A xylene tolerance adjustable adduct type curing agent and a preparation method thereof

Abstract

The application discloses a xylene tolerance adjustable adduct type curing agent and a preparation method thereof. The adduct type curing agent comprises a combination of TDI monomers and halogenated methyl phenyl isocyanate in raw materials; in the combination of TDI monomers and halogenated methyl phenyl isocyanate, the proportion of halogenated methyl phenyl isocyanate is 0.2-60wt%. The application can obtain adduct products with different molecular weight distribution by adjusting the content of halogenated methyl phenyl isocyanate in TDI under the same formula system, and when the hydroxyl resin component of the paint is changed, the actual use condition can be flexibly adjusted, and the purpose of changing the compatibility of the adduct product and the hydroxyl resin by single adjustment of the composition of the TDI component raw material is achieved.

Description

Technical Field

[0001] This invention belongs to the field of polyurethane technology and relates to an adduct-type curing agent with adjustable xylene tolerance and its preparation method. Background Technology

[0002] Polyurethane coatings are the preferred type of coating for home decoration, electrical corrosion protection, and other fields. Because isocyanates can combine with hydroxyl groups in the substrate to form strong chemical bonds such as hydrogen bonds, they can adhere well to the coating surface, giving polyurethane coatings excellent protective functions. The presence of a large number of repeating units in the structure also endows polyurethane coatings with good mechanical properties, and at the same time, various functional coatings are derived.

[0003] TDI-TMP adducts are a common curing agent component in two-component polyurethane coatings. Their application enables the coating film to achieve high hardness and fast drying properties, and they are widely used in various types of coatings, including wood varnishes, matte finishes, and primers. However, current research on adduct-based curing agents faces two major drawbacks that urgently need to be addressed: poor compatibility with hydroxyl resins and high levels of free monomers.

[0004] In practical paint formulation, there is a limit to the solubility of polar TDI-TMP adducts and non-polar hydroxyl resins. Xylene tolerance is determined to characterize the degree of miscibility between the two components when the adduct is formulated into a two-component polyurethane coating. Higher xylene tolerance indicates better compatibility of the adduct in paint formulation. This xylene tolerance index can provide direct guidance for the formulation of the final paint film.

[0005] Studies have shown that to improve the compatibility of adducts with hydroxyl resins, the reaction can be stopped when it reaches 2 / 3 of the theoretical reaction extent, allowing for the removal of free monomers. This can yield products with low viscosity, uniform molecular weight distribution, and high xylene tolerance. However, this undoubtedly presents a more severe challenge to the removal of free monomers, increasing costs and operational difficulty. The study "Synthesis and Performance Research of Polyurethane Curing Agents with Low Free TDI and High Solid Content" proposes replacing 20% ​​TMP with a mixed diol (diethylene glycol / propylene glycol / neopentyl glycol) in a mass ratio of approximately 1:1:1, which can yield a curing agent with better compatibility. Some researchers have added small molecule alcohols such as n-butanol during the curing agent prepolymer preparation stage to urethane-modify the curing agent, reducing polarity and increasing its compatibility with hydroxyl resins. However, this means that improving the xylene tolerance of the curing agent product requires a complete redesign of the formulation, including the content and raw materials. In addition, during the actual paint mixing process, the hydroxyl resin components may change due to variations in storage conditions and the paint mixing environment. In some cases, the curing agent components produced according to a fixed formula may not be well matched and may not achieve optimal performance.

[0006] Therefore, in response to the current problems and development trends in the industry, there is an urgent need to develop a method for preparing an adduct-type curing agent with adjustable xylene tolerance, so as to achieve the goal of changing the compatibility of adduct products with hydroxyl resins by simply adjusting the composition of TDI component raw materials. Summary of the Invention

[0007] To achieve the above objectives, this invention provides an adduct-type curing agent with adjustable xylene tolerance and its preparation method. Under the same formulation system, adduct products with different molecular weight distributions can be obtained by adjusting the content of halomethyl phenyl isocyanate in TDI (toluene diisocyanate). When the hydroxyl resin component of the paint changes, it can be flexibly adjusted according to the actual use, thereby achieving the purpose of changing the compatibility between the adduct product and the hydroxyl resin by simply adjusting the composition of the TDI component raw material.

[0008] The experiments of this invention have found that introducing halomethylphenyl isocyanate substances into the preparation process of TDI adducts can effectively limit the final reaction extent of the adduct reaction. Its monofunctionality makes it act like a capping agent, which can control the molecular weight distribution in the adduct reaction system, limit the proportion of macromolecular structures in the final product during the adduct synthesis stage, which is beneficial to the compatibility when formulating paints, and ultimately improves the xylene tolerance of TDI adduct products.

[0009] This invention further discovers through experiments that the refined TDI collected from the TDI refining tower, after being processed by distillation separation, can yield TDI with different halomethylphenyl isocyanate contents, which can be directly used to prepare adduct curing agents with adjustable xylene tolerance. In existing technologies, the refined TDI collected from the TDI refining tower contains a small amount of halomethylphenyl isocyanate. The presence of such substances reduces the purity of the refined TDI product, affecting its application in certain fields with high requirements for raw material activity. Therefore, during TDI production, multiple distillation purification methods or separation and incineration are used to reduce the content of halomethylphenyl isocyanates in the TDI product. This invention proposes a diversified development direction for TDI products by utilizing halomethylphenyl isocyanates in the preparation of adduct-type curing agents.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] This invention provides an adduct-type curing agent with adjustable xylene tolerance, the raw material of which contains a composition of TDI monomer and halomethylphenyl isocyanate;

[0012] In the composition of the TDI monomer and the halomethylphenyl isocyanate, the halomethylphenyl isocyanate accounts for 0.2-60 wt%, preferably 55-60 wt%.

[0013] In this invention, the halomethylphenyl isocyanate is selected from one or more of 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate, and 3-trichloromethyl-4-methylphenyl isocyanate, preferably one or more of 3-chloro-4-methylphenyl isocyanate and 5-chloro-2-methylphenyl isocyanate.

[0014] Preferably, in this invention, the composition of the TDI monomer and the halomethylphenyl isocyanate has the following mass percentage composition: 0.1-20 wt% of 3-chloro-4-methylphenyl isocyanate, preferably 18-20 wt%; 0.1-40 wt% of 5-chloro-2-methylphenyl isocyanate, preferably 37-40 wt%; and 40-99.8 wt% of toluene diisocyanate, preferably 40-45 wt%.

[0015] In this invention, the composition of TDI monomer and halomethylphenyl isocyanate does not have special requirements regarding its source. For example, it can be obtained by directly mixing TDI and halomethylphenyl isocyanate, or halomethylphenyl isocyanate can be introduced by enriching impurities inherent in TDI monomer.

[0016] Preferably, the composition of the TDI monomer and the halomethyl phenyl isocyanate is derived from the purified TDI obtained from the TDI refining tower. After further distillation and separation, TDI with different halomethyl phenyl isocyanate contents can be obtained, which can be directly used to prepare adduct curing agents with adjustable xylene tolerance.

[0017] Preferably, the composition of the TDI monomer and the chloro monoisocyanate is obtained by distillation separation of TDI from the TDI refining tower, and its composition includes 0.1-20 wt% of 3-chloro-4-methylphenyl isocyanate, 0.1-40 wt% of 5-chloro-2-methylphenyl isocyanate, and 40-99.8 wt% of toluene diisocyanate.

[0018] The distillation separation conditions are: pressure 1-10 kPaA, preferably 4-5 kPaA, and temperature 110-160℃, preferably 143-148℃.

[0019] Preferably, the purification is carried out by distillation separation using a plate column or a structured packed column.

[0020] The present invention also provides a method for preparing the above-mentioned xylene-tolerant adduct-type curing agent. The xylene-tolerant adduct-type curing agent of the present invention can be prepared using any method disclosed in the prior art, using the above-mentioned TDI monomer raw material of the present invention.

[0021] The xylene-tolerant adduct-type curing agent provided by the present invention can be used to obtain adduct-type curing agent products with xylene tolerance varying in the range of 1.5-4 by adjusting the content of halomethylphenyl isocyanate in the composition, thereby adapting to different working conditions.

[0022] The xylene-tolerant adduct-type curing agent provided by this invention has the advantages of low viscosity, easy processing and use, free monomer content of less than 0.5%, low content of harmful substances, and friendliness to the construction environment and users.

[0023] Preferably, the present invention also provides a method for preparing the above-mentioned xylene-tolerant adduct-type curing agent, the steps of which include:

[0024] 1) A composition of TDI monomer and halomethylphenyl isocyanate, alcohol, and solvent are mixed and a prepolymerization reaction is carried out under stirring to obtain an adduct prepolymer;

[0025] 2) Add a catalyst to the adduct prepolymer of step 1), carry out the polymerization reaction under stirring, then add an inhibitor and mix evenly, stop stirring and carry out the heat preservation reaction to obtain an adduct-type curing agent with adjustable xylene tolerance.

[0026] In this invention, the alcohol in step 1) is a mixture of trimethylolpropane and alcohols with a molecular weight of less than 150. The alcohols with a molecular weight of less than 150 are preferably one or more of isopentyl glycol, isobutanol, diethylene glycol, and neopentyl glycol, and more preferably isopentyl glycol and isobutanol.

[0027] Preferably, the alcohol is a mixture of trimethylolpropane, isopentyl glycol, and isobutanol in a mass ratio of 1:0.4-0.7:0.05-0.2, more preferably 1:0.5-0.6:0.1-0.15.

[0028] In this invention, the solvent in step 1) is selected from one or more inert solvents of polyurethane system, preferably one or more of ethyl acetate, butyl acetate, toluene, xylene, and cyclohexanone, more preferably ethyl acetate.

[0029] In this invention, the mass ratio of the TDI monomer and halomethylphenyl isocyanate composition to the alcohol in step 1) is 1.1-5:1, preferably 2.5-3.5:1;

[0030] In step 1), the total mass ratio of the TDI monomer and halomethylphenyl isocyanate composition and alcohol to solvent is 2.1-15:1, preferably 3.5-4:1.

[0031] In this invention, the prepolymerization reaction in step 1) is carried out at a temperature of 68-75°C for 2-5 hours.

[0032] Preferably, the stirring speed is 200-400 rpm.

[0033] In this invention, when mixing the composition of TDI monomer and halomethylphenyl isocyanate, alcohol, and solvent in step 1), the preferred mixing method is as follows:

[0034] S1: Mix the alcohol and solvent evenly to obtain a mixed alcohol, and keep it warm for later use;

[0035] S2: Add the mixed alcohol to the composition of TDI monomer and halomethylphenyl isocyanate and stir until homogeneous.

[0036] Wherein, the mixing temperature in S1 is 45-50℃; preferably, the stirring speed is 400-500 rpm;

[0037] Preferably, the heat preservation condition is to place the product in a forced-air drying oven at 45-50℃.

[0038] The mixed alcohol material in S2 is added in a segmented or continuous manner, preferably in two segments (e.g., each segment is added in equal mass), and the second segment is added dropwise after an interval of 20-30 minutes.

[0039] In this invention, the catalyst in step 2) is selected from one or more of tertiary amine catalysts, quaternary amine catalysts, and metal catalysts, preferably one or more of 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylammonium iodide, tributyltin oxide, bismuth isooctanoate, and sodium oxalate, more preferably one or more of 2,4,6-tris(dimethylaminomethyl)phenol and sodium oxalate, and even more preferably 2,4,6-tris(dimethylaminomethyl)phenol;

[0040] Preferably, the amount of catalyst used is 0.1-3% of the mass of the adduct prepolymer;

[0041] Preferably, the catalyst is added in a segmented or continuous manner, preferably by dripping, with a feeding time of 10-30 minutes (the feeding time is not included in the polymerization reaction time);

[0042] Preferably, the temperature of the adduct prepolymer is 50-55℃ and the rotation speed is 200-400 rpm during feeding.

[0043] In this invention, the polymerization inhibitor in step 2) is selected from one or more acidic polymerization inhibitors, preferably one or more of benzoyl chloride, chloroacetyl, phosphoric acid, and citric acid, and more preferably phosphoric acid;

[0044] Preferably, the amount of the polymerization inhibitor is 0.05-8% of the mass of the adduct prepolymer;

[0045] Preferably, the polymerization inhibitor is added in a segmented or continuous manner, preferably by dripping, with a feeding time of 10-30 minutes;

[0046] Preferably, the mixing speed during feeding is 300-500 rpm.

[0047] In this invention, the polymerization reaction in step 2) is carried out at a temperature of 60-65°C for 1-3 hours.

[0048] Preferably, the stirring speed is 200-400 rpm.

[0049] In this invention, the heat preservation reaction in step 2) is carried out at a temperature of 60-70℃ for a time of 0.5-3h.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] (1) The present invention provides an adduct curing agent with higher xylene tolerance than conventional adduct curing agent products, and the curing agent has good compatibility with hydroxyl resin.

[0052] (2) The present invention provides a method for preparing an adduct curing agent, which can obtain an adduct curing agent product with xylene tolerance varying in the range of 1.5-4 by adjusting the content of halomethyl phenyl isocyanate in TDI, thereby adapting to different working conditions.

[0053] (3) This invention provides a method for the resource utilization of halomethyl phenyl isocyanate in purified TDI. Detailed Implementation

[0054] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0055] The main raw material sources involved in the various embodiments and comparative examples of this invention are as follows; unless otherwise specified, all raw materials were obtained from ordinary commercial channels:

[0056] Trimethylolpropane, purity ≥99%, Pastor Company;

[0057] Isopentyl glycol, purity ≥99%, Wanhua Chemical Group Co., Ltd.

[0058] TDI-80, purity ≥99.9%, Wanhua Chemical Group Co., Ltd.

[0059] Ethyl acetate, butyl acetate, toluene, xylene, cyclohexanone, phosphoric acid, analytical grade, Tianjin Kemeo Chemical Reagent Co., Ltd.

[0060] 2,4,6-Tris(dimethylaminomethyl)phenol, tetramethylammonium iodide, tributyltin oxide, bismuth isooctanoate, sodium oxalate, benzoyl chloride, chloroacetyl, citric acid, isobutanol, 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, analytical grade, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0061] The main analytical methods used in the embodiments and comparative examples of this invention are as follows:

[0062] Composition of the TDI monomer and halomethylphenyl isocyanate: analyzed by Agilent 7890B gas chromatograph.

[0063] Physical property testing methods for adduct products:

[0064] 1) The content of free monomers in the product was analyzed by pre-column derivatization using an Agilent 1260 liquid chromatography system.

[0065] 2) The method for testing the xylene tolerance of the product is to accurately weigh a quantitative sample into a dry beaker, and record the sample mass as m1. Add xylene dropwise to the beaker until a white turbidity appears and the insoluble part appears. Record the mass of xylene used as m2. m2 / m1 is the xylene tolerance of the sample.

[0066] 3) The viscosity of the product was tested using a BROOKFIELD DV2T viscometer at 25°C.

[0067]

Example 1

[0068] TDI collected from the TDI refining column was further purified by distillation to obtain a composition of TDI monomer and halomethylphenyl isocyanate. The distillation conditions were: temperature 110℃ and pressure 1.0 kPaA, using a plate column for separation and purification. Gas chromatography analysis of the TDI monomer and halomethylphenyl isocyanate composition showed the following mass percentage composition: 0.1 wt% 3-chloro-4-methylphenyl isocyanate, 0.1 wt% 5-chloro-2-methylphenyl isocyanate, and 99.8 wt% TDI.

[0069] The steps for preparing an adduct-type curing agent with adjustable xylene tolerance are as follows:

[0070] (1) Mix 20g of trimethylolpropane, 8g of isopentyl glycol, 1g of isobutanol and 5.8g of cyclohexanone at 45℃ and 400rpm to obtain a mixed alcohol material, and keep it warm in a 45℃ forced-air oven for later use.

[0071] (2) Accurately weigh 50g of the composition of TDI monomer and halomethylphenyl isocyanate and place it in a flask. Add 15g of the mixed alcohol from step (1) dropwise under stirring at 200rpm. After the addition is completed, add another 15g of the mixed alcohol from step (1) dropwise after an interval of 20min. The prepolymerization reaction is carried out at 68℃ and 200rpm for 2.5h to obtain 80g of adduct prepolymer.

[0072] (3) Reduce the temperature of the adduct prepolymer from step (2) to 55°C, add 0.08g sodium oxalate dropwise over 10 min with stirring at 200 rpm, and polymerize at 65°C and 200 rpm for 1 h. Then add 0.04g benzoyl chloride dropwise over 10 min, mix evenly with stirring at 300 rpm, stop stirring, and keep the mixture at 65°C for 0.5 h to obtain adduct type curing agent 1.

[0073]

Example 2

[0074] TDI collected from the TDI refining column was further purified by distillation to obtain a composition of TDI monomer and halomethylphenyl isocyanate. The distillation conditions were: temperature 122℃, pressure 2.8 kPaA, and purification was carried out in a structured packed column. Gas chromatography analysis of the TDI monomer and halomethylphenyl isocyanate composition showed the following mass percentage composition: 6.1 wt% 3-chloro-4-methylphenyl isocyanate, 7.6 wt% 5-chloro-2-methylphenyl isocyanate, 5.6 wt% 4-bromo-2-methylphenyl isocyanate, and 80.7 wt% TDI.

[0075] The steps for preparing an adduct-type curing agent with adjustable xylene tolerance are as follows:

[0076] (1) Mix 20g of trimethylolpropane, 14g of neopentyl glycol, 4g of diethylene glycol and 38g of butyl acetate at 50℃ and 500rpm to obtain a mixed alcohol material, and keep it warm in a 50℃ forced-air oven for later use.

[0077] (2) Accurately weigh 45g of the composition of TDI monomer and halomethyl phenyl isocyanate and place it in a flask. Add 15g of the mixed alcohol from step (1) dropwise under stirring at 300rpm. After the addition is completed, add another 15g of the mixed alcohol from step (1) dropwise after an interval of 20min. The prepolymerization reaction is carried out at 70℃ and 300rpm for 3.5h to obtain 75g of adduct prepolymer.

[0078] (3) Reduce the temperature of the adduct prepolymer from step (2) to 50°C, add 1.5g of tetramethylammonium iodide dropwise over 20 minutes while stirring at 300 rpm, and polymerize at 60°C and 300 rpm for 2 hours. Then add 0.45g of chloroacetyl dropwise over 20 minutes, mix evenly while stirring at 400 rpm, and stop stirring. Keep the mixture at 70°C for 1.5 hours to obtain adduct type curing agent 2.

[0079]

Example 3

[0080] TDI collected from the TDI refining tower was further purified by distillation to obtain a composition of TDI monomer and halomethylphenyl isocyanate. The distillation conditions were: temperature 135℃ and pressure 4.6 kPaA, followed by separation and purification in a structured packed column. Gas chromatography analysis of the TDI monomer and halomethylphenyl isocyanate composition showed the following mass percentage composition: 10 wt% 3-trichloromethyl-4-methylphenyl isocyanate, 11.1 wt% 3-chloro-4-methylphenyl isocyanate, 12.1 wt% 5-chloro-2-methylphenyl isocyanate, and 66.8 wt% TDI.

[0081] The steps for preparing an adduct-type curing agent with adjustable xylene tolerance are as follows:

[0082] (1) Mix 20g of trimethylolpropane, 12g of diethylene glycol, 2g of isopentyl glycol and 34g of toluene at 47℃ and 450rpm to obtain a mixed alcohol material, and keep it warm in a 47℃ forced-air oven for later use.

[0083] (2) Accurately weigh 75g of the composition of TDI monomer and halomethylphenyl isocyanate and place it in a flask. Add 15g of the mixed alcohol from step (1) dropwise under stirring at 400rpm. After the addition is completed, add another 15g of the mixed alcohol from step (1) dropwise after an interval of 30min. The prepolymerization reaction is carried out at 75℃ and 400rpm for 5h to obtain 105g of adduct prepolymer.

[0084] (3) Reduce the temperature of the adduct prepolymer from step (2) to 52°C, add 1.05g of tributyltin oxide dropwise over 30 minutes with stirring at 400 rpm, and polymerize at 63°C and 400 rpm for 3 hours. Then add 3.15g of phosphoric acid dropwise over 30 minutes, mix evenly with stirring at 500 rpm, stop stirring, and keep warm at 68°C for 3 hours to obtain adduct type curing agent 3.

[0085]

Example 4

[0086] TDI collected from the TDI refining tower was further purified by distillation to obtain a composition of TDI monomer and halomethylphenyl isocyanate. The distillation conditions were: 160℃ and 10.0 kPaA, followed by separation and purification in a structured packed column. Gas chromatography analysis of the TDI monomer and halomethylphenyl isocyanate composition showed the following mass percentage composition: 10.5 wt% 3-chloro-4-methylphenyl isocyanate, 11.3 wt% 5-chloro-2-methylphenyl isocyanate, 20.1 wt% 4-bromo-2-methylphenyl isocyanate, and 58.1 wt% TDI.

[0087] The steps for preparing an adduct-type curing agent with adjustable xylene tolerance are as follows:

[0088] (1) Mix 20g of trimethylolpropane, 10g of neopentyl glycol, 4g of isobutanol and 34g of xylene at 46℃ and 430rpm to obtain a mixed alcohol material, and keep it warm in a 46℃ forced-air oven for later use.

[0089] (2) Accurately weigh 60g of the composition of TDI monomer and halomethyl phenyl isocyanate and place it in a flask. Add 10g of the mixed alcohol from step (1) dropwise under stirring at 350rpm. After the addition is completed, add another 20g of the mixed alcohol from step (1) dropwise after an interval of 20min. The prepolymerization reaction is carried out at 73℃ and 350rpm for 4h to obtain 90g of adduct prepolymer.

[0090] (3) Reduce the temperature of the adduct prepolymer from step (2) to 53°C, add 2.7g of bismuth isooctanoate dropwise over 25 minutes with stirring at 400 rpm, and polymerize at 65°C and 400 rpm for 2.5 hours. Then add 7.2g of citric acid dropwise over 30 minutes, mix evenly with stirring at 400 rpm, and stop stirring. Keep the mixture at 70°C for 2 hours to obtain adduct-type curing agent 4.

[0091]

Example 5

[0092] TDI collected from the TDI refining tower was further purified by distillation to obtain a composition of TDI monomer and halomethylphenyl isocyanate. The distillation conditions were: temperature 145℃ and pressure 4.7 kPaA, followed by separation and purification in a structured packed column. Gas chromatography analysis of the TDI monomer and halomethylphenyl isocyanate composition showed the following mass percentage composition: 19.8 wt% 3-chloro-4-methylphenyl isocyanate, 39.6 wt% 5-chloro-2-methylphenyl isocyanate, and 40.6 wt% TDI.

[0093] The steps for preparing an adduct-type curing agent with adjustable xylene tolerance are as follows:

[0094] (1) Mix 20g of trimethylolpropane, 11g of isopentyl glycol, 3g of isobutanol and 34g of diethyl acetate at 48℃ and 450rpm to obtain a mixed alcohol material, and keep it warm in a 48℃ forced-air oven for later use.

[0095] (2) Accurately weigh 42g of the composition of TDI monomer and chloro monoisocyanate and place it in a flask. Add 15g of the mixed alcohol from step (1) dropwise under stirring at 300rpm. After the addition is completed, add another 15g of the mixed alcohol from step (1) dropwise after an interval of 20min. The prepolymerization reaction is carried out at 72℃ and 300rpm for 2.5h to obtain 72g of adduct prepolymer.

[0096] (3) Reduce the temperature of the adduct prepolymer from step (2) to 52°C, add 0.36g of 2,4,6-tris(dimethylaminomethyl)phenol dropwise over 20 min while stirring at 300 rpm, and polymerize at 62°C and 300 rpm for 2 h. Then add 0.072g of phosphoric acid dropwise over 20 min, mix evenly under stirring at 350 rpm, stop stirring, and keep the mixture at 65°C for 1.5 h to obtain adduct-type curing agent 5.

[0097] Comparative Example 1

[0098] The adduct-type curing agent was prepared according to the method of Example 1, except that the composition of the raw material TDI monomer and halomethylphenyl isocyanate was replaced with TDI-80 product (mass percentage composition: 0.005 wt% 3-chloro-4-methylphenyl isocyanate, 0.006 wt% 5-chloro-2-methylphenyl isocyanate, 0.002 wt% 4-bromo-2-methylphenyl isocyanate, 0.001 wt% 3-trichloromethyl-4-methylphenyl isocyanate, and 99.986 wt% TDI).

[0099] With all other operations and parameters unchanged, an adduct-type curing agent was obtained.

[0100] Comparative Example 2

[0101] The adduct-type curing agent was prepared according to the method of Example 1, except that 3-chloro-4-methylphenyl isocyanate and 5-chloro-2-methylphenyl isocyanate were added to the composition of raw material TDI monomer and chloro monoisocyanate, and mixed evenly. The composition was analyzed by gas chromatography, and the mass percentage composition was: 26.9 wt% 3-chloro-4-methylphenyl isocyanate, 44.8 wt% 5-chloro-2-methylphenyl isocyanate, and 28.3 wt% TDI.

[0102] With all other operations and parameters unchanged, an adduct-type curing agent was obtained.

[0103] The viscosity, free monomer, and xylene tolerance of the adducts prepared in each embodiment and comparative example were tested. The test results are shown in Table 1 below:

[0104] Table 1. Results of physical property tests on adduct products

[0105]

[0106]

[0107] As can be seen from the performance test results in Table 1, using the preparation method of the adduct-type curing agent mentioned in this invention, adduct products with a xylene tolerance range of 1.5-4 can be obtained by adjusting the content of halomethylphenyl isocyanate in TDI. The adduct products prepared by the various embodiments of this invention all have higher xylene tolerance than Comparative Example 1, lower free monomer content, and lower viscosity than Comparative Example 1. This indicates that distilling TDI and increasing the content of halomethylphenyl isocyanate substances within a certain range can improve the xylene tolerance of the adduct-type curing agent, while reducing the free monomer content of the product. It also keeps the viscosity of the adduct product at a lower level, which is more beneficial for later construction. In Comparative Example 2, although the xylene tolerance of the adduct product prepared using TDI with a chloromonoisocyanate content exceeding the range specified in the instructions was improved, the free monomer content also increased.

[0108] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. An adduct-type curing agent with adjustable xylene tolerance, characterized in that, The raw material contains a composition of TDI monomer and halomethylphenyl isocyanate; In the composition of TDI monomer and halomethylphenyl isocyanate, the halomethylphenyl isocyanate accounts for 55-60 wt%; The xylene-tolerant adduct-type curing agent has a tolerance that varies in the range of 1.5-4. The preparation method of the xylene-tolerant adduct-type curing agent includes the following steps: Step 1) The composition of TDI monomer and halomethylphenyl isocyanate, alcohol and solvent are mixed and prepolymerized under stirring to obtain adduct prepolymer; Step 2) Add a catalyst to the adduct prepolymer from Step 1), carry out the polymerization reaction under stirring, then add an inhibitor and mix evenly. Stop stirring and carry out the reaction at a constant temperature to obtain an adduct-type curing agent with adjustable xylene tolerance.

2. The xylene-tolerant adduct-type curing agent according to claim 1, characterized in that, The halomethylphenyl isocyanate is selected from one or more of 3-chloro-4-methylphenyl isocyanate, 5-chloro-2-methylphenyl isocyanate, 4-bromo-2-methylphenyl isocyanate, and 3-trichloromethyl-4-methylphenyl isocyanate.

3. The xylene-tolerant adduct-type curing agent according to claim 1, characterized in that, The composition of the TDI monomer and halomethylphenyl isocyanate has the following composition by mass percentage: 18-20 wt% 3-chloro-4-methylphenyl isocyanate, 37-40 wt% 5-chloro-2-methylphenyl isocyanate, and 40-45 wt% toluene diisocyanate.

4. A method for preparing an adduct-type curing agent with adjustable xylene tolerance as described in any one of claims 1-3, characterized in that the step... include: Step 1) The composition of TDI monomer and halomethylphenyl isocyanate, alcohol and solvent are mixed and prepolymerized under stirring to obtain adduct prepolymer; Step 2) Add a catalyst to the adduct prepolymer from Step 1), carry out the polymerization reaction under stirring, then add an inhibitor and mix evenly. Stop stirring and carry out the reaction at a constant temperature to obtain an adduct-type curing agent with adjustable xylene tolerance.

5. The preparation method according to claim 4, characterized in that, Step 1) The alcohol is a mixture of trimethylolpropane and alcohols with a molecular weight of less than 150; and / or Step 1) The solvent is selected from one or more inert solvents in the polyurethane system; and / or Step 1) The mass ratio of the TDI monomer and halomethylphenyl isocyanate composition to the alcohol is 1.1-5:1; and / or Step 1) The total mass ratio of the TDI monomer and halomethylphenyl isocyanate composition and alcohol to solvent is 2.1-15:

1.

6. The preparation method according to claim 5, characterized in that, The alcohol with a molecular weight of less than 150 is selected from one or more of isopentyl glycol, isobutanol, diethylene glycol, and neopentyl glycol.

7. The preparation method according to claim 6, characterized in that, The alcohol is a mixture of trimethylolpropane, isopentyl glycol, and isobutanol in a mass ratio of 1:0.4-0.7:0.05-0.

2.

8. The preparation method according to claim 7, characterized in that, The alcohol is a mixture of trimethylolpropane, isopentyl glycol, and isobutanol in a mass ratio of 1:0.5-0.6:0.1-0.

15.

9. The preparation method according to claim 5, characterized in that, The solvent is selected from one or more of ethyl acetate, butyl acetate, toluene, xylene, and cyclohexanone.

10. The preparation method according to claim 5, characterized in that, The mass ratio of the TDI monomer and halomethylphenyl isocyanate composition to the alcohol is 2.5-3.5:

1.

11. The preparation method according to claim 5, characterized in that, The total mass ratio of the TDI monomer and halomethylphenyl isocyanate composition and alcohol to solvent is 3.5-4:

1.

12. The preparation method according to claim 4, characterized in that, The prepolymerization reaction described in step 1) is carried out at a temperature of 68-75℃ for 2-5 hours.

13. The preparation method according to claim 4, characterized in that, In step 1), the prepolymerization reaction is carried out at a stirring speed of 200-400 rpm.

14. The preparation method according to claim 4, characterized in that, Step 1) When mixing the TDI monomer with the halomethylphenyl isocyanate composition, alcohol, and solvent, the mixing method used is as follows: S1: Mix the alcohol and solvent evenly to obtain a mixed alcohol, and keep it warm for later use; S2: Add the metered mixed alcohol to the composition of TDI monomer and halomethylphenyl isocyanate and stir until homogeneous.

15. The preparation method according to claim 14, characterized in that, The mixing temperature described in S1 is 45-50℃; and / or The mixed alcohol material described in S2 is fed in stages or continuously.

16. The preparation method according to claim 14, characterized in that, The mixing described in S1 is performed at a speed of 400-500 rpm.

17. The preparation method according to claim 14, characterized in that, The conditions described in S1 for heat preservation and standby use are: placing the product in a forced-air drying oven at 45-50℃.

18. The preparation method according to claim 14, characterized in that, The mixed alcohol material described in S2 is added in two stages, with the second stage being added dropwise after an interval of 20-30 minutes.

19. The preparation method according to claim 4, characterized in that, Step 2) The catalyst is selected from one or more of tertiary amine catalysts, quaternary amine catalysts, and metal catalysts; and / or Step 2) The polymerization inhibitor is selected from one or more acidic polymerization inhibitors.

20. The preparation method according to claim 19, characterized in that, The catalyst is selected from one or more of 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylammonium iodide, tributyltin oxide, bismuth isooctanoate, and sodium oxalate.

21. The preparation method according to claim 19, characterized in that, The polymerization inhibitor is selected from one or more of benzoyl chloride, chloroacetyl, phosphoric acid, and citric acid.

22. The preparation method according to claim 4, characterized in that, Step 2) The amount of catalyst used is 0.1-3% of the mass of the adduct prepolymer.

23. The preparation method according to claim 4, characterized in that, Step 2) The catalyst is fed in a segmented or continuous manner, with a feeding time of 10-30 minutes.

24. The preparation method according to claim 23, characterized in that, The catalyst is added dropwise.

25. The preparation method according to claim 23, characterized in that, The temperature of the adduct prepolymer is 50-55℃ and the rotation speed is 200-400 rpm when the catalyst is added.

26. The preparation method according to claim 4, characterized in that, Step 2) The amount of polymerization inhibitor used is 0.05-8% of the mass of the adduct prepolymer.

27. The preparation method according to claim 4, characterized in that, Step 2) The polymerization inhibitor is fed in a segmented or continuous manner, with a feeding time of 10-30 minutes.

28. The preparation method according to claim 27, characterized in that, The polymerization inhibitor is added dropwise.

29. The preparation method according to claim 27, characterized in that, The mixing speed during the addition of the polymerization inhibitor is 300-500 rpm.

30. The preparation method according to claim 4, characterized in that, Step 2) describes the polymerization reaction at a temperature of 60-65℃ for 1-3 hours; and / or The heat preservation reaction described in step 2) is carried out at a temperature of 60-70℃ for a time of 0.5-3h.

31. The preparation method according to claim 4, characterized in that, The polymerization reaction in step 2) is carried out at a stirring speed of 200-400 rpm.

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