JPH0449873B2 - - 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 a thermoplastic resin composition that provides stable conductivity or semiconductivity that can be used in the fields of electrical parts and electronic devices. (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 particularly remarkable in both the fields of electronic materials and electronic equipment. Furthermore, the phenomenon is rapidly progressing that parts and components that were made of metal until yesterday are now being replaced with plastic. but,
On the other hand, mechanical strength and other mechanical properties, which were not a problem with conventional metal parts and members,
Various problems such as antistatic performance and conductive performance have become apparent, and research to solve these problems is being actively carried out in various fields. 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 article 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 expensive 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, the actual situation is that the blending of conductive carbon black in an amount of 7% by weight or more significantly reduces the mechanical strength of the target molded product, so its application range is naturally limited to a relatively narrow range. The biggest drawback of resin compositions imparted with conductivity by the sole addition of conductive carbon black is that it is difficult to impart a reproducible specific resistance value to the resin composition. To explain this in more detail, resin compositions containing less than 7% by weight of conductive carbon black exhibit high electrical resistance values inherent to thermoplastic resins, whereas those containing 10% by weight or more of the former exhibit high electrical resistance values inherent to thermoplastic resins. On the contrary, the resin composition added at a ratio of 7 to 10 exhibits the low resistance value inherent to conductive carbon black.
In the intermediate range of weight percentages, the resistance changes very slightly with increasing conductive carbon black loading. 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, due to a slight change in the amount of conductive carbon black blended, the electrical properties of the compound or the resulting molded product change rapidly from an insulating region to a low resistance region, so it is difficult to consistently impart the desired semiconductivity. It is extremely difficult. In addition, the thermal stability of the blended resin deteriorates, and due to thermal decomposition that occurs during molding,
This causes many drawbacks, such as the appearance of the obtained molded product being significantly changed and the impact strength and bending strength of the molded product being significantly reduced. Another method is to mix carbon fiber, but in addition to being expensive, this tends to impair the surface smoothness of the molded product, and it also has partial electrical conductivity. It has the disadvantage that variations tend to occur. Furthermore, as another method, conductive potassium titanate (hereinafter referred to as "conductive PTW"), which has been given conductive performance as a fibrous reinforcing agent, was discovered by the inventors.
There is a way to use this. That is, conductivity
When PTW is blended with thermoplastic resin, it not only improves various mechanical properties, but also improves physical properties that cannot be expected when blending carbon fiber, such as making the surface of the molded product smooth and less anisotropic. Can be seen. However, in order to obtain the desired high conductivity, it is necessary to mix the PTW at a high filling rate level of, for example, about 40% or more, but mixing at such a high filling rate inevitably increases the cost. and put them at a disadvantage in competition with other competing means. Moreover, even if the amount exceeds the above level, an improvement in conductivity commensurate with the amount exceeding the above level is not observed. (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 has stable arbitrary conductivity. It is an object of the present invention to provide a thermoplastic resin composition that gives a molded article that exhibits the desired properties. (Structure of the Invention) In order to achieve the above object, the resin composition of the present invention contains 10 to 40% by weight of conductive potassium titanate fibers and 0.3 to 7% by weight of conductive carbon black. It is characterized by being blended with. In view of the above circumstances, the present inventor conducted further research and found that thermoplastic resin has an electrical conductivity of 10 to 40% by weight.
A conductive thermoplastic resin composition containing PTW and 0.3 to 7% by weight of conductive carbon black can have arbitrary conductivity depending on the blending ratio and amount of conductive PTW and conductive carbon black. With good reproducibility, and even with a lower filling amount of PTW than when using conductive PTW alone, conductive
It has been found that this resin composition is economically extremely advantageous because it fully exhibits the characteristics of PTW. According to the new findings obtained by the present inventor, conductive
It was not only discovered that by using PTW and conductive carbon black together within the above quantitative range, the resistance value was much lower than the expected value.
It has been discovered that stable electrical resistance values without variation can be easily reproduced in the semiconducting region.
In other words, the present invention makes it possible to reliably reproduce any conductivity between the insulation region and the low resistance region. Moreover, in the present invention, the amount of conductive carbon black, which is problematic in handling, is added in a relatively small to small amount, and a larger amount of conductive carbon black is added.
Since it is used in a dispersed state during PTW, there is no risk of the conductive carbon black scattering except during weighing, so the combined use of conductive PTW and conductive carbon black significantly improves the working environment. A secondary effect of improvement was also found. 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, an average fiber length of 1 to 100 μm, and an average fiber length/average fiber diameter ( aspect ratio) is 10
That's all. K ₂ O・n (TiO _2-x ) ... (In the formula, n means a positive 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 reducing and firing it at a temperature of 500 to 1500°C either as it is or by mixing it with an oxygen acceptor such as a carbon material. Incidentally, examples of the carbon material used at this time include carbon black, graphite, coke, and petroleum pitch. In addition, the mixing ratio of potassium titanate whiskers and carbon material varies depending on the size and material of the reduction furnace, but the amount of carbon material mixed is usually
The amount is 1 to 50% by weight based on the potassium titanate whiskers. In addition, as other conductive PTW, conductive or semiconductive substances such as metals and metal oxides are attached to the surface of potassium titanate whiskers by electroless plating, dipping, or spray coating, or You can also use the deposited one.
For reference, to electrolessly plate potassium titanate whiskers, place them in a plating solution of nickel, copper, platinum, silver, etc. in the alkaline range at 100℃ for 5 minutes.
Soak for 1 hour to 1 hour, stir, and plate the metal. In addition, in the spray coating method, 200 to 900
Potassium titanate whiskers heated to ℃
An aqueous solution or an aqueous organic solvent solution of a halide, sulfate, or oxide of tin, nickel, indium, antimony, etc. is sprayed and applied using a spray gun or the like to coat the surface of the whiskers. 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 content of conductive PTW is 10 to 40% by weight in the composition, from the viewpoint of reinforcing effect, especially improvement of rigidity, creep resistance and heat distortion temperature, improvement of critical PV value, and improvement of dimensional accuracy. It is preferable to mix within a range. If the blending amount is less than 10% by weight, the mechanical strength of the molded article cannot be sufficiently improved. On the other hand, even if it is used in excess of 40% by weight,
It is difficult to see an effect of improving mechanical strength commensurate with the amount exceeding the limit amount, and it tends to be difficult to granulate the composition. 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 butt-engaging black, which is a member of conductive furnaces, is optimal among furnace blacks. The amount of conductive carbon black used in combination with conductive PTW is preferably within the range of 0.3 to 7% by weight in the composition. If the amount used is 0.3% by weight or less,
Structures sufficient to impart conductivity are not formed in the resin, and therefore, almost no effect can be expected when used in combination with conductive PTW. On the other hand, the blending amount is 7% by weight.
If it exceeds this value, not only the mechanical properties of the molded article will be significantly lowered, but also the heat distortion temperature of the resin composition will be lowered, and furthermore, granulation will become difficult. However, depending on how well the kneading technology and molding technology have been refined, it cannot be said that there is no point in implementing it if the purpose is simply to improve conductivity. The thermoplastic resin referred to in the present invention includes polyethylene,
In addition to general-purpose thermoplastics such as polypropylene and polyvinyl chloride resin, it includes all engineering plastics such as polyamide, thermoplastic polyester, polyacetal, polyphenylene sulfide, polysulfone, polyetherimide, and polyetheretherketone. The method of blending conductive PTW and conductive carbon black into the thermoplastic resin is arbitrary;
As a method for dry blending the former three, any known blending method can be freely adopted, such as a method of mixing the latter two into a molten thermoplastic resin using an extruder. However, in order to prevent or suppress the cutting of the conductive PTW fibers and the destruction of the conductive carbon black structure, a gentle kneading method, such as an extruder, is used to mix the conductive PTW and conductive A preferred method is to incorporate carbon black. The resin composition of the present invention further includes, if desired,
Heat stabilizers, light stabilizers, antioxidants, lubricants, flame retardants, dyes, pigments, etc., which are known per se, may be optionally added as necessary and within the range that does not impair the effects of the present invention. can. (Examples) Examples of embodiments of the invention, specific effects, etc. will be explained below using examples, but the examples are of course for illustrative purposes and do not mean limitations on the idea of the invention. Example 1 Noblen H501 [Mitsui Toatsu Chemical Co., Ltd., polypropylene], conductive PTW made by reducing and firing potassium titanate whiskers at 1000°C in an inert atmosphere [manufactured by Otsuka Chemical Co., Ltd.], and Ketsutien Black EC -P [manufactured by Lion Akzo Co., Ltd.] with the composition shown in Table 1 below in a 45 mmφ twin screw extruder set at 220°C.
The above-mentioned conductive PTW and Ketchen Black EC-P were mixed into the molten Noblen H501 and granulated by extrusion. Thereafter, injection molding was performed under the following conditions to create a test piece for measuring physical properties. Cylinder temperature: 210°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】

[Table] Example 2 Diuracon M90-02 [Polyplastic Co., Ltd.; Polyacetal], same conductive PTW as Example 1
[Manufactured by Otsuka Chemical Co., Ltd.] and Ketsutien Black EC-
DJ500 [manufactured by Lion Akzo Co., Ltd.] was mixed with the composition shown in Table 2 below, and the above-mentioned conductive PTW and KETSUCHEN BLACK EC- DJ500 was mixed and extrusion granulated. 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】

[Table] Example 3 RENY6001 [Mitsubishi Gas Chemical Co., Ltd.; Nylon
MXD6], a conductive material obtained by mixing potassium titanate whiskers and coke and reducing and firing 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.] was mixed with the above-mentioned conductive PTW and KETSUCHEN BLACK EC into melted RENY6001 using a 45 mmφ twin-screw extruder set at 270°C with the composition shown in Table 3 below. -P was mixed and extrusion granulated. 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] Example 4 Teijin PBTCL7000 [Teijin Ltd., polybutylene terephthalate], potassium titanate whiskers were heated to 300°C, and the surface was conductively coated with an aqueous solution of stannic chloride [ Otsuka Chemical Co., Ltd.] and Ketsutien Black EC-P [Lion Akzo Co., Ltd.] were melted in a 45 mmφ twin-screw extruder set at 240°C with the composition shown in Table 4 below. The above-mentioned conductive PTW and Ketchen Black EC-P were mixed into PBTCL7000 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 properties of the molded product are high;
Furthermore, it is possible to easily obtain a resin composition that has excellent dimensional accuracy and can reproduce arbitrary conductivity from an insulating region to a conductive region. 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 ⁰
Since we can provide conductive molding materials of Ω/cm, they can be used as packing materials for electronic parts, storage materials, copying machines, printers, etc.
We provide resin materials suitable for mechanical parts and housings of OA equipment.

Claims (1)

[Claims] 1. Stable conductivity or semiconductivity characterized by blending 10 to 40% by weight of conductive potassium titanate fibers and 0.3 to 7% by weight of conductive carbon black. A thermoplastic resin composition comprising: 2. The thermoplastic resin composition according to claim 1, wherein the conductive carbon black is a furnace black. 3. The thermoplastic resin composition according to claim 1, wherein the conductive potassium titanate fiber, the conductive carbon black, and the thermoplastic resin are blended by a melting method.