene resin or a polyolefin resin such as a polypropylene resin is selected as the pipe material resin 8a.

FIG. 1 is a cross-sectional view of a main part centered on a die 10 showing a method of molding the product P1 shown in FIG. Extruder 1 for material resin 8a
3 is connected to an extruder 12 for a cover material resin 9a, such as foamed polyethylene resin.

As shown in the figure, the pipe material molten resin 8a is extruded from the rear of the die 10 onto the outer periphery of the core bar 11, and at the same time, the cover material molten resin 9a is extruded from the rear of the die 10 onto the outer periphery of the pipe material molten resin 8a. is extruded. At this time, the cover material resin 9a is still in an unfoamed state, and since it is the same type of resin or a compatible resin with the pipe material resin 8a,
They are joined by welding.

This molded product is extruded from the exit of the die 10 while maintaining the integrally welded state of both molten resins. After extrusion, the cover material resin 9a begins to foam, but since the inside thereof is integrally welded with the pipe material resin 8a, it does not foam inward, but only in the outward direction. In this way, the pipe 8a having the desired pipe diameter and the pipe cover 9 made of a foamed layer around its outer periphery can be integrally and continuously extruded.

Thereafter, the product is made into a product through a known cooling process and cutting process, but in some cases, an extrusion process may be performed to further form a film on the outer periphery of the pipe cover 9.

(Effects) As described above, according to the invention method shown here, a pipe cover made of foamed synthetic resin can be integrally molded around the outer circumference of a pipe, so it is possible to mold the pipe cover made of foamed synthetic resin on the outside of the pipe. There is no need for the process of applying Moreover, by integrally molding the pipe cover, the pipe cover tightly adheres to the outer periphery of the pipe, which is effective in maintaining the appearance, and since there are no cracks or the like, its heat insulating effect is also improved.

Further, in this invention, since the pipe and the pipe cover are integrally and continuously molded, it contributes to economy such as simplifying the work process and reducing costs.

[Brief explanation of drawings]

Fig. 1 is a sectional view centered on a die showing an embodiment of the method of this invention, Fig. 2 is a partial perspective view of a product obtained by the method, and Fig. 3 is a conventional extrusion molding of a pipe cover. FIG. 3 is a cross-sectional view of the main parts of the extrusion head showing the process. 8...pipe, 9...pipe cover, 10, 20...
Dice, 12, 13...extruder.

Claims (1)

[Claims] 1. Into a single die, a pipe material molten resin made of non-foaming synthetic resin is fed from one extruder, and a cover material made of a foamable synthetic resin of the same type or compatible with the synthetic resin is fed from another extruder. A molten resin is supplied, a pipe is formed using the molten resin of the pipe material in the die, and the molten resin of the cover material is welded to the outer circumferential surface of the pipe in a non-foamed state, and the molded product is released from the die. A method for integrally molding a pipe cover made of foamed synthetic resin around the outer periphery of a synthetic resin pipe, which comprises foaming the foamed synthetic resin layer of the covering material on the outer periphery of the pipe after extrusion.