Polyisocyanate as well as preparation method and application thereof

Abstract

The invention provides polyisocyanate as well as a preparation method and application thereof. The polyisocyanate can be used for preparing a reactive adhesive, and the adhesive is easy to quickly react with nucleophilic groups to form a three-dimensional network structure with multiple hydrogen bonds and Pi-Pi stacking action, so that the adhesive property is good. In a polyisocyanate structure, the mass ratio of isocyanate groups is as high as 31.7%, so that very high adhesive strength and reaction activity can be maintained; the polyisocyanate can also be used as a raw material component of the adhesive for preparing an organic transparency high-end liquid adhesive and improving the mechanical property of the liquid adhesive, and then is used for bonding metal-metal, metal-plastic, metal-rubber, honeycomb sandwich structure-wallboard and other fields, so that the problems that the polyisocyanate is too few in variety, and the product quality is poor are effectively solved. And therefore, the requirements under different service conditions in practical application can be well met.

Description

Technical Field

[0001] The present application relates to the technical field of polyurethane adhesives, and in particular to a polyisocyanate, a preparation method and an application thereof. Background Art

[0002] Polyurethane (PU) was first developed by German scientists in the 1930s. It is widely used in military and civilian fields such as automobiles, construction, high-speed rail, aerospace, and ships due to its excellent wear resistance, durability, and tensile strength. Many polyurethane foams, coatings, polymer castings, and adhesives are based on the reaction of polyisocyanates, so isocyanate compounds containing isocyanate functional groups (-N=C=O) in the molecules have become key raw materials for the production of polyurethane products.

[0003] Polyurethanes are usually produced by the polyaddition reaction between diisocyanates and polyols. Among them, the most commonly used diisocyanates are aromatic methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), accounting for 61%, 34%, 3.4% and 1.2% of the global polyisocyanate demand respectively.

[0004] Compared with diisocyanates, triisocyanates are not commonly used. However, in the preparation process of polyurethane, adding a small amount of triisocyanates plays a very important role in enhancing the mechanical properties of polyurethane. For example, triisocyanates derived from HDI (such as Desmodur N100 and Desmodur N3390, etc.), Lekna glue (or Desmodur RE), and toluene triisocyanate (TTI) developed by Huang Muhua's research group at Beijing Institute of Technology in recent years, these triisocyanates are expected to be used for the bonding of rubber and metal, leather and rubber, synthetic fibers, cotton fabrics and rubber, rubber and rubber, etc.

[0005] However, there are too few types of polyisocyanates at present, which limits their application. Therefore, it is urgent to develop a polyisocyanate material with novel structure and excellent performance to better meet the needs of different service conditions in practical applications. Summary of the invention

[0006] In order to solve the above problems, the present application provides a polyisocyanate, a preparation method and its application. In the polyisocyanate provided in the present application, the mass proportion of isocyanate groups is as high as 31.7%, which is significantly higher than the mass proportion of isocyanate groups in existing isocyanate adhesives (such as the mass proportion of isocyanate groups in Lekna glue is 23%), so the adhesive prepared by the polyisocyanate provided in the present application has stronger bonding force. Or the polyisocyanate provided in the present application can be used as a raw material component of the adhesive to prepare an organic transparency high-end liquid adhesive to improve the mechanical properties of the adhesive, so that the adhesive can be better used for bonding metal-metal, metal-plastic, metal-rubber, honeycomb sandwich structure-wallboard and other fields, effectively solving the problem of limited application of polyisocyanates, and can better meet the needs of different service conditions in actual applications.

[0007] In a first aspect, the present application provides a polyisocyanate, wherein the polyisocyanate comprises: a polyisocyanate represented by the following formula I:

[0008] Formula I; and / or, The polyisocyanate is an isomer of the polyisocyanate structure shown in the above formula I; The mass percentage of isocyanate groups in the polyisocyanate is 31.7%.

[0009] In a second aspect, the present application provides a method for preparing the above-mentioned polyisocyanate, the method comprising: Under an inert environment, toluene triisocyanate is dissolved in a solvent, 1,4-butanediol is added after mechanical stirring, and a polyaddition reaction is carried out at a temperature of 30°C-60°C to generate polyisocyanate; Wherein, the solvent includes any one of ethyl acetate, butyl acetate, dichloromethane, tetrahydrofuran and chloroform.

[0010] Furthermore, the molar ratio of the toluene triisocyanate to the 1,4-butanediol is (2-2.5):1.

[0011] Furthermore, the inert gas in the inert environment includes any one of argon, helium, neon and nitrogen.

[0012] Furthermore, the addition polymerization reaction is carried out at a temperature of 40°C-50°C, and the reaction time is 0.5 h-1 h.

[0013] Furthermore, the mass volume ratio of the toluene triisocyanate to the solvent is (3.0-4.0) g: (10-20) ml.

[0014] In a third aspect, the present application provides an application of a polyisocyanate, wherein the polyisocyanate described in the first aspect is used for the preparation of an adhesive.

[0015] Furthermore, the polyisocyanate is mixed with an ethyl acetate solution to form the adhesive.

[0016] Furthermore, the adhesive is used to bond metal to metal, metal to plastic, metal to rubber or honeycomb sandwich structure to wall panel.

[0017] Furthermore, the adhesive is used to bond 45# steel-5470# rubber, and the bonding strength between the 45# steel and 5470# rubber is 6.07 Mpa.

[0018] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present application provides a polyisocyanate, which contains a carbamate structural unit in its structure and can be used as a raw material for preparing an adhesive. The mass proportion of isocyanate groups in its structure is as high as 31.7%, which is significantly higher than the mass proportion of isocyanate groups in existing isocyanate adhesives (such as the mass proportion of isocyanate groups in Lekna glue is 23%), so that it has the characteristics of high adhesion and good reactivity. The structural formula of the polyisocyanate is shown in Formula I below:

[0019] Formula I; and / or, Isomers of the polyisocyanate structure shown in the above formula I; 2. The preparation method of polyisocyanate provided in the present application, by introducing toluene triisocyanate and 1,4-butanediol to undergo addition polymerization reaction, synthesizes a polyisocyanate material with novel structure, and the method provides a more diversified and high-performance raw material selection for the preparation of polyisocyanate materials, thereby broadening its application scope and effectively solving the problem of limited application; 3. When used, the polyisocyanate provided in the present application can be mixed with an ethyl acetate solution to form a reactive adhesive, which can easily form a three-dimensional network structure with multiple hydrogen bonds and Pi-Pi stacking effects, thereby maintaining stable and lasting adhesion. It can also be used as a raw material component of an adhesive to prepare a liquid adhesive with high transparency. The resulting adhesive has better mechanical properties, higher adhesion, and a wider range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 The hydrogen nuclear magnetic resonance spectrum of the polyisocyanate provided in the examples of the present application is shown; Figure 2 The infrared spectrum of the polyisocyanate provided in the examples of the present application is shown; Figure 3 The flowchart of the method for preparing polyisocyanate provided in the examples of the present application is shown. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on the present invention and its application or use. Based on the embodiments of the present invention, any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work belong to the scope of protection of the present invention.

[0023] In the embodiment, no specific experimental steps or conditions are indicated, and the operation or conditions of the conventional experimental steps described in the prior art in this field can be carried out. The reagents used and other instruments that do not indicate the manufacturer are conventional reagent products that can be obtained commercially. In addition, the accompanying drawings are only schematic diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0024] Technologies, methods, and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the description of the present invention.

[0025] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0026] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] In the related technologies, polyurethane (PU) has been widely used in many military-civilian integration fields such as automobiles, construction, high-speed rail, aerospace and ships due to its excellent wear resistance, durability and high tensile strength. The synthesis of polyurethane mainly depends on the addition polymerization between diisocyanate and polyol. In this process, the isocyanate functional group (-N=C=O) in the diisocyanate molecule and the hydroxyl group (-OH) in the polyol undergo addition polymerization to form a polyurethane chain segment.

[0028] However, after research, it was found that in the polyurethane preparation process, the addition of triisocyanates, although the amount may be small, can significantly enhance the mechanical properties of polyurethane. Triisocyanate molecules can form more cross-linking points in the polyurethane chain segments, thereby increasing the reactivity of the material. For example, triisocyanates derived from HDI (such as Desmodur N100 and Desmodur N3390) and Lekna glue (or Desmodur RE), as well as toluene triisocyanate (TTI) developed by Huang Muhua's team at Beijing Institute of Technology in recent years, have shown excellent performance in the bonding of rubber to metal, leather to rubber and other materials.

[0029] However, the types of polyisocyanates available are relatively limited, and the bonding strength of adhesives made from them is limited, which to a certain extent limits their application in a wider range of fields. In order to break this bottleneck, the present application further explores new synthesis methods to obtain polyisocyanates with novel structures and excellent performance.

[0030] The present application provides a polyisocyanate, wherein the polyisocyanate comprises: a polyisocyanate shown in the following formula I:

[0031] Formula I; and / or, The polyisocyanate is an isomer of the polyisocyanate structure shown in the above formula I; The mass percentage of isocyanate groups in the polyisocyanate is 31.7%.

[0032] The structural formula of the polyisocyanate provided in the present application contains multiple isocyanate functional groups (-NCO), and the mass proportion of the isocyanate functional groups is as high as 31.7%. The strength of the bonding force is positively correlated with the mass proportion of the isocyanate groups. Therefore, compared with existing adhesives, the adhesive prepared from the polyisocyanate provided in the embodiments of the present application has stronger bonding force.

[0033] For specific implementation, see Figure 1 , Figure 1 The hydrogen nuclear magnetic resonance spectrum of the polyisocyanate provided in the examples of the present application is shown; See also Figure 2 , Figure 2 The infrared spectrum of the polyisocyanate provided in the examples of the present application is shown.

[0034] In specific implementation, the polyisocyanate provided by the present invention includes multiple isomers, and Formula I only shows one of the structural formulas, that is, in the polyisocyanate provided by the present invention, the methyl group on the benzene ring can also be substituted at any position except the -NCO connecting carbon to form isomers.

[0035] See also Figure 3 , Figure 3 The preparation method of the polyisocyanate provided in the embodiment of the present application is shown, and the specific steps include: S1: Under an inert environment, dissolve toluene triisocyanate in a solvent; S2: After mechanical stirring, 1,4-butanediol is added and polyaddition reaction is carried out at a temperature of 30 ℃-60 ℃ to generate polyisocyanate.

[0036] Wherein, the solvent includes any one of ethyl acetate, butyl acetate, dichloromethane, tetrahydrofuran and chloroform.

[0037] In this reaction process, the hydroxyl group of 1,4-butanediol reacts with the isocyanate functional group of toluene triisocyanate to form a new polyisocyanate segment, and at the same time introduces more isocyanate functional groups to prepare a polyisocyanate with high bonding strength, rich variety and green environmental protection. The successful implementation of this synthesis method not only enriches the types of polyisocyanates, but also provides a broader space for the further development and application of polyisocyanate materials.

[0038] Moreover, it can be seen from the structural formula that the polyisocyanate has unique advantages in the synthesis of polyurethane, and can form more stable and tough polyurethane segments, thereby improving the mechanical properties of polyurethane materials; in the synthesis process of polyurethane, the isocyanate functional groups can be more effectively utilized to form more cross-linking points, thereby further enhancing the strength and toughness of the polyurethane material.

[0039] In the specific implementation, an inert environment is selected to ensure that the reaction process will not be affected by oxygen, moisture or other impurities in the air or cause the product to deteriorate.

[0040] During specific implementation, the solvent is selected from urethane grade materials, and the ethyl acetate, butyl acetate, dichloromethane, tetrahydrofuran or chloroform used are all urethane grade.

[0041] Urethane grade refers to high-quality materials used in the polyurethane (PU) field. It usually has higher purity, lower impurity content and specific performance indicators to meet the strict requirements in the polyisocyanate manufacturing process.

[0042] Urethane grade materials are selected as solvents because they have good solubility and chemical stability, can be fully mixed with toluene triisocyanate, and will not produce other side reactions during the reaction.

[0043] In some embodiments, preferably, the solvent is any one of ethyl acetate, butyl acetate, dichloromethane and chloroform.

[0044] In a specific implementation, toluene triisocyanate is slowly added to the solvent under an inert environment and properly stirred to ensure that the toluene triisocyanate is completely dissolved.

[0045] In the specific implementation, before adding 1,4-butanediol, mechanical stirring is first performed, the purpose of which is to ensure that the solution is evenly mixed, which is conducive to the smooth progress of the reaction and improve the reaction efficiency; The added 1,4-butanediol is a polyol containing two hydroxyl groups. As one of the reactants, it undergoes a polyaddition reaction with the isocyanate functional group in toluene triisocyanate to generate a polyisocyanate with a novel structure, thereby expanding the types of polyisocyanates.

[0046] In specific implementation, the reaction temperature is controlled between 30°C and 60°C, which is conducive to the reaction and avoids side reactions or product decomposition caused by excessively high temperature.

[0047] In summary, under the temperature and stirring conditions, the hydroxyl groups in 1,4-butanediol react with the isocyanate functional groups in toluene triisocyanate to generate new polyisocyanate segments, and more isocyanate functional groups are introduced into the generated polyisocyanate structure to give the polyisocyanate higher adhesion.

[0048] In some embodiments, a method for preparing toluene triisocyanate is provided, which specifically comprises the following steps: Under the catalytic action of nitrogen-doped porous carbon supported palladium, 2,4,6-trinitrotoluene was used as the raw material to obtain 2,4,6-triaminotoluene hydrochloride; Toluene triisocyanate was prepared from 2,4,6-triaminotoluene hydrochloride by phosgenation and vacuum distillation.

[0049] The preparation method has the advantages of simple operation, high reaction conversion rate, easy separation and collection of intermediate and final products, etc., and is conducive to achieving high-quality production of toluene triisocyanate.

[0050] In some embodiments, the molar ratio of the toluene triisocyanate to the 1,4-butanediol is (2-2.5):1.

[0051] In specific implementation, toluene triisocyanate is used as an isocyanate component, which reacts with 1,4-butanediol to form the hard segment part of the polyisocyanate. The hard segment content is increased by increasing the molar ratio of toluene triisocyanate. The increase in the hard segment content helps to enhance the strength and hardness of the polyisocyanate as an adhesive, giving it better mechanical properties and wear resistance.

[0052] In the polyisocyanate segments formed by the reaction of toluene triisocyanate and 1,4-butanediol, the compatibility between the hard segment and the soft segment has an important influence on the performance of the adhesive. By controlling the molar ratio, the ratio of the hard segment to the soft segment can be optimized, thereby improving the compatibility between the segments and making the adhesive made of polyisocyanate have better bonding performance.

[0053] In addition, controlling the addition polymerization reaction between toluene triisocyanate and 1,4-butanediol is a key step in the synthesis of polyisocyanates, and controlling the molar ratio can ensure sufficient contact and reaction between the reactants, thereby improving the reaction efficiency, reducing the formation of by-products, and improving the purity and quality of the product. It can also avoid the waste caused by excessive toluene triisocyanate and 1,4-butanediol, which is conducive to saving resources.

[0054] In a specific implementation, the molar ratio of toluene triisocyanate to 1,4-butanediol is 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1.

[0055] In some embodiments, the inert gas in the inert environment includes any one of argon, helium, neon and nitrogen.

[0056] During specific implementation, preferably, the inert gas in the inert environment is argon.

[0057] In some embodiments, the addition polymerization reaction is carried out at a temperature of 40° C.-50° C., and the reaction time is 0.5 h-1 h.

[0058] In a specific implementation, the addition polymerization reaction is carried out at a temperature of 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, and 50°C.

[0059] The reaction time is 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h or 1 h.

[0060] In some embodiments, the mass volume ratio of the toluene triisocyanate to the solvent is (3.0-4.0) g: (10-20) ml.

[0061] In specific implementation, by controlling the mass volume ratio of toluene triisocyanate to solvent, it is possible to ensure that toluene triisocyanate is evenly dispersed in the solvent, thereby increasing the contact area with 1,4-butanediol and promoting uniform reaction. In addition, the appropriate solvent ratio can reduce the viscosity of the reaction system, making it easier for the two reactant molecules to move and collide, thereby accelerating the reaction.

[0062] An embodiment of the present application provides an application of the above-mentioned polyisocyanate, wherein the polyisocyanate is used for the preparation of an adhesive.

[0063] The polyisocyanate molecular chains provided in the embodiments of the present application are rich in polar groups - carbamate groups and isocyanate groups. These groups can form good chemical bonds or physical adsorption with the surfaces of various materials, thereby giving the polyisocyanate better bonding properties; more cross-linking points can be formed, further enhancing its bonding strength and durability.

[0064] In some embodiments, the polyisocyanate is mixed with an ethyl acetate solution to form the adhesive. The preparation method is simple, uses fewer reagents, and is more practical.

[0065] In some embodiments, the adhesive is used to bond metal to metal, metal to plastic, metal to rubber or honeycomb sandwich structure to wall panel.

[0066] The polyisocyanate adhesive with a new structure provided in the embodiments of the present application can be applied to bonding of more types of materials, including metal-metal, metal-plastic, metal-rubber, and honeycomb sandwich structure-wallboard, etc. To a certain extent, the application field of polyisocyanate with a new structure as an adhesive is broadened, the problem of its limited application is solved, and the needs of different service conditions in practical applications can be better met.

[0067] In some embodiments, the adhesive is used to bond 45# steel-5470# rubber, and the bonding strength between the 45# steel and 5470# rubber is 6.07 Mpa.

[0068] When the polyisocyanate in the embodiment of the present application is used to bond 45# steel to 5470# rubber, the bonding strength reaches 6.07 MPa (megapascals), which is much higher than the bonding strength that can be provided by traditional isocyanate adhesives, and is sufficient to meet the structural stability requirements of 45# steel to 5470# rubber connectors in most industrial applications. The 45# steel to 5470# rubber bonded by the adhesive provided in the embodiment of the present application can withstand greater tensile, shear and compressive loads, ensuring that the connector will not break or loosen during long-term use, thereby improving the stability and safety of the overall structure.

[0069] When the adhesive in the embodiment of the present application is used for bonding, the operation is simple and environmentally friendly. It can be evenly coated on the surface of the 45# steel and 5470# rubber to be bonded by coating, spraying or injection, and then cured at appropriate temperature and pressure. No large amount of solvents or harmful substances are required in the whole process, which is beneficial to protecting the environment and the health of operators. However, the bonding method is not specifically limited in the embodiment of the present application.

[0070] In some embodiments, the above polyisocyanate is used as a raw material for preparing other types of adhesives, and the resulting adhesive has better performance and can be used in more fields such as bonding metal-metal, metal-plastic, metal-rubber or honeycomb sandwich structure-wall panel.

[0071] In specific implementation, the method of using polyisocyanate to prepare other types of adhesives with high transparency is not specifically limited in the embodiments of the present application, and can be achieved by conventional technical means.

[0072] In order to enable those skilled in the art to understand the present application more clearly, the preparation method of a polyisocyanate provided in the present application is now described in detail through the following examples.

[0073] Example Example 1 Preparation of a polyisocyanate: Step 1: Weigh 3.0 g of toluene triisocyanate and add it into a three-necked flask, then evacuate and fill with argon, repeating the operation three times to obtain an inert environment; Step 2: Measure 20 ml of urethane-grade ethyl acetate and place it in the three-necked flask in step 1, then start mechanical stirring to completely dissolve toluene triisocyanate to obtain a mixed solution; Step 3: Add 0.61 g of 1,4-butanediol to the mixed solution in the three-necked flask, carry out polyaddition reaction at 30°C for 0.5 h, then stop stirring to generate polyisocyanate, which is mixed with ethyl acetate solution to prepare a liquid adhesive.

[0074] Example 2 Preparation of a polyisocyanate: The difference between Example 2 and Example 1 is that the temperature and time of the polyaddition reaction are different.

[0075] Step 1: Weigh 3.0 g of toluene triisocyanate and add it into a three-necked flask, then evacuate and fill with argon, repeating the operation three times to obtain an inert environment; Step 2: Measure 20 ml of urethane-grade ethyl acetate and place it in the three-necked flask in step 1, then start mechanical stirring to completely dissolve toluene triisocyanate to obtain a mixed solution; Step 3: Add 0.61 g of 1,4-butanediol to the mixed solution in the three-necked flask, carry out polyaddition reaction at 50°C for 1 hour, then stop stirring to generate polyisocyanate, which is mixed with ethyl acetate solution to prepare a liquid adhesive.

[0076] Example 3 Preparation of a polyisocyanate: The difference between Example 3 and Example 1 is that the qualities of toluene triisocyanate and the solvent are different.

[0077] Step 1: Weigh 3.35 g of toluene triisocyanate and add it into a three-necked flask, then evacuate and fill with argon, repeating the operation three times to obtain an inert environment; Step 2: Measure 18 ml of urethane-grade ethyl acetate and place it in the three-necked flask in step 1, then start mechanical stirring to completely dissolve toluene triisocyanate to obtain a mixed solution; Step 3: Add 0.61 g of 1,4-butanediol to the mixed solution in the three-necked flask, carry out polyaddition reaction at 50°C for 0.5 h, then stop stirring to generate polyisocyanate, which is mixed with ethyl acetate solution to prepare a liquid adhesive.

[0078] Example 4 Preparation of a polyisocyanate: The difference between Example 4 and Example 1 is that the mass of toluene triisocyanate is different, and the temperature and time of the addition polymerization reaction are different.

[0079] Step 1: Weigh 3.35 g of toluene triisocyanate and add it into a three-necked flask, then evacuate and fill with argon, repeating the operation three times to obtain an inert environment; Step 2: Measure 20 ml of urethane-grade ethyl acetate and place it in the three-necked flask in step 1, then start mechanical stirring to completely dissolve toluene triisocyanate to obtain a mixed solution; Step 3: Add 0.61 g of 1,4-butanediol to the mixed solution in the three-necked flask, carry out polyaddition reaction at 40°C for 1 hour, then stop stirring to generate polyisocyanate, which is mixed with ethyl acetate solution to prepare a liquid adhesive.

[0080] Example 5 Preparation of a polyisocyanate: The difference between Example 5 and Example 1 is that the mass of toluene triisocyanate is different, and the temperature and time of the polyaddition reaction are different.

[0081] Step 1: Weigh 3.7 g of toluene triisocyanate and add it into a three-necked flask, then evacuate and fill with argon, repeating the operation three times; Step 2: Measure 20 ml of urethane-grade ethyl acetate and place it in the three-necked flask in step 1, then start mechanical stirring to completely dissolve toluene triisocyanate to obtain a mixed solution; Step 3: Add 0.61 g of 1,4-butanediol to the mixed solution in the three-necked flask, carry out polyaddition reaction at 50°C for 1.0 h, then stop stirring to generate polyisocyanate, which is mixed with ethyl acetate solution to prepare a liquid adhesive.

[0082] Example 6 Preparation of a polyisocyanate: The difference between Example 6 and Example 1 is that the mass of toluene triisocyanate and the mass of the solvent are different, and the temperature and time of the polyaddition reaction are different.

[0083] Step 1: Weigh 3.7 g of toluene triisocyanate and add it into a three-necked flask, then evacuate and fill with argon, repeating the operation three times; Step 2: Measure 17 ml of urethane-grade ethyl acetate and place it in the three-necked flask in step 1, then start mechanical stirring to completely dissolve toluene triisocyanate to obtain a mixed solution; Step 3: Add 0.61 g of 1,4-butanediol to the mixed solution in the three-necked flask, carry out polyaddition reaction at 50°C for 1.0 h, then stop stirring to generate polyisocyanate, which is mixed with ethyl acetate solution to prepare a liquid adhesive.

[0084] Performance Testing Experiment 1: The performance of the polyisocyanate adhesive provided in Example 1 of the present application was compared with the performance of the existing triisocyanate adhesive (such as Lekna adhesive).

[0085] Test content: 1. Adhesion performance test The test was carried out using a microcomputer-controlled universal electronic tensile testing machine (NLFRM-63), which needed to comply with the requirements of HG / T2369, and the speed of the fixture movement was set to 25 mm / min±5 mm / min.

[0086] 2. Mechanical properties test The static tensile test (GB / T 1040.2-2022) was used to determine the mechanical properties of the adhesive, and the tensile shear strength of the adhesive was determined according to GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)".

[0087] Test method: 1. Standard specimen: a rubber cylinder with a thickness of 3 mm ± 0.1 mm and a diameter between 35 mm and 40 mm; its circular end faces are bonded to two metal plates of equivalent diameter; the diameter of the metal plates is approximately 0.1 mm smaller than the diameter of the rubber cylinder; the thickness of the metal plates is not less than 9 mm; 2. Install the sample on the positioning device of the testing machine and adjust the sample to make it centered so that the force during the test is evenly distributed on the entire cross section; apply tension to the fixture and move the fixture at a constant speed of 25 mm / min±5 mm / min until the sample is destroyed, and record the maximum force value; 3. Calculate the bonding strength by dividing the maximum force by the cross-sectional area of ​​the specimen in MPa, and record the failure type.

[0088] Table 1 below records the performance comparison between the polyisocyanate adhesive provided in Example 1 of the present application and the existing triisocyanate adhesive products: Table 1. Performance comparison of the polyisocyanate adhesive provided in Example 1 of the present application and the existing triisocyanate adhesive

[0089] According to the data in Table 1, the bonding performance of the polyisocyanate adhesive provided in the embodiment of the present application is better than that of the existing triisocyanate adhesive product Lekna glue. Especially when bonding 45# steel and 5470# rubber, the bonding strength of the adhesive is greater than that of Lekna glue, which can better meet the material requirements for bonding performance.

[0090] In summary, the present application provides a polyisocyanate, a preparation method and an application thereof. In the polyisocyanate, the mass proportion of isocyanate groups is as high as 31.7%, which is significantly higher than the mass proportion of isocyanate groups in existing triisocyanate adhesives (such as the mass proportion of isocyanate groups in Lekna glue is 23%). Compared with existing adhesives, the polyisocyanate provided in the present application can be mixed with ethyl acetate solution to produce an adhesive with stronger bonding strength.

[0091] The present application provides a method for preparing polyisocyanates, which synthesizes a polyisocyanate material with a novel structure by introducing toluene triisocyanate and 1,4-butanediol for a polyaddition reaction. This method provides a more diverse and high-performance raw material selection for the preparation of polyisocyanate materials, thereby broadening their application range and effectively solving the problem of limited application.

[0092] The adhesive made from the polyisocyanate provided in the present application can also be used as one of the raw materials for preparing a liquid adhesive with high transparency. The obtained adhesive has good mechanical properties, higher bonding strength, and a wider range of applications. It can be used to bond metal-metal, metal-plastic, metal-rubber, and honeycomb sandwich structures-wall panels, effectively solving the problem of limited application of polyisocyanates due to the small number of types, and can well meet the needs of different service conditions in actual applications.

[0093] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0094] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present application.

[0095] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0096] The above is a detailed introduction to a polyisocyanate, a preparation method and an application thereof provided in the present application. Specific examples are used herein to illustrate the principle and implementation method of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for a person skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A polyisocyanate, characterized in that: The polyisocyanate includes: a polyisocyanate shown in the following formula I: Formula I; and / or, The polyisocyanate is an isomer of the polyisocyanate structure shown in the above formula I; The mass percentage of isocyanate groups in the polyisocyanate is 31.7%.

2. A method for preparing the polyisocyanate according to claim 1, characterized in that: The method comprises: Under an inert environment, toluene triisocyanate is dissolved in a solvent, 1,4-butanediol is added after mechanical stirring, and a polyaddition reaction is carried out at a temperature of 30°C-60°C to generate polyisocyanate; Wherein, the solvent includes any one of ethyl acetate, butyl acetate, dichloromethane, tetrahydrofuran and chloroform.

3. The method for preparing polyisocyanate according to claim 2, characterized in that: The molar ratio of the toluene triisocyanate to the 1,4-butanediol is (2-2.5):

1.

4. The method for preparing polyisocyanate according to claim 2, characterized in that: The inert gas in the inert environment includes any one of argon, helium, neon and nitrogen.

5. The method for preparing polyisocyanate according to claim 2, characterized in that: The polyaddition reaction is carried out at a temperature of 40°C-50°C and a reaction time of 0.5 h-1 h.

6. The method for preparing polyisocyanate according to claim 2, characterized in that: The mass volume ratio of the toluene triisocyanate to the solvent is (3.0-4.0) g: (10-20) ml.

7. An application of polyisocyanate, characterized in that: The polyisocyanate described in claim 1 is used for preparing an adhesive.

8. The use of the polyisocyanate according to claim 7, characterized in that: The polyisocyanate is mixed with ethyl acetate solution to form the adhesive.

9. The use of the polyisocyanate according to claim 7, characterized in that: The adhesive is used for bonding metal to metal, metal to plastic, metal to rubber or honeycomb sandwich structure to wallboard.

10. The use of the polyisocyanate according to claim 7, characterized in that: The adhesive is used to bond 45# steel and 5470# rubber, and the bonding strength between the 45# steel and 5470# rubber is 6.07 MPa.

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