Polyurethane as well as preparation method and application thereof

Abstract

The invention relates to polyurethane as well as a preparation method and application thereof. The preparation method of the polyurethane comprises the following steps: mixing isocyanate and polyether, adding a composite catalyst for reaction, and adding an inhibitor after the reaction is finished to obtain the polyurethane. The preparation method is simple in process, high in production efficiency, economical and environment-friendly, the solid content of the prepared polyurethane is 100%, and the problems of insufficient solid content, low production efficiency, environmental pollution and the like in the existing polyurethane synthesis process are well solved.

Description

Technical Field

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

[0002] Polyurethane (PU) is a polymer material between rubber and plastic, combining the high strength of plastic and the excellent elasticity of rubber. With its high strength, hardness, flexibility, excellent oil resistance, low temperature resistance, wear resistance and radiation resistance, polyurethane has become one of the six most promising synthetic materials in the world.

[0003] At present, the main synthesis methods of polyurethane can be divided into two categories: one-step method and two-step method (prepolymer method). The one-step process is relatively simple and suitable for large-scale production, but it requires high precision control of reaction conditions, and the interaction between reactants may lead to uneven polymerization degree; the two-step method (prepolymer method) can control the molecular weight and cross-linking degree of polyurethane, and is suitable for polyurethane materials that require specific physical properties, but its production process is relatively complex and the operating conditions are also required to be strict.

[0004] The performance of polyurethane is affected by indicators such as solid content, viscosity and isocyanate (NCO) content. Among them, solid content refers to the ratio of the weight of the residue after polyurethane is dried at a certain temperature to the weight of the sample (expressed as a percentage), which is an important parameter affecting the performance and application of polyurethane materials. High solid content can improve the tensile strength, toughness and wear resistance of polyurethane, while enhancing the hardness, durability, chemical resistance, temperature resistance and aging resistance of the material, making it suitable for harsh environments. In addition, high solid content can shorten the drying time, improve processing performance, and reduce the use of organic solvents, thereby reducing production costs and expanding the scope of application, such as coatings, adhesives and sealants. Therefore, researchers continue to optimize the solid content of polyurethane products to improve economic benefits and environmental protection effects while achieving specific performance requirements.

[0005] CN114752035B discloses a high solid content aqueous polyurethane dispersion and a preparation method thereof, the method comprising three steps: first preparing a polyurethane prepolymer, then reacting a chain extender, and finally reacting with a neutralizer and a sulfonate chain extender and dispersing in water. After the reaction is completed, the product is dried to obtain an aqueous polyurethane dispersion with a solid content of 65%, a particle size of less than 250nm, and long-term stable storage.

[0006] CN110713808A discloses a high-solid content polyurethane-modified EVA composite emulsion, which aims to solve the problems of low solid content, slow drying speed and insufficient bonding strength of commercially available water-based polyurethane-modified EVA adhesives. The EVA composite emulsion prepared by the invention has a solid content of 60% after drying, has a faster drying speed and higher bonding strength, can replace solvent-based adhesives, reduce environmental pollution, and has more environmentally friendly characteristics.

[0007] CN106750084A discloses a high-solid content two-component adhesive layer polyurethane resin and a preparation method thereof. A polyol that is partially liquid at room temperature is used to obtain a polyurethane resin with a solid content of 90% after drying, which significantly reduces the amount of solvent used. The tensile strength is as high as 22MPa, showing excellent mechanical properties.

[0008] Although the above polyurethane synthesis process has made some progress in increasing the solid content, organic solvents, water and chain extenders are still left in the polyurethane, and the use of organic solvents will reduce the viscosity of the system and increase the environmental burden. In addition, the complex process flow and long production cycle have led to high production costs and low production efficiency, making it difficult to meet market demand.

[0009] Therefore, it is of great significance to provide a method for preparing high-solid content polyurethane with a simple process. Summary of the invention

[0010] In order to solve the above technical problems, the present invention provides a polyurethane and a preparation method and application thereof. The preparation method is simple in process, does not use solvents in the preparation process, is economical and environmentally friendly, and the solid content of the polyurethane product prepared is 100%, which well solves the problems of insufficient solid content, low production efficiency and environmental pollution in the existing polyurethane synthesis process.

[0011] To achieve this object, the present invention adopts the following technical solutions:

[0012] In a first aspect, the present invention provides a method for preparing polyurethane, the preparation method comprising the following steps:

[0013] The isocyanate and the polyether are mixed, a composite catalyst is added to react, and an inhibitor is added after the reaction is completed to obtain the polyurethane.

[0014] The present invention is a one-step method for synthesizing polyurethane. By using a composite catalyst, the reaction of isocyanate and polyether can be regulated, thereby increasing the solid content of the obtained polyurethane, thereby facilitating the improvement of the mechanical properties and durability of the obtained polyurethane; at the same time, the high solid content can also make the polyurethane cure quickly, have strong adhesion, and have a smooth surface without cracks after drying. The addition of an inhibitor can further regulate the reaction, which is not only conducive to increasing the solid content of the obtained polyurethane, but also conducive to adjusting the NCO content and viscosity in the polyurethane, thereby meeting different market demands. In addition, the preparation process of the polyurethane provided by the present invention is simple, convenient for industrial large-scale production, reduces the requirements for production equipment and technology, and does not use organic solvents in the entire preparation process, thereby reducing environmental pollution.

[0015] Polyurethane with high solid content has excellent mechanical properties and durability. Since high solid content means that the proportion of effective ingredients in polyurethane is high, the cross-linking density between molecules increases, and the interaction between molecular chains is enhanced. When subjected to external forces, this tight molecular structure can better disperse stress and avoid local stress concentration leading to material damage, thereby improving the tensile strength, toughness and other mechanical properties of polyurethane. At the same time, the tight molecular structure also enhances the material's ability to resist external environmental factors, thereby improving durability; at the same time, high solid content can also make polyurethane cure quickly, have strong adhesion, and have a smooth and crack-free surface after drying. In a high solid content system, the reactant concentration is high, the distance between molecules is small, and the reaction rate is faster, so it can cure quickly. Its large number of active groups can form strong physical or chemical forces with the molecules on the surface of the bonded material, thereby achieving strong adhesion. In addition, due to sufficient reaction and few impurities in the system, the molecules are arranged more orderly during the drying process, and no pores or uneven shrinkage will be generated due to factors such as solvent volatilization, so the surface is smooth and crack-free after drying.

[0016] The addition of inhibitors can further regulate the reaction. After the inhibitor is added to the reaction system, it will react with the active intermediates or unreacted isocyanates in the reaction, changing the equilibrium state of the reaction, thereby inhibiting the further progress of the reaction. When the inhibitor combines with the isocyanate, the number of NCO groups participating in the reaction is reduced, thereby regulating the NCO content in the polyurethane. At the same time, the control of the inhibitor on the reaction process affects the growth and cross-linking degree of the polyurethane molecular chain, causing the length and distribution of the molecular chain to change, ultimately achieving the adjustment of viscosity, thereby meeting different market needs.

[0017] In the present invention, the NCO groups in the isocyanate react with the OH groups in the multiple polyether molecules to form a polyurethane chain. The reaction can be expressed as:

[0018] R-NCO+R′-OH→R-NH-CO-OR′.

[0019] Preferably, the composite catalyst includes a first catalyst and a second catalyst.

[0020] Preferably, the first catalyst comprises polyethyleneimine.

[0021] Preferably, the second catalyst comprises any one of an organic metal catalyst, an amine catalyst or a metal salt catalyst, or a combination of at least two of them.

[0022] Preferably, the organometallic catalyst comprises any one of organotin, organozinc, organolead or organobismuth, or a combination of at least two thereof.

[0023] Preferably, the organic tin comprises any one of dibutyltin dilaurate (DBTL), stannous octoate, dibutyltin (DBTDA) or dialkyltin dimaleate or a combination of at least two thereof.

[0024] Preferably, the organic zinc includes any one of zinc isooctanoate, organic zinc catalyst DY-5350 or organic zinc catalyst DY-5390, or a combination of at least two thereof.

[0025] Preferably, the organic lead comprises any one of lead naphthenate, lead isooctanoate, n-butyl lead ester or isopropyl lead ester, or a combination of at least two thereof.

[0026] Preferably, the organic bismuth comprises bismuth neodecanoate or NIAX MC-710.

[0027] Preferably, the amine catalyst includes any one of bis(dimethylaminoethyl)ether, N,N-dimethylcyclohexylamine, N,N,N',N'-tetramethylalkylenediamine, triethylamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, N,N'-dimethylpyridine or a combination of at least two of triazine trimerization.

[0028] Preferably, the metal salt catalyst comprises a metal organic salt and / or a metal inorganic salt.

[0029] Preferably, the metal organic salt includes any one of potassium octoate, sodium p-toluenesulfonate or potassium acetate, or a combination of at least two thereof.

[0030] Preferably, the metal inorganic salt includes any one of sodium chloride, sodium carbonate, potassium carbonate or sodium nitrate, or a combination of at least two thereof.

[0031] Preferably, the mass ratio of the composite catalyst to isocyanate is (0.00001-0.001):1, wherein (0.00001-0.001) can be, for example, 0.00001, 0.00003, 0.00005, 0.00007, 0.0001, 0.0003, 0.0005, 0.0008 or 0.001, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0032] Preferably, the molar ratio of the first catalyst to the second catalyst is (0.01-0.1):1, wherein (0.01-0.1) can be, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0033] The role of the catalyst is to accelerate the reaction between polyols and isocyanates and promote the formation of polyurethane polymers. The catalyst can increase the nucleophilicity of the polyols, promote their reaction with isocyanates, and affect the structure and properties of the polymer, such as density, cell structure and mechanical properties.

[0034] The composite catalyst in the present invention includes a first catalyst and a second catalyst, wherein the first catalyst can improve the nucleophilicity of the hydroxyl (OH) in the polyether, making it easier to react with the NCO group in the isocyanate, increase the number of reactive sites, and accelerate the reaction process; the second catalyst can form a specific intermediate transition state with the reactant, reduce the activation energy of the reaction, and make the reaction easier to carry out. The two synergistically act, can effectively regulate the reaction of isocyanate and polyether, promote the reaction to be more sufficient, improve the solid content and mechanical properties of the obtained polyurethane, and can also adjust the NCO content and viscosity of the polyurethane to meet different market demands. Further, when the molar ratio of the two is (0.01-0.1): 1, the catalytic effect is better, and the solid content of the obtained polyurethane reaches 100%, thereby improving the mechanical properties and durability of the polyurethane, and when the molar ratio of the two is lower than or higher than the specific molar ratio range (0.01-0.1): 1, the tensile strength of the obtained polyurethane is reduced.

[0035] Preferably, the isocyanate includes any one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), hexamethylene diisocyanate biuret, hexamethylene diisocyanate trimer or hexamethylene diisocyanate-toluene diisocyanate polymer, or a combination of at least two thereof.

[0036] In the present invention, toluene diisocyanate (TDI) can also be a TDI derivative formed by chemically modifying TDI and introducing different functional groups.

[0037] Preferably, the polyether includes any one of polyethylene glycol, polypropylene glycol, polytetrahydrofuran or polyethylene oxide, or a combination of at least two thereof.

[0038] In the present invention, polyethylene glycol, polypropylene glycol, polytetrahydrofuran and polyethylene oxide may all be corresponding derivatives (compounds formed by introducing different functional groups after chemical modification).

[0039] Preferably, the mass ratio of the isocyanate to the polyether is (2-19):1, (2-19) can be, for example, 2, 4, 6, 8, 10, 13, 15, 17 or 19, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0040] Preferably, the composite catalyst needs to be stirred and kept warm before being added.

[0041] Preferably, the temperature of the heat preservation and stirring is 80-130°C, for example, it can be 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, and specific values ​​between the above points. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific points included in the range.

[0042] Preferably, the time for heat preservation and stirring is 1-2h, for example, it can be 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h or 2h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0043] Preferably, the reaction temperature is 90-150°C, for example, it can be 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0044] Preferably, the reaction time is 0.5-3h, for example, it can be 0.5h, 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h or 3h, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0045] Preferably, the reaction is carried out under a protective gas atmosphere.

[0046] Preferably, the protective gas includes any one of nitrogen, argon or helium, or a combination of at least two of them.

[0047] Preferably, the inhibitor comprises any one or a combination of at least two of carbamate, dimethylacetamide, dimethylformamide, sodium bicarbonate, sodium nitrite, difluorophosphoric acid or dibutyl phosphate.

[0048] Preferably, the mass ratio of the inhibitor to the isocyanate is (0.00001-0.001):1, wherein (0.00001-0.001) can be, for example, 0.00001, 0.00003, 0.00005, 0.00007, 0.0001, 0.0003, 0.0005, 0.0008 or 0.001, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0049] Preferably, the first cooling treatment is required before the inhibitor is added.

[0050] Preferably, the temperature of the first cooling treatment is 40-85°C, for example, it can be 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or 85°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0051] Preferably, the stirring time after the inhibitor is added is 20-40 min, for example, it can be 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, 32 min, 35 min, 38 min or 40 min, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0052] Preferably, the polyurethane needs to be subjected to a second cooling treatment before being obtained.

[0053] Preferably, the temperature of the second cooling treatment is 35-55°C, for example, it can be 35°C, 37°C, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 53°C or 55°C, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0054] Preferably, the preparation method of the polyurethane specifically comprises the following steps:

[0055] (1) mixing isocyanate and polyether in a mass ratio of (2-19):1, and stirring at 80-130° C. for 1-2 hours;

[0056] (2) adding a composite catalyst and reacting at 90-150° C. for 0.5-3 h;

[0057] (3) After the reaction is completed, the temperature is lowered to 40-85° C., an inhibitor is added, and the mixture is stirred and mixed for 20-40 minutes, and then the temperature is lowered to 35-55° C. to obtain the polyurethane.

[0058] In a second aspect, the present invention provides a polyurethane, which is prepared by the preparation method described in the first aspect.

[0059] Preferably, the solid content of the polyurethane is 100%.

[0060] Preferably, the NCO content of the polyurethane is 16-21%, for example, it can be 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5% or 21%, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0061] Preferably, the viscosity of the polyurethane is 2000-16000 cP, for example, it may be 2000 cP, 2050 cP, 2100 cP, 2300 cP, 2500 cP, 3000 cP, 5000 cP, 10000 cP, 13000 cP or 16000 cP, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0062] In a third aspect, the present invention provides a use of the polyurethane as described in the second aspect in coatings, adhesives, and sealants.

[0063] In the field of coatings, since the solid content of the polyurethane of the present invention is 100%, the surface is smooth and crack-free after drying, and has strong bonding force, which can significantly improve the hardness, durability, chemical resistance, temperature resistance and aging resistance of the coating, and can be widely used in the coating of industrial equipment, building exterior walls, etc.; in the field of adhesives, the high solid content of the polyurethane of the present invention makes the drying speed fast, and at the same time has high tensile strength, can firmly bond a variety of materials, and is suitable for the bonding of metals, plastics, wood and other materials; in the field of sealants, the excellent flexibility and wear resistance of the polyurethane of the present invention enable it to effectively fill gaps and maintain a sealing effect for a long time, playing an important role in automobile manufacturing, electronic equipment packaging, etc.

[0064] Compared with the prior art, the present invention has at least the following beneficial effects:

[0065] (1) The polyurethane preparation method provided by the present invention can directly obtain a high-solid content polyurethane product with a solid content of 100% after drying, so that it has excellent performance in mechanical properties and durability.

[0066] (2) The polyurethane preparation process provided by the present invention is simple, has high production efficiency, and does not use organic solvents during the preparation process, which is economical and environmentally friendly.

[0067] (3) In the polyurethane preparation method provided by the present invention, by further optimizing the dosage of the composite catalyst and the inhibitor and the reaction conditions, polyurethane products with different NCO contents and viscosities can be obtained, thereby being able to well meet the market demand for polyurethane products with different properties, reducing the requirements for production equipment and technology, and facilitating industrial large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 It is a schematic flow diagram of the preparation method of the present invention;

[0069] Figure 2 It is a schematic diagram of the process of the two-step method (prepolymer method);

[0070] Figure 3 It is a reaction device diagram of the preparation method of the present invention;

[0071] Figure 4 is a potentiometric titration curve of the polyurethane obtained in Example 1;

[0072] Figure 5 This is a potentiometric titration curve of the polyurethane obtained in Comparative Example 1. DETAILED DESCRIPTION

[0073] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0074] The preparation method of the present invention is as follows Figure 1 The preparation is carried out according to the process schematic diagram shown in FIG. 1 , and the corresponding reaction device is as follows Figure 2 As shown; the schematic diagram of the two-step method (prepolymer method) in the prior art is as follows Figure 3 shown.

[0075] Unless otherwise specified, the raw materials and reagents used in the following examples and comparative examples are commercially available. Information on some of the raw materials is shown in Table 1.

[0076] Table 1

[0077] Specific selection / purchase manufacturer Isocyanate HDI, Wanhua Chemical Polyether PEG-600A, Zhide Chemical Polyethyleneimine PEI-1800, Gaide Chemical Organic bismuth NIAX MC-710, Gaide Chemical Organic zinc DY-5350, Deyin Chemical Organic tin Dibutyltin dilaurate, Deyin Chemical Inhibitors Dibutyl phosphate, MacLean Chain Extender 1,4-Butanediol, MacLean

[0078] Example 1

[0079] This embodiment provides a polyurethane, and the preparation method thereof comprises the following steps:

[0080] (1) Under nitrogen protection, 980 g of isocyanate was placed in a stirring kettle and stirred, then 120 g of polyether was added, and the temperature was raised. When the temperature reached 90° C., the timing was started, and the temperature was continued to rise to 120° C., and the mixture was kept stirred for 1.5 h;

[0081] (2) adding 0.35 g of composite catalyst (the molar ratio of polyethyleneimine to organic bismuth is 0.01:1), and continuing to raise the temperature to 130° C. and react for 2 h;

[0082] (3) After the reaction was completed, the temperature was lowered to 82° C., 0.25 g of an inhibitor was added, and the mixture was stirred for 30 min to mix evenly. The temperature was quickly lowered to 53° C. to obtain the polyurethane.

[0083] Wherein, the potentiometric titration curve when the polyurethane NCO content is measured is as follows: Figure 4 As shown, the abscissa is the amount of hydrochloric acid used during titration (principle: the product sample reacts with excess di-n-butylamine, and the remaining di-n-butylamine is titrated with a standard hydrochloric acid solution to determine the NCO content of the product).

[0084] Example 2

[0085] This embodiment provides a polyurethane, which is different from Example 1 in that the amount of polyether in step (1) is adjusted from 120 g to 53 g, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0086] Example 3

[0087] This embodiment provides a polyurethane, which is different from Example 1 in that the amount of polyether in step (1) is adjusted from 120 g to 350 g, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0088] Example 4

[0089] This embodiment provides a polyurethane, which differs from Embodiment 1 in that the temperature of the heat preservation and stirring in step (1) is adjusted from 120°C to 95°C, and the heat preservation and stirring time is adjusted from 1.5h to 1h. Other raw materials, amounts and preparation methods are the same as those in Embodiment 1.

[0090] Example 5

[0091] This embodiment provides a polyurethane, which differs from Embodiment 1 in that the reaction time in step (2) is adjusted from 130°C to 125°C, and the reaction time is adjusted from 2h to 1h. Other raw materials, amounts and preparation methods are the same as those in Embodiment 1.

[0092] Example 6

[0093] This embodiment provides a polyurethane, which is different from Embodiment 1 in that the amount of the composite catalyst in step (2) is adjusted from 0.35 g to 0.07 g, and other raw materials, amounts and preparation methods are the same as those in Embodiment 1.

[0094] Example 7

[0095] This embodiment provides a polyurethane, which is different from Example 1 in that the amount of the composite catalyst in step (2) is adjusted from 0.35 g to 0.15 g, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0096] Example 8

[0097] This embodiment provides a polyurethane, which differs from Embodiment 1 in that the organic bismuth in step (2) is replaced by an equimolar amount of organic zinc, and other raw materials, amounts and preparation methods are the same as those in Embodiment 1.

[0098] Example 9

[0099] This embodiment provides a polyurethane, which differs from Embodiment 1 in that the organic bismuth in step (2) is replaced by an equimolar amount of organic tin, and other raw materials, amounts and preparation methods are the same as those in Embodiment 1.

[0100] Example 10

[0101] This embodiment provides a polyurethane, which is different from Example 1 in that the amount of the inhibitor in step (3) is adjusted from 0.35 g to 1 g, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0102] Embodiment 11

[0103] This embodiment provides a polyurethane, which differs from Example 1 in that the composite catalyst in step (2) (the molar ratio of polyethyleneimine to organic bismuth is 0.01:1) is replaced by an equal mass of composite catalyst (the molar ratio of polyethyleneimine to organic bismuth is 0.1:1), and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0104] Example 12

[0105] This embodiment provides a polyurethane, which differs from Example 1 in that the composite catalyst in step (2) (the molar ratio of polyethyleneimine to organic bismuth is 0.01:1) is replaced by an equal mass of composite catalyst (the molar ratio of polyethyleneimine to organic bismuth is 0.005:1), and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0106] Embodiment 13

[0107] This embodiment provides a polyurethane, which differs from Example 1 in that the composite catalyst in step (2) (the molar ratio of polyethyleneimine to organic bismuth is 0.01:1) is replaced by an equal mass of composite catalyst (the molar ratio of polyethyleneimine to organic bismuth is 0.11:1), and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0108] Embodiment 14

[0109] This embodiment provides a polyurethane, and the preparation method thereof comprises the following steps:

[0110] (1) Under nitrogen protection, 980 g of isocyanate was placed in a stirring kettle and stirred, then 490 g of polyether was added, and the temperature was raised. When the temperature reached 80° C., the timing was started, and the temperature was continued to rise to 130° C., and the mixture was kept stirred for 1.0 h;

[0111] (2) adding 1 g of composite catalyst (the molar ratio of polyethyleneimine to triethylamine is 0.05:1), and continuing to raise the temperature to 150°C and react for 0.5 h;

[0112] (3) After the reaction is completed, the temperature is lowered to 60° C., 0.1 g of an inhibitor is added, and the mixture is stirred for 20 min to mix evenly. The temperature is rapidly lowered to 45° C. to obtain the polyurethane.

[0113] Embodiment 15

[0114] This embodiment provides a polyurethane, and the preparation method thereof comprises the following steps:

[0115] (1) Under nitrogen protection, 980 g of isocyanate was placed in a stirring kettle and stirred, then 65 g of polyether was added, and the temperature was raised. When the temperature reached 90° C., the timing was started, and the temperature was kept and stirred for 2 h;

[0116] (2) adding 0.01 g of composite catalyst (the molar ratio of polyethyleneimine to organic bismuth is 0.01:1) and reacting at 90 °C for 3 h;

[0117] (3) After the reaction is completed, the temperature is lowered to 40° C., 0.01 g of an inhibitor is added, and the mixture is stirred for 40 min to mix evenly. The temperature is rapidly lowered to 35° C. to obtain the polyurethane.

[0118] Comparative Example 1

[0119] This comparative example provides a polyurethane, which differs from Example 1 in that the composite catalyst in step (2) is replaced by an equal mass of organic bismuth, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0120] Wherein, the potentiometric titration curve when the polyurethane NCO content is measured is as follows: Figure 5 As shown, the abscissa is the amount of hydrochloric acid used during titration.

[0121] Comparative Example 2

[0122] This comparative example provides a polyurethane, which differs from Example 1 in that the composite catalyst in step (2) is replaced by an equal mass of polyethyleneimine, and other raw materials, amounts and preparation methods are the same as those in Example 1.

[0123] Comparative Example 3

[0124] This comparative example provides a polyurethane, which is prepared by a two-step method (prepolymer method), and the specific preparation method comprises the following steps:

[0125] (1) 980 g of isocyanate was placed in a stirring kettle and stirred, then 120 g of polyether was added, and the temperature was raised. When the temperature reached 90° C., the timing was started, and the temperature was continued to rise to 120° C., and the mixture was stirred for 1.5 hours at the temperature to form a polyurethane prepolymer;

[0126] (2) After the reaction is completed, a degassing treatment is performed; the mixture in the reaction kettle is degassed under vacuum conditions to remove the gas generated during the reaction;

[0127] (3) adding 150 g of chain extender to the polyurethane prepolymer after degassing in step (2);

[0128] (4) adding 0.25 g of organic bismuth, continuing to raise the temperature to 130° C., and reacting for 2 h to allow the chain extender to fully react with the prepolymer to obtain the polyurethane.

[0129] The polyurethanes obtained in Examples 1-15 and Comparative Examples 1-3 were subjected to performance tests, and the test methods / standards were as follows:

[0130] (1) NCO content: Potentiometric titration according to HG / T 2409-1992;

[0131] (2) Viscosity: tested using a rheometer;

[0132] (3) Solid content: Tested according to polyurethane waterproof coating G / T 19250-2013;

[0133] (4) Mechanical properties: According to GB / T 1040.3-2006 tensile properties test.

[0134] The test results are shown in Table 2.

[0135] Table 2

[0136] NCO content (%) Viscosity(cP) Solid content (%) Tensile strength(Mpa) Example 1 19.0 3924 100 56.1 Example 2 16.3 3194 100 55.5 Example 3 17.2 9462 100 56.6 Example 4 19.7 2484 100 55.1 Example 5 19.1 3829 100 55.9 Example 6 19.4 2947 100 55.3 Example 7 16.0 15622 100 56.9 Example 8 18.2 5831 100 56.3 Example 9 18.3 5529 100 56.2 Example 10 20.8 2053 100 55.1 Embodiment 11 20.5 2101 100 55.3 Example 12 16.5 15813 100 53.5 Embodiment 13 21.0 2011 100 53.6 Embodiment 14 16.8 4227 100 55.7 Embodiment 15 20.8 2089 100 54.2 Comparative Example 1 21.4 1247 96 37.8 Comparative Example 2 21.8 16154 92 31.2 Comparative Example 3 18.0 1024 90 22

[0137] The test results show that:

[0138] (1) It can be seen from Examples 1 to 15 that the preparation method of the polyurethane provided by the present invention is simple in process, and the prepared polyurethane has a solid content of 100%, an NCO content of 16-21%, a viscosity of 2000-16000 cP, and a tensile strength of 53.5-56.9 MPa.

[0139] (2) It can be seen from Example 1 and Examples 11-13 that the present invention can effectively adjust the NCO content and viscosity of polyurethane by regulating the molar ratio of the first catalyst to the second catalyst, thereby better meeting the different market demands of polyurethane; further, when the molar ratio of the two is lower than or higher than a specific molar ratio range (0.01-0.1):1, the tensile strength is reduced.

[0140] (3) By comparing Example 1 with Comparative Examples 1-2, it can be seen that the composite catalyst selected in the present invention has a better technical effect. By compounding and regulating the reaction of the first catalyst and the second catalyst, a polyurethane with a higher solid content, better mechanical properties, and an NCO content and viscosity that are more in line with the requirements of polyurethane can be obtained. When a certain type of catalyst is not used / lacking, the corresponding solid content of the polyurethane obtained is less than 100%, the mechanical properties are poor, and the NCO content and viscosity will change, which cannot better meet the actual market demand for polyurethane.

[0141] (4) By comparing Example 1 with Comparative Example 3, it can be seen that the preparation method of the polyurethane provided by the present invention is simpler, and the obtained polyurethane has a higher solid content and has better mechanical properties and viscosity.

[0142] In summary, the present invention synthesizes polyurethane through a one-step method, and the use of a composite catalyst and an inhibitor can effectively regulate the reaction, which is not only beneficial to increasing the solid content of the obtained polyurethane, but also beneficial to adjusting the NCO content and viscosity in the polyurethane, thereby meeting different market demands.

[0143] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing polyurethane, characterized in that: The preparation method comprises the following steps: The isocyanate and the polyether are mixed, a composite catalyst is added to react, and an inhibitor is added after the reaction is completed to obtain the polyurethane.

2. The method for preparing polyurethane according to claim 1, characterized in that: The composite catalyst comprises a first catalyst and a second catalyst; Preferably, the first catalyst comprises polyethyleneimine; Preferably, the second catalyst comprises any one or a combination of at least two of an organic metal catalyst, an amine catalyst or a metal salt catalyst; Preferably, the organometallic catalyst comprises any one or a combination of at least two of organotin, organozinc, organolead or organobismuth; Preferably, the mass ratio of the composite catalyst to isocyanate is (0.00001-0.001):1; Preferably, the molar ratio of the first catalyst to the second catalyst is (0.01-0.1):

1.

3. The method for preparing polyurethane according to claim 1 or 2, characterized in that: The isocyanate includes any one of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate biuret, hexamethylene diisocyanate trimer or hexamethylene diisocyanate-toluene diisocyanate polymer, or a combination of at least two thereof.

4. The method for preparing the polyurethane according to any one of claims 1 to 3, characterized in that: The polyether includes any one of polyethylene glycol, polypropylene glycol, polytetrahydrofuran or polyethylene oxide, or a combination of at least two of them.

5. The method for preparing the polyurethane according to any one of claims 1 to 4, characterized in that: The mass ratio of the isocyanate to the polyether is (2-19):

1.

6. The method for preparing the polyurethane according to any one of claims 1 to 5, characterized in that: The composite catalyst needs to be stirred and kept warm before being added; Preferably, the temperature of the heat preservation and stirring is 80-130°C; Preferably, the time of heat preservation and stirring is 1-2h; Preferably, the reaction temperature is 90-150°C; Preferably, the reaction time is 0.5-3h.

7. The method for preparing polyurethane according to any one of claims 1 to 6, characterized in that: The inhibitor comprises any one or a combination of at least two of carbamate, dimethylacetamide, dimethylformamide, sodium bicarbonate, sodium nitrite, difluorophosphoric acid or dibutyl phosphate; Preferably, the mass ratio of the inhibitor to the isocyanate is (0.00001-0.001):1; Preferably, the first cooling treatment is required before the inhibitor is added; Preferably, the temperature of the first cooling treatment is 40-85°C; Preferably, the stirring time after the inhibitor is added is 20-40 min; Preferably, the polyurethane is subjected to a second cooling treatment before being obtained; Preferably, the temperature of the second cooling treatment is 35-55°C.

8. The method for preparing polyurethane according to any one of claims 1 to 7, characterized in that: The preparation method specifically comprises the following steps: (1) mixing isocyanate and polyether in a mass ratio of (2-19):1, and stirring at 80-130° C. for 1-2 hours; (2) adding a composite catalyst and reacting at 90-150° C. for 0.5-3 h; (3) After the reaction is completed, the temperature is lowered to 40-85° C., an inhibitor is added, and the mixture is stirred and mixed for 20-40 minutes, and then the temperature is lowered to 35-55° C. to obtain the polyurethane.

9. A polyurethane, characterized in that The polyurethane is prepared by the preparation method according to any one of claims 1 to 8; Preferably, the solid content of the polyurethane is 100%; Preferably, the NCO content of the polyurethane is 16-21%; Preferably, the viscosity of the polyurethane is 2000-16000 cP.

10. Use of the polyurethane as described in claim 9 in coatings, adhesives and sealants.

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