Low-viscosity curing agent composition, preparation method and application of low-viscosity curing agent composition in polyurethane adhesive

Abstract

The invention discloses a low-viscosity curing agent composition, a preparation method and application of the low-viscosity curing agent composition in a polyurethane adhesive. The curing agent composition comprises the following components based on the total mass of the composition: A) an isocyanurate derivative of trimethylol alkane modified aliphatic polyisocyanate, the content of which is K1; (B) an isocyanurate derivative of unmodified aliphatic polyisocyanate, wherein the content of the isocyanurate derivative is K2; c) a carbamic acid ester derivative of xylylene diisocyanate, wherein the content of the carbamic acid ester derivative is K3; the curing agent is low in viscosity and high in bonding strength, does not need to be diluted by an additional solvent, and is suitable for preparing a high-strength polyurethane adhesive.

Description

Technical Field

[0001] The present invention relates to an isocyanate curing agent composition, and particularly to a low-viscosity curing agent composition for preparing high-strength polyurethane adhesives and a preparation method thereof. Background Art

[0002] Two-component polyurethane adhesives have been maturely applied in fields such as shoe adhesives, sealants, and packaging laminating adhesives. However, with the continuous enrichment of downstream application scenarios, the demand for the bonding strength of adhesives has also been continuously increasing. The most widely circulated in the market is aromatic polyisocyanate curing agents. For example, Patent CN112341595A discloses a preparation method of a toluene diisocyanate composition, synthesizing a TDI-TMP type aromatic polyisocyanate curing agent, which can be applied to scenarios such as structural adhesives that require high bonding strength. The viscosity of such aromatic polyisocyanates is relatively high. Therefore, during the production of curing agents, organic solvents are usually added for dilution to reduce the viscosity for subsequent processing and use. However, there are also some problems: (1) After long-term storage of the sample, the solvent content is prone to change, resulting in fluctuations in the curing agent indicators, thereby reducing the fault tolerance rate of downstream manufacturers' production equipment and affecting product quality; (2) The solvent in the curing agent needs to be removed by high temperature or long-time air drying, increasing the production cost.

[0003] Based on the above problems, there is temporarily no solvent-free polyisocyanate curing agent product with both high bonding strength and low viscosity on the market. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a low-viscosity curing agent composition and a preparation method. The curing agent has low viscosity, high bonding strength, and does not require external solvent dilution, and is suitable for preparing high-strength polyurethane adhesives.

[0005] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0006] On the one hand, the present invention provides a low-viscosity curing agent composition. In the curing agent composition, based on the total mass of the composition, it contains the following components:

[0007] A) An isocyanurate derivative of an aliphatic polyisocyanate modified with trimethylolalkane, with a content of K 1 ;

[0008] B) An isocyanurate derivative of an unmodified aliphatic polyisocyanate, with a content of K 2 ;

[0009] C) A urethane derivative of benzenedimethyl diisocyanate, with a content of K 3 ;

[0010] The content of each component satisfies: For example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, preferably

[0011] In the present invention, the content of each component can be tested by any method capable of detecting the component content in the composition, preferably by 13 testing by C-NMR nuclear magnetic resonance method.

[0012] In the present invention, the urethane derivative of the benzylidene diisocyanate in component C) comprises a urethane derivative obtained by reacting benzylidene diisocyanate with at least one, preferably 1-2 kinds of trimethylolalkanes; preferably, in the trimethylolalkane, the alkyl group is a straight-chain alkyl group or a cycloalkyl group, and more preferably, the alkyl group has 2-5 carbon atoms, such as 2, 3, 4, 5;

[0013] Further preferably, the trimethylolalkane is selected from one or more of trimethylolpropane, trimethylolcyclohexane, trimethylolbutane, trimethylolpentane, preferably trimethylolpropane.

[0014] In the present invention, the trimethylolalkane in the isocyanurate derivative of the trimethylolalkane-modified aliphatic polyisocyanate in component A) is the same as the trimethylolalkane involved in the above component C).

[0015] In the present invention, the isocyanurate derivative of the trimethylolalkane-modified aliphatic polyisocyanate in component A) and the isocyanurate derivative of the unmodified aliphatic polyisocyanate in component B), wherein the isocyanurate derivative refers to a derivative containing at least an aliphatic polyisocyanate trimer structure, preferably, the aliphatic polyisocyanate trimer is selected from one or more of hexamethylene diisocyanate trimer, pentamethylene diisocyanate trimer, and aliphatic polyisocyanate-modified trimer; wherein the aliphatic polyisocyanate is a straight-chain aliphatic diisocyanate, preferably pentamethylene diisocyanate and / or hexamethylene diisocyanate.

[0016] In the present invention, the low-viscosity curing agent composition has a viscosity of 3200-5350 cP / 25 °C, such as 3200, 3500, 3700, 4000, 4300, 4500, 4800, 5000, 5300 cP / 25 °C.

[0017] The curing agent composition of the present invention has a low viscosity and does not require external solvent dilution. However, it should be noted that even if a solvent is added to the curing agent, its use performance will not be affected. Therefore, the preparation method of diluting the curing agent with a solvent in any ratio also belongs to the protection scope of the present invention.

[0018] On the other hand, the present invention provides a method for preparing the above-mentioned low-viscosity curing agent composition. Those skilled in the art should understand that the following preparation method is only an exemplary illustration of the source mode of the curing agent composition product having the above characteristics of the present invention, but does not constitute any limitation.

[0019] In a preferred embodiment, the present invention provides a method for preparing a low-viscosity curing agent composition, comprising the following steps:

[0020] (1) Reacting xylylene diisocyanate, an isocyanurate derivative of an aliphatic polyisocyanate with a trimethylolalkane to form an NCO-terminated isocyanate prepolymer;

[0021] (2) Subjecting the NCO-terminated isocyanate prepolymer to thin-film evaporation to remove free monomers, thereby obtaining a low-viscosity curing agent composition.

[0022] In step (1) of the present invention, the addition sequence of the xylylene diisocyanate and the isocyanurate derivative of the aliphatic polyisocyanate is not fixed, and the number of additions is not fixed. Preferably, when the xylylene diisocyanate is added for the first time, it should be added earlier than the trimethylolalkane.

[0023] In step (1) of the present invention, the isocyanurate derivative of the aliphatic polyisocyanate refers to a derivative containing at least an aliphatic polyisocyanate trimer structure; preferably, the aliphatic polyisocyanate is selected from linear aliphatic diisocyanates, preferably pentamethylene diisocyanate and / or hexamethylene diisocyanate;

[0024] Preferably, the aliphatic polyisocyanate trimer is selected from one or more of hexamethylene diisocyanate trimer, pentamethylene diisocyanate trimer, and aliphatic polyisocyanate-modified trimer.

[0025] It should be noted that the isocyanurate derivative of the aliphatic polyisocyanate described in the present invention is an existing product and can be synthesized by itself based on the methods disclosed in the prior art. For example, it can be prepared by referring to the methods disclosed in patents CN107531874 and CN116854890; for simplicity of the process, commercially available products can also be directly used, such as HT-100 (Wanhua Chemical), N3300 (Covestro), N7300 (Covestro), etc.

[0026] In step (1) of the present invention, for the trimethylolalkane, the alkyl group is a linear alkyl group or a cycloalkyl group. Preferably, the number of carbon atoms of the alkyl group is 2-5, such as 2, 3, 4, 5;

[0027] Preferably, the trimethylolalkane is selected from one or more of trimethylolpropane, trimethylolcyclohexane, trimethylolbutane, and trimethylolpentane, preferably trimethylolpropane.

[0028] In step (1) of the present invention, the molar ratio of the isocyanurate derivative of the aliphatic polyisocyanate to xylylene diisocyanate is 0.04 - 0.5, preferably 0.04 - 0.45, both calculated based on the isocyanate group (-NCO).

[0029] In step (1) of the present invention, xylylene diisocyanate, calculated based on the isocyanate group (-NCO), and trimethylolalkane, calculated based on the hydroxyl group (-OH), have a molar ratio of 4 - 7, such as 4, 4.5, 5, 5.5, 6, 6.5, 7, preferably 4.3 - 5.6.

[0030] In step (1) of the present invention, for the reaction, the reaction temperature is 55 - 100 °C, such as 55 °C, 65 °C, 75 °C, 85 °C, 95 °C, 100 °C, preferably 55 - 90 °C; the reaction time is 1.2 - 6.0 h, such as 1.2 h, 2 h, 3 h, 4 h, 5 h, 6 h, preferably 1.2 - 5.5 h.

[0031] It should be noted that in the above step (1), if any of the raw materials, namely xylylene diisocyanate, the isocyanurate derivative of the aliphatic polyisocyanate, and trimethylolalkane, are added in multiple batches, the reaction time only needs to ensure that the total time after each addition is within 1.2 - 6.0 h, and the reaction temperature can be adjusted after each addition of the raw material, but the temperature range still needs to be within 55 - 100 °C.

[0032] In step (2) of the present invention, for the thin-film evaporation, the residence time is 6 - 60 min, such as 6 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, preferably 6 - 50 min; the temperature is 140 - 200 °C, such as 140 °C, 150 °C, 160 °C, 120 °C, 180 °C, 190 °C, 200 °C, preferably 140 - 195 °C; the pressure is 0.1 - 120 Pa, such as 0.1 Pa, 5 Pa, 20 Pa, 40 Pa, 60 Pa, 80 Pa, 100 Pa, 120 Pa, preferably 20 - 100 Pa.

[0033] The curing agent composition prepared in step (2) of the present invention does not need to be diluted with an external solvent, but a solvent can also be added for dilution. Specifically, it can be diluted with the solvent in any ratio, but when calculating the component content, the mass of the solvent needs to be deducted;

[0034] If a solvent is to be added to the curing agent composition, the solvent used may be one or more of toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene cyclohexanone, cyclohexane, n-hexane, tetrahydrofuran, chlorobenzene, dichlorobenzene, dichloromethane, dichloroethane, 1,3-dioxane, methyl acetate, ethyl acetate, butyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, ethyl propionate, propyl propionate, butyl propionate.

[0035] In the present invention, the operation processes involved in the above steps (1) and (2) are preferably carried out under an environment of a protective gas (such as nitrogen).

[0036] The low-viscosity curing agent composition of the present invention can be used in the fields of electronic component potting adhesives, automotive structural adhesives, solvent-free wood adhesives, etc., and is particularly suitable for preparing high-strength polyurethane adhesives in the wood field.

[0037] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0038] Due to the low-viscosity characteristic of the curing agent of the present invention, the cumbersome steps of adding a solvent for dilution during the use of traditional polyurethane curing agents are effectively simplified, and at the same time, its products also have the characteristic of high strength. From the perspective of customers, the dilution link is an important factor causing fluctuations in the quality of the final product. The directly usable curing agent can significantly improve the yield rate of the downstream production process. From the perspective of safety and hygiene, the use of solvents is reduced, which is beneficial to the downstream construction environment and the use by end customers. Detailed implementation manners

[0039] The following examples will deeply illustrate the method provided by the present invention. However, the present invention is not limited to the listed examples, and should also include any other well-known changes within the scope of the claims of the present invention. The specific applications of the present invention are not limited to those mentioned in the examples. Those skilled in the art can make extended modifications to the present invention through the concept of the present invention, and these simple changes are within the protection scope of the present invention.

[0040] The following test methods are adopted in the examples of the present invention:

[0041] (1) Test method for the content of derivatives: The 13C-NMR nuclear magnetic resonance method is adopted. The curing agent is prepared into a solution with a concentration of 50% (by mass) CDCl 3 solution, and the instrument used for testing is Bruker 400MHz, and the test condition is 100MHz.

[0042] The signal peak area of the methylene carbon atoms near 40.0 - 40.8 (40.3) ppm represents: the content K of the isocyanurate derivative of the trimethylolalkane - modified aliphatic polyisocyanate in component A 1 ;

[0043] The signal peak area of the methylene carbon atoms near 43.0 - 44.2 (43.8) ppm represents: the content K of the isocyanurate derivative of the unmodified aliphatic polyisocyanate in component B 2 ;

[0044] The signal peak area of the carbonyl carbon atoms near 156.0 - 157.0 (156.2) ppm represents: the content K of the carbamate derivative of benzylidene diisocyanate in component C 3 ;

[0045] (2) Test method for the content of free unreacted isocyanate monomers: Using the national standard GB / T18446 - 2009, it is tested by an Agilent GC - 7890B gas chromatograph of Agilent;

[0046] (3) Test method for viscosity: The dynamic mechanical viscosity is measured using a BrookField DV - I Prime viscometer with an S21 rotor at 25 °C;

[0047] (4) Mechanical property test of the product: The prepared curing agent is formulated according to the "Adhesive Preparation Method". According to JIS K 7110 - 1999, the adhesive is coated on board 1 and bonded to board 2 (bonding area 25 mm × 12.5 mm, bonding layer thickness 0.3 mm). Then, it is cured at 25 °C for 1.5 hours and then cured at room temperature (18 - 28 °C, 45 - 55% RH) for 6 days. Using a sungoll SGL - 8000 tensile testing machine, the peel strength of the bonded boards is measured at a tensile speed of 50 mm / min.

[0048] Adhesive preparation method: The prepared curing agent composition and the mixed polyol are mixed at a ratio such that the equivalent ratio of the isocyanate group in the curing agent to the hydroxyl group in the polyol (NCO / OH) is 1.065. Among them, the mixed polyol is prepared by mixing ACR7502 (Tongde Chemical Industry) and ACTCOL (Mitsui Chemicals) at a mass ratio of 3:2.

[0049] (5) Test method for reactivity: The curing agent and isobutanol are mixed at a ratio of NCO:OH = 1:2 and reacted at 25 °C. Record the change of NCO over time, and the time required for the NCO conversion rate of the curing agent to reach 60% is regarded as the reaction time of the curing agent.

[0050] In the following examples, the raw material information used is as follows:

[0051] m-Xylylene diisocyanate (XDI): Wanhua Chemical, purity > 99%;

[0052] Trimethylolpropane: Pasto, purity > 99%;

[0053] Polyol: ACR7502, Tongde Chemical Industry, purity > 99%;

[0054] Polyol: ACTCOL, Mitsui Chemicals, purity > 99%;

[0055] HT-100: Wanhua Chemical, purity > 99%;

[0056] N3300: Covestro, purity > 99%;

[0057] N7300: Covestro, purity > 99%;

[0058] D-127N: Isocyanurate form of hydrogenated m-xylylene diisocyanate, Mitsui Chemicals, purity > 99%.

[0059] Unless otherwise specified, other raw materials and reagents can be obtained through commercial channels.

[0060] The reaction, separation, and dilution processes of the following examples and comparative examples were all carried out in an environment with sufficient dry nitrogen.

[0061]

Example 1

[0062] Preparation of a low-viscosity curing agent composition:

[0063] Weigh 1200 g (12.75 mol - NCO) of m-xylylene diisocyanate, add 126.75 g (2.87 mol - OH) of trimethylolpropane to it, then add 862.46 g (4.72 mol - NCO) of HT-100, react in a water bath at 65 °C for 2.5 h while keeping stirring, then add 95.83 g (0.52 mol - NCO) of HT-100, and continue to stir for 0.5 h to obtain an isocyanate prepolymer reaction solution containing terminal NCO.

[0064] Separate the residual isocyanate monomer from the reaction solution through a thin-film evaporator. The separation conditions are as follows: residence time 12 min, separation temperature 155 °C, separation pressure 20 Pa. Collect the heavy components, which are the low-viscosity curing agent composition. The performance test results are shown in Table 1.

[0065]

Example 2

[0066] Preparation of a low-viscosity curing agent composition:

[0067] Weigh 1200 g (12.75 mol - NCO) of xylylene diisocyanate, add 129.63 g (3.24 mol - OH) of trimethylolethane to it, then add 287.49 g (1.57 mol - NCO) of HT - 100, react in a water bath at 65 °C for 3.0 h while keeping stirring, and then add 31.94 g (0.17 mol - NCO) of HT - 100 and continue stirring for 0.5 h to obtain an isocyanate prepolymer reaction solution containing terminal NCO.

[0068] Separate the residual isocyanate monomer from the reaction solution through a thin - film evaporator. The separation conditions are as follows: residence time 18 min, separation temperature 165 °C, separation pressure 45 Pa. Collect the heavy fraction, which is the low - viscosity curing agent composition. The performance test results are shown in Table 1.

[0069]

Example 3

[0070] Prepare a low - viscosity curing agent composition:

[0071] Weigh 1200 g (12.75 mol - NCO) of xylylene diisocyanate, add 109.69 g (2.45 mol - OH) of trimethylolpropane to it, then add 442.29 g (2.42 mol - NCO) of N3300, react in a water bath at 55 °C for 4.5 h while keeping stirring, and then add 49.14 g (0.27 mol - NCO) of N3300 and continue stirring for 1.0 h to obtain an isocyanate prepolymer reaction solution containing terminal NCO.

[0072] Separate the residual isocyanate monomer from the reaction solution through a thin - film evaporator. The separation conditions are as follows: residence time 28 min, separation temperature 160 °C, separation pressure 35 Pa. Collect the heavy fraction, which is the low - viscosity curing agent composition. The performance test results are shown in Table 1.

[0073]

Example 4

[0074] Prepare a low - viscosity curing agent composition:

[0075] Weigh 1200 g (12.75 mol - NCO) of xylylene diisocyanate, add 125.09 g (2.80 mol - OH) of trimethylolpropane to it, then add 995.14 g (5.45 mol - NCO) of HT - 100, react in a water bath at 90 °C for 1.0 h while keeping stirring, and then add 110.57 g (0.61 mol - NCO) of HT - 100 and continue stirring for 0.2 h to obtain an isocyanate prepolymer reaction solution containing terminal NCO.

[0076] The reaction solution was separated from the residual isocyanate monomer by a thin-film evaporator under the following separation conditions: residence time of 45 min, separation temperature of 140 °C, and separation pressure of 25 Pa. The heavy fraction was collected, which was the low-viscosity curing agent composition, and the performance test results are shown in Table 1.

[0077]

Example 5

[0078] Preparation of low-viscosity curing agent composition:

[0079] Weigh 1200 g (12.75 mol-NCO) of xylylene diisocyanate, add 300.06 g (1.64 mol-NCO) of HT-100 thereto, then add 126.75 g (2.83 mol-OH) of trimethylolpropane, react in a water bath at 80 °C for 0.5 h, then add 407.60 g (2.23 mol-NCO) of HT-100, react in a water bath at 80 °C for 1.0 h while maintaining stirring, then add 78.63 g (0.43 mol-NCO) of HT-100, and continue to stir for 0.5 h to obtain an isocyanate prepolymer reaction solution composition containing terminal NCO, and the performance test results are shown in Table 1.

[0080] The reaction solution was separated from the residual isocyanate monomer by a thin-film evaporator under the following separation conditions: residence time of 6 min, separation temperature of 195 °C, and separation pressure of 100 Pa. The heavy fraction was collected, which was the low-viscosity curing agent.

[0081]

Example 6

[0082] Preparation of low-viscosity curing agent composition:

[0083] Weigh 1200 g (12.75 mol-NCO) of xylylene diisocyanate, add 118.83 g (2.66 mol-OH) of trimethylolpropane thereto, then add 309.6 g (1.70 mol-NCO) of N7300, react in a water bath at 70 °C for 2.0 h while maintaining stirring, then add 34.40 g (0.19 mol-NCO) of N7300, and continue to stir for 1.0 h to obtain an isocyanate prepolymer reaction solution containing terminal NCO.

[0084] The reaction solution was separated from the residual isocyanate monomer by a thin-film evaporator under the following separation conditions: residence time of 60 min, separation temperature of 180 °C, and separation pressure of 80 Pa. The heavy fraction was collected, which was the low-viscosity curing agent composition, and the performance test results are shown in Table 1.

[0085]

Example 7

[0086] Preparation of low-viscosity curing agent composition:

[0087] Weigh 1200 g (12.75 mol - NCO) of xylylene diisocyanate, add 81.86 g (1.83 mol - OH) of trimethylolpropane to it, then add 88.46 g (0.48 mol - NCO) of HT - 100, react in a 70 °C water bath for 3.0 h while keeping stirring, add another 20 g (0.45 mol - OH) of trimethylolpropane, react in a 70 °C water bath for 0.5 h, and finally add 9.83 g (0.05 mol - NCO) of HT - 100, continue to stir for 1.0 h to obtain an isocyanate prepolymer reaction solution containing terminal NCO.

[0088] Separate the residual isocyanate monomer from the reaction solution through a thin - film evaporator. The separation conditions are as follows: residence time 50 min, separation temperature 155 °C, separation pressure 25 Pa. Collect the heavy fraction, which is the low - viscosity curing agent composition. The performance test results are shown in Table 1.

[0089]

Example 8

[0090] Prepare a low - viscosity curing agent composition:

[0091] Weigh 1200 g (12.75 mol - NCO) of xylylene diisocyanate, add 132.65 g (2.97 mol - NCO) of trimethylolpropane to it, then add 192.39 g (1.05 mol - NCO) of HT - 100, react in a 65 °C water bath for 2.5 h while keeping stirring, add another 21.38 g (0.12 mol - NCO) of HT - 100, and continue to stir for 1.5 h to obtain an isocyanate prepolymer reaction solution containing terminal NCO.

[0092] Separate the residual isocyanate monomer from the reaction solution through a thin - film evaporator. The separation conditions are as follows: residence time 36 min, separation temperature 170 °C, separation pressure 70 Pa. Collect the heavy fraction, which is the low - viscosity curing agent composition. The performance test results are shown in Table 1.

[0093]

Comparative Example 1

[0094] Prepare a curing agent:

[0095] Weigh 1200 g (12.75 mol - NCO) of xylylene diisocyanate, add 126.75 g (2.87 mol - OH) of trimethylolpropane to it, then add 176.91 g (0.97 mol - NCO) of HT - 100, react in a 65 °C water bath for 2.5 h while keeping stirring, add another 19.66 g (0.11 mol - NCO) of HT - 100, and continue to stir for 0.5 h to obtain an isocyanate prepolymer reaction solution containing terminal NCO.

[0096] The reaction solution was separated from the residual isocyanate monomer by a thin-film evaporator under the following separation conditions: residence time 12 min, separation temperature 155 °C, separation pressure 20 Pa. The heavy fraction was collected, which was the curing agent.

[0097]

Comparative Example 2

[0098] Preparation of curing agent:

[0099] Weighed 1200 g (12.75 mol - NCO) of xylylene diisocyanate, added 126.75 g (2.87 mol - NCO) of trimethylolpropane thereto, then added 1194.17 g (6.54 mol - NCO) of HT - 100, reacted in a water bath at 65 °C for 2.5 h while keeping stirring, then added 132.69 g (0.73 mol - NCO) of HT - 100, and continued to stir for 0.5 h to obtain a reaction solution of an isocyanate prepolymer containing terminal NCO.

[0100] The reaction solution was separated from the residual isocyanate monomer by a thin-film evaporator under the following separation conditions: residence time 12 min, separation temperature 155 °C, separation pressure 20 Pa. The heavy fraction was collected, which was the curing agent.

[0101]

Comparative Example 3

[0102] Referring to the method of Example 1, the difference was only that: xylylene diisocyanate was replaced with an equal amount of hydrogenated xylylene diisocyanate, and other operations and conditions remained unchanged. The curing agent was prepared, and the performance test results are shown in Table 1.

[0103]

Comparative Example 4

[0104] Referring to the method of Example 1, the difference was only that: HT - 100 was not added, and other operations and conditions remained unchanged. The curing agent was prepared, and the performance test results are shown in Table 1.

[0105]

Comparative Example 5

[0106] Referring to the method of Example 1, the difference was only that: HT - 100 was replaced with an equal amount of D - 127N, and other operations and conditions remained unchanged. The curing agent was prepared, and the performance test results are shown in Table 1.

[0107]

Comparative Example 6

[0108] Referring to the method of Example 1, the difference was only that: trimethylolpropane was not added, and other operations and conditions remained unchanged. The curing agent was prepared, and the performance test results are shown in Table 1.

[0109] Table 1 Basic indicators and performance test results of examples and comparative examples

[0110]

[0111]

Claims

1. A low-viscosity curing agent composition, characterized in that it contains the following components based on the total mass of the composition: A) Isocyanurate derivatives of trimethylolalkane-modified aliphatic polyisocyanates, content K 1 ; B) Isocyanurate derivatives of unmodified aliphatic polyisocyanates, content being K 2 ; C) Carbamate derivatives of xylylene diisocyanate, with a content of K 3 ; The content of each component satisfies: Preferably 2. The low-viscosity curing agent composition according to claim 1, characterized in that the urethane derivative of the benzylidene diisocyanate in component C) contains a urethane derivative obtained by reacting benzylidene diisocyanate with at least one, preferably 1-2, trimethylolalkanes; preferably, in the trimethylolalkane, the alkyl group is a straight-chain alkyl group or a cycloalkyl group, and more preferably, the alkyl group has 2-5 carbon atoms; more preferably, the trimethylolalkane is selected from one or more of trimethylolpropane, trimethylolcyclohexane, trimethylolbutane, and trimethylolpentane, preferably trimethylolpropane; preferably, the trimethylolalkane in the isocyanurate derivative of the trimethylolalkane-modified aliphatic polyisocyanate in component A) is the same as the trimethylolalkane in component C).

3. The low-viscosity curing agent composition according to claim 1, characterized in that the isocyanurate derivative of the trimethylolalkane-modified aliphatic polyisocyanate in component A) and the isocyanurate derivative of the unmodified aliphatic polyisocyanate in component B), wherein the isocyanurate derivative refers to a derivative containing at least an aliphatic polyisocyanate trimer structure, preferably, the aliphatic polyisocyanate trimer is selected from one or more of hexamethylene diisocyanate trimer, pentamethylene diisocyanate trimer, and aliphatic polyisocyanate-modified trimer; wherein the aliphatic polyisocyanate is a straight-chain aliphatic diisocyanate, preferably pentamethylene diisocyanate and / or hexamethylene diisocyanate.

4. The low-viscosity curing agent composition according to any one of claims 1-3, characterized in that the low-viscosity curing agent composition has a viscosity of 3200-5350 cP / 25 °C.

5. A method for preparing the low-viscosity curing agent composition according to any one of claims 1-4, characterized in that it comprises the following steps: (1) Reacting benzylidene diisocyanate, the isocyanurate derivative of the aliphatic polyisocyanate, and the trimethylolalkane to form an isocyanate prepolymer with terminal NCO; (2) Subjecting the isocyanate prepolymer with terminal NCO to thin-film evaporation to remove free monomers to obtain the low-viscosity curing agent composition.

6. The preparation method according to claim 5, characterized in that in step (1), the isocyanurate derivative of the aliphatic polyisocyanate refers to a derivative containing at least an aliphatic polyisocyanate trimer structure; preferably, the aliphatic polyisocyanate is selected from straight-chain aliphatic diisocyanates, more preferably pentamethylene diisocyanate and / or hexamethylene diisocyanate; preferably, the aliphatic polyisocyanate trimer is selected from one or more of hexamethylene diisocyanate trimer, pentamethylene diisocyanate trimer, and aliphatic polyisocyanate-modified trimer. Preferably, the isocyanurate derivative of the aliphatic polyisocyanate is one or more of Wanhua Chemical HT-100, Covestro N3300, and Covestro N7300.

7. The preparation method according to claim 5, characterized in that, in step (1), for the trimethylolalkane, the alkyl group therein is a straight-chain alkyl group or a cycloalkyl group. Preferably, the number of carbon atoms of the alkyl group is 2-5; preferably, the trimethylolalkane is selected from one or more of trimethylolpropane, trimethylolcyclohexane, trimethylolbutane, trimethylolpentane, and preferably trimethylolpropane.

8. The preparation method according to claim 5, characterized in that, in step (1), the molar ratio of the isocyanurate derivative of the aliphatic polyisocyanate to xylylene diisocyanate is 0.04-0.5, preferably 0.04-0.45, both calculated based on the isocyanate group (-NCO); and / or in step (1), xylylene diisocyanate calculated based on the isocyanate group (-NCO) and the trimethylolalkane calculated based on the hydroxyl group (-OH) have a molar ratio of 4-7, preferably 4.3-5.6; and / or in step (1), for the reaction, the reaction temperature is 55-100 °C, preferably 55-90 °C; the reaction time is 1.2-6.0 h, preferably 1.2-5.5 h.

9. The preparation method according to claim 5, characterized in that, in step (2), for the thin-film evaporation, the residence time is 6-60 min, preferably 6-50 min; the temperature is 140-200 °C, preferably 140-195 °C; the pressure is 0.1-120 Pa, preferably 20-100 Pa.

10. The application of the low-viscosity curing agent composition according to any one of claims 1-4 or the low-viscosity curing agent composition prepared by the method according to any one of claims 5-9 in the fields of electronic component potting adhesives, automotive structural adhesives, and solvent-free wood adhesives, and is particularly suitable for preparing high-strength polyurethane adhesives in the wood field.

Images