JPH0249901B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to a method for producing a plastic thread-shaped molded body, particularly a plastic thread-shaped molded body highly reinforced with reinforcing fibers. (Prior Art) As a method for manufacturing a thread-shaped molded body, a rolling method for manufacturing metal bolts and nuts has been conventionally known. This method has the highest production speed for thread processing, and the dimensional accuracy of the obtained thread-shaped molded product is also extremely high. Fiber-reinforced plastic thread-shaped bodies are produced using this rolling method in order to obtain thread-shaped bodies that are light, have excellent corrosion resistance, and have high strength, compared to heavy metal screw-shaped bodies that are prone to rust. has been done. For example, a glass fiber-reinforced plastic bolt can be obtained by forming threads on a cylindrical material made of a thermoplastic resin containing glass fibers by a rolling method. When rolling is performed on such a cylindrical material,
The glass fibers contained in the surface layer of the cylindrical material are pressed under the rotational pressure of the rolling die, and a portion of the glass fibers breaks. As a result, the ends of the broken glass fibers are exposed on the screw thread surface, and microcracks are generated around the glass fibers. Therefore, for example, when a bolt is tightened to a nut, there is a large friction between the thread and the nut, and repeated tightening can destroy the thread. In particular, the bolt cannot withstand long-term use under vibration loads due to microcracks that occur at the root of the thread.
Thus, the fatigue strength of the bolt is low. Because of the large friction, sufficient axial fastening force (axial force) cannot be obtained. When manufacturing metal bolts by rolling, oil, etc. are used to reduce the friction between the metal rod, which is the forming material, and the rolling die, and to cool the rolling die, which becomes hot due to the heat generated by rolling. is brought into contact with the forming material as a rolling lubricant. Even if this method is applied to the rolling of the above-mentioned cylindrical material made of glass fiber-containing thermoplastic resin, the objectives of reducing friction and cooling can be achieved, but the glass fibers are broken during rolling, resulting in microcracks. The condition in which scratches occur and the threads become rough still remains unimproved. (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,
It is an object of the present invention to provide a method for producing a thread-shaped molded body that has electrical insulation properties, is highly reinforced with reinforcing fibers, and has a high fastening force. Another object of the present invention is to provide a method for manufacturing a thread-shaped molded body that has low friction on the thread surface during fastening and can withstand repeated use without damaging the threads. Another object of the present invention is to provide a high-strength plastic thread-shaped molded product by rolling, which is the most economical method for thread processing. (Means for Solving the Problems) The present invention is characterized in that micro-cracks that are generated when threads are formed by rolling on a molded material containing glass fibers are filled with a lubricant, and the thread surface is further coated with a lubricant. This invention was completed based on the inventor's knowledge that a thread-shaped molded body with low friction on the thread surface can be obtained by forming a coating with a lubricant. Therefore, in the method for manufacturing a fiber-reinforced plastic thread-shaped molded article of the present invention, when a thread is formed by rolling on the surface layer of a molding material made of a thermoplastic resin containing glass fibers, the process is performed at room temperature. The method includes rolling a solid lubricant while bringing it into contact with a rolling die heated to a temperature higher than the melting point of the lubricant to form a coating made of the lubricant on the thread surface, thereby forming a coating made of the lubricant on the thread surface. The purpose is achieved. 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. Thermoplastic resins used in the present invention include polyamides such as nylon 6, nylon 66, and nylon MXD6; polyethylene; polypropylene; polyethylene terephthalate; polybutylene terephthalate; polyacetal; polycarbonate; and polyphenylene sulfite, which are melted by heating and solidified by cooling. A general thermoplastic resin is used. If necessary, these compounds can be used by modifying their side chains or forming copolymers. For example, acid-modified polypropylene resins are used to improve the adhesion between thermoplastic resins and glass fibers, and copolymers of polyethylene terephthalate and elastomers are used to provide impact resistance. The above resins may be used alone or in combination of two or more. The glass fibers mixed into the thermoplastic resin should have a diameter of 1 to 100 ml in order to be uniformly dispersed in the thermoplastic resin.
Preferably, the length is 60 μm and the length is 0.01 to 1.00 mm. However, even if the length deviates from this range by a few mm, it will be cut during kneading with the thermoplastic resin and the length will be 0.01~
Since the length is 1.00 mm, the length may be 5 to 60 mm. Glass fibers are mixed in the mixture with thermoplastic resin in a proportion of 10 to 60% by weight. Within the above range, the greater the amount of glass fiber, the more pronounced the effect of the lubricant. If it is less than 10% by weight, the strength of the thread-shaped molded product obtained will be insufficient. If necessary, a filler, a treatment agent for improving the adhesion between the glass fiber and the resin, a flame retardant, an antioxidant, and the like may be added to the thermoplastic resin. These and glass fiber are kneaded using a normal plastic molding machine, such as an extrusion molding machine,
It is molded into a molding material having an appropriate size and shape. For example, when manufacturing JIS M10 size bolts, a sizing die with a circular cross section is attached to an extrusion molding machine to obtain a cylindrical material with a diameter of 9 mm. The lubricant mainly contains higher alcohol and/or higher fatty acid. Both higher alcohols and higher fatty acids used in lubricants have a carbon number of
14 or above. Since such higher alcohols and higher fatty acids are solid at room temperature, the lubricant coating formed on the thread surface may exist as a solid at room temperature. The melting points of higher alcohols and higher fatty acids are 40°C or higher, preferably 40 to 150°C. Examples of higher fatty acids include stearic acid, lauric acid, myristic acid, palmitic acid, and margaric acid. For example, the melting points of stearic acid and lauric acid are 69°C and 48°C, respectively. Examples of higher alcohols include hexadecanol, heptadecanol, octadecanol, and pentadecanol. For example, hexadecanol has a melting point of 49°C. In order to enhance the effect of the lubricant, at least one of fluororesin fine particles, molybdenum disulfide fine particles, and carbon fine particles may be blended. Examples of the fluororesin include tetrafluoroethylene,
Examples include fluorinated ethylene propylene ether, polychlorotrifluoroethylene, fluorinated alkoxyethylene, fluoroalkyl acrylate, perfluoroalkyl polyether, tetrafluoroethylene telomer, fluorocarboxylic acid and ester. The side chains of these compounds include vinyl groups, sulfonic acid groups, phosphoric acid groups, carboxyl groups,
It may be substituted with a functional group such as an epoxy group, an amide group, or a halogen group. The particle size of such fine particles is usually 0.1 to 50 μm, and they may be used alone or in combination of two or more types. These fine particles are contained in an amount of 0.2 to 100 parts by weight of the total amount of higher alcohol and/or higher fatty acid in the lubricant.
It is contained in the lubricant at a ratio of 100 parts by weight. If the content is too low, the blending effect cannot be obtained. If it is in excess, these solid particles will act as foreign matter during rolling, making it impossible to obtain threads with high precision.
In some cases, slipping occurs and rolling cannot be performed. The rolling method adopted for threading the thread-shaped molded body of the present invention does not need to be special, and a rolling machine commonly used for thread forming of metal screws can be applied as is. An example of this is a hydraulically operated two-roll rolling machine that rotates a pair of rolling rolls with threaded surfaces in the same direction to hold and extrude a cylindrical material to form threads. For example, when manufacturing bolts, when a cylindrical material is run through a rolling machine, threads are formed in the cylindrical material by the threads of a rolling die. At this time, since glass fiber is contained in the cylindrical material, as explained in the conventional technology section, the glass fiber is broken and exposed on the thread surface, and the surrounding area is surrounded by micro-organisms mainly made of glass fiber. A crack occurs. In the method of the present invention, rolling is performed while bringing the lubricant, which is solid at room temperature, into contact with a rolling die heated to a temperature higher than the melting point of the lubricant. melts and forms a liquid film of lubricant on the surface of the formed thread. The micro-cracks are filled with lubricant by the pressure applied during rolling, and the surface of the glass fibers exposed on the thread surface is also covered with lubricant. The formed liquid film becomes a solid film at room temperature. Therefore, the resulting bolt has less friction on the threaded surface and can withstand repeated use over a long period of time.
The axial fastening force (axial force) is also sufficient. Since the lubricant comes into contact with the material during rolling, there is little risk or degree of deformation of the cylindrical material due to rolling. Reduces micro-cracks at the root of the thread in the formed thread,
The fatigue resistance of the bolt is further improved. When the lubricant contains fine particles such as fluororesin, these fine particles are filled into microcracks or uniformly dispersed in the coating. Therefore, the friction on the thread surface is further reduced, and a bolt with excellent fatigue resistance can be obtained. During rolling, the rolling die is heated to an appropriate temperature depending on the type of lubricant. Prevents deformation of cylindrical materials,
Needless to say, in order to obtain a highly accurate thread, the temperature must be below the melting point of the thermoplastic resin that makes up the cylindrical material. The rolling die is heated to a predetermined temperature by blowing hot air controlled to a predetermined temperature; by incorporating a heater into the die; and the like. (Example) The present invention will be described below with reference to Examples. Example 1 Polyethylene terephthalate (manufactured by Kaneka Co., Ltd.; Velpet DFG-1) was used as the thermoplastic resin,
90% by weight of thermoplastic resin and 10% by weight of glass fiber with a diameter of 9 μm and a tip of 6 mm were dry-blended and molded into a round bar with a diameter of 9 mm using an extruder. This was cut into a length of 10 cm to obtain a cylindrical material. JIS M10×1.5
Threads were formed on the cylindrical material using a two-roll rolling machine equipped with a die. At this time, rolling was performed while a cake-like lubricant obtained by mixing 100 parts by weight of stearic acid with 10 parts by weight of fine particles of ethylene tetrafluoride having a diameter of 5 to 10 μm was brought into contact with a rolling die.
The temperature of the rolling die was maintained at 100°C. obtained
The tensile strength, axial force value, and fatigue cycle of M10 size bolts were measured. The results are shown in Table 1. These tests were conducted using five bolts each using the test method described below, and the average value was determined. The nuts used in each test were made of the same material as the bolts, and were made by injection molding with a distance between surfaces of 17 mm and a height of 12 mm.
This is an M10 size nut obtained by molding a hexagonal nut base material with an inner diameter of 8.7mm and cutting it with an M10 screw tap. Tensile test Attach nuts to both ends of the bolt and
The distance between the nuts was 70mm. Autograph the nuts on both ends of the bolt (IS made by Shimadzu Corporation)
5000) at a tensile speed of 5 mm/min.
The maximum load just before the bolt breaks was measured and defined as the tensile strength. Torque - Axial force value test Fix one end of the bolt in a vise, and attach a washer to the bolt with an inner diameter of 11 mm and an outer diameter of 11 mm.
A 15mm and 60mm long iron pipe was passed through. Furthermore, a nut was attached via a washer, and the nut was gently tightened with a wrench that could detect the torque value. At this time, a strain gauge was attached to the center of the outer surface of the iron pipe, and the compressive force applied to the iron pipe was measured and determined as an axial force value. Fatigue Cycle Nuts were attached to both ends of the bolt, and a tensile force equivalent to 55% of the tensile strength was applied between both nuts. A force of 15% of the tensile strength was applied as a vibration load (f) in the longitudinal direction of the bolt at a vibration cycle of 400 cycles/minute. In this way, a load of tensile strength x 0.5±f was repeatedly applied to the bolt, and the number of cycles at which the bolt broke due to fatigue was measured, and this was defined as the fatigue cycle. Example 2 Example 1 except that 75% by weight of polyethylene terephthalate and 25% by weight of glass fiber were used.
It is similar to Example 3 Same as Example 1 except that 60% by weight of polyethylene terephthalate and 40% by weight of glass fiber were used. Example 4 Same as Example 1 except that 45% by weight of polyethylene terephthalate and 55% by weight of glass fiber were used. Example 5 Same as Example 1 except that 35% by weight of polyethylene terephthalate and 65% by weight of glass fiber were used. Example 6 The same as Example 1 except that 60% by weight of polyphenylene sulfide and 40% by weight of glass fiber were used as the thermoplastic resin. Example 7 The same as Example 1 except that 60% by weight of polypropylene and 40% by weight of glass fiber were used as the thermoplastic resin. Example 8 Polyamide (nylon 6,
The procedure was the same as in Example 1 except that 60% by weight of 6) and 40% by weight of glass fiber were used. Example 9 The same as Example 3 except that a cake-like lubricant consisting only of stearic acid was used. Example 10 Same as Example 1 except that hexadecanol was used instead of stearic acid. Comparative Example 1 Same as Example 1 except that no lubricant was used. 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 Example 3 except that no lubricant was used. Comparative Example 3 Same as Example 5 except that no lubricant was used. Comparative Example 4 Same as Example 3 except that liquid silicone oil was used as the lubricant. Comparative Example 5 Same as Example 6 except that no lubricant was used. Comparative Example 6 Same as Example 7 except that no lubricant was used. Comparative Example 7 Same as Example 8 except that no lubricant was used.

【table】

[Table] (Effects of the Invention) According to the method of the present invention, a plastic screw-shaped molded body that is highly reinforced with glass fiber and has high strength and high fastening force can be produced in the most economical way for screw processing. Manufactured by molding. Rolling is performed while the lubricant, which is solid at room temperature, is brought into contact with a rolling die heated to a temperature higher than the melting point of the lubricant. During this time, the main components of the lubricant, such as higher alcohols and higher fatty acids, melt and form. A liquid film of lubricant is formed on the thread surface, and the micro-cracks are filled with lubricant due to the pressure during rolling, and the surface of the glass fibers exposed on the thread surface is also covered with the lubricant, and the liquid film becomes solid at room temperature. A film is formed. As a result, a thread-shaped molded body is obtained in which the friction on the threaded surface is small during fastening, and the threads are not damaged and can withstand repeated fastening. If the lubricant contains fine particles such as fluororesin, the friction on the thread surface is further reduced, and a thread-shaped molded product with excellent durability can be obtained.
This thread-shaped molded body is lightweight and has the characteristics inherent to plastics, such as corrosion resistance, chemical resistance, and electrical insulation. The thread-shaped molded body thus obtained is particularly useful for structural fastening.

Claims (1)

[Claims] 1. When forming a thread by rolling on the surface layer of a molded material made of a thermoplastic resin containing glass fibers, a lubricant that is solid at room temperature is heated to a temperature higher than the melting point of the lubricant. A method for producing a plastic screw-shaped molded article, which comprises rolling the article while bringing it into contact with a rolling die heated to a certain temperature, and forming a coating made of the lubricant on the surface of the screw thread. 2. The manufacturing method according to claim 1, wherein the lubricant has at least one selected from the group consisting of higher alcohols having 14 or more carbon atoms and higher fatty acids as a main component. 3. The manufacturing method according to claim 1, wherein the lubricant contains at least one of fluororesin fine particles, molybdenum disulfide fine particles, and carbon fine particles. 4. A patent claim in which at least one of the fluorine fine particles, molybdenum disulfide fine particles, and carbon fine particles is contained in a proportion of 0.2 to 100 parts by weight based on 100 parts by weight of the total amount of higher alcohol and/or higher fatty acid in the lubricant. The manufacturing method according to item 3. 5. The manufacturing method according to claim 1, wherein the heating temperature of the rolling die is higher than the melting point of the lubricant and lower than the melting point of the thermoplastic resin.