JP2015143027A - Flame-retardant sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin sheet with high flame retardancy.SOLUTION: A flame-retardant sheet comprises a first layer comprising flaked graphite and first thermoplastic resin, and a second layer put on the first layer and comprising second thermoplastic resin.

Description

  The present invention relates to a flame resistant sheet in which a carbon material is dispersed in a thermoplastic resin, and more particularly to a flame resistant sheet in which the carbon material is exfoliated graphite.

  Conventionally, thermoplastic resins have been utilized in many industrial fields such as building materials, home appliances, vehicles, and the like because of their excellent durability, light weight, and moldability. However, the thermoplastic resin, which is an organic material, has a problem that it is vulnerable to fire because it is generally easy to burn.

  Therefore, in recent years, a thermoplastic resin material having high flame retardancy has been demanded. For example, Patent Document 1 below proposes a method of adding a flame retardant such as aluminum hydroxide or magnesium hydroxide to a vinyl chloride resin. Patent Document 2 below proposes a method of adding graphite to a vinyl chloride resin.

Japanese Patent Laid-Open No. 5-25347 JP-A-9-227747

  However, in the thermoplastic resin compositions described in Patent Documents 1 and 2, it is necessary to add a large amount of flame retardant in order to obtain sufficient flame retardancy. Therefore, there has been a problem that impact resistance and secondary processability of the thermoplastic resin composition are remarkably lowered.

  An object of the present invention is to provide a resin sheet having high combustion resistance.

  A combustion-resistant sheet according to the present invention includes a first layer containing exfoliated graphite and a first thermoplastic resin, and is laminated on the first layer and includes a second thermoplastic resin. A second layer.

  In a specific aspect of the combustion-resistant sheet according to the present invention, the ratio of exfoliated graphite contained in the first layer is 100 parts by weight in total of the components contained in the first layer other than the exfoliated graphite. On the other hand, it is 0.1 to 50 parts by weight. In this case, since the thermal conductivity of the first layer becomes higher, heat can be released efficiently. Therefore, the combustion resistance of the first layer becomes higher. Therefore, the flame retardance of the flame resistant sheet can be further increased.

In another specific aspect of the burning resistance sheet according to the present invention, the specific surface area of flaked ^graphite, is 50m ² / g~2600m 2 / g. In this case, heat can be efficiently released in the direction of the laminated surface of exfoliated graphite. Therefore, the combustion resistance of the combustion resistant sheet can be increased efficiently.

  In another specific aspect of the flame resistant sheet according to the present invention, the first layer further includes an acrylic processing aid. In this case, the secondary workability of the flame resistant sheet, particularly the vacuum formability can be further improved.

  In still another specific aspect of the combustion resistant sheet according to the present invention, the second thermoplastic resin is a vinyl chloride resin, and the second layer further includes an impact modifier and a processing aid. In this case, the combustion resistance, impact resistance and secondary workability of the flame resistant sheet can be further enhanced.

  In still another specific aspect of the combustion resistant sheet according to the present invention, the second thermoplastic resin is a styrene resin.

  According to the combustion resistant sheet according to the present invention, the first layer has high combustion resistance due to the high thermal conductivity and the large specific surface area of exfoliated graphite. Moreover, since sufficient flame retardance can be obtained with a small amount of exfoliated graphite, the high impact resistance and secondary workability provided in the first thermoplastic resin are not significantly impaired. In addition, since the second layer containing the second thermoplastic resin is laminated on the first layer, the impact resistance and secondary workability of the flame resistant sheet are not affected without impairing the flame resistance. Can be increased efficiently.

It is a schematic diagram for demonstrating the process of preparing a graphite sheet in the manufacturing method of exfoliated graphite used for an Example. It is a typical perspective view for demonstrating the process of inserting an electrode in graphite in the manufacturing method of exfoliated graphite used for an Example. It is a figure which shows the voltage application pattern at the time of applying a voltage to a graphite sheet by the electrochemical process in the manufacturing method of exfoliated graphite used for an Example.

  Hereinafter, the present invention will be clarified by describing embodiments of the present invention.

  The combustion-resistant sheet of the present invention includes a first layer and a second layer laminated on the first layer.

  In the combustion resistant sheet of the present invention, it is preferable to laminate the second layer on a surface that does not directly contact the flame. However, the flame resistant sheet of the present invention may have a three-layer structure in which the second layer is laminated on both the front and back surfaces of the first layer, and the first and second layers are alternately laminated. A laminated structure of four or more layers may be used. The second layer may be a coating layer that coats the first layer.

  The surface of the first layer and / or the second layer may be printed. Moreover, the decoration layer may be provided in the combustion-resistant sheet | seat. In this case, the designability of the combustion resistant sheet can be improved.

  In addition to these layers, the combustion-resistant sheet may be provided with various functional layers such as a protective layer and an antireflection layer.

  The first layer includes exfoliated graphite and a first thermoplastic resin. The first layer may be a single layer or a multilayer structure in which a plurality of layers are stacked. When the first layer has a multilayer structure, the first layer includes, in addition to a layer containing a thermoplastic resin and exfoliated graphite, other fillers different from exfoliated graphite, such as copper, A layer containing fine particles such as aluminum or fine fibers may be provided. In this case, the excellent characteristics of the other fillers described above, such as flame retardancy, can be sufficiently exhibited.

  In the present invention, exfoliated graphite is obtained by exfoliating original graphite, and refers to a graphene sheet laminate that is thinner than the original graphite. The number of graphene sheets laminated in exfoliated graphite should be less than the original graphite, but is usually about 1 to 200 layers.

  Since exfoliated graphite is obtained by exfoliating the original graphite, it has a shape that is thinner than normal graphite and has a relatively high aspect ratio. In addition, exfoliated graphite has a high thermal conductivity. Therefore, the exfoliated graphite can efficiently release heat in the direction of the laminated surface. Therefore, the exfoliated graphite can enhance the flame resistance of the first layer and the flame resistant sheet. In the present invention, the aspect ratio refers to the ratio of the maximum dimension of the exfoliated graphite in the laminated surface direction to the thickness of the exfoliated graphite.

When the aspect ratio of exfoliated graphite increases due to the exfoliation treatment of the original graphite, the specific surface area of the exfoliated graphite increases. Therefore, it is desirable that the specific surface area of the exfoliated graphite is large. A preferable lower limit of the specific surface area of the exfoliated graphite is 50 m ² / g, and a preferable upper limit is 2600 m ² / g. If the specific surface area of the exfoliated graphite is too small, that is, if the aspect ratio of the exfoliated graphite is too low, the combustion resistance may not be sufficiently improved. On the other hand, if the specific surface area of the exfoliated graphite is too large, that is, if the aspect ratio of the exfoliated graphite is too high, the effect may be saturated and further combustion resistance may not be desired.

  Although the ratio of the exfoliated graphite contained in the first layer is not particularly limited, it is 0.1 to 50 parts by weight with respect to a total of 100 parts by weight of the components contained in the first layer other than the exfoliated graphite. It is preferable to be in the range. If it is less than 0.1 part by weight, the combustion resistance may not be sufficiently improved. If it exceeds 50 parts by weight, it may be brittle and easily cracked, and the impact resistance and secondary formability may deteriorate. Preferably, the ratio of exfoliated graphite is in the range of 0.5 to 30 parts by weight, and more preferably in the range of 1 to 15 parts by weight. In addition, when providing a decoration layer in the flame-resistant sheet | seat of this invention, it is preferable that the ratio of the said exfoliated graphite is the range of 0.5-50 weight part.

  It is desirable that the exfoliated graphite is uniformly dispersed in the first thermoplastic resin contained in the first layer. Thereby, the improvement effect of the combustion resistance by exfoliated graphite can be exhibited efficiently. Therefore, the combustion resistance of the first layer and the combustion resistant sheet can be efficiently increased.

  The first thermoplastic resin is not particularly limited, and various resins can be used. By using a thermoplastic resin for the first layer, the first layer and the flame resistant sheet can be easily molded under heating. Therefore, the moldability of the first layer and the flame resistant sheet can be improved.

  Examples of the first thermoplastic resin include polypropylene resins, polyethylene resins, poly (1-) butene resins, polypentene resins and other polyolefin resins; polycarbonate resins; polyphenylene ether resins; acrylic resins; Polystyrene (including impact-resistant polystyrene), acrylonitrile-butadiene-styrene (ABS) resin, acrylonitrile-styrene (AS) resin, acrylonitrile-ethylene-propylene-styrene (AES) resin, acrylonitrile-acrylate-styrene (AAS) resin, etc. Styrene resin; polyamide resin; chlorinated polyolefin such as chlorinated polyethylene; vinyl chloride resin; chlorinated vinyl chloride resin; ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer EMA), ethylene - ethyl acrylate copolymer (EEA), ethylene - butyl acrylate copolymer (EBA), ethylenemethyl - methyl methacrylate copolymer (EMMA), include ethylene copolymers such as AES described above. These thermoplastic resins may be used independently and may use 2 or more types together. Of these, vinyl chloride resins excellent in flame retardancy, impact resistance and secondary processability, and chlorinated polyolefin excellent in impact resistance and secondary processability are preferable. Further, when a vinyl chloride resin is used for the second thermoplastic resin included in the second layer, the vinyl chloride resin is also used for the first thermoplastic resin included in the first layer. The adhesion between the first and second layers can be made stronger.

  Although the molecular weight of a 1st thermoplastic resin is not specifically limited, For example, the weight average molecular weight of about 10,000-1 million is mentioned. In addition, in this invention, a weight average molecular weight is a weight average molecular weight of polystyrene conversion measured by GPC (gel permeation chromatography) of a styrene-type elastomer. Specifically, the weight average molecular weight of the (meth) acrylate polymer can be a value measured under the following conditions. Using a device: HLC-8120 (manufactured by Tosoh Corporation) and a solvent: THF, a calibration curve is prepared based on the molecular weight of polystyrene having a known molecular weight. The column and sample concentration used for measurement are appropriately selected depending on the weight average molecular weight of each (meth) acrylate polymer to be measured. For example, when the molecular weight is 3 million, depending on the column used: GMHHR-H (30) × 2, solvent: THF, sample concentration: 0.05%, injection amount: 50 μl, flow rate: 0.5 ml / min, taking measurement.

  Vinyl chloride resin is a copolymer of vinyl chloride homopolymer (vinyl chloride homopolymer), a monomer having an unsaturated bond copolymerizable with vinyl chloride monomer, and vinyl chloride monomer (preferably containing 50% by weight or more). Examples thereof include a graft copolymer obtained by graft copolymerizing a vinyl chloride monomer with a polymer or a polymer. These polymers may be used alone or in combination of two or more.

  Examples of monomers having an unsaturated bond copolymerizable with vinyl chloride monomer include α-olefins such as ethylene, propylene, and butylene; vinyl esters such as vinyl acetate and vinyl propionate; butyl vinyl ether, acetyl vinyl ether, and the like. Vinyl ethers; (meth) acrylic esters such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and phenyl methacrylate; aromatic vinyls such as styrene and α-methylstyrene; vinylidene chloride, fluorine And vinyl halides such as vinylidene chloride; N-substituted maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide; (meth) acrylic acid, maleic anhydride, acrylonitrile and the like. These may be used alone or in combination of two or more.

  The polymer for graft copolymerization of vinyl chloride is not particularly limited as long as it is a graft polymer of vinyl chloride. Examples of the polymer include ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-carbon monoxide copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate-carbon monoxide copolymer, ethylene-methyl. Examples thereof include methacrylate copolymers, ethylene-propylene copolymers, acrylonitrile-butadiene copolymers, polyurethanes, chlorinated polyethylenes, and chlorinated polypropylenes. These may be used alone or in combination of two or more.

  The polymerization method of the vinyl chloride resin is not particularly limited, and any conventionally known polymerization method can be used. Examples thereof include a bulk polymerization method, a solution polymerization method, an emulsion polymerization method, and a suspension polymerization method.

  The chlorinated vinyl chloride resin may be polymerized by using chlorination before polymerization of the vinyl chloride monomer, or may be chlorinated after polymerization of the vinyl chloride resin. The method for chlorinating the vinyl chloride resin is not particularly limited, and methods known in the art can be used. Examples of the chlorination method include a thermal chlorination method and a photochlorination method.

  When the degree of polymerization of the vinyl chloride decreases, the impact resistance tends to decrease, and when it increases, the secondary formability tends to deteriorate. Therefore, the degree of polymerization is preferably about 400 to 2500, more preferably about 600 to 2000, and still more preferably about 600 to 1600. In addition, as a method of adjusting a polymerization degree, polymerization temperature etc. are mentioned, for example. In general, the higher the polymerization temperature, the lower the degree of polymerization. The degree of polymerization can be measured according to JIS K 6720-2.

  Chlorinated polyolefin is generally used alone as an elastomer having excellent flexibility, weather resistance, heat aging resistance, flame retardancy, and chemical resistance. The chlorinated polyolefin is also used as a physical property improving material for rubbers such as general-purpose resins such as vinyl chloride resins, olefin resins and ABS, or EPDM, chlorosulfonated polyethylene, chloroprene and SBR. Among them, chlorinated polyethylene is preferably used as the chlorinated polyolefin. Chlorinated polyethylene can be obtained using a conventionally known chlorination method.

  When exfoliated graphite is added to the first thermoplastic resin, the elastic modulus is remarkably increased, and the entire first layer becomes rigid. Therefore, the extensibility at a high temperature required for impact resistance and secondary workability of the first layer may be lowered. At this time, when chlorinated polyethylene is used, the chlorinated polyethylene is hardened by the addition of exfoliated graphite, can take a network structure in a matrix that has become brittle, and can impart flexibility to the first layer. Therefore, by using chlorinated polyethylene as the first thermoplastic resin, it is possible to efficiently compensate for the impact resistance and high-temperature extensibility of the first layer, which are reduced by exfoliated graphite.

  The molecular weight of the chlorinated polyethylene is suitably a weight average molecular weight of about 50,000 to 400,000, and is preferably in a relatively high range (for example, about 320,000 or more). By setting the molecular weight of the chlorinated polyethylene in the above range, in particular, when other resins such as vinyl chloride resin and acrylic processing aid are contained in the first layer, molecules with other resins are used. By developing the entanglement at the level, compatibility can be enhanced.

  Moreover, 20-40% is suitable for the chlorination degree of the said chlorinated polyethylene. By setting the degree of chlorination of the chlorinated polyethylene in the above range, particularly when other resins such as vinyl chloride resin and acrylic processing aid are contained in the first layer, By showing close polarity, compatibility can be improved. More preferably, the chlorinated polyethylene has a weight average molecular weight of about 150,000 to 350,000 and a chlorination degree of 25% to 36%.

  The amount of the first thermoplastic resin added is not particularly limited, and is preferably adjusted appropriately in consideration of the type of the first thermoplastic resin, secondary processability such as vacuum forming, moldability, and flame retardancy. . For example, the first thermoplastic resin is 1% by weight or more, preferably 5% by weight or more, more preferably 8% by weight or more, and particularly preferably 15% by weight or more based on the entire first layer. If the amount of the first thermoplastic resin added is too small, the physical properties may deteriorate.

  It is preferable that an acrylic processing aid for improving secondary processability is added to the first layer. In particular, the vacuum formability can be improved by adding an acrylic processing aid. The acrylic processing aid is excellent in compatibility with various substances contained in the first layer.

  Examples of acrylic processing aids include (meth) acrylate polymers. The (meth) acrylate polymer is a general term for polymers mainly composed of acrylate monomers or methacrylate monomers, and serves as a processing aid. For example, homopolymers or copolymers of (meth) acrylate monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate; the above (meth) acrylate monomers and styrene, vinyltoluene, acrylonitrile And copolymers with other monomers. These may be used alone or in combination of two or more.

  The amount of acrylic processing aid added can be adjusted as appropriate in consideration of the amount of exfoliated graphite added, secondary workability such as vacuum forming reduced by the addition of exfoliated graphite, formability and flame retardancy. . When the content of exfoliated graphite increases in the first layer, it is necessary to increase the amount of the acrylic processing aid added in order to prevent the moldability from decreasing. On the other hand, it is necessary to further increase the amount of exfoliated graphite (ratio to the composition) in order to determine that there is no ignition (non-combustion) in the vehicle flammability test when a decorative layer is provided. Therefore, the amount of acrylic processing aid that can be added is limited. Therefore, the addition amount of the acrylic processing aid is 1% by weight or more, preferably 4% by weight or more, more preferably 12% by weight or more, particularly preferably based on the total weight of the composition constituting the first layer. Is 23% by weight or more. Moreover, as an upper limit, it is 60 weight% or less, Preferably it is 40 weight% or less, More preferably, it is 30 weight% or less. As for the said addition amount, 1-60 weight%, 4-40 weight%, 12-30 weight% etc. are mentioned, for example. By setting the addition amount in this range, it is possible to achieve both improvement in combustion resistance due to the addition of exfoliated graphite and secondary workability. When the addition amount is too large, the ratio of the first thermoplastic resin is decreased, so that the impact resistance and the secondary workability may be deteriorated.

  The vacuum forming of the composition constituting the first layer is generally performed by heating the surface temperature of the composition constituting the first layer to about 180 ° C. to 220 ° C. In such a high temperature state, the tension of the resin that constitutes the first layer, for example, a polyvinyl chloride resin, may be reduced and may be easily broken. Therefore, a (meth) acrylate polymer having higher tension in the high temperature region is suitably used as the acrylic processing aid. When an inorganic material, particularly a non-spherical type inorganic material such as exfoliated graphite, is added, it tends to break at a high temperature, so the addition of a (meth) acrylate polymer is effective.

  As a compound that improves elongation at high temperatures, thermoplastic elastomers such as NBR and Elvalloy, and plasticizers such as DOP can also be used. However, a (meth) acrylate polymer is particularly preferable from the viewpoint of imparting tension at a high temperature.

  The weight average molecular weight of the (meth) acrylate polymer is not particularly limited. However, from the viewpoint of higher tension at high temperatures, the polymerization average molecular weight is preferably higher molecular weight. The weight average molecular weight is, for example, preferably 1 million or more, and more preferably 3 million or more. On the other hand, if the molecular weight is too high, the moldability and impact resistance may be adversely affected. Therefore, the weight average molecular weight is preferably 6 million or less, and more preferably 5 million or less.

  It is preferable that an impact modifier excellent in impact resistance is added to the first layer. The impact modifier is not particularly limited as long as it is usually used in the field. For example, methyl methacrylate-butadiene-styrene graft copolymer (MBS resin), chlorinated polyethylene (CPE), ABS. Examples thereof include resins and acrylic modifiers. These may be used alone or in combination of two or more.

  In the present invention, the acrylic modifier is at least one acrylic copolymer selected from the group consisting of one of acrylic acid ester or methacrylic acid ester. It is a spherical shape. Among them, chlorinated polyethylene that can efficiently compensate for the impact resistance reduced by exfoliated graphite by adopting a network structure in a matrix that has become harder and brittle by the addition of exfoliated graphite and imparting flexibility is provided. Preferably used.

  In addition to the acrylic processing aid and / or impact modifier described above, various additives may be added to the first layer. Examples of the additive include a flame retardant, a heat stabilizer, a stabilizing aid, a lubricant, an antioxidant, a light stabilizer, a pigment and the like for the purpose of assisting the combustion suppressing effect. These may be used alone or in combination of two or more.

  Examples of the flame retardant include antimony oxide such as antimony dioxide, antimony trioxide, and antimony pentoxide; molybdenum compounds such as molybdenum trioxide, molybdenum disulfide, and ammonium molybdate; bromine compounds such as tetrabromobisphenol A and tetrabromoethane. Compound: Phosphorus compounds such as triphenyl phosphate and ammonium polyphosphate are exemplified.

  Examples of the heat stabilizer include dimethyltin mercapto, dibutyltin mercapto, dioctyltin mercapto, dibutyltin malate, dibutyltin malate polymer, dioctyltin malate, dioctyltin malate polymer, dioctyltin laurate, dibutyltin laurate, dibutyl Organotin stabilizers such as tin laurate polymer; lead white, lead stearate, dibasic lead stearate, dibasic phosphite, basic lead sulfite, dibasic lead sulfite, tribasic lead sulfide Lead stabilizers such as silica gel, lead co-precipitated oxalate, lead benzoate, lead naphthenate; metal soap stabilizers such as calcium stearate, barium stearate, zinc stearate, calcium-zinc stabilizer, barium-zinc System stabilizers, barium-cadmium katsura stabilizer, hydrotalcite, zeolite, etc. Machine based stabilizer and the like.

  Examples of the stabilizing aid include epoxidized soybean oil, epoxidized linseed oil, epoxidized tetrahydrophthalate, epoxidized polybutadiene, and butyl stearate.

  Examples of the lubricant include montanic acid wax, paraffin wax, polyethylene wax, stearic acid, stearyl alcohol, and butyl stearate.

  Examples of the antioxidant include phenolic antioxidants, sulfur antioxidants, phosphite antioxidants, and the like.

  Examples of the light stabilizer include salicylic acid ester-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based ultraviolet absorbers, hindered amine-based light stabilizers, and the like.

  Examples of the pigment include organic pigments such as azo, phthalocyanine, selenium, and dye lake; inorganic pigments such as oxide, molybdenum chromate, sulfide / selenide, and ferrocyanide It is done.

  The addition method and order of addition of additives are not particularly limited, and can be any method and order. As an addition method, for example, it can be added to a vinyl chloride resin by a hot blend method, a cold blend method or the like.

  The second layer contains a second thermoplastic resin. By using a thermoplastic resin for the second layer, the second layer and the flame resistant sheet can be easily molded under heating. Therefore, the secondary formability of the second layer and the flame resistant sheet can be improved.

  The second thermoplastic resin is not particularly limited. As said 2nd thermoplastic resin, the thermoplastic resin etc. which can be used as a 1st thermoplastic resin mentioned above are mentioned, for example. These thermoplastic resins may be used independently and may use 2 or more types together. Among them, as the second thermoplastic resin, it is preferable to use a thermoplastic resin having high flame retardancy in consideration of flame retardancy. Examples of the highly flame-retardant thermoplastic resin include a styrene resin and / or a vinyl chloride resin. The styrenic resin includes the above-described polymer alloys of the styrenic resin and other resins. Examples of the polymer alloy include alloys of polycarbonate resin and ABS resin (PC / ABS), alloys of polycarbonate resin and AES resin) and PC / ABS).

  Preferably, the second layer contains an impact modifier and / or a processing aid in addition to the second thermoplastic resin. In this case, the amount of the impact modifier is 1 to 30 parts by weight with respect to 100 parts by weight of the second thermoplastic resin in consideration of improvement in impact resistance, combustion resistance, mechanical strength, and the like. Is preferable, and 3 to 20 parts by weight is more preferable. The processing aid is preferably 1 to 30 parts by weight and more preferably 3 to 20 parts by weight with respect to 100 parts by weight of the second thermoplastic resin in consideration of improvement in vacuum formability and surface smoothness of the sheet. The second layer more preferably includes both an impact modifier and a processing aid.

  As said impact modifier, 1 or more types can be suitably selected from what was mentioned above, for example. As said processing aid, the acrylic processing aid mentioned above is preferable. Among them, as a combination of the impact modifier and the processing aid, methyl methacrylate-butadiene-styrene graft copolymer (MBS resin) and (meth) acrylate polymer having a weight average molecular weight of 1,000,000 to 6,000,000 are used. An acrylic impact modifier and a (meth) acrylate polymer having a weight average molecular weight of 1,000,000 to 6,000,000, or a combination thereof are preferred. In this case, the combustion resistance, impact resistance, and secondary workability of the second layer and the flame resistant sheet can be improved more effectively.

  Moreover, the 2nd layer may contain various additives similarly to the 1st layer.

  The combustion resistant sheet of the present invention may be provided with various functional layers such as a decorative layer, a protective layer, and an antireflection layer. For these functional layers, it is preferable to use a material having high flame retardancy in consideration of combustion resistance. That is, it is preferable to set the thickness to the minimum so that the thermal conductivity is as high as possible so that the influence on the combustion resistance of the combustion resistant sheet is reduced. Examples of the highly flame retardant material include vinyl chloride resin.

  For example, when the combustion-resistant sheet of the present invention is used as an interior material of a railway vehicle or the like, the flammability is evaluated by the ignitability of the surface exposed to the passenger. For example, a combustion test conducted by a method in accordance with Article 83 of Section 5 of the Ministerial Ordinance (Ministry of Land, Infrastructure, Transport and Tourism Ordinance No. 151, December 25, 2001) that establishes technical standards related to railways is based on this evaluation. It becomes one index.

  The flame resistant sheet of the present invention can be formed by any method known in the art. The flame resistant sheet of the present invention is, for example, a method in which the first layer and the second layer are separately formed into a sheet shape, and the two layers are bonded together, and either the first layer or the second layer is a sheet. It can be formed by a lamination integration method by co-extrusion by a known method such as a method of applying the other raw material, an inflation method, a T-die method or the like.

  The thickness of the first layer is not particularly limited and can be any thickness. Note that the greater the thickness of the first layer, the greater the combustion resistance effect. When the thickness of the first layer is increased, the amount of exfoliated graphite necessary for ensuring the combustion resistance of the first layer can be reduced. Therefore, the impact resistance and secondary workability of the first layer and the combustion resistant sheet are increased.

  The thickness of the second layer is not particularly limited, but is preferably determined according to the thickness of the first layer and the amount of exfoliated graphite added. That is, in order to reduce the influence on the flame resistance of the first layer or to increase the thermal conductivity of the flame resistant sheet as much as possible within a range that does not impair the flame resistance of the first layer. It is preferred that the two layers have a minimum thickness. For example, the thickness of the second layer is about 3 mm or less, preferably 0.5 mm or less, more preferably 0.05 to 0.3 mm. Thereby, the impact resistance and secondary workability of the flame resistant sheet can be efficiently enhanced without impairing the flame resistance of the first layer.

  In the flame resistant sheet of the present invention, the flame resistance is enhanced by the flame resistant effect of the first layer containing exfoliated graphite. Therefore, in order to efficiently exhibit the combustion resistance effect, it is preferable to dispose the second layer on a surface that does not directly contact the flame in the flame resistance sheet of the present invention. For example, when the combustion-resistant sheet of the present invention is used as an interior material for a railway vehicle or the like, it is preferable to provide the first layer on the surface exposed to the passenger side. However, the flame resistant sheet of the present invention may have a three-layer structure in which the second layer is laminated on both the front and back surfaces of the first layer according to the purpose, and these layers are alternately laminated. It may be a laminated structure of four or more layers. Moreover, the combustion resistant sheet of the present invention may be subjected to printing, and may be provided with various functional layers such as a decorative layer, a protective layer, and an antireflection layer.

  The flame-resistant sheet of the present invention can be used in all fields where flame resistance is required. The combustion-resistant sheet of the present invention can be suitably used as an interior material for a vehicle or the like, particularly as an interior material for a railway vehicle, an automobile, an airplane, or the like. Furthermore, the combustion resistant sheet of the present invention can be suitably used as a functional sheet or the like having various functionalities.

  Hereinafter, the present invention will be clarified by giving specific examples and comparative examples of the present invention. In addition, this invention is not limited to a following example.

  Unless otherwise indicated, the part and% in a following example show the value of a weight reference | standard. In addition, the composition of each component in the table indicates% by weight unless otherwise specified.

(Flaky graphite)
Exfoliated graphite used in Examples and Comparative Examples of the present invention was prepared by the following method.

  A graphite sheet (trade name “PF100-UHP”, manufactured by Toyo Tanso Co., Ltd.) was prepared as a preformed sheet. As shown in FIG. 1, this preformed sheet 1 was supplied between rolls 2 and 3 and rolled by rolls 2 and 3. Thus, a low density graphite sheet having a density of 0.7 and a thickness of 1 mm was prepared.

  The graphite sheet having a density of 0.7 obtained as described above was cut into a size of 3 cm × 3 cm to obtain a graphite sheet as an electrode material. As shown in FIG. 2, two slits 11a and 11b were formed in the graphite sheet 11 by cutting with a cutter knife so that the slit length was 1 cm and the width was 1 cm. Inserted pieces 12a and 12b of the electrode 12 made of Pt shown in FIG. 2 were inserted into the graphite sheet 11 on which the two slits 11a and 11b were formed. The graphite sheet 11 thus prepared was immersed in a 60% by weight aqueous nitric acid solution together with a reference electrode (cathode) made of Pt and a reference electrode made of Ag / AgCl, using the prepared graphite sheet 11 as a working electrode (anode). Applied and subjected to electrochemical treatment. In the electrochemical treatment, a voltage was applied for 2.5 hours as shown in FIG. Thus, the graphite used as the working electrode for the anode was used as expanded graphite.

The obtained expanded graphite was cut into 1 cm square, one of which was put into a carbon crucible and subjected to electromagnetic induction heat treatment. As the induction heating device, MU 1700D manufactured by SK Medical Co., Ltd. was used, and the current was 10 A so that the maximum temperature reached 550 ° C. in an argon gas atmosphere. When the temperature of the expanded graphite surface was measured with a radiation thermometer during the above treatment, it took 12 seconds for the temperature of the expanded graphite surface to reach 550 ° C. from room temperature. The expanded graphite was exfoliated by the above treatment. When the obtained exfoliated graphite powder was measured with a specific surface area measuring device (trade name “ASAP-2000”, manufactured by Shimadzu Corporation) using nitrogen gas, the specific surface area of 830 m ² / g was measured once. showed that.

  In addition, the materials used in Examples and Comparative Examples of the present invention are as follows.

(1) Vinyl chloride resin: Trade name “TS-800E”, manufactured by Tokuyama Sekisui Industry Co., Ltd., degree of polymerization 800 (2) Chlorinated polyethylene (CPE): Trade name “Tyrin 3615P”, manufactured by Dow Chemical Co., Ltd. (3) Impact modification Material (Methyl methacrylate / butadiene / styrene copolymer (MBS)): Trade name “M511”, manufactured by Kaneka Corporation (4) Processing aid ((meth) acrylate polymer): Trade name “Metablene P-530A”, Made by Mitsubishi Rayon Co., Ltd., molecular weight 3.1 million,
(5) Thermal stabilizer: Trade name “TVS # 1380”, manufactured by Nitto Kasei Kogyo Co., Ltd. (6) Lubricant 1 (HW220MP): Trade name “Hiwax220MP”, manufactured by Mitsui Chemicals (7) Lubricant 3 (G70S): Trade name “LOXIOL G70S”, manufactured by Emery Oleochemicals Japan Co., Ltd. (8) Crushed graphite after expansion: Trade name “CS-F400”, manufactured by Maruho Foundry Co., Ltd., BET specific surface area 18.7 m ² / g
(9) PC / ABS alloy resin: Trade name “Techniace T-105”, manufactured by Nippon A & L Co. (10) ABS resin: Trade name “Clarastic GA-501”, manufactured by Nippon A & L

A. Example 1 and Comparative Example 1
A predetermined amount (% by weight) of each component shown in Table 1 below was supplied to a 20 L super mixer (manufactured by Kawata), and mixed by stirring to obtain a resin composition.

  The obtained resin composition was supplied to an 8-inch mixing roll kneader (manufactured by Yasuda Seiki Co., Ltd.) and melt-kneaded at a temperature of 185 ° C. to obtain a roll sheet having a thickness of 1 mm.

  Subsequently, it was supplied to a hot press molding machine (manufactured by Toho Machinery Co., Ltd.) and pressurized at a temperature of 190 ° C. and 20 MPa to obtain a B5 size press sheet (first or second layer) having the thickness described in Table 1. .

  Further, the first layer and the second layer (back side) are superposed, supplied to a hot press molding machine (manufactured by Toho Machinery Co., Ltd.), pressurized at a temperature of 190 ° C. and 20 MPa, and B5 having a thickness described in Table 1 A size-sized press sheet was obtained (combustion-resistant sheet).

<Vehicle combustion test>
The vehicle combustion test was evaluated in accordance with Article 83 of Section 5 of the Fire Countermeasures for Vehicles in the Ministerial Ordinance for Establishing Technical Standards on Railways (Ministry of Land, Infrastructure and Transport Ordinance No. 151 on December 25, 2001). All surfaces with which the alcohol flame was brought into contact were from the first layer side.

  The criteria for the vehicle combustion test were as follows. The results are shown in Table 1 below.

A: No ignition (equivalent to incombustibility)
○: Ignition time is 70 seconds or more and the fire power after ignition is weak (equivalent to extremely flame retardant)
Δ: Ignition over 30 seconds and less than 70 seconds (equivalent to flame retardancy)
X: Ignition within 30 seconds

B. Examples 2-3 and Comparative Examples 2-3
A predetermined amount (% by weight) of each component shown in Table 1 below was supplied to an 8-inch mixing roll kneader (manufactured by Yasuda Seiki Co., Ltd.) and melt-kneaded at a temperature of 190 ° C. to obtain a roll sheet.

  Then, it supplied to the hot press molding machine (made by Toho Machinery Co., Ltd.), and pressurized at 200 degreeC and 20 Mpa, and obtained the B5 size press sheet of each thickness described in Table 1.

(Second layer: ABS)
The raw material resin was supplied to an 8-inch mixing roll kneader (manufactured by Yasuda Seiki Co., Ltd.) and melt-kneaded at a temperature of 190 ° C. to obtain a roll sheet.

  Then, it supplied to the hot press molding machine (made by Toho Machinery Co., Ltd.), and pressurized at 200 degreeC and 20 Mpa, and obtained the B5 size press sheet of each thickness described in Table 1.

(Second layer: PC / ABS alloy)
The raw material resin was supplied to an 8-inch mixing roll kneader (manufactured by Yasuda Seiki Co., Ltd.) and melt-kneaded at a temperature of 220 ° C. to obtain a roll sheet.

  Subsequently, it supplied to the hot press molding machine (made by Toho Machinery Co., Ltd.), pressurized at 220 degreeC and 20 Mpa, and obtained the press sheet of B5 size size of each thickness described in Table 1.

(Production of laminate)
The first and second layers were overlaid, supplied to a hot press molding machine (manufactured by Toho Machinery Co., Ltd.), and pressurized at a temperature of 220 ° C. and 20 MPa to obtain a B5-size press sheet having a thickness of 3.5 mm. (Three-layer sheet). The decorative layer was an acrylic resin laminate film having a thickness of 120 μm.

  Next, a vehicle combustion test was performed in the same manner as in Example 1 and Comparative Example 1. The results are shown in Table 1 below.

  As is apparent from Table 1, the press sheets of Examples 1 to 3 according to the present invention have higher combustion resistance than the press sheets of Comparative Examples 1 to 3. This is because exfoliated graphite having a large specific surface area is contained in the first layers of Examples 1 to 3. It is considered that the exfoliated graphite effectively improved the combustion resistance of the press sheet.

DESCRIPTION OF SYMBOLS 1 ... Preliminarily molded sheet 2, 3 ... Roll 11 ... Graphite sheet 11a, 11b ... Slit 12 ... Electrode 12a, 12b ... Insert piece

Claims (4)

A first layer comprising exfoliated graphite and a first thermoplastic resin;
A second layer laminated to the first layer and containing a second thermoplastic resin,
The specific surface area of the exfoliated graphite is ^{50m 2} / ^g~2600m 2 / g, burning resistance sheet.   The ratio of exfoliated graphite contained in the first layer is 0.1 to 50 parts by weight with respect to 100 parts by weight in total of components contained in the first layer other than the exfoliated graphite. 1. The flame resistant sheet according to 1.   The flame resistant sheet according to claim 1 or 2, wherein the first layer further contains an acrylic processing aid.   The combustion-resistant sheet according to any one of claims 1 to 3, wherein the second thermoplastic resin is a styrene resin.

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