Preparation method and application of a water repellent with self-recovering water repellency after washing

Abstract

The present invention discloses a preparation method and application of a water repellent with self-recovering water repellency after washing, belonging to the field of environmentally friendly polymer technology. The present invention utilizes the unsaturated double bonds contained in the surface of modified titanium dioxide to undergo free radical polymerization with the acrylic ester monomers used in the synthesis of the water repellent, and the titanium dioxide and the main skeleton of the water repellent are connected by chemical groups, so that the titanium dioxide particles and the water repellent polymer are stably present in the water repellent emulsion, and the water repellent has high film fastness. The light-heat conversion ability of nano titanium dioxide and its contribution to the roughness of the fabric surface make the finished fabric have water repellency such as high static water contact angle, high hydrostatic pressure resistance, and high spray resistance. The fabric does not need to be dried after washing, and the spray resistance level can be effectively restored by conventional natural drying. At the same time, the ultraviolet shielding performance of nano titanium dioxide gives the fabric treated with the water repellent prepared by the present invention an anti-ultraviolet function.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a water repellent with self-recovering water repellency after washing, belonging to the technical field of environmentally friendly polymers. Background Art

[0002] As consumer demand for functional textiles gradually increases, various functional textiles have received widespread attention and development. Hydrophobic fabrics are widely used due to their excellent water-repellent, anti-fouling, and self-cleaning properties. However, water-repellent fabrics generally have the problem that their water-repellent effect decreases after washing and drying naturally, while the effect is restored by high-temperature drying (≥55°C). The surface temperature of the fabric cannot reach high temperatures when dried naturally, resulting in a decrease in consumer satisfaction with water-repellent textiles, which are mainly dried naturally.

[0003] Fabrics have a long history of water repellency, and commonly used water repellents are mainly fluorine-containing compounds, silicones and aliphatic hydrocarbon compounds. Fluorine-containing water repellents can give fabrics excellent water repellency, but during the synthesis and use process, fluorine-containing water repellents have certain bioaccumulation and toxicity, so there is an ecological pollution problem; at the same time, they are expensive, resulting in high production and use costs. Silicone water repellents can give fabrics better water repellency and softness, but their disadvantage is that they increase pilling and seam separation on the fabric surface. Long-chain aliphatic hydrocarbon water repellents are mainly acrylate compounds, which can give fabrics better hydrophobic properties, but the water repellency is slightly lower than that of fluorine-containing water repellents. Water repellents use the long alkane chains or fluorocarbon chains on their structural units to reduce the surface energy of the fabric and thus give it water repellency. The water-repellent finishing adopts the rolling baking method. At high temperatures, the alkane chains or fluorocarbon chains are free to stretch to form an effective coverage of the fabric.

[0004] Alkane chains or fluorocarbon chains are non-polar groups, which have a large difference in polarity from water (polar group). During the washing process, the alkane chains or fluorocarbon chains curl up to reduce the interfacial energy between the non-polar and polar groups. It takes energy for the curled non-polar groups to stretch again to effectively cover the fabric. The energy obtained by the fabric during the natural drying process is low and insufficient to support the re-stretching of its non-polar groups. Photothermal conversion materials can absorb ultraviolet rays in sunlight and convert light energy into heat energy. They can enhance the amount of heat obtained by water-repellent finished fabrics under sunlight and promote the re-stretching of curled non-polar groups during the washing process. Common photothermal conversion materials such as carbon-based materials, metal materials, semiconductor materials, etc. are mostly black or other dark colors, have high photothermal conversion capabilities, and can increase the material temperature in a short time, but their inherent color will interfere with or directly cover the color of the textile, and are not suitable for textile fields that require color. Summary of the Invention

[0005] To address these issues, the present invention aims to provide a fluorine-free acrylic water repellent that self-restores its hydrophobic properties after washing and air-drying. Nano-titanium dioxide is a white powder that, when used in appropriate amounts, does not affect the existing color of fabrics. By incorporating nano-titanium dioxide into the repellent's molecular structure, it achieves fluorine-free, highly water-repellent properties, eliminating the need for drying fabrics after washing and allowing them to self-restore their water repellency under air-drying conditions.

[0006] In view of the above objectives, the present invention first provides a method for preparing a water repellent having self-recovering water repellency after washing, the method comprising:

[0007] (1) preparing nano-titanium dioxide with a titanium source, an organic solvent, a reaction inhibitor and deionized water, modifying the nano-titanium dioxide with a modifier, removing the solvent by rotary evaporation and aging to obtain modified nano-titanium dioxide;

[0008] (2) taking a cationic surfactant and a nonionic surfactant, dissolving them in deionized water, and then adding the modified nano-titanium dioxide obtained in step (1) to prepare an emulsion;

[0009] (3) mixing part of the acrylic ester monomer and part of the emulsion containing modified nano-titanium dioxide obtained in step (2), and emulsifying the mixture with an ultrasonic cell crusher to obtain a pre-emulsion A;

[0010] (4) mixing the remaining acrylic ester monomer and the remaining titanium dioxide-containing emulsion and emulsifying them with an ultrasonic cell crusher to obtain pre-emulsion B;

[0011] (5) Under nitrogen protection, the pre-emulsion B and the aqueous solution of the initiator are slowly added to the pre-emulsion A, and after the reaction is kept warm, the material is cooled and discharged to obtain a water repellent agent with self-recovering water repellency.

[0012] The present invention utilizes cationic surfactants to increase the adsorption of water repellent polymers by fabrics during water repellent finishing; employs acrylate monomers to avoid environmental pollution caused by fluorine-containing groups; utilizes the reaction between epoxy groups of acrylate monomers and fabrics and water repellent groups to enhance the anchoring of water repellent polymers on fabrics, thereby solving the problem of fabric water resistance; and utilizes the photothermal conversion capability of nano-titanium dioxide components to increase the surface energy of fabrics during natural drying, thereby promoting the reorientation of non-polar groups that curl during washing, thereby restoring a highly efficient water repellent effect.

[0013] In one embodiment of the present invention, the titanium source in step (1) includes at least one of tetrabutyl titanate, tetraethyl titanate, and tetraisopropyl titanate; the organic solvent includes at least one of ethanol, propanol, or isopropanol; the reaction inhibitor includes one or more of glacial acetic acid, nitric acid, or hydrochloric acid; and the modifier includes at least one of γ-methacryloyloxypropyltrimethoxysilane, vinyltrimethoxysilane, and dimethoxymethylvinylsilane.

[0014] In one embodiment of the present invention, the components in the preparation of nano-titanium dioxide in step (1) include 5-20% titanium source, 60-80% organic solvent, 5-20% reaction inhibitor, and the rest is water in terms of mass percentage; after adding the modifier, the concentration of the modifier in the solution is 1-20 g / L.

[0015] In one embodiment of the present invention, the preparation method of the modified titanium dioxide in step (1) is to mix a titanium source, an organic solvent, a reaction inhibitor and deionized water, and stir at room temperature at 100-1000 r / min for 1-8 hours to obtain nano titanium dioxide, and then add a modifier, react at 20-60°C for 4-24 hours, remove the solvent by rotary evaporation, and then age for 12-24 hours.

[0016] In one embodiment of the present invention, the cationic surfactant in step (2) is one or a mixture of octadecyltrimethylammonium chloride and hexadecyltrimethylammonium chloride; the nonionic surfactant is one or more mixtures of polyoxyethylene ether surfactants; and the mass ratio of the cationic surfactant to the nonionic surfactant is (0.2-0.8):1.

[0017] In one embodiment of the present invention, the mass ratio of the total amount of the cationic surfactant and the nonionic surfactant to the total amount of the acrylate monomer is (0.05-0.15):1; the mass ratio of the amount of the modified nano-titanium dioxide to the total amount of the acrylate monomer is (0.01-0.1):1; and the mass concentration of the modified nano-titanium dioxide in the emulsion is 0.15-3%.

[0018] In one embodiment of the present invention, the acrylic acid ester monomer in step (3) includes any one or more of methyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, octadecyl acrylate, methyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, and octadecyl methacrylate.

[0019] In one embodiment of the present invention, the mass of the emulsion containing modified nano-titanium dioxide in step (3) is 50-80% of the mass of the total modified nano-titanium dioxide emulsion.

[0020] In one embodiment of the present invention, the acrylate monomer in step (3) accounts for 40-60% of the total acrylate monomer mass; the total mass of the acrylate monomer accounts for 15-30% of the total mass of the water repellent.

[0021] In one embodiment of the present invention, the initiator in step (5) includes one or more of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisobutyramidine hydrochloride, potassium persulfate, ammonium persulfate, and dibenzoyl peroxide; the mass of the initiator accounts for 0.1 to 1% of the total mass percentage of the acrylate monomer; and the aqueous solution of the initiator is a solution in which the initiator is diluted 10 to 100 times with deionized water.

[0022] In one embodiment of the present invention, the reaction temperature in step (5) is 70-80° C., and the reaction time is 2-4 hours.

[0023] The present invention also provides a water repellent with self-recovering water repellency after washing, which is prepared according to the above preparation method.

[0024] The present invention also provides a method for treating a fabric with self-recovering water-repellent properties after washing, comprising first immersing the fabric in an aqueous solution of a water-repellent agent (40-100 g / L) prepared by the above method, followed by padding and baking with a padding rate of 80-200%, pre-baking at 80-110° C. for 3-5 minutes, and baking at 120-160° C. for 1-5 minutes.

[0025] The present invention also provides a fabric with self-recovering water repellency after washing, wherein the fabric comprises the above-mentioned titanium dioxide-based water repellent agent with self-recovering water repellency after washing, or is prepared by using the above-mentioned treatment method.

[0026] The present invention has the following beneficial effects:

[0027] 1. In the process of synthesizing the water repellent, the present invention adds modified nano-titanium dioxide, which undergoes free radical copolymerization with the acrylate monomer. The modified nano-titanium dioxide and the acrylate main chain are linked by chemical bonds. The modified nano-titanium dioxide and the water repellent main chain exist stably without phase separation.

[0028] 2. The present invention uses modified nano-titanium dioxide to copolymerize with acrylic monomers to prepare a water repellent. Nano-titanium dioxide has excellent light-to-heat conversion properties. By adding nano-titanium dioxide during the preparation of the water repellent, the surface energy of the fabric can be increased during the natural drying process, which can promote the reorientation of non-polar groups that curl during washing, thereby restoring the efficient water repellency. The water repellent synthesized using the method of the present invention can give the fabric the ability to self-restore its water repellency under natural drying conditions after washing without drying. In addition, nano-titanium dioxide is a white powder, and its use in appropriate amounts does not affect the existing color of the fabric.

[0029] 3. The present invention uses cationic and nonionic surfactants to prepare an emulsifier solution, which can make the acrylate molecules uniformly dispersed in the water phase to form a stable emulsion, thereby improving the performance.

[0030] 4. The cationic fluorine-free acrylate water repellent prepared by the present invention avoids the environmental pollution and bioaccumulation toxicity problems caused by the use of fluorine-containing water repellents, has extremely low VOC emissions, and meets environmental protection requirements.

[0031] 5. The water repellent prepared by the present invention is cationic and can be tightly adsorbed to the fabric (the aqueous phase system is negatively charged), which facilitates the uniform film formation of the water repellent macromolecules on the fabric surface. The crosslinkable groups contained in the water repellent improve the water resistance of the water repellent.

[0032] 6. The present invention first uses part of the acrylic acid monomer and part of the modified titanium dioxide to prepare an emulsion as the reaction base liquid, and then slowly adds the emulsion prepared with the remaining substances and an aqueous solution of the initiator to prepare a water repellent. This method can prevent the polymer precipitation and uneven molecular weight distribution caused by the monomer explosion, and is conducive to the preparation of a stable emulsion. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to specific examples. The examples are only used to explain the present invention and are not used to limit the scope of the present invention.

[0034] Test method:

[0035] The spray resistance of the fabric's water repellency is assessed by the water level, and the water level of the fabric after drying is tested according to GB / T 4745-2012 Testing and evaluation of water repellency of textiles - Water level test method.

[0036] The water repellency and water wetting resistance of the fabric are evaluated by the static water contact angle. The static contact angle of the fabric after water repellent finishing is measured using a contact angle meter: 5 μL of water droplets are added to five different positions of the fabric and the static contact angles are measured.

[0037] The static water resistance of the fabric water repellency is carried out according to the AATCC-127-2013 "Water Resistance: Hydrostatic Pressure Test" standard.

[0038] Fabric washing and drying parameters: The fabric was washed according to GB / T8629-2017 "Household Washing and Drying Procedure for Textile Experiments" and then exposed to sunlight for 1 hour in a sunlight fastness meter at 30°C.

[0039] The evaluation of fabric softness was carried out in accordance with AATCC TM 202 “Evaluation of Relative Handle of Textiles and Garments: Instrumental Method”.

[0040] The fabric anti-ultraviolet evaluation shall be carried out in accordance with GB / T 18830-2009 “Evaluation of the UV protection properties of textiles”.

[0041] Example 1:

[0042] Prepare the self-recovering water repellent after washing and finish the fabric according to the following steps:

[0043] (1) A titanium source (tetrabutyl titanate), an organic solvent (ethanol), a reaction inhibitor (glacial acetic acid) and deionized water were mixed (titanium source: organic solvent: reaction inhibitor: deionized water = 10:70:5:15, mass ratio) and stirred at 500 r / min at room temperature for 8 h to obtain nano-titanium dioxide. A modifier (γ-methacryloyloxypropyltrimethoxysilane) was added, and the concentration of the modifier in the solution was 10 g / L. After reacting at 40°C for 12 h, the mixture was cooled to room temperature and aged for 16 h to obtain modified nano-titanium dioxide.

[0044] (2) Cationic surfactant octadecyltrimethylammonium chloride, nonionic surfactant polyoxyethylene stearate (polyoxyethylene number is 20, the mass ratio of cationic surfactant to nonionic surfactant is 0.2:1) and modified nano-titanium dioxide are dissolved in deionized water to prepare an emulsion containing modified nano-titanium dioxide, wherein the mass concentration of modified nano-titanium dioxide is 1%, the mass ratio of the total amount of cationic surfactant and nonionic surfactant to the total amount of acrylate monomer is 0.05:1, the ratio of the amount of modified nano-titanium dioxide to the total mass of acrylate monomer is 0.05:1, and the total mass of acrylate monomer accounts for 20% of the total mass of the water repellent.

[0045] (3) Octadecyl acrylate (accounting for 40% of the total mass of the acrylate monomer) was added to a portion of the emulsion containing modified nano-titanium dioxide (accounting for 50% of the total mass of the emulsion), and the mixture was ultrasonically treated in an ice bath for 30 minutes in a cell crusher to obtain pre-emulsion A. Butyl acrylate (accounting for 30% of the total mass of the acrylate monomer), methyl methacrylate (accounting for 20% of the total mass of the acrylate monomer), and glycidyl acrylate (accounting for 10% of the total mass of the acrylate monomer) were added to the remaining emulsion containing modified nano-titanium dioxide, and the mixture was ultrasonically treated in an ice bath for 30 minutes in an ultrasonic cell crusher to obtain pre-emulsion B.

[0046] (4) Under nitrogen protection, pre-emulsion B and initiator azobisisobutylamidine hydrochloride (accounting for 1% of the total mass of the acrylate monomer and diluted 100 times with deionized water) were simultaneously added dropwise into the reactor containing pre-emulsion A at a temperature of 75°C with mechanical stirring (300 r / min). The addition rate was 2 g / L. After reacting for 3 hours, the mixture was naturally cooled to room temperature to obtain a water repellent with self-recovering water repellency after washing.

[0047] Fabrics treated with water repellent that recovers water repellency after washing:

[0048] The above water repellent was used to treat cotton fabric using a padding and baking process at 60 g / L. The fabric was impregnated and then padded at a 100% padded rate, pre-baked at 105°C for 3 minutes, and then baked at 160°C for 2 minutes. The relevant parameters of the treated fabric are shown in Table 1.

[0049] Example 2:

[0050] Prepare the self-recovering water repellent after washing and finish the fabric according to the following steps:

[0051] (1) A titanium source (tetraethyl titanate), an organic solvent (propanol), a reaction inhibitor (nitric acid, 5 g / L) and deionized water were mixed (titanium source: organic solvent: reaction inhibitor: deionized water = 5:60:5:30, mass ratio) and stirred at 100 r / min at room temperature for 4 h to obtain nano-titanium dioxide. A modifier (vinyltrimethoxysilane) solution was added to a modifier concentration of 1 g / L. The mixture was reacted at 60°C for 4 h, then cooled to room temperature and aged for 24 h to obtain modified nano-titanium dioxide.

[0052] (2) Cationic surfactant hexadecyltrimethylammonium chloride, nonionic surfactant polyoxyethylene stearate (polyoxyethylene number is 40, the mass ratio of cationic surfactant to nonionic surfactant is 0.2:1) and modified nano-titanium dioxide are dissolved in deionized water to prepare an emulsion containing modified nano-titanium dioxide, wherein the mass concentration of modified nano-titanium dioxide is 0.15%, the mass ratio of the total amount of cationic surfactant and nonionic surfactant to the total amount of acrylate monomer is 0.05:1, the ratio of the amount of modified nano-titanium dioxide to the total mass of acrylate monomer is 0.01:1, and the total mass of acrylate monomer accounts for 30% of the total mass of the water repellent.

[0053] (3) Hexadecyl acrylate (accounting for 50% of the total mass of the acrylate monomer) was added to a portion of the emulsion containing modified nano-titanium dioxide (accounting for 40% of the total mass of the emulsion), and the mixture was ultrasonically treated in an ice bath for 30 minutes in a cell crusher to obtain pre-emulsion A. Butyl acrylate (accounting for 25% of the total mass of the acrylate monomer), hexyl methacrylate (accounting for 20% of the total mass of the acrylate monomer), and glycidyl methacrylate (accounting for 5% of the total mass of the acrylate monomer) were added to the remaining emulsion containing modified nano-titanium dioxide, and the mixture was ultrasonically treated in an ice bath for 30 minutes in an ultrasonic cell crusher to obtain pre-emulsion B.

[0054] (4) Under nitrogen protection, pre-emulsion B and initiator potassium persulfate (accounting for 0.1% of the total mass of the acrylate monomer and diluted 100 times with deionized water) were simultaneously added dropwise into the reactor containing pre-emulsion A at a temperature of 70°C with mechanical stirring (500 r / min). The addition rate was 2 g / L. After reacting for 2 hours, the mixture was naturally cooled to room temperature to obtain a water repellent agent with self-recovering water repellency after washing.

[0055] Fabrics treated with water repellent that recovers water repellency after washing:

[0056] The above water repellent was used to treat cotton fabric using a padding and baking process at a concentration of 100 g / L. The fabric was impregnated with the solution at a padding rate of 80%, pre-baked at 80°C for 5 minutes, and then baked at 150°C for 3 minutes. The relevant parameters of the treated fabric are shown in Table 1.

[0057] Example 3:

[0058] Prepare the self-recovering water repellent after washing and finish the fabric according to the following steps:

[0059] (1) A titanium source (tetraisopropyl titanate), an organic solvent (isopropyl alcohol), a reaction inhibitor (hydrochloric acid, 10 g / L) and deionized water were mixed (titanium source: organic solvent: reaction inhibitor: deionized water = 20:60:10:10, mass ratio) and stirred at 1000 r / min at room temperature for 5 h to obtain nano-titanium dioxide. A modifier (dimethoxymethylvinylsilane) was added to the solution with a modifier concentration of 20 g / L. The mixture was reacted at 20°C for 24 h, then cooled to room temperature and aged for 12 h to obtain modified nano-titanium dioxide.

[0060] (2) Cationic surfactant octadecyltrimethylammonium chloride, nonionic surfactant polyoxyethylene stearate (polyoxyethylene number is 60, the mass ratio of cationic surfactant to nonionic surfactant is 0.8:1) and modified nano-titanium dioxide are dissolved in deionized water to prepare an emulsion containing modified nano-titanium dioxide, wherein the mass concentration of modified nano-titanium dioxide is 3%, the mass ratio of the total amount of cationic surfactant and nonionic surfactant to the total amount of acrylate monomer is 0.15:1, the ratio of the amount of nano-titanium dioxide to the total mass of acrylate monomer is 0.1:1, and the total mass of acrylate monomer accounts for 15% of the total mass of the water repellent.

[0061] (3) Tetradecyl acrylate (accounting for 60% of the total mass of the acrylate monomer) was added to a portion of the emulsion containing modified nano-titanium dioxide (accounting for 80% of the total mass of the emulsion), and the mixture was ultrasonically treated in an ice bath for 30 minutes in a cell crusher to obtain pre-emulsion A. Hexyl methacrylate (accounting for 12% of the total mass of the acrylate monomer), methyl acrylate (accounting for 20% of the total mass of the acrylate monomer), and glycidyl acrylate (accounting for 8% of the total mass of the acrylate monomer) were added to the remaining emulsion containing modified nano-titanium dioxide, and the mixture was ultrasonically treated in an ice bath for 30 minutes in an ultrasonic cell crusher to obtain pre-emulsion B.

[0062] (4) Under nitrogen protection, pre-emulsion B and initiator ammonium persulfate (accounting for 1% of the total mass of the acrylate monomer and diluted 100 times with deionized water) were simultaneously added dropwise into the reactor containing pre-emulsion A at a temperature of 80°C with mechanical stirring (300 r / min). The addition rate was 2 g / L. After reacting for 4 hours, the mixture was naturally cooled to room temperature to obtain a water repellent agent with self-recovering water repellency after washing.

[0063] Fabrics treated with water repellent that recovers water repellency after washing:

[0064] The above water repellent was used to treat cotton fabric using a padding and baking process at a concentration of 40 g / L. The fabric was impregnated and then padded at a 100% padded rate, pre-baked at 105°C for 2 minutes, and then baked at 120°C for 5 minutes. The relevant parameters of the treated fabric are shown in Table 1.

[0065] Example 4-5:

[0066] Prepare the self-recovering water repellent after washing and finish the fabric according to the following steps:

[0067] Preparation of water repellent:

[0068] Same as Example 1.

[0069] Water repellent treated fabrics:

[0070] Only the type of fabric was changed to polyester (Example 4) and nylon (Example 5), and the rest was the same as in Example 1. The relevant parameters of the treated fabrics are shown in Table 1.

[0071] Comparative Example 1:

[0072] The fabric was treated as follows: the fabric was impregnated with a 60 g / L aqueous solution of a domestically produced commercial fluorine-free acrylic water repellent, then squeezed out at a 100% squeeze rate. The fabric was then pre-baked at 105°C for 3 minutes and then baked at 160°C for 2 minutes. The fabric parameters after treatment are shown in Table 1.

[0073] Comparative Example 2:

[0074] Follow these steps to prepare the water repellent and finish the fabric:

[0075] Preparation of water repellent:

[0076] No modified nano titanium dioxide was added, and the rest was the same as in Example 1.

[0077] Water repellent treated fabrics:

[0078] Same as Example 1. The relevant parameters of the treated fabric are shown in Table 1.

[0079] Comparative Example 3:

[0080] Follow these steps to prepare the water repellent and finish the fabric:

[0081] Preparation of water repellent:

[0082] The ratio of the amount of nano-titanium dioxide to the total mass of the acrylic ester monomers is 0.2:1, and the rest is the same as in Example 1.

[0083] Water repellent treated fabrics:

[0084] Same as Example 1. The relevant parameters of the treated fabric are shown in Table 1.

[0085] Comparative Example 4:

[0086] Follow these steps to prepare the water repellent and finish the fabric:

[0087] Preparation of water repellent:

[0088] The nano-titanium dioxide was not modified, and the other steps were the same as in Example 1.

[0089] Water repellent treated fabrics:

[0090] Same as Example 1. The relevant parameters of the treated fabric are shown in Table 1.

[0091] Comparative Example 5:

[0092] Follow these steps to prepare the water repellent and finish the fabric:

[0093] Preparation of water repellent:

[0094] The modified nano-titanium dioxide is the same as in Example 1. The cationic surfactant octadecyltrimethylammonium chloride and the nonionic surfactant polyoxyethylene stearate (polyoxyethylene number is 20, the mass ratio of the cationic surfactant to the nonionic surfactant is 1.5:1) and the modified nano-titanium dioxide are dissolved in deionized water to prepare an emulsion containing modified nano-titanium dioxide, wherein the mass concentration of the modified nano-titanium dioxide is 2%, the mass ratio of the total amount of the cationic surfactant and the nonionic surfactant to the total amount of the acrylate monomer is 0.25:1, the amount of nano-titanium dioxide is 0.2:1 of the total mass of the acrylate monomer, and the total mass of the acrylate monomer accounts for 10% of the total mass of the water repellent. Octadecyl acrylate (80% by weight of the total acrylate monomer) was added to a portion of an emulsion containing modified nano-titanium dioxide (40% by weight of the total emulsion), and ultrasonicated in an ice-bath for 30 minutes in an ultrasonic cell pulverizer to obtain pre-emulsion A. Butyl acrylate (5% by weight of the total acrylate monomer), methyl methacrylate (10% by weight of the total acrylate monomer), and glycidyl acrylate (5% by weight of the total acrylate monomer) were added to the remaining emulsion containing modified nano-titanium dioxide, and ultrasonicated in an ice-bath for 30 minutes in an ultrasonic cell pulverizer to obtain pre-emulsion B. Under nitrogen protection, pre-emulsion B and the initiator azobisisobutylamidine hydrochloride (2% by weight of the total acrylate monomer and diluted 100-fold with deionized water) were simultaneously added dropwise to a reactor containing pre-emulsion A at 60°C with mechanical stirring (300 rpm) at a rate of 2 g / L. The mixture was allowed to react for 3 hours and then naturally cooled to room temperature to obtain a water repellent with self-recovering water repellency after washing.

[0095] Water repellent treated fabrics:

[0096] Same as Example 1. The relevant parameters of the treated fabric are shown in Table 1.

[0097] Comparative Examples 6-7:

[0098] Follow these steps to create water repellency and finish fabrics:

[0099] Preparation of water repellent:

[0100] Same as Example 1.

[0101] Water repellent treated fabrics:

[0102] Only the amount of water repellent was changed to 20 g / L (Comparative Example 6) and 200 g / L (Comparative Example 7), and the rest was the same as in Example 1. The relevant parameters of the treated fabrics are shown in Table 1.

[0103] Table 1 Relevant parameters of treated fabrics

[0104]

[0105] Note: Untreated cotton fabric was completely wetted by water before and after washing and drying, and had a hydrostatic pressure resistance of 170 mm, a softness of 53.8, an ultraviolet protection factor (UPF) of 5.3, and an ultraviolet transmittance (T(UVA)) of 24.6. Untreated polyester fabric was completely wetted by water before and after washing and drying, and had a hydrostatic pressure resistance of 210 mm, a softness of 48.8, an ultraviolet protection factor (UPF) of 23.3, and an ultraviolet transmittance (T(UVA)) of 22.1. Untreated nylon fabric was completely wetted by water before and after washing and drying, and had a hydrostatic pressure resistance of 190 mm, a softness of 66.8, an ultraviolet protection factor (UPF) of 10.2, and an ultraviolet transmittance (T(UVA)) of 23.2.

[0106] The static water contact angle of fabrics treated with washable water repellent changes little after washing, but the fabric spray resistance level varies under different drying methods (according to the detection characterization method, the highest water repellency level of fabric is 5). There is a common problem that the spray resistance level of fabric decreases after natural drying after washing, that is, the water adhesion residue on the fabric increases.

[0107] As can be seen from Examples 1-3 in the table, the fabrics treated with the water repellent containing nano-titanium dioxide in the chemical structure prepared according to the method provided by the present invention all have good spray resistance after washing and natural drying. This is mainly because titanium dioxide can increase the surface roughness of the fabric and has light-to-heat conversion ability. It can effectively convert light into heat under the same sunlight irradiation, thereby promoting the recovery of the water repellency of the fabric. At the same time, Examples 1-3 also have good static water contact angle, hydrostatic pressure resistance, softness, pre-wash spray resistance and UV resistance (according to the test standard GB / T 18830-2009, when the UPF value of the fabric is greater than 40 and the UVA transmittance is less than 5%, it can be called a "UV protection product", and after the UPF is greater than 50, the impact on the human body can be completely ignored). The UV resistance of the fabric is derived from the UV shielding ability of nano-titanium dioxide.

[0108] It can be seen from Example 1 (cotton fabric), Example 4 (polyester fabric), and Example 5 (nylon fabric) in the table that the water repellent containing nano-titanium dioxide in the chemical structure prepared according to the method provided by the present invention has good spray resistance after washing and natural drying, static water contact angle, hydrostatic pressure resistance, softness, spray resistance before washing, and UV resistance for common textile fabrics.

[0109] By comparing Example 1 and Control Example 1, it can be seen that compared with the fabric finished with a commercial fluorine-free water repellent (not containing titanium dioxide) (Control Example 1), the fabric finished with a water repellent containing nano-titanium dioxide in the chemical structure prepared by the method provided by the present invention (Example 1) has better spray resistance, static water contact angle, hydrostatic pressure resistance and UV resistance after washing and natural drying. The main reason is that the water repellent polymer chain prepared by the present invention is chemically linked to nano-titanium dioxide, and titanium dioxide can convert solar radiation into heat energy to promote the reorientation of curled non-polar groups during the washing process. At the same time, titanium dioxide can increase the roughness of the fabric surface, and water droplets have a larger static water contact angle on the surface of the fabric containing it and are easy to roll off.

[0110] Comparing Example 1 and Control Example 2, it can be seen that compared with the fabric finished with the same water-repellent polymer structure but without nano-titanium dioxide product (the amount of modified titanium dioxide exceeds the parameters involved in the method of the present invention, the amount is 0, Control Example 2), the fabric (Example 1) prepared by the method provided by the present invention having a water-repellent containing nano-titanium dioxide in the chemical structure has better spray resistance, static water contact angle, hydrostatic pressure resistance and UV resistance after washing. The main reason is that the water-repellent polymer chain prepared by the present invention is chemically linked to the nano-titanium dioxide, and titanium dioxide can convert solar radiation into heat energy to promote the reorientation of the curled non-polar groups during the washing process. At the same time, titanium dioxide can increase the surface roughness of the fabric, and water droplets have a larger static water contact angle on the surface of the fabric containing it and are easy to roll off.

[0111] Comparing Example 1 and Reference Example 3, it can be seen that compared to the fabric (reference example 3) in which the amount of modified titanium dioxide used in the preparation process of the water repellent exceeds the parameters involved in the method of the present invention (excessive amount), the fabric (example 1) prepared by the water repellent containing nano-titanium dioxide in the chemical structure prepared by the present invention has better spray resistance after washing and drying, static water contact angle, hydrostatic pressure resistance and softness. The main reason is that the acrylate monomer undergoes free radical polymerization on the surface of the modified titanium dioxide to form a polymer, and the excessive modified titanium dioxide causes the polymer molecular weight to decrease, the polymer size to decrease, and it cannot form an effective coverage of the fabric, thereby reducing the water repellency of the fabric. At the same time, the excessive modified titanium dioxide deposited on the surface of the fabric easily fills the voids between the fibers, affecting the mutual movement between the fibers during the stress process of the fabric, which is manifested as a decrease in softness. The anti-ultraviolet performance of the control column 3 is better than that of Example 1 because the titanium dioxide content on the surface of the fabric increases, and titanium dioxide has anti-ultraviolet performance.

[0112] Comparing Example 1 and Control Example 4, it can be seen that the static water contact, hydrostatic pressure resistance, spray resistance before and after washing, and UV resistance of the fabric finished with the water repellent product prepared by directly participating in the polymer reaction without modification of nano-titanium dioxide (Control Example 4) are lower than those of the fabric finished with the water repellent containing nano-titanium dioxide in the chemical structure prepared according to the method provided by the present invention (Example 1). The reason is that the hydroxyl groups on the surface of nano-titanium dioxide are ionized in the aqueous phase system to show negative charge, and electrostatic adsorption occurs with the cationic surfactant, causing the surfactant to lose its emulsification of titanium dioxide and acrylic ester monomers, resulting in a decrease in the stability of the synthesized product and a decrease in the water repellency of the finished fabric.

[0113] By comparing Example 1 and Control Example 5, it can be seen that the water repellent properties (static water contact, hydrostatic pressure resistance, spray resistance before and after washing) of the fabric finished with the product obtained by exceeding the parameters involved in the method provided by the present invention (Control Example 5) are lower than those of the fabric finished with the water repellent containing nano-titanium dioxide in the chemical structure prepared according to the method provided by the present invention (Example 1).

[0114] Comparative Example 1 and Reference Examples 6-7 show that when the water repellent prepared by the present invention is used to finish fabrics in too low a dosage (reference example 6), the various water repellent properties of the fabric (static water contact, hydrostatic pressure resistance, spray resistance before and after washing) and anti-ultraviolet performance are relatively low, and the reason is that the water repellent is used too little, and its contained macromolecule is difficult to form an effective coverage on the fabric surface, and the hydrophilic group of the fabric part is still retained. When the water repellent prepared by the present invention is used to finish fabrics in too high a dosage (reference example 7), although the various water repellent properties of the fabric (static water contact, hydrostatic pressure resistance, spray resistance before and after washing) and anti-ultraviolet performance are relatively good, its softness (feel) decreases significantly, and the reason is that the fabric surface has too many water repellent macromolecular polymers and titanium dioxide particles, and the macromolecular cross-linking is formed into thick film and solid particles, which fill the gaps between the fabric fibers and hinder the mutual movement between the fibers when the fabric is stressed.

Claims

1. A method for preparing a water repellent having self-recovering water repellency after washing, characterized in that: The method comprises: (1) preparing nano-titanium dioxide with a titanium source, an organic solvent, a reaction inhibitor, and deionized water, modifying the nano-titanium dioxide with a modifier, removing the solvent by rotary evaporation, and aging to obtain modified nano-titanium dioxide; the modifier comprises one or more of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and dimethoxymethylvinylsilane; (2) dissolving a cationic surfactant and a nonionic surfactant in deionized water and then adding the modified nano-titanium dioxide obtained in step (1) to prepare an emulsion; (3) mixing part of the acrylic ester monomer and part of the emulsion containing modified nano-titanium dioxide obtained in step (2), and emulsifying the mixture with an ultrasonic cell crusher to obtain a pre-emulsion A; (4) mixing the remaining acrylic ester monomer and the remaining emulsion containing modified nano-titanium dioxide, and emulsifying the mixture using an ultrasonic cell crusher to obtain pre-emulsion B; (5) Under nitrogen protection, the pre-emulsion B and the aqueous solution of the initiator are slowly added to the pre-emulsion A, and after the reaction is kept warm, the material is cooled and discharged to obtain a water repellent agent with self-recovering water repellency.

2. The preparation method according to claim 1, wherein In the step (1), the titanium source includes one or more of tetrabutyl titanate, tetraethyl titanate, and tetraisopropyl titanate; the organic solvent includes one or more of ethanol, propanol, and isopropanol; the reaction inhibitor includes one or more of glacial acetic acid, nitric acid, or hydrochloric acid; when preparing nano-titanium dioxide, the components include, by mass percentage, 5-20% of the titanium source, 60-80% of the organic solvent, 5-20% of the reaction inhibitor, and the rest is water; after the modifier is added, the concentration of the modifier in the solution is 1-20 g / L.

3. The preparation method according to claim 1 or 2, characterized in that The preparation method of the modified nano-titanium dioxide comprises mixing a titanium source, an organic solvent, a reaction inhibitor and deionized water, stirring the mixture at 100-1000 r / min at room temperature for 1-8 hours to obtain nano-titanium dioxide, adding a modifier, and reacting the mixture at 20-60° C. for 4-24 hours; and the aging time is 12-24 hours.

4. The method according to claim 1, wherein In the step (2), the cationic surfactant is one or a mixture of octadecyltrimethylammonium chloride and hexadecyltrimethylammonium chloride; the nonionic surfactant is a mixture of one or more polyoxyethylene ether surfactants; the mass ratio of the cationic surfactant to the nonionic surfactant is (0.2-0.8):1; the mass ratio of the total amount of the cationic surfactant and the nonionic surfactant to the total amount of the acrylate monomer is (0.05-0.15):1; the mass ratio of the amount of the modified nano-titanium dioxide to the total amount of the acrylate monomer is (0.01-0.1):1; and the mass concentration of the modified nano-titanium dioxide in the emulsion is 0.15-3%.

5. The method according to claim 1, wherein The acrylic acid ester monomer in step (3) includes any one or more of methyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate, tetradecyl acrylate, hexadecyl acrylate, octadecyl acrylate, methyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, tetradecyl methacrylate, hexadecyl methacrylate, and octadecyl methacrylate.

6. The method according to claim 1, characterized in that The mass of the modified nano-titanium dioxide emulsion in step (3) is 50-80% of the mass of the total modified nano-titanium dioxide emulsion; the mass of the acrylate monomer is 40-60% of the mass of the total acrylate monomer; and the total mass of the acrylate monomer accounts for 15-30% of the total mass of the water repellent.

7. The method according to claim 1, characterized in that In step (5), the initiator comprises one or more of azobisisobutyronitrile, azobisisoheptanenitrile, azobisisobutyramidine hydrochloride, potassium persulfate, ammonium persulfate, and dibenzoyl peroxide; the mass of the initiator accounts for 0.1-1% of the total mass percentage of the acrylate monomer; the reaction temperature is 70-80° C., and the reaction time is 2-4 hours.

8. A water-repellent agent with self-recovering water-repellency after washing, prepared by the method according to any one of claims 1 to 7.

9. A method for hydrophobic treatment of fabric, characterized in that, The method comprises the following steps: firstly immersing the fabric in an aqueous solution of the water repellent according to claim 8, then padding and baking the fabric, wherein the padding rate is 80-200%, the fabric is pre-baked at 80-110° C. for 3-5 minutes, and then baked at 120-160° C. for 1-5 minutes, wherein the concentration of the water repellent in the aqueous solution is 40-100 g / L.

10. A hydrophobic fabric, characterized in that: The fabric comprises the water repellent having self-recovering water repellency after washing according to claim 8, or is prepared by the hydrophobic treatment method according to claim 9.

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