A polyurethane and a method for its preparation and use

Abstract

The application relates to a polyurethane and a preparation method and application thereof. The preparation method of the polyurethane comprises the following steps: mixing isocyanate with polyether, adding a composite catalyst to react, adding an inhibitor after the reaction is completed, and obtaining the polyurethane. The preparation method is simple in process, high in production efficiency, economic and environment-friendly, the polyurethane prepared by the method has a solid content of 100%, and the problems of insufficient solid content, low production efficiency and environmental pollution in the existing polyurethane synthesis process are well solved.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a polyurethane, its preparation method, and its applications. Background Technology

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

[0003] Currently, the main synthesis methods for 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 precise control of reaction conditions, and the interaction between reactants may lead to uneven polymerization. The two-step method (prepolymer method) can control the molecular weight and crosslinking degree of polyurethane, and is suitable for polyurethane materials that require specific physical properties, but its production process is more complex and requires strict operating conditions.

[0004] The performance of polyurethane is affected by factors such as solid content, viscosity, and isocyanate (NCO) content. Solid content, expressed as a percentage, is the ratio of the weight of the residue after drying at a specific temperature to the weight of the sample, and is a crucial parameter influencing the performance and applications of polyurethane materials. High solid content can improve the tensile strength, toughness, and abrasion resistance of polyurethane, while also enhancing its hardness, durability, chemical resistance, temperature resistance, and aging resistance, making it suitable for harsh environments. Furthermore, high solid content can shorten drying time, improve processing performance, and reduce the use of organic solvents, thereby lowering production costs and expanding its application range, such as in coatings, adhesives, and sealants. Therefore, researchers are continuously optimizing the solid content of polyurethane products to achieve specific performance requirements while improving economic efficiency and environmental benefits.

[0005] CN114752035B discloses a high-solids-content aqueous polyurethane dispersion and its preparation method. The method includes three steps: first, preparing a polyurethane prepolymer; then, reacting it with a chain extender; and finally, reacting it with a neutralizing agent and a sulfonate chain extender before dispersing it in water. After the reaction, the product is dried to obtain an aqueous polyurethane dispersion with a solids content of 65%, a particle size of less than 250 nm, and the ability to be stored stably for a long period.

[0006] CN110713808A discloses a high-solids-content polyurethane-modified EVA composite emulsion, aiming to solve the problems of low solids content, slow drying speed, and insufficient adhesion of commercially available water-based polyurethane-modified EVA adhesives. The EVA composite emulsion prepared by this invention has a solids content of up to 60% after drying, exhibits a faster drying speed and higher adhesion, and can replace solvent-based adhesives, reducing environmental pollution and demonstrating more environmentally friendly characteristics.

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

[0008] Although the aforementioned polyurethane synthesis processes have made some progress in increasing solids content, residual organic solvents, water, and chain extenders remain in the polyurethane. Furthermore, the use of organic solvents reduces system viscosity and increases environmental burden. In addition, the complex process and long production cycle result in persistently high production costs and low production efficiency, making it difficult to meet market demand.

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

[0010] To address the aforementioned technical problems, this invention provides a polyurethane, its preparation method, and its applications. The preparation method is simple, solvent-free, economical, and environmentally friendly. The resulting polyurethane product has a 100% solid content, effectively solving the problems of insufficient solid content, low production efficiency, and environmental pollution inherent in existing polyurethane synthesis processes.

[0011] To achieve this objective, the present invention adopts the following technical solution:

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

[0013] Isocyanate and polyether are mixed, and a composite catalyst is added to react. After the reaction is complete, an inhibitor is added to obtain the polyurethane.

[0014] This invention provides a one-step synthesis of polyurethane. By using a composite catalyst, the reaction between isocyanate and polyether can be controlled, thereby increasing the solid content of the resulting polyurethane. This, in turn, improves the mechanical properties and durability of the polyurethane. Simultaneously, the high solid content enables rapid curing of the polyurethane, resulting in strong adhesion and a smooth, crack-free surface after drying. The addition of inhibitors further regulates the reaction, not only increasing the solid content of the polyurethane but also adjusting the NCO content and viscosity to meet diverse market demands. Furthermore, the polyurethane preparation process provided by this invention is simple, facilitating large-scale industrial production, reducing the requirements for production equipment and technology, and eliminating the use of organic solvents throughout the process, thus reducing environmental pollution.

[0015] High-solids-content polyurethane exhibits excellent mechanical properties and durability. High solids content means a higher proportion of active ingredients in the polyurethane, increased cross-linking density between molecules, and enhanced intermolecular forces. Under external forces, this compact molecular structure better disperses stress, preventing localized stress concentration that could lead to material failure, thus improving the tensile strength, toughness, and other mechanical properties of polyurethane. Simultaneously, the compact molecular structure enhances the material's resistance to external environmental factors, further improving durability. Furthermore, high solids content allows for rapid curing of polyurethane, resulting in strong adhesion and a smooth, crack-free surface after drying. In high-solids-content systems, the high reactant concentration and small intermolecular distance lead to a faster reaction rate, enabling rapid curing. Its numerous active groups can form strong physical or chemical forces with the molecules on the surface of the bonded materials, achieving strong adhesion. Moreover, due to the thorough reaction and low impurity content, the molecules are more orderly arranged during drying, preventing pores or uneven shrinkage caused by solvent evaporation, resulting in a smooth, crack-free surface after drying.

[0016] The addition of inhibitors can further regulate the reaction. After being added to the reaction system, inhibitors react with reactive intermediates or unreacted isocyanates, altering the reaction equilibrium and thus inhibiting further reaction. When inhibitors bind to isocyanates, they reduce the number of NCO groups participating in the reaction, thereby regulating the NCO content in the polyurethane. Simultaneously, the inhibitors' control over the reaction process affects the growth and cross-linking degree of the polyurethane molecular chains, causing changes in the length and distribution of the molecular chains, ultimately achieving viscosity regulation to meet different market demands.

[0017] In this invention, the NCO groups in the isocyanate undergo an addition reaction with the OH groups in multiple polyether molecules to form a polyurethane chain. The reaction can be represented as follows:

[0018] R-NCO+R′-OH→R-NH-CO-OR′.

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

[0020] Preferably, the first catalyst comprises polyethyleneimine.

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

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

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

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

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

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

[0027] Preferably, the amine catalyst comprises any one or a combination of at least two of the following: dimethylaminoethyl ether, N,N-dimethylcyclohexylamine, N,N,N',N'-tetramethylalkyldiamine, triethylamine, N,N-dimethylbenzylamine, N-ethylmorpholine, N-methylmorpholine, N,N'-diethylpiperazine, N,N'-dimethylpyridine, or triazine trimers.

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

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

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

[0031] Preferably, the mass ratio of the composite catalyst 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, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific 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, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0033] The role of a catalyst is to accelerate the reaction between polyols and isocyanates, promoting the formation of polyurethane polymers. Catalysts can increase the nucleophilicity of polyols, promoting their reaction with isocyanates, while also influencing the structure and properties of the polymer, such as density, pore structure, and mechanical properties.

[0034] The composite catalyst in this invention comprises a first catalyst and a second catalyst. The first catalyst enhances the nucleophilicity of the hydroxyl (OH) groups in the polyether, making them more readily capable of addition reactions with the NCO groups in the isocyanate, increasing the number of active reaction sites and accelerating the reaction process. The second catalyst forms a specific intermediate transition state with the reactants, lowering the activation energy of the reaction and making it easier to proceed. The synergistic effect of these two catalysts effectively regulates the reaction between the isocyanate and the polyether, promoting a more complete reaction, increasing the solid content and mechanical properties of the resulting polyurethane, and also adjusting the NCO content and viscosity of the polyurethane to meet different market demands. Furthermore, when the molar ratio of the two catalysts is (0.01-0.1):1, the catalytic effect is even better, resulting in a polyurethane with 100% solid content, thereby improving the mechanical properties and durability of the polyurethane. When the molar ratio is lower or higher than this specific range (0.01-0.1):1, the tensile strength of the resulting polyurethane decreases.

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

[0036] In this invention, toluene diisocyanate (TDI) can also be a TDI derivative formed by chemically modifying TDI to introduce different functional groups.

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

[0038] In this invention, polyethylene glycol, polypropylene glycol, polytetrahydrofuran, and polyethylene oxide can all be their respective derivatives (compounds formed by introducing different functional groups after chemical modification).

[0039] Preferably, the mass ratio of isocyanate to polyether is (2-19):1, where (2-19) can be, for example, 2, 4, 6, 8, 10, 13, 15, 17 or 19, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

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

[0041] Preferably, the temperature for heat preservation and stirring is 80-130℃, for example, it can be 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0042] Preferably, the heat preservation and stirring time is 1-2 hours, for example, it can be 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0043] Preferably, the reaction temperature is 90-150℃, for example, it can be 90℃, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0044] Preferably, the reaction time is 0.5-3 hours, for example, it can be 0.5 hours, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours or 3 hours, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific 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 or a combination of at least two of nitrogen, argon, or helium.

[0047] Preferably, the inhibitor comprises any one or a combination of at least two of the following: carbamate, dimethylacetamide, dimethylformamide, sodium bicarbonate, sodium nitrite, difluorophosphate, 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 values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific values ​​included in the range.

[0049] Preferably, the inhibitor needs to undergo a first cooling treatment before being added.

[0050] Preferably, the temperature of the first cooling treatment is 40-85℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃ or 85℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific 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 values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0052] Preferably, the polyurethane needs to undergo a second cooling treatment before it is obtained.

[0053] Preferably, the temperature of the second cooling process is 35-55℃, for example, it can be 35℃, 37℃, 40℃, 42℃, 44℃, 46℃, 48℃, 50℃, 53℃ or 55℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0054] Preferably, the method for preparing the polyurethane specifically includes the following steps:

[0055] (1) Mix isocyanate and polyether at a mass ratio of (2-19):1, and stir at 80-130℃ for 1-2 hours.

[0056] (2) Add a composite catalyst and react at 90-150℃ for 0.5-3h;

[0057] (3) After the reaction is complete, cool down to 40-85℃, add inhibitor, stir and mix for 20-40 minutes, and then cool down to 35-55℃ to obtain the polyurethane.

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

[0059] Preferably, the polyurethane has a solid content of 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%, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0061] Preferably, the viscosity of the polyurethane is 2000-16000 cP, for example, it can 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 values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0062] Thirdly, the present invention provides the application of polyurethane as described in the second aspect in coatings, adhesives, and sealants.

[0063] In the coatings field, the polyurethane of this invention has a 100% solids content, resulting in a smooth, crack-free surface after drying and strong adhesion. It significantly improves the hardness, durability, chemical resistance, temperature resistance, and aging resistance of the coating, making it widely applicable to coating industrial equipment, building exteriors, etc. In the adhesives field, the high solids content of the polyurethane of this invention enables rapid drying and provides high tensile strength, allowing for strong bonding of various materials, including metals, plastics, and wood. In the sealants field, the excellent flexibility and abrasion resistance of the polyurethane of this invention effectively fill gaps and maintain a long-term sealing effect, playing a crucial role in automotive manufacturing and electronic device packaging.

[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, which makes it perform well in terms of 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) The polyurethane preparation method provided by the present invention can obtain polyurethane products with different NCO contents and viscosities by further optimizing the amount of composite catalyst and inhibitor and the reaction conditions, thereby well meeting the market demand for polyurethane products with different performance, reducing the requirements for production equipment and technology, and facilitating large-scale industrial production. Attached Figure Description

[0068] Figure 1 This is a schematic flowchart of the preparation method of the present invention;

[0069] Figure 2 This is a flowchart of the two-step method (prepolymer method);

[0070] Figure 3 This is a diagram of the reaction apparatus for the preparation method of this invention;

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

[0072] Figure 5 This is the potentiometric titration curve of the polyurethane obtained in Comparative Example 1. Detailed Implementation

[0073] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely 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 is determined by the claims.

[0074] The preparation methods of this invention are all in accordance with the following Figure 1 The process flow diagram shown illustrates the preparation method, and the corresponding reaction apparatus is as follows: Figure 2 As shown; a flowchart of the existing two-step method (prepolymer method) is shown below. Figure 3 As shown.

[0075] Unless otherwise specified, all raw materials and reagents used in the following examples and comparative examples are commercially available. Some raw material information is shown in Table 1.

[0076] Table 1

[0077] Specific selection / purchase manufacturers Isocyanates HDI, Wanhua Chemical polyether PEG-600A, Zhide Chemical Polyethyleneimine PEI-1800, Gaide Chemicals Organic bismuth NIAX MC-710, Gaide Chemicals Organic zinc DY-5350, Deyin Chemicals Organotin Dibutyltin dilaurate, Deyin Chemicals Inhibitors Dibutyl phosphate, Maclean Chain extender 1,4-Butanediol, Maclean

[0078] Example 1

[0079] This embodiment provides a polyurethane, the preparation method of which includes the following steps:

[0080] (1) Under nitrogen protection, 980g of isocyanate was placed in a stirred tank and stirred. Then 120g of polyether was added and the temperature was raised. The timer was started when the temperature reached 90℃ and the temperature was raised to 120℃. The mixture was kept warm and stirred for 1.5h.

[0081] (2) Add 0.35g of composite catalyst (molar ratio of polyethyleneimine to organic bismuth is 0.01:1), continue heating to 130℃, and react for 2h;

[0082] (3) After the reaction is complete, cool down to 82°C and add 0.25g of inhibitor. Stir for 30 minutes to mix evenly and then quickly cool down to 53°C to obtain the polyurethane.

[0083] The potentiometric titration curve for determining the NCO content of the polyurethane is shown in the figure below. Figure 4 As shown, the horizontal axis represents 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 differs from Embodiment 1 in that the amount of polyether used in step (1) is adjusted from 120g to 53g, while the other raw materials, amounts and preparation methods are the same as in Embodiment 1.

[0086] Example 3

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

[0092] Example 6

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

[0094] Example 7

[0095] This embodiment provides a polyurethane, which differs from Example 1 in that the amount of composite catalyst in step (2) is adjusted from 0.35g to 0.15g, while the other raw materials, amounts and preparation methods are the same as 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 with an equimolar amount of organic zinc, while the other raw materials, amounts and preparation methods are the same as 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 with an equimolar amount of organic tin, while the other raw materials, amounts and preparation methods are the same as in Embodiment 1.

[0100] Example 10

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

[0102] Example 11

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

[0104] Example 12

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

[0106] Example 13

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

[0108] Example 14

[0109] This embodiment provides a polyurethane, the preparation method of which includes the following steps:

[0110] (1) Under nitrogen protection, 980g of isocyanate was placed in a stirring vessel and stirred. Then 490g of polyether was added and the temperature was raised. The timer was started when the temperature reached 80℃ and the temperature was raised to 130℃. The mixture was kept warm and stirred for 1.0h.

[0111] (2) Add 1g of composite catalyst (molar ratio of polyethyleneimine to triethylamine is 0.05:1), continue to heat to 150℃, and react for 0.5h;

[0112] (3) After the reaction is complete, cool down to 60°C and add 0.1g of inhibitor. Stir for 20 minutes to mix evenly, and then quickly cool down to 45°C to obtain the polyurethane.

[0113] Example 15

[0114] This embodiment provides a polyurethane, the preparation method of which includes the following steps:

[0115] (1) Under nitrogen protection, 980g of isocyanate was placed in a stirring vessel and stirred. Then 65g of polyether was added and the temperature was raised. The time was started when the temperature reached 90℃ and the mixture was kept warm and stirred for 2 hours.

[0116] (2) Add 0.01g of composite catalyst (molar ratio of polyethyleneimine to organic bismuth is 0.01:1) and react at 90℃ for 3h;

[0117] (3) After the reaction is complete, cool down to 40°C and add 0.01g of inhibitor. Stir for 40min to mix evenly and then quickly cool down to 35°C to obtain the polyurethane.

[0118] Comparative Example 1

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

[0120] The potentiometric titration curve for determining the NCO content of the polyurethane is shown in the figure below. Figure 5 As shown in the figure, the horizontal axis represents the amount of hydrochloric acid used during titration.

[0121] Comparative Example 2

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

[0123] Comparative Example 3

[0124] This comparative example provides a polyurethane prepared using a two-step method (prepolymer method), the specific preparation method including the following steps:

[0125] (1) Put 980g of isocyanate into a mixing tank and stir. Then add 120g of polyether and start heating. Start timing when the temperature reaches 90℃ and continue heating to 120℃. Keep stirring for 1.5h to form polyurethane prepolymer.

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

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

[0128] (4) Add 0.25g of organic bismuth, continue heating to 130℃, and react for 2h 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 are as follows:

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

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

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

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

[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 Example 11 20.5 2101 100 55.3 Example 12 16.5 15813 100 53.5 Example 13 21.0 2011 100 53.6 Example 14 16.8 4227 100 55.7 Example 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) As can be seen from Examples 1 to 15, the polyurethane preparation method provided by the present invention is simple and the polyurethane prepared 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) As can be seen from Examples 1 and 11-13, the present invention can effectively adjust the NCO content and viscosity of polyurethane by controlling the molar ratio of the first catalyst and the second catalyst, thereby better meeting the different market demands of polyurethane; furthermore, when the molar ratio of the two is lower or higher than a specific molar ratio range (0.01-0.1):1, their 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 this invention has better technical effects. By combining the first catalyst and the second catalyst to regulate the reaction, it is possible to obtain polyurethane with higher solid content, better mechanical properties, and NCO content and viscosity that are more in line with the requirements of polyurethane. However, when a certain type of catalyst is not used or is missing, the corresponding solid content of the obtained polyurethane 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 of polyurethane.

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

[0142] In summary, this invention utilizes a one-step polyurethane synthesis method and the use of composite catalysts and inhibitors to effectively regulate the reaction. This not only improves the solid content of the resulting polyurethane but also allows for the adjustment of the NCO content and viscosity, thereby meeting diverse market demands.

[0143] The applicant declares that the above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing polyurethane, characterized in that, The preparation method includes the following steps: (1) Mix isocyanate and polyether at a mass ratio of (2-19):1 and stir at 80-130℃ for 1-2 h; (2) Add a composite catalyst and react at 90-150℃ for 0.5-3 h; (3) After the reaction is complete, cool down to 40-85℃, add inhibitor, stir and mix for 20-40 min, then cool down to 35-55℃ to obtain the polyurethane; The isocyanate includes any one or a combination of at least two of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, hexamethylene diisocyanate biuret, hexamethylene diisocyanate trimer, or hexamethylene diisocyanate-toluene diisocyanate polymer. The polyether includes any one or a combination of at least two of polyethylene glycol, polypropylene glycol, polytetrahydrofuran, or polyethylene oxide. The mass ratio of the composite catalyst to isocyanate is (0.00001-0.001):1; The composite catalyst comprises a first catalyst and a second catalyst; the molar ratio of the first catalyst and the second catalyst is (0.01-0.1):1; The first catalyst comprises polyethyleneimine; The second catalyst includes any one of organotin, organozinc, organobismuth, or triethylamine.

2. The method for preparing polyurethane according to claim 1, characterized in that, The inhibitors include any one or a combination of at least two of the following: carbamate, dimethylacetamide, dimethylformamide, sodium bicarbonate, sodium nitrite, difluorophosphate, or dibutyl phosphate.

3. The method for preparing polyurethane according to claim 1 or 2, characterized in that, The mass ratio of the inhibitor to isocyanate is (0.00001-0.001):

1.

4. A polyurethane, characterized in that, The polyurethane is prepared using the polyurethane preparation method as described in any one of claims 1-3.

5. The polyurethane according to claim 4, characterized in that, The polyurethane has a solid content of 100%.

6. The polyurethane according to claim 4, characterized in that, The NCO content of the polyurethane is 16-21%.

7. The polyurethane according to claim 4, characterized in that, The viscosity of the polyurethane is 2000-16000 cP.

8. The use of polyurethane as described in any one of claims 4-7 in coatings, adhesives, and sealants.

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