Battery upper cover and preparation method thereof

Abstract

The invention belongs to the field of composite material forming processes, and particularly relates to a battery upper cover and a preparation method thereof, and the battery upper cover is prepared by carrying out processes such as pre-cutting, baking and preheating, transferring, compression molding, trimming and the like on a continuous fiber reinforced flame-retardant bio-based polyamide composite board. The battery upper cover provided by the invention has the characteristics of light weight, high forming efficiency, recyclable materials, high strength, fire resistance and good weather resistance, and simultaneously meets the requirements of the battery upper cover on air tightness and flame retardance.

Description

Technical Field

[0001] The present invention belongs to the field of composite material forming processes, and particularly relates to a battery upper cover and a preparation method thereof. Background Art

[0002] With the rapid development of new energy vehicles, the requirement for lightweighting is gradually increasing. As one of the key components of new energy vehicles, the battery upper cover usually uses sheet metal parts, which have the problem of large weight. Composite materials are gradually widely used in battery upper covers due to their advantages of high strength and low density.

[0003] Currently, the forming processes of composite upper covers are mostly SMC, HP-RTM, PCM and other methods. The resin matrices involved are all thermosetting resins, including epoxy resins, polyurethanes, unsaturated resins, etc. It is difficult to recycle and reuse them, which cannot meet the environmental protection requirements, and the forming cycle is relatively long. The thermoplastic resin matrix has become a potential material for upper covers favored by vehicle manufacturers due to its excellent performance and recyclability. However, currently, the thermoplastic materials mainly adopt the process method of long fiber reinforced compression molding (LFT-D), which makes the strength of the battery upper cover lower than that of the thermosetting composite with continuous fiber reinforcement, the thickness of the parts is large, the internal space of the shell is reduced, and the battery capacity is decreased.

[0004] Therefore, there is an urgent need in this field to develop a battery upper cover with a simple preparation method, suitable for mass production in the automotive industry, higher strength, and recyclable materials. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a battery upper cover and a preparation method thereof. The battery upper cover prepared by processes such as pre-cutting - baking and preheating - transfer - compression molding - trimming from a continuous fiber reinforced flame-retardant bio-based polyamide composite sheet has the characteristics of light weight, high forming efficiency, recyclable materials, high strength, better fire resistance and weather resistance, and at the same time meets the requirements for airtightness and flame retardancy of the battery upper cover.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a battery upper cover, which includes a cover body. The cover body has an opening, and a cover edge protruding outward is provided around the opening. The cover body and the cover edge are each independently composed of a fiber reinforced flame-retardant bio-based polyamide composite sheet.

[0008] In one embodiment, the fiber reinforced flame-retardant bio-based polyamide composite sheet is formed by hot pressing after alternately laying n layers of fiber reinforced flame-retardant grade unidirectional prepregs, where 2 ≤ n ≤ 10 and n is an integer, and the laying method between adjacent two layers of fiber reinforced flame-retardant grade unidirectional prepregs is 0 - 90° cross laying.

[0009] In some embodiments, the cross-ply means that the layers are cross-laid at a certain angle, meeting the principle of balanced and symmetric laying, such as 0° / 90° cross, 45° / 45° cross, 0° / 30° cross, 0° / 60° cross, etc.

[0010] In some embodiments, the thickness of the fiber-reinforced flame-retardant unidirectional prepreg tape is 0.15 - 0.5 mm, further 0.15 - 0.3 mm, still further 0.2 - 0.25 mm, for example, 0.22 mm, 0.24 mm, 0.28 mm, 0.35 mm, 0.4 mm, etc.

[0011] In some embodiments, the fiber-reinforced flame-retardant bio-based polyamide composite board further includes at least one fireproof and heat-insulating layer, and the fireproof and heat-insulating layer is disposed between adjacent two layers of fiber-reinforced flame-retardant unidirectional prepreg tapes.

[0012] In some specific embodiments, the fiber-reinforced flame-retardant bio-based polyamide composite board includes one fireproof and heat-insulating layer, and the fireproof and heat-insulating layer is disposed between the outermost layer of fiber-reinforced flame-retardant unidirectional prepreg tape and the sub-outermost layer of fiber-reinforced flame-retardant unidirectional prepreg tape.

[0013] In some embodiments, the fireproof and heat-insulating layer is selected from one of alumina film, aramid, and mica sheet.

[0014] In some embodiments, the thickness of the fireproof and heat-insulating layer is 0.03 - 0.15 mm, further 0.03 - 0.1 mm, for example, 0.05 mm, 0.08 mm, 0.1 mm, 0.12 mm, etc.

[0015] In some embodiments, the thickness of the fiber-reinforced flame-retardant bio-based polyamide composite board is > 1 mm, preferably 1.2 - 1.8 mm, further 1.2 - 1.5 mm, for example, 1.3 mm, 1.4 mm, 2 mm, etc.

[0016] In some embodiments, the fiber-reinforced flame-retardant unidirectional prepreg tape includes continuous long fibers and a flame-retardant bio-based polyamide material, and the mass percentage of the continuous long fibers in the fiber-reinforced flame-retardant unidirectional prepreg tape is 50 - 75%.

[0017] In some embodiments, the continuous long fibers include one or a combination of several of carbon fiber, glass fiber, silicon carbide fiber, basalt fiber, natural flax fiber, aramid fiber, semi-aromatic polyamide fiber, or polyolefin fiber.

[0018] Preferably, the continuous long fibers are continuous long glass fibers, and the single filament diameter can be 8-15 μm, and further 8-10 μm. Preferably, the linear density of the continuous glass fibers is 1200-4800 Tex, such as 1200 Tex, 2400 Tex, 3600 Tex. The continuous glass fibers are, for example, continuous long glass fibers with a specification of 1200 Tex purchased from Owens Corning (OC), and continuous long glass fibers with a specification of 2400 Tex purchased from Jushi.

[0019] In some embodiments, the flame-retardant bio-based polyamide material comprises a bio-based polyamide resin and a flame retardant.

[0020] In some specific embodiments, the flame-retardant bio-based polyamide material comprises the following components in parts by weight: 80-95 parts of bio-based polyamide resin, 5-12 parts of flame retardant, 0.1-1 part of antioxidant, 0.1-1 part of coupling agent, 0.1-1 part of lubricant, 0-5 parts of color masterbatch, and 0.1-1 part of flow modifier.

[0021] In a specific embodiment, the bio-based polyamide resin contains at least one diamine unit and at least one diacid unit. The diacid unit contains at least one aliphatic diacid unit, or contains at least one aromatic diacid unit, or contains at least one aliphatic diacid and at least one aromatic diacid unit. The diamine unit contains at least a pentamethylenediamine unit.

[0022] In one embodiment, the molar ratio of the diamine unit to the diacid unit is 0.9-1.2, and further 0.95-1.1, such as 1.05:1.

[0023] In one embodiment, the molar ratio of the aliphatic diacid unit to the aromatic diacid unit is 10-80:20-90, and further 20-50:50-75, such as 50:50, 30:70 or 35:65.

[0024] In one embodiment, the molar percentage of the pentamethylenediamine unit in the diamine unit is 20%-100%, preferably 20%-70%, such as 50.25%.

[0025] In a specific embodiment, the diamine unit is derived from an aliphatic diamine, preferably butanediamine, pentamethylenediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine or a combination thereof, such as derived from pentamethylenediamine and / or hexanediamine; the hexanediamine can be 1,6-hexanediamine.

[0026] In some specific embodiments, the pentamethylenediamine unit may be derived from bio - based pentamethylenediamine, which refers to pentamethylenediamine synthesized from biomass - derived compounds such as glucose and lysine through enzyme reactions, yeast reactions, or fermentation reactions during the monomer synthesis process. Among them, the bio - based content of the bio - based pentamethylenediamine can be determined by measuring the radioactive C14 content, such as the ASTM - D6866 method of the American Society for Testing and Materials.

[0027] In the present invention, the aliphatic diacid unit is derived from aliphatic short - chain diacids and / or aliphatic long - chain diacids.

[0028] In some specific embodiments, the aliphatic short - chain diacids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, or a combination thereof, preferably adipic acid, such as 1,6 - adipic acid.

[0029] In some specific embodiments, the aliphatic long - chain diacids include azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, or a combination thereof, preferably sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, or a combination thereof.

[0030] In some specific embodiments, the aliphatic diacid unit is derived from a combination of aliphatic short - chain diacids and aliphatic long - chain diacids. The aliphatic short - chain diacid is, for example, adipic acid, and the aliphatic long - chain diacid is selected from sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, or a combination thereof.

[0031] In the present invention, the aromatic diacid unit may be derived from aromatic diacids and / or aromatic diacid derivatives, preferably phthalic acid and / or phthalate.

[0032] In some specific embodiments, the phthalic acid may be one or more of terephthalic acid, isophthalic acid, and phthalic acid, such as terephthalic acid.

[0033] In some preferred embodiments, the diamine unit is derived from pentamethylenediamine; the aliphatic diacid unit is derived from adipic acid; the aromatic diacid unit is derived from terephthalic acid.

[0034] In some preferred embodiments, the diamine unit is derived from pentamethylenediamine; the aliphatic diacid unit is selected from any one of sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, and hexadecanedioic acid; the aromatic diacid unit is derived from terephthalic acid.

[0035] In some preferred embodiments, the bio-based polyamide resin contains diamine units, aliphatic diacid units and aromatic diacid units, wherein the diamine units are derived from pentamethylenediamine, the aliphatic diacid units are derived from aliphatic long-chain diacids, such as dodecanedioic acid, and the aromatic diacid units are derived from terephthalic acid, and the molar ratio of diamine units / [aliphatic diacid units + aromatic diacid units] is (0.99 - 1.1):1, and the molar ratio of aliphatic diacid units / aromatic diacid units is 1:(0.1 - 2.9), further 1:(0.3 - 1.2) or 1:(1.5 - 2.9).

[0036] In some specific embodiments, the bio-based polyamide resin is selected from bio-based polyamide PA56 / 5T, bio-based polyamide PA510 / 5T, bio-based polyamide PA511 / 5T, bio-based polyamide PA512 / 5T, bio-based polyamide PA513 / 5T, bio-based polyamide PA514 / 5T, bio-based polyamide PA515 / 5T, bio-based polyamide PA516 / 5T, bio-based polyamide PA56 / 5I, commercially available 6638, 6308, 6300, 6290, 6635, 6631, 6632, 6520, 5000, 3600, 3601, 3100, 3102, 3300, 3500, 2260, 2262, 1273, 1251, one or more of 1320.

[0037] In some specific embodiments, the relative viscosity of the bio-based polyamide resin can be 1.2 - 6.0, preferably 2.0 - 5.2, such as 2.57, 2.73, 3.15, 3.20, 3.27, 3.34, 3.50, 4.20, 4.50, 5.00 or 5.20. Among them, the relative viscosity is measured by the Ubbelohde viscometer concentrated sulfuric acid (concentration 96%) method.

[0038] In some specific embodiments, the melting point of the bio-based polyamide resin can be 190°C - 320°C, preferably 250°C - 320°C, more preferably 280°C - 310°C, such as 267°C, 279°C, 275°C, 287°C, 289°C, 298°C or 300°C.

[0039] In some specific embodiments, the saturated water absorption rate of the bio-based polyamide resin is below 15, preferably below 10, specifically such as 6.5, 7.8, 8.3, 9.2, 10.5, 11.2, 12.5, 13, etc.

[0040] In some embodiments, the flame retardant includes one or more of a phosphorus-containing flame retardant, a halogen flame retardant, a nitrogen-based flame retardant, or an inorganic flame retardant.

[0041] In one embodiment, the phosphorus-containing flame retardant includes, but is not limited to, one or more of red phosphorus, aryl monophosphate, aryl bisphosphate, dimethyl alkylphosphonate, triphenyl phosphate, tricresyl phosphate, tris(xylenyl) phosphate, propylbenzene-based phosphate, butylbenzene-based phosphate, or hypophosphite. Preferably, the hypophosphite can be a metal salt of an organic hypophosphonic acid, such as a metal salt of methyl ethyl phosphinic acid (aluminum methyl ethyl phosphinate, zinc methyl ethyl phosphinate) and a metal salt of diethyl phosphinic acid (aluminum diethyl phosphinate, zinc diethyl phosphinate). The hypophosphite can also be aluminum hypophosphite, magnesium hypophosphite, calcium hypophosphite, and / or zinc hypophosphite.

[0042] In one embodiment, the halogen flame retardant is, but is not limited to, selected from one or more of hexabromocyclododecane, decabromodiphenyl ether, octabromodiphenyl ether, tetrabromobisphenol A, bis(tribromophenoxy)ethane, bis(pentabromophenoxy)ethane, tetrabromobisphenol A epoxy resin, tetrabromobisphenol A carbonate, ethylenebis(tetrabromophthalimide), ethylenebis(pentabromobiphenyl), tris(tribromophenoxy)triazine, bis(dibromopropyl)tetrabromobisphenol A, bis(dibromopropyl)tetrabromobisphenol S, brominated polyphenylene ether, brominated polystyrene, brominated crosslinked aromatic polymer, brominated epoxy resin, brominated phenoxy resin, brominated styrene-maleic anhydride copolymer, tetrabromobisphenol S, tris(tribromoneopentyl)phosphate, polybromotrimethylphenyl indane, tris(dibromopropyl)isocyanurate.

[0043] In one embodiment, the nitrogen-based flame retardant includes, but is not limited to, melamine cyanurate, melamine polyphosphate, melamine pyrophosphate, melamine phosphate, bis(melamine)pyrophosphate, melam polyphosphate, or melamine polyphosphate.

[0044] In one embodiment, the inorganic flame retardant includes, but is not limited to, metal hydroxides such as magnesium hydroxide, calcium hydroxide, calcium aluminate, aluminum hydroxide, and other zinc salts such as zinc borate, zinc phosphate, etc.

[0045] In a specific embodiment, the flame retardant is a compound of a halogen flame retardant and a phosphorus-containing flame retardant or a compound of a halogen flame retardant and a nitrogen-based flame retardant.

[0046] In one embodiment, the flame retardant is a combination of any two selected from aluminum diethylphosphinate, decabromodiphenyl ether, and melamine polyphosphate.

[0047] In one embodiment, the flame retardant is a compound of aluminum diethylphosphinate and decabromodiphenyl ether, and the weight ratio of aluminum diethylphosphinate to decabromodiphenyl ether is 3-5:1, such as 3:1, 4:1, or 5:1.

[0048] In one embodiment, the flame retardant is a compound of melamine polyphosphate and decabromodiphenyl ether, and the weight ratio of melamine polyphosphate to decabromodiphenyl ether is 4-6:1.

[0049] In some specific embodiments, the masterbatch is selected from a black masterbatch and a yellow masterbatch. The masterbatch is conventional in the art. For example, it is the PA3785 black masterbatch purchased from Cabot.

[0050] In one embodiment, the antioxidant is selected from one or more of phenolic antioxidants, hindered amine antioxidants, or phosphite antioxidants. Preferably, the antioxidant is selected from one or more of commercially available antioxidant 168, antioxidant 1098, antioxidant 1010, and antioxidant S9228.

[0051] In one embodiment, the lubricant includes, but is not limited to, one or several of stearate lubricants, fatty amide lubricants, silicone powder or silicone masterbatch, PE wax, and ethylene-acrylic acid copolymer.

[0052] In one embodiment, the coupling agent includes, but is not limited to, one or more of silane coupling agents, carbonate coupling agents, and aluminate coupling agents.

[0053] In one embodiment, the flow dispersant includes at least one of organosilicon polymers, polyester resins, and long-chain dibasic acids. Further, the polyester resin includes, but is not limited to, MF-3332. Further, the long-chain dibasic acid includes undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, or octadecanedioic acid, and is further preferably dodecanedioic acid or tridecanedioic acid.

[0054] In some specific embodiments, the fiber-reinforced flame-retardant unidirectional prepreg tape is prepared by the melt impregnation method, and the specific preparation process can be obtained with reference to the preparation processes disclosed in CN115260752A, CN115260753A or CN115536876A.

[0055] In one embodiment, the thickness of the battery upper cover is 1 - 1.5 mm.

[0056] In one embodiment, the airtightness of the battery upper cover is qualified.

[0057] In one embodiment, the flame retardant grade of the battery upper cover is V0 or above.

[0058] In one embodiment, when the battery upper cover is burned by a flame at a temperature of 1200 ± 50 °C until it is burned through, the time ≥ 20 min, further ≥ 30 min, and it has good fire resistance.

[0059] In one embodiment, after the battery upper cover is aged for 1000 h under the conditions of 85 °C / 85% RH, its tensile strength ≥ 300 MPa, further ≥ 360 MPa, and even further ≥ 375 MPa; the tensile modulus ≥ 18 GPa, further ≥ 19 GPa; the mechanical property retention rate (tensile strength retention rate) reaches more than 60%, further reaches more than 70%, and even further reaches more than 75%, and it has good weather resistance.

[0060] In one embodiment, according to needs, the cover body of the battery upper cover can be a smooth planar structure, or a structure with several protrusions added on the plane. The present invention has no special limitation on the shape of the protrusions, and the protrusions are composed of a fiber-reinforced flame-retardant bio-based polyamide composite board.

[0061] The present invention also provides a preparation method for the above-mentioned battery upper cover, and the method includes:

[0062] S1. According to the pre-designed shape of the target product, cut the fiber-reinforced flame-retardant bio-based polyamide composite board, lay the cut special-shaped materials according to the design method, and preheat and plasticize at 230 - 340 °C for 30 - 120 s;

[0063] S2. Quickly transfer the preheated and plasticized special-shaped materials into the mold, quickly close the mold and keep the pressure, take out the hot-pressed product, and trim the edge part to obtain the product.

[0064] In one embodiment, in step S1, the temperature for preheating and plasticizing is 310 - 340 °C, preferably 320 - 340 °C, and the time is 60 - 120 s.

[0065] In one embodiment, in step S2, the time for quickly transferring the preheated and plasticized profiled material to the mold does not exceed 15 s, preferably 5 - 15 s, more preferably 8 - 12 s.

[0066] In one embodiment, in step S2, during the rapid mold closing process, the time from the start of mold closing and pressurization to reaching the target pressure is controlled to be 5 - 10 s.

[0067] In one embodiment, in step S2, the temperature of the upper mold is controlled to be 80 - 120 °C, preferably 90 - 110 °C.

[0068] In one embodiment, in step S2, the temperature of the lower mold is controlled to be 85 - 125 °C, preferably 95 - 115 °C.

[0069] In one embodiment, in step S2, the holding pressure is controlled to be 8 - 20 MPa, preferably 10 - 20 MPa.

[0070] In one embodiment, in step S2, the holding time is controlled to be 30 - 90 s, preferably 60 - 90 s, such as 60 s.

[0071] In one embodiment, in step S1, the pre-designed shape of the target product may include a main structure, or may include a main structure and a local reinforcement structure. The specific reinforcement position depends on the shell structure, including but not limited to the raised part on the battery upper cover, or the connecting part at the edge of the battery upper cover, such as the flange area around the opening.

[0072] In the present invention, the cutting method may be mechanical cutting, laser cutting, water cutting, etc., preferably laser cutting.

[0073] In step S2 of the present invention, the cut profiled material is laid according to the designed laying method by using a holding device, and then preheated and plasticized.

[0074] The present invention also provides a battery case, which includes an upper cover and a lower housing. The upper cover is connected to the lower housing, and the upper cover adopts the battery upper cover as described above or the battery upper cover prepared by the above method.

[0075] The present invention also provides a power battery pack, which includes a battery case and a power battery module located inside the battery case. The battery case adopts the battery case structure as described above.

[0076] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0077] The reagents and raw materials used in the present invention are all commercially available.

[0078] The positive and progressive effects of the present invention are as follows:

[0079] 1. The present invention uses a continuous fiber-reinforced flame-retardant bio-based polyamide composite sheet to prepare a battery upper cover, which has a better lightweight effect, achieving the purpose of energy conservation and environmental protection; and the product is easy to recycle and can be recycled.

[0080] 2. The battery upper cover prepared by the present invention using a continuous fiber-reinforced flame-retardant bio-based polyamide composite sheet has the characteristics of higher strength, can effectively reduce the thickness of the part, improve the internal use space of the housing, increase the battery capacity, and the product has qualified airtightness, a flame retardant grade of V0 or above, and excellent fire resistance and weather resistance.

[0081] 3. The battery upper cover of the present invention is prepared by processes such as pre-cutting - reinforcement - baking and preheating - transfer - molding - trimming of the continuous fiber-reinforced flame-retardant bio-based polyamide composite sheet, and the rapid hot pressing molding time is short, enabling continuous and automated production, and greatly improving the molding efficiency. Specific Embodiments

[0082] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product instructions. In the following examples and comparative examples, the raw materials are commercially available unless otherwise specified: the antioxidant is purchased from BASF Group, Germany; the lubricant silicone masterbatch is purchased from Chengdu Silike Technology Co., Ltd.; the coupling agent is purchased from Hangzhou Jessica Chemical Co., Ltd.; the continuous long glass fiber is purchased from Owens Corning (OC) with a specification of 1200 Tex; the flow modifier MF-3332 is purchased from Beijing Weisheng Hongda Technology Co., Ltd., the flow modifier dodecanedioic acid is provided by Shanghai Kaisai Biotechnology Co., Ltd., and the color masterbatch PA3785 black masterbatch is purchased from Cabot (USA) Corporation.

[0083] Preparation Example 1 - Continuous Long Glass Fiber Reinforced Flame-Retardant Bio-Based Polyamide PA5T / 56 Composite Sheet

[0084] (1) Weigh the following components according to parts by weight: 85 parts of bio-based polyamide resin PA5T / 56, 3 parts of color masterbatch PA3785, 10 parts of flame retardant red phosphorus, 0.2 part of antioxidant 1098, 0.3 part of silane coupling agent, 0.5 part of lubricant silicone masterbatch, 1 part of flow modifier MF-3332, and add the above components to a high-speed mixer for mixing to obtain a flame-retardant bio-based polyamide material;

[0085] Among them, the bio-based polyamide resin PA5T / 56 is prepared by referring to the method of bio-based copolyamide A (PA56T-A) in Chinese invention patent CN115536876A, with a relative viscosity of 2.45, a melting point of 270 °C, and a saturated water absorption rate of 12.5;

[0086] (2) Refer to the melt impregnation method in Example 3 of Chinese invention patent CN115536876A to prepare a flame-retardant unidirectional prepreg tape with a thickness of 0.25 mm. Among them, the weight ratio of the flame-retardant bio-based polyamide material to the continuous long glass fiber is 35:65;

[0087] (3) Lay 5 layers of the flame-retardant unidirectional prepreg tape alternately in a 0° / 90° cross pattern, and continuously composite it with a double steel belt machine to obtain a composite plate with a thickness of 1.2 mm.

[0088] Preparation Example 2 - Continuous Long Glass Fiber Reinforced Flame-Retardant Bio-Based Polyamide PA5T / 512 Composite Plate

[0089] (1) Weigh the following components by weight: 92 parts of bio-based polyamide resin PA5T / 512, 1 part of color masterbatch PA3785, 5 parts of flame retardant red phosphorus, 0.5 part of antioxidant 1098, 0.3 part of silane coupling agent, 0.2 part of lubricant silicone masterbatch, and 1 part of flow modifier dodecanedioic acid. Add the above components to a high-speed mixer and mix to obtain a flame-retardant bio-based polyamide material;

[0090] Among them, the bio-based polyamide PA5T / 512 contains the following structural units (Ⅰ), (Ⅱ) and (Ⅲ);

[0091]

[0092] The molar sum ratio of structural unit (Ⅰ) to structural units (Ⅱ) and (Ⅲ) is 1.01:1; the molar ratio of structural unit (Ⅱ) to structural unit (Ⅲ) is 1:0.88; the relative viscosity is 2.65, the melting point is 293 °C, and the saturated water absorption rate is 8.3; it is provided by Shanghai Kaisai Biotechnology Co., Ltd.

[0093] (2) Refer to the melt impregnation method in Example 3 of Chinese invention patent CN115536876A to prepare a fiber-reinforced flame-retardant unidirectional prepreg tape with a thickness of 0.25 mm. Among them, the weight ratio of the flame-retardant bio-based polyamide material to the continuous long glass fiber is 30:70;

[0094] (3) Lay 5 layers of the flame-retardant unidirectional prepreg tape alternately in a 0° / 90° cross pattern, and continuously composite it with a double steel belt machine to obtain a composite plate with a thickness of 1.2 mm.

[0095] Preparation Example 3 - Continuous Long Glass Fiber Reinforced Flame-Retardant Bio-Based Polyamide PA5T / 512 Composite Plate Including a Fireproof and Heat Insulating Layer

[0096] Steps (1) and (2) are the same as those in Preparation Example 2;

[0097] (3) After alternately laying 4 layers of fiber-reinforced flame-retardant unidirectional prepreg tapes in a 0° / 90° cross pattern, then laying a 0.05-mm-thick fireproof and heat-insulating layer (aluminum oxide film) and a layer of fiber-reinforced flame-retardant unidirectional prepreg tape (i.e., the outermost layer) in sequence, and with the laying pattern of the 4th layer and the outermost layer of fiber-reinforced flame-retardant unidirectional prepreg tape being 0° / 90° cross, a composite board with a thickness of 1.25 mm is obtained through continuous compounding by a double steel belt machine.

[0098] Preparation Example 4 - Continuously Long Glass Fiber Reinforced Flame-Retardant Bio-Based Polyamide PA5T / 512 Composite Board

[0099] It is basically the same as Preparation Example 2, with the differences being: in step (1), in the bio-based polyamide PA5T / 512, the molar sum ratio of structural unit (Ⅰ) to structural units (Ⅱ) and (Ⅲ) is 1.01:1; the molar ratio of structural unit (Ⅱ) to structural unit (Ⅲ) is 1:1.5; the relative viscosity is 2.42, the melting point is 303 °C, and the saturated water absorption rate is 11.2 (provided by Shanghai Kaisai Biotechnology Co., Ltd.);

[0100] Steps (2) and (3) are the same as those in Preparation Example 2.

[0101] Preparation Example 5 - Continuously Long Glass Fiber Reinforced Flame-Retardant PP Composite Board

[0102] It is basically the same as Preparation Example 2, with the difference being: in step (1), the bio-based polyamide resin PA5T / 512 is replaced with PP (purchased from ExxonMobil Corporation);

[0103] In step (3), the flame-retardant unidirectional prepreg tapes are alternately laid 7 layers in a 0° / 90° cross pattern, and a composite board with a thickness of 1.7 mm is obtained through continuous compounding by a double steel belt machine.

[0104] Example 1

[0105] S1 According to the pre-designed shape of the target product, the continuously long glass fiber reinforced flame-retardant bio-based polyamide PA5T / 56 composite board prepared in Preparation Example 1 is laser cut, and the cut special-shaped materials are placed in the designed manner using a clamping device and preheated and plasticized at 310 °C for 60 s;

[0106] S2 The preheated and plasticized special-shaped materials are quickly transferred to a mold, quickly clamped and pressure-maintained, and the product after hot pressing is taken out and the edge part is trimmed to obtain the product.

[0107] The time for quickly transferring the preheated and plasticized special-shaped materials to the mold is 10 s; during the quick clamping process, the time from the start of clamping and pressurizing to reaching the target pressure is controlled to be 8 s; the temperature of the upper mold is controlled to be 100 °C, the temperature of the lower mold is 105 °C, the pressure-maintaining pressure is 15 MPa, and the pressure-maintaining time is 60 s.

[0108] Example 2

[0109] S1 According to the pre-designed shape of the target product, the continuous long glass fiber reinforced flame-retardant bio-based polyamide PA5T / 56 composite sheet prepared in Preparation Example 1 is laser cut, and the cut special-shaped material is laid according to the designed method by using a clamping device, and preheated and plasticized at 310 °C for 30 s;

[0110] S2 The preheated and plasticized special-shaped material is quickly transferred to the mold, quickly clamped and pressure-maintained, and the product after hot pressing is taken out, and the edge part is trimmed to obtain the product.

[0111] The time for quickly transferring the preheated and plasticized special-shaped material to the mold is 10 s; during the quick clamping process, the time from the start of clamping and pressurizing to reaching the target pressure is controlled to be 8 s; the temperature of the upper mold is controlled to be 102 °C, the temperature of the lower mold is controlled to be 106 °C, the pressure-maintaining pressure is 14 MPa, and the pressure-maintaining time is 65 s.

[0112] Example 3

[0113] S1 According to the pre-designed shape of the target product, the continuous long glass fiber reinforced flame-retardant bio-based polyamide PA5T / 512 composite sheet prepared in Preparation Example 2 is laser cut, and the cut special-shaped material is laid according to the designed method by using a clamping device, and preheated and plasticized at 330 °C for 80 s;

[0114] S2 The preheated and plasticized special-shaped material is quickly transferred to the mold, quickly clamped and pressure-maintained, and the product after molding is taken out, and the edge part is trimmed to obtain the product.

[0115] The time for quickly transferring the preheated and plasticized special-shaped material sheet to the mold is 9 s; during the quick clamping process, the time from the start of clamping and pressurizing to reaching the target pressure is controlled to be 9 s; the temperature of the upper mold is controlled to be 105 °C, the temperature of the lower mold is controlled to be 110 °C, the pressure-maintaining pressure is 18 MPa, and the pressure-maintaining time is 75 s.

[0116] Example 4

[0117] S1 According to the pre-designed shape of the target product, the continuous long glass fiber reinforced flame-retardant bio-based polyamide PA5T / 512 composite sheet prepared in Preparation Example 3 is laser cut, and the cut special-shaped material is laid according to the designed method by using a clamping device, and preheated and plasticized at 330 °C for 80 s;

[0118] S2 The preheated and plasticized special-shaped material is quickly transferred to the mold, quickly clamped and pressure-maintained, and the product after molding is taken out, and the edge part is trimmed to obtain the product.

[0119] The time for quickly transferring the preheated and plasticized profiled sheet into the mold is 9 s; during the rapid mold closing process, the time from the start of mold closing and pressurization to reaching the target pressure is controlled to be 9 s; the temperature of the upper mold is controlled at 110 °C, the temperature of the lower mold is controlled at 110 °C, the holding pressure is 20 MPa, and the holding time is 75 s.

[0120] Example 5

[0121] S1 According to the pre-designed shape of the target product, the continuous long glass fiber reinforced flame-retardant bio-based polyamide PA5T / 512 composite sheet prepared in Preparation Example 2 is laser cut, and the cut profiled material is laid in the designed manner by using a clamping device, and preheated and plasticized at 310 °C for 80 s;

[0122] S2 The preheated and plasticized profiled material is quickly transferred into the mold for rapid mold closing and pressure holding, the molded product is taken out, and the edge part is trimmed to obtain the product.

[0123] The time for quickly transferring the preheated and plasticized profiled sheet into the mold is 9 s; during the rapid mold closing process, the time from the start of mold closing and pressurization to reaching the target pressure is controlled to be 9 s; the temperature of the upper mold is controlled at 105 °C, the temperature of the lower mold is controlled at 110 °C, the holding pressure is 18 MPa, and the holding time is 75 s.

[0124] Example 6

[0125] S1 According to the pre-designed shape of the target product, the continuous long glass fiber reinforced flame-retardant bio-based polyamide PA5T / 512 composite sheet prepared in Preparation Example 2 is laser cut, and the cut profiled material is laid in the designed manner by using a clamping device, and preheated and plasticized at 340 °C for 80 s;

[0126] S2 The preheated and plasticized profiled material is quickly transferred into the mold for rapid mold closing and pressure holding, the hot-pressed product is taken out, and the edge part is trimmed to obtain the product.

[0127] The time for quickly transferring the preheated and plasticized profiled sheet into the mold is 15 s; during the rapid mold closing process, the time from the start of mold closing and pressurization to reaching the target pressure is controlled to be 9 s; the temperature of the upper mold is controlled at 105 °C, the temperature of the lower mold is controlled at 110 °C, the holding pressure is 18 MPa, and the holding time is 75 s.

[0128] Example 7

[0129] The battery upper cover is prepared by a process similar to that of Example 3, except that in step S1, the continuous long glass fiber reinforced flame-retardant bio-based polyamide PA5T / 512 composite sheet prepared in Preparation Example 4 is laser cut, and the others are the same as in Example 3.

[0130] Comparative Example 1

[0131] The battery upper cover was prepared using a process similar to that of Example 3, except that: in step S1, there was no preheating and plasticizing step, and the rest was the same as in Example 3.

[0132] Comparative Example 2

[0133] S1 According to the pre-designed shape of the target product, the continuous long glass fiber-reinforced flame-retardant PP composite sheet prepared in Preparation Example 5 was laser cut. The cut special-shaped material was laid according to the designed method using a clamping device and preheated and plasticized at 210 °C for 80 s.

[0134] S2 The preheated and plasticized special-shaped material was quickly transferred to the mold, the mold was quickly closed and pressure was maintained. The molded product was taken out and the edge part was trimmed to obtain the product.

[0135] The time for quickly transferring the preheated and plasticized special-shaped material sheet to the mold was 15 s; during the quick mold closing process, the time from the start of mold closing and pressurization to reaching the target pressure was controlled to be 9 s; the temperature of the upper mold was controlled to be 85 °C, the temperature of the lower mold was 90 °C, the pressure holding pressure was 18 MPa, and the pressure holding time was 75 s.

[0136] Performance Test

[0137] The following performance tests were carried out on the battery upper covers provided in the above examples and comparative examples:

[0138] Fire resistance test: A single-point burning experiment was carried out using a propane flame gun. Experimental conditions: oxygen: 0.5 MPa, propane: 0.07 MPa, nozzle distance: 100 mm, flame temperature: 1200 ± 50 °C. Record the time from when the flame burns until the battery upper cover is burned through.

[0139] Flame retardant grade: A UL94 horizontal burning experiment was carried out. According to UL94 requirements, a specimen with a thickness of 1.5 mm was placed in the center of an alcohol lamp flame with a flame length of 50 mm, the coated surface was kept horizontally downward for 20 s, and the time until the flame went out was measured after taking it out to evaluate the flame retardant grade.

[0140] Weather resistance test: After aging a standard specimen for 1000 h under constant temperature and humidity conditions of 85 °C / 85% RH, a tensile test was carried out in accordance with GB / T 1447-2005. The test speed was 2 mm / min. The tensile strength and tensile modulus of the test specimen were measured and compared with the data before the aging test to obtain the retention rate of the tensile strength.

[0141] Air tightness detection: After installing the battery upper cover prepared in the above examples on the battery case, in accordance with the national standard GB / T31467.3-2015 "Lithium-ion power battery pack and box system for electric vehicles - Part 3: Safety requirements and test methods", its air tightness was detected.

[0142] The preparation processes of the examples and comparative examples are shown in Table 1, and the test results are shown in Table 2.

[0143] Table 1

[0144]

[0145] Table 2

[0146]

[0147]

[0148] As can be seen from the above table, by optimizing the resin for the continuous fiber-reinforced flame-retardant bio-based polyamide composite sheet and the process conditions, the obtained battery upper cover has qualified airtightness, a high flame-retardant grade, excellent fire resistance and weather resistance, meets the basic requirements of the battery upper cover, and has a wide application prospect.

[0149] The above is an exemplary description of the embodiments of the present invention. However, the protection scope of the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A battery upper cover, which comprises a cover body. The cover body has an opening, and a cover edge protruding outward is provided around the opening. The cover body and the cover edge are each independently composed of a fiber-reinforced flame-retardant bio-based polyamide composite sheet.

2. The battery upper cover according to claim 1, characterized in that, The fiber-reinforced flame-retardant bio-based polyamide composite sheet is formed by hot pressing after alternately laying n layers of fiber-reinforced flame-retardant grade unidirectional prepreg tapes, where 2 ≤ n ≤ 10 and n is an integer. The laying method between adjacent two layers of fiber-reinforced flame-retardant grade unidirectional prepreg tapes is 0-90° cross laying; The thickness of the fiber-reinforced flame-retardant grade unidirectional prepreg tape is 0.15 - 0.5 mm, further 0.15 - 0.3 mm, and still further 0.2 - 0.25 mm.

3. The battery upper cover according to claim 2, wherein The fiber-reinforced flame-retardant bio-based polyamide composite sheet further comprises at least one fireproof and heat-insulating layer, and the fireproof and heat-insulating layer is arranged between adjacent two layers of fiber-reinforced flame-retardant grade unidirectional prepreg tapes; The fireproof and heat-insulating layer is selected from one of alumina film, aramid, and mica sheet; The thickness of the fireproof and heat-insulating layer is 0.03 - 0.15 mm.

4. The battery top cover according to claim 2, characterized in that, The thickness of the fiber-reinforced flame-retardant bio-based polyamide composite sheet is > 1 mm, preferably 1.2 - 1.8 mm; and / or, The fiber-reinforced flame-retardant grade unidirectional prepreg tape comprises continuous long fibers and a flame-retardant bio-based polyamide material, and the mass percentage of the continuous long fibers in the fiber-reinforced flame-retardant grade unidirectional prepreg tape is 50 - 75%; The continuous long fibers include one or a combination of several of carbon fiber, glass fiber, silicon carbide fiber, basalt fiber, natural flax fiber, aramid fiber, semi-aromatic polyamide fiber, or polyolefin fiber; The flame-retardant bio-based polyamide material comprises a bio-based polyamide resin and a flame retardant.

5. The battery upper cover according to claim 4, characterized in that, The bio-based polyamide resin contains at least one diamine unit and at least one diacid unit. The diacid unit contains at least one aliphatic diacid unit, or contains at least one aromatic diacid unit, or contains at least one aliphatic diacid unit and at least one aromatic diacid unit. The diamine unit contains at least pentamethylenediamine unit; The molar ratio of the diamine unit to the diacid unit is (0.9 - 1.2):1, preferably (0.95 - 1.1):1; The molar ratio of the aliphatic diacid unit to the aromatic diacid unit is (10 - 80):(20 - 90), preferably (20 - 50):(50 - 75); The molar percentage of the pentamethylenediamine unit in the diamine unit is 20% - 100%, preferably 20% - 70%; and / or, the relative viscosity of the bio-based polyamide resin is 1.2 - 6.0, preferably 2.0 - 5.2; the melting point is 190°C - 320°C, preferably 250°C - 320°C, and more preferably 280°C - 310°C; and / or, the saturated water absorption rate of the bio-based polyamide resin is below 15, preferably below 10.

6. A method for preparing a battery upper cover according to any one of claims 1-5, characterized in that, The method includes: S1. According to the pre-designed shape of the target product, cut the fiber-reinforced flame-retardant bio-based polyamide composite sheet, lay the cut special-shaped materials in the designed manner, and preheat and plasticize at 230 - 340°C for 30 - 120 s; S2. Rapidly transfer the preheated and plasticized profiled material into the mold, quickly close the mold and apply pressure, take out the product after hot pressing and forming, and trim the edge part to obtain the product.

7. The preparation method according to claim 6, characterized in that, In step S1, the temperature for preheating and plasticizing is 310 - 340 °C, preferably 320 - 340 °C, and the time is 60 - 120 s. In step S2, the time for rapidly transferring the preheated and plasticized profiled material into the mold does not exceed 15 s, preferably 5 - 15 s, more preferably 8 - 12 s; and / or In step S2, during the rapid mold closing process, control the time from the start of mold closing and pressurization to reaching the target pressure to be 5 - 10 s.

8. The preparation method according to claim 6, characterized in that, In step S2, control the temperature of the upper mold to be 80 - 120 °C, preferably 90 - 110 °C; and / or In step S2, control the temperature of the lower mold to be 85 - 125 °C, preferably 95 - 115 °C; and / or In step S2, control the pressure holding pressure to be 8 - 20 MPa, preferably 10 - 20 MPa; and / or In step S2, control the pressure holding time to be 30 - 90 s, preferably 60 - 90 s.

9. A battery case, which comprises an upper cover and a lower housing, the upper cover is connected to the lower housing, and the upper cover is the battery upper cover as described in any one of claims 1 - 5 or the battery upper cover prepared by the method as described in any one of claims 6 - 8.

10. A power battery pack, which comprises a battery case and a power battery module located inside the battery case, and the battery case has the structure of the battery case as described in claim 9.

Images