A high alkali-resistant bio-based polyurethane fluorine-free waterproofing agent, its preparation method and application

Abstract

This invention belongs to the field of polymers and discloses a high-alkali-resistant bio-based polyurethane fluorine-free waterproofing agent, its preparation method, and its application. The preparation method includes: firstly, a polyol composed of castor oil-based polyol, polycarbonate diol, and dihydroxyalkyl polydimethylsiloxane is polymerized with diisocyanate to form a polyurethane prepolymer; then, after chain extension with a carboxyl-containing hydrophilic chain extender and end-capping with an isocyanate-containing hydrophobic end-capping agent, a diketone carbonyl first internal crosslinking agent is added for modification to obtain the polymer; next, the carboxyl groups are neutralized with an organic base, and self-emulsification is completed by water shearing; finally, a second internal crosslinking agent that can react with ketone carbonyl groups is compounded, and a water-based modified epoxy resin external crosslinking agent is added during use. The raw material of this waterproofing agent uses castor oil-based bio-polyol to achieve bio-based properties. The fluorine-free system is environmentally friendly and safe. The siloxane and the multi-crosslinking system work synergistically, and the finished product has excellent hydrophobicity, ultra-long wash resistance, and extremely strong alkali resistance. After treatment, the fabric has a soft hand feel and good breathability, with significant comprehensive performance advantages.

Description

Technical Field

[0001] This invention relates to the field of polymers, and mainly discloses a highly alkali-resistant bio-based polyurethane fluorine-free waterproofing agent, its preparation method, and its application. Background Technology

[0002] With the rapid development of textiles, outdoor products, home textiles and other fields, the market demand for functional finishing of fabrics continues to upgrade. Waterproofing, stain resistance, washability, breathability and comfort have become the core added properties of textiles, and are widely used in various product scenarios such as outdoor jackets, tents, bag fabrics, home textiles, and industrial protective fabrics. Waterproof finishing technology has become one of the key core technologies to enhance the competitiveness of textiles in the market.

[0003] Currently, the mainstream fabric waterproofing agents on the market are mainly fluorinated waterproofing agents. Relying on the unique low surface energy properties of fluorine atoms, fluorinated waterproofing agents can give fabrics excellent comprehensive waterproof, oil-proof, and stain-proof properties, and outstanding wash resistance, making them the preferred material for traditional high-end waterproofing finishing. However, traditional fluorinated waterproofing agents generally contain perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and other perfluoroalkyl compounds. These substances are persistent organic pollutants that are difficult to degrade, have extremely strong bioaccumulation, environmental residues, and potential biotoxicity. They can remain in the natural environment for hundreds of years and easily accumulate in the human body and other organisms through the food chain. Long-term exposure can harm the health of the human metabolic, immune, and reproductive systems, while also causing continuous damage to the ecological environment.

[0004] With the continuous upgrading of global ecological and environmental protection management, many countries and regions have successively introduced strict laws, regulations, and industry standards, explicitly restricting or prohibiting the production, sale, and application of perfluorinated compounds such as PFOA and PFOS. This has comprehensively promoted the "fluorine-free and green" upgrade in the textile waterproofing field, and fluorinated waterproofing agents have gradually withdrawn from the mainstream market. Developing environmentally friendly, non-toxic, and high-performance fluorine-free waterproofing agents has become the core trend of industry technology research and development. Based on the green upgrade of fluorine-free waterproofing technology and relying on the industry development orientation of green chemical industry and low-carbon production, bio-based fluorine-free waterproofing agents have become the cutting-edge research and development direction in this sub-sector. The core raw materials of traditional polyurethane waterproofing agents are mostly petroleum-based polyols, which are non-renewable petrochemical resources. They not only consume a lot of resources and have a high carbon footprint, which does not conform to the dual-carbon development concept, but also have high pollution emissions during the raw material preparation process. Bio-based fluorine-free waterproofing agents use renewable bio-based raw materials such as vegetable oils and biomass polyols to replace traditional petroleum-based polyols, which can effectively reduce dependence on petrochemical resources and significantly reduce pollutant and carbon emissions throughout the production process. The raw materials are renewable and biodegradable, making it a core green direction for achieving low-carbon and sustainable development in the textile waterproofing field, with excellent environmental value and promising prospects for industrial promotion.

[0005] However, current bio-based fluorine-free waterproofing agents on the market and in existing technologies have significant performance shortcomings, and the industry generally faces the technical pain point of "difficulty in balancing environmental protection and functionality." The root cause of this pain point lies in the inherent characteristics of bio-based raw materials, such as strong hydrophilicity and poor hydrolysis resistance. In order to achieve bio-based raw material substitution, most products sacrifice the structural stability and comprehensive mechanical properties of the polyurethane system, resulting in a significant decrease in the film density and structural strength of the finished waterproofing agent. Specifically, this manifests as poor water wash resistance and weak alkali resistance. After alkaline washing and repeated water washing, the surface waterproof film of the fabric is easily damaged and falls off, and the hydrophobic properties decay rapidly. At the same time, the film layer lacks flexibility and adhesion, and the mechanical durability is difficult to meet the requirements of normal washing and complex working conditions of textiles, which greatly limits the large-scale industrial application of bio-based fluorine-free waterproofing agents.

[0006] Based on this, the technical problem to be solved by the present invention is: how to prepare a bio-based polyurethane fluorine-free waterproofing agent with excellent comprehensive properties such as ultra-long-lasting wash resistance, extreme alkali resistance and soft feel. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a bio-based polyurethane fluorine-free waterproofing agent, so as to overcome the shortcomings of the prior art.

[0008] Meanwhile, the present invention also provides a bio-based polyurethane fluorine-free waterproofing agent prepared by the same method.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] A method for preparing a bio-based polyurethane fluorine-free waterproofing agent includes the following steps:

[0011] Step 1: Polymerization reaction is carried out using polyols and diisocyanates as raw materials to obtain polyurethane prepolymer;

[0012] Step 2: First, use a carboxyl-containing hydrophilic chain extender to extend the polyurethane prepolymer, then use a capping agent containing isocyanate groups and hydrophobic segments to cap it, and finally add a first internal crosslinking agent containing at least two ketone carbonyl groups to the segments of the capped polyurethane prepolymer to obtain the polymer.

[0013] Step 3: Add an organic base to neutralize the carboxyl groups in the polymer, and add deionized water to perform shear emulsification, so that the polymer self-emulsifies;

[0014] Step 4: Add a second internal crosslinking agent to react with the ketone carbonyl group after polymer demulsification;

[0015] When using the bio-based fluorine-free waterproofing agent, an external crosslinking agent is added; the external crosslinking agent is a water-based modified epoxy resin, and the amount added is 5-10% of the weight of the bio-based polyurethane fluorine-free waterproofing agent.

[0016] The polyol is composed of castor oil-based polyol, polycarbonate diol, and hydroxyl-terminated polydimethylsiloxane.

[0017] The weight ratio of castor oil-based polyol, polycarbonate diol, and dihydroxyl-terminated polydimethylsiloxane is 45~55:30~40:15.

[0018] In this invention, bio-based castor oil-based polyols account for more than 45 wt% of the total polyols. Compared with other petroleum-based polyols, although they can bring more obvious environmental protection, they are relatively weaker in terms of wash resistance, alkali resistance and hand feel improvement.

[0019] To overcome this problem, the present invention has optimized performance from the following perspectives:

[0020] 1. Alkali resistance;

[0021] The alkali resistance is mainly achieved by replacing the traditional polyester diol with polycarbonate diol (PCDL). The hydrolytic stability of the carbonate bond is much higher than that of the carboxylic acid ester bond, which gives the product higher alkali resistance.

[0022] The double cross-linking system makes a significant contribution to alkali resistance. The double cross-linking system can form a dense three-dimensional network with internal and external double cross-linking, which has higher alkali resistance than the system with only internal cross-linking.

[0023] In the modification of polyurethane prepolymers, chain extension, end-capping, and introduction of ketone carbonyl groups are carried out sequentially. In particular, introducing ketone carbonyl groups in the final stage of modification can make the distribution of ketone carbonyl groups more uniform, increase the number of reactive active groups, improve the uniformity of internal crosslinking after demulsification, and significantly improve alkali resistance.

[0024] By combining the above three methods, it can resist strong alkaline erosion under pH 12 and 60℃ conditions for 24 hours, and still maintain a water repellency level of 4 after treatment.

[0025] 2. Washability

[0026] The primary factor related to the wash resistance of fabric treatment agents is the stability and tightness of the covalent bond between the polymer and the fabric itself, followed by factors such as surface tension, alkali resistance, and the hydrophilicity of the monomers.

[0027] In this invention, epoxy resin is used as an external crosslinking agent, which covalently bonds with polyurethane carboxyl groups, hydroxyl groups and fabric fiber hydroxyl groups, greatly improving the adhesion between the film and the fiber.

[0028] Furthermore, the internal crosslinking system of the present invention can improve the compactness of the film layer, improve the water resistance of the film layer itself, and reduce the surface tension of the film layer, which contributes to improving wash resistance.

[0029] In this invention, the "ketone-hydrazine dormancy" process is used to achieve simultaneous internal and external crosslinking. This simultaneous and immediate formation of internal and external crosslinking can improve the uniformity of external crosslinking, enabling the polymer to perform immediate internal and external crosslinking and film formation on the fabric surface. Compared with the traditional pre-crosslinking or sequential crosslinking methods of fabric treatment agents, the uniformity and density of the film layer are improved, thereby improving its wash resistance.

[0030] In this invention, the use of large doses of bio-based polyols is the main factor contributing to the reduction in wash resistance. By employing main-chain block-terminated dihydroxyalkyl polydimethylsiloxane (PDMS) instead of side-linked branches, PDMS segments are more easily migrated and enriched to the membrane surface, significantly reducing surface energy and improving hydrophobicity. At the same time, the long-chain alkyl end-capping synergistically hydrophobizes, achieving an initial water contact angle of up to 145°. Polycarbonate diols are used to improve alkali resistance. Through sequential chain extension, end-capping, and the introduction of ketone carbonyl groups, the molecular weight is increased and molecular uniformity is improved, thereby enhancing wash resistance. Simultaneously, the internal and external cross-linking structure simultaneously improves wash resistance.

[0031] Therefore, the improvement in washability is the result of the combined effect of multiple factors. Through the combined effect of these factors, the initial water repellency level can reach level 5.

[0032] In addition to the above effects, the product of this invention also has excellent softness and high breathability. The natural soft structure of bio-based castor oil polyol and the low glass transition temperature of PDMS segments work synergistically to give the membrane excellent flexibility. The microphase separation structure formed by the double crosslinking system retains the breathable channels, and the moisture permeability can reach 8500g / (m²・24h), without affecting the comfort of the fabric. This invention adopts the "ketone-hydrazine dormancy" process, which confines ADH in the aqueous phase rather than inside the polyurethane particles. During the storage period, the ketone carbonyl group and the hydrazine group cannot come into contact, and the emulsion can be stably stored for more than 6 months without gelation or stratification. The bio-based carbon content of this invention is ≥52%, and it does not contain any perfluorinated or polyfluoroalkyl compounds (PFAS), which meets the most stringent global environmental standards such as EU REACH and OEKO-TEX® Standard 100.

[0033] Preferably, the castor oil-based polyol has a hydroxyl value of 200±10 mgKOH / g and a number-average functionality of 2.7; the polycarbonate diol has a number-average molecular weight of 800~2000; and the dihydroxyl-terminated polydimethylsiloxane has a number-average molecular weight of 2000~3000.

[0034] Preferably, the diisocyanate is one or more combinations of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

[0035] Preferably, in step 1, the molar ratio of isocyanate groups to hydroxyl groups is 1.3 to 1.5.

[0036] Preferably, the hydrophilic chain extender is one or more combinations of 2,2-dimethylolbutyric acid, 2,2-dimethylolpropionic acid, and N-methyldiethanolamine; the end-capping agent is one or more combinations of octadecyl isocyanate, hexadecyl isocyanate, and dodecyl isocyanate; and the first internal crosslinking agent is one or more combinations of diacetone acrylamide, diacetone methacrylamide, and ethyl acetoacetate methacrylate.

[0037] More preferably, the hydrophilic chain extender is 2,2-dimethylolbutyric acid; and the end-capping agent is octadecyl isocyanate.

[0038] With the polyol accounting for 100% by weight, the amount of the hydrophilic chain extender is 6-8%; the amount of the end-capping agent is 2-4%; and the amount of the first internal crosslinking agent is 3-5%.

[0039] Preferably, the organic base is one or a combination of TEA, triethylamine, and dimethylethanolamine; the degree of neutralization in step 3 is 100-110%.

[0040] More preferably, the organic base is TEA.

[0041] Preferably, the second internal crosslinking agent is one or more combinations of adipate dihydrazide, sebacic dihydrazide, and isophthalic dihydrazide;

[0042] The amount of the second internal crosslinking agent is 2-3%, with the polyol accounting for 100% by weight.

[0043] Preferably, the epoxy value of the water-based modified epoxy resin is 0.12~0.15;

[0044] The solid content of the bio-based fluorine-free waterproofing agent is 100%, the amount of the water-based modified epoxy resin is 5-10%, and the amount of the deionized water is 100-120%.

[0045] Preferably, the reaction temperature in step 1 is 85~90℃, and the reaction time is 1~3h;

[0046] In step 2, the hydrophilic chain extender, the end-capping agent, and the first internal crosslinking agent react sequentially with the polyurethane prepolymer. The reaction temperature between the hydrophilic chain extender and the polyurethane prepolymer is 70-85°C, and the reaction time is 1-2 hours. The reaction temperature between the end-capping agent and the polyurethane prepolymer is 70-85°C, and the reaction time is 15-45 minutes. The reaction temperature between the first internal crosslinking agent and the polyurethane prepolymer is 70-85°C, and the reaction time is 15-45 minutes.

[0047] The reaction temperature in steps 3 and 4 is 40°C or below.

[0048] Finally, this invention discloses a bio-based polyurethane fluorine-free waterproofing agent, which is prepared using the method described above.

[0049] Compared with the prior art, the beneficial effects of the present invention are:

[0050] The bio-based polyurethane fluorine-free waterproofing agent of this invention has a bio-based carbon content of ≥52%, and can resist strong alkaline erosion at pH 12 and 60℃ for 24 hours, maintaining a water repellency rating of 4 after treatment; its initial water contact angle can reach 145°, with an initial water repellency rating of 5, and after 30 standard washes, the water repellency rating still remains at 4; in addition, its hand feel rating is 4.5, and its moisture permeability can reach 8500g / (m²・24h); it can be stored stably for more than 6 months without gelation or delamination; this shows that the bio-based polyurethane fluorine-free waterproofing agent of this invention achieves a high bio-based carbon content while realizing excellent hydrophobicity, ultra-long-lasting wash resistance, extreme alkali resistance, soft hand feel, high air permeability and excellent storage stability. Detailed Implementation

[0051] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0052] Product Information:

[0053] All raw materials are commercially available industrial grade, with specific specifications as follows:

[0054] Castor oil-based polyol: an exchange product of castor oil and trimethylolpropane, with a hydroxyl value of 200±10 mgKOH / g and a number-average functionality of 2.7;

[0055] Polycarbonate diol (PCDL-1000): Mn=1000;

[0056] Bis-hydroxyl-terminated polydimethylsiloxane (PDMS-2500): Hydroxypropyl-terminated, Mn=2500;

[0057] Hexamethylene diisocyanate (HMDI): Purity ≥ 99.5%;

[0058] 2,2-Dimethylolbutyric acid (DMBA): Purity ≥99%;

[0059] Diacetone acrylamide (DAAM), adipate dihydrazide (ADH): Industrial grade;

[0060] Waterborne modified epoxy resins: epoxy values ​​of 0.12, 0.13, and 0.15, respectively;

[0061] Octadecyl isocyanate (C 18- NCO), hexadecyl isocyanate, dodecyl isocyanate: industrial grade;

[0062] Triethanolamine (TEA), triethylamine, dimethylethanolamine: purity ≥99%;

[0063] Deionized water: conductivity ≤10μS / cm.

[0064] Example 1

[0065] A method for preparing a bio-based polyurethane fluorine-free waterproofing agent includes the following steps:

[0066] Step 1: Polymerize polyol and diisocyanate at 85°C for 2 hours to obtain polyurethane prepolymer;

[0067] Step 2: Add a carboxyl-containing hydrophilic chain extender, an isocyanate-containing and hydrophobic segment capping agent, and a first internal crosslinking agent for introducing ketone carbonyl groups to the polyurethane prepolymer, and react to obtain the polymer.

[0068] Step 3: Add an organic base to neutralize the carboxyl groups in the polymer, and add deionized water to perform shear emulsification, so that the polymer self-emulsifies;

[0069] Step 4: Add a second internal crosslinking agent to react with the ketone carbonyl group after polymer demulsification;

[0070] The polyol is composed of castor oil-based polyol, polycarbonate diol, and dihydroxyl-terminated polydimethylsiloxane; the weight ratio of castor oil-based polyol, polycarbonate diol, and dihydroxyl-terminated polydimethylsiloxane is 50:35:15.

[0071] In step 1, the molar ratio of isocyanate groups to hydroxyl groups is 1.4; the diisocyanate is hexamethylene diisocyanate.

[0072] Based on the weight of the polyol (100%), the hydrophilic chain extender is 2,2-dimethylolbutyric acid (7%); the end-capping agent is octadecyl isocyanate (3%); the first internal crosslinking agent is diacetone acrylamide (3.7%); the organic base is TEA; and the second internal crosslinking agent is adipic acid dihydrazide (2.3%).

[0073] The neutralization degree in step 3 is 105%;

[0074] When using the prepared bio-based polyurethane fluorine-free waterproofing agent, add water-based modified epoxy resin (epoxy value 0.13) at a rate of 7% of the solid content of the bio-based polyurethane fluorine-free waterproofing agent, and use 110% deionized water.

[0075] The reaction temperature of the hydrophilic chain extender and the polyurethane prepolymer is 70°C, and the reaction time is 2 hours; the reaction temperature of the end-capping agent and the polyurethane prepolymer is 70°C, and the reaction time is 30 minutes; the reaction temperature of the first internal crosslinking agent and the polyurethane prepolymer is 70°C, and the reaction time is 30 minutes; the reaction temperature of steps 3 and 4 is 40°C.

[0076] Example 2

[0077] The process is basically the same as in Example 1, except that in step 1, the molar ratio of isocyanate groups to hydroxyl groups is 1.3; and the diisocyanate is isophorone diisocyanate.

[0078] Based on the weight of the polyol (100%), the hydrophilic chain extender is 2,2-dimethylolpropionic acid, used at 6%; the end-capping agent is hexadecyl isocyanate, used at 2%; the first internal crosslinking agent is diacetone methacrylamide, used at 3%; the organic base is triethylamine; and the second internal crosslinking agent is sebacic acid dihydrazide, used at 2%.

[0079] The neutralization degree in step 3 is 100%;

[0080] When using the prepared bio-based polyurethane fluorine-free waterproofing agent, add water-based modified epoxy resin (epoxy value 0.12) at a concentration of 5% of the solid content of the bio-based polyurethane fluorine-free waterproofing agent.

[0081] Example 3

[0082] The process is basically the same as in Example 1, except that in step 1, the molar ratio of isocyanate groups to hydroxyl groups is 1.5; and the diisocyanate is toluene diisocyanate.

[0083] Based on the weight of the polyol (100%), the hydrophilic chain extender is N-methyldiethanolamine at 8%; the end-capping agent is dodecyl isocyanate at 4%; the first internal crosslinking agent is ethyl acetoacetate methacrylate at 5%; the organic base is dimethylethanolamine; and the second internal crosslinking agent is isophthalic acid dihydrazide at 3%.

[0084] The neutralization degree in step 3 is 110%;

[0085] When using the prepared bio-based polyurethane fluorine-free waterproofing agent, add water-based modified epoxy resin (epoxy value 0.15) at a concentration of 10% of the solid content of the bio-based polyurethane fluorine-free waterproofing agent.

[0086] Example 4

[0087] The method is basically the same as in Example 1, except that the weight ratio of castor oil-based polyol, polycarbonate diol, and dihydroxyl-terminated polydimethylsiloxane is 55:30:15.

[0088] Example 5

[0089] The method is basically the same as in Example 1, except that the weight ratio of castor oil-based polyol, polycarbonate diol, and dihydroxyl-terminated polydimethylsiloxane is 45:40:15.

[0090] Comparative Example 1

[0091] It is basically the same as Example 1, except that the polycarbonate diol is replaced with polybutylene adipate (PBA-1000) in equimolar form.

[0092] Comparative Example 2

[0093] It is basically the same as Example 1, except that water-based modified epoxy resin is not added during use, and the finishing is done directly with emulsion.

[0094] Comparative Example 3

[0095] The process is basically the same as in Example 1, except that in step 2, diacetone acrylamide is added first for reaction, followed by chain extension with 2,2-dihydroxymethylbutyric acid and end-capping with octadecyl isocyanate.

[0096] Comparative Example 4

[0097] The example is basically the same as in Example 1, except that the double-ended hydroxyl polydimethylsiloxane is replaced with an equal mass of single-ended hydroxyl polydimethylsiloxane (Mn=2500, side-linked branched type).

[0098] Comparative Example 5

[0099] The process is basically the same as in Example 1, except that in step 2, after adding diacetone acrylamide, adipic acid dihydrazide is added for pre-crosslinking, followed by neutralization and emulsification.

[0100] Comparative Example 6 (directly lacking siloxane, i.e., neither block nor grafted).

[0101] It is basically the same as Example 1, except that no bi-hydroxyl-terminated polydimethylsiloxane is added, and an equal amount of castor oil-based polyol is added.

[0102] Comparative Example 7

[0103] The example is basically the same as in Example 1, except that the water-based modified epoxy resin is replaced by an aziridine crosslinking agent.

[0104] Performance testing

[0105] The waterproofing agents prepared in each embodiment and comparative example were used to treat the fabrics as follows:

[0106] 200g / m² pure cotton twill fabric 2 ): Two dips and two nips (working solution concentration 80g / L, liquid carryover rate 70%), pre-dry at 110℃ for 3min, bake at 130℃ for 2min.

[0107] The finished pure cotton twill fabric was tested according to the method in Table 1:

[0108] Table 1 Test Methods

[0109] Initial water repellency level AATCC 22-2021 Water repellency rating after 30 washes AATCC 135-2020 (5A Procedure) Extreme alkali resistance followed by water repellency rating Soak at pH 12 and 60℃ for 24 hours, rinse with clean water, wash 10 times according to AATCC 135, and then test the water repellency rating. Initial water contact angle GB / T 30693-2014 Bio-based carbon content ASTM D6866-2021 VOC emissions GB 38508-2020 Color difference ΔE GB / T 250-2008 Feel rating AATCC EP5-2011 PFAS residue SGS No PFAS Testing Method Moisture permeability GB / T 12704.1-2009 Dry friction fastness GB / T 3920-2008 wet friction fastness GB / T 3920-2008 Anion resistance stability Let it stand in the same bath as a 10 g / L anionic leveling agent and observe whether the emulsion breaks down.

[0110] The test results are shown in Table 2 below;

[0111] Table 2 Test Results

[0112] Initial water repellency level Level 5 Level 5 Level 5 Level 5 Level 5 Level 4 Level 5 Level 4 Level 4 Level 4 Level 3 Level 5 Water repellency rating after 30 washes Level 4 Level 4 Level 4 Level 4 Level 4 Level 2-3 Level 2 Level 2 Level 3 Level 3 Level 1 Level 3 Extreme alkali resistance followed by water repellency rating Level 4 Level 4 Level 4 Level 4 Level 4 Level 0 Level 1 Level 1 Level 3 Level 2 Level 0 Level 2 Initial water contact angle / ° 145 143 142 146 143 128 144 125 132 130 112 143 Bio-based carbon content / % 55 54 54 58 52 54 55 55 55 55 62 55 VOCs / (g / L) 6.8 7.0 6.9 6.7 6.9 6.8 6.8 6.8 6.8 6.8 6.7 6.9 Color difference ΔE 0.6 0.7 0.7 0.6 0.6 0.6 0.6 0.7 0.6 0.7 0.6 0.6 Feel rating / level 4.5 4.5 4.5 4.5 4.5 4.0 4.5 4.0 4.5 4.0 3.5 4.0 PFAS residues Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected Not detected Moisture permeability / (g / (m²・24h)) 8500 8400 8300 8600 8400 7800 8500 7500 8400 7900 7200 7800 Dry friction fastness / grade 4-5 4-5 4-5 4-5 4-5 4 4 3-4 4 4 3-4 4 Wet rubbing fastness / grade 3-4 3-4 3-4 3-4 3-4 3 3 2-3 3 3 2-3 3 Anion resistance stability No change in 30 days No change in 30 days No change in 30 days No change in 30 days No change in 30 days No change in 30 days No change in 30 days No change in 30 days No change in 30 days 15-day gel No change in 30 days No change in 30 days Storage stability No change in 6 months No change in 6 months No change in 6 months No change in 6 months No change in 6 months No change in 6 months No change in 6 months No change in 6 months No change in 6 months 15-day gel No change in 6 months No change in 6 months

[0113] Results analysis:

[0114] 1. Examples 1-5 all achieved core performance of bio-based carbon content ≥52%, initial water repellency level 5, water repellency level still 4 after 30 washes, and water repellency level 4 after pH12 alkali resistance, with a hand feel rating of 4.5. This proves that the technical solutions of the present invention can all prepare high bio-based polyurethane fluorine-free waterproofing agents with excellent comprehensive performance such as ultra-long-lasting wash resistance, extreme alkali resistance and soft hand feel.

[0115] 2. Comparative Example 1 showed that the water repellency level dropped to level 0 after extreme alkali resistance, proving that the hydrolysis-resistant skeleton of polycarbonate diol is the core structure for achieving high alkali resistance. The hydrolytic stability of carbonate bonds is much higher than that of carboxylic acid ester bonds, which can give the product higher alkali resistance. This proves that polycarbonate diol is a special key choice rather than conventional parameter optimization.

[0116] 3. Comparative Example 2: After 30 washes, the water repellency level was only level 2, proving that the dual crosslinking system makes a significant contribution to alkali resistance. The dual crosslinking system can form a dense three-dimensional network with internal and external crosslinking. External crosslinking covalent anchoring is a necessary condition for improving wash resistance. Single internal crosslinking cannot prevent the coating from peeling off from the fiber surface, verifying the synergistic effect of the dual crosslinking system.

[0117] 4. Comparative Example 3 showed a significant decrease in both wash resistance and alkali resistance, demonstrating that the stepwise feeding sequence of "chain extension-end capping-ketone carbonyl functionalization" can ensure that ketone carbonyl groups are evenly distributed at the ends of the molecular chains and on the side groups, thereby improving the uniformity of the crosslinking network. This is a key process to ensure wash resistance and alkali resistance.

[0118] 5. Comparative Example 4 showed weaker hydrophobicity and washability compared to the main-chain block scheme, demonstrating that the main-chain block double-terminated hydroxyl group polydimethylsiloxane structure can better utilize the low surface energy effect compared to traditional side-linked branches, and has no risk of free silicone oil migration, resulting in better feel and batch stability.

[0119] 6. Comparative Example 5 showed that gelation occurred after 15 days of storage, proving that the ketone-hydrazine dormancy process is the core to ensure the storage stability of the product, and achieves the isolation of the internal cross-linking groups during the storage period and the precise triggering of the film formation period.

[0120] 7. Comparative Example 6 showed a significant decrease in hydrophobic properties and feel, proving that PDMS main chain blocks are key components for constructing low surface energy hydrophobic surfaces and improving feel.

[0121] 8. Comparative Example 7 showed lower wash and alkali resistance than the epoxy external crosslinking system, proving that waterborne epoxy resin, as an external crosslinking agent, can simultaneously form stable covalent bonds with polyurethane and fibers, making it the optimal choice for achieving interfacial anchoring.

[0122] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a bio-based polyurethane fluorine-free waterproofing agent, characterized in that, Includes the following steps: Step 1: Polymerization reaction is carried out using polyols and diisocyanates as raw materials to obtain polyurethane prepolymer; Step 2: First, use a carboxyl-containing hydrophilic chain extender to extend the polyurethane prepolymer, then use a capping agent containing isocyanate groups and hydrophobic segments to cap it, and finally add a first internal crosslinking agent containing at least two ketone carbonyl groups to the segments of the capped polyurethane prepolymer to obtain the polymer. Step 3: Add an organic base to neutralize the carboxyl groups in the polymer, and add deionized water to perform shear emulsification, so that the polymer self-emulsifies; Step 4: Add a second internal crosslinking agent to react with the ketone carbonyl group after polymer demulsification; When using the bio-based polyurethane fluorine-free waterproofing agent, an external crosslinking agent is added; the external crosslinking agent is a water-based modified epoxy resin, and the amount added is 5-10% of the weight of the bio-based polyurethane fluorine-free waterproofing agent. The polyol is composed of castor oil-based polyol, polycarbonate diol, and hydroxyl-terminated polydimethylsiloxane. The weight ratio of castor oil-based polyol, polycarbonate diol, and dihydroxyl-terminated polydimethylsiloxane is 45~55:30~40:

15.

2. The preparation method according to claim 1, characterized in that, The castor oil-based polyol has a hydroxyl value of 200±10 mgKOH / g and a number-average functionality of 2.7; the polycarbonate diol has a number-average molecular weight of 800~2000; and the dihydroxyl-terminated polydimethylsiloxane has a number-average molecular weight of 2000~3000.

3. The preparation method according to claim 1, characterized in that, The diisocyanate is one or more combinations of hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.

4. The preparation method according to claim 1, characterized in that, In step 1, the molar ratio of isocyanate groups to hydroxyl groups is 1.3 to 1.

5.

5. The preparation method according to claim 1, characterized in that, The hydrophilic chain extender is one or more of 2,2-dimethylolbutyric acid, 2,2-dimethylolpropionic acid, and N-methyldiethanolamine; the end-capping agent is one or more of octadecyl isocyanate, hexadecyl isocyanate, and dodecyl isocyanate; and the first internal crosslinking agent is one or more of diacetone acrylamide, diacetone methacrylamide, and ethyl acetoacetate methacrylate. With the polyol accounting for 100% by weight, the amount of the hydrophilic chain extender is 6-8%; the amount of the end-capping agent is 2-4%; and the amount of the first internal crosslinking agent is 3-5%.

6. The preparation method according to claim 1, characterized in that, The organic base is one or a combination of TEA, triethylamine, and dimethylethanolamine; the degree of neutralization in step 3 is 100-110%.

7. The preparation method according to claim 1, characterized in that, The second internal crosslinking agent is one or more combinations of adipate dihydrazide, sebacic dihydrazide, and isophthalic dihydrazide; The amount of the second internal crosslinking agent is 2-3%, with the polyol accounting for 100% by weight.

8. The preparation method according to claim 1, characterized in that, The epoxy value of the water-based modified epoxy resin is 0.12~0.15; The solid content of the bio-based fluorine-free waterproofing agent is 100%, the amount of the water-based modified epoxy resin is 5-10%, and the amount of the deionized water is 100-120%.

9. The preparation method according to claim 1, characterized in that, The reaction temperature in step 1 is 85~90℃, and the reaction time is 1~3h; In step 2, the hydrophilic chain extender, the end-capping agent, and the first internal crosslinking agent react sequentially with the polyurethane prepolymer. The reaction temperature between the hydrophilic chain extender and the polyurethane prepolymer is 70-85°C, and the reaction time is 1-2 hours. The reaction temperature between the end-capping agent and the polyurethane prepolymer is 70-85°C, and the reaction time is 15-45 minutes. The reaction temperature between the first internal crosslinking agent and the polyurethane prepolymer is 70-85°C, and the reaction time is 15-45 minutes. The reaction temperature in steps 3 and 4 is 40°C or below.

10. A bio-based polyurethane fluorine-free waterproofing agent, characterized in that, It is prepared by the method described in any one of claims 1 to 9.