JPH05169560A - Method for molding pipe-shaped molded product - Google Patents

Abstract

(57) [Summary] [Purpose] Using a composite material of thermoplastic resin,
A pipe-shaped molded product having an arbitrary shape such as a curved shape can be easily molded. [Structure] A flexible tube made of a resin having a melting point higher than that of the matrix component of the molded article is placed around a flexible tube, and a molding material composed of reinforcing fibers and thermoplastic resin fibers or powder is placed in the hollow tube. Put in the mold, and while heating the molding material to a temperature higher than the melting temperature of the thermoplastic resin fiber or powder, apply the fluid pressure in the tube and press the molding material onto the inner surface of the mold. A pipe-shaped molded product is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a pipe-shaped molded article used in fields requiring lightweight and tough performance such as sporting goods and general mechanical parts, and more particularly to a pipe made of fiber reinforced thermoplastic resin. The present invention relates to a method for molding a molded article.

[0002]

2. Description of the Related Art Lighter composite materials have been used in place of conventional metals in fields requiring lightweight and tough performance such as sports equipment. In particular, polymer composite materials using carbon fibers as reinforcing fibers have a specific strength,
It is a well-known fact that carbon fiber reinforced resin is widely used in the field of sports goods as a material having excellent specific rigidity, and is used in tennis rackets, golf clubs and the like.

Conventionally, all the resins used in such composite materials are thermosetting resins, but in recent years, the superiority of thermoplastic resins as matrix resins for composite materials has been recognized. Thermoplastic resins have greater toughness, impact resistance, and fatigue resistance than thermosetting resins.
It is suitable as an article that is exposed to a severe impact, such as sports equipment.

A filament winding method is generally used as a method for molding a pipe-shaped molded article made of a composite material. There is also known a method in which a composite material is wound around the outer circumference of a hollow tube made of an elastic material, and the composite material is set in a mold having a predetermined shape and molded (for example, JP-A-57).
-22016, JP-A-61-2820828, JP-A-2-263624, and JP-A-3-21434).

[0005]

However, all of these conventional methods have problems. That is, in the filament winding method, in addition to the problem that only a straight pipe with a constant cross section can be molded, in order to obtain the accuracy of the pipe outer diameter necessary for making a structure, the outer diameter is cut and ground again. There was a disadvantage that it was necessary. On the other hand, in the method using the hollow tube, by bending the hollow pipe into a predetermined shape in advance,
Although it is possible to mold a molded product having a curved shape, there is a problem that it is difficult to wind the molding material around the outer circumference of the hollow tube. That is, a molding material such as prepreg is relatively hard, and it is difficult to evenly wind the molding material around the hollow tube without crushing the hollow tube. Especially when molding a thermoplastic resin, unlike a prepreg of a thermosetting resin, the molding material is already hardened before molding, so it is less flexible and should be wrapped around an elastic hollow tube. Is extremely difficult.
In order to prevent the hollow tube from collapsing when winding the molding material around it, it is necessary to take measures such as increasing the wall thickness of the hollow tube to give it rigidity, or inserting a core other than the tube. However, in that case, it is necessary to remove the hollow tube or core from the molded product after molding, which complicates the process.

The present invention has been made in view of the above conventional problems, and can easily form a pipe-shaped molded article having an arbitrary shape such as a linear shape or a curved shape by using a composite material of a thermoplastic resin. An object is to provide a molding method.

[0007]

Means for Solving the Problems As a result of intensive studies made by the present inventors to solve the above-mentioned problems, as a composite material of thermoplastic resin, a molding material composed of reinforcing fiber and thermoplastic resin fiber, or reinforcing fiber The present invention has been completed by discovering that the use of a molding material composed of and a thermoplastic resin powder makes it possible to wind or cover the molding material on the outer periphery of a thin resin tube very easily. ..

That is, the present invention relates to a method for molding a pipe-shaped molded article made of a fiber reinforced thermoplastic resin, which is made of a resin having a melting point or a thermal decomposition temperature higher than the melting point of the matrix component of the molded article. Around the sex tube,
A molding material composed of reinforcing fibers and thermoplastic resin fibers or powder is arranged, and it is placed in a hollow mold, and the molding material is higher than the melting temperature of the thermoplastic resin fiber or powder,
While heating to a temperature lower than the melting temperature or the thermal decomposition temperature of the flexible tube, exert a fluid pressure in the tube,
A gist of the present invention is a method for molding a pipe-shaped molded article, which is characterized in that a molding material is pressure-bonded to an inner surface of a mold.

The resin flexible tube used in the present invention is used as a core during molding.
It is not necessary for itself to have the strength to act as a core, but it is flexible enough to expand when the fluid pressure is applied to the inside and to apply the molding pressure to the molding material placed on the outer periphery of the core. As long as it has a property. However, the property that the flexible tube can retain a predetermined shape at least at room temperature so that the molding material can be wound or covered around the flexible tube and set in the mold at room temperature ( It is desirable to have shape retention. In some cases, a flexible mandrel is placed in the tube, the molding material is wound, the mandrel is pulled out, and then the mandrel is set in a mold, thereby improving flexibility. It is possible to wind the molding material without making the tube too thick. Since the flexible tube is left in the molded product after molding, it is desirable that it is lightweight, and therefore it is desirable that the thickness thereof is as thin as possible. Considering these points,
The thickness of the flexible tube is usually 0.05 to 0.5
mm, and preferably 0.15 to 0.35
It is selected to be about mm. This flexible tube is made to have a shape substantially equal to the inner surface shape required for the molded product in advance.

The material of the flexible tube may be either a thermoplastic resin or a thermosetting resin.
A material having a melting point or a thermal decomposition temperature higher than the molding temperature is used so as to withstand pressurization. More specifically, the melting point of the matrix resin in the molding material is 30 to 200
A substance having a melting point or a thermal decomposition temperature higher than 70 ° C, preferably 70 to 150 ° C is used. The material of the flexible tube is polyether ether ketone, polyether ketone, polyether nitrile, polyphenylene sulfide, polyether imide, polyether sulfone, plasticized polyimide, thermoplastic polyimide, so-called super engineering such as polyfluorocarbon resin. In addition to plastics, various polyamides, various polyesters, polycarbonates, polypropylenes and the like can be mentioned, and super engineering plastics are particularly preferable. Of these, an appropriate one may be selected according to the matrix resin to be molded.

The molding material used in the present invention is required to be supple before molding, and in order to ensure it, the thermoplastic resin as the matrix resin is used in the form of fiber or powder. Has been done. That is, the molding material is one composed of reinforcing fibers and thermoplastic resin fibers, or one in which thermoplastic resin powder is attached to the reinforcing fibers. Examples of the former include one in which reinforcing fibers and thermoplastic resin fibers are mixed, and a woven fabric or a braid is formed from the mixed yarn, and the reinforcing fibers and the thermoplastic resin fibers are used as separate yarns. Mention may be made of woven fabrics and braids. Examples of the latter are those in which a woven fabric or braid is formed by using reinforcing fibers sprinkled with a thermoplastic resin powder, or a woven fabric or braid is formed with reinforcing fibers and then sprinkled with a thermoplastic resin powder. You can list things like When the braid is used here, it is preferable that the braid has a tubular shape having a diameter capable of being covered with the flexible tube. As described above, in the present invention, as the molding material, one made of reinforcing fibers and thermoplastic resin fibers or powder is used, but not limited to the case of using only this molding material, a flexible film of matrix resin is used. You may use together.

The reinforcing fibers used in the molding material can be applied to all fibers used for fiber reinforced plastics such as carbon fibers, glass fibers, aramid fibers, silicon carbide fibers and alumina fibers. The fiber form of the reinforcing fibers and the thermoplastic resin fibers may be either long fibers or short fibers.

As the thermoplastic resin used as the matrix resin, so-called super engineering plastics such as polyether ether ketone, polyether ketone, polyether nitrile, polyphenylene sulfide, polyether imide and polyether sulfone, as well as various polyamides, It can be applied to various thermoplastic resins such as various polyesters, polycarbonates and polypropylenes that can be made into fibers or powders.

The mold used in the molding of the present invention is optional as long as it has a hollow portion in which a molding material can be set around a flexible tube, and in order to facilitate attachment and detachment, A separable structure is preferable, and in the case of a molded product such as a straight pipe that can be easily attached and detached, it may have an integral structure. A gas such as air or nitrogen may be used, or a liquid such as oil may be used to exert a fluid pressure in the flexible tube. Pressurization is achieved by a means such as a compressor, and usually a pressure of about 3 to 10 kg / cm ² is used. For heating for molding, the mold may be put in a heating furnace or the like to be heated from the outside, or may be heated by passing a gas or a liquid passed through a tube. Of course,
You may use these two together.

[0015]

As described above, in the present invention, as the molding material to be arranged around the flexible tube, the one composed of the reinforcing fiber and the thermoplastic resin fiber, or the one composed of the reinforcing fiber and the thermoplastic resin powder is used. Since these molding materials have flexibility, not only when the flexible tube is straight, but also when the flexible tube has a complicated curved shape, it is extremely easy to wind or cover it. Can be arranged. Especially when using a tubular braid,
The work is easier because the flexible tube is simply inserted into the assembly. In addition, when winding or covering the flexible tube with the molding material, in some cases,
A rigid mandrel may be inserted in the flexible tube.

Next, at the time of molding, the molding material placed around the flexible tube and set in the mold is pressure-bonded to the mold outside by the pressure applied to the flexible tube inside. By heating a temperature which is sufficient to melt the matrix resin and is equal to or lower than the melting point or the thermal decomposition temperature of the resin forming the flexible tube, the matrix resin is melted and integrated with the reinforcing fiber to obtain a molded article. Becomes
After that, the molded product is taken out of the mold to obtain a fiber-reinforced thermoplastic resin pipe-shaped molded product having a predetermined shape. Here, the flexible tube is left as it is in the pipe-shaped molded product. As a result, the work of removing the flexible tube becomes unnecessary and the process is simplified. Further, since the flexible tube is made of a thin resin, its weight is extremely small, and therefore, the lightweight characteristic of the composite material is not hindered. Since the outer surface of the obtained molded product was regulated by the mold, the molded product had a clean appearance and had a predetermined size, and cutting and polishing were hardly required.

[0017]

[Examples] In FIGS. 1 and 2, carbon fiber (3K)
A tubular braid 1 having a diameter of 2.5 cm, a length of 50 cm, and an apparent thickness of 1.0 mm, which was assembled from a yarn in which Nylon-6 fiber (200 tex) was aligned, was used as a molding material.
A diameter of 2.0c with one end closed in a stack of sheets
After inserting a flexible tube 2 made of PEEK (polyetheretherketone) having a length of m, a length of 50 cm and a thickness of 0.3 mm, and connecting an air pipe 4 to the open mouth of the flexible tube 2, This is placed in a mold 3 divided into two parts, a seal member 6 having an air vent hole 5 is attached to one end of the mold 3, and the mold 3 is closed. Next, this whole thing is put into a 280 degreeC oven and heated. After allowing the whole to reach this temperature for 30 minutes, 5 kg / cm ² of air was blown through the air pipe 4 to inflate the flexible tube 2 and thereby the carbon fiber and nylon fiber (which had already melted at this temperature). The assembly of (1) is crimped to the inner surface of the mold 3. It takes 5 minutes to complete the crimping, and then the whole is taken out of the oven while keeping the air pressure and left to stand at room temperature. After that, the mold 3 was split, the formed product was taken out, and only the air pipe 4 was cut off to obtain a pipe-shaped formed product. The thickness of the obtained molded product was 1.45 mm on average, the surface was smooth like the finished surface of the mold, and its outer diameter was 2.4.
It was 8 mm.

Although the embodiment shown in FIGS. 1 and 2 shows a case where a pipe-shaped molded product having a straight and circular cross section is molded, the present invention is not limited to this case, and a flexible tube and By changing the shape of the mold, it is possible to manufacture various pipe-shaped molded products. For example, as shown in FIG. 3, a flexible tube 2A having a frame shape of a racket as a whole is used, and a mold 3A having a cavity 7 having a shape into which the flexible tube 2A can be mounted is divided into upper and lower split molds. By using it, a racket frame having a hollow structure can be formed.

[0019]

As described above, according to the present invention, a flexible molding material made of a reinforcing fiber and a thermoplastic resin fiber or powder is attached around a resin flexible tube as a core. Since it is set in a mold and heated and pressed to mold, it is extremely easy to handle the molding material, and even for thin flexible tubes with complicated shapes such as curved shapes. A molding material can be easily attached, and a lightweight and high-strength fiber-reinforced thermoplastic resin pipe-shaped molded article can be manufactured. Also, since the flexible tube used as the core during molding can be made of a thin resin, its weight is extremely small, and there is no problem even if it is left in the pipe-shaped molded product as it is. This eliminates the need to remove the flexible tube and simplifies the process.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing members used in one embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a state of molding using an upper member.

FIG. 3 is a schematic perspective view showing a flexible tube and a mold used in another embodiment of the present invention.

[Explanation of symbols]

 1 Assembly (molding material) 2, 2A Flexible tube 3, 3A Mold 4 Air pipe 5 Air vent hole 6 Seal member

Claims (1)

[Claims] 1. A method for molding a pipe-shaped molded article made of a fiber-reinforced thermoplastic resin, comprising: a flexible tube made of a resin having a melting point or a thermal decomposition temperature higher than a melting point of a matrix component of the molded article. In, a molding material consisting of reinforcing fibers and thermoplastic resin fibers or powder is placed, it is placed in a hollow mold, the molding material is higher than the melting temperature of the thermoplastic resin fibers or powder, A pipe shape characterized by applying a fluid pressure to the inside of the flexible tube while heating it to a temperature lower than the melting temperature or the thermal decomposition temperature of the flexible tube and press-molding the molding material onto the inner surface of the mold. Molding method for molded products.