Anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion, and preparation method and application thereof

Abstract

The present application belongs to the technical field of polyurethane emulsion, and particularly relates to an anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion, a preparation method and application thereof. In the present application, a neutralizing agent can pre-neutralize 2,2-dimethylol butyric acid, and further, a branched soybean oil-based polyol can copolymerize with the pre-neutralized 2,2-dimethylol butyric acid and isophorone diisocyanate, thereby improving the ionization degree of the hyperbranched polyurethane network and promoting the formation of a more stable polyurethane emulsion. The branched structure of the branched soybean oil-based polyol is used to construct the hyperbranched waterborne polyurethane, which can be applied to waterborne wood paint, and the dense crosslinking structure can improve the water resistance and hardness of the vegetable oil-based waterborne polyurethane wood paint coating.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyurethane emulsion, and particularly relates to an anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion, a preparation method and application thereof. BACKGROUND

[0002] With the development of economy and the improvement of environmental awareness, people's pursuit of living standards and high concern for health, the application of home decoration and furniture coatings has quietly changed from oil paint to water paint. Today, when more attention is paid to paint safety and environmental indicators, the promotion of water-based wood paint plays a very positive role in the rational use of resources and the improvement of environmental protection, and is increasingly popular in the market due to its low hazard and low pollution characteristics.

[0003] Waterborne polyurethane wood paint is a kind of paint with polyurethane resin as the main component and film-forming material, which has the advantages of good workability, high solid content, high film hardness, excellent wear resistance and impact resistance, etc. However, the preparation of waterborne polyurethane still mainly relies on petrochemical resources, which makes the waterborne polyurethane wood paint affected by many factors such as the increasing consumption of petrochemical resources and the unstable price of fossil raw materials, which is not conducive to the long-term and sustainable development of waterborne polyurethane wood paint. Vegetable oil is a typical renewable biomass resource, and natural oils such as tung oil have been used in wood coatings for a long time. Developing bio-based waterborne polyurethane for wood paint by replacing petrochemical resources with vegetable oil not only has theoretical feasibility but also has the advantages of sustainable and easy availability. However, as the main film-forming component in waterborne wood paint, the practical performance of vegetable oil-based waterborne polyurethane is still limited, such as poor water resistance and low hardness of vegetable oil-based waterborne polyurethane wood paint.

[0004] Therefore, it is necessary to design a vegetable oil-based waterborne polyurethane wood paint with high water resistance and high hardness to meet its use requirements. SUMMARY

[0005] The purpose of the present application is to provide an anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion, a preparation method and application thereof. The waterborne polyurethane emulsion provided by the present application has the advantages of excellent water resistance and high hardness after film formation.

[0006] In order to achieve the above purpose, the present application provides the following technical scheme:

[0007] The present application provides an anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion, which comprises the following components in parts by weight: branched soybean oil-based polyol 80-120 parts, isophorone diisocyanate 30-70 parts, 2,4-dihydroxymethyl butyric acid 8-20 parts, neutralizing agent 5-12 parts and water 500-800 parts.

[0008] Preferably, the neutralizing agent comprises one or more of triethylamine, triethanolamine, aqueous ammonia, diethanolamine, sodium hydroxide, potassium hydroxide, trimethylamine and tripropylamine.

[0009] Preferably, the solid content of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion is 20-40%.

[0010] Preferably, the bio-based content of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion is 40-60%.

[0011] The present application also provides a preparation method of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion described in the above technical solution, comprising the following steps:

[0012] Mixing 2,4-dihydroxymethyl butyric acid and a neutralizing agent to obtain pre-neutralized 2,4-dihydroxymethyl butyric acid;

[0013] Mixing the pre-neutralized 2,4-dihydroxymethyl butyric acid, branched soybean oil-based polyol and isophorone diisocyanate to carry out polymerization, adding an organic solvent to dilute when the viscosity of the obtained prepolymer increases, and continuing to react until the NCO group content in the system decreases to below 5% to obtain a polymer system;

[0014] Cooling the polymer system to room temperature, emulsifying after adding water, and removing the organic solvent to obtain the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion.

[0015] Preferably, the molar ratio of active groups in the pre-neutralized 2,4-dihydroxymethyl butyric acid, branched soybean oil-based polyol and isophorone diisocyanate is: -OH group: -OH group: -NCO group = 0.69-1.19: 1: 1.7-2.2.

[0016] Preferably, the temperature of the polymerization is 65-90°C, and the time is 5-30 min.

[0017] Preferably, the organic solvent comprises one or more of methyl ethyl ketone and acetone;

[0018] Based on the weight fraction of the branched soybean oil-based polyol, the weight fraction of the organic solvent is 120-300 parts.

[0019] Preferably, the NCO group content is determined by back titration, bromocresol green is used as an indicator in the titration solution, and 0.5 mol / L KOH solution is used as a standard titrant.

[0020] The application further provides application of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion in water-based wood paint.

[0021] The application provides an anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion, which comprises the following components in parts by weight: branched soybean oil-based polyol 80-120 parts, isophorone diisocyanate 30-70 parts, 2,4-dimethylol butyric acid 8-20 parts, neutralizing agent 5-12 parts and water 500-800 parts. In the application, the neutralizing agent can pre-neutralize the 2,2-dimethylol butyric acid, and further, the copolymerization reaction can occur between the branched soybean oil-based polyol, the pre-neutralized 2,2-dimethylol butyric acid and the isophorone diisocyanate, so that the ionization degree of the hyperbranched polyurethane network is improved, and a more stable polyurethane emulsion is formed. In the application, the branched structure of the branched soybean oil-based polyol is used to construct the hyperbranched waterborne polyurethane, which can be applied to water-based wood paint, and the water resistance and hardness of the vegetable oil-based waterborne polyurethane wood paint coating can be improved through the dense crosslinking structure.

[0022] The application further provides a preparation method of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion, which comprises the following steps: mixing 2,4-dimethylol butyric acid and a neutralizing agent to obtain pre-neutralized 2,4-dimethylol butyric acid; mixing the pre-neutralized 2,4-dimethylol butyric acid, branched soybean oil-based polyol and isophorone diisocyanate to perform polymerization, adding an organic solvent to dilute when the viscosity of the obtained prepolymer increases, and continuing to react until the NCO group content in the system is reduced to less than 5% to obtain a polymer system; and cooling the polymer system to room temperature, adding water to emulsify and removing the organic solvent to obtain the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion. In the application, only the branched soybean oil-based polyol is used as a single polyol, and the reaction conditions without toxic and harmful catalysts make the synthesis route of the polyurethane safer and greener, the reaction degree is high, the use of the branched soybean oil-based polyol improves the tensile strength and hardness of the waterborne polyurethane, the operation is simple, the paint film has higher water resistance compared with the same type of material, the application can be applied to water-based wood paint, and the application field is further widened. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a schematic diagram of the technical route for preparing the polyurethane emulsion in Example 1;

[0024] Figure 2 It is an appearance and particle size distribution diagram of the polyurethane emulsion obtained in the examples and comparative examples;

[0025] Figure 3 It is a water resistance test result of the polyurethane emulsion obtained in the examples and comparative examples;

[0026] Figure 4 The hardness test results of the polyurethane emulsion obtained from the examples and comparative examples after film formation are shown in the following table. DETAILED DESCRIPTION

[0027] The present application provides an anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion, which comprises the following components in parts by weight: branched soybean oil-based polyol 80-120 parts, isophorone diisocyanate 30-70 parts, 2,4-dihydroxymethyl butyric acid 8-20 parts, neutralizing agent 5-12 parts and water 500-800 parts.

[0028] In the present application, all components are commercially available products well known to those skilled in the art unless otherwise specified.

[0029] The anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion provided by the present application comprises branched soybean oil-based polyol 80-120 parts, further preferably 90-110 parts, and more preferably 95-100 parts, in parts by weight. In the present application, the branched soybean oil-based polyol is preferably commercially available from Nantong Haoluoma Science and Technology Co., Ltd., and the model number is preferably HM-11350, HM-635A, HM-635C, HM-10100, HM-10200, HM-1070, HM-13150, HM-11350B, HM-13160, HM-13160A, HM-13200 or HM-828T-165.

[0030] The anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion provided by the present application comprises isophorone diisocyanate 30-70 parts, further preferably 40-60 parts, and more preferably 50 parts, in parts by weight based on the branched soybean oil-based polyol.

[0031] The anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion provided by the present application comprises 2,4-dihydroxymethyl butyric acid 8-20 parts, further preferably 10-18 parts, and more preferably 12-15 parts, in parts by weight based on the branched soybean oil-based polyol.

[0032] The anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion provided by the present application comprises neutralizing agent 5-12 parts, further preferably 6-11 parts, and more preferably 7-10 parts, in parts by weight based on the branched soybean oil-based polyol. In the present application, the neutralizing agent preferably comprises one or more of triethylamine, triethanolamine, aqueous ammonia, diethanolamine, sodium hydroxide, potassium hydroxide, trimethylamine and tripropylamine.

[0033] The anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion provided by the application includes 500-800 parts of water, and is further preferably 600-700 parts, based on the parts by weight of the branched soybean oil-based polyol.

[0034] In the application, the solid content of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion is preferably 20-40%, and is further preferably 30%. In the application, the bio-based content of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion is preferably 40-60%, and is further preferably 50%.

[0035] The application also provides a preparation method of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion described in the above technical solution, including the following steps:

[0036] The pre-neutralized 2,4-dimethylol butyric acid is obtained by mixing 2,4-dimethylol butyric acid and a neutralizing agent.

[0037] The polymer system is obtained by mixing the pre-neutralized 2,4-dimethylol butyric acid, the branched soybean oil-based polyol and isophorone diisocyanate, polymerizing, adding an organic solvent for dilution when the viscosity of the obtained prepolymer increases, and continuing the reaction until the NCO group content in the system is reduced to below 5%.

[0038] The anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion is obtained by adding water for emulsification after the polymer system is reduced to room temperature and the organic solvent is removed.

[0039] In the application, the pre-neutralized 2,4-dimethylol butyric acid is obtained by mixing 2,4-dimethylol butyric acid and a neutralizing agent.

[0040] The application does not have special limitations on the mixing process, and any process known to those skilled in the art can be used.

[0041] After obtaining the pre-neutralized 2,4-dimethylol butyric acid, the pre-neutralized 2,4-dimethylol butyric acid, the branched soybean oil-based polyol and isophorone diisocyanate are mixed, polymerized, an organic solvent is added for dilution when the viscosity of the obtained prepolymer increases, and the reaction is continued until the NCO group content in the system is reduced to below 5%, to obtain a polymer system.

[0042] In the application, the molar ratio of active groups in the pre-neutralized 2,4-dimethylol butyric acid, the branched soybean oil-based polyol and isophorone diisocyanate is preferably: -OH group: -OH group: -NCO group = 0.69-1.19: 1: 1.7-2.2.

[0043] In the present application, the temperature of the polymerization is preferably 65-90°C, and the time is preferably 5-30 min. No catalyst is added during the polymerization in the present application.

[0044] In the present application, the organic solvent preferably includes one or more of butanone and acetone; the weight fraction of the organic solvent is preferably 120-300 parts, further preferably 150-280 parts, and more preferably 200-250 parts, based on the weight fraction of the branched soybean oil-based polyol.

[0045] In the present application, the content of the NCO groups is preferably determined by back titration, preferably using bromocresol green as an indicator in the titration solution, and preferably using 0.5 mol / L KOH solution as a standard titrant. The process of the back titration in the present application is not particularly limited, and any process known to those skilled in the art can be used.

[0046] After obtaining the polymer system, the polymer system is cooled to room temperature, and then emulsified by adding water to remove the organic solvent, thereby obtaining the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion.

[0047] In the present application, the emulsification is performed under stirring, and the stirring speed is preferably 300-500 rpm, and the time is preferably 2 h.

[0048] In the present application, the method for removing the organic solvent is preferably rotary evaporation. The process of the rotary evaporation in the present application is not particularly limited, and any process known to those skilled in the art can be used.

[0049] The present application also provides the use of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion described in the above technical solution or prepared by the preparation method described in the above technical solution in waterborne wood paint. The specific implementation of the use in the present application is not particularly limited, and any implementation known to those skilled in the art can be used.

[0050] The technical solutions in the present application will be described clearly and completely in combination with the embodiments in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0051] Example 1

[0052] Triethylamine (5.4 g) and 2,4-dihydroxybutyric acid (8.1 g) were mixed to obtain pre-neutralized 2,4-dihydroxybutyric acid;

[0053] The branched soybean oil polyol (HM-13160, 90 g), isophorone diisocyanate (48.5 g) and the pre-neutralized 2,4-dihydroxybutanoic acid obtained above were added into a dry two-neck flask and stirred for 25 minutes, without adding any catalyst during the reaction, at a reaction temperature of 75 °C;

[0054] When the viscosity of the prepolymer in the system increased, 150 g of butanone was added to reduce the viscosity of the prepolymer, the reaction was continued, the NCO groups were determined by back titration, bromocresol green was used as the indicator in the titration solution, 0.5 mol / L KOH solution was used as the standard titrant, the NCO group content of the polymer was determined until it decreased to below 5%, and the temperature of the system was reduced to room temperature. Finally, deionized water (641.1 g) was added into a double-neck flask, stirred at a speed of 380 rpm, and the polyurethane was emulsified for 2 hours; after removing the butanone by a rotary evaporator, the anionic hyperbranched soybean oil-based waterborne polyurethane emulsion was obtained.

[0055] Example 2

[0056] The triethylamine (8.55 g) and 2,4-dihydroxybutanoic acid (13.05 g) were mixed to obtain the pre-neutralized 2,4-dihydroxybutanoic acid;

[0057] The branched soybean oil polyol (HM-13160, 90 g), isophorone diisocyanate (48.5 g) and the pre-neutralized 2,4-dihydroxybutanoic acid obtained above were added into a dry two-neck flask and stirred for 25 minutes, without adding any catalyst during the reaction, at a reaction temperature of 75 °C;

[0058] When the viscosity of the prepolymer in the system increased, 150 g of butanone was added to reduce the viscosity of the prepolymer, the reaction was continued, the NCO groups were determined by back titration, bromocresol green was used as the indicator in the titration solution, 0.5 mol / L KOH solution was used as the standard titrant, the NCO group content of the polymer was determined until it decreased to below 5%, and the temperature of the system was reduced to room temperature. Finally, deionized water (641.1 g) was added into a double-neck flask, stirred at a speed of 380 rpm, and the polyurethane was emulsified for 2 hours; after removing the butanone by a rotary evaporator, the anionic hyperbranched soybean oil-based waterborne polyurethane emulsion was obtained.

[0059] Example 3

[0060] The triethylamine (10.2 g) and 2,4-dihydroxybutanoic acid (15.6 g) were mixed to obtain the pre-neutralized 2,4-dihydroxybutanoic acid;

[0061] The branched soybean oil polyol (HM-13150, 90 g), isophorone diisocyanate (57.45 g) and the pre-neutralized 2,4-dihydroxybutanoic acid obtained above were added into a dry two-neck flask and stirred for 20 minutes, without adding any catalyst during the reaction, and the reaction temperature was 80°C;

[0062] When the viscosity of the prepolymer in the system increased, 180 g of butanone was added to reduce the viscosity of the prepolymer, the reaction was continued, the NCO groups were determined by back titration, the NCO group content of the polymer was determined by using bromocresol green as an indicator in the titration solution and 0.5 mol / L KOH solution as a standard titrant until it was reduced to below 5%, and the temperature of the system was reduced to room temperature. Finally, deionized water (693.9 g) was added into the double-port bottle, and the polyurethane was emulsified at a stirring speed of 400 rpm for 2 hours; after the butanone was removed by a rotary evaporator, the anionic hyperbranched soybean oil-based waterborne polyurethane emulsion was obtained.

[0063] Example 4

[0064] The triethylamine (10.8 g) and 2,4-dihydroxybutanoic acid (16.35 g) were mixed to obtain pre-neutralized 2,4-dihydroxybutanoic acid;

[0065] The branched soybean oil polyol (HM-13200, 90 g), isophorone diisocyanate (60.6 g) and the pre-neutralized 2,4-dihydroxybutanoic acid obtained above were added into a dry two-neck flask and stirred for 13 minutes, without adding any catalyst during the reaction, and the reaction temperature was 85°C;

[0066] When the viscosity of the prepolymer in the system increased, 220 g of butanone was added to reduce the viscosity of the prepolymer, the reaction was continued, the NCO groups were determined by back titration, the NCO group content of the polymer was determined by using bromocresol green as an indicator in the titration solution and 0.5 mol / L KOH solution as a standard titrant until it was reduced to below 5%, and the temperature of the system was reduced to room temperature. Finally, deionized water (711.1 g) was added into the double-port bottle, and the polyurethane was emulsified at a stirring speed of 430 rpm for 2 hours; after the butanone was removed by a rotary evaporator, the anionic hyperbranched soybean oil-based waterborne polyurethane emulsion was obtained.

[0067] Example 5

[0068] The triethylamine (10.8 g) and 2,4-dihydroxybutanoic acid (16.35 g) were mixed to obtain pre-neutralized 2,4-dihydroxybutanoic acid;

[0069] The branched soybean oil polyol (HM-10200, 90 g), isophorone diisocyanate (60.6 g) and the pre-neutralized 2,4-dihydroxybutyric acid obtained above were added into a dry two-neck flask and stirred for 10 minutes, without adding any catalyst during the reaction, and the reaction temperature was 88°C;

[0070] When the viscosity of the prepolymer in the system increased, 270 g of butanone was added to reduce the viscosity of the prepolymer, the reaction was continued, the NCO groups were determined by back titration, the NCO group content of the polymer was determined by titration solution with bromocresol green as indicator and 0.5 mol / L KOH solution as standard titrant until it was reduced to below 5%, and the system temperature was reduced to room temperature. Finally, deionized water (750.6 g) was added into the double-port bottle, and the polyurethane was emulsified by stirring at a speed of 480 rpm for 2 hours; after removing the butanone by a rotary evaporator, the anionic hyperbranched soybean oil-based waterborne polyurethane emulsion was obtained.

[0071] Comparative Example 1

[0072] The branched soybean oil polyol (HM-10100, 90 g), isophorone diisocyanate (30.3 g) and 2,4-dihydroxybutyric acid (8.1 g) were added into a dry two-neck flask and stirred for 30 minutes, without adding any catalyst during the reaction, and the reaction temperature was 68°C;

[0073] When the viscosity of the prepolymer in the system increased, 120 g of butanone was added to reduce the viscosity of the prepolymer, the reaction was continued, the NCO groups were determined by back titration, the NCO group content of the polymer was determined by titration solution with bromocresol green as indicator and 0.5 mol / L KOH solution as standard titrant until it was reduced to below 5%, and the system temperature was reduced to room temperature; triethylamine (5.4 g) was added to neutralize the carboxyl group for 0.5 h, and finally deionized water (535.6 g) was added into the double-port bottle, and the polyurethane was agglomerated in the deionized water and could not be dispersed to form an emulsion by stirring at a speed of 350 rpm.

[0074] Comparative Example 2

[0075] The pre-neutralized 2,4-dihydroxybutyric acid was obtained by mixing triethylamine (5.4 g) and 2,4-dihydroxybutyric acid (8.1 g);

[0076] The branched soybean oil polyol (HM-10100, 90 g), isophorone diisocyanate (30.3 g) and the pre-neutralized 2,4-dihydroxybutyric acid obtained above were added into a dry two-neck flask and stirred for 30 minutes, then an appropriate amount of dibutyltin dilaurate (15 μL) was added as a catalyst, and the reaction temperature was 68°C;

[0077] When the viscosity of the prepolymer in the system increased, 120 g of butanone was added to reduce the viscosity of the prepolymer, and the reaction was continued. The NCO groups were determined by back titration. The NCO group content of the polymer was determined by titration with bromocresol green as the indicator and 0.5 mol / L KOH solution as the standard titrant in the titration solution until it decreased to below 5%. The temperature of the system was reduced to room temperature. Finally, deionized water (535.6 g) was added to a double-neck flask, and the polyurethane was emulsified at a stirring speed of 350 rpm for 2 hours. After removing the butanone by a rotary evaporator, an aqueous polyurethane emulsion was obtained.

[0078] Comparative Example 3

[0079] Triethylamine (8.7 g) and 2,4-dihydroxybutyric acid (13.2 g) were mixed to obtain pre-neutralized 2,4-dihydroxybutyric acid;

[0080] Castor oil polyol (90 g), isophorone diisocyanate (49.05 g), and the pre-neutralized 2,4-dihydroxybutyric acid obtained above were added to a dry two-neck flask and stirred for 30 minutes. No catalyst was added during the reaction, and the reaction temperature was 68°C;

[0081] When the viscosity of the prepolymer in the system increased, 120 g of butanone was added to reduce the viscosity of the prepolymer, and the reaction was continued. The NCO groups were determined by back titration. The NCO group content of the polymer was determined by titration with bromocresol green as the indicator and 0.5 mol / L KOH solution as the standard titrant in the titration solution until it decreased to below 5%. The temperature of the system was reduced to room temperature. Finally, deionized water (644.7 g) was added to a double-neck flask, and the polyurethane was emulsified at a stirring speed of 400 rpm for 2 hours. After removing the butanone by a rotary evaporator, an aqueous polyurethane emulsion was obtained.

[0082] Performance Test

[0083] Test Example 1

[0084] The properties of the polyurethane emulsions obtained in Examples 1-5 and Comparative Examples 1-3 were tested.

[0085] Sample Preparation: The sample to be tested was diluted to 0.01 wt% and tested in parallel 4 times at room temperature, and the data were recorded as the average value ± standard deviation.

[0086] The particle size, distribution, and Zeta potential of all samples were tested on a Zeta-sizer Nano ZSE instrument.

[0087] The storage stability of the WPU dispersion was evaluated by centrifugation at 3000 rpm for 30 min in a Tomos 3-18 centrifuge. The test results are shown in Table 1, and the appearance photos and particle size distribution of the emulsion are shown in Figure 2 ​

[0088] Table 1 Test results of properties of polyurethane emulsion obtained from examples and comparative examples

[0089] Group Appearance Storage period (years) Particle size (nm) Zeta potential (mV) Comparative Example 1 WPU-HM-10100A - - - - Comparative Example 2 WPU-HM-10100B milky white 2 223.2±0.66 -41.3±0.13 Comparative Example 3 WPU-CO milky white 0.5 245.7±0.10 -40.4±0.02 Example 1 WPU-HM-10100 milky white 2 200.7±0.10 -42.2±0.23 Example 2 WPU-HM-13160 milky white 2 194.4±0.23 -59.8±1.28 Example 3 WPU-HM-13150 blue transparent 2 130.4±0.21 -50.8±2.38 Example 4 WPU-HM-13200 blue transparent 2 45.7±0.10 -49.8±1.28 Example 5 WPU-HM-10200 blue transparent 2 34.4±0.23 -50.4±0.38

[0090] As can be seen from Table 1, the difference between Comparative Example 1 WPU-HM-10100A and Example 1 WPU-HM-10100 is that in the preparation scheme of Comparative Example 1 WPU-HM-10100A, the neutralizing agent triethylamine is added to the system after the polyurethane polymerization reaction is completed to neutralize the carboxylic acid. Due to the formation of hyperbranched structure of polyurethane, the carboxylic acid groups in the polyurethane are distributed in the hyperbranched structure, and the neutralization of triethylamine to carboxylic acid will be affected by the hyperbranched structure, so that the neutralization of triethylamine to carboxylic acid groups is insufficient, and the insufficient hydrophilic groups in the polymer structure lead to difficulty in dispersion during emulsification. In the scheme of Example 1 WPU-HM-10100, the neutralizing agent triethylamine is first neutralized with 2,4-dihydroxybutyric acid before the reaction, and the neutralized 2,4-dihydroxybutyric acid is then polymerized with isocyanate and polyol to prepare polyurethane. The salted carboxylic acid groups distributed in the hyperbranched structure of polyurethane provide sufficient hydrophilicity for the polyurethane segment to promote the dispersion of polyurethane in water.

[0091] The difference between Comparative Example 2 WPU-HM-10100B and Example 1 WPU-HM-10100 is that a catalyst dibutyltin dilaurate is added in the preparation process of Comparative Example 2 WPU-HM-10100B to promote the polymerization rate, and the acceleration of polymerization rate will lead to local over-crosslinking of the polymerization inhomogeneity, which will further lead to uneven particle size distribution of the polyurethane during dispersion (see Figure 2 ). While Example 1 WPU-HM-10100 has 2,4-dihydroxybutyric acid neutralized by triethylamine, the basic triethylamine has weak catalytic effect, which ensures the polymerization rate of polyurethane, while avoiding local over-crosslinking, and can form a homogeneous dispersion during emulsification.

[0092] In addition, as can be seen from Table 1, the storage period of all examples is longer than that of Comparative Example 3, which is because the waterborne polyurethane prepared from branched soybean oil-based polyol has a more compact crosslinked structure than the waterborne polyurethane prepared from castor oil, so that the formed polyurethane emulsion has a smaller particle size. In addition, the relatively small particle size has a large specific surface area, which increases the Zeta potential of the emulsion. Small particle size and large Zeta potential provide double protection for the storage stability of the emulsion.

[0093] Test Example 2

[0094] The polyurethane emulsions obtained from Examples 1-5 and Comparative Examples 2-3 were film formed; the film forming process: a certain amount of emulsion was poured into a glass dish which was previously siliconized, and placed in a horizontal area to dry naturally for one week, then the film was placed in an oven to further dry at 50°C for 48h to obtain the final film sample;

[0095] The water resistance of the obtained film was evaluated by immersion method. The film was cut into a square with a length of 10mm (thickness about 0.5mm), first dried at 60°C for 12h, then the dried film was immersed in deionized water for 72h. Finally, the water absorption rate of the film in water was calculated, the formula is as follows:

[0096] Water absorption rate (%) = (m1-m0) / m0x100%

[0097] The weight of the sample before and after immersion was measured as m0and m1. Each sample was measured more than four times, and the average value was taken. The test results are shown in Figure 3

[0098] As can be seen from Figure 3 , the water absorption rate of Comparative Example 3 WPU-CO is as high as 32.36% after immersion in deionized water for 72h. Compared with the comparative example, the water absorption rate of the example with hyperbranched structure after 72h of water absorption is much lower than that of Comparative Example 3. Among them, Example 4 has the highest water absorption rate of 9.53%, which is 70% lower than that of Comparative Example 3 WPU-CO. In addition, the water absorption rate of the film is also closely related to the hydroxyl value and molecular weight of the polyol. The HM-10200 used in Example 5 has the highest hydroxyl value and the largest molecular weight, which indicates that HM-10200 has a highly branched structure, and the prepared waterborne polyurethane has the highest degree of hyperbranched and the most compact crosslinked structure, resulting in the material having the best water resistance (water absorption rate: 5.32%). The water absorption rate of the film of Comparative Example 2 WPU-HM-10100B is twice that of the film of Example 1 WPU-HM-10100, which is due to the addition of catalyst in Comparative Example 2 WPU-HM-10100B, resulting in uneven distribution of hydrophilic groups and hydrophobic structures in the material structure, and the hydrophilic groups are more easily contacted with water molecules.

[0099] Test Example 3

[0100] The pencil hardness of the coating prepared from the polyurethane emulsion of Examples 1-5 and Comparative Examples 2-3 was tested;

[0101] The pencil hardness of the coating was tested by ASTM D-3363. 1mL of polyurethane emulsion was cast on a tinplate with a size of 5x10cm 2 and dried in vacuum to prepare a sample. Each sample was tested in 4 parallel samples.

[0102] The test results obtained are shown in​Figure 4 As shown;

[0103] like Figure 4 As shown, Comparative Example 3WPU-CO, prepared from castor oil, exhibited the worst pencil hardness of HB. This is because the flexible triglyceride structure of castor oil is relatively loose, resulting in a loose and soft three-dimensional network structure, leading to a lower pencil hardness in the coating. Compared to castor oil with its flexible triglyceride structure, branched soybean oil-based polyols have denser reactive sites, resulting in a polyurethane coating with more concentrated hard segments and exhibiting higher pencil hardness. Furthermore, the branched crosslinking points act as hard segment crosslinks in the coating, further enhancing its pencil hardness. Therefore, the coating prepared from HM-10200, which has the highest hydroxyl value and molecular weight, has the highest pencil hardness of 3H, representing a three-level improvement in pencil hardness compared to Comparative Example 3WPU-CO. In addition, there is a significant difference in pencil hardness between Comparative Example 2WPU-HM-10100B and Example 1WPU-HM-10100. The accumulation of flexible structures in Comparative Example 2WPU-HM-10100B results in a pencil hardness of only HB.

[0104] Test Example 4

[0105] Testing of the tensile properties of thin films;

[0106] Sample preparation and testing methods: The obtained polyurethane emulsion film samples, after being dried at room temperature, were cut into rectangular samples of 30mm × 10mm × 1mm (length × width × thickness). The tensile properties of the film were measured on a tensile testing machine at an elongation rate of 50mm / min. At least three replicate tests were performed on all samples, and the data were recorded as mean ± standard deviation. Detailed data are shown in Table 2.

[0107] Table 2. Tensile property test results of polyurethane emulsion films obtained in the examples and comparative examples.

[0108] Sample Tensile strength (MPa) Elongation at break (%) Comparative Example 1 WPU-HM-10100A - - Comparative Example 2 WPU-HM-10100B 10.56±0.25 145.86±30.89 Comparative Example 3 WPU-CO 6.73±0.50 257.07±75.25 Example 1 WPU-HM-10100 17.02±0.54 350.35±31.97 Example 2 WPU-HM-13160 14.80±0.38 318.63±56.85 Example 3 WPU-HM-13150 22.03±0.18 308.23±43.75 Example 4 WPU-HM-13200 16.25±0.56 337.26±34.52 Example 5 WPU-HM-10200 20.03±0.86 284.13±35.62

[0109] As can be seen from Table 2, in the comparative example 1 WPU-HM-10100A, the neutralizing agent triethylamine is added to the system after the polyurethane polymerization reaction is completed to neutralize the carboxylic acid. Due to the formation of hyperbranched structure of polyurethane, the carboxylic acid groups in the polyurethane are distributed in the hyperbranched structure, and the neutralization of triethylamine to carboxylic acid will be affected by the hyperbranched structure, so that the neutralization of triethylamine to carboxylic acid groups is insufficient, and the insufficient hydrophilic groups in the polymer structure lead to difficulty in dispersion during emulsification. Therefore, it is impossible to prepare a film by emulsion film forming method for tensile test. The tensile strength and elongation at break of the film of the example 1 WPU-HM-10100 are 17.02 MPa and 350.35%, respectively, while the tensile strength and elongation at break of the film of the comparative example 2 WPU-HM-10100B are both lower than those of the example 1 WPU-HM-10100, which are 10.56 MPa and 145.86%, respectively. The main reason is that the catalyst dibutyltin dilaurate promotes the non-uniform polymerization of the comparative example 2 WPU-HM-10100B, resulting in uneven distribution of soft and hard segments in the film, causing stress concentration in the film during stretching. In addition, as can be seen from Table 2, the tensile strength of all examples is higher than that of the comparative example 3 WPU-CO (tensile strength is 6.73 MPa, and elongation at break is 257.07%), which is because the branched soybean oil-based polyurethane has a hyperbranched structure, and has a higher crosslinking density compared with the castor oil-based waterborne polyurethane.

[0110] Although the above examples make a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which all belong to the protection scope of the present application.

Claims

1. An anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion, characterized in that, By weight, the components are: 80-120 parts of branched soybean oil-based polyol, 30-70 parts of isophorone diisocyanate, 8-20 parts of 2,4-dimethylolbutyric acid, 5-12 parts of neutralizing agent and 500-800 parts of water. The preparation method of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion includes the following steps: 2,4-Dihydroxymethylbutyric acid was mixed with a neutralizing agent to obtain pre-neutralized 2,4-dihydroxymethylbutyric acid; The pre-neutralized 2,4-dihydroxymethylbutyric acid, branched soybean oil-based polyol and isophorone diisocyanate were mixed and polymerized. When the viscosity of the obtained prepolymer increased, an organic solvent was added for dilution. The reaction continued until the NCO group content in the system dropped to below 5% to obtain the polymer system. The polymer system was cooled to room temperature, emulsified with water, and the organic solvent was removed to obtain the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion. The neutralizing agent is triethylamine; The branched soybean oil-based polyols are designated as HM-10100, HM-10200, HM-13150, or HM-13160.

2. The anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion according to claim 1, characterized in that, The solid content of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion is 20-40%.

3. The anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion according to claim 2, characterized in that, The bio-based content of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion is 40-60%.

4. The method for preparing the anionic hyperbranched vegetable oil-based aqueous polyurethane emulsion according to any one of claims 1 to 3, characterized in that, The steps are as follows: 2,4-Dihydroxymethylbutyric acid was mixed with a neutralizing agent to obtain pre-neutralized 2,4-dihydroxymethylbutyric acid; The pre-neutralized 2,4-dihydroxymethylbutyric acid, branched soybean oil-based polyol and isophorone diisocyanate were mixed and polymerized. When the viscosity of the obtained prepolymer increased, an organic solvent was added for dilution. The reaction continued until the NCO group content in the system dropped to below 5% to obtain the polymer system. The polymer system was cooled to room temperature, emulsified with water, and the organic solvent was removed to obtain the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion. The neutralizing agent is triethylamine; The branched soybean oil-based polyols are designated as HM-10100, HM-10200, HM-13150, or HM-13160.

5. The preparation method according to claim 4, characterized in that, The molar ratio of active groups in the pre-neutralized 2,4-dihydroxymethylbutyric acid, branched soybean oil-based polyol, and isophorone diisocyanate is: -OH group: -OH group: -NCO group = 0.69~1.19:1:1.7~2.

2.

6. The preparation method according to claim 4, characterized in that, The polymerization temperature is 65~90℃ and the time is 5~30min.

7. The preparation method according to claim 4, characterized in that, The organic solvent includes one or more of butanone and acetone; Based on the weight parts of the branched soybean oil-based polyol, the weight parts of the organic solvent are 120 to 300 parts.

8. The preparation method according to claim 4, characterized in that, The NCO group content was determined by back titration, with bromocresol green as an indicator in the titration solution and 0.5 mol / L KOH solution as the standard titrant.

9. The application of the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion according to any one of claims 1 to 3 or the anionic hyperbranched vegetable oil-based waterborne polyurethane emulsion prepared by the preparation method according to any one of claims 4 to 8 in waterborne wood coatings.

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