JPH0588171B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a resin extruder that is provided at a discharge port of a resin extruder,
The present invention relates to a mouthpiece for an apparatus for manufacturing a composite pipe having an intermediate layer of foamable resin between inner and outer layers made of synthetic resin.

[Conventional technology]

polyvinyl chloride, polyethylene, propylene,
Between the inner and outer layers made of synthetic resin such as polystyrene,
polyvinyl chloride, polystyrene, polyethylene,
In manufacturing a composite pipe made of synthetic resin having an intermediate layer of foamable resin made of polypropylene or the like, as shown in Japanese Patent Application Laid-Open No. 55-152030, a pipe is formed between a die ring and a mandrel. A die lip with an annular discharge port for extruding the foamable resin is disposed in the annular resin passage, and the foamable resin constituting the intermediate layer and the resin constituting the inner and outer layers are transferred to the outlet of the resin extruder for the inner and outer layers. The structure is such that they merge nearby.

[Problem to be solved by the invention]

However, it is desirable to foam the foamable resin inside the extruder as much as possible, and keep it at a low temperature in the nozzle to maintain that state. Of course, sufficient heating is required within the mouthpiece as well.

However, in the die shown in JP-A-55-152030, the outlet of the die lip is located near the outlet of the resin extruder for the inner and outer layers, so the foaming material is placed near the outlet of the resin extruder for the inner and outer layers. When the resin is introduced, the intermediate layer is affected by the heat of the resin extruder for the inner and outer layers, and the intermediate layer is unable to form closed cells due to abnormal foaming.
There is a problem with strength.

In addition, since the discharge port of the die lip is located upstream of the three-arm support member as a spider that supports the mandrel on the die ring, the three-arm support member, which is a spider that supports the mandrel on the die ring, The resin flow in the layer is divided by the three-arm support member, the resin flow is disturbed due to the difference in adhesion between the two types of resin, and even if they merge after passing through the three-arm support member, turbulence traces will appear on the outer surface.
This had a negative effect on the appearance of the extruded product.

Therefore, the present invention has been developed to provide a composite pipe that can obtain high-quality composite pipes without causing abnormal foaming of the foamable resin, improve the appearance of extruded products, and allow the use of ordinary single-layer resin extrusion ferrules as is. The purpose of the present invention is to provide a cap for a resin composite pipe manufacturing device.

[Means to solve the problem]

Therefore, in order to achieve the above object, the present invention provides a base for a manufacturing apparatus for extrusion molding a composite pipe having an intermediate layer of foamable resin between inner and outer layers made of synthetic resin.
An annular resin passage is provided between the die ring and the mandrel, a die lip having an annular discharge opening for extrusion molding the foamable resin is disposed in the resin passage, and the mandrel is supported by the die ring with the discharge opening. It is characterized by being located downstream of the spider.

[Effect]

In this way, because the die lip that forms the intermediate layer is placed in the resin passage between the die ring and the mandrel, the foamable resin can be foamed in a stable state without being affected by the heat of the extruder that extrudes the inner and outer layer resin. A middle layer can be constructed.

In addition, since three layers are formed behind the spider that supports the mandrel, the resin flow is not divided by the spider, so the resin flow is not disturbed by the difference in adhesiveness between the two types of resin, and the extruded product is The appearance becomes better.

〔Example〕

The embodiments shown in the drawings will be described below.

FIG. 1 shows, in a sectional front view, an embodiment in which a die ring is provided with a die lip forming an intermediate layer on a spider supporting a mandrel.

Inside the die ring 1, a mandrel 2 is supported by a plurality of spiders 4 with the torpedo 3 facing a resin extruder (not shown) for forming the inner and outer layers.
An annular resin passage is formed between the die ring 1 and the mandrel 2. The spider 4 is provided with an annular die lip 5, which divides the resin flow 6 supplied from the resin extruder for forming the inner and outer layers into two to form an inner layer 7 and an outer layer 8, and a foamable resin flow in the downstream direction of the die lip 5. The annular discharge port 10 of the die lip 5 is positioned downstream of the spider 4 so as to supply the foamed resin intermediate layer 1 between the inner and outer layers 7 and 8.
form 1. Further, a gate 12 is provided for supplying the foamable resin 9 from the outside of the die ring 1 to the discharge port 10 from a foamable resin extruder (not shown).

Therefore, the resin flow 6 supplied from the resin extruder for forming the inner and outer layers is divided into two at the die lip 5 to form an inner layer 7 and an outer layer 8, and between the inner and outer layers 7 and 8, there is a A foamable resin flow 9 is supplied from a foamable resin extruder into the die lip 5 through a gate 12 from an annular discharge port 10 to form an intermediate layer 11.
The inner and outer layers 7, 8 and intermediate layer 11 flow together and are sent to a former (not shown) to produce a composite tube.

FIG. 2 shows another embodiment, in which parts common to the embodiment of FIG. 1 are designated by the same reference numerals.

In this embodiment, a crosshead die 20 is disposed immediately after the spider 4, that is, on the former side, and a die lip 5 is provided on the crosshead die 20, and an annular discharge opening of the die lip 5 is provided on the downstream side of the spider 4. 10 to form a composite tube in the same manner as in the embodiment of FIG.

Therefore, in both embodiments, since three layers are formed behind the spider 4 that supports the mandrel 2, the resin flow is not divided by the spider, and two layers are formed.
The flow of the resin is not disturbed even by the difference in adhesiveness of the seed resin, and the appearance of the extruded product is improved.

〔Effect of the invention〕

As described above, the present invention provides an annular resin passage between a die ring and a mandrel, a die lip having an annular discharge opening for extrusion molding a foamable resin in the resin passage, and a die lip having an annular discharge opening for extrusion molding a foamable resin. Because the die ring is located on the downstream side of the spider that supports the mandrel, the foamable resin that makes up the intermediate layer does not reach high temperatures, preventing abnormal foaming, etc., and producing closed cells to produce a good composite pipe. can do.

Moreover, since three layers are formed behind the spider that supports the mandrel, the resin flow is not divided by the spider, so the flow of resin is not disturbed even by the difference in adhesiveness between two types of resin, and the extruded product is The appearance becomes better.

Furthermore, with this configuration, a normal die for extruding a single layer resin can also be used.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional front view showing one embodiment of the present invention;
FIG. 2 is a front sectional view showing another embodiment. 1... Dairing, 2... Mandrel, 3...
Torpedo, 4...Spider, 5...Die lip, 7...Inner layer, 8...Outer layer, 10...Discharge port,
11... middle class, 20... cross-headed die.

Claims (1)

[Claims] 1. In a manufacturing device for extrusion molding a composite pipe having an intermediate layer of foamable resin between inner and outer layers made of synthetic resin, an annular resin passage is provided between the die ring and the mandrel, and the resin passage is filled with foamable resin. Manufacture of a composite pipe made of synthetic resin, characterized in that a die lip having an annular discharge port for extrusion molding resin is provided, and the discharge port is located downstream of a spider supporting a mandrel on the die ring. Device cap.