Process for the preparation of an aqueous polyurethane composition and use thereof

Abstract

The application provides a preparation method and application of an aqueous polyurethane composition. The preparation method of the aqueous polyurethane composition comprises the following steps: synthesizing an isocyanate-terminated prepolymer, adding an organic solvent and a binary secondary amine chain extender, obtaining an aqueous polyurethane coarse emulsion through neutralization and dispersion after reaction, and finally removing all low-boiling-point solvents to obtain the aqueous polyurethane composition. The prepared aqueous polyurethane composition has the advantages of simple and controllable preparation process, low-cost synthesized resin, excellent performance and meeting the application requirements of wood paint coatings.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a waterborne polyurethane composition and its use, in particular to a preparation method of a high-activity isocyanate waterborne polyurethane composition and its application in the field of wood paint coatings. BACKGROUND

[0002] Nowadays, with the gradual enhancement of people's health and environmental protection awareness and the increasingly strict relevant laws and regulations of the country, the living space of solvent-based polyurethane is continuously squeezed, and waterborne polyurethane emerges as the times require, and it has become the consensus of the industry to promote the oil-to-water of the entire coating industry; however, the traditional waterborne polyurethane has a large difference in application performance, especially in the price, compared with the solvent-based polyurethane, and cannot meet the needs of customers with strict cost requirements, making it difficult to broaden the application field of waterborne polyurethane.

[0003] Aromatic isocyanate has the advantages of low price, and a large number of rigid structures such as benzene rings are introduced into the prepared waterborne polyurethane, and its performance has obvious advantages in fullness, chemical resistance, aging resistance, wear resistance, hardness and other aspects compared with traditional aliphatic waterborne polyurethane, and it has become the object of people's research. However, due to the influence of the electron-withdrawing effect of the benzene ring on the active group -NCO of aromatic isocyanate, the reaction activity is much higher than that of aliphatic isocyanate, and the degree of side reaction in the preparation of waterborne polyurethane water dispersion is large, and it is difficult to prepare waterborne polyurethane emulsion, and the waterborne process is hindered.

[0004] At present, the industry reduces the NCO of the prepolymer before dispersion and mixes a certain proportion of aliphatic isocyanate to weaken the occurrence of side reactions in the dispersion process: generally, the NCO before dispersion is reduced by chain extension reaction of small molecule polyols, due to the reduction of NCO concentration in the later stage of reaction, the molecular weight of the prepolymer is large, and the small molecule alcohol needs a higher temperature to react with NCO, which prolongs the prepolymerization time and increases the viscosity of the system, which has the risk of gelation, and is not conducive to large-scale industrial production; although mixing aliphatic isocyanate can reduce the occurrence of side reactions, aliphatic isocyanate is expensive and is not conducive to the purpose of low cost, and in addition, due to the reduction of the introduction of rigid groups such as benzene rings, the application performance is also lost.

[0005] Therefore, how to develop a low-cost and excellent performance waterborne polyurethane resin product has become one of the technical difficulties to be solved in the field. SUMMARY

[0006] In order to make up for the deficiencies of the prior art, the present application provides a preparation method of a waterborne polyurethane composition and the application of the composition prepared by the preparation method in wood paint coatings, and the preparation method provided by the present application is especially suitable for the preparation of high-activity isocyanate waterborne polyurethane resin, the preparation process of the prepared waterborne polyurethane composition is simple and controllable, the synthesized resin has low cost and excellent performance, and meets the application requirements of wood paint coatings.

[0007] The present application is to achieve its purpose, the technical solution is as follows:

[0008] The present application provides a preparation method of water-based polyurethane composition, comprising the following steps:

[0009] First, the isocyanate-terminated prepolymer is synthesized, the low-boiling-point organic solvent is added into the isocyanate-terminated prepolymer and mixed and dissolved, the secondary diamine chain extender is added, the neutralizing agent is added after the chain extension is completed, then the deionized water is dispersed under high-speed shearing, the water-based polyurethane coarse emulsion is obtained after the dispersion is completed, and finally the low-boiling-point organic solvent is removed.

[0010] The isocyanate-terminated prepolymer is prepared by mixing and reacting the following components: polyisocyanate, macromolecular polyol, small molecular polyol, hydrophilic chain extender and polyamine chain extender.

[0011] The preparation method of the present application, the use amount of each raw material for preparing the water-based polyurethane composition is:

[0012] 1) the use amount of the polyisocyanate is 30-42wt% of the mass of the isocyanate-terminated prepolymer;

[0013] 2) the use amount of the macromolecular polyol is 39-60% of the mass of the isocyanate-terminated prepolymer;

[0014] 3) the use amount of the small molecular polyol is 2-10wt% of the mass of the isocyanate-terminated prepolymer;

[0015] 4) the use amount of the hydrophilic chain extender is 4-8wt% of the mass of the isocyanate-terminated prepolymer;

[0016] 5) the use amount of the polyamine chain extender is 1-3% of the mass of the isocyanate-terminated prepolymer;

[0017] 6) the use amount of the neutralizing agent is 20%-60% of the amount of substance of the hydrophilic chain extender;

[0018] 7) the use amount of the low-boiling-point solvent is 0.8-1.6 times of the mass of the isocyanate-terminated prepolymer;

[0019] 8) the use amount of the secondary diamine chain extender is 2.5-7% of the mass of the isocyanate-terminated prepolymer.

[0020] The polyisocyanate in the method of making the present invention can be an aliphatic polyisocyanate, a cycloaliphatic polyisocyanate, an aromatic polyisocyanate, or a mixture thereof, preferably including one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, piperazine diisocyanate, hexahydrotoluene diisocyanate, trimethylhexane diisocyanate, xylylene diisocyanate, 1,4-cyclohexane diisocyanate, dodecane diisocyanate, 1,5-naphthalene diisocyanate, and dicyclohexylmethane diisocyanate, more preferably diphenylmethane diisocyanate and / or toluene diisocyanate.

[0021] The polyol in the method of making the present invention has a number average molecular weight of 600 to 8000, and includes one or more of a polyether polyol, a polyester polyol, a polycarbonate polyol, preferably including one or more of polyethylene glycol, polypropylene glycol, polyethylene glycol-propylene glycol, polytetrahydrofuran ether glycol, dimer acid polyester polyol, polyolefin polyol, polycaprolactone diol, polycarbonate diol, polyethylene glycol adipate diol, polybutylene glycol adipate diol, polyneopentyl glycol adipate diol, polyhexane glycol adipate diol, and polyneopentyl glycol hexane glycol adipate diol, more preferably polypropylene glycol ether diol.

[0022] The polyol in the method of making the present invention has a number average molecular weight of 600 to 8000, and includes one or more of a polyether polyol, a polyester polyol, a polycarbonate polyol, preferably including one or more of polyethylene glycol, polypropylene glycol, polyethylene glycol-propylene glycol, polytetrahydrofuran ether glycol, dimer acid polyester polyol, polyolefin polyol, polycaprolactone diol, polycarbonate diol, polyethylene glycol adipate diol, polybutylene glycol adipate diol, polyneopentyl glycol adipate diol, polyhexane glycol adipate diol, and polyneopentyl glycol hexane glycol adipate diol, more preferably polypropylene glycol ether diol.

[0023] The hydrophilic chain extender in the method of making the present invention includes an isocyanate-reactive compound with an ionic or potentially ionic group, including one or both of dimethylolpropionic acid, dimethylolbutanoic acid, an amino acid, an aminosulfonate, tartaric acid, N,N-dimethylolmaleamic acid, diaminobenzoic acid, and sodium dihydroxypropyl sulfonate, preferably dimethylolpropionic acid.

[0024] The polyamine chain extender in the method of making the present invention includes one or more of ethylenediamine, hydroxyethylethylenediamine, hexamethylenediamine, pentamethylenediamine, diethylenetriamine, isophorone diamine, and 4,4-diphenylmethane diamine, preferably one or more of hydroxyethylethylenediamine and isophorone diamine, more preferably isophorone diamine.

[0025] The preparation method of the present application, the neutralizing agent includes one or more of sodium hydroxide, potassium hydroxide, triethylamine, N, N-dimethyl ethanolamine, dimethylcyclohexylamine, triethanolamine, methyldiethanolamine, diisopropanolamine, ethyldiisopropylamine, diisopropylcyclohexylamine, N-methylmorpholine, 2-amino-2-methyl-1-propanol, ammonia. The preferred neutralizing agent is sodium hydroxide, triethylamine and / or N, N-dimethyl ethanolamine, and further preferably N, N-dimethyl ethanolamine.

[0026] The preparation method of the present application, the secondary diamine chain extender has the following general structure and isomers 2) and / or 3) at least 50% by mass:

[0027]

[0028] R1=C x H y R2=C x H y x=1-10, y=2-21

[0029] The preparation method of the present application, the low boiling point solvent is an organic solvent with a boiling point below 100°C, including one or more of acetone, methyl ethyl ketone, cyclohexane, dichloromethane, dichloroethane, trichloroethane, ethyl acetate, pentane, heptane, hexane, and preferably acetone.

[0030] The preparation method of the present application, the reaction temperature used in the preparation of the isocyanate-terminated prepolymer is 60-70°C; the reaction is carried out to the theoretical design residual NCO value (the residual theoretical NCO value according to the formula design is not the same, and specific values are provided in the examples below). The prepolymer can be prepared using industry-recognized methods.

[0031] The low boiling point organic solvent is mixed and dissolved with the isocyanate-terminated prepolymer at a temperature below 60°C.

[0032] The reaction temperature of the secondary diamine and the isocyanate prepolymer is 40-60°C, and the reaction time is 20-60 minutes.

[0033] The preparation method of the present application further includes the following steps after the dispersion is complete: removing the low boiling point solvent from the aqueous polyurethane composition, which is a method known in the industry.

[0034] The second aspect of the present application also provides a wood paint coating, which includes the aqueous polyurethane composition prepared by the preparation method described above.

[0035] The third aspect of the present application provides the use of the aqueous polyurethane composition prepared by the above-mentioned preparation method, preferably for one-component or two-component wood paint coating applications.

[0036] The technical solution provided by the present application has the following effects:

[0037] In the synthesis process of the aqueous polyurethane composition, a secondary diamine is introduced to reduce the occurrence of side reactions between NCO and water during the dispersion process. Since the activity of the secondary diamine is significantly lower than that of the primary amine and higher than that of the hydroxyl group, the reaction speed of the primary amine is fast, and even at a lower temperature, the primary amine will rapidly react with NCO, resulting in a local molecular weight that is too large and causing gelation. The hydroxyl group needs a higher temperature to react with NCO. Since the viscosity becomes large in the later stage of the reaction, it is difficult to add a low-boiling-point solvent to dilute the system to reach the reaction temperature of the hydroxyl group. Therefore, the secondary diamine is the best choice, which is added in the later stage of the prepolymerization reaction. The system has a large viscosity, and the addition of a low-boiling-point solvent to dilute the system still has a moderate reaction rate at a low temperature, thereby reducing NCO before dispersion and reducing the occurrence of side reactions during the dispersion process.

[0038] The secondary diamine used in the present application has the following three isomers:

[0039] 2)、

[0041]

[0042] R1=C x H y ,R2=C x H y x=1-10,y=2-21

[0043] The isomer 1) has the highest activity due to the effect of steric hindrance. However, in some high-activity aromatic isocyanate reaction systems (MDI, TDI), the isomer 1) still exhibits a high reaction rate. By increasing the content of the isomers 2) and 3) of the secondary diamine, the reaction activity of the amine can be further reduced, and the reaction can be more easily controlled.

[0044] The composition prepared by the present application has an average particle size in the range of 20-150 nm, and in a preferred embodiment, in the range of 30-90 nm. DETAILED DESCRIPTION

[0045] In order to better understand the technical solutions of the present application, the content of the present application will be further described below in conjunction with examples, but the content of the present application is not limited to the following examples.

[0046] In the examples or comparative examples, "%" refers to "wt%" if not specifically stated.

[0047] The test methods used in the examples or comparative examples are introduced as follows:

[0048] Solid content test method: take a proper amount of emulsion in a tin foil container, weigh the weight change before and after 150°C for 20 minutes, and calculate the solid content.

[0049] Particle size test method: Malvern particle size analyzer was used.

[0050] The formulations used in preparing coatings for the emulsions prepared in the following examples or comparative examples are shown in Table 1 below:

[0051] Table 1

[0052]

[0053] The method for detecting the application performance of the examples and comparative examples is introduced as follows:

[0054] Sample board construction process: substrate - water-based base color - water-based head degree primer - water-based glaze - water-based transparent primer - water-based transparent primer - water-based surface color - water-based topcoat.

[0055] Alcohol resistance test: 50% concentration ethanol solution was soaked on the finished sample board for 1h and 24h respectively, and after wiping dry, the film state was observed.

[0056] Water resistance test: deionized water was soaked on the finished sample board for 24h, and after wiping dry the water stains, the film state was observed.

[0057] Gloss test method: according to "Paint Film Gloss Determination Method" GB 1743-79, the 60° angle gloss was tested.

[0058] Pendulum hardness test method: according to "Paint Film Hardness Determination Method Pendulum Damping Test" GB / T1730-1993, the hardness was tested.

[0059] The raw materials used in the examples or comparative examples are introduced as follows:

[0060] MDI-50 (diphenylmethane diisocyanate, Wanhua Chemical Group Co., Ltd.);

[0061] TDI-80 (toluene diisocyanate, Wanhua Chemical Group Co., Ltd.);

[0062] IPDI (isophorone diisocyanate, Wanhua Chemical Group Co., Ltd.);

[0063] PPG1000 (polypropylene glycol ether diol, hydroxyl value 112 mgKOH / g, number average molecular weight = 1000, functionality 2, Wanhua Chemical Group Co., Ltd.);

[0064] CHDM (1,4-cyclohexane dimethanol, Eastman Chemical Company)

[0065] TMP (trimethylolpropane, Perstorp)

[0066] DMPA (dimethylol propionic acid, Perstorp)

[0067] BiCat 8108 (organic bismuth catalyst, American Elements)

[0068] DMEA (N,N-dimethyl ethanol amine, BASF, Germany)

[0069] Acetone (refined by Wanhua Chemical Group Co., Ltd.)

[0070] MDBA (bis-sec-butyl amino diphenyl methane, Wanhua Chemical Group Co., Ltd.)

[0071] U605 (thickening agent, Wanhua Chemical Group Co., Ltd.)

[0072] BYK024 defoamer, BYK-Chemie

[0073] Tego 270 (wetting agent, Degussa, Germany)

[0074] Tego 245 (wetting agent, Degussa, Germany)

[0075] DPM (film forming aid, Dow Chemical)

[0076] DPnB (film forming aid, Dow Chemical)

[0077] Bis-sec-amyl amino diphenyl methane was prepared by Michael addition reaction of diphenyl methane diamine (MDA) with n-pentene in a molar ratio of 1:2, using 50 ppm lithium hydroxide as catalyst, at 80-100 °C and 0.5 MPa pressure for 6 hours.

[0078] Comparative Example 1:

[0079] Into a four-necked flask equipped with a reflux condenser, thermometer and mechanical stirring, 41 g of MDI-50 (diphenyl methane diisocyanate), 41 g of TDI-80 (Toluene diisocyanate), 110 g PPG1000 (Polypropylene ether glycol), 2.4 g Trimethylolpropane, 13.4 g Dimethylolpropionic acid, 11.2 g CHDM, 0.1 g BiCat 8108, 76 g Acetone, heated to 70 °C until the theoretical NCO value of 2.42%, obtained capped prepolymer 219 g, stop the reaction. Cool to below 60 °C, add 132 g acetone, stir evenly and cool to below 30 °C, add 8 g DMEA neutralization reaction for 3 minutes, weigh 400 g deionized water in a dispersion cup, pour into the prepolymer under the condition of high speed shearing of 1500 r / min for 6 minutes, after dispersion, add 3.2 g IPDA chain extension reaction for 5 minutes, obtain waterborne polyurethane composition pre-emulsion, remove acetone in the emulsion by reduced pressure distillation method (60 °C, 0.1 MPa), obtain 35% solid content, 2000 nm particle size, milky white waterborne polyurethane emulsion.

[0080] Comparative Example 2:

[0081] Into a four-necked flask equipped with reflux condenser, thermometer and mechanical stirring, add 41 g MDI-50 (Diphenylmethane diisocyanate), 41 g TDI-80 (Toluene diisocyanate), 110 g PPG1000 (Polypropylene ether glycol), 2.4 g Trimethylolpropane, 13.4 g Dimethylolpropionic acid, 11.2 g CHDM, 0.1 g BiCat 8108, 76 g Acetone, heated to 70 °C until the theoretical NCO value of 2.42%, obtained capped prepolymer 219 g, stop the reaction. Cool to below 60 °C, add 132 g acetone, stir evenly and cool to below 30 °C, add 8 g DMEA neutralization reaction for 3 minutes, weigh 400 g deionized water in a dispersion cup, pour into the prepolymer under the condition of high speed shearing of 1500 r / min for 6 minutes, after dispersion, add 3.2 g IPDA chain extension reaction for 5 minutes, obtain waterborne polyurethane composition pre-emulsion, remove acetone in the emulsion by reduced pressure distillation method (60 °C, 0.1 MPa), obtain 35% solid content, 2000 nm particle size, milky white waterborne polyurethane emulsion.

[0082] Comparative Example 3:

[0083] Into a four-necked flask equipped with reflux condenser, thermometer and mechanical stirring, add 20 g MDI-50 (Diphenylmethane diisocyanate), 20 g TDI-80 (Toluene diisocyanate), 110 g PPG1000 (Polypropylene ether glycol), 2.4 g Trimethylolpropane, 13.4 g Dimethylolpropionic acid, 11.2 g CHDM, 0.1 g BiCat 8108, 76 g Acetone, heated to 70 °C until the theoretical NCO value of 2.42%, obtained capped prepolymer 219 g, stop the reaction. Cool to below 60 °C, add 132 g acetone, stir evenly and cool to below 30 °C, add 8 g DMEA neutralization reaction for 3 minutes, weigh 400 g deionized water in a dispersion cup, pour into the prepolymer under the condition of high speed shearing of 1500 r / min for 6 minutes, after dispersion, add 3.2 g IPDA chain extension reaction for 5 minutes, obtain waterborne polyurethane composition pre-emulsion, remove acetone in the emulsion by reduced pressure distillation method (60 °C, 0.1 MPa), obtain 35% solid content, 2000 nm particle size, milky white waterborne polyurethane emulsion. IPDI (isophorone diisocyanate), 108g PPG1000 (polypropylene oxide diol), 2.2g trimethylolpropane, 13.2g dimethylolpropionic acid, 10g CHDM, 0.1g BiCat8108, and 60g acetone were reacted at 70°C until the theoretical NCO value reached 2.29%, yielding 213.45g of end-capped prepolymer. The reaction was then stopped. Cool to below 60℃, add 104g acetone, stir evenly, cool to below 30℃, add 7.89g DMEA and react for 3 minutes. Weigh 396g deionized water into a dispersion cup, pour it into the prepolymer within 6 minutes under high-speed shear conditions of 1500r / min, and after dispersion, add 5g IPDA and react for 5 minutes to obtain an aqueous polyurethane composition preemulsion. Remove the acetone from the emulsion by vacuum distillation (60℃, 0.1MPa) to obtain a 35% solids content, 56nm particle size, semi-transparent bluish aqueous polyurethane emulsion.

[0084] Example 1:

[0085] Add 41g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. MDI-50 (diphenylmethane diisocyanate), 41g TDI-80 (toluene diisocyanate), 110g PPG1000 (polypropylene oxide diol), 2.4g trimethylolpropane, 13.4g dimethylolpropionic acid, 11.2g CHDM, 0.1g BiCat8108, and 76g acetone were reacted at 70°C until the theoretical NCO value reached 2.42%, yielding 219g of end-capped prepolymer. The temperature was lowered to below 60°C, and 132g acetone and 11g MDBA (100% 4,4-MDBA content) were added. The temperature was controlled at 50°C and reacted for 30 minutes. The reaction was stopped, and 132g acetone was added. The mixture was stirred until homogeneous, and the temperature was lowered to below 30°C. 8g of [unspecified ingredient] was added. After DMEA neutralization reaction for 3 minutes, 420g of deionized water was weighed into a dispersion cup and poured into the prepolymer within 6 minutes under high-speed shear conditions of 1500r / min. After dispersion, 3.2g of IPDA was added and the chain extension reaction was carried out for 5 minutes to obtain a waterborne polyurethane composition preemulsion. The acetone in the emulsion was removed by vacuum distillation (60℃, 0.1MPa) to obtain a semi-transparent bluish waterborne polyurethane emulsion with 35% solid content and a particle size of 42nm.

[0086] Example 2:

[0087] Add 41g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. MDI-50 (diphenylmethane diisocyanate), 41g TDI-80 (toluene diisocyanate), 110g PPG1000 (polypropylene oxide diol), 2.4g trimethylolpropane, 13.4g dimethylolpropionic acid, 11.2g CHDM, 0.1g BiCat8108, and 76g acetone were reacted at 70°C until the theoretical NCO value reached 2.42%, yielding 219g of end-capped prepolymer. The temperature was lowered to below 60°C, and 132g acetone and 11g MDBA (4,4-MDBA content approximately 50%) were added. The temperature was controlled at 50°C and reacted for 30 minutes. The reaction was stopped, and 132g acetone was added. The mixture was stirred until homogeneous, and the temperature was lowered to below 30°C. 8g of [unspecified ingredient] was added. After DMEA neutralization reaction for 3 minutes, 420g of deionized water was weighed into a dispersion cup and poured into the prepolymer within 6 minutes under high-speed shear conditions of 1500r / min. After dispersion, 3.2g of IPDA was added and the chain extension reaction was carried out for 5 minutes to obtain a waterborne polyurethane composition preemulsion. The acetone in the emulsion was removed by vacuum distillation (60℃, 0.1MPa) to obtain a semi-transparent bluish waterborne polyurethane emulsion with 35% solid content and a particle size of 36nm.

[0088] Example 3:

[0089] Add 48g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer.

[0090] MDI-50 (Diphenylmethane diisocyanate), 48g TDI-80 (toluene diisocyanate), 98g PPG1000 (polypropylene oxide diol), 2g trimethylolpropane, 13.4g dimethylolpropionic acid, 18g CHDM, 0.1g BiCat8108, and 80g acetone were reacted at 70°C until the theoretical NCO value reached 3.23%, yielding 227.46g of end-capped prepolymer. The temperature was then lowered to below 60°C, and 136g acetone and 14g MDBA (4,4-MDBA content approximately 50%) were added. The temperature was maintained at 50°C for 30 minutes, and the reaction was stopped. 136g acetone was added, and the mixture was stirred until homogeneous. The temperature was then lowered to below 30°C, and 8g of [unclear text - possibly a continuation of the previous sentence] was added. After DMEA neutralization reaction for 3 minutes, 420g of deionized water was weighed into a dispersion cup and poured into the prepolymer within 6 minutes under high-speed shear conditions of 1500r / min. After dispersion, 6.8g of IPDA was added and chain extension reaction was carried out for 5 minutes to obtain a waterborne polyurethane composition preemulsion. The acetone in the emulsion was removed by vacuum distillation (60℃, 0.1MPa) to obtain a semi-transparent bluish waterborne polyurethane emulsion with 35% solid content and a particle size of 39nm.

[0091] Example 4:

[0092] Add 35g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer.

[0093] MDI-50 (Diphenylmethane diisocyanate), 35g TDI-80 (toluene diisocyanate), 120g PPG1000 (polypropylene oxide diol), 2.4g trimethylolpropane, 12g dimethylolpropionic acid, 5g CHDM, 0.1g BiCat8108, and 73g acetone were reacted at 70°C until the theoretical NCO value reached 2.09%, yielding 209.5g of end-capped prepolymer. The temperature was then lowered to below 60°C, and 125g acetone and 6g MDBA (4,4-MDBA content approximately 50%) were added. The reaction was maintained at 50°C for 30 minutes. The reaction was then stopped, and 125g acetone was added. The mixture was stirred until homogeneous, and the temperature was lowered to below 30°C. Finally, 7.17g of [unspecified ingredient] was added. After DMEA neutralization reaction for 3 minutes, 450g of deionized water was weighed into a dispersion cup and poured into the prepolymer within 6 minutes under high-speed shear conditions of 1500r / min. After dispersion, 4g of IPDA was added and chain extension reaction was carried out for 5 minutes to obtain a waterborne polyurethane composition preemulsion. The acetone in the emulsion was removed by vacuum distillation (60℃, 0.1MPa) to obtain a semi-transparent bluish waterborne polyurethane emulsion with 35% solid content and a particle size of 34nm.

[0094] Example 5:

[0095] Add 41g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer.

[0096] MDI-50 (diphenylmethane diisocyanate), 41g TDI-80 (toluene diisocyanate), 110g PPG1000 (polypropylene oxide diol), 2.4g trimethylolpropane, 13.4g dimethylolpropionic acid, 11.2g CHDM, 0.1g BiCat8108, and 76g acetone were reacted at 70°C until the theoretical NCO value reached 2.42%, yielding 219g of end-capped prepolymer. The temperature was lowered to below 60°C, and 132g acetone and 11.6g di-sec-pentanaminodiphenylmethane were added. The temperature was controlled at 50°C and the reaction was carried out for 30 minutes. The reaction was stopped, and 132g acetone was added. The mixture was stirred until homogeneous, and the temperature was lowered to below 30°C. 8g of [unspecified ingredient] was added. After DMEA neutralization reaction for 3 minutes, 430g of deionized water was weighed into a dispersion cup and poured into the prepolymer within 6 minutes under high-speed shear conditions of 1500r / min. After dispersion, 3.2g of IPDA was added and chain extension reaction was carried out for 5 minutes to obtain a waterborne polyurethane composition preemulsion. The acetone in the emulsion was removed by vacuum distillation (60℃, 0.1MPa) to obtain a semi-transparent bluish waterborne polyurethane emulsion with 35% solid content and a particle size of 36nm.

[0097] The compositions prepared in each example and comparative example were prepared into two-component wood coating according to the coating formula listed in the specific embodiments, and performance tests were conducted. The performance test results of the obtained wood coatings are shown in the following table:

[0098]

[0099]

[0100] Note: “--” means that the emulsion is not applicable to the relevant test.

[0101] As can be seen from the test data in the above table, the secondary diamine chain extender provided by the present application is suitable for the preparation of high-activity isocyanate water-based resin, and has better performance in terms of chemical resistance, gloss and hardness.

[0102] From the production practice, the preparation method of the waterborne polyurethane resin of the present application is simple and controllable, and has low cost, and excellent use performance can be obtained, and has great practical use value.

[0103] Those skilled in the art can understand that, under the teaching of the present specification, some modifications or adjustments can be made to the present application. These modifications or adjustments should also be within the scope defined by the claims of the present application.

Claims

1. A method for preparing an aqueous polyurethane composition, characterized in that, Includes the following steps: First, an isocyanate-terminated prepolymer is prepared. Then, a low-boiling-point organic solvent is added to the isocyanate-terminated prepolymer and thoroughly mixed and dissolved. A diamine chain extender is then added. After chain extension is complete, a neutralizing agent is added. Then, water is added under high-speed shearing to disperse the mixture. After dispersion, an aqueous polyurethane crude emulsion is obtained. Finally, the low-boiling-point organic solvent is removed. The diamine chain extender has the following general structural formula, and isomers 2) and / or 3) account for at least 50% by mass fraction of the diamine chain extender. 1)、 2)、 3)、 Where R1 = C x H y R2=C x H y x = 1 - 10, y = 2 - 21.

2. The preparation method according to claim 1, characterized in that, The isocyanate-terminated prepolymer is prepared by mixing and reacting raw materials containing the following components: polyisocyanate, macromolecular polyol, small molecule polyol, hydrophilic chain extender, and polyamine chain extender.

3. The preparation method according to claim 2, characterized in that, The amounts of each raw material used in preparing the waterborne polyurethane composition are as follows: 1) The amount of polyisocyanate used is 30-42 wt% of the mass of the isocyanate-terminated prepolymer; 2) The amount of the macromolecular polyol used is 39-60% of the mass of the isocyanate-terminated prepolymer; 3) The amount of the small molecule polyol used is 2-10 wt% of the isocyanate-terminated prepolymer; 4) The amount of the hydrophilic chain extender is 4-8 wt% of the isocyanate-terminated prepolymer; 5) The amount of the polyamine chain extender is 1-3% of the mass of the isocyanate-terminated prepolymer; 6) The amount of the neutralizing agent is 20%-60% of the amount of the hydrophilic chain extender; 7) The amount of the low-boiling-point organic solvent used is 0.8-1.6 times the mass of the isocyanate-terminated prepolymer; 8) The amount of the diamine chain extender is 2.5-7% of the mass of the isocyanate-terminated prepolymer.

4. The preparation method according to claim 2 or 3, characterized in that, The polyisocyanate is an aliphatic polyisocyanate, an alicyclic polyisocyanate, an aromatic polyisocyanate, or a mixture thereof.

5. The preparation method according to claim 4, characterized in that, The polyisocyanates include one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, pentane diisocyanate, hexahydrotoluene diisocyanate, trimethylhexane diisocyanate, phenylene diisocyanate, 1,4-cyclohexane diisocyanate, dodecyl diisocyanate, 1,5-naphthalene diisocyanate, and dicyclohexylmethane diisocyanate.

6. The preparation method according to claim 2 or 3, characterized in that, The macromolecular polyol is one or more of polyether polyol, polyester polyol, and polycarbonate polyol.

7. The preparation method according to claim 6, characterized in that, The macromolecular polyols include one or more of the following: polyethylene glycol, polypropylene glycol, polyethylene glycol-propylene glycol, polytetrahydrofuran ether diol, dimer acid polyester polyol, polyolefin polyol, polycaprolactone diol, polycarbonate diol, polyethylene adipate diol, 1,4-butanediol adipate diol, neopentyl adipate diol, 1,6-hexanediol adipate diol, and neopentyl adipate diol.

8. The preparation method according to claim 2 or 3, characterized in that, The small molecule polyol is a polyol with a molecular weight of less than 300 g / mol.

9. The preparation method according to claim 8, characterized in that, The small molecule polyol is one or more selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methylpentane-1,5-pentanediol, 1,6-hexanediol, neopentanediol, 1,4-cyclohexyldiethanol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 2-ethyl-3-propylpentanediol, 2,2-dimethylpentanediol, diethylene glycol, glycerol, and trimethylolpropane.

10. The preparation method according to claim 2 or 3, characterized in that, The hydrophilic chain extender comprises a compound with ionic or potentially ionic groups that can react with isocyanates, including one or more of dimethylolpropionic acid, dimethylolbutyric acid, amino acids, aminosulfonates, tartaric acid, N,N-dimethylolmaleamic acid, diaminobenzoic acid, and sodium dihydroxypropanesulfonate; and / or, the polyamine chain extender comprises one or more of ethylenediamine, hydroxyethylethylenediamine, hexamethylenediamine, pentamethylenediamine, diethylenetriamine, isophoronediamine, and 4,4-diphenylmethanediamine.

11. The preparation method according to any one of claims 1-3, characterized in that, The neutralizing agent includes one or more of sodium hydroxide, potassium hydroxide, triethylamine, N,N-dimethylethanolamine, dimethylcyclohexylamine, triethanolamine, methyldiethanolamine, diisopropanolamine, ethyldiisopropylamine, diisopropylcyclohexylamine, N-methylmorpholine, 2-amino-2-methyl-1-propanol, and ammonia; and / or, the low-boiling solvent is an organic solvent with a boiling point below 100°C, including one or more of acetone, methyl ethyl ketone, cyclohexane, dichloromethane, dichloroethane, trichloroethane, ethyl acetate, pentane, heptane, and hexane.

12. The preparation method according to claim 11, characterized in that, The neutralizing agent is one or more of sodium hydroxide, triethylamine, and N,N-dimethylethanolamine.

13. The preparation method according to any one of claims 1-3, characterized in that, The reaction temperature used to prepare the isocyanate-terminated prepolymer is 60-70℃, and the reaction proceeds to the theoretically designed residual NCO value; and / or, The low-boiling-point organic solvent is mixed and dissolved with the isocyanate-terminated prepolymer at a temperature below 60°C; and / or, The reaction temperature of the diamine with the isocyanate-terminated prepolymer is 40-60℃, and the reaction time is 20-60 minutes.

14. Use of the waterborne polyurethane composition prepared by any one of claims 1-13 in the preparation of waterborne wood coatings.

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