JPH0134784B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a synthetic resin lined pipe, which is a metal pipe whose inner surface is coated with a synthetic resin layer.

Conventionally, the method for producing synthetic resin lined pipes as described above involves applying an adhesive to the outer circumferential surface of a heat-expandable synthetic resin pipe whose diameter expands when heated, and inserting this into a metal pipe. A method has been adopted in which the diameter of the synthetic resin pipe is expanded by heating, and the synthetic resin pipe is brought into close contact with the inner surface of the metal pipe.

However, since a solution type adhesive is usually used in this method, there are disadvantages such as harmful organic solvents volatilizing and contaminating the working environment, and requiring a drying pace. Moreover, since it is difficult to uniformly apply the adhesive to the outer circumference of the synthetic resin pipe, the thickness of the adhesive layer tends to be uneven, which causes variations in the adhesive strength between the synthetic resin pipe and the metal pipe.
The major drawback was that the quality of the product was difficult to stabilize. Furthermore, in order to eliminate the above-mentioned drawbacks, a method of using a heat-sensitive adhesive that does not contain a solvent has also been considered.
However, in order to carry out extrusion coating using a so-called cross-head die, which is the usual method of applying heat-sensitive adhesive,
The heat-sensitive adhesive is extruded into a cylindrical shape through the annular discharge port of the crosshead die, and coated on the outer surface of the synthetic resin tube that is passed through the die. When a heat-sensitive adhesive is coated on a synthetic resin pipe as a thin film, the adhesion of the heat-sensitive adhesive to the synthetic resin pipe is weak, and the adhesive layer peels off when inserted into a metal pipe, making it difficult to insert the heat-sensitive adhesive into the synthetic resin pipe. Even if it could be inserted, it had a quality defect in that the synthetic resin tube could not be evenly and strongly bonded to the metal tube.

The present invention solves the above-mentioned drawbacks and provides a method for manufacturing a high-quality synthetic resin lined pipe that can strongly bond a synthetic resin pipe to a metal pipe by coating a synthetic resin pipe with a heat-sensitive adhesive with strong adhesive strength. The gist of this method is to apply a diluted solvent solution of heat-sensitive adhesive with a weight concentration of 10 to 25% on the surface of a heat-expandable synthetic resin pipe, dry it, and apply heat-sensitive adhesive to the synthetic resin pipe using an extrusion coating device. The present invention relates to a method for manufacturing a synthetic resin lined pipe, which comprises coating the pipe with an adhesive, inserting the resin pipe coated with the adhesive into a metal pipe, and expanding the diameter of the pipe by heating.

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

The figure is an explanatory diagram showing an example of the manufacturing process of an adhesive-coated synthetic resin pipe used for manufacturing the synthetic resin lined pipe of the present invention, and 1 in the figure is a heat-expandable synthetic resin pipe. This synthetic resin pipe 1 has the property that its diameter increases when it is heated and softened, and during molding of the synthetic resin pipe, it is extruded into a cylindrical shape from an extruder, and while it is in a softened state, it is extruded by a forming device. It is produced by a method such as cooling and solidifying while reducing the diameter to a smaller diameter than the original state.

A diluted heat-sensitive adhesive solution 3 is applied to the synthetic resin tube 1 by a coating device 2, and the solvent in the applied solution is evaporated and dried in a drying chamber 7. Coating device 2
The diluent 3 may be applied uniformly to the outer circumferential surface of the synthetic resin pipe 1, and the illustrated example consists of a diluent tank 4, a coating machine 5, and a circulation pump 6, and is supplied from the diluent tank 4. Applicator 5 for applying diluted liquid 3
The diluent 3 is applied to the synthetic resin pipe 1, and the excess diluent 3 is returned to the tank 4 by the circulation pump 6. The coating machine 5 has an inlet 51 through which the synthetic resin pipe 1 is inserted.
An annular brush 53 is provided in a container 50 having an outlet 52 and an annular brush 53 facing the passage of the synthetic resin pipe 1. It is designed to be applied evenly over the entire outer circumferential surface. The amount of application is adjusted by the concentration of diluent 3.

The synthetic resin pipe 1 coated with the diluted heat-sensitive adhesive 3 in the coating device 2 is then dried in a drying chamber 7 by evaporating the solvent. Heated air is supplied to the drying chamber 7 to evaporate the solvent, which is then discharged to the outside.

The synthetic resin tube 1 coated with a diluted heat-sensitive adhesive solution 3 and dried is transferred to an extrusion coating device 8, where a heat-sensitive adhesive layer is extrusion coated. The extrusion coating device 8 attaches a mold such as a crosshead die to an extruder, melts and extrudes the heat-sensitive adhesive into a cylindrical shape, inserts the synthetic resin pipe 1 into the mold, and tightly coats the outer periphery of the heat-sensitive adhesive. The one that makes it happen is used.

The synthetic resin pipe 1 coated with the heat-sensitive adhesive in this way is inserted into the metal pipe to be lined in the same manner as before, and the synthetic resin pipe 1 is heated to expand its diameter and bonded to the inner surface of the metal pipe. It forces you.

In the present invention, heat-sensitive adhesives include polyolefin, ethylene-vinyl acetate resin, polyamide, polyester, polyurethane, rubber, and the like, but are not limited to these. When using a vinyl chloride resin pipe as the synthetic resin pipe 1, a pipe whose main component is a styrene-butadiene copolymer is suitable. The solvent may be any solvent as long as it can dissolve the heat-sensitive adhesive and evaporates easily, and ethyl acetate or chloroform is preferred.

Further, the heat-sensitive adhesive to be extrusion coated is preferably of the same type as the heat-sensitive adhesive to be diluted with a solvent.

Further, in the present invention, the concentration of the solvent diluted solution of the heat-sensitive adhesive is 10 to 25% by weight. This means that the weight concentration is
If the concentration is less than 10%, no significant improvement in the adhesion between the synthetic resin pipe 1 and the extrusion-coated heat-sensitive adhesive layer will be observed; on the other hand, if the concentration is high, the thickness of the coating layer will become thicker and the solvent will increase. If evaporation does not occur quickly and exceeds 25%, there is a risk that solvent will remain in the coating layer and this solvent will evaporate due to the heat during extrusion coating of the heat-sensitive adhesive, weakening the adhesive force between both adhesive layers. This is because it occurs. In the present invention, the weight concentration is particularly 15 to 20.
% was the best because it had a high adhesive strength.

If such a diluted solution is applied to the synthetic resin pipe 1, dried, and then extruded and coated with a heat-sensitive adhesive, the adhesive layer will firmly adhere to the synthetic resin pipe, and when inserted into the metal pipe, it will not stick to the metal pipe. It will not peel off even if rubbed. The reason for this is not clear, but fine irregularities occur on the surface of synthetic resin pipes during extrusion molding, and if heat-sensitive adhesive is directly extruded and coated, the coating layer will only adhere to the convex parts of the pipe surface. , if the diluent is applied to the tube surface in advance,
The uneven dents on the tube surface are filled with the heat-sensitive adhesive and become flat, and the heat-sensitive adhesive layer that is extruded and coated on top of it is bonded to the tube surface through the coating layer, and the coating layer It is thought that peeling will disappear.

In the present invention, when extrusion coating a synthetic resin pipe with a heat-sensitive adhesive using an extrusion coating device, the adhesive layer extruded from a mold is coated on the synthetic resin pipe while applying liquid pressure such as air pressure. Alternatively, by applying negative pressure between the adhesive layer and the synthetic resin pipe, the adhesive layer can be bonded even more firmly.

The method for manufacturing a synthetic resin lined pipe of the present invention is as described above, and when coating a synthetic resin pipe with a heat-sensitive adhesive by extrusion, a diluted solvent solution of the heat-sensitive adhesive is applied to the surface of the synthetic resin pipe in advance and dried. So,
The extruded coating layer firmly adheres to the synthetic resin pipe, and when inserted into a metal pipe, the heat-sensitive adhesive layer is prevented from peeling off, allowing easy insertion.

In addition, since the heat-sensitive adhesive layer firmly adheres to the synthetic resin pipe, this adhesive strength is maintained even after lining the metal pipe, and the adhesive strength between the metal pipe and the synthetic resin pipe that is the lining layer is uniform. Moreover, a strong and high-quality lining pipe can be obtained.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the manufacturing process of a heat-sensitive adhesive-coated synthetic resin pipe used in the method for manufacturing a synthetic resin-lined pipe of the present invention, and FIG. 2 is a detailed enlarged view of the main part of FIG. 1. It is an explanatory diagram. 1: Heat-expandable synthetic resin pipe, 2: Coating device,
3: diluted heat-sensitive adhesive solution, 4: tank, 5: coating machine, 6: circulation pump, 7: drying chamber, 8: extrusion coating device.

Claims (1)

[Claims] 1 The surface of the heat-expandable synthetic resin tube has a weight concentration of
Apply and dry a 10-25% diluted solution of heat-sensitive adhesive in a solvent, coat the synthetic resin pipe with a heat-sensitive adhesive layer using an extrusion coating device, insert the adhesive-coated synthetic resin pipe into a metal pipe, and heat it. A method for manufacturing a synthetic resin lined pipe characterized by expanding the diameter.