Composite sheet, method for producing composite sheet, and molded body

Abstract

Provided is a composite sheet which comprises a thermoplastic resin composition (X) and inorganic fibers (Y), wherein the thermoplastic resin composition (X) contains a thermoplastic resin and a thermally expandable flame retardant, while having a density of 1.3 g / cm3 or less.　The present invention is able to provide a composite sheet which has high flame barrier properties and lightweight properties.

Description

Composite sheet, method for producing composite sheet, and molded product

[0001] The present invention relates to a composite sheet, a method for producing the composite sheet, and a molded article obtained by molding the composite sheet.

[0002] In recent years, research and development of electric and hybrid vehicles has been progressing as part of environmental conservation efforts. The development of high-energy-density batteries and their lightweight construction are being actively pursued to improve driving range. Such high-energy-density batteries are susceptible to fire in the event of an accident. To ensure passenger safety, their housings must be highly flame-resistant, often combining metals such as iron with fire-resistant materials. However, metals have the disadvantage of being heavy, and the use of fire-resistant materials poses challenges, such as processability and increased costs due to the increased number of parts. Therefore, attempts have been made to develop resins that offer both lightweight and flame-resistant properties. Currently, carbon dioxide reduction and recyclability are gaining importance in order to achieve a sustainable society. While thermosetting materials often have high flame retardancy and are commonly used in composites, thermoplastic resins offer advantages in terms of recyclability.

[0003] Additionally, China has announced a safety standard called GB 38031-2020, "Safety Requirements for Electric Vehicle Power Batteries," which requires a warning to be issued five minutes before the battery experiences thermal runaway. However, it is believed that this can be achieved by using a housing material that can block flames for at least five minutes after the battery ignites.

[0004] To address these issues, for example, Patent Document 1 proposes the addition of a bromine-based flame retardant or an antimony oxide compound to a carbon fiber-reinforced polypropylene resin. However, the additives used therein have the problem of biopersistence. In response to this, Patent Document 2 proposes a flame-retardant polyolefin composition in which a polyolefin resin contains a (poly)phosphate compound as a technology for flame-retarding a polypropylene resin while taking biopersistence into consideration. Furthermore, Patent Document 3 proposes a flame-retardant resin composition in which a polypropylene resin contains long glass fibers and a phosphate compound.

[0005] JP 2014-62189 A JP 2013-119575 A JP 2011-88970 A

[0006] Conventional fiber-reinforced composite materials have the potential to achieve both lightweight and flame-resistant properties for high-energy-density batteries, but they are lacking in many areas. Specifically, fiber-reinforced composite materials are required to have high flame-resistant properties and further improved lightness.

[0007] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a molded article having high flame-proofing properties and light weight, and a composite sheet for obtaining the molded article.

[0008] In order to solve the above-mentioned problems, the present inventors have found that a composite sheet containing a thermoplastic resin and inorganic fibers, in which the thermoplastic resin contains a thermally expandable flame retardant, and a molded article obtained by molding the composite sheet, can solve the above-mentioned problems, and have completed the present invention based on this finding. That is, aspects of the present invention provide the following [1] to

[15] . [1] A composite sheet containing a thermoplastic resin composition (X) and inorganic fibers (Y), in which the thermoplastic resin composition (X) contains a thermoplastic resin and a thermally expandable flame retardant, and has a density of 1.3 g / cm ３ [2] A composite sheet having a cross-sectional area of ​​0.01 mm or less when observed from a cut surface. ２ There are multiple voids with a cross-sectional area of ​​0.01 mm or more. ２ The average cross-sectional area of ​​the above voids is 0.03 mm ２ More than 0.8 mm ２[3] The composite sheet according to [1] above, wherein the thickness ratio (thickness after high-temperature test / thickness before high-temperature test) before and after heating at 1200°C for 15 minutes is 5 times or less. [4] The composite sheet according to any of [1] to [3] above, which has a topsheet, and the topsheet comprises a nonwoven fabric made of resin fibers. [5] The composite sheet according to any of [1] to [4] above, wherein the thermally expandable flame retardant comprises a phosphorus-based flame retardant. [6] The composite sheet according to any of [1] to [5] above, wherein the thermoplastic resin constituting the thermoplastic resin composition (X) comprises a polyolefin resin. [7] The composite sheet according to any of [1] to [6] above, wherein the thermoplastic resin composition (X) further comprises a dispersant. [8] The composite sheet according to [7] above, wherein the dispersant comprises a copolymer of an α-olefin and an unsaturated carboxylic acid. [9] The composite sheet according to [7] or [8] above, wherein the content of the dispersant is more than 0 and not more than 25 parts by mass per 100 parts by mass of the thermally expandable flame retardant.

[10] The composite sheet according to any one of [1] to [9] above, wherein the inorganic fibers (Y) comprise at least one fiber selected from glass fibers, ceramic fibers, metal fibers, and metal oxide fibers.

[11] The composite sheet according to any one of [1] to

[10] above, wherein the thermoplastic resin composition (X) is impregnated into a mat of inorganic fibers (Y).

[12] A method for producing the composite sheet according to any one of [1] to

[11] above, comprising laminating a sheet of the thermoplastic resin composition (X) on a mat of inorganic fibers (Y), heating and melting the laminate, and impregnating the mat with the thermoplastic resin composition (X).

[13] The method for producing the composite sheet according to

[12] above, wherein the mat of inorganic fibers (Y) is laminated between two sheets of the thermoplastic resin composition (X).

[14] A molded article obtained by molding the composite sheet according to any one of [1] to

[11] above.

[15] The molded article according to

[14] above, which is used for a battery case.

[0009] According to the present invention, it is possible to provide a molded article having high flame-proofing properties and light weight, and a composite sheet for obtaining the molded article.

[0010] 1 is a schematic diagram showing a manufacturing process of a composite sheet of the present invention.

[0011] Hereinafter, the embodiments of the present invention will be described in detail, but the following description is merely an example of an embodiment of the present invention, and the present invention is not limited to the contents thereof in any way.

[0012] [Composite Sheet] The composite sheet of the present invention comprises a thermoplastic resin composition (X) and inorganic fibers (Y), the thermoplastic resin composition (X) comprising a thermoplastic resin and a thermally expandable flame retardant, and a density of 1.3 g / cm ３ The density of the composite sheet is 1.3 g / cm or less. ３ From the above viewpoints, the density of the composite sheet is set to 1.2 g / cm or less, and the light weight that is an object of the present invention is ensured. ３ or less, or 1.0 g / cm ３ or less, or 0.7 g / cm ３ On the other hand, from the viewpoint of flame resistance and strength of the composite sheet, the density of the composite sheet is 0.1 g / cm ３ From this viewpoint, the density of the composite sheet is preferably 0.2 g / cm ３ or more, or 0.3 g / cm ３ It is generally expected that the flame-blocking properties of a composite sheet will decrease as the density of the composite sheet decreases. However, the present inventors have surprisingly found that the composite sheet of the present invention can ensure flame-blocking properties at a relatively low density. The reason for this is not yet clear, but it is believed that the flame-blocking properties of a composite sheet with a density of 1.3 g / cm ３ It is believed that if the temperature is below this range, the volume of the interstitial spaces in the composite sheet increases, and the thermally expandable flame retardant contained in the composite sheet of the present invention expands in those spaces to form dense char.

[0013] The density of the composite sheet is 1.3 g / cm ３To achieve a density of 1.3 g / cm or less, there is a method in which a resin-impregnated sheet, which will be described later, is heated to expand, and then the resin-impregnated sheet placed in a mold is compressed under pressure by adjusting the space within the mold until the resin-impregnated sheet reaches a predetermined density. The heating temperature is preferably in the range of 180 to 250°C, more preferably 200 to 240°C, and even more preferably 210 to 230°C. By setting the heating temperature within these ranges, appropriate expansion occurs, and the density is reduced to 1.3 g / cm or less. ３ By satisfying the following conditions, a composite sheet can be obtained in which the decrease in strength is suppressed. The method for producing the composite sheet will be described in detail below.

[0014] [Manufacturing Method of Composite Sheet] The manufacturing method of the composite sheet of the present invention will be described in detail below. Here, each step will be described using a glass fiber mat, a top sheet, and a thermoplastic resin sheet, with reference to FIG. 1 . The following description will be made using an example in which glass fiber is used as the inorganic fiber (Y). Step (a): Top sheets 12 are laid on both sides of a glass fiber mat 11, and a thermoplastic resin sheet 13 is laid on the outside of the top sheets 12. That is, the glass fiber mat 11 is sandwiched between the top sheets 12, and the top sheet 12 is sandwiched between the glass fiber mat 11 and the thermoplastic resin sheet 13 ( FIG. 1( a)). Step (b): The laminate 10 having the above-described layer structure is then heated and pressurized. By heating and pressurizing, the thermoplastic resin sheet 13 melts and is impregnated into the voids in the glass fiber mat 11 and the top sheet 12, obtaining a resin-impregnated sheet 20 ( FIG. 1( b)). Step (c): The resin-impregnated sheet 20 is cooled and pressurized, solidifying the thermoplastic resin in the voids in the glass fiber mat 11 and the top sheet 12, resulting in a layered structure in which the top sheet 12 is bonded to both sides of the glass fiber mat 11. Step (d): The resin-impregnated sheet 20 obtained in step (c) is heated, melting the thermoplastic resin that has solidified in the voids in the glass fiber mat 11 and the top sheet 12, causing the glass fiber mat 11 to expand due to fiber springback. This springback causes the void ratio in the top sheet 12 to become smaller than that in the glass fiber mat 11. The thermoplastic resin then solidifies in the voids in the glass fiber mat 11 and the top sheet 12 due to natural cooling, resulting in a composite sheet that is thicker than after step (c), for example, more than twice as thick.

[0015] The top sheet 12 used in the above process is preferably a nonwoven fabric. Therefore, as shown in FIG. 1( b), the composite sheet of the present invention preferably has a top sheet 12, which includes a nonwoven fabric made of resin fibers. The fibers used here are preferably made of a resin fiber selected from, for example, polypropylene, polyester, polyethylene, nylon, vinylon, rayon, acrylic, aramid, polylactic acid, etc. By using a nonwoven fabric, when the thermoplastic resin sheet 13 melts, it is more likely to penetrate into the voids in the glass fiber mat 11 through the voids in the top sheet 12. Furthermore, because the softening temperature of the resin fibers constituting the top sheet 12 is higher than the softening temperature of the thermoplastic resin sheet 13, the shape of the top sheet 12 can be maintained even when the thermoplastic resin sheet 13 melts and the voids in the glass fiber mat 11 and the top sheet 12 are impregnated with the thermoplastic resin. Furthermore, when the thermoplastic resin is impregnated, the adhesive strength of the top sheet 12 to the glass fiber mat 11 is increased, thereby improving the non-peeling properties of the top sheet 12. Here, the thermoplastic resin sheet 13 is preferably formed from one resin selected from the group consisting of polypropylene, polyethylene, polyamide, and polyester.

[0016] Furthermore, the composite sheet of the present invention has a cross-sectional area of ​​0.01 mm when observed from a cut surface of the composite sheet. ２ There are multiple voids with a cross-sectional area of ​​0.01 mm or more. ２ The average cross-sectional area of ​​the above voids is 0.03 mm ２ More than 0.8 mm ２ When the average value of the cross sections of the voids in the composite sheet is within the above range, it is possible to achieve high levels of both flame retardancy and light weight. ２ The average cross-sectional area of ​​the above voids is 0.05 mm ２ or more, or 0.1 mm ２ or more, or 0.15 mm ２ or more, or 0.2 mm ２ On the other hand, 0.7 mm ２ Less than or equal to 0.6 mm２ Less than or equal to 0.5 mm ２ The voids can be observed and the cross-sectional area can be measured by cutting the composite sheet using a cutter or the like and observing the cut surface using an optical microscope or the like. The cross-sectional area of ​​the voids can be measured using general image analysis software.

[0017] Furthermore, the composite sheet of the present invention preferably has a thickness ratio (thickness after high-temperature test / thickness before high-temperature test) of 5 times or less before and after heating at 1200°C for 15 minutes. If it is 5 times or less, a decrease in density due to expansion is suppressed, and a decrease in strength due to density decrease is suppressed. From the above perspectives, the thickness ratio before and after heating is more preferably 4 times or less, and even more preferably 3.5 times or less. On the other hand, if the thickness ratio before and after heating is 1.2 times or more, a thermal expansion layer is formed by expansion, and excellent flame protection properties are obtained. From the above perspectives, the thickness ratio before and after heating is more preferably 1.5 times or more. Below, each component used in the present invention and the resulting composite sheet will be described in detail.

[0018] <Thermoplastic Resin Composition (X)> The thermoplastic resin composition (X) used in the composite sheet of the present invention is characterized by containing (a) a thermoplastic resin and (b) a thermally expandable flame retardant.

[0019] (a) Thermoplastic Resin) The thermoplastic resin contained in the thermoplastic resin composition (X) according to the present invention is not particularly limited, and examples thereof include polyolefin resins, polycarbonate resins, polyester resins, acrylonitrile-styrene resins, ABS resins, polyamide resins, and modified polyphenylene oxides. Of these, polyolefin resins are preferred in the present invention. These may be used alone or in combination of two or more. For example, the thermoplastic resin (a) may be a composite resin of two or more of the above thermoplastic resins.

[0020] The polyolefin resin is not particularly limited, and examples thereof include the resins described below. The polyester resin is not particularly limited, and examples thereof include polybutylene terephthalate. The polyamide resin is not particularly limited, and examples thereof include nylon 66 and nylon 6. Among these, the present invention is particularly useful when at least a polyolefin resin is included as the (a) thermoplastic resin. In the present invention, "polyolefin resin" means a resin in which the proportion of olefin units or cycloolefin units is 90 mol% or more relative to 100 mol% of all structural units constituting the resin. The proportion of olefin units or cycloolefin units relative to 100 mol% of all structural units constituting the polyolefin resin is preferably 95 mol% or more, particularly preferably 98 mol% or more.

[0021] Examples of polyolefin resins include α-olefin polymers such as polyethylene, polypropylene, polybutene, poly(3-methyl-1-butene), poly(3-methyl-1-pentene), and poly(4-methyl-1-pentene); α-olefin copolymers such as ethylene-propylene block or random copolymers, α-olefin-propylene block or random copolymers having 4 or more carbon atoms, ethylene-methyl methacrylate copolymers, and ethylene-vinyl acetate copolymers; and cycloolefin polymers such as polycyclohexene and polycyclopentene. Examples of polyethylene include low-density polyethylene, linear low-density polyethylene, and high-density polyethylene. Examples of polypropylene include isotactic polypropylene, syndiotactic polypropylene, hemiisotactic polypropylene, and stereoblock polypropylene. In α-olefin-propylene block or random copolymers having 4 or more carbon atoms, examples of the α-olefin having 4 or more carbon atoms include butene, 3-methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene. These polyolefin resins may be used alone or in combination of two or more. Of the above olefin resins, polypropylene resin (hereinafter sometimes referred to as "PP resin") is particularly preferred.

[0022] (Melt Flow Rate (MFR)) The melt flow rate (hereinafter sometimes abbreviated as MFR) (230°C, 2.16 kg load) of the (a) thermoplastic resin used in the present invention is preferably 40 to 500 g / 10 min. If the MFR is 40 g / 10 min or more, no defects will occur when obtaining a molded body by stamping, for example, and processability will not be reduced. Furthermore, if the MFR is 500 g / 10 min or less, no burrs will be generated during the production of a composite sheet. From the above viewpoints, the MFR is preferably 50 to 400 g / 10 min, more preferably 60 to 400 g / 10 min, and more preferably 70 to 300 g / 10 min. The MFR of the (a) thermoplastic resin can be adjusted, for example, by controlling the hydrogen concentration during polymerization. The MFR is a value measured in accordance with JIS K7210.

[0023] (Content of (a) Thermoplastic Resin) The content of the (a) thermoplastic resin in the composite sheet of the present invention is not particularly limited, but is preferably 15 to 80 mass% in the thermoplastic resin composition (X). When the content of the (a) thermoplastic resin is 15 mass% or more, the molding processability is particularly good, and molding of the composite sheet becomes easy. On the other hand, when the content is 80 mass% or less, sufficient amounts of flame retardant, dispersant, and inorganic fiber can be contained, and good flame protection properties can be obtained. From the above viewpoints, the content of the (a) thermoplastic resin in the thermoplastic resin composition (X) is preferably 35 to 70 mass%, more preferably 40 to 60 mass%.

[0024] <(a-1) Polypropylene-Based Resin> The thermoplastic resin (a) used in the composite sheet of the present invention preferably contains a polypropylene-based resin. Examples of the polypropylene-based resin include a propylene homopolymer and a propylene-α-olefin copolymer. Here, the propylene-α-olefin copolymer may be either a random copolymer or a block copolymer.

[0025] (α-Olefins) Examples of the α-olefins constituting the copolymer include ethylene, 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, ethyl-1-pentene, trimethyl-1-butene, and 1-octene. One of these may be copolymerized with propylene, or two or more may be copolymerized with propylene. Among these, from the viewpoint of improving the impact strength of the composite sheet, ethylene or 1-butene are preferred, as they are highly effective, and ethylene is most preferred.

[0026] (Propylene-Ethylene Random Copolymer) In the case of a random copolymer of propylene and ethylene, it preferably contains 90 to 99.5% by mass of propylene units, more preferably 92 to 99% by mass, and 0.5 to 10% by mass of ethylene units, more preferably 1 to 8% by mass. When the ethylene unit content is equal to or greater than the lower limit, the composite sheet can achieve sufficient impact strength. When the ethylene unit content is equal to or less than the upper limit, sufficient rigidity can be maintained. The propylene unit and ethylene unit contents in the random copolymer of propylene and ethylene can be adjusted by controlling the composition ratio of propylene to ethylene during polymerization of the random copolymer of propylene and ethylene. The propylene content of the random copolymer of propylene and ethylene is measured using a cross-fractionator or FT-IR, and the measurement conditions can be determined using, for example, the method described in JP-A-2008-189893.

[0027] (Melt Flow Rate (MFR)) The MFR (230°C, 2.16 kg load) of the (a-1) polypropylene resin used in the present invention is preferably 40 to 500 g / 10 min. When the MFR is 40 g / 10 min or more, no defects are generated when obtaining a molded body by stamping or the like, and processability is not impaired. Furthermore, when the MFR is 500 g / 10 min or less, no burrs are generated during the production of a composite sheet. From the above viewpoints, the MFR is preferably 50 to 400 g / 10 min, more preferably 60 to 400 g / 10 min, and even more preferably 70 to 300 g / 10 min. The MFR of the (a-1) polypropylene resin (propylene homopolymer) can be adjusted by controlling the hydrogen concentration during polymerization, etc. The MFR is a value measured in accordance with JIS K7210.

[0028] ((a-1) Content of Polypropylene Resin) The content of (a-1) polypropylene resin in the composite sheet of the present invention is not particularly limited, but is preferably 15 to 80% by mass. When the content of polypropylene resin is 15% by mass or more, sufficient molding processability is achieved, and molding of the composite sheet becomes easy. On the other hand, when it is 80% by mass or less, the contents of flame retardant, dispersant, and inorganic fiber become sufficient, and sufficient flame resistance is obtained. From the above viewpoints, the content of polypropylene resin in the composite sheet is more preferably 35 to 70% by mass, and even more preferably 40 to 60% by mass.

[0029] <Modified Polyolefin Resin> The composite sheet of the present invention can further contain a modified polyolefin resin in addition to the polypropylene resin. Specific examples of the modified polyolefin resin include acid-modified polyolefin resins and hydroxy-modified polyolefin resins, which can be used alone or in combination. The types of acid-modified polyolefin resins and hydroxy-modified polyolefin resins used as the modified polyolefin resin are not particularly limited, and conventionally known resins may be used.

[0030] (Acid-Modified Polyolefin Resin) Examples of acid-modified polyolefin resins include those obtained by graft copolymerizing polyolefins such as polyethylene, polypropylene, ethylene-α-olefin copolymers, ethylene-α-olefin-non-conjugated diene compound copolymers (such as EPDM), and ethylene-aromatic monovinyl compound-conjugated diene compound copolymer elastomers with an unsaturated carboxylic acid such as maleic acid or maleic anhydride, thereby chemically modifying the polyolefin. This graft copolymerization is carried out, for example, by reacting the polyolefin with an unsaturated carboxylic acid in a suitable solvent using a radical generator such as benzoyl peroxide. The unsaturated carboxylic acid or a derivative thereof can also be introduced into the polymer chain by random or block copolymerization with a polyolefin monomer.

[0031] Examples of unsaturated carboxylic acids used for modification include compounds having a carboxyl group, such as maleic acid, fumaric acid, itaconic acid, acrylic acid, and methacrylic acid, and a polymerizable double bond into which a functional group, such as a hydroxyl group or an amino group, has been introduced as needed. Derivatives of unsaturated carboxylic acids include their acid anhydrides, esters, amides, imides, and metal salts, and specific examples thereof include maleic anhydride, itaconic anhydride, methyl acrylate, ethyl acrylate, butyl acrylate, and methyl methacrylate. Of these, maleic anhydride is preferred.

[0032] Preferred acid-modified polyolefin resins include those modified by graft polymerization of maleic anhydride onto an olefin polymer having ethylene and / or propylene as the main polymer structural unit, those modified by copolymerization of an olefin mainly composed of ethylene and / or propylene with maleic anhydride, etc. Specific examples include a combination of polyethylene / maleic anhydride-grafted ethylene-butene-1 copolymer, or a combination of polypropylene / maleic anhydride-grafted polypropylene.

[0033] (Hydroxy-modified polyolefin resin) The hydroxy-modified polyolefin resin is a modified polyolefin resin containing a hydroxy group. The hydroxy-modified polyolefin resin may have the hydroxy group at an appropriate site, for example, at the end of the main chain or on a side chain. Examples of the olefin resin constituting the hydroxy-modified polyolefin resin include homopolymers or copolymers of α-olefins such as ethylene, propylene, butene, 4-methylpentene-1, hexene, octene, nonene, decene, and dodecene, and copolymers of the above-mentioned α-olefins with copolymerizable monomers. Preferred examples of the hydroxy-modified polyolefin resin include hydroxy-modified polyethylene resins such as low-density, medium-density, or high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, ethylene-(meth)acrylic acid ester copolymer, and ethylene-vinyl acetate copolymer; and hydroxy-modified polypropylene resins such as polypropylene homopolymers such as isotactic polypropylene, random copolymers of propylene and α-olefins (e.g., ethylene, butene, hexane, etc.), propylene-α-olefin block copolymers, and hydroxy-modified poly(4-methylpentene-1).

[0034] <(b) Thermally Expandable Flame Retardant> The thermoplastic resin composition (X) forming the composite sheet of the present invention contains a thermally expandable flame retardant (b). The thermally expandable flame retardant (b) suppresses combustion of materials by forming a surface intumescent layer that prevents the diffusion of radiant heat from the combustion source and combustion gases and smoke from the burning material to the outside. Among thermally expandable flame retardants, phosphorus-based flame retardants are preferred, including salts of (poly)phosphoric acid and nitrogen compounds (hereinafter also referred to as "compound (b1)"). Specific examples include ammonium salts and amine salts of (poly)phosphoric acid, such as ammonium polyphosphate, melamine polyphosphate, piperazine polyphosphate, ammonium pyrophosphate, melamine pyrophosphate, and piperazine pyrophosphate.Examples of the nitrogen compounds include ammonia, melamine, piperazine, and other nitrogen compounds. Examples of the other nitrogen compounds include N,N,N',N'-tetramethyldiaminomethane, ethylenediamine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, and N,N,N',N'-diethylethylenediamine. diamine, 1,2-propanediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, trans-2,5-dimethylpiperazine, 1,4-bis(2-aminoethyl)piperazine, 1,4-bis(3-aminopropyl)piperazine, acetoguanamine, benzoguanamine, acryloylguanamine namin, 2,4-diamino-6-nonyl-1,3,5-triazine, 2,4-diamino-6-hydroxy-1,3,5-triazine, 2-amino-4,6-dihydroxy-1,3,5-triazine, 2,4-diamino-6-methoxy-1,3,5-triazine, 2,4-diamino-6-ethoxy-1,3,5-triazine, 2,4-diamino-6-propoxy-1,3,5-triazine, 2,4-diamino-6-isopropoxy-1,3,5-triazine, Examples of the methyl methyl acrylate include 2,4-diamino-6-mercapto-1,3,5-triazine, 2-amino-4,6-dimercapto-1,3,5-triazine, ammeline, benzguanamine, acetoguanamine, phthalodiguanamine, melamine cyanurate, butylenediguanamine, norbornenediguanamine, methylenediguanamine, ethylenedimelamine, trimethylenedimelamine, tetramethylenedimelamine, hexamethylenedimelamine, and 1,3-hexylenedimelamine.

[0035] <Other Flame Retardants> As described above, the composite sheet of the present invention is characterized by containing a thermally expandable flame retardant. However, other flame retardants may be used in addition to the thermally expandable flame retardant. The other flame retardants are not particularly limited, and conventionally used flame retardants can be used. Specific examples include phosphorus-based flame retardants, bromine-based flame retardants, and antimony-based flame retardants other than the above-mentioned thermally expandable flame retardants. Among these, phosphorus-based flame retardants are preferred from the viewpoint of improving flame resistance.

[0036] (Phosphorus-based flame retardant) A phosphorus-based flame retardant is a phosphorus compound, i.e., a compound containing a phosphorus atom in the molecule. The phosphorus-based flame retardant exerts a flame retardant effect by forming char when the composite sheet is burned. The phosphorus-based flame retardant may be a known compound, such as a (poly)phosphate or a (poly)phosphate ester. Here, "(poly)phosphate" refers to a phosphate or a polyphosphate, and "(poly)phosphate ester" refers to a phosphate ester or a polyphosphate ester. It is preferable that the phosphorus-based flame retardant is solid at 80°C.

[0037] As the phosphorus-based flame retardant, (poly)phosphates are preferred in terms of flame retardancy. Examples of (poly)phosphates include ammonium polyphosphate, melamine polyphosphate, piperazine polyphosphate, piperazine orthophosphate, melamine pyrophosphate, piperazine pyrophosphate, melamine polyphosphate, and melamine orthophosphate. Other phosphorus-based flame retardants include calcium phosphate and magnesium phosphate. In addition, compounds in which melamine or piperazine is replaced with other nitrogen compounds in the above examples can also be used. These (poly)phosphates may be used alone or in combination of two or more.

[0038] Commercially available phosphorus-based flame retardants include Adekastab FP-2100J, FP-2200, and FP-2500S (manufactured by ADEKA Corporation).

[0039] (Brominated Flame Retardants) Examples of brominated flame retardants include decabromodiphenyl ether, tetrabromobisphenol A, tetrabromobisphenol S, 1,2-bis(2',3',4',5',6'-pentabromophenyl)ethane, 1,2-bis(2,4,6-tribromophenoxy)ethane, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, 2,6-dibromophenol, 2,4-dibromophenol, Examples of the brominated polystyrene include ethylene bistetrabromophthalimide, hexabromocyclododecane, hexabromobenzene, pentabromobenzyl acrylate, 2,2-bis[4'(2'',3''-dibromopropoxy)-3',5'-dibromophenyl]-propane, bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl]sulfone, and tris(2,3-dibromopropyl)isocyanurate.

[0040] (Antimony-Based Flame Retardants) Examples of antimony-based flame retardants include antimony trioxide, antimony tetroxide, antimony pentoxide, sodium pyroantimonate, antimony trichloride, antimony trisulfide, antimony oxychloride, antimony dichloride perchloropentane, and potassium antimonate, with antimony trioxide and antimony pentoxide being particularly preferred.

[0041] Among the above flame retardants, phosphorus-based flame retardants are preferred because they are non-bioresistent and have excellent flame retardancy, and non-halogen flame retardants are preferred from the viewpoint of environmental friendliness. The above flame retardants can be used alone or in combination of two or more.

[0042] (b) Content of thermally expandable flame retardant) The content of the thermally expandable flame retardant in the composite sheet of the present invention is not particularly limited, but is preferably in the range of 1 to 30 mass %. When it is 1 mass % or more, good flame retardancy can be imparted to the composite sheet, and good flame blocking properties can be obtained. On the other hand, when the flame retardant is 30 mass % or less, a sufficient content ratio of the thermoplastic resin can be contained, resulting in better molding processability. From the above viewpoints, the content of the thermally expandable flame retardant in the composite sheet is more preferably in the range of 1 to 25 mass %, and even more preferably in the range of 3 to 20 mass %.

[0043] <(c) Dispersant> The thermoplastic resin composition (X) according to the present invention preferably further contains a dispersant. The (c) dispersant is not particularly limited as long as it can disperse the (b) thermally expandable flame retardant in the (a) thermoplastic resin. However, polymeric dispersants are suitable in terms of compatibility with the (a) thermoplastic resin. Preferably, a dispersant capable of dispersing the (b) thermally expandable flame retardant in the (a-1) polypropylene-based resin can be used. Polymeric dispersants having functional groups are preferred, and from the viewpoint of dispersion stability, polymeric dispersants having functional groups such as carboxyl groups, phosphate groups, sulfonic acid groups, primary, secondary, or tertiary amino groups, quaternary ammonium bases, or groups derived from nitrogen-containing heterocycles such as pyridine, pyrimidine, and pyrazine are preferred. In the present invention, polymeric dispersants having carboxyl groups are preferred, and in particular, when a phosphorus-based flame retardant suitable as a flame retardant is used, a copolymer of an α-olefin and an unsaturated carboxylic acid is preferred. The use of such a dispersant can improve the dispersibility of the phosphorus-based thermally expandable flame retardant and reduce the content of the thermally expandable flame retardant.

[0044] (Copolymer of α-olefin and unsaturated carboxylic acid) In the "copolymer of α-olefin and unsaturated carboxylic acid" according to the present invention (hereinafter referred to as "copolymer (c1)"), the proportion of α-olefin units in a total of 100 mol% of α-olefin units and unsaturated carboxylic acid units is preferably 20 mol% or more and 80 mol% or less. In copolymer (c1), the proportion of α-olefin units relative to the total amount of α-olefin units and unsaturated carboxylic acid units is more preferably 30 mol% or more, and more preferably 70 mol% or less. When the proportion of α-olefin is equal to or more than the lower limit, the compatibility with polyolefin resins is improved, and when it is equal to or less than the upper limit, the compatibility with (b) thermally expandable flame retardant is improved.

[0045] In the copolymer (c1), the α-olefin is preferably an α-olefin having 5 or more carbon atoms, and more preferably an α-olefin having 10 to 80 carbon atoms. If the α-olefin has 5 or more carbon atoms, compatibility with the thermoplastic resin (a) tends to be better, and if it has 80 or less carbon atoms, it is advantageous in terms of raw material costs. From the above viewpoints, the number of carbon atoms in the α-olefin is more preferably 12 to 70, and particularly preferably 18 to 60.

[0046] In the copolymer (c1), examples of the unsaturated carboxylic acid include (meth)acrylic acid, maleic acid, methylmaleic acid, fumaric acid, methylfumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, glutaconic acid, norbornane-5-ene-2,3-dicarboxylic acid, and esters, anhydrides, and imides of these unsaturated carboxylic acids. The term "(meth)acrylic acid" refers to acrylic acid or methacrylic acid. Specific examples of the esters, anhydrides, and imides of unsaturated carboxylic acids include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and glycidyl (meth)acrylate; dicarboxylic acid anhydrides such as maleic anhydride, itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride; and maleimide compounds such as maleimide, N-ethylmaleimide, and N-phenylmaleimide. These may be used alone or in combination of two or more. Among the above, esters and dicarboxylic acid anhydrides are preferred from the viewpoint of copolymerization reactivity. Among them, dicarboxylic acid anhydrides are preferred, and maleic anhydride is particularly preferred from the viewpoint of compatibility with thermally expandable phosphorus-based flame retardants suitable as flame retardants.

[0047] The weight-average molecular weight of copolymer (c1) is preferably 2,000 or more, more preferably 3,000 or more, and is preferably 50,000 or less, more preferably 30,000 or less. If the weight-average molecular weight of copolymer (c1) is within the above range, the dispersibility of the flame retardant (b) will be better. The weight-average molecular weight of copolymer (c1) is a value calculated in terms of standard polystyrene, measured by dissolving copolymer (c1) in tetrahydrofuran (THF) and performing gel permeation chromatography.

[0048] Commercially available copolymers (c1) include Ricorb CE2 (manufactured by Clariant Japan KK) and Diacarna 30M (manufactured by Mitsubishi Chemical Corporation).

[0049] In the composite sheet of the present invention, the content of (c) dispersant per 100 parts by mass of (b) thermally expandable flame retardant is in the range of more than 0 and not more than 25 parts by mass, preferably in the range of 0.01 to 10 parts by mass. According to the inventors' studies, the flame-resistant properties of the composite sheet can be significantly improved by uniformly dispersing the thermally expandable flame retardant in the inorganic fibers constituting the composite sheet with a thermoplastic resin as the matrix resin. While the detailed mechanism is unclear, the inventors speculate as follows: When the thermally expandable flame retardant is uniformly dispersed in the resin between the inorganic fibers, char formed upon contact with the thermally expandable flame retardant is fixed in the gaps between the inorganic fibers. Furthermore, the gaps between the inorganic fibers limit the size of the char formed by expansion upon contact with the flame, resulting in a uniform size of the char formed. It is believed that the combination of the char fixing effect of the inorganic fibers and the uniform size of the char results in the formation of a dense char, significantly improving the flame-resistant properties of the composite sheet. Based on these findings, the inventors discovered that by setting the ratio of the dispersant content to the thermally expandable flame retardant within a specific range, the thermally expandable flame retardant can be controlled to be uniformly distributed in the resin between the inorganic fibers, thereby significantly improving the flame-blocking properties of the composite sheet. For these reasons, when the content of (c) dispersant is greater than 0, the dispersion of (b) flame retardant is sufficient, and sufficient flame-blocking properties can be imparted to the composite sheet. On the other hand, when the content of (c) dispersant is 25 parts by mass or less, the physical properties of the composite sheet are sufficient. From the same perspective, the content of (c) dispersant is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, even more preferably 1 part by mass or more, and particularly preferably 2 parts by mass or more. Meanwhile, the upper limit is preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less.

[0050] Furthermore, the proportion of (c) dispersant relative to 100 parts by mass of the combined total of (a) thermoplastic resin and (b) thermally expandable flame retardant is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more. On the other hand, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, and even more preferably 1.0 part by mass or less. When the proportion of (c) dispersant is above the lower limit, the (b) thermally expandable flame retardant is more effectively dispersed, resulting in improved flame resistance, physical properties, and appearance of the resulting composite sheet. When the proportion of (c) dispersant is below the upper limit, the impact of the (c) dispersant on the flame resistance of the composite sheet can be further suppressed. In particular, the proportion of (c) dispersant relative to 100 parts by mass of the polyolefin resin and (b) thermally expandable flame retardant combined is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, while being preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, and even more preferably 1.0 part by mass or less.

[0051] Furthermore, for the (Y) inorganic fibers described in detail below, the ratio of the (c) dispersant per 100 parts by mass of the (Y) inorganic fibers is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more. On the other hand, it is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 2.0 parts by mass or less. When the ratio of the (c) dispersant is equal to or greater than the lower limit, the flame-blocking properties, physical properties, and appearance of the resulting composite sheet are improved. When the ratio of the (c) dispersant is equal to or less than the upper limit, the effect of the (c) dispersant on the flame-blocking properties of the composite sheet can be further suppressed.

[0052] <(Y) Inorganic Fibers> The composite sheet of the present invention contains (Y) inorganic fibers. Various fibers can be used as the (Y) inorganic fibers, including metal oxide fibers such as glass fibers, rock wool, alumina fibers, and silica-alumina fibers; ceramic fibers such as potassium titanate fibers, calcium silicate (wollastonite) fibers, and ceramic fibers; carbon fibers; and metal fibers. These inorganic fibers may be used alone or in combination of two or more. Among the above inorganic fibers, at least one selected from glass fibers and alumina fibers is preferred from the viewpoints of flame resistance and processability. The (Y) inorganic fibers may contain two or more inorganic fibers with different melting temperatures. A combination of two or more inorganic fibers with different melting temperatures is preferably such that at least one is glass fiber and the other one or more is one or more inorganic fibers selected from the group consisting of alumina fibers, silica fibers, alkaline earth silicate fibers (biosoluble), and carbon fibers. The inclusion of two or more inorganic fibers with different melting temperatures effectively prevents a decrease in flame resistance. The inorganic fibers used in the present invention may be used in combination with a sizing agent or a surface treatment agent, such as a compound having a functional group, such as an epoxy compound, a silane compound, or a titanate compound.

[0053] The average fiber diameter of the inorganic fibers is preferably 3 to 25 μm. The average fiber length is preferably 0.1 mm or more, more preferably 1 mm or more, and even more preferably 5 mm or more. The preferred ranges for the average fiber diameter and average fiber length vary depending on the type of inorganic material constituting the inorganic fibers, and specific preferred ranges will be described later. The fiber diameter can be measured using a scanning electron microscope or the like. The average fiber diameter can be obtained, for example, by measuring the fiber diameters of 10 randomly selected fibers and calculating the average value. The fiber length can be measured, if necessary, using a ruler, calipers, or the like from an image magnified with a microscope or the like. The average fiber length can be obtained, for example, by measuring the fiber lengths of 10 randomly selected fibers and calculating the average value.

[0054] The content of inorganic fibers in the composite sheet of the present invention is preferably 1 to 80% by mass. When the content of inorganic fibers is 1% by mass or more, the strength, rigidity, and impact resistance of the composite sheet are good. Furthermore, when the content of inorganic fibers is 80% by mass or less, the production and processing of the composite sheet are facilitated. Furthermore, when the content of inorganic fibers is 80% by mass or less, the specific gravity of the composite sheet is reduced, and the weight-saving effect as a metal substitute is remarkable. From the above viewpoints, the content of (Y) inorganic fibers in the composite sheet is more preferably 3 to 60% by mass, even more preferably 10 to 50% by mass, and particularly preferably 30 to 45% by mass.

[0055] (Glass Fiber) One example of the inorganic fiber (Y) suitable for the composite sheet of the present invention is glass fiber. The glass fiber may be, for example, a long fiber having an average fiber length of 30 mm or more, or a fiber (chopped strand) having a short average fiber length. However, from the viewpoints of flame retardancy, rigidity, impact resistance, etc., it is preferable to use glass fiber having a long average fiber length. More specifically, the average fiber length is preferably 5 mm or more. When the average fiber length is 5 mm or more, the strength and impact resistance of the composite sheet are improved. From the above viewpoints, the average fiber length of the glass fiber is preferably 5 mm or more, and more preferably 30 mm or more. There is no particular upper limit to the average fiber length of the glass fiber. For example, when pellets produced by a pultrusion method using glass fiber are used, the length of the pellets becomes the fiber length of the glass fiber, and therefore, the maximum fiber length is about 20 mm. In addition, in the case of a swirl mat system using long glass fibers, the maximum fiber length is the length of the glass fibers in the roving used in production, which can be as long as 17,000 m (17 km). However, when the fiber is cut to fit the size of the composite sheet, the cut length becomes the maximum fiber length.

[0056] The average fiber diameter of the glass fibers is preferably in the range of 9 to 25 μm. When the average fiber diameter is 9 μm or more, the composite sheet has sufficient rigidity and impact resistance, while when the average fiber diameter is 25 μm or less, the composite sheet has good strength. From the above viewpoints, the average fiber diameter of the glass fibers is more preferably in the range of 10 to 15 μm. The average fiber diameter and average fiber length of the glass fibers can be measured by the above-mentioned method.

[0057] The material of the glass fiber used in the present invention is not particularly limited, and may be any of alkali-free glass, low-alkali glass, and alkali-containing glass, and various compositions that have conventionally been used as glass fibers can be used.

[0058] (Alumina Fiber) One of the inorganic fibers (Y) suitable for the composite sheet of the present invention is alumina fiber. Alumina fiber is usually a fiber made of alumina and silica, and in the composite sheet of the present invention, the alumina / silica composition ratio (mass ratio) of the alumina fiber is preferably in the range called a mullite composition or high alumina composition of 65 / 35 to 98 / 2, more preferably 70 / 30 to 95 / 5, and particularly preferably 70 / 30 to 74 / 26.

[0059] The average fiber diameter of the alumina fibers is preferably in the range of 3 to 25 μm, and it is preferable that the fibers are substantially free of fibers with a fiber diameter of 3 μm or less. Here, "substantially free of fibers with a fiber diameter of 3 μm or less" means that fibers with a fiber diameter of 3 μm or less account for 0.1 mass% or less of the total inorganic fiber mass. Furthermore, the average fiber diameter of the alumina fibers is more preferably 5 to 8 μm. If the average fiber diameter of the inorganic fibers is too large, the resilience and toughness of the mat-like inorganic fiber assembly layer will decrease. Conversely, if the average fiber diameter is too small, the amount of dust floating in the air will increase, and the probability of containing inorganic fibers with a fiber diameter of 3 μm or less will increase. The alumina fibers preferably have an average fiber length of 5 mm or more, more preferably 30 mm or more, and even more preferably 50 mm or more. Furthermore, the average fiber length is preferably 3.0 × 10 ３ mm or less, more preferably 1.0 × 10 ３If the average fiber length and average fiber diameter of the alumina fibers are within this range, the strength and impact resistance of the composite sheet will be good.

[0060] (Carbon Fiber) The preferable range for carbon fiber is the same as that for glass fiber.

[0061] <Optional Additives> In addition to the above components, the composite sheet of the present invention may contain optional additives to further enhance the effects of the present invention or to provide other effects, as long as they do not significantly impair the effects of the present invention. Specific examples include colorants such as pigments, light stabilizers such as hindered amines, UV absorbers such as benzotriazoles, nucleating agents such as sorbitols, antioxidants such as phenols and phosphorus-based antioxidants, antistatic agents such as nonionic surfactants, neutralizing agents such as inorganic compounds, antibacterial and antifungal agents such as thiazoles, flame retardants and flame retardant aids such as halogen compounds and lignophenols, plasticizers, dispersants such as organic metal salts, lubricants such as fatty acid amides, metal deactivators such as nitrogen compounds, polyolefin resins other than the polypropylene resins, thermoplastic resins such as polyamide resins and polyester resins, and elastomers (rubber components) such as olefin elastomers and styrene elastomers. Two or more of these optional additives may be used in combination.

[0062] As colorants, for example, inorganic or organic pigments are effective in imparting or improving the colored appearance, appearance, texture, commercial value, weather resistance, durability, etc., of the composite sheet of the present invention. Specific examples of inorganic pigments include carbon black such as furnace carbon and ketjen carbon; titanium oxide; iron oxide (e.g., red iron oxide); chromic acid (e.g., lead chrome); molybdic acid; selenide sulfide; and ferrocyanide. Specific examples of organic pigments include azo pigments such as sparingly soluble azo lake, soluble azo lake, insoluble azo chelate, condensed azo chelate, and other azo chelates; phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; threne pigments such as anthraquinone, perinone, perylene, and thioindigo; dye lake; quinacridone; dioxazine; and isoindolinone. To achieve a metallic or pearlescent finish, aluminum flakes or pearl pigments can be added. Dyes can also be added.

[0063] Light stabilizers and ultraviolet absorbers, such as hindered amine compounds, benzotriazoles, benzophenones, and salicylates, are effective in imparting or improving the weather resistance and durability of the composite sheet of the present invention, and are also effective in further improving weather discoloration resistance. Specific examples of the hindered amine compound include a condensation product of dimethyl succinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine; poly[[6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]]; tetrakis(2,2,6,6-tetramethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate; tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate; bis(1,2,2,6,6-pentamethyi) Examples of the benzotriazole-based stabilizers include 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole and 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole. Examples of the benzophenone-based stabilizers include 2-hydroxy-4-methoxybenzophenone and 2-hydroxy-4-n-octoxybenzophenone. Examples of the salicylate-based stabilizers include 4-t-butylphenyl salicylate and 2,4-di-t-butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate. Here, the method of using the light stabilizer and the ultraviolet absorber in combination is preferred because it has a significant effect of improving weather resistance, durability, weather discoloration resistance, etc.

[0064] Antioxidants such as phenolic, phosphorus-based, and sulfur-based antioxidants are effective in imparting and improving the heat resistance, processing stability, and heat aging resistance of the composite sheet of the present invention. Additionally, antistatic agents such as nonionic and cationic antistatic agents are effective in imparting and improving the antistatic properties of the composite sheet of the present invention.

[0065] Examples of olefin-based elastomers include ethylene-α-olefin copolymer elastomers such as ethylene-propylene copolymer elastomer (EPR), ethylene-butene copolymer elastomer (EBR), ethylene-hexene copolymer elastomer (EHR), and ethylene-octene copolymer elastomer (EOR); ethylene-α-olefin-diene terpolymer elastomers such as ethylene-propylene-ethylidenenorbornene copolymer, ethylene-propylene-butadiene copolymer, and ethylene-propylene-isoprene copolymer; and styrene-butadiene-styrene triblock copolymer elastomer (SBS). Examples of styrene-based elastomers include styrene-based elastomers such as styrene-isoprene-styrene triblock copolymer elastomer (SIS), styrene-ethylene-butylene copolymer elastomer (SEB), styrene-ethylene-propylene copolymer elastomer (SEP), styrene-ethylene-butylene-styrene copolymer elastomer (SEBS), styrene-ethylene-butylene-ethylene copolymer elastomer (SEBC), hydrogenated styrene-butadiene elastomer (HSBR), styrene-ethylene-propylene-styrene copolymer elastomer (SEPS), styrene-ethylene-ethylene-propylene-styrene copolymer elastomer (SEEPS), styrene-butadiene-butylene-styrene copolymer elastomer (SBBS), partially hydrogenated styrene-isoprene-styrene copolymer elastomer, and partially hydrogenated styrene-isoprene-butadiene-styrene copolymer elastomer; and hydrogenated polymer-based elastomers such as ethylene-ethylene-butylene-ethylene copolymer elastomer (CEBC). Among these, the use of an ethylene-octene copolymer elastomer (EOR) and / or an ethylene-butene copolymer elastomer (EBR) is preferred because it is easy to impart appropriate flexibility and the like to the polypropylene resin composition and composite sheet of the present invention, and they tend to have excellent impact resistance.

[0066] <Method for Producing Thermoplastic Resin Composition (X)> As described above, the thermoplastic resin composition (X) according to the present invention contains (a) a thermoplastic resin, a modified polyolefin resin added as needed, (b) a thermally expandable flame retardant, and (c) a dispersant. Optional additional components may also be blended. In the thermoplastic resin composition (X), when the (a) thermoplastic resin is (a-1) a polypropylene resin, the composition may be referred to as a polypropylene resin composition (hereinafter, sometimes referred to as a "PP composition"). Conventionally known methods can be used to produce the thermoplastic resin composition (X) or the PP composition, and the composition can be produced by blending, mixing, and melt-kneading the above components. Mixing is carried out using a mixer such as a tumbler, V-blender, or ribbon blender, and melt-kneading is carried out using equipment such as a single-screw extruder, a twin-screw extruder, a Banbury mixer, a roll mixer, a Brabender plastograph, or a kneader, followed by melt-kneading and granulation.

[0067] <Method for Manufacturing Composite Sheet> The composite sheet of the present invention is not particularly limited by its manufacturing method, but is preferably manufactured by impregnating a mat made of inorganic fibers (Y) (hereinafter sometimes referred to as an "inorganic fiber mat") with the thermoplastic resin composition (X) or the PP composition. That is, one embodiment of the composite sheet is obtained by impregnating a mat made of inorganic fibers (Y) with the thermoplastic resin composition (X). Impregnation methods include a method of applying the thermoplastic resin composition (X) or the PP composition to the inorganic fiber mat (Y), and a method of preparing a sheet of the thermoplastic resin composition (X) or the PP composition (hereinafter sometimes referred to as a "thermoplastic resin sheet" or a "PP sheet"), laminating the thermoplastic resin sheet or the PP sheet on the inorganic fiber mat (Y), and heating and melting the sheet to impregnate the inorganic fiber mat (Y). In the present invention, from the viewpoint of the resin's ability to impregnate the fibers in the composite sheet, a method of laminating a thermoplastic resin sheet or a PP sheet on the inorganic fiber mat (Y), and heating and melting the sheet is preferred. In particular, the composite sheet of the present invention can be obtained by laminating an inorganic fiber mat between two thermoplastic resin sheets or PP sheets, then heating and pressing the laminate, and then cooling and solidifying it. The thickness of the thermoplastic resin sheet or PP sheet is not particularly limited as long as it allows good impregnation of the fiber mat. As described above, the composite sheet of the present invention has a density of 1.3 g / cm. ３ It is important to do the following, and the resin-impregnated sheet can be expanded by heating or the like to reduce its density and obtain a composite sheet.

[0068] (Inorganic fiber mat) The form of the inorganic fiber used in the manufacturing method of the composite sheet is not particularly limited, and various forms can be used, but those formed in a mat or sheet form are preferred. More specifically, a mat formed from glass fiber (hereinafter referred to as a "glass fiber mat") and a mat formed from metal oxide fiber, typified by alumina fiber (hereinafter referred to as a "metal oxide mat") are preferred.

[0069] The basis weight (mass per unit area) of the inorganic fiber mat is not particularly limited and is determined appropriately depending on the application, but is preferably 300 g / m２ More preferably, 800 g / m ２ More preferably, 1500 g / m ２ The basis weight of the inorganic fiber mat is not particularly limited, but is preferably 5000 g / m ２ or less, more preferably 4500 g / m ２ More preferably, 4000 g / m or less ２ Particularly preferably 3500 g / m ２ The thickness of the inorganic fiber mat according to the present invention is not particularly limited, but is preferably 4 mm or more, more preferably 5 mm or more, and even more preferably 6 mm or more. The thickness of the fiber mat is preferably 40 mm or less, more preferably 35 mm or less, and particularly preferably 30 mm or less.

[0070] The basis weight per unit area of ​​the inorganic fiber mat can be set within the above range by adjusting the amount of fiber per unit area when the inorganic fiber aggregates constituting the inorganic fiber mat are stacked using a folding device. The inorganic fiber mat of the present invention may be configured by bonding multiple inorganic fiber mats together or may be configured as a single unit, but a single unit is preferred from the standpoints of handleability and peel strength at the bonding interface.

[0071] (Glass fiber mat) Examples of the form of the glass fiber mat used in the present invention include felt and blanket processed with short fiber glass wool, chopped strand mat processed with continuous glass fiber, swirl (spiral) mat of continuous glass fiber, unidirectionally aligned mat, etc. Among these, the use of a glass fiber mat obtained by needle-punching a swirl (spiral) mat of continuous glass fiber is particularly preferred, as it provides a composite sheet with excellent strength and impact resistance.

[0072] (Metal Oxide Fiber Mat) The metal oxide fiber mat according to the present invention is a mat made of metal oxide fibers such as alumina fibers and subjected to a needling treatment.

[0073] In the method of laminating a thermoplastic resin sheet or a PP sheet to an inorganic fiber mat and heating and melting it, the heating temperature is preferably 170 to 300°C. When the heating temperature is 170°C or higher, the flowability of the polypropylene resin is sufficient, allowing the inorganic fiber mat to be sufficiently impregnated with the PP composition, resulting in a suitable resin-impregnated sheet. On the other hand, when the heating temperature is 300°C or lower, the thermoplastic resin composition or PP composition does not deteriorate. Furthermore, the pressurizing pressure is preferably 0.1 to 1 MPa. When the pressurizing pressure is 0.1 MPa or higher, the inorganic fiber mat can be sufficiently impregnated with the thermoplastic resin composition or PP composition, resulting in a suitable resin-impregnated sheet. On the other hand, when the pressurizing pressure is 1 MPa or lower, the thermoplastic resin composition or PP composition flows, preventing the formation of burrs. The cooling temperature is not particularly limited as long as it is below the freezing point of the thermoplastic resin in the thermoplastic resin composition (X) or the PP composition. However, when the cooling temperature is 80°C or lower, the resulting resin-impregnated sheet does not deform when removed. From the above perspectives, the cooling temperature is preferably room temperature to 80°C.

[0074] The composite sheet can be produced by heating, pressurizing, and cooling the resin-impregnated sheet, for example, by press molding in a mold equipped with a heating device, or by laminating the sheet between two pairs of rollers equipped with a heating device to apply heat and pressure. Laminating is particularly preferred because it allows continuous production and is therefore highly productive.

[0075] <Thickness of Composite Sheet> The thickness of the composite sheet of the present invention is usually 1 to 10 mm, preferably 2 to 5 mm. When the thickness of this composite sheet is 1 mm or more, the composite sheet is easy to produce, while when the thickness of the composite sheet is 10 mm or less, long-term preheating is not required when processing the composite sheet by stamping molding or the like, and good molding processability is obtained.

[0076] <Molded Article> The molded article of the present invention is obtained by molding the composite sheet described above. The molding method is not particularly limited, but the composite sheet can be stamped in a conventional manner to obtain a desired shape.

[0077] (Applications) Examples of applications of the molded article of the present invention include various parts in the industrial field such as automobile parts and electrical and electronic equipment parts. In particular, the molded article of the present invention has excellent strength, rigidity, and conductivity, and can be suitably used for applications requiring a high level of balance of these properties, such as various housings and cases such as battery cases.

[0078] [Structure] The structure formed using the molded article of the present invention is not particularly limited, and may include, for example, a battery housing and a battery cell. A battery is preferred as a structure formed using the molded article of the present invention, and the battery is not particularly limited. Examples of the battery include secondary batteries such as lithium ion batteries, nickel-metal hydride batteries, lithium-sulfur batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, sodium-sulfur batteries, lead-acid batteries, and air batteries. Of these, lithium ion batteries are preferred, and the battery housing of the present invention is particularly suitable for use in suppressing thermal runaway of lithium ion batteries.

[0079] [Electric Mobility] A structure using the molded article of the present invention is also useful for electric mobility. Here, electric mobility refers to transportation equipment such as vehicles, ships, and airplanes that run on electricity as an energy source. Note that vehicles include hybrid cars in addition to electric vehicles (EVs). Structures such as battery housings and batteries having battery cells using the molded article of the present invention are highly safe and very useful for electric mobility that uses battery modules with increased energy density to extend driving distance.

[0080] The present invention will be described in detail below using examples, but the present invention is not limited to these examples.

[0081] (Evaluation Method) 1. Evaluation of Flame Barrier Property The composite sheets prepared in each Example and Comparative Example were each subjected to a burner flame at 1300°C on one side, and evaluated based on whether the flame penetrated after 15 minutes. The distance from the burner nozzle to the sample was 160 mm. The flame front temperature was set to 1200°C. The flame front temperature was confirmed with a thermocouple thermometer.

[0082] 2. Evaluation of Heat Insulation Properties In the flame-shielding evaluation described in 1. above, the temperature of the surface (back surface) of the test piece opposite to the surface exposed to the burner flame was measured using a non-contact radiation thermometer (Keyence Corporation, "FT-H50K"). The measurement area was φ35 mm. The center of the measurement area was visually determined to be immediately above the position of the burner flame. Table 1 shows the maximum temperature (°C) reached on the back surface within 600 seconds and the elapsed time (seconds) when the back surface temperature first reached 500°C.

[0083] 3. Evaluation of Flame Retardancy The composite sheets prepared in each Example and Comparative Example were evaluated for flame retardancy based on the UL94 50W (20 mm) vertical flame test. The evaluation was judged based on whether or not V-1 was achieved.

[0084] 4. Expansion Coefficient The thickness of the test piece of the composite sheet prepared in each Example was measured before and after the heating test, and the expansion coefficient was evaluated based on the ratio of the thickness of the test piece after heating to the thickness of the test piece before the heating test. (Heating Test Conditions) The test piece was heat-treated in air at 1200°C for 15 minutes.

[0085] 5. Measurement of void cross-sectional area The composite sheets prepared in each example were cut using a cutting machine manufactured by DAHLE, and the cross-sections were observed at 30x magnification using a digital microscope "VHX-6000" manufactured by Keyence Corporation to obtain cross-sectional images. The cross-sectional areas of the voids in the obtained cross-sectional images were measured using the automatic area measurement tool of the VHX-6000. Of these, the cross-sectional areas of voids with a cross-sectional area of ​​0.01 mm were measured. ２ The average cross-sectional area of ​​the voids was calculated.

[0086] 6. Measurement of bending strength after firing The composite sheets prepared in each example were heat-treated in a nitrogen atmosphere (oxygen-free) at 700°C for 20 minutes. Test pieces of 100 mm x 50 mm were cut out from the heat-treated sheets, and the bending strength of these test pieces was measured using an AUTOGRAPH "AG-10TA" (manufactured by Shimadzu Corporation) at a test speed of 20 mm / min and a span of 100 mm.

[0087] 7. Measurement of thermal conductivity after firing The composite sheets prepared in each example were heat-treated in a nitrogen atmosphere (oxygen-free) at 700°C for 20 minutes. Test pieces measuring 150 mm x 100 mm were cut out from the heat-treated sheets. The test samples were heated on one side, and the temperature difference between the heating surface and the heat-dissipating surface was compared with that of a sheet sample with known thermal conductivity to calculate the thermal conductivity of the sample.

[0088] (Materials Used) 1. Polypropylene Resin (Component a) "Novatec PP SA06GA" (melt flow rate: 60 g / 10 min) manufactured by Japan Polypropylene Corporation was used.

[0089] 2. Thermally expandable flame retardant (component b): Phosphorus-based flame retardant composition (manufactured by ADEKA Corporation, Adeka STAB FP-2500S, containing 50 to 60 mass% of piperazine pyrophosphate, 35 to 45 mass% of melamine pyrophosphate, and 3 to 6 mass% of zinc oxide relative to the total mass of the phosphorus-based flame retardant composition).

[0090] 3. Dispersant (component c) α-olefin-maleic anhydride copolymer (manufactured by Mitsubishi Chemical Corporation, Diacarna 30M, weight average molecular weight 7,800).

[0091] 4. Glass fiber mat (component Y) A swirl mat (basis weight 880 g / m) made from continuous glass fibers (fiber diameter 23 μm) of roving. ２ ) was used as a needle-punched glass fiber mat.

[0092] 5. PET nonwoven fabric: PET nonwoven fabric ("Volance (registered trademark) 3401ND", manufactured by Toyobo Co., Ltd., basis weight 40 g / m ２ )

[0093] Preparation Example 1 (Preparation of PP Composition) The above-mentioned components a, b, and c were mixed in proportions of 68 mass%, 30 mass%, and 2 mass%, respectively, and melt-kneaded (230°C) to prepare pellets of a polypropylene resin composition (PP composition).

[0094] Comparative Preparation Example 1 Pellets of a polypropylene resin composition (PP composition) were prepared in the same manner as in Preparation Example 1, except that the components b and c were not used.

[0095] Example 1: The manufacturing method of the composite sheet 30 of the present invention is described below with reference to FIG. 2. FIG. 2 shows the layer structure before the glass fiber mat is impregnated with the thermoplastic resin composition. The PP composition pellets granulated in Preparation Example 1 were placed in an extruder, melted, and extruded into a sheet. The extruded PP sheet 31 was sandwiched between glass fiber mats 32 and laminated. PET nonwoven fabrics 34 were then laminated on both sides of the extruded PP sheet 31, and PP sheets 33 were laminated on both sides of the extruded PP sheet 31 as the outermost layers. The resulting sheet was then heated and pressed at 230°C for 1 minute and 30 seconds under a pressure of 0.3 MPa using a laminator, and then cooled and solidified to obtain a resin-impregnated sheet (thickness: 2.5 mm). The PP sheet was impregnated into the glass fiber mat, resulting in an integrated resin-impregnated sheet. The mass ratio of the resin-impregnated sheet was PP sheet:PET nonwoven fabric:glass fiber mat = 25:1:16. The resin-impregnated sheet was heated at 220°C for 2 minutes to expand it, and compressed in a mold adjusted to a predetermined thickness to a density of 0.67 g / cm. ３ A composite sheet of 0.01 mm or more was obtained. The results of evaluation by the above method are shown in Table 1. The thickness of the composite sheet before heating in the flame-proofing test was 5.4 mm, and the thickness after heating was 10.1 mm. The expansion ratio before and after the heating test was 1.9 times. When the cross section of the composite sheet was observed, multiple voids with a cross-sectional area of ​​0.01 mm or more were observed. The average cross-sectional area of ​​the voids with a cross-sectional area of ​​0.01 mm or more was 0.21 mm. ２ It was.

[0096] Example 2: The same procedure as in Example 1 was carried out except that the mold was adjusted to obtain a predetermined thickness, and the density was 0.84 g / cm３ A composite sheet of 1000 sq. mm was obtained. The results of evaluation in the same manner as in Example 1 are shown in Table 1. The thickness of the composite sheet before heating in the flame-proofing test was 4.3 mm, and the thickness after heating was 8.3 mm. The expansion ratio before and after the heating test was 1.9 times. The average cross-sectional area of ​​voids with a cross-sectional area of ​​0.01 mm or more, obtained by observing the cross section of the composite sheet, was 0.15 mm. ２ It was.

[0097] Example 3: The same procedure as in Example 1 was carried out except that the mold was adjusted to obtain a predetermined thickness, and the density was 1.12 g / cm ３ A composite sheet of 1000 mm thick was obtained. The results of evaluation in the same manner as in Example 1 are shown in Table 1. The thickness of the composite sheet before heating in the flame-proofing test was 3.3 mm, and the thickness after heating was 10.1 mm. The expansion ratio before and after the heating test was 3.1 times. The average cross-sectional area of ​​voids with a cross-sectional area of ​​0.01 mm or more, obtained by observing the cross section of the composite sheet, was 0.06 mm. ２ It was.

[0098] Comparative Example 1 A composite sheet was obtained in the same manner as in Example 1, except that the pellets of the PP composition granulated in Preparation Example 1 were used instead of the pellets of the PP composition granulated in Comparative Preparation Example 1. The density of the composite sheet was 0.61 g / cm ３ The evaluation results are shown in Table 1. The thickness of the composite sheet before heating in the flame-proofing test was 5.3 mm. Because the flame penetrated to the back surface during the flame-proofing test, creating holes, the thickness after heating could not be measured.

[0099] Comparative Example 2: The same procedure as in Comparative Example 1 was repeated except that the mold was adjusted to obtain a predetermined thickness, and the density was 0.76 g / cm ３ A composite sheet of the above formula was obtained. The results of evaluation in the same manner as in Example 1 are shown in Table 1. The thickness of the composite sheet before heating in the flame-proofing test was 4.3 mm. Because the flame penetrated to the back surface during the flame-proofing test, creating holes, it was not possible to measure the thickness after heating.

[0100] Comparative Example 3: A density of 1.02 g / cm was obtained in the same manner as in Comparative Example 1, except that the mold was adjusted to obtain a predetermined thickness. ３A composite sheet of the above formula was obtained. The results of evaluation in the same manner as in Example 1 are shown in Table 1. The thickness of the composite sheet before heating in the flame-proofing test was 3.3 mm. Because the flame penetrated to the back surface during the flame-proofing test, creating holes, it was not possible to measure the thickness after heating.

[0101]

[0102] As shown in Examples 1 to 3, the composite sheet of the present invention had excellent flame-blocking properties, blocking flames even after 15 minutes. It also achieved a result equivalent to V-1 in the UL94 test. In contrast, flames penetrated to the backside in 87 seconds in Comparative Example 1, 94 seconds in Comparative Example 2, and 95 seconds in Comparative Example 3. Furthermore, Comparative Examples 1 and 3 did not meet the V-1 standard.

[0103] Furthermore, as shown in Table 1, the composite sheets of the Examples had better bending strength after firing and higher thermal conductivity after firing than the composite sheets of the Comparative Examples. Good bending strength after firing allows the composite sheets to withstand shock waves caused by an explosion when a high-energy density battery goes out of control. Furthermore, high thermal conductivity after firing allows the heat provided by the flame to be efficiently transported to the opposite side of the flame-contact surface and dissipated, thereby suppressing the temperature rise on the reverse side of the flame-contact surface.

[0104] As described above, the composite sheet of the present invention has high flame-shielding and combustion resistance, and is low-density and lightweight, making it useful as a material for various industrial parts that require high safety, such as aircraft, ships, automobile parts, electrical and electronic equipment parts, and building materials. In particular, it can be suitably used for various battery housings and cases, for which metal has traditionally been used, and contributes to the safety of automobiles while also improving energy efficiency and reducing CO2 emissions by reducing weight. ２ Furthermore, the composite sheet of the present invention has excellent flame resistance, and because it is mainly composed of resin, it is easy to process and lightweight, so that structures using the composite sheet of the present invention are useful as electric mobility.

[0105] REFERENCE SIGNS LIST 10 Laminate 11 Glass fiber mat 12 Surface sheet 13 Thermoplastic resin sheet 20 Resin-impregnated sheet 30 Composite sheet 31 PP sheet 32 ​​Glass fiber mat 33 PP sheet 34 PET nonwoven fabric

Claims

1. A composite sheet comprising a thermoplastic resin composition (X) and inorganic fibers (Y), The thermoplastic resin composition (X) comprises a thermoplastic resin and a heat-expandable flame retardant. Density is 1.3 g / cm³ ３ The following: A composite sheet in which, when the cross-section is observed, multiple voids with a cross-sectional area of ​​0.01 mm² or more are present, and the average value of the cross-sectional areas of the voids with a cross-sectional area of ​​0.01 mm² or more is between 0.03 mm² and 0.8 mm².

2. The composite sheet according to claim 1, wherein the thickness ratio (thickness after high-temperature test / thickness before high-temperature test) before heating at 1200°C for 15 minutes is 5 times or less.

3. The composite sheet according to claim 1, wherein the surface sheet comprises a nonwoven fabric made of resin fibers.

4. The composite sheet according to claim 1, wherein the thermally expandable flame retardant comprises a phosphorus-based flame retardant.

5. The composite sheet according to claim 1 or 3, wherein the thermoplastic resin constituting the thermoplastic resin composition (X) includes a polyolefin resin.

6. The composite sheet according to claim 1, wherein the thermoplastic resin composition (X) further comprises a dispersant.

7. The composite sheet according to claim 6, wherein the dispersant comprises a copolymer of an α-olefin and an unsaturated carboxylic acid.

8. The composite sheet according to claim 6 or 7, wherein the content of the dispersant is greater than 0 and less than or equal to 25 parts by mass per 100 parts by mass of the thermally expandable flame retardant.

9. The composite sheet according to claim 1 or 3, wherein the inorganic fiber (Y) includes at least one selected from glass fiber, ceramic fiber, metal fiber, and metal oxide fiber.

10. The composite sheet according to claim 1 or 3, obtained by impregnating a mat made of inorganic fibers (Y) with the thermoplastic resin composition (X).

11. A method for producing a composite sheet according to claim 1 or 3, comprising laminating a sheet made of the thermoplastic resin composition (X) onto a mat made of the inorganic fibers (Y), and then heating and melting to impregnate the sheet with the thermoplastic resin composition (X).

12. A method for manufacturing a composite sheet according to claim 11, wherein a mat made of the inorganic fibers (Y) is laminated between two sheets made of the thermoplastic resin composition (X).

13. A molded article obtained by molding the composite sheet described in claim 1 or 3.

14. A molded body according to claim 13 for use in a battery case.