JPH04336235A - Fiber reinforced thermoplastic resin pipe - Google Patents

Abstract

PURPOSE:To prevent the generation of electrolcorrosion in a metal joint when pipes are connected by the metal joint by forming an electric insulating layer composed of a thermoplastic resin to the inner surface and/or outer surface of the pipe. CONSTITUTION:A conductive prepreg containing a thermoplastic resin as a Matrix and an electric insulating prepreg composed of a thermoplastic resin are interposed between a thermally expansible core 3 and the cylindrical outer mold 1 arranged outside the core 3. The core 3 is thermally expanded to obtain a fiber reinforced thermoplastic resin pipe. As mentioned above, since an electric insulating layer composed of a thermoplastic resin is formed to the inner surface and/or outer surface of the pipe, a metal joint becomes the state coming into contact with the electric insulating layer when the metal joint is arranged to the end parts of the pipes to connect the pipes and, therefore, the metal joint can be prevented from being deteriorated by the generation of electrocorrosion.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber-reinforced thermoplastic resin pipe having an electrically insulating layer made of thermoplastic resin on either or both of its inner and outer surfaces.

0002

[Prior Art] Continuous fiber-reinforced composite materials (prepregs) that have a matrix of so-called engineering plastics, such as polyetheretherketone (PEEK), which is a thermoplastic resin, generally have good toughness, heat resistance, and environmental resistance. The properties are much superior to composite materials whose matrix is thermosetting resin such as epoxy resin. Therefore, in recent years, attempts have been made to make fiber-reinforced resin pipes from prepreg having a thermoplastic resin matrix and use these pipes as structural members for bicycles, for example.

However, when conductive fibers such as carbon fibers are used in the prepreg of this pipe,
The pipes themselves are also conductive, so when pipes are connected using metal joints, there is a problem of electrical corrosion, where the metal joints corrode due to the conductivity of the pipes.

0004

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a fiber-reinforced thermoplastic resin pipe that prevents electrolytic corrosion from occurring in metal joints. .

[0005]

[Means for Solving the Problems] The fiber-reinforced thermoplastic resin pipe of the present invention combines a conductive prepreg having a thermoplastic resin as a matrix and an electrically insulating prepreg made of a thermoplastic resin with a thermally expandable core. An electrically insulating layer made of a thermoplastic resin is formed on the inner and/or outer surface of the inner and/or outer surface formed by thermally expanding the inner core, which is interposed between the core and a cylindrical outer mold placed on the outside of the core. do.

[0006] As described above, in the present invention, since the electrical insulating layer made of thermoplastic resin is formed on the inner and/or outer surfaces, it is possible to arrange metal joints at the ends of the pipes and connect the pipes with the metal joints. Since the metal joint comes into contact with the electrically insulating layer, it is possible to prevent the metal joint from deteriorating due to electrolytic corrosion. Hereinafter, the configuration of the present invention will be explained in detail.

[0007] Conventionally, when manufacturing a pipe using prepreg having a thermoplastic resin as a matrix, a winding method was used, for example, by winding a strip-shaped prepreg sheet around a mandrel made of metal or the like. However, prepregs with thermoplastic resin as a matrix not only have no tackiness or plasticity at room temperature, but also have high rigidity because even when formed into a thin sheet, they are still hard plate-like materials reinforced with fibers. For this reason, when making a pipe by the winding method, it is difficult to bring the laminated plies of the prepreg sheet into close contact with each other, and voids are likely to be formed between the laminated plies, resulting in variations in the quality of the resulting pipe.

[0008] Therefore, in the present invention, in order to solve such problems and stabilize the quality, the following (a) conductive prepreg having a thermoplastic resin as a matrix and the following (b) thermoplastic resin are used. A fiber-reinforced thermoplastic resin pipe is produced by interposing an electrically insulating prepreg consisting of I am getting . This fiber-reinforced thermoplastic resin pipe includes not only straight pipes with a circular cross section, but also bent pipes, pipes that are partially collapsed in the longitudinal direction, pipes with flat cross sections, tapered pipes, and other irregularly shaped pipes. It may also be a combination of shapes.

(a) Conductive prepreg having a thermoplastic resin as a matrix. Conductive prepreg with a thermoplastic resin as a matrix (hereinafter referred to as prepreg A) is made by forming a matrix into a fiber bundle generally called a tow, which is made up of multiple continuous fibers arranged in a band shape in one direction. Impregnated with thermoplastic resin (unidirectionally aligned prepreg (
UD prepreg)). It is in the form of a sheet or strip (slit tape). The fibers used in the fiber bundle constituting this prepreg are conductive fibers such as carbon fibers.

The thermoplastic resin of the matrix is not particularly limited, but includes, for example, polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polyetherimide (PEI),
Polyether sulfone (PES), polyarylene ketone, polyarylene sulfide, polyallylimide,
It is a thermoplastic resin with a high melting point or a high softening point, such as polyamideimide, polyimide, polyimide sulfone, polysulfone, and polyester.

(b) Electrically insulating prepreg made of thermoplastic resin (hereinafter referred to as prepreg B). It is a prepreg made of a thermoplastic resin alone or a thermoplastic resin and electrically insulating fibers such as glass fiber, aramid fiber (aromatic polyamide fiber), silicon carbide fiber, boron fiber, alumina fiber, etc. The thermoplastic resin is the above (a)
This is similar to that in prepreg A. This prepreg is also in the form of a sheet or strip.

The fiber-reinforced thermoplastic resin pipe of the present invention can be obtained as described in (2) below. (2) First, prepreg A and prepreg B are loaded into a cylindrical outer mold 1 as shown in FIG. 1 so that the cross section thereof becomes hollow. In this case, a cylindrical preform braided with strips of prepreg B is placed on the inner and/or outer surface of the cylindrical preform braided with strips of prepreg A, that is, on either or both of the inner and outer surfaces. This composite prepreg is made into a cylindrical outer mold 1.
Just insert it inside. Alternatively, the sheet-like prepregs A and B may be stacked and spirally wound to form a cylindrical composite prepreg, and this may be inserted into the cylindrical outer mold 1. The cylindrical outer mold 1 is preferably one having excellent heat resistance that can withstand processing temperatures during molding, and is, for example, a metal pipe such as a copper pipe.

Next, as shown in FIG. 2, the core 3 is inserted into the hollow part of the composite prepreg 2. The core 3 is thermally expandable, and specifically is a solid or hollow mandrel made of fluororesin. Examples of fluororesins include polytetrafluoroethylene (PTFE, trade name Teflon) and polyfluoroalkoxyethylene resin (PFA).
, fluorinated ethylene propylene ether copolymer resin (F
Examples include resins with high thermal expansion and high heat resistance such as EP).

Next, the composite prepreg 2 and the core 3 are heated to a temperature higher than the plasticizing temperature of the thermoplastic resin constituting the composite prepreg 2, and the core 3 is thermally expanded within the hollow part of the composite prepreg 2. The composite prepreg 2 is mold-clamped by the pressing force caused by the thermal expansion of the core 3 while melting the resin. Thereafter, the composite prepreg 2 and the core 3 are cooled together with the cylindrical outer mold 1, and the core 3 is pulled out from the hollow part of the composite prepreg 2 and the cylindrical outer mold 1 is removed, thereby creating a structure as shown in FIG. A pipe 4 can be obtained in which an electrically insulating layer made of thermoplastic resin is formed on the inner and/or outer surface of the shape. In order to obtain a deformed tube, for example, as shown in FIG. 2, a core 3 may be inserted into a hollow portion of a composite prepreg 2, and then the entire prepreg may be subjected to plastic deformation. Specifically, for example, the entire cylindrical outer mold 1 may be curved in the longitudinal direction, thereby making it possible to obtain a bent pipe. In this way, the pressing force due to the thermal expansion of the core 3 causes the composite prepreg 2 to
Since no voids are formed between the laminated plies, a fiber-reinforced thermoplastic resin pipe with stable quality can be obtained.

■ FIG. 4 shows a longitudinal section of the pipe 4 of FIG. 3. In FIG. 4, 5 is a thick wall portion of the pipe 4. 5 and 6 each show a part of the thick portion 5 of FIG. 4 in an enlarged manner. In FIG. 5, an electrically insulating layer 7 made of prepreg B is formed on the outside of a conductive layer 6 made of prepreg A. In FIG. 6, an electrically insulating layer 7 is formed inside the conductive layer 6. The electrical insulating layer 7 may be formed either on the outside of the conductive layer 6 as shown in FIG. 5 or on the inside as shown in FIG. 6, or on both the inside and outside. good.

FIG. 7 shows a case in which a metal joint is fitted on the outside of the end of a pipe having a thick wall portion 5 as shown in FIG. Fig. 8 shows the case where it is fitted. As shown in FIGS. 7 and 8, since the metal joint 8 is in contact with the electrical insulating layer 7, there is no risk of electrolytic corrosion occurring. Here, the metal joint 8 is made of iron or aluminum.

The electrically insulating layer 7 does not necessarily need to be formed over the entire inner and outer surfaces of the conductive layer 6, but may be formed at least in the portion that contacts the metal joint 8.

[0018]

【Example】

Example 1 Prepreg with PEEK as matrix and carbon fiber as reinforcing fiber (APC-2/AS4; ICI-Fib
Manufactured by erite, thickness per ply is 0.125m
m) with 8 plies and prepreg (A
PC-2/D/S2Glass:ICI-Fiberi
(manufactured by TE, thickness per ply is 0.125mm)
A fiber-reinforced thermoplastic resin pipe (hereinafter referred to as TPC pipe) was obtained by laminating two plies of the same as an electrical insulating layer and molding the pipe so that the inner surface of the pipe consisted of two plies containing glass. In the molding process, the prepreg is first rolled into a preform to form a predetermined laminated structure, then the preform is placed in an outer mold made of copper pipe, and inside the preform, PT
After inserting an FE mandrel and heating them to 380°C, they were poured into cold water and solidified.

[0019] As for the specifications of this pipe, the outer diameter is 28
．． It is a so-called hybrid pipe with a diameter of 6 mm, a wall thickness of 1.25 mm, and a fiber orientation of ±30° with respect to the axis of the pipe. Silver paste was applied to the inner and outer surfaces of this pipe to form band-shaped electrodes facing each other across the 20 mm wide pipe, and the insulation resistance between them was measured at 500 V using the DC 1 minute method.

[0020] Measurement was carried out after molding and before applying environmental load.
The test was carried out three times: when it was soaked in seawater at 0°C for 24 hours and then taken out, and again when it was soaked in boiling water for 24 hours and taken out. The results are shown in Table 1 together with other examples, and there was hardly any decrease in insulation properties, and sufficient resistance to electrical corrosion was confirmed. Comparative Example 1 Prepreg with PEEK as the matrix and glass fiber as the reinforcing fiber (APC-2/D/S2Glass;
10 plies (manufactured by ICI-Fiberite, each ply having a thickness of 0.125 mm) were laminated, and a pipe was then formed in the same manner as in Example 1.

The dimensions, lamination angle, total number of plies, etc. are exactly the same as in Example 1. This pipe has a higher specific gravity of 2.1 than that of Example 1 (specific gravity of 1.6 in Example 1),
However, since both the strength and rigidity are lower than those of Example 1, the values obtained by dividing the strength and rigidity by the specific gravity, that is, the specific strength and specific rigidity, are significantly inferior. As in Example 1, electrical insulation was measured in this example as well.

The results are summarized in Table 1 together with other examples, and it was confirmed that there was almost no deterioration in insulation properties, and sufficient resistance to electrical corrosion was observed. In this example, the mechanical properties are inferior to those in Example 1, but the electrical insulation properties are equivalent. Comparative Example 2 Instead of the glass-containing layer of Example 1, the same A as the other layers was used.
A TPC pipe made entirely of carbon fiber-reinforced PLY in the same manner as in Example 1 except for using PC-2/AS4. The results are shown in Table 1 together with other examples, and conductivity was observed from the beginning, which was thought to be due to the contact between the carbon fibers. However, no increase in conductivity due to environmental loads was observed, confirming that the PEEK matrix is not susceptible to deterioration due to water, etc.

Comparative Example 3 A pipe having the same structure as Comparative Example 2 except that the matrix was an epoxy resin. The results are shown in Table 1 together with other examples, and conductivity was observed from the beginning, which was thought to be due to the contact between the carbon fibers. However, a significant increase in electrical conductivity due to environmental loads was observed, demonstrating once again that the epoxy resin matrix is susceptible to deterioration due to water, etc.

Comparative Example 4 The results of a pipe having the same structure as Example 1 except that the matrix was epoxy resin are shown in Table 1 together with other examples, but before adding the environmental load, Similarly, although it showed excellent insulating properties, it showed considerable deterioration after being exposed to environmental loads, and especially after being immersed in seawater and then boiling water, almost all insulating properties were lost, resulting in no resistance to electrical corrosion at all. Met.

Example 2 A TPC pipe was formed by wrapping a 100 μm thick PEEK film around the outermost layer of Comparative Example 2. The outermost layer of the pipe is 80 to 120 μm, which does not include the carbon fiber reinforcing layer.
A skin layer consisting only of PEEK was confirmed. The results are shown in Table 1 together with other examples, and as in Example 1, excellent insulation was exhibited even before environmental load.
Table 1
Initial stage After soaking in seawater
After soaking in boiling water Example 1 1
08 108
107 Example 2
108 108
107 Comparative Example 1 109
109 1
08 Comparative example 2 102
101
101 Comparative Example 3 10
2 10-1
10-3 Comparative example 4
107 105
101
The unit is (×104Ω) Example 3 An aluminum ring was inserted inside the same pipe as obtained in Example 1 and fixed with an epoxy adhesive to produce an adhesive joint. In addition, the thickness of the adhesive is 200μm
It has been adjusted so that

[0026] This joint was erected with the joint part facing up, and after applying a load of salt water spray for 2000 hours, the joint was broken and the degree of corrosion of the aluminum was examined. As a result, almost no corrosion was observed except for a slight corrosion and whitening in the areas exposed to the outside air. Comparative Example 5 An adhesive joint was made inside the same pipe as used in Comparative Example 4 in the same manner as in Example 3.

After applying a load of salt water spray for 2000 hours in the same manner as in Example 3, the joint was broken and the degree of corrosion of the aluminum was examined. As a result, white corrosive substances were deposited on the parts that were in contact with the outside air to the extent that the shape was unrecognizable, and on the adhesive surface, there were many holes due to corrosion of about 1 mm, which accounted for about 30% of the contact area.
was corroded.

[0028]

Effects of the Invention As explained above, according to the present invention, an electrical insulating layer made of thermoplastic resin is formed on the inner and/or outer surfaces, so that when connecting pipes with a metal joint, there is no electric charge in the metal joint. Eclipse can be prevented from occurring. In addition, the TPC pipe of the present invention is comparable in strength and rigidity to TPC pipes that are entirely reinforced with carbon fibers, and has better electrical insulation than TPC pipes that are entirely reinforced with glass fibers. It has almost no inferiority in practical terms, and has high specific strength, high specific rigidity, and high electrolytic corrosion resistance.

Furthermore, compared to the case where the matrix is made of epoxy resin or the like, even if the structure is the same, the level of electrolytic corrosion resistance after environmental load is high, and the reliability is high with little deterioration. Therefore, the TPC pipe of the present invention has the advantage of increased reliability, such as a longer product life, for applications where it is often used outdoors in environments susceptible to corrosion.

[0030]

[Brief explanation of drawings]

FIG. 1 is a perspective explanatory view showing a cylindrical outer mold used in the present invention.

FIG. 2 is a perspective explanatory view showing the positional relationship among a cylindrical outer mold, a composite prepreg, and a core.

FIG. 3 is a perspective explanatory view showing an example of a fiber-reinforced thermoplastic resin pipe.

FIG. 4 is a longitudinal cross-sectional view of the pipe shown in FIG. 3;

FIG. 5 is an enlarged view of a portion of the thick portion of FIG. 4;

FIG. 6 is an enlarged view of a portion of the thick portion of FIG. 4;

7 is an explanatory diagram showing a state in which a metal joint is fitted to the outside of the end of the pipe having the thick wall portion shown in FIG. 5; FIG.

8 is an explanatory view showing a state in which a metal joint is fitted inside the end of the pipe having the thick wall portion shown in FIG. 6; FIG.

[Explanation of symbols]

Claims (1)

[Claims] Claim 1: A conductive prepreg having a thermoplastic resin as a matrix and an electrically insulating prepreg made of a thermoplastic resin are placed between a thermally expandable core and a cylindrical outer mold disposed outside the core. A fiber-reinforced thermoplastic resin pipe in which an electrically insulating layer made of a thermoplastic resin is formed on the inner and/or outer surface formed by thermally expanding the core.