Conductive floor material, and manufacturing method of the same

Abstract

To provide a conductive floor material with excellent anti-static properties and a manufacturing method of the same.SOLUTION: In a conductive floor material containing a polyvinyl chloride resin composition, 100 mass% of the polyvinyl chloride resin composition contains 30 to 45 mass% of polyvinyl chloride resin (A), 15 to 30 mass% of plasticizer (B), 20 to 40 mass% of aluminum fine particles (C), and 1 to 10 mass% of carbon black (D); the aluminum fine particles (C) have an average particle size of 500 μm or less as measured by a sieving method; and the polyvinyl chloride resin composition has a surface resistance of less than 1×108 Ω as measured in accordance with JIS C 2139, a volume resistance of less than 1×108 Ω as measured in accordance with JIS C 2139, and a ground-to-ground resistance of less than 1×108 Ω as measured in accordance with JIS C 61340.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrically conductive flooring material and a method for manufacturing the same. [Background technology]

[0002] Static electricity is generated by friction between flooring and shoes and can build up on the human body, potentially causing various problems such as computer malfunctions and semiconductor breakdown. To prevent such problems, conductive flooring materials with anti-static properties are commonly used in semiconductor factories and other factories, office computer rooms, and even general office spaces, where electronic devices have become widespread. For example, Patent Document 1 discloses a conductive flooring material that includes a conductive dimensional reinforcement layer containing conductive fibers containing glass fibers and carbon fibers, the conductive fibers being impregnated with a polymer resin such as polyvinyl chloride resin.

[0003] Meanwhile, resin molded articles are known in which metals such as aluminum are used in the form of metal particles, short metal fibers, metal foil, etc., and these are incorporated into resin. For example, Patent Document 2 discloses that resin molded articles obtained by adding small pieces of rectangular aluminum foil (leaf) having a specific thickness and size to a thermoplastic resin at a ratio of 0.1 to 10% have high designability. Patent Document 3 discloses that a resin molded article containing foil-like metal pieces, in which small pieces of a laminate of metal foil and plastic film are randomly bonded to each other or randomly dispersed in another substrate, has excellent electromagnetic wave shielding properties.

[0004] Furthermore, Patent Document 4 describes a thermoplastic resin and a material having an average main surface area of ​​0.3 to 50.0 mm 2 and foil-shaped metal pieces, and the conductive resin molding containing the foil-shaped metal pieces is disclosed, and the conductive resin molding, in which the content of the foil-shaped metal pieces in the molding is 10.0 to 60.0 mass %, has excellent mechanical strength and conductivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2012-524851 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-255836 [Patent Document 3] Japanese Patent Application Publication No. 58-84856 [Patent Document 4] Japanese Patent Publication No. 2023-29054 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the conductive flooring material of Patent Document 1 exhibits a certain level of anti-static properties, further improvement in the anti-static properties is desired. To improve anti-static properties, it is conceivable to add a metal such as aluminum to flooring materials instead of carbon fibers. However, the metal foils disclosed in Patent Documents 2 and 3 are not intended to provide anti-static properties, and the improvement effect is insufficient. Although the foil-like metal pieces used in the molded product of Patent Document 4 exhibit a certain level of anti-static properties, flooring materials with even better anti-static properties are desired.

[0007] An object of the present invention is to provide a conductive flooring material with excellent anti-static properties and a method for producing the same. [Means for solving the problem]

[0008] The present invention relates to the following [1] and [2]. [1] A conductive flooring material containing a polyvinyl chloride resin composition, the polyvinyl chloride resin composition containing 30 to 45 mass% of polyvinyl chloride resin (A), 15 to 30 mass% of plasticizer (B), 20 to 40 mass% of aluminum fine particles (C), and 1 to 10 mass% of carbon black (D), based on 100 mass% of the polyvinyl chloride resin composition; the aluminum fine particles (C) have an average particle size of 500 μm or less as determined by a sieving method; and the polyvinyl chloride resin composition has a surface resistance of 1×10 measured in accordance with JIS C 2139. 8The volume resistivity measured in accordance with JIS C 2139 is less than 1×10 8 Ω or less, and the resistance between grounds measured in accordance with JIS C 61340 is 1 x 10 8 Conductive flooring with a resistance of less than Ω. [2] A method for producing the conductive flooring material according to [1], which comprises a step of molding the polyvinyl chloride resin composition by a roll sheet molding method or a calendar molding method. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a conductive flooring material with excellent anti-static properties and a method for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0010] In this specification, the content of each component in a composition means the total amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition, unless otherwise specified.

[0011] The conductive flooring material of the present invention comprises a polyvinyl chloride resin composition, and the polyvinyl chloride resin composition contains, in 100% by mass, 30 to 45% by mass of a polyvinyl chloride resin (A), 15 to 30% by mass of a plasticizer (B), 20 to 40% by mass of aluminum fine particles (C), and 1 to 10% by mass of carbon black (D); the aluminum fine particles (C) have an average particle size of 500 μm or less as determined by a sieving method; and the polyvinyl chloride resin composition has a surface resistance of 1×10 measured in accordance with JIS C 2139. 8 The volume resistivity measured in accordance with JIS C 2139 is less than 1×10 8 Ω or less, and the resistance between grounds measured in accordance with JIS C 61340 is 1 x 10 8 The average particle size of the aluminum fine particles (C) measured by a sieving method is 500 μm or less, and by using a polyvinyl chloride resin composition in which the contents of the aluminum fine particles (C) and the carbon black (D) are within the above ranges, a conductive flooring material with excellent antistatic properties can be obtained.

[0012] [Polyvinyl chloride resin composition] The polyvinyl chloride resin composition contains, based on 100% by mass of the composition, 30 to 45% by mass of polyvinyl chloride resin (A), 15 to 30% by mass of plasticizer (B), 20 to 40% by mass of aluminum fine particles (C), and 1 to 10% by mass of carbon black (D). Each component will be described below.

[0013] <Polyvinyl chloride resin (A)> Examples of the polyvinyl chloride resin (A) include vinyl chloride homopolymers and copolymers of vinyl chloride with other monomers. Examples of other monomers include vinyl acetate, ethylene, propylene, butene, 1-pentene, butadiene, styrene, α-methylstyrene, acrylonitrile, vinylidene chloride, vinylidene cyanide, alkyl vinyl ethers, vinyl carboxylate esters, aryl ethers, dialkyl maleates, fumarate esters, N-vinylpyrrolidone, vinylpyridine, vinylsilanes, alkyl acrylates, and alkyl methacrylates. The polyvinyl chloride resin (A) may also be a graft copolymer such as an ethylene-vinyl acetate-vinyl chloride graft polymer or a vinyl chloride-urethane copolymer. Among these, vinyl chloride homopolymers and copolymers of vinyl chloride and vinyl acetate are preferred. The polyvinyl chloride resin (A) may be used alone or in combination.

[0014] The average degree of polymerization of the polyvinyl chloride resin (A) is preferably from 500 to 4,000, more preferably from 600 to 2,000, and even more preferably from 700 to 1,200.

[0015] In terms of the anti-static properties and mechanical strength of the resulting conductive flooring material, the content of polyvinyl chloride resin (A) in 100% by mass of the polyvinyl chloride resin composition is 30 to 45% by mass, more preferably 37 to 45% by mass, and even more preferably 38 to 45% by mass.

[0016] <Plasticizer (B)> The plasticizer (B) is a component that imparts flexibility to the polyvinyl chloride resin (A). Examples of the plasticizer (B) include phthalate ester plasticizers such as diisononyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodecyl phthalate, and dibenzyl phthalate; aliphatic dicarboxylic acid ester plasticizers such as di-n-octyl adipate, di-2-ethylhexyl adipate, and di-2-ethylhexyl sebacate; and trimellitate ester plasticizers such as tri-n-octyl trimellitate and tri-2-ethylhexyl trimellitate. Among these, from the viewpoints of balance of performance and ease of availability, diisononyl phthalate, di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodecyl phthalate, di-2-ethylhexyl adipate, or tri-2-ethylhexyl trimellitate is preferred, and diisononyl phthalate, di-2-ethylhexyl phthalate, or di-n-octyl phthalate is particularly preferred. The plasticizer (B) may be used singly or in combination of two or more.

[0017] From the viewpoint of imparting sufficient flexibility to the polyvinyl chloride resin (A), the content of the plasticizer (B) in 100% by mass of the polyvinyl chloride resin composition is 15 to 30% by mass, more preferably 18 to 30% by mass, and even more preferably 18 to 28% by mass.

[0018] <Aluminum fine particles (C)> The polyvinyl chloride resin composition contains aluminum fine particles (C) having an average particle size of 500 μm or less as determined by a sieving method. By containing the aluminum fine particles (C) in the composition, a conductive flooring material with excellent antistatic properties and appearance can be obtained. The aluminum fine particles (C) may be used alone or in combination of two or more.

[0019] From the viewpoint of the antistatic property and appearance of the obtained conductive flooring material, the average particle size of the aluminum fine particles (C) measured by a sieving method is 500 μm or less, preferably 400 μm or less, and more preferably 300 μm or less. The lower limit of the average particle size of the aluminum fine particles (C) measured by a sieving method is not particularly limited, but is preferably 100 μm or more.

[0020] In the present invention, the content of aluminum fine particles (C) is a value obtained by heating and burning a polyvinyl chloride resin composition, and then weighing the remaining aluminum fine particles (C). Specifically, the polyvinyl chloride resin composition is placed in a ceramic crucible and heated to a temperature below which the aluminum fine particles (C) do not melt and up to a temperature at which the other components are completely burned or decomposed, thereby completely burning or decomposing the polyvinyl chloride resin (A), plasticizer (B), carbon black (D), and other components (E), and the remaining aluminum fine particles (C) are weighed. The content of aluminum fine particles (C) is a value expressed as a percentage of the mass of the remaining aluminum fine particles (C) relative to the mass of the polyvinyl chloride resin composition before burning or decomposing. In the present invention, the average particle size of the aluminum fine particles (C) is a value calculated from the mass of each classified fraction obtained by sieving the remaining aluminum fine particles (C). Specifically, the remaining aluminum fine particles (C) are sieved using a plurality of stainless steel test sieves (manufactured by Nonaka Rikaki Seisakusho Co., Ltd., φ75 mm, mesh sizes 2,000 μm, 1,400 μm, 1,000 μm, 600 μm, 425 μm, 300 μm, 180 μm, and 90 μm) while vibrating. Next, the mass of the residue on the sieves and the mass of the particles that have passed through all the sieves and are deposited in a receiver are weighed. The mesh size versus the passing mass of each sieve is plotted and interpolated, and the mesh size at which the passing mass is 50% is defined as the average particle size of the aluminum fine particles (C).

[0021] As long as the aluminum fine particles (C) have an average particle size of 500 μm or less as determined by a sieving method, the shape of the aluminum fine particles (C) is not particularly limited, and may be approximately spherical. As will be described later, in the production of a polyvinyl chloride resin composition, aluminum foil or a laminate containing at least aluminum foil may be used as a raw material, and aluminum fine particles (C) may be formed from the aluminum foil during the production process. In this case, it is preferable that the aluminum foil does not remain in a foil-like shape, but is folded, curled, or the like to form a granular shape as a whole.

[0022] From the viewpoint of the antistatic properties, appearance, and mechanical strength of the resulting conductive flooring material, the content of aluminum fine particles (C) in 100% by mass of the polyvinyl chloride resin composition is 20 to 40% by mass, more preferably 22 to 40% by mass, and even more preferably 22 to 38% by mass. If the content of aluminum fine particles (C) is less than 20% by mass, the antistatic properties of the conductive flooring material will be insufficient, and if it exceeds 40% by mass, the moldability of the composition and the mechanical strength of the flooring material will decrease.

[0023] <Carbon black (D)> The polyvinyl chloride resin composition contains carbon black (D). By including carbon black (D) in the composition, the resulting conductive flooring material can have good antistatic properties. The carbon black (D) may be used alone or in combination of two or more.

[0024] The carbon black (D) is not particularly limited, and examples thereof include furnace black, channel black, acetylene black, and thermal black.

[0025] From the viewpoint of improving the antistatic properties of the conductive flooring material, the average primary particle size of the carbon black (D) is preferably 5 to 100 nm, more preferably 10 to 70 nm. In the present invention, the average primary particle size of the carbon black (D) is a catalog value.

[0026] From the viewpoint of improving the anti-static properties of conductive flooring materials, the DBP absorption of carbon black (D) is 100 to 600 cm 3 / 100g is preferable, and 150 to 600cm 3 In the present invention, the DBP absorption amount is a value measured in accordance with JIS K6217-4.

[0027] In order to improve the anti-static properties of conductive flooring materials, the BET specific surface area of ​​carbon black (D) is 50m 2 / g or more, and 200m 2 / g or more is more preferable. In the present invention, the BET specific surface area is a value measured by the nitrogen adsorption method in accordance with JIS K6217-2.

[0028] From the viewpoint of the anti-static properties of the conductive flooring material, the content of carbon black (D) in 100% by mass of the polyvinyl chloride resin composition is 1 to 10% by mass, and more preferably 2 to 8% by mass.

[0029] From the viewpoint of the anti-static properties of the resulting conductive flooring material, the total content of the aluminum fine particles (C) and carbon black (D) in 100% by mass of the polyvinyl chloride resin composition is preferably 25 to 45% by mass, and more preferably 28 to 42% by mass.

[0030] <Other ingredients (E)> The polyvinyl chloride resin composition may contain other components (E) to the extent that the effects of the present invention are not impaired. Examples of the other components (E) include aluminum fine particles other than the aluminum fine particles (C), metal fine particles other than aluminum, inorganic fine particles other than metal, organic fine particles other than carbon black (D), antioxidants, crystal nucleating agents, crystallization accelerators, heat resistance agents, weather resistance agents, flame retardants, flame retardant assistants, mold release agents, and flowability modifiers.

[0031] [Method of producing polyvinyl chloride resin composition] The method for producing the polyvinyl chloride resin composition is not particularly limited, and examples thereof include a method of melt-kneading polyvinyl chloride resin (A), plasticizer (B), aluminum fine particles (C), carbon black (D), and any other component (E) using a known melt-kneader such as a single-screw or twin-screw extruder, a Banbury mixer, a kneader, or a mixing roll; and a method of melt-kneading polyvinyl chloride resin (A), plasticizer (B), foil-like aluminum and carbon black (D), and any other component (E) using the above-mentioned melt-kneader, and forming aluminum fine particles (C) from the foil-like aluminum during the melt-kneading, thereby obtaining a polyvinyl chloride resin composition.

[0032] In the method for producing a polyvinyl chloride resin composition, pellets, films, etc. containing these components may be used in place of part or all of the polyvinyl chloride resin (A) and plasticizer (B).Further, in the method for producing a polyvinyl chloride resin composition, pellets, films, etc. containing these components may be used in place of part or all of the polyvinyl chloride resin (A), plasticizer (B), and carbon black (D).

[0033] The polyvinyl chloride resin composition produced by the above method can be made into the form of pellets, beads, powder, paste, film, etc. by known methods.

[0034] <Laminate> When a polyvinyl chloride resin composition is produced using foil aluminum, the foil aluminum may be laminated with a layer containing a polyvinyl chloride resin and an optional plasticizer. The use of such a laminate improves the compatibility of the polyvinyl chloride resin (A), the optional plasticizer (B), and the aluminum fine particles (C) formed from the foil aluminum, thereby improving the antistatic properties, uniformity, and appearance of the resulting polyvinyl chloride resin composition and conductive flooring material.

[0035] The laminate containing a layer containing polyvinyl chloride resin and an optional plasticizer and an aluminum foil layer is not particularly limited as long as it contains these two layers, and can be produced by heating a polyvinyl chloride resin film and aluminum foil at a temperature equal to or higher than the softening point of the polyvinyl chloride resin and pressing them together, etc. If necessary, an adhesive layer may be provided between the layer containing polyvinyl chloride resin and an optional plasticizer and the aluminum foil layer. Such laminates may also be made from pharmaceutical packaging (PTP) sheets, waste pharmaceutical packaging (PTP) sheets generated during the production or use of pharmaceutical packaging (PTP) sheets, aluminum laminate sheets for food packaging and their waste materials, aluminum laminate sheets for semiconductor packaging and their waste materials, aluminum vapor-deposited sheets and their waste materials, etc. Pharmaceutical packaging (PTP) sheets and their waste materials may also include a layer containing polyvinyl chloride resin and any plasticizer that corresponds to the pocket portion for storing the pharmaceutical. Using waste pharmaceutical packaging (PTP) sheets, aluminum laminate sheets for food packaging, aluminum laminate sheets for semiconductor packaging, and aluminum vapor-deposited sheets can also contribute to environmental protection and recycling.

[0036] The content of the aluminum foil in 100% by mass of the laminate is preferably 50 to 85% by mass, more preferably 55 to 85% by mass, in order to achieve the aluminum content in the polyvinyl chloride resin composition. The content of the layer containing the polyvinyl chloride resin and an optional plasticizer in 100% by mass of the laminate is preferably 15 to 50% by mass, more preferably 15 to 45% by mass.

[0037] The shape of the laminate is not particularly limited, but is preferably a sheet. The total thickness of the laminate is preferably 10 to 1,000 μm, more preferably 20 to 800 μm, and even more preferably 50 to 500 μm. In pharmaceutical packaging (PTP) sheets and their waste materials, voids are present in the pockets that contain the pharmaceuticals, making the apparent thickness thicker, but this thickness does not take into account the thickness of such portions.

[0038] <Strips of laminate> When the polyvinyl chloride resin composition is produced using the laminate, the method preferably includes a step of cutting and / or pulverizing the laminate to obtain small pieces of the laminate. The remaining polyvinyl chloride resin (A), the remaining plasticizer (B), carbon black (D), and any other component (E) are added to and mixed with the obtained small pieces to obtain a mixture, which is then melt-kneaded, whereby aluminum fine particles (C) can be easily formed from the aluminum foil in the small pieces.

[0039] The shape and size of the thin pieces of the laminate are not particularly limited. For example, when the laminate is in the form of a sheet, the shape of the thin pieces when viewed from the thickness direction may be any of polygonal shapes such as triangles and rectangles, circular shapes, ovals, irregular shapes, etc. The size of the thin pieces when viewed from the thickness direction is 0.3 to 50.0 mm 2 It is preferable that the thickness is 3.0 to 30.0 mm. 2 It is more preferable that the average thickness of the aluminum foil in the flakes is 0.005 to 80 μm. By using flakes having such a shape and size, aluminum fine particles (C) having an average particle diameter of 500 μm or less can be easily formed from the aluminum foil in the flakes when the mixture is melt-kneaded.

[0040] Examples of methods for cutting and / or pulverizing the laminate include methods using a cutting device such as a shredder, slitter, or cutter, or a pulverizing device such as a mixer or grinder. When pulverization is performed using a pulverizer, the stirring speed is preferably 500 to 30,000 rpm, more preferably 1,000 to 25,000 rpm, and even more preferably 3,000 to 20,000 rpm. The stirring time is preferably 1 to 10 minutes, more preferably 2 to 5 minutes. The stirring temperature is preferably 0 to 80°C, more preferably 0 to 60°C. Stirring within the above temperature range can prevent the polyvinyl chloride resin from melting due to heat generated by stirring.

[0041] The mixture is obtained by adding and mixing the remaining polyvinyl chloride resin (A), the remaining plasticizer (B), carbon black (D), and any other component (E) to the laminate strips. The laminate strips, the remaining polyvinyl chloride resin (A), the remaining plasticizer (B), and carbon black (D) are preferably blended so that, based on 100% by mass of the mixture, the total amount of polyvinyl chloride resin (A) is 30 to 45% by mass, the total amount of plasticizer (B) is 15 to 30% by mass, the content of aluminum foil is 20 to 40% by mass, and the content of carbon black (D) is 1 to 10% by mass. Other components (E) may also be added to the mixture. The method for mixing the laminate pieces, the remainder of the polyvinyl chloride resin (A), the remainder of the plasticizer (B), the carbon black (D), and any other component (E) is not particularly limited, and for example, various blenders can be used.

[0042] By melt-kneading the mixture, fine aluminum particles (C) having an average particle size of 500 μm or less are formed from the aluminum foil in the small pieces. Examples of melt-kneading devices include batch mixers (e.g., Plasticoda manufactured by Brabender), single-screw or twin-screw melt-kneading devices, etc. From the viewpoint of forming aluminum fine particles (C) having an average particle size of 500 μm or less from the aluminum foil in the small pieces, the melt-kneading conditions are preferably as follows. That is, when a batch mixer is used, the screw rotation speed is preferably 2 to 100 rpm, more preferably 5 to 80 rpm, and the kneading time is preferably 1 to 20 minutes, more preferably 2 to 10 minutes. When a twin-screw melt-kneading device is used, the screw rotation speed is preferably 20 to 600 rpm, more preferably 50 to 500 rpm, and the extrusion rate during melt-kneading is preferably 10 to 100 kg / hr, more preferably 15 to 80 kg / hr. In addition, the kneading temperature is preferably (the softening point of the polyvinyl chloride resin) to (the softening point of the polyvinyl chloride resin + 80°C), more preferably (the softening point of the polyvinyl chloride resin) to (the softening point of the polyvinyl chloride resin + 60°C).

[0043] <Various resistance values ​​of polyvinyl chloride resin compositions> The polyvinyl chloride resin composition has various resistance values ​​that satisfy the following: A conductive flooring material containing such a polyvinyl chloride resin composition has good anti-static properties. The surface resistance of the polyvinyl chloride resin composition measured in accordance with JIS C 2139 is 1 x 10 8 Ω less than 1×10 6 The lower limit of the surface resistance is not particularly limited, but is, for example, 1×10 2 It can be Ω or more. The volume resistivity of the polyvinyl chloride resin composition measured in accordance with JIS C 2139 is 1 x 10 8 Ω less than 1×10 5 The lower limit of the volume resistivity is not particularly limited, but is, for example, 1×10 2 It can be Ω or more. The resistance between the ground and the polyvinyl chloride resin composition measured in accordance with JIS C 61340 is 1 x 10 8 Ω less than 5 × 10 7 The lower limit of the resistance between the ground terminals is not particularly limited, but it is preferably 1×10 2 It can be Ω or more.

[0044] [Conductive flooring] The conductive flooring material contains a polyvinyl chloride resin composition. The conductive flooring material is made by molding a polyvinyl chloride resin composition, optionally blended with the other component (E), into a sheet.

[0045] The conductive flooring material has at least one layer containing a polyvinyl chloride resin composition. The conductive flooring material may be a single layer or a laminate of two or more layers. When the conductive flooring material is a single layer containing a polyvinyl chloride resin composition, its thickness is preferably 0.2 to 5.0 mm, and more preferably 0.3 to 3.0 mm.

[0046] When the conductive flooring material is a laminate of two or more layers, the thickness of the layer containing the polyvinyl chloride resin composition is preferably 0.2 to 5.0 mm, more preferably 0.3 to 3.0 mm.

[0047] In addition to the laminate, the conductive flooring material may also be made by laminating a base fabric made of glass fiber, glass nonwoven fabric, polyester fiber, polyester nonwoven fabric, cotton, or the like.

[0048] Conductive flooring materials have excellent anti-static properties and can be suitably used as flooring materials in various factories such as semiconductor factories, office computer rooms, general office spaces, etc.

[0049] [Manufacturing method for conductive flooring] The method for producing the conductive flooring material is not particularly limited, and known molding methods such as roll sheet molding, calendar molding, press molding, extrusion molding, etc. Among these, from the viewpoint of improving antistatic properties, the method for producing the conductive flooring material preferably includes a step of molding the polyvinyl chloride resin composition by roll sheet molding or calendar molding, and more preferably includes a step of molding by calendar molding. In the present invention, the roll sheet molding method refers to a method in which a resin is melted while being kneaded between heated rolls, and then passed through several rolls to be hot-stretched and molded to a predetermined thickness. In the present invention, the calendar molding method refers to a method in which a resin is melted while being kneaded using a Banbury mixer or the like, and then passed through several rolls to be hot-stretched and molded to a predetermined thickness. The molding temperature is preferably 140 to 180°C, more preferably 150 to 170°C. [Example]

[0050] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0051] [Evaluation method] 1. Content of aluminum fine particles (C) in polyvinyl chloride resin composition 2 g of the polyvinyl chloride resin composition was placed in a ceramic crucible, and the polyvinyl chloride resin (A), plasticizer (B), and carbon black (D) were completely burned or decomposed, and the remaining aluminum fine particles (C) were weighed. The content (mass%) of the aluminum fine particles (C) was calculated as the mass of the remaining aluminum fine particles (C) relative to the mass of the polyvinyl chloride resin composition before burning or decomposition.

[0052] 2. Average particle size of aluminum particles (C) The remaining aluminum fine particles (C) obtained in step 1 above were sieved using a number of stainless steel test sieves (manufactured by Nonaka Rikaki Seisakusho Co., Ltd., φ75 mm, mesh sizes 2,000 μm, 1,400 μm, 1,000 μm, 600 μm, 425 μm, 300 μm, 180 μm, and 90 μm) while vibrating. Next, the mass of the residue on the sieves and the mass of the material that had passed through all the sieves and was deposited in a receiver were weighed. The mesh size versus the passing mass of each sieve was plotted and interpolated, and the mesh size at which the passing mass was 50% was determined as the average particle size of the aluminum fine particles (C).

[0053] 3. Fabrication of roll sheet molded products Each of the polyvinyl chloride resin compositions of the Examples and Comparative Examples was charged into a 6-inch test roll with the roll temperature set at 160°C, kneaded for 5 minutes, and molded by a roll sheet molding method to obtain a roll sheet molded product having a thickness of 0.5 mm.

[0054] 4.Measurement of surface resistance of molded products The surface resistance of the molded article obtained in 3 above was measured at 23° C. and 50% RH in accordance with JIS C 2139.

[0055] 5. Measurement of volume resistivity of molded products The volume resistivity of the molded article obtained in 3 above was measured at 23° C. and 50% RH in accordance with JIS C 2139.

[0056] 6.Measurement of the resistance between the molded product and ground The molded article obtained in 3 above was measured for ground resistance at 23° C. and 50% RH in accordance with JIS C 61340.

[0057] [Raw materials used] In the examples and comparative examples, the following raw materials were used. (1) Laminate including a polyvinyl chloride resin layer and an aluminum foil layer (aluminum content: 70% by mass, polyvinyl chloride resin content: 30% by mass) (2) Carbon black-containing polyvinyl chloride resin pellets (containing 18% by mass of carbon black, 46% by mass of polyvinyl chloride resin, and 36% by mass of diisononyl phthalate (plasticizer)) (3) Soft polyvinyl chloride sheet (manufactured by Achilles Corporation, containing 56% by mass of polyvinyl chloride resin and 44% by mass of di-2-ethylhexyl phthalate (plasticizer))

[0058] [Fracture of laminated body] A laminate including a polyvinyl chloride resin layer and an aluminum foil layer was continuously fed into a crusher (manufactured by HORAI Co., Ltd.) at a rate of 20 kg / hr, and crushed while controlling the temperature inside the machine to less than 60°C, to obtain small pieces of the laminate.

[0059] Example 1 The fragments obtained by crushing the laminate, pellets of the carbon black-containing polyvinyl chloride resin, and a soft polyvinyl chloride sheet were mixed in a mass ratio of 35.7 / 27.8 / 36.5. The resulting mixture was fed into a twin-screw extruder (manufactured by AIKI LIOTECH Co., Ltd.) at a rate of 3 kg / hr and extruded into strands at 170°C and 150 rpm. The strands were then introduced into a water bath, cooled, cut, and vacuum dried to obtain a polyvinyl chloride resin composition. When the cross section of the polyvinyl chloride resin composition was observed with an SEM, it was confirmed that the aluminum in the laminate was granular and that foil-like aluminum was substantially absent. The content and average particle diameter of the aluminum fine particles (C) in the polyvinyl chloride resin composition were 25 mass% and 250 μm, respectively. The formulation of the polyvinyl chloride resin composition of Example 1 and the average particle diameter of the aluminum fine particles (C) are shown in Table 1.

[0060] Example 2 The polyvinyl chloride resin composition of Example 2 was obtained in the same manner as in Example 1, except that the amounts (mass ratio) of the fragments obtained by crushing the laminate, the pellets of the carbon black-containing polyvinyl chloride resin, and the soft polyvinyl chloride sheet used were changed to 42.9 / 27.8 / 29.3. When the cross section of the polyvinyl chloride resin composition was observed with an SEM, it was confirmed that the aluminum in the laminate was granular and that foil-like aluminum was substantially absent. The content and average particle diameter of the aluminum fine particles (C) in the polyvinyl chloride resin composition were 30 mass% and 250 μm, respectively. The formulation of the polyvinyl chloride resin composition of Example 2 and the average particle diameter of the aluminum fine particles (C) are shown in Table 1.

[0061] Example 3 The polyvinyl chloride resin composition of Example 3 was obtained in the same manner as in Example 1, except that the amounts (mass ratio) of the fragments obtained by crushing the laminate, the pellets of the carbon black-containing polyvinyl chloride resin, and the soft polyvinyl chloride sheet used were changed to 50 / 27.8 / 22.2. When the cross section of the polyvinyl chloride resin composition was observed with an SEM, it was confirmed that the aluminum in the laminate was granular and that foil-like aluminum was substantially absent. The content and average particle diameter of the aluminum fine particles (C) in the polyvinyl chloride resin composition were 35 mass% and 250 μm, respectively. The formulation of the polyvinyl chloride resin composition of Example 3 and the average particle diameter of the aluminum fine particles (C) are shown in Table 1.

[0062] Comparative Example 1 A polyvinyl chloride resin composition of Comparative Example 1 was obtained in the same manner as in Example 1, except that the unshredded laminate was used as is instead of the small pieces obtained by shredding the laminate. The content and average particle diameter of the aluminum fine particles (C) in the polyvinyl chloride resin composition were 25 mass% and 1200 μm, respectively. The formulation of the polyvinyl chloride resin composition of Comparative Example 1 and the average particle diameter of the aluminum fine particles (C) are shown in Table 1.

[0063] Using each of the polyvinyl chloride resin compositions of Examples 1 to 3 and Comparative Example 1, a roll sheet was produced, and its surface resistance, volume resistance, and resistance to ground were evaluated. The results are shown in Table 1. In Table 1, the lower limit of detection for each resistance value is 1×10 5 If it is below Ω, it is <1×10 5 Denoted as Ω, upper limit of detection: 1×10 9 If it exceeds Ω, it is >1×10 9 It is denoted as Ω.

[0064] [Table 1]

[0065] It can be seen from Table 1 that the polyvinyl chloride resin compositions of Examples 1 to 3 were excellent in all resistance values. Comparative Example 1, which had the same formulation as Example 1 but contained fine aluminum particles with an average particle size of 1200 μm, had surface resistance, volume resistance, and resistance to ground all exceeding the upper limit of detection, and was therefore inferior in antistatic properties. [Industrial Applicability]

[0066] The conductive flooring material of the present invention can be suitably used as a flooring material in various factories such as semiconductor factories, office computer rooms, general office spaces, and the like.

Claims

1. A conductive flooring material containing a polyvinyl chloride resin composition, the polyvinyl chloride resin composition contains, per 100 mass% of the polyvinyl chloride resin composition, 30 to 45 mass% of a polyvinyl chloride resin (A), 15 to 30 mass% of a plasticizer (B), 20 to 40 mass% of aluminum fine particles (C), and 1 to 10 mass% of carbon black (D), and the aluminum fine particles (C) have an average particle size of 500 μm or less as determined by a sieving method; The polyvinyl chloride resin composition has a surface resistance of 1×10 measured in accordance with JIS C 2139. ８ The volume resistivity measured in accordance with JIS C 2139 is less than 1 × 10 ８ Ω or less, and the resistance between the ground terminals measured in accordance with JIS C 61340 is 1 × 10 ８ Conductive flooring that is less than Ω.

2. The method for producing the conductive flooring material according to claim 1, further comprising the step of molding the polyvinyl chloride resin composition by a roll sheet molding method or a calendar molding method.

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