Synthesis and application of an aromatic waterborne polyurethane / acrylate composition

Abstract

This invention provides a method for preparing and applying an aqueous aromatic polyurethane composition, comprising the following steps: (1) synthesizing an isocyanate-terminated prepolymer, adding an organic solvent diluent to fully mix and dissolve the isocyanate-terminated prepolymer; (2) adding an organic solvent solution of an aromatic diamine, followed by adding an acrylate monomer and a neutralizing agent, then adding deionized water for shear dispersion, and after dispersion, adding a polyamine chain extender to obtain a pre-modified emulsion; (3) emulsifying another portion of the modified monomer in the pre-modified emulsion, performing free radical polymerization, and finally removing the low-boiling-point organic solvent. The modified aromatic aqueous polyurethane composition prepared by the method provided by this invention can effectively control the side reactions between isocyanate and water, resulting in small particle size and excellent performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of aromatic waterborne polyurethane / acrylate composition and application, in particular to the application of an aromatic waterborne polyurethane / acrylate wood paint coating. BACKGROUND

[0002] In recent years, with the continuous improvement of environmental regulations, the proportion of waterborne coatings in the market is increasing. As a kind of waterborne coatings, waterborne polyurethane emulsion is widely used in wood coatings, textiles, synthetic leather, adhesives, glass fiber sizing agent and personal care due to its excellent low VOC, fullness, chemical resistance, mechanical properties and mechanical properties. However, in recent years, due to the price surge of isocyanate, one of the important raw materials of waterborne polyurethane emulsion, especially the price of 4,4'-dicyclohexyl methane diisocyanate from 50 yuan / kg to 90 yuan / kg, which greatly limits the development and application of waterborne polyurethane emulsion.

[0003] Therefore, it is urgent to use relatively low-cost aromatic isocyanate such as toluene diisocyanate and diphenylmethane diisocyanate to produce waterborne polyurethane. Aromatic isocyanate has high reactivity, which is easy to react with water during dispersion, resulting in large particle size and a large amount of carbon dioxide. In order to reduce the side reaction between isocyanate and water during dispersion, small molecule diol chain extender is generally added to reduce the final isocyanate content, but this will cause the problem of long pre-polymerization time and high viscosity of pre-polymer. It brings many difficulties to the production of waterborne polyurethane.

[0004] The present application uses aromatic secondary amine which can be added after the pre-polymerization is completed, solving the problem of side reaction between aromatic isocyanate and water. SUMMARY

[0005] In order to make up for the shortcomings of the prior art, the present application provides a preparation method of aromatic waterborne polyurethane / acrylate composition and the application of the composition prepared by the preparation method. The modified aromatic waterborne polyurethane composition prepared by the preparation method can well control the side reaction between isocyanate and water, has small particle size and excellent performance.

[0006] In order to achieve the purpose, the technical scheme adopted by the present application is as follows:

[0007] The present application provides a preparation method of modified aromatic waterborne polyurethane composition, comprising the following steps:

[0008] (1) synthesis of isocyanate-terminated prepolymer, adding organic solvent diluent and mixing with isocyanate-terminated prepolymer, (2) adding aromatic secondary diamine organic solvent solution, then adding acrylate monomer and neutralizing agent, and then adding deionized water for shearing dispersion, after dispersion, adding polyamine chain extender to obtain pre-modified emulsion, (3) emulsifying another part of modified monomer in the pre-modified emulsion, and then performing free radical polymerization, and finally removing low-boiling organic solvent.

[0009] In the present application, the isocyanate-terminated prepolymer in step (1) is prepared by mixing and reacting the following raw materials: aromatic polyisocyanate, macromolecular polyol, small molecular polyol, monol and / or diol containing polyethylene oxide chain segment in main chain and / or side chain, hydrophilic chain extender, polyamine chain extender, neutralizing agent, low-boiling point solvent, and aromatic secondary diamine.

[0010] In the present application, based on the total mass of the isocyanate-terminated prepolymer for preparing the modified waterborne polyurethane composition, the preparation of the modified waterborne polyurethane composition comprises the following amounts of each component:

[0011] 1) the amount of the aromatic polyisocyanate is 20-50 wt% of the mass of the isocyanate-terminated prepolymer, preferably 22.8-43.8 wt%;

[0012] 2) the amount of the macromolecular polyol is 20-65 wt% of the mass of the isocyanate-terminated prepolymer, preferably 28.7-56.3 wt%;

[0013] 3) the amount of the small molecular polyol is 0.5-15 wt% of the mass of the isocyanate-terminated prepolymer, preferably 1.06-10.6 wt%;

[0014] 4) the amount of the monol and / or diol containing polyethylene oxide chain segment in main chain and / or side chain is 0.2-10 wt% of the mass of the isocyanate-terminated prepolymer, preferably 0.6-3.3 wt%;

[0015] 5) the amount of the hydrophilic chain extender is 3-15 wt% of the mass of the isocyanate-terminated prepolymer, preferably 4.16-9.44 wt%;

[0016] 6) the amount of the polyamine chain extender is 0.2-5 wt% of the mass of the isocyanate-terminated prepolymer, preferably 0.6-1.3 wt%;

[0017] 7) the amount of the neutralizing agent is 1.0-10 wt% of the mass of the isocyanate-terminated prepolymer, preferably 2.4-7.1 wt%;

[0018] 8) the amount of the aromatic secondary diamine is 1-10 wt% of the mass of the isocyanate-terminated prepolymer, preferably 3.3-7.6 wt%;

[0019] 9) the low boiling point solvent is used in an amount of 0.7-1.45 times the mass of the isocyanate-terminated prepolymer;

[0020] 10) the modified monomer is used in an amount of 0.7-1.4 times, preferably 0.7-1.1 times, the mass of the isocyanate-terminated prepolymer;

[0021] 11) the initiator is used in an amount of 0.05-0.3%, preferably 0.1-0.2%, of the total mass of the modified monomer.

[0022] In the preparation method of the present application, the aromatic polyisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, dimethyl diphenyl diisocyanate, dimethyl diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, and the like, preferably toluene diisocyanate.

[0023] In the preparation method of the present application, the macromolecular polyol is one or more of polypropylene glycol, polyethylene glycol-propylene glycol, polytetrahydrofuran ether glycol, dimer acid polyester polyol, polyolefin polyol, polycaprolactone diol, hydrogenated castor oil, polycarbonate diol, polyethylene glycol adipate diol, poly-1,4-butanediol adipate diol, polyneopentyl glycol adipate diol, poly-1,6-hexanediol adipate diol, and polyneopentyl glycol adipate-1,6-hexanediol diol, further polypropylene glycol with a number average molecular weight of 2000 daltons.

[0024] In the preparation method of the present application, the small molecular polyol is one or more of 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, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 2-ethyl-3-propyl pentanediol, 2,2-dimethyl pentanediol, diethylene glycol, glycerol, and trimethylolpropane, preferably 1,4-cyclohexanedimethanol.

[0025] In the preparation method of the present application, the monohydric alcohol and / or dihydric alcohol containing polyoxyethylene chain segments in the main chain and / or side chain contain 90-100 wt% of ethylene oxide in the polymeric unit containing polyoxyethylene chain segments, preferably TegoChemie's D-3403, Ymer™ N120 from Perstrop and MPEG1200 from Lotte Chemicals, South Korea, or one or more of these, more preferably Ymer™ N120 from Perstrop and / or MPEG1200 from Lotte Chemicals, South Korea, with MPEG1200 being the preferred choice.

[0026] In the preparation method of the present invention, the hydrophilic chain extender includes a compound with ionic or potential ionic groups that can react with isocyanates, including one or two of sodium ethylenediamine ethanesulfonate, dimethylolpropionic acid, dimethylolbutyric acid, amino acids, aminosulfonates, tartaric acid, N,N-dimethylolmaleamic acid, diaminobenzoic acid, sodium dihydroxypropanesulfonate, etc., preferably dimethylolpropionic acid.

[0027] In the preparation method of the present invention, the initiator initiation system is a redox system.

[0028] Preferably, the oxidant includes one or more of ammonium persulfate, sodium persulfate, potassium persulfate, di-tert-butyl peroxide, benzoyl peroxide, hydrogen peroxide, cumene hydrogen peroxide, and tert-butyl hydrogen peroxide, with tert-butyl hydrogen peroxide being more preferred.

[0029] Preferably, the reducing agent includes one or more of sodium hydrosulfite, FF6M, N,N-dimethylaniline, ferrous sulfate, silver nitrate, thiols, ferrous chloride, tetraethyleneimine, sodium metabisulfite, sodium formaldehyde sulfoxylate, sodium bisulfite, and isoascorbic acid, with sodium metabisulfite being more preferred.

[0030] In the preparation method of the present invention, the reaction temperature used to prepare the isocyanate-terminated prepolymer is 65-80℃;

[0031] Preferably, the reaction temperature of the aromatic diamine and the isocyanate-terminated prepolymer is 40-65℃;

[0032] Preferably, the modified monomer and the isocyanate-terminated prepolymer are mixed and dissolved at 60-70°C;

[0033] Preferably, the initiation temperature of the pre-modified emulsion-initiated polymerization is 30-45°C.

[0034] In this invention, the organic solvent in step (1) is an organic solvent with a boiling point below 100°C, selected from one or more of acetone, methyl ethyl ketone, cyclohexane, dichloromethane, dichloroethane, trichloroethane, ethyl acetate, pentane, heptane, and hexane, preferably acetone.

[0035] In this invention, the mixing and dissolving time in step (1) is 5 min to 30 min;

[0036] In this invention, the aromatic diamine in step (2) has the following general structural formula:

[0037]

[0038] Where R1 = C x H y R2=C x H y 1≤x≤6, 3≤y≤20.

[0039] Specifically, the aromatic diamine can be selected from one or more of 4,4'-bis(methylamino)diphenylmethane, 4,4'-bis(sec-butylamino)diphenylmethane, 4,4'-bis(butylamino)diphenylmethane, 4,4'-bis(ethylamino)diphenylmethane, and 4,4'-bis(hexylamino)diphenylmethane.

[0040] Referring to CN107501524A, the synthesis process of the aromatic diamine is as follows: 4,4-diaminodiphenylmethane, haloalkanes, and morpholine are heated and stirred to dissolve, macroporous strong base anion exchange resin is added, nitrogen is used for purging, the temperature is raised to 40-180℃, the pressure is controlled at 1-5 MPa, the reaction is stirred for 1-5 hours, and fractional distillation is performed to obtain the aromatic diamine.

[0041] In this invention, the organic solvent in step (2) is selected from one or more of acetone, butanone, and cyclohexanone;

[0042] In this invention, the neutralizing agent in step (2) is selected from 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. Preferred neutralizing agents are sodium hydroxide, triethylamine, and / or N,N-dimethylethanolamine, with N,N-dimethylethanolamine being more preferred.

[0043] In this invention, the polyamine chain extender in step (2) is an organic or inorganic primary or secondary amine functional compound containing at least two active hydrogen atoms, specifically selected from one or more of ethylenediamine, 2-methyl-1,5-pentanediamine, isophorone diamine, hydrazine, hydroxyethyl ethylenediamine, hexanediamine, diethylenetriamine, triethylenetetramine, cyclohexanediamine, phenylenediamine, toluenediamine, and dicyclohexylmethanediamine, preferably isophorone diamine.

[0044] In this invention, the shearing and dispersion time in step (2) is not particularly limited and is 6 min to 1 h.

[0045] In this invention, the modified monomer in step (3) includes at least one of the olefinic unsaturated monomers capable of free radical polymerization, specifically selected from one or more of the following olefinic unsaturated monomers: methyl acrylate, phosphate acrylate, siloxane acrylate, allyl methacrylate, ethyl acrylate, hydroxypropyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, hydroxyethyl methacrylate, butyl methacrylate, tetrahydrofuran acrylate, styrene, allyl methylstyrene, isobornyl acrylate, and isooctyl acrylate, with methyl methacrylate and styrene being preferred.

[0046] In this invention, the reactor for the free radical polymerization in step (3) is a reaction vessel; the temperature for free radical polymerization is 25-45℃, preferably 30-38℃, the time is 10min-2h, preferably 20min-1h, and the pressure is 0-100kPa, preferably 0-50kPa. In this invention, the method for removing low-boiling-point organic solvents is vacuum distillation.

[0047] A second aspect of the present invention also provides a wood coating comprising the modified waterborne polyurethane composition prepared by the aforementioned preparation method.

[0048] The third aspect of the present invention provides the application of the modified waterborne polyurethane composition prepared by the preparation method described above, preferably suitable for single-component wood coating applications.

[0049] The technical solution provided by this invention has the following advantages:

[0050] The use of aromatic diamines to reduce the isocyanate content of the prepolymer before dispersion significantly reduces the probability of side reactions between isocyanate and water during dispersion. The reaction between water and isocyanate produces carbon dioxide; adding aromatic diamines reduces carbon dioxide production, making the production process safer and more controllable. The reaction between water and isocyanate also produces polyurethane urea, which further reacts with isocyanate, increasing the emulsion viscosity and molecular weight. Adding aromatic diamines reduces the probability of polyurethane urea formation, resulting in a clear emulsion with small particle size and controllable viscosity.

[0051] Aromatic secondary diamines exhibit reactivity between that of aliphatic diols and isocyanates, meaning they can be added after the reaction of aliphatic diols with isocyanates has concluded and a diluent has been added. They react gently with isocyanates at 40-60°C without gelation due to excessively rapid reaction. When reducing isocyanate content using aliphatic diols, the reaction temperature needs to reach 65-75°C, necessitating a reduction in the amount of low-boiling-point solvents. This results in excessively high prepolymer viscosity, making it impossible to dilute and dissolve or disperse with low-boiling-point solvents. Conversely, reducing isocyanate content using aliphatic diamines, due to their high reactivity, causes a rapid increase in molecular weight, leading to gelation.

[0052] Aromatic diamines can form polybenzene ring structures with isocyanates with the following special structure, which can effectively improve the chemical resistance and water resistance of resins.

[0053] Polybenzene ring structure:

[0054]

[0055] The stepwise addition of acrylate monomers used in this invention can reduce the hydrophilic group content of the prepolymer, so that only a lower number of hydrophilic groups are needed to obtain a transparent emulsion.

[0056] The preparation method of this invention is simple, safe, efficient, and has low VOC content. Detailed Implementation

[0057] To better understand the technical solution of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0058] Unless otherwise specified, "%" in the examples or comparative examples refers to "wt%".

[0059] The test methods used in the embodiments or comparative examples are described below:

[0060] Solid content test method: Take an appropriate amount of emulsion in a container made of tin foil, weigh the weight change before and after 20 minutes at 150℃, and calculate its solid content.

[0061] Particle size testing method: Malvern particle size analyzer was used, and the particle size was diluted 1000 times with distilled water at room temperature.

[0062] pH testing method: A Metrohm pH meter from Switzerland was used.

[0063] The formulations used in preparing coatings with the emulsions obtained in the following examples or comparative examples are shown in Table 1 below:

[0064] Table 1

[0065] Name Material Mass / g Emulsion prepared in example or comparative example Emulsion 80 BYK 024 Defoamer 0.4 Tego 245 Wetting agent 0.4 Tego 270 Wetting agent 0.4 DPM Coalescing agent 3 DPnB Coalescing agent 3 Vesmody® U605 Polyurethane thickener 0.2 Water Diluent 12.55

[0066] The methods for testing the application performance of the examples and comparative examples are described below:

[0067] Sample application process: Substrate — Water-based base color correction — Water-based first coat primer — Water-based Glaze — Water-based clear primer — Water-based clear primer — Water-based top color correction — Water-based topcoat.

[0068] Alcohol resistance test: The finished product sample was immersed in 50% ethanol solution for 1 hour and 24 hours respectively. After removing and drying, the condition of the paint film was observed.

[0069] Water resistance test: Immerse the finished sample in deionized water for 24 hours, remove it, wipe off the water stains, and observe the condition of the paint film.

[0070] Gloss test method: According to GB 1743-79 "Determination of Gloss of Coating Film", the gloss at a 60° angle is tested.

[0071] Pendulum hardness test method: The hardness is tested according to GB / T1730-1993, "Determination of Hardness of Paint Film - Pendulum Damping Test".

[0072] The raw materials used in the examples or comparative examples are described below:

[0073] (Toluene diisocyanate, Wanhua Chemical Group Co., Ltd.);

[0074] (4,4'-Diphenylmethane diisocyanate, Wanhua Chemical Group Co., Ltd.);

[0075] PPG2000 (polypropylene oxide diol, number average molecular weight = 2000, functionality = 2, Wanhua Chemical Group Co., Ltd.);

[0076] PCL2000 (polycaprolactone diol, number average molecular weight = 2000, functionality = 2, Daicel Ltd.);

[0077] HB (hydrogenated castor oil, BASF, Germany)

[0078] MPEG1200 (methoxy polyethylene glycol ether, Lotte Korea);

[0079] DMPA (dimethylolpropionic acid, Persto);

[0080] BiCat8108 (organic bismuth catalyst, leading in the United States);

[0081] DMEA (N,N-dimethylethanolamine, BASF, Germany);

[0082] TEA (Triethylamine, Aladdin Reagent Co., Ltd.)

[0083] Acetone (refined by Wanhua Chemical Group Co., Ltd., water content 200ppm);

[0084] TMP (Trimethylolpropane, Wanhua Chemical Group Co., Ltd.);

[0085] EDA (ethylenediamine, Yangzi Petrochemical);

[0086] MMA (methyl methacrylate, Qilu Petrochemical);

[0087] MDBA: (4,4'-bis-sec-butylaminodiphenylmethane, Wanhua Chemical)

[0088] MDMA: 4,4'-dimethylaminodiphenylmethane

[0089] In a 1L autoclave, add 99g (0.5 mol) of 4,4-diaminodiphenylmethane, 142g (1 mol) of iodomethane, and 400g of morpholine. Heat and stir to dissolve. Add 6g of macroporous strong base anion exchange resin (D201). Close the autoclave and purge with N2 3-5 times. Start heating to 50℃ and control the pressure of the reaction system at about 2MPa. Stir the reaction for 2 hours and then fractionate.

[0090] MDAA: 4,4'-Dihexylaminodiphenylmethane;

[0091] In a 1L autoclave, add 99g (0.5 mol) of 4,4-diaminodiphenylmethane, 198g (1.2 mol) of hexane, and 300g of morpholine. Heat and stir to dissolve. Add 14g of macroporous strong base anion exchange resin (D201). Close the autoclave and purge with N2 3-5 times. Start heating to 140℃, control the pressure of the reaction system at about 5MPa, stir the reaction for 4 hours, and then fractionate.

[0092] ST (Styrene, Qilu Petrochemical)

[0093] Sodium metabisulfite (Xilong Chemical Co., Ltd.)

[0094] BDO (1,4-Butanediol, Aladdin Reagent Co., Ltd.)

[0095] CHDM (1,4-cyclohexanediethanol, Eastman Ltd.)

[0096] TBHP (tert-butyl hydroperoxide, 70%, Xilong Chemical Co., Ltd.)

[0097] (Thickener, Wanhua Chemical Group Co., Ltd.)

[0098] BYK 024 (Defoamer, BYK Corporation)

[0099] Tego 245 (wetting agent, Tego GmbH, Germany)

[0100] Tego 270 (wetting agent, Tego GmbH, Germany)

[0101] DPM (film-forming aid, Dow Chemical)

[0102] DPnB (film-forming aid, Dow Chemical)

[0103] NPG: (Neopentyl Glycol, Wanhua Chemical Group Co., Ltd.)

[0104] Example 1:

[0105] Add 98.0g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. The following ingredients were added: 115g PPG2000 (polypropylene oxide diol), 23g HB (hydrogenated castor oil), 2.6g TMP, 2.6g MPEG1200, 16.5g dimethylolpropionic acid, 0.05g BiCat8108, 30.7g CHDM, and 70g acetone. The mixture was heated to 80°C and reacted until the theoretical NCO value was reached, at which point the reaction was stopped. The temperature was lowered to below 60°C, and 264g acetone was added. The mixture was stirred until homogeneous, and then cooled to 50°C. A mixed solution of 14g MDBA and 56g acetone was added, and the reaction was continued until the theoretical NCO value was reached. 275g MMA was then added. The temperature was lowered to 30°C, and 9.6g DMEA was added. The mixture was stirred for 5 minutes, and then 1000g deionized water was added under high-speed shear. After dispersion, 2g EDA diluted with four times its volume of water was added to obtain a pre-emulsion of the modified waterborne polyurethane composition. The emulsion was transferred to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. 60 g of MMA was added, and the mixture was heated to 35 °C and stirred for 1 h. 0.96 g of TBHP and 0.67 g of sodium metabisulfite were added sequentially to initiate free radical polymerization. After polymerization, the acetone in the emulsion was removed by vacuum distillation to obtain a modified waterborne polyurethane composition with 40% solid content and a particle size of 75 nm that is semi-transparent and bluish in color.

[0106] Example 2:

[0107] Add 56g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. The following ingredients were added: 115g PCL2000 (polycaprolactone diol), 23g HB (hydrogenated castor oil), 2.6g TMP, 8g MPEG1200, 19g dimethylolpropionic acid, 0.05g BiCat8108, and 70g acetone. The mixture was heated to 65°C and reacted until the theoretical NCO value was reached, at which point the reaction was stopped. The temperature was lowered to below 60°C, and 68g acetone was added. The mixture was stirred until homogeneous, and then cooled to 40°C. A mixed solution of 8g MDBA and 32g acetone was added, and the reaction was continued until the theoretical NCO value was reached. 275g MMA was then added. The temperature was lowered to 35°C, and 11g DMEA was added. The mixture was stirred for 10 minutes, and then 900g deionized water was added under high-speed shear. After dispersion, 2.5g IPDA diluted with four times its volume of water was added to obtain a modified waterborne polyurethane composition pre-emulsion. The emulsion was transferred to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. 53g of MMA was added, and the mixture was heated to 45°C and stirred for 1 hour. 0.47g of TBHP and 0.33g of sodium metabisulfite were added sequentially to initiate free radical polymerization. After polymerization, the acetone in the emulsion was removed by vacuum distillation to obtain a modified waterborne polyurethane composition with 40% solid content and a particle size of 70nm that is semi-transparent and bluish in color.

[0108] Example 3:

[0109] Add 130.0g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. The following ingredients were added: toluene diisocyanate (Toluene), 170g PPG2000 (polypropylene oxide diol), 2.6g TMP, 2.6g MPEG1200, 16.5g dimethylolpropionic acid, 0.05g BiCat8108, 30g BDO, and 70g acetone. The mixture was heated to 75°C and reacted until the theoretical NCO value was reached, at which point the reaction was stopped. The temperature was lowered to below 60°C, and 230g acetone was added. A mixed solution of 30g MDAA and 120g acetone was added, and the reaction was continued until the theoretical NCO value was reached. Then, 275g MMA was added. The temperature was lowered to 30°C, and 9.6g DMEA was added. The mixture was stirred for 5 minutes, and 1200g deionized water was added under high-speed shear. After dispersion, 5g IPDA diluted with four times its volume of water was added to obtain a pre-emulsion of the modified waterborne polyurethane composition. The emulsion was transferred to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. 60g of styrene was added, and the temperature was raised to 40°C. 0.72g of TBHP and 0.5g of sodium metabisulfite were added sequentially to initiate free radical polymerization. After polymerization, the acetone in the emulsion was removed by vacuum distillation to obtain a modified waterborne polyurethane composition with 40% solid content, 100nm particle size, and semi-transparent bluish luster.

[0110] Example 4:

[0111] Add 130.0g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. 85g of 4,4'-diphenylmethane diisocyanate, 2.6g of PPG1000 (polypropylene oxide diol), 2.6g of MPEG1200, 28g of dimethylolpropionic acid, 0.05g of BiCat8108, 6g of BDO, and 50g of acetone were added. The mixture was heated to 75°C and reacted until the theoretical NCO value was reached, at which point the reaction was stopped. The temperature was lowered to below 60°C, and 220g of acetone was added. A mixed solution of 20g of MDAA and 80g of acetone was added, and the reaction was continued until the theoretical NCO value was reached. Then, 160g of MMA was added. The temperature was lowered to 30°C, and 18.5g of DMEA was added. The mixture was stirred for 5 minutes, and 900g of deionized water was added under high-speed shear. After dispersion, 4g of EDA diluted with four times its volume of water was added to obtain a pre-emulsion of the modified waterborne polyurethane composition. The emulsion was transferred to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. 33g of MMA was added, and the temperature was raised to 35°C. 0.55g of TBHP and 0.39g of sodium metabisulfite were added sequentially to initiate free radical polymerization. After polymerization, the acetone in the emulsion was removed by vacuum distillation to obtain a modified waterborne polyurethane composition with 40% solid content and a particle size of 65nm that is semi-transparent and bluish in color.

[0112] Comparative Example 1:

[0113] Add 98.0g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. The following ingredients were added: toluene diisocyanate (TPI), 115g PPG2000 (polypropylene oxide diol), 23g HB (hydrogenated castor oil), 2.6g TMP, 2.6g MPEG1200, 16.5g dimethylolpropionic acid, 0.05g BiCat8108, 30.7g CHDM, and 70g acetone. The mixture was heated to 80°C and reacted until the theoretical NCO value was reached, at which point the reaction was stopped. The temperature was lowered to below 60°C, and 264g acetone was added. The mixture was stirred until homogeneous, and then cooled to 50°C. 275g MMA was added. The temperature was lowered to 30°C, and 9.6g DMEA was added. The mixture was stirred for 5 minutes, and then 1000g deionized water was added under high-speed shear. After dispersion, 2g EDA diluted with four times its volume of water was added to obtain a pre-emulsion of the modified waterborne polyurethane composition. The emulsion was transferred to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. 60 g of MMA was added, and the mixture was heated to 35 °C and stirred for 1 h. 0.96 g of TBHP and 0.67 g of sodium metabisulfite were added sequentially to initiate free radical polymerization. After polymerization, the acetone in the emulsion was removed by vacuum distillation to obtain a modified waterborne polyurethane composition with 40% solid content and a particle size of 200 nm with a bluish tint.

[0114] Comparative Example 2:

[0115] Add 98.0g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. The following ingredients were added: toluene diisocyanate, 115g PPG2000 (polypropylene oxide diol), 23g HB (hydrogenated castor oil), 2.6g TMP, 2.6g MPEG1200, 16.5g dimethylolpropionic acid, 0.05g BiCat8108, 30.7g CHDM, and 70g acetone. The mixture was heated to 80°C and reacted until the theoretical NCO value was reached, at which point the reaction was stopped. The temperature was lowered to below 60°C, and 264g acetone was added. The mixture was stirred until homogeneous, and then cooled to 50°C. 275g MMA was added. The temperature was lowered to 30°C, and 9.6g DMEA was added. The mixture was stirred for 5 minutes, and then 1000g deionized water was added under high-speed shear. After dispersion, 14g MDBA and 2g EDA diluted with four times the amount of water were added to obtain a modified waterborne polyurethane composition pre-emulsion. The emulsion was transferred to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. 60g of MMA was added, and the mixture was heated to 35°C and stirred for 1 hour. 0.96g of TBHP and 0.67g of sodium metabisulfite were added sequentially to initiate free radical polymerization. After polymerization, the acetone in the emulsion was removed by vacuum distillation to obtain a modified waterborne polyurethane composition with 40% solid content and a particle size of 180nm with a bluish tint.

[0116] Comparative Example 3:

[0117] Add 98.0g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. The following ingredients were added: 115g PPG2000 (polypropylene oxide diol), 23g HB (hydrogenated castor oil), 2.6g TMP, 2.6g MPEG1200, 16.5g dimethylolpropionic acid, 0.05g BiCat8108, 30.7g CHDM, and 70g acetone. The mixture was heated to 80°C and reacted until the theoretical NCO value was reached, at which point the reaction was stopped. The mixture was cooled to below 60°C, and 264g acetone was added. After stirring until homogeneous, the mixture was cooled to 50°C, and a mixed solution of 14g NPG and 56g acetone was added. The mixture was heated to 60°C and reacted until the theoretical NOC value was reached, at which point the reaction was stopped, and the mixture was stirred until homogeneous. The mixture was cooled to 50°C, and 275g MMA was added. The mixture was cooled to 30°C, and 9.6g DMEA was added. After stirring for 5 minutes, 1000g deionized water was added under high-speed shear. After dispersion, 2g EDA diluted with four times its volume of water was added to obtain a pre-emulsion of the modified waterborne polyurethane composition. The emulsion was transferred to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. 60g of MMA was added, and the mixture was heated to 35°C and stirred for 1 hour. 0.96g of TBHP and 0.67g of sodium metabisulfite were added sequentially to initiate free radical polymerization. After polymerization, the acetone in the emulsion was removed by vacuum distillation to obtain a modified waterborne polyurethane composition with 40% solid content and a particle size of 150nm that is semi-transparent and bluish in color.

[0118] Comparative Example 4:

[0119] Add 98.2g to a four-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer. The following ingredients were added: toluene diisocyanate, 115g PPG2000 (polypropylene oxide diol), 23g HB (hydrogenated castor oil), 2.6g TMP, 2.6g MPEG1200, 16.5g dimethylolpropionic acid, 0.05g BiCat8108, 30.7g CHDM, and 56g acetone. The mixture was heated to 75°C and reacted until the theoretical NCO value was reached, at which point the reaction was stopped. The temperature was then lowered to below 60°C, and 264g acetone was added. The mixture was stirred until homogeneous, and then cooled to 30°C. A mixed solution of 9g IPDA and 36g acetone was added. The viscosity was too high, and the prepolymer exhibited a climbing effect. The prepolymer could not be dispersed properly.

[0120] The compositions obtained in each embodiment and comparative example were used to prepare wood coatings according to the coating formulations listed in the specific embodiments, and performance tests were conducted. The performance test results of the obtained wood coatings are shown in the table below:

[0121]

[0122] Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing a modified aromatic waterborne polyurethane composition, comprising the following steps: (1) Synthesize the isocyanate-terminated prepolymer, add an organic solvent diluent and mix thoroughly with the isocyanate-terminated prepolymer to dissolve it, (2) add an organic solvent solution of an aromatic diamine, then add an acrylate monomer and a neutralizing agent, then add deionized water for shear dispersion, after dispersion, add a polyamine chain extender to obtain a pre-modified emulsion, (3) add a modified monomer to the pre-modified emulsion for emulsification, carry out free radical polymerization, and finally remove the low-boiling-point organic solvent; the aromatic diamine in step (2) has the following general structural formula: Where R1=CxHy, R2=CxHy, 1≤x≤6, 3≤y≤20; the modified monomer in step (3) includes at least one of the olefinic unsaturated monomers that can undergo free radical polymerization.

2. The preparation method according to claim 1, characterized in that, In step (1), the organic solvent is an organic solvent with a boiling point below 100°C, selected from one or more of acetone, methyl ethyl ketone, cyclohexane, dichloromethane, dichloroethane, trichloroethane, ethyl acetate, pentane, heptane, and hexane.

3. The preparation method according to claim 1, characterized in that, The aromatic diamine is selected from one or more of 4,4'-bis(methylamino)diphenylmethane, 4,4'-bis(sec-butylamino)diphenylmethane, 4,4'-bis(butylamino)diphenylmethane, 4,4'-bis(ethylamino)diphenylmethane, and 4,4'-bis(hexylamino)diphenylmethane.

4. The preparation method according to any one of claims 1-3, characterized in that, In step (2), the neutralizing agent is selected from 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, in step (2), the polyamine chain extender is an organic or inorganic primary or secondary amine functional compound containing at least two active hydrogens, selected from one or more of ethylenediamine, 2-methyl-1,5-pentanediamine, isophorone diamine, hydrazine, hydroxyethylethylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, cyclohexanediamine, phenylenediamine, toluenediamine, and dicyclohexylmethanediamine.

5. The preparation method according to any one of claims 1-3, characterized in that, In step (3), the modified monomer is selected from one or more of the following unsaturated monomers: methyl acrylate, phosphate acrylate, siloxane acrylate, allyl methacrylate, ethyl acrylate, hydroxypropyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, hydroxyethyl methacrylate, butyl methacrylate, tetrahydrofuran acrylate, styrene, allyl methylstyrene, isobornyl acrylate, and isooctyl acrylate.

6. A modified aromatic waterborne polyurethane composition obtained by any one of the preparation methods of claims 1-5.

7. A single-component wood coating, characterized in that, The single-component wood coating includes a modified aromatic waterborne polyurethane composition obtained by any one of the preparation methods of claims 1-5 or as described in claim 6.

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