JPH0741628B2 - Manufacturing method of multilayer pipe joint - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multilayer pipe joint used for connecting a water supply pipe, a hot water supply pipe, and the like, and more specifically, a synthetic resin in which an inner layer and an outer layer are formed of different resins. The present invention relates to a method for manufacturing a multi-layer pipe joint made of steel.

(Prior Art) In a synthetic resin pipe joint, various performances can be improved by forming the outer layer and the inner layer with different resins.

For example, the inner layer that is in contact with the liquid is molded with a molding material that is made of a resin that has excellent heat resistance, hot water resistance, chemical resistance, etc., and the outer layer that is exposed to the outside and is susceptible to external loads is impact resistant. Molding with a molding material made of a resin having excellent properties and weather resistance can be considered.

In manufacturing a pipe joint having a multilayer structure having such an outer layer and an inner layer, after molding the outer layer, the outer layer is inserted into a mold for secondary injection molding, and the molding material for the inner layer is injected in this state, Due to heat shrinkage of the molding material for the inner layer, displacement occurs between the molding material for the inner layer and the outer layer, so that the adhesion of the inner and outer layer pipes is poor, and cracks may occur in the outer layer due to injection pressure of the molding material for the inner layer.

Therefore, for example, in Japanese Patent Laid-Open No. 61-189913, after molding an outer layer, the outer layer is inserted into a mold for secondary injection molding, and secondary injection is performed between the outer surface of the outer layer and the inner surface of the mold. A technique has been proposed in which a gap corresponding to the molding shrinkage amount of the inner layer is provided. According to this method, the outer layer shrinks following the molding shrinkage of the inner layer, whereby the above problem can be solved to some extent.

(Problems to be Solved by the Invention) Generally, since the outer layer of a multilayer pipe joint is required to have strength,
A highly rigid outer layer molding material is often used, but when a multilayer pipe joint is manufactured based on the above method using such a molding material, a highly rigid molding material is obtained.
Generally, since the elasticity is poor, the secondary injection pressure of the inner layer molding material causes cracks. If the secondary injection pressure is lowered in order to prevent the cracks in the outer layer, there is a drawback that a pressure non-pressure portion (a portion where the molding material does not exist) is generated in the inner layer.

Further, in the above method, for example, when the fluidity of the molding material for the inner layer is poor, the inner layer having a small thickness cannot be molded.

The present invention was made by paying attention to such actual situation,
Provided is a method for producing a multilayer pipe joint which does not cause a crack in an outer layer during injection molding, and can form an outer layer and an inner layer with good adhesion even when the inner layer is thin. The purpose is to

(Means for Solving the Problem) The method for manufacturing a multilayer pipe joint of the present invention comprises a step of injection-molding a cylindrical outer layer, a step of taking the outer layer out of a mold, and heating the outer layer to an extent not deformed, It includes a step of incorporating the heated outer layer into an inner layer injection molding die and a step of injection molding a cylindrical inner layer on the inner peripheral side of the outer layer, thereby achieving the above object. .

The present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the present invention. First, as shown in FIG. 1 (a), a cylindrical outer layer 1 is injection-molded by using an outer die 3 for outer layer injection molding and an inner die 3'for outer layer injection molding. Next, the outer layer 1 is taken out from the mold 3 and the first
After processing as required as shown in FIG. 2B, the outer layer 1 is heated at a temperature not higher than its deformation. The processing is, for example, cutting a portion corresponding to a runner generated by the primary molding or both end portions of the outer layer 1. To heat the outer layer 1,
This can be performed by leaving the outer layer 1 in an oven or blowing hot air onto the outer layer 1. The heating temperature of these heating means 4 needs to be lower than the temperature at which the outer layer 1 is not deformed. When the heating temperature is higher than the deformation temperature of the outer layer 1, the dimensional accuracy required for the multilayer pipe joint is reduced.

Next, as shown in FIG. 1 (c), the heated outer layer 1 is incorporated into the outer layer injection molding outer die 3 again. Next, as shown in FIG. 1 (d), as the inner die, an inner die 5 for inner layer injection molding having a diameter smaller than that of the inner die 3'for outer layer injection molding by a thickness of the inner layer 2 is used. The inner layer molding material is injected to the inner peripheral side of 1 to mold the inner layer 2. The mold 3 is preferably heated.

Next, the multi-layer pipe joint A having the inner layer 2 and the outer layer 1 taken out from the mold 3 can be obtained.

A thermoplastic resin is preferably used as a molding material for forming the outer layer 1 and the inner layer 2 used in the present invention. In particular,
As the molding material for the inner layer, polyether ether ketone (hereinafter referred to as PEEK) or polyether nitrile is preferably used. This PEEK is a special engineering plastic developed by ICI and its melting point is 334
℃. PEEK is lightweight and has excellent physical properties such as heat resistance, hot water resistance, and chemical resistance. As a commercially available product of PEEK, VICTREX PEEK (trademark of ICI) can be mentioned. Also,
The molding material forming the inner layer 2 contains PEEK as a main component and may contain other additives. Polyether nitrile is a special engineering plastic developed by Idemitsu Kosan Co., Ltd., and its melting point is 340 ° C. Polyether nitrile is lightweight and has excellent physical properties such as heat resistance, hot water resistance, and chemical resistance. Polyether nitrile has a structure having the following repeating units.

A commercially available product of polyether nitrile is ID300 (trademark of Idemitsu Kosan Co., Ltd.).

As the resin forming the outer layer 1, for example, polyamide,
Examples of the resin include polyethylene, polypropylene, polybutylene terephthalate, polyvinyl chloride, polyacetal, polycarbonate, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, polysulfone, and polyetherimide, and particularly, polyetherimide, polysulfone, polyether sulfone, Polyphenylene sulfide is preferred. These resins are
It has excellent heat-sealing properties with PEEK and polyether nitrile, and has relatively good heat resistance, weather resistance, pressure resistance, and impact resistance, and can be colored.

A filler for reinforcement, a coloring agent, an antioxidant, etc. are added to the molding material forming the outer layer 1 and the inner layer 2 as required.

Examples of the filler include glass fiber, carbon fiber, boron fiber, silicon carbide fiber, alumina fiber, amorphous fiber, inorganic fiber such as silicon / titanium / carbon fiber, and organic fiber such as aramid fiber. Short fibers (fiber length 2-3 mm or less, fiber diameter 5-25 μm
However, it is added to the extent that practical use is not impaired.

In this way, by heating the outer layer 1, flexibility can be imparted to the outer layer 1. Therefore, when the heated outer layer 1 is incorporated into the inner layer injection molding die 5 and the inner layer molding material is injected. In addition, the secondary injection pressure hardly causes cracks in the outer layer 1, and the shrinkage of the outer layer 1 does not cause cracks or the like even if a gap is formed between the outer peripheral surface of the outer layer 1 and the inner peripheral surface of the mold 5. Absent. Further, the molding material for the inner layer, which is injected to the inner peripheral side of the heated outer layer 1, is difficult to be cooled by the outer layer 1. Therefore, the viscosity of the injected molding material is relatively high, and the thickness of the inner layer 2 is set thin. Even if the inner layer 2 has a predetermined thickness, the molding material is sufficiently distributed in the space for forming the inner layer, and the inner layer 2 having a predetermined thickness does not cause a short shot.
Can be molded. Moreover, since the temperature difference between the injected molding material for the inner layer and the temperature of the outer layer 1 is not significantly different,
Since the shrinkage of the molding material for the inner layer and the shrinkage of the outer layer 1 are substantially similar to each other, a large strain does not occur between the inner and outer layers 2 and 1, and therefore a sufficient adhesive strength between the inner and outer layers 2 and 1 is obtained. can get.

Further, as the mold 5 incorporating the heated outer layer 1 as described above, the outer layer injection molding mold 3 can be used, so that it is economical to manufacture a new mold.

The method for manufacturing the multilayer pipe joint of the present invention is not limited to two layers,
It can also be applied to a method for manufacturing a multi-layer pipe joint having three or more layers, and in that case as well, the pipe joint member to be inserted can be heated at a temperature at which it does not deform, and the same procedure as above can be performed. Further, the shape of the multilayer pipe joint is not limited to the straight type shown in FIG. 1 (e), but can be applied to the elbow type shown in FIG.

(Example) Hereinafter, the present invention will be specifically described based on Examples.

Example 1 The multilayer pipe joint shown in FIG. 1 (e) was molded using a multilayer injection molding machine.

In the figure, 1 is a cylindrical outer layer, 2 is a cylindrical inner layer provided outside the outer layer 1, and the thin portion 2a of the inner layer 2 has a thickness of 1 mm.

First, pellets for the inner layer were made of polyetheretherketone (PEEK), and pellets for the outer layer were made of a molding material in which 30% of glass fibers were mixed with polyetherimide. Next, as shown in FIG. 1A, the outer layer 1 was molded by supplying the outer layer molding material 3 with the molding material for the outer layer and performing injection molding.

Next, as shown in FIG. 1 (b), a portion corresponding to the runner of the outer layer 1 and both end portions of the outer layer 1 were cut. Next, the outer layer 1 is heated in the oven 4 to 160 ° C. and immediately
As shown in FIG. (C), the outer layer injection molding outer mold 3 was set again. The deformation temperature of PEEK is 170 ° C.

Next, as shown in FIG. 1 (d), as the inner die, an inner layer injection molding die 5 having a diameter smaller than that of the outer layer injection molding inner die 3'by the thickness of the inner layer 2 is used. The molding material for the inner layer was injected into, and then heat treated at 180 ° C. for 1 hour to crystallize PEEK to obtain a multilayer pipe joint. The adhesion strength of the inner and outer layer pipes of the obtained multilayer pipe joint was measured and found to be 300 kg / cm ² .

Example 2 A multilayer pipe joint was obtained in the same manner as in Example 1 except that the heating temperature of the outer layer was 60 ° C. The adhesion strength between the inner and outer layers of the obtained multilayer pipe joint was measured and found to be 205 kg / cm ² .

Comparative Example 1 Example 1 except that the heating temperature of the outer layer was normal temperature (10 ° C.)
A multilayer pipe joint was obtained in the same manner as in. The adhesion strength between the inner and outer layers of the obtained multilayer pipe joint was measured and found to be 50 kg / cm ² . In addition, cracks were formed in the outer layer, and pressure imperfections were also observed inside.

Comparative Example 2 A multilayer pipe joint was obtained in the same manner as in Example 1 except that the thickness of the inner layer was set to 1.25 mm and the heating temperature of the outer layer was room temperature (10 ° C). The adhesion strength between the inner and outer layers of the obtained multilayer pipe joint was measured and found to be 50 kg / cm ² or less. Further, the outer layer 1 was cracked.

Comparative Example 3 The thickness of the inner layer was set to 2.0 mm, and the heating temperature of the outer layer was room temperature (1
A multilayer pipe joint was obtained in the same manner as in Example 1 except that the temperature was set to 0 ° C.

The adhesion strength between the inner and outer layers of the obtained multilayer pipe joint was measured and found to be 50 kg / cm ² or less. In addition, the multilayer pipe joint had a crack in the outer layer at a rate of 1 in 10.

(Effects of the Invention) In the present invention, since the heated outer layer is incorporated into the molding die and the inner layer molding material is injected, the multilayer pipe joint can be obtained without causing cracks in the outer layer. Therefore, a multilayer pipe joint in which the outer layer is reinforced with reinforcing fibers or a multilayer pipe joint in which the inner layer is thin can be manufactured without any trouble.

[Brief description of drawings]

1 (a) to 1 (e) are schematic views showing an embodiment of the method for producing a multilayer pipe joint of the present invention, and FIG. 2 is a sectional view of another embodiment of the multilayer pipe joint. 1 ... Outer layer, 2 ... Inner layer, 3 ... Outer layer injection molding outer die, 4 ... Heating means, 5 ... Inner layer injection molding inner die, A
... Multi-layer pipe joint, 3 '... Inner mold for outer layer injection molding.

Claims (1)

[Claims] 1. A step of injection-molding a cylindrical outer layer, a step of removing the outer layer from a mold and heating the outer layer to an extent not deformed, and a step of incorporating the heated outer layer into an inner-layer injection molding mold. And a step of injection-molding a cylindrical inner layer on the inner peripheral side of the outer layer, the method comprising: