JPS623922A - Manufacture of heat insulating pipe - Google Patents

Abstract

PURPOSE:To continuously manufacture a uniform expanded layer with high expansion ratio in a short period of time by a method wherein a stock pipe as core material, the expanded layer and a skin layer are extruded simultaneously by employing a long land die as the extruder die of an extruder. CONSTITUTION:Composition for forming expanded layer 2, composition for forming core material pipe 3 and composition for forming skin layer are simultaneously supplied to an extruder 1 so as to be extruded in the predetermined order at a long land die 5. The expanded layer formed onto the surface of a core material pipe is typically polyethylene expanded layer and formed at the expansion ratio of 20-60%. Because the forming is fully developed in the long die, the length in extrusion direction of which is at least 5 times and preferably 10 times as long as the diameter of a stock pipe, the extent of foaming of the expanded layer becomes nearly uniform and, in addition, the expansion ratio of the expanded layer is also improved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing an insulated pipe, and more particularly to a method for manufacturing an insulated pipe having a foam layer and a skin layer formed on the surface of the pipe by co-extrusion molding.

[Conventional technology]

One of the methods of manufacturing conventional insulated pipes, more specifically, insulated pipes with a foam layer formed on the surface of the pipe, is to extrude and form a foam layer on the surface of a pre-fabricated pipe using an extrusion molding machine. . In this method, a foamed composition for forming a foamed layer is extruded onto the surface of a pipe through an extrusion die using an ordinary extruder, and then foamed to form a foamed layer.

However, with this conventional manufacturing method using an extruder, it is very difficult to uniformly form a heat insulating foam layer on the pipe surface, and it is very difficult to continuously extrude a pipe with a uniform heat insulating foam layer formed. It's difficult. In particular, as the diameter of the pipe becomes larger, this disadvantage tends to become more severe. A pipe on which such a non-uniform foam layer is formed not only has a problem with its appearance, but also has a non-uniform diameter, which is a fatal drawback in that it is impossible to manufacture a pipe with a uniform diameter.

Furthermore, in the conventional extrusion molding method, the foaming ratio of the foamed layer is low, and there is also the drawback that it is difficult to form a foamed layer with a high expansion ratio on the pipe-1-.

In addition, in the conventional method, extrusion molding is performed on a separately manufactured pipe, and the steps of manufacturing the pipe and forming the heat insulating foam layer are performed separately, which not only requires multiple steps, but also requires multiple steps. This method requires additional equipment and manufacturing time, and is not necessarily an industrially optimal method.

[Purpose and outline of the invention]

The purpose of the present invention is to provide an extrusion molding method that can solve the problems of the conventional extrusion molding method. The objective is to develop a method that can be easily manufactured.

Another object of the present invention is to provide a method for manufacturing an insulated pipe in which pipe manufacturing and foam layer formation can be performed simultaneously. The purpose of the present invention is to manufacture an insulated pipe in which a foam layer and a skin layer are formed on the surface of the pipe.
This is achieved by coextruding the pipe, the foam layer and the skin layer using an extrusion molding machine and using a Longland die as the extrusion die.

[Structure of the invention]

The structure of the present invention basically consists of simultaneously extruding a pipe, a heat insulating layer, and a skin layer using an extrusion molding machine, and using a conventional conventional extrusion die as an extrusion die of the extrusion molding machine. The key is to use maple long land dice.

The long land die is a die that is considerably longer in the extrusion direction than the ordinary extrusion die used in conventional extrusion molding machines. Its length in the extrusion direction is l
This die has a length that is at least 5 times, preferably 10 times or more, the diameter of the material pipe that is the core material of the 1fI heat pipe, that is, the material pipe on which the foam layer is to be formed, and is different from a conventional ordinary die. are fundamentally different in this respect.

In the present invention, when using this long land die, its length is appropriately determined within the above range according to the diameter of the target pipe. At this time, if the length of the long land die is not particularly long compared to the diameter of the pipe, it will be difficult to form a uniform foam layer, and the foaming ratio will not improve significantly.

The long land die itself is the same as a normal extrusion die, except that its length in the extrusion direction is longer than a normal extrusion die.For example, there are no particular differences from a normal extrusion die, such as its material. do not have.

In carrying out the present invention, a long land die is used as an extrusion die of an extrusion molding machine, and a material pipe as a core material, a foam layer, and a skin layer are simultaneously extruded. A more detailed explanation will be given below using the drawings. However, FIG. 1 is a flow sheet showing a specific example of implementing the method of the present invention. FIG. 2 also shows a heat insulating pipe with a foam layer formed thereon for reference.

In Fig. 1, (1) is a pipe extrusion molding machine,
(2) shows an extruder for forming a foam layer, (3) shows a composition for forming a core pipe, and (4) shows an extruder for forming a skin layer. This extrusion molding machine (1) is equipped with an r=land die (5), and is supplied to the foam layer forming extruder (1), and is simultaneously extruded in a predetermined order by the long land die (5). At this time, the extrusion molding machine (1) can also be cooled with cooling air or gas. - The force land die (5) is supplied with lubricant from a lubricant tank (7) via a pump (8) and a pipe (6) in order to perform extrusion molding smoothly. By extrusion molding in the long runt die (5), the composition for forming a core pipe is formed into a core pipe of a predetermined size, and the composition for forming a foam layer is foamed on the surface of this core pipe. A foam layer is formed with a predetermined thickness, and a skin layer is further formed on the foam layer.

A heat insulating pipe extruded from the longland die (5) is thus formed continuously and cooled, for example, in a water bath (9). At this time, it is preferable to cool the surface of the long land die, preferably near the outlet side, using a shower (10) or the like.

The structure of the insulated pipe of the present invention thus manufactured is as shown in FIG. In Figure 2, (11) is the core pipe, and (12) is the fil! The layer (13) is a skin layer.

The present invention further includes the following aspects. That is, when carrying out the present invention, it is usual to carry out the invention while supplying lubricant to the long land die as explained above, but at this time, a pressure gauge is provided on the pump for supplying lubricant, By detecting the press-in pressure of the supplied lubricant, extrusion conditions such as extrusion temperature and extrusion speed can be adjusted, and the degree of foaming of the foam layer can be easily adjusted.

This is based on the reason that when the degree of foaming in the long land die changes, the supply pressure of the lubricant to be supplied changes, so the degree of foaming can be determined by detecting the supply pressure. Therefore, by this detection, it becomes possible to adjust the foaming conditions, especially the foaming temperature, and the degree of foaming can be controlled extremely easily. This means of adjusting the degree of foaming by detecting the lubricant injection pressure is extremely suitable for manufacturing long insulated pipes, and enables extrusion molding of long insulated pipes under stable conditions. .

In the method of the present invention, the core pipe, the foam layer, and the skin layer are extruded at the same time, but it has never been known to extrude these three structural parts at the same time. This is a new method, and it is completely unknown whether or not these three structural parts can be extruded at the same time. It was previously unknown whether a pipe with a uniform foam layer could be produced by simultaneous extrusion molding using a new extrusion die that had never been used before, and the inventor of the present invention This is a completely new technical means discovered for the first time through research.

In the present invention, a composition capable of forming a pipe is used as the composition for forming the core pipe, and a preferable example is a composition mainly composed of a synthetic resin. As the composition for molding synthetic resin pipes in this case, any composition that has been conventionally used for manufacturing synthetic resin pipes can be effectively used, such as polyolefins, particularly crosslinkable polyolefins (for example, crosslinkable polyethylene).
An example is a composition mainly composed of.

The foam layer formed on the surface of the core material pipe is typically a 3 m regular polyethylene foam layer, with a foaming ratio of 10 to 70.
%, preferably about 20 to 60%. In addition, in the method of the present invention, since a long land die is particularly used, foaming is significantly suppressed compared to the conventional method, and there is a great effect that a foamed layer with a high foaming rate can be formed. A foam layer with a high expansion ratio reaching 50 to 70% can only be achieved by sufficiently foaming in a long land die, that is, a die with a particularly large length in the extrusion direction, as in the present invention. This is one of the key features of the present invention.

Further, as the composition for forming the skin layer used in the present invention, any of the skin layer forming compositions conventionally used are effective in a wide range.

Can be used.

In the method of the present invention, not only long insulated pipes can be manufactured, but also pipes with large diameters can be manufactured.

□In the present invention, when forming a foam layer on a pipe, a skin layer, that is, an outer skin protection layer, is usually extruded at the same time. A conventionally known skin layer itself is sufficient.

[Effects of the present invention]

In the method of the present invention, as described above, a long land die is particularly used as an extrusion die, so that a uniform foam layer can be obtained, and a foam layer with a high expansion ratio can also be obtained. More specifically, since we use an extrusion die with a particularly long length in the extrusion direction, sufficient foaming occurs within this long die, so the degree of foaming is almost uniform, and the foaming ratio is also greatly improved. . Even though the pipe is extruded between long dies called long land dies, by supplying lubricant to the long land dies, effective and smooth extrusion is possible.

In addition, by detecting the press-in pressure when lubricant is supplied, the degree of foaming can be easily determined, and the foaming conditions can be adjusted very easily. This effect is particularly suitable for extruding long pipes, and allows a stable and uniform foam layer to be formed on long pipes.

A particularly significant effect of the present invention is that the core material pipe and the foam layer can be formed at the same time by extrusion molding, which makes it possible to manufacture an insulated pipe in a single process in an extremely short period of time. be.

〔Example〕

Examples and comparative examples are shown below to make the features of the present invention more clear.

Examples 1 and 2 and Comparative Examples 1 and 2 Vibrators were manufactured using the flow sheet shown in FIG. 1 under the conditions shown in Table 1 below. However, the numerical values in the section of constituent materials in Table 1 below indicate the actual value. Further, the physical properties of the obtained pipe are shown in Table 2.

Table 1 However, Notes 1) to (Note 5) indicate the following, respectively.

Note 1: P, P-oxybis-(henzensulfonylhydraside) Chemical formula 2 = Extrusion of the foam layer and extrusion of the skin layer are performed separately in separate processes on a pre-fabricated specified pipe material. .

Note 3: A foam layer and a skin layer are simultaneously extruded onto a pre-fabricated specified pipe material.

E4: Material pipe, foam layer, and skin layer extruded at the same time.

Note 5: Polyoxymethylene-polyoxypropylene copolymer (manufactured by NOF Corporation) Table 2

[Brief explanation of drawings]

FIG. 1 is a drawing showing a flow sheet of the present invention, and FIG. 2 is a drawing showing a cross-sectional view of an insulated pipe. (1) Pipe extrusion molding machine (2)
, Extruder for forming foam layer (3), Composition for forming core pipe (4), Extruder for forming skin layer (5), Length Land dice (6), Pipe (7), Lubricant tank (8), Pump (9), Water tank (10), , Shower (11) , Core material pipe (12) , Foam layer (13) , Skin layer (hereinafter referred to as -F-)

Claims (3)

[Claims] (1) When manufacturing a heat insulating pipe in which a foam layer and a skin layer are formed on the pipe surface, an extrusion molding machine is used, and a Nagaland die is used as the extrusion die to form the pipe, foam layer, and skin layer. A method for producing an insulated pipe, characterized by co-extrusion molding. (2) The method for manufacturing a heat insulating pipe according to claim 1, wherein extrusion molding is carried out while supplying a lubricant to a long land die. (3) The method for manufacturing an insulated pipe according to claim 2, wherein the extrusion conditions are adjusted by detecting the supply pressure when supplying the lubricant.