JP2024060487A - Molded body - Google Patents

Abstract

[Problem] To provide a molded article that can retain high flame retardancy and strength after combustion. [Solution] The molded article contains a thermoplastic resin composition (X) and inorganic fibers (Y), and the thermoplastic resin composition (X) contains a thermoplastic resin and a thermally expandable flame retardant, and has a bending strength of 10 kPa or more according to ASTM D-638 when heated in the absence of oxygen at 700°C for 20 minutes. [Selected Figure] None

Description

The present invention relates to a molded body.

In recent years, research and development of electric and hybrid vehicles has been promoted as part of environmental measures, and the development of high-energy density batteries and weight reduction are being actively promoted in order to improve the driving range. Such high-energy density batteries are at risk of catching fire in the event of an accident, so as a safety measure for passengers, the housing material must have high flame retardancy, and therefore, in many cases, metal materials such as iron are used in combination with fire-resistant materials.
However, metal materials have the drawback of being heavy, and when fire-resistant materials are used in combination, issues arise regarding workability and increased costs due to the increased number of parts. Therefore, attempts are being made to use resins, which have the potential to achieve both weight reduction and flame resistance. Currently, in order to create a sustainable society, emphasis is being placed on reducing carbon dioxide emissions and recyclability. Many thermosetting materials have high flame retardancy and are common as composite materials, but in terms of recyclability, thermoplastic resin materials are advantageous.

In addition, China has announced a safety standard called GB 38031-2020 "Safety Requirements for Electric Vehicle Power Batteries," which requires that a warning be issued five minutes before the battery experiences thermal runaway. It is believed that this can be achieved by using housing materials that provide flame protection for at least five minutes after the battery ignites.

To address these issues, for example, Patent Document 1 proposes adding a brominated flame retardant or an antimony oxide compound to a carbon fiber reinforced polypropylene resin, but the additives used therein have a problem in terms of their persistence in living organisms.
In response to this, Patent Document 2 proposes a flame-retardant polyolefin-based composition in which a polyolefin-based resin contains a (poly)phosphate compound, as a technology for making polypropylene-based resin flame-retardant while taking into consideration bioretention.
Moreover, Patent Document 3 proposes a flame-retardant resin composition comprising a polypropylene resin, long glass fibers, and a phosphate compound.

JP 2014-62189 A JP 2013-119575 A JP 2011-88970 A

As described above, conventional technologies have many shortcomings in terms of resinification, which has the potential to achieve both lightweight and flame-resistant properties for high-energy density batteries.
Flame retardants that form an expanded carbonized layer (intemescent layer) are known as highly effective flame retardants. These flame retardants can obtain flame-shielding properties by forming a thermal expansion layer, but the expansion is likely to reduce density, and there is concern about a decrease in strength due to the reduced density. In particular, when used in battery cases, it is expected that the battery will go into thermal runaway and the contents will erupt in a high-temperature environment, so it is required that the molded body after expansion maintains its strength even in a high-temperature environment.

The present invention was made to solve the above problems, and aims to provide a molded body that has high flame retardancy and can retain its strength after combustion.

In order to solve the above problems, the inventors discovered that a molded body containing a thermoplastic resin that contains a thermally expandable flame retardant and inorganic fibers can solve the above problems, and based on this knowledge, they have completed the present invention.

That is, the present invention provides the following [1] to [9].
[1] A molded article comprising a thermoplastic resin composition (X) and inorganic fibers (Y), the thermoplastic resin composition (X) comprising a thermoplastic resin and a thermally expandable flame retardant, the molded article having a bending strength of 10 kPa or more when heated at 700°C for 20 minutes in the absence of oxygen, as measured in accordance with ASTM D-638.
[2] The molded article according to the above [1], in which the thickness ratio (thickness after high-temperature test/thickness before high-temperature test) before and after heating at 700° C. for 20 minutes in an oxygen-free environment is 1.5 times or more.
[3] The molded body according to [1] or [2] above, having a bending strength of 50 MPa or more before heating at 700°C for 20 minutes.
[4] The molded article according to any one of the above [1] to [3], wherein the thermoplastic resin constituting the thermoplastic resin composition (X) is a polyolefin resin.
[5] The molded article according to any one of the above [1] to [4], wherein the thermally expandable flame retardant is a phosphorus-based flame retardant.
[6] The molded article according to any one of the above [1] to [5], wherein the thermoplastic resin composition (X) further contains a dispersant.
[7] The molded article according to the above [6], wherein the dispersant is a copolymer of an α-olefin and an unsaturated carboxylic acid.
[8] The molded body according to [6] or [7] 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 phosphorus-based flame retardant.
[9] The molded body according to any one of the above [1] to [8], wherein the inorganic fiber (Y) is at least one selected from glass fibers, ceramic fibers, metal fibers, and metal oxide fibers.

The present invention provides a molded body that has high flame retardancy and can retain its strength after combustion.

FIG. 2 is a schematic diagram showing a sheet for forming a molded body according to Example 1.

The following describes in detail the embodiments of the present invention, but the following description is merely an example of an embodiment of the present invention, and the present invention is not limited to these contents in any way.

[Molded body]
The molded article of the present invention contains a thermoplastic resin composition (X) and inorganic fibers (Y), and the thermoplastic resin composition (X) contains a thermoplastic resin and a thermally expandable flame retardant.
In addition, the molded article of the present invention has a bending strength of 10 kPa or more according to ASTM D-638 when heated at 700 ° C. for 20 minutes in the absence of oxygen. If the bending strength after heat treatment is 10 kPa or more, the strength can be maintained even if the molded article is burned. For example, when the molded article of the present invention is used in a battery case, even if the battery experiences thermal runaway, the contents can be prevented from erupting in a high-temperature environment. From the above viewpoints, the bending strength after heating is preferably 100 kPa or more, more preferably 150 kPa or more, even more preferably 200 kPa or more, and particularly preferably 250 kPa or more.
Here, "oxygen-free" means that there is no oxygen in the heating atmosphere, and specifically, the oxygen content is 10 ppm by volume or less. The heating atmosphere may be an inert gas, a reducing gas, or a vacuum, but an inert gas such as nitrogen or argon is preferred. In an inert gas atmosphere, no gas-induced reaction occurs, and no special equipment such as a vacuum device is required.
Furthermore, the molded body of the present invention preferably has a thickness ratio (thickness after high-temperature test/thickness before high-temperature test) of 1.5 times or more before and after heating at 700 ° C. for 20 minutes in the absence of oxygen. If the thickness ratio before and after heating is 1.5 times or more, a thermal expansion layer is formed by expansion, and excellent flame insulation properties are obtained. From the above viewpoints, the thickness ratio before and after heating is more preferably 2 times or more, and even more preferably 2.5 times or more. On the other hand, the thickness ratio before and after heating is preferably 10 times or less. If it is 10 times or less, the decrease in density due to expansion is suppressed, and the decrease in strength due to the decrease in density is suppressed. From the above viewpoints, the thickness ratio before and after heating is more preferably 7 times or less, and even more preferably 5 times or less.
In addition, the molded body of the present invention preferably has a bending strength of 50 MPa or more before heating at 700° C. for 20 minutes (before high-temperature test). If the bending strength before the high-temperature test is 50 MPa or more, the bending strength after the high-temperature test also tends to be maintained at a high level. From the above viewpoint, it is more preferable that the bending strength before the high-temperature test is 100 MPa or more.
Each component used in the present invention and the resulting molded article will now be described in detail.

<Thermoplastic resin composition (X)>
The thermoplastic resin composition (X) used in the molded article of the present invention is characterized by containing (a) a thermoplastic resin and (b) a thermally expandable flame retardant.

((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 resin, polycarbonate resin, polyester resin, acrylonitrile styrene resin, ABS resin, polyamide resin, modified polyphenylene oxide, etc. Among these, in the present invention, polyolefin resin is preferred. These may be used alone or in combination of two or more. For example, the (a) thermoplastic resin may be a composite resin of two or more of the above thermoplastic resins.

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 them, the present invention is particularly useful when the thermoplastic resin (a) contains at least a polyolefin resin. In the present invention, the term "polyolefin resin" refers to 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, and particularly preferably 98 mol % or more.

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 the α-olefin-propylene block or random copolymers having 4 or more carbon atoms, examples of the α-olefins 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.

(Melt Flow Rate (MFR))
The melt flow rate (hereinafter sometimes abbreviated as MFR) (230°C, 2.16 kg load) of the thermoplastic resin (a) used in the present invention is preferably 40 to 500 g/10 min. If the MFR is 40 g/10 min or more, for example, no chipping occurs when obtaining a molded body by stamping molding, and the processability does not decrease. Also, if it is 500 g/10 min or less, no burrs are generated in the production of the molded body. 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.

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

<(a-1) Polypropylene Resin>
The thermoplastic resin (a) used in the molded article 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.

(α-Olefin)
Examples of the α-olefin 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 them, from the viewpoint of improving the impact strength of the molded article, ethylene or 1-butene, which have a large effect, are preferred, and ethylene is most preferred.

(Propylene-ethylene random copolymer)
In the case of a random copolymer of propylene and ethylene, it preferably contains 90 to 99.5% by mass, more preferably 92 to 99% by mass, of propylene units and preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass of ethylene units. When the ethylene units are equal to or more than the lower limit, sufficient impact strength of the molded article is obtained, and when the ethylene units are equal to or less than the upper limit, sufficient rigidity is maintained.
The contents of propylene units and ethylene units in the random copolymer of propylene and ethylene can be adjusted by controlling the composition ratio of propylene and ethylene during polymerization of the random copolymer of propylene and ethylene.
The propylene content of the random copolymer of propylene and ethylene is a value measured using a cross fractionation device, FT-IR, or the like, and the measurement conditions and the like may be, for example, those described in JP-A-2008-189893.

(Melt Flow Rate (MFR))
The MFR (230°C, 2.16 kg load) of the polypropylene resin (a-1) used in the present invention is preferably 40 to 500 g/10 min. If the MFR is 40 g/10 min or more, no chipping occurs when obtaining a molded body by stamping molding or the like, and the processability does not decrease. If the MFR is 500 g/10 min or less, no burrs are generated in the production of a sheet used to prepare a molded body. 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-1) polypropylene resin (propylene homopolymer) can be adjusted by controlling the hydrogen concentration during polymerization.
The MFR is a value measured in accordance with JIS K7210.

((a-1) Content of polypropylene resin)
The content of the polypropylene resin (a-1) in the molded article of the present invention is not particularly limited, but is preferably 15 to 80% by mass. When the content of the polypropylene resin is 15% by mass or more, the molding processability is sufficient, and molding of the molded article is easy. On the other hand, when the content is 80% by mass or less, the content of the flame retardant, dispersant, and inorganic fiber is sufficient, and sufficient flame shielding properties are obtained. From the above viewpoints, the content of the polypropylene resin in the molded article is more preferably 35 to 70% by mass, and even more preferably 40 to 60% by mass.

<Modified polyolefin resin>
The molded article 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, and these can be used alone or in combination.
The types of acid-modified polyolefin resins and hydroxy-modified polyolefin resins used as the modified polyolefin resins are not particularly limited, and may be any of the conventionally known resins.

(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 unsaturated carboxylic acids such as maleic acid or maleic anhydride, thereby chemically modifying the polyolefins.
The 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 its derivative component can also be introduced into the polymer chain by random or block copolymerization with a polyolefin monomer.

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 necessary.
Derivatives of unsaturated carboxylic acids include their acid anhydrides, esters, amides, imides, metal salts, etc., and specific examples thereof include maleic anhydride, itaconic anhydride, methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, etc. Of these, maleic anhydride is preferred.

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

(Hydroxy-modified polyolefin resin)
The hydroxy-modified polyolefin resin is a modified polyolefin resin containing a hydroxyl group. The hydroxy-modified polyolefin resin may have a hydroxyl 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.
Examples of preferred hydroxy-modified polyolefin resins include hydroxy-modified polyethylene resins such as low-, medium- or high-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, ethylene-(meth)acrylic acid ester copolymers, and ethylene-vinyl acetate copolymers; 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).

<(b) Thermally Expandable Flame Retardant>
The thermoplastic resin composition (X) forming the molded article of the present invention contains (b) a thermally expandable flame retardant, which is a flame retardant that suppresses combustion of a material by forming a surface intumescent layer that prevents the diffusion of radiant heat from a combustion source and combustion gases and smoke from a combustion product to the outside.
Thermally expandable flame retardants provide flame insulation by forming a thermally expandable layer. However, according to conventional knowledge, the expansion is thought to reduce density, and there is concern about a decrease in strength due to the reduced density.
However, as a result of the investigations of the present inventors, it was found that the presence of a thermally expandable flame retardant in the inorganic fibers constituting the molded body with a thermoplastic resin as a matrix resin can achieve both flame resistance and strength after combustion of the molded body. This is thought to be because the char formed by the thermally expandable flame retardant is fixed to the inorganic fibers as a base material, so that the strength of the inorganic fibers is maintained even after combustion.
From the above viewpoint, among thermally expandable flame retardants, phosphorus-based flame retardants are preferred, and examples thereof include salts of (poly)phosphoric acid and nitrogen compounds (hereinafter also referred to as "compound (b1)"). Specific examples thereof 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, for example, N,N,N',N'-tetramethyldiaminomethane, ethylenediamine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-diethylethylenediamine, amine, 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, acrylguanamine, 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, 2,4-diamino 1,3-hexylene dimelamine, ...

<Other flame retardants>
As described above, the molded article of the present invention is characterized by containing a thermally expandable flame retardant, but 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.
Specifically, for example, phosphorus-based flame retardants other than the above-mentioned thermally expandable flame retardants, bromine-based flame retardants, antimony-based flame retardants, etc. Among them, phosphorus-based flame retardants are preferred from the viewpoint of improving flame-shielding properties.

(Phosphorus-based flame retardant)
The phosphorus-based flame retardant is a phosphorus compound, i.e., a compound containing a phosphorus atom in the molecule, and exerts a flame retardant effect by forming char when the resin composition is burned.
The phosphorus-based flame retardant may be a known one, and examples thereof include (poly)phosphates, (poly)phosphate esters, etc. Here, "(poly)phosphates" refers to phosphates or polyphosphates, and "(poly)phosphate esters" refers to phosphate esters or polyphosphate esters.
The phosphorus-based flame retardant is preferably a solid at 80°C.

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, melamine orthophosphate, calcium phosphate, and magnesium phosphate.
In the above examples, compounds in which melamine or piperazine is replaced with other nitrogen compounds can also be used. These (poly)phosphates may be used alone or in combination of two or more.

Commercially available phosphorus-based flame retardants include Adeka STAB FP-2100J, FP-2200, and FP-2500S (manufactured by ADEKA Corporation).

(Brominated flame retardants)
Examples of bromine-based 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 polybrominated polystyrene include brominated polystyrene, 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.

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

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 environmental standpoint.
The flame retardants may be used alone or in combination of two or more.

((b) Content of thermally expandable flame retardant)
The content of the thermally expandable flame retardant in the molded product of the present invention is not particularly limited, but is preferably in the range of 1 to 30% by mass. When the content is 1% by mass or more, the molded product can be given good flame retardancy and good flame shielding properties can be obtained. On the other hand, when the content of the flame retardant is 30% by mass or less, the thermoplastic resin can be contained in a sufficient content ratio, so that the moldability becomes better. From the above viewpoints, the content of the thermally expandable flame retardant in the molded product is more preferably in the range of 1 to 25% by mass, and even more preferably in the range of 3 to 20% by mass.

<(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, but a polymer dispersant can be suitably used in terms of compatibility with the (a) thermoplastic resin. Preferably, a polymer dispersant capable of dispersing the (b) thermally expandable flame retardant in the (a-1) polypropylene resin can be used. As the polymer dispersant, a polymer dispersant having a functional group is preferred, and from the viewpoint of dispersion stability, a polymer dispersant having a functional group such as a carboxyl group, a phosphoric acid group, a sulfonic acid group, a primary, secondary or tertiary amino group, a quaternary ammonium base, a group derived from a nitrogen-containing heterocycle such as pyridine, pyrimidine or pyrazine is preferred.
In the present invention, a polymer dispersant having a carboxyl group is 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. By using such a dispersant, the dispersibility of the phosphorus-based thermally expandable flame retardant can be improved, and the content of the thermally expandable flame retardant can be reduced.

(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 the 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 the copolymer (c1), the ratio of the α-olefin units to the total amount of the α-olefin units and the unsaturated carboxylic acid units is more preferably 30 mol % or more, and more preferably 70 mol % or less. If the ratio of the α-olefins is equal to or more than the lower limit, the compatibility with the polyolefin resin is better, and if it is equal to or less than the upper limit, the compatibility with the (b) thermally expandable flame retardant is better.

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, it tends to have better compatibility with the thermoplastic resin (a), and if it has 80 or less carbon atoms, it is advantageous in terms of raw material costs. From the above viewpoints, it is even more preferable that the α-olefin has 12 to 70 carbon atoms, and particularly preferably 18 to 60 carbon atoms.

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, imides, etc. of these unsaturated carboxylic acids. Note that "(meth)acrylic acid" refers to acrylic acid or methacrylic acid.
Specific examples of the ester, anhydride or imide of an unsaturated carboxylic acid 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 acid anhydride; 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 anhydrides are preferred from the viewpoint of copolymerization reactivity, and among these, dicarboxylic anhydrides are preferred, with maleic anhydride being particularly preferred, from the viewpoint of compatibility with thermally expandable phosphorus-based flame retardants that are suitable as flame retardants.

The weight average molecular weight of the 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. When the weight average molecular weight of the copolymer (c1) is within the above range, the dispersibility of the flame retardant (b) is more excellent.
The weight average molecular weight of the copolymer (c1) is a value calculated as standard polystyrene by dissolving the copolymer (c1) in tetrahydrofuran (THF) and measuring the result by gel permeation chromatography.

Commercially available copolymers (c1) include Ricorb CE2 (Clariant Japan Co., Ltd.) and Diacalna 30M (Mitsubishi Chemical Co., Ltd.).

The content of the dispersant (c) relative to 100 parts by mass of the thermally expandable flame retardant (b) in the molded article of the present invention is in the range of more than 0 and not more than 25 parts by mass, and preferably in the range of 0.01 to 10 parts by mass.
According to the study by the present inventors, the flame-proofing property of the molded body can be significantly improved by uniformly dispersing the thermally expandable flame retardant in the inorganic fibers constituting the molded body with the thermoplastic resin as the matrix resin. Although the detailed mechanism is unclear, the present inventors speculate as follows. That is, when the thermally expandable flame retardant is uniformly dispersed in the resin between the inorganic fibers, the char formed by the thermally expandable flame retardant coming into contact with the flame is fixed in the gaps between the inorganic fibers. Furthermore, the size of the char formed by expansion upon contact with the flame is restricted by the gaps between the inorganic fibers, so that the size of the char formed becomes uniform. It is believed that the combination of the fixing effect of the char by the inorganic fibers and the uniformity of the char size results in the formation of a dense char, and the flame-proofing property of the molded body is significantly improved. Based on these findings, the present inventors have found that by setting the ratio of the content of the dispersant to the thermally expandable flame retardant to a specific range, the thermally expandable flame retardant can be controlled to be uniformly present in the resin between the inorganic fibers, and the flame-proofing property of the molded body can be significantly improved.
For the above reasons, when the content of the (c) dispersant is more than 0, the dispersibility of the (b) flame retardant is sufficient, and sufficient flame-shielding properties can be imparted to the molded body. On the other hand, when the content is 25 parts by mass or less, the physical properties of the molded body are sufficient. From the same viewpoint, the content of the (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. On the other hand, the upper limit is more 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.

In addition, the ratio of the (c) dispersant to the total of 100 parts by mass of the (a) thermoplastic resin and the (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 parts by mass or less. If the ratio of the (c) dispersant is equal to or more than the lower limit, the (b) thermally expandable flame retardant is better dispersed, and the flame-resistant properties, physical properties, and appearance of the resulting molded body are better. If the ratio of the (c) dispersant is equal to or less than the upper limit, the influence of the (c) dispersant on the flame-resistant properties of the molded body can be further suppressed. In particular, the ratio of the (c) dispersant to the total of 100 parts by mass of the polyolefin resin and the (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, 10 parts by mass or less is preferable, 5.0 parts by mass or less is more preferable, 2.0 parts by mass or less is even more preferable, 1.5 parts by mass or less is even more preferable, and 1.0 parts by mass or less is even more preferable.

For the (Y) inorganic fibers described in detail below, the ratio of the (c) dispersant to 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. If the ratio of the (c) dispersant is equal to or greater than the lower limit, the flame retardancy, physical properties, and appearance of the resulting molded body will be better. If the ratio of the (c) dispersant is equal to or less than the upper limit, the effect of the (c) dispersant on the flame retardancy of the molded body can be further suppressed.

<(Y) Inorganic Fiber>
The molded article of the present invention contains (Y) inorganic fiber. As the (Y) inorganic fiber, various fibers can be used, for example, glass fiber, rock wool, alumina fiber, silica alumina fiber and other metal oxide fibers, potassium titanate fiber, calcium silicate (wollastonite) fiber, ceramic fiber such as ceramic fiber, carbon fiber, metal fiber, etc. These inorganic fibers may be used alone or in combination of two or more.
Of 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 fiber may contain two or more inorganic fibers having different melting temperatures. As a combination of two or more inorganic fibers having different melting temperatures, at least one of the fibers is preferably glass fiber, and the other one or more is preferably one or more inorganic fibers selected from the group consisting of alumina fiber, silica fiber, alkaline earth silicate fiber (biosoluble), and carbon fiber. By containing two or more inorganic fibers having different melting temperatures, it is possible to effectively prevent the deterioration of the flame-shielding function.
The inorganic fibers used in the present invention may be used in combination with a sizing agent or a surface treatment agent, such as compounds having a functional group, such as epoxy compounds, silane compounds, and titanate compounds.

The inorganic fibers preferably have an average fiber diameter of 3 to 25 μm, and an average fiber length of 0.1 mm or more, more preferably 1 mm or more, and even more preferably 5 mm or more.
As for the average fiber diameter and the average fiber length, the preferred ranges 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, and the average fiber diameter can be obtained by, for example, measuring the fiber diameters of 10 randomly selected fibers and calculating the average value. The fiber length can be measured using a ruler, calipers, or the like from an image enlarged by a microscope or the like as necessary, and the average fiber length can be obtained by, for example, measuring the fiber lengths of 10 randomly selected fibers and calculating the average value.

The content of inorganic fibers in the molded article 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 molded article are good. When the content of inorganic fibers is 80% by mass or less, the molded article is easily manufactured and processed. When the content of inorganic fibers is 80% by mass or less, the specific gravity of the molded article is light, and the weight reduction effect as a metal substitute is remarkable.
From the above viewpoints, the content of the (Y) inorganic fiber in the molded product is more preferably 3 to 60 mass %, further preferably 10 to 50 mass %, and particularly preferably 30 to 45 mass %.

(Glass fiber)
One of the inorganic fibers (Y) suitable for the molded article 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 having a short average fiber length (chopped strand), but it is preferable to use a glass fiber having a long average fiber length from the viewpoints of flame retardancy, rigidity, impact resistance, etc.
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 molded article become good. 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 glass fibers, and when using pellets produced by the pultrusion method using glass fibers, the length of the pellets is the fiber length of the glass fibers, which is a maximum of about 20 mm. In addition, in a swirl mat system using long glass fibers, the length of the glass fibers in the roving used for production is the maximum fiber length, which can be as long as 17,000 m (17 km), but when cut to fit the size of the molded product, the cut length is the maximum fiber length.

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 rigidity and impact resistance of the molded article are sufficient, while when the average fiber diameter is 25 μm or less, the strength of the molded article is good. 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.

There are no particular limitations on the material of the glass fiber used in the present invention, and it may be any of alkali-free glass, low-alkali glass, and alkali-containing glass, and any of the various compositions that have been used conventionally as glass fibers can be used.

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

The average fiber diameter of the alumina fibers is preferably in the range of 3 to 25 μm, and it is preferable that the alumina 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 the amount of fibers with a fiber diameter of 3 μm or less is 0.1 mass % or less of the total inorganic fiber mass.
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 repulsive force and toughness of the mat-like inorganic fiber assembly layer will decrease, while if the average fiber diameter is too small, the amount of dust suspended in the air will increase, and the probability of containing inorganic fibers having a fiber diameter of 3 μm or less will increase.
The alumina fibers have an average fiber length of preferably 5 mm or more, more preferably 30 mm or more, and even more preferably 50 mm or more. Also, the average fiber length and average fiber diameter of the alumina fibers are preferably 3.0×10 mm or less, and more preferably 1.0×10 mm or less. When the average fiber length and average fiber diameter of the alumina fibers are within these ranges, the strength and impact resistance of the molded product are good.

(Carbon fiber)
The suitable range for carbon fiber is similar to that for glass fiber.

<Optionally Added Ingredients>
In addition to the above-mentioned components, any additive components may be blended into the molded article of the present invention for the purpose of further improving the effects of the present invention or imparting other effects, within a range that does not significantly impair the effects of the present invention.
Specific examples of the additives include colorants such as pigments, light stabilizers such as hindered amines, ultraviolet absorbers such as benzotriazoles, nucleating agents such as sorbitols, antioxidants such as phenols and phosphorus, antistatic agents such as nonionic surfactants, neutralizing agents such as inorganic compounds, antibacterial and antifungal agents such as thiazoles, flame retardants and flame retardant assistants 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.
These optional components may be used in combination of two or more kinds.

Colorants such as inorganic or organic pigments are effective in imparting or improving the colored appearance, appearance, texture, commercial value, weather resistance, durability, etc. of the molded article 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., yellow lead); 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. In order to achieve a metallic or pearlescent look, aluminum flakes and pearl pigments can be added. Dyes can also be added.

Light stabilizers and ultraviolet absorbers, for example, hindered amine compounds, benzotriazoles, benzophenones, and salicylates, are effective in imparting or improving the weather resistance and durability of the molded article of the present invention and are 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-butane tetracarboxylate; tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)1,2,3,4-butane tetracarboxylate; bis(1,2,2,6,6-pentamethoxy) 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole;2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole;2-hydroxy-4-methoxybenzophenone;2-hydroxy-4-n-octoxybenzophenone; and the like. Examples of the salicylate-based compounds include 4-t-butylphenyl salicylate; 2,4-di-t-butylphenyl 3',5'-di-t-butyl-4'-hydroxybenzoate; and the like.
Here, the method of using the light stabilizer and the ultraviolet absorber in combination is preferable because it has a large effect of improving weather resistance, durability, weather discoloration resistance, and the like.

Antioxidants such as phenol-based, phosphorus-based and sulfur-based antioxidants are effective in imparting or improving the heat resistance, processing stability and heat aging resistance of the molded article of the present invention.
Furthermore, antistatic agents such as nonionic and cationic antistatic agents are effective in imparting and improving the antistatic properties of the molded article of the present invention.

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 the styrene-based elastomer 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, as well as 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 since it is easy to impart appropriate flexibility to the molded article of the present invention and the molded article tends to have excellent impact resistance.

<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 necessary, (b) a thermally expandable flame retardant, and (c) a dispersant. In addition, optional additive components may be further blended. In the thermoplastic resin composition (X), when the thermoplastic resin (a) is (a-1) a polypropylene resin, it may be particularly called a polypropylene resin composition (hereinafter, sometimes referred to as a "PP composition").
The thermoplastic resin composition (X) or the PP composition can be produced by a conventionally known method, and can be produced by blending, mixing, and melt-kneading the above-mentioned components.
The mixing is carried out using a mixer such as a tumbler, a V blender, or a ribbon blender, and the 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, and the materials are melt kneaded and granulated.

<Method of manufacturing a sheet for manufacturing a molded product>
Regarding the sheet for producing the molded article of the present invention, the production method thereof is not particularly limited, but it is preferable to produce it 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. The impregnation method includes a method of applying the thermoplastic composition (X) or the PP composition to the inorganic fiber mat (Y), 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), and the like.
In the present invention, from the viewpoint of impregnation of the resin of the sheet for producing the molded product into the fibers, a method of laminating a thermoplastic resin sheet or a PP sheet on an inorganic fiber mat (Y) and heating and melting it is preferred. In particular, the molded product can be obtained by laminating the inorganic fiber mat between two thermoplastic resin sheets or PP sheets, and then heating and pressing the laminate, followed by 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.

(Inorganic fiber mat (Y))
The form of the inorganic fibers used in the method for producing a sheet for producing a molded product is not particularly limited, and various forms can be used, but it is preferable that the inorganic fibers are formed into a mat or sheet shape.
More specifically, a mat formed from glass fibers (hereinafter referred to as a "glass fiber mat") and a mat formed from metal oxide fibers such as alumina fibers (hereinafter referred to as a "metal oxide mat") are preferred.

The basis weight (mass per unit area) of the inorganic fiber mat is not particularly limited and is appropriately determined depending on the application, but is preferably 300 g/m ² or more, more preferably more than 800 g/m ² , and more preferably more than 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 or less, even more preferably 4000 g/m ² or less, and particularly preferably 3500 g/m ² or less.
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.

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 that make up the inorganic fiber mat are stacked using a folding device. The inorganic fiber mat of the present invention may be composed of multiple inorganic fiber mats bonded together or may be composed of a single material, but is preferably composed of a single material in terms of handling properties and peel strength at the adhesive interface.

(fiberglass 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 preferable because the strength and impact resistance of the sheet for producing a molded product are excellent.

(Metal oxide fiber mat)
The metal oxide fiber mat according to the present invention is a mat that is made of metal oxide fibers such as alumina fibers and that has been subjected to a needling treatment.

In the method of laminating a thermoplastic resin sheet or a PP sheet on an inorganic fiber mat and heating and melting the sheet, the heating temperature is preferably 170 to 300° C. If the heating temperature is 170° C. or higher, the flowability of the polypropylene resin is sufficient, and the inorganic fiber mat can be sufficiently impregnated with the PP composition, resulting in a suitable resin-impregnated sheet. On the other hand, if the heating temperature is 300° C. or lower, the thermoplastic resin composition or the PP composition does not deteriorate.
Furthermore, the pressure applied is preferably 0.1 to 1 MPa. If the pressure applied is 0.1 MPa or more, the inorganic fiber mat can be sufficiently impregnated with the thermoplastic resin composition or the PP composition, and a suitable resin-impregnated sheet can be obtained. On the other hand, if the pressure applied is 1 MPa or less, the thermoplastic resin composition or the PP composition flows, and no burrs are generated.
The cooling temperature is not particularly limited as long as it is equal to or lower than the freezing point of the thermoplastic resin in the thermoplastic resin composition (X) or the PP composition, but if the cooling temperature is equal to or lower than 80° C., the resin-impregnated sheet obtained will not deform when it is taken out. From the above viewpoints, the cooling temperature is preferably from room temperature to 80° C.

The resin-impregnated sheet is heated, pressurized, and cooled to obtain a sheet for use in producing molded articles. This can be done by press molding in a mold equipped with a heating device, or by laminating, which involves passing the sheet through two pairs of rollers equipped with a heating device to apply heat and pressure. Laminating is particularly preferred as it allows for continuous production and has good productivity.

<Thickness of sheet for producing molded body>
The thickness of the sheet for producing the molded product of the present invention is usually 1 to 10 mm, preferably 2 to 5 mm. If the thickness of the sheet is 1 mm or more, the sheet can be easily produced, while if the thickness of the sheet is 10 mm or less, long-term preheating is not required when the sheet is processed by stamping molding or the like, and good moldability can be obtained.

<Molded body>
The molded article of the present invention can be obtained in a desired shape by stamping the above-mentioned sheet in a conventional manner.

(Application)
Examples of applications of the molded article of the present invention include various industrial parts such as automobile parts and electrical and electronic equipment parts. In particular, the molded article of the present invention is suitable for applications requiring excellent strength, rigidity, and electrical conductivity and a good balance of these properties, such as various housings and cases such as battery cases.

[Structure]
The structures made of the molded article of the present invention include battery housings and battery cells.
The structure in the present invention is preferably a battery, and the battery is not particularly limited. For example, secondary batteries such as lithium ion batteries, nickel-hydrogen batteries, lithium-sulfur batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, sodium-sulfur batteries, lead-acid batteries, and air batteries can be mentioned. Among these, lithium ion batteries are preferable, and the battery housing of the present invention is particularly suitable for use in suppressing thermal runaway of lithium ion batteries. That is, the battery housing of the present invention is preferably a battery housing for lithium ion batteries.

[Electric Mobility]
In the present invention, 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).
The above-described battery housing and battery structures having battery cells of the present invention are highly safe and extremely useful for electric mobility using battery modules with high energy density to extend driving distance.

The present invention will be described in detail below using examples, but the present invention is not limited to these examples.
(Evaluation method)
1. Evaluation of flame barrier properties For the sheet-like molded bodies prepared in each Example and Comparative Example, a flame from a burner at 1300°C was applied from one surface, and after 15 minutes, it was evaluated whether the flame penetrated. The distance from the burner nozzle to the sample was 160 mm. The flame surface was set to 1200°C. The flame surface temperature was confirmed with a thermocouple thermometer.

2. Bending strength (before heat test)
Test pieces measuring 100 mm x 25.4 mm were cut out from the sheet-like molded products obtained in the Examples and Comparative Examples. The bending strength of the test pieces was measured using an AUTOGRAPH "AG-10TA" (manufactured by Shimadzu Corporation) at a test speed of 2 mm/min and a span of 50 mm (in accordance with ASTM D-638).
(After heating test)
The test pieces were heat-treated in a nitrogen atmosphere (oxygen-free) at 700° C. for 20 minutes, and the bending strength of the test pieces after heat treatment was measured (unit: kPa).

3. Expansion coefficient The thickness of the test piece after the heating test was measured, and the expansion coefficient was evaluated based on the ratio of the thickness to the thickness before the heating test. The heating test conditions were the same as those in the bending strength measurement.

(Materials used)
1. Polypropylene resin (component a)
"Novatec PP SA06GA" (melt flow rate: 60 g/10 min) manufactured by Japan Polypropylene Corporation was used.

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

3. Dispersant (component c)
α-Olefin/maleic anhydride copolymer (Mitsubishi Chemical Corporation, Diacalna 30M, weight average molecular weight 7,800).

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

Preparation Example 1 (Preparation of PP Composition)
The above 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).

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.

Example 1
A method for producing a resin sheet for forming a laminate of the present invention will be described below with reference to Fig. 1. Fig. 1 shows the layer structure before the glass fiber mat is impregnated with the thermoplastic resin composition.
The pellets of the thermoplastic resin composition (X) granulated in Preparation Example 1 were put into an extruder, melted, and then extruded into a sheet. The extruded sheet-like thermoplastic resin composition (X) (hereinafter referred to as "sheet X"; 11 in FIG. 1) was sandwiched with a glass fiber mat 12 from both sides to obtain a laminate. Next, sheets X (13 in FIG. 1) were laminated on both sides of the laminate, and the laminate was heated and pressed at 230° C. for 4 minutes while applying a pressure of 0.3 MPa using a laminator, and then cooled and solidified to obtain a laminate (thickness: 2.5 mm). The sheet X was impregnated into the glass mat fiber, and an integrated sheet-like molded product was obtained. The results of the evaluation by the above method are shown in Table 1. The thickness ratio before and after the heating test was 2.7 times.

Comparative Example 1
A sheet was obtained in the same manner as in Example 1, except that the pellets of the PP composition granulated in Comparative Preparation Example 1 were used instead of the pellets of the PP composition granulated in Preparation Example 1. The evaluation results are shown in Table 1.
Incidentally, the bending strength after the heating test was too small to be measured, and was therefore indicated as 0 kPa.

As shown in Table 1, it was found that the sheet of Example 1 was not penetrated by flames in the flame-proofing test and had a certain bending strength even after the heating test. On the other hand, the sheet of Comparative Example 1 was penetrated by flames in the flame-proofing test and had a bending strength that was too low to be measured after the heating test.
From the above results, it is clear that the sheet of the present invention has high flame-proofing properties and is capable of retaining its strength after combustion, and that the molded article of the present invention using said sheet similarly has high flame-proofing properties and is capable of retaining its strength after combustion.

As described above, the molded article of the present invention is a molded article that can retain high flame retardancy and strength after combustion, and is therefore useful as a material for various industrial parts that require high safety, such as aircraft, ships, automobile parts, electrical and electronic equipment parts, building materials, etc. In particular, it can be suitably used for various battery housings and cases that have traditionally been made of metal, and is expected to contribute to the safety of automobiles as well as improve energy efficiency and reduce _CO2 emissions by reducing weight.
Furthermore, the molded article of the present invention has excellent flame resistance, and since it is mainly composed of resin, it has excellent processability and is lightweight, so that a structure using the molded article of the present invention is useful as electric mobility.

10: Sheet for forming molded body 11: PP sheet 12: Glass fiber mat 13: PP sheet

Claims (9)

A molded article comprising a thermoplastic resin composition (X) and inorganic fibers (Y),
The thermoplastic resin composition (X) contains a thermoplastic resin and a thermally expandable flame retardant,
A molded article having a bending strength of 10 kPa or more according to ASTM D-638 when heated in the absence of oxygen at 700° C. for 20 minutes. The molded body according to claim 1, in which the thickness ratio (thickness after high-temperature test/thickness before high-temperature test) before and after heating at 700°C for 20 minutes in the absence of oxygen is 1.5 times or more. The molded body according to claim 1, which has a bending strength of 50 MPa or more before being heated at 700°C for 20 minutes. The molded article according to claim 1, wherein the thermoplastic resin constituting the thermoplastic resin composition (X) is a polyolefin resin. The molded article according to claim 1, wherein the thermally expandable flame retardant is a phosphorus-based flame retardant. The molded article according to claim 1, wherein the thermoplastic resin composition (X) further contains a dispersant. The molded article according to claim 6, wherein the dispersant is a copolymer of an α-olefin and an unsaturated carboxylic acid. The molded body according to claim 6 or 7, 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 phosphorus-based flame retardant. The molded article according to claim 1, wherein the inorganic fiber (Y) is at least one selected from the group consisting of glass fiber, ceramic fiber, metal fiber, and metal oxide fiber.