JPH0446218B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a plastic thread-shaped molded body, and in particular to a plastic thread-shaped molded body highly reinforced with reinforcing fibers. (Prior Art) Metal bolts and nuts have been known as thread-shaped molded bodies. This is manufactured by the rolling method, which has the fastest production speed for thread processing. Although metal screw-shaped molded bodies are manufactured with high productivity in this manner, they have the fatal disadvantage of being heavy and prone to rust. In contrast, plastic thread-shaped molded bodies that are lightweight and have excellent corrosion resistance have been produced. For example, there is a plastic bolt obtained by rolling a hard vinyl chloride resin. However, such plastic bolts can only exhibit the strength of the plastic material itself, and cannot have the strength normally required for bolts. Its tensile strength is at most 4 to 6 kg/mm ² and cannot withstand use as a bolt that requires strong fastening force. In order to increase the strength of bolts, for example, Japanese Patent Laid-Open No. 56-82219 discloses bolts made of fiber reinforced plastic. Fiber-reinforced plastics are unidirectionally reinforced materials, so they have high strength in the reinforcing direction, but low strength in the direction perpendicular to the reinforcing direction. The strength in the direction perpendicular to the reinforcement direction is the same or lower than that of non-fiber reinforced plastics. Therefore, when this is formed into a bolt that is subjected to multiaxial stresses such as tensile stress, compressive stress, and shear stress, the material properties of fiber-reinforced plastic cannot be fully exhibited. By the way, the strength of bolts according to JIS standards is 70% or less of the strength of the material. It is known that the direction of the maximum stress applied to a bolt varies greatly depending on the angle of the thread of the bolt. Bolts made of isotropic material such as metal have equal material strength in each direction. Therefore, for example, for two bolts with different thread angles,
Although the direction in which the maximum stress is applied is different, the strength of the bolt itself remains the same. Bolts made of fiber-reinforced plastic have anisotropic material strength, so the strength varies greatly depending on the angle of the thread.
The JIS standard bolt thread angle is 60°,
Fiber-reinforced plastic bolts with such thread angles do not have sufficient strength. (Objective of the Invention) The object of the present invention is to provide a plastic screw-shaped molded article that is lightweight, has corrosion resistance, chemical resistance, and electrical insulation properties, is highly reinforced with reinforcing fibers, and has high fastening force. be. Another object of the present invention is to provide a plastic screw-shaped molded article that can fully utilize the material strength of fiber-reinforced plastic, which is a unidirectionally reinforced material. (Structure of the Invention) The present invention uses a fiber-reinforced plastic columnar body in which the ratio of the compressive elastic modulus in the longitudinal direction to the compressive elastic modulus in the direction perpendicular to the longitudinal axis is within a specific range, and is provided with threads having an angle in a specific range. This work was completed based on the inventor's knowledge that if formed, a high-strength screw-shaped molded body that effectively utilizes the strength of fiber-reinforced plastic materials can be obtained. The present invention is a fiber-reinforced plastic screw-shaped molded article having a thread on a fiber-reinforced plastic column, wherein the plastic column is mainly composed of a thermoplastic resin and reinforcing fibers, and the reinforcing fibers have a diameter of 1 μm to 60 μm. length is 1
mm to 10 mm, the reinforcing fibers are contained in the plastic columnar body at a proportion of 10 to 40% by volume, and the compressive elastic modulus (E _P ) in the longitudinal direction of the plastic columnar body is
and the compressive modulus of elasticity (E _R ) in the direction perpendicular to it (k=E _P /E _R ) is 2.0 or more, and the fiber-reinforced plastic column has a thread angle (θ° ) is formed, thereby achieving the above object. 90+2k-40/√k≦θ≦90+2k The thread-shaped molded body in the present invention refers to a molded body having a thread such as a bolt or a nut. Plastics used in the present invention include thermoplastic resins such as polybutylene terephthalate, polyamide, polyacetal, and polyether terephthalate. Examples of reinforcing fibers include glass fibers, carbon fibers, and aramid fibers. It is also possible to use a mixture of two or more of these fibers. Fibers are usually
A tip with a diameter of 1 μm to 60 μm and a length of about 1 mm to 10 mm is used. The amount of reinforcing fibers mixed is selected depending on the strength of the bolt to be obtained, but is usually 10 to 40% by volume, preferably 15 to 40% by volume of the entire mixture. If it exceeds this value, the reinforcing effect will actually decrease. For the purpose of improving the adhesion between the reinforcing fibers and the plastic, various additives such as processing agents, flame retardants, and antioxidants may be added as necessary. If necessary, the above-mentioned various additives are added to the above-mentioned plastic and reinforcing fibers, and the resulting mixture is melted and mixed using an extruder or the like to prepare a columnar body. This columnar body has _a ratio ₍ k=
E _P /E _R ; degree of anisotropy) is adjusted to be 2 or more. When the degree of anisotropy is less than 2, the material becomes close to an isotropic material such as metal, and therefore, as will be described later, there is no change in the strength of the thread-shaped molded body even if the angle of the thread is specified. When manufacturing a bolt, a thread as shown in the figure is formed on this columnar body by appropriate means such as rolling, cutting, pressing, or the like. The angle (θ°) of the thread is formed so that 90+2k−40/√k≦θ≦90+2k. If the thread angle is too small, the bolt will not have sufficient strength. If the angle of the thread is too large, the angle at which the thread engages becomes small, causing slippage or loosening of the nut that engages with the thread. Moreover, the threads become too large to be used as practical bolts. In this manner, by forming threads at an optimal angle in a fiber-reinforced plastic columnar body having an anisotropy of 2 or more, a bolt having a strength of 90% or more of the material strength can be obtained. When the plastic bolt of the present invention obtained in this manner is compared with a plastic bolt having a thread angle (60°) according to the JIS standard, the tensile strength is
It improves by 20-60%. (Example) The following example of the present invention will be described. Example 1 100 parts by weight of polyamide (nylon 66; Amiran manufactured by Toray Industries, Inc.) was mixed with 30 parts by weight of glass fibers with a diameter of 13 μm and a length of 3 mm and extruded to form a product with a diameter of 9.0 mm.
A columnar body with a length of 100 mm was obtained. The anisotropy of this columnar body was 2.2. This was subjected to rolling processing, and as shown in the figure, the outer diameter a was 10.00 mm, the effective diameter b was 9.02 mm,
A bolt with an inner diameter c of 8.38 mm and a thread angle θ of 70° was obtained. I attached nuts to both ends of this bolt and pulled it using an autograph. The load immediately before the bolt was broken was measured and defined as the tensile strength.
Separately, the tensile strength of the columnar body was measured, and the tensile strength of the bolt relative to the tensile strength of the columnar body was calculated. The results are shown in Table 1. The compressive elastic modulus used in calculating the degree of anisotropy in this example was measured by cutting the above-mentioned columnar body to prepare a test piece according to the method of JIS K7208. Example 2 The same as Example 1 except that the thread angle of the bolt was 85°. Example 3 The same as Example 1 except that the thread angle of the bolt was 90°. Example 4 This was the same as in Example 1, except that 80 parts by weight of glass fiber was used to obtain a columnar body with an anisotropy of 4.0, and a bolt with a thread angle of 80° was manufactured. Example 5 The same as Example 4 except that the thread angle of the bolt was 85°. Example 6 The same as Example 4 except that the thread angle of the bolt was 95°. Example 7 This was the same as Example 1, except that 150 parts by weight of glass fiber was used to obtain a columnar body with an anisotropy of 6.0, and a bolt with a thread angle of 90° was manufactured. Example 8 The same as Example 7 except that the thread angle of the bolt was 95°. Example 9 The same as Example 7 except that the thread angle of the bolt was 100°. Comparative Example 1 This was the same as in Example 1, except that a columnar body with an anisotropy of 1.0 was obtained without using glass fiber, and a bolt with a thread angle of 60° was manufactured. The results are shown in Table 2. All the results of the comparative examples are shown in Table 2 below. Comparative Example 2 Same as Comparative Example 1 except that the thread angle of the bolt was 85°. Comparative Example 3 The same as Comparative Example 1 except that 10 parts by weight of glass fiber was used to obtain a columnar body with an anisotropy of 1.5. Comparative Example 4 The same as Comparative Example 2 except that 10 parts by weight of glass fiber was used to obtain a columnar body with an anisotropy of 1.5. Comparative Example 5 Same as Example 1 except that the thread angle of the bolt was 60°. Comparative Example 6 Same as Example 1 except that the thread angle of the bolt was 100°. Comparative Example 7 Same as Example 4 except that the thread angle of the bolt was 60°. Comparative Example 8 Same as Example 4 except that the thread angle of the bolt was 75°. Comparative Example 9 Same as Example 4 except that the thread angle of the bolt was 100°. Comparative Example 10 Same as Example 7 except that the thread angle of the bolt was 60°. Comparative Example 11 Same as Example 7 except that the thread angle of the bolt was 85°. Comparative Example 2 Same as Example 7 except that the thread angle of the bolt was 105°.

【table】

【table】

[Table] (Effects of the Invention) As described above, the plastic thread-shaped molded article of the present invention is obtained by forming threads with angles in a specific range in a fiber-reinforced plastic columnar body having an anisotropy in a specific range. The strength is 90% of the material strength.
It becomes more than that. It also has the inherent characteristics of plastic, such as being lightweight, corrosion resistant, chemical resistant, and electrically insulating.
This thread-shaped molded body can be manufactured by rolling, which is the most economical method for thread processing. The thread-shaped molded body thus obtained can be used in a wide range of structural fastening members such as fastening parts for marine structures and parts for automobiles.

[Brief explanation of drawings]

The figure is a partial sectional view of a bolt for explaining the terminology of bolt in one embodiment of the present invention. a...Outer diameter, b...Effective diameter, c...Inner diameter, θ...
...thread angle.

Claims (1)

[Scope of Claims] 1. A fiber-reinforced plastic screw-shaped molded article having a thread in a fiber-reinforced plastic column, wherein the plastic column is mainly composed of a thermoplastic resin and reinforcing fiber, and the reinforcing fiber has a diameter of 1 μm. ~60μm, length 1mm
~10 mm, the reinforcing fibers are contained in the plastic columnar body at a ratio of 10 to 40% by volume, and the compressive elastic modulus (E _P ) in the long axis direction of the plastic columnar body and the compressive elastic modulus in the direction perpendicular thereto. (E _R ) (k=E _P /E _R ) is 2.0 or more, and a thread with a thread angle (θ°) shown by the following formula is formed on the fiber-reinforced plastic columnar body. Fiber-reinforced plastic screw-shaped molded body: 90+2k-40/√k≦θ≦90+2k. 2. The thread-shaped molded body according to claim 1, which is obtained by rolling the fiber-reinforced plastic columnar body.