JP3143754B2 - Method for producing deformed tube made of fiber-reinforced thermoplastic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an advantageous method for producing a deformed tube made of a fiber-reinforced thermoplastic resin.

[0002]

2. Description of the Related Art Conventionally, when a deformed pipe is made of a fiber reinforced thermoplastic resin, that is, a continuous fiber reinforced composite material (hereinafter, referred to as TPC) having a thermoplastic resin as a matrix, the resulting product shape is It was indispensable to first make a preform so as to fit, and then use a mold that matched the product shape. However, using a mold that matches the product shape is satisfactory in terms of product shape accuracy, but on the other hand, a complex shape mold is expensive, so it is uneconomical when only a small number of products are produced. It is. In addition, the production of a preform conforming to the shape of a deformed pipe requires more labor than the production of a preform of a simple-shaped pipe having a circular cross section and being straight in the longitudinal direction.

Further, when a preform and a metal mold are used in accordance with the shape of the product as described above, the preform and the degree of freedom of the shape are superior, but the curve may be slightly curved in the longitudinal direction (for example, 100 mm of the pipe radius). It has been difficult to efficiently produce pipes that are slightly flat (for example, a curvature ratio of about 0.8) or slightly flat (for example, a flatness ratio of about 0.8).

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and provides a method for easily and inexpensively manufacturing a deformed pipe made of a fiber-reinforced thermoplastic resin, that is, a TPC deformed pipe. The purpose is to do. Here, the deformed pipe means a pipe other than a pipe having a circular cross section and being straight in the longitudinal direction, for example, a bent pipe having a circular cross section and bent in a direction intersecting the axis, a triangular cross section, a rectangular shape, etc. Examples include a polygonal straight pipe in the longitudinal direction, a polygonal cross section such as a triangle or a quadrangle, a curved pipe bent in a direction intersecting the axis, and a partially collapsed pipe in the longitudinal direction.

[0005]

According to the method of manufacturing a TPC shaped pipe of the present invention, a plastic film or a metal foil is adhered to the surface of a pipe made of a fiber-reinforced thermoplastic resin to coat the surface, and then the pipe is formed. A thermally expandable mandrel is inserted into the hollow portion, and then the pipe is plastically deformed together with the mandrel while heating the mandrel to thermally expand the mandrel.

Hereinafter, the configuration of the present invention will be described in detail. In the present invention, first, a plastic film or a metal foil is brought into close contact with the surface of a pipe made of a fiber-reinforced thermoplastic resin to cover the surface. In this case, for example, as shown in FIG. 1, a prepreg 2 having a matrix of a thermoplastic resin is disposed between a cylindrical outer mold 1 having a circular cross section and a straight shape in the longitudinal direction and a thermally expandable mandrel 3. A plastic film or a metal foil is interposed between the cylindrical outer mold 1 and the prepreg 2 as a mold release means for mold release. The plastic film used here has heat resistance enough to withstand the plasticizing temperature of the thermoplastic resin constituting the prepreg 2, and examples thereof include a polyimide film and a polytetrafluoroethylene film. The metal foil also has heat resistance enough to withstand the plasticizing temperature of the thermoplastic resin, and is, for example, an aluminum foil, a copper foil, a stainless steel foil, or the like.

Next, the prepreg 2 and the mandrel 3 are heated to a temperature equal to or higher than the plasticizing temperature of the thermoplastic resin constituting the prepreg 2 to thermally expand the mandrel 3 in the hollow portion of the prepreg 2 to melt or soften the thermoplastic resin. At the same time, the prepreg 2 is clamped by the pressing force due to the thermal expansion of the mandrel 3. Thereafter, the prepreg 2 and the mandrel 3 are cooled together with the cylindrical outer mold 1, the mandrel 3 is pulled out from the hollow portion of the prepreg 2, and the cylindrical outer mold 1 is removed. As a result, a plastic film or a metal foil adheres to the surface, and the surface is covered by the plastic film or the metal foil (hereinafter referred to as “skin covering”). Hereinafter, a straight pipe is obtained.

The prepreg 2 using a thermoplastic resin as a matrix is made by impregnating a thermoplastic fiber of a matrix into a fiber bundle, generally called tow, in which a plurality of continuous fibers are aligned and arranged in a band in one direction. (One-way aligned prepreg (UD prepreg)).
It is in the form of a sheet or a strip (slit tape). The fibers used in the fiber bundle constituting the prepreg 2 include continuous fibers having high heat resistance and high strength such as carbon fibers, glass fibers, aramid fibers (aromatic polyamide fibers), silicon carbide fibers, boron fibers, and alumina fibers. Can be exemplified.

The thermoplastic resin of the matrix is not particularly limited. For example, polyetheretherketone (PEEK), polyphenylenesulfide (PPS), polyetherimide (PEI), polyethersulfone (PES) ), Polyarylene ketone, polyarylene sulfide, polyallylimide, polyamideimide,
Polyimide, polyimide sulfone, polysulfone,
It is a thermoplastic resin having a high melting point or a high softening point such as polyester.

The mandrel 3 is a heat-expandable material, and is specifically a solid or hollow material made of a fluororesin. As the fluorine resin, polytetrafluoroethylene (PTFE, trade name Teflon), polyfluoroalkoxyethylene resin (PFA), fluoroethylene propylene ether copolymer resin (FEP), etc. have large thermal expansion and heat resistance Resin having a high viscosity.

The cylindrical outer die 1 has excellent heat resistance to withstand the processing temperature during molding, and is, for example, a metal pipe such as a copper pipe. In order for the prepreg 2 having a thermoplastic resin as a matrix to be interposed between the mandrel 3 and the cylindrical outer mold 1, since the prepreg is cured, the cured sheet-shaped prepreg is spirally wound to form a surface. A plastic film or a metal foil is put on the mold for mold release, and this is inserted into the cylindrical outer mold 1. Further, when spirally wound, the prepreg may be temporarily welded by spot welding with a soldering iron or the like.

[0012] In addition to obtaining a straight pipe covered with a skin as described above, a plastic film or a metal foil is wound around a surface of a generally commercially available pipe made of a fiber-reinforced thermoplastic resin to cover the surface. Is also good. Next, as shown in FIG. 2, another heat-expandable mandrel 3 is inserted into the hollow portion of the covering straight pipe 4 obtained as described above, and then these are heated to thermally expand the mandrel 3. Then, the straight tube 4 is plastically deformed together with the mandrel 3. In this case, the heating is performed at a temperature equal to or higher than the plasticizing temperature of the thermoplastic resin. The skin of the straight tube 4 functions as an outer mold and restrains the thermal expansion of the mandrel 3. As the plastic deformation, specifically, for example, the straight tube 4 is curved in the longitudinal direction of the straight tube 4. That is, the straight pipe 4 is bent in a direction intersecting with the axis. At this time, since the skin of the straight pipe 4 is extended while being in close contact with the surface of the pipe, there is no unevenness or wrinkles on the surface of the straight pipe. The thermal expansion of the mandrel 3 can be performed a plurality of times with mandrels having the same or different outer diameters.

Thereafter, the curved straight pipe 4 is cooled together with the mandrel 3, and the mandrel 3 is pulled out from the hollow portion of the straight straight pipe 4 and the skin is removed. Can be obtained. In this case, since the diameter of the mandrel 3 is contracted by cooling, the mandrel 3 can be easily pulled out. Also, the skin may be removed, for example, mechanically or by dissolving the skin with a chemical.

The above-mentioned plastic deformation is preferably performed in a split mold in which a layer having heat resistance and heat retention is provided on the inner surface (molding surface).
FIG. 4 shows an example of the split mold. FIG. 4 shows a split mold composed of an upper mold 6 and a lower mold 7.
The inner surface 6a of the lower mold 7 and the inner surface 6b of the lower mold 7 are provided with layers having heat resistance and heat retention, respectively. The reason why this layer has heat resistance and heat retaining property is to make it possible to withstand the temperature at the time of plastic deformation and to prevent rapid cooling of the mold. As this layer, for example,
What is necessary is just to arrange | position a silicone rubber sheet. Further, as the material of the split mold, a metal having heat resistance enough to withstand the temperature during plastic deformation may be used.

When plastic deformation is performed using this split mold, the covering straight tube 4 and the mandrel 3 are heated in an oven to thermally expand the mandrel 3 and to form the thermoplastic covering tube 4. The resin may be melted or softened, and then the skinned straight pipe 4 and the mandrel 3 may be taken out of the oven in this state and placed in a split mold under a room temperature atmosphere for molding. This molding operation in a room temperature atmosphere has higher safety and is advantageous compared to the case where plastic deformation is performed in an oven. In addition, cooling may be performed by submerging the split mold in which the skin covering straight pipe 4 and the mandrel 3 are still contained. As a result, the cooling is performed uniformly, so that a TPC deformed pipe excellent in quality with less variation in shape can be finally obtained.

[0016]

【Example】

Example 1 A straight pipe covered with a skin (outer diameter 30 mm, wall thickness 1 mm, laminated structure ± 30
°, length 500 mm, PEEK / carbon fiber, skin is polyimide film (UPIREX 25R, Ube Industries, registered trademark))
Then, insert a hollow PTFE mandrel having an outer diameter of 26 mm and an inner diameter of 13 mm, and support both ends of the mandrel in a 400 ° C oven for about 1 hour.
The sample was allowed to stand for a while, and was bent at its center by about 10 mm under its own weight.

At this time, the straight pipe covered with the skin was bent, and the skin closely adhered to the surface of the tube followed the surface of the tube while maintaining the close contact state, and no wrinkles or loosening occurred. At the same time, the mandrel thermally expanded and came into close contact with the inner surface of the tube, and the molten or softened matrix sandwiched between the skin and the mandrel was pressed to clamp the tube. This bent skin tube is then thrown into the water with the mandrel to cool the matrix and mandrel,
A TPC bent tube was obtained by withdrawing the mandrel from the tube and removing the skin. The skin was removed by hand while tearing from the end of the tube. When a polyimide film coated with a small amount of a release agent was used as a skin, it could be peeled off from the pipe surface with a slight force.

The obtained bent pipe was free from defects such as disturbance of the reinforcing fiber, voids, cracks and delamination, and the inner and outer surfaces were smooth and good as in the case of the straight pipe. Example 2 A straight pipe covered with a skin (outer diameter 20 mm, wall thickness 1 mm, laminated structure ± 45
°, length 300 mm, PEEK / carbon fiber, skin is polyimide film (UPILEX 25R, Ube Industries, registered trademark))
Then, insert a solid PTFE mandrel with a diameter of 16 mm, sandwich one end of the straight pipe about 100 mm between two iron plates, and
Spacers were provided so as to narrow the interval to 16 mm, and these were suspended in an oven at 400 ° C. while applying a load of about 50 kgf to the iron plate. After about one hour, one end of the straight pipe had been deformed to a thickness of 16 mm.

These are then poured into water, the matrix and mandrel are cooled, the mandrel is pulled out of the tube and the skin is removed, so that the TPC has a flat end and a circular cross-section in the other part. I got a tube. The skin was removed in the same manner as in Example 1.
The resulting deformed pipe was free of defects such as turbulence of the reinforcing fibers, voids, cracks and delamination, and the inner and outer surfaces were smooth and good as in the case of the straight pipe.

Example 3 A straight pipe covered with a skin (outer diameter 24 mm, wall thickness 1.75 mm, laminated structure ±
A PTFE mandrel having a diameter of 19 mm was inserted into a polyimide film (UPILEX 25R, Ube Industries, registered trademark) of 25 °, 400 mm in length, PEEK / carbon fiber, and leather.
Next, the straight pipe covered with the mandrel inserted in this manner is placed on a flat table and allowed to stand in an oven at 380 ° C for about 1 hour, and the PEEK / carbon fiber pipe in which the matrix resin has melted is heated. The state was sandwiched between the expanded mandrel and the polyimide film skin.

The mold in this state was placed in a split mold shown in FIG. 4, and before the molten matrix resin was solidified, the mold was closed and shaping was performed (this may be performed within about 2 minutes). In the split mold used in this case, a cloth-pulled silicone rubber pad of 3 mm thickness is stuck on the inner surface, and the inner diameter when the mold is closed substantially matches the outer diameter of the pipe in which the matrix resin is melted. And the bend is about 300 mmR
The bending angle of that portion was 6 °.

Next, the closed mold was immersed in cold water to solidify the pipe. The obtained bent tube was excellent in appearance and shape as in Examples 1 and 2. In addition, when the above procedure was performed on 20 straight pipes having the same covering, the resulting bent pipe had a very small bending angle error, and the bending angle was 20 mm.
19 of the books were in the range of 6 ° ± 0.2 °. On the other hand, when the same operation was performed using a split mold having no cloth-pulled silicone rubber pad on the inner surface, 19 out of 20
The book ranged 6.5 ° ± 2.0 °. Therefore, the use of a split mold having a cloth-pulled silicone rubber pad adhered to the inner surface can significantly improve the accuracy and accuracy in the shape of the bent tube obtained compared to the case of using a split mold without the paste. I understand.

Comparative Example 1 A bent tube was produced in the same procedure and in the same manner as in Example 1 except that a peeled straight tube was used. In the obtained tube, delamination occurred in some places, and swelling occurred outside. Also,
The outer surface lost luster and was full of irregularities. The product could not be expected to be strong as a pipe.

Comparative Example 2 A flat tube having a flat end was manufactured in the same manner as in Example 2 except that no mandrel was used. In the obtained pipe, no problem was found in the straight part, but delamination occurred in the part where the radius of curvature of the flattened part was small, and delamination also occurred in the part connected from the flattened part to the straight pipe And the strength of the deformed portion could not be expected.

Comparative Example 3 An outer mold having the same shape of the final product as in Example 1 (split mold for convenience of taking out the product), the production cost of this mold is the standard used for obtaining the straight pipe in Example 1. The braided (brader) preform and a PTFE mandrel.
A release agent for releasing the mold was applied to the inner surface of the mold.

Then, these were placed in an oven at 400 ° C., and the mandrel was sufficiently thermally expanded to perform mold clamping. However, the preform of the braider system (it is indispensable to use the braider system in order to bend it into the mold)
Therefore, the gap of the preform is large, and therefore, the mold clamping is performed by gradually changing the mandrel to a gradually thick one.
Had to be done times.

Finally, a tube having the same size and shape as in Example 1 was obtained. Since the preform was removed from the outer mold using a point where the preform was a braider and a release agent, the tube was as good as the surface gloss except that it was slightly inferior. However, there are problems that the mold is very expensive and the number of times of mold clamping is large. Therefore, it is not suitable for the production of many kinds in small quantities.

[0028]

As described above, according to the present invention, a plastic film or a metal foil is brought into close contact with the surface of a pipe made of a fiber-reinforced thermoplastic resin to cover the surface, and then the hollow portion of the pipe is heated. In order to insert an expandable mandrel and then heat them to thermally expand the mandrel and plastically deform the pipe together with the mandrel, it is not necessary to use a complicated and expensive split mold as in the past, and it is complicated. Since a troublesome preform is not required, it is possible to easily and inexpensively manufacture a TPC deformed tube. In addition, since an outer die adjusted to the minimum shape is not required, it is suitable for high-mix low-volume production.
Furthermore, by repeating a part of the process, a product having a considerably complicated shape can be produced. The TPC deformed pipe obtained by the present invention is used, for example, for a pipe part constituting a bicycle frame or a tennis racket, a structural or plumbing pipe, and the like.

[Brief description of the drawings]

FIG. 1 is an explanatory perspective view showing a positional relationship among a cylindrical outer mold, a prepreg, and a mandrel.

FIG. 2 is a perspective explanatory view showing a state in which a thermally expandable mandrel is inserted into a hollow portion of a straight pipe made of a fiber-reinforced thermoplastic resin whose surface is covered with a plastic film or a metal foil adhered thereto.

FIG. 3 is an explanatory view showing an example of a deformed tube obtained by the present invention.

FIG. 4 is an explanatory view showing an example of a mold used for manufacturing a deformed tube. 1 cylindrical outer mold, 2 prepreg, 3 mandrel, 4
Skin-covered straight pipe.

Claims (2)

(57) [Claims] After a plastic film or a metal foil is adhered to the surface of a pipe made of a fiber-reinforced thermoplastic resin to cover the surface, a thermally expandable mandrel is inserted into a hollow portion of the pipe. A method for producing a deformed pipe made of a fiber-reinforced thermoplastic resin, wherein the pipe is plastically deformed together with the mandrel while heating the mandrel to thermally expand the mandrel. 2. The method according to claim 1, wherein the plastic deformation is performed in a split mold having an inner surface provided with a layer having heat resistance and heat retention.