Waterborne polyurethane resin for waterproof moisture-permeable film

Abstract

The invention provides waterborne polyurethane resin for a waterproof moisture-permeable film. The waterborne polyurethane resin is prepared from the following components in parts by weight: 25 to 70 parts of common hydroxyl polyol, 5 to 50 parts of hydrophilic hydroxyl polyol, 25 to 65 parts of a diisocyanate curing agent, 0 to 10 parts of a hydrophilic chain extender, 1 to 8 parts of a chain extender, 30 to 80 parts of a solvent, 0 to 5 parts of a salt forming agent, 1 to 8 parts of a post-chain extender and 300 to 600 parts of pure water. The preparation process is simple, the prepared waterborne polyurethane resin is good in environmental protection performance and good in stability, and a film prepared from the waterborne polyurethane resin has excellent waterproof and moisture permeable performance.

Description

Technical Field

[0001] The present application relates to the technical field of preparation of waterborne polyurethane resins, and in particular to a waterborne polyurethane resin for waterproof and breathable membranes. Background Art

[0002] Waterproof and breathable membrane is a new type of polymer waterproof material. It uses polyurethane (PU) as the main material and introduces hydrophilic groups. The film surface has no micropores, so it can be windproof and water-repellent. Because the film has a hydrophilic group, it has the function of moisture permeability through moisture absorption and conduction. It is often used in clothing fabrics, home textile composites, mountaineering clothes, ski boots and other fields.

[0003] In view of the current waterproof and breathable membranes on the market, some are made of solvent-based polyurethane resins. Due to the volatilization of solvents during the production process and the residual solvents in the final product, it does not comply with environmental protection policies and people's health needs. Therefore, it is necessary to produce a water-based polyurethane resin for waterproof and breathable membranes. Summary of the invention

[0004] The present application provides a water-based polyurethane resin for a waterproof and breathable membrane, so as to solve the problem that the waterproof and breathable membrane in the prior art is made of solvent-based polyurethane resin and has poor environmental performance, and the prepared water-based polyurethane resin has good environmental performance and good stability. The membrane prepared by using the water-based polyurethane resin has excellent waterproof and breathable properties.

[0005] The present application provides a water-based polyurethane resin for a waterproof and breathable membrane. The water-based polyurethane resin component includes a sample test by weight to see whether the NCO content meets the design target. The preferred component ratio of the water-based polyurethane resin component includes 25-70 parts of ordinary hydroxyl polyol, 5-50 parts of hydrophilic hydroxyl polyol, 25-65 parts of diisocyanate curing agent, 0-10 parts of hydrophilic chain extender, 1-8 parts of chain extender, 30-80 parts of solvent, 0-5 parts of salt former, 1-8 parts of post-chain extender, and 300-600 parts of pure water.

[0006] Preferably, the common hydroxy polyol is a mixture of one or more of polyoxypropylene diol and triol with a molecular weight of 1000-4000, polytetramethylene ether diol with a molecular weight of 600-3000, polyester diol with a molecular weight of 1000-4000, polycaprolactone diol or triol with a molecular weight of 600-3000, and polycarbonate diol with a molecular weight of 500-3000.

[0007] Preferably, the hydrophilic hydroxy polyol is a mixture of one or more of polyethylene oxide diol with a molecular weight of 200-4000, polyethylene oxide-propylene copolymer diol with a molecular weight of 200-4000, polyethylene glycol monomethyl ether with a molecular weight of 200-4000, and polyethylene oxide-tetrahydrofuran copolymer diol with a molecular weight of 500-3000.

[0008] Preferably, the diisocyanate curing agent is a mixture of one or more of HDI, IPDI and HMDI.

[0009] Preferably, the hydrophilic chain extender is a mixture of one or more of dimethylolpropionic acid, dimethylolbutyric acid, sodium ethylenediamine sulfonate, diethylenetriamine, dihydroxy half ester, and methyldiethanolamine; the chain extender is a mixture of one or more of ethylene glycol, propylene glycol, 1,4-butanediol, hexanediol, trimethylolpropane, diethylene glycol, dipropylene glycol, and 1,4-cyclohexanedimethanol; the post-chain extender is a mixture of one or more of ethylenediamine, hexamethylenediamine, 1,3-cyclohexanedimethylamine, a polyetheramine with a molecular weight of 230 or 400, isophoronediamine, 4,4-diaminodicyclohexylmethane, and 3,3-dimethyl-4,4-diaminodicyclohexylmethane.

[0010] Preferably, the solvent is any one of acetone, butanone and ethyl acetate.

[0011] Preferably, the salt-forming agent is a mixture of one or more of triethylamine, ammonia sodium hydroxide, hydrochloric acid, and epichlorohydrin acetate.

[0012] Preferably, a method for preparing an aqueous polyurethane resin for a waterproof and breathable membrane comprises the following steps:

[0013] A. First, add ordinary hydroxy polyol, hydrophilic hydroxy polyol and diisocyanate curing agent into a reaction kettle, and heat the reaction kettle to 80-100 degrees, keep the temperature for 2-3 hours, and react to obtain isocyanate prepolymer;

[0014] B. Then, a hydrophilic chain extender and an appropriate amount of solvent are added to the reactor for stirring reaction, and the temperature is kept at 60-80 degrees for 1-2 hours to obtain a mixture A;

[0015] C. Add a chain extender to mixture A, stir and mix at 60-80 degrees for reaction, and keep warm for 1-2 hours to obtain mixture B;

[0016] D. Cool the mixture B to 30-50 degrees, add a salt-forming agent, stir and mix thoroughly, and keep warm at 30-50 degrees for 0.5-1 hour to obtain a mixture C;

[0017] E. Pour the mixture C into the tank, add 0-10 degree pure water, and put the tank into a high-speed disperser for high-speed dispersion for 5-20 minutes to disperse the solution into a dispersion;

[0018] F. Then, add the post-chain extender dropwise into the dispersion, ensuring that the addition is completed within 10-30 minutes, and stir and mix to obtain an aqueous dispersion;

[0019] G. Pour the aqueous dispersion into a glass bottle and continue to keep the temperature at 50-60 degrees for reaction for 1 hour, then pour it into a rotary evaporator, heat it at 50-70 degrees, maintain the vacuum degree of -0.095, remove the solvent, and obtain an emulsion;

[0020] H. Finally, the emulsion is filtered to obtain a water-based polyurethane resin with a solid content of 20-30%.

[0021] Beneficial effects: The preparation process of the present invention is simple, the prepared waterborne polyurethane resin has good environmental performance and good stability, and the film prepared by using the waterborne polyurethane resin has excellent waterproof and moisture permeability.

[0022] The above description is only an overview of the technical solution of the embodiment of the present application. In order to more clearly understand the technical means of the embodiment of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the embodiment of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0025] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase "embodiments" in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0026] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application is clearly and completely described below.

[0027] The present application provides a water-based polyurethane resin for a waterproof and breathable membrane. The water-based polyurethane resin components include, by weight, 25-70 parts of a common hydroxyl polyol, 5-50 parts of a hydrophilic hydroxyl polyol, 25-65 parts of a diisocyanate curing agent, 0-10 parts of a hydrophilic chain extender, 1-8 parts of a chain extender, 30-80 parts of a solvent, 0-5 parts of a salt-forming agent, and 1-8 parts of a post-chain extender.

[0028] Embodiment 1:

[0029] The waterborne polyurethane resin components are proportioned in parts by weight as follows

[0030]

[0031]

[0032] In this embodiment, a method for preparing an aqueous polyurethane resin for a waterproof and breathable membrane comprises the following steps:

[0033] A. First, add polytetramethylene glycol, polyoxypropylene glycol, polyoxyethylene glycol, isophorone diisocyanate, and hexamethylene diisocyanate into a reaction kettle, and heat the reaction kettle to 80-85 degrees, keep the temperature for 2 hours, and react to obtain an isocyanate prepolymer;

[0034] B. Then, dimethylolbutyric acid and 10 parts of acetone were added to the reaction kettle for stirring reaction, and the temperature was kept at 75-80 degrees for 1.5 hours to obtain a mixture A;

[0035] C. Add 40 parts of 1-4-butanediol and acetone to mixture A, stir and mix at 60-65 degrees for reaction, and keep warm for 1 hour to obtain mixture B;

[0036] D. Cool mixture B to 45 degrees, add triethylamine, stir and mix thoroughly, and keep warm at 45 degrees for 0.5 hours to obtain mixture C;

[0037] E. Pour the mixture C into the tank, add 400 parts of 0-10 degree pure water, and put the tank into a high-speed disperser for high-speed dispersion for 15 minutes to disperse the solution into a dispersion;

[0038] F. Then, 44.66 parts of a mixture of ethylenediamine and pure water were added dropwise into the dispersion, and the mixture was added within 15 minutes, and stirred to obtain an aqueous dispersion;

[0039] G. Pour the aqueous dispersion into a glass bottle and continue to keep the temperature at 60 degrees for 1 hour, then pour it into a rotary evaporator, heat it to 55 degrees, maintain a vacuum degree of -0.095, remove the solvent and excess water, and obtain an emulsion;

[0040] H. Finally, the emulsion is filtered to obtain a water-based polyurethane resin with a solid content of 23%-25%.

[0041] Embodiment 2:

[0042] The waterborne polyurethane resin components are proportioned in parts by weight as follows

[0043]

[0044]

[0045] In this embodiment, a method for preparing an aqueous polyurethane resin for a waterproof and breathable membrane comprises the following steps:

[0046] A. First, add polytetramethylene glycol, polyoxypropylene glycol, polyoxyethylene glycol, isophorone diisocyanate, and hexamethylene diisocyanate into a reaction kettle, and heat the reaction kettle to 80-85 degrees, keep the temperature for 2.5 hours, and react to obtain an isocyanate prepolymer;

[0047] B. Then, dimethylolbutyric acid and 10 parts of acetone were added to the reaction kettle for stirring reaction, and the temperature was kept at 75-80 degrees for 1.2 hours to obtain a mixture A;

[0048] C. Add 45 parts of 1-4-butanediol and acetone to mixture A, stir and mix at 60-65 degrees for reaction, and keep warm for 1.2 hours to obtain mixture B;

[0049] D. Cool the mixture B to 45 degrees, add triethylamine, stir and mix thoroughly, and keep warm at 45 degrees for 0.4 hours to obtain a mixture C;

[0050] E. Pour the mixture C into the tank, add 400 parts of 0-10 degree pure water, and put the tank into a high-speed disperser for high-speed dispersion for 15 minutes to disperse the solution into a dispersion;

[0051] F. Then, 53.84 parts of a mixture of ethylenediamine and pure water were added dropwise into the dispersion, and the mixture was added within 15 minutes, and stirred to obtain an aqueous dispersion;

[0052] G. Pour the aqueous dispersion into a glass bottle and continue to keep the temperature at 60 degrees for 1 hour, then pour it into a rotary evaporator, heat it to 55 degrees, maintain a vacuum degree of -0.095, remove the solvent and excess water, and obtain an emulsion;

[0053] H. Finally, the emulsion is filtered to obtain a water-based polyurethane resin with a solid content of 20%-23%.

[0054] Embodiment three:

[0055] The waterborne polyurethane resin components are proportioned in parts by weight as follows

[0056] Polytetramethylenetetrahydrofuran ether molecular weight 2000 42 Polyoxypropylene glycol, molecular weight 3000 15 Polyoxyethylene propylene copolymer glycol molecular weight 3000 15 Isophorone diisocyanate 15 Hexamethylene diisocyanate 3.5 Dicyclohexylmethane diisocyanate 12 dimethylolbutyric acid 2 1-4-Butanediol 5 acetone 55 Triethylamine 2.05 Ethylenediamine 1.5 0-10 degrees pure water 500

[0057] In this embodiment, a method for preparing an aqueous polyurethane resin for a waterproof and breathable membrane comprises the following steps:

[0058] A. First, add polytetramethylene ether, polyoxypropylene glycol, polyoxyethylene propylene copolymer glycol, isophorone diisocyanate, and hexamethylene diisocyanate into a reaction kettle, and heat the reaction kettle to 80-85 degrees, keep the temperature for 2 hours, and react to obtain an isocyanate prepolymer;

[0059] B. Then, 15 parts of dimethylolbutyric acid and acetone were added into the reaction kettle for stirring reaction, and the mixture was kept at 60-70 degrees for 1 hour to obtain a mixture A;

[0060] C. Add 40 parts of 1-4-butanediol and acetone to mixture A, stir and mix at 60-70 degrees for reaction, and keep warm for 1 hour to obtain mixture B;

[0061] D. Cool mixture B to 45 degrees, add triethylamine, stir and mix thoroughly, and keep warm at 35 degrees for 0.5 hours to obtain mixture C;

[0062] E. Pour the mixture C into the tank, add 450 parts of 0-10 degree pure water, and put the tank into a high-speed disperser for high-speed dispersion for 12 minutes to disperse the solution into a dispersion;

[0063] F. Then, 51.5 parts of a mixture of ethylenediamine and pure water were added dropwise into the dispersion, and the mixture was added within 12 minutes, and stirred to obtain an aqueous dispersion;

[0064] G. Pour the aqueous dispersion into a glass bottle and continue to keep the temperature at 58 degrees for 1 hour, then pour it into a rotary evaporator, heat it to 58 degrees, maintain the vacuum degree of -0.095, remove the solvent, and obtain an emulsion;

[0065] H. Finally, the emulsion is filtered to obtain an aqueous polyurethane resin with a solid content of 20-24%.

[0066] Embodiment 4:

[0067] The waterborne polyurethane resin components are proportioned in parts by weight as follows

[0068] Polytetramethylenetetrahydrofuran ether molecular weight 3000 25 Polycaprolactone diol, molecular weight 3000 10 Polyoxyethylene glycol molecular weight 1000 25 Dicyclohexylmethane diisocyanate 23 Hexamethylene diisocyanate 4 dimethylolbutyric acid 3 1-6 Hexanediol 4 acetone 45 Triethylamine 2.05 Isophorone diamine 3 0-10 degrees pure water 440

[0069] In this embodiment, a method for preparing a water-based polyurethane resin for a waterproof and breathable membrane is provided, and the preparation method comprises the following steps:

[0070] A. First, add polytetramethylene glycol, polycaprolactone diol, polyethylene glycol, dicyclohexylmethane diisocyanate and hexamethylene diisocyanate into a reaction kettle, and heat the reaction kettle to 80-90 degrees, keep the temperature for 2.3 hours, and react to obtain an isocyanate prepolymer;

[0071] B. Then, dimethylolbutyric acid and 10 parts of acetone were added into the reaction kettle for stirring reaction, and the temperature was kept at 68 degrees for 1 hour to obtain a mixture A;

[0072] C. Add 35 parts of 1-6 hexanediol and acetone to mixture A, stir and mix at 60-68 degrees for reaction, and keep warm for 1.2 hours to obtain mixture B;

[0073] D. Cool mixture B to 38 degrees, add triethylamine, stir and mix thoroughly, and keep warm at 38 degrees for 0.6 hours to obtain mixture C;

[0074] E. Pour the mixture C into the tank, add 0-10 degree pure water, and put the tank into a high-speed disperser for high-speed dispersion for 13 minutes to disperse the solution into a dispersion;

[0075] F. Then, add isophorone diamine and pure water dropwise into the dispersion, ensure that the addition is completed within 14 minutes, and stir and mix to obtain an aqueous dispersion;

[0076] G. Pour the aqueous dispersion into a glass bottle and continue to keep the temperature at 56 degrees for 1 hour, then pour it into a rotary evaporator, heat it to 60 degrees, maintain the vacuum degree of -0.095, remove the solvent, and obtain an emulsion;

[0077] H. Finally, the emulsion is filtered to obtain a water-based polyurethane resin with a solid content of 23-30%.

[0078] Embodiment five:

[0079] The waterborne polyurethane resin components are proportioned in parts by weight as follows

[0080] Polycarbonate diol molecular weight 2000 20 Polycaprolactone diol, molecular weight 3000 23 Polyoxyethylene glycol molecular weight 3000 7 Polyoxyethylene glycol molecular weight 2000 15 Isophorone diisocyanate 15 Hexamethylene diisocyanate 5 dimethylolbutyric acid 1 Diethylene glycol 3 Butanone 40 Triethylamine 0.68 Isophorone diamine 5 0-10 degrees pure water 420

[0081] In this embodiment, a method for preparing a water-based polyurethane resin for a waterproof and breathable membrane is provided, and the preparation method comprises the following steps:

[0082] A. First, add polycarbonate diol, polycaprolactone diol, polyethylene oxide diol, polyethylene oxide diol, isophorone diisocyanate, and hexamethylene diisocyanate into a reaction kettle, and heat the reaction kettle to 90-100 degrees, keep the temperature for 2.2 hours, and react to obtain an isocyanate prepolymer;

[0083] B. Then, 10 parts of dimethylolbutyric acid and butanone were added to the reactor for stirring reaction, and the mixture was kept at 65 degrees for 1.8 hours to obtain a mixture A;

[0084] C. Add 30 parts of diethylene glycol and butanone to mixture A, stir and mix at 70-80 degrees for reaction, and keep warm for 1 hour to obtain mixture B;

[0085] D. Cool mixture B to 42 degrees, add triethylamine, stir and mix thoroughly, and keep warm at 42 degrees for 0.7 hours to obtain mixture C;

[0086] E. Pour the mixture C into the tank, add 0-10 degree pure water, and put the tank into a high-speed disperser for high-speed dispersion for 14 minutes to disperse the solution into a dispersion;

[0087] F. Then, add isophorone diamine and pure water dropwise into the dispersion, ensure that the addition is completed within 20 minutes, and stir and mix to obtain an aqueous dispersion;

[0088] G. Pour the aqueous dispersion into a glass bottle and continue to keep the temperature at 55 degrees for 1 hour, then pour it into a rotary evaporator, heat it to 60 degrees, maintain the vacuum degree of -0.095, remove the solvent, and obtain an emulsion;

[0089] H. Finally, the emulsion is filtered to obtain a water-based polyurethane resin with a solid content of 25-30%.

[0090] Experimental example:

[0091] The performance test of the waterborne polyurethane resin coating film prepared by each embodiment of the present invention was carried out after drying, with a film thickness of 20-30 microns, and the data obtained are as follows:

[0092]

[0093]

[0094] In summary, the preparation process of the present invention is simple, the prepared waterborne polyurethane resin has good environmental performance and good stability, and the film prepared by using the waterborne polyurethane resin has excellent waterproof and moisture permeability.

[0095] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A water-based polyurethane resin for a waterproof and breathable membrane, characterized in that: The waterborne polyurethane resin components include, by weight, 25-70 parts of common hydroxy polyol, 5-50 parts of hydrophilic hydroxy polyol, 25-65 parts of diisocyanate curing agent, 0-10 parts of hydrophilic chain extender, 1-8 parts of chain extender, 30-80 parts of solvent, 0-5 parts of salt former, 1-8 parts of post-chain extender and 300-600 parts of pure water.

2. The water-based polyurethane resin for waterproof and breathable membrane according to claim 1, characterized in that: The preferred composition ratio of the waterborne polyurethane resin component includes 25-70 parts of ordinary hydroxy polyol, 5-50 parts of hydrophilic hydroxy polyol, 25-65 parts of diisocyanate curing agent, 0-10 parts of hydrophilic chain extender, 1-8 parts of chain extender, 30-80 parts of solvent, 0-5 parts of salt former, 1-8 parts of post-chain extender, and 300-600 parts of pure water.

3. The water-based polyurethane resin for waterproof and breathable membrane according to claim 1, characterized in that: The common hydroxy polyol is a mixture of one or more of polyoxypropylene diol and triol with a molecular weight of 1000-4000, polytetramethylene ether diol with a molecular weight of 600-3000, polyester diol with a molecular weight of 1000-4000, polycaprolactone diol or triol with a molecular weight of 600-3000, and polycarbonate diol with a molecular weight of 500-3000.

4. The water-based polyurethane resin for waterproof and breathable membrane according to claim 1, characterized in that: The hydrophilic hydroxy polyol is a mixture of one or more of polyethylene oxide diol with a molecular weight of 200-4000, polyethylene oxide-propylene copolymer diol with a molecular weight of 200-4000, polyethylene glycol monomethyl ether with a molecular weight of 200-4000, and polyethylene oxide-tetrahydrofuran copolymer diol with a molecular weight of 500-3000.

5. The water-based polyurethane resin for waterproof and breathable membrane according to claim 1, characterized in that: The diisocyanate curing agent is a mixture of one or more of HDI, IPDI and HMDI.

6. The water-based polyurethane resin for waterproof and breathable membrane according to claim 1, characterized in that: The hydrophilic chain extender is a mixture of one or more of dimethylolpropionic acid, dimethylolbutyric acid, sodium ethylenediamine sulfonate, diethylenetriamine, dihydroxy half ester, and methyldiethanolamine; the chain extender is a mixture of one or more of ethylene glycol, propylene glycol, 1,4-butanediol, hexanediol, trimethylolpropane, diethylene glycol, dipropylene glycol, and 1,4-cyclohexanedimethanol; the post-chain extender is a mixture of one or more of ethylenediamine, hexamethylenediamine, 1,3-cyclohexanedimethylamine, polyetheramine with a molecular weight of 230 or 400, isophoronediamine, 4,4-diaminodicyclohexylmethane, and 3,3-dimethyl-4,4-diaminodicyclohexylmethane.

7. The water-based polyurethane resin for waterproof and breathable membrane according to claim 1, characterized in that: The solvent is any one of acetone, butanone and ethyl acetate.

8. The water-based polyurethane resin for waterproof and breathable membrane according to claim 1, characterized in that: The salt-forming agent is a mixture of one or more of triethylamine, ammonia water, sodium hydroxide, hydrochloric acid, acetic acid and epichlorohydrin.

9. A method for preparing a water-based polyurethane resin for a waterproof and breathable membrane according to claim 1, characterized in that: The preparation method comprises the following steps: A. First, add ordinary hydroxy polyol, hydrophilic hydroxy polyol and diisocyanate curing agent into a reaction kettle, and heat the reaction kettle to 60-100 degrees, keep the temperature for 2 hours, and react to obtain isocyanate prepolymer; B. Then, a hydrophilic chain extender and an appropriate amount of solvent are added to the reactor for stirring reaction, and the temperature is kept at 60-80 degrees for 1-2 hours to obtain a mixture A; C. Add a chain extender to mixture A, stir and mix at 60-80 degrees for reaction, and keep warm for 1-2 hours to obtain mixture B; D. Cool the mixture B to 30-60 degrees, add a salt-forming agent, stir and mix thoroughly, and keep warm at 30-60 degrees for 0.5-1 hour to obtain a mixture C; E. Pour the mixture C into the tank, add 0-10 degree pure water, and put the tank into a high-speed disperser for high-speed dispersion for 5-20 minutes to disperse the solution into a dispersion; F. Then, add the post-chain extender dropwise into the dispersion, ensuring that the addition is completed within 10-30 minutes, and stir and mix to obtain an aqueous dispersion; G. Pour the aqueous dispersion into a glass bottle and continue to keep the temperature at 50-60 degrees for reaction for 1 hour, then pour it into a rotary evaporator, heat it at 50-70 degrees, maintain the vacuum degree of -0.095, remove the solvent, and obtain an emulsion; H. Finally, the emulsion is filtered to obtain waterborne polyurethane resin.

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