Battery box

Abstract

A battery box according to the present invention includes a battery cover, a battery tray, and a sealing material that is provided in a proximity region in which the battery cover and the battery tray are close to each other and closes a gap between the battery cover and the battery tray. At least one of the battery cover and the battery tray is a fiber-reinforced plastic that includes discontinuous reinforcing fibers and a thermoplastic resin.　The battery box satisfies expression (1).　Expression (1): t1×E>t1+t2. In expression (1), t1 is the thickness of the fiber-reinforced plastic in the proximity region, t2 is the clearance between the battery cover and the battery tray in the proximity region, and E is the expansion coefficient of the thickness of the fiber-reinforced plastic 600 seconds after the surface of the fiber-reinforced plastic is brought into contact with the flame of a burner such that the flame front is at 950°C–1000°C relative to the thickness of the fiber-reinforced plastic before contact with the flame.

Description

Battery box

[0001] The present invention relates to a battery box in which at least one of the battery cover or battery tray is made of fiber-reinforced plastic comprising discontinuous reinforcing fibers and thermoplastic resin.

[0002] Fiber-reinforced plastics, which use reinforcing fibers as a reinforcing material, have high tensile strength and tensile modulus, and a low coefficient of linear expansion, resulting in excellent dimensional stability. Furthermore, they possess superior heat resistance, chemical resistance, fatigue resistance, and abrasion resistance. For these reasons, fiber-reinforced plastics using reinforcing fibers are widely applied in automotive, sports and leisure, aerospace, and general industrial applications.

[0003] The invention described in Patent Document 1 relates to a stampable sheet having high flame-retardant and heat-insulating properties. It comprises a thermoplastic resin composition (X) and inorganic fibers (Y), and in particular, by including a thermoplastic resin and a phosphorus-based flame retardant, it has two or more layers with different expansion ratios when heated at 1200°C for 5 minutes. The layer structure, which combines short inorganic fibers and long inorganic fibers, exhibits excellent performance.

[0004] The invention described in Patent Document 2 also relates to a stampable sheet with high flame-retardant and heat-insulating properties. It comprises a thermoplastic resin composition (X) and inorganic fibers (Y), and in particular, by including a thermoplastic resin and a phosphorus-based flame retardant, it has the characteristic of expanding by 300% or more when heated at 1200°C for 5 minutes.

[0005] Patent Document 3 describes a stampable sheet and a stampable sheet molded product that are excellent in flame retardancy and are produced by a papermaking method.

[0006] Patent Document 4 states that the amount of work per unit area in a tensile test using a 25 mm wide test piece is 1 × 10⁻¹⁶. －３ ~30 x 10 －３ [(N・mm) / (g / m ２ A carbon fiber composite material is described, in which a carbon fiber sheet is used as a reinforcing material and a thermoplastic resin is used as the matrix resin.

[0007] The invention described in Patent Document 5 relates to a vehicle battery case. It comprises a battery tray having a bottom wall on which the battery is placed and a circumferential side wall surrounding it, and a battery cover that covers the tray. A groove is formed on the upper surface of the circumferential side wall of the battery tray, and a sealing member is housed therein. The sealing member is held in place by fixing the battery tray and the battery cover together, ensuring airtightness. Furthermore, the battery cover has a projection that presses against the sealing member, and a frame-shaped frame is provided on the outside of the circumferential side wall.

[0008] Japanese Patent Publication No. 2024-60541, Japanese Patent Publication No. 2024-60542, Japanese Patent Publication No. 11-49869, Japanese Patent Publication No. WO2013 / 179891, Japanese Patent Publication No. 2011-194982

[0009] However, the stampable sheet invention described in Patent Documents 1 and 2 does not consider the configuration of the battery box.

[0010] The invention described in Patent Document 3 is manufactured using a papermaking method, resulting in excessively high springback during molding and poor moldability. Furthermore, no consideration has been given to its use as a battery box.

[0011] The invention described in Patent Document 4 does not consider the flame retardant properties of the battery box at all. Furthermore, because the work rate is increased by increasing the single-fiber ratio, the springback rate becomes too large, resulting in extremely poor moldability.

[0012] The invention described in Patent Document 5 does not consider what happens when the sealing member is exposed to high temperatures.

[0013] Therefore, the present invention provides a battery box in which at least one of the battery cover or battery tray is made of fiber-reinforced plastic, and the sealing structure of the battery cover and battery tray is devised, thereby suppressing deterioration of the sealing material even when the battery box is exposed to flames and the inside of the battery box becomes hot.

[0014] To solve the above problems, the present invention provides the following means: 1. A battery box having a battery cover, a battery tray, and a sealing material disposed in a proximity region where the battery cover and the battery tray are in close proximity and in contact with the battery cover and the battery tray, wherein at least one of the battery cover and the battery tray is a fiber-reinforced plastic containing discontinuous reinforcing fibers and a thermoplastic resin, and the following formula (1) is satisfied: Formula (1): t1 × E > ​​t1 + t2 In Formula (1), t1 is the thickness of the fiber-reinforced plastic in the proximity region; t2 is the clearance between the battery cover and the battery tray in the proximity region; E is the expansion rate of the thickness of the fiber-reinforced plastic after 600 seconds of being exposed to flame from a burner such that the flame surface temperature is between 950°C and 1000°C, relative to the thickness of the fiber-reinforced plastic before exposure to flame. 2. 1. The battery box according to claim 1, wherein the battery cover has a first flange constituting the proximity region, the battery tray has a second flange constituting the proximity region, and the sealing material is sandwiched between the first flange and the second flange. 3. The battery box according to claim 1 or 2, wherein when the battery box is heated, the fiber-reinforced plastic expands in the proximity region. 4. The battery box according to any one of claims 1 to 3, wherein when the battery box is heated, the expansion of the fiber-reinforced plastic seals the gap between the battery cover and the battery tray. 5. The battery box according to any one of claims 1 to 4, wherein the springback rate of the fiber-reinforced plastic is 1.05 or more and 8.0 or less. 6. The battery box according to any one of claims 1 to 5, wherein the weight-average fiber length of the discontinuous reinforcing fibers is 1 mm or more and 100 mm or less. 7. The aforementioned fiber-reinforced plastic contains 1 to 50 parts by mass of a flame retardant per 100 parts by mass of thermoplastic resin, and the battery box according to any one of 1 to 6 satisfies the following conditions (a) and (b).(a) The tensile strength retention rate shown by formula (a1) is more than 0.03%. Formula (a1) Tensile strength retention rate (%) = (Tensile strength B after combustion ÷ Tensile strength A before combustion) × 100 (b) The work per unit area in the tensile test of the test piece after the combustion test with a width of 25 mm is 0.1×10. －３ [(N·mm) / (g / m ２ )] or more and 300×10 －３ [(N·mm) / (g / m ２ )] or less, and the maximum load per unit area is 1.1×10 －３ [N / (g / m ２ )] or more. 8. The fiber reinforced plastic has a maximum load per unit area in the range of more than 0% and less than 5% strain in the tensile test of the test piece after the combustion test with a width of 25 mm, for the battery box according to item 7 above. 9. The fiber reinforced plastic satisfies the following (c), for the battery box according to any one of items 7 or 8 above. (c) In the tensile test of the test piece after the combustion test with a width of 25 mm, the average change rate of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% is 0.05×10 －３ [N / (g / m ２ )] or more and 300×10 －３ [N / (g / m ２ )] less. 10. The fiber reinforced plastic satisfies the following (c0), for the battery box according to any one of items 7 or 8 above. (c0) In the tensile test of the test piece after the combustion test with a width of 25 mm, the change amount of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% is 0.005×10 －３ [N / (g / m ２ )] or more and 30×10 －３ [N / (g / m ２ )] less. 11. The fiber reinforced plastic satisfies the following (d), for the battery box according to any one of items 7 to 10 above. (d) In the tensile test of the test piece after the combustion test with a width of 25 mm, the average change rate of the load [N / (g / m ２ )] at a strain of 0.5% to 3% is -3.0×10 －３ [N / (g / m ２)] Above - 0.005 × 10 －３ [N / (g / m) ２ )] is within the following range. 12. The fiber-reinforced plastic is a battery box according to any one of 7 to 10 above, satisfying (d0) below. (d0) In a tensile test of a 25 mm wide test piece after a combustion test, the load at strains from 0.5% to 3% [N / (g / m ２ The average rate of change of ) ] is -7.5 × 10 －３ [N / (g / m) ２ ) ] Above - 0.0125 × 10 －３ [N / (g / m) ２ ) ] The range is as follows:

[0015] In the battery box of the present invention, a sealing material is placed in the area adjacent to the battery cover and the battery tray. When the battery box is heated, the fiber-reinforced plastic satisfies formula (1), so the fiber-reinforced plastic expands and can close the gap between the battery cover and the battery tray, thereby preventing the sealing material from being exposed to high temperatures.

[0016] Cross-sectional view showing the battery box of this embodiment. Enlarged view of part II in Figure 1. An example of a graph showing the load-strain curve in a tensile test of a test piece of Reference Example 1. An example of a graph showing the load-strain curve in a tensile test of Reference Example 5. A schematic diagram showing how the battery cover expands due to a fire that occurs inside the battery box, and how the expanded portion 14 of the fiber-reinforced plastic seals the part inside the sealing material 30. A schematic diagram of the battery box 101 of Modification 1. A schematic diagram showing the state in which a fire has occurred inside the battery box 101. A schematic diagram of the battery box 201 of Modification 2. A schematic diagram showing the state in which a fire has occurred inside the battery box 201. A schematic diagram of the battery box 301 of Modification 3. A schematic diagram showing the state in which a fire has occurred inside the battery box 301. A schematic diagram showing the state in which a solidified layer P1 in which no springback has occurred and an expanded layer P2 in which springback has occurred have been formed in the fiber-reinforced plastic material when exposed to fire. Sealing test. A schematic diagram showing the state before combustion. Sealing test. A schematic diagram showing the state after combustion. A schematic diagram showing the combustion test of a test specimen.

[0017] [First Embodiment] Figure 1 is a cross-sectional view showing an example of a battery box according to an embodiment of the present invention. As shown in Figure 1, the battery box 1 comprises a battery cover 10, a battery tray 20, and a sealing material 30. A battery 2 is stored inside the battery box 1. The battery box 1 is preferably for use in a vehicle.

[0018] Figure 2 is an enlarged view of part II of Figure 1. As shown in Figure 2, the sealing material 30 is positioned in the proximity area where the battery cover 10 and the battery tray 20 are in close proximity. Specifically, the battery cover 10 has a first flange 11 that constitutes the proximity area with the battery tray 20, and the battery tray 20 has a second flange 21 that constitutes the proximity area with the battery cover 10. The sealing material 30 contacts the first flange 11 and the second flange 21, thereby sealing the internal space of the battery box 1 from the external space of the battery box 1.

[0019] The battery cover 10 and the battery tray 20 are joined in the proximity region. The "proximity region" is the area for joining the battery cover 10 and the battery tray 20. More specifically, the proximity region may be defined as the area where the clearance between the battery cover 10 and the battery tray 20 is 10 mm or less, or the area where the clearance between the battery cover 10 and the battery tray 20 is 5 mm or less. Specifically, as shown in Figure 2, the first flange 11 and the second flange 21 constitute the proximity region.

[0020] The first flange 11 is provided with a through hole 12 into which the shaft of the bolt 3 is inserted. The second flange 21 is also provided with a through hole 22 into which the shaft of the bolt 3 is inserted. With a sealing material 30 sandwiched between the first flange 11 and the second flange 21, the shaft of the bolt 3, inserted from above the through hole 12, is inserted into the through hole 22 of the second flange 21 and fastened with a nut 4 below the second flange 21, thereby fixing the battery cover 10 to the battery tray 20. Note that the method of fixing the battery cover 10 to the battery tray 20 is not limited to fastening with a bolt 3 and a nut 4; any joining method such as welding or adhesive may be used.

[0021] In Figure 2, a groove 13 for fixing the sealing material 30 is provided in the first flange 11, but the groove 13 is not required. Alternatively, a groove for fixing the sealing material 30 may be provided in the second flange.

[0022] In the battery box 1 of this embodiment, at least one of the battery cover 10 and the battery tray 20 is a fiber-reinforced plastic containing discontinuous reinforcing fibers and a thermoplastic resin. The battery cover 10 or battery tray 20, which is fiber-reinforced plastic, is formed from a composite material containing discontinuous reinforcing fibers and a thermoplastic resin.

[0023] [Discontinuous Reinforcing Fibers] In this specification, discontinuous reinforcing fibers are preferably at least one selected from the group consisting of carbon fibers, aramid fibers, and glass fibers. More preferably, discontinuous reinforcing fibers are carbon fibers or glass fibers.

[0024] [Discontinuous Reinforcement Fibers: Carbon Fibers] 1. Carbon Fibers in General As carbon fibers, polyacrylonitrile (PAN) carbon fibers, petroleum / coal pitch carbon fibers, rayon carbon fibers, cellulose carbon fibers, lignin carbon fibers, and phenolic carbon fibers are generally known, and any of these carbon fibers can be suitably used. Among them, polyacrylonitrile (PAN) carbon fibers are preferred because they have excellent tensile strength. As an example of PAN carbon fibers, Teijin Limited's carbon fiber "Tenax" (registered trademark) STS40-24KS (average fiber diameter 7 μm) can be used.

[0025] 2. Sizing agent for carbon fiber The carbon fiber may have a sizing agent attached to its surface. When using carbon fiber with a sizing agent attached, the type of sizing agent can be appropriately selected according to the type of carbon fiber and the type of resin used in the fiber-reinforced plastic, and is not particularly limited.

[0026] [Discontinuous Reinforcement Fibers: Glass Fibers] This section explains the case where the discontinuous reinforcement fiber is glass fiber. 1. Glass Fibers in General Any glass fiber that is generally referred to as glass fiber is acceptable. The glass composition is not particularly limited to A glass, C glass, E glass, etc., and TiO may be used depending on the case. ２ SO ３ , P ２ O ５ It may also contain components such as the above. As for glass fibers, for example, RV P204-4800TEX manufactured by Owens Corning can be used.

[0027] 2. Sizing agent for glass fibers The glass fibers may have a sizing agent attached to their surface. When using glass fibers with a sizing agent attached, the type of sizing agent can be appropriately selected according to the type of glass fiber and the type of resin, and is not particularly limited. Preferably, glass fibers that have been pre-treated with conventionally known coupling agents such as organosilane compounds, organotitanium compounds, organoborane compounds and epoxy compounds can be used.

[0028] 3. For single-ended roving and multi-ended roving fiber-reinforced plastics, it is preferable to use multi-ended roving glass fibers GFm, and more preferably, the glass fibers GFs of single-ended roving and the glass fibers GFm of multi-ended roving are mixed in a volume ratio of GFm:GFs of 50:50 to 90:10. If the proportion of GFm is 50% or more, the work rate can be easily kept below the upper limit. If the proportion of GFm is 90% or less, the work rate can be easily kept above the lower limit.

[0029] Multi-end roving refers to roving where the ends of the glass strands are not aligned. In multi-end roving, the glass fibers have multiple ends. Single-end roving refers to roving where the ends of the glass strands are aligned to a single point. In single-end roving, the glass fibers have only one end.

[0030] [Dispersed in the in-plane direction] It is preferable that the discontinuous reinforcing fibers contained in fiber-reinforced plastics are dispersed in the in-plane direction. Furthermore, fiber-reinforced plastics are molded from composite materials containing discontinuous reinforcing fibers and thermoplastic resin. Therefore, it is even more preferable that the discontinuous reinforcing fibers contained in the composite material are also dispersed in the in-plane direction. Dispersion of discontinuous reinforcing fibers in the in-plane direction means that the fiber axes of the discontinuous reinforcing fibers are dispersed so that they are oriented in the in-plane direction. It is preferable that the angle that the fiber axes of the discontinuous reinforcing fibers make with the in-plane direction is 45° or less.

[0031] 1. The composite material for manufacturing in-plane fiber-reinforced plastics is preferably a plate-shaped material. The in-plane direction refers to an undefined direction of parallel planes perpendicular to the thickness direction of the composite material.

[0032] 2. Randomly Dispersed in Two Dimensions It is preferable that the discontinuous reinforcing fibers are randomly dispersed in two dimensions in the in-plane direction. When the composite material is press-molded without flowing (non-flow molding), the shape of the discontinuous reinforcing fibers is largely maintained before and after molding. In the case of non-flow molding, it is preferable to orient the discontinuous reinforcing fibers contained in the composite material randomly in two dimensions so that the discontinuous reinforcing fibers contained in the fiber-reinforced plastic (molded body) formed from the composite material are similarly dispersed randomly in two dimensions in the in-plane direction.

[0033] Here, "randomly dispersed in two dimensions" means that the discontinuous reinforcing fibers are oriented in a disordered manner within the in-plane direction of the fiber-reinforced plastic (or composite material), rather than in a specific direction such as one direction, and are arranged within the sheet surface without exhibiting a particular direction overall. The fiber-reinforced plastic (or composite material) obtained using these randomly dispersed discontinuous reinforcing fibers is substantially isotropic, without anisotropy within the plane.

[0034] The degree of two-dimensional random orientation is evaluated by determining the ratio of the tensile moduli in two mutually orthogonal directions. If the ratio (Eδ) obtained by dividing the larger of the measured tensile moduli in any direction and in a direction orthogonal thereto by the smaller value is 5 or less, more preferably 2 or less, and even more preferably 1.5 or less, then it can be evaluated that the discontinuous reinforcing fibers are dispersed randomly in two dimensions. When the fiber-reinforced plastic includes a curved surface, a good method for evaluating the two-dimensional random dispersion in the in-plane direction is to heat it above the softening temperature to return it to a flat plate shape and then solidify it. After that, by cutting out a test piece and determining the tensile modulus, the random dispersion state in the two-dimensional direction can be confirmed.

[0035] [Fiber Length] The weight-average fiber length of the discontinuous reinforcing fibers is preferably 1 mm or more and 100 mm or less. Since the weight-average fiber length does not change before and after molding of composite materials and fiber-reinforced plastics (molded articles), the weight-average fiber length Lw of the discontinuous reinforcing fibers contained in the composite material can be determined by examining the weight-average fiber length of the discontinuous reinforcing fibers contained in the fiber-reinforced plastics (molded articles).

[0036] The lower limit of the weight-average fiber length of the discontinuous reinforcing fibers is preferably 5 mm or more, and more preferably 10 mm or more. Conversely, the upper limit of the weight-average fiber length is preferably 80 mm or less, and more preferably 70 mm or less. When the weight-average fiber length is 1 mm or more, the mechanical strength of the resulting fiber-reinforced plastic does not tend to decrease, which is preferable. When the weight-average fiber length is 100 mm or less, the fluidity of the material does not tend to decrease when the composite material is manufactured by press molding, and it is easier to create the composite material into the desired shape. The preferred weight-average fiber length range for the discontinuous reinforcing fibers is 5 mm or more and 80 mm or less, and more preferably 10 mm or more and 60 mm or less.

[0037] [Number-average fiber length Ln and weight-average fiber length Lw] Generally, if the fiber length of each reinforcing fiber is Li, the number-average fiber length Ln and the weight-average fiber length Lw can be calculated using the following equations (X) and (Y). Note that the units of the number-average fiber length Ln and the weight-average fiber length Lw are mm.

[0038] Here, "I" indicates the number of reinforced fibers measured.

[0039] When the fiber length is constant, the number-average fiber length and the weight-average fiber length will be the same value. Reinforcement fibers from fiber-reinforced plastics can be extracted, for example, by heat treatment at approximately 500°C for 1 hour and removing the resin in the furnace.

[0040] The average fiber length can be determined, for example, by measuring the fiber length of 100 randomly selected fibers from fiber-reinforced plastic to the nearest 1 mm using a caliper or similar device, and then calculating it based on formula (X).

[0041] If short fibers that cannot be measured with calipers are present, the resin is removed, and the resulting reinforced fibers are placed in water containing a surfactant and thoroughly stirred using ultrasonic vibration. A random sample of the stirred dispersion is taken using a measuring spoon to obtain an evaluation sample, and the length of 3000 fibers is measured using a Nireco Luzex AP image analysis device. Using the measured fiber lengths, the number-average fiber length Ln and the weight-average fiber length Lw can be determined in the same manner as the above-mentioned equations (X) and (Y).

[0042] [Volume Percentage] The volume percentage (Vf) of discontinuous reinforcing fibers contained in fiber-reinforced plastic can be calculated using the following formula (Z): Volume percentage (Vf) = 100 × Volume of discontinuous reinforcing fibers / (Volume of discontinuous reinforcing fibers + Volume of thermoplastic resin) Formula (Z) There are no particular limitations on the volume percentage (Vf), but it is preferably 10 to 60 Vol%, more preferably 20 to 50 Vol%, and even more preferably 25 to 45 Vol%.

[0043] [Analysis of Volume Percentage (Vf)] There are no limitations to the analysis of the volume percentage (Vf) of discontinuous reinforcing fibers, but it is recommended to measure it as follows: Cut a sample from the fiber-reinforced plastic, burn off the thermoplastic resin in a furnace at 500°C for 1 hour, and weigh the sample before and after treatment to calculate the mass of the discontinuous reinforcing fibers and resin. Next, calculate the volume of the discontinuous reinforcing fibers by dividing the mass of the discontinuous reinforcing fibers by the density of the reinforcing fibers, and calculate the volume of the thermoplastic resin by dividing the mass of the thermoplastic resin by the density of the resin. Next, calculate the ratio Vf of the volume of the discontinuous reinforcing fibers to the total volume of the discontinuous reinforcing fibers and thermoplastic resin.

[0044] [Thermoplastic Resin] The type of thermoplastic resin used in fiber-reinforced plastics is not particularly limited, and one having a desired softening point or melting point can be appropriately selected and used. The thermoplastic resin used is usually one with a softening point in the range of 80°C to 350°C, preferably 100°C to 350°C, and more preferably 180°C to 350°C, but is not limited thereto.

[0045] Examples of thermoplastic resins include polyolefin resins, polystyrene resins, polyamide resins, polyester resins, polyacetal resins (polyoxymethylene resins), polycarbonate resins, (meth)acrylic resins, polyarylate resins, polyphenylene ether resins, polyimide resins, polyethernitrile resins, phenoxy resins, polyphenylene sulfide resins, polysulfone resins, polyketone resins, polyetherketone resins, thermoplastic urethane resins, fluoropolymer resins, thermoplastic polybenzimidazole resins, and the like.

[0046] The thermoplastic resin used in fiber-reinforced plastics may be of one type or two or more types. Examples of using two or more thermoplastic resins in combination include, but are not limited to, using thermoplastic resins with different softening or melting points, or using thermoplastic resins with different average molecular weights. When using thermoplastic resins, it is more preferable to use polyolefin resin, and even more preferable to use polypropylene resin.

[0047] [Flame Retardants] 1. Overview Fiber-reinforced plastics preferably contain flame retardants. The flame retardants are not particularly limited and include, for example, phosphorus-based flame retardants, bromine-based flame retardants, antimony-based flame retardants, etc. Among these, phosphorus-based flame retardants are preferred from the viewpoint of improving flame resistance. Furthermore, in a classification focusing on the mechanism of action of flame retardants, it is preferable that the flame retardant be an intomessecent flame retardant from the viewpoint of improving flame resistance.

[0048] 2. Phosphorus-based flame retardants Phosphorus-based flame retardants are phosphorus compounds, that is, compounds that contain phosphorus atoms in their molecules. Phosphorus-based flame retardants exert their flame-retardant effect by forming char during the combustion of resin compositions.

[0049] The phosphorus-based flame retardant may be any known substance, such as (poly)phosphate or (poly)phosphate ester. Here, "(poly)phosphate" refers to a phosphate or polyphosphate, and "(poly)phosphate ester" refers to a phosphate ester or polyphosphate ester. It is preferable that the phosphorus-based flame retardant is solid at 80°C.

[0050] As a 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 orphosphate, calcium phosphate, and magnesium phosphate.

[0051] Furthermore, compounds in which melamine or piperazine is replaced with other nitrogen compounds in the above examples can also be used. Examples of other nitrogen compounds include N,N,N',N'-tetramethyldiaminomethane, ethylenediamine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-diethylethylenediamine, 1,2-propanediamine, 1,3-propanediamine, and tetramethyl Diadiamine, 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, acrylicguanamine, 2,4-diamino-6-nonyl-1,3,5-triamine Zin, 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-6-mercapto-1, Examples include 3,5-triazine, 2-amino-4,6-dimercapto-1,3,5-triazine, ammeline, benzguanamine, acetoguanamine, phthalodiguanamine, melamine cyanurate, melamine pyrophosphate, butylenediguanamine, norbornenediguanamine, methylenediguanamine, ethylenedimelamine, trimethylenedimelamine, tetramethylenedimelamine, hexamethylenedimelamine, and 1,3-hexylenedimelamine. These (poly)phosphates may be used individually or in combination of two or more.

[0052] Examples of commercially available phosphorus-based flame retardants include ADEKA® FP-2100J, FP-2200, FP-2500S (manufactured by ADEKA Corporation), ADEKA® FP-2100 JC, and Exolit® AP462 and Exolit OP1230 manufactured by Clariant.

[0053] 3. Intomessent Flame Retardants Intomessent flame retardants are flame retardants that suppress the combustion of materials by forming a surface expansion layer (intumescent) that prevents radiant heat from the combustion source and the diffusion of combustion gases and smoke from the burning material to the outside.

[0054] Intomessent flame retardants cause the resin composition to form a surface expansion layer (intomescent), which is a foamed char, during combustion. The formation of this surface expansion layer suppresses the diffusion of decomposition products and heat transfer, resulting in excellent flame retardancy. Examples of intomessent flame retardants include salts of (poly)phosphate and nitrogen compounds, specifically ammonium salts and amine salts of (poly)phosphate.

[0055] 4. Brominated Flame Retardants Examples of brominated flame retardants include decabromodiphenyl ether, tetrabromobisphenol A, tetrabromobisphenol S, 1,2-bis(2',3',4',5',6'-pentabromophenyl)ethane, 1,2-bis(2,4,6-tribromophenoxy)ethane, 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, 2,6-dibromophenol, and 2,4-dibromophenoxy. Examples include polystyrene, brominated polystyrene, ethylenebistetrabromophthalimide, 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.

[0056] 5. Antimony-based flame retardants Examples of antimony-based flame retardants include antimony trioxide, antimony tetroxide, antimony pentoxide, sodium pyroantimonate, antimony trichloride, antimony trisulfide, antimony oxychloride, antimony perchloropentane dichloride, and potassium antimonate, with antimony trioxide and antimony pentoxide being particularly preferred.

[0057] [Flame retardant content] The flame retardant content in fiber-reinforced plastics is preferably 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of thermoplastic resin. More preferably, it is in the range of 1 part by mass or more and 30 parts by mass or less, and even more preferably, in the range of 5 parts by mass or more and 25 parts by mass. If the amount is 1 part by mass or more, good flame retardancy can be imparted to the fiber-reinforced plastic, and good flame shielding properties can be obtained. On the other hand, if the amount of flame retardant is 50 parts by mass or less, the moldability is further improved.

[0058] [Dispersant] 1. Overview As a dispersant, it is sufficient if it can disperse the flame retardant in the thermoplastic resin, and is not particularly limited, but polymer dispersants can be suitably used in terms of compatibility with the resin. Preferably, a dispersant that can disperse the flame retardant in polypropylene resin can be used. As a polymer dispersant, a polymer dispersant having a functional group is preferred, and from the viewpoint of dispersion stability, polymer dispersants having functional groups such as carboxyl groups, phosphate groups, sulfonic acid groups, primary, secondary or tertiary amino groups, quaternary ammonium bases, pyridine, pyrimidine, pyrazine, and other nitrogen-containing heterocycle-derived groups are preferred.

[0059] A polymeric dispersant having a carboxyl group is preferred, and in particular, when using a phosphorus-based flame retardant suitable as a flame retardant, a copolymer of α-olefin and an unsaturated carboxylic acid is preferred. By using this dispersant, the dispersibility of the phosphorus-based flame retardant can be improved, and the flame retardant content can be reduced.

[0060] 2. The necessity of dispersants: Fiber-reinforced plastics (or composite materials) do not necessarily need to contain dispersants. They are not necessarily required if flame retardancy can be ensured.

[0061] [Other agents] Fiber-reinforced plastics may contain additives such as various fibrous or non-fibrous fillers of organic or inorganic fibers, UV resistant agents, stabilizers, mold release agents, pigments, softeners, plasticizers, and surfactants, to the extent that they do not impair the purpose of the present invention.

[0062] [Method for Manufacturing Fiber-Reinforced Plastic] A composite material is a material used to create fiber-reinforced plastic, and the composite material is preferably in the form of a flat plate. On the other hand, fiber-reinforced plastic is a molded body and has a defined shape. At least one of the battery cover and the battery tray is made of fiber-reinforced plastic, and these have a defined shape.

[0063] 1. Cold Press (Molding) Method When manufacturing a battery cover 10 or battery tray 20 made of fiber-reinforced plastic, press molding (sometimes called compression molding) is used as the molding method, and it is particularly preferable to use press molding using cold press. In the cold press molding method, for example, a composite material heated to a first predetermined temperature is placed into a mold set to a second predetermined temperature, and then pressurized and cooled.

[0064] Specifically, if the thermoplastic resin constituting the composite material is crystalline, the first predetermined temperature is above the melting point of the thermoplastic resin, and the second predetermined temperature is below the melting point. If the thermoplastic resin is amorphous, the first predetermined temperature is above the glass transition temperature of the thermoplastic resin, and the second predetermined temperature is below the glass transition temperature.

[0065] In other words, the cold press molding method includes at least the following steps A-1) to A-2). Step A-1) A step of heating the composite material to a temperature above the melting point of the thermoplastic resin and below the decomposition temperature of the thermoplastic resin if the thermoplastic resin is crystalline, and above the glass transition temperature and below the decomposition temperature of the thermoplastic resin if the thermoplastic resin is amorphous. Step A-2) A step of placing the composite material heated in step A-1) into a mold whose temperature is controlled to below the melting point of the thermoplastic resin if the thermoplastic resin is crystalline, and below the glass transition temperature if the thermoplastic resin is amorphous, and applying pressure. By performing these steps, the molding of the composite material can be completed.

[0066] Each of the above steps must be performed in the order specified above, but other steps may be included between each step. Other steps include, for example, a forming step performed before step A-2) in which a different forming die from the one used in step A-2) is used to pre-form the shape of the cavity of the forming die.

[0067] 2. Hot Pressing Method The hot pressing method involves, for example, placing a composite material into a mold, applying pressure while raising the temperature of the mold to a first predetermined temperature, and then cooling the mold to a second predetermined temperature. Specifically, if the thermoplastic resin constituting the composite material is crystalline, the first predetermined temperature is above the melting point of the thermoplastic resin, and the second predetermined temperature is below the melting point. If the thermoplastic resin constituting the composite material is amorphous, the first predetermined temperature is above the glass transition temperature of the thermoplastic resin, and the second predetermined temperature is below the glass transition temperature.

[0068] The hot press molding method preferably includes at least the following steps B-1) to B-4): B-1) A step of placing the composite material in the mold (lower mold). B-2) A step of heating and pressurizing the mold to a temperature above the melting point of the thermoplastic resin but below the thermal decomposition temperature if the thermoplastic resin is crystalline, or to a temperature above the glass transition temperature of the thermoplastic resin but below the thermal decomposition temperature if the thermoplastic resin is amorphous (first pressing step). B-3) A step of pressurizing in one or more stages, such that the pressure in the final stage is 1.2 times or more but 100 times or less the pressure in the first pressing step (second pressing step). B-4) A step of adjusting the mold temperature to below the melting point if the thermoplastic resin is crystalline, or below the glass transition temperature if the thermoplastic resin is amorphous. By performing these steps, the molding of the composite material can be completed.

[0069] 3. Common aspects of cold press molding and hot press molding Steps A-2) and B-3) are steps in which pressure is applied to the composite material to obtain a molded body of the desired shape. There are no particular limitations on the molding pressure at this time, but it is preferable to keep it as low as possible within the range in which the desired molded body shape can be obtained. Specifically, it is preferable to have a molding pressure of less than 30 MPa relative to the projected area of ​​the mold cavity, more preferably 20 MPa or less, and even more preferably 10 MPa or less. When the molding pressure is less than 30 MPa, it is preferable because it does not require capital investment or maintenance costs for the press machine. Also, naturally, various steps may be inserted between the above steps during compression molding, for example, vacuum compression molding, which is performed while compressing under vacuum, may be used.

[0070] [Springback] 1. Springback of Composite Materials In order to cold-press mold composite materials, it is necessary to preheat and heat the composite material to a predetermined temperature to soften and melt it. When the thermoplastic resin becomes plastic during preheating of a composite material containing discontinuous reinforcing fibers with a weight-average fiber length of 1 mm to 100 mm (especially when the reinforcing fibers are in a mat state), the preheated composite material expands due to the springback of the discontinuous reinforcing fibers, and the bulk density of the composite material changes. When the bulk density changes during preheating, the composite material becomes porous, the surface area increases, and air flows into the interior of the composite material, promoting the thermal decomposition of the thermoplastic resin.

[0071] The springback rate tends to increase when the reinforcing fiber bundles in the composite material are highly open (single-fiber rich) or when the fiber length is increased. Here, the springback rate is the value obtained by dividing the thickness of the composite material after preheating by the thickness of the composite material before preheating.

[0072] In this invention, it is preferable that the springback rate of the composite material is 1.05 or more and 8.0 or less. If the springback rate of the composite material is 8.0 or less, it is possible to prevent the battery cover from expanding too much and coming into contact with the battery when the composite material is burned. Conversely, if the springback rate is 1.05 or more, the composite material using the composite material expands easily when heated, making it easier to obtain an insulating effect.

[0073] A preferred springback ratio for composite materials is 2.0 to 8.0, a more preferred springback ratio for composite materials is 3.0 to 7.0, and an even more preferred springback ratio is 4.0 to 6.0.

[0074] 2. Similar to the springback composite material of fiber-reinforced plastic, the springback rate of the battery cover 10 or battery tray 20, which is made of fiber-reinforced plastic, is preferably 1.05 or more and 8.0 or less. Here, the springback rate of fiber-reinforced plastic is the ratio of the thickness of the fiber-reinforced plastic after preheating to the thickness of the fiber-reinforced plastic before preheating, when the fiber-reinforced plastic is placed in a preheating furnace heated to a heater temperature of 280°C, removed from the furnace when the thermocouple temperature reaches 210°C, and cooled and solidified, and is expressed by the following formula: Springback rate = Thickness of fiber-reinforced plastic after preheating (mm) / Thickness of fiber-reinforced plastic before preheating (mm) A more preferable springback rate for fiber-reinforced plastic is 2.0 or more and 8.0 or less, an even more preferable springback rate for fiber-reinforced plastic is 3.0 or more and 7.0 or less, and an even more preferable springback rate is 4.0 or more and 6.0 or less. If the springback rate of fiber-reinforced plastic is 1.05 or more, the fiber-reinforced plastic is likely to expand when heated.

[0075] The "springback" and "expansion" of fiber-reinforced plastics refer to the phenomenon where the volume of the fiber-reinforced plastic changes when the thermoplastic resin becomes plastic, and thus both originate from discontinuous reinforcing fibers. However, the "springback rate" of fiber-reinforced plastics and the "expansion rate E," which will be discussed later, do not necessarily coincide. This is because the "springback rate" and the "expansion rate E" are measured using different methods.

[0076] [Tensile Test Before and After Fire Resistance] The fiber-reinforced plastic preferably satisfies the following (a): (a) The tensile strength retention rate, as shown by formula (a1), is greater than 0.03%. A preferred tensile strength retention rate is 0.05% or higher, more preferably 0.06% or higher, and even more preferably 0.1% or higher. Furthermore, the range of the tensile strength retention rate is preferably 0.04% to 50%, more preferably 0.05% to 40%, even more preferably 0.06% to 30%, and even more preferably 1% to 25%. If the tensile strength retention rate is greater than 0.03%, it is possible to maintain the shape of the fiber-reinforced plastic battery cover 10 or battery tray 20 after combustion without resin dripping. Tensile strength retention rate (%) = (Tensile strength B after combustion ÷ Tensile strength A before combustion) × 100 ... formula (a1)

[0077] In measuring the tensile strength retention rate, as described later, ten test pieces measuring 25 mm in width and 150 mm in length are cut from the fiber-reinforced plastic. The tensile strength of five of the cut test pieces is measured, and the measurement result is designated as tensile strength A before the combustion test. The remaining five test pieces are subjected to a combustion test, and the tensile strength of the five test pieces after the combustion test is measured, and the measurement result is designated as tensile strength B after the combustion test.

[0078] 1. When the battery cover 10 is made of fiber-reinforced plastic, it is necessary to have fire resistance against flames from the battery 2 located inside the battery box 1. Furthermore, in the event of an accident, if leaked gasoline burns, the battery cover 10 may be exposed to flames of 700 to 800°C. Therefore, fire resistance under more severe conditions is required. Thus, fire resistance is important for the interior of the battery box 1. In this case, if the tensile strength retention rate of the fiber-reinforced plastic is greater than 0.03%, the battery cover 10 will not drip resin after combustion and will not easily come into contact with the battery 2 itself. When the battery cover 10 is made of fiber-reinforced plastic, it is preferable that the tensile strength retention rate of the fiber-reinforced plastic is 0.05% or more, and even more preferable that it is 0.07% or more.

[0079] Furthermore, after combustion, the battery cover 10 preferably has a stress of 100 N or more when pressed from the non-flame side (upper side) with a push-pull gauge, more preferably 150 N or more, and even more preferably 200 N or more.

[0080] 2. When the battery tray 20 is made of fiber-reinforced plastic: If the battery tray 20 is made of fiber-reinforced plastic, the battery box 1 needs to be fire-resistant against flames from outside the vehicle, so the fire resistance performance toward the outside of the battery box 1 is important. When the battery tray 20 is made of fiber-reinforced plastic, it is preferable that the tensile strength retention rate of the fiber-reinforced plastic is 0.04% or more, more preferably 0.06% or more, and even more preferably 0.1% or more.

[0081] [Workload] Fiber-reinforced plastics preferably satisfy the following (b): (b) The amount of work per basis in a tensile test of a 25 mm wide test specimen after a combustion test is 0.1 × 10 －３ [(N・mm) / (g / m ２ ) ] 300 x 10 －３ [(N・mm) / (g / m ２ The following applies: Here, work is the value obtained by integrating the tensile force in the tensile test with respect to the amount of strain. Work per unit weight in the tensile test is the value obtained by integrating the load per unit weight in the tensile test with respect to the strain displacement.

[0082] For example, in the load-strain [%] curve for a tensile test shown in Figure 3, the work done in the tensile test can be calculated by integrating the load per unit area with respect to the strain amount [mm] in the load-strain [%] curve obtained by converting the displacement ratio of the strain on the horizontal axis [unit: %] to the displacement amount (unit: mm).

[0083] If the work done is above the lower limit, the fiber-reinforced plastic will not sag or the resin will not drape down during combustion. Conversely, if it is below the upper limit, a large pressure will not be required during press molding, making it easy to mold the composite material into fiber-reinforced plastic. The preferred work done per basis weight in the tensile test of a 25 mm wide test specimen after combustion testing is 0.5 × 10⁻⁶. －３[(N・mm) / (g / m ２ ) ] 100 x 10 －３ Less than [(N・mm) / (g / m2)], more preferably 0.5 × 10 －３ [(N・mm) / (g / m ２ ) ] 50 x 10 －３ [(N・mm) / (g / m ２ )] less than 1.0 × 10 －３ [(N・mm) / (g / m ２ ) ] 30 x 10 －３ [(N・mm) / (g / m ２ )] less than 1.5 × 10 －３ [(N・mm) / (g / m ２ ) ] 20 x 10 －３ [(N・mm) / (g / m ２ )] less than 1.5 × 10 －３ [(N・mm) / (g / m ２ ) ] 10 x 10 －３ [(N・mm) / (g / m ２ It is less than ).

[0084] [Change in Load] Fiber-reinforced plastics preferably satisfy the following (c0): (c0) In a tensile test on a 25 mm wide specimen after a combustion test, the load [N / (g / m)] at a strain of 0.1% to 0.2% ２ The change in ) is 0.005 × 10 －３ [N / (g / m) ２ ) ] 30 x 10 －３ [N / (g / m) ２ It is preferable that the following conditions are met.

[0085] A more favorable change is 0.01 × 10⁻⁶. －３ [N / (g / m) ２ ) ] 10 x 10 －３ [N / (g / m) ２ )] is within the following range, and a more preferable change is 0.05 × 10 －３ [N / (g / m) ２ )] 0.9 x 10 －３ [N / (g / m) ２ )] The range is as follows, and a more preferable change is 0.15 × 10 －３[N / (g / m ２ )] is 0.8×10 －３ [N / (g / m ２ ) or less, and the most preferable change amount is 0.15×10 －３ [N / (g / m ２ ) or more and 0.7×10 －３ [N / (g / m ２ ) or less.

[0086] The change amount of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% being 0.005×10 －３ [N / (g / m ２ )] or more means that a certain amount of stress is required to deform the fiber. That is, if the change amount of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% is 0.005×10 －３ [N / (g / m ２ )] or more, it is preferable because when the fiber reinforced plastic burns, the fiber does not sag. If the change amount of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% is 30×10 －３ [N / (g / m ２ )] or less, it means that in the initial stage when a load is applied, a large load is not required and it is a material that can be easily molded.

[0087] [Average change rate of load] 1. The fiber reinforced plastic preferably satisfies the following (c). (c) In a tensile test on a test piece after a combustion test with a width of 25 mm, the average value (average change rate) of the change amount of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% is 0.05×10 －３ [N / (g / m<o000089>)] or more and 300×10 －３ [N / (g / m[[ID=4​​​​​​​​​​​is within the following range, and a more preferable average rate of change is 0.5 × 10 －３ [N / (g / m ２ )] or more and 9.0 × 10 －３ [N / (g / m ２ )] or less, and an even more preferable average rate of change is 1.5 × 10 －３ [N / (g / m ２ )] or more and 8.0 × 10 －３ [N / (g / m ２ )] or less, and the most preferable average rate of change is 1.5 × 10 －３ [N / (g / m ２ )] or more and 7.0 × 10 －３ [N / (g / m ２ )] or less.

[0089] The average rate of change of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% being 0.05 × 10 －３ [N / (g / m ２ )] or more means that a certain amount of stress is required to deform the fiber reinforced plastic. That is, if the average rate of change of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% is 0.05 × 10 －３ [N / (g / m ２ )] or more, when the fiber reinforced plastic burns, the fibers do not sag, which is preferable. If the average rate of change of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% is 300 × 10 －３ [N / (g / m ２ )] or less, it means that at the initial stage when a load is applied, a large load is not required and it is a material that can be easily formed. Here, the average rate of change of the load [N / (g / m ２ )] at a strain of 0.1% to 0.2% is, for example, the slope of the arrow indicated by reference numeral 301 in the load [N / (g / m ２ )] - strain [%] curve in FIG. 3.

[0090] 2. The fiber reinforced plastic preferably satisfies the following (d0). (d0) In a tensile test on a test piece after a combustion test with a width of 25 mm, the load [N / (g / m２ The change in ) is -7.5 × 10 －３ [N / (g / m) ２ ) ] Above - 0.0125 × 10 －３ [N / (g / m) ２ )] is within the following range. More preferably, -2.5 × 10 －３ [N / (g / m) ２ )] Above - 0.025 × 10 －３ [N / (g / m) ２ The range is as follows: Load [N / (g / m)] ２ If the change in [ ] is a negative value, and within this range, it means that no large load other than the initial load during molding was required, and the material could be easily molded.

[0091] 2. Fiber-reinforced plastics preferably satisfy the following (d): (d) In a tensile test of a 25 mm wide test specimen after a combustion test, the load [N / (g / m)] at strains of 0.5% to 3.0% ２ The average rate of change of ) ] is -3.0 × 10 －３ [N / (g / m) ２ )] Above - 0.005 × 10 －３ [N / (g / m) ２ )] is within the following range. More preferably, -1.0 × 10 －３ [N / (g / m) ２ )] Above - 0.01 x 10 －３ [N / (g / m) ２ )] is within the following range. Here, the load at strains from 0.5% to 3.0% is [N / (g / m ２ The average rate of change of the load [N / (g / m) in Figure 3 is, for example, the load [N / (g / m) ２ )] - Strain [%] curve, this is the slope of the arrow indicated by symbol 302. Load [N / (g / m ２ If the average rate of change of ) is a negative value, it means that within this range, no large load other than the initial load during molding is required, and the material can be easily molded.

[0092] [Range of strain at which the load per unit weight is maximum] Fiber-reinforced plastics preferably satisfy the following (e): (e) In a tensile test on a 25 mm wide specimen after a combustion test, the maximum load value is in the range of strain greater than 0% and less than 5%. It is more preferable that the maximum load value is in the range of strain greater than 0% and less than 2%, even more preferable that the maximum load value is in the range of strain greater than 0% and less than 1%, and even more preferable that the maximum load value is in the range of strain greater than 0% and less than 0.5%.

[0093] Having a maximum load value in the range of 0% to less than 5% strain means that the load obtained in a tensile test on a 25 mm wide test specimen after a combustion test is [N / (g / m)]. ２ )] - Strain [%] curve means that the peak of the maximum load is in the range of strain greater than 0% and less than 5%. Load [N / (g / m) ２ The strain[%] curve preferably has a peak of maximum load in the strain range of over 0% and less than 1%, and more preferably has a peak of maximum load in the strain range of over 0% and less than 0.5%.

[0094] When press-molding composite materials using upper and lower molds, it is possible to apply stress to the composite material immediately after closing the molds and sandwiching the composite material between them. By designing the process to have a maximum load value within the above range (the initial stage where strain is large), composite materials (or fiber-reinforced plastics) with the same amount of work can be molded more easily.

[0095] [Maximum load per unit weight] Fiber-reinforced plastics preferably satisfy the following (f): (f) In a tensile test on a 25 mm wide test piece after a combustion test, the maximum load per unit weight is 1.1 × 10 －３ [N / (g / m) ２ ) ] or more. The maximum load per unit area is 1.15 × 10 －３ [N / (g / m) ２ It is more preferable that it be 1.5 × 10 －３ [N / (g / m) ２ It is even more preferable that it be 2.0 × 10 －３ [N / (g / m) ２It is even more preferable that it be 3.0 × 10 －３ [N / (g / m) ２ It is most preferable that the maximum load per unit area be 1.1 × 10 －３ [N / (g / m) ２ ) ] ] is preferable because when the fiber-reinforced plastic burns, the fibers do not hang down. Also, the maximum load per unit area for the same amount of work is 1.1 × 10 －３ [N / (g / m) ２ By doing so, if a large load is applied at a specific molding stage, molding can be easily performed with a small load at other stages, eliminating the need to continuously apply a large load throughout the entire molding process.

[0096] On the other hand, the maximum load per unit area is 10 x 10 －３ [N / (g / m) ２ It is more preferable that the maximum load per unit area for the same amount of work is 10 × 10 －３ [N / (g / m) ２ If the following conditions are met, a large load is not required when molding the battery cover 10 or battery tray 20, and it can be easily molded.

[0097] [Air volume blown onto the reinforcing fibers after cutting] There are no particular limitations on the method for manufacturing a composite material in which the above-mentioned [workload], [average rate of change of load], [range of strain where the load per unit weight is the maximum], and [maximum load per unit weight] satisfy values ​​from (b) to (f). However, after cutting the reinforcing fibers, compressed air can be supplied using a compressor directly below the cutting device, and the amount of airflow of this compressed air can be adjusted to the desired range of [workload], [average rate of change of load-strain curve], and [maximum load per unit weight].

[0098] 3. Sealing Material 30 For example, silicone, polyurethane, epoxy resin, etc., can be used for the sealing material 30. The sealing material 30 is used (1) to prevent water and dust from entering the battery box 1 and damaging the battery 2 and other electronic components inside the battery box 1, or (2) to absorb vibrations and shocks that occur during use of the vehicle or equipment on which the battery box 1 is mounted. In addition, since the battery 2 generates heat during use, the sealing material 30 needs to withstand high temperatures and therefore heat resistance is required. Furthermore, it is required to be resistant to chemicals that may leak from the battery 2 and therefore chemical resistance is required.

[0099] [Sealing by Expansion of Fiber-Reinforced Plastic] 1. Overview In case of a fire occurring in the battery 2 stored in the battery box 1, heat-resistant agents may be added to the sealant 30 to improve its heat resistance. However, sealant 30 mixed with additives to improve heat resistance is expensive and difficult to mass-produce. Furthermore, sealant 30 mixed with additives tends to become less elastic and harder, reducing the airtightness of the battery box 1.

[0100] Therefore, the present inventors devised a method to seal the battery 2 with fiber-reinforced plastic when exposed to flames, in order to prevent damage to the sealing material 30 when a fire occurs in the battery 2, while maintaining the elasticity of the sealing material 30. Specifically, in the battery box 1, when heated, it is preferable that the portion inside the sealing material 30 is sealed by the expanded fiber-reinforced plastic as the fiber-reinforced plastic expands in the adjacent area. Figure 5 shows how, when the battery cover 10 is made of fiber-reinforced plastic, the battery cover 10 expands due to a fire that occurs inside the battery box 1, and the portion inside the sealing material 30 is sealed by the expanded portion 14 of the fiber-reinforced plastic.

[0101] 2. Sealing Mechanism 2.1 Overview The battery box satisfies the following equation (1): Equation (1): t1 × E > ​​t1 + t2 where t1: Thickness of the fiber-reinforced plastic in the proximity region t2: Clearance between the battery cover 10 and the battery tray 20 in the proximity region E: Expansion rate of the thickness of the fiber-reinforced plastic after 600 seconds of contact with a burner so that the flame surface is between 950°C and 1000°C, relative to the thickness of the fiber-reinforced plastic before contact with the flame. The range of E is preferably 1.05 to 100, more preferably 1.05 to 50, even more preferably 1.1 to 25, even more preferably 2.0 to 10, and most preferably 3.0 to 7.0.

[0102] 2.2 Thickness t1 of Fiber-Reinforced Plastic in Proximity Area At least one of the battery cover 10 and the battery tray 20 is made of fiber-reinforced plastic. Therefore, the thickness t1 of the fiber-reinforced plastic in proximity area is the thickness of the proximity area (first flange 11) if the battery cover 10 is made of fiber-reinforced plastic, and the thickness of the proximity area (second flange 21) if the battery tray 20 is made of fiber-reinforced plastic. If the thickness is not constant, the average value of the thickness of the fiber-reinforced plastic in proximity area measured at 10 points may be used.

[0103] In the present invention, the thickness t1 of the fiber-reinforced plastic is preferably 1.3 mm < t1 < 10.0 mm, given by formula (2). Formula (2) is preferably formula (2a), more preferably formula (2b), and even more preferably formula (2c). Formula (2a) is 1.5 mm < t1 < 8.0 mm, more preferably formula (2b) is 2.0 mm < t1 < 7.0 mm, and even more preferably formula (2c) is 2.5 mm < t1 < 6.0 mm.

[0104] If t1 is 1.3 mm or more, the fiber-reinforced plastic can expand sufficiently when exposed to flame. If t1 is 10.0 mm or less, when fiber-reinforced plastic is used as a battery cover or battery tray, the thickness of these can be reduced to make them lighter, and the design space for the battery box in the interior design of an automobile can be increased.

[0105] If both the battery cover and the battery tray are made of fiber-reinforced plastic, it is preferable that at least one of them is within the range of formula (2) above, and it is even more preferable that both satisfy formula (2) above. In addition, the average value of the thickness of the fiber-reinforced plastic in the aforementioned proximity region, measured at 10 points, is measured separately for the battery cover and the battery tray.

[0106] 2.3 Clearance between Battery Cover and Battery Tray in Proximity Area The clearance between the battery cover and battery tray in proximity area refers to the distance of the gap between the battery cover and battery tray in proximity. For example, as shown in Figure 2, when the sealing material 30 is in place, the battery cover 10 and the battery tray 20 do not make complete contact, and a very small gap exists. This gap is defined as the clearance t2 between the battery cover 10 and the battery tray 20. The clearance can be measured using a commercially available thickness gauge or similar device.

[0107] 2.4 Expansion Rate E The expansion rate E is the expansion rate of the thickness of the fiber-reinforced plastic after 600 seconds of being exposed to a flame from a burner so that the flame surface temperature is between 950°C and 1000°C, relative to the thickness of the fiber-reinforced plastic before exposure to the flame. In other words, the expansion rate E is the value obtained by dividing the thickness t5 of the fiber-reinforced plastic after 600 seconds of being exposed to a flame from a burner so that the flame surface temperature is between 950°C and 1000°C by the thickness t1 of the fiber-reinforced plastic before exposure to the flame.

[0108] In other words, the expansion rate E is given by the following formula (5). Formula (5) E = t5 / t1 t1: Thickness of the fiber-reinforced plastic before flame contact t5: Thickness of the fiber-reinforced plastic 600 seconds after the surface of the fiber-reinforced plastic is exposed to flame from a burner so that the flame surface is between 950°C and 1000°C. If the battery cover 10 is made of fiber-reinforced plastic, t1 is the thickness of the first flange 11 shown in Figure 2, and t5 is the thickness of the first flange 11 including the expanded portion 14, as shown in Figure 5.

[0109] Apply a burner flame to the material so that the flame surface reaches a temperature between 950°C and 1000°C. After 600 seconds, if the fiber-reinforced plastic ignites and burns, extinguish the flame after another 600 seconds and observe the result. Observe the area where the burner flame directly contacted the material.

[0110] 2.5 By satisfying the sealing method (1), as shown in Figure 5, if the fire 5 is inside the battery box 1, the temperature of the parts of the first flange 11 and the second flange 21 inside the sealing material 30 will rise. If the battery cover 10 is made of fiber-reinforced plastic, as shown in Figure 5, the temperature of the first flange 11 will rise and an expansion portion 14 will be formed. Then, the expansion portion 14 will seal the gap between the battery cover 10 and the battery tray 20, so the sealing material 30 will not be exposed to the flame. As a result, the temperature of the sealing material 30 will not rise easily, and deterioration of the sealing material 30 due to heating can be suppressed. Note that sealing the gap between the battery cover 10 and the battery tray 20 does not necessarily mean that the entire gap between the battery cover 10 and the battery tray 20 is sealed. To prevent heating from the direction of exposure to the flame, it is sufficient that the gap between the battery cover 10 and the battery tray 20 is at least partially sealed inside the sealing material 30.

[0111] 3. Expansion Direction When the battery box is heated, it is preferable for the fiber-reinforced plastic to expand toward the opposing member. In Figure 5, the expanded portion 14 of the first flange 11 of the battery cover 10, which is made of fiber-reinforced plastic, is expanding toward the second flange 21 of the opposing battery tray 20. When the battery box is heated, the fiber-reinforced plastic may expand toward the out-of-plane direction of the adjacent region. Specifically, the "out-of-plane direction" is either upward (direction of arrow U in Figure 5) or downward (direction of arrow D in Figure 5). Also, when the battery box is heated, the fiber-reinforced plastic may expand toward the in-plane direction of the adjacent region. Specifically, the "in-plane direction" of the adjacent region is either outward (direction of arrow O in Figure 5) or inward (direction of arrow I in Figure 5).

[0112] 4. For the sealing material 30 to be sealed by the fiber-reinforced plastic when the fiber-reinforced plastic battery box 1 is heated, it is necessary that at least one of the battery cover 10 and the battery tray 20 be made of fiber-reinforced plastic containing discontinuous reinforcing fibers and thermoplastic resin. If at least one of the battery cover 10 and the battery tray 20 is made of fiber-reinforced plastic containing discontinuous fibers and thermoplastic resin, the fiber-reinforced plastic can expand by satisfying formula (1). Preferably, the battery cover 10 is made of fiber-reinforced plastic.

[0113] The battery cover 10 or battery tray 20, which is not made of fiber-reinforced plastic containing discontinuous reinforcing fibers and thermoplastic resin, may be made of metal such as iron or aluminum, or it may be made of fiber-reinforced plastic containing continuous fibers. Both the battery cover 10 and the battery tray 20 may be made of fiber-reinforced plastic containing discontinuous reinforcing fibers and thermoplastic resin.

[0114] <Modification 1> Figure 6 is a schematic diagram of a battery box 101 according to Modification 1 of this embodiment. Note that components similar to those in the first embodiment are denoted by the same last two digits as reference numerals and their explanations are omitted. In Modification 1, a projection 115 is provided at the inner end of the first flange 111, projecting toward the second flange 121. In Modification 1, the battery cover 110 is made of fiber-reinforced plastic.

[0115] Figure 7 is a schematic diagram showing a state in which a fire 105 occurs inside the battery box 101. When the battery cover 110 is made of fiber-reinforced plastic, as shown in Figure 7, the temperature of the protrusion 115 rises and an expanded portion 114 is formed. In the modified example 1, it is preferable that the expansion rate E1 of the protrusion 115, the height h1 of the protrusion 115, and the maximum clearance h2 between the protrusion 115 and the battery tray 120 satisfy the following formula (1a). Formula (1a): h1 × E1 > h1 + h2 Here, the expansion rate E1 of the protrusion 115 is the expansion rate of the height of the protrusion 115 after 600 seconds when the protrusion 115 is exposed to a flame from a burner such that the flame surface temperature is between 950°C and 1000°C, relative to the height h1 of the protrusion 115 before exposure to the flame.

[0116] In other words, the expansion rate E1 is given by the following formula (5-1). Formula (5-1) E1 = h5 / h1 h1: Height of the protrusion 115 in the adjacent region h5: Height of the protrusion 115 after 600 seconds when the protrusion 115 is exposed to a flame from a burner so that the flame surface is between 950°C and 1000°C

[0117] As shown in Figure 7, if the fire 105 is inside the battery box 101, the temperature of the protrusion 115 rises when equation (1a) is satisfied. If the battery cover 110 is made of fiber-reinforced plastic, the temperature of the protrusion 115 rises and an expansion portion 114 is formed, as shown in Figure 7. The expansion portion 114 seals the gap between the battery cover 110 and the battery tray 120, so the sealing material 130 is not exposed to flames. As a result, the temperature of the sealing material 130 does not rise easily, and deterioration of the sealing material 130 due to heating can be suppressed.

[0118] Thus, when the battery box 101 is heated, the protrusion 115 may expand out of the plane of the adjacent region. Expanding "out of the plane" of the adjacent region means expanding upward (in the direction of arrow U in Figure 7) or downward (in the direction of arrow D in Figure 7), and expanding in a direction perpendicular to the plane of the adjacent region (first flange 111).

[0119] <Modification 2> Figure 8 is a schematic diagram of a battery box 201 according to Modification 2 of this embodiment. Note that components similar to those in the first embodiment are denoted by the same last two digits as reference numerals and their explanations are omitted. In Modification 2, a projection 215 is provided at the inner end of the first flange 211, projecting toward the inside of the battery tray 220. In Modification 2, the battery cover 210 is made of fiber-reinforced plastic.

[0120] Figure 9 is a schematic diagram showing a state in which a fire 205 occurs inside the battery box 201. When the battery cover 210 is made of fiber-reinforced plastic, as shown in Figure 9, the temperature of the first flange 211 and the protrusion 215 rises, and an expanded portion 214 is formed. In the modified example 2, it is preferable that the expansion rate E' of the protrusion 215, the thickness t1' of the protrusion 215, and the maximum clearance t2' between the protrusion 215 and the battery tray 220 satisfy the following formula (1b). Formula (1b): t1' × E' > t1' + t2' Here, the expansion rate E' of the protrusion 215 is the expansion rate of the thickness of the protrusion 215 after 600 seconds of being exposed to a flame from a burner such that the flame surface temperature is between 950°C and 1000°C, relative to the thickness t1' of the protrusion 215 before exposure to the flame.

[0121] In other words, the expansion rate E' is given by the following equation (5-2). Equation (5-2) E' = t5' / t1' t1': Thickness of the protrusion 215 in the adjacent region t5': Thickness of the protrusion 215 after 600 seconds when the protrusion 215 is exposed to a flame from a burner so that the flame surface is between 950°C and 1000°C.

[0122] By satisfying equation (1b), as shown in Figure 9, if the fire 205 is inside the battery box 201, the temperature of the protrusion 215 rises. If the battery cover 210 is made of fiber-reinforced plastic, as shown in Figure 9, the temperature of the protrusion 215 rises and an expansion portion 214 is formed. At this time, the first flange 211 may also expand. Because the expansion portion 214 seals the gap between the battery cover 210 and the battery tray 220, the sealing material 230 is not exposed to flames. As a result, the temperature of the sealing material 230 does not rise easily, and deterioration of the sealing material 230 due to heating can be suppressed.

[0123] Thus, when the battery box 201 is heated, the protrusion 215 may expand in the in-plane direction of the adjacent region. Expanding in the "in-plane direction" of the adjacent region means expanding outward (direction of arrow O in Figure 9) or inward (direction of arrow I in Figure 9), and means expanding in a direction along the plane of the adjacent region (first flange 211).

[0124] <Modification 3> Figure 10 is a schematic diagram of a battery box 301 according to Modification 3 of this embodiment. Note that components similar to those in the first embodiment are denoted by the same last two digits as reference numerals and their explanation is omitted. In Modification 3, a projection 316 is provided at the inner end of the first flange 311, projecting toward the second flange 321. The second flange 321 is also provided with a groove 326 at a position opposite to the projection 316 into which the projection 316 is inserted. Furthermore, the second flange 321 is provided with a projection 327 that projects toward the first flange 311, located outside the groove 326 and inside the sealing material 330. The first flange 311 is also provided with a groove 317 at a position outside the projection 316 and inside the sealing material 330, opposite to the projection 327.

[0125] In the modified example 3, it is preferable that the expansion rate E6 of the protrusion 316, the thickness t6 of the protrusion 316, and the width w6 of the groove 326 satisfy the following formula (1c): Formula (1c): t6 × E6 > w6. Furthermore, it is preferable that the expansion rate E7 of the protrusion 327, the thickness t7 of the protrusion 327, and the width w7 of the groove 317 satisfy the following formula (1d): Formula (1d): t7 × E7 > w7.

[0126] Here, the expansion rate E6 of the protrusion 316 is the expansion rate of the thickness of the protrusion 316 after 600 seconds when the flame surface of the protrusion 316 is exposed to a burner so that the flame surface temperature is between 950°C and 1000°C, relative to the thickness t6 of the protrusion 316 before exposure to the flame. Similarly, the expansion rate E7 of the protrusion 327 is the expansion rate of the thickness of the protrusion 327 after 600 seconds when the flame surface of the protrusion 327 is exposed to a burner so that the flame surface temperature is between 950°C and 1000°C, relative to the thickness t7 of the protrusion 327 before exposure to the flame.

[0127] By satisfying equations (1c) and (1d), as shown in Figure 11, if the fire 305 is inside the battery box 301, the temperatures of the protrusions 316 and 327 rise. If the battery cover 310 is made of fiber-reinforced plastic, as shown in Figure 11, the temperature of the protrusion 316 rises and an expansion portion 314 is formed. The expansion portion 314 seals the gap between the battery cover 310 and the battery tray 320, so the sealing material 330 is not exposed to flames. As a result, the temperature of the sealing material 330 does not rise easily, and deterioration of the sealing material 330 due to heating can be suppressed. Also, if the battery tray 320 is made of fiber-reinforced plastic, as shown in Figure 11, the temperature of the protrusion 327 rises and an expansion portion 324 is formed. The expansion portion 324 seals the gap between the battery cover 310 and the battery tray 320, so the sealing material 330 is not exposed to flames. As a result, the temperature of the sealing material 330 does not rise easily, and deterioration of the sealing material 330 due to heating can be suppressed.

[0128] Thus, when the battery box 301 is heated, the protrusions 316 and 327 may expand in the in-plane direction of the adjacent region. Expanding in the "in-plane direction" of the adjacent region means expanding outward (direction of arrow O in Figure 11) or inward (direction of arrow I in Figure 11), and means expanding in a direction along the plane of the adjacent region (first flange 311 and second flange 321).

[0129] [Solidified and Expanded Layers After Combustion] 1. As shown in the schematic diagram 12, when exposed to flame, fiber-reinforced plastic may partially experience springback, forming a solidified layer P1 where springback has not occurred and an expanded layer P2 where springback has occurred. The formation of the expanded layer P2 is due to the softening of the thermoplastic resin when the fiber-reinforced plastic is exposed to flame, which causes springback of the reinforcing fibers. The fiber-reinforced plastic forms the expanded layer P2 sequentially from the flame-exposed side, and the solidified layer P1 transitions in such a way that the original composite material remains. In other words, the portion of the fiber-reinforced plastic where the thermoplastic resin softens due to heating and springback of the reinforcing fibers occurs is the expanded layer P2, and the portion where springback has not occurred is the solidified layer P1.

[0130] In other words, when the surface of fiber-reinforced plastic is exposed to flame from the composite material side with a burner so that the flame surface is between 950°C and 1000°C, and the fiber-reinforced plastic is observed after 600 seconds, it is preferable that the fiber-reinforced plastic transitions into a solidified layer P1 and an expanded layer P2, and that the thickness t3 of the solidified layer P1 satisfies equation (3) and the thickness t4 of the expanded layer P2 satisfies equation (4) relative to the thickness t1 of the fiber-reinforced plastic before exposure to flame. Equation (3) t1 × 0.1 < t3 < t1 × 0.7 Equation (4) t1 × 0.3 × 1.05 < t4 < t1 × 0.9 × 8 where, t3: thickness of solidified layer P1 t4: thickness of expanded layer P2.

[0131] 2. The solidification layer formula (3) refers to the range of thickness of the solidification layer, meaning that 600 seconds after the surface of the fiber-reinforced plastic is flammed with a burner so that the flame surface reaches 1000°C, more than 10% and less than 70% of the thickness t1 of the fiber-reinforced plastic before flammation remains as a solidification layer. Formula (3) is preferably formula (3a), more preferably formula (3b), and even more preferably formula (3c). Formula (3a) t1 × 0.2 < t3 < t1 × 0.6 Formula (3b) t1 × 0.25 < t3 < t1 × 0.5 Formula (3c) t1 × 0.3 < t3 < t1 × 0.4

[0132] More specifically, the thickness t3 of the solidified layer P1 preferably satisfies the following equation (3d), and more preferably satisfies equation (3e): Equation (3d) 0.1 mm < t3 < 5 mm Equation (3e) 0.5 mm < t3 < 3 mm

[0133] 3. The expansion layer formula (4) refers to the range of the expansion layer thickness, meaning that 600 seconds after the surface of the fiber-reinforced plastic is exposed to a flame from a burner so that the flame surface reaches 1000°C, the portion of the fiber-reinforced plastic thickness t1 other than the solidified layer P1 (30% to 90% of t1) expands in the thickness direction by more than 1.05 times and less than 8 times. Formula (4) is preferably formula (4a), more preferably formula (4b), and even more preferably formula (4c). Formula (4a) t1 × 0.4 × 1.05 < t4 < t1 × 0.8 × 8 Formula (4b) t1 × 0.5 × 1.05 < t4 < t1 × 0.75 × 8 Formula (4c) t1 × 0.6 × 1.05 < t4 < t1 × 0.7 × 8

[0134] More specifically, the thickness t4 of the expansion layer P2 preferably satisfies the following equation (4d), more preferably satisfies equation (4e), and even more preferably satisfies equation (4f): Equation (4d) 1 mm < t4 < 20 mm Equation (4e) 1.5 mm < t4 < 15 mm Equation (4f) 2 mm < t4 < 10 mm

[0135] [Preparation of Composite Materials] [Materials] 1. Reinforcing Fibers Two types of reinforcing fibers were prepared: (1) Glass fiber multi-end roving (Owens Corning: OC Paneluxe® 2400Tex) (2) Glass fiber single-end roving (Owens Corning: SE2348 roving 2000Tex)

[0136] 2. Resin: Polypropylene resin, Novatec® PP BC03C, manufactured by Nippon Polypropylene Co., Ltd. 3. Flame retardant: ADEKA® FP2100-JC, manufactured by ADEKA Corporation 4. Sealing material: Commercially available silicone O-ring, 6 mm in diameter

[0137] [Example 1] 1. Manufacturing of Composite Materials As a thermoplastic resin, a mixture of polypropylene resin (Novatec PPBC03C from Nippon Polypropylene Co., Ltd.) and 11 parts by mass of a flame retardant (Adeka Stab FP2100-JC) was prepared. A unidirectional, continuously moving, permeable support with a suction mechanism at its bottom was installed below the polypropylene resin dispenser. While moving the permeable support at 2 m / min, the polypropylene resin was sprayed from the dispenser onto the permeable support, and the polypropylene resin was fixed onto the permeable support to prepare a polypropylene resin aggregate.

[0138] A rotary cutter was placed above the breathable support, and the glass fiber multi-end roving (1) was cut to a constant length of 20 mm using the rotary cutter. At this time, compressed air was supplied directly below the rotary cutter, and the negative pressure generated in the airflow separated the glass fibers from the roll. The compressed air flow rate was 170 L / min.

[0139] Cut glass fibers were scattered onto a pre-fabricated polypropylene resin aggregate on a breathable support and fixed to create a composite composition consisting of the polypropylene resin aggregate and the glass fiber aggregate, with a width of 600 mm and a length of 3 m. The manufacturing speed of the composite composition was 2 m / min. The composite composition consisting of the prepared glass fiber aggregate and polypropylene resin aggregate was heated in a continuous impregnation device to impregnate the glass fibers with polypropylene resin and then cooled to obtain composite material 1. When cutting to a fixed length of 20 mm using a rotary cutter, the amount of glass fiber supplied was set so that the volume ratio of glass fiber to composite material 1 was 40%, and the average thickness of the composite material was 3.0 mm.

[0140] 2. Test sealing A sheet of fiber-reinforced plastic 901 was prepared by press molding of composite material 1, as shown in Figure 13. The thickness t1 of the fiber-reinforced plastic was 3.0 mm. When the sealing material 903 was sandwiched between the fiber-reinforced plastic 901 and the aluminum plate 902, the clearance t2 between the fiber-reinforced plastic 901 and the aluminum plate 902 was 1 mm. At a position horizontally away from the sealing material 903, a burner was applied to the surface of the fiber-reinforced plastic 901 from the fiber-reinforced plastic 901 side, so that the flame surface temperature was between 950°C and 1000°C, and the flame was extinguished after 600 seconds. Clearance measurement The clearance was measured using a commercially available thickness gauge (BerryKoKo berrykoko-YTX). Upon observation after the test, as shown in Figure 14, an expanded portion 904 was formed on the upper part of the fiber-reinforced plastic 901, and the upper end of the expanded portion 904 was in contact with the aluminum plate 902. In other words, the gap between the reinforced plastic 901 and the aluminum plate 902 was sealed, satisfying equation (1): t1 × E > ​​t1 + t2.

[0141] [Reference Examples] The following reference examples and reference comparative examples are described for the purpose of evaluating only fiber-reinforced plastics.

[0142] [Reference Example 1] A polypropylene resin composition was prepared by adding 11 parts by mass of a flame retardant (Adekastab FP2100-JC) to polypropylene (PP) resin (Novatec PPBC03C from Nippon Polypropylene Co., Ltd.). A unidirectional, continuously moving, permeable support having a suction mechanism at its bottom was installed below the polypropylene resin composition dispenser. While moving the permeable support at 2 m / min, the polypropylene resin composition was sprayed from the dispenser onto the permeable support, and the polypropylene resin composition was fixed onto the permeable support to prepare a polypropylene resin assembly.

[0143] A rotary cutter was placed above the breathable support, and the multi-end roving (1) was cut to a constant length of 20 mm using the rotary cutter. At this time, compressed air was supplied directly below the rotary cutter, and the negative pressure generated in the airflow separated the glass fibers from the roll. The compressed air flow rate was 170 L / min.

[0144] Cut glass fibers were scattered onto a pre-fabricated polypropylene resin aggregate on a breathable support and fixed to create a composite composition consisting of the polypropylene resin aggregate and the glass fiber aggregate, with a width of 600 mm and a length of 3 m. The manufacturing speed of the composite composition was 2 m / min. The prepared composite composition consisting of the polypropylene resin aggregate and the glass fiber aggregate was heated in a continuous impregnation device, impregnating the glass fiber aggregate with the polypropylene resin aggregate, and then cooled to obtain reference composite material 1. When cutting the glass fibers to a constant length of 20 mm using a rotary cutter, the supply amount of glass fibers was set so that the volume ratio of the glass fiber aggregate to reference composite material 1 was 40%, the volume ratio of the polypropylene resin aggregate to reference composite material 1 was 60%, and the average thickness of reference composite material 1 was 2.0 mm. The prepared reference composite material 1 was cold-pressed to obtain reference fiber-reinforced plastic.

[0145] [Reference Example 2] A reference fiber-reinforced plastic was prepared in the same manner as in Reference Example 1, except that the airflow rate when supplying compressed air was 50 L / min. [Reference Example 3] A reference fiber-reinforced plastic was prepared in the same manner as in Reference Example 1, except that the airflow rate when supplying compressed air was 230 L / min. [Reference Example 4] A reference fiber-reinforced plastic was prepared in the same manner as in Reference Example 1, except that the airflow rate when supplying compressed air was 300 L / min. [Reference Example 5] As a resin composition, a polypropylene resin composition was prepared by adding 11 parts by mass of a flame retardant (Adekastab FP2100-JC) to a polypropylene resin (Novatec PPBC03C from Nippon Polypropylene Co., Ltd.).

[0146] A unidirectional, continuously moving, breathable support with a suction mechanism at its bottom was installed below the polypropylene resin composition feeder. While moving the breathable support at 2 m / min, the polypropylene resin composition was sprayed from the feeder onto the breathable support, fixing the polypropylene resin composition onto the breathable support to prepare a polypropylene resin assembly. The glass fiber multi-end roving (1) was slit to a target fiber width of 1 mm using a slitting device (cutting by pressing against a rubber roll) to separate the fibers. The slit glass fiber multi-end roving (1) and the glass fiber single-end roving (2) were supplied to a rotary cutter installed above the breathable support in a 1:1 volume ratio, and cut to a constant length of 20 mm using the rotary cutter. At this time, compressed air was supplied directly below the rotary cutter, and the negative pressure generated by the airflow separated the glass fibers from the roll. The compressed air flow rate was 170 L / min. Cut glass fibers were scattered onto a pre-fabricated polypropylene resin aggregate on a breathable support and fixed to create a composite composition of the polypropylene resin aggregate and glass fiber aggregate with a width of 600 mm and a length of 3 m. The manufacturing speed of the composite composition was 2 m / min. The composite composition consisting of the prepared polypropylene resin aggregate and glass fiber aggregate was heated in a continuous impregnation device, impregnating the glass fiber aggregate with the polypropylene resin aggregate and then cooling to obtain reference composite material 5. When cutting the glass fibers to a constant length of 20 mm using a rotary cutter, the supply amount of glass fibers was set so that the volume ratio of the glass fiber aggregate to reference composite material 5 was 38%, the volume ratio of the polypropylene resin aggregate was 62%, and the average thickness of reference composite material 5 was 2.0 mm. The prepared reference composite material 5 was cold-pressed to create reference fiber-reinforced plastic.

[0147] [Reference Example 1] Fiber-reinforced plastic is prepared in the same manner as in Reference Example 1, except that the airflow rate when supplying compressed air is set to 0 L / min.

[0148] Table 1 shows the materials, volume percentage or parts by mass, and compressed air volume for Reference Examples 1 to 5 and Reference Comparative Example 1.

[0149] [Evaluation of Reference Examples and Reference Comparison Examples] 1. Tensile Strength Retention Rate 1.1 Ten test pieces measuring 25 mm in width and 150 mm in length are cut from the fiber-reinforced plastic prepared in Reference Examples 1 to 5 and Reference Comparison Example 1. 1.2 Tensile tests are performed on five of the obtained test pieces in accordance with ASTM D3039 (2019) at a loading speed of 1 mm / min., and the tensile strength is measured. The average value of the five pieces is taken as the tensile strength A before the combustion test. 1.3 Combustion Test A combustion test is performed on the remaining five test pieces. As shown in Figure 15, both ends of the test piece 904 are sandwiched between aluminum plates 906 with a 40 mm gap in the length direction, and the resin in the 40 mm region (combustion region 905) in the length direction of the center of the test piece 904 is directly burned with a gas burner flame 907 between 950°C and 1000°C. The burner nozzle 908 is kept 60 mm away from the test piece 904 during combustion. Depending on the test specimen, the temperature and time required to completely burn the resin in the combustion region 905 may vary. Therefore, the back surface temperature of the test specimen 904 is measured using a non-contact thermometer (A&D AD-5611A, Inc.) at a distance of 30 cm from the back surface on the opposite side (upper side of Figure 15) from the gas burner flame 907 in the center of the specimen 904. After confirming that the back surface temperature is 350 degrees Celsius or higher, the test specimen 904 is burned for 5 minutes. If the flame that ignited the test specimen 904 does not go out even after the gas burner flame 907 is extinguished after 5 minutes of burning, wait until it is completely extinguished and do not actively extinguish the flame. Depending on the type of resin, the resin in the combustion region 905 may not be completely burned off even under the above conditions. In this case, additional heating is recommended. 1.4 Tensile tests are performed on five test specimens after the combustion test in accordance with ASTM D3039 (2019) at a load rate of 1 mm / min. to measure the tensile strength. The average value of the five points is defined as the tensile strength B after the combustion test. 1.5 The tensile strength retention rate is calculated using formula (a1) from the tensile strength A before the combustion test and the tensile strength B after the combustion test.

[0150] 2. Work done and average rate of change after initial load application 2.1 Six test pieces, 25 mm wide and 150 mm long, are cut from the fiber-reinforced plastic prepared in Reference Examples 1 to 5 and Reference Comparative Example 1, respectively. 2.2 The test pieces are burned under the same conditions as in "1.3 Combustion Test" in "1. Tensile Strength Retention Rate" above. 2.3 According to Method A (strip method) of 8.14.1a) of JIS L 1096:2010, each of the six burnt test pieces is stretched at a tensile speed of 1 mm / min using a constant-speed elongation tensile testing machine with a gripping distance of 100 mm. The work done is calculated for each of the six test pieces by integrating the load in the tensile test with respect to the strain amount [mm], and the average value of the six test pieces is determined. Furthermore, by dividing the difference between the load at 0.2% strain and the load at 0.1% strain by the strain change of 0.1%, the average value (average rate of change) of the load change per unit of strain change from 0.1% to 0.2% strain was calculated, and the average value for the six test specimens was determined. In addition, by dividing the difference between the load at 3.0% strain and the load at 0.5% strain by the strain change of 2.5%, the average value (average rate of change) of the load change per unit of strain change from 0.5% to 3.0% strain was calculated, and the average value for the six test specimens was determined. Note that in Reference Comparative Example 1, the strain at which the load was maximum was less than 0.1%, and the loads at strains of 0.1%, 0.2%, 0.5%, and 3% were below the measurement limit.

[0151] 3. Springback Rate Two pieces of fiber-reinforced plastic prepared in Reference Examples 1-5 and Reference Comparative Example 1 are cut to 100 mm x 100 mm and stacked together. A thermocouple is inserted in the center of the joining surface. The pieces are then placed in a preheating furnace heated to 280°C (top and bottom heater temperature) and heated until the thermocouple temperature reaches 275°C. When the thermocouple temperature reaches 210°C, the pieces are removed from the furnace, cooled and solidified, and the thickness after preheating is measured. The ratio of the thickness before preheating to the thickness after preheating, expressed by the following formula, is calculated as the springback rate: Springback Rate = Thickness of fiber-reinforced plastic after preheating (mm) / Thickness of fiber-reinforced plastic before preheating (mm)

[0152] 4. For moldability, the reference composite material (flat plate) prepared in Reference Examples 1-5 and Reference Comparative Example 1 is cut to a length of 205 mm x width of 95 mm, two plates are stacked to a thickness of 2 mm, and dried in a hot air dryer at 120°C for 4 hours, after which the temperature is raised to 240°C using an infrared heater. Next, a flat plate-shaped mold is prepared and set to 60°C, and the two stacked reference composite materials are placed on top of it so as to overlap the opening. The mold is then closed by clamping it using a mechanical servo press (ZENFormer® MPS4200, manufactured by Hodenshimitsu Kako Kenkyusho Co., Ltd.). The thickness of the resulting press-molded body is observed, and the moldability is evaluated by comparing the thickness with that of the reference composite material prepared in Reference Examples 1-5 and Reference Comparative Example 1 to determine how much it has decreased. Perfect: Thickness reduction rate of 30% or more Excellent: Thickness reduction rate of 20% or more and less than 30% Better: Thickness reduction rate of 10% or more and less than 20% Good: Thickness reduction rate of 5% or more and less than 10% Bad: Thickness reduction rate of less than 5%

[0153] 5. Prepare 10 test pieces, each 300 mm wide and 300 mm long, of the composite material prepared in Reference Examples 1-5 and Reference Comparative Example 1 for thermal insulation. Place the test pieces on a frame-mounted test stand capable of accommodating a 300 mm square, and directly burn the center of each test piece with a burner flame between 950°C and 1000°C. Burn for 3 minutes with the burner nozzle 60 mm away from the test piece, and measure the temperature of the back surface opposite the burner flame at a distance of 30 cm from the test piece using a non-contact thermometer (A&D AD-5611A). Excellent: The back surface temperature during measurement is 200°C or less for 3 minutes from the start of flame contact. Very Good: The back surface temperature exceeds 200°C between 70 seconds and less than 3 minutes from the start of flame contact. Good: The back surface temperature exceeds 200°C between 10 seconds and 70 seconds from the start of flame contact. Unacceptable: The back surface temperature exceeds 200°C within 10 seconds of flame application. The evaluation results are shown in Table 2.

[0154]

Claims

1. A battery box comprising: a battery cover; a battery tray; and a sealing material disposed in a proximity region where the battery cover and the battery tray are in close proximity and in contact with the battery cover and the battery tray, wherein at least one of the battery cover and the battery tray is made of fiber-reinforced plastic containing discontinuous reinforcing fibers and thermoplastic resin, and the battery box satisfies the following formula (1): Formula (1): t1 × E > ​​t1 + t2 In Formula (1), t1 is the thickness of the fiber-reinforced plastic in the proximity region; t2 is the clearance between the battery cover and the battery tray in the proximity region; and E is the expansion rate of the thickness of the fiber-reinforced plastic after 600 seconds of being exposed to flame from a burner such that the flame surface temperature is between 950°C and 1000°C, relative to the thickness of the fiber-reinforced plastic before exposure to flame.

2. The battery box according to claim 1, wherein the battery cover has a first flange constituting the proximity region, the battery tray has a second flange constituting the proximity region, and the sealing material is sandwiched between the first flange and the second flange.

3. The battery box according to claim 1 or 2, wherein when the battery box is heated, the fiber-reinforced plastic expands in the adjacent region.

4. The battery box according to any one of claims 1 to 3, wherein when the battery box is heated, the fiber-reinforced plastic expands, thereby sealing the gap between the battery cover and the battery tray.

5. A battery box according to any one of claims 1 to 4, wherein the springback rate of the fiber-reinforced plastic is 1.05 or more and 8.0 or less.

6. The battery box according to any one of claims 1 to 5, wherein the weight-average fiber length of the discontinuous reinforcing fiber is 1 mm or more and 100 mm or less.

7. The battery box according to any one of claims 1 to 6, wherein the fiber-reinforced plastic contains 1 to 50 parts by mass of a flame retardant per 100 parts by mass of thermoplastic resin, and satisfies the following (a) and (b): (a) The tensile strength retention rate, shown by formula (a1), is greater than 0.03%. Formula (a1) Tensile strength retention rate (%) = (Tensile strength B after combustion ÷ Tensile strength A before combustion) × 100 (b) The amount of work per basis in a tensile test of a test piece with a width of 25 mm after a combustion test is 0.1 × 10 －３ [(N・mm) / (g / m ２ ) ] 300 x 10 －３ [(N・mm) / (g / m ２ )] Below, and with a maximum load per unit area of ​​1.1 × 10 －３ [N / (g / m) ２ That's all.

8. The battery box according to claim 7, wherein the fiber-reinforced plastic has a maximum load per unit weight in a tensile test of a 25 mm wide test piece after a combustion test, with the strain in the range of more than 0% and less than 5%.

9. The battery box according to any one of claims 7 or 8, wherein the fiber reinforced plastic satisfies the following (c). (c) In the tensile test on a test piece after the combustion test with a width of 25 mm, the average change rate of the load [N / (g / m ２ )] from a strain of 0.1% to 0.2% is in the range of 0.05×10 －３ [N / (g / m ２ )] or more and less than 300×10 －３ [N / (g / m ２ )].

10. The fiber-reinforced plastic is the battery box according to any one of claims 7 or 8, satisfying (c0) below: (c0) In a tensile test of a 25 mm wide test specimen after a combustion test, the load at a strain of 0.1% to 0.2% [N / (g / m ２ The change in ) ] is 0.005 × 10 －３ [N / (g / m) ２ ) ] 30 x 10 －３ [N / (g / m) ２ It is in the range of less than ).

11. The fiber-reinforced plastic is the battery box according to any one of claims 7 to 10, satisfying (d) below: (d) In a tensile test of a 25 mm wide test specimen after a combustion test, the load at strains from 0.5% to 3% [N / (g / m ２ The average rate of change of ) ] is -3.0 × 10 －３ [N / (g / m) ２ )] Above - 0.005 × 10 －３ [N / (g / m) ２ ) ] The range is as follows:

12. The fiber-reinforced plastic is the battery box according to any one of claims 7 to 10, satisfying (d0) below: (d0) In a tensile test of a 25 mm wide test specimen after a combustion test, the load at strains from 0.5% to 3% is [N / (g / m ２ The change in ) is -7.5 × 10 －３ [N / (g / m) ２ ) ] Above - 0.0125 × 10 －３ [N / (g / m) ２ ) ] The range is as follows:

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