Polyurethane stock solution as well as preparation method and application thereof

Abstract

The invention relates to a polyurethane stock solution as well as a preparation method and application thereof. The polyurethane stock solution comprises a component A and a component B, the component A comprises epoxypropane-tetrahydrofuran copolyether, castor oil polyol, a chain extender, a catalyst, a water absorption stabilizer, a silane coupling agent and a foaming agent; the component B is a product of a prepolymerization reaction of isocyanate and polyester polyol; the mass ratio of the component A to the component B is 1: (0.3-0.6). The polyurethane stock solution provided by the invention can be used for preparing the engine hood, so that the engine hood has relatively high tear strength, and after damp-heat aging, the tear strength retention rate is relatively high, the hardness change is relatively small, and meanwhile, pulverization is not easy, so that the engine hood has excellent comprehensive performance.

Description

Technical Field

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

[0002] Polyurethane (PU) is a widely used polymer material. It is widely used in the automotive industry due to its excellent physical and mechanical properties and chemical stability. The engine hood can fill the internal gaps of the engine and reduce the vibration of the air and internal components. It can not only achieve sound insulation and heat insulation effects, but also reduce vibration and protect the engine as a whole. Traditional polyurethane easily absorbs water and powders in a humid environment, resulting in a decrease in the performance of the material. This problem is especially obvious in a hot and humid environment. Therefore, it is of great significance to develop a polyurethane engine hood with excellent moisture and heat resistance.

[0003] In the prior art, the moisture and heat resistance of polyurethane is usually improved by adding water-absorbing stabilizers, using special polyethers and special isocyanates, etc. Although this can improve the moisture and heat resistance of polyurethane to a certain extent, it will lead to a decrease in the mechanical properties of polyurethane and a significant increase in the cost of polyurethane. Therefore, it is of great significance to develop a polyurethane stock solution that can improve the moisture and heat resistance of polyurethane without significantly affecting its mechanical properties, and has a simple production process and low cost. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a polyurethane stock solution and a preparation method and application thereof. Through the design of the various components of the polyurethane stock solution, it can be used to prepare engine hoods, which can solve the technical problems of traditional polyurethane engine hoods having poor physical properties and easy powdering under hot and humid conditions.

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

[0006] In a first aspect, the present invention provides a polyurethane stock solution, comprising component A and component B; component A comprises a combination of propylene oxide-tetramethylene oxide copolyether, castor oil polyol, a chain extender, a catalyst, a water absorption stabilizer, a silane coupling agent and a foaming agent; component B is a product of a prepolymerization reaction of isocyanate and polyester polyol; and 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 higher tear strength, and after wet heat 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, propylene oxide-tetrahydrofuran copolyether is a random copolymer, which can improve the tear strength and wet heat aging resistance of polyurethane; castor oil polyol can make polyurethane have excellent thermal stability, water resistance and scratch resistance. The present invention improves the tear strength of the engine hood through propylene oxide-tetrahydrofuran copolyether and castor oil polyol, and improves the tear strength retention rate of the engine hood through the coordinated use of components such as propylene oxide-tetrahydrofuran copolyether, water absorption stabilizer, silane coupling agent, etc.

[0009] The mass ratio of component A to component B is 1:(0.3-0.6), 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 preferred technical solutions of the present invention, but are not intended to limit 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 copolyether comprises:

[0012] With the first diol as an initiator and Lewis acid as a catalyst, tetrahydrofuran and propylene oxide undergo a cationic active polymerization reaction to obtain the propylene oxide-tetrahydrofuran copolyether.

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

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

[0015] Preferably, the molar ratio of tetrahydrofuran to propylene oxide is (1-4):1, 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, 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 100% of the mass of the propylene oxide, the mass of the Lewis acid is 0.1-0.3%, 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 active polymerization reaction is -5~10°C, 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 cationic living polymerization reaction time is 6-10 h, for example, it can be 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 copolyether is 30-120 mgKOH / g, for example, it can be 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 copolyether is 500-1000 mPa·s, for example, it may be 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, 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, for example, 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 of URIC AC-005 (Ito Oil Co., Ltd.), URIC H-368 (Ito Oil Co., Ltd.), Sovermol 819 (BASF) or THCM-625 (Zhongji Chemical Co., Ltd.) or a combination of at least two thereof.

[0025] Preferably, 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.

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

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

[0028] In the present invention, the water absorption stabilizer is illustratively purchased from, but not limited to, HyMax 1010 from Langyi New Materials, UN-150 from Youen Chemicals, or Stabaxol P from Rhein Chemie.

[0029] Preferably, the blowing agent comprises water.

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

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

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

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

[0034] Chain extender 0.5-20 parts by weight.

[0035] Catalyst 0.1-2 parts by weight.

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

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

[0038] Foaming agent 0.1-5 parts by weight.

[0039] The amount of propylene oxide-tetrahydrofuran copolyether in component A is 30-70 parts by weight, 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, 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, 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, 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, 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, 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 foaming 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 comprises a plasticizer and / or a foam stabilizer.

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

[0048] Preferably, the mass ratio of the plasticizer to 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 leveling agent includes any one of Niax L-1507 (Momentive High-Tech Materials Group), TEGOSTAB® B 8946PF (Evonik Specialty Chemicals), TEGOSTAB® B 8168 (Evonik Specialty Chemicals) or US-5262 (Osga Material Technology) or a combination of at least two thereof.

[0050] Preferably, the mass ratio of the foam leveling agent 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 of hexamethylene diisocyanate, isophorone diisocyanate, 4,4-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate or naphthalene diisocyanate, or a combination of at least two thereof.

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

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

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

[0055] Preferably, the number average molecular weight of the polyester polyol is 1800-2000, for example, it may 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, 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), 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, 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 prepolymerization reaction time is 2-3 h, 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 comprises any one of phosphoric acid, adipoyl chloride or benzoyl chloride, or a combination of at least two thereof.

[0062] Preferably, based on the total mass of the isocyanate, polyester polyol and side reaction inhibitor as 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, the preparation method comprising the following steps:

[0064] 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; polyester polyol and isocyanate are prepolymerized to obtain component B.

[0065] Preferably, the mixing temperature 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 mixing time 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 material further comprises 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, wherein the engine hood is prepared 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 according to the third aspect, the method comprising:

[0071] After the A component and the B component of the polyurethane stock solution described in the first aspect react in a mold, demoulding and aging are performed 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, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, etc.

[0074] Preferably, the aging 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 ripening 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, so that the engine hood has a higher tear strength. The tear strength before wet heat aging is 502-530 N / m, and after wet heat aging, the tear strength is 403-432 N / m, the tear strength retention rate is relatively high at 80.1-83.1%, the hardness change is relatively small at 7-9C, and it is not easy to powderize and deform, and has good wet heat resistance. DETAILED DESCRIPTION

[0078] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

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

[0080] (1) Propylene oxide-tetrahydrofuran copolyether a, 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 are added into a nitrogen-substituted reaction vessel, and reacted at 0° C. for 6 h. After terminating the reaction, unreacted monomer small molecules and water are removed by vacuuming, the product is dissolved in toluene, and the aluminum chloride-cyclohexanol complex is removed by filtration. The filtrate is subjected to reduced pressure distillation to obtain the propylene oxide-tetrahydrofuran copolyether a;

[0082] The hydroxyl value measured according to GB / T 12008.3-2009 is 35 mgKOH / g, and the viscosity measured according to GB / T12008.8-1992 is 600 mPa·s (40°C).

[0083] (2) Propylene oxide-tetrahydrofuran copolyether b, prepared by the following method:

[0084] 1000 g of tetrahydrofuran, 500 g of propylene oxide, 75 g of diethylene glycol and 0.8 g of boron trifluoride ether complex are added into a nitrogen-substituted reaction vessel, and the reaction is carried out at 10° C. for 6 h. After the reaction is terminated, unreacted monomer small molecules and water are removed by vacuuming, the product is dissolved in toluene, the boron trifluoride ether complex is removed by filtration, and the filtrate is subjected to reduced pressure distillation to obtain the propylene oxide-tetrahydrofuran copolyether b;

[0085] The hydroxyl value measured according to GB / T 12008.3-2009 is 56 mgKOH / g, and the viscosity measured according to GB / T12008.8-1992 is 800 mPa·s (40°C).

[0086] (3) Propylene oxide-tetrahydrofuran copolyether c, prepared by the following method:

[0087] 1200 g of tetrahydrofuran, 500 g of propylene oxide, 145 g of propylene glycol and 0.5 g of niobium pentachloride complex are added into a nitrogen-substituted reaction vessel, reacted at 5° C. for 6 h, and after terminating the reaction, unreacted monomer small molecules and water are removed by vacuuming, the product is dissolved in toluene, the niobium pentachloride complex is removed by filtration, and the filtrate is subjected to reduced pressure distillation to obtain the propylene oxide-tetrahydrofuran copolyether c;

[0088] The hydroxyl value measured according to GB / T 12008.3-2009 is 100 mgKOH / g, and the viscosity measured according to GB / T12008.8-1992 is 500 mPa·s (40°C).

[0089] (4) Propylene oxide-tetrahydrofuran copolyether d, prepared by the following method:

[0090] 670 g of tetrahydrofuran, 330 g of propylene oxide, 50 g of ethylene glycol and 0.5 g of boron trifluoride ether complex were added into a nitrogen-substituted reaction vessel, and the reaction was carried out at -5°C for 6 h. After the reaction was terminated, unreacted monomer small molecules and water were removed by vacuum, the product was dissolved in toluene, the boron trifluoride ether complex was removed by filtration, and the filtrate was subjected to reduced pressure distillation to obtain the propylene oxide-tetrahydrofuran copolyether d;

[0091] The hydroxyl value measured according to GB / T 12008.3-2009 is 75 mgKOH / g, and the viscosity measured according to GB / T12008.8-1992 is 600 mPa·s (40°C).

[0092] (5) Propylene oxide-tetrahydrofuran copolyether e, prepared by the following method:

[0093] 780 g of tetrahydrofuran, 220 g of propylene oxide, 50 g of ethylene glycol and 0.5 g of boron trifluoride ether complex were added into a nitrogen-substituted reaction vessel, and the reaction was carried out at 0° C. for 6 h. After the reaction was terminated, unreacted monomer small molecules and water were removed by vacuum pumping. The product was dissolved in toluene, and the boron trifluoride ether complex was removed by filtration. The filtrate was subjected to reduced pressure distillation to obtain the propylene oxide-tetrahydrofuran copolyether e;

[0094] The hydroxyl value measured according to GB / T 12008.3-2009 was 45 mgKOH / g, and the viscosity measured according to GB / T12008.8-1992 was 900 mPa·s (40°C).

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

[0096] 1000 g of tetrahydrofuran, 50 g of ethylene glycol and 0.5 g of aluminum chloride-cyclohexanol complex are added into a nitrogen-substituted reaction container, reacted at 0° C. for 6 h, and after terminating the reaction, unreacted monomer small molecules and water are removed by vacuum, the product is dissolved in toluene, the aluminum chloride-cyclohexanol complex is removed by filtration, and the filtrate is subjected to reduced pressure distillation to obtain the polytetrahydrofuran ether;

[0097] The hydroxyl value tested according to GB / T 12008.3-2009 is 35 mgKOH / g, and the viscosity tested according to GB / T12008.8-1992 is 1500 mPa·s (40°C).

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

[0099] 1000 g of propylene oxide, 50 g of ethylene glycol and 0.5 g of aluminum chloride-cyclohexanol complex are added into a nitrogen-substituted reaction vessel, and the reaction is carried out at 0° C. for 6 h. After the reaction is terminated, unreacted monomer small molecules and water are removed by vacuuming, the product is dissolved in toluene, the aluminum chloride-cyclohexanol complex is removed by filtration, and the filtrate is subjected to reduced pressure distillation to obtain the polypropylene oxide ether;

[0100] The hydroxyl value tested according to GB / T 12008.3-2009 is 35mgKOH / g, and the viscosity tested according to GB / T12008.8-1992 is 600mPa·s (40℃).

[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 to the reactor in sequence, stir, start heating, and introduce nitrogen into the upper part of the reactor at the same time. When the temperature reaches 135° C. and the temperature is kept constant for 1 hour, the temperature is continued to be raised. When the temperature reaches about 180° C., the nitrogen is switched to be introduced from the lower part of the reaction liquid surface, and the amount of nitrogen is gradually increased to enhance dehydration. The temperature is raised to 225° C. and the temperature is kept constant for 1 hour. After that, 0.5 g of tetrabutyl titanate is added and vacuum is started to be drawn to -10 kPa. The ester exchange reaction is carried out for 4 hours to obtain the polyester polyol a.

[0103] The hydroxyl value was measured according to HG / T 2709-1995 and was 56 mgKOH / g, and the number average molecular weight was 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 to the reactor in sequence, stir, start heating, and introduce nitrogen into the upper part of the reactor at the same time. When the temperature reaches 135° C. and the temperature is kept constant for 1 hour, the temperature is continued to be raised. When the temperature reaches about 180° C., the nitrogen is switched to be introduced from the lower part of the reaction liquid surface, and the amount of nitrogen is gradually increased to enhance dehydration; the temperature is raised to 225° C. and the temperature is kept constant for 1 hour, and 0.5 g of tetrabutyl titanate is added and vacuum is started to be drawn to -10 kPa, and the ester exchange reaction is carried out for 4 hours to obtain the polyester polyol b;

[0106] The hydroxyl value was measured according to HG / T 2709-1995 and was 62 mgKOH / g, and the number average molecular weight was 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 to the reactor in sequence, stir, start heating, and introduce nitrogen into the upper part of the reactor at the same time. When the temperature reaches 140° C. and the temperature is kept constant for 1 hour, the temperature is continued to be raised. When the temperature reaches about 180° C., the nitrogen is switched to be introduced from the lower part of the reaction liquid surface, and the amount of nitrogen is gradually increased to enhance dehydration; the temperature is raised to 225° C. and the temperature is kept constant for 1 hour, and 0.5 g of tetrabutyl titanate is added and vacuum is started to be drawn to -10 kPa, and the ester exchange reaction is carried out for 4 hours to obtain the polyester polyol c;

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

[0110] (11) Castor oil polyol: purchased from Ito Oil Corporation, URIC AC-005, with a hydroxyl value of 210 mgKOH / g and a functionality of 2; Ito Oil Corporation, URIC H-368, with a hydroxyl value of 195 mgKOH / g and a functionality of 2.5; Initial Chemical Industry, 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 leveling agent: Niax L-1507 purchased from Momentive High-Tech Materials Group, TEGOSTAB® B8168 purchased from Evonik Specialty Chemicals, and US-5262 purchased from Osgaard Materials Technology.

[0112] (13) Water-absorbing stabilizer: purchased from Langyi New Materials HyMax 1010, Youen Chemical UN-150, and Rhein Chemical Stabaxol P.

[0113] Other reagents, unless otherwise specified, are commercially available.

[0114] Example 1

[0115] A polyurethane stock solution, comprising a component A and a component B; the mass ratio of the component A to the 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 copolyether 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 parts by weight of foam leveling agent (Niax L-1507), 1 part by weight of water absorption stabilizer (HyMax 1010), 0.6 parts by weight of silane coupling agent KH550 and 0.9 parts by weight of water are put into a reaction kettle, the temperature is raised to 60° C., mixed and stirred for 2 hours, and then cooled to 40° C. before discharging to obtain the A component, 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 of which in component B is 100 ppm) are placed in a reaction kettle, heated to 75° C. under nitrogen protection, and prepolymerized for 2.5 hours, then cooled to 45° C. to obtain the component B, with a free -NCO content of 26.2%, and sealed for storage;

[0119] The component A and the component B are weighed in a mass ratio of 1:0.45 to obtain the polyurethane stock solution.

[0120] Example 2

[0121] A polyurethane stock solution, comprising a component A and a component B; the mass ratio of the component A to the 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 copolyether 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 trimethylhydroxyethylpropylene diamine, 0.9 parts by weight of foam leveling agent (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 to 60°C, mix and stir for 2h, cool to 40°C and then discharge to obtain the A component, which is sealed and stored;

[0124] 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 of which in component B is 100 ppm) are placed in a reaction kettle, heated to 75° C. under nitrogen protection, and prepolymerized for 2.5 hours, then cooled to 45° C. to obtain the component B, with a free -NCO content of 26.2%, and sealed for storage;

[0125] The component A and the component B are weighed in a mass ratio of 1:0.45 to obtain the polyurethane stock solution.

[0126] Example 3

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

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

[0129] 40 parts by weight of propylene oxide-tetrahydrofuran copolyether 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 leveling agent (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 are put into a reaction kettle, the temperature is raised to 60° C., mixed and stirred for 2 hours, and then cooled to 40° C. before discharging to obtain the A component, which is sealed and stored;

[0130] 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 of which in component B is 100 ppm) are placed in a reaction kettle, heated to 75° C. under nitrogen protection, and prepolymerized for 2.5 hours, then cooled to 45° C. to obtain the component B, with a free -NCO content of 26.2%, and sealed for storage;

[0131] The component A and the component B are weighed in a mass ratio of 1:0.45 to obtain the polyurethane stock solution.

[0132] Example 4

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

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

[0135] 52 parts by weight of propylene oxide-tetrahydrofuran copolyether 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 tetramethyl dipropylene triamine, 0.4 parts by weight of foam leveling agent (US-5262), 1.5 parts by weight of water absorption stabilizer (Stabaxol P), 1.4 parts by weight of silane coupling agent A171 and 0.9 parts by weight of water are added into a reaction kettle, the temperature is raised to 60° C., mixed and stirred for 2 hours, and then cooled to 40° C. before discharging to obtain the A component, which is sealed and stored;

[0136] 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 of which in component B is 100 ppm) are placed in a reaction kettle, heated to 75° C. under nitrogen protection, and prepolymerized for 2.5 hours, then cooled to 45° C. to obtain the component B, with a free -NCO content of 26.3%, and sealed for storage;

[0137] The component A and the component B are weighed in a mass ratio of 1:0.45 to obtain the polyurethane stock solution.

[0138] Example 5

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

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

[0141] 60 parts by weight of propylene oxide-tetrahydrofuran copolyether e, 21 parts by weight of castor oil polyol (Sovermol 819), 10 parts by weight of diisononyl phthalate plasticizer, 5 parts by weight of dipropylene glycol chain extender, 1.5 parts by weight of trimethylolhydroxyethylpropylenediamine catalyst, 0.3 parts by weight of foam leveling agent (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 are added into a reaction kettle, the temperature is raised to 60° C., mixed and stirred for 2 hours, and then cooled to 40° C. before discharging to obtain the A component, which is sealed and stored;

[0142] 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 (the content of which in component B is 100 ppm) are placed in a reaction kettle, heated to 75° C. under nitrogen protection, and prepolymerized for 2.5 hours, then cooled to 45° C. to obtain the component B, with a free -NCO content of 26.2%, and sealed for storage;

[0143] The component A and the component B are weighed in a mass ratio of 1:0.45 to obtain the polyurethane stock solution.

[0144] Example 6

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

[0146] Example 7

[0147] A polyurethane stock solution and a preparation method thereof, which differs from Example 1 only in 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 components A and B are the same as those in Example 1.

[0148] Comparative Example 1

[0149] A polyurethane stock solution and a preparation method thereof, wherein the polyurethane stock solution comprises a component A and a component B, wherein the mass ratio of the component A to the component B is 1:0.45; the polyurethane stock solution adopts the same preparation method as that of Example 1, except that no propylene oxide-tetrahydrofuran copolyether a is added to the component A.

[0150] Comparative Example 2

[0151] A polyurethane stock solution and a preparation method thereof, wherein the polyurethane stock solution comprises a component A and a component B, wherein the mass ratio of the component A to the component B is 1:0.45; the same preparation method is adopted as in Example 1, except that castor oil polyol (URIC AC-005) is not added to the component A.

[0152] Comparative Example 3

[0153] A polyurethane stock solution and a preparation method thereof, wherein the polyurethane stock solution comprises a component A and a component B, wherein the mass ratio of the component A to the component B is 1:0.45; the same preparation method is adopted as in Example 1, except that no water-absorbing stabilizer (HyMax 1010) is added to the component A.

[0154] Comparative Example 4

[0155] A polyurethane stock solution and a preparation method thereof, wherein the polyurethane stock solution comprises a component A and a component B, wherein the mass ratio of the component A to the component B is 1:0.45; the same preparation method is adopted as in Example 1, except that no silane coupling agent KH550 is added to the component A.

[0156] Comparative Example 5

[0157] A polyurethane stock solution and a preparation method thereof, wherein the polyurethane stock solution comprises a component A and a component B, wherein the mass ratio of the component A to the component B is 1:0.45; the same preparation method is adopted as in Example 1, except that the propylene oxide-tetrahydrofuran copolyether a in the component A is replaced by polytetrahydrofuran ether of the same mass.

[0158] Comparative Example 6

[0159] A polyurethane stock solution and a preparation method thereof, wherein the polyurethane stock solution comprises a component A and a component B, wherein the mass ratio of the component A to the component B is 1:0.45; the same preparation method is adopted as in Example 1, except that the propylene oxide-tetrahydrofuran copolyether a in the component A is replaced by polypropylene oxide ether of the same mass.

[0160] Comparative Example 7

[0161] A polyurethane stock solution and a preparation method thereof, which differs from Example 1 only in that the mass ratio of component A to component B of the polyurethane stock solution is 1:0.25, and the raw materials, process parameters and steps for preparing components A and B are the same as those in Example 1.

[0162] Comparative Example 8

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

[0164] Application Example 1

[0165] An engine hood and a preparation method thereof, the preparation method comprising:

[0166] The temperature of the A and B material tanks of the low-pressure foaming machine was maintained at 25°C, and the A component and the B component of the polyurethane stock solution provided in Example 1 were fully mixed by the low-pressure foaming machine, injected into a 45°C engine hood mold to react for 4 minutes to form, demolded, and aged 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 a preparation method thereof, which differs from Application Example 1 only in that the polyurethane stock solution provided in Example 1 is replaced in equal amounts by the polyurethane stock solutions provided in Examples 2-7 and Comparative Examples 1-8, and the remaining process parameters and steps are the same as those in Application Example 1.

[0169] Comparative Application Example 9

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

[0171] Performance Testing

[0172] Wet heat aging test: According to GB / T9640-2008 "Accelerated aging test method for soft and rigid foam polymer materials", the wet heat aging test conditions are 120℃ 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 polymer porous elastic materials”, the tear strength test of the engine hood was carried out, and the tear strength retention rate before and after wet heat aging was calculated. Tear strength retention rate = tear strength after wet heat aging / tear strength before wet heat aging × 100%.

[0174] (2) Change in indentation hardness: In accordance with GB / T 531.1-2008 "Test method for indentation hardness of vulcanized rubber or thermoplastic rubber Part 1: Shore hardness method (Shore hardness)", the hardness of the engine hood is tested and the change in indentation hardness before and after wet heat aging is calculated. The change in indentation hardness is the absolute value of the difference between the hardness before and after wet heat aging.

[0175] (3) Product powdering judgment standard: After the wet heat aging test, if there is no stickiness on the surface of the sample, no cracking when folded in half, and no debris falling off inside after cutting the product, it is judged that there is no powdering phenomenon. Otherwise, powdering has occurred.

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

[0177] Table 1

[0178]

[0179] Note: In Table 1, “-” means the result was not measured.

[0180] It can be seen from the data in Table 1 that the engine hood prepared using the polyurethane stock solution provided by the present invention has a tear strength of 502-530 N / m before wet heat aging, a tear strength retention rate of more than 80% after wet heat aging, and a depression hardness change of 7-9C. It has the characteristics of not being easily degraded in physical properties after long-term use and not being easily powdered.

[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 not as good as that of application example 1. Without adding propylene oxide-tetrahydrofuran copolyether (comparative application example 1), the tear strength and tear strength retention rate before wet heat aging decrease, the depression hardness changes greatly, and it is easy to pulverize after wet heat aging; without adding castor oil polyol (comparative application example 2), the tear strength before wet heat aging decreases, the depression hardness changes greatly; without adding water-absorbing stabilizer (comparative application example 3), the tear strength retention rate decreases, the depression hardness changes greatly, and it is easy to pulverize after wet heat aging; without adding silane coupling agent (comparative application example 4), the tear strength retention rate decreases, the depression hardness changes greatly, and it is easy to pulverize after wet heat aging. It can be seen that the present invention improves the tear strength of the engine hood by adding propylene oxide-tetrahydrofuran copolyether and castor oil polyol, and improves the tear strength retention rate of the engine hood by using propylene oxide-tetrahydrofuran copolyether, water-absorbing stabilizer, silane coupling agent and other components.

[0182] It can be seen from Comparative Application Example 5 that polytetrahydrofuran ether has high viscosity and strong crystallinity. When it is mixed with other raw materials, its compatibility deteriorates and it is easy to stratify and precipitate, resulting in local defects in the engine hood, severe overall shrinkage and poor surface, severe deformation of the product, and inability to carry out performance testing.

[0183] From the comparison between Comparative Application Example 6 and Application Example 1, it can be seen that if polypropylene oxide ether is used instead of propylene oxide-tetrahydrofuran copolyether, the tear strength and tear strength retention rate of the prepared engine hood before wet heat aging become lower. This is because the chain segment regularity of polypropylene oxide ether is not as good as that of polytetrahydrofuran, which is not conducive to the formation of a microphase separation structure between the soft and hard segments of the polyurethane, and has poor crystallinity, making the engine hood more easily penetrated by water vapor in a high temperature and humid environment, resulting in hydrolysis of the engine hood and a decrease in the tear strength retention rate, and a large change in the indentation hardness after wet heat 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 be matured and the product cannot be formed. It can be seen that the present invention controls the mass ratio of component A to component B of the polyurethane stock solution within a specific range, so that the polyurethane stock solution has better maturation and formability.

[0185] From the comparison between comparative application example 9 and application examples 1-7, it can be seen that the engine hood prepared using the polyurethane stock solution provided by the present invention has high tear strength before wet heat aging, high tear strength retention rate after wet heat aging, is not easy to powderize after wet heat aging, has little change in indentation hardness, and has better comprehensive performance.

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

[0187] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the polyurethane stock solution and its preparation method and application, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and 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 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 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 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 molar ratio of tetrahydrofuran to propylene oxide is (1-4):1; 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 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 Foaming agent 0.1-5 parts by weight.

5. 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.

6. The polyurethane stock solution according to claim 1, characterized in that: 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 number average molecular weight of the polyester polyol is 1800-2000; The hydroxyl value of the polyester polyol is 56-62 mgKOH / g; The mass ratio of the isocyanate to the polyester polyol is 1:(0.1-0.8); 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%.

7. A method for preparing the polyurethane stock solution according to any one of claims 1 to 6, 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.

8. The preparation method according to claim 7, 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.

9. 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 6.

10. A method for preparing an engine hood according to claim 9, 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 6 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.

Images