JPH0423909B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a hollow rod made of thermoplastic resin having high strength. Prior art and its problems Corrosion-resistant bolts, rivets, etc. must be used in equipment and equipment installed in environments where corrosion is likely to occur, such as offshore structures, chemical factories, and coastal industrial areas. Conventionally, corrosion-resistant bolts, rivets, etc. made of stainless steel or copper alloys have been used, but their corrosion resistance is not necessarily satisfactory, and in addition, their conductivity is There are cases where it cannot be used due to its nature. On the other hand, thermoplastic resin has insulation properties,
Since it is easy to mold and process, it has already been used as a material for bolts, screws, and rivets. However, when manufacturing bolts of a certain diameter or more by molding such thermoplastic resins, so-called "porosity" occurs due to shrinkage during molding, which reduces the inherent strength of the material. The problem is that they cannot perform to their full potential. Means for Solving the Problems In view of the problems of the prior art as described above, the present inventor first made thermoplastic short fibers such as glass fibers, carbon fibers, and metal whiskers used as reinforcing materials for reinforced plastics. In addition to resin, we tried molding it into bolts and rivets. However, it has been found that the bolts and rivets obtained as described above may be less strong than those without reinforcement. Therefore, as a result of further research, the present inventor found that
Unexpectedly, bolts and rivets made of thermoplastic resin made into a hollow shape using short fibers such as carbon fiber as a reinforcing material are significantly stronger than solid bolts and rivets of the same outer diameter made only of thermoplastic resin. It was found that it exhibits high strength. The present invention has been completed based on the above new findings, namely, a thermoplastic resin containing 5 to 25% by volume of at least one short fiber of carbon fiber, glass fiber, and aramid fiber. , a hollow rod characterized in that it has holes continuous in the axial direction, and the short fibers present at least near the inner and outer surfaces are oriented in the axial direction; and at least carbon fiber, glass fiber, and aramid fiber. A thermoplastic resin containing 5 to 25% by volume of one type of short fiber is molded under heat using a mold with a core to form pores that are continuous in the axial direction, and are present at least near the inner and outer surfaces. The present invention relates to a method for manufacturing a hollow rod, characterized in that the short fibers are oriented in the axial direction. In the present invention, the term "hollow rod" refers not only to bolts with holes penetrating in the axial direction, double-sided bolts, rivets, etc., but also to pipes (not only circular,
(including irregularly shaped pipes such as oval and square). The material used in the present invention is 5 to 25% by volume of the total amount.
It is made up of at least one of carbon fiber, glass fiber, and aramid fiber, and the remainder is a thermoplastic resin. In the present invention, when the fibers are mixed into the thermoplastic resin, they are uniformly dispersed in the resin,
Furthermore, when molding is performed using a mold having a core, the fibers present at least near the inner and outer surfaces must be oriented in the axial direction. Therefore, the short fibers that can be uniformly dispersed and oriented are used as the fibers. In the present invention, fibers having such properties are referred to as "short fibers". If the amount of the above-mentioned fibers used is less than 5% by volume, the effect of fiber mixing will not be so great, while if it exceeds 25% by volume, not only will the fluidity of the material during molding decrease and molding become difficult, but also the amount of fibers will increase. The distribution becomes uneven and the strength of the molded product decreases. There are no particular restrictions on the thermoplastic resin, and examples include polyamide resin, vinyl chloride resin, vinyl acetate resin,
A wide range of materials can be used including polystyrene, ABS resin, acrylic resin, polyethylene, polypropylene, fluorine resin, polycarbonate, acetal resin, cellulose plastic, etc. The wall thickness of the hollow rod in the present invention is usually 0.1 to 6
It is good to set it to about mm, preferably about 2.5 to 4 mm. If this wall thickness becomes too large, cavities are likely to occur, and the axial orientation of the fibers existing between the outer and inner surfaces of the hollow rod decreases, resulting in insufficient improvement in strength. . On the other hand, if the wall thickness is too thin, molding becomes difficult. If thermosetting resin is used instead of thermoplastic resin, the molding time will be longer, there will be technical limitations, and it will be economically disadvantageous, but it will still be possible to make practical rivets, bolts, and pipes. It is possible to manufacture etc. The hollow rod of the present invention is manufactured, for example, as follows. First, a predetermined amount of at least one of carbon fibers, glass fibers, and aramid fibers is blended and mixed with a thermoplastic resin, and the fibers are uniformly dispersed. After heating the resin blended with fibers to a predetermined temperature, it is molded into a hollow rod shape having holes continuous in the axial direction using a mold having a core. In this case, the molding method may be an injection molding method or an extrusion molding method. By forming the hollow rod using a mold having a core in this way, short fibers are present near the outer surface of the hollow rod that contacts the inner surface of the mold and near the inner surface of the hollow rod that contacts the outer surface of the core mold. is oriented in the axial direction by friction and viscosity. The hollow rod thus obtained is characterized in that the short fibers present at least in the vicinity of the inner and outer surfaces are oriented in the axial direction and are substantially free of voids. Effects of the Invention The hollow rod of the present invention does not substantially contain nests, and short fibers are present over the entire cross section in the case of a thin wall, or at least near the inner and outer surfaces in the case of a thick wall. Since it is oriented in the axial direction, its strength is extremely high. Moreover, since the material has excellent corrosion resistance, it can be effectively used in equipment used in corrosive environments. Furthermore, when glass fiber or aramid fiber is used, excellent insulation properties can be exhibited, making it ideal for insulating joints and the like. Examples Examples and comparative examples will be shown below to further clarify the features of the present invention. Example 1 A uniform composition consisting of 80% by volume of polyamide 6-6 and 20% by volume of carbon fiber (about 10 μm in diameter, about 0.3 mm in length) was molded into a core at a temperature of 285°C and an injection pressure of 660 kg/ ^cm2. Injection molded using a mold with JIS
Same shape as M16 bolt (however, diameter 5 in the center axial direction)
A plastic bolt with a through hole of mm was manufactured. When the cross section of the resulting bolt was observed under a microscope, it was found that the short fibers present near the inner and outer surfaces were oriented in the axial direction. This bolt was subjected to a tensile test according to JIS K1051, and the results are shown in Table 1. Comparative Example 1 Polyamide 6-6 was injection molded in the same manner as in Example 1 (however, no core was used) to produce a plastic bolt having the same shape as a JIS M16 bolt (without through holes). This bolt was subjected to a tensile test according to JIS K1051, and the results are shown in Table 1. Comparative Example 2 A homogeneous composition made of polyamide 6-6 and carbon fiber similar to that in Example 1 was injection molded in the same manner as in Example 1 (however, no core was used), and the same shape as a JIS M16 bolt (through-hole) was molded. A plastic bolt (without holes) was manufactured. When the cross section of the resulting bolt was observed under a microscope, it was found that the short fibers present near the outer surface were oriented in the axial direction, but the short fibers in the center were not oriented in the axial direction. this bolt
Table 1 shows the results of tensile testing according to JIS K1051. Example 2 Polyamide 12 90% by volume and carbon fiber (diameter approx.
A plastic bolt was manufactured in the same manner as in Example 1 using a uniform composition consisting of 10% by volume (10 μm, length approximately 0.3 mm). When the cross section of the resulting bolt was observed under a microscope, it was found that the short fibers present near the inner and outer surfaces were oriented in the axial direction. This bolt was subjected to a tensile test according to JIS K1051, and the results are shown in Table 1. Comparative Example 3 Using the same uniform composition of polyamide 12 and carbon fiber as in Example 2, and using the same method as in Example 1 (however, no core was used), a bolt with the same shape as a JIS M16 bolt (through hole) was prepared. A plastic bolt was manufactured. When the cross section of the obtained bolt was observed under a microscope, the results were the same as those of Comparative Example 2.

[Table] As shown in Table 1, it can be seen that the bolt of the present invention has extremely high strength. That is, the tensile strength of the bolt of Example 1, which is made of polyamide 6-6 and carbon fiber and has a through hole, is higher than that of polyamide 6.
-6 and carbon fiber as raw materials, and its strength is dramatically improved compared to the case (Comparative Example 2) that does not have through holes. In addition, the bolt of Example 2, which is made of polyamide 12 and carbon fiber and has through holes, has a lower temperature than the bolt of Example 2, which uses the same material but does not have through holes (Comparative Example 3). It can be seen that the strength has increased significantly. This is considered to be due to the fact that in the bolt of the present invention, the short fibers near the inner and outer surfaces are oriented in the axial direction.

Claims (1)

[Scope of Claims] 1. Made of a thermoplastic resin containing 5 to 25% by volume of at least one kind of short fibers such as carbon fibers, glass fibers, and aramid fibers, having pores continuous in the axial direction, and having at least inner and outer surfaces. A hollow rod characterized in that the short fibers present in the vicinity are oriented in the axial direction. 2 A thermoplastic resin containing 5 to 25 volume % of short fibers of at least one of carbon fibers, glass fibers, and aramid fibers is heated using a mold having a core to form holes continuous in the axial direction. A method for manufacturing a hollow rod, characterized in that the short fibers present at least near the inner and outer surfaces are oriented in the axial direction.