A method for producing a polyurethane composite

Abstract

The application provides a method for preparing a polyurethane composite material by a transfer molding process, which comprises the following steps: spraying, injecting or pouring a polyurethane composition on at least one surface of at least one fiber layer in a spraying, injecting or pouring manner to obtain a preform; placing the preform in a mold with a mold temperature of 50-180 DEG C, closing the mold to perform hot pressing, applying a clamping pressure of 0.5-10 MPa on the mold during hot pressing, and demolding. The composite material of the application is suitable for the application of an electric vehicle battery shell box, especially an upper cover and a bottom guard plate, and can be used to manufacture parts with the same performance requirements at a lower cost.

Description

Technical Field

[0001] This invention relates to the field of polyurethane composite materials, and more particularly to a method for preparing polyurethane composite materials. Background Technology

[0002] The market share and demand for electric vehicles are increasing year by year. The battery packs used in electric vehicles typically need to have good flame retardancy, airtightness, and weather resistance.

[0003] To meet the requirements of battery packs, traditional processes primarily employ high-pressure resin transfer molding (HP-RTM) and prepreg molding (PCM) to fabricate the top cover or bottom cover of the battery pack. These traditional processes involve high equipment investment, complex procedures, and significant personnel involvement, resulting in high product costs. Furthermore, conventional spray transfer molding (STM) processes often lead to a large number of air bubbles in the manufactured parts, resulting in poor airtightness. An additional sandwich layer is typically needed as an auxiliary material to improve airtightness. A common method is to add a layer of thermoplastic polyurethane (TPU) film, which not only significantly increases the cost of the component but also complicates the process.

[0004] CN114672149A discloses a lightweight, thinner, flame-retardant polyurethane composite material, primarily used in the manufacture of cover products, which can be used as top covers for battery packs. This patent application also discloses a spray transfer molding method for preparing the polyurethane composite material. The polyol component used in this method includes a polyol, optional chain extender and / or crosslinking agent, flame retardant, optional filler, foaming agent, catalyst, and optional additives and / or auxiliaries. The polyurethane formulation must contain a foaming agent, which would introduce an airtightness risk to the battery top cover, hindering battery pack design.

[0005] CN112011027A discloses a method for preparing polyurethane composite materials using a high-pressure injection molding process. The method includes mixing an isocyanate component and an isocyanate reactive component, injecting the mixture into a mold with embedded reinforcing material under a pressure of 80-200 bar, controlling the vacuum degree during injection at -0.08 to -0.1 MPa, and obtaining the composite material after the reaction. The isocyanate reactive component includes a polyether polyol and a catalyst; the catalyst includes at least one thermosensitive catalyst, and the activation temperature of the thermosensitive catalyst is not lower than 50°C. This preparation method requires a pressure of at least 80 bar when injecting the polyurethane mixture into the mold. Comparative studies show that, with the same polyurethane formulation, if the pressure requirement is not met, the composite material sample exhibits poor wettability, multiple exposed glass fibers on the inner and outer surfaces, and significant voids and pores within the composite material. This results in the inability to produce test strips that meet mechanical and other performance testing standards, making performance testing impossible.

[0006] Therefore, there is a need to develop a polyurethane composite material formulation and process that is applicable to spray transfer molding without producing the aforementioned defects. Summary of the Invention

[0007] This invention provides a method for preparing polyurethane composite materials using a transfer molding process, comprising the following steps: spraying, injecting, or casting a polyurethane composition onto at least one surface of at least one fiber layer to obtain a preform; hot-pressing the preform in a mold at a temperature of 50-180°C and demolding; wherein the polyurethane composite material comprises 40%-75% fiber layer and 25%-60% polyurethane resin, based on the total mass of the polyurethane composite material; the polyurethane resin is obtained from a polyurethane composition comprising:

[0008] Component A: One or more organic polyisocyanates;

[0009] Component B: Isocyanate reactive component, comprising one or more organic polyols and optional chain extenders and / or crosslinking agents.

[0010] The content of the isocyanate reactive component is 20%-95%, preferably 30%-85%, based on the total mass of components B to E; and the average functionality of the isocyanate reactive component is 3.01-8.0, preferably 3.01-7.0.

[0011] Component C: A catalyst mixture comprising at least one thermosensitive catalyst C1 and at least one organometallic catalyst C2.

[0012] The content of the thermosensitive catalyst C1 is 0.15%-0.9%, and the content of the organometallic catalyst C2 is 0.001%-0.5%, based on the total mass of components B to E;

[0013] Optional component D: flame retardant; and

[0014] Optional component E: Additive;

[0015] Wherein, the molar ratio of isocyanate groups in component A to active hydrogen in component B is 0.9-1.5, preferably 0.95-1.3;

[0016] The fiber layer includes at least one layer of fiber felt and / or fiber fabric.

[0017] In this invention, the total mass of components B to E refers to the sum of the masses of components B, C, D, and E.

[0018] The present invention also provides a method for preparing polyurethane composite materials using the aforementioned transfer molding process.

[0019] The present invention also provides a polyurethane composition for preparing polyurethane composites by transfer molding process, comprising the following components:

[0020] Component A: One or more organic polyisocyanates;

[0021] Component B: Isocyanate reactive component, comprising one or more organic polyols, and optionally chain extenders and / or crosslinking agents.

[0022] The content of the isocyanate reactive component is 20%-95%, preferably 30%-85%, based on the total mass of components B to E; wherein the average functionality of the isocyanate reactive component is 3.01-8.0, preferably 3.01-7.0.

[0023] Component C: A catalyst mixture comprising at least one thermosensitive catalyst C1 and at least one organometallic catalyst C2.

[0024] The content of the thermosensitive catalyst C1 is 0.15%-0.9%, preferably 0.15%-0.8%, and the content of the organometallic catalyst C2 is 0.001%-0.5%, based on the total mass of components B to E;

[0025] Optional component D: flame retardant; and

[0026] Optional component E: Additive;

[0027] The molar ratio of isocyanate groups in component A to active hydrogen in component B is 0.9-1.5, preferably 0.95-1.3.

[0028] The present invention also provides the use of the polyurethane composition in a transfer molding process.

[0029] The present invention also provides an article comprising the aforementioned polyurethane composite material, preferably a battery pack cover, bottom plate or shell of an electric vehicle or energy storage box, or an energy storage box shell, and similar product applications in the art. Detailed Implementation

[0030] General definitions and terms

[0031] Unless otherwise stated, all publications, patent applications, patents and other references mentioned herein are incorporated herein in their entirety by way of citation.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of any conflict, the definitions provided herein shall prevail.

[0033] Unless otherwise stated, all percentages, parts, proportions, etc., are by weight. Those skilled in the art will understand that the sum of all components in a composition may suitably be 100%. When quantities, concentrations, or other values ​​or parameters are given as ranges, preferred ranges, or preferred upper and lower limits, or specific values, they should be understood as specifically disclosing all ranges formed by paired values ​​of any upper or preferred range and any lower or preferred range, regardless of whether the range is disclosed individually. Unless otherwise stated, when numerical ranges are referred to herein, the range means including its endpoints and all integers and fractions within that range.

[0034] When used with a numerical variable, the terms "about" or "approximately" usually mean that the value of the variable and all values ​​of the variable are within the experimental error (e.g., within a 95% confidence interval for the mean) or within ±10% of the specified value, or a wider range.

[0035] As used herein, the terms “optional” or “optionally” mean that an event or situation described below may or may not occur. This description includes both the occurrence and non-occurrence of the event or situation, as well as any arbitrary selection of the content described below. For example, when the content of a certain ingredient in this document is 0%-5%, it means that the component may be optionally present, i.e., it covers the cases of its absence (0%) and its presence (>0-5%).

[0036] The terms “comprising,” “including,” “having,” “containing,” or “involving,” and their other variations herein, are inclusive or open-ended and do not exclude other unlisted elements or method steps. Those skilled in the art will understand that the foregoing terms such as “comprising” encompass the meaning of “consisting of.” The expression “consisting of” excludes any unspecified elements, steps, or ingredients. The expression “substantially constitutes” limits the scope to the specified elements, steps, or ingredients, plus optional elements, steps, or ingredients that do not materially affect the essential and novel features of the claimed subject matter. It should be understood that the expression “comprising” encompasses both the expressions “substantially constitutes” and “consisting of.” The term “selected from” refers to one or more elements from the group listed below, selected independently, and may include combinations of two or more of these elements.

[0037] As used herein, the terms “one or more” or “at least one” refer to one, two, three, four, five, six, seven, eight, nine or more.

[0038] As used herein, the term "and / or" encompasses both "and" and "or". Multiple elements, components, or steps defined by "and / or" represent any one of those elements, components, or steps and any combination thereof. For example, A and / or B encompasses A, B, and A+B; A, B, and / or C encompasses A, B, C, A+B, A+C, B+C, and A+B+C.

[0039] Unless otherwise stated, the terms "combinations thereof", "any combination thereof" and "mixtures thereof" refer to multi-component mixtures of the elements, such as two, three, four, and up to the maximum possible multi-component mixtures.

[0040] Furthermore, if the number of components or parts of the present invention is not previously specified, it indicates that there is no limitation on the number of times a component or part may appear (or be present). Therefore, it should be interpreted as including one or at least one, and the singular form of a component or part also includes the plural, unless the value clearly indicates a singular number.

[0041] In this article, "multiple" or "several" means two or more, without specifying which ones unless otherwise explicitly defined. Unless the context clearly indicates otherwise, "one" can encompass both singular and plural references.

[0042] This invention provides a method for preparing polyurethane composite materials using a transfer molding process, comprising the following steps: spraying, injecting, or casting a polyurethane composition onto at least one surface of at least one fiber layer to obtain a preform; hot-pressing the preform in a mold at a temperature of 50-180°C and demolding; wherein the polyurethane composite material comprises 40%-75% fiber layer and 25%-60% polyurethane resin, based on the total mass of the polyurethane composite material; the polyurethane resin is obtained from a polyurethane composition comprising:

[0043] Component A: One or more organic polyisocyanates;

[0044] Component B: Isocyanate reactive component, comprising one or more organic polyols and optional chain extenders and / or crosslinking agents.

[0045] The content of the isocyanate reactive component is 20%-95%, preferably 30%-85%, based on the total mass of components B to E; and the average functionality of the isocyanate reactive component is 3.01-8.0, preferably 3.01-7.0.

[0046] Component C: A catalyst mixture comprising at least one thermosensitive catalyst C1 and at least one organometallic catalyst C2;

[0047] The content of the thermosensitive catalyst C1 is 0.15%-0.9%, and the content of the organometallic catalyst C2 is 0.001%-0.5%, based on the total mass of components B to E;

[0048] Optional component D: flame retardant; and

[0049] Optional component E: Additive;

[0050] Wherein, the molar ratio of isocyanate groups in component A to active hydrogen in component B is 0.9-1.5;

[0051] The fiber layer includes at least one layer of fiber felt and / or fiber fabric.

[0052] In this invention, the thermosensitive catalyst C1 is a catalyst that can accelerate catalysis or has catalytic activity at temperatures above 50°C, preferably within the temperature range of 50°C to 180°C. It is typically a terminally capped amine catalyst and / or a terminally capped amidine catalyst, including acid- or phenol-terminated amine catalysts and / or amidine catalysts (acid- or phenol-terminated amine salts and / or amidine salts). The thermosensitive catalyst used in this invention can be a commercially available product or can be terminally capped by reacting amines and / or amidines with carboxylic acids or phenols. The carboxylic acid can be one or more of formic acid, ethylhexanoic acid, acetic acid, oleic acid, isooctanoic acid, methacrylic acid, trifluoroacetic acid, benzoic acid, cyanoacetic acid, and 5-hydroxyisophthalic acid. The phenol can be one or more of phenol, catechol, and 2-hydroxyacetophenone. The amine catalyst can be a tertiary amine, its salt, and / or its complex, such as 1,4-diazabicyclo[2.2.2]octane (DABCO), bis(dimethylaminoethyl) ether, trimethylamine, triethylamine, tripropylamine, tributylamine, dimethylcyclohexylamine, dimethylbenzylamine, dibutylcyclohexylamine, dimethylethanolamine, triethanolamine, diethylethanolamine, ethyldiethanolamine, dimethylisopropanolamine, dimethyloctylamine, triisopropanolamine, triethylenediamine, tetramethyl-1,3-butanediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, N,N,N',N',N"-pentamethyldiethylenetriamine, bis(2-dimethylaminoethoxy) The amidine catalyst may be one or more of the following: 1,4-dimethylpiperidine, N,N,N'-trimethyl-N'-(2-hydroxyethyl)ethylenediamine, N,N-dimethyl-N',N'-(2-hydroxyethyl)ethylenediamine, tetramethylguanidine, N-methylpiperidine, N-ethylpiperidine, N-methylmorpholine, N-ethylmorpholine, 1,4-dimethylpiperidine, 1,2,4-trimethylpiperidine, N-(2-dimethylaminoethyl)morpholine, and 1-methyl-4-(2-dimethylamino)piperidine. The amidine catalyst may be an amidine compound, its salt, and / or its complex, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and / or 1,5-diazabicyclo[4.3.0]non-5-ene (DBN).

[0053] In this invention, the thermosensitive catalyst C1 can be, for example, DABCO 8154 (acid-terminated DABCO), DABCO BL-17 (acid-terminated bis(dimethylaminoethyl) ether), DABCO WT, DABCO KTM 60, or from Evonik. SA-1 / 10 (phenol-terminated DBU) SA-1, SA-2, SA-8, SA-101, SA-102, SA-102 / 10 or SA-610 / 50; from Tosoh Corporation DB 2, DB 30, DB 31, DB 40, DB 41, DB 42, DB 60, or DB 70; ACCELERATOR DY 9577 from Huntsman Corporation; WANALYST KC110 or WANALYST KC101 from Wanhua Chemical; CUCAT-RM90, RM60, RM301, RM401, or RM9100 from Guangzhou Yourun Synthetic Materials Co., Ltd.; Niax from Momentive Corporation. TM catalyst A-577 or Niax TM catalyst A-575.

[0054] In this invention, the content of the thermosensitive catalyst C1 ranges from 0.15% to 0.9%, preferably 0.15% to 0.8%, based on the total mass of components B to E. When the polyurethane composition contains an appropriate amount of thermosensitive catalyst, its combination with other components, especially organometallic catalysts, can achieve better surface finishes, with the number of bubbles and pinholes per square meter controlled within the range of 0-10, or even zero. Using a high content of thermosensitive catalyst results in poor reduction of surface defects.

[0055] In this invention, the organometallic catalyst C2 may include metal carboxylates and / or metal alkyl compounds, etc., wherein the metal element is mainly one or more selected from tin, potassium, titanium, zirconium, hafnium, bismuth, zinc, aluminum, and iron, preferably one or more selected from potassium, tin, and bismuth. The organometallic catalyst C2 may be an organotin catalyst, such as one or more selected from dibutyltin dilaurate, stannous octoate, stannous octoate, dioctyltin dithiol, dibutyltin oxide, dibutyltin diacetate, di(dodecyl sulfide)dibutyltin, stannous acetate, stannous ethylhexanoate, stannous laurate, dibutyltin diacetate, dibutyltin maleate, and dioctyltin diacetate. The organometallic catalyst C2 may also be an organopotassium catalyst, such as one or more selected from potassium acetate, potassium formate, potassium isooctanoate, and potassium acetate. The organometallic catalyst C2 may also be an organobismuth catalyst, such as one or more selected from bismuth carboxylate, bismuth neodecanoate, bismuth ethylhexanoate, and bismuth octanoate.

[0056] In this invention, the typical metal catalyst may be, for example, UL-6, UL-28, UL29 or UL-32 from Momentive.

[0057] In this invention, the content of the organometallic catalyst C2 ranges from 0.001% to 0.5%, preferably from 0.002% to 0.2%, based on the total mass of components B to E.

[0058] Chemically, polyurethane is a polymer containing repeating urethane units. In the context of this invention, it includes addition polymerization products of polyfunctional isocyanates and polyols (sometimes, though not entirely accurate, also referred to as condensation polymerization products). In addition to the basic polyurethane structure described above, polyurethane products typically contain other structures, such as those with urea bonds. Polyurethanes containing both these structures and the basic polyurethane structure that differ from the pure polyurethane structure are also included within the scope of the polyurethanes of this invention and do not depart from the scope of this invention. The polyurethane described in this invention is a thermosetting polyurethane.

[0059] In this invention, component A comprises one or more organic polyisocyanates, preferably composed of one or more organic polyisocyanates.

[0060] The organic polyisocyanate can be a known organic polyisocyanate containing an active isocyanate group (-NCO) used in the preparation of polyurethanes, including one or more of any pure aliphatic, alicyclic, and aromatic polyisocyanates, preferably aromatic polyisocyanates. The organic polyisocyanate of the present invention is an organic polyisocyanate containing two or more isocyanate groups, and therefore includes diisocyanates and triisocyanates.

[0061] Examples of aromatic polyisocyanates include, but are not limited to: toluene diisocyanate (TDI), terephthalic diisocyanate (PPDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl polyisocyanate (pMDI), 1,5-naphthalene diisocyanate (NDI), phenylmethylene diisocyanate (XDI), tetramethyl-methylene diisocyanate (TMXDI), trimethyl-1,6-hexamethylene diisocyanate (TMHDI), dimethyl biphenyl diisocyanate (TODI), prepolymers thereof, polymers thereof, and combinations thereof. The aromatic polyisocyanates include their isomers; for example, diphenylmethane diisocyanate (MDI) includes 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, and mixtures thereof.

[0062] Pure aliphatic polyisocyanates include, but are not limited to: hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), their prepolymers, polymers and combinations thereof.

[0063] Alicyclic polyisocyanates include, but are not limited to: methylcyclohexyl diisocyanate (HTDI), 4,4'-dicyclohexylmethane diisocyanate (H 12MDI, isophorone diisocyanate (IPDI), naphthalene diisocyanate (NDI), 1,4-cyclohexane diisocyanate (CHDI), cyclohexane dimethylene diisocyanate (HXDI), methylcyclohexyl diisocyanate (HTDI), norbornene diisocyanate (NBDI), their prepolymers, polymers and combinations thereof.

[0064] In this invention, the organic polyisocyanate is preferably polymethylene polyphenyl polyisocyanate, also known in the art as crude MDI.

[0065] In this invention, the viscosity of the organic polyisocyanate is preferably 20-300 mPa·s, particularly preferably 50-250 mPa·s, and is determined at 25°C according to DIN 53019-1-3.

[0066] The organic polyisocyanate may include polyisocyanate dimers, trimers, tetramers, pentamers, other polymers, or combinations thereof.

[0067] The organic polyisocyanates of the present invention naturally include embodiments of two or more different organic polyisocyanates (e.g., mixtures of MDI and TDI). This is also true within the same category of organic polyisocyanates, and therefore also applies to, for example, different types of MDI. All organic polyisocyanates used in the preparation of polyurethane resins are collectively referred to as Component A.

[0068] In this invention, the molar ratio of isocyanate groups in component A to active hydrogen in component B is 0.9-1.5, or may be 0.95-1.3. Active hydrogen in component B refers to hydrogen atoms capable of reacting with the isocyanate groups in component A, including hydrogen atoms on hydroxyl groups and hydrogen atoms on amino groups.

[0069] In this invention, the isocyanate reactive component B comprises one or more organic polyols, and may optionally include chain extenders and / or crosslinking agents.

[0070] In one embodiment of the present invention, the isocyanate reactive component is composed of one or more organic polyols, or of one or more organic polyols and one or more chain extenders and / or crosslinking agents. Typically, component B does not include non-isocyanate reactive components, or additives other than chain extenders and crosslinking agents, such as reactive flame retardants.

[0071] In this invention, the average functionality of the isocyanate reactive component B is 3.01-8.0, preferably 3.01-7.0. The average functionality (F) is the weighted mean of the individual functionalities of all organic polyols, chain extenders, and crosslinking agents in the isocyanate reactive component, and can be expressed by formula (a), wherein... The functionality of each organic polyol, chain extender, and crosslinking agent. The mass percentages of each organic polyol, chain extender, and crosslinking agent based on the isocyanate reactive component B are as follows:

[0072]

[0073] The functionality of the organic polyols, chain extenders, or crosslinking agents described in this invention refers to the number of active hydrogen atoms in each molecular chain. For active hydrogen atoms located at hydroxyl groups, the functionality can be obtained using the formula: Functionality = Hydroxyl value × Number-average molecular weight / 56100. For active hydrogen atoms located at amino groups, the functionality can be obtained using the formula: Functionality = Amine value × Number-average molecular weight / 56100. The number-average molecular weight is determined by gel permeation chromatography (GPC) according to GB / T 21863-2008, the hydroxyl value is determined according to ISO 14900-2017, and the amine value is determined according to ASTM D 2073.

[0074] The organic polyols described in this invention include all polyols known to those skilled in the art in the field of polyurethanes, particularly one or more of the following: polyether polyols, polyester polyols, polyether ester polyols, polycarbonate polyols, polyolefin polyols, and natural oil-based polyols. The organic polyols of this invention also include embodiments of two or more different organic polyols, such as combinations of polyether polyols and polyester polyols. This is also true within the same category of organic polyols, including one or more organic polyols of the same type, such as combinations of two polyether polyols.

[0075] The polyether polyol is a conventional oligomer or polymer in the art, containing ether bonds (-O-) in its molecular chain and with two or more hydroxyl groups at the end groups and / or side groups. The polyether polyol can be prepared by known processes, such as reacting an olefin oxide with an initiator in the presence of a catalyst. Catalysts include, but are not limited to, basic hydroxides, basic alkoxides, antimony pentachloride, boron fluoride ether, or combinations thereof. The olefin oxide includes, but is not limited to, tetrahydrofuran, ethylene oxide, propylene oxide, 1,2-epoxybutane, 2,3-epoxybutane, styrene oxide, and any two or more combinations thereof, with ethylene oxide and / or propylene oxide being particularly preferred. The initiator can be adjusted according to the functionality, viscosity, and other properties of the polyether polyol, and is preferably, but not limited to, one or more of polyols, polyamines, and alkanolamine compounds. The polyols include, but are not limited to, sorbitol, water, ethylene glycol, 1,2-propanediol, 1,3-propanediol, diethylene glycol, dipropylene glycol, trimethylolpropane, glycerol, pentaerythritol, xylitol, mannitol, sucrose, bisphenol A, bisphenol S, and combinations thereof. The polyamines include, but are not limited to, ethylenediamine, propylenediamine, butanediamine, ethylenediamine, hexamethylenediamine, diethylenetriamine, toluenediamine, and combinations thereof, or one or more. The alkanolamine compounds include triethanolamine.

[0076] In one embodiment of the present invention, the isocyanate reactive component includes at least one polyether polyol, and may also include two or more polyether polyols.

[0077] In one embodiment of the present invention, the number average molecular weight of the polyether polyol is 300-2000, as determined according to GB / T21863-2008.

[0078] This invention does not require that the functionality of each organic polyol be in the range of 3.01-8.0 or 3.01-7.0, but only requires that the average functionality of the isocyanate reactive component be in the range.

[0079] In one embodiment of the present invention, the functionality of the polyether polyol is 2.0-8.0, preferably 3.0-8.0.

[0080] In one embodiment of the present invention, the hydroxyl value of the polyether polyol is 200-1000 mg KOH / g; the hydroxyl value refers to the number of milligrams of potassium hydroxide equivalent to the hydroxyl groups in 1 g of sample, determined according to ISO 14900-2017.

[0081] In this invention, the polyester polyol can be an aliphatic or aromatic polyester polyol, preferably an aliphatic polyester polyol. The polyester polyol can be prepared by reacting a dicarboxylic acid or a dicarboxylic acid anhydride with a polyol. The dicarboxylic acid includes aliphatic and aromatic carboxylic acids containing 2-12 carbon atoms, including succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, maleic acid, trans-butenedioic acid, phthalic acid, isophthalic acid, isophthalic acid, terephthalic acid, and combinations thereof. The dicarboxylic acid anhydride includes phthalic anhydride, tetrachlorophthalic anhydride, maleic anhydride, and combinations thereof. Polyols that react with the said dicarboxylic acid or the said dicarboxylic acid anhydride include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, 1,3-butanediol, methylpropanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, neopentanediol, 1,10-decanediol, glycerol, trimethylolpropane, and combinations thereof. Polyester polyols may also include polyester polyols prepared from lactones. The polyester polyols prepared from lactones are preferably, but not limited to, ε-caprolactone.

[0082] In one embodiment of the present invention, the number average molecular weight of the polyester polyol is 400-3000, as determined according to GB / T21863-2008.

[0083] In one embodiment of the present invention, the functionality of the polyester polyol is 2.0-6.0.

[0084] In one embodiment of the present invention, the hydroxyl value of the polyester polyol is 80-600 mgKOH / g, where the hydroxyl value refers to the number of milligrams of potassium hydroxide equivalent to the hydroxyl group in 1 g of sample, as determined according to ISO 14900-2017.

[0085] Component B of the present invention optionally includes a crosslinking agent and / or a chain extender. Suitable crosslinking agents and / or chain extenders are generally multifunctional compounds having multiple isocyanate reactive groups and a number-average molecular weight of 60-400 as determined according to GB / T 21863-2008, such as one or more of polyamines, polyols and alkanolamines.

[0086] In one embodiment of the present invention, the functionality of the crosslinking agent and / or chain extender is 2.0-8.0, preferably 2.0-4.0.

[0087] In one embodiment of the present invention, the crosslinking agent and / or chain extender includes one or more of ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, 1,3-butanediol, methylpropanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, neopentanediol, 2-methyl-2,4-pentanediol, 1,10-decanediol, glycerol, trimethylolpropane, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), dimethylthiotoluenediamine (DMTDA), diethyltoluenediamine (DETDA), 4,4'-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA), ethanolamine, diethanolamine, and triethanolamine.

[0088] In one embodiment of the present invention, the content of the crosslinking agent and / or chain extender is 0.1%-30%, preferably 3%-27%, based on the total mass of components B to E.

[0089] In this invention, the polyurethane composition may also include optional component D: flame retardant.

[0090] In this invention, the flame retardant can be any of the conventional flame retardants in the art, including but not limited to reactive flame retardant D1 and / or non-reactive flame retardant D2.

[0091] The reactive flame retardant D1 is a flame retardant that allows flame retardant components to be chemically bonded to polyurethane materials, including but not limited to one or more of the following: tetrabromophthalic anhydride diol, tetrabromophthalate, tris(dipropylene glycol) phosphite (P430), tris(polyoxyolefin) phosphate, tris(polyoxyolefin) phosphite, dimethyl N,N-di(2-hydroxyethyl)aminomethylphosphonate, diethyl N,N-di(2-hydroxyethyl)aminomethylenephosphonate, polyether polyol solution of tris(cyanopolyol) phosphate dibromopentanediol, pentaerythritol bromide, and bromination, dechlorination, and methoxylation products of polymers of 2-butyn-1,4-diol and 2-(chloromethyl)ethylene oxide (CAS No. 68441-62-3).

[0092] In one embodiment of the present invention, the reactive flame retardant D1 is a bromination, dechlorination and methoxylation product of a polymer of tetrabromophthalate and / or 2-butyn-1,4-diol and 2-(chloromethyl)ethylene oxide (CAS No. 68441-62-3).

[0093] The non-reactive flame retardant D2 refers to a flame retardant that has flame-retardant effects but does not participate in the polyurethane reaction, including but not limited to one or more of halophosphate flame retardants, phosphonate flame retardants, and inorganic solid flame retardants. The halophosphate flame retardant can be selected from one or more of tris(2-chloropropyl) phosphate (TCPP), tris(2-chloroethyl) phosphate (TCEP), tris(dichloropropyl) phosphate (TDCPP), tris(dibromopropyl) phosphate, tetra(2-chloroethyl) ethylene diphosphate, bis[di(2-chloroethyl)]diethylene glycol phosphate, 2,2-dimethyl-3-chloropropyl bis(1,3-dichloro-2-propyl) phosphate, 2,2-dimethyl-3-bromopropyl-β-bromoethyl phosphate, and dimer and polyphosphate esters. The phosphonate flame retardant may be selected from one or more of dimethyl methylphosphonate (DMMP), diethyl ethylphosphonate, dimethyl propylphosphonate, triisopropylphenyl phosphate, and triethyl phosphate. The inorganic solid flame retardant may be selected from one or more of melamine and its derivatives, red phosphorus and its complexes, and aluminum hydroxide.

[0094] In one embodiment of the present invention, the non-reactive flame retardant D2 is one or more of tris(2-chloropropyl) phosphate (TCPP), tris(2-chloroethyl) phosphate (TCEP), dimethyl methylphosphonate (DMMP), diethyl ethylphosphonate, and dimethyl propylphosphonate.

[0095] The flame retardant in the polyurethane composition generally needs to reach a certain content to achieve a flame retardant effect. In one embodiment of the present invention, the content of the flame retardant component D is 5%-60%, preferably 15%-55%, based on the total mass of components B to E. The polyurethane composite material of the present invention can achieve a flame retardant rating of UL-94V-2, preferably UL-94V-1, more preferably UL-94V-0, or UL-945VA, and the test sample thickness is 1.5 mm according to the UL-94 standard.

[0096] In one embodiment of the present invention, the flame retardant component D is a combination of reactive flame retardant D1 and non-reactive flame retardant D2, and the mass ratio of D1:D2 is preferably (0-2):1, (0.01-2):1, and more preferably (0.1-1):1.

[0097] In this invention, the polyurethane composition may further include optional component E: one or more additives conventional in the art. The additives refer to additives other than the chain extenders and crosslinking agents in component B, the catalysts in component C, and the flame retardants in component D, including water absorbers, light stabilizers, antioxidants, defoamers, internal release agents, colorants, UV absorbers, colorants, fillers, smoke inhibitors, antistatic agents, diluents, coupling agents, surface wetting agents, leveling agents, thixotropic agents, plasticizers, foam levelers, and free radical reaction inhibitors, or combinations thereof.

[0098] In a preferred embodiment of the present invention, the polyurethane composition does not include a foaming agent.

[0099] In one embodiment of the present invention, the content of component E is 0.01%-10%, preferably 0.5%-5%, based on the total mass of components B to E.

[0100] In this invention, the fiber layer may include at least one layer of fiber felt and / or fiber fabric, or may include two or more layers of fiber felt, two or more layers of fiber fabric, or a combination of two or more layers of fiber felt and fiber fabric. For the configuration of two or more fiber layers, it may be a combination of two or more layers of the same fiber felt or fiber fabric, or a combination of different fiber felts or fiber fabrics.

[0101] In this invention, the fiber felt is a sheet-like product conventionally made in the art by bonding long fibers and / or chopped fibers together in a directional or non-directional manner through chemical adhesives, thermal bonding, or mechanical action, and may also include nonwoven fabrics and non-woven textiles. The fiber fabrics include woven fabrics, knitted fabrics, and woven fabrics. Examples of the fibers can be natural fibers, glass fibers, carbon fibers, polyester fibers, nylon fibers, basalt fibers, boron fibers, silicon carbide fibers, asbestos fibers, metal fibers, or combinations thereof. The natural fibers can include natural plant fibers such as cotton, hemp, flax, and grass, as well as natural animal fibers such as wool, silk, and alpaca wool.

[0102] In one embodiment of the present invention, the fiber felt further includes a fiber composite felt, for example, one side is a fiber felt and the other side is a fiber fabric.

[0103] In a preferred embodiment of the invention, the fiber layer consists of at least one layer of glass fiber mat and / or at least one layer of glass fiber fabric.

[0104] In this invention, the fiber layer preferably comprises 1-8 layers, more preferably 1-5 layers of fiber felt and / or fiber fabric. The unit weight of each layer of fiber felt or fiber fabric can be, for example, 20-1200 g / m². 2 The optimal concentration is 300-800 g / m³. 2 .

[0105] In one embodiment of the present invention, the fiber mat is a glass fiber mat. The unit weight of the fiber mat can be, for example, 20-1200 g / m³. 2 The optimal concentration is 300-800 g / m³. 2 .

[0106] In one embodiment of the present invention, the fiber fabric is a glass fiber fabric. The unit weight of the fiber fabric is, for example, 20-1200 g / m². 2 The optimal concentration is 300-800 g / m³. 2 .

[0107] In one embodiment of the present invention, the fiber layer is a glass fiber composite mat, with one side being a glass fiber mat and the other side being a glass fiber fabric. The unit weight of the glass fiber composite mat is, for example, 20-1200 g / m². 2 The optimal concentration is 300-800 g / m³. 2 .

[0108] In this invention, the fiber layer content in the polyurethane composite material is 40%-75%, preferably 50%-60%, based on the total mass of the polyurethane composite material.

[0109] In this invention, the transfer molding process includes spray transfer molding (STM) and wet transfer molding (WTM).

[0110] Spray transfer molding typically involves spraying a polyurethane composition onto a fiber layer outside a mold, then transferring the polyurethane-coated fiber layer into the mold, closing the mold, and hot-pressing. Wet transfer molding typically involves injecting or casting a polyurethane composition onto a fiber layer outside a mold, then transferring the polyurethane-coated fiber layer into the mold, closing the mold, and hot-pressing. The polyurethane composition is usually thoroughly mixed before spraying, casting, or injection; that is, the components of the polyurethane composition are mixed using conventional methods, preferably immediately after thorough mixing.

[0111] The spraying method described in this invention typically employs a spraying device, such as a nozzle or atomizer, to apply the polyurethane composition to the fiber layer in the form of droplets or atomized liquid. The injection or casting method typically involves pouring the polyurethane composition into the fiber layer as a liquid fluid. Optionally, methods such as smearing, vibrating, or swaying the fiber layer can also be used to spread the liquid fluid on the fiber layer. During hot pressing, the liquid fluid can also spread on the fiber layer; therefore, the smearing, vibrating, and swaying steps are not necessary.

[0112] In this invention, before applying the polyurethane composition to the fiber layer, components B to E are usually mixed to obtain a mixture, which is then mixed with component A to obtain the polyurethane composition, and then sprayed, injected or cast immediately.

[0113] In this invention, by screening the organic polyols, chain extenders, and crosslinking agents in component B, it is possible to ensure that the polyurethane composition does not drip or pass through the fiber layer during the process of transferring the fiber layer coated with the polyurethane composition to the mold, while at the same time the polyurethane composition can penetrate into the pores in the fiber layer.

[0114] In this invention, a polyurethane composition is sprayed, injected, or cast onto at least one surface of the fiber layer, and the same operation can be performed on both surfaces of the fiber layer. For example, after coating one surface of the fiber layer, it is flipped over and then coated onto the other surface. During the coating process, the fiber layer is preferably placed parallel to the ground to ensure more uniform coating. Placing it perpendicular to the ground is not recommended, as it can easily lead to uneven coating and even flow marks. Coating here includes spraying, injection, and casting.

[0115] In this invention, conventional support devices, such as robotic arms, can be used to fix the fiber layer during coating, and preferably the fiber layer is suspended in the air.

[0116] In this invention, when the fiber layer comprises two or more layers of fiber felt and / or fiber fabric, it is preferable to stack all the fiber felt and / or fiber fabric together to form the fiber layer. The spraying, injection, and casting are still performed on one or two surfaces of the fiber layer, without having to coat each layer of fiber felt and / or fiber fabric before stacking to form the fiber layer.

[0117] In this invention, the preform is placed in front of the mold, and the mold temperature is preferably controlled at 50℃-180℃, more preferably at 90℃-130℃, which is beneficial for the curing of the polyurethane composition in the mold.

[0118] In this invention, after the preform is placed in the mold, the hot pressing temperature is 50°C-180°C, more preferably 90°C-130°C.

[0119] In this invention, during hot pressing, a pressure is applied to the mold, such that the mold closing pressure is 0.5 MPa-10 MPa, preferably 0.5 MPa-5 MPa. The mold closing pressure is the intensity of the clamping force applied to the mold when the mold is closed, expressed as the clamping force divided by the mold area.

[0120] In this invention, the preform is preferably hot-pressed in a mold for a certain period of time so that the polyurethane composition can spread and cure in the mold. The hot-pressing time is generally 2 min to 10 min, preferably 2 min to 4 min.

[0121] The present invention also provides a method for preparing polyurethane composite materials using the aforementioned transfer molding process.

[0122] In this invention, the thickness of the polyurethane composite material is typically 0.4mm-10mm, and can be adjusted according to application requirements, for example, 2mm-8mm or 2mm-5mm.

[0123] In this invention, the density of the polyurethane composite material is typically 1.5 g / cm³. 3 -2.2g / cm 3 It can be adjusted according to application requirements.

[0124] The polyurethane composite material of the present invention can be used for battery pack covers, bottom plates or shells of electric vehicles or energy storage boxes, or energy storage box shells and similar product applications in this technical field.

[0125] The present invention also provides a polyurethane composition for preparing polyurethane composites by transfer molding process, comprising the following components:

[0126] Component A: One or more organic polyisocyanates;

[0127] Component B: Isocyanate reactive component, comprising one or more organic polyols and optional chain extenders and / or crosslinking agents.

[0128] The content of the isocyanate reactive component is 20%-95%, preferably 30%-85%, based on the total mass of components B to E; and the average functionality of the isocyanate reactive component is 3.01-8.0, preferably 3.01-7.0.

[0129] Component C: A catalyst mixture comprising at least one thermosensitive catalyst C1 and at least one organometallic catalyst C2;

[0130] The content of the thermosensitive catalyst C1 is 0.15%-0.9%, and the content of the organometallic catalyst C2 is 0.001%-0.5%, based on the total mass of components B to E;

[0131] Optional component D: flame retardant; and

[0132] Optional component E: Additive;

[0133] The molar ratio of isocyanate groups in component A to active hydrogen in component B is 0.9-1.5, preferably 0.95-1.3.

[0134] In this invention, the gelation time of the polyurethane composition at room temperature is preferably 2-20 minutes, more preferably 3-15 minutes, and even more preferably 4-10 minutes.

[0135] The present invention also provides the use of the polyurethane composition in a transfer molding process.

[0136] The present invention also provides an article comprising the aforementioned polyurethane composite material, preferably a battery pack cover, bottom plate or shell of an electric vehicle or energy storage box, or an energy storage box shell, and similar product applications in the art.

[0137] In one embodiment of the present invention, component B comprises a polyether polyol.

[0138] In one embodiment of the present invention, component B comprises a polyether polyol and a crosslinking agent and / or chain extender.

[0139] In one embodiment of the present invention, the number-average molecular weight of the polyether polyol is 350-

[0140] 1000, tested according to GB / T 21863-2008.

[0141] In one embodiment of the present invention, the functionality of the polyether polyol is 3-7.

[0142] In one embodiment of the present invention, the polyether polyol is a propoxylated polyether polyol starting with glycerol and / or sucrose.

[0143] In one embodiment of the present invention, the crosslinking agent and / or chain extender is glycerol and / or diethyltoluenediamine.

[0144] In one embodiment of the present invention, the content of the crosslinking agent and / or chain extender is 15%-20%, based on the total mass of components B to E.

[0145] In one embodiment of the present invention, the content of the isocyanate reactive component B is 40%-60% based on the total mass of components B to E.

[0146] In one embodiment of the present invention, the average functionality of the isocyanate reactive component B is 3.04 to 7.

[0147] In one embodiment of the present invention, the content of the thermosensitive catalyst C1 is 0.15%-0.9%, and the content of the organometallic catalyst C2 is 0.05%-0.15%, based on the total mass of components B to E.

[0148] In one embodiment of the present invention, the thermosensitive catalyst C1 is a DBU with end caps, preferably an acid- or phenol-end capped DBU.

[0149] In one embodiment of the present invention, the organometallic catalyst C2 is an organotin catalyst.

[0150] In one embodiment of the present invention, the organometallic catalyst C2 is dibutyltin dilaurate.

[0151] In one embodiment of the present invention, the thermosensitive catalyst C1 is a salt of 1,8-diazabicyclo[5.4.0]undec-7-ene, a carboxylic acid-terminated tertiary amine, and a carboxylic acid-terminated cyclic amine.

[0152] In one embodiment of the present invention, the reactive flame retardant D1 is tetrabromophthalate.

[0153] In one embodiment of the present invention, the non-reactive flame retardant D2 is tris(2-chloropropyl) phosphate.

[0154] In one embodiment of the present invention, the mass ratio of the reactive flame retardant D1 to the non-reactive flame retardant D2 is 0.5:1 to 0.9:1.

[0155] In a preferred embodiment of the present invention, the content of component E is 2%-8%, based on the total mass of components B to E.

[0156] In one embodiment of the present invention, the fiber layer is a fiber composite felt.

[0157] In one embodiment of the present invention, the method for preparing polyurethane composite material by transfer molding process includes the following steps: spraying the polyurethane composition onto at least one surface of at least one fiber layer to obtain a preform.

[0158] In a further embodiment of the present invention, the method includes: hot pressing the preform in a mold with a mold temperature of 90-130°C.

[0159] In a further embodiment of the present invention, the method includes: applying a mold closing pressure of 0.5-3 MPa on the mold during hot pressing, and then demolding.

[0160] In one embodiment of the present invention, the polyurethane composite material comprises 50%-70% fiber layers and 50%-30% polyurethane resin, based on the total mass of the polyurethane composite material.

[0161] Beneficial effects

[0162] In this invention, by adjusting the polyurethane composition, a polyurethane composition suitable for the transfer molding process was selected. This process is simple and fast, and the polyurethane composition will not drip or penetrate the fiber layer during preparation. Therefore, the composite material prepared by the transfer molding process has small surface defects, good weather resistance, uniform polyurethane resin distribution, and good sealing performance.

[0163] The polyurethane composite material of the present invention can achieve UL94 V-0 and 5VA flame retardant effects, and is particularly suitable for electric vehicle battery boxes, especially for the application of top covers and bottom protection plates, allowing for the production of components with the same performance requirements at a lower cost.

[0164] Example

[0165] The present invention will be further illustrated below with reference to specific embodiments. However, it should be understood that these embodiments are for illustrative purposes only and do not constitute a limitation on the scope of the invention.

[0166] Unless otherwise specified, the test methods in the following examples are generally performed under standard conditions. All percentages and parts are by weight.

[0167] The test standards for the test methods involved in the embodiments are as follows:

[0168] Number-average molecular weight was tested according to GB / T 21863-2008.

[0169] Isocyanate viscosity was determined according to DIN 53019-1-3.

[0170] The tensile strength of the resin was tested according to ISO 527-2, and the flexural strength of the resin was tested according to ISO 178. Samples for tensile and flexural strength were prepared by mixing components A through E, injecting the mixture into a mold, and curing at 110°C. The mold dimensions were consistent with the sample dimensions in the aforementioned test standards.

[0171] Flowability test: Mix 200g of the mixture of components B to E and 200g of component A in a cup. After mixing for 80 seconds, tilt the cup 90 degrees and observe whether the liquid flows.

[0172] Gel time: The time from the start of mixing components B to E and component A (defined as 0 seconds) to the time during which the polyurethane composition cures (until the composition begins to thicken and can be drawn into filaments when touched with a rod-shaped solid).

[0173] The sources and descriptions of the components used in the embodiments of this invention are listed in Table 1.

[0174] Table 1

[0175]

[0176]

[0177]

[0178] The formulations of the polyurethane compositions in Examples 1-8 and Comparative Examples 1-5 are shown in Tables 2-3.

[0179] Example 1

[0180] Step 1: Preheat the mold at 110℃.

[0181] Step 2: Mix components B, C, D and E, and then mix the above mixture with component A to obtain a polyurethane composition. Use a robotic arm to clamp the glass fiber composite mat and spray it onto one surface of the glass fiber composite mat in an atmospheric environment to obtain a preform. The mass ratio of the polyurethane composition to the glass fiber composite mat is 40:60.

[0182] Step 3: Move the preform obtained in Step 2 into the mold, close the mold and hot press it, keeping the mold temperature at 110℃;

[0183] Step 4: Apply a mold closing pressure of 1 MPa to the mold; demold after 3 minutes to obtain the polyurethane composite material.

[0184] Table 2

[0185]

[0186]

[0187] *The average functionality of component B is the average functionality of components B1 to B5.

[0188] Examples 2-8 and Comparative Examples 1-5 used the same process as Example 1, the difference being the different polyurethane composition formulations.

[0189] As can be seen from Table 2, the poor flowability of Comparative Example 1 leads to the polyurethane composition dripping or penetrating through the fiber layer when applied, requiring a larger total amount of resin and making it difficult to guarantee the weight ratio of polyurethane resin to fiber layer and batch-to-batch quality stability.

[0190] As shown in Table 3, under the same catalyst dosage, Example 2, which uses both a thermosensitive catalyst and an organometallic catalyst, has better surface properties, toughness, and strength compared to Comparative Example 2 and Comparative Example 5.

[0191]

[0192]

[0193] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A method for preparing a polyurethane composite material using a transfer molding process, comprising the following steps: spraying, injecting, or casting a polyurethane composition onto at least one surface of at least one fiber layer to obtain a preform; hot-pressing the preform in a mold at a temperature of 50-180°C, and demolding; wherein the polyurethane composite material comprises 40%-75% fiber layer and 25%-60% polyurethane resin, based on the total mass of the polyurethane composite material; wherein the polyurethane resin is obtained from a polyurethane composition comprising: Component A: One or more organic polyisocyanates; Component B: Isocyanate reactive component, comprising one or more organic polyols and optional chain extenders and / or crosslinking agents. The content of the isocyanate reactive component is 20%-95%, preferably 30%-85%, based on the total mass of components B to E; and the average functionality of the isocyanate reactive component is 3.01-8.0, preferably 3.01-7.

0. Component C: A catalyst mixture comprising at least one thermosensitive catalyst C1 and at least one organometallic catalyst C2; The content of the thermosensitive catalyst C1 is 0.15%-0.9%, preferably 0.15%-0.8%, and the content of the organometallic catalyst C2 is 0.001%-0.5%, preferably 0.002%-0.2%, based on the total mass of components B to E; Optional component D: flame retardant; and Optional component E: Additive; Wherein, the molar ratio of isocyanate groups in component A to active hydrogen in component B is 0.9-1.5, preferably 0.95-1.3; The fiber layer includes at least one layer of fiber felt and / or fiber fabric.

2. The method as described in claim 1, characterized in that: The thermosensitive catalyst is an acid or phenol-terminated amine catalyst and / or amidine catalyst, which achieves end-capping through the reaction of amine and / or amidine with carboxylic acid or phenol.

3. The method as described in claim 2, characterized in that: The carboxylic acid is selected from one or more of formic acid, ethylhexanoic acid, acetic acid, oleic acid, isooctanoic acid, methacrylic acid, trifluoroacetic acid, benzoic acid, cyanoacetic acid, and 5-hydroxyisophthalic acid; the phenol is selected from one or more of phenol, catechol, and 2-hydroxyacetophenone; the amine catalyst is selected from 1,4-diazabicyclo[2.2.2]octane, bis(dimethylaminoethyl) ether, trimethylamine, triethylamine, tripropylamine, tributylamine, dimethylcyclohexylamine, dimethylbenzylamine, dibutylcyclohexylamine, dimethylethanolamine, triethanolamine, diethylethanolamine, ethyldiethanolamine, dimethylisopropanolamine, dimethyloctylamine, triisopropanolamine, triethylenediamine, tetramethyl-1,3-butanediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N' The amidine catalyst is selected from one or more of the following: N'-tetramethyl-1,6-hexanediamine, N,N,N',N',N"-pentamethyldiethylenetriamine, bis(2-dimethylaminoethoxy)methane, N,N,N'-trimethyl-N'-(2-hydroxyethyl)ethylenediamine, N,N-dimethyl-N',N'-(2-hydroxyethyl)ethylenediamine, tetramethylguanidine, N-methylpiperidine, N-ethylpiperidine, N-methylmorpholine, N-ethylmorpholine, 1,4-dimethylpiperidine, 1,2,4-trimethylpiperidine, N-(2-dimethylaminoethyl)morpholine, and 1-methyl-4-(2-dimethylamino)piperidine; the amidine catalyst is selected from 1,8-diazabicyclo[5.4.0]undec-7-ene and / or 1,5-diazabicyclo[4.3.0]non-5-ene.

4. The method according to any one of claims 1-3, characterized in that: The organometallic catalyst C2 is a metal carboxylate and / or a metal alkyl compound, and the metal element is preferably selected from one or more of tin, potassium, titanium, zirconium, hafnium, bismuth, zinc, aluminum and iron, with potassium, tin and bismuth being more preferred.

5. The method according to any one of claims 1-4, characterized in that: The organometallic catalyst C2 is selected from one or more of the following: dibutyltin dilaurate, stannous octanoate, stannous octanoate, dioctyltin dithiol, dibutyltin oxide, dibutyltin diacetate, di(dodecyl sulfide)dibutyltin, stannous acetate, stannous ethylhexanoate, stannous laurate, dibutyltin diacetate, dibutyltin diacetate, potassium acetate, potassium formate, potassium isooctanoate, potassium acetate, bismuth carboxylate, bismuth neodecanoate, bismuth ethylhexanoate, and bismuth octanoate.

6. The method according to any one of claims 1-5, characterized in that: The organic polyols include one or more of polyether polyols, polyester polyols, polyether ester polyols, polycarbonate polyols, polyolefin polyols, and natural oil-based polyols, preferably polyether polyols and / or polyester polyols, and more preferably two or more polyether polyols.

7. The method as described in claim 6, characterized in that: The polyether polyol has a number-average molecular weight of 300-2000, as tested according to GB / T 21863-2008; the polyether polyol has a functionality of 2-8, preferably 3-8; the polyether polyol has a hydroxyl value of 200-1000 mgKOH / g, as tested according to ISO 14900-2017; the polyester polyol has a number-average molecular weight of 400-3000, as tested according to GB / T 21863-2008; the polyester polyol has a functionality of 2-6; the polyester polyol has a hydroxyl value of 80-600 mgKOH / g, as tested according to ISO 14900-2017.

8. The method according to any one of claims 1-7, characterized in that: The crosslinking agent and / or chain extender are multifunctional compounds with a number average molecular weight of 60-400 and having multiple groups reactive to isocyanates, including one or more of polyamines, polyols and alkanolamines; the functionality of the crosslinking agent and / or chain extender is 2-8, preferably 2-4.

9. The method as described in claim 8, characterized in that: The crosslinking agent and / or chain extender includes one or more of ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, 1,3-butanediol, methylpropanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, neopentanediol, 2-methyl-2,4-pentanediol, 1,10-decanediol, glycerol, trimethylolpropane, 3,3'-dichloro-4,4'-diaminodiphenylmethane, dimethylthiotoluenediamine, diethyltoluenediamine, 4,4'-methylenebis(3-chloro-2,6-diethylaniline), ethanolamine, diethanolamine, and triethanolamine.

10. The method according to any one of claims 1-9, characterized in that: The content of the crosslinking agent and / or chain extender is 0.1%-30%, preferably 3%-27%, based on the total mass of components B to E.

11. The method according to any one of claims 1-10, characterized in that: The flame retardant component D includes reactive flame retardant D1 and / or non-reactive flame retardant D2; the reactive flame retardant D1 is preferably selected from tetrabromophthalic anhydride diol, tetrabromophthalate, tris(dipropylene glycol) phosphite, tris(polyoxyolefin) phosphate, tris(polyoxyolefin) phosphite, dimethyl N,N-di(2-hydroxyethyl)aminomethylphosphonate, diethyl N,N-di(2-hydroxyethyl)aminomethylenephosphonate, a polyether polyol solution of dibromopentanediol tris(cyanide polyol) phosphate, pentaerythritol bromide, and bromination and dechlorination of polymers of 2-butynedi-1,4-diol and 2-(chloromethyl)ethylene oxide. And one or more of the methoxylated products; the non-reactive flame retardant D2 preferably includes one or more of tris(2-chloropropyl) phosphate, tris(2-chloroethyl) phosphate, tris(dichloropropyl) phosphate, tris(dibromopropyl) phosphate, tetra(2-chloroethyl) ethylidene diphosphate, bis[di(2-chloroethyl)] diethylene glycol phosphate, 2,2-dimethyl-3-chloropropyl bis(1,3-dichloro-2-propyl) phosphate, 2,2-dimethyl-3-bromo-propyl-β-bromoethyl phosphate, dimethyl methylphosphonate, diethyl ethylphosphonate, dimethyl propylphosphonate, triisopropylphenyl phosphate, and triethyl phosphate.

12. The method according to any one of claims 1-11, characterized in that: The content of component D flame retardant is 5%-60%, preferably 15%-55%, based on the total mass of components B to E; the mass ratio of the reactive flame retardant D1 to the non-reactive flame retardant D2 is preferably (0-2):1, more preferably (0.1-1):

1.

13. The method according to any one of claims 1-12, characterized in that: The fiber layer comprises 1-8 layers, preferably 1-5 layers of fiber felt and / or fiber fabric; the unit weight of each layer of fiber felt or fiber fabric is 20-1200 g / m². 2 The optimal concentration is 300-800 g / m³. 2 .

14. The method according to any one of claims 1-13, characterized in that: The hot pressing temperature is 50℃-180℃, preferably 90℃-130℃; and / or, the hot pressing clamping pressure is 0.5MPa-10 MPa, preferably 0.5MPa-5 MPa; and / or, the hot pressing time is 2min-10min, preferably 2min-4min.

15. A polyurethane composite material prepared by a method for preparing polyurethane composite materials using the transfer molding process as described in any one of claims 1-14.

16. A polyurethane composition for preparing polyurethane composites by transfer molding process, comprising the following components: Component A: One or more organic polyisocyanates; Component B: Isocyanate reactive component, comprising one or more organic polyols and optional chain extenders and / or crosslinking agents. in, The content of the isocyanate reactive component is 20%-95%, preferably 30%-85%, based on the total mass of components B to E; wherein the average functionality of the isocyanate reactive component is 3.01-8.0, preferably 3.01-7.

0. Component C: A catalyst mixture comprising at least one thermosensitive catalyst C1 and at least one organometallic catalyst C2; The content of the thermosensitive catalyst C1 is 0.15%-0.9%, preferably 0.15%-0.8%, and the content of the organometallic catalyst C2 is 0.001%-0.5%, preferably 0.002%-0.2%, based on the total mass of components B to E; Optional component D: flame retardant; and Optional component E: Additive; The molar ratio of isocyanate groups in component A to active hydrogen in component B is 0.9-1.5, preferably 0.95-1.

3.

17. The polyurethane composition of claim 16, characterized in that: Its gelation time at room temperature is 2 minutes to 20 minutes, preferably 3 minutes to 15 minutes, and more preferably 4 minutes to 10 minutes.

18. Use of a polyurethane composition as described in claim 16 or 17 in a transfer molding process.

19. An article comprising the polyurethane composite material as described in claim 15.

20. The article of claim 19, characterized in that: It is the battery pack cover, bottom protection plate or shell of an electric vehicle or energy storage box, or the outer shell of an energy storage box.

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