Carbodiimide modified TDI catalyst, preparation method and application thereof

Abstract

The invention provides a carbodiimide modified TDI catalyst, a preparation method and application thereof, the structure of the carbodiimide modified TDI catalyst is shown as a formula 1: in the formula 1 # imgabs0 #, R is selected from C1-C5 alkyl groups and C6-C9 alkaryl groups, preferably C1-C3 alkyl groups, such as methyl, ethyl, propyl, phenyl and benzyl. Compared with a conventional catalyst, the catalyst has the greatest advantages that the selectivity to 2, 4-TDI and 2, 6-TDI is the same, and the reduction of 2, 6-TDI monomers in TDI curing agent raw materials is realized, so that the preparation of a TDI tripolymer curing agent with low dissociation (less than 0.4%), low viscosity and high tolerance is realized.

Description

Technical Field

[0001] The invention relates to a method for preparing a novel catalyst for carbodiimide-modified TDI, and also relates to application of the novel catalyst-modified TDI in synthesizing a low-free TDI trimer curing agent. Background Art

[0002] Toluene diisocyanate (TDI) is the main raw material for the preparation of polyurethane foams, elastomers, coatings and adhesives. As a curing agent, TDI trimer has the advantages of low volatility, high functionality, and excellent paint film properties. Under appropriate temperature and catalyst, TDI will undergo trimerization reaction, and trimers, pentamers, heptamers and polymers with larger molecular weights will be generated according to the number of molecules involved in the reaction.

[0003] Free TDI monomers can cause irreversible damage to the respiratory system of construction workers, so reducing the free TDI content in polyurethane curing agents has become a key research direction for curing agent research at home and abroad. The national standard GB1858-2009 "Limits of Harmful Substances in Solvent-Based Wood Coatings for Indoor Decoration and Renovation Materials" stipulates that the limit value of free TDI after paint preparation should be ≤0.4%, which means that the free TDI content in the curing agent must be reduced to below 0.7% to meet the national standard.

[0004] So far, the methods reported to reduce the free monomer content include solvent extraction, thin film evaporation, molecular sieve absorption, chemical method, supercritical extraction, etc. In order to improve the compatibility of the product with the hydroxy resin and make the molecular weight distribution of the product uniform, the incomplete reaction method is generally adopted, that is, the reaction is terminated when the reaction reaches about 60%, and a thin film evaporator is used to remove the unreacted monomer. In recent years, thin film evaporation technology has been continuously improved and equipment has been continuously upgraded. Representative companies at home and abroad that adopt this technology route, such as Bayer, Dow, BASF, Wanhua, and Bogao, can reduce the free TDI content of curing agent products to ≤0.2%. However, the paint film prepared by the trimer under this process dries very slowly, especially in the winter in the north, and the performance of the paint film is not as good as the trimer prepared by the chemical method.

[0005] The chemical process is achieved by changing the formula and increasing the degree of reaction. Under the premise of ensuring low free monomers, it will directly lead to excessive product viscosity, poor compatibility with hydroxyl resins, dark color, and unstable process. Therefore, through the chemical process, low free monomer content is achieved, and extremely low viscosity is guaranteed to provide fluidity and high tolerance to ensure compatibility with hydroxyl resins. There is still great prospect in the curing agent.

[0006] TDI is limited in its application in certain areas of polyurethane due to its low viscosity, low functionality, and high volatility. According to the reaction characteristics of isocyanate, it can be modified in a variety of ways to expand the application of TDI and improve the comprehensive performance of downstream products.

[0007] At present, the commonly used methods and main uses of modified TDI are: TDI-carbamate modification, mainly used in HR foam, integral foam, coating, adhesive; TDI-isocyanurate modification, mainly used in HR foam, coating, adhesive; TDI-alophanate modification and TDI-polyamine condensation modification, used in HR foam; TDI-prepolymer modification, used in sealing materials, microporous foam; and modified TDI-polymerized MDI mixture, etc. At present, TDI-carbodiimide modified products and their applications in the field of curing agents have not been seen. The main reason is that the effective components of existing catalyst-modified TDI are low, and low molecular weight effective components cannot be selectively synthesized, resulting in the problem of product solidification precipitation. Summary of the invention

[0008] The above description shows that the chemical process for preparing TDI trimer curing agent cannot take into account the performance of low free, low viscosity and high tolerance, and there is no TDI-carbodiimide modified product. In view of this, the present invention first provides a new catalyst preparation method for carbodiimide modified TDI, and uses the TDI modified by the new catalyst to chemically synthesize a TDI trimer curing agent with low free, low viscosity and high tolerance.

[0009] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0010] In the first aspect, the present invention provides a catalyst for carbodiimide-modified TDI, the structure of which is shown in Formula 1:

[0011]

[0012] In formula 1, R is selected from C1-C5 alkyl, C6-C9 alkylaryl, preferably C1-C3 alkyl, such as methyl, ethyl, propyl, phenyl, benzyl.

[0013] In a second aspect, the present invention provides a method for preparing the catalyst represented by the above formula 1, comprising the following steps:

[0014] 1) The carboxyl-substituted benzenesulfonate shown in Formula 2 is reacted with an amide to prepare an intermediate A shown in Formula 3

[0015] 2) using the intermediate A shown in formula 3 and 1-chloromethyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane di(tetrafluoroborate) salt as raw materials to react and prepare the intermediate B shown in formula 4;

[0016] 3) using N-chlorosuccinimide (NCS) and thiocyanate as raw materials to react to prepare the intermediate C described in formula 5;

[0017] 4) using the intermediate B prepared in step 2) and the intermediate C prepared in step 3) as raw materials and a chiral dinitrogen oxide ligand as a catalyst to react and prepare a catalyst shown in formula 1;

[0018] Among them, the carboxyl-substituted benzenesulfonate shown in Formula 2, the intermediate A shown in Formula 3, the intermediate B shown in Formula 4, and the intermediate C shown in Formula 5 have the structure:

[0019]

[0020] In Formula 2 and Formula 3, the definition of R is the same as that of R in Formula 1.

[0021] In the present invention, the carboxyl-substituted benzenesulfonate in step 1) is selected from at least one of carboxyl-substituted benzenesulfonate methyl ester, carboxyl-substituted benzenesulfonate ethyl ester, carboxyl-substituted benzenesulfonate butyl ester, and carboxyl-substituted benzenesulfonate phenol ester, preferably at least one of carboxyl-substituted benzenesulfonate methyl ester and carboxyl-substituted benzenesulfonate phenol ester.

[0022] In the present invention, the amide in step 1) is selected from 2-benzoylacetamide.

[0023] In the present invention, the molar ratio of the carboxyl-substituted benzene sulfonate to 2-benzoyl acetamide in step 1) is 1:1-4:1, the reaction temperature is 60-100°C, the reaction time is 0.5-5h, and the solvent can be acetonitrile or dioxane. Preferably, the molar ratio of the carboxyl-substituted benzene sulfonate to 2-benzoyl acetamide is 2:1-3:1, the reaction temperature is 70-90°C, the reaction time is 1-3h, and the reaction solvent is dioxane.

[0024] In the present invention, the 1-chloromethyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane di(tetrafluoroborate) salt in step 2) is 1-chloromethyl-4-fluoro-1,4-diazobicyclo-2.2.2octane ditetrafluoroborate (CAS140681-55-6).

[0025] In the present invention, the molar ratio of the intermediate A in step 2) to 1-chloromethyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane di(tetrafluoroborate) salt is 1:0.5 to 1:4, for example, 1:0.5, 1:1, 1:2, 1:3, 1:4, preferably 1:0.8 to 1:1.2.

[0026] In the present invention, in the reaction of step 2), the system further comprises an optional solvent, and the solvent is selected from at least one of an acetonitrile aqueous solution, an N-methylformamide aqueous solution, and an N-methylpyrrolidone aqueous solution, and preferably the volume ratio of acetonitrile or N-methylformamide or N-methylpyrrolidone to water is 1:2 to 2:1; for example, 1:2, 1:1, 2:1.

[0027] In the present invention, the amount of the solvent in step 2) is 150-250 ml / mol of intermediate A, for example, 150, 175, 200, 225, 250 ml / mol of intermediate A.

[0028] In the present invention, the reaction in step 2) is carried out at a temperature of 20 to 40°C, such as 20, 25, 30, 35, 40°C, preferably 25-30°C, and for a time of 2 to 8h, such as 2, 4, 6, 8h, preferably 3 to 6h.

[0029] After the reaction in step 2) is completed, the process further includes extraction with an organic solvent such as ethyl acetate, standing for phase separation, and removing the extractant by rotary evaporation, which are all conventional operation methods in the field and are not particularly required by the present invention.

[0030] In the present invention, the thiocyanate in step 3) is selected from at least one of potassium thiocyanate, sodium thiocyanate and ammonium thiocyanate.

[0031] In the present invention, the molar ratio of N-chlorosuccinimide to thiocyanate in step 3) is 1:1 to 1:4, for example, 1:1, 1:2, 1:3, 1:4, preferably 1:2 to 1:3.

[0032] In the present invention, in the reaction of step 3), the system further comprises an optional solvent, and the solvent is selected from at least one of N-methylformamide, N-methylpyrrolidone, and acetonitrile, preferably acetonitrile.

[0033] Preferably, the amount of the solvent is 150-250 ml / mol N-chlorosuccinimide, for example 150, 175, 200, 225, 250 ml / mol N-chlorosuccinimide.

[0034] In the present invention, the reaction temperature in step 3) is 20-40°C, such as 20, 25, 30, 35, 40°C, preferably 25-30°C, and the reaction time is 15-60 min, such as 15, 30, 45, 60 min, preferably 30-45 min.

[0035] After the reaction is completed, post-treatment processes such as filtering to remove salt and rotary evaporation to remove solvent are also included, which are conventional operation methods in the field and have no special requirements in the present invention.

[0036] In the present invention, the molar ratio of the intermediate B to the intermediate C in step 4) is 2:1 to 1:4, for example, 2:1, 1:1, 1:2, 1:3, 1:4, preferably 1:1 to 1:1.5.

[0037] In the present invention, the chiral dinitrogen oxide ligand in step 4) is selected from at least one of 2,3-bipyridine dinitrogen oxide, 2,5-dimethylpyrazine dinitrogen oxide, and phenolazine dinitrogen oxide.

[0038] Preferably, the amount of the chiral dinitrogen oxide ligand catalyst is 1-10% of the total mass of intermediate A and intermediate B, such as 1, 3, 6, 9, 10%, preferably 3-7%.

[0039] In the present invention, in the reaction of step 4), the system optionally further comprises a solvent, and the solvent is selected from at least one of petroleum ether, dichloromethane, chloroform, and dichloroethane, preferably chloroform.

[0040] Preferably, the amount of the solvent is 150-250 ml / mol (intermediate B + intermediate C), for example 150, 175, 200, 225, 250 ml / mol (intermediate A + intermediate B).

[0041] In the present invention, the reaction in step 4) is carried out at a temperature of 25 to 50°C, such as 20, 25, 30, 35, 40, 45, 50°C, preferably 25 to 35°C, and for a time of 0.5 to 8h, such as 0.5, 2, 4, 6, 8h, preferably 1 to 3h.

[0042] After the reaction is completed, the post-treatment processes include silica gel column separation, elution, and solvent removal by rotary evaporation, which are all conventional operating methods in the field. The present invention has no special requirements. It is preferred to use 300-400 mesh silica gel column chromatography to separate the catalyst and the product, and use n-hexane: ethyl acetate = 1:1 for elution.

[0043] In a third aspect, the present invention provides a method for preparing a TDI trimer curing agent, the method comprising the following steps:

[0044] 1) Under nitrogen protection, a catalyst is added to toluene diisocyanate monomer, and the mixture is stirred at a certain temperature for 1 to 4 hours to obtain carbodiimide-modified TDI;

[0045] 2) Under nitrogen protection, polar solvent and hydroxyl trimerization catalyst are added to modified TDI, and the mixture is kept warm at 50-60°C for 4-8 hours to obtain a modified TDI prepolymer; then small molecule alcohol is added to the modified TDI prepolymer, and the mixture is kept warm at 50-60°C for 1-2 hours; finally, an inhibitor is added, and the mixture is kept warm for another 1-2 hours, and the temperature is lowered and the material is discharged to obtain a modified TDI trimer curing agent.

[0046] The toluene diisocyanate in step 1) is 2,4-toluene diisocyanate (2,4-TDI) or 2,6-toluene diisocyanate (2,6-TDI) or a mixture of the two, preferably TDI-80 (2,4-TDI / 2,6-TDI=80 / 20);

[0047] The amount of the modified catalyst in step 1) is 0.05-1% of the mass of the TDI monomer, and the catalyst structural formula is as follows:

[0048] As shown in formula 1:

[0049]

[0050] In step 1), the reaction temperature is 100-150° C. and the stirring speed is 100-300 r / min.

[0051] In step 2), the polar solvent is one or more of ethyl acetate, butyl acetate, and sec-butyl acetate, and the amount of the polar solvent added is 0.5 to 2 times the mass of the modified TDI.

[0052] The hydroxyl-containing trimerization catalyst in step 2) is one or more of DMP-30, Mannich base, trimethylhydroxypropyl ammonium salt, preferably DMP-30. The amount of the hydroxyl-containing trimerization catalyst added is 0.05% to 0.5% of the total mass of the modified TDI and the polar solvent.

[0053] The small molecule alcohol in step 2) is one or more of ethylene glycol, propylene glycol, n-butanol, n-pentanol, n-decanol, n-dodecyl alcohol, and trimethylolpropane, and the added amount is 1-4% of the total mass of the modified TDI and the polar solvent.

[0054] The inhibitor in step 2) is one or more of phosphoric acid, benzoyl chloride, and oxalyl chloride, and the added amount is 0.1-1% of the total amount of the hydroxyl-containing small molecule alcohol, modified TDI, and polar solvent.

[0055] Compared with the prior art, the present invention has the following advantages:

[0056] 1. The present invention synthesizes a new catalyst to catalyze the polymerization modification of TDI monomer. The biggest advantage of the catalyst over conventional catalysts is that the selectivity for 2,4-TDI and 2,6-TDI is the same, which reduces the 2,6-TDI monomer in the TDI curing agent raw material, thereby realizing the preparation of a TDI trimer curing agent with low free (<0.4%), low viscosity and high tolerance;

[0057] 2. The present invention uses chemical method to achieve the modification of carbodiimide in TDI system. The molecular weight of carbodiimide is controllable, and the degree of polymerization is 1-3, which ensures the reaction activity when synthesizing trimer. When the content of modified component reaches 50%, there will be no solid precipitation and deterioration problem. This is impossible to achieve with conventional catalysts. DETAILED DESCRIPTION

[0058] The sources of the chemical reagents and raw materials in the following examples are shown in the following table. Unless otherwise specified, other raw materials and reagents were purchased from commercial sources:

[0059]

[0060]

[0061] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0062] In the following examples, unless otherwise specified, percentages (%) are all mass percentages. The free monomer content is determined according to GB / T18446-2009, the NCO percentage is determined according to HG / T2409-1992, and the solid content is determined according to GB / 2793-1995.

[0063] A method for preparing carbodiimide-modified TDI and its application in synthesizing a low-free TDI trimer curing agent, comprising the following steps:

[0064] 1. Preparation of catalyst:

[0065] Preparation Example

[0066] Synthesis of Catalyst Intermediate B - Example 1:

[0067] In a 500ml reactor with a reflux condenser, add 2mol of methyl p-toluenesulfonate, 300ml of 50% acetic acid aqueous solution, and 2.5mol of KMnO4 in sequence, reflux for 1h, cool, filter, and spin-dry the solvent. Dissolve it in 200ml of tetrahydrofuran and add 2mol of NH3.H2O in a 500ml round-bottom flask, reflux for 1h, then add 2mol of benzoylacetic acid, and continue to reflux for 1.5h. After cooling to room temperature, add 200ml of water, extract with ethyl acetate, stand for phase separation, take out the organic phase, and remove the ethyl acetate extractant by rotary evaporation at 50°C and 25mmHg to obtain intermediate A1.

[0068] Dissolve 1 mol of intermediate A1 and 0.8 mol of 1-chloromethyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane di(tetrafluoroborate) salt in 200 ml of acetonitrile and water mixture (V:V=1:1), add into a 500 ml reactor equipped with a thermometer and a reflux condenser, control the temperature of the reaction system at 25°C, and stir to react for 4 hours. After the reaction is completed, extract the reactant with ethyl acetate, stand for phase separation, take out the organic phase, and remove the ethyl acetate extractant by rotary evaporation at 50°C and 25 mmHg pressure to obtain intermediate B1; the reaction formula is as follows:

[0069]

[0070] 1H NMR(DMSO-d6,300MHz):3.85(s,3H),5.77(s,1H),7.55(dd,2H),7.68(d,1H),7.98(d,2H),8.00(d,2H)8.39(d,2H)11.69(s,1H).

[0071] Synthesis of Catalyst Intermediate B - Example 2:

[0072] In a 500ml reactor with a reflux condenser, add 2mol of phenyl p-toluenesulfonate, 300ml of 50% acetic acid aqueous solution, and 2.5mol of KMnO4 in sequence, reflux for 1h, cool, filter, and spin-dry the solvent. Dissolve it in 200ml of tetrahydrofuran and add 2mol of NH3.H2O in a 500ml round-bottom flask, reflux for 1h, then add 2mol of benzoylacetic acid, and continue to reflux for 1.5h. After cooling to room temperature, add 200ml of water, extract with ethyl acetate, stand for phase separation, take out the organic phase, and remove the ethyl acetate extractant by rotary evaporation at 50°C and 25mmHg to obtain intermediate A2

[0073] Dissolve 1 mol of intermediate A2 and 1.2 mol of 1-chloromethyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane di(tetrafluoroborate) salt in 200 ml of N-methylformamide and water mixture (V:V=1.5:1), add into a 500 ml reactor equipped with a thermometer and a reflux condenser, control the temperature of the reaction system at 25°C, and stir the reaction for 6 hours. After the reaction is completed, extract the reactants with ethyl acetate, stand for phase separation, take out the organic phase, and remove the ethyl acetate extractant by rotary evaporation at 50°C and 25 mmHg pressure to obtain intermediate A-2; the reaction formula is as follows:

[0074]

[0075] 1 H NMR(DMSO-d6,300MHz):5.79(s,1H),6.92(m,2H),7.02(m,1H),7.3(m,2H),7 .55(m,2H),7.68(m,1H),7.98(d,2H),8.0(d,2H),8.4(d,2H),11.68(s,1H).

[0076] Synthesis of Catalyst Intermediate C - Example 1:

[0077] Dissolve 1 mol of NCS (N-chlorosuccinimide) and 2 mol of potassium thiocyanate in 200 ml of acetonitrile solvent, add into a 500 ml reactor equipped with a thermometer and a reflux condenser, control the temperature of the reaction system at 25°C, stir and react for 30 minutes, filter out excess salt, and evaporate the solvent and unreacted NCS at 50°C and 25 mmHg to obtain intermediate C; the reaction formula is as follows:

[0078]

[0079] 1 H NMR (DMSO-d6, 300MHz): 2.64 (s, 4H).

[0080] Synthesis of Catalyst Intermediate C-Example 2:

[0081] 1 mol of NCS (N-chlorosuccinimide) and 3 mol of ammonium thiocyanate were dissolved in 250 ml of N-methylpyrrolidone solvent, added into a 500 ml reactor equipped with a thermometer and a reflux condenser, the temperature of the reaction system was controlled at 30°C, stirred for 40 min, excess salt was filtered out, and the solvent and unreacted NCS were evaporated at 50°C and 25 mmHg to obtain intermediate B; the reaction formula is as follows:

[0082]

[0083] 1 H NMR (DMSO-d6, 300MHz): 2.64 (s, 4H).

[0084] Synthetic Catalyst - Example 1:

[0085] Dissolve 0.5 mol of intermediate B-1 (R group is methyl) and 0.5 mol of intermediate C in 200 ml of chloroform solvent, add 3% of the total mass of intermediate B + intermediate C catalyst 2,3'-bipyridine-diazolyl oxide, add to a 500 ml reactor equipped with a thermometer and a reflux condenser, stir and react at 25°C for 2h, and separate the catalyst and product by 300-400 mesh silica gel column chromatography, use n-hexane: ethyl acetate = 1:1 for elution, and evaporate the solvent at 50°C and 25 mmHg pressure to obtain catalyst-1; the reaction formula is as follows:

[0086]

[0087] 1 H NMR (DMSO-d6, 300MHz): 3.85 (s, 3H), 7.55 (m, 2H), 7.68 (s, 1H), 7.98 (d, 2H), 8.00 (d, 2H), 8.39 (d, 2H), 11.69 (s, 1H).

[0088] Synthetic Catalyst - Example 2:

[0089] 0.5 mol of intermediate B-2 (R group is phenyl) and 0.4 mol of C are dissolved in 200 ml of chloroform solvent, and 4% of the total mass of intermediate B + intermediate C catalyst 2,3'-bipyridine-diazolyl oxide is added, and added into a 500 ml reactor equipped with a thermometer and a reflux condenser, and stirred at 35°C for 2 hours. The reaction liquid is separated from the catalyst and the product by 300-400 mesh silica gel column chromatography, and eluted with n-hexane: ethyl acetate = 1:2, and the solvent is evaporated at 50°C and 25 mmHg pressure to obtain catalyst-2; the reaction formula is as follows:

[0090]

[0091] 1 H NMR(DMSO-d6,300MHz):6.92(d,2H),7.02(m,1H),7.30(m,2H),7.55(m,2H),7.68(m,1H),7.98(d,2H),8.00(d,2H),8.40(d,2H),11.69(s,1H).

[0092] Example 1

[0093] Under nitrogen protection, 300 g of TDI-80 was added to a 500 ml four-necked flask equipped with a stirring paddle and a thermometer, the stirring speed was 200 r / min, 1.5 g of catalyst-1 was added, the temperature was raised to 100 ° C, and the temperature was kept for 2 h to obtain modified carbodiimide modified TDI;

[0094] Under nitrogen protection, add 300g of modified TDI and 300g of butyl acetate to a 1000ml four-necked flask equipped with a stirring paddle and a thermometer, heat to 50°C, add 0.3g of DMP-30 with a dropper and keep warm for 8h. Then add 6g of n-butanol, keep warm for 1h, add 0.6g of benzoyl chloride to terminate the reaction and keep warm for 1h, cool down and discharge to obtain TDI trimer curing agent.

[0095] The physical and chemical properties of the modified TDI and trimer curing agent obtained by the above preparation method are as follows:

[0096] Modified TDI: colorless transparent liquid, TDI monomer content 90%, dicyclic CDI content 9.5%, UTI content 0.5%;

[0097] Curing agent: colorless transparent liquid, solid content 50.5%, NCO=7.83, viscosity 356mPa·s, free TDI content 0.36%.

[0098] Example 2

[0099] Under nitrogen protection, add 300g of TDI-80 to a 500ml four-necked flask equipped with a stirring paddle and a thermometer, stir at a speed of 200r / min, add 3g of catalyst-1, heat to 110°C, and keep the temperature for 1h to obtain modified carbodiimide modified TDI;

[0100] Under nitrogen protection, add 300g of modified TDI and 300g of ethyl acetate to a 1000ml four-necked flask equipped with a stirring paddle and a thermometer, heat to 55°C, add 0.6g of DMP-30 with a dropper and keep warm for 6h. Then add 24g of n-dodecyl alcohol and keep warm for 1h, add 6g of benzoyl chloride to terminate the reaction and keep warm for 1h, cool down and discharge to obtain a polyurethane curing agent.

[0101] The physical and chemical properties of the modified TDI and trimer curing agent obtained by the above preparation method are as follows:

[0102] Modified TDI: colorless transparent liquid, TDI monomer content 88%, dicyclic CDI content 11.2%, UTI content 0.8%;

[0103] Curing agent: colorless transparent liquid, solid content 51%, NCO=8.12, viscosity 342mPa·s, free TDI content 0.26%.

[0104] Example 3

[0105] Under nitrogen protection, 300 g of TDI-80 was added to a 500 ml four-necked flask equipped with a stirring paddle and a thermometer, the stirring speed was 200 r / min, 0.15 g of catalyst-1 was added, the temperature was raised to 150°C, and the reaction was kept warm for 4 hours to obtain modified carbodiimide modified TDI;

[0106] Under nitrogen protection, add 300g of modified TDI and 300g of ethyl acetate to a 1000ml four-necked flask equipped with a stirring paddle and a thermometer, heat to 60°C, add 3g of DMP-30 with a dropper and keep warm for 4h. Then add 12g of n-dodecyl alcohol and keep warm for 1h, add 3g of benzoyl chloride to terminate the reaction and keep warm for 1h, cool down and discharge to obtain a polyurethane curing agent.

[0107] The physical and chemical properties of the modified TDI and trimer curing agent obtained by the above preparation method are as follows:

[0108] Modified TDI: colorless transparent liquid, TDI monomer content 85%, dicyclic CDI content 14.2%, UTI content 0.8%;

[0109] Curing agent: colorless transparent liquid, solid content 50.5%, NCO=7.95, viscosity 361mPa·s, free TDI content 0.23%.

[0110] Example 4

[0111] Under nitrogen protection, add 300g of TDI-80 to a 500ml four-necked flask equipped with a stirring paddle and a thermometer, stir at a speed of 200r / min, add 0.2g of catalyst-2, heat to 130°C, and keep warm for 4h to obtain modified carbodiimide modified TDI;

[0112] Under nitrogen protection, add 300g of modified TDI and 300g of butyl acetate to a 1000ml four-necked flask equipped with a stirring paddle and a thermometer, heat to 60°C, add 3g of DMP-30 with a dropper and keep warm for 4h. Then add 12g of n-decanol and keep warm for 1h, add 0.6g of benzoyl chloride to terminate the reaction and keep warm for 1h, cool down and discharge to obtain a polyurethane curing agent.

[0113] The physical and chemical properties of the modified TDI and trimer curing agent obtained by the above preparation method are as follows:

[0114] Modified TDI: colorless transparent liquid, TDI monomer content 87.5%, dicyclic CDI content 12%, UTI content 0.5%;

[0115] Curing agent: colorless transparent liquid, solid content 49.8%, NCO=8.05, viscosity 348mPa·s, free TDI content 0.18%.

[0116] Example 5

[0117] Under nitrogen protection, add 300g of TDI-80 to a 500ml four-necked flask equipped with a stirring paddle and a thermometer, stir at a speed of 200r / min, add 2g of catalyst-2, heat to 100°C, and keep warm for 3h to obtain modified carbodiimide modified TDI;

[0118] Under nitrogen protection, add 300g of modified TDI and 300g of butyl acetate to a 1000ml four-necked flask equipped with a stirring paddle and a thermometer, heat to 55°C, add 2.4g of DMP-30 with a dropper and keep warm for 6h. Then add 12g of n-butanol and keep warm for 1h, add 0.6g of benzoyl chloride to terminate the reaction and keep warm for 1h, cool down and discharge to obtain a polyurethane curing agent.

[0119] The physical and chemical properties of the modified TDI and trimer curing agent obtained by the above preparation method are as follows:

[0120] Modified TDI: colorless transparent liquid, TDI monomer content 86.5%, dicyclic CDI content 12%, UTI content 1.5%;

[0121] Curing agent: colorless transparent liquid, solid content 51%, NCO=7.7, viscosity 330mPa·s, free TDI content 0.21%.

[0122] To illustrate the advantages of the self-made catalyst in the present invention, the TDI polymer modified by the conventional catalyst increases, and even milky white fogging problem occurs. The viscosity and free monomer of the curing agent synthesized by using the modified TDI as the raw material are both high. The specific effects are as follows: Comparative Example 1

[0123] Under nitrogen protection, add 300g of TDI-80 to a 500ml four-necked flask equipped with a stirring paddle and a thermometer, stir at a speed of 200r / min, add 2g of triphenylphosphine, heat to 100°C, and keep warm for 3h to obtain modified carbodiimide modified TDI;

[0124] Under nitrogen protection, add 300g of modified TDI and 300g of butyl acetate to a 1000ml four-necked flask equipped with a stirring paddle and a thermometer, heat to 55°C, add 2.4g of DMP-30 with a dropper and keep warm for 6h. Then add 12g of n-butanol and keep warm for 1h, add 0.6g of benzoyl chloride to terminate the reaction and keep warm for 1h, cool down and discharge to obtain a polyurethane curing agent.

[0125] The physical and chemical properties of the modified TDI and trimer curing agent obtained by the above preparation method are as follows:

[0126] Modified TDI: colorless transparent liquid, TDI monomer content 80.5%, dicyclic CDI content 1.5%, UTI content 18%; Curing agent: milky white liquid, solid content 51.2%, NCO=6.5, viscosity 1330mPa·s, free TDI content 0.87%.

[0127] Comparative Example 2

[0128] Under nitrogen protection, add 300g of TDI-80 to a 500ml four-necked flask equipped with a stirring paddle and a thermometer, stir at a speed of 200r / min, add 2g of triethyl phosphate, heat to 100°C, and keep warm for 3h to obtain modified carbodiimide modified TDI;

[0129] Under nitrogen protection, add 300g of modified TDI and 300g of butyl acetate to a 1000ml four-necked flask equipped with a stirring paddle and a thermometer, heat to 55°C, add 2.4g of DMP-30 with a dropper and keep warm for 6h. Then add 12g of n-butanol and keep warm for 1h, add 0.6g of benzoyl chloride to terminate the reaction and keep warm for 1h, cool down and discharge to obtain a polyurethane curing agent.

[0130] The physical and chemical properties of the modified TDI and trimer curing agent obtained by the above preparation method are as follows:

[0131] Modified TDI: milky white misty liquid, TDI monomer content 75%, dicyclic CDI content 2%, UTI content 23%; curing agent: milky white liquid, solid content 51.2%, NCO=6.5, viscosity 1850mPa·s, free TDI content 1.2%.

Claims

1. A catalyst for carbodiimide-modified TDI, the structure of which is shown in Formula 1: In formula 1, R is selected from C1-C5 alkyl, C6-C9 alkylaryl, preferably C1-C3 alkyl, such as methyl, ethyl, propyl, phenyl, benzyl.

2. The method for preparing the catalyst according to claim 1, characterized in that: The following steps are involved: 1) The carboxyl-substituted benzenesulfonate shown in Formula 2 is reacted with an amide to prepare an intermediate A shown in Formula 3 2) using the intermediate A shown in formula 3 and 1-chloromethyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane di(tetrafluoroborate) salt as raw materials to react and prepare the intermediate B shown in formula 4; 3) using N-chlorosuccinimide (NCS) and thiocyanate as raw materials to react to prepare the intermediate C described in formula 5; 4) using the intermediate B prepared in step 2) and the intermediate C prepared in step 3) as raw materials and a chiral dinitrogen oxide ligand as a catalyst to react and prepare a catalyst shown in formula 1; Among them, the carboxyl-substituted benzenesulfonate shown in Formula 2, the intermediate A shown in Formula 3, the intermediate B shown in Formula 4, and the intermediate C shown in Formula 5 have the structure: In Formula 2 and Formula 3, the definition of R is the same as that of R in Formula 1.

3. The preparation method according to claim 2, characterized in that: The carboxyl-substituted benzenesulfonate in step 1) is selected from at least one of carboxyl-substituted benzenesulfonate methyl ester, carboxyl-substituted benzenesulfonate ethyl ester, carboxyl-substituted benzenesulfonate butyl ester and carboxyl-substituted benzenesulfonate phenol ester, preferably at least one of carboxyl-substituted benzenesulfonate methyl ester and carboxyl-substituted benzenesulfonate phenol ester; and / or, the amide in step 1) is selected from 2-benzoylacetamide; and / or, in step 1), the molar ratio of carboxyl-substituted benzenesulfonate to 2-benzoylacetamide in the reaction is 1:1-4:1, the reaction temperature is 60-100°C, the reaction time is 0.5-5h, the solvent can be acetonitrile or dioxane, preferably the molar ratio of carboxyl-substituted benzenesulfonate to 2-benzoylacetamide is 2:1-3:1, the reaction temperature is 70-90°C, the reaction time is 1-3h, and the reaction solvent is dioxane.

4. The preparation method according to claim 2 or 3, characterized in that: The 1-chloromethyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane di(tetrafluoroborate) salt in step 2) is 1-chloromethyl-4-fluoro-1,4-diazobicyclo 2.2.2 octane di(tetrafluoroborate) salt (CAS140681-55-6); and / or, the molar ratio of the intermediate A in step 2) to the 1-chloromethyl-4-fluoro-1,4-diazabicyclo[2.2.2]octane di(tetrafluoroborate) salt is 1:0.5 to 1:4, preferably 1:0.8 to 1:1.2; and / or, the reaction in step 2) is performed at a temperature of 20 to 40°C, preferably 25 to 30°C, and the reaction time is 2 to 8 hours, preferably 3 to 6 hours.

5. The preparation method according to any one of claims 2 to 4, characterized in that: In step 3), the thiocyanate is selected from at least one of potassium thiocyanate, sodium thiocyanate and ammonium thiocyanate; and / or, in step 3), the molar ratio of N-chlorosuccinimide to thiocyanate is 1:1 to 1:4, preferably 1:2 to 1:3; and / or, in step 3), the reaction temperature is 20 to 40°C, preferably 25 to 30°C, and the reaction time is 15 to 60 min, preferably 30 to 45 min.

6. The preparation method according to any one of claims 2 to 5, characterized in that: The molar ratio of intermediate B to intermediate C in step 4) is 2:1 to 1:4, preferably 1:1 to 1:1.5; and / or, the chiral dinitrogen oxide ligand in step 4) is selected from at least one of 2,3-bipyridine dinitrogen oxide, 2,5-dimethylpyrazine dinitrogen oxide, and phenolazine dinitrogen oxide; and / or, the amount of the chiral dinitrogen oxide ligand catalyst is 1 to 10% of the total mass of intermediate A and intermediate B; and / or, the reaction in step 4) is performed at a temperature of 25 to 50°C, preferably 25 to 35°C, and the reaction time is 0.5 to 8h, preferably 1 to 3h.

7. A method for preparing a TDI trimer curing agent, the method comprising the following steps: 1) Under nitrogen protection, a catalyst is added to toluene diisocyanate monomer, and the mixture is stirred and reacted at a certain temperature for 1 to 4 hours to obtain carbodiimide-modified TDI; 2) under nitrogen protection, adding a polar solvent and a hydroxyl-containing trimerization catalyst to the modified TDI, keeping the temperature at 50-60° C. for 4-8 hours to obtain a modified TDI prepolymer; then adding a small molecule alcohol to the modified TDI prepolymer, keeping the temperature at 50-60° C. for 1-2 hours; finally adding an inhibitor and keeping the temperature for another 1-2 hours, cooling and discharging the material to obtain a modified TDI trimer curing agent; the catalyst in step 1) comprises the catalyst for carbodiimide-modified TDI as claimed in claim 1 or the catalyst for carbodiimide-modified TDI prepared by the preparation method according to any one of claims 2-6.

8. The preparation method according to claim 7, characterized in that: The toluene diisocyanate in step 1) is 2,4-toluene diisocyanate (2,4-TDI) or 2,6-toluene diisocyanate (2,6-TDI) or a mixture of the two, preferably TDI-80 (2,4-TDI / 2,6-TDI=80 / 20); and / or, the amount of the modified catalyst in step 1) is 0.05-1% of the mass of TDI monomer; and / or, the reaction temperature in step 1) is 100-150° C., and the stirring speed is 100-300 r / min.

9. The preparation method according to claim 7 or 8, characterized in that: The polar solvent in step 2) is one or more of ethyl acetate, butyl acetate, and sec-butyl acetate, and the amount of the polar solvent added is 0.5 to 2 times the mass of the modified TDI; and / or, the hydroxyl-containing trimerization catalyst in step 2) is one or more of DMP-30, Mannich base, and trimethylhydroxypropyl ammonium salt, preferably DMP-30; and / or, the amount of the hydroxyl-containing trimerization catalyst added is 0.05% to 0.5% of the total mass of the modified TDI and the polar solvent.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The small molecule alcohol in step 2) is one or more of ethylene glycol, propylene glycol, n-butanol, n-pentanol, n-decanol, n-dodecyl alcohol, and trimethylolpropane, and the added amount is 1 to 4% of the total mass of the modified TDI and the polar solvent; and / or, the inhibitor in step 2) is one or more of phosphoric acid, benzoyl chloride, and oxalyl chloride, and the added amount is 0.1 to 1% of the total amount of the hydroxyl-containing small molecule alcohol, the modified TDI, and the polar solvent.

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