A polyurethane stock solution, its preparation method and application

Abstract

The present invention relates to a polyurethane stock solution, a preparation method thereof and an application thereof. The polyurethane stock solution comprises component A and component B; component A comprises a combination of propylene oxide-tetrahydrofuran copolymer polyether, castor oil polyol, chain extender, catalyst, water absorption stabilizer, silane coupling agent and foaming agent; component B is a product of a prepolymerization reaction of isocyanate and polyester polyol; the mass ratio of component A to component B is 1:(0.3-0.6). The polyurethane stock solution provided by the present invention can be used to prepare an engine hood, which can endow the engine hood with a relatively high tear strength. After hydrothermal aging, the tear strength retention rate is relatively high, the hardness change is small, and it is not easy to powder, so that the engine hood has excellent comprehensive performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyurethane materials, and particularly relates to a polyurethane stock solution, a preparation method thereof, and an application thereof. Background Art

[0002] Polyurethane (PU) is a widely used polymer material. Due to its excellent physical and mechanical properties and chemical stability, it is widely used in the automotive industry. The engine hood can fill the internal voids of the engine, reduce the vibration of air and internal components, and not only achieve sound insulation and heat insulation effects, but also dampen and protect the overall engine. Traditional polyurethanes are prone to water absorption and powdering in humid environments, resulting in a decline in the performance of the material. Especially in high-temperature and humid environments, this problem is more obvious. Therefore, it is of great significance to develop a polyurethane engine hood with excellent heat and humidity resistance.

[0003] In the prior art, methods such as adding water absorption stabilizers, using special polyethers and special isocyanates are usually adopted to improve the heat and humidity resistance of polyurethanes; although this can improve the heat and humidity resistance of polyurethanes to a certain extent, it will lead to a decline in the mechanical properties of polyurethanes, and the cost of polyurethanes increases significantly. Therefore, it is of great significance to develop a polyurethane stock solution that can improve the heat and humidity resistance of polyurethanes without significantly affecting their mechanical properties, and has a simple production process and low cost. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a polyurethane stock solution, a preparation method thereof, and an application thereof. Through the design of each component of the polyurethane stock solution, it can be used to prepare an engine hood, and can solve the technical problems of poor physical properties of traditional polyurethane engine hoods and easy powdering under heat and humidity conditions.

[0005] To achieve this purpose, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides a polyurethane stock solution, which includes component A and component B; component A includes a combination of propylene oxide-tetrahydrofuran copolymer polyether, castor oil polyol, chain extender, catalyst, water absorption stabilizer, silane coupling agent, and foaming agent; component B is the product of the pre-polymerization reaction of isocyanate and polyester polyol; the mass ratio of component A to component B is 1:(0.3 - 0.6).

[0007] The polyurethane stock solution provided by the present invention can be used to prepare an engine hood. Through the design of component A and component B and the synergistic compounding between the components, the engine hood can have a high tear strength, and after heat and humidity aging, the tear strength retention rate is high, the hardness change is small, and it is not easy to powder, so that the engine hood has excellent comprehensive performance.

[0008] In the present invention, the propylene oxide-tetrahydrofuran copolymer ether is a random copolymer, which can improve the tear strength and the resistance to damp heat aging of the polyurethane; the castor oil polyol can endow the polyurethane with excellent thermal stability, water resistance and scratch resistance. In the present invention, the tear strength of the engine hood is improved by the propylene oxide-tetrahydrofuran copolymer ether and the castor oil polyol, and the retention rate of the tear strength of the engine hood is improved by the combined use of components such as the propylene oxide-tetrahydrofuran copolymer ether, the water absorption stabilizer and the silane coupling agent.

[0009] The mass ratio of the component A to the component B is 1:(0.3-0.6), and for example, it can be 1:0.32, 1:0.34, 1:0.36, 1:0.38, 1:0.4, 1:0.42, 1:0.44, 1:0.46, 1:0.48, 1:0.5, 1:0.52, 1:0.54, 1:0.56, 1:0.58, etc.

[0010] The following are the preferred technical solutions of the present invention, but are not limitations to the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0011] As a preferred technical solution, the preparation method of the propylene oxide-tetrahydrofuran copolymer ether includes:

[0012] Using a first diol as the initiator, a Lewis acid as the catalyst, and carrying out a cationic living polymerization reaction on tetrahydrofuran and propylene oxide to obtain the propylene oxide-tetrahydrofuran copolymer ether.

[0013] Preferably, the first diol includes any one or a combination of at least two of ethylene glycol, propylene glycol, diethylene glycol or butanediol.

[0014] Preferably, the Lewis acid includes any one or a combination of at least two of boron trifluoride ether complex, aluminum chloride-cyclohexanol complex, niobium pentachloride complex or trifluoromethanesulfonate of lanthanide elements.

[0015] Preferably, the molar ratio of the tetrahydrofuran to the propylene oxide is (1-4):1, and for example, it can be 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, etc.

[0016] Preferably, the mass ratio of the propylene oxide to the first diol is (3-10):1, and for example, it can be 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1, etc.

[0017] Preferably, based on the mass of the propylene oxide being 100%, the mass of the Lewis acid is 0.1-0.3%, and can be, for example, 0.12%, 0.14%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.26%, 0.28%, etc.

[0018] Preferably, the temperature of the cationic living polymerization reaction is -5 to 10 °C, and can be, for example, -4.5 °C, -4 °C, -3.5 °C, -3 °C, -2.5 °C, -2 °C, -1.5 °C, -1 °C, -0.5 °C, 0 °C, 0.5 °C, 1 °C, 1.5 °C, 2 °C, 2.5 °C, 3 °C, 4 °C, 5 °C, 6 °C, 7 °C, 8 °C, 9 °C, etc.

[0019] Preferably, the time of the cationic living polymerization reaction is 6-10 h, and can be, for example, 6.2 h, 6.5 h, 6.8 h, 7 h, 7.2 h, 7.5 h, 7.8 h, 8 h, 8.2 h, 8.5 h, 8.8 h, 9 h, 9.2 h, 9.5 h, 9.8 h, etc.

[0020] Preferably, the hydroxyl value of the propylene oxide-tetrahydrofuran copolymer ether is 30-120 mgKOH / g, and can be, for example, 35 mgKOH / g, 40 mgKOH / g, 45 mgKOH / g, 50 mgKOH / g, 55 mgKOH / g, 60 mgKOH / g, 65 mgKOH / g, 70 mgKOH / g, 75 mgKOH / g, 80 mgKOH / g, 85 mgKOH / g, 90 mgKOH / g, 95 mgKOH / g, 100 mgKOH / g, 105 mgKOH / g, 110 mgKOH / g, 115 mgKOH / g, etc.

[0021] Preferably, the viscosity of the propylene oxide-tetrahydrofuran copolymer ether is 500-1000 mPa·s, and can be, for example, 550 mPa·s, 600 mPa·s, 650 mPa·s, 700 mPa·s, 750 mPa·s, 800 mPa·s, 850 mPa·s, 900 mPa·s, 950 mPa·s, 1000 mPa·s, etc.

[0022] Preferably, the hydroxyl value of the castor oil polyol is 180 - 300 mgKOH / g, and for example, it can be 185 mgKOH / g, 190 mgKOH / g, 195 mgKOH / g, 200 mgKOH / g, 205 mgKOH / g, 210 mgKOH / g, 220 mgKOH / g, 230 mgKOH / g, 240 mgKOH / g, 250 mgKOH / g, 260 mgKOH / g, 270 mgKOH / g, 280 mgKOH / g, 290 mgKOH / g, etc.

[0023] Preferably, the functionality of the castor oil polyol is 2 - 3, and for example, it can be 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, etc.

[0024] Preferably, the castor oil polyol includes any one or a combination of at least two of URIC AC - 005 (ITO OIL & FAT CO., LTD.), URIC H - 368 (ITO OIL & FAT CO., LTD.), Sovermol 819 (BASF), or THCM - 625 (Preliminary Chemical Industry).

[0025] Preferably, the chain extender includes any one or a combination of at least two of 3,5 - diethyltoluenediamine, N - methyldiethanolamine, isophoronediamine, butanediol, or dipropylene glycol.

[0026] Preferably, the catalyst includes any one or a combination of at least two of N - (dimethylaminopropyl)diisopropanolamine, tetramethyldipropylenetriamine, or trimethylhydroxyethylpropylenediamine.

[0027] Preferably, the water absorption stabilizer includes any one or a combination of at least two of carbodiimide monomer, polycarbodiimide, or glycerol triglycidyl ether.

[0028] In the present invention, the water absorption stabilizer is exemplarily purchased from but not limited to Langyi New Materials HyMax 1010, Youen Chemical Industry UN - 150, or Rhein Chemie StabaxolP.

[0029] Preferably, the blowing agent includes water.

[0030] Preferably, the silane coupling agent includes any one or a combination of at least two of γ - aminopropyltriethoxysilane, γ - glycidoxypropyltrimethoxysilane, or vinyltrimethoxysilane.

[0031] Preferably, the component A includes the following components in parts by weight:

[0032] Propylene oxide - tetrahydrofuran copolymer ether 30 - 70 parts by weight.

[0033] 10 - 50 parts by weight of castor oil polyol.

[0034] 0.5 - 20 parts by weight of chain extender.

[0035] 0.1 - 2 parts by weight of catalyst.

[0036] 0.5 - 2 parts by weight of water absorption stabilizer.

[0037] 0.1 - 2 parts by weight of silane coupling agent.

[0038] 0.1 - 5 parts by weight of foaming agent.

[0039] In the component A, the propylene oxide - tetrahydrofuran copolymer ether is 30 - 70 parts by weight, and can be, for example, 32 parts by weight, 35 parts by weight, 38 parts by weight, 40 parts by weight, 42 parts by weight, 45 parts by weight, 48 parts by weight, 50 parts by weight, 52 parts by weight, 55 parts by weight, 58 parts by weight, 60 parts by weight, 62 parts by weight, 65 parts by weight, 68 parts by weight, etc.

[0040] The castor oil polyol is 10 - 50 parts by weight, and can be, for example, 12 parts by weight, 15 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, 25 parts by weight, 28 parts by weight, 30 parts by weight, 32 parts by weight, 35 parts by weight, 38 parts by weight, 40 parts by weight, 42 parts by weight, 45 parts by weight, 48 parts by weight, etc.

[0041] The chain extender is 0.5 - 20 parts by weight, and can be, for example, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 6 parts by weight, 8 parts by weight, 10 parts by weight, 12 parts by weight, 14 parts by weight, 16 parts by weight, 18 parts by weight, etc.

[0042] The catalyst is 0.1 - 2 parts by weight, and can be, for example, 0.2 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 0.8 parts by weight, 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, etc.

[0043] The water absorption stabilizer is 0.5 - 2 parts by weight, and can be, for example, 0.6 parts by weight, 0.8 parts by weight, 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, etc.

[0044] The silane coupling agent is 0.1 - 2 parts by weight, and can be, for example, 0.2 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 0.8 parts by weight, 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, etc.

[0045] The blowing agent is 0.1 - 5 parts by weight, for example, it can be 0.2 parts by weight, 0.4 parts by weight, 0.6 parts by weight, 0.8 parts by weight, 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 2.5 parts by weight, 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight, etc.

[0046] Preferably, the component A further includes a plasticizer and / or a foam stabilizer.

[0047] Preferably, the plasticizer includes any one or a combination of at least two of dioctyl adipate, dibutyl sebacate, diisononyl phthalate, dimethyl adipate, or diisopropyl adipate.

[0048] Preferably, the mass ratio of the plasticizer to the castor oil polyol is (0.05 - 2):1, for example, it can be 0.1:1, 0.2:1, 0.4:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.4:1, 1.5:1, 1.6:1, 1.8:1, etc.

[0049] Preferably, the foam stabilizer includes any one or a combination of at least two of Niax L-1507 (Momentive Performance Materials), TEGOSTAB® B 8946PF (Evonik Degussa), TEGOSTAB® B 8168 (Evonik Degussa), or US-5262 (Ausga Materials Technology).

[0050] Preferably, the mass ratio of the foam stabilizer to the water absorption stabilizer is (0.15 - 5):1, for example, it can be 0.2:1, 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, etc.

[0051] Preferably, the isocyanate includes any one or a combination of at least two of hexamethylene diisocyanate, isophorone diisocyanate, 4,4-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, or naphthalene diisocyanate.

[0052] Preferably, the polyester polyol is obtained by polycondensation of a dibasic acid and a second diol.

[0053] Preferably, the dibasic acid includes any one or a combination of at least two of succinic acid, adipic acid, azelaic acid, or sebacic acid.

[0054] Preferably, the second diol includes small molecule diols containing at least two side alkyl groups, such as any one or a combination of at least two of 2-butyl-2-ethyl-1,3-propanediol, trimethylpentanediol, or neopentyl glycol.

[0055] Preferably, the number average molecular weight of the polyester polyol is 1800 - 2000, and for example, it can be 1820, 1840, 1860, 1880, 1900, 1920, 1940, 1960, 1980, etc.

[0056] Preferably, the hydroxyl value of the polyester polyol is 56 - 62 mgKOH / g, and for example, it can be 56.5 mgKOH / g, 57 mgKOH / g, 57.5 mgKOH / g, 58 mgKOH / g, 58.5 mgKOH / g, 59 mgKOH / g, 59.5 mgKOH / g, 60 mgKOH / g, 60.5 mgKOH / g, 61 mgKOH / g, 61.5 mgKOH / g, etc.

[0057] Preferably, the mass ratio of the isocyanate to the polyester polyol is 1:(0.1 - 0.8), and for example, it can be 1:0.12, 1:0.14, 1:0.16, 1:0.18, 1:0.2, 1:0.22, 1:0.24, 1:0.26, 1:0.28, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, etc.

[0058] Preferably, the temperature of the prepolymerization reaction is 70 - 80 °C, and for example, it can be 70.5 °C, 71 °C, 71.5 °C, 72 °C, 72.5 °C, 73 °C, 73.5 °C, 74 °C, 74.5 °C, 75 °C, 75.5 °C, 76 °C, 76.5 °C, 77 °C, 77.5 °C, 78 °C, 78.5 °C, 79 °C, 79.5 °C, etc.

[0059] Preferably, the time of the prepolymerization reaction is 2 - 3 h, and for example, it can be 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h, etc.

[0060] Preferably, the prepolymerization reaction is carried out in the presence of a side reaction inhibitor.

[0061] Preferably, the side reaction inhibitor includes any one or a combination of at least two of phosphoric acid, adipoyl chloride, or benzoyl chloride.

[0062] Preferably, based on the total mass of the isocyanate, polyester polyol and side reaction inhibitor being 100%, the mass of the side reaction inhibitor is 0.001 - 0.02%, for example, it can be 0.002%, 0.003%, 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.01%, 0.012%, 0.014%, 0.016%, 0.018%, etc.

[0063] In a second aspect, the present invention provides a method for preparing the polyurethane stock solution as described in the first aspect, and the preparation method includes the following steps:

[0064] Propylene oxide - tetrahydrofuran copolymer polyether, castor oil polyol, chain extender, catalyst, water absorption stabilizer, silane coupling agent and foaming agent are mixed to obtain component A; polyester polyol and isocyanate are subjected to a prepolymerization reaction to obtain component B.

[0065] Preferably, the temperature of the mixing is 50 - 80 °C, for example, it can be 52 °C, 55 °C, 58 °C, 60 °C, 62 °C, 65 °C, 68 °C, 70 °C, 72 °C, 75 °C, 78 °C, etc.

[0066] Preferably, the time of the mixing is 0.5 - 3 h, for example, it can be 0.6 h, 0.8 h, 1 h, 1.2 h, 1.4 h, 1.6 h, 1.8 h, 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, etc.

[0067] Preferably, the mixed materials further include a foam stabilizer and / or a plasticizer.

[0068] Preferably, the prepolymerization reaction is carried out in the presence of a side reaction inhibitor.

[0069] In a third aspect, the present invention provides an engine hood, and the engine hood is prepared by using the polyurethane stock solution as described in the first aspect.

[0070] In a fourth aspect, the present invention provides a method for preparing the engine hood as described in the third aspect, and the preparation method includes:

[0071] After the A component and B component of the polyurethane stock solution as described in the first aspect react in a mold, demolding and curing are carried out in sequence to obtain the engine hood.

[0072] Preferably, the reaction time is 4 - 20 min, for example, it can be 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, etc.

[0073] Preferably, the reaction temperature is 40 - 60 °C, for example, it can be 42 °C, 44 °C, 46 °C, 48 °C, 50 °C, 52 °C, 54 °C, 56 °C, 58 °C, etc.

[0074] Preferably, the curing temperature is 25 - 50 °C, for example, it can be 26 °C, 28 °C, 30 °C, 32 °C, 34 °C, 36 °C, 38 °C, 40 °C, 42 °C, 44 °C, 46 °C, 48 °C, etc.

[0075] Preferably, the curing time is 12 - 24 h, for example, it can be 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, etc.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] The polyurethane stock solution provided by the present invention can be used to prepare an engine hood, which can endow the engine hood with a relatively high tear strength. The tear strength before hygrothermal aging is 502 - 530 N / m, and after hygrothermal aging, the tear strength is 403 - 432 N / m. The tear strength retention rate is relatively high, being 80.1 - 83.1%, the hardness change is small, being 7 - 9 C, and at the same time, it is not easily powdered and deformed, having good hygrothermal resistance. Detailed Embodiments

[0078] For ease of understanding the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0079] The sources of some components in the examples and comparative examples are as follows:

[0080] (1) Propylene oxide - tetrahydrofuran copolymer ether a was prepared by the following method:

[0081] 600 g of tetrahydrofuran, 400 g of propylene oxide, 50 g of ethylene glycol, and 0.5 g of aluminum chloride - cyclohexanol complex were added to a reaction vessel purged with nitrogen. The reaction was carried out at 0 °C for 6 h. After terminating the reaction, the unreacted monomer small molecules and water were removed by vacuum pumping. The product was dissolved with toluene, and the aluminum chloride - cyclohexanol complex was removed by filtration. After the filtrate was subjected to vacuum distillation, the propylene oxide - tetrahydrofuran copolymer ether a was obtained;

[0082] The hydroxyl value measured according to GB / T 12008.3-2009 is 35 mg KOH / g, and the viscosity measured according to GB / T 12008.8-1992 is 600 mPa·s (40 °C).

[0083] (2) Propylene oxide-tetrahydrofuran copolymer ether b is prepared by the following method:

[0084] Add 1000 g of tetrahydrofuran, 500 g of propylene oxide, 75 g of diethylene glycol, and 0.8 g of boron trifluoride ether complex into a reaction vessel purged with nitrogen. React at 10 °C for 6 h. After terminating the reaction, evacuate to remove unreacted monomer small molecules and water. Dissolve the product with toluene, filter to remove the boron trifluoride ether complex, and after vacuum distillation of the filtrate, obtain the propylene oxide-tetrahydrofuran copolymer ether b;

[0085] The hydroxyl value measured according to GB / T 12008.3-2009 is 56 mg KOH / g, and the viscosity measured according to GB / T 12008.8-1992 is 800 mPa·s (40 °C).

[0086] (3) Propylene oxide-tetrahydrofuran copolymer ether c is prepared by the following method:

[0087] Add 1200 g of tetrahydrofuran, 500 g of propylene oxide, 145 g of propylene glycol, and 0.5 g of niobium pentachloride complex into a reaction vessel purged with nitrogen. React at 5 °C for 6 h. After terminating the reaction, evacuate to remove unreacted monomer small molecules and water. Dissolve the product with toluene, filter to remove the niobium pentachloride complex, and after vacuum distillation of the filtrate, obtain the propylene oxide-tetrahydrofuran copolymer ether c;

[0088] The hydroxyl value measured according to GB / T 12008.3-2009 is 100 mg KOH / g, and the viscosity measured according to GB / T 12008.8-1992 is 500 mPa·s (40 °C).

[0089] (4) Propylene oxide-tetrahydrofuran copolymer ether d is prepared by the following method:

[0090] Add 670 g of tetrahydrofuran, 330 g of propylene oxide, 50 g of ethylene glycol, and 0.5 g of boron trifluoride ether complex into a reaction vessel purged with nitrogen. React at -5 °C for 6 h. After terminating the reaction, evacuate to remove unreacted monomer small molecules and water. Dissolve the product with toluene, filter to remove the boron trifluoride ether complex, and after vacuum distillation of the filtrate, obtain the propylene oxide-tetrahydrofuran copolymer ether d;

[0091] The hydroxyl value measured according to GB / T 12008.3-2009 is 75 mg KOH / g, and the viscosity measured according to GB / T 12008.8-1992 is 600 mPa·s (40 °C).

[0092] (5)Propylene oxide-tetrahydrofuran copolymer ether e is prepared by the following method:

[0093] Add 780 g of tetrahydrofuran, 220 g of propylene oxide, 50 g of ethylene glycol, and 0.5 g of boron trifluoride diethyl ether complex into a reaction vessel purged with nitrogen, react at 0 °C for 6 h, evacuate to remove unreacted monomer small molecules and water after terminating the reaction, dissolve the product with toluene, filter to remove the boron trifluoride diethyl ether complex, and obtain the propylene oxide-tetrahydrofuran copolymer ether e after vacuum distillation of the filtrate;

[0094] The hydroxyl value measured according to GB / T 12008.3-2009 is 45 mg KOH / g, and the viscosity measured according to GB / T 12008.8-1992 is 900 mPa·s (40 °C).

[0095] (6)Polytetrahydrofuran ether is prepared by the following method:

[0096] Add 1000 g of tetrahydrofuran, 50 g of ethylene glycol, and 0.5 g of aluminum chloride-cyclohexanol complex into a reaction vessel purged with nitrogen, react at 0 °C for 6 h, evacuate to remove unreacted monomer small molecules and water after terminating the reaction, dissolve the product with toluene, filter to remove the aluminum chloride-cyclohexanol complex, and obtain the polytetrahydrofuran ether after vacuum distillation of the filtrate;

[0097] The hydroxyl value tested according to GB / T 12008.3-2009 is 35 mg KOH / g, and the viscosity tested according to GB / T 12008.8-1992 is 1500 mPa·s (40 °C).

[0098] (7)Polypropylene oxide ether is prepared by the following method:

[0099] Add 1000 g of propylene oxide, 50 g of ethylene glycol, and 0.5 g of aluminum chloride-cyclohexanol complex into a reaction vessel purged with nitrogen, react at 0 °C for 6 h, evacuate to remove unreacted monomer small molecules and water after terminating the reaction, dissolve the product with toluene, filter to remove the aluminum chloride-cyclohexanol complex, and obtain the polypropylene oxide ether after vacuum distillation of the filtrate;

[0100] The hydroxyl value tested according to GB / T 12008.3-2009 is 35 mg KOH / g, and the viscosity tested according to GB / T 12008.8-1992 is 600 mPa·s (40 °C).

[0101] (8) Polyester polyol a, prepared by the following method:

[0102] Add 1500 g of adipic acid, 1100 g of trimethylpentanediol, and 500 g of neopentyl glycol into the reaction kettle in sequence, stir, start heating up, and at the same time introduce nitrogen gas from the upper part of the reaction kettle. When the temperature rises to 135 °C, keep it constant for 1 h and then continue heating up. When the temperature rises to about 180 °C, switch the nitrogen gas to be introduced from the lower part of the reaction liquid surface, and gradually increase the amount of nitrogen gas to strengthen dehydration; heat up to 225 °C and keep it constant. After keeping it constant for 1 h, add 0.5 g of tetrabutyl titanate and start vacuum pumping to -10 kPa, and carry out transesterification reaction for 4 h to obtain the polyester polyol a;

[0103] The hydroxyl value measured according to HG / T 2709-1995 is 56 mg KOH / g, and the number average molecular weight is 2000.

[0104] (9) Polyester polyol b, prepared by the following method:

[0105] Add 1500 g of adipic acid, 500 g of 2-butyl-2-ethyl-1,3-propanediol, and 1500 g of trimethylpentanediol into the reaction kettle in sequence, stir, start heating up, and at the same time introduce nitrogen gas from the upper part of the reaction kettle. When the temperature rises to 135 °C, keep it constant for 1 h and then continue heating up. When the temperature rises to about 180 °C, switch the nitrogen gas to be introduced from the lower part of the reaction liquid surface, and gradually increase the amount of nitrogen gas to strengthen dehydration; heat up to 225 °C and keep it constant. After keeping it constant for 1 h, add 0.5 g of tetrabutyl titanate and start vacuum pumping to -10 kPa, and carry out transesterification reaction for 4 h to obtain the polyester polyol b;

[0106] The hydroxyl value measured according to HG / T 2709-1995 is 62 mg KOH / g, and the number average molecular weight is 1800.

[0107] (10) Polyester polyol c, prepared by the following method:

[0108] Add 1500 g of adipic acid, 1100 g of neopentyl glycol, and 400 g of 2-butyl-2-ethyl-1,3-propanediol into the reaction kettle in sequence, stir, start heating up, and at the same time introduce nitrogen gas from the upper part of the reaction kettle. When the temperature rises to 140 °C, keep it constant for 1 h and then continue heating up. When the temperature rises to about 180 °C, switch the nitrogen gas to be introduced from the lower part of the reaction liquid surface, and gradually increase the amount of nitrogen gas to strengthen dehydration; heat up to 225 °C and keep it constant. After keeping it constant for 1 h, add 0.5 g of tetrabutyl titanate and start vacuum pumping to -10 kPa, and carry out transesterification reaction for 4 h to obtain the polyester polyol c;

[0109] The hydroxyl value measured according to HG / T 2709-1995 is 56 mg KOH / g, and the number average molecular weight is 2000.

[0110] (11)Castor oil polyol: Purchased from Itochu Oil Co., Ltd., URIC AC-005, with a hydroxyl value of 210 mgKOH / g and a functionality of 2; Itochu Oil Co., Ltd., URIC H-368, with a hydroxyl value of 195 mgKOH / g and a functionality of 2.5; Chubu Chemical Industry Co., Ltd., THCM-625, with a hydroxyl value of 260 mgKOH / g and a functionality of 2; BASF, Sovermol 819, with a hydroxyl value of 240 mgKOH / g and a functionality of 2.6.

[0111] (12)Foam stabilizer: Purchased from Momentive Performance Materials Inc., Niax L-1507; Evonik Degussa GmbH, TEGOSTAB® B8168; Auspicious Materials Technology Co., Ltd., US-5262.

[0112] (13)Water absorption stabilizer: Purchased from Langyi New Materials Co., Ltd., HyMax 1010; Youen Chemical Industry Co., Ltd., UN-150; Rhein Chemie, StabaxolP.

[0113] Other reagents can be obtained if not specified otherwise.

[0114] Example 1

[0115] A polyurethane stock solution, the polyurethane stock solution comprising Component A and Component B; the mass ratio of Component A to Component B is 1:0.45;

[0116] The preparation method of the polyurethane stock solution is as follows:

[0117] 60 parts by weight of propylene oxide-tetrahydrofuran copolymer ether a, 30 parts by weight of castor oil polyol (URIC AC-005), 5 parts by weight of plasticizer dioctyl adipate, 7 parts by weight of chain extender N-methyldiethanolamine, 1 part by weight of catalyst N-(dimethylaminopropyl) diisopropanolamine, 0.4 part by weight of foam stabilizer (Niax L-1507), 1 part by weight of water absorption stabilizer (HyMax 1010), 0.6 part by weight of silane coupling agent KH550 and 0.9 part by weight of water are put into a reaction kettle, heated to 60 °C, mixed and stirred for 2 h, then cooled to 40 °C and discharged to obtain Component A, which is sealed and stored;

[0118] 100 parts by weight of 4,4-diphenylmethane diisocyanate, 10 parts by weight of carbodiimide-modified diphenylmethane diisocyanate, 25 parts by weight of polyester polyol a and phosphoric acid (the content thereof in Component B is 100 ppm) are placed in a reaction kettle, heated to 75 °C under nitrogen protection, and subjected to a prepolymerization reaction for 2.5 h, then cooled to 45 °C to obtain Component B, with a free -NCO content of 26.2%, which is sealed and stored;

[0119] After weighing Component A and Component B according to a mass ratio of 1:0.45, the polyurethane stock solution is obtained.

[0120] Example 2

[0121] A polyurethane stock solution, the polyurethane stock solution comprising component A and component B; the mass ratio of component A to component B is 1:0.45;

[0122] The preparation method of the polyurethane stock solution is as follows:

[0123] Put 50 parts by weight of propylene oxide-tetrahydrofuran copolymer ether b, 33 parts by weight of castor oil polyol (THCM-625), 5 parts by weight of plasticizer dibutyl sebacate, 8 parts by weight of chain extender isophorone diamine, 0.6 parts by weight of catalyst trimethylol ethyl propanediamine, 0.9 parts by weight of foam stabilizer (TEGOSTAB® B 8168), 1 part by weight of water absorption stabilizer (UN-150), 1.5 parts by weight of silane coupling agent A171 and 1 part by weight of water into a reaction kettle, heat up to 60 °C and mix and stir for 2 h, then cool to 40 °C and discharge to obtain component A, and store it sealed;

[0124] Put 50 parts by weight of hexamethylene diisocyanate, 50 parts by weight of carbodiimide-modified diphenylmethane diisocyanate, 43 parts by weight of polyester polyol b and benzoyl chloride (the content thereof in component B is 100 ppm) into a reaction kettle, heat up to 75 °C under nitrogen protection, carry out pre-polymerization reaction for 2.5 h, then cool to 45 °C to obtain component B, and the free -NCO content is 26.2%, and store it sealed;

[0125] Weigh the component A and component B according to the mass ratio of 1:0.45 to obtain the polyurethane stock solution.

[0126] Example 3

[0127] A polyurethane stock solution, the polyurethane stock solution comprising component A and component B; the mass ratio of component A to component B is 1:0.45;

[0128] The preparation method of the polyurethane stock solution is as follows:

[0129] Put 40 parts by weight of propylene oxide-tetrahydrofuran copolymer ether c, 43 parts by weight of castor oil polyol (Sovermol 819), 7 parts by weight of plasticizer diisopropyl adipate, 1 part by weight of chain extender butanediol, 1.2 parts by weight of catalyst tetramethyl dipropylene triamine, 0.8 parts by weight of foam stabilizer (Niax L-1507), 1 part by weight of water absorption stabilizer (UN-150), 1 part by weight of silane coupling agent KH560 and 1 part by weight of water into a reaction kettle, heat up to 60 °C and mix and stir for 2 h, then cool to 40 °C and discharge to obtain component A, and store it sealed;

[0130] Put 20 parts by weight of isophorone diisocyanate, 40 parts by weight of 4,4-diphenylmethane diisocyanate, 25 parts by weight of polyester polyol c, and phosphoric acid (the content in component B is 100 ppm) into a reaction kettle, heat up to 75 °C under nitrogen protection, carry out prepolymerization reaction for 2.5 h, then cool down to 45 °C to obtain component B with a free -NCO content of 26.2%, and store it sealed;

[0131] After weighing the component A and component B according to a mass ratio of 1:0.45, the polyurethane stock solution is obtained.

[0132] Example 4

[0133] A polyurethane stock solution, the polyurethane stock solution includes component A and component B; the mass ratio of component A to component B is 1:0.45;

[0134] The preparation method of the polyurethane stock solution is as follows:

[0135] Put 52 parts by weight of propylene oxide - tetrahydrofuran copolymer ether d, 35 parts by weight of castor oil polyol (URIC H - 368), 3 parts by weight of plasticizer diisopropyl adipate, 6 parts by weight of chain extender isophorone diamine, 0.7 parts by weight of catalyst tetramethyldipropylenetriamine, 0.4 parts by weight of foam stabilizer (US - 5262), 1.5 parts by weight of water absorption stabilizer (StabaxolP), 1.4 parts by weight of silane coupling agent A171, and 0.9 parts by weight of water into a reaction kettle, heat up to 60 °C and mix and stir for 2 h, then cool to 40 °C and discharge to obtain component A, and store it sealed;

[0136] Put 30 parts by weight of hexamethylene diisocyanate, 30 parts by weight of 4,4-diphenylmethane diisocyanate, 30 parts by weight of polyester polyol a, and phosphoric acid (the content in component B is 100 ppm) into a reaction kettle, heat up to 75 °C under nitrogen protection, carry out prepolymerization reaction for 2.5 h, then cool down to 45 °C to obtain component B with a free -NCO content of 26.3%, and store it sealed;

[0137] After weighing the component A and component B according to a mass ratio of 1:0.45, the polyurethane stock solution is obtained.

[0138] Example 5

[0139] A polyurethane stock solution, the polyurethane stock solution includes component A and component B; the mass ratio of component A to component B is 1:0.45;

[0140] The preparation method of the polyurethane stock solution is as follows:

[0141] Put 60 parts by weight of propylene oxide - tetrahydrofuran copolymer ether e, 21 parts by weight of castor oil polyol (Sovermol 819), 10 parts by weight of plasticizer diisononyl phthalate, 5 parts by weight of chain extender dipropylene glycol, 1.5 parts by weight of catalyst trimethylhydroxyethylpropylenediamine, 0.3 parts by weight of foam stabilizer (TEGOSTAB® B 8168), 1.5 parts by weight of water absorption stabilizer (UN - 150), 0.7 parts by weight of silane coupling agent KH560 and 1.1 parts by weight of water into a reaction kettle, heat up to 60 °C, mix and stir for 2 h, then cool to 40 °C and discharge to obtain the component A, and store it sealed;

[0142] Put 45 parts by weight of 4,4 - diphenylmethane diisocyanate, 5 parts by weight of isophorone diisocyanate, 15 parts by weight of polyester polyol b and benzoyl chloride (its content in component B is 100 ppm) into a reaction kettle, heat up to 75 °C under nitrogen protection for pre - polymerization reaction for 2.5 h, then cool to 45 °C to obtain the component B, and the free - NCO content is 26.2%, and store it sealed;

[0143] Weigh the component A and component B according to the mass ratio of 1:0.45 to obtain the polyurethane stock solution.

[0144] Example 6

[0145] A polyurethane stock solution and its preparation method, the difference from Example 1 is only that the mass ratio of component A to component B of the polyurethane stock solution is 1:0.4, and the preparation raw materials, process parameters and steps of component A and component B are the same as those in Example 1.

[0146] Example 7

[0147] A polyurethane stock solution and its preparation method, the difference from Example 1 is only that the mass ratio of component A to component B of the polyurethane stock solution is 1:0.5, and the preparation raw materials, process parameters and steps of component A and component B are the same as those in Example 1.

[0148] Comparative Example 1

[0149] A polyurethane stock solution and its preparation method, the polyurethane stock solution includes component A and component B, and the mass ratio of component A to component B is 1:0.45; it adopts the same preparation method as Example 1, the difference is only that propylene oxide - tetrahydrofuran copolymer ether a is not added to component A.

[0150] Comparative Example 2

[0151] A polyurethane stock solution and its preparation method. The polyurethane stock solution includes component A and component B, and the mass ratio of component A to component B is 1:0.45. It uses the same preparation method as Example 1, with the only difference being that castor oil polyol (URIC AC-005) is not added to component A.

[0152] Comparative Example 3

[0153] A polyurethane stock solution and its preparation method. The polyurethane stock solution includes component A and component B, and the mass ratio of component A to component B is 1:0.45. It uses the same preparation method as Example 1, with the only difference being that water absorption stabilizer (HyMax 1010) is not added to component A.

[0154] Comparative Example 4

[0155] A polyurethane stock solution and its preparation method. The polyurethane stock solution includes component A and component B, and the mass ratio of component A to component B is 1:0.45. It uses the same preparation method as Example 1, with the only difference being that silane coupling agent KH550 is not added to component A.

[0156] Comparative Example 5

[0157] A polyurethane stock solution and its preparation method. The polyurethane stock solution includes component A and component B, and the mass ratio of component A to component B is 1:0.45. It uses the same preparation method as Example 1, with the only difference being that propylene oxide-tetrahydrofuran copolymer ether a in component A is replaced with the same mass of polytetrahydrofuran ether.

[0158] Comparative Example 6

[0159] A polyurethane stock solution and its preparation method. The polyurethane stock solution includes component A and component B, and the mass ratio of component A to component B is 1:0.45. It uses the same preparation method as Example 1, with the only difference being that propylene oxide-tetrahydrofuran copolymer ether a in component A is replaced with the same mass of polypropylene oxide ether.

[0160] Comparative Example 7

[0161] A polyurethane stock solution and its preparation method. The difference from Example 1 is only that the mass ratio of component A to component B of the polyurethane stock solution is 1:0.25, and the preparation raw materials, process parameters and steps of component A and component B are the same as those in Example 1.

[0162] Comparative Example 8

[0163] A polyurethane stock solution and its preparation method, the difference from Example 1 is only that the mass ratio of component A to component B of the polyurethane stock solution is 1:0.65, and the raw materials, process parameters and steps for preparing component A and component B are the same as those in Example 1.

[0164] Application Example 1

[0165] An engine hood and its preparation method, the preparation method includes:

[0166] Keep the temperatures of the A and B tanks of the low-pressure foaming machine at 25°C, fully mix component A and component B of the polyurethane stock solution provided in Example 1 through the low-pressure foaming machine, inject into the engine hood mold at 45°C for reaction for 4 minutes to form, demold, and cure at 25°C for 12 hours to obtain the engine hood.

[0167] Application Examples 2-7, Comparative Application Examples 1-8

[0168] An engine hood and its preparation method, the difference from Application Example 1 is only that the polyurethane stock solution provided in Example 1 is sequentially and equally replaced with the polyurethane stock solutions provided in Examples 2-7 and Comparative Examples 1-8, and the other process parameters and steps are the same as those in Application Example 1.

[0169] Comparative Application Example 9

[0170] An engine hood, the engine hood is a commercially available polyurethane engine hood, purchased from Chejia Products Co., Ltd.

[0171] Performance Test

[0172] Damp heat aging test: According to GB / T9640-2008 "Accelerated Aging Test Method for Flexible and Rigid Cellular Plastics", the damp heat aging test conditions are 120°C and 100% relative humidity. After 16 hours of water vapor aging, take it out and place it under standard conditions for 24 hours, and then test the engine hood according to the following method.

[0173] (1) Tear strength: According to GB / T 10808-2006 "Determination of Tear Strength of Cellular Rubbers and Thermoplastic Elastomers", conduct a tear strength test on the engine hood, calculate the tear strength retention rate before and after damp heat aging, and the tear strength retention rate = tear strength after damp heat aging / tear strength before damp heat aging × 100%.

[0174] (2) Indentation hardness change: According to GB / T 531.1-2008 "Rubber, vulcanized or thermoplastic - Determination of indentation hardness - Part 1: Durometer method (Shore hardness)", conduct a hardness test on the engine hood, and calculate the indentation hardness change before and after damp heat aging. The indentation hardness change is the absolute value of the difference between the hardness before damp heat aging and the hardness after damp heat aging.

[0175] (3)Product pulverization judgment criteria: After the damp heat aging test, there is no adhesion on the surface of the sample, no cracking when folded in half, and no chipping inside the product after cutting. If so, it is judged that there is no pulverization phenomenon; otherwise, pulverization occurs.

[0176] The engine hoods provided in the application example and the comparative application example were tested according to the above method, and the results are shown in Table 1:

[0177] Table 1

[0178]

[0179] Note: In Table 1, "-" represents that the result was not measured.

[0180] From the data in Table 1, it can be seen that for the engine hood prepared with the polyurethane stock solution provided by the present invention, the tear strength before damp heat aging is 502 - 530 N / m, the retention rate of tear strength after damp heat aging is above 80%, the change in indentation hardness is 7 - 9 C, and it has the characteristics that the physical properties are not easy to decline during long-term use and it is not easy to pulverize.

[0181] From the comparison between Comparative Application Examples 1 - 4 and Application Example 1, it can be seen that the comprehensive performance of Comparative Application Examples 1 - 4 is inferior to that of Application Example 1. Without adding propylene oxide - tetrahydrofuran copolymer ether (Comparative Application Example 1), the tear strength before damp heat aging and the retention rate of tear strength decrease, the change in indentation hardness is large, and it is easy to pulverize after damp heat aging; without adding castor oil polyol (Comparative Application Example 2), the tear strength before damp heat aging decreases, and the change in indentation hardness is large; without adding water absorption stabilizer (Comparative Application Example 3), the retention rate of tear strength decreases, the change in indentation hardness is large, and it is easy to pulverize after damp heat aging; without adding silane coupling agent (Comparative Application Example 4), the retention rate of tear strength decreases, the change in indentation hardness is large, and it is easy to pulverize after damp heat aging. It can be seen from this that the present invention improves the tear strength of the engine hood by adding propylene oxide - tetrahydrofuran copolymer ether and castor oil polyol, and improves the retention rate of tear strength of the engine hood by the combined use of components such as propylene oxide - tetrahydrofuran copolymer ether, water absorption stabilizer, and silane coupling agent.

[0182] From Comparative Application Example 5, it can be seen that polytetrahydrofuran ether has high viscosity and strong crystallinity, and its compatibility becomes poor and it is easy to stratify and precipitate when blended with other raw materials, resulting in local defects in the engine hood, serious overall shrinkage, poor skin, serious product deformation, and inability to perform performance testing.

[0183] It can be seen from the comparison between Comparative Application Example 6 and Application Example 1 that if polypropylene glycol ether is used instead of propylene oxide-tetrahydrofuran copolymer ether, the tear strength and tear strength retention rate of the engine hood before hygrothermal aging are lower. This is because the chain segment regularity of polypropylene glycol ether is not as good as that of polytetrahydrofuran, which is not conducive to the formation of a microphase separation structure between the hard and soft segments of polyurethane, resulting in poor crystallinity. This makes the engine hood more easily penetrated by water vapor in a high-temperature and humid environment, causing hydrolysis of the engine hood and a decrease in the tear strength retention rate, and a large change in the indentation hardness after hygrothermal aging.

[0184] If the mass ratio of Component A to Component B of the polyurethane stock solution is greater than 1:0.3 (Comparative Application Example 7) or less than 1:0.6 (Comparative Application Example 8), the polyurethane stock solution cannot cure and the product cannot be formed. It can be seen from this that the present invention controls the mass ratio of Component A to Component B of the polyurethane stock solution within a specific range, enabling the polyurethane stock solution to have good curing and formability.

[0185] It can be seen from the comparison between Comparative Application Example 9 and Application Examples 1-7 that the engine hood prepared using the polyurethane stock solution provided by the present invention has a high tear strength before hygrothermal aging, a high tear strength retention rate after hygrothermal aging, is not easily pulverized after hygrothermal aging, has a small change in indentation hardness, and has better comprehensive performance.

[0186] In summary, the present invention effectively improves the tear strength and the tear strength retention rate after hygrothermal aging of the engine hood, and the engine hood is not easily pulverized after hygrothermal aging by compounding propylene oxide-tetrahydrofuran copolymer ether, castor oil polyol, chain extender, catalyst, water absorption stabilizer, silane coupling agent, foaming agent, isocyanate, and polyester polyol.

[0187] The applicant declares that the present invention uses the above-mentioned examples to illustrate the polyurethane stock solution, its preparation method and application of the present invention, but the present invention is not limited to the above-mentioned examples, that is, it does not mean that the present invention must rely on the above-mentioned examples to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A polyurethane stock solution, characterized in that: The polyurethane stock solution comprises component A and component B; The component A comprises a combination of propylene oxide-tetrahydrofuran copolyether, castor oil polyol, chain extender, catalyst, water absorption stabilizer, silane coupling agent and foaming agent; The B component is a product of a prepolymerization reaction of isocyanate and polyester polyol; The isocyanate includes any one or a combination of at least two of hexamethylene diisocyanate, isophorone diisocyanate, 4,4-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate or naphthalene diisocyanate; The A component includes the following components in parts by weight: Propylene oxide-tetrahydrofuran copolyether 30-70 parts by weight Castor oil polyol 10-50 parts by weight Chain extender 0.5-20 parts by weight Catalyst 0.1-2 parts by weight Water absorption stabilizer 0.5-2 parts by weight Silane coupling agent 0.1-2 parts by weight 0.1-5 parts by weight of foaming agent; The mass ratio of the isocyanate to the polyester polyol is 1:(0.1-0.8); The preparation method of the propylene oxide-tetrahydrofuran copolyether comprises: Using the first diol as an initiator and Lewis acid as a catalyst, tetrahydrofuran and propylene oxide undergo a cationic living polymerization reaction to obtain the propylene oxide-tetrahydrofuran copolyether; The molar ratio of tetrahydrofuran to propylene oxide is (1-4):1; The mass ratio of component A to component B is 1:(0.3-0.6).

2. The polyurethane stock solution according to claim 1, characterized in that: The first diol includes any one of ethylene glycol, propylene glycol, diethylene glycol or butanediol, or a combination of at least two thereof; The Lewis acid includes any one or a combination of at least two of a boron trifluoride ether complex, an aluminum chloride-cyclohexanol complex, a niobium pentachloride complex or a trifluoromethanesulfonate of a lanthanide element; The mass ratio of propylene oxide to the first diol is (3-10):1; Based on the mass of the propylene oxide being 100%, the mass of the Lewis acid is 0.1-0.3%; The temperature of the cationic active polymerization reaction is -5 to 10°C; The time of the cationic living polymerization reaction is 6-10 hours.

3. The polyurethane stock solution according to claim 1, characterized in that: The hydroxyl value of the castor oil polyol is 180-300 mgKOH / g; The functionality of the castor oil polyol is 2-3; The chain extender includes any one of 3,5-diethyltoluenediamine, N-methyldiethanolamine, isophoronediamine, butanediol or dipropylene glycol, or a combination of at least two thereof; The catalyst comprises any one of N-(dimethylaminopropyl)diisopropanolamine, tetramethyldipropylenetriamine or trimethylhydroxyethylpropylenediamine or a combination of at least two thereof; The water absorption stabilizer includes any one of carbodiimide monomer, polycarbodiimide or glycerol triglycidyl ether or a combination of at least two thereof; The silane coupling agent includes any one of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane or vinyltrimethoxysilane or a combination of at least two thereof; The blowing agent includes water.

4. The polyurethane stock solution according to claim 1, characterized in that: The A component also includes a plasticizer and / or a foam stabilizer; The mass ratio of the plasticizer to castor oil polyol is (0.05-2):1; The mass ratio of the foam leveling agent to the water absorbing stabilizer is (0.15-5):

1.

5. The polyurethane stock solution according to claim 1, characterized in that: The number average molecular weight of the polyester polyol is 1800-2000; The hydroxyl value of the polyester polyol is 56-62 mgKOH / g; The temperature of the prepolymerization reaction is 70-80°C; The prepolymerization reaction time is 2-3h; The prepolymerization reaction is carried out in the presence of a side reaction inhibitor; Based on the total mass of the isocyanate, the polyester polyol and the side reaction inhibitor being 100%, the mass of the side reaction inhibitor is 0.001-0.02%.

6. A method for preparing the polyurethane stock solution according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: Propylene oxide-tetrahydrofuran copolyether, castor oil polyol, chain extender, catalyst, water absorption stabilizer, silane coupling agent and foaming agent are mixed to obtain component A; The polyester polyol and the isocyanate are prepolymerized to obtain the B component.

7. The preparation method according to claim 6, characterized in that: The mixing temperature is 50-80°C; The mixing time is 0.5-3h; The mixed material also includes a foam leveler and / or a plasticizer; The prepolymerization reaction is carried out in the presence of a side reaction inhibitor.

8. An engine hood, characterized in that: The engine hood is prepared using the polyurethane stock solution as described in any one of claims 1 to 5.

9. A method for preparing an engine hood as claimed in claim 8, characterized in that: The preparation method comprises: After component A and component B of the polyurethane stock solution according to any one of claims 1 to 5 react in a mold at 40-60° C. for 4-20 min, demolding and aging are performed in sequence to obtain the engine hood; the aging temperature is 25-50° C.; and the aging time is 12-24 h.

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