JPH0565753B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a highly rigid pipe in which the outer peripheral surface of a thermoplastic resin pipe is coated with a fiber reinforced plastic layer (hereinafter referred to as "FRP layer"), and Specifically, the present invention relates to a method for manufacturing a highly rigid pipe in which the outer peripheral surface of a resin pipe stretched in the axial or radial direction is coated with an FRP layer to dramatically improve tensile strength, rigidity, impact resistance, etc.

(Prior art) Highly rigid pipes made of hard vinyl chloride resin pipes whose outer circumferential surface is covered with an FRP layer are well known, and because these pipes have excellent heat and impact resistance, they are used as mining pipes, hot water supply pipes, and electric wires. Used for insertion piping, etc.

Conventionally, this high-rigidity pipe was made by impregnating glass fiber with a thermosetting resin on the outer peripheral surface of an unstretched hard vinyl chloride resin pipe obtained by extrusion molding.
It was manufactured by wrapping FRP sheets, etc.

(Problem to be solved by the invention) This high-rigidity pipe manufactured using the conventional method has a tensile strength of the outer layer of the hard PVC resin pipe that is higher than that of the inner layer of the hard PVC resin pipe.
The FRP layer was much higher, and the resin pipe had a higher elongation rate than the FRP layer, so the fracture strength of the pipe depended on the FRP layer, which had a lower elongation rate.

Therefore, when the absolute strength of the FRP layer is lower than that of the resin pipe, the inner resin pipe may also propagate and fail at the same time as the outer FRP layer ruptures.

(Means for solving the problem) The present invention solves the problem by increasing the tensile strength of the thermoplastic resin pipe, and the present invention solves the problem by increasing the tensile strength of the thermoplastic resin pipe. The resin tube is stretched in the axial or radial direction to increase its tensile strength, and the outer peripheral surface of this resin tube is covered with an FRP layer.
The present invention provides a method for manufacturing a highly rigid pipe that has dramatically improved tensile strength, rigidity, impact resistance, etc.

Hereinafter, the specific configuration of the present invention will be explained in detail with reference to the drawings.

(Example) FIG. 1 is a vertical cross-sectional view of a high-rigidity pipe showing an example of the present invention, in which reference numeral 1 indicates a thermoplastic resin pipe as an inner layer, and 2 indicates an FRP layer as an outer layer.

The thermoplastic resin pipe 1 is a resin pipe made of vinyl chloride resin, polyethylene resin, polypropylene resin, etc. In the present invention, this resin pipe obtained by extrusion molding is heated at a temperature higher than the softening temperature of the resin and at a melting temperature. After heating to a lower temperature suitable for stretching, the resin tube is stretched in either the axial direction or the radial direction, or in both the axial and radial directions.

For example, when stretching a thermoplastic resin tube in two directions, the resin tube is softened by heating to the appropriate temperature for stretching and is set in a cylindrical die, and then a pressurized liquid is introduced into the resin tube to stretch it in the radial direction. At the same time, it is preferable to stretch the tube in the axial direction.

In this way, a resin pipe stretched in two directions or one direction has a dramatically improved tensile strength compared to an unstretched resin pipe obtained by simply extrusion molding. For example, a hard vinyl chloride resin pipe stretched in both the axial and radial directions has a tensile strength of 800 to 1200 Kg/cm ² , about twice as high as that of a non-stretched resin pipe.

In the present invention, the outer circumferential surface of the stretched resin tube 1 is roughened by a chemical method or a physical method, and the outer circumferential surface of the tube is made of FRP of an appropriate thickness.
It is covered with layer 2.

FRP layer 2 is made of glass fiber roving cloth,
Formed into a tape, mat, etc., impregnated with a thermosetting resin such as polyester resin, epoxy resin, phenol resin, etc., and formed into a sheet, which is then wrapped around the outer peripheral surface of the resin pipe 1 and hardened. do.

Note that when forming this FRP layer 2, an appropriate adhesive is applied to the outer peripheral surface of the resin pipe 1 in advance.
It is a good idea to wrap the FRP sheet over this adhesive.

Further, if necessary, a filler such as sand, aggregate, calcium carbonate, etc. may be mixed into the two FRP layers.

(Effects of the Invention) The present invention improves the tensile strength by stretch-molding a thermoplastic resin pipe in one or both of the axial and radial directions, and the outer circumferential surface of the resin pipe is
Since it was coated with an FRP layer, it was possible to dramatically improve tensile strength, rigidity, impact resistance, etc. compared to conventional high-rigidity pipes of this type.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a highly rigid pipe showing one embodiment of the present invention. 1...Thermoplastic resin pipe, 2...FRP layer.

Claims (1)

[Claims] 1. A method for producing a high-rigidity pipe, which comprises stretching a thermoplastic resin pipe that has been softened by heating to an appropriate stretching temperature in the axial or radial direction, and then covering the outer peripheral surface of the resin pipe with a fiber-reinforced plastic layer.