JPH0468348B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field of the Invention) The present invention relates to a conductive thermoplastic resin composition having excellent mechanical strength and other mechanical properties. More specifically, the present invention relates to thermoplastic resins that have stable conductivity or semiconductivity and have excellent mechanical performance, which can be used in the fields of precision mechanical parts, electrical parts, and electronic devices having complex shapes. Regarding the composition. (Background and issues) In recent years, as technology has become more sophisticated and precise, there has been an increasing demand for various devices and their component parts to be lighter, thinner, shorter, and smaller in terms of materials and structure.
This trend is remarkable in both the fields of electronic materials and electronic devices. Furthermore, the phenomenon is rapidly progressing that parts and components that were made of metal until yesterday are now being replaced with plastic. However, on the other hand, various problems such as mechanical strength and other mechanical properties, antistatic performance, and conductivity, which were not problems with conventional metal parts and members, have become apparent, and it is necessary to solve these problems in each field. Research is being actively carried out. By the way, in order to improve the low Young's modulus and other low mechanical strength that can be said to be the fate of plastics, one effective solution is to incorporate a fibrous reinforcing agent into plastics. On the other hand, as a method of imparting antistatic performance,
There is a method of adding a compound having a hydrophilic group such as a polyhydric alcohol, a fatty acid ester of a polyhydric alcohol, a polyalkylene glycol, or an alkylamine. However, this method of adding a hydrophilic substance has the disadvantage that the surface resistance of the resin molded product is reduced to about 10 ¹¹ Ω at most, and the resistance value changes significantly depending on the environmental humidity. Another method is to mix conductive carbon black into the resin. However, as is well known, conductive carbon black has the disadvantage that it is very bulky and easily scatters when handled, making it easy to pollute the workplace. Moreover, in order to impart conductivity to the resin composition using this product alone, it is necessary to add at least about 10% by weight. However, when 7% by weight or more of conductive carbon black is added, the mechanical strength of the molded article is significantly reduced. Therefore,
The scope of its application is naturally limited to a relatively narrow range, but the biggest drawback in resin compositions that have been given conductivity by adding conductive carbon black alone is that This is difficult to add to the composition. To explain this in more detail, 7% by weight of conductive carbon black
In resin compositions added and blended at a ratio of less than
While thermoplastic resins exhibit high electrical resistance values, resin compositions containing the former at a ratio of 10% or more by weight conversely exhibit low resistance values characteristic of conductive carbon black. In the intermediate range of % by weight or more and less than 10% by weight, the resistance value changes very slightly as the amount of conductive carbon black added increases. Therefore, it is extremely difficult to freely and stably provide an intermediate design resistance value between the resin specific resistance value and the specific resistance value of conductive carbon black. In other words, a slight change in the amount of conductive carbon black mixed can cause the electrical properties of the compound or molded product made from it to change rapidly from an insulating region to a resistive region, so it is extremely difficult to consistently impart the desired semiconductivity. It's difficult. In addition, the blending of conductive carbon black deteriorates the thermal stability of the blended resin, and due to thermal decomposition that occurs during molding, the appearance of the resulting molded product changes significantly, and the impact strength of the molded product decreases. , many disadvantages occur, such as a significant decrease in bending strength. As a means to solve the above problems,
There is a method of utilizing conductive potassium titanate (hereinafter referred to as "conductive PTW") imparted with conductivity as a fibrous reinforcing agent, which was previously discovered by the present inventors. However, in order to obtain the desired high conductivity, it is necessary to incorporate the conductive PTW at a high filling rate level of, for example, about 40% or more. On the other hand, small parts with a product weight of 10mg to 1g and parts with thin internal parts with a wall thickness of 0.5mm or less,
If a composition containing only glass fiber or carbon fiber is used when molding parts such as gears that have sharp edges at their tips, the reinforcing material may not be distributed in narrow areas such as thin parts or tooth tips. If the reinforcing material becomes insufficient, it will not be possible to obtain a sufficient reinforcing effect, resulting in insufficient strength and rigidity, as well as warping due to anisotropy based on the orientation of the reinforcing material, and furthermore, surface roughness will increase, making precision Molding is also difficult. (Objective of the Invention) The present invention has practically sufficient mechanical strength and other mechanical properties (hereinafter referred to as "mechanical properties"), maintains a smooth surface, and is stable against molded objects. An object of the present invention is to provide a thermoplastic resin composition that can exhibit arbitrary conductivity. (Structure of the Invention) In order to achieve the above object, the resin composition of the present invention contains 10 to 30% by weight of conductive potassium titanate fibers and 0.3 to 5% by weight of conductive carbon. It is characterized by containing black and 5 to 30% by weight of glass fiber and/or carbon fiber. As a result of various research aimed at solving the above problems, the present inventor discovered that thermoplastic resin
A conductive thermoplastic resin composition containing 30% by weight of conductive PTW, 0.3 to 5% by weight of conductive carbon black, and 5 to 30% by weight of glass fiber and/or carbon fiber is conductive. Depending on the blending ratio and amount of conductive PTW, conductive carbon black, glass fiber and/or carbon fiber, arbitrary conductivity can be imparted to the molded article with good reproducibility, and the above composition. The object is, surprisingly, conductive PTW
A conductive resin composition that allows the properties of the conductive PTW to be fully exhibited in the molded object even with a filling amount of the PTW that is lower than that when used alone, and that this composition is economically extremely advantageous. I discovered that it is a thing. According to the new findings obtained by the present inventor, conductive
By using PTW, conductive carbon black, and glass fiber and/or carbon fiber together within the above-mentioned optimum range, the resistance value is not only much lower than expected, but also stable with no variation in the semiconductive region. The electrical resistance value can be easily reproduced, and it is also possible to perform precise injection molding for molded products that require precise dimensional accuracy, such as thin-walled parts or sharp-angled parts.
Moreover, the obtained molded product has uniformly high strength all the way to its end (a position far from the gate) and has excellent heat resistance. Therefore, according to the present invention, it is possible to uniformly manufacture molded products that require arbitrary conductive performance from an insulating range to a low resistance range, high mechanical strength, and precise dimensions. The conductive PTW used in the present invention is a single crystal fiber having a composition represented by the following general formula (), with an average fiber diameter of 0.01 to 1 μm and an average fiber length of 1 to 1 μm.
100 μm, and the average fiber length/average fiber diameter ratio (aspect ratio) is 10 or more. K ₂ O・n (TiO _2-x ) ...() (In the formula, n means a real number of 8 or less, and x means a real number of less than 2.) This conductive PTW is expressed by the general formula, K ₂ O・n (TiO ₂ ) (In the formula, n is a positive real number of 8 or less.) Potassium titanate whiskers expressed as It is obtained by reductively firing the mixture at a temperature of 500 to 1500°C either as it is or mixed with an oxygen acceptor such as a carbon material. Incidentally, the carbon materials used at this time include carbon black,
Examples include graphite, coke, and petroleum pitch. At this time, the mixing ratio of the potassium titanate whiskers and the carbon material varies depending on the size and material of the reduction furnace, but is usually in the range of 1 to 50% by weight relative to the potassium titanate whiskers. In addition, as other conductive PTW, metal,
Materials to which conductive or semiconductive substances such as metal oxides are attached or deposited can also be used. For reference, to electrolessly plate potassium titanate whiskers, place the whiskers in an alkaline plating solution of nickel, copper, platinum, silver, etc. at 100℃ for 5 minutes.
Soak and stir for 1 minute to 1 hour. In addition, in the spray coating method, an aqueous solution or an aqueous organic medium solution of a halide, sulfate, or oxide such as tin, nickel, indium, or antimony is applied to potassium titanate whiskers heated to 200 to 900°C using a spray gun or the like. The whisker surface is coated by spraying and coating. Each of the above conductive PTWs can normally be used in an untreated state, but in order to improve the interfacial adhesion with thermoplastic resins, surface treatments such as silane coupling agents or titanate coupling agents are applied depending on the purpose. The use of agents generally gives better results. The above amount of conductive PTW imparts conductivity,
From the viewpoint of improving dimensional accuracy, rigidity, and mechanical strength, it is preferably blended in an amount of 10 to 30% by weight in the composition. If the blending amount is less than 10% by weight, the mechanical strength and conductivity of the thin-walled part of the molded article cannot be sufficiently improved. Meanwhile, 30% by weight
Even if it is used in an amount exceeding the limit amount, it is difficult to see an effect of improving mechanical strength and increasing conductivity commensurate with the amount exceeding the limit amount. Examples of the conductive carbon black used in the present invention include furnace black, thermal black, channel black, and graphite. However, structures are particularly susceptible to development. Particle size is small. Large surface area. There are fewer impurities that capture π electrons. Graphite is progressing. Considering the performance required for conductivity, the most suitable furnace black is a conductive furnace. The amount of conductive carbon black used in combination with conductive PTW is preferably within the range of 0.3 to % by weight of the composition, depending on the target degree of conductivity and semiconductivity. If the amount used is 0.3% by weight or less, structures sufficient to impart conductivity will not be formed in the resin, and therefore, almost no effect can be expected when used in combination with conductive PTW. On the other hand, if the blending amount exceeds 5% by weight, not only the mechanical properties of the molded article will deteriorate significantly, but also the thermal stability of the resin composition will decrease.
In addition, the processability during granulation also deteriorates. The glass fibers used in the present invention are SiO ₂ ,
It is obtained from inorganic glass containing oxides such as B ₂ O ₃ Al ₂ O ₃ , CaO, Na ₂ O, and K ₂ O. Depending on the purpose, it can be used as alkali-free glass (E glass) or alkali-containing glass (C glass). Glass), alkali-resistant glass (A glass), etc. are selected and used, but E glass, which is generally used for resin reinforcement, is preferable in terms of its reinforcing effect. The fiber length of these glass fibers is
For blending into resin, 0.1 to 10 mm is preferable, and chopped strands having a length of about 3 mm or 6 mm, which are usually used for resin filling, are particularly suitable. The above-mentioned glass fibers can be used in an untreated state, but it is better to treat them with a silane coupling agent such as aminosilane or epoxysilane, a chromium-based coupling agent, or a plastic-based sizing agent for the purpose of bundling the fibers. suitable. The carbon fibers that can be used in the present invention may be acrylonitrile-based, pitch-based, or the like. Also, the fiber length is 0.1~10mm
A chopped fiber having a length of about 3 to 6 mm, which is normally used for resin filling, is preferably used. It is preferable to use carbon fibers whose surfaces have been treated with various treatment agents such as epoxy resin, polyamide resin, polycarbonate resin, or polyacetal resin, or whose surfaces have been oxidized with plasma or the like. However, surface treatment is not essential for the purpose of the invention. The amount of glass fiber and/or carbon fiber blended is preferably within the range of 5 to 30% by weight in the composition. If the amount of these fibers is less than 5% by weight, the strength improving effect will be insufficient. Furthermore, even if it is used in an amount exceeding 30% by weight, not only is it not possible to expect an effect of improving mechanical strength commensurate with the limit amount, but also the surface roughness of the molded product becomes large, and in addition, the composition This is not preferable because it not only makes granulation difficult but also causes severe wear on the granulator. The thermoplastic resin referred to in the present invention includes polyethylene,
In addition to general-purpose thermoplastics such as polypropylene and polyvinyl chloride resin, aliphatic polyamide,
Includes all engineering plastics such as aromatic polyamide, thermoplastic polyester, polyacetal, polyphenylene sulfide, polysulfone, polyetherimide, and polyether ketone. The method of blending conductive PTW, conductive carbon black, glass fiber and/or carbon fiber with the above thermoplastic resin is arbitrary, and methods include dry blending, melting the thermoplastic resin using an extruder, etc. Known formulation methods such as mixing methods can be freely employed. However, in order to prevent or suppress the cutting of conductive PTW fibers, carbon fibers, and glass fibers and the destruction of the conductive carbon black structure during the kneading process, it is necessary to use mild kneading means, such as an extruder, to melt the thermoplastic material. It is preferable to adopt a method of blending conductive PTW, conductive carbon black, carbon fiber, or glass fiber into the resin. The resin composition of the present invention further includes, if desired,
A heat stabilizer, a light stabilizer, a plasticizer, a lubricant, a flame retardant, a dye or a pigment, etc., which are known per se, may be added as necessary and within the range that does not impair the effects of the present invention. Can be added arbitrarily. (Examples) Examples of embodiments of the invention and specific effects of the invention will be described below using examples, but the examples are of course for illustrative purposes and are not intended to define the connotation or extension of the idea of the invention. do not have. Example 1 Conductive PTW made by reducing and firing polypropylene [manufactured by Mitsui Toatsu Chemical Co., Ltd.; Noblen H501] and potassium titanate whiskers at 1000°C in an inert atmosphere.
[manufactured by Otsuka Chemical Co., Ltd.], Ketsutien Black EC-P [manufactured by Lion Akzo Co., Ltd.], and glass fiber with an average fiber length of 3 mm [manufactured by Asahi Fiberglass Co., Ltd.; CS03-
MA497] with the composition shown in Table 1 below, 220
In a 4 mmφ twin-screw extruder set at .degree. C., the above conductive PTW, Ketting Black EC-P and glass fiber were mixed into the molten Noblen H501, and the mixture was extruded and granulated. Thereafter, injection molding was performed under the following conditions to create a test piece for measuring physical properties. Cylinder temperature: 21°C Injection pressure: 500Kg/cm ² Injection time: 15 seconds Mold temperature: 60°C The electrical properties and mechanical strength of each test piece obtained were measured. The results are shown in Table-1 below.
Shown below.

[Table] As is clear from the volume resistivity and bending strength shown in the table, excellent conductivity can be obtained by using conductive PTW and conductive carbon black in combination, and by further using glass fiber in combination, High strength can be achieved with little change in properties. In addition, thin cases with a thickness of 0.5 mm, a length of 65 mm, and a width of 50 mm were injection molded, and all of Examples 1-1 to 1-5 had good surface smoothness, no warping, and good dimensional accuracy. This was confirmed. Example 2 Diuracon M90-02 [Polyplastic Co., Ltd.; polyacetal], the same conductive PTW as Example 1
[Manufactured by Otsuka Chemical Co., Ltd.] Ketuchen Black EC-DJ50
[manufactured by Lion Akzo Co., Ltd.] and carbon fiber with a cross-sectional diameter of 9 μm and an average fiber length of 6 mm [manufactured by Hercules, USA;
Magnamite 1810AS] was mixed with the composition shown in Table 2 below, and the above-mentioned conductive PTW ketschen black EC-DJ500 and carbon fiber were added to the melted Jyuracon M90-02 using a 4 mmφ twin-screw extruder set at 220°C. The mixture was mixed and extruded into granules. Thereafter, injection molding was performed under the following conditions to create a test piece for measuring physical properties. Cylinder temperature: 200°C Injection pressure: 1000Kg/cm ² Injection time: 30 seconds Mold temperature: 80°C Subsequently, electrical properties and mechanical strength were measured.
The results are shown in Table 2 below.

[Table] As is clear from Table 2 above, when the amount of carbon fiber blended is less than 5% by weight, the effect of improving mechanical properties is small, while when it exceeds 30% by weight, surface roughness increases and precision There was a tendency that it was not suitable as a molding material for molded products. In addition, in the pellet production (granulation) of Example 2-3, it was difficult to fill the pellet with 30% by weight of carbon fiber due to the ease of taking it off, probably because conductive PTW and conductive carbon black were used together. . Example 3 RENY6001 [manufactured by Mitsubishi Gas Chemical Co., Ltd.; nylon
MXD6], an electrically conductive product obtained by mixing potassium titanate whiskers and coke and reducing and calcining the mixture in a mixed flow of hydrogen gas and propane gas.
PTW [manufactured by Otsuka Chemical Co., Ltd.] and Ketsutien Black
EC-P [manufactured by Lion Akzo Co., Ltd.], a 45 mmφ twin shaft set at 270°C with the composition shown in Table 3 below, a glass chopped stride with a length of 3 mm and a carbon fiber with a length of 6 mm. Melted in an extruder
Mix RENY6001 with the above conductive PTW, Ketsuen Black EC-P glass fiber and carbon fiber,
Extrusion granulation was performed. Thereafter, injection molding was performed under the following conditions to create a test piece for measuring physical properties. Cylinder temperature: 285°C Injection pressure: 1000 Kg/cm ² Injection time: 20 seconds Mold temperature: 120°C The electrical properties and mechanical strength of the obtained test piece were measured. The results are shown in Table 3 below.

[Table] As is clear from Table 3 above, conductive PTW10
~20% by weight, 2-5% by weight of conductive carbon black, 5-20% by weight of glass fiber and/or carbon fiber.
It has been found that it is possible to provide a material for molded articles having any desired electrical conductivity of 10 ² to ^{10 10} Ω·cm and high strength in the formulation. Example 4 Conductive PTW obtained by heating Teijin PBT CL7000 [Teijin Ltd.; polybutylene terephthalate] and potassium titanate whiskers to 300°C and conductive coating the surface with a spray of an aqueous solution of stannic chloride.
[manufactured by Otsuka Chemical Co., Ltd.], Ketsutien Black EC-P [manufactured by Lion Akzo Co., Ltd.] and carbon fiber with a length of 6 mm,
The composition shown in Table 4 below was melted using a 45mmφ twin-screw extruder set at 240°C.
The above-mentioned conductive PTW, Ketchen Black EC-P and carbon fiber were mixed into PBT CL7000 and granulated by extrusion. After that, injection molding is performed under the following conditions,
A test piece for measuring physical properties was created. Cylinder temperature: 245°C Injection pressure: 1000 Kg/cm ² Injection time: 20 seconds Mold temperature: 100°C Next, the electrical properties and mechanical strength of the obtained test piece were measured. The results are shown in Table 4 below.

[Table] (Effects of the invention) According to the present invention, the mechanical strength of the molded product is high;
Furthermore, it is possible to easily obtain a resin composition that has excellent dimensional accuracy and can reproduce any desired electrical conductivity from an insulating to a conductive range. In particular, the conductive thermoplastic resin composition of the present invention is
Antistatic materials with a volume resistivity of 10 ¹⁴ to 10 ¹⁰ Ω・cm, semiconductive materials with a volume resistivity of 10 ¹⁰ to 10 ⁴ Ω・cm, and 10 4 to 10 ⁴ Ω・cm
Since we can provide conductive molding materials with a resistance of ¹⁰⁰ Ω・cm,
We provide resin materials suitable for packaging electronic parts, storage materials, and molding of mechanical parts and housings for OA equipment such as copiers and printers.

Claims (1)

[Claims] 1. It is characterized by containing 10-30% by weight of conductive potassium titanate fibers, 0.3-5% by weight of conductive carbon black, and 5-30% by weight of glass fibers and/or carbon fibers. A conductive thermoplastic resin composition that has stable conductivity or semiconductivity and excellent strength.