Flame-retardant resin composition and insulation sheet

Abstract

To provide a flame-retardant resin composition having excellent tracking resistance and an insulation sheet.SOLUTION: A flame-retardant resin composition contains a polymer alloy obtained by alloying an aromatic polycarbonate resin, and a compatible resin which has higher tracking resistance than that of the aromatic polycarbonate resin and is compatible with the aromatic polycarbonate resin. An insulation sheet contains the flame-retardant resin composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a flame-retardant resin composition and an insulating sheet. [Background technology]

[0002] Polycarbonate resins have excellent mechanical properties and heat resistance and are widely used in electrical and electronic component materials, automotive component materials, building materials, sheet materials, food container materials, and the like. When used as electrical and electronic component materials, good electrical insulation properties are required. Therefore, by forming polycarbonate resins into sheets, insulating sheets that can be stored in narrow gaps in electronic devices, for example, can be produced. The insulating sheets can insulate areas within electronic devices where short circuits are a concern.

[0003] For example, Patent Document 1 discloses a flame-retardant resin composition containing a polycarbonate resin, a phosphoric acid ester compound, and a fibrous material, and also discloses an insulating sheet formed by molding the flame-retardant resin composition into a sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-030209 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the flame-retardant resin composition described in Patent Document 1 has a problem of low tracking resistance. Because tracking resistance affects the spatial distance and creepage distance required for electrical insulation, there is a demand for improving this property.

[0006] An object of the present invention is to provide a flame-retardant resin composition and an insulating sheet that are excellent in tracking resistance. [Means for solving the problem]

[0007] These objects can be achieved by the present invention as set forth in (1) to (11) below. (1) A flame-retardant resin composition used in the manufacture of an insulating sheet, comprising: A flame-retardant resin composition comprising a polymer alloy obtained by alloying an aromatic polycarbonate resin with a compatible resin that has higher tracking resistance than the aromatic polycarbonate resin and is compatible with the aromatic polycarbonate resin.

[0008] (2) The flame-retardant resin composition according to (1), wherein the compatible resin has an aromatic ring ratio of 90% by mass or less.

[0009] (3) The flame-retardant resin composition according to (1) or (2), wherein the compatible resin is a heat-resistant polycarbonate resin containing bisphenol A carbonate units and bisphenol isophorone carbonate units.

[0010] (4) The flame-retardant resin composition according to (1) or (2), wherein the compatible resin is an aliphatic polycarbonate resin containing a structure in which two tetrahydrofuran rings are condensed.

[0011] (5) The flame-retardant resin composition according to (1) or (2), wherein the compatible resin is a polyamide resin.

[0012] (6) The flame-retardant resin composition according to (1) or (2), wherein the compatible resin is a polyolefin resin. (7) A flame-retardant resin composition according to any one of (1) to (6) above, which contains a flame retardant.

[0013] (8) An insulating sheet comprising the flame-retardant resin composition according to any one of (1) to (7) above.

[0014] (9) having a multilayer structure; The insulating sheet according to (8) above, wherein at least one layer of the multilayer structure contains the flame-retardant resin composition.

[0015] (10) An insulating sheet according to (8) or (9) above, which has a comparative tracking index (CTI), which is an index of tracking resistance measured in accordance with ASTM D3638, of 600 V or more.

[0016] (11) The flame-retardant resin composition contains a flame retardant, An insulating sheet according to any one of (8) to (10) above, wherein the flame retardancy rank determined in accordance with the UL94 standard is V-0 or VTM-0 for a test piece having a thickness of 0.4 mm or more. [Effects of the Invention]

[0017] According to the present invention, a flame-retardant resin composition and an insulating sheet having excellent tracking resistance can be obtained. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a cross-sectional view showing an insulating sheet according to the embodiment. [Figure 2] FIG. 10 is a cross-sectional view showing an insulating sheet according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE INVENTION The flame-retardant resin composition and insulating sheet according to the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings.

[0020] 1. Flame-retardant resin composition First, the flame-retardant resin composition according to the embodiment will be described. A flame-retardant resin composition according to an embodiment is a flame-retardant resin composition used in the manufacture of insulating sheets, and includes a polymer alloy formed by alloying an aromatic polycarbonate resin with a compatible resin. A polymer alloy refers to a single-phase material or a stable multi-phase material formed by mixing multiple polymers, preferably a single-phase material. In this specification, "alloying" refers to the preparation of such a single-phase or multi-phase material by kneading raw materials containing multiple polymers. Aromatic polycarbonate resins are polycarbonate resins containing aromatic ring structures in their main chains. Due to the high proportion of aromatic ring structures, they have excellent heat resistance and impart flame retardancy to resin compositions. Therefore, by alloying such aromatic polycarbonate resins with compatible resins, a flame-retardant resin composition can be obtained that combines the flame retardancy inherent in the aromatic polycarbonate resin with other properties inherent in the compatible resin.

[0021] The compatible resin is a resin having higher tracking resistance than the aromatic polycarbonate resin. Tracking resistance refers to resistance to the phenomenon of a conductive path (tracking) being formed due to discharge occurring on the surface of an insulator. Such tracking resistance can be quantified, for example, by the comparative tracking index (CTI), which is an index of tracking resistance measured in accordance with ASTM D3638. Therefore, the compatible resin is, for example, a resin having a comparative tracking index (CTI) higher than that of the aromatic polycarbonate resin. This allows for the production of a resin composition that has both flame retardancy and tracking resistance.

[0022] 1.1. Aromatic polycarbonate resin (A) The aromatic polycarbonate resin (A) can be obtained by a phosgene method in which various dihydroxydiaryl compounds are reacted with phosgene, a transesterification method in which a dihydroxydiaryl compound is reacted with a carbonate ester such as diphenyl carbonate, a ring-opening polymerization method of a cyclic carbonate compound, an interfacial polycondensation method, etc. Such an aromatic polycarbonate resin (A) imparts excellent heat resistance and flame retardancy derived from the aromatic ring structure to the flame-retardant resin composition.

[0023] Dihydroxydiaryl compounds include, in addition to bisphenol A, bis(hydroxyaryl)alkanes such as bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane, 2,2-bis(4-hydroxyphenyl-3-methylphenyl)propane, and 1,1-bis(4-hydroxy-3-tert-butylphenyl)propane; and bis(hydroxyaryl)cycloalkanes such as 1,1-bis(4-hydroxyphenyl)cyclopentane and 1,1-bis(4-hydroxyphenyl)cyclohexane. dihydroxydiaryl ethers such as 4,4'-dihydroxydiphenyl ether and 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether, dihydroxydiaryl sulfides such as 4,4'-dihydroxydiphenyl sulfide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfide, dihydroxydiaryl sulfoxides such as 4,4'-dihydroxydiphenyl sulfoxide and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone, dihydroxydiaryl sulfones such as 4,4'-dihydroxydiphenyl sulfone and 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfone, etc. These may be used alone or in combination of two or more.

[0024] The aromatic polycarbonate resin (A) particularly includes those having a structural unit represented by the following formula (1).

[0025] [ka] (In formula (1), R 1 and R 2 are independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a halogen atom. m and n are independently an integer of 0 to 4. X is a direct bond, O, S, SO, SO2, CR3 R 4 (R 3 and R 4 are independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and may be the same or different from each other.), an alkylene group having 2 to 10 carbon atoms, a polydimethylsiloxane group, or C(CF3)2.

[0026] The aromatic polycarbonate resin (A) having the structural unit represented by the above formula (1) imparts particularly excellent heat resistance and flame retardancy to the flame-retardant resin composition.

[0027] Of all the structural units constituting the aromatic polycarbonate resin (A), the proportion of the structural units represented by the above formula (1) is preferably 55 mol % or more, more preferably 70 mol % or more, and even more preferably 80 mol % or more.

[0028] In addition, from the viewpoint of ease of acquisition and cost, R 1 and R 2 are each preferably a hydrogen atom, and X is preferably CR 3 R 4 and R 3 and R 4 are preferably each a methyl group or a hydrogen atom.

[0029] The aromatic polycarbonate resin (A) is preferably a polycarbonate resin having structural units derived from bisphenol A (2,2-bis(4-hydroxyphenyl)propane), which can further enhance the flame retardancy and heat resistance of the flame-retardant resin composition.

[0030] The viscosity average molecular weight (M) of the aromatic polycarbonate resin is not particularly limited, but is preferably 5,000 or more and 100,000 or less, more preferably 12,000 or more and 35,000 or less, even more preferably 15,000 or more and 30,000 or less, and particularly preferably 18,000 or more and 28,000 or less.

[0031] The viscosity average molecular weight (M) is calculated from the viscosity (η) of the resin in methylene chloride solution, η = kM α The viscosity is calculated using the formula below. k and α are constants specific to polymers. Viscosity is measured using an Ubbelohde viscometer at 20°C.

[0032] The aromatic polycarbonate resin (A) may also be a blend of a resin with a high viscosity average molecular weight (high viscosity resin) and a resin with a low viscosity average molecular weight (low viscosity resin), thereby obtaining a flame-retardant resin composition with excellent moldability without impairing the heat resistance and flame retardancy of the aromatic polycarbonate resin (A).

[0033] The difference between the viscosity average molecular weight of the high-viscosity resin and the viscosity average molecular weight of the low-viscosity resin is not particularly limited, but is preferably from 3,000 to 20,000, and more preferably from 5,000 to 10,000. This allows for a flame-retardant resin composition with particularly good moldability to be obtained.

[0034] When the amount of the high-viscosity resin is M1 and the amount of the low-viscosity resin is M2, the mass ratio M1 / M2 is preferably 0.5 to 8.0, more preferably 0.8 to 6.0, and even more preferably 0.9 to 5.0, thereby obtaining a flame-retardant resin composition with particularly good moldability.

[0035] The glass transition temperature Tg of the aromatic polycarbonate resin (A) is preferably 130°C or higher and lower than 160°C, and more preferably 140°C or higher and 155°C or lower. When the glass transition temperature Tg of the aromatic polycarbonate resin (A) is within the above range, the solidification rate of the kneaded product can be optimized even when the glass transition temperature Tg of the compatible resin (B) is high. As a result, alloying can be more easily performed.

[0036] 1.2.Compatible resin (B) The compatible resin (B) is a resin that is compatible with the aromatic polycarbonate resin (A). "Compatibility" is synonymous with the aforementioned "alloying" and refers to the formation of a single-phase or stable multiphase material by kneading or other processes with the aromatic polycarbonate resin (A). Specifically, compatibility is considered to exist if a sheet strong enough to withstand its own weight can be produced when extruded into a sheet shape with the aromatic polycarbonate resin (A) using a counter-rotating twin-screw extruder and a T-die. Compatibility can also be evaluated by DSC (differential scanning calorimetry) or visual turbidity. The former method involves comparing the glass transition temperature (Tg) of the polymer alloy measured by DSC with the glass transition temperatures (Tg) of the aromatic polycarbonate resin (A) and the compatible resin (B) homopolymers. The heating rate in the DSC method is 10°C / min. The latter is a method for evaluating compatibility based on the light transmittance of the sheet.

[0037] The proportion of the compatible resin (B) in the polymer alloy is not particularly limited, but is preferably 5% by mass to 80% by mass, more preferably 10% by mass to 75% by mass, even more preferably 20% by mass to 70% by mass, and particularly preferably 40% by mass to 65% by mass. This configuration makes it possible to realize a flame-retardant resin composition that has a good balance between the properties of the aromatic polycarbonate resin (A), such as heat resistance and flame retardancy, and the properties of the compatible resin (B).

[0038] The comparative tracking index CTI of the compatible resin (B) should be higher than the comparative tracking index CTI of the aromatic polycarbonate resin (A), and is preferably 400 V or higher, and more preferably 600 V or higher, thereby obtaining a flame-retardant resin composition with particularly good tracking resistance.

[0039] The comparative tracking index CTI of the compatible resin (B) is preferably at least 50 V higher than the comparative tracking index CTI of the aromatic polycarbonate resin (A), and more preferably at least 100 V higher, thereby providing a flame-retardant resin composition that better balances flame retardancy and tracking resistance.

[0040] The glass transition temperature Tg of the compatible resin (B) is preferably 125°C or higher, and more preferably 130°C or higher and lower than 200°C. This provides heat resistance to the compatible resin (B), making it easier to suppress coloration due to carbonization even if creeping discharge occurs in the insulating sheet. As a result, the occurrence of poor appearance in the insulating sheet and the deterioration of insulating properties due to carbonization can be suppressed.

[0041] Furthermore, the compatible resin (B) preferably has a ratio of aromatic rings of 90% by mass or less, more preferably 70% by mass or less, even more preferably 50% by mass or less, and particularly preferably 30% by mass or less. Such a compatible resin (B) has a relatively high ratio of aliphatic structures. This makes it possible to impart good tracking resistance to the flame-retardant resin composition. This allows for the production of a flame-retardant resin composition that can be used to produce an insulating sheet that is excellent in both flame retardancy and tracking resistance. Furthermore, even if creeping discharge occurs in the insulating sheet, for example, coloration due to carbonization can be easily suppressed. As a result, the occurrence of poor appearance in the insulating sheet and the deterioration of insulating properties due to carbonization can be suppressed.

[0042] Furthermore, the ratio of aromatic rings in the entire polymer alloy is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. Such a polymer alloy has a relatively high ratio of aliphatic structures. This allows the flame-retardant resin composition to have good tracking resistance. This allows for the production of an insulating sheet that is excellent in both flame retardancy and tracking resistance. Furthermore, even if creeping discharge occurs in the insulating sheet, coloration due to carbonization can be easily suppressed. As a result, the occurrence of poor appearance in the insulating sheet and the deterioration of insulating properties due to carbonization can be suppressed.

[0043] The ratio of aromatic rings can be determined as follows: Here, as an example, the ratio of aromatic rings in carbonate units represented by the following formula is calculated.

[0044] [ka]

[0045] The carbonate unit has 16 carbon atoms, 3 oxygen atoms, and 14 hydrogen atoms. Therefore, the molecular weight of the carbonate unit is 254.

[0046] In addition, one aromatic ring has 6 carbon atoms and 4 hydrogen atoms. Therefore, the molecular weight of one aromatic ring is 12 × 6 + 1 × 4 = 76.

[0047] The number of aromatic rings in the carbonate unit is 2. Therefore, the ratio [mass %] of aromatic rings in the carbonate unit is 76×2 / 254×100=59.8.

[0048] Examples of the compatible resin (B) include polyolefin resins, polyamide resins, polyester resins, aliphatic polycarbonate resins, heat-resistant polycarbonate resins, polyarylate resins, polyethylene terephthalate resins, polybutylene terephthalate resins, polylactic acid, styrene copolymers, polyacetal resins, polyphenylene ether resins, polyphenylene sulfide resins, polymethyl methacrylate resins, and cellulose ester resins. The compatible resin (B) may be a combination of one or more of these resins. Among these, polyolefin resins, polyamide resins, aliphatic polycarbonate resins, and heat-resistant polycarbonate resins are preferably used.

[0049] 1.2.1. Polyolefin resin Examples of polyolefin resins include high-density polyethylene resins, polypropylene resins, polybutene resins, ethylene-(meth)acrylic acid copolymers, ethylene-methyl (meth)acrylate copolymers, ethylene-ethyl (meth)acrylate copolymers, ethylene-vinyl acetate copolymers, maleic anhydride-modified polyethylene, carboxylic acid-modified polyethylene, ethylene-propylene copolymers, and ethylene-propylene-diene copolymers.

[0050] Polyolefin resins have superior chemical resistance to various chemicals compared to aromatic polycarbonate resins. Furthermore, polyolefin resins have good tracking resistance due to their hydrocarbon chain structure. Therefore, polyolefin resins contribute to improving the chemical resistance and tracking resistance of flame-retardant resin compositions.

[0051] Of these, polypropylene resin is preferably used, as it particularly improves the chemical resistance and tracking resistance of the flame-retardant resin composition.

[0052] 1.2.2. Polyamide resin Examples of polyamide resins include polycaproamide (polyamide 6), polytetramethylene adipamide (polyamide 46), polyhexamethylene adipamide (polyamide 66), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), polyundecamethylene adipamide (polyamide 116), polyundecane amide (polyamide 11), polydodecanamide (polyamide 12), polytrimethylhexamethylene terephthalamide (polyamide TMHT), polyhexamethylene terephthalamide (polyamide 6T), polyhexamethylene isophthalamide (polyamide 6I), and polyhexamethylene. Examples of the polyisopropyl terephthalamide include polyethylene terephthalate / isophthalamide (polyamide 6T / 6I), polybis(4-aminocyclohexyl)methanedodecamide (polyamide PACM12), polybis(3-methyl-4-aminocyclohexyl)methanedodecamide (polyamide dimethyl PACM12), polymetaxylylene adipamide (polyamide MXD6), polynonamethylene terephthalamide (polyamide 9T), polydecamethylene terephthalamide (polyamide 10T), polyundecamethylene terephthalamide (polyamide 11T), and polyundecamethylene hexahydroterephthalamide (polyamide 11T(H)). These may also be copolymers or mixtures thereof.

[0053] The polyamide resin can be obtained by polymerizing or copolymerizing, for example, nylon salts composed of diamines and dicarboxylic acids as raw materials by known methods such as melt polymerization, solution polymerization, solid-state polymerization, etc. By using a polyamide resin as the compatible resin (B), the tracking resistance of the flame-retardant resin composition can be further improved.

[0054] The diamine may be an aliphatic diamine, but an alicyclic diamine or an aromatic diamine is preferably used, and an alicyclic diamine is more preferably used. By using these, a polyamide resin having a cyclic structure such as an aromatic ring structure or an alicyclic structure can be prepared. Such a polyamide resin contributes to improving the heat resistance of the flame-retardant resin composition. Furthermore, the alicyclic diamine in particular contributes to improving the tracking resistance of the flame-retardant resin composition.

[0055] Examples of alicyclic diamines include 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 1,3-cyclohexanedimethylamine, 1,4-cyclohexanedimethylamine, bis(4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)propane, bis(3-methyl-4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)propane, 5-amino-2,2,4-trimethyl-1-cyclopentanemethylamine, 5-amino-1,3,3-trimethylcyclohexanemethylamine (isophoronediamine), bis(aminopropyl)piperazine, bis(aminoethyl)piperazine, norbornanedimethylamine, and tricyclodecanedimethylamine, and one or more of these may be used.

[0056] Examples of aromatic diamines include m-xylylenediamine and p-xylylenediamine.

[0057] The dicarboxylic acid may be an alicyclic dicarboxylic acid or an aromatic dicarboxylic acid, but an aliphatic dicarboxylic acid is preferably used. This allows the preparation of a polyamide resin having a hydrocarbon chain structure. Such a polyamide resin contributes to improving the tracking resistance of the flame-retardant resin composition.

[0058] Examples of dicarboxylic acids include aliphatic dicarboxylic acids such as adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, octadecanedioic acid, and eicosanedioic acid; alicyclic dicarboxylic acids such as 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, dicyclohexanemethane-4,4'-dicarboxylic acid, and norbornanedicarboxylic acid; and aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid. One or more of these may be used.

[0059] As the compatible resin (B), polyamide 6T, polyamide PACM12, polyamide dimethyl PACM12, polyamide MXD6, polyamide 9T, polyamide 10T, polyamide 11T, or polyamide 11T(H) is preferably used, and polyamide PACM12 or polyamide dimethyl PACM12 is more preferably used. These have both a cyclic structure such as an aromatic ring structure or an alicyclic structure, and an aliphatic structure, and therefore contribute to improving both the heat resistance and tracking resistance of the flame-retardant resin composition. Polyamide PACM12 contains a structural unit represented by the following formula (2).

[0060] [ka]

[0061] The polyamide PACM12 is synthesized from bis(4-aminocyclohexyl)methane (PACM) and dodecanedioic acid. Polyamide dimethyl PACM12 contains a structural unit represented by the following formula (3).

[0062] [ka]

[0063] The polyamide dimethyl PACM12 is synthesized using bis(3-methyl-4-aminocyclohexyl)methane (MACM) and dodecanedioic acid as raw materials.

[0064] 1.2.3. Aliphatic polycarbonate resin Examples of aliphatic polycarbonate resins include those containing an aliphatic carbonate unit having a carbon number of 2 to 12. Specific examples include polyethylene carbonate, polypropylene carbonate, polytrimethylene carbonate, polytetramethylene carbonate, polypentamethylene carbonate, polyhexamethylene carbonate, polyheptamethylene carbonate, polyoctamethylene carbonate, polynonamemethylene carbonate, polydecamethylene carbonate, polyoxydiethylene carbonate, poly-3,6-dioxyoctane carbonate, poly-3,6,9-trioxyundecane carbonate, polyoxydipropylene carbonate, polycyclopentene carbonate, and polycyclohexene carbonate.

[0065] The aliphatic polycarbonate resin may also be a resin containing an aliphatic carbonate unit containing a diol residue represented by the following formula (4).

[0066] [ka] (In formula (4), R 5 ~R 8 are each independently a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group.

[0067] The aliphatic polycarbonate resin preferably contains 30 mol % to 100 mol %, and more preferably 50 mol % to 90 mol %, of all structural units of the aliphatic carbonate unit containing the diol residue represented by the above formula (4).

[0068] The diol residue represented by the above formula (4) has a structure in which two tetrahydrofuran rings are fused. By including such a structure in the structural unit, the glass transition temperature (Tg) of the polymer alloy can be increased. As a result, a flame-retardant resin composition with excellent heat resistance and tracking resistance can be obtained.

[0069] Examples of diols constituting the diol residue represented by the above formula (4) include isosorbide, isomannide, isoidide, etc. These carbohydrate-derived diols are useful in that they are substances that can also be obtained from natural biomass.

[0070] 1.2.4.Heat-resistant polycarbonate resin The compatible resin (B) may be a polycarbonate resin other than an aliphatic polycarbonate resin.

[0071] Other polycarbonate resins include, for example, resins containing carbonate units (bisphenolisophorone carbonate units) represented by the following formula (5). Such polycarbonate resins have higher heat resistance than the aromatic polycarbonate resin (A). Hereinafter, polycarbonate resins containing bisphenolisophorone carbonate units may be referred to as "heat-resistant polycarbonate resins."

[0072] [ka] (In formula (5), R a and R b are each independently an alkyl group having 1 to 12 carbon atoms, and R g is an alkyl group having 1 to 12 carbon atoms, p and q each independently represent an integer of 0 to 4, and t represents an integer of 0 to 10.

[0073] In addition, each R a and R b Preferably, at least one of is positioned meta to the cyclohexylidene bridging group.

[0074] Also, R a and R b are each independently an alkyl group having 1 to 4 carbon atoms, and R g is an alkyl group having 1 to 4 carbon atoms, p and q are each 0 or 1, and t may be 0 to 5.

[0075] Furthermore, R a , R b , and R g are each a methyl group, p and q are each 0 or 1, and t is 0 or 3, preferably 0.

[0076] A specific example of such a heat-resistant polycarbonate resin is a resin containing carbonate units (bisphenol A carbonate units) derived from bisphenol A (2,2-bis(4-hydroxyphenyl)propane) and carbonate units (bisphenol isophorone carbonate units) represented by formula (5). In this case, p and q in the bisphenol isophorone carbonate units are each 0, and each R g is preferably a methyl group, and t is preferably 3. In this case, the bisphenol isophorone carbonate unit is particularly a carbonate unit containing a structure derived from bisphenol TMC (1,1-bis-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane).

[0077] Such bisphenol isophorone carbonate units contain both an aromatic ring structure and an alicyclic structure, and therefore contribute particularly to improving both the heat resistance (flame retardancy) and tracking resistance of the flame-retardant resin composition.

[0078] Of all structural units constituting the heat-resistant polycarbonate resin, the proportion of bisphenol isophorone carbonate units is preferably 30 mol% or more, more preferably 50 mol% or more, and even more preferably 55 mol% or more, which contributes to improving both the heat resistance (flame retardancy) and tracking resistance of the flame-retardant resin composition.

[0079] The glass transition temperature Tg of the heat-resistant polycarbonate resin is preferably higher (preferably by at least 5°C) than the glass transition temperature Tg of the aromatic polycarbonate resin, more preferably 160°C or higher but 200°C or lower, and even more preferably 165°C or higher but lower than 200°C. When the glass transition temperature Tg of the heat-resistant polycarbonate resin is within the above range, the heat resistance of the flame-retardant resin composition can be particularly improved. As a result, even if creeping discharge occurs in the flame-retardant resin composition, coloration due to carbonization can be particularly suppressed, and the occurrence of poor appearance and a decrease in insulation due to carbonization can be particularly suppressed.

[0080] The polymer alloy may contain a resin other than the aromatic polycarbonate resin (A) and the compatible resin (B). In other words, the polymer alloy may be an alloy of three or more resins. Examples of resins that can be contained include the resins listed as the compatible resin (B).

[0081] 1.2.5. Distance between HSP values ​​of aromatic polycarbonate resin and compatible resin The distance between the HSP values ​​of the aromatic polycarbonate resin (A) and the compatible resin (B) is preferably 0 or more and 15 or less, more preferably 0 or more and 10 or less, and even more preferably 0 or more and 7 or less. By selecting the compatible resin (B) so as to satisfy such a distance between the HSP values, a flame-retardant resin composition having excellent homogeneity and further improved flame retardancy and heat resistance can be obtained.

[0082] The HSP value is calculated by multiplying the solubility parameter SP of each substance by the dispersion force term (δ D ), polarity term (δ P ), hydrogen bond term (δH ) and the value of each term is regarded as a coordinate in three-dimensional space. It is also called the Hansen solubility parameter. D ) is a value that represents the square root of the cohesive energy density of a substance, and takes into account the dispersion forces between molecules. P ) is a value that indicates the polarity of a substance and takes into account the polar interactions between molecules. H ) is a value that represents the hydrogen bonding ability of a substance and takes into account hydrogen bonds between molecules.

[0083] The distance between the HSP values ​​of the aromatic polycarbonate resin (A) and the compatible resin (B) can be calculated by the following formula.

[0084] Distance between HSP values ​​= {4×(δ D1 -δ D2 ) 2 +(δ P1 -δ P2 ) 2 +(δ H1 -δ H2 ) 2} 0.5

[0085] In addition, δ in the above formula D1 , δ D2 , δ P1 , δ P2 , δ H1 , δ H2 is as follows:

[0086] δ D1 is the dispersion force term of the aromatic polycarbonate resin (A) δ D2 is the dispersion force term of the compatible resin (B) δ P1 is the polar term of the aromatic polycarbonate resin (A). δ P2 is the polar term of the compatible resin (B) δ H1 is the hydrogen bond term of the aromatic polycarbonate resin (A). δ H2 is the hydrogen bond term of the compatible resin (B)

[0087] 1.3.Flame retardants The flame-retardant resin composition according to the embodiment may contain a flame retardant. By adding a flame retardant, the flame retardancy of the flame-retardant resin composition can be improved.

[0088] Examples of the flame retardant include inorganic phosphorus-based flame retardants such as halogen-based flame retardants, red phosphorus and polyphosphate-based flame retardants such as ammonium polyphosphate, organic phosphorus-based flame retardants such as triaryl phosphate ester compounds, metal hydroxide-based compounds, antimony oxide-based compounds, nitrogen-containing compounds, etc. Furthermore, the flame retardant may be a combination of two or more of these.

[0089] Among these, a phosphorus-based flame retardant or a nitrogen-containing compound is preferably used as the flame retardant, and a nitrogen-containing compound is more preferably used. When the flame retardant contains a nitrogen-containing compound, the flame retardancy of the flame-retardant resin composition can be further improved. Furthermore, since the nitrogen-containing compound does not contain a halogen atom, a so-called halogen-free or fluorine-free flame-retardant resin composition can be realized.

[0090] Examples of the nitrogen-containing compound include compounds having a triazine skeleton. Examples of compounds having a triazine skeleton include melamine, melamine derivatives such as butylmelamine, trimethylolmelamine, hexamethylolmelamine, hexamethoxymethylmelamine, and melamine phosphate, cyanuric acid, cyanuric acid derivatives such as methyl cyanurate, diethyl cyanurate, trimethyl cyanurate, and triethyl cyanurate, isocyanuric acid, isocyanuric acid derivatives such as methyl isocyanurate, N,N'-diethyl isocyanurate, trismethyl isocyanurate, trisethyl isocyanurate, bis(2-carboxyethyl) isocyanurate, 1,3,5-tris(2-carboxyethyl) isocyanurate, and tris(2,3-epoxypropyl) isocyanurate, melamine cyanurate, and melamine isocyanurate. These compounds can be used alone or in combination of two or more.

[0091] Among these, the compound having a triazine skeleton is preferably one or more melamine-based compounds selected from the group consisting of melamine, melamine cyanurate, melamine isocyanurate, and derivatives thereof, and more preferably melamine cyanurate, which can particularly enhance the flame retardancy of the flame-retardant resin composition.

[0092] The amount of flame retardant added to the flame-retardant resin composition is preferably 0.1 to 30 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 3 to 10 parts by mass, per 100 parts by mass of the polymer alloy. By setting the amount of flame retardant added within this range, the effect of enhancing flame retardancy is fully exerted, and side effects such as deterioration of tracking resistance and mechanical properties due to an excess of flame retardant can be suppressed.

[0093] The flame retardant is, for example, in particulate form. In this case, the average particle size of the flame retardant is preferably 0.01 μm or more and 10 μm or less, more preferably 0.05 μm or more and 5 μm or less, and even more preferably 0.2 μm or more and 2 μm or less. When the average particle size of the flame retardant is within the above range, the dispersibility of the flame retardant is particularly good, thereby particularly improving the flame retardancy of the flame-retardant resin composition. The average particle size of the flame retardant is the particle size at which the cumulative total from the small diameter side in the volume-based particle size distribution measured using a laser diffraction particle size distribution analyzer is 50%.

[0094] 1.4.Additives The flame-retardant resin composition according to the embodiment may contain any additive. Examples of the additive include colorants, stabilizers, lubricants, processing aids, antistatic agents, antioxidants, neutralizing agents, UV absorbers, dispersants, thickeners, release agents, fillers, flow improvers, plasticizers, and antibacterial agents. The additive may be one type or two or more types in any combination.

[0095] Among these, examples of coloring materials include organic and inorganic pigments, dyes, and the like. The color of the coloring material is not particularly limited, but is preferably black. Specific examples of black coloring materials include carbon black, titanium black, iron oxide, and graphite, with carbon black being preferred. The coloring materials may be used alone or in combination of two or more different types.

[0096] The average particle size of the coloring material is not particularly limited, but is preferably 3 nm or more and 500 nm or less.

[0097] The total amount of additives added is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 0.3 parts by mass or more and 10 parts by mass or less, and even more preferably 0.5 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the polymer alloy.

[0098] 1.5. Properties of Resin Composition Next, the properties of the flame-retardant resin composition according to the embodiment will be described.

[0099] 1.5.1. Tracking resistance The tracking resistance of the flame-retardant resin composition according to the embodiment can be quantified by the comparative tracking index CTI, which is an index of tracking resistance measured in accordance with ASTM D3638.

[0100] The comparative tracking index CTI (CTI value) of the flame-retardant resin composition according to the embodiment is preferably 600 V or more. If the CTI value is within the above range, the rank PLC, which indicates tracking resistance, will be the highest rank of 0. Therefore, it can be said that a flame-retardant resin composition having a CTI value within the above range has particularly good tracking resistance.

[0101] The measurement method specified in ASTM D3638 measures the CTI value using a 0.1% by mass aqueous solution of ammonium chloride and a platinum electrode. More specifically, the ammonium chloride aqueous solution is dropped a specified number of times (50 drops) and the voltage at which none of the test pieces (n=5) breaks down is determined, and this is taken as the CTI value.

[0102] The test piece used is a sheet having a thickness of 3 mm or more obtained by extrusion molding of the flame-retardant resin composition, but the test piece may also be one in which a plurality of sheets are stacked.

[0103] The comparative tracking index CTI of the compatible resin (B) and the comparative tracking index CTI of the aromatic polycarbonate resin (A) are measured in the same manner as above. In this case, the test specimens used are sheets of 3 mm or more in thickness obtained by extrusion molding of these resins.

[0104] 1.5.2.Flame retardancy The flame retardancy of the flame retardant resin composition according to the embodiment can be quantified by the flame retardancy rank determined in accordance with the UL94 standard (rank determined by the UL94V test or UL94VTM test).

[0105] The flame retardancy of the flame-retardant resin composition according to the embodiment is preferably such that the UL94V test rank is V-0 for a test piece having a thickness of 0.4 mm or more, or the UL94VTM test rank is VTM-0 for a test piece having a thickness of 0.4 mm or more.

[0106] A flame-retardant resin composition that satisfies such a judgment rank satisfies the highest rank in each test, and therefore can be said to have particularly good flame retardancy.

[0107] In the UL94V test, a vertical combustion test is performed using test pieces measuring 125±5mm x 13.0±0.5mm.

[0108] The UL94VTM test is performed when the test specimen is too thin to perform the UL94V test. The UL94VTM test is a vertical flame test using a test specimen measuring 200mm x 50mm. The test specimen is a sheet obtained by extrusion molding a flame-retardant resin composition.

[0109] 1.5.3.Breakdown voltage The breakdown voltage of the insulating sheet according to the embodiment is a breakdown voltage measured in accordance with the standard test method for breakdown voltage specified in ASTM D149.

[0110] The breakdown voltage of the insulating sheet according to the embodiment is preferably 15 kV / mm or more, more preferably 18 kV / mm to 300 kV / mm, and even more preferably 20 kV / mm to 200 kV / mm. An insulating sheet 1 satisfying such a breakdown voltage contributes to ensuring sufficient insulation even with a short insulation clearance. This contributes to reducing dead space in spaces where components to which high voltages are applied are housed, thereby enabling the miniaturization of electronic devices. While the breakdown voltage may exceed the upper limit, it is preferable that the breakdown voltage be equal to or less than the upper limit in order to minimize individual variations.

[0111] 1.6.Method for producing flame-retardant resin composition Next, an example of a method for producing a flame-retardant resin composition will be described. First, the raw materials are premixed and melted and kneaded using a batch kneader, twin-screw extruder, or the like. This mechanically stirs the raw materials, resulting in a kneaded product containing a polymer alloy. The kneading and melting conditions are appropriately set depending on the types and blending ratios of the raw materials, and examples include a temperature of 200 to 250°C, a screw rotation speed of 300 to 1000 rpm, and a kneading time of about 3 to 20 minutes. Next, the kneaded product is pelletized to prepare pellets of the flame-retardant resin composition.

[0112] Furthermore, a compatibilizer may be added to the raw materials as needed, which can further enhance the compatibility between the aromatic polycarbonate resin (A) and the compatible resin (B).

[0113] The amount of the compatibilizer added is preferably 2 parts by mass or more and 30 parts by mass or less, and more preferably 5 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the flame-retardant resin composition.

[0114] The flame-retardant resin composition may be in the form of, for example, pellets, tablets, flakes, powder, granules, fibers, liquid, or the like.

[0115] 2.Insulation sheet Next, an insulating sheet according to an embodiment will be described. FIG. 1 is a cross-sectional view showing an insulating sheet 1 according to an embodiment.

[0116] 1 is produced using the flame-retardant resin composition according to the embodiment. Examples of methods for producing the insulating sheet 1 include calendaring, extrusion, pressing, and casting.

[0117] An example of a method for producing the insulating sheet 1 is described below. First, the flame-retardant resin composition according to the embodiment is charged into a counter-rotating twin-screw extruder. Then, it is extruded into a sheet using a T-die or the like. In this way, the insulating sheet 1 is obtained.

[0118] The thickness of the insulating sheet 1 is not particularly limited, but is preferably 10 μm or more and 1500 μm or less, more preferably 50 μm or more and 1200 μm or less, and even more preferably 100 μm or more and 1000 μm or less. This results in an insulating sheet 1 with excellent flame retardancy, tracking resistance, and insulation. If the thickness of the insulating sheet 1 is below the lower limit, the flame retardancy, tracking resistance, and insulation may be reduced. On the other hand, the thickness of the insulating sheet 1 may exceed the upper limit, but in that case, the insulating sheet 1 may be too thick, reducing flexibility and making it difficult to handle, and reducing heat dissipation and shape accuracy during molding.

[0119] FIG. 2 is a cross-sectional view showing an insulating sheet 2 according to a modified example of the embodiment. The insulating sheet 2 shown in Fig. 2 has a multilayer structure formed by laminating two insulating sheets 1. At least one layer of the multilayer structure contains a flame-retardant resin composition. Preferably, all layers of the multilayer structure contain the flame-retardant resin composition.

[0120] With this configuration, an insulating sheet 2 can be obtained that has the effects of a single-layer insulating sheet 1 as well as the effects of a multilayer structure. One of the effects of a multilayer structure is improved pinhole resistance. Improved pinhole resistance results in an insulating sheet 2 with even better insulation, flame retardancy, and tracking resistance. The thickness of the insulating sheet 2 is the same as that of the insulating sheet 1. The multilayer structure may also include any sheet other than the insulating sheet 1. In this case, the pinhole resistance can still be improved.

[0121] The obtained insulating sheets 1 and 2 are placed in areas where insulation is required in, for example, electrical or electronic devices. The insulating sheets 1 and 2 have good flame retardancy and tracking resistance, and also have a sufficiently high breakdown voltage. This allows the insulating sheets 1 and 2 to be placed close to electrodes, etc., which has the effect of shortening the insulation spatial distance. As a result, when a circuit board, etc. is housed inside an electrical or electronic device, the volume of the space can be reduced, making it easier to miniaturize the device.

[0122] The obtained insulating sheets 1 and 2 can also be subjected to secondary processing such as thermoforming. Thermoforming generally refers to heating and softening a plastic sheet and then pressing it against a desired mold to form it. Examples of thermoforming include vacuum forming, in which air in the gap between the mold and the material is removed and the material is pressed into close contact with the mold using atmospheric pressure; pressure forming, in which compressed air at or above atmospheric pressure is used for forming; and vacuum pressure forming, which uses a combination of vacuum and pressure. The thermoformability of insulating sheets 1 and 2 allows insulating sheets to be formed into any desired uneven shape.

[0123] 3. Effects of the above embodiment The flame-retardant resin composition according to the embodiment is a flame-retardant resin composition used in the production of insulating sheets 1 and 2, and includes a polymer alloy obtained by alloying an aromatic polycarbonate resin (A) with a compatible resin (B) that has higher tracking resistance than the aromatic polycarbonate resin (A) and is compatible with the aromatic polycarbonate resin (A).

[0124] According to this configuration, a flame-retardant resin composition can be obtained that has both the flame retardancy derived from the aromatic polycarbonate resin (A) and the tracking resistance derived from the compatible resin (B).

[0125] Furthermore, the compatible resin (B) preferably has an aromatic ring ratio of 90 mass % or less. According to this configuration, the compatible resin (B) has a relatively high ratio of aliphatic structures. This allows the flame-retardant resin composition to have good tracking resistance. This allows for a flame-retardant resin composition with better flame retardancy and tracking resistance. Furthermore, even if creeping discharge occurs in the flame-retardant resin composition, discoloration due to carbonization can be easily suppressed. As a result, the occurrence of poor appearance and deterioration of insulating properties due to carbonization in the insulating sheets 1 and 2 can be suppressed.

[0126] The compatible resin (B) may also be a heat-resistant polycarbonate resin containing bisphenol A carbonate units and bisphenol isophorone carbonate units.

[0127] According to this configuration, since the bisphenol isophorone carbonate unit contains both an aromatic ring structure and an alicyclic structure, the flame-retardant resin composition can be particularly improved in both heat resistance (flame retardancy) and tracking resistance.

[0128] The compatible resin (B) may also be an aliphatic polycarbonate resin containing a structure formed by two condensed tetrahydrofuran rings.

[0129] According to this configuration, the glass transition temperature Tg of the polymer alloy can be increased, and therefore a flame-retardant resin composition having excellent heat resistance and tracking resistance can be obtained.

[0130] The compatible resin (B) may also be a polyamide resin. According to this configuration, a flame-retardant resin composition having particularly high tracking resistance can be obtained.

[0131] The compatible resin (B) may also be a polyolefin resin. According to this configuration, a flame-retardant resin composition having particularly high chemical resistance and tracking resistance can be obtained.

[0132] The flame-retardant resin composition according to the embodiment preferably contains a flame retardant. According to this configuration, the flame retardancy of the flame retardant resin composition can be improved.

[0133] Moreover, the insulating sheets 1 and 2 according to the above-described embodiments contain the flame-retardant resin composition according to the above-described embodiments.

[0134] With this configuration, the insulating sheets 1 and 2 have good flame retardancy and tracking resistance.

[0135] The insulating sheet 2 according to the embodiment may have a multi-layer structure, in which case at least one layer of the multi-layer structure contains a flame-retardant resin composition.

[0136] This configuration provides an insulating sheet 2 that combines the effects of a multilayer structure with the effects of a single-layer insulating sheet 1. One of the effects of a multilayer structure is improved pinhole resistance. Improved pinhole resistance results in an insulating sheet 2 with improved insulation, flame retardancy, and tracking resistance.

[0137] Furthermore, the insulating sheets 1 and 2 according to the above-described embodiments have a comparative tracking index CTI, which is an index of tracking resistance measured in accordance with ASTM D3638, of 600 V or more.

[0138] With this configuration, the insulating sheets 1 and 2 have particularly good tracking resistance.

[0139] The flame-retardant resin composition may contain a flame retardant. The insulating sheets 1 and 2 according to the above embodiments have a flame retardancy rating of V-0 or VTM-0 when tested in accordance with the UL94 standard using a test piece with a thickness of 0.4 mm or more. With this configuration, the insulating sheets 1 and 2 have particularly good flame retardancy.

[0140] Although the flame-retardant resin composition and insulating sheet of the present invention have been described above, the present invention is not limited to the above-described embodiments.

[0141] For example, the flame-retardant resin composition of the present invention may contain additives other than the additives described in the above embodiment.

[0142] Furthermore, the insulating sheet of the present invention may have a layer having any desired function added to the layer structure described in the above embodiment, such as an adhesive layer, a bonding layer, a protective layer, or a release layer. [Example]

[0143] Next, specific examples of the present invention will be described, but the present invention is not limited to the descriptions of these examples.

[0144] 4. Preparation of flame-retardant resin composition and insulating sheet A pellet-shaped flame-retardant resin composition was prepared by melting and kneading the materials shown in Table 1 using a twin-screw extruder. The produced flame-retardant resin composition was extruded into a sheet using a counter-rotating twin-screw extruder and a T-die, etc., to prepare insulating sheets with the layer structures and thicknesses shown in Tables 2 to 5.

[0145] Table 1 shows the attributes of each material, such as the compound name, viscosity average molecular weight, tracking resistance (CTI value), glass transition temperature, average particle size, etc.

[0146] The compatible resin b1 shown in Table 1 is a heat-resistant polycarbonate resin derived from bisphenol A and bisphenol TMC. The content of structural units derived from bisphenol TMC in the compatible resin b1 is 60 mol %.

[0147] Furthermore, the compatible resin b2 shown in Table 1 is an aliphatic polycarbonate resin containing 60 mol % of carbonate units containing the diol residue represented by the formula (4).

[0148] [Table 1]

[0149] 5. Evaluation of insulation sheets Next, the prepared insulating sheets were evaluated for the following items.

[0150] 5.1.Flame retardancy The insulating sheets of each example and each comparative example were tested in accordance with the UL94 standard and ranked for flame retardancy. The thickness of the test specimen was the same as the thickness of one layer shown in Tables 2 to 5. The results were evaluated in accordance with the following evaluation criteria. The evaluation results are shown in Tables 2 to 5.

[0151] A: Flame retardancy rating is V-0 or VTM-0 B: Flame retardancy rating is V-1 or V-2, or VTM-1 or VTM-2 C: Flame retardancy rating is less than V-2 or VTM-2

[0152] 5.2. Tracking resistance The CTI values ​​of the insulating sheets of each example and each comparative example were measured by the above-mentioned tracking resistance evaluation test. The test pieces used were 3 mm or more thick, each made by stacking sheets with a single layer thickness shown in Tables 2 to 5. The measured CTI values ​​were evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 2 to 5.

[0153] A: The CTI value is 600V or more (rank is PLC0) B: The CTI value is 400V or more and less than 600V (rank is PLC1) C: The CTI value is less than 400V (rank is PLC2 or lower)

[0154] 5.3.Carbonization due to tracking For the insulating sheets of each example and each comparative example, the above-mentioned tracking resistance evaluation test was carried out, and then the test site was visually observed. The observation results were then evaluated in accordance with the following evaluation criteria. The evaluation results are shown in Tables 2 to 5.

[0155] A: Little discoloration due to carbonization (good appearance) B: There is a little bit of coloring due to carbonization (appearance is a little poor) C: A lot of discoloration due to carbonization (poor appearance)

[0156] 5.4. Processability The insulating sheets of each of the examples and comparative examples were subjected to bending processing as described below, and the appearance of the processed result was evaluated to evaluate the processability of the insulating sheets.

[0157] [1] Cut the insulating sheet into roughly square test pieces measuring 15 mm ± 1 mm in the MD direction and 15 mm ± 1 mm in the TD direction. [2] The test piece is bent in the center, a 3 kg weight is placed on it, and after leaving it for 1 minute, the weight is removed. [3] Open the test piece and visually observe the condition of the bent part and record it. [4] With the test piece open, place a 3 kg weight on it, leave it for 1 minute, and then remove the weight. [5] Visually inspect the condition of the bent part and record it. [6] Repeat steps [2] to [5] above and count the number of repetitions until cracks or holes appear in the folded part. [7] The number of repetitions was evaluated against the following evaluation criteria to evaluate the processability of the insulating sheet. The evaluation results are shown in Tables 2 to 5.

[0158] A: No cracks or holes were observed even after 10 or more repeated tests. B: Either cracks or holes occurred after 5 to 9 cycles C: Either cracks or holes occurred after 4 or fewer cycles

[0159] In Tables 2 to 5, examples corresponding to the present invention are designated as "Examples," and examples not corresponding to the present invention are designated as "Comparative Examples."

[0160] [Table 2]

[0161] [Table 3]

[0162] [Table 4]

[0163] [Table 5]

[0164] From the results shown in Tables 2 to 5, the following was observed. The insulating sheets of the examples, which contained a polymer alloy having an aromatic polycarbonate resin (A) and a compatible resin (B), had better flame retardancy and tracking resistance than the insulating sheets of the comparative examples.

[0165] - It was found that the flame retardancy was particularly improved when polycarbonate resin was used as the compatible resin (B).

[0166] It was found that when a resin with a low ratio of aromatic rings is used as the compatible resin (B) (compatible resins b3 and b4), or when a resin with a high glass transition temperature (compatible resin b1) is used, carbonization due to tracking can be suppressed.

[0167] Although not shown in Tables 2 to 5, it was also found that a two-layer structure provided better pinhole resistance than a single-layer structure. [Explanation of symbols]

[0168] 1 Insulation sheet 2 Insulation sheet

Claims

1. A flame-retardant resin composition used in the production of an insulating sheet, comprising: A flame-retardant resin composition comprising a polymer alloy obtained by alloying an aromatic polycarbonate resin with a compatible resin that has higher tracking resistance than the aromatic polycarbonate resin and is compatible with the aromatic polycarbonate resin.

2. The flame-retardant resin composition according to claim 1 , wherein the compatible resin has an aromatic ring ratio of 90% by mass or less.

3. 3. The flame-retardant resin composition according to claim 1, wherein the compatible resin is a heat-resistant polycarbonate resin containing bisphenol A carbonate units and bisphenol isophorone carbonate units.

4. 3. The flame-retardant resin composition according to claim 1, wherein the compatible resin is an aliphatic polycarbonate resin containing a structure in which two tetrahydrofuran rings are condensed.

5. 3. The flame-retardant resin composition according to claim 1, wherein the compatible resin is a polyamide resin.

6. 3. The flame-retardant resin composition according to claim 1, wherein the compatible resin is a polyolefin resin.

7. The flame-retardant resin composition according to claim 1 or 2, further comprising a flame retardant.

8. An insulating sheet comprising the flame-retardant resin composition according to claim 1 or 2.

9. It has a multilayer structure, The insulating sheet according to claim 8 , wherein at least one layer of the multilayer structure contains the flame-retardant resin composition.

10. 9. The insulating sheet according to claim 8, wherein a comparative tracking index (CTI), which is an index of tracking resistance, measured in accordance with ASTM D3638 is 600 V or more.

11. The flame-retardant resin composition contains a flame retardant, 9. The insulating sheet according to claim 8, wherein the flame retardancy rank determined in accordance with the UL94 standard is V-0 or VTM-0 for a test piece having a thickness of 0.4 mm or more.

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