JPS638984B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resin composition comprising an ethylene polymer modified with a vinyl monomer and carbon black, which has excellent moldability, molded product appearance, molded product strength, and electrical conductivity. It is known to obtain a conductive resin by blending carbon black with a thermoplastic resin, and conductive resin compositions containing carbon black have also been studied for polyolefins, and have been put into practical use in some cases. However, conventional polyolefin compositions containing carbon black generally have poor molding processability, poor molded product appearance, and poor molded product strength, and those with a high blending ratio of carbon black are particularly poor. A major problem was that it was extremely restrictive. In order to alleviate this problem, the present inventors first applied several known techniques to a polyolefin composition containing carbon black and confirmed their effects. First, carbon black and certain liquid additives (wax, fatty acids, metal soap, etc.) were added to polyethylene or ethylene polymer to improve the moldability of thermoplastic resin compositions containing carbon black. ) was applied to polyethylene and studied in detail. As a result, it was found that although a certain degree of moldability is certainly observed compared to a product simply blending carbon black with polyethylene, the degree of moldability is not very large, and the conductivity tends to deteriorate rather. Second, in order to further improve the conductivity of thermoplastic resin compositions containing carbon black, we have proposed a method that uses two or more materials (polyurethane and butyl rubber, etc.) as main materials that are difficult to mix with each other. The method of making carbon black exist at the interface of the main material (Japanese Patent Publication No. 49-14532) was applied to polypropylene and polyethylene and studied in detail. As a result, although a certain degree of improvement in electrical conductivity was observed compared to polyolefins simply blended with carbon black, the desired improvements in moldability and molded product strength (including flexibility) were not observed. I couldn't help it. That is, the known technology mainly consists of two or more materials that are difficult to be compatible with each other, but as specified in the examples, the main materials are rubber or rubber and an elastomer, and plastics such as polyolefins are The effects are not clear. The inventors have found that when the main materials are plastics with different solubility parameters (SP values), such as polyethylene and polymethyl acrylate, delamination occurs during molding due to their poor compatibility. Shion) manifested,
Even if carbon black was interposed at the interface between the two components, flexibility could not be imparted to the material, and the resulting blended composition was found to be extremely brittle and impractical. In light of this situation, the inventors of the present invention have conducted intensive studies and found that by blending a predetermined amount of a specific carbon black into an ethylene polymer modified by a specific method with a vinyl monomer. The present invention was completed by discovering that a resin composition containing carbon black can be obtained which has excellent molding processability, molded product appearance, molded product strength, and has dramatically improved conductivity. That is, the present invention is a conductive resin composition characterized by blending each of the following components (a) to (c). (a) At least 80% by weight of the vinyl monomer is dissolved in an aqueous suspension containing 95 to 40% by weight of ethylene polymer particles, 5 to 60% by weight of vinyl monomer, and a polymerization initiator. 10 to 100 parts by weight of a modified ethylene polymer obtained by impregnating into the combined particles and then polymerizing the monomer. (b) 90 to 0 parts by weight of olefin polymer. (c) Super Conductive Furness (S.
CF), Conductive Furness (CF)
and at least one type of carbon black selected from Extra Conductive Furnace (XCF) 3 to 100 parts by weight per 100 parts by weight of the above components (a) and (b). The content of the present invention will be described in detail below. (1) Olefin polymer The ethylene polymer as the base resin of component (a) and the olefin polymer as component (b) refer to aliphatic mono- or diolefin polymers, and are a group of such polymers. are homopolymers of aliphatic mono- or diolefins (component (a) is polyethylene), and the other group are copolymers of these olefins with each other or with comonomers (the latter copolymers). , the content of these olefins is 50% by weight or more). (In the case of component (a), a copolymer containing at least 50% by weight of ethylene). "Copolymers" shall include random, block and graft copolymers. Moreover, such polymers may be a mixture of these mutually, and the
It may also be a mixture with up to 40% by weight of other compatible polymers. Examples of classification of such polymers by monomer type include homopolymers of α-olefins (including ethylene) having about 2 to 20 carbon atoms, and copolymers of these with each other. , and copolymers with monomers copolymerizable with these (preferably those with an α-olefin content of 60% by weight or more). Specifically, for example, high pressure method, medium pressure method or low pressure method polyethylene, polypropylene, polybutene.
1. Ethylene-propylene copolymer, ethylene-
Propylene-butene-1 random copolymer, ethylene-vinyl acetate copolymer, ethylene-(meth)
Representative examples include acrylic acid copolymers, ethylene-(meth)acrylic ester copolymers, and unsaturated carboxylic acid-modified polyethylene. Among these, polyethylene and ethylene-vinyl acetate copolymer are preferred. Furthermore, these polymers do not exclude those containing other miscible resins or elastomers in an amount of less than 50% by weight. Component (b) is used in a range of 0 to 90 parts by weight based on 100 parts by weight of the total amount of component (a), but when using an olefin polymer containing 50% by weight or more of propylene as component (b), , preferably 60 parts by weight or less. The purpose of using component (b) is when using a modified ethylene polymer with a large number of vinyl monomer units (generally about 40 parts by weight or more of vinyl monomer) or when a large amount of carbon black is blended (generally is 20
In many cases, it is not possible to obtain the required mechanical strength for parts (by weight or more), but in such cases it is used for the purpose of reinforcing quality. (2) Vinyl Monomer Specific examples of vinyl monomers that can be used in the present invention include styrene and styrene derivatives, such as α-methylstyrene, vinyltoluene, chlorostyrene, and methacrylic acid esters such as methyl methacrylate. (especially _C1 - _C8 alkyl esters), acrylic esters (especially _C1 - _C8 alkyl esters), such as ethyl acrylate, etc.
Conjugated dienes such as 1,3-butadiene and isoprene, vinyl esters such as vinyl acetate, unsaturated nitriles such as acrylonitrile and methacrylonitrile, unsaturated mono- or dihalides such as vinyl chloride and vinylidene chloride, etc. . These can be used together. Further, a very small amount of a crosslinkable diene or polyene monomer, such as divinylbenzene, can be used in combination with such monomers. The modified amount of the vinyl monomer is 40 to 95% by weight of the ethylene polymer and 60 to 5% by weight of the vinyl monomer, based on the total weight with the ethylene polymer. If the amount is less than 5% by weight, the effect of the present invention will not be achieved. on the other hand
When the amount exceeds 60% by weight, the contribution of the ethylene polymer to the mechanical strength of the resulting resin material decreases. The following method is adopted for modifying the ethylene polymer with the vinyl monomer in the present invention. That is, ethylene polymer particles (generally 1
~7 mm, preferably 2 to 5 mm) in an aqueous suspension comprising 40 to 95% by weight of vinyl monomer, 5 to 60% by weight of vinyl monomer and a polymerization initiator. % into the polymer particles and then polymerize the monomer to obtain a modified ethylene polymer. The method of impregnating the polymerization initiator and monomer used here,
Details of the polymerization method are as follows. (3) radical polymerization initiator: impregnating ethylene polymer particles with a vinyl monomer in an aqueous medium without substantially polymerizing the vinyl monomer;
This aqueous dispersion is then heated to polymerize the monomers, and the polymerization is usually promoted by a radical polymerization initiator. This polymerization initiator must be able to be impregnated into the ethylene polymer particles together with the monomer. Therefore, the radical polymerization initiator used is oil-soluble. Preferably, the decomposition temperature is 50 to 150°C to obtain a half-life of 10 hours. Here, "decomposition temperature to obtain a half-life of 10 hours" means that when 0.1 mole of a polymerization initiator is added to 1 liter of benzene and left at a certain temperature for 10 hours, the decomposition rate of the polymerization initiator is It means that temperature which is 50%. It goes without saying that if the impregnation step is carried out at a sufficiently low temperature, a polymerization initiator that is more decomposable at lower temperatures can be used. Specific examples of radical polymerization initiators that can be used include lauroyl peroxide (62°C), benzoyl peroxide (74°C), t-butyl peroxybenzoate (104°C), dicumyl peroxide (117°C), etc. There are organic peroxides such as, azo compounds such as azobisisobutyronitrile (65°C), and others (the temperature in the above-mentioned cup is the above-mentioned half-life temperature). There is no limit to the amount of polymerization initiator, but it is generally about 0.01 to 10% by weight of the monomer weight used, usually 0.1 to 10% by weight.
It is about 2.0% by weight. The polymerization initiator is usually used dissolved in the vinyl monomer. (4) Impregnation of ethylene polymer particles with monomer in an aqueous medium A typical method for impregnating ethylene polymer particles with a vinyl monomer in an aqueous medium is the aqueous dispersion of ethylene polymer particles. It consists of adding a monomer, preferably in which a polymerization initiator (and other additives as necessary) is dissolved, to the liquid and stirring. Another method is to add ethylene polymer particles to an aqueous dispersion of a monomer dissolved in a polymerization initiator and stir the mixture. During the impregnation process, virtually no polymerization occurs.
It should be operated at a sufficiently low temperature in relation to the decomposition temperature of the polymerization initiator used, generally between room temperature and 100°C. In this step, the monomer is impregnated so that the amount of free monomer is 80% by weight or less of the amount of monomer used. Ethylene polymers are relatively compatible with vinyl monomers, so even if 80% by weight or more of the monomers are liberated before the start of polymerization, these monomers will form into ethylene polymer particles during polymerization. Since these monomers are impregnated, the polymer particles obtained by polymerizing these monomers do not precipitate independently from the modified ethylene polymer particles. The impregnation time is usually about 2 to 8 hours. The content of ethylene polymer particles and vinyl monomer in the aqueous dispersion is 5 to 100 parts by weight per 100 parts by weight of water.
It is usually about parts by weight. Such aqueous dispersions can be maintained in a stable dispersed state simply by sufficient stirring, but dispersions can be prepared more easily and stably by using an appropriate suspension stabilizer. can. In this case, suspension stabilizers that can be used generally include those that can be used as suspension stabilizers during aqueous suspension polymerization of vinyl monomers, and specific examples include polyvinyl alcohol, methyl cellulose,
Water-soluble polymer substances such as hydroxycellulose, anionic surfactants such as alkylbenzene sulfonates, nonionic surfactants such as polyoxyethylene alkyl ethers, or water-insoluble inorganic salts such as magnesium oxide and calcium phosphate, etc. 0.01 for water alone or in combination
It is used in amounts of ~10% by weight. When impregnating ethylene polymer particles with vinyl monomer (and polymerization initiator), plasticity, lubricant,
Auxiliary materials such as antioxidants, blowing agents, mold release agents, and colorants can be impregnated at the same time (these auxiliary materials may already be added to the ethylene polymer, or they may be added after polymerization). can also be done). (5) Polymerization If the aqueous dispersion thus prepared is heated to a temperature above which the polymerization initiator used decomposes at an appropriate rate, the impregnated vinyl monomer will polymerize. Modified ethylene polymer particles are produced. Since radical polymerization is to be carried out, heating should be carried out in an atmosphere substantially free of oxygen, and it is preferable to appropriately stir the aqueous dispersion during polymerization. The polymerization temperature is determined in relation to the decomposition temperature of the polymerization initiator used, but is generally about 50 to 150°C.
The polymerization temperature need not be constant throughout the polymerization period. The polymerization time is usually about 2 to 10 hours. The polymerization pressure is usually about normal pressure to 10 kg/cm ² . In addition, n-butyl mercaptan,
It is preferable to add a chain transfer agent such as n-dodecyl mercaptan or t-dodecyl mercaptan. After polymerization, if a treatment similar to that used in aqueous suspension polymerization of ordinary vinyl monomers (e.g. styrene) is carried out, the shape of the ethylene polymer particles used will be maintained almost unchanged and they can be used immediately as a molding material. Modified ethylene polymer particles are obtained which can be used. The modified ethylene polymer of the present invention is an ethylene polymer containing a homogeneously dispersed vinyl monomer, a vinyl monomer grafted onto an ethylene polymer backbone, or a mixture thereof. It is assumed that the vinyl monomer-specific polymer particles do not exist separately from the ethylene polymer particles. (6) Carbon black The carbon black used in the present invention is SCF (Super Conductive Furnace), which has a large specific surface area.
CF (Conductive Furnace) and XCF (Fxtra
conductive furnace), and these are advantageous in that a high degree of conductivity can be obtained with a small amount of blending. You can select and use these commercially available products as appropriate.
For example, the SCF is "Vulcan SC" manufactured by Cabot.
and "Vulcan P", CF is also "Vulcan C", and XCF is AKZO's "Ketschienbrak" as well as Cabot's "Vulcan".
Representative examples include ``XC-72'' and ``CSX-99.'' The carbon black used in the present invention is different from the carbon black used for coloring and filling, which has extremely poor conductivity due to its amorphous structure. A highly conductive furnace black is selectively used. In addition,
A conductive composite carbon black obtained by blending other carbon blacks such as channel black and acetylene black with the specific furnace black in a suitable weight ratio range can also be used as an embodiment of the present invention. The blending amount is 3 parts by weight per 100 parts by weight of the above-mentioned modified ethylene polymer and olefin polymer.
~100 parts by weight. If the blending amount of carbon black is less than the above range, the conductivity will be poor, and if it exceeds the above range, the strength of the material will decrease, which is not preferable. The composition of the present invention can be used in Banbury mixers, rolls,
In addition to batch-type kneaders such as Brabender Plastograph, it can be easily obtained using continuous extruders such as single-screw extruders and twin-screw extruders. The order of compounding is not particularly limited, and in addition to mixing and kneading the compounds at once, it is also possible to first knead the modified ethylene polymer and carbon black in a batch or continuous extruder. It is also possible to knead the kneaded product with the modified ethylene polymer or olefin polymer. It is also possible to dry blend these without going through a kneading process and then subject them to a molding process such as injection molding. The following effects were found by using the modified ethylene polymer as the resin in a resin composition containing carbon black. Compared to a system containing an olefin polymer and carbon black, a system containing the modified ethylene polymer of the present invention and carbon black significantly improves the conductivity at the same amount of carbon black. That is, when imparting a certain level of conductivity, the system of the present invention can greatly reduce the amount of carbon black blended compared to the conventional system. This effect is particularly remarkable in low-density polyethylene (with many long chain branched structures), which is difficult to impart electrical conductivity to, and ethylene-vinyl acetate copolymers with a high vinyl acetate content. Furthermore, these technical requirements discovered by the present inventors differ from the technical content included in Japanese Patent Publication No. 14532/1983 in the following points. In Japanese Patent Publication No. 49-14532, it is stated that a conductive flexible mixture is provided, which is made of two or more types of materials that are difficult to mix with each other, and in which a conductive material is mixed and dispersed. The conductive material mixed into the main material has a bonding force with both the rubber and thermoplastic plastic that make up the main material, so fine particles of the conductive material form at the interface between adjacent main materials that are difficult to mix with each other. It is said that good flexibility is achieved by the apparent compatibility between adjacent main materials through these conductive materials. However, as mentioned above, when the main materials are plastics with poor compatibility, especially when one of them is a nonpolar olefin polymer, there is almost no tendency for the compatibility to be improved through the conductive material, and delamination occurs. This results in a fragile composition that cannot withstand severe practical use. The present invention uses a modified ethylene polymer obtained by polymerizing a vinyl monomer under specific conditions in the presence of an ethylene polymer, and the polymer is uniformly dispersed in micron units. Ethylene-based polymers containing polymers from vinyl monomers or vinyl monomers grafted onto resin backbones,
Alternatively, it is presumed to be a mixture of these, and because the vinyl monomer-specific polymer particles do not exist separately from the ethylene polymer particles, it has an extremely homogeneous dispersion structure despite the mixed system of different types of polymers. It is a composite resin that can maintain its material strength even when a considerable amount of carbon black is added, and furthermore, compared to a simple blend system of different polymers, it has superior conductivity at the same amount of carbon black. It has a novel point that could not be analogized at all. Due to the above effects, the amount of carbon black can generally be reduced compared to conventional technology.
It has been found that it has the following advantages. 1. Processability during compound production has been significantly improved, making it easier to mix using continuous kneading machines such as single-screw extruders and twin-screw extruders. 2. Various molding properties, especially film (including stretching) molding properties and injection molding properties, have been improved. 3. Defects in the appearance of molded products, such as flow marks and uneven gloss, have been significantly improved, and molded products with a beautiful appearance can now be obtained. 4 Due to the effects of 1) to 3) above, it has become possible to expand into various applications that were previously not possible, such as permanent antistatic materials, highly conductive materials, and ultra-high conductive materials. Hereinafter, the effects of the present invention will be explained using Examples. Reference Example 1 20 kg of pure water and 600 g of tribasic calcium phosphate and 0.6 g of sodium dodecylbenzenesulfonate as suspending agents were added to an autoclave with a capacity of 50 mm to create an aqueous medium, and low-density polyethylene (with a particle size of 2 to 3 mm) was added to this. MI.7, density 0.918 Yucalon LM-30) particles manufactured by Mitsubishi Yuka Co., Ltd. 7 kg were suspended by stirring. Separately, 8 g of benzoyl peroxide and 4 g of t-butyl peroxybenzoate as polymerization initiators.
g was dissolved in 3 kg of styrene (30% by weight of styrene), this was added to the suspension system, the temperature inside the autoclave was raised to 70°C, and the temperature was maintained at this temperature for 3 hours to dissolve the styrene containing the polymerization initiator. Impregnated into low density polyethylene particles. This aqueous suspension was heated to 90°C, maintained at this temperature for 7 hours to carry out polymerization, and further heated to 120°C,
The temperature was maintained for 5 hours to complete the polymerization. After cooling, the contents were taken out and washed with water to obtain 10 kg of styrene-modified low-density polyethylene particles with a particle size of 3 to 4 mm. Reference Example 2 20 kg of pure water and 600 g of tribasic calcium phosphate and 0.6 g of sodium dodecylbenzenesulfonate as suspending agents were added to an autoclave with a capacity of 50 mm to create an aqueous medium, and ethylene-vinyl acetate copolymer (MI15 , 5 kg of Yucalon Eva X502 (manufactured by Mitsubishi Yuka Co., Ltd.) particles having a vinyl acetate content of 28% by weight were suspended by stirring. Separately, 10 g of benzoyl peroxide and 5 g of t-butyl peroxybenzoate as polymerization initiators were dissolved in 5 kg of styrene (50% by weight of styrene), and this was added to the suspension system, and the temperature inside the autoclave was raised to 45°C. The temperature was maintained for 3 hours to impregnate styrene containing a polymerization initiator into the ethylene-vinyl acetate copolymer particles. This aqueous suspension was heated to 80℃ for 5 hours, and then
Polymerization was completed by maintaining the temperature at 125°C for 5 hours. After cooling, the contents were taken out and washed with water to obtain 10 kg of styrene-modified ethylene-vinyl acetate copolymer particles. Furthermore, polymerization was carried out in the same manner using 5 kg of ethylene-vinyl acetate copolymer, 3.75 kg of styrene, and 1.25 kg of acrylonitrile (both monomers 50% by weight) to obtain a styrene-acrylonitrile modified ethylene-vinyl acetate copolymer. 10Kg of particles were obtained. Reference example 3 Pure water 100% in an autoclave with a content of 200%
2 kg of tribasic calcium phosphate as a suspending agent, and 3 g of sodium dodecylbenzenesulfonate as a suspending agent to prepare an aqueous medium, and 35 kg of the same low density polyethylene pellets used in Reference Example 1 were suspended in this by stirring. I let it happen. Separately, 142g of t-butyl peroxybenzoate as a polymerization initiator
was dissolved in 15 kg (30% by weight) of methyl methacrylate, this was added to the above aqueous medium, the inside of the autoclave was replaced with nitrogen gas, and the system temperature was raised to 90°C and maintained for 3 hours. Polyethylene pellets were impregnated with methyl methacrylate containing a polymerization initiator. This aqueous suspension was heated to 105°C and held for 3 hours to effect polymerization, and then heated to 120°C and held for 2 hours to complete polymerization. After cooling, pickling and water washing were performed to obtain 50 kg of methyl methacrylate-modified low-density polyethylene particles (methyl methacrylate modified amount: 20% by weight). Example 1 To the styrene-modified low-density polyethylene particles obtained in Reference Example 1, 8 parts by weight of Kettien Black,
Melt kneading using a Brabender Plastograph (temperature
The resulting composition was press-molded (temperature: 160°C, pressure: 150 kg/cm ² ) to produce a sheet, and the conductivity and material strength were evaluated. The results are shown in Table-1. Comparative Example 1 A composition obtained by melt-kneading 8 parts by weight of Ketchen Black into the same low-density polyethylene resin used in Reference Example 1 was evaluated in the same manner as in Example 1. The results are shown in Table-1. Comparative Example 2 70 parts by weight of the same low-density polyethylene resin used in Comparative Example 1 was melt-kneaded with 30 parts by weight of commercially available polystyrene (HF-77 manufactured by Mitsubishi Monsanto) and 8 parts by weight of Ketsuen Black. The composition was evaluated in the same manner as in Example 1. The results are shown in Table-1. Example 2 Styrene-modified ethylene obtained in Reference Example 2
A predetermined amount of vinyl acetate copolymer particles were melt-kneaded with 8 parts by weight of ethylene-vinyl acetate copolymer at the same time using a Brabender plastograph, and the styrene modification amount was 10%, 30%, and 50% (both Each composition with a different weight ratio) was press-molded and evaluated for electrical conductivity and material strength. Furthermore, styrene-acrylonitrile modified ethylene-vinyl acetate copolymer particles were similarly evaluated. The results are shown in Table-2. Comparative Example 3 The same ethylene-vinyl acetate copolymer used in Reference Example 2 was melt-kneaded with 8 parts by weight of Ketchen Black, and evaluated in the same manner as in Example 2. The results are shown in Table-2. Comparative Example 4 70 parts by weight of the same ethylene-vinyl acetate copolymer as used in Comparative Example 3, 30 parts by weight of commercially available polystyrene (HF-77 manufactured by Mitsubishi Monsanto) and 8 parts by weight of Kettien Black were melt-kneaded, The same evaluation as in Example 2 was performed. Furthermore, a commercially available acrylonitrile-styrene copolymer (AS) resin (SAN-C manufactured by Mitsubishi Monsanto) was added to 70 parts by weight of ethylene-vinyl acetate copolymer.
A composition obtained by melt-kneading 30 parts by weight and 8 parts by weight of Ketchen black was evaluated in the same manner as in Example 2. The results are shown in Table-2. Example 3 Composition obtained by melt-kneading the methyl methacrylate-modified low-density polyethylene particles obtained in Reference Example 3 with 8 parts by weight of Ketschen Black in a Brabender Plastograph (temperature: 160°C, time: 5 minutes) A sheet was produced by press molding (temperature: 160°C, pressure: 150 kg/cm ² ), and the conductivity and material strength were evaluated. The results are shown in Table-3. Examples 4 and 5 In Example 1, "Butt Embellishment" 8
"Vulcan SC", "Vulcan C" instead of weight part
A similar experiment was conducted using 30 parts by weight of each. The results are shown in Table 4. <Remarks> 1. Volume specific resistivity was measured using a Wheatstone bridge type measuring device manufactured by Yokogawa Electric Corporation, and was conducted according to the Japan Rubber Association standard "Test method for volumetric resistivity of conductive rubber and plastics" 2301-1969. Measured according to. 2 Tensile strength and elongation were measured according to JISK-7113.

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Claims (1)

[Scope of Claims] 1. A conductive resin composition comprising the following components (a) to (c). (a) At least 80% by weight of the vinyl monomer is dissolved in an aqueous suspension containing 95 to 40% by weight of ethylene polymer particles, 5 to 60% by weight of vinyl monomer, and a polymerization initiator. 10 to 100 parts by weight of a modified ethylene polymer obtained by impregnating into the combined particles and then polymerizing the monomer. (b) 90 to 0 parts by weight of olefin polymer. (c) Super Conductive Furness (S.
CF), Conductive Furness (CF)
and at least one type of carbon black selected from Extra Conductive Furnace (XCF) 3 to 100 parts by weight per 100 parts by weight of the above components (a) and (b).