JPS6255533B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a conductive resin composition. More specifically, the present invention
The present invention relates to a method for producing a conductive resin composition with excellent properties by uniformly dispersing conductive carbon black in a thermoplastic resin. The conductive resin composition referred to in the present invention has a volume resistivity of 10 ⁶ Ωcm or less, generally 1×10 ⁻¹ to 1
×10 ⁴ Ωcm, and is a resin composition exhibiting conductive or semiconducting properties. Thermoplastic resin compositions containing conductive carbon black uniformly dispersed have excellent electrical properties and are widely used in various fields as materials for various electrical parts and building materials. In recent years, carbon black and thermoplastic resins have attracted increasing attention as conductive materials due to their ease of availability and ease of molding into various shapes. Usually, this conductive resin composition is produced by kneading a mixture of carbon black powder and thermoplastic resin powder or pellets at a temperature higher than the melting temperature of the resin, and then uniformly kneading the carbon black into the resin. prepared. However, because carbon black and thermoplastic resin have different physical properties such as specific gravity, particle size, and fluidity, it is difficult to uniformly disperse carbon black even if they are kneaded for a considerable amount of time. In molded products, it is inevitable that variations in volume resistivity will occur. Furthermore, if the dispersion of conductive carbon black is uneven, even if a large amount of conductive carbon black, which is a relatively expensive raw material, is used,
However, there is also the drawback that the volume resistivity value cannot be lowered. Therefore, in the technical field of manufacturing conductive resin compositions, one of the challenges is to obtain a material with a low volume resistivity value using as little amount of conductive carbon black as possible by uniformly dispersing the conductive carbon black. It was becoming. Up until now, in order to uniformly disperse carbon black in a thermoplastic resin, it has been necessary to add a dispersant to the carbon black that gives it an affinity with the thermoplastic resin, or to surface treat the carbon black to make it easier to disperse. Methods such as kneading with thermoplastic resin have been used. However, these methods
If carbon black for reinforcement or carbon black for pigment is simply kneaded into resin, the purpose can be achieved to some extent, but it is better to use as little carbon black as possible to create a conductive resin composition with a low volume resistivity value. As for the method of obtaining it, it cannot be said that it is yet fully satisfactory. The present inventors have conducted extensive research in order to develop a method for producing a conductive resin composition that exhibits excellent electrical properties by uniformly dispersing conductive carbon black in a resin. As a result, it was discovered that the objective could be achieved by kneading each component in the presence of fibrillated polytetrafluoroethylene, and based on this knowledge, the present invention was accomplished. That is, in the present invention, when kneading a thermoplastic resin and conductive carbon black, each component is heated and mixed at a temperature below the melting point of the polytetrafluoroethylene in the presence of fibrillated polytetrafluoroethylene. The present invention provides a method for producing a conductive resin composition, characterized in that the powder portion therein is brought into a restricted state and then kneaded. Dispersions obtained by emulsion polymerization of certain types of polytetrafluoroethylene, such as tetrafluoroethylene, or fine powders for paste extrusion obtained by separating and granulating the same, can be produced by compression,
It is known that fibrillation occurs by applying shear. This fibrillable polytetrafluoroethylene has an average particle size of approximately
Particles of 0.2 microns form a colloidal aqueous suspension of about 60%, and in the case of fine powder, primary particles with an average particle size of about 0.2 microns form an agglomerated powder with an average particle size of about 0.5 mm. It's summery. All of these are commercially available and can be easily obtained. The fibrillated polytetrafluoroethylene used in the present invention may be made into fibrils by previously compressing and shearing the particles, or
Alternatively, the particles may be added as they are to a mixture of thermoplastic resin and conductive carbon black, then compressed and sheared to form fibrils.
When the fibrillated state is sufficiently mixed with each component, the powder portion in the mixture, that is, the conductive carbon black and the powdered thermoplastic resin, are captured by the fibrils and become agglomerated. . In the present invention, fibrillated polytetrafluoroethylene is present in the mixture in an amount necessary for agglomerating the powder portion.
This amount depends on the type of powder part, particle size, blending ratio with resin, presence or absence of other additives such as lubricants and antistatic agents, the type of mixer used, mixing conditions, etc. Usually, the solid content of polytetrafluoroethylene is selected in the range of 0.02 to 5 parts by weight per 100 parts by weight of the powder portion in the mixture. Generally, the larger the blending ratio of the powder part in the composition, the smaller the powder particle size, the smaller the bulk specific gravity of the filler, and the smaller the shear energy and heat supply of the mixer, the greater the amount of polytetrafluorocarbon. Requires addition of ethylene. Examples of raw materials for obtaining fibrillated polytetrafluoroethylene in the present invention include Teflon 6J (registered trademark, manufactured by Mitsui Fluorochemical Co., Ltd.), Teflon 6JC (registered trademark, manufactured by Mitsui Fluorochemical Co., Ltd.), Polyflon F103 (registered trademark, Commercial products such as Polyflon D-1 (registered trademark, manufactured by Daikin Industries, Ltd.) and Polyflon D-1 (registered trademark, manufactured by Daikin Industries, Ltd.) are suitable. Furthermore, examples of the thermoplastic resin used in the present invention include polyvinyl chloride, low density polyethylene, high density polyethylene, polypropylene, polystyrene, polyamide, polyester, polycarbonate, ABS resin, and the like. These may be used alone or in combination of two or more. The shape in use may be pellets, granules or powder. Next, the conductive carbon black used in the present invention can be arbitrarily selected from carbon blacks commonly used in the production of general conductive resin compositions. Examples of such carbon black include acetylene black, conductive furnace black, by-product carbon black, etc., but especially those with high oil absorption (DBP value)
One having a volume of 100 to 400 ml/100 is suitable. The appropriate amount of carbon black is 5 to 50% by weight based on the total amount of the resin composition. This amount is 5
If it is less than 50% by weight, sufficient electrical properties cannot be obtained, and if it exceeds 50% by weight, mechanical strength and moldability will deteriorate, which is not preferable. In carrying out the present invention, in addition to the above-mentioned components, long fiber reinforcing agents such as glass fibers and asbestos fibers, pigments, antistatic agents, lubricants, antioxidants, ultraviolet absorbers, and coupling agents may be added as desired. You can also. In the present invention, there are no particular restrictions on the mixer used to agglomerate the powder portion of the mixture of thermoplastic resin and inorganic filler with fibrillated polytetrafluoroethylene, and the mixer is not particularly limited, but can be compressed to a level sufficient to cause fibrillation. Any material can be selected as long as it can apply shear. Examples of such devices include batch mixers such as ribbon blenders, Henschel mixers and kneaders, and screw mixers equipped with heat medium jackets. Since this mixture self-heats during compression and shearing, external heating is not necessarily necessary. Further, the agglomerate treatment does not need to be performed on the entire mixture at once, but can be performed on a part of the mixture and then on the remaining part. For example, a thermoplastic resin, conductive carbon black, and polytetrafluoroethylene that can be fibrillated may be heated and mixed to fibrillate the polytetrafluoroethylene, thereby restraining the powdered raw material. After heating and mixing one of the plastic resin and conductive carbon black with polytetrafluoroethylene that can be fibrillated to fibrillate the polytetrafluoroethylene, the other raw material is added to this, and either heated or simply mixed. Alternatively, polytetrafluoroethylene, which can be fibrillated, may be mixed with all of the raw materials for one of the thermoplastic resin and conductive carbon black, and a part of the other raw material, by heating. After ethylene is fibrillated, all of the remaining raw materials may be added and further heated and mixed or simply mixed to form agglomerates. In the method of the present invention, the mixture thus obtained is fed to a machine with kneading ability and kneaded while maintaining the temperature above the melting point of the thermoplastic resin used, thereby obtaining the desired conductive resin composition. be able to. Examples of machines having kneading ability used in this case include batch kneaders such as Banbury mixer and Intermix, but a commonly used continuous extruder is particularly suitable. The conductive resin composition obtained according to the present invention may be extruded as it is into a desired product, or may be processed into pellets and supplied as a molding raw material. This conductive resin composition is extremely homogeneous, and the carbon black is evenly dispersed in the resin, so even if the amount of carbon black used is small, it exhibits a relatively low volume resistivity value. There is a characteristic that In addition, in terms of mechanical strength, it exhibits a significantly higher value than conventional products, and has the advantage of not causing problems such as poor ejection or deterioration due to overheating during or after molding. As described above, according to the present invention, it is possible to use commonly used machines having various kneading capacities and also to obtain a high-quality product, which has a very high industrial significance. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 100 parts by weight of polyvinyl chloride resin powder, 3 parts by weight of stabilizer (manufactured by Adeka Argus Chemical Co., Ltd., trade name Mark 1500), 1.5 parts by weight of wax, carbon black (manufactured by Akzo Corporation, trade name Ketjenblack)
EC) 6.6 parts by weight and different amounts of Teflon 6J (manufactured by Mitsui Fluorochemical Co., Ltd., fine powder for paste extrusion molding) were blended, each was placed in a super mixer with an internal volume of 20, and the jacket temperature was 70℃ and the blade The mixture was heated and mixed for 5 minutes at a rotation speed of 750 rpm. The seven types of samples thus obtained were fed to a 40 mm diameter bent type single screw extruder (L/D = 28, dullage type screw, screw compression ratio 3.5, screw rotation speed 80 rpm), and the thickness It was extruded into a 2 mm plate. Next, cut this to 150×150×
Three 2 mm test pieces were prepared. The volume resistivity value (Ωcm) of each test piece was measured in accordance with ASTM-D991, and the results are shown in Table 1.

[Table] As is clear from this table, the amount of Teflon used in the composition of the present invention ranges from 0.02 to 0.02 per weight of the powder portion.
The 5.0% by weight sample showed particularly low volume resistivity, and the variation among test pieces was also small. Example 2 Among the compositions obtained in Example 1, the compositions of sample numbers 1 and 4 were selected, mixed in a super mixer, and then mixed in a 40 mm diameter vent type single screw extruder (L/D =
28, Dalmage type screw, screw compression ratio 3.5, screw rotation speed 80 rpm),
Made into pellets. Next, this pellet was press-molded to create 5 test pieces each measuring 150 x 150 x 2 mm.
Regarding this, the volume resistivity value (Ωcm) was measured in accordance with ASTM-D991. The results are shown in Table 2.

[Table] As is clear from this table, those that do not use Teflon have large specific volume resistivities and their dispersion is significant, while those that use Teflon have small specific volume resistivities and There is no variation. Example 3 Stabilizer (manufactured by Adeka Argus Chemical Co., Ltd., trade name mark) was added to 100 parts by weight of polyvinyl chloride powder.
1500) 3 parts by weight, 1.5 parts by weight of wax, 26 parts by weight of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: Denka Black), and 0.3 parts by weight of Teflon 6J (manufactured by Mitsui Fluorochemical Co., Ltd., fine powder for paste extrusion molding). This was placed in a super mixer with an internal volume of 20, and heated and mixed for 5 minutes at a jacket temperature of 70°C and a blade rotation speed of 750 rpm. The raw material obtained in this way was transferred to a 90 mm diameter bent type single screw extruder (L/D = 28, dullage type screw, screw compression ratio 3.5, screw rotation speed).
80 rpm) and extrusion molded into a 2 mm thick plate. Next, this plate was cut into five test pieces measuring 150 x 150 x 2 mm. For each test piece
Volume resistivity (Ω) in accordance with ASTM-D991
cm) was measured. Also, for comparison, Teflon 6J
Five test pieces containing no oxide were prepared, and their volume resistivity values were measured in the same manner. These results are shown in Table 3.

[Table] As is clear from this table, those that do not contain Teflon 6J have a large volume resistivity value with a large amount of variation, while those that contain Teflon 6J have a small volume resistivity value with a small amount of variation. do not have. Example 4 In place of the acetylene black in Example 3, a conductive furnace black (manufactured by Cabot, trade name: Vulcan The volume resistivity value was measured. The results are shown in Table 4.

[Table] As is clear from this table, those that do not contain Teflon 6J have a large volume resistivity value, and some variation is observed, whereas those that contain Teflon 6J have a small volume resistivity value, and no variation is observed. . Example 5 Carbon black (manufactured by Akzo, trade name: Ketjen) was added to 100 parts by weight of high-density polyethylene powder.
-Black EC) 8 parts by weight and Teflon 6J 0.3 parts by weight and for comparison, one without Teflon 6J were mixed in a super mixer and then placed in a 90mm diameter vent type single screw extruder (L/
D = 28, Dalmage type screw, screw compression ratio 3.5, screw rotation speed (80 rpm) were supplied, and extrusion molded to a thickness of 2 mm. Next, this board was cut into five test pieces each measuring 150 x 150 x 2 mm. The volume resistivity value of this was measured in accordance with ASTM-D991. The results are shown in Table 5.

【table】

Claims (1)

[Scope of Claims] 1. When kneading the thermoplastic resin and conductive carbon black, each component is heated and mixed in the presence of fibrillated polytetrafluoroethylene below the melting point of this polytetrafluoroethylene. After bringing the powder part of the ingredients into a restrained state,
A method for producing a conductive resin composition, which comprises kneading. 2. Claim 1, wherein the amount of conductive carbon black is 5 to 50% by weight based on the total amount of the composition.
The method described in section. 3. The method according to claim 1, wherein the amount of fibrillated polytetrafluoroethylene is 0.02 to 5 parts by weight per 100 parts by weight of the powder portion.