Flame-retardant vinyl chloride resin composition

Abstract

To provide a flame-retardant vinyl chloride resin composition that exhibits superior flame retardancy with an oxygen index of 40% or more, and demonstrates hardness suitable for coating wires and cables.SOLUTION: A flame-retardant vinyl chloride resin composition contains a vinyl chloride resin, a plasticizer, and an inorganic flame retardant. Relative to 100 pts.mass of the vinyl chloride resin, the content of the plasticizer is 35-60 pts.mass and the content of the inorganic flame retardant is 70-100 pts.mass. The plasticizer is a mixture of general plasticizer and flame-retardant plasticizer. Relative to the total content of the mixture, the content of the flame-retardant plasticizer is 45 mass% or more. An oxygen index, as measured in accordance with JIS K 7201-2, is 40 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a flame-retardant vinyl chloride resin composition. [Background technology]

[0002] Conventionally, vinyl chloride resin compositions have been used as molding materials for automobile parts, electronic and electric device parts, etc., and as covering materials for communication cables, electric wires, etc. These molding materials and covering materials are sometimes required to be flame retardant. Patent Document 1, for example, is an example of a flame-retardant vinyl chloride resin composition whose flame retardancy is enhanced by containing an inorganic flame retardant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-070066 Summary of the Invention [Problem to be solved by the invention]

[0004] The oxygen index defined in JIS K7201-2 is known as an index of the flame retardancy of plastic materials. The flame-retardant vinyl chloride resin composition disclosed in Patent Document 1 achieves an oxygen index of 35% or more, but no compositions with an oxygen index of more than 40% or more have been disclosed.

[0005] The present invention has been made in view of the above circumstances, and provides a flame-retardant vinyl chloride resin composition that has excellent flame retardancy with an oxygen index of 40% or more and can exhibit hardness suitable for use in covering electric wires and cables. [Means for solving the problem]

[0006] [1] A flame-retardant vinyl chloride resin composition comprising a vinyl chloride resin, a plasticizer, and an inorganic flame retardant, wherein the composition contains 35 to 60 parts by mass of the plasticizer and 70 to 100 parts by mass of the inorganic flame retardant per 100 parts by mass of the vinyl chloride resin, the plasticizer is a mixture of a general plasticizer and a flame-retardant plasticizer, the content of the flame-retardant plasticizer relative to the total content of the mixture is 45% by mass or more, and the flame-retardant vinyl chloride resin composition has an oxygen index of 40 or more as measured in accordance with JIS K 7201-2. [2] The flame-retardant vinyl chloride resin composition according to [1], wherein when the flame-retardant vinyl chloride resin composition is formed into a sheet, the hardness after 10 seconds measured in accordance with JIS K 7215 using a durometer A type is 95 or less. [3] The flame-retardant vinyl chloride resin composition according to [1] or [2], wherein the flame-retardant plasticizer is a phosphate ester plasticizer. [4] The flame-retardant vinyl chloride resin composition according to any one of [1] to [3], wherein the inorganic flame retardant comprises antimony trioxide, zinc borate, calcium carbonate, and a metal hydroxide. [5] The flame-retardant vinyl chloride resin composition according to any one of [1] to [4], containing 6 parts by mass or more of antimony trioxide per 100 parts by mass of the vinyl chloride resin. [6] The flame-retardant vinyl chloride resin composition according to any one of [1] to [5], which contains 6 parts by mass or more of zinc borate per 100 parts by mass of the vinyl chloride resin. [Effects of the Invention]

[0007] The flame-retardant vinyl chloride resin composition of the present invention has excellent flame retardancy with an oxygen index of 40% or more, and can also exhibit hardness suitable for use in covering electric wires and cables. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Flame-retardant vinyl chloride resin composition> A first embodiment of the present invention is a flame-retardant vinyl chloride resin composition (hereinafter sometimes simply referred to as a "PVC composition") containing a vinyl chloride resin, a plasticizer, and an inorganic flame retardant. In this embodiment, it is preferable that the plasticizer is contained in an amount of 35 to 60 parts by mass and the inorganic flame retardant is contained in an amount of 70 to 100 parts by mass relative to 100 parts by mass of the vinyl chloride resin. When the content of the inorganic flame retardant is within the above range, excellent flame retardancy can be obtained. The content of the inorganic flame retardant in the above range is relatively high, so the hardness tends to be high, but by keeping the content of the plasticizer in the above range, it is possible to obtain a hardness suitable for use in covering electric wires and cables.

[0009] The plasticizer used in this embodiment is a mixture of a general plasticizer and a flame-retardant plasticizer, and the content of the flame-retardant plasticizer relative to the total content of the mixture is preferably 45% by mass or more, more preferably 48% by mass or more, even more preferably 51% by mass or more, and most preferably 54% by mass or more. While there is no particular upper limit, from the viewpoint of further enhancing the effect of the plasticizer and reducing hardness, it is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, and most preferably 60% by mass or less.

[0010] Examples of general plasticizers include carboxylic acid ester plasticizers and epoxidized vegetable oils, with carboxylic acid ester plasticizers being preferred. Examples of carboxylic acid ester plasticizers include phthalates, terephthalates, adipates, trimellitates, citrates, sebacates, azelates, and benzoates. Low-molecular-weight polyesters composed of carboxylic acids and alcohols such as glycols, and polyesters such as phthalates, can also be used as general plasticizers. The alcohols may be aliphatic, aromatic, or heterocyclic.

[0011] Examples of flame-retardant plasticizers include phosphate ester plasticizers, chlorinated paraffin, and chlorinated fatty acid esters. From the viewpoint of achieving both excellent flame retardancy and reduced hardness, phosphate ester plasticizers are preferred. Examples of phosphate ester plasticizers include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tris(2-ethylhexyl) phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, and 2-ethylhexyl diphenyl phosphate.

[0012] The inorganic flame retardant of this embodiment preferably contains four types of metal hydroxides: antimony trioxide, zinc borate, calcium carbonate, and metal hydroxide. Aluminum hydroxide and magnesium hydroxide are preferred as metal hydroxides. Here, metal hydroxides are collectively treated as one type of inorganic flame retardant, regardless of the type of metal. The metal hydroxide of this embodiment may contain one type of metal, or two or more types of metals. Other known inorganic flame retardants may be included, but it is most preferable to include only the above four types of inorganic flame retardants, since a combination of the above four types of inorganic flame retardants can achieve both excellent flame retardancy and hardness suitable for use in covering electric wires and cables. The inorganic flame retardant is usually contained in particulate form, and the particle size can be, for example, about 0.1 to 30 μm.

[0013] In this embodiment, the content of the four inorganic flame retardants is preferably 6 to 20 parts by mass of antimony trioxide, more preferably 8 to 17 parts by mass, and even more preferably 10 to 15 parts by mass, relative to 100 parts by mass of vinyl chloride resin. The content of metal hydroxide is preferably 10 to 50 parts by mass, more preferably 20 to 40 parts by mass, and even more preferably 25 to 35 parts by mass. The content of calcium carbonate is preferably 10 to 50 parts by mass, more preferably 20 to 40 parts by mass, and even more preferably 25 to 35 parts by mass. The content of zinc borate is preferably 6 to 20 parts by mass, more preferably 8 to 17 parts by mass, and even more preferably 10 to 15 parts by mass.

[0014] In this embodiment, the mass ratio of the four inorganic flame retardants is preferably 1.0 to 5.0, more preferably 2.0 to 4.0, and even more preferably 2.5 to 3.5 for (metal hydroxide / antimony trioxide), 1.0 to 5.0, more preferably 2.0 to 4.0, and even more preferably 2.5 to 3.5 for (calcium carbonate / antimony trioxide), and 0.5 to 2.0, more preferably 0.7 to 1.5, and even more preferably 0.8 to 1.2 for (zinc borate / antimony trioxide).

[0015] From the viewpoint of not only enhancing the flame retardancy of the vinyl chloride resin composition of the present embodiment but also realizing a low hardness suitable for use in covering electric wires and cables, it is preferable that inorganic flame retardants and inorganic fillers (e.g., silicon oxide) other than the above four types are not contained, or if contained, the amount is less than 1 mass % relative to the total mass of the vinyl chloride resin composition.

[0016] The vinyl chloride resin of this embodiment may be a vinyl chloride homopolymer (PVC) or a copolymer. Examples of copolymerizable monomers include ethylene, propylene, acrylonitrile, vinyl acetate, maleic acid or its ester, acrylic acid or its ester, methacrylic acid or its ester, and vinylidene chloride. The vinyl chloride resin of this embodiment is preferably a vinyl chloride homopolymer. When it is a copolymer, the content of repeating units other than vinyl chloride is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of repeating units derived from vinyl chloride. The vinyl chloride resin of this embodiment may be chlorinated after the resin is formed.

[0017] The average degree of polymerization of the vinyl chloride resin of the present embodiment is not particularly limited, but is, for example, preferably 1000 to 4000, more preferably 1300 to 3000, and even more preferably 1300 to 2000. Within the above preferred range, it becomes easy to obtain a hardness suitable for use in covering electric wires and cables. Here, the average degree of polymerization of the vinyl chloride resin is the average degree of polymerization measured in accordance with JIS K6720-2. The average degree of polymerization is calculated from the K value. The K value is a value measured in accordance with JIS K7367-2 (ISO1628-2).

[0018] The content of the vinyl chloride resin relative to the total mass of the PVC composition of this embodiment is preferably 25 to 53 mass%, more preferably 30 to 50 mass%, even more preferably 35 to 48 mass%, and most preferably 40 to 45 mass%. Within this preferred range, the blending ratio with other components becomes appropriate, making it easy to obtain sufficient flame retardancy.

[0019] The PVC composition of the present embodiment may contain a resin other than a vinyl chloride resin. From the viewpoint of fully achieving the effects of the present invention, the content of the resin other than a vinyl chloride resin is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the vinyl chloride resin.

[0020] The PVC composition of the present embodiment may contain any additives, such as a heat stabilizer, a processing aid (lubricant), an ultraviolet absorber, a light stabilizer, an antioxidant, a crystal nucleating agent, an antistatic agent, a metal deactivator, an antibacterial agent, or a pigment, as long as the effects of the present invention are not impaired.

[0021] Examples of the heat stabilizer include a lead-based stabilizer, a tin-based stabilizer, a silver-based stabilizer, a calcium-magnesium-zinc-based stabilizer, a calcium-zinc-based stabilizer, a barium-zinc-based stabilizer, a barium-cadmium-based stabilizer, and a hydrotalcite-based stabilizer. One type of heat stabilizer may be included, or two or more types may be included. The total content of the heat stabilizer is preferably 1 to 10 parts by mass, more preferably 2 to 8 parts by mass, and even more preferably 3 to 7 parts by mass, relative to 100 parts by mass of the vinyl chloride resin.

[0022] Examples of processing aids include acrylic lubricants such as methyl acrylate and methyl methacrylate, fatty acid amide lubricants such as stearic acid amide and oleic acid amide, waxes such as paraffin wax, polyolefin wax, ester wax, montanic acid wax, and polyethylene wax, higher fatty acids such as stearic acid and behenic acid, higher alcohols such as stearyl alcohol and cetyl alcohol, fatty acid esters such as butyl stearate and monoglyceryl stearate, metallic soaps such as calcium stearate and magnesium stearate, and oils such as silicone oil and process oil. One type of processing aid may be included, or two or more types may be included. The total content of the processing aids is preferably 0.1 to 10 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 1 to 3 parts by mass with respect to 100 parts by mass of the vinyl chloride-based resin.

[0023] <Method for producing PVC composition> The method for producing the PVC composition according to the present invention is not particularly limited, and it can be obtained by mixing and kneading by a conventional method so that each component becomes uniform in the composition. Examples of the method for mixing and kneading the vinyl chloride-based resin, plasticizer, inorganic flame retardant, etc. include methods using a pressure kneader, Banbury mixer, etc. When mixing, it is preferable to mix and knead at a resin temperature of 180°C or lower from the viewpoint of preventing the decomposition of PVC.

[0024] <Form of PVC composition> Specific forms of the PVC composition of this embodiment may be pellets, beads, or powders that are easy to use for other molding processes, or molded products formed by known molding methods such as press molding, injection molding, and extrusion molding. The molded product is not particularly limited, and examples include automobile parts, electronic and electrical equipment parts such as personal computers and copiers, and coating materials for electric wires and cables. The PVC composition of this embodiment has excellent flame retardancy and relatively low hardness, and is particularly useful as a coating material for electric wires and cables.

[0025] <Physical properties of the PVC composition> (Oxygen index) The oxygen index measured by molding the PVC composition of this embodiment into a Type IV test piece specified in JIS K 7201-2:2021 and conforming to Procedure A (upper end ignition) of JIS K 7201-2:2021 is 40 or more. The upper limit value of the oxygen index is not particularly limited, and as a guideline, 50 or less can be mentioned.

[0026] (Hardness) The PVC composition of this embodiment is preferably molded into a sheet shape, and the hardness after 10 seconds measured with a durometer A type in accordance with JIS K 7215:1986 is 95 or less. Here, the hardness after 10 seconds refers to the measured value 10 seconds after continuing the pressing from the time when the indenter touches the surface of the test piece and starts pressing. When the hardness after 10 seconds is 95 or less, it is particularly useful as a coating material for electric wires and cables.

[0027] (Specific gravity) The specific gravity of the PVC composition of this embodiment measured in accordance with Method A (water substitution method) of JIS K 7112:1999 is preferably 1.6 or less.

[0028] (Tensile strength) The tensile strength of the PVC composition of this embodiment measured in accordance with JIS K7127:1999 using test piece type 5 is preferably 14 MPa or more, more preferably 16 MPa or more, and even more preferably 18 MPa or more. The upper limit value is not particularly limited, and for example, about 30 MPa can be mentioned as a guideline.

[0029] (Tensile elongation) The tensile elongation of the PVC composition of this embodiment measured in accordance with JIS K7127:1999 using test piece type 5 is preferably 150% or more, more preferably 200% or more, and even more preferably 220% or more. The upper limit value is not particularly limited, and for example, about 300% can be mentioned as a guideline.

Examples

[0030] The present invention will be specifically explained below by showing examples, but the present invention is not limited to these examples.

[0031] The details of the raw materials listed in Table 1 are as follows: "PVC with a degree of polymerization of 1300" is TK-1300 manufactured by Shin-Etsu Chemical Co., Ltd. The "Ca-Mg-Zn stabilizer" is Adeka Stab RUP-103 manufactured by ADEKA Corporation. The "phthalate plasticizer" is DINP manufactured by J-Plus Corporation, a general-purpose plasticizer. The "trimellitic acid ester plasticizer" is W-700 manufactured by DIC Corporation, a general-purpose plasticizer. "Phosphate ester plasticizer" is CDP manufactured by Daihachi Chemical Industry Co., Ltd., and is a flame-retardant plasticizer. The "acrylic processing aid" is Mitsubishi Chemical's Metablen P-551A. "Antimony trioxide" is PATOX-M manufactured by Nippon Seiko Co., Ltd. The "aluminum hydroxide" is Suisanka Aluminum BF013 manufactured by Nippon Light Metal Co., Ltd. The "calcium carbonate" is Whiten SB manufactured by Shiraishi Calcium Co., Ltd. "Zinc borate" is ALCANEX FR-100 manufactured by Mizusawa Industrial Chemicals.

[0032] <Preparation of Composition> A PVC composition was obtained by mixing the raw materials in the amounts (parts by mass) shown in Table 1 using a twin-screw kneader. For example, in Example 1, the target PVC composition was obtained by blending 5 parts by mass of a stabilizer, 20 parts by mass of a phthalate-based plasticizer, 25 parts by mass of a phosphate ester-based plasticizer, 2 parts by mass of an acrylic processing aid, and a total of 80 parts by mass of four inorganic flame retardants per 100 parts by mass of PVC.

[0033] <Creating a sheet> 100 g of each PVC composition of each test example was kneaded for 10 minutes on a 3.5-inch roll set at 155°C to produce a 0.5 mm thick sheet. The direction in which the sheet passed through the roll (machine direction) and the direction perpendicular to it could be distinguished for the sheet produced here. Two sheets were prepared, stacked with their machine directions crossing each other, preheated at 170°C for 4 minutes, and then heat-compressed and molded at 170°C and 15 MPa for 4 minutes. Subsequently, the sheets were slowly cooled to room temperature (25°C) while still under pressure to obtain sheets of the specified thickness required for each test, which were then subjected to tests such as oxygen index and hardness.

[0034] <Oxygen index measurement> In accordance with JIS K 7201-2:2021, the oxygen index was measured using the IV-type test specimen specified in the standard, following procedure A (top ignition).

[0035] <Hardness measurement after 10 seconds> Durometer hardness was measured in accordance with JIS K 7215: 1986 using a Type A indenter specified in the standard. The test piece was the sheet prepared as described above, and after conditioning as specified in the standard, the indenter was brought into contact with the surface of the test piece and pressure was started. The value measured 10 seconds later was defined as the "hardness after 10 seconds."

[0036] <Specific gravity> The specific gravity of the sheet prepared as described above was measured using an MD-300S electronic hydrometer manufactured by Alpha Mirage.

[0037] <Tensile strength> The 1 mm thick sheet prepared as described above was punched out into Type 5 test pieces as specified in JIS K 7127:1999, and the resulting test pieces were left to stand in an environment of 23±1°C for 24 hours, after which the tensile strength was measured. The tensile strength was measured in accordance with JIS K 7127:1999 at a pulling rate of 200 mm per minute.

[0038] <Tensile elongation> The 1 mm thick sheet prepared as described above was punched out into a type 5 test piece as specified in JIS K 7127:1999, and the resulting test piece was left to stand in an environment of 23±1°C for 24 hours, after which the tensile elongation was measured. The tensile elongation was measured in accordance with JIS K 7127:1999 at a pulling rate of 200 mm per minute.

[0039] [Table 1]

[0040] The PVC composition of Example 1 contained 35 to 60 parts by mass of plasticizer and 70 to 100 parts by mass of inorganic flame retardant per 100 parts by mass of vinyl chloride resin, and thus exhibited excellent flame retardancy with an oxygen index of 40 or more. In particular, the composition contained approximately 56% by mass (25 parts by mass) of a phosphate ester plasticizer, an example of a flame-retardant plasticizer, relative to the total plasticizer content (55 parts by mass), which resulted in an oxygen index of 40 or more and a hardness after 10 seconds of 95 or less. On the other hand, in the PVC composition of Comparative Example 1, the content of the flame-retardant plasticizer was low, so the oxygen index did not reach 40 or more. In addition, in the PVC compositions of Comparative Examples 2 to 5, the oxygen index did not reach 40 or more due to the influence of the content of the inorganic flame retardant. The PVC compositions of Reference Examples 1 and 2 had oxygen indices of 40 or more, but because they contained only one of a general plasticizer and a flame-retardant plasticizer, the hardness after 10 seconds was high and was not suitable for use in covering electric wires and cables.

Claims

1. A flame-retardant vinyl chloride resin composition comprising a vinyl chloride resin, a plasticizer, and an inorganic flame retardant, the plasticizer is contained in an amount of 35 to 60 parts by mass and the inorganic flame retardant is contained in an amount of 70 to 100 parts by mass relative to 100 parts by mass of the vinyl chloride resin; the plasticizer is a mixture of a general plasticizer and a flame-retardant plasticizer, and the content of the flame-retardant plasticizer relative to the total content of the mixture is 51 mass% or more; the general plasticizer is at least one of a carboxylic acid ester plasticizer and an epoxidized vegetable oil, A flame-retardant vinyl chloride resin composition having an oxygen index of 40 or more as measured in accordance with JIS K 7201-2.

2. 2. The flame-retardant vinyl chloride resin composition according to claim 1, wherein the flame-retardant vinyl chloride resin composition has a hardness of 95 or less after 10 seconds as measured with a durometer A type in accordance with JIS K 7215.

3. 3. The flame-retardant vinyl chloride resin composition according to claim 1, wherein the flame-retardant plasticizer is a phosphate ester plasticizer.

4. 4. The flame-retardant vinyl chloride resin composition of claim 3, wherein said inorganic flame retardant comprises antimony trioxide, zinc borate, calcium carbonate and a metal hydroxide.

5. 5. The flame-retardant vinyl chloride resin composition according to claim 4, comprising 6 parts by mass or more of antimony trioxide per 100 parts by mass of the vinyl chloride resin.

6. 6. The flame-retardant vinyl chloride resin composition according to claim 5, comprising 6 parts by mass or more of zinc borate per 100 parts by mass of the vinyl chloride resin.

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