JPS6225693B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Fields] This invention is applicable to electric wire-related applications such as high-voltage cables and communication cables, plastic-related applications such as fuel tanks, electronic parts, packaging materials, and automobile parts, hoses, belts, safety shoes, and flooring materials. The present invention relates to conductive resin compositions that are widely used today in rubber-related applications such as switching elements, ignition cables, and static elimination rolls, and electrode-related applications. [Prior Art] Conventionally, as this type of conductive resin composition, one in which conductive solid powder such as carbon black or graphite is kneaded into a resin has been known. For applications below ⁵ Ωcm, for example, it is difficult to mold carbon black mixed into polyethylene by extrusion molding or injection molding, so it is necessary to add a rubbery substance to improve the kneading and molding properties. Therefore, a decrease in physical properties is unavoidable. Therefore, in recent years, Ketchen black, which is a type of carbon black, has been developed as a solid powder to be added to such conductive resin compositions, and other carbon blacks such as acetylene black, furnace black, lamp black, and thermal black have been developed. , channel black, roll black, disk black, etc., it exhibits extremely superior conductivity, and provides excellent conductivity with a low additive amount.
Moreover, it has the feature that there is little decrease in conductivity during kneading. Nowadays, in fields where high conductivity is required, this Ketchen Black is the predominant conductive solid powder used in conductive resin compositions. In addition, by using a mixture of carbon black and graphite containing 40 to 80% by weight of carbon black as a conductive solid powder, and using this mixture at a ratio of 35 to 85% by weight with respect to the thermoplastic resin. It has also been proposed to obtain an excellent conductive material (Japanese Patent Application Laid-Open No. 48-4989). [Problems to be solved by the invention] However, the butcher black is extremely expensive compared to other carbon blacks, and
If the blending ratio of ketchen black is increased for the purpose of improving the conductivity of the resin composition, not only will the product cost increase, but the kneading properties and moldability of the resulting resin composition will decrease. When only 25% by weight is used, the maximum amount that can be kneaded into polyethylene resin using a Banbury mixer is approximately 25% by weight.
With this amount added, the conductivity was not satisfactory for a conductive resin composition used in fields where high conductivity is required. Furthermore, even in conductive resin compositions that use a mixture of carbon black and graphite as conductive solid powder, it is possible to heat them up without reducing mechanical strength compared to when carbon black or graphite is used alone. The ratio of conductive solid powder that can be blended into the plastic resin increases, and the conductivity can be improved accordingly, but on the other hand, the compatibility between the thermoplastic resin and these conductive solid powders is poor, The kneadability when kneading the two and the moldability when molding the obtained resin composition are poor, and a paste is formed using a plasticizer or solvent during kneading or molding. The problem is that the deplasticizer and solvent must be removed, resulting in poor workability during kneading and molding. [Means for Solving the Problems] The present invention was devised in view of this point of view, and it not only has excellent conductivity, but also has excellent conductivity.
It is an object of the present invention to provide a conductive resin composition that does not cause deterioration in physical properties, has excellent kneading properties and moldability, and is inexpensive in product cost. That is, in the present invention, the solid surface of one or both of conductive solid powders consisting of 30 to 80% by weight of polyolefin resin, 1 to 30% by weight of carbon black, and 10 to 50% by weight of graphite is coated with resin. This is a conductive resin composition containing a solid-resin composite powder obtained by coating. The polyolefin resin used in the present invention includes high-pressure polyethylene produced by a high-pressure method at a polymerization pressure of 1000 atmospheres or more;
Medium- and low-pressure polyethylene produced under pressures of about 20 to 70 Kg/cm ³ and 10 Kg/cm ³ , copolymers made by copolymerizing small amounts of propylene, butene-1, and hexene-1, and other vinyl acetate. Examples include copolymers of acrylic acid, alkyl acrylates, vinyl acetate-vinyl chloride, lower α-olefins, and polypropylene, polyisobutylene, polyenes, and various copolymers thereof. In particular, the present invention exhibits its effects on polyethylene, polypropylene, or various copolymers thereof. These polyolefin resins may be blended with various additives such as lubricants, plasticizers, stabilizers, etc. in advance. Further, examples of the carbon black used as the conductive solid powder in the present invention include conventionally known ketone black, acetylene black, furnace black, lamp black, thermal black, channel black, roll black, disk black, etc. I can do it. Among these carbon blacks, particularly preferred is ketthiene, which is known to have excellent conductivity, provide an excellent conductive material with a small amount of addition, and cause little decrease in conductivity during kneading. It's black. Furthermore, the graphite used together with carbon black as the conductive solid powder may be natural graphite or artificial graphite. The above carbon black has a particle size of 15~60Om.
On the other hand, graphite is a particle and has higher conductivity than carbon black. In the present invention, by using both together, it is possible to obtain a resin composition that exhibits high conductivity that cannot be expected when used alone. Carbon black and graphite used as conductive solid powders in the present invention have at least one or both solid surfaces coated with a resin, and are blended into a polyolefin resin as a solid-resin composite powder. Methods for coating the surface of this conductive solid powder with resin include the commonly known interfacial polymerization method, in situ polymerization method, in-liquid curing coating method, phase separation method from an aqueous solution, and phase separation method from an organic solution. method, submerged drying method, melting dispersion cooling method, inclusion exchange method, powder bed method,
There are air suspension coating methods, spray drying methods, vacuum evaporation methods, electrostatic coalescence methods, etc., but preferably, vinyl monomers are graft-polymerized on the solid surface, or
Alternatively, after adsorbing a metal salt capable of imparting a charge to the solid surface, the solid surface is brought into contact with a resin solution or dispersion containing one or more oligomers and/or polymers having an opposite charge to that of the metal salt. It's a method. As a method for graft polymerizing the vinyl monomer onto the solid surface of the carbon black and/or graphite, various polymerization methods such as bulk motion method and solution polymerization method may be used in the presence of a radical polymerization initiator. However, a method in which a conductive solid powder and a vinyl monomer are subjected to suspension polymerization in an aqueous medium in the presence of a compound that generates sulfite ions is particularly preferred, and water is used as the medium for suspension polymerization. Other aqueous media can be used, such as, but not limited to, a mixture of water and methanol. In addition, as a polymerization initiator in suspension polymerization, a compound that generates sulfite ions in an aqueous medium, such as the injection of sulfur dioxide gas, an aqueous solution of sulfite, or a sulfite such as sodium hydrogen sulfite or ammonium hydrogen sulfite; , potassium persulfate, sodium persulfate, ammonium persulfate, and other persulfates can be used alone or in combination. The solid-resin composite powder thus obtained is
A portion of the vinyl resin produced by the polymerization reaction is chemically grafted onto the free radical active sites on the surface of the conductive solid powder. Vinyl monomers used for this purpose include ionically dissociable vinyl monomers such as unsaturated carboxylic acids such as acrylic acid, methacrylic acid, α-chloroacrylic acid, itaconic acid, maleic anhydride, maleic acid, and fumaric acid. system monomers, vinyl halides such as vinyl chloride and vinyl fluoride, styrene, α-
Non-ionically dissociable vinyl monomers such as styrene compounds such as methylstyrene, aliphatic vinyl esters such as vinyl acetate and vinyl propionate, and unsaturated carboxylic acid esters such as methyl acrylate and lauryl methacrylate. can be mentioned. These vinyl monomers graft-polymerize on the surface of the conductive solid powder to form a resin film on the surface of the conductive solid powder that is highly compatible with the polyolefin resin, thereby improving the dispersibility of the conductive solid powder. is significantly improved. The amount of resin when coating the surface of the conductive solid powder with resin by graft polymerization is 0.1 to 30% by weight, preferably 0.5 to 15% by weight, based on the conductive solid powder. In addition, after adsorbing a metal salt capable of imparting an electric charge to the solid surface of carbon black and/or graphite, oligomers and/or
Or in the method of contacting with a resin solution or dispersion containing one or more types of polymers, examples of metal salts used include Agl, FeCl ₃ ,
_Fe2O3 , _MgCl2 , _AlCl3 , Fe(OH) ₃ , _{FeSO4 ,}
Examples include positive charge imparting substances such as Na ₂ SO ₄ or cathodic charge imparting substances such as BaCl ₂ , and
Examples of the resin solution or dispersion containing one or more oligomers and/or polymers include acrylic and methacrylic polymer or copolymer dispersions, and acrylic-styrene copolymers. Examples include dispersions, ethylene-acrylic copolymer dispersions, epoxy resin aqueous solutions, and phenolic resin aqueous solutions. Preferred aqueous solutions or dispersions of these resins are aqueous solutions or dispersions of resins that are compatible with polyolefin resins, such as aqueous solutions of ethylene-acrylic copolymers and aqueous dispersions of resins. ,
Examples include acrylic copolymer emulsions having ester groups such as butyl, lauryl, and stearyl. The amount of resin in the solid-resin composite powder thus obtained is 0.1 to 30% by weight, preferably 0.5 to 15% by weight, based on the conductive solid powder. Note that the conductive solid powder may be coated with both carbon black and graphite.
Moreover, either one may be used. The blending ratio of polyolefin resin, carbon black, and graphite constituting the conductive resin composition of the present invention is changed depending on the physical properties such as electrical conductivity, kneadability, moldability, etc. required for this conductive resin composition. However, in order to achieve the purpose of the present invention, usually 30 to 80% by weight of polyolefin resin, 1 to 30% by weight of carbon black, and 10 to 10% by weight of graphite are used.
50% by weight, preferably polyolefin resin 45-70% by weight, carbon black 10-25% by weight
and graphite 15-40% by weight. If the polyolefin resin content is less than 30% by weight, it will give satisfactory physical properties in terms of electrical conductivity, but moldability, especially extrusion moldability will deteriorate, and if it exceeds 80% by weight, satisfactory properties in terms of electrical conductivity will not be obtained. I can't. In addition, if the graphite content is less than 10% by weight, the economic effect of using graphite in place of the expensive butt-en-black will be poor, and if it exceeds 50% by weight, the effect of extrusion molding will be less than the effect of improving conductivity. The decline in sex becomes noticeable. Furthermore, if the amount of carbon black added is less than 1% by weight, it will be difficult to improve the conductivity, and if it is more than 40% by weight, problems will arise in moldability. From the viewpoint of conductivity, it is desirable that the carbon black be at least 5% by weight when acetylene black is used, and at least 10% by weight when furnace black or thermal black is used. In the present invention, the amount of resin when coated with conductive solid powder was calculated as part of the polyolefin resin, and carbon black and graphite were calculated by subtracting this amount of resin from the added solid-resin composite powder. . Preparation of the conductive resin composition containing the above polyolefin resin, carbon black and graphite is as follows:
It is preferable to uniformly mix and knead in a conventional manner using an appropriate blender such as a co-kneader, a Banbury mixer, a mixing roll, a pressure kneader, etc. within the range of the above-mentioned blending ratio, and form the pellets into pellets. The desired product is formed by press molding, extrusion molding, injection molding, sheeting, etc. In addition, when molding this conductive resin composition, flame retardants, pigments, plasticizers, stabilizers, antioxidants, ultraviolet absorbers, crosslinking agents, wetting agents, and other materials such as carbon black and other materials commonly used in polyolefin resins are added. A modifier or the like can be used to improve the adhesion between graphite and polyolefin resin. [Examples] The present invention will be specifically described below based on Examples and Comparative Examples. Examples 1 to 11 and Comparative Examples 1 and 2 100 parts by weight of Ketchen black with an average particle size of 30μ was suspended in 1200 parts by weight of water, and 0.7 parts by weight of sodium oleate, 7.3 parts by weight of lauryl methacrylate, and FeCl Add 00.3 parts by weight of ₃・6H ₂ , 0.7 parts by weight of potassium persulfate, and 0.7 parts by weight of sodium bisulfite, react at 55°C with stirring for 5 hours, then filter, wash with water and dry. 107 parts by weight of a black/lauryl methacrylate polymer composite powder having a lauryl methacrylate polymer coated on the surface of the black was obtained. The amount of resin in this composite powder was 6.5% by weight. In addition, 100 parts by weight of natural graphite powder with an average particle size of 6 μm was suspended in 400 parts by weight of water, and 0.2 parts by weight of sodium oleate and 7.5 parts by weight of lauryl methacrylate were added.
106.8 parts by weight of graphite/lauryl methacrylate polymer composite powder in which the surface of graphite is coated with lauryl methacrylate polymer by adding 11.7 parts by weight of 6% by weight aqueous sulfite solution and reacting at 60°C with stirring for 3 hours. I got it. The resin content of this composite powder was 6.4% by weight. Next, polyethylene (product name: SHOREX F6050C manufactured by Showa Denko Co., Ltd.), the above-mentioned KETSUCHEN BLACK-lauryl methacrylate polymer composite powder, and the above-mentioned graphite-lauryl methacrylate polymer composite powder were blended in the proportions shown in Table 1, The conductive resin compositions of Examples 1 to 11 and Comparative Examples 1 and 2 were prepared by kneading at 150°C using a kneading roll. Regarding the obtained resin compositions of each example and each comparative example,
A sheet with a thickness of 1 mm was formed using a hot press at a press temperature of 200℃ and a press pressure of 40Kg/ ^cm2 .
The volume resistivity value was measured. The results are shown in Table 1. In addition, for the resin compositions of each of the above examples and comparative examples, a twin screw extruder (manufactured by Ikegai Iron Works Co., Ltd.: PCM-
30) at a screw rotation speed of approximately 50 r.pm.
Extrusion molding was carried out under molding conditions of temperatures of 200℃, 230℃ and 260℃, and the extrusion moldability was investigated.The screw rotation speed was 20 to 40r.pm using sheet manufacturing equipment (Tanabe Plastics: VS-50). at temperature
Sheeting was performed under molding conditions of 250°C, and the sheet moldability was investigated. The results are shown in Table 1. Example 12 100 parts by weight of the above ketone black or graphite were placed in 1000 parts by weight of water, 00.5 parts by weight of FeCl ₃ 6H ₂ was added thereto as a charge imparting substance, and then ethylene/acrylic copolymer Add 5 parts by weight of a combined aqueous solution (trade name: Deiksen, manufactured by Seitetsu Kagaku Co., Ltd.) and let it come into contact for 1 hour, filter and dry to determine the amount of resin.
105 parts by weight of a 4.8% by weight solid-resin composite powder was obtained. Table 1 shows the volume resistivity, kneadability, and moldability of the conductive resin composition obtained using this solid-resin composite powder in the same manner as in the above examples. Example 13 About a conductive resin composition obtained by using the solid-resin composite powder used in Examples 1 to 11 above and using polypropylene (grade name: F109T, manufactured by Ube Industries, Ltd.) as the polyolefin resin. Table 1 shows the volume resistivity values, kneading properties, and moldability obtained in the same manner as in the above examples. Example 14 Butt chain black used in Examples 1 to 11
For conductive resin compositions obtained using the lauryl methacrylate polymer composite powder and untreated graphite and the polyolefin resin used in Examples 1 to 11, the volume specificity was determined in the same manner as in each of the above Examples. Table 1 shows the resistance value, kneadability and moldability. Comparative Examples 3 and 4 Conductive resin compositions obtained using untreated butcher black and untreated graphite and the polyolefin resin used in Examples 1 to 11 were treated in the same manner as in each of the above examples. Table 1 shows the volume resistivity, kneadability, and moldability determined by the following methods.

【table】

〔Effect of the invention〕

According to the present invention, at least one of the solid surfaces of carbon black and graphite as conductive solid powders is coated with a resin and used as a solid-resin composite powder. To provide, at a low price, a conductive resin composition which can significantly improve adhesion and conductivity without deteriorating kneading properties or moldability, and has a high degree of conductivity. I can do it.

Claims (1)

[Scope of Claims] 1. 30 to 80% by weight of polyolefin resin;
~30% by weight carbon black and 10-50% by weight
A solid obtained by coating the solid surface of one or both of conductive solid powders made of graphite with a resin.
A conductive resin composition characterized by containing a resin composite powder. 2. The conductive resin composition according to claim 1, wherein the solid-resin composite powder is obtained by graft polymerizing a vinyl monomer onto the solid surface of carbon black and/or graphite. 3. The solid-resin composite powder is produced by adsorbing a metal salt capable of imparting an electric charge onto the solid surface of carbon black and/or graphite, and then adsorbing one or more oligomers and/or polymers having an opposite electric charge to the metal salt. 2
2. The conductive resin composition according to claim 1, wherein the solid surface of the conductive resin composition is coated with a resin by contacting with a resin solution or dispersion containing at least one species. 4. The conductive resin composition according to any one of claims 1 to 3, wherein the carbon black is butcher black.