A fluorine-free waterproofing agent and its preparation method

Abstract

This invention discloses a fluorine-free waterproofing agent and its preparation method, relating to the field of waterproofing agent technology. The preparation method involves mixing nano-silica with acrylate-terminated polydimethylsiloxane, octadecyl methacrylate, and methacryloxypropyltrimethoxysilane, followed by dropwise addition of azobisisobutyronitrile (AIBN) to obtain an organic-inorganic hybrid prepolymer acetone solution. Polycaprolactone diol, isophorone diisocyanate, and dibutyltin dilaurate react to prepare a polyurethane prepolymer. The mixture is then cooled and reacted with dimethylolpropionic acid and acetone, followed by further cooling, neutralization, and emulsification to obtain an aqueous polyurethane dispersion. This dispersion is then emulsified with the hybrid prepolymer, reacted with methyl methacrylate and hydroxyethyl acrylate, and finally reacted with glycerol polyglycidyl ether to obtain a composite emulsion. An antifoaming agent, leveling agent, and bactericide are added to the composite emulsion to obtain the fluorine-free waterproofing agent. The waterproofing agent of this invention provides durable waterproofing performance after being applied to fabrics.

Description

Technical Field

[0001] This invention relates to the field of waterproofing agent technology, specifically to a fluorine-free waterproofing agent and its preparation method. Background Technology

[0002] In the textile industry, waterproofing agents are an important class of auxiliaries that impart waterproof properties to fabrics, expanding their application scenarios. Fluorinated waterproofing agents once dominated the market due to their excellent waterproofing effects; however, the perfluorinated compounds in them have bioaccumulation properties, causing lasting environmental impacts. Therefore, the development of fluorine-free waterproofing agents has become a hot topic in the industry.

[0003] Fluorine-free waterproofing agents are environmentally friendly textile auxiliaries that do not contain fluorocarbon resins. Due to their excellent waterproofing properties and harmlessness to the environment and human health, they are gradually gaining market acceptance. Their main types include paraffin-based, silicone-based, acrylic-based, polyurethane-based, and dendritic macromolecular polymer-based agents. For example, silicone-based fluorine-free waterproofing agents, with their low surface tension due to the siloxane structure, can impart good waterproofing properties to fabrics, resulting in a soft hand feel, less scratching, and less color change. Polyurethane-based fluorine-free waterproofing agents have good overall performance, forming a very soft film that improves the water-repellent and wash-resistant properties of the treated fabric and reduces scratching after treatment.

[0004] While fluorine-free waterproofing agents offer numerous advantages, including environmental friendliness, their poor durability and stability in waterproofing remain a significant issue when applied to fabrics. Regarding washability, the protective structure formed by the fluorine-free waterproofing agent on the fabric surface is easily damaged after multiple washes, leading to a significant decrease in waterproofing performance. For example, some fabrics treated with fluorine-free waterproofing agents may fail to achieve the desired waterproofing effect after only 10 washes. Furthermore, during daily wear and use, the bonding force between the fluorine-free waterproofing agent and the fabric fibers may weaken when the fabric is subjected to friction, stretching, and other external forces, thus affecting the durability and stability of the waterproofing. Summary of the Invention

[0005] The purpose of this invention is to provide a fluorine-free waterproofing agent and its preparation method, thereby solving the technical problems mentioned in the background section. The fluorine-free waterproofing agent prepared by this invention has high bonding strength with fabrics, thus giving the fabrics a durable and stable hydrophobic effect.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a fluorine-free waterproofing agent includes the following steps:

[0008] S1. Add nano-silica to n-butanol and stir to form a suspension. Then add acrylate-terminated polydimethylsiloxane, octadecyl methacrylate and γ-methacryloyloxypropyltrimethoxysilane, stir and mix evenly, then add azobisisobutyronitrile dropwise to react and obtain an organic-inorganic hybrid prepolymer solution. Then distill off the n-butanol and add acetone to dilute to obtain an organic-inorganic hybrid prepolymer acetone solution.

[0009] S2. Under nitrogen protection, polycaprolactone diol, isophorone diisocyanate and dibutyltin dilaurate are mixed and reacted to form a polyurethane prepolymer. Then, the mixture is cooled, dimethylolpropionic acid and acetone are added, and the reaction continues. The mixture is then cooled again, triethylamine is added for neutralization, and then deionized water is added for emulsification to obtain an aqueous polyurethane dispersion. Then, an organic-inorganic hybrid prepolymer acetone solution is added, and after emulsification and dispersion, methyl methacrylate, hydroxyethyl acrylate and potassium persulfate are added and heated for reaction. Finally, glycerol polyglycidyl ether is added and reacted to obtain a composite emulsion.

[0010] S3. Add defoamer, leveling agent and bactericide to the composite emulsion, mix well, adjust the pH value with ammonia water to obtain fluorine-free waterproofing agent.

[0011] In this invention, on one hand, highly reactive acrylate-terminated polysiloxanes are used to efficiently copolymerize with long-chain alkyl acrylates and γ-methacryloxypropyltrimethoxysilane. This ensures that the low surface energy organosilicon molecular chains are firmly integrated into the polymer backbone, providing the extremely low surface energy required for superhydrophobicity. Furthermore, nano-silica is grafted onto the polymer network through the reaction of nano-silica with γ-methacryloxypropyltrimethoxysilane, constructing an organic-inorganic hybrid structure. These rigid nanoparticles can be uniformly distributed on the film surface during subsequent film formation, forming a stable micro-nano-level rough structure, achieving a high static contact angle and excellent initial water repellency. Simultaneously, these covalently bonded nano-silica particles act as strong anchors, greatly enhancing the mechanical strength, abrasion resistance, and tear resistance of the coating film, enabling it to withstand friction and washing during daily use, effectively delaying the degradation of waterproof performance caused by film wear.

[0012] On the other hand, by synthesizing a polyurethane prepolymer containing hydrophilic carboxyl groups, and emulsifying it to form a highly stable aqueous dispersion, an organic-inorganic hybrid prepolymer acetone solution is uniformly dispersed in the polyurethane system through high-speed shear emulsification. Then, acrylic monomers are introduced for free radical copolymerization, ultimately forming a PU / PA interpenetrating network structure. The polyurethane segments impart excellent elasticity and flexibility to the coating film, enabling it to withstand repeated bending of the fabric; the acrylic segments provide high adhesion and rigidity, ensuring the coating film adheres tightly to the fiber surface. The multifunctional epoxy crosslinking agent glycerol polyglycidyl ether crosslinks with carboxyl and hydroxyl groups on the polyurethane and acrylic segments, forming a high-density three-dimensional covalent network. This network firmly locks the hydrophobic segments of the organic-inorganic hybrid prepolymer and nano-silica particles within it, greatly improving the chemical resistance (such as resistance to soaping, acids, and alkalis) and swelling resistance of the coating film, further enhancing the waterproof durability of the fabric coating. Figure 1 The image shows a surface SEM image of the fabric after it has been treated with the waterproofing agent of this invention. It can be observed that the surface of the fabric fibers exhibits a rough structure.

[0013] Preferably, in step S1, the nano-silica undergoes a modification treatment, including the following steps:

[0014] Nano-silica was dispersed in a mixed solution of ethanol and water and stirred until homogeneous. Then, γ-glycidoxypropyltrimethoxysilane was added and heated to react. After the reaction was completed, polyetheramine was added and heated to react again. After the reaction was completed, the product was obtained by centrifugation, washing and drying.

[0015] In the technical solution of this invention, the team discovered through in-depth research that, because nano-silica is a rigid inorganic particle, its coefficient of thermal expansion and elastic modulus do not match with the surrounding organic polyurethane-acrylate polymer matrix. Under external stress (such as fabric bending, friction, and thermal cycling), microcracks and defects easily form at the interface. These microcracks can further extend into the weaker polymer matrix and connect, eventually forming a macroscopic crack network, destroying the coating's micro / nano structure, causing a sharp decrease in hydrophobicity and abrasion resistance, severely limiting the durability of waterproof performance. To further solve this technical problem, this invention pre-modifies the nano-silica. Using nano-silica as the core, highly reactive epoxy groups are first introduced onto its surface via a hydrolysis-condensation reaction using γ-glycidyl etheroxypropyltrimethoxysilane. Then, the amino groups of polyetheramine undergo a ring-opening reaction with the epoxy groups, grafting long-chain flexible polyether segments onto the silica surface through stable covalent bonds, ultimately forming a core-shell structure. As a stress buffer layer, the flexible polyether shell can establish an intermediate phase with a continuous transition in modulus and coefficient of thermal expansion between the inorganic core and the organic matrix, fundamentally inhibiting the initiation and propagation of interfacial microcracks, thereby significantly improving the durability of the composite system, greatly reducing the generation of interfacial microcracks, and directly improving the hydrophobic and long-lasting stability of the coating.

[0016] Preferably, the mass ratio of the nano-silica to polyetheramine is 10:3 to 5.

[0017] Preferably, in step S1, the mass ratio of acrylate-terminated polydimethylsiloxane, octadecyl methacrylate, and γ-methacryloyloxypropyltrimethoxysilane is 20:13-16:8-12.

[0018] Preferably, in step S2, the mass ratio of polycaprolactone diol to isophorone diisocyanate is 3:1 to 2.

[0019] Preferably, in step S2, the mass ratio of polycaprolactone diol to dimethylolpropionic acid is 10:1 to 3.

[0020] Preferably, in step S2, the mass ratio of methyl methacrylate to hydroxyethyl acrylate is 5:1 to 3.

[0021] Preferably, in step S3, the defoamer is an organosilicone defoamer.

[0022] Preferably, in step S3, the leveling agent is a polyether-modified siloxane leveling agent.

[0023] A fluorine-free waterproofing agent is prepared by the method described in the preceding claims.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. By constructing a polyurethane-acrylate interpenetrating network structure and using an epoxy crosslinking agent to form a high-density three-dimensional covalent network, the organosilicon / nano-silica hybrid prepolymer is firmly locked, which greatly improves the coating's abrasion resistance, washability, and resistance to physical wear, thereby achieving a durable waterproof effect.

[0026] 2. Polyetheramine is used to modify the core-shell structure of nano-silica, and a flexible interface layer is constructed on its surface. This effectively buffers the mismatch between the coefficient of thermal expansion and elastic modulus between inorganic nanoparticles and organic polymer matrix, fundamentally inhibiting the generation and propagation of interfacial microcracks, and significantly improving the flexibility, adhesion and mechanical strength of the composite coating, thereby further improving the hydrophobic and durable stability. Attached Figure Description

[0027] Figure 1 This is a SEM image of the fabric surface after treatment with the waterproofing agent of this invention. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0029] Example 1

[0030] A method for preparing a fluorine-free waterproofing agent includes the following steps:

[0031] Step 1: Disperse 10.0g of nano-silica in a mixed solution of 100mL ethanol and 20mL deionized water in a three-necked flask and stir at 500rpm for 30min to ensure thorough dispersion. Then add 3.5g of γ-glycidyl etheroxypropyltrimethoxysilane, heat to 70℃, and react under nitrogen protection for 3h. Then add 4.5g of polyetheramine D230, raise the temperature to 80℃, and continue the reaction for 4h. After the reaction is complete, centrifuge the mixture, wash three times with ethanol, and dry in a vacuum drying oven at 60℃ for 12h to obtain modified nano-silica powder.

[0032] 5.0 g of modified nano-silica powder was dispersed in 50 mL of n-butanol and sonicated for 30 min to form a stable suspension. Then, 20.0 g of acrylate-terminated polydimethylsiloxane (Mn=5000), 15.0 g of octadecyl methacrylate, and 11.0 g of γ-methacryloyloxypropyltrimethoxysilane were added sequentially, and the mixture was stirred at 300 rpm for 30 min at 75 °C. Next, an initiator solution consisting of 0.3 g of azobisisobutyronitrile dissolved in 12 mL of n-butanol was slowly added dropwise using a constant-pressure dropping funnel over a controlled dropping time of 30 min. After the addition was complete, the reaction was continued at 75 °C for 6 h to obtain an organic-inorganic hybrid prepolymer solution. Finally, the n-butanol was removed by distillation using a rotary evaporator at 60 °C and -0.09 MPa. The solution was diluted with 30 mL of acetone to obtain a hybrid prepolymer acetone solution, which was then sealed for later use.

[0033] Step 2: In a four-necked flask equipped with a condenser, thermometer, and mechanical stirrer, nitrogen gas was introduced for protection. 30.0 g of polycaprolactone diol (Mn=2000), 18.0 g of isophorone diisocyanate, and 0.04 g of dibutyltin dilaurate were added sequentially. The mixture was stirred at 200 rpm at 85°C for 2.5 h. The system was then cooled to 60°C, and 8.0 g of dimethylolpropionic acid and 20 mL of acetone diluent were added. The reaction was maintained at 60°C for another 2 h. Subsequently, the temperature was lowered to 35°C, and 4.0 g of triethylamine was added for neutralization. The reaction was carried out for 15 min. Then, 120 mL of deionized water was slowly added under stirring at 10000 rpm in a high-speed disperser for emulsification. The emulsification process lasted for 40 min to obtain an aqueous polyurethane dispersion. The entire acetone solution of the hybrid prepolymer was added to the system, and emulsified at a high-speed shear rate of 12,000 rpm for 15 min. Then, 5.0 g of methyl methacrylate, 2.5 g of hydroxyethyl acrylate, and 0.2 g of potassium persulfate (dissolved in 10 mL of water) were added. The temperature was slowly increased to 80 °C, and the reaction was carried out for 4 h to complete the free radical copolymerization. Finally, 2.0 g of glycerol polyglycidyl ether was added, and the reaction was continued at 75 °C for 2 h to complete the crosslinking, yielding the composite emulsion.

[0034] Step 3: While stirring the obtained composite emulsion at 300 rpm, add 1.0 g of silicone defoamer (BYK-024), 1.5 g of polyether-modified siloxane leveling agent (BYK-346), and 0.5 g of isothiazolinone bactericide (BIT-20) sequentially. After stirring continuously for 30 min to ensure full dispersion of the additives, slowly adjust the pH of the system to the range of 7.5-8.0 with an appropriate amount of ammonia. Finally, filter the product through a 200-mesh nylon filter cloth to obtain a fluorine-free waterproofing agent.

[0035] Example 2

[0036] A method for preparing a fluorine-free waterproofing agent includes the following steps:

[0037] Step 1: Disperse 10.0g of nano-silica in a mixed solution of 100mL ethanol and 20mL deionized water in a three-necked flask and stir at 500rpm for 30min to ensure thorough dispersion. Then add 3.5g of γ-glycidyl etheroxypropyltrimethoxysilane, heat to 70℃, and react under nitrogen protection for 3h. Then add 3.5g of polyetheramine D230, raise the temperature to 80℃, and continue the reaction for 4h. After the reaction is complete, centrifuge the mixture, wash three times with ethanol, and dry in a vacuum drying oven at 60℃ for 12h to obtain modified nano-silica powder.

[0038] 5.0 g of modified nano-silica powder was dispersed in 50 mL of n-butanol and sonicated for 30 min to form a stable suspension. Then, 20.0 g of acrylate-terminated polydimethylsiloxane (Mn=5000), 14.0 g of octadecyl methacrylate, and 9.0 g of γ-methacryloyloxypropyltrimethoxysilane were added sequentially, and the mixture was stirred at 300 rpm for 30 min at 75 °C. Next, an initiator solution consisting of 0.3 g of azobisisobutyronitrile dissolved in 12 mL of n-butanol was slowly added dropwise using a constant-pressure dropping funnel over a time of 30 min. After the addition was complete, the reaction was continued at 75 °C for 6 h to obtain an organic-inorganic hybrid prepolymer solution. Finally, the n-butanol was removed by distillation at 60 °C and -0.09 MPa using a rotary evaporator. The solution was diluted with 30 mL of acetone to obtain an acetone solution of the hybrid prepolymer, which was then sealed for later use.

[0039] Step 2: In a four-necked flask equipped with a condenser, thermometer, and mechanical stirrer, nitrogen gas was introduced for protection. 30.0 g of polycaprolactone diol (Mn=2000), 13.0 g of isophorone diisocyanate, and 0.04 g of dibutyltin dilaurate were added sequentially. The mixture was stirred at 200 rpm at 85°C for 2.5 h. The system was then cooled to 60°C, and 5.0 g of dimethylolpropionic acid and 20 mL of acetone diluent were added. The reaction was maintained at 60°C for another 2 h. Subsequently, the temperature was lowered to 35°C, and 4.0 g of triethylamine was added for neutralization. The reaction was carried out for 15 min. Then, 120 mL of deionized water was slowly added under stirring at 10000 rpm in a high-speed disperser for emulsification. The emulsification process lasted for 40 min to obtain an aqueous polyurethane dispersion. The entire acetone solution of the hybrid prepolymer was added to the system, and emulsified at a high-speed shear rate of 12,000 rpm for 15 min. Then, 5.0 g of methyl methacrylate, 1.5 g of hydroxyethyl acrylate, and 0.2 g of potassium persulfate (dissolved in 10 mL of water) were added. The temperature was slowly increased to 80 °C, and the reaction was carried out for 4 h to complete the free radical copolymerization. Finally, 2.0 g of glycerol polyglycidyl ether was added, and the reaction was continued at 75 °C for 2 h to complete the crosslinking, yielding the composite emulsion.

[0040] Step 3: While stirring the obtained composite emulsion at 300 rpm, add 1.0 g of silicone defoamer (BYK-024), 1.5 g of polyether-modified siloxane leveling agent (BYK-346), and 0.5 g of isothiazolinone bactericide (BIT-20) sequentially. After stirring continuously for 30 min to ensure full dispersion of the additives, slowly adjust the pH of the system to the range of 7.5-8.0 with an appropriate amount of ammonia. Finally, filter the product through a 200-mesh nylon filter cloth to obtain a fluorine-free waterproofing agent.

[0041] Example 3

[0042] A method for preparing a fluorine-free waterproofing agent includes the following steps:

[0043] Step 1: Disperse 10.0g of nano-silica in a mixed solution of 100mL ethanol and 20mL deionized water in a three-necked flask and stir at 500rpm for 30min to ensure thorough dispersion. Then add 3.5g of γ-glycidyl etheroxypropyltrimethoxysilane, heat to 70℃, and react under nitrogen protection for 3h. Then add 4.0g of polyetheramine D230, raise the temperature to 80℃, and continue the reaction for 4h. After the reaction is complete, centrifuge the mixture, wash three times with ethanol, and dry in a vacuum drying oven at 60℃ for 12h to obtain modified nano-silica powder.

[0044] 5.0 g of modified nano-silica powder was dispersed in 50 mL of n-butanol and sonicated for 30 min to form a stable suspension. Then, 20.0 g of acrylate-terminated polydimethylsiloxane (Mn=5000), 14.5 g of octadecyl methacrylate, and 10.0 g of γ-methacryloyloxypropyltrimethoxysilane were added sequentially, and the mixture was stirred at 300 rpm for 30 min at 75 °C. Next, an initiator solution consisting of 0.3 g of azobisisobutyronitrile dissolved in 12 mL of n-butanol was slowly added dropwise using a constant-pressure dropping funnel over a controlled dropping time of 30 min. After the addition was complete, the reaction was continued at 75 °C for 6 h to obtain an organic-inorganic hybrid prepolymer solution. Finally, the n-butanol was removed by distillation using a rotary evaporator at 60 °C and -0.09 MPa. The solution was diluted with 30 mL of acetone to obtain a hybrid prepolymer acetone solution, which was then sealed for later use.

[0045] Step 2: In a four-necked flask equipped with a condenser, thermometer, and mechanical stirrer, nitrogen gas was introduced for protection. 30.0 g of polycaprolactone diol (Mn=2000), 15.0 g of isophorone diisocyanate, and 0.04 g of dibutyltin dilaurate were added sequentially. The mixture was stirred at 200 rpm at 85°C for 2.5 h. The system was then cooled to 60°C, and 6.0 g of dimethylolpropionic acid and 20 mL of acetone diluent were added. The reaction was maintained at 60°C for another 2 h. Subsequently, the temperature was lowered to 35°C, and 4.0 g of triethylamine was added for neutralization. The reaction was carried out for 15 min. Then, 120 mL of deionized water was slowly added under stirring at 10000 rpm in a high-speed disperser for emulsification. The emulsification process lasted for 40 min to obtain an aqueous polyurethane dispersion. The entire acetone solution of the hybrid prepolymer was added to the system, and emulsified at a high-speed shear rate of 12,000 rpm for 15 min. Then, 5.0 g of methyl methacrylate, 2.0 g of hydroxyethyl acrylate, and 0.2 g of potassium persulfate (dissolved in 10 mL of water) were added. The temperature was slowly increased to 80 °C, and the reaction was carried out for 4 h to complete the free radical copolymerization. Finally, 2.0 g of glycerol polyglycidyl ether was added, and the reaction was continued at 75 °C for 2 h to complete the crosslinking, yielding the composite emulsion.

[0046] Step 3: While stirring the obtained composite emulsion at 300 rpm, add 1.0 g of silicone defoamer (BYK-024), 1.5 g of polyether-modified siloxane leveling agent (BYK-346), and 0.5 g of isothiazolinone bactericide (BIT-20) sequentially. After stirring continuously for 30 min to ensure full dispersion of the additives, slowly adjust the pH of the system to the range of 7.5-8.0 with an appropriate amount of ammonia. Finally, filter the product through a 200-mesh nylon filter cloth to obtain a fluorine-free waterproofing agent.

[0047] Example 4

[0048] A method for preparing a fluorine-free waterproofing agent includes the following steps:

[0049] Step 1: Disperse 10.0g of nano-silica in a mixed solution of 100mL ethanol and 20mL deionized water in a three-necked flask and stir at 500rpm for 30min to ensure thorough dispersion. Then add 3.5g of γ-glycidyl etheroxypropyltrimethoxysilane, heat to 70℃, and react under nitrogen protection for 3h. Then add 5.0g of polyetheramine D230, raise the temperature to 80℃, and continue the reaction for 4h. After the reaction is complete, centrifuge the mixture, wash three times with ethanol, and dry in a vacuum drying oven at 60℃ for 12h to obtain modified nano-silica powder.

[0050] 5.0 g of modified nano-silica powder was dispersed in 50 mL of n-butanol and sonicated for 30 min to form a stable suspension. Then, 20.0 g of acrylate-terminated polydimethylsiloxane (Mn=5000), 16.0 g of octadecyl methacrylate, and 12.0 g of γ-methacryloyloxypropyltrimethoxysilane were added sequentially, and the mixture was stirred at 300 rpm for 30 min at 75 °C. Next, an initiator solution consisting of 0.3 g of azobisisobutyronitrile dissolved in 12 mL of n-butanol was slowly added dropwise using a constant-pressure dropping funnel over a time of 30 min. After the addition was complete, the reaction was continued at 75 °C for 6 h to obtain an organic-inorganic hybrid prepolymer solution. Finally, the n-butanol was removed by distillation at 60 °C and -0.09 MPa using a rotary evaporator. The solution was diluted with 30 mL of acetone to obtain an acetone solution of the hybrid prepolymer, which was then sealed for later use.

[0051] Step 2: In a four-necked flask equipped with a condenser, thermometer, and mechanical stirrer, nitrogen gas was introduced for protection. 30.0 g of polycaprolactone diol (Mn=2000), 20.0 g of isophorone diisocyanate, and 0.04 g of dibutyltin dilaurate were added sequentially. The mixture was stirred at 200 rpm at 85°C for 2.5 h. The system was then cooled to 60°C, and 9.0 g of dimethylolpropionic acid and 20 mL of acetone diluent were added. The reaction was maintained at 60°C for another 2 h. Subsequently, the temperature was lowered to 35°C, and 4.0 g of triethylamine was added for neutralization. The reaction was carried out for 15 min. Then, 120 mL of deionized water was slowly added under stirring at 10000 rpm in a high-speed disperser for emulsification. The emulsification process lasted for 40 min to obtain an aqueous polyurethane dispersion. The entire acetone solution of the hybrid prepolymer was added to the system, and emulsified at a high-speed shear rate of 12,000 rpm for 15 min. Then, 5.0 g of methyl methacrylate, 3.0 g of hydroxyethyl acrylate, and 0.2 g of potassium persulfate (dissolved in 10 mL of water) were added. The temperature was slowly raised to 80 °C, and the reaction was carried out for 4 h to complete the free radical copolymerization. Finally, 2.0 g of glycerol polyglycidyl ether was added, and the reaction was continued at 75 °C for 2 h to complete the crosslinking, yielding the composite emulsion.

[0052] Step 3: While stirring the obtained composite emulsion at 300 rpm, add 1.0 g of silicone defoamer (BYK-024), 1.5 g of polyether-modified siloxane leveling agent (BYK-346), and 0.5 g of isothiazolinone bactericide (BIT-20) sequentially. After stirring continuously for 30 min to ensure full dispersion of the additives, slowly adjust the pH of the system to the range of 7.5-8.0 with an appropriate amount of ammonia. Finally, filter the product through a 200-mesh nylon filter cloth to obtain a fluorine-free waterproofing agent.

[0053] Example 5

[0054] A method for preparing a fluorine-free waterproofing agent includes the following steps:

[0055] Step 1: Disperse 10.0g of nano-silica in a mixed solution of 100mL ethanol and 20mL deionized water in a three-necked flask and stir at 500rpm for 30min to ensure thorough dispersion. Then add 3.5g of γ-glycidyl etheroxypropyltrimethoxysilane, heat to 70℃, and react under nitrogen protection for 3h. Then add 3.0g of polyetheramine D230, raise the temperature to 80℃, and continue the reaction for 4h. After the reaction is complete, centrifuge the mixture, wash three times with ethanol, and dry in a vacuum drying oven at 60℃ for 12h to obtain modified nano-silica powder.

[0056] 5.0 g of modified nano-silica powder was dispersed in 50 mL of n-butanol and sonicated for 30 min to form a stable suspension. Then, 20.0 g of acrylate-terminated polydimethylsiloxane (Mn=5000), 13.0 g of octadecyl methacrylate, and 8.0 g of γ-methacryloyloxypropyltrimethoxysilane were added sequentially, and the mixture was stirred at 300 rpm for 30 min at 75 °C. Next, an initiator solution consisting of 0.3 g of azobisisobutyronitrile dissolved in 12 mL of n-butanol was slowly added dropwise using a constant-pressure dropping funnel over a time of 30 min. After the addition was complete, the reaction was continued at 75 °C for 6 h to obtain an organic-inorganic hybrid prepolymer solution. Finally, the n-butanol was removed by distillation at 60 °C and -0.09 MPa using a rotary evaporator. The solution was diluted with 30 mL of acetone to obtain an acetone solution of the hybrid prepolymer, which was then sealed for later use.

[0057] Step 2: In a four-necked flask equipped with a condenser, thermometer, and mechanical stirrer, nitrogen gas was introduced for protection. 30.0 g of polycaprolactone diol (Mn=2000), 10.0 g of isophorone diisocyanate, and 0.04 g of dibutyltin dilaurate were added sequentially. The mixture was stirred at 200 rpm at 85°C for 2.5 h. The system was then cooled to 60°C, and 3.0 g of dimethylolpropionic acid and 20 mL of acetone diluent were added. The reaction was maintained at 60°C for another 2 h. Subsequently, the temperature was lowered to 35°C, and 4.0 g of triethylamine was added for neutralization. The reaction was carried out for 15 min. Then, 120 mL of deionized water was slowly added under stirring at 10000 rpm in a high-speed disperser for emulsification. The emulsification process lasted for 40 min to obtain an aqueous polyurethane dispersion. The entire acetone solution of the hybrid prepolymer was added to the system, and emulsified at a high-speed shear rate of 12,000 rpm for 15 min. Then, 5.0 g of methyl methacrylate, 1.0 g of hydroxyethyl acrylate, and 0.2 g of potassium persulfate (dissolved in 10 mL of water) were added. The temperature was slowly increased to 80 °C, and the reaction was carried out for 4 h to complete the free radical copolymerization. Finally, 2.0 g of glycerol polyglycidyl ether was added, and the reaction was continued at 75 °C for 2 h to complete the crosslinking, yielding the composite emulsion.

[0058] Step 3: While stirring the obtained composite emulsion at 300 rpm, add 1.0 g of silicone defoamer (BYK-024), 1.5 g of polyether-modified siloxane leveling agent (BYK-346), and 0.5 g of isothiazolinone bactericide (BIT-20) sequentially. After stirring continuously for 30 min to ensure full dispersion of the additives, slowly adjust the pH of the system to the range of 7.5-8.0 with an appropriate amount of ammonia. Finally, filter the product through a 200-mesh nylon filter cloth to obtain a fluorine-free waterproofing agent.

[0059] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that step 1 is missing in the preparation process of the fluorine-free waterproofing agent, and the hybrid prepolymer acetone solution is not added in step 2.

[0060] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that step 2 is missing in the preparation process of the fluorine-free waterproofing agent, and in step 3, the composite emulsion is replaced with a hybrid prepolymer acetone solution.

[0061] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the nano-silica in step 1 of the preparation process of the fluorine-free waterproofing agent is not modified.

[0062] Performance testing:

[0063] 1. Hydrophobicity Test: The static contact angle was tested using a contact angle meter with the seated drop method. Before testing, a fluorine-free waterproofing agent was mixed with tap water to prepare a 20 g / L working solution. This solution was then applied to pure cotton twill fabric (specifications: 21×21 threads, 128×68 threads / inch) using the padding method (80% pick-up rate). The fabric was then cured by drying at 120℃ for 3 minutes and baking at 150℃ for 2 minutes. During the static contact angle test, three test points were randomly selected on the fabric surface. 5 μL of deionized water was added to each point, and the reading was taken after the droplets stabilized for 10 seconds. The average value was recorded. A larger contact angle indicates better waterproofing performance. The test results are shown in Table 1.

[0064] 2. Washability Test: The washability test was conducted according to ISO 6330-2012 standard using a household washing machine (program: standard wash, water temperature 40±2℃, detergent: phosphate-free laundry powder 2g / L, liquor ratio 1:20), completing 20 washes (dried at 100℃ for 10 minutes after each wash). After washing, the static contact angle was measured using the previously described hydrophobicity test method. The smaller the decrease in static contact angle, the stronger the washability. The test results are shown in Table 1.

[0065] 3. Abrasion Resistance Test: According to GB / T 21196.2-2007 standard, a Martindale abrasion tester was used with a load of 12 kPa and standard wool cloth as the abrasive. After 500 cycles of abrasion, the static contact angle in the worn area was measured. The contact angle retention rate was calculated as "contact angle after wear / initial contact angle × 100%". A higher retention rate indicates better abrasion resistance. The test results are shown in Table 1.

[0066] Table 1:

[0067] Initial contact angle (°) Contact angle (°) after 20 water washes Contact angle retention rate (%) Example 1 155.1 150.7 93.0 Example 2 153.7 149.8 92.1 Example 3 154.6 150.4 92.5 Example 4 155.8 151.5 93.8 Example 5 152.8 149.3 91.4 Comparative Example 1 105.6 78.6 68.2 Comparative Example 2 117.7 62.5 56.3 Comparative Example 3 138.3 91.7 75.6

[0068] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a fluorine-free water repellent, characterized by comprising the steps of, It comprises the following steps: S1, dispersing nano-silica in a mixed solution of ethanol and water, stirring uniformly, then adding γ-glycidyl ether oxypropyl trimethoxysilane, heating and reacting, adding polyether amine after the reaction is completed, heating and reacting, and obtaining modified nano-silica powder after centrifugal separation, washing and drying; adding acrylate-terminated polydimethylsiloxane, stearyl methacrylate and γ-methacryloyloxypropyl trimethoxysilane into the suspension of n-butanol, stirring and mixing uniformly, then adding azobisisobutyronitrile dropwise, and obtaining an organic-inorganic hybrid prepolymer solution after reaction, then distilling n-butanol, and adding acetone for dilution to obtain an organic-inorganic hybrid prepolymer acetone solution; S2, mixing polycaprolactone diol, isophorone diisocyanate and dibutyl tin dilaurate under nitrogen protection, and forming a polyurethane prepolymer after reaction, then cooling, adding dimethylol propionic acid and acetone for continuous reaction, again cooling, adding triethylamine for neutralization, then adding deionized water for emulsification, obtaining an aqueous polyurethane dispersion, then adding the organic-inorganic hybrid prepolymer acetone solution, and adding methyl methacrylate, hydroxyethyl acrylate and potassium persulfate after emulsification and dispersion, heating and reacting, and finally adding glycerol polyglycidyl ether for reaction to obtain a composite emulsion; S3, adding a defoaming agent, a leveling agent and a bactericide into the composite emulsion, mixing uniformly, adjusting the pH value with ammonia water, and obtaining a fluorine-free waterproof agent.

2. The method for preparing a fluorine-free waterproofing agent according to claim 1, characterized in that, The mass ratio of the nano-silica to the polyether amine is 10: (3-5).

3. The method for preparing a fluorine-free waterproofing agent according to claim 1, characterized in that, In the step S1, the mass ratio of the acrylate-terminated polydimethylsiloxane, the stearyl methacrylate and the γ-methacryloyloxypropyl trimethoxysilane is 20: (13-16): (8-12).

4. The method for preparing a fluorine-free waterproofing agent according to claim 1, characterized in that, In the step S2, the mass ratio of the polycaprolactone diol to the isophorone diisocyanate is 3: (1-2).

5. The method for preparing a fluorine-free waterproofing agent according to claim 1, characterized in that, In the step S2, the mass ratio of the polycaprolactone diol to the dimethylol propionic acid is 10: (1-3).

6. The method for preparing a fluorine-free waterproofing agent according to claim 1, characterized in that, In the step S2, the mass ratio of the methyl methacrylate to the hydroxyethyl acrylate is 5: (1-3).

7. The method for preparing a fluorine-free waterproofing agent according to claim 1, characterized in that, In the step S3, the defoaming agent is an organic silicon defoaming agent.

8. The method for preparing a fluorine-free waterproofing agent according to claim 1, characterized in that, In the step S3, the leveling agent is a polyether-modified siloxane leveling agent.

9. A fluorine-free water repellent agent characterized by comprising: Prepared by the method of any one of claims 1-8.

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