JPS5935766B2 - Molding method of fiber reinforced plastic pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming fiber reinforced plastic (hereinafter referred to as FRP) pipes.

Conventionally, one method for forming FRP pipes is to impregnate glass fibers, carbon fibers, or aromatic polyamide fibers with thermosetting resins such as epoxy resins, unsaturated polyester resins, or phenol resins to create a semi-cured prepreg sheet or There is a method in which cloth (including mixed weaves) is wrapped around a core metal and laminated, a cellulose tape is further wrapped helically around the surface of this laminate, heated and hardened, and after cooling, the core metal is removed and the tape is peeled off. It is being

However, in this molding method that uses cellulose tape, even under careful handling and setting of curing conditions, a large amount of resin flows to the outer surface due to a decrease in the viscosity of the thermosetting resin due to heating, and a large amount of resin flows to the outer surface of the laminated core metal. The fibers are likely to move or fall off, and furthermore, the fibers may meander partially in the longitudinal direction of the molded product. This phenomenon causes uneven distribution of resin and boards in the molded product, and when the meandering of the fibers applies external force to the molded product, there is a risk that the molded product will be damaged at that portion. Furthermore, cellulose tape completely deteriorates under the curing temperature conditions and has poor peelability from the cured resin, so a rotating metal plan or the like must be used to remove it, resulting in a rough surface of the molded product. , requires finishing processing such as painting. The present inventors have investigated the causes of these problems in the conventional molding method using cellulose tape.
As a result, we found that the main reason for this is that the cellulose tape shrinks in the transverse direction when the resin heats and hardens, and also generates shrinkage stress as the tape shrinks in the longitudinal direction at relatively low temperatures. Ta.

That is, in general, cellulose tapes contain a relatively large amount of softener, which is polyalcohol, which also easily absorbs water, in addition to cellulose, which easily absorbs water.
When such a cellulose tape is heated, it shrinks both in the vertical and horizontal directions, and according to experimental results, it shrinks in the horizontal direction by 110 to 14
It shrinks by around 3.5% until it reaches around 0℃, and it shrinks to 170~180℃.
It was found that the shrinkage occurred by 4.0 to 4.5% in the vicinity of ℃, and further contraction in the longitudinal direction by 2 to 2.5% and 3.0 to 3.5%, respectively.In addition, the shrinkage stress in the longitudinal direction was 40~ with 20mm width tape
It was found that the occurrence started at 50°C. 5 Furthermore, as a result of various studies on the pressure molding conditions of fiber prepreg or cloth impregnated with thermosetting resin, we found that these pressure molding conditions are necessary to prevent uneven distribution of resin and board formation in the molded product. In this method, we discovered that the relationship between the start of pressurization and the gelation point of the resin is extremely important, and if we start pressurization after heating the resin to near the gelation point, the resin flow will be appropriate and the uneven distribution of the resin will be reduced. It has been found that moldings without boards can be obtained.

On the other hand, molded products obtained by starting pressurization before the gelling point have a large amount of resin flow, resulting in continuous or independent boards; The resulting molded product has almost no resin flow and relatively little board, but the resin is unevenly distributed. We found that the mechanical properties of molded products are sensitive to the internal structure, especially the uneven distribution of the board and resin, and that applying pressure near the gelation point gives the greatest mechanical properties compared to applying pressure at other points. L In the present invention, in a molding method in which prepreg or cloth of fibers impregnated with a thermosetting resin is wrapped around a core bar and laminated, and a tape is wrapped around the surface of the fabric and cured, the heating curing conditions of the thermosetting resin are At the bottom, the tape does not shrink in the horizontal direction, but contracts in the vertical direction near the gel point of the resin, pressurizes the laminate, adheres tightly to the laminate, is easily rolled, does not deteriorate after curing, and easily connects to the cured resin. The present invention was achieved by searching for tapes that can be peeled off and giving gloss to the surface, and finding a crystalline thermoplastic resin tape as a material whose properties can be controlled arbitrarily under the manufacturing conditions of tapes having such properties. It is ivy.

That is, in the present invention, a fiber prepreg sheet or cloth impregnated with a thermosetting resin is wound around a core bar, and the surface of the laminate is free from shrinkage in the lateral direction due to heat during curing.
A crystalline thermoplastic resin tape that has been previously controlled by heat treatment so that it shrinks in the longitudinal direction near the gelation point of the resin is crimped, wrapped helically in the longitudinal direction of the laminate, heated to harden, and cooled to form a core metal. By removing the tape and peeling off the tape, there is little resin flow on the outer surface, there is no meandering along the longitudinal direction of the fibers, there is no uneven distribution of resin in the molded product, there is no board formation, and the mechanical properties are good. The present invention provides a method for molding an FRP pipe that can be easily peeled off continuously from the surface of a cured resin, has a glossy surface, and does not require post-processing of the surface.

The crystalline thermoplastic resin tape used in the present invention is made of polyethylene terephthalate or its copolymer, nylon 6, nylon 66, or polypropylene, and polyethylene terephthalate or its copolymer is particularly heat resistant. It can be effectively used because of its control of heat shrinkage temperature, releasability from resin, etc.

The width of these tapes can be selected depending on the length, thickness, or taper of the laminate, but is usually 5 to 20 nm, preferably 10 to 15 nm in width for ease of winding. The thickness can be selected arbitrarily, but it is usually 20 to 1
00μ and 20 to 50μ is preferable from the viewpoint of ease of winding work. Control of the start of heat shrinkage stress generation in these tapes is set in relation to the gel point according to the type of resin used, curing conditions, etc., but when using ordinary epoxy resin and polyethylene terephthalate tape, In this case, a commercially available polyester film is heated at 100 to 160°C through a roller or in an oven, and the temperature is set to generate heat shrinkage stress at around 90 to 140°C.
It is preferable that heat treatment at around 40°C causes heat shrinkage stress at around 120°C. Due to this heat treatment, there is almost no lateral shrinkage of the tape, and there is no movement at all during curing on the surface of the laminate wound around the core metal. Note that it is possible to increase the shrinkage stress in the longitudinal direction by stretching the polyester film to a wide width at a temperature slightly higher than its secondary transition temperature, but in the case of such a tape, the curing temperature of the resin Rapid shrinkage stress occurs from the relatively low temperature region of the resin, which increases resin flow to the outer surface, which is undesirable. The method for winding the tape laminate is the same as in conventional cellulose tapes, with helical winding being particularly preferred. The fiber prepreg or cloth used in the present invention is a state in which fibers such as glass fibers, carbon fibers, and aromatic polyamide fibers are arranged in parallel in one direction, or woven fabrics or mixed woven fabrics of these fibers, and epoxy resin, unsaturated It is made by blending uncured thermosetting resin such as polyester resin or phenolic resin with a curing agent such as BF3/MEA or butyl peroxide, and then impregnating it with a highly permeable resin liquid whose viscosity has been lowered with an organic solvent and drying it. Those manufactured by semi-curing are used.

It goes without saying that the molding method of the present invention can be applied not only to pipes but also to methods for manufacturing molded products such as rods using the conventional method of winding cellulose tape, and the significance of the present invention is extremely large. The present invention will be explained below with reference to Examples.

Example 1 125 parts by weight of Ciel Epicote DX-210 (epoxy resin manufactured by Ciel Chemical Co., Ltd.) as a thermosetting resin, BF3/ME
Using a resin solution consisting of 3 parts by weight of A and 65 parts by weight of methyl ethyl ketone, the thickness was 0.15 mm) resin content was 42.5 mm.
% of unidirectionally aligned carbon fiber prepreg sheets were made.

Cut out 10 square pieces of 100 x 100 mm from this prepreg sheet, stack them 10 times in one direction,
Insert a thermocouple and sandwich this laminate between aluminum electrodes insulated with polyethylene terephthalate film.
Place on a flat plate of a pressure molding machine heated to 70°C.

The gel point of this laminate, obtained from the dielectric constant that records the change in dielectric constant between both electrodes and the temperature change of the laminate, is 1 after 18 minutes.
It was 58°C. Based on this result, a commercially available 38μ polyester tape was heat-treated on a roll at 140°C.

This heat-treated tape begins to shrink in the longitudinal direction at around 130° C., and at the same time, heat shrinkage stress begins to occur. And 17
There was no lateral shrinkage at 0°C. On the other hand, a commercially available cellulose tape was prepared.

This tape has a thickness of 45μ, a width of 18mm, and a heat shrinkage stress of 4
The shrinkage occurred at around 0°C, and at 170°C, the shrinkage in the transverse direction was 4% and the shrinkage in the longitudinal direction was 3.3%. Cut out a trapezoidal piece from the above prepreg sheet and taper rate 1/500
The core of chrome-molybdenum steel with a center diameter of 29.5m7n was wound three times using a rolling machine.

The above-mentioned polyethylene terephthalate tape and cellulose tape were each attached to the surface of the laminate using a tape winding machine to the extent that no wrinkles were formed in the tape, and
It was rolled up into a helical structure with n pitches. These two scrolls were suspended in a furnace preheated to 170° C. for 120 minutes to completely cure the resin, and then cooled. In the case of the polyethylene terephthalate tape, there was almost no resin flow to the outer surface and no tape movement at all.

When the end of the tape was lifted up and the end of the tape was pulled while rotating the pipe, the tape was continuously peeled off and a glossy surface was obtained. No meandering of the fibers was observed, and when a part of the pipe was cut and the cross section was observed under an electron microscope, no uneven distribution of resin or board was found, and a uniform molded product was obtained. On the other hand, in the case of cellulose tape,
There were several streaks of resin flow to the outer surface, and the tape was completely degraded and had already broken in parts.

The tape had moved from both ends toward the center of the pipe by a maximum of about 2% from its initial position. When a part of the pipe was cut and observed under an electron microscope, a continuous board was found, with uneven distribution of resin in some parts. Also, the upper surface layer of the tape is
Although easy to remove, the bottom layer in contact with the resin adhered and required a rotating metal brush to remove it. As a result, the surface became dull. The fibers meandered along the circumference of the pipe at various points. Example 2 Ciel Epicoat DX-210125 parts by weight was applied to a glass fiber satin woven fabric having a thickness of 0.10 mm in the same manner as in Example 1.
BF3/MEA 3 parts by weight and methyl ethyl ketone 29
Impregnated with 0 parts by weight of resin liquid and dried to obtain a resin adhesion amount of 40 parts by weight.
．． A 5% glass fiber cloth prepreg was obtained.

The gelation point was measured in the same manner as in Example 1 and was found to be 145°C after 15 minutes.

Using this glass fiber cloth prepreg, it was wrapped five times around the same metal core in the same manner as in Example 1, and the same polyethylene tyrephthalate tape as in Example 1 was wrapped tightly around the surface thereof.

Then, it was cured at 170°C for 120 minutes. The tape could be easily and continuously peeled off, yielding a pipe-shaped molded product free of meandering fibers, uneven distribution of resin, and boards.

On the other hand, in a pipe-shaped product formed in the same manner using cellulose tape, the tape was shifted, the fibers were slightly meandering, and boards were observed.

Example 3 In the same manner as in Example 1, a prepreg of Kepler cloth was obtained by adhering 38% of Ciel Epicoat DX-210 resin to a 0.11 mm thick Kepler (aromatic polyamide fiber manufactured by Dupont) plain woven cloth.

The genolization point was measured in the same manner as in Example 1 and was found to be 131°C after 12 minutes. A commercially available polyethylene terephthalate tape was heat treated at 120°C.

Cut this prepreg into trapezoidal pieces with a taper ratio of 2.1/
1000, and three flies were wound around a stainless steel core metal having a center diameter of 10.93n. The above-mentioned tape was wrapped around this surface and cured by heating at 170° C. for 120 minutes, and after cooling, the core metal was removed. There was no tape movement, no laminate shedding, and no resin flow to the outside surface.

The tape was continuously peeled off to obtain a shiny surface, no meandering of fibers, and a pipe-shaped molded product without a board. On the other hand, when the cellulose tape used in Example 1 was used, the tape deviated from its initial position, and the fibers meandered partially around the circumference of the pipe, and the meandering reached the innermost layer.

Claims (1)

[Claims] 1. When forming a fiber-reinforced plastic pipe by wrapping prepreg sheets or cloth of fibers impregnated with a thermosetting resin around a core metal and curing them by heating, the surface of the laminate before curing is coated with a lateral direction caused by heating. A method for forming a fiber-reinforced plastic pipe, characterized by wrapping a tape of a crystalline thermoplastic resin that does not shrink and shrinks in the longitudinal direction near the gelling point of the resin, and then peeling off the tape after curing by heating.