JPH0221929B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for rolling a plastic thread-shaped molded article such as a plastic bolt, and particularly to a method for threading a plastic material highly reinforced with reinforcing fibers by rolling. (Prior Art) Metal bolts have been known as thread-shaped molded bodies, such as bolts. This is manufactured by the rolling method, which has the fastest production speed for thread processing. Although metal bolts are manufactured with such high productivity, they have the fatal disadvantage of being heavy and prone to rust. On the other hand, plastic bolts that are lightweight and have excellent corrosion resistance are already in practical use. However, plastic materials to which rolling can be applied are limited to non-fiber reinforced plastic materials such as hard vinyl chloride resin. This is because fiber-reinforced plastic materials have poor plastic deformability due to their high strength, and cannot be threaded by rolling, which requires plastic deformability. Even if this is forcibly rolled, the threads will not form a triangular shape, and the top of the triangle will become two threads, or cracks will occur in the threads. Therefore, the strength is low,
It doesn't form a body like a screw. Bolts obtained by rolling non-fiber reinforced plastic materials have poor strength. Its tensile strength is at most 4-6
Kg/mm ² , so it cannot be used as a bolt that requires strong fastening force. (Problems to be Solved by the Invention) The present invention solves the above-mentioned problems of the prior art, and aims to be lightweight, corrosion resistant, chemical resistant,
The object of the present invention is to provide a method for rolling a plastic screw-shaped molded article having electrical insulation properties and highly reinforced with reinforcing fibers. Another object of the present invention is to provide a method for manufacturing a plastic thread-shaped molded body having high strength and excellent durability by thread rolling, which is the most economical method for thread processing. (Means for Solving the Problems) The method for rolling a fiber-reinforced plastic thread-shaped molded article of the present invention is characterized in that at least the surface layer of a molding material is made of a thermoplastic resin in which reinforcing fibers are dispersed. When forming a thread with a rolling die, at least a part of the thread forming area of the surface layer is heated to a temperature higher than the melting point of the thermoplastic resin, and the thread rolling die is heated to a temperature higher than the melting point of the thermoplastic resin. The above-mentioned object is achieved by performing the rolling process while controlling the temperature below. The term "thread-shaped molded body" as used in the present invention refers to a molded body having a thread such as a bolt or a nut. Examples of reinforcing fibers include inorganic fibers such as glass fibers, carbon fibers, boron fibers, silicon carbide fibers, and potassium titanate fibers; and organic fibers such as aramid fibers. It is also possible to use a mixture of two or more of these fibers. There is no particular restriction on the length of the fibers, as long as they can be dispersed in the thermoplastic resin molded into the molding material. These reinforcing fibers are melt-mixed with a thermoplastic resin using a kneading means such as an extruder, and are uniformly dispersed in the resin. The reinforcing fibers are contained in a range of 10 to 40% by volume, preferably 15 to 35% by volume. If the fiber content is too low, a high-strength plastic screw-shaped molded article cannot be obtained. If the fiber content is too high, it will become brittle and the reinforcing effect will decrease. Examples of thermoplastic resins include polyamide,
polyethylene terephthalate, polybutylene terephthalate, polyacetal, polysulfone,
Polyphenylene sulfide, polyetheretherketone, polyimide, etc. are used. Needless to say, there is no need to be limited to this.
These resins may be mixed with various additives such as fillers, processing agents for improving adhesion to fibers, flame retardants, and antioxidants, if necessary. In the molding material used in the present invention, at least the surface layer portion subjected to rolling processing is composed of a thermoplastic resin in which the reinforcing fibers described above are dispersed. For example, the center part of a cylindrical material used when manufacturing bolts has the same structure as the surface layer, but it is a core material made of a high-strength metal material such as iron, a fiber-reinforced thermosetting resin material, etc. Good too. When a core material is used, the surface of the core material may be provided with irregularities or grooves to improve bondability with the thermoplastic resin. By the method of the present invention, for example, when rolling the above-mentioned cylindrical material, at least a part of the thread forming region of the surface layer is heated to a temperature higher than the melting point of the thermoplastic resin constituting the cylindrical material. be done. Here, the thread forming area refers to a portion where a thread is to be formed. The surface layer portion heated to a temperature above the melting point is a region having a depth of 1/20 to 1 times the height of the thread to be formed in the radial direction from the surface layer surface of the cylindrical material. If it is less than 1/20 times, the reinforcing fibers will peel off from the thermoplastic resin during rolling, and the degree of adhesion at the interface between the reinforcing fibers and the thermoplastic resin at the deformed part due to rolling will deteriorate. Therefore, the resulting thread-shaped molded product has poor durability. If it exceeds 1, the cylindrical material itself will be greatly deformed during rolling, making it impossible to form good threads. The surface layer portion is preferably heated to a temperature above the [melting point] of the thermoplastic resin and below [the melting point of the thermoplastic resin plus 100°C]. At excessively high temperatures, it is difficult to heat only the surface layer of the cylindrical material. To heat the surface layer of the cylindrical material, there are methods such as heating the cylindrical material with hot air controlled at a predetermined temperature; immersing the cylindrical material in a liquid controlled at a predetermined temperature for a short time; etc. will be adopted. The temperature of the rolling die during rolling is controlled to be below the melting point of the thermoplastic resin constituting the cylindrical material. If the temperature is higher than the melting point, a thread with a normal shape will not be formed. The temperature of the rolling die is not particularly limited as long as it is below the melting point, but it is preferably maintained at a constant temperature. When heating the rolling die, a method is used in which a heater is built into the die. The rolling method does not need to be special, and rolling machines such as a round die rolling machine and a flat die rolling machine, which are commonly used for forming the threads of metal screws, can be applied. (Function) According to the method for producing a thread-shaped molded body of the present invention, at least a part of the thread forming region of the surface layer of the molding material is heated to a temperature higher than the melting point of the thermoplastic resin constituting the molding material. The plastic deformability of the heated surface layer improves, making thread processing possible. It is also possible to perform rolling while keeping the forming material or rolling die at an appropriate temperature below the melting point of the thermoplastic resin, or by contacting a heating medium at an appropriate temperature below the melting point of the thermoplastic resin during rolling. Although it is possible to obtain a high-strength screw-shaped molded article having a well-shaped thread, in such a method, the reinforcing fibers peel off from the thermoplastic resin at the deformed portions during rolling. Therefore, the degree of adhesion at the interface between the reinforcing fiber and the thermoplastic resin is poor. Although such a thread-shaped molded body has good initial strength, it is inferior in durability such as fatigue resistance and creep resistance. In the method of the present invention, the surface layer of the molding material is heated above the melting point of the thermoplastic resin and rolled, so the reinforcing fibers do not separate from the thermoplastic resin. Therefore, the obtained thread-shaped molded product can withstand, for example, vibration stress over a long period of time, and has excellent durability such as fatigue resistance and creep resistance. (Example) The present invention will be described below with reference to Examples. Example 1 (A) Preparation of cylindrical material: First, polyamide resin (Amiran Nylon 66 manufactured by Toray Industries, Inc.; melting point 265°C) and
Volume ratio of glass fiber with 9μm diameter and 6mm tip
Dry blending was performed at a ratio of 70:30, and this was molded into a round bar with a diameter of 9 mm using an extruder. Next, this was cut into 20 cm lengths to obtain 11 cylindrical materials. (B) Preparation of plastic bolt: One end of the cylindrical material obtained in section (A) was placed in a hot air oven controlled at 300°C while rotating, and heated for 6 seconds. This was taken out and quickly rolled using a three-roll rolling machine that forms M10, P1.5 screw threads controlled at 220°C. The other end of the cylindrical material was rolled in the same manner, yielding 10 M10 bolts with 3 cm threads formed on each end. The following test was conducted to find out the depth of the surface layer where the cylindrical material was heated to a temperature above its melting point. (A)
The cylindrical material obtained in Section 1 was cut at a position 1 cm from one end. Prepare an adhesive mixed with a paint that irreversibly changes color at 270℃,
Using this adhesive, the cylindrical material whose ends had been cut was glued back together. This cylindrical material was placed in a hot air oven under the same conditions as above. After cooling this, we observed the cross section of the part bonded with adhesive, and found that the discolored part extended to a depth of approximately 0.8 mm in the radial direction from the surface layer of the cylindrical material. (C) Bolt performance test: Five of the bolts obtained in section (B) were used to measure tensile strength, and the remaining five were used to measure fatigue cycles. The results are shown in the table below. These were measured by the following test method, and the average value of the measurements for five bolts was determined. Tensile strength M10 size nuts were attached to both ends of the bolt, and the breaking strength was measured according to the method of JIS B1051. Fatigue Cycle M10 size nuts were attached to both ends of the bolt, and a tensile load of 500 kg was applied.
Furthermore, a vibration load of ±200 kg was applied, and the number of vibrations until the bolt broke was measured. Example 2 (A) Preparation of cylindrical material: Same as Example 1 (A). (B) Preparation of plastic bolt: Same as Example 1 (B) except that the temperature of the rolling die was 150°C. (C) Bolt performance test: Same as Example 1 (C). Example 3 (A) Preparation of cylindrical material: Same as Example 1 (A). (B) Preparation of plastic bolts: Heat stove to 330℃
A bolt was prepared in the same manner as in Example 1(B) except that the heating time of the cylindrical material was controlled to 4 seconds. The discolored portion of the adhesive was located at a depth of approximately 1.1 mm in the radial direction from the surface layer of the cylindrical material. (C) Bolt performance test: Same as Example 1 (C). Example 4 (A) Preparation of cylindrical material: Same as Example 1 (A). (B) Preparation of plastic bolt: A bolt was prepared in the same manner as in Example 1 (B) except that the heating time of the cylindrical material was 2 seconds. The discolored portion of the adhesive was in an area approximately 0.3 mm in the radial direction from the surface layer of the cylindrical material. (C) Bolt performance test: Same as Example 1 (C). Comparative Example 1 (A) Preparation of cylindrical material: Same as Example 1 (A). (B) Preparation of plastic bolts: Heat the hot air oven to 240℃
A bolt was prepared in the same manner as in Example 1 (B) except that the bolts were controlled. No discoloration of the adhesive was observed. (C) Bolt performance test: Same as Example 1 (C). Comparative Example 2 (A) Preparation of cylindrical material: Same as Example 1 (A). (B) Preparation of plastic bolt: Rolling die
A bolt was prepared in the same manner as in Example 1 (B) except that the temperature was controlled at 270°C. (C) Bolt performance test: Same as Example 1 (C). Comparative Example 3 (A) Preparation of cylindrical material: Same as Example 1 (A). (B) Preparation of plastic bolt: A bolt was prepared in the same manner as in Example 1 (B) except that the cylindrical material was heated for 20 seconds. The discolored portion of the adhesive was located in an area approximately 2.5 mm in the radial direction from the surface of the cylindrical material. (C) Bolt performance test: Same as Example 1 (C). Comparative Example 4 (A) Preparation of cylindrical material: Same as Example 1 (A). (B) Preparation of plastic bolt: A bolt was prepared in the same manner as in Example 1 (B) except that the cylindrical material was not heated. (C) Bolt performance test: Same as Example 1 (C).

【table】

[Table] (Effects of the Invention) According to the present invention, it is extremely easy to perform thread forming by rolling on a plastic molding material highly reinforced with reinforcing fibers.
Since thread forming by rolling is highly productive, thread-shaped formed bodies such as bolts can be produced economically. Moreover, the thread shape of the resulting plastic screw-shaped molded product is good, and the top of the thread does not form two threads or crack or break. The thread-shaped molded body has high strength and excellent durability such as fatigue resistance and creep resistance. Furthermore, it has all the characteristics inherent to plastic materials, such as being lightweight and highly corrosion resistant. The thread-shaped molded product obtained by the method of the present invention can be used in a wide range of fields such as structural fastening.

Claims (1)

[Claims] 1. When forming a thread using a rolling die in the surface layer of a molded material whose surface layer is made of a thermoplastic resin in which reinforcing fibers are dispersed, at least a part of the thread forming area of the surface layer is Production of a fiber-reinforced plastic screw-shaped molded article, which includes rolling processing by heating to a temperature higher than the melting point of the thermoplastic resin and controlling a rolling die to a temperature lower than the melting point of the thermoplastic resin. Method.