A zero-VOC waterborne polyurethane resin emulsion, its preparation method and application

Abstract

This invention discloses a zero-VOC waterborne polyurethane resin emulsion, which is prepared by first synthesizing sulfonate-modified diisocyanate, small molecule diol, and small molecule diacid into sulfonate polyester polyol, then reacting it with other polyols and diisocyanate, and finally emulsifying it with deionized water and / or a polyamine aqueous solution. This invention also discloses a two-step preparation method for this zero-VOC waterborne polyurethane resin emulsion. The first step prepares the sulfonate polyester polyol, and the second step uses two methods to prepare the zero-VOC waterborne polyurethane resin emulsion, using water instead of solvent. This eliminates the need for solvent removal and distillation purification processes, simplifying existing waterborne polyurethane production processes, reducing energy consumption, and saving costs. The zero-VOC waterborne polyurethane resin emulsion of this invention contains no organic solvents, making it a truly green and environmentally friendly product. Furthermore, the raw materials for producing the emulsion are widely available, allowing for the preparation of a series of zero-VOC waterborne polyurethane products with wide applications in construction, manufacturing, and daily life.

Description

Technical Field

[0001] This invention relates to the field of waterborne polyurethane resin technology, and particularly to a method for preparing and applying a zero-VOC waterborne polyurethane resin emulsion. Background Technology

[0002] Zero-VOC waterborne polyurethane resin emulsions have the advantage of being completely free of volatile organic compounds (VOCs), making them a target for the research and application of waterborne polyurethanes in industries such as coatings, adhesives, leather, and inks. This is because existing waterborne polyurethanes are not completely VOC-free; they contain varying amounts of organic solvents during their preparation, such as acetone, N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF). For low-boiling-point solvents like acetone, although vacuum removal is performed after the waterborne polyurethane is produced, it is incomplete, with generally more than 5% solvent remaining in the emulsion. For high-boiling-point solvents (NMP, DMF), they are essentially not removed after the polyurethane emulsion is made. Furthermore, the removed low-boiling-point solvents require fractionation and purification for reuse. Vacuum removal is time-consuming, and fractionation processes are complex, resulting in high costs and energy consumption, as well as safety hazards from leaks and spills in the production environment.

[0003] With increasing global demands for ecological and environmental governance, the control of VOCs in chemical products is becoming increasingly stringent. Existing methods for producing waterborne polyurethane using solvents are gradually being replaced by solvent-free production technologies. For example, CN 115612053A discloses a method for preparing a zero-VOC, high-solids-content, flexible waterborne polyurethane emulsion. This method uses a very small amount of hydroxysulfonate as a hydrophilic group, combined with polyethylene glycol monomethyl ether as a hydrophilic soft segment, to synthesize a high-solids-content emulsion. This solves the difficulty of synthesizing high-solids-content, low-modulus waterborne polyurethane using solvent-free methods. Due to the low strength of the polyethylene glycol monomethyl ether segments, this type of polyurethane emulsion can only be used as a foaming material, suitable for applications requiring lower strength, such as synthetic leather, genuine leather, and textiles. CN115785367 A discloses a method for preparing and applying a solvent-free waterborne polyurethane resin emulsion. The method involves reacting a polyol with a sulfonate-modified diisocyanate to obtain a prepolymer containing -OH or -NCO groups at the sulfonate end. Water and / or a polyamine are then added for emulsification to obtain the waterborne polyurethane emulsion. Although no solvent is added during the preparation process, the sulfonate-modified diisocyanate contains 20% solvent, so the resulting waterborne polyurethane emulsion still contains a certain amount of organic solvent. CN111333808A discloses a solvent-free method for preparing waterborne polyurethane. By controlling the ratio of isocyanate and polyol, as well as chain extenders and hydrophilic chain extenders, the molecular weight and viscosity of the prepolymer can be controlled, achieving good emulsification without the addition of any organic solvent. However, this technique is difficult to implement using dry dimethylolpropionic acid solids at 85°C for chain extension, and the resulting waterborne polyurethane has a relatively low number-average molecular weight (5000-8000), limiting its application range. CN114181357A discloses a bio-based solvent-free waterborne polyurethane emulsion and its use in preparing printing inks. However, this is limited to the preparation of waterborne polyurethane using poly(1,3-propanediol), IPDI, and HDI as raw materials, and lacks general applicability. In summary, although the aforementioned patent literature suffers from problems such as low molecular weight, poor strength properties, narrow application range, and complex processes, it represents a first step towards solvent-free production of waterborne polyurethane. Due to the dual pressures of environmental protection and production costs, those skilled in the art are continuing to develop simple, efficient, and low-cost solvent-free waterborne polyurethane production technologies to solve various challenges in the preparation of zero-VOC waterborne products in the polyurethane coatings, adhesives, leather, and ink industries. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a zero-VOC waterborne polyurethane resin emulsion.

[0005] The second objective is to provide a method for preparing this zero-VOC waterborne polyurethane resin emulsion.

[0006] The third objective is to provide applications for this zero-VOC waterborne polyurethane resin emulsion in industries such as polyurethane coatings, adhesives, leather, and inks.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a zero-VOC waterborne polyurethane resin emulsion, which is prepared by first preparing a sulfonate-modified diisocyanate, a small molecule diol and a small molecule dicarboxylic acid into a sulfonate polyester polyol, then reacting it with other polyols and diisocyanate, and finally emulsifying it with deionized water and / or a polyamine aqueous solution.

[0008] The sulfonate-modified diisocyanate used in this invention is prepared by reacting diisocyanate with a small molecule sulfonate diol, and has the following structural formula. , In formula (1), M is K or Na; n = 1~3; R and R' represent hydrocarbon groups respectively.

[0009] Preferably, the sulfonate-modified diisocyanate has an average molecular weight of 350-1500.

[0010] The sulfonate-modified diisocyanate used in this invention has the following structural characteristics: the molecular structure contains at least one sulfonate group and the two ends are -NCO groups.

[0011] The sulfonate-modified diisocyanate used in this invention undergoes a blocked NCO reaction with an excess of small-molecule diols to generate a prepolymer with terminal dihydroxyl groups and containing sulfonate groups. This terminal dihydroxyl sulfonate prepolymer exhibits hydroxyl properties similar to ordinary diols and can undergo polycondensation reactions with small-molecule diacids and small-molecule diols to produce sulfonate polyester polyols. Sulfonate polyester polyols possess excellent hydrophilicity and can react with other polyols and diisocyanates to prepare polyurethane prepolymers containing sulfonate groups. These prepolymers can then be emulsified with water and / or amines to obtain zero-VOC waterborne polyurethane resin emulsions.

[0012] Preferably, the diisocyanate includes at least one of IPDI, HDI, TDI, MDI, and HMDI.

[0013] Preferably, the small molecule sulfonate diol includes at least one of sodium 1,2-dihydroxy-3-propanesulfonate, sodium 1,4-dihydroxybutane-2-sulfonate, sodium dicarboxybenzenesulfonate, and esters of small molecule polyols.

[0014] The zero-VOC waterborne polyurethane resin emulsion provided by this invention also includes the following raw materials: Preferably, the sulfonate-modified diisocyanate includes at least one of sulfonate-modified IPDI, sulfonate-modified HDI, sulfonate-modified TDI, sulfonate-modified MDI, and sulfonate-modified HMDI.

[0015] Preferably, the small molecule diol includes at least one selected from 3-methyl-1,5-pentanediol, neopentanediol, ethylene glycol, cyclohexanediol, methylpropanediol, 1,3-propanediol, 1,4-dihydroxymethylcyclohexane, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,2-propanediol, diethylene glycol, tetrahydrofurandiol, 1,6-hexanediol, trimethylpentanediol, butyl ethyl propylene glycol, dipropylene glycol, tripropylene glycol, and ethylhexanediol.

[0016] Preferably, the small molecule dicarboxylic acid includes at least one of adipic acid, sebacic acid, phthalic anhydride, isophthalic acid, terephthalic acid, and maleic anhydride.

[0017] Preferably, the other polyols include polyester polyols and polyether polyols.

[0018] Preferably, the polyester polyol comprises at least one of the following: poly(ethylene adipate-propylene glycol), poly(butylene adipate), poly(neopentyl adipate), poly(neopentyl adipate-hexanediol), poly(1,6-hexanediol adipate), poly(decanedioic acid-ethylene adipate-neopentyl adipate), poly(isophthalic acid-neopentyl adipate-diethylene glycol), poly(terephthalic acid-neopentyl adipate-1,4-butanediol), polycarbonate diol, and polycaprolactone diol.

[0019] Preferably, the polyether polyol includes at least one of polyoxypropylene diol, polyethylene oxide-propylene diol, and polytetrahydrofuran diol.

[0020] Preferably, the diisocyanate includes at least one of IPDI (isophorone diisocyanate), HDI (hexamethylene diisocyanate), TDI (toluene diisocyanate), MDI (diphenylmethane diisocyanate), and HMDI (4,4'-dicyclohexylmethane diisocyanate).

[0021] Preferably, the polyamine includes at least one selected from ethylenediamine, hexamethylenediamine, isophoronediamine, hexamethylenediamine, sodium ethylenediaminoethanesulfonate, sodium 2,4-diaminobenzenesulfonate, 4,4-diphenylmethanediamine, 1,2-cyclohexanediamine, diethylenetriamine, and triethylenetetramine.

[0022] A second aspect of the present invention provides a method for preparing a zero-VOC waterborne polyurethane resin emulsion according to the first aspect of the present invention, characterized by comprising two steps: The first step involves the preparation of sulfonate polyester polyols. a) Add sulfonate-modified diisocyanate and dehydrated small molecule diol to a reaction flask equipped with a fractionation device, stir to carry out the reaction, control the reaction temperature to rise slowly, react at 80℃-90℃ for 2-10 hours, and stop the reaction when NCO is undetectable. b) Continue to add small molecule dicarboxylic acid, antioxidant and catalyst to the reaction flask, introduce nitrogen gas, raise the temperature to 120°C and react for 1 hour, then raise the temperature to 140°C and react for 3 hours, continue to slowly raise the temperature to 220-240°C and react, and control the temperature of the water outlet at the top of the condenser tube to not exceed 102°C. When the water output reaches the theoretical value, continue to output water for 1 hour; turn on the vacuum pump to evacuate for 3 hours, cool down to 70°C, and discharge the material to obtain sulfonate polyester polyol.

[0023] The second step involves preparing a zero-VOC waterborne polyurethane resin emulsion, which can be achieved using two methods: a one-step method and a two-step method. One-step method In a four-necked reaction flask, add the formulated amount of sulfonate polyester polyol and other polyols, dehydrate under vacuum at 120°C for 2 hours, cool to 50-80°C, add the formulated amount of diisocyanate using a high-power stirrer, purge with nitrogen, and react at 50-130°C for 3-15 hours until NCO is undetectable; slowly add deionized water while stirring to emulsify, and continue stirring for 0.5-1 hour after the water is added to obtain a zero-VOC waterborne polyurethane resin emulsion.

[0024] Two-step method a) In a four-necked reaction flask, add the formulated amount of sulfonate polyester polyol and other polyols, dehydrate under vacuum at 120°C for 2 hours, cool to 50-80°C, add the formulated amount of diisocyanate using a high-power stirrer, introduce nitrogen gas, and react at 50-130°C for 3-15 hours to obtain NCO-terminated sulfonate prepolymer. b) Cool to 100℃, slowly add deionized ice water while stirring to disperse, then slowly add a mixture of polyamine and deionized water to extend the chain, end-cap and emulsify, and continue the reaction at 50℃ for 1-2 hours. Discharge to obtain zero-VOC waterborne polyurethane resin emulsion.

[0025] The first step of the method for preparing a zero-VOC waterborne polyurethane resin emulsion of the present invention, a) the chemical reaction formula for the reaction of sulfonate-modified diisocyanate with small molecule diol to generate terminal dihydroxy sulfonate prepolymer is as follows: , In formula (2), M is K or Na; R and R' represent hydrocarbon groups respectively.

[0026] Step b) of the first step process involves the esterification and dehydration reaction of the prepolymer with terminal dihydroxyl sulfonate, a small molecule diol, and a small molecule diacid under the action of a catalyst, resulting in the condensation polymerization of hydroxyl-terminated sulfonate polyester polyol. The chemical reaction formula is as follows: , In equation (3), M is K or Na; n = 1~15; R, R', R ，，， These represent hydrocarbon groups.

[0027] Preferably, the raw material ratio for the first step of the preparation method to prepare sulfonate polyester polyol is as follows: the ratio of the sum of the moles of sulfonate-modified diisocyanate and small molecule dicarboxylic acid to the moles of small molecule diol is 1:(1.1-2); the molar ratio of sulfonate-modified diisocyanate to small molecule dicarboxylic acid is 1:(1-10).

[0028] Preferably, in the first step (b) of the preparation method, the catalyst is tetrabutyl titanate, antimony trioxide, or zinc acetate, and the amount of catalyst added is 0.05%-0.15% of the total weight of the raw materials.

[0029] Preferably, the molecular weight of the sulfonate polyester polyol prepared in the first step of the preparation method is 1000-5000; more preferably, the molecular weight of the sulfonate polyester polyol prepared in the first step of the preparation method is 1000-3000.

[0030] Preferably, when preparing sulfonate polyester polyols according to the present invention, different types of sulfonate-modified diisocyanates and different molar ratios of them with small molecule dicarboxylic acids can be selected to prepare a series of polyester polyols with different sulfonate contents (hydrophilicity) to meet the user's requirements for waterborne polyurethane raw materials for preparing products with different technical performance.

[0031] Preferably, the raw material ratio of the one-step method for preparing zero-VOC waterborne polyurethane resin emulsion in the second step of the preparation method is as follows: the ratio of the sum of the moles of sulfonate polyester polyol and polyol to the moles of diisocyanate is (1.2-1.8):1, and the molar ratio of sulfonate polyester polyol to polyol is 1:(1-4).

[0032] Preferably, the raw material ratio of the second step of the preparation method for preparing zero-VOC waterborne polyurethane resin emulsion is as follows: the ratio of the sum of the moles of sulfonate polyester polyol and polyol to the moles of diisocyanate is 1:(1.5-2), and the molar ratio of sulfonate polyester polyol to polyol is 1:(0-4).

[0033] Preferably, when preparing zero-VOC waterborne polyurethane resin emulsions, the hydrophilicity of the product can be designed based on the molar ratio of sulfonate polyester polyol to other polyols, and the molecular weight of the product can be designed based on the ratio of the sum of the molar numbers of sulfonate polyester polyol and other polyols to the molar number of diisocyanate. Furthermore, by selecting different types of sulfonate polyester polyol and other polyols, as well as different diisocyanates, the relationship between the product's performance and hydrophilicity can be balanced to meet the different performance requirements of users.

[0034] Preferably, in step b) of the two-step method for preparing zero-VOC waterborne polyurethane resin emulsion in the second step of the preparation method, the amount of polyamine added is such that the molar ratio of the remaining NCO to the amine group after the reaction in step a) is 1:(0.9-1.1).

[0035] Preferably, the power of the high-power stirrer used in the second step of the preparation method to prepare the zero-VOC waterborne polyurethane resin emulsion is above 1000W to ensure that the reaction system can be stirred normally.

[0036] This invention typically employs a two-step method for preparing high-molecular-weight waterborne polyurethane resin emulsions. First, the molecular weight of the NCO-terminated prepolymer is designed to be as small as possible to ensure low system viscosity, which is beneficial for the normal reaction. The prepolymer viscosity is lowest when the equivalence ratio NCO / OH = 2. Since the NCO-terminated prepolymer contains sulfonate groups in its molecular structure, it has excellent hydrophilicity. Therefore, after preparing the sulfonate-containing prepolymer, water can be used as a solvent to reduce the system viscosity, thus avoiding the need to add solvents to reduce viscosity in existing processes where the prepolymer is insoluble in water. To increase the molecular weight of the sulfonate-based polyurethane prepolymer, this invention first adds ice water to dilute the system viscosity at a high temperature, then stirs and disperses the mixture while lowering the temperature. Next, a polyamine aqueous solution is added for chain extension, end-capping, and emulsification to generate a branched emulsion. With proper molecular design of the NCO-terminated prepolymer and reasonable use of water as a solvent to control the viscosity of the system during the production process, this invention can produce waterborne polyurethane resin emulsions with molecular weights ranging from several thousand to tens of thousands without adding any solvent.

[0037] The third aspect of the present invention provides the application of a zero-VOC waterborne polyurethane resin emulsion according to the first aspect of the present invention in the preparation of waterborne polyurethane coatings, waterborne polyurethane adhesives, waterborne polyurethane inks, etc., especially in the fields of waterborne shoe adhesives, waterborne laminating adhesives, waterborne decorative coatings, waterborne fabric finishing agents, and waterborne leather treatment liquids.

[0038] Preferably, the zero-VOC waterborne polyurethane resin emulsion prepared by the present invention can be used as a single component, or it can be used in combination with a waterborne polyurethane curing agent to form two-component waterborne polyurethane coatings, waterborne polyurethane paints, waterborne polyurethane adhesives, waterborne polyurethane binders, waterborne leather finishing agents, waterborne fabric finishing agents, or waterborne ink binders, etc., which are widely used in various fields such as construction, automobiles, manufacturing, and people's lives.

[0039] Beneficial effects of the present invention This invention produces a zero-VOC waterborne polyurethane resin emulsion containing no organic solvents, making it a truly green and environmentally friendly product that fundamentally solves the environmental pollution problem caused by organic solvents. The process of preparing waterborne polyurethane resin emulsions by replacing some or all of the polyols with sulfonate polyester polyols in the reaction with diisocyanates completely changes the shortcomings of existing technologies that require the addition of solvents in the production of waterborne polyurethanes. It eliminates the need for solvent removal, distillation purification, and other steps, simplifying the production process and reducing costs.

[0040] Specifically, compared with the prior art, the present invention has the following advantages: 1. Truly zero-VOC product. The raw materials and the entire production process of waterborne polyurethane produced by this invention do not involve any solvents; instead, water is used as the solvent, making it a truly zero-VOC environmentally friendly polyurethane product.

[0041] 2. Environmentally friendly process technology. This invention first introduces the hydrophilic group of sulfonate into the structure of polyester polyol. Therefore, when preparing waterborne polyurethane, there is no need to introduce the hydrophilic group again, eliminating the step of adding solvent to dissolve the hydrophilic raw materials (dimethylolcarboxylic acid, sulfonate). Because the polyurethane prepolymer prepared by this invention contains the hydrophilic group of sulfonate, it has excellent hydrophilicity and can be directly diluted with water to reduce the viscosity of the system. This changes the existing technology where solvent must be added to reduce the viscosity of the system when adding hydrophilic agents for chain extension, thus avoiding the safety risks associated with subsequent solvent removal, distillation purification, etc.

[0042] 3. Energy saving. This invention uses water as a solvent in the preparation of zero-VOC waterborne polyurethane resin emulsion, thus eliminating the need for vacuum solvent removal and distillation purification of distillates, which are common processes in existing technologies. This shortens the production cycle, improves efficiency, and reduces energy consumption.

[0043] 4. Low production cost. This invention uses water as a solvent in the preparation of zero-VOC waterborne polyurethane resin emulsion, saving solvent costs, eliminating the need for distillation equipment, improving production efficiency, and reducing production costs.

[0044] 5. Excellent emulsion stability. The sulfonate group content in the resin structure of the zero-VOC waterborne polyurethane resin emulsion of this invention can be adjusted through molecular design to meet the hydrophilicity requirements of different products, thus the prepared emulsion has excellent stability.

[0045] 6. Wide range of products. The raw materials for preparing zero-VOC waterborne polyurethane resin emulsions using this invention are widely available. The raw materials for preparing sulfonate polyester polyols can be selected based on user performance requirements, and the formulation of the waterborne polyurethane resin emulsion can be designed to prepare zero-VOC waterborne polyurethane resin emulsions with different performance requirements, meeting the needs of various fields such as construction, automotive, manufacturing, and daily life.

[0046] 7. Simple and easy to promote. The process for preparing zero-VOC waterborne polyurethane resin emulsion in this invention is simple, solves the technical problem of producing solvent-free waterborne polyurethane, and is conducive to the widespread application of this technology in manufacturing enterprises. Detailed Implementation

[0047] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments can be obtained from conventional commercial sources or by existing technical methods. Unless otherwise specified, the experimental or testing methods are conventional methods in the art.

[0048] The raw materials used in the examples are described below: 1. SSTD-80 diisocyanate (sulfonate modified TDI) is produced by Foshan Jingxin Huiming Technology Co., Ltd., with a solid content of 80%, a viscosity of 2500 mPa·s / 25℃, and an NCO content of 14.1% (i.e., the average molecular weight of the prepolymer is 477 g / mol).

[0049] 2. SSIPD-75 diisocyanate (sulfonate modified IPDI) is produced by Foshan Jingxin Huiming Technology Co., Ltd., with a solid content of 75%, a viscosity of 2800 mPa·s / 25℃, and an NCO content of 13.5% (i.e., the average molecular weight of the prepolymer is 467 g / mol).

[0050] 3. SSHD-80 diisocyanate (sulfonate modified HDI) is produced by Foshan Jingxin Huiming Technology Co., Ltd., with a solid content of 80%, a viscosity of 11500 mPa·s / 25℃, and an NCO content of 16.0% (i.e., the average molecular weight of the prepolymer is 420 g / mol).

[0051] 4. SSMD-80 diisocyanate (sulfonate modified MDI) is produced by Foshan Jingxin Huiming Technology Co., Ltd., with a solid content of 80%, a viscosity of 16000mPa·s / 25℃, and an NCO content of 11.0% (i.e., the average molecular weight of the prepolymer is 551g / mol).

[0052] 5. HDX-100 waterborne polyurethane curing agent is produced by Foshan Jingxin Huiming Technology Co., Ltd., with a solid content of 100%, an NCO content of 21.4%, and a viscosity of 7000 mPa·s / 25℃.

[0053] 6. Covestro water-based blocking curing agent Imprafix 2794 XP, solid content 39-41%, viscosity (23℃) <1500mpa.s, pH value (20℃) 6.5-8.5, NCO content (blocking) 5.0%.

[0054] Unless otherwise specified, all percentages used in this article refer to mass percentages.

[0055] The methods for detecting the raw materials or products used in the examples are described below: 1. Solid content testing shall be conducted in accordance with the national standard GB / T 2793-1995 Determination of nonvolatile matter content in adhesives.

[0056] 2. The acid value was tested according to the national standard GB / T2895-2008 "Determination of Acid Value of Unsaturated Polyester Resins".

[0057] 3. The hydroxyl value was tested according to the standard "HG / T2709-1995 Determination of Hydroxyl Value in Polyester Polyols".

[0058] 4. Molecular weight was determined using gel permeation chromatography.

[0059] Example 1 A method for preparing a zero-VOC waterborne polyurethane resin emulsion, comprising two steps: The first step involves the preparation of sulfonate polyester polyols. a) In a reaction flask equipped with a fractionation apparatus, add 180g of SSTD-80 diisocyanate and 133g of dehydrated 1,4-butanediol, stir and react, control the reaction temperature to rise slowly, and detect NCO after reacting at 80℃-85℃ for 3 hours. Stop the reaction when NCO can no longer be detected.

[0060] b) Continue adding 130g of adipic acid, 1.2g of antioxidant 1010, and 0.4g of tetrabutyl titanate to the reaction flask. Purge with nitrogen, raise the temperature to 120℃ and react for 1 hour, then raise the temperature to 140℃ and react for 3 hours. Slowly raise the temperature to 220-230℃ to continue the esterification reaction and water separation. Control the temperature of the water outlet at the top of the condenser to not exceed 102℃. When the water output reaches the theoretical value, continue water extraction for another hour. Turn on the vacuum pump and gradually increase the vacuum degree to above 0.09MPa for 3 hours to remove residual alcohol. Cool down to 70℃ and discharge the material to obtain a light yellow transparent sulfonate polyester polyol. The hydroxyl value was measured to be 51.65mg / KOH, the acid value to be 4.25mg / KOH, and the molecular weight to be 2007.

[0061] The second step involves preparing a zero-VOC waterborne polyurethane resin emulsion, using a one-step method: In a four-necked reaction flask, 200g of the sulfonate polyester polyol obtained in the first step and 200g of dehydrated poly(adipate-neopentyl glycol) diol (molecular weight 2000) were added. Using a 1500 rpm adjustable stirrer, 25g of TDI monomer and 0.5g of antioxidant 1010 were added. Nitrogen gas was introduced, and the reaction was controlled at 60℃ for 2 hours and 70℃ for 1 hour. Then, the temperature was naturally increased as the viscosity increased, and the maximum reaction temperature was controlled at 130℃. The NCO content was monitored during the reaction, and the reaction was stopped when NCO could not be detected. 425g of deionized water was slowly added under stirring to emulsify the mixture. The stirring speed was gradually increased as water was added. After the water was added, stirring was continued for 0.5 hours to obtain a zero-VOC waterborne polyurethane resin emulsion with a solid content of 50%.

[0062] Example 2 A method for preparing a zero-VOC waterborne polyurethane resin emulsion, comprising two steps: The first step involves the preparation of sulfonate polyester polyols. a) In a reaction flask equipped with a fractionation apparatus, add 200g of SSMD-80 diisocyanate and 168.4g of dehydrated 1,6-hexanediol, stir and react, control the reaction temperature to rise slowly, and detect NCO after reacting at 78℃-82℃ for 3 hours. Stop the reaction when NCO can no longer be detected.

[0063] b) Continue adding 134g of adipic acid, 1.5g of antioxidant 1010, and 0.4g of tetrabutyl titanate to the reaction flask. Purge with nitrogen, raise the temperature to 120℃ and react for 1 hour, then raise the temperature to 140℃ and react for 3 hours. Slowly raise the temperature to 220-230℃ to continue the esterification reaction and water separation. Control the temperature of the water outlet at the top of the condenser to not exceed 102℃. When the water output reaches the theoretical value, continue water discharge for another hour. Turn on the vacuum pump and gradually increase the vacuum degree to above 0.09MPa for 3 hours to remove residual alcohol. Cool down to 70℃ and discharge the material to obtain a light yellow transparent sulfonate polyester polyol. The hydroxyl value was measured to be 33.18mg / KOH, the acid value to be 4.02mg / KOH, and the molecular weight to be 3016.

[0064] The second step involves preparing a zero-VOC waterborne polyurethane resin emulsion, using a one-step method: In a four-necked reaction flask, 150g of the sulfonate polyester polyol obtained in the first step and 200g of dehydrated poly(decanedioic acid-adipic acid-ethylene glycol-neopentyl glycol) diol (molecular weight 2000) were added. Using a 1500 rpm adjustable stirrer, 25g of MDI monomer and 0.5g of antioxidant 1010 were added. Nitrogen gas was introduced, and the temperature was controlled at 50-55℃ for 2 hours and 65-70℃ for 1 hour. Then, the temperature was naturally increased as the viscosity increased, and the maximum reaction temperature was controlled at 130℃. The NCO content was monitored during the reaction, and the reaction was stopped when NCO could not be detected. 375g of deionized water was slowly added under stirring to emulsify the mixture. The stirring speed was gradually increased as water was added. After the water was added, stirring was continued for 0.5 hours to obtain a zero-VOC waterborne polyurethane resin emulsion with a solid content of 50%.

[0065] Example 3 A method for preparing a zero-VOC waterborne polyurethane resin emulsion, comprising two steps: The first step involves the preparation of sulfonate polyester polyols. a) In a reaction flask equipped with a fractionation apparatus, add 200g of SSIPD-75 diisocyanate, 108.1g of dehydrated 1,4-butanediol and 82.1g of neopentyl glycol, stir and react, control the reaction temperature to rise slowly, and detect NCO after reacting at 85℃-90℃ for 5 hours. Stop the reaction when NCO is no longer detectable.

[0066] b) Continue adding 187.9g of adipic acid, 1.5g of antioxidant 1010, and 0.5g of tetrabutyl titanate to the reaction flask. Purge with nitrogen, raise the temperature to 120℃ and react for 1 hour, then raise the temperature to 140℃ and react for 3 hours. Slowly raise the temperature to 230-240℃ to continue the esterification reaction and water separation. Control the temperature of the water outlet at the top of the condenser to not exceed 102℃. When the water output reaches the theoretical value, continue water extraction for another hour. Turn on the vacuum pump and gradually increase the vacuum degree to above 0.09MPa for 3 hours to remove residual alcohol. Cool down to 70℃ and discharge the material to obtain a light yellow transparent sulfonate polyester polyol. The hydroxyl value was measured to be 52.55mg / KOH, the acid value to be 3.75mg / KOH, and the molecular weight to be 1993.

[0067] The second step involves preparing a zero-VOC waterborne polyurethane resin emulsion, using a two-step method: a) In a four-necked reaction flask, add 200g of the sulfonate polyester polyol obtained in the first step, heat to 80°C, use a stirrer with a speed of 1500 rpm, add 35.6g of IPDI monomer, mix evenly, then heat to 90°C for 1 hour, react at 100°C for 1 hour, and react at 120°C for 8 hours to obtain the NCO-terminated sulfonate prepolymer. b) Reduce the temperature of the reaction system to 100°C, and slowly add 230g of deionized ice water while stirring to disperse it. Gradually increase the rotation speed as the ice water is added. After the ice water is added, slowly add a mixture of 50g of water and 3.2g of ethylenediamine. After the addition is complete, continue to react at 50°C for 1 hour. Discharge the product to obtain a zero-VOC waterborne polyurethane resin emulsion with a solid content of 46%.

[0068] Example 4 A method for preparing a zero-VOC waterborne polyurethane resin emulsion The sulfonate polyester polyol prepared in the first step of Example 3 was selected. The second step involves preparing a zero-VOC waterborne polyurethane resin emulsion, using a one-step method: In a four-necked reaction flask, 200g of the sulfonate polyester polyol obtained in the first step of Example 3 and 200g of dehydrated poly(decanedioic acid-adipic acid-ethylene glycol-neopentyl glycol) diol (molecular weight 2000) were added. Using a 1500 rpm adjustable stirrer, 32g of IPDI monomer and 0.5g of antioxidant 1010 were added. Nitrogen gas was introduced, and the temperature was controlled at 60°C for 2 hours and 70°C for 1 hour. Then, the temperature was naturally increased as the viscosity increased, and the maximum reaction temperature was controlled at 130°C. The NCO content was monitored during the reaction, and the reaction was stopped when no NCO was detected. 432g of deionized water was slowly added under stirring to emulsify the mixture. The stirring speed was gradually increased as water was added. After the water was added, stirring was continued for 1 hour to obtain a zero-VOC waterborne polyurethane resin emulsion with a solid content of 50%.

[0069] Example 5 A method for preparing a zero-VOC waterborne polyurethane resin emulsion, comprising two steps: The first step involves the preparation of sulfonate polyester polyols. a) In a reaction flask equipped with a fractionation apparatus, add 200g of SSHD-80 diisocyanate, 144.2g of dehydrated 1,4-butanediol and 161.4g of hexanediol, stir to carry out the reaction, control the reaction temperature to rise slowly, and start to detect NCO after reacting at 80℃-85℃ for 6 hours. Stop the reaction when NCO can no longer be detected.

[0070] b) Continue adding 278.4g of adipic acid, 1.6g of antioxidant 1010, and 0.6g of tetrabutyl titanate to the reaction flask. Purge with nitrogen, raise the temperature to 120℃ and react for 1 hour, then raise the temperature to 140℃ and react for 3 hours. Slowly raise the temperature to 220-230℃ to continue the esterification reaction and water separation. Control the temperature of the water outlet at the top of the condenser to not exceed 102℃. When the water output reaches the theoretical value, continue water extraction for another hour. Turn on the vacuum pump and gradually increase the vacuum degree to above 0.09MPa for 3 hours to remove residual alcohol. Cool down to 70℃ and discharge the material to obtain a light yellow transparent sulfonate polyester polyol. The hydroxyl value was measured to be 70.51mg / KOH, the acid value to be 4.25mg / KOH, and the molecular weight to be 1500.8.

[0071] The second step involves preparing a zero-VOC waterborne polyurethane resin emulsion, using a two-step method: a) In a four-necked reaction flask, add 150g of the sulfonate polyester polyol obtained in the first step and 200g of dehydrated poly(1,6-hexanediol adipate) diol (molecular weight 2000), heat to 80°C, add 88.9g of IPDI monomer using a 1500 rpm speed-adjustable stirrer, mix evenly, then heat to 90°C for 1 hour, react at 100°C for 1 hour, and react at 120°C for 9 hours to obtain NCO-terminated sulfonate prepolymer; b) Reduce the temperature of the reaction system to 100°C, and slowly add 342g of deionized ice water while stirring to disperse it. Gradually increase the rotation speed as the ice water is added. After the ice water is added, slowly add a mixture of 200g water, 5.9g ethylenediamine and 16.7g isophorone diamine. After the addition is complete, continue to react at 50°C for 1.5 hours. Discharge the product to obtain a zero-VOC waterborne polyurethane resin emulsion with a solid content of 46%.

[0072] Example 6 A method for preparing a zero-VOC waterborne polyurethane resin emulsion The sulfonate polyester polyol prepared in the first step of Example 5 was selected. The second step involves preparing a zero-VOC waterborne polyurethane resin emulsion, using a two-step method: a) In a four-necked reaction flask, add 150g of the sulfonate polyester polyol obtained in the first step of Example 5 and 150g of dehydrated poly(adipate-neopentyl glycol-1,4-butanediol) diol (molecular weight 1000), heat to 80°C, add 63g of HDI monomer using a 1500 rpm speed-adjusting stirrer, mix evenly, then heat to 90°C for 1 hour, react at 100°C for 1 hour, react at 120°C for 12 hours to obtain NCO-terminated sulfonate prepolymer. b) Reduce the temperature of the reaction system to 100°C, and slowly add 315g of deionized ice water while stirring to disperse it. Gradually increase the rotation speed as the ice water is added. After the ice water is added, slowly add a mixture of 120g of water and 7g of ethylenediamine. After the addition is complete, continue to react at 50°C for 1.5 hours. Discharge the product to obtain a zero-VOC waterborne polyurethane resin emulsion with a solid content of 46%.

[0073] Application Example 1 This application example provides a zero-VOC two-component waterborne polyurethane coating, the preparation method of which includes the following steps: Take 200g of the zero-VOC waterborne polyurethane emulsion from Example 1, add 40g of HDX-100 waterborne polyurethane curing agent, mix and stir evenly to obtain a zero-VOC two-component waterborne polyurethane coating. Apply this coating to a tinplate sample, cure at 50℃ for 48 hours, and after standing at room temperature for 24 hours, test the film properties as follows: film appearance (visual inspection) smooth and even; gloss (60°): ≥90%; hardness: Shore D52; impact strength: 56KJ / m 2 Adhesion: Grade 1; Flexibility: 1mm; Water resistance (72h) showed no abnormalities.

[0074] The test methods are as follows: gloss (60°) according to GB / T 9754-2007, hardness according to GB / T 1730-2007, impact strength according to GB / T 1732-2020, adhesion according to GB / T 1720-2020, flexibility according to GB / T 1731-2020, and water resistance according to GB / T1733-1993.

[0075] Application Example 2 This application example provides a zero-VOC two-component waterborne polyurethane adhesive, the preparation method of which includes the following steps: Take 200g of the zero-VOC waterborne polyurethane emulsion from Example 2, add 20g of HDX-100 waterborne polyurethane curing agent, mix and stir evenly to obtain a zero-VOC two-component waterborne polyurethane adhesive. This adhesive is used for bonding PVC film to solid wood board. The adhesive is applied to the PVC film by a coating machine, and after exiting the drying tunnel, it is bonded to the solid wood board. After curing at room temperature for 72 hours, a peel strength test at 180℃ is performed according to GB / T 2790-1995 "Adhesives - Peel Strength Test Method at 180℃ - Flexible Materials to Rigid Materials". The PVC film is torn.

[0076] Application Example 3 This application example provides a zero-VOC two-component waterborne polyurethane adhesive, the preparation method of which includes the following steps: Take 200g of the zero-VOC waterborne polyurethane emulsion from Example 3, add 15g of HDX-100 waterborne polyurethane curing agent, mix and stir evenly to obtain a zero-VOC two-component waterborne polyurethane adhesive. This adhesive is used for PET film to PET film lamination. The adhesive is coated onto a PET film using a coating machine, placed in an oven at 150℃ and baked for 2 minutes. After removal, another uncoated PET film is laminated onto it. The lamination is then hot-pressed by rolling at a roller temperature of 80~90℃. After being left at room temperature for 72 hours, a T-peel strength test is performed according to GB / T 2791-1995 "Adhesives T-Peel Strength Test Method Flexible Materials to Flexible Materials". The PET film is torn.

[0077] Application Example 4 This application example provides a zero-VOC two-component waterborne polyurethane baking varnish, the preparation method of which includes the following steps: Take 200g of the zero-VOC waterborne polyurethane emulsion from Example 4, add 40g of the waterborne blocking curing agent Imprafix 2794 XP, mix and stir evenly to obtain a zero-VOC two-component waterborne polyurethane baking paint. Spray this baking paint onto a tinplate sample, cure in an oven at 160℃ for 60 minutes, and after standing at room temperature for 24 hours, the properties of the obtained paint film are as follows: Paint film appearance (visual inspection) smooth and even; gloss (60°): ≥90%; hardness: Shore D60; impact strength: 52KJ / m 2 Adhesion: Grade 1; Flexibility: 1mm; Water resistance (72h) showed no abnormalities.

[0078] Application Example 5 This application example provides a zero-VOC two-component waterborne polyurethane adhesive, the preparation method of which includes the following steps: Take 200g of the zero-VOC waterborne polyurethane emulsion from Example 5, add 20g of HDX-100 waterborne polyurethane curing agent, mix and stir evenly to obtain a zero-VOC two-component waterborne polyurethane adhesive. This adhesive is used for laminating PET film and aluminum foil. First, the adhesive is coated onto the PET film, and after exiting the drying tunnel, it is hot-pressed onto the aluminum foil. After curing at room temperature for 72 hours, a 180° peel strength test is performed according to G / T2790-1995 "Test Method for 180° Peel Strength of Adhesives - Flexible Materials vs. Rigid Materials". The PET film is torn.

[0079] Application Example 6 This application example provides a zero-VOC two-component water-based high-temperature flocking adhesive, the preparation method of which includes the following steps: Take 200g of the zero-VOC waterborne polyurethane emulsion from Example 6, add 20g of waterborne blocking curing agent Imprafix2794 and stir to mix evenly to obtain zero-VOC waterborne polyurethane high-temperature flocking adhesive. Apply the adhesive to the fabric surface using a coating machine, flock the fabric, and then place it in an oven at 140℃ for 40 minutes to cure. After being left at room temperature for 24 hours, the tensile strength, elongation at break, abrasion resistance, and dimensional stability after washing of the flocked fabric were tested and all met the strength performance requirements of the flocked fabric. The appearance, feel, and comfort also met the requirements of the flocked fabric.

[0080] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A zero-VOC waterborne polyurethane resin emulsion, characterized in that, It is made by first preparing sulfonate-modified diisocyanate, small molecule diol and small molecule dicarboxylic acid into sulfonate polyester polyol, then reacting it with other polyols and diisocyanate, and finally emulsifying it with deionized water and / or polyamine aqueous solution. The sulfonate-modified diisocyanate is prepared by reacting a small molecule sulfonate diol with a diisocyanate, and has a molecular weight of 380-1500. The small molecule sulfonate diols include at least one of sodium 1,2-dihydroxy-3-propanesulfonate, sodium 1,4-dihydroxybutane-2-sulfonate, sodium dicarboxybenzenesulfonate, and esters of small molecule polyols. The diisocyanate includes at least one of IPDI, HDI, TDI, MDI, and HMDI; The sulfonate-modified diisocyanate includes at least one of sulfonate-modified IPDI, sulfonate-modified HDI, sulfonate-modified TDI, sulfonate-modified MDI, and sulfonate-modified HMDI; The small molecule diols include at least one of 3-methyl-1,5-pentanediol, neopentanediol, ethylene glycol, cyclohexanediol, methylpropanediol, 1,3-propanediol, 1,4-dihydroxymethylcyclohexane, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,2-propanediol, diethylene glycol, tetrahydrofurandiol, 1,6-hexanediol, trimethylpentanediol, butyl ethyl propylene glycol, dipropylene glycol, tripropylene glycol, and ethylhexanediol. The small molecule dicarboxylic acids include at least one of adipic acid, sebacic acid, isophthalic acid, and terephthalic acid; The other polyols mentioned include polyester polyols or polyether polyols; The polyester polyols include at least one of the following: poly(ethylene adipate-propylene glycol) diol, poly(butylene adipate) diol, poly(neopentyl adipate) diol, poly(neopentyl adipate-hexanediol) diol, poly(1,6-hexanediol) diol, poly(decanedioic acid-ethylene adipate-neopentyl adipate) diol, poly(isophthalic acid-neopentyl adipate-diethylene glycol) diol, poly(terephthalic acid-neopentyl adipate-1,4-butanediol) diol, and polycaprolactone diol. The polyether polyols include at least one of polypropylene oxide diol, polyethylene oxide-propylene oxide diol, and polytetrahydrofuran diol; The polyamines include at least one of ethylenediamine, hexamethylenediamine, isophoronediamine, sodium ethylenediaminoethanesulfonate, sodium 2,4-diaminobenzenesulfonate, 4,4'-diphenylmethanediamine, 1,2-cyclohexanediamine, diethylenetriamine, and triethylenetetramine.

2. A method for preparing a zero-VOC waterborne polyurethane resin emulsion as described in claim 1, characterized in that... The process involves two steps, and the specific preparation method is as follows: The first step involves the preparation of sulfonate polyester polyols. a) Add sulfonate-modified diisocyanate and dehydrated small molecule diol to a reaction flask equipped with a fractionation device, stir to carry out the reaction, control the reaction temperature to rise slowly, react at 80℃-90℃ for 2-10 hours, and stop the reaction when NCO is undetectable. b) Continue adding small molecule dicarboxylic acid, antioxidant and catalyst to the reaction flask, introduce nitrogen gas, raise the temperature to 120°C and react for 1 hour, then raise the temperature to 140°C and react for 3 hours, continue to slowly raise the temperature to 220-240°C and react, while controlling the temperature of the water outlet at the top of the condenser tube to not exceed 102°C. When the water output reaches the theoretical value, continue to output water for another hour; turn on the vacuum pump to evacuate for 3 hours, cool down to 70°C, and discharge the material to obtain sulfonate polyester polyol; The second step involves preparing a zero-VOC waterborne polyurethane resin emulsion, which can be achieved using two methods: a one-step method and a two-step method. One-step method In a four-necked reaction flask, add the formulated amount of sulfonate polyester polyol and other polyols, dehydrate under vacuum at 120°C for 2 hours, cool to 50-80°C, add the formulated amount of diisocyanate using a high-power stirrer, purge with nitrogen, and react at 50-130°C for 3-15 hours until NCO is undetectable; slowly add deionized water while stirring to emulsify, and continue stirring for 0.5-1 hour after the water is added to obtain a zero-VOC waterborne polyurethane resin emulsion. Two-step method a) In a four-necked reaction flask, add the formulated amount of sulfonate polyester polyol and other polyols, dehydrate under vacuum at 120°C for 2 hours, cool to 50-80°C, add the formulated amount of diisocyanate using a high-power stirrer, introduce nitrogen gas, and react at 50-130°C for 3-15 hours to obtain NCO-terminated sulfonate prepolymer. b) Cool to 100℃, slowly add deionized ice water while stirring to disperse, then slowly add a mixture of polyamine and deionized water to extend the chain, end-cap and emulsify, and continue the reaction at 50℃ for 1-2 hours. Discharge to obtain zero-VOC waterborne polyurethane resin emulsion.

3. The method for preparing a zero-VOC waterborne polyurethane resin emulsion according to claim 2, characterized in that, The raw material ratio for preparing sulfonate polyester polyol in the first step is as follows: the ratio of the sum of the moles of sulfonate-modified diisocyanate and small molecule dicarboxylic acid to the moles of small molecule diol is 1:(1.1-2); the molar ratio of sulfonate-modified diisocyanate to small molecule dicarboxylic acid is 1:(1-10).

4. The method for preparing a zero-VOC waterborne polyurethane resin emulsion according to claim 2, characterized in that, In step b) of the first step, the catalyst is tetrabutyl titanate, antimony trioxide or zinc acetate, and the amount of catalyst added is 0.05%-0.15% of the total weight of the raw materials.

5. The method for preparing a zero-VOC waterborne polyurethane resin emulsion according to claim 2, characterized in that, The high-power stirrer has a power of over 1000W to ensure that the reaction system can be stirred normally.

6. The method for preparing a zero-VOC waterborne polyurethane resin emulsion according to claim 2, characterized in that, The raw material ratio for the one-step method of preparing zero-VOC waterborne polyurethane resin emulsion in the second step is as follows: the ratio of the sum of the moles of sulfonate polyester polyol and other polyols to the moles of diisocyanate is (1.2-1.8):1, and the molar ratio of sulfonate polyester polyol to other polyols is 1:(1-4).

7. The method for preparing a zero-VOC waterborne polyurethane resin emulsion according to claim 2, characterized in that, The raw material ratio for the two-step process of preparing zero-VOC waterborne polyurethane resin emulsion in the second step is as follows: the ratio of the sum of the moles of sulfonate polyester polyol and other polyols to the moles of diisocyanate is 1:(1.5-2), and the molar ratio of sulfonate polyester polyol to other polyols is 1:(0-4).

8. The method for preparing a zero-VOC waterborne polyurethane resin emulsion according to claim 2, characterized in that, In step b) of the two-step process of the second step, the amount of polyamine added is such that the molar ratio of the remaining NCO to the amine group after the reaction in step a) is 1:(0.9-1.1).

9. The application of the zero-VOC waterborne polyurethane resin emulsion according to claim 1 in the preparation of waterborne polyurethane coatings, waterborne polyurethane adhesives, and waterborne polyurethane inks.

10. The use of the zero-VOC waterborne polyurethane resin emulsion prepared by the preparation method according to any one of claims 2-7 in the preparation of waterborne polyurethane coatings, waterborne polyurethane adhesives, and waterborne polyurethane inks.