Polyurethane composites, methods of making the same, and cover articles containing the polyurethane composites

Abstract

The present invention relates to a novel polyurethane (PU) composite, a process for preparing the PU composite and a coated article containing the PU composite; the PU composite comprising 35 to 75 wt.-% of reinforcing fibers, based on the total weight of the PU composite; wherein the reinforcing fibers comprise 75 to 100 wt.-% of reinforcing fibers in the form of a continuous phase and 0 to 25 wt.-% of reinforcing fibers in the form of a discontinuous phase, based on the total weight of the reinforcing fibers.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to International Application No. PCT / CN2021 / 117427, filed on September 9, 2021, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] This invention relates to a novel polyurethane (PU) composite material, a method for preparing the PU composite material, and a covering article containing the PU composite material. The PU composite material comprises 35 to 75% by weight of reinforcing fibers, based on the total weight of the PU composite material; wherein the reinforcing fibers comprise 75 to 100% by weight of continuous phase reinforcing fibers and 0 to 25% by weight of discontinuous phase reinforcing fibers, based on the total weight of the reinforcing fibers. Background Technology

[0004] With the development of electric vehicles, lightweight design and capacity limitations of batteries are receiving increasing attention. Currently, stamped metal sheets are mainly used as covers for battery packs to protect the battery components. Although metal materials exhibit good mechanical properties, their density and consequently, the weight of the components are high. Therefore, there is an urgent need to provide a new lightweight, thin, and flame-retardant component to replace the metal cover.

[0005] Existing technologies disclose injection-molded parts based on polypropylene or polyamide as battery pack covers. However, such injection molding solutions using polypropylene or polyamide materials are difficult to implement for very large parts; their injection molding requires high processing costs, high injection pressure, and high temperatures. To date, there are no publications or patents that disclose or suggest spray transfer molding (STM) products or long fiber injection (LFI) products, such as the resulting PU composites, as usable as battery pack covers.

[0006] For example, US2019 / 0153185A1 discloses a sandwich component comprising a polyurethane foam core and two building material panels, used as a non-load-bearing wall element, exterior wall cladding, and ceiling element. Specifically, it discloses that the building panels may also include fibers, textiles, or reinforcing materials, which improve the tensile strength of the building material panels. However, it does not disclose or imply that the polyurethane foam core can be modified and then specifically applied in the battery field, for example, as a cover for a battery pack. Furthermore, those skilled in the art will understand that polyurethane foam in the construction field is relatively thick, hindering its use as a thinner cover for battery packs.

[0007] Furthermore, existing technologies disclose a sheet molding compound (SMC) method for preparing polyurethane foam sheets, characterized by impregnating chopped glass fibers with resin. However, this SMC method typically suffers from drawbacks such as high density, thicker parts, uneven distribution of reinforcing glass fibers in the final part, and high cost of post-processing steps.

[0008] Therefore, there is a persistent need for a composite material that is lightweight, has reduced thickness, good mechanical properties and flame retardancy, and can be prepared in a cost-effective manner. Furthermore, the composite material should be easy to prepare from a wide range of raw materials and provide a covering article with good electromagnetic interface (EMI) shielding performance and the aforementioned advantages of the composite material. Summary of the Invention

[0009] One object of the present invention is to overcome the problems of the prior art and to provide a composite material that is lightweight, has reduced thickness, good mechanical strength and good flame retardancy, and can be prepared in a cost-effective manner.

[0010] Surprisingly, the inventors have discovered that the aforementioned objective can be achieved using a polyurethane (PU) composite material comprising 35 to 75% by weight reinforcing fibers and 25 to 65% by weight polyurethane foam, based on the total weight of the polyurethane composite material.

[0011] The polyurethane foam is obtained from a two-component reaction system containing the following substances:

[0012] Isocyanate components composed of the following substances:

[0013] (a) at least one isocyanate or isocyanate prepolymer, and

[0014] Polyol components composed of the following substances:

[0015] (b) at least one polyol that is reactive to isocyanates.

[0016] (c) Optionally, chain extenders and / or crosslinking agents,

[0017] (d) Flame retardants,

[0018] (e) Optional filler,

[0019] (f) Foaming agent,

[0020] (g) catalyst, and

[0021] (h) Optional additives and / or auxiliaries,

[0022] The reinforcing fibers are selected from glass fibers, basalt fibers, carbon fibers, and natural fibers; and

[0023] The reinforcing fiber comprises 75 to 100% by weight of a continuous phase reinforcing fiber and 0 to 25% by weight of a discontinuous phase reinforcing fiber, based on the total weight of the reinforcing fiber.

[0024] In another aspect, the present invention relates to a method for preparing the PU composite material as described above, wherein the method comprises the following steps:

[0025] 1) Provides reinforcing fibers in the form of a continuous phase;

[0026] 2) Polyol components are prepared by mixing the following materials in a container at a temperature of 20 to 80°C:

[0027] (b) at least one polyol that is reactive to isocyanates.

[0028] (c) Optionally, chain extenders and / or crosslinking agents,

[0029] (d) Flame retardants,

[0030] (e) Optional filler,

[0031] (f) Foaming agent,

[0032] (g) catalyst, and

[0033] (h) Optional additives and / or auxiliaries,

[0034] 3) The polyol component obtained in step 2) is mixed with the isocyanate component and optionally the reinforcing fiber in the form of a discontinuous phase at a temperature of 20 to 80°C to obtain a mixture;

[0035] 4) Spray or inject the mixture obtained in step 3) onto the reinforcing fibers in the form of the continuous phase provided in step 1) through a first nozzle or injection head, and optionally spray the reinforcing fibers in the form of the discontinuous phase onto the reinforcing fibers in the form of the continuous phase provided in step 1) through a second nozzle to obtain a sprayed or injected product.

[0036] 5) Hot-pressing the sprayed or injection-molded product obtained in step 4) in a mold at a temperature of 40 to 180°C under a hot-pressing clamping force of 100 to 2000 tons; and

[0037] 6) Demolding and optional trimming;

[0038] The polyurethane composite obtained in step 6) comprises 35 to 75% by weight of reinforcing fibers and 25 to 65% by weight of polyurethane foam, based on the total weight of the polyurethane composite; and

[0039] The reinforcing fiber comprises 75 to 100% by weight of the reinforcing fiber in the form of a continuous phase and 0 to 25% by weight of the reinforcing fiber in the form of a discontinuous phase, based on the total weight of the reinforcing fiber;

[0040] The reinforcing fiber is selected from glass fiber, basalt fiber, carbon fiber and natural fiber, with glass fiber and basalt fiber being preferred, and glass fiber being more preferred.

[0041] Surprisingly, the PU composite material described above, or the PU composite material prepared by the method described above, exhibits reduced weight, reduced thickness, good mechanical strength, and flame retardancy in this application. Furthermore, the method is carried out in a robust and easy manner. Consequently, the PU composite material is obtained cost-effectively.

[0042] In another aspect, the present invention relates to a covering article comprising a PU composite material as described above or a PU composite material prepared by the method described above. Attached Figure Description

[0043] Figure 1 The STM method for preparing PU composites is shown.

[0044] Figure 2 The LFI method for preparing PU composites is shown.

[0045] Figure 3 The image shows a cover containing PU composite material and metal sheets. Detailed Implementation

[0046] Unless otherwise defined, all technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains. As used herein, unless otherwise stated, the following terms have the meanings assigned to them hereinafter.

[0047] As used in this article, the articles “a” and “an” refer to one or more (i.e., at least one) grammatical objects of an article. For example, “an element” refers to one or more elements.

[0048] As used in this article, the expression "contains" also includes the expression "composes of".

[0049] Unless otherwise stated, all percentages (%) refer to "weight percentage".

[0050] Unless otherwise stated, temperature refers to room temperature and pressure refers to ambient pressure.

[0051] As used herein, the term "reinforcing fiber in continuous phase form" refers to a fiber layer in which fibers contained within the layer are combined or connected to each other to form an integral layer.

[0052] As used in this article, the term "reinforcing fiber in discontinuous phase form" refers to fibers that are not connected to each other or are not in a monolithic form.

[0053] PU composite materials

[0054] In one aspect, the present invention relates to polyurethane (PU) composites, wherein the polyurethane composite comprises 35 to 75% by weight reinforcing fibers and 25 to 65% by weight polyurethane foam, based on the total weight of the polyurethane composite.

[0055] Polyurethane foam is obtained from a two-component reaction system containing the following substances:

[0056] Isocyanate components composed of the following substances:

[0057] (a) at least one isocyanate or isocyanate prepolymer, and

[0058] Polyol components composed of the following substances:

[0059] (b) at least one polyol that is reactive to isocyanates.

[0060] (c) Optionally, chain extenders and / or crosslinking agents,

[0061] (d) Flame retardants,

[0062] (e) Optional filler,

[0063] (f) Foaming agent,

[0064] (g) catalyst, and

[0065] (h) Optional additives and / or auxiliaries,

[0066] The reinforcing fibers are selected from glass fibers, basalt fibers, carbon fibers, and natural fibers, preferably glass fibers and basalt fibers, and more preferably glass fibers; and

[0067] The reinforcing fiber comprises 75 to 100% by weight of a continuous phase reinforcing fiber and 0 to 25% by weight of a discontinuous phase reinforcing fiber, based on the total weight of the reinforcing fiber.

[0068] In one embodiment, the reinforcing fibers are impregnated with polyurethane foam.

[0069] In one embodiment, the continuous phase reinforcing fiber is in the form of a mat, a woven fabric, or a combination thereof. In one specific embodiment, the continuous phase reinforcing fiber is an assembled roving E512 commercially available from China Jushi Co., Ltd. In this application, the term "mat" means a material in the form of felt, cloth, a relatively thin sheet, knitted fabric, etc. In one embodiment, the mat is formed by methods known in the art, such as conventional methods using warp and weft yarns or electrospinning methods. Based on these, it should be understood that the continuous phase reinforcing fiber can be in the form of a mesh, chopped strand mat, woven fabric, nonwoven fabric, fiber cloth, stitch-woven felt, etc.

[0070] In one embodiment, the reinforcing fibers in the form of a continuous phase have a density of 200 to 1600 g / m², preferably 400 to 900 g / m².

[0071] In one embodiment, the PU composite material comprises one to four layers of pad, woven fabric, or a combination thereof, preferably one to four layers of reinforcing fiber pad in the form of a continuous phase, such as one, two, three, or four layers.

[0072] In one embodiment, the PU composite material comprises reinforcing fibers in a discontinuous phase. In one embodiment, the discontinuous phase reinforcing fibers have a length of 6 to 100 mm, preferably 8 to 80 mm, more preferably 10 to 50 mm, and even more preferably 12 to 25 mm. In a specific embodiment, the discontinuous phase reinforcing fibers are assembled roving E440, commercially available from China Jushi Co., Ltd.

[0073] In one embodiment, the density of the PU composite material is less than 2.2 g / cm³. 3 Preferably less than 1.8 g / cm³ 3 Preferably less than 1.6 g / cm³ 3 More preferably less than 1.5 g / cm³ 3 Even more preferred is less than 1.3 g / cm³ 3 The optimal value is less than 1.2 g / cm³. 3 .

[0074] In one embodiment, the PU composite material is made in the form of a sheet with a thickness of 0.5 to 10 mm, preferably 1 to 5 mm, more preferably 1 to 3 mm, and even more preferably 1 to 2 mm.

[0075] In one embodiment, the polyurethane composite material comprises a flame retardant selected from the following (d): expandable graphite, red phosphorus, ammonium polyphosphate, triethyl phosphate, tris(2-chloroisopropyl) phosphate, melamine, tris(1-chloro-2-propyl) phosphate (TCPP), chlorinated and bromine-containing polyols, such as epichlorohydrin, chlorobacterial anhydride and trichlorobutane (TCBO), and phosphorus-containing polyols, such as orthophosphate, phosphite, phosphonate polyol, phosphine oxide polyol and phosphoramide polyol.

[0076] In one embodiment, the PU composite material has a tensile strength of at least 90 MPa, preferably at least 95 MPa, more preferably at least 100 MPa, even more preferably at least 120 MPa, and most preferably at least 130 MPa, as determined according to GB / T1447-2005.

[0077] In one embodiment, the PU composite material has a flexural strength of at least 180 MPa, preferably at least 185 MPa, more preferably at least 190 MPa, even more preferably at least 200 MPa, and most preferably at least 230 MPa, as determined according to GB / T1449-2005.

[0078] In one embodiment, the PU composite material passes the UL94 V0 fire resistance test. In another embodiment, the PU composite material passes the UL 94 5VA fire resistance test.

[0079] polyurethane

[0080] In the preparation of PU composites, an "isocyanate component" and a "polyol component" (hereinafter also referred to as a "resin component" or "resin") are used, wherein the "polyol component" is a mixture of a polyol (b) reactive to isocyanate, optionally a chain extender and / or a crosslinking agent (c), a flame retardant (d), optionally a filler (e), a foaming agent (f), a catalyst (g), and optionally auxiliaries and additives (h), and the "isocyanate component" is at least one isocyanate or isocyanate prepolymer (a). The polyol component reacts with the isocyanate to form urethane bonds. Such systems are disclosed, for example, in U.S. Patent No. 4,218,543.

[0081] It is worth noting that in this application, the polyol component does not include reinforcing fibers, i.e., reinforcing fibers in both continuous and discontinuous forms.

[0082] In a preferred embodiment, the isocyanate component and the polyol component are mixed by impact and sprayed or injected into a mold at approximately atmospheric pressure, after which the mold is closed. The mold is preheated at 40 to 180°C, preferably 70 to 150°C, more preferably 90 to 130°C, and optionally inserts (such as metal sheets, metal foils, or solid flame-retardant layers) are provided on the mold surface. The raw materials are uniformly sprayed or injected onto the fibrous fabric in the mold, and then the molded part is demolded after a period of time typically 1 to 15 minutes, preferably 90 seconds to 10 minutes, more preferably 2 to 8 minutes.

[0083] Isocyanates or isocyanate prepolymers (a)

[0084] The isocyanate component used to prepare the polyurethane of the present invention includes any isocyanate known for preparing polyurethanes. These include aliphatic, alicyclic, aryliphatic, and / or aromatic isocyanates, such as tri-, tetra-, penta-, hexa-, hepta-, and / or octamethylene diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, 2-ethylbutylene 1,4-diisocyanate, pentamethylene 1,5-diisocyanate, butylene 1,4-diisocyanate, 1-isocyano-3,3,5-trimethyl-5-isocyano-methylcyclohexane (isophorone diisocyanate, IPDI), 1,4- and / or 1,3-bis(isocyano-methyl)cyclohexane (HXDI), cyclohexane, etc. Hexane 1,4-diisocyanate, 1-methylcyclohexane 2,4- and / or 2,6-diisocyanate and / or dicyclohexylmethane 4,4'- / 2,4'- and 2,2'-diisocyanate, diphenylmethane 2,2'-, 2,4'- and / or 4,4'-diisocyanate (MDI), polymeric MDI, naphthyl 1,5-diisocyanate (NDI), toluene 2,4- and / or 2,6-diisocyanate (TDI), 3,3'-dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate and / or phenylene diisocyanate. 2,2'-, 2,4'- and / or 4,4'-diisocyanates and polymeric MDI are particularly preferred.

[0085] Other possible isocyanates are given, for example, in "Kunststoffhandbuch, Band 7, Polyurethane" [Plastics handbook, Volume 7, Polyurethanes], Carl Hanser Verlag, 3rd edition, 1993, Chapters 3.2 and 3.3.2.

[0086] Furthermore, the isocyanate component can also be used in the form of an isocyanate prepolymer. The isocyanate prepolymer can be obtained by reacting the aforementioned isocyanate with another polyol (a'), for example, at a temperature of 30-100°C, preferably about 80°C. Preferably, 4,4'-MDI, together with urea-ketimide-modified MDI and commercially available polyols based on polyesters (e.g., polyesters derived from their own diacids) or polyethers (e.g., polyethers derived from ethylene oxide and / or propylene oxide), are used to prepare the prepolymer used according to the invention. Preferably, 4,4'-MDI and polyols derived from ethylene oxide and / or propylene oxide are used to prepare the prepolymer used according to the invention.

[0087] Other polyols (a') are known to those skilled in the art and are described, for example, in "Kunststoffhandbuch [Plastics handbook], Volume 7, Polyurethane [Polyurethanes]", Carl Hanser Verlag, 3rd edition, 1993, Chapter 3.1.

[0088] Ether-based prepolymers are preferably obtained by reacting isocyanates, particularly 4,4'-MDI, with 2- to 3-functional polyoxypropylene polyols and / or polyoxypropylene-polyoxyethylene polyols. They are typically prepared by the base-catalyzed addition of propylene oxide alone or in mixtures with ethylene oxide to an H-functional, particularly OH-functional, initiating material. The starting materials used are, for example, water, ethylene glycol, or propylene glycol, and glycerol or trimethylolpropane. Furthermore, polymetallic cyanide compounds known as DMC catalysts can also be used as catalysts. For example, polyethers described below under component (b) can be used as additional polyols (a').

[0089] When using an ethylene oxide / propylene oxide mixture, ethylene oxide is preferably used in an amount of 10-50% by weight, based on the total amount of alkyl epoxides. Alkoxides can be incorporated in a block form or as a random mixture. It is particularly preferred to introduce ethylene oxide terminal blocks (“EO-terminated”) to increase the content of more reactive primary OH terminal groups. The number average molecular weight of the polyol (a') is preferably in the range of 1750 to 5500 g / mol.

[0090] If appropriate, conventional chain extenders or crosslinkers may be added to the additional polyols mentioned in the preparation of the isocyanate prepolymer. Conventional chain extenders or crosslinkers may be the same as those described in c) below. Dipropylene glycol, tripropylene glycol, or monoethylene glycol (MEG) is particularly preferred as the chain extender or crosslinker.

[0091] Polyols reactive to isocyanates (b)

[0092] The polyol (b) that is reactive to isocyanates can be any polyol in the art that can be used in the preparation of polyurethanes and has at least two reactive hydrogen atoms. For example, polyether polyamines and / or polyols selected from polyether polyols and polyester polyols, or mixtures thereof, can be used.

[0093] The preferred polyols used are polyether polyols with a weight-average molecular weight of 200 to 10,000, preferably 300 to 8,000, more preferably 500 to 6,000, and most preferably 2,500 to 3,500, and an OH value of 20 to 1,200 mg KOH / g, preferably 30 to 1,000 mg KOH / g, and more preferably 40 to 500 mg KOH / g; and / or polyester polyols with a molecular weight of 350 to 2,000, preferably 350 to 650, and an OH value of 60 to 650 mg KOH / g, preferably 120 to 310 mg KOH / g. In this invention, the following polyols are preferred: 2095 (BASF) 2090(BASF)、LUPRANOL 3505 / 1(BASF)、 3905 (BASF) 3907 (BASF) 3909 (BASF) PS 3152, PS2412, PS 1752, CF 6925 (Stepan Company).

[0094] The polyether polyols used in this invention can be prepared by known methods. For example, they can be prepared by anionic polymerization of one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene group, using an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, or an alkali metal alkoxide such as sodium methoxide, sodium ethoxide, potassium ethoxide, or potassium propoxide as a catalyst, with the addition of at least one initiator molecule containing 2 to 8 reactive hydrogen atoms; or by cationic polymerization, using Lewis acids such as antimony pentachloride, boron fluoride ethers, or bleaching earth as a catalyst.

[0095] Suitable examples of epoxides are tetrahydrofuran, 1,2-epoxidepropane, 1,2-epoxidebutane or 2,3-epoxidebutane, styrene oxide, and preferably ethylene oxide and 1,2-epoxidepropane. Epoxides can be used alone, alternately or continuously, or as a mixture.

[0096] Examples of initiator molecules that may be used are: water, organic dicarboxylic acids such as succinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic diamines optionally N-mono-, N,N- and N,N'-dialkyl-substituted in the alkyl group, such as optionally mono- and dialkyl-substituted ethylenediamine, diethylenetriamine, triethylenetetramine, 1,3-propanediamine, 1,3- or 1,4-butanediamine, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamine, 2,3-, 2,4- and 2,6-methylenediamine and 4,4'-, 2,4'- and 2,2'-diaminodiphenylmethane.

[0097] Polyester polyols can be prepared, for example, from dicarboxylic acids having 2 to 12 carbon atoms, preferably 4 to 6 carbon atoms, and polyols. Examples of dicarboxylic acids that can be used are aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, octanoic acid, azelaic acid, and sebacic acid, and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid. Dicarboxylic acids can be used alone or in mixtures, for example, in the form of a mixture of succinic acid, glutaric acid, and adipic acid. Examples of polyols are diols having 2 to 10, preferably 2 to 6, carbon atoms, such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 2,2-dimethyl-1,3-propanediol, 1,3-propanediol, and dipropylene glycol; triols having 3 to 6 carbon atoms, such as glycerol and trimethylolpropane; and pentaerythritol as a higher functional alcohol. Depending on the desired properties, polyols can be used alone or optionally mixed with each other.

[0098] The amount of polyether polyol and / or polyester polyol is preferably 0 to 40% by weight, particularly preferably 15 to 35% by weight, based on the total weight of the resin.

[0099] Chain extenders and / or crosslinking agents (c)

[0100] The chain extenders and / or crosslinking agents (c) that can be used are substances with a molar mass preferably less than 500 g / mol, particularly preferably 60 to 400 g / mol, wherein the chain extender has two hydrogen atoms reactive to isocyanates and the crosslinking agent has three hydrogen atoms reactive to isocyanates. These substances can be used alone or preferably in mixtures. Diols and / or triols with a molecular weight less than 500, particularly 60 to 400, particularly 60 to 350, are preferred. Examples of substances that may be used are aliphatic, alicyclic, and / or aryliphatic diols having 2 to 14, preferably 2 to 10, carbon atoms, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 1,2-, 1,3-, and 1,4-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, tripropylene glycol, diethanolamine, or triols, such as 1,2,4- or 1,3,5-trihydroxycyclohexane, glycerol, and trimethylolpropane. The chain extender and / or crosslinking agent (c) is preferably selected from ethylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol, and glycerol.

[0101] The amount of chain extender and / or crosslinker c (if present) is preferably 0 to 50% by weight, particularly preferably 10 to 40% by weight, based on the total weight of the resin.

[0102] Flame retardant (d)

[0103] The flame retardants that can be used (d) are additive flame retardants and reactive flame retardants, or combinations thereof. Additive flame retardants are monomer molecules that are not chemically bonded to the polymer. Additive flame retardants can be in the form of solid flame retardants, liquid flame retardants, or combinations thereof. Commercially available additive flame retardants include tris(2-chloroisopropyl) phosphate, melamine, expandable graphite (EG), red phosphorus, ammonium polyphosphate, tris(1-chloro-2-propyl) phosphate (TCPP), and triethyl phosphate (TEP). Reactive flame retardants are typically polyols containing halogens and / or phosphorus. Flame retardant polyols have terminal hydroxyl groups that can react with polyisocyanates in PU synthesis. Halogenated FR polyols can be chlorinated and bromine-containing polyols, such as epichlorohydrin, chlorobenzyl anhydride, and trichlorobutyronitrile (TCBO); phosphorus-containing polyols, such as orthophosphates, phosphites, phosphonates, phosphonium oxides, and phosphorusamides.

[0104] For flame retardant purposes, the total amount of flame retardant is preferably 5 to 30% by weight, more preferably 10 to 25% by weight, based on the total weight of the resin.

[0105] Packing material (e)

[0106] The fillers that can be used are commonly known organic or inorganic fillers. Individual examples that may be mentioned include: inorganic fillers such as silicate minerals, and metal oxides such as alumina, titanium dioxide, and iron oxide. In this application, the average particle size of the filler is less than 600 μm, preferably less than 500 μm, and more preferably less than 400 μm. The filler (e) is preferably selected from titanium dioxide and iron oxide.

[0107] The amount of filler is 0 to 30% by weight, preferably 0 to 15% by weight, based on the total weight of the resin. The weight ratio of flame retardant (d) to filler (e) is 0.1 to 10, preferably 0.5 to 2.

[0108] Fillers can be used to reduce the coefficient of thermal expansion of polyurethane foam (which is greater than, for example, the coefficient of thermal expansion of metals), and thus match the coefficient of thermal expansion with that of metals. This is particularly advantageous for a durable and strong bond between the metal sheet and the polyurethane core layer, as it results in lower stress between the layers when they are subjected to thermal loads.

[0109] In this application, the filler (e) does not include reinforcing fibers, i.e., continuous and discontinuous reinforcing fibers. In other words, the polyol component does not include reinforcing fibers, i.e., continuous and discontinuous reinforcing fibers.

[0110] Foaming agent (f)

[0111] The foaming agent (f) used according to the invention preferably comprises water. The foaming agent (f) may also comprise other chemical and / or physical foaming agents in the art, as well as water. Chemical foaming agents are compounds that react with isocyanates to form gaseous products; examples are water or formic acid. Physical foaming agents are compounds that have been dissolved or emulsified in the starting materials used for polyurethane preparation and evaporated under the conditions for polyurethane formation. Examples of these substances are hydrocarbons, halogenated hydrocarbons, and other compounds such as perfluoroalkanes, e.g., perfluorohexane, chlorofluorocarbons, and ethers, esters, ketones, and / or acetals. In a preferred embodiment, water is used as the sole foaming agent (f). In this case, the polyurethane foam according to the invention is a water-blown polyurethane spray foam. There are no particular limitations regarding the water. Mineral water, deionized water, or tap water can be used.

[0112] The amount of foaming agent is 0 to 5% by weight, preferably 0.1 to 3% by weight, based on the total weight of the resin.

[0113] Catalyst (g)

[0114] As a catalyst (g), any compound that accelerates the isocyanate-polyol reaction can be used. Such compounds are known and described, for example, in "Kunststoffhandbuch, Vol. 7, Polyurethane", Carl Hanser Verlag, 3rd ed., 1993, Chapter 3.4.1. These substances include amine catalysts and organometallic compound-based catalysts.

[0115] As catalysts based on organometallic compounds, such as organotin compounds, tin(II) salts of organic carboxylic acids, such as tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate, and tin(II) laurate, and dialkyltin(IV) salts of organic carboxylic acids, such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, and dioctyltin diacetate, and bismuth carboxylic acids, such as bismuth(III) neodecanoate, bismuth 2-ethylhexanoate, and bismuth octoate, or alkali metal salts of carboxylic acids, such as potassium acetate or potassium formate.

[0116] Preferably, amine-based catalysts are used as catalysts (g), such as N,N,N',N'-tetramethyldipropylenetriamine, 2-[2-(dimethylamino)ethyl-methylamino]ethanol, N,N,N'-trimethyl-N'-2-hydroxyethyl-bis-(aminoethyl)ether, bis(2-dimethylaminoethyl)ether, N,N,N,N,N-pentamethyldiethylenetriamine, N,N,N-triethylaminoethoxyethanol, dimethylcyclohexylamine, trimethylhydroxyethylethylenediamine, dimethylbenzylamine, triethylamine, triethylenediamine, pentamethyldipropylenetriamine, dimethylethanolamine, N-methylimidazole, N-ethylimidazole, tetramethylhexamethylenediamine, tri(dimethylaminopropyl)hexahydrotriazine, dimethylaminopropylamine, N-ethylmorpholine, diazabicycloundecene, and diazabicyclononene. Examples that may be mentioned here are Jeffcat ZF10 (CAS No. 83016-70-0), Jeffcat DMEA (CAS No. 108-01-0), and Dabco T (CAS No. 2212-32-0). This reactive catalyst has the effect of reducing VOC values.

[0117] The amount of catalyst (g) is preferably 0.1 to 5% by weight, particularly preferably 0.1 to 3.5% by weight, based on the total weight of the resin.

[0118] Additives and / or auxiliaries (h)

[0119] The additives and / or auxiliaries that may be used include, but are not limited to, surfactants, preservatives, colorants, antioxidants, reinforcing agents, stabilizers, and water-absorbing agents. In the preparation of polyurethane foam, it is generally highly preferred to use a small amount of surfactant to stabilize the foaming reaction mixture until it cures. Such surfactants advantageously include liquid or solid organosiloxane surfactants, used in an amount sufficient to stabilize the foaming reaction mixture. Typically, the amount of auxiliaries, especially surfactants, is preferably 0 to 15% by weight, more preferably 0.5 to 6% by weight, based on the total weight of the resin.

[0120] Further information on the use and mode of action of the aforementioned adjuvants and additives, as well as other examples, are given, for instance, in "Kunststoffhandbuch, Band 7, Polyurethane" ["Plastics handbook, Volume 7, Polyurethanes"], Carl Hanser Verlag, 3rd edition, 1993, Chapter 3.4.

[0121] The weight ratio of the polyol component to the isocyanate component is 1:0.6 to 1:2, preferably 1:0.7 to 1:1.

[0122] Methods for preparing PU composite materials

[0123] In another aspect, the present invention relates to a method for preparing the PU composite material as described above, wherein the method comprises the following steps:

[0124] 1) Provides reinforcing fibers in the form of a continuous phase;

[0125] 2) Polyol components are prepared by mixing the following materials in a container at a temperature of 20 to 80°C:

[0126] (b) at least one polyol that is reactive to isocyanates.

[0127] (c) Optionally, chain extenders and / or crosslinking agents,

[0128] (d) Flame retardants,

[0129] (e) Optional filler,

[0130] (f) Foaming agent,

[0131] (g) catalyst, and

[0132] (h) Optional additives and / or auxiliaries,

[0133] 3) The polyol component obtained in step 2) is mixed with the isocyanate component and optionally the reinforcing fiber in the form of a discontinuous phase at a temperature of 20 to 80°C to obtain a mixture;

[0134] 4) Spray or inject the mixture obtained in step 3) onto the reinforcing fibers in the form of the continuous phase provided in step 1) through a first nozzle or injection head, and optionally spray the reinforcing fibers in the form of the discontinuous phase onto the reinforcing fibers in the form of the continuous phase provided in step 1) through a second nozzle to obtain a sprayed or injected product.

[0135] 5) Hot-pressing the sprayed or injection-molded product obtained in step 4) in a mold at a temperature of 40 to 180°C under a hot-pressing clamping force of 100 to 2000 tons; and

[0136] 6) Demolding and optional trimming;

[0137] The polyurethane composite material obtained in step 6) comprises 35 to 75% by weight of reinforcing fibers and 25 to 65% by weight of polyurethane foam based on the total weight of the polyurethane composite material; and

[0138] The reinforcing fiber comprises 75 to 100% by weight of the reinforcing fiber in the form of a continuous phase and 0 to 25% by weight of the reinforcing fiber in the form of a discontinuous phase, based on the total weight of the reinforcing fiber;

[0139] The reinforcing fiber is selected from glass fiber, basalt fiber, carbon fiber and natural fiber, with glass fiber and basalt fiber being preferred, and glass fiber being more preferred.

[0140] In one embodiment, the total amount of the continuous phase reinforcing fibers and optionally the discontinuous phase reinforcing fibers used in steps 1), 3), and 4) is in a weight ratio of about (35-75):(25-65) to the total amount of the polyol component and isocyanate component used in step 3).

[0141] In one embodiment, the discontinuous phase reinforcing fiber in step 3) is obtained by in-situ stubbed long fiber and added at a constant rate to a mixture of the isocyanate component and the polyol component of the polyurethane, and the length of the stubbed reinforcing fiber is 6 to 100 mm, preferably 8 to 80 mm, more preferably 10 to 50 mm, and even more preferably 12 to 25 mm.

[0142] In one implementation, the reinforcing fiber in the form of a continuous phase in step 1) is in the form of a pad, a woven fabric, or a combination thereof.

[0143] Spray Transfer Molding (STM) Method

[0144] In one aspect, the present invention provides a spray transfer molding (STM) method for preparing the PU composite material as described above, comprising the following steps:

[0145] 1) Provides reinforcing fibers in the form of a continuous phase;

[0146] 2) Polyol components are prepared by mixing the following materials in a container at a temperature of 20 to 80°C:

[0147] (b) at least one polyol that is reactive to isocyanates.

[0148] (c) Optionally, chain extenders and / or crosslinking agents,

[0149] (d) Flame retardants,

[0150] (e) Optional filler,

[0151] (f) Foaming agent,

[0152] (g) catalyst, and

[0153] (h) Optional additives and / or auxiliaries,

[0154] 3) The polyol component obtained in step 2) and the isocyanate component are mixed at a temperature of 20 to 80°C to obtain a mixture;

[0155] 4) The mixture obtained in step 3) is sprayed or injected through a first nozzle onto the reinforcing fibers in the form of the continuous phase provided in step 1), and optionally, the reinforcing fibers in the form of the discontinuous phase are sprayed through a second nozzle onto the reinforcing fibers in the form of the continuous phase provided in step 1) to obtain a sprayed product.

[0156] 5) The coated product obtained in step 4) is hot-pressed in a mold at a temperature of 40 to 180°C under a hot-pressing clamping force of 100 to 2000 tons; and

[0157] 6) Demolding and optional trimming;

[0158] The polyurethane composite material obtained in step 6) comprises 35 to 75% by weight reinforcing fibers and 25 to 65% by weight polyurethane foam, based on the total weight of the polyurethane composite material.

[0159] The reinforcing fibers comprise 75 to 100% by weight of continuous phase reinforcing fibers and 0 to 25% by weight of discontinuous phase reinforcing fibers, based on the total weight of the reinforcing fibers; and

[0160] The reinforcing fiber is selected from glass fiber, basalt fiber, carbon fiber and natural fiber, with glass fiber and basalt fiber being preferred, and glass fiber being more preferred.

[0161] In one embodiment, the method includes, in step 1), providing reinforcing fibers in the form of a continuous phase of 1 to 4 layers, such as 1, 2, 3 or 4 layers.

[0162] In one embodiment, in step 1), the opening mold is preheated at a temperature of 40 to 180°C, preferably 70 to 150°C, more preferably 90 to 130°C.

[0163] In one embodiment, in step 4), the mixture obtained in step 3) is sprayed onto the reinforcing fiber layer using a first nozzle. In one embodiment, in step 4), the first nozzle moves at a speed that makes the resulting PU composite material relatively thin, for example, with a thickness of 0.5 to 10 mm, preferably 1 to 5 mm, more preferably 1 to 3 mm, or even more preferably 1 to 2 mm.

[0164] In one embodiment, in step 4), the mixture is sprayed onto both surfaces of the reinforcing fiber layer by continuously transferring the spray from one edge to the other using a first nozzle. In this embodiment, spraying can be performed on the first surface of the reinforcing fiber layer, followed by continuous picking, flipping, and laying of the PU with the reinforcing fiber layer, and then spraying on the second surface of the reinforcing fiber layer.

[0165] In another embodiment, in step 4), the mixture is sprayed onto one surface of the reinforcing fiber layer.

[0166] In a preferred embodiment, the method includes spraying reinforcing fibers in the form of a discontinuous phase onto the reinforcing fiber layer using a second nozzle in step 4). In this embodiment, the reinforcing fibers in the form of a discontinuous phase can be sprayed over the entire area or a portion of the target composite material as needed. In this embodiment, the discontinuous reinforcing fibers are sprayed simultaneously with the mixture obtained in step 3). Thus, the discontinuous reinforcing fibers can be arranged and distributed into the mixture obtained in step 3).

[0167] In one embodiment, the total amount of the continuous phase reinforcing fibers and optionally the discontinuous phase reinforcing fibers used in steps 1) and 4) is in a weight ratio of about (35-75):(25-65) to the total amount of the polyol component and isocyanate component used in step 3).

[0168] In one specific embodiment, the reinforcing fiber comprises 100% by weight of the reinforcing fiber in the form of a continuous phase, based on the total weight of the reinforcing fiber.

[0169] In one embodiment, in step 5), the mold is closed and held for 1 to 15 minutes, preferably 90 seconds to 10 minutes, more preferably 2 to 8 minutes.

[0170] In one embodiment, in step 5), the mold is closed and maintained at a temperature of 40 to 180°C, preferably 70 to 150°C, more preferably 90 to 130°C. In another embodiment, in step 5), the mold is closed and maintained under a hot-pressing clamping force of 100 to 2000 tons, preferably 200 to 1500 tons, more preferably 300 to 1000 tons.

[0171] In one embodiment, the PU composite material may optionally be prepared to contain at least one insert such as a metal sheet, metal foil, or solid flame-retardant layer. In one embodiment, a cover article comprising a PU composite material and at least one metal sheet is obtained. In another embodiment, a cover article comprising a PU composite material and a solid flame-retardant layer is obtained.

[0172] In one embodiment, in step 6), a trimming step is performed simultaneously with demolding, and the mold is designed with a tool for cutting the trimming edge in the STM method. In this embodiment, the apparatus used in the STM method is designed with a tool on the mold for cutting the trimming edge.

[0173] Long fiber injection molding (LFI) method

[0174] In one aspect, the present invention also provides a long fiber injection molding (LFI) method for preparing the PU composite material as described above, comprising the following steps:

[0175] 1) Provides reinforcing fibers in the form of a continuous phase;

[0176] 2) Polyol components are prepared by mixing the following materials in a container at a temperature of 20 to 80°C:

[0177] (b) at least one polyol that is reactive to isocyanates.

[0178] (c) Optionally, chain extenders and / or crosslinking agents,

[0179] (d) Flame retardants,

[0180] (e) Optional filler,

[0181] (f) Foaming agent,

[0182] (g) catalyst, and

[0183] (h) Optional additives and / or auxiliaries;

[0184] 3) The polyol component obtained in step 2) is mixed with the isocyanate component and the reinforcing fiber in the form of a discontinuous phase at a temperature of 20 to 80°C to obtain a mixture;

[0185] 4) Inject the mixture obtained in step 3) into the reinforcing fibers in the form of the continuous phase provided in step 1) through the injection head to obtain the injected product;

[0186] 5) The injection-molded product obtained in step 4) is hot-pressed in a mold at a temperature of 40 to 180°C under a hot-pressing clamping force of 100 to 2000 tons; and

[0187] 6) Demolding and optional trimming;

[0188] The polyurethane composite material obtained in step 6) comprises 35 to 75% by weight reinforcing fibers and 25 to 65% by weight polyurethane foam, based on the total weight of the polyurethane composite material.

[0189] The reinforcing fiber comprises 75 to <100% by weight of the reinforcing fiber in the form of a continuous phase and >0 to 25% by weight of the reinforcing fiber in the form of a discontinuous phase, based on the total weight of the reinforcing fiber;

[0190] The reinforcing fiber is selected from glass fiber, basalt fiber, carbon fiber and natural fiber, with glass fiber and basalt fiber being preferred, and glass fiber being more preferred.

[0191] In one embodiment, the method includes, in step 1), providing reinforcing fibers in the form of a continuous phase of 1 to 4 layers, such as 1, 2, 3 or 4 layers.

[0192] In one embodiment, in step 1), the opening mold is preheated at a temperature of 40 to 180°C, preferably 70 to 150°C, more preferably 90 to 130°C.

[0193] In one embodiment, in step 3), the mixture is immediately mixed in the mixing chamber before injection.

[0194] In one embodiment, in step 3), the discontinuous phase reinforcing fibers are obtained by in-situ stubbed-out of long fibers, which are then fed into a mixing chamber and added at a constant rate to the mixture of the isocyanate component and the polyol component (i.e., added to the mixing chamber). In this embodiment, the reinforcing fibers prior to stubbed-out are in the form of fiber coils wound on a spool.

[0195] In one embodiment, reinforcing fibers are added at a rate that gives the resulting PU composition a fiber content of 35 to 75% by weight of reinforcing fibers, based on the total weight of the PU composite.

[0196] In one embodiment, the total amount of continuous phase reinforcing fibers and discontinuous phase reinforcing fibers used in steps 1) and 3) is approximately (35-75):(25-65) by weight to the total amount of polyol components and isocyanate components used in step 3).

[0197] In one embodiment, in step 3), the length of the reinforcing fiber in the form of a discontinuous phase is 6 to 100 mm, preferably 8 to 80 mm, more preferably 10 to 50 mm, and even more preferably 12 to 25 mm.

[0198] In one embodiment, in step 4), the mixture obtained in step 3) is injected onto the surface of the reinforcing fiber layer in the open mold using an injection head.

[0199] In one embodiment, in step 5), the mold is closed and maintained at a temperature of 40 to 180°C, preferably 70 to 150°C, more preferably 90 to 130°C. In one embodiment, in step 5), the mold is closed and maintained under a hot-pressing clamping force of 100 to 2000 tons, preferably 200 to 1500 tons, more preferably 300 to 1000 tons. In one embodiment, in step 5), the mold is closed and maintained for 1 to 15 minutes, preferably 90 seconds to 10 minutes, more preferably 2 to 8 minutes.

[0200] In one embodiment, the PU composite material may optionally be prepared to contain at least one insert such as a metal sheet, metal foil, or solid flame-retardant layer. In one embodiment, a cover article comprising a PU composite material and at least one metal sheet is obtained. In another embodiment, a cover article comprising a PU composite material and at least one metal foil is obtained.

[0201] In one embodiment, in step 6), a trimming step is performed simultaneously with demolding, wherein the mold is designed with a tool for cutting and trimming in the LFI method. In this embodiment, the apparatus used in the LFI method is designed to have a tool on the mold for cutting and trimming.

[0202] Surprisingly, the inventors discovered that all of the above methods allow for the preparation of materials with a thickness of 0.5 to 10 mm, preferably 1 to 5 mm, more preferably 1 to 3 mm, and even more preferably 1 to 2 mm, and a reduced density, for example, less than 1.8 g / cm³. 3 Preferably less than 1.6 g / cm³ 3 More preferably less than 1.5 g / cm³ 3 Even more preferably, less than 1.3 g / cm³ 3 The optimal value is less than 1.2 g / cm³. 3 These are PU composite materials with low density. Furthermore, they offer advantages such as fewer requirements for raw materials, good impregnation between fibers and PU, low cost, and short production cycle.

[0203] Furthermore, the relatively low pressure and temperature requirements of the STM and LFI methods translate into lower tooling costs. Additionally, STM and LFI can successfully mold complex parts with high-resolution features, including both thick and thin walls.

[0204] Cover products

[0205] In one aspect, the present invention provides a covering article comprising a polyurethane composite material as described above or a polyurethane composite material obtained by the method described above.

[0206] In one embodiment, the thickness of the cover article is 1 to 5 mm, preferably 1.2 to 3 mm.

[0207] In one embodiment, the cover article further comprises at least one metal sheet located on the side of the PU composite sheet. In a preferred embodiment, the cover article comprises two metal sheets located on both sides of the PU composite sheet. In this embodiment, the cover article contains a PU composite sheet as a core layer and two metal sheets located on both sides of the core layer, forming a sandwich structure. In another preferred embodiment, the cover article comprises one metal sheet located on one side of the PU composite sheet. In one embodiment, the metal sheet is independently selected from aluminum alloy, iron, steel, and aluminum sheet.

[0208] The thickness of the metal sheet can be 0.08 to 1.2 mm, preferably 0.08 to 0.6 mm, more preferably 0.12 to 0.4 mm, and most preferably 0.2 to 0.3 mm.

[0209] In a preferred embodiment, the thickness of the metal sheet is 0.2 to 1.2 mm, preferably 0.5 to 1.0 mm. It has been found that a metal sheet of this thickness advantageously provides improved mechanical strength, enabling cover articles having such a metal sheet to further meet mechanical strength requirements.

[0210] The cover article according to the invention can be used as a top cover for a battery pack.

[0211] The cover article according to the present invention has good fire resistance and electromagnetic interface (EMI) shielding performance, making it suitable for use as a top cover for battery packs. Furthermore, the cover article according to the present invention passes the UL94 V0 fire resistance test at a thickness of 2 mm. Battery packs containing the cover article according to the present invention as a top cover have passed the external burning test according to GB 38031-2020.

[0212] The covering article according to the invention also has good shielding efficiency (SE). In one embodiment, the covering article exhibits a shielding ratio (dB) of at least 40, preferably at least 50, more preferably at least 60. The dB value is calculated using the formula [dB] = 20 × log(E0 / E1), where E0 represents the field strength without the covering article and E1 represents the field strength with the covering article. For example, a dB value of 60 indicates that the covering article reflects and / or absorbs 99.9% of electromagnetic energy.

[0213] It should be noted that throughout the application, the materials mentioned in the method embodiments have the same meaning as those in the product embodiments, and unless otherwise stated, each of the general, preferred, more preferred, and most preferred definitions and the amounts of materials described in the product section also applies to the method of preparing the product and the articles made from the product.

[0214] Example

[0215] The invention will now be described with reference to embodiments and comparative examples, which are not intended to limit the invention.

[0216] I. General Instructions

[0217] The following starting materials were used in the embodiments:

[0218]

[0219]

[0220] The following methods are used to determine properties:

[0221] In kg / m 3 Density measured in GB / T 6343-2008

[0222] Flammability UL94 V0

[0223] UL 94 5VA standard

[0224] Tensile strength / modulus GB / T1447-2005

[0225] Flexural strength / modulus GB / T1449-2005

[0226] II. Preparation Examples

[0227] The PU composites of Examples 1 to 5 and Comparative Example 1 were prepared using the amounts of polyol component, isocyanate component, and reinforcing fiber as defined in Table 1. The PU composite of Comparative Example 2 was purchased from HUAYUAN ADV. MATERIALS under the trade name HY3102SMC and was prepared using the conventional sheet molding compound (SMC) method.

[0228] Table 1

[0229]

[0230]

[0231] *As mentioned above, the fillers contained in the polyol component do not include reinforcing fibers.

[0232] Examples 1-3

[0233] The PU composite materials according to the present invention are each prepared by long fiber injection molding (LFI) method, including the following steps.

[0234] Materials as described in Table 1 under polyol component A are mixed to form polyol component A. Materials as described in Table 1 under isocyanate component B are mixed to form isocyanate component B. The resulting polyol component A and isocyanate component B are statically mixed at a pressure of 4 bar to obtain a mixture with a viscosity of approximately 200 mPa·s. Reinforcing fibers are chopped and added to the resulting mixture under stirring to obtain a final mixture, wherein the chopped reinforcing fibers have a length of 15 mm. The final mixture is then subjected to a reaction at approximately 650 g / m³. 2 The amount is injected into an open mold, which has been preheated at approximately 110°C and is designed with tools for cutting trimming and drilling screw holes, and allows for the fixing of inserts (e.g., fiberglass pads and / or metal sheets, metal foils, or solid flame-retardant layers), in which two layers of fiberglass pads are placed. The mold is then closed and clamped at approximately 800 tons.

[0235] The part is molded for 5 minutes, then demolded. A product with a thickness of approximately 1.8 mm is obtained.

[0236] As can be seen from Table 1, the ratio of the amount of continuous and discontinuous reinforcing fibers used to the amount of polyol component A and isocyanate component B used as starting materials is (35-55):(45-65).

[0237] Examples 4 and 5

[0238] The PU composite materials according to the present invention are each prepared by spray transfer molding (STM) method, including the following steps.

[0239] Materials under polyol component A as described in Table 1 were mixed and maintained at a tank temperature of 30°C to 40°C to prepare polyol component A with reduced viscosity. Materials under isocyanate component B as described in Table 1 were mixed to form isocyanate component B. Polyol component A and isocyanate component B were impact-mixed at a pressure of about 150 bar to obtain a mixture with a viscosity of about 500 mPa·s. The mixture was then subjected to a pressure of about 650 g / m³. 2 A certain amount is sprayed onto the surface of two layers of fiberglass mat, while a specified amount of discontinuous phase reinforcing fibers is sprayed onto the desired area of ​​the final product using another nozzle.

[0240] At approximately atmospheric pressure, the resulting PU with glass fiber is placed onto an open mold by a robot. The mold has been preheated at approximately 110°C and is designed with tools for cutting trimming and excavating screw holes, and allows for the fixing of inserts (e.g., glass fiber pads and / or metal sheets, metal foils, or solid flame-retardant layers). The mold is then closed and clamped at approximately 500 tons.

[0241] The part is molded for 5 minutes, then demolded. A product with a thickness of approximately 1.8mm to 2.4mm is obtained.

[0242] Comparative Example 1

[0243] PU composite materials were prepared using the same method as described in Examples 1-3. A product with a thickness of approximately 1.4 mm was obtained.

[0244] III. Effects of the Example

[0245] PU composite material product performance testing

[0246] The physical and chemical properties of the PU composite materials prepared in the examples are listed in Table 2.

[0247] Table 2

[0248]

[0249]

[0250] Examples 6-7 - Electromagnetic shielding performance testing of covering products

[0251] Cover articles of Examples 6 and 7 were prepared, respectively comprising the PU composite materials of Examples 2 and 4. The cover articles contained a PU composite sheet as a core layer and an aluminum alloy sheet with a thickness of 0.2 mm located on one side of the core layer.

[0252] The electromagnetic shielding performance of these covering products was tested. The results are listed in Table 3.

[0253] Table 3

[0254] sample Example 6 Example 7 E0 / E1 1000:1 10,000:1 SE[dB] 60 80

[0255] Examples 8-10 - Fire resistance performance test of battery packs

[0256] Battery packs of Examples 8 to 10 were prepared, each comprising a cover article of Examples 3 to 5. Each battery pack includes a cover article and a bottom tray. The bottom tray is made of stamped aluminum alloy sheet.

[0257] The fire resistance of these battery packs was tested. The results are listed in Table 4.

[0258] External flammability test: GB 38031-2020

[0259] ■Test Method: (8.2.7.1)

[0260] ■ Ignite the fuel disc from a distance of ≥3m from the target.

[0261] Preheat the fire for 60 seconds.

[0262] ■ Move the fuel pan below the battery pack

[0263] ■ Expose the battery pack directly to fire for 70 seconds

[0264] ■ Add a cap to the fuel plate and continue testing for 60 seconds.

[0265] ■Remove fuel pan

[0266] ■Observe the battery pack for 2 hours

[0267] ■Requirement: (5.2.7)

[0268] ■ The battery pack should not explode.

[0269] ■ Not using nickel-metal hydride batteries

[0270] Table 4

[0271] sample Example 8 Example 9 Example 10 Combustion test pass pass pass

[0272] As can be seen from Table 3, the covering articles containing the PU composite material according to the present invention have good EMI shielding performance.

[0273] As can be seen from Table 4, the battery pack containing the cover article according to the present invention as the top cover passed the external combustion test.

[0274] The structures, materials, components, compositions, and methods described herein are intended as representative examples of the invention, and it should be understood that the scope of the invention is not limited to the scope of these examples. Those skilled in the art will recognize that the invention can be practiced with variations of the disclosed structures, materials, compositions, and methods, and that such variations are considered to be within the scope of the invention. Therefore, the invention is intended to cover these modifications and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. A polyurethane composite material for battery pack covering articles, wherein the polyurethane composite material comprises 35 to 75% by weight reinforcing fibers and 25 to 65% by weight polyurethane foam, based on the total weight of the polyurethane composite material, Polyurethane foam is obtained from a two-component reaction system containing the following substances: Isocyanate components composed of the following substances: (a) at least one isocyanate or isocyanate prepolymer, and Polyol components composed of the following substances: (b) at least one polyol that is reactive to isocyanates. (c) Optionally, chain extenders and / or crosslinking agents, (d) Flame retardants, (e) Optionally, filler, (f) Foaming agent, (g) catalyst, and (h) Optionally, additives and / or auxiliaries, The reinforcing fibers are selected from glass fibers, basalt fibers, carbon fibers, and natural fibers; The reinforcing fibers comprise 75 to 100% by weight of continuous phase reinforcing fibers and 0 to 25% by weight of discontinuous phase reinforcing fibers, based on the total weight of the reinforcing fibers; and The total amount of flame retardant is 5 to 30% by weight, based on the total weight of the resin.

2. The polyurethane composite material according to claim 1, wherein the reinforcing fibers are impregnated with polyurethane foam.

3. The polyurethane composite material according to claim 1, wherein the reinforcing fiber is selected from glass fiber and basalt fiber.

4. The polyurethane composite material according to claim 3, wherein the reinforcing fiber is glass fiber.

5. The polyurethane composite material according to claim 1 or 2, wherein the reinforcing fibers in the form of a continuous phase are in the form of a pad.

6. The polyurethane composite material according to claim 1 or 2, wherein the reinforcing fibers in the form of a continuous phase are in the form of a woven fabric.

7. The polyurethane composite material according to claim 5, wherein the polyurethane composite material comprises one to four layers of pad.

8. The polyurethane composite material according to claim 6, wherein the polyurethane composite material comprises one to four layers of woven fabric.

9. The polyurethane composite material according to claim 1 or 2, wherein the reinforcing fibers in the form of discontinuous phases have a length of 6 to 100 mm.

10. The polyurethane composite material according to claim 1 or 2, wherein the density of the polyurethane composite material is less than 2.2 g / cm³. 3 .

11. The polyurethane composite material according to claim 1 or 2, wherein the polyurethane composite material is made in the form of a sheet with a thickness of 0.5 to 10 mm.

12. The polyurethane composite material according to claim 1 or 2, wherein the polyurethane composite material comprises a flame retardant (d) selected from the following: expandable graphite, red phosphorus, ammonium polyphosphate, triethyl phosphate, tri(2-chloroisopropyl) phosphate, melamine, tri(1-chloro-2-propyl) phosphate, chlorine- or bromine-containing polyols, and phosphorus-containing polyols.

13. The polyurethane composite material according to claim 1 or 2, wherein the polyurethane composite material comprises a flame retardant selected from the group consisting of epichlorohydrin and chlorobenzyl anhydride.

14. The polyurethane composite material according to claim 12, wherein the phosphorus-containing polyol is a phosphonate polyol, a phosphonium oxide polyol, or a phosphorus amide polyol.

15. The polyurethane composite material according to claim 1 or 2, wherein the polyurethane composite material comprises a flame retardant selected from the group consisting of: orthophosphate, phosphite.

16. The polyurethane composite material according to claim 1 or 2, wherein the polyurethane composite material passes the UL94 V0 fire resistance test.

17. A method for preparing the polyurethane composite material according to claim 1, wherein the method comprises the following steps: 1) Provides reinforcing fibers in the form of a continuous phase; 2) Polyol components are prepared by mixing the following materials in a container at a temperature of 20 to 80°C: (b) at least one polyol that is reactive to isocyanates. (c) Optionally, chain extenders and / or crosslinking agents, (d) Flame retardants, (e) Optionally, filler, (f) Foaming agent, (g) catalyst, and (h) Optionally, additives and / or auxiliaries; 3) The polyol component obtained in step 2) is mixed with the isocyanate component and optionally the reinforcing fiber in the form of a discontinuous phase at a temperature of 20 to 80°C to obtain a mixture; 4) Spray or inject the mixture obtained in step 3) onto the reinforcing fibers in the form of the continuous phase provided in step 1) through a first nozzle or injection head, and optionally spray the reinforcing fibers in the form of the discontinuous phase onto the reinforcing fibers in the form of the continuous phase provided in step 1) through a second nozzle to obtain a sprayed or injected product. 5) Hot-pressing the sprayed or injection-molded product obtained in step 4) in a mold at a temperature of 40 to 180°C under a hot-pressing clamping force of 100 to 2000 tons; and 6) Demolding and optional trimming; The polyurethane composite material obtained in step 6) comprises 35 to 75% by weight of reinforcing fibers and 25 to 65% by weight of polyurethane foam, based on the total weight of the polyurethane composite material. The reinforcing fiber comprises 75 to 100% by weight of the reinforcing fiber in the form of a continuous phase and 0 to 25% by weight of the reinforcing fiber in the form of a discontinuous phase, based on the total weight of the reinforcing fiber; The reinforcing fibers are selected from glass fibers, basalt fibers, carbon fibers, and natural fibers; and The total amount of flame retardant is 5 to 30% by weight, based on the total weight of the resin.

18. The method of claim 17, wherein the discontinuous phase reinforcing fiber in step 3) is obtained by in-situ stubbed long fiber and added at a constant rate to a mixture of the isocyanate component and the polyol component of the polyurethane, and the length of the stubbed reinforcing fiber is 6 to 100 mm.

19. The method of claim 17, wherein the reinforcing fiber is selected from glass fiber and basalt fiber.

20. The method of claim 19, wherein the reinforcing fiber is glass fiber.

21. The method according to claim 17 or 18, wherein the reinforcing fiber in the form of the continuous phase in step 1) is in the form of a pad.

22. The method according to claim 17 or 18, wherein the reinforcing fiber in the form of a continuous phase in step 1) is in the form of a woven fabric.

23. A covering article comprising a polyurethane composite material according to any one of claims 1 to 16 or a polyurethane composite material obtained by the method according to any one of claims 17 to 22.

24. The covering article of claim 23, further comprising at least one metal sheet located on at least one side of the polyurethane composite material.

25. The cover article of claim 24, comprising two metal sheets located on each side of the polyurethane composite material.

26. The covering article according to claim 24 or 25, wherein the metal sheet is selected from aluminum alloys, iron, steel and aluminum sheets.

27. The covering article according to claim 24 or 25, wherein the thickness of the metal sheet is 0.08 to 1.2 mm.

28. The covering article according to claim 24 or 25, wherein the thickness of the metal sheet is 0.2 to 1.2 mm.

29. The covering article according to claim 28, wherein the thickness of the metal sheet is 0.5 to 1.0 mm.

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