Flame-retardant finishing method for cotton fabric

Abstract

The invention belongs to the technical field of flame retardance of textiles, and particularly relates to a flame-retardant finishing method of a cotton fabric. The method comprises the following steps: dipping the cotton fabric in a flame-retardant finishing liquid, and then carrying out padding, pre-drying, baking, washing, sizing and drying. Wherein the flame-retardant finishing liquid is formed by mixing a flame retardant, a catalyst and a penetrant in water, and formaldehyde is not used in the synthesis of the flame retardant, so that the finished cotton fabric does not have the problems of formaldehyde release, smoke toxicity and poor color fastness to sunlight. The flame retardant contains more hydroxyl groups, so that the covalent bond reaction grafting binding force of the flame retardant and hydroxyl groups in cotton fabric fibers can be improved, the durability is further improved, and the flame retardant still has high flame retardance after being washed for 100 times. The flame-retardant finishing process of the cotton fabric is free of environmental pollution and pungent smell, the use process is simple and convenient, special treatment equipment is not needed, the process cost, the workshop production environment and the operation difficulty are greatly reduced, and the product is washable, non-toxic and pollution-free.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant textiles, and particularly relates to a flame retardant finishing method for cotton fabrics. Background Art

[0002] Cotton fabrics are widely used in textile industries such as clothing and home textiles. However, since cotton fabrics are flammable, they need to be flame-retardant finished and ensure that the flame-retardant finished cotton fabrics still have flame-retardant properties after multiple washings.

[0003] However, current flame-retardant finishing technologies suffer from high formaldehyde emissions. For example, Pyrovatex CP, a flame retardant commonly used in flame-retardant finishing of cotton fabrics, continuously releases formaldehyde during subsequent use. Frequent human contact with cotton fabrics undoubtedly poses a health risk. Furthermore, treatment with this flame retardant can cause significant discoloration, affecting the original color of the cotton fabric, and reduces its flame-retardant effectiveness after washing. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a flame retardant finishing method for cotton fabrics. After the flame retardant finishing of the present invention, no formaldehyde release is detected in the cotton fabrics, and the cotton fabrics have less color change, are resistant to sunlight, and still have excellent flame retardant effects after 100 washes, with performance superior to current flame retardant finishing technologies.

[0005] The present invention is achieved through the following technical solutions.

[0006] The present invention provides a flame retardant finishing method for cotton fabric, comprising the following steps: The flame retardant, carboxyl acid catalyst and penetrant are mixed in water to prepare a flame retardant finishing liquid.

[0007] The cotton fabric is immersed in a flame retardant finishing liquid, padded, pre-baked, baked, washed, shaped and dried to obtain the flame retardant finished cotton fabric.

[0008] The structure of the flame retardant is shown below: , wherein R is hydroxy or methoxy.

[0009] Preferably, the method for preparing the flame retardant comprises the following steps: Under nitrogen protection, the compound of formula (1) is dissolved in anhydrous methanol, and then a methanol solution of sodium methoxide and acrylamide represented by formula (2) are added to prepare the compound of formula (3) through addition reaction.

[0010] Using a mixture of water and THF as solvent, at a pH of 2-3, the compound of formula (3) and glyoxylic acid undergo a nucleophilic addition-dehydration reaction to generate an intermediate of formula (4). The pH is adjusted to 5-6, and sodium cyanoborohydride is added. Sodium cyanoborohydride selectively reduces the C=N double bond to generate a compound of formula (5).

[0011] Under a protective gas atmosphere, LiAlH4 is placed in anhydrous ether, and then a THF solution of the compound of formula (5) is added. LiAlH4 reduces the carboxyl group to a hydroxymethyl group to prepare the compound of formula (6).

[0012] The synthetic route is as follows: ; Wherein, R is hydroxyl or methoxy.

[0013] Preferably, the molar ratio of the compound of formula (1) to acrylamide is 1:1, the mass concentration of the sodium methoxide methanol solution is 27% to 31%, the amount ratio of the sodium methoxide methanol solution to acrylamide is 13 to 14 mL: 1 mol, the temperature of the addition reaction is room temperature, and the time is 2 to 3 h.

[0014] Preferably, the molar ratio of the compound of formula (3) to glyoxylic acid is 2:3-4, and the reaction temperature is 3°C-5°C during the nucleophilic addition-dehydration reaction; when sodium cyanoborohydride selectively reduces the C=N double bond, the reaction temperature is 5°C-10°C, and the molar ratio of sodium cyanoborohydride to the compound of formula (3) is 1:1.

[0015] Preferably, the mass ratio of LiAlH4 to the compound of formula (5) is 1:7-9, and the reaction is carried out at room temperature for 2h-2.5h.

[0016] Preferably, in the flame retardant finishing liquid, the mass concentration of the flame retardant is 30% to 50%, the mass ratio of the flame retardant to the carboxyl acid catalyst is 6.25:1, the mass concentration of the penetrant is 1% to 3%, and the temperature of the flame retardant finishing liquid is 10° C. to 35° C. The carboxyl acid catalyst is preferably citric acid.

[0017] Preferably, during padding, the liquid rolling rate is 70% to 75%, the pre-baking temperature is 90° C. to 125° C., the pre-baking time is 30s to 170s, and the water content retained after pre-baking is 5% to 15%.

[0018] Preferably, the baking temperature is 150° C. to 190° C., and the baking time is 150s to 210s.

[0019] Preferably, when the cotton fabric is a woven fabric, the washing step is: soap washing in the first to fourth tanks at 75°C to 85°C for 1 to 2.5 minutes, wherein the first to fourth tanks contain soda ash, hydrogen peroxide and soap powder, wherein the mass concentrations of soda ash in the first to fourth tanks are 4%, 3%, 2% and 2% respectively, the mass concentrations of hydrogen peroxide in the first to fourth tanks are 2%, 1%, 1% and 1% respectively, and the mass concentrations of soap powder in the first to fourth tanks are 1%, 1%, 1% and 1% respectively, rolling dry, and then passing through high-temperature water at 60°C to Soap wash in tanks 5 through 8 at 70°C for 1–2.5 minutes. Tanks 5 through 8 contain sodium metabisulfite or sodium bisulfite, and soap powder, respectively. The mass concentrations of sodium metabisulfite or sodium bisulfite in tanks 5 through 8 are 2%, 1%, 1%, and 1%, respectively; the mass concentrations of soap powder in tanks 5 through 8 are 1%, 1%, 1%, and 1%, respectively. Roll dry. Rinse in running water in tanks 9 through 10 at 25–35°C for 1–2 minutes, followed by rolling dry. Change the water in tanks 1 through 8 for every ton of cloth washed.

[0020] Preferably, when the cotton fabric is a knitted fabric, the washing steps are: first, soaping in a solution containing soda ash, hydrogen peroxide and soap powder at 50°C to 60°C for 5min to 15min, wherein the mass concentration of soda ash is 3% to 4%, the mass concentration of hydrogen peroxide is 2%, and the mass concentration of soap powder is 1%, and the sewage is drained; then, washing in a solution containing sodium metabisulfite or sodium bisulfite and soap powder at 50°C to 60°C for 5min to 15min, wherein the mass concentration of sodium metabisulfite or sodium bisulfite is 1% to 2%, and the mass concentration of soap powder is 1% to 2%, spin drying, and finally rinsing with running clean water at 25°C to 35°C on a splay machine for 1min to 2min and squeezing dry; timing is started after the fabric is completely put into the vat.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention involves immersing cotton fabric in a flame-retardant finishing solution, followed by padding, pre-baking, baking, washing, shaping, and drying. The flame-retardant finishing solution is a mixture of a flame retardant, a catalyst, and a penetrant in water. Because formaldehyde is not used in the synthesis of the flame retardant, the finished cotton fabric is free of formaldehyde release. The flame retardant contains a high concentration of hydroxyl groups, which enhance crosslinking and bonding with the hydroxyl groups in the cotton fabric fibers, improving durability. The fabric retains high flame retardancy after washing, and the flame-retardant finished cotton fabric exhibits minimal discoloration.

[0022] The process of the cotton fabric flame-retardant finishing of the application has no environmental pollution, no irritating smell, simple and convenient use process, no need of special treatment equipment, greatly reduces the process cost and operation difficulty. The product is washable, non-toxic and non-polluting, and has no import and export barriers. When the open flame is close, it burns less smoke, has no smell, and automatically extinguishes without continuing to burn after the fire source is removed, has no smoldering, is not salted, and has no moisture return, and is very suitable for natural fiber fabrics such as cotton, hemp and silk, and is also suitable for other flame-retardant fabrics that cannot be achieved by other flame-retardant agents, and is the best choice for bed sheets, bed covers, children's bedding, clothing, military uniforms and special work clothes. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The nuclear magnetic spectrum of the compound shown in formula (61).

[0024] Figure 2 The nuclear magnetic spectrum of the compound shown in formula (62).

[0025] Figure 3 The color change comparison of the flame-retardant product of the application and other flame-retardant products.

[0026] Figure 4 The sunlight resistance comparison of the flame-retardant product of the application and other flame-retardant products.

[0027] Figure 5 The tearing strength comparison of the flame-retardant product of the application and other flame-retardant products.

[0028] Figure 6 The color change, sunlight resistance and tearing strength test reports.

[0029] Figure 7 The flame-retardant detection results of the flame-retardant product of the application after 100 times of washing.

[0030] Figure 8 The formaldehyde content detection results of the flame-retardant product of the application.

[0031] Figure 9 The antibacterial effect of the flame-retardant product of the application after 100 times of washing.

[0032] Figure 10 The antiviral effect of the flame-retardant product of the application after 100 times of washing. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solutions of the application and implement them, the application will be further described below in combination with specific embodiments and drawings, but the embodiments are not limiting to the application. The experimental methods and detection methods described in the following embodiments are all conventional methods unless otherwise specified; and the reagents and materials described are all commercially available unless otherwise specified.

[0034] The present invention provides a flame retardant finishing method for cotton fabric, comprising the following steps: Step 1: Mixing a flame retardant, a carboxyl acid catalyst and a penetrant in water to prepare a flame retardant finishing liquid; Among them, the structure of the flame retardant is as follows: , wherein R is hydroxy or methoxy.

[0035] The preparation method of the flame retardant comprises the following steps: Under nitrogen protection, the compound of formula (1) is dissolved in anhydrous methanol, and then a sodium methoxide methanol solution and acrylamide represented by formula (2) are added to prepare the compound of formula (3) through addition reaction; Using a mixture of water and THF as solvent, at a pH of 2-3, the compound of formula (3) and glyoxylic acid undergo a nucleophilic addition-dehydration reaction to generate an intermediate of formula (4); adjusting the pH to 5-6, adding sodium cyanoborohydride, which selectively reduces the C=N double bond to generate a compound of formula (5); Under a protective gas atmosphere, LiAlH4 is placed in anhydrous ether, and then a THF solution of the compound of formula (5) is added. LiAlH4 reduces the carboxyl group to a hydroxymethyl group to prepare the compound of formula (6); The synthetic route is as follows: .

[0036] Wherein, R is hydroxyl or methoxy.

[0037] It should be noted that, in the process of preparing the flame retardant of the present invention, the hydroxy phosphide represented by formula (1) is used as a raw material (specifically phosphorous acid or monomethyl phosphate) to synthesize the compound represented by formula (3). Then, the present invention uses glyoxylic acid to react with the compound represented by formula (3), and then reduces the carboxyl group to prepare the flame retardant represented by formula (6). Glyoxylic acid is used to replace the formaldehyde used in the traditional process. By rationally designing the route, the use of formaldehyde is avoided, and the flame retardant can be cross-linked with the cotton fabric. In addition, the flame retardant has a large amount of hydroxyl groups, which helps to increase the cross-linking reaction between the flame retardant and the cellulose hydroxyl groups in the cotton fabric, thereby improving the bonding strength.

[0038] Preferably, the molar ratio of the compound of formula (1) to acrylamide is 1:1, the mass concentration of the sodium methoxide methanol solution is 27% to 31%, the amount ratio of the sodium methoxide methanol solution to acrylamide is 13 to 14 mL: 1 mol, the temperature of the Michael addition reaction is room temperature, and the time is 2 to 3 h.

[0039] Preferably, the molar ratio of the compound of formula (3) to glyoxylic acid is 2:3-4, and the reaction temperature is 3°C-5°C during the nucleophilic addition-dehydration reaction; when sodium cyanoborohydride selectively reduces the C=N double bond, the reaction temperature is 5°C-10°C, and the molar ratio of sodium cyanoborohydride to the compound of formula (3) is 1:1.

[0040] Preferably, the mass ratio of LiAlH4 to the compound of formula (5) is 1:7-9, and the reaction is carried out at room temperature for 2h-2.5h.

[0041] Preferably, in the flame retardant finishing liquid, the mass concentration of the flame retardant is 30% to 50%, the mass ratio of the flame retardant to the carboxyl acid catalyst is 6.25:1, the mass concentration of the penetrant is 1% to 3%, and the temperature of the flame retardant finishing liquid is 10°C to 35°C.

[0042] Step 2: immersing the cotton fabric in the flame retardant finishing liquid, padding, pre-drying, baking, washing, shaping and drying to obtain the flame retardant finished cotton fabric.

[0043] It should be noted that cotton fabrics that have undergone color fixing or softening treatments will result in a low liquid pick-up rate and uneven liquid distribution on the fabric surface, making it relatively difficult to achieve the expected flame retardant effect. Therefore, the fabric before flame retardant finishing has not undergone any finishing (no softening, waterproofing or other film-forming treatments), and must have good water absorption, be clean, and have a neutral surface.

[0044] Preferably, during padding, the liquid filling rate is 70% to 75%, the pre-baking temperature is 90°C to 125°C, the pre-baking time is 30s to 170s, and the moisture content after pre-baking is 5% to 15%. The baking temperature is 150°C to 190°C, and the time is 150s to 210s.

[0045] The above-mentioned method for calculating the liquid squeeze rate is as follows: cut 2-3 meters of cloth, weigh the dry weight, soak it in flame retardant liquid, start the rollers at the set speed and pressure, and after 2 minutes of stable operation, spread the liquid-soaked cloth flat on the rollers and weigh the wet weight after squeezing; liquid squeeze rate = (wet weight - dry weight) / dry weight.

[0046] It should be noted that the baking temperature and baking time should be selected according to the weight of different cotton fabrics; the air supply should be 80%, the cloth should not be stretched tight, but loose, 2%-3% lower than the width requirement, water should be pumped from the rear of the car and steam should be pumped from the rear of the car to soften it and maintain its strength.

[0047] Preferably, when the cotton fabric is a woven fabric, the washing step is as follows: soap washing in the first to fourth tanks at 75°C to 85°C for 1 to 2.5 minutes, wherein the first to fourth tanks contain soda ash, hydrogen peroxide and soap powder, wherein the mass concentrations of soda ash in the first to fourth tanks are 4%, 3%, 2% and 2% respectively, the mass concentrations of hydrogen peroxide in the first to fourth tanks are 2%, 1%, 1% and 1% respectively, and the mass concentrations of soap powder in the first to fourth tanks are 1%, 1%, 1% and 1% respectively, rolling dry, and then passing through high-temperature water at 60°C. Soaping is performed in tanks 5 through 8 at 70°C for 1-2.5 minutes. Tanks 5 through 8 contain sodium metabisulfite or sodium bisulfite, and soap powder, respectively. The mass concentrations of sodium metabisulfite or sodium bisulfite in tanks 5 through 8 are 2%, 1%, 1%, and 1%, respectively, and the mass concentrations of soap powder in tanks 5 through 8 are 1%, 1%, 1%, and 1%, respectively. The fabric is then squeezed dry. Rinse with running water in tanks 9 through 10 at 25-35°C for 1-2 minutes, followed by squeezing dry. The water in tanks 1 through 8 is changed every ton of fabric washed.

[0048] Preferably, when the cotton fabric is a knitted fabric, the washing steps are: first, soaping in a solution containing soda ash, hydrogen peroxide and soap powder at 50°C to 60°C for 5min to 15min, wherein the mass concentration of soda ash is 3% to 4%, the mass concentration of hydrogen peroxide is 2%, and the mass concentration of soap powder is 1%, and the sewage is drained; then, washing in a solution containing sodium metabisulfite or sodium bisulfite and soap powder at 50°C to 60°C for 5min to 15min, wherein the mass concentration of sodium metabisulfite or sodium bisulfite is 1% to 2%, and the mass concentration of soap powder is 1% to 2%, spin drying, and finally rinsing with running clean water at 25°C to 35°C on a splay machine for 1min to 2min and squeezing dry; timing is started after the fabric is completely put into the vat.

[0049] The above production process is environmentally friendly and odorless, and its simple and convenient application process requires no special processing equipment, significantly reducing process costs and operational difficulty. The product is washable, non-toxic, pollution-free, and easily accessible. It produces little smoke and is odorless when exposed to an open flame, and automatically extinguishes itself after the fire is removed, preventing smoldering, salt stains, and moisture retention. It is ideally suited for natural fiber fabrics such as cotton, linen, and silk, as well as for cotton-nylon blends, which other flame retardants cannot. It is an excellent choice for bed sheets, quilt covers, children's bedding, clothing, military uniforms, and specialized workwear.

[0050] The present invention is described in detail below through the following examples: First, a specific preparation method of the flame retardant of the present invention is provided.

[0051] The flame retardant was synthesized according to the following synthetic route: S1. Synthesis of compound of formula (3): The compound of formula (1) (1.0 mol) and anhydrous methanol (100 mL) were nitrogen-purged three times to maintain an inert atmosphere. A sodium methoxide methanol solution (30% by mass, 13.5 mL) was placed in a dropping funnel and sodium methoxide was slowly added dropwise. The temperature was controlled at 0°C for 30 min, and the mixture was stirred for 15 min (to generate phosphorus anions). Acrylamide (1.0 mol) was added in five batches, with the temperature controlled below 5°C for 5 min between each batch (to prevent polymerization). After the addition was complete, the ice bath was removed and the temperature was slowly raised to 25°C. The reaction was stirred at 25°C for 3 h. The methanol was then evaporated under reduced pressure (40°C, 0.1 MPa). The residue was dissolved in ice water (200 mL) and extracted with dichloromethane (3 × 100 mL). The organic phases were combined and dried over anhydrous MgSO4. The solid was filtered and rotary evaporated to obtain a solid. The solid was recrystallized from ethyl acetate / n-hexane (volume ratio 1:5) and dried in vacuo to obtain the compound of formula (3).

[0052] S2. Synthesis of compound of formula (5): The compound of formula (3) (40 mmol) was dissolved in a mixed solvent of 50 mL of water and 50 mL of THF and cooled to 3°C in an ice bath. Glyoxylic acid (63 mmol) was slowly added, maintaining the temperature below 5°C, at which point the pH was approximately 2. The pH was adjusted to 5.0 with 1 M NaOH solution. Sodium cyanoborohydride (40 mmol) was added in portions, controlling the temperature not to exceed 10°C. After the addition was complete, the ice bath was removed, the reaction mixture was allowed to warm to room temperature, and stirred for 12 hours. After the reaction was completed, the pH was adjusted to 3 with 1 M HCl, and the THF was removed by rotary evaporation. The remaining aqueous phase was extracted with dichloromethane (3 × 50 mL) to remove non-polar impurities. The aqueous phase was adjusted to pH 8 with sodium hydroxide solution and then concentrated to dryness using a rotary evaporator to obtain the crude product of the compound of formula (5). It was used directly in the next step without further purification.

[0053] S3. Synthesis of compound of formula (6): Lithium aluminum hydride (1.5 g) and anhydrous ether (50 mL) were added to a dry three-necked flask, cooled in an ice bath, and stirred under nitrogen. The crude product (11.2 g) of the compound of formula (5) obtained in the previous step was dissolved in anhydrous THF (approximately 30 mL) and slowly added dropwise to the LiAlH4 suspension using a constant pressure dropping funnel. The addition rate was controlled to maintain the reaction temperature at 3°C. After the addition was complete, the ice bath was removed and the reaction mixture was allowed to warm to room temperature. The reaction was then allowed to proceed for 2 hours. The mixture was then cooled to 0°C and water (1.5 mL) was carefully added dropwise to quench the excess LiAlH4. A 15% mass concentration NaOH solution (1.5 mL) was then added dropwise, followed by water (4.5 mL). The mixture was stirred for 15 minutes until a precipitate formed. The mixture was filtered through celite and the filter cake was washed with ether. The filtrate and washings were combined and dried over anhydrous sodium sulfate. The mixture was filtered and the ether was removed by rotary evaporation to obtain a light yellow transparent viscous liquid, which was the compound of formula (6).

[0054] The compound of formula (6) is specifically: or: Among them, the NMR spectrum of the compound represented by formula (61) is as follows Figure 1 The NMR spectrum of the compound represented by formula (62) is shown as Figure 2 shown.

[0055] When the flame retardant represented by the above formula (61) is used, the flame retardant finishing method of cotton fabric of the present invention is provided below, and the specific operation steps are as follows: Step 1: Prepare a flame retardant finishing liquid according to the weight of the cotton fabric. Specifically, the flame retardant represented by formula (61), the citric acid catalyst, and the penetrant are mixed in 35°C water to prepare the flame retardant finishing liquid. The amount of each component is shown in Table 1.

[0056] Step 2: immersing the cotton fabric in the flame retardant finishing liquid, padding, pre-drying, and baking.

[0057] Among them, when the cotton fabric is woven fabric, the flame retardant finishing liquid formula, padding, pre-baking and baking parameters are shown in Table 1.

[0058] Table 1 Flame retardant finishing parameters of woven fabrics When the cotton fabric is knitted, based on the parameters in Table 1, the pre-baking time needs to be extended by 0.5 minutes and the baking temperature needs to be increased by 1°C.

[0059] Step 3, washing: When the cotton fabric is woven, the washing steps are as follows: soaping in the 1st to 4th tanks at 80°C for 2.5 minutes, the 1st to 4th tanks contain soda ash, hydrogen peroxide and soap powder, wherein the mass concentrations of soda ash in the 1st to 4th tanks are 4%, 3%, 2% and 2%, respectively, the mass concentrations of hydrogen peroxide in the 1st to 4th tanks are 2%, 1%, 1% and 1%, respectively, and the mass concentrations of soap powder in the 1st to 4th tanks are 1%, 1%, 1% and 1%, respectively; rolling drying; then soaping in high-temperature water at 70°C in the 5th to 8th tanks for 2.5 minutes, wherein the 5th to 8th tanks contain sodium metabisulfite and soap powder, the mass concentrations of sodium metabisulfite in the 5th to 8th tanks are 2%, 1%, 1% and 1%, respectively, and the mass concentrations of soap powder in the 5th to 8th tanks are 1%, 1%, 1% and 1%, respectively; rolling drying; then rinsing with running water in the 9th to 10th tanks at 25°C for 2 minutes, and rolling drying. Change the water in tanks 1 to 8 every time you wash 1 ton of cloth.

[0060] When the cotton fabric is a knitted fabric, the washing steps are as follows: first, soap washing in a solution containing soda ash, hydrogen peroxide and soap powder at 50°C for 10 minutes, wherein the soda ash mass concentration is 3%, the hydrogen peroxide mass concentration is 2%, and the soap powder mass concentration is 1%, and the sewage is drained; then, at 50°C, washing in a solution containing sodium metabisulfite and soap powder for 10 minutes, wherein the sodium metabisulfite mass concentration is 1%, and the soap powder mass concentration is 1%, spin drying, and finally, rinsing with running water at 25°C for 1 minute on a splay machine and rolling dry; timing starts after the fabric is completely put into the tank.

[0061] Step 4: shaping and drying to obtain flame-retardant finished cotton fabric.

[0062] When the flame retardant represented by formula (62) is used, the flame retardant finishing method of cotton fabric of the present invention is provided below, and the specific operation steps are as follows: Step 1: Prepare a flame retardant finishing liquid according to the weight of the cotton fabric. Specifically, the flame retardant, catalyst and penetrant shown in formula (62) are mixed in 35° C. water to prepare the flame retardant finishing liquid; Step 2: immersing the cotton fabric in the flame retardant finishing liquid, padding, pre-drying, and baking.

[0063] Among them, when the cotton fabric is woven fabric, the flame retardant finishing liquid formula, padding, pre-baking and baking parameters are shown in Table 2.

[0064] Table 2 Flame retardant finishing parameters of woven fabrics When the cotton fabric is knitted, based on the parameters in Table 2, the pre-baking time needs to be extended by 0.5 minutes and the baking temperature needs to be increased by 1°C.

[0065] Step 3, washing: When the cotton fabric is woven, the washing steps are as follows: soap washing for 2.5 minutes in the 1st to 4th tanks at 75°C, wherein the 1st to 4th tanks contain soda ash, hydrogen peroxide and soap powder, wherein the mass concentrations of soda ash in the 1st to 4th tanks are 4%, 3%, 2% and 2%, respectively; the mass concentrations of hydrogen peroxide in the 1st to 4th tanks are 2%, 1%, 1% and 1%, respectively; the mass concentrations of soap powder in the 1st to 4th tanks are 1%, 1%, 1% and 1%, respectively; squeeze drying; and then soap washing for 2.5 minutes in the 5th to 8th tanks at 60°C in high-temperature water, wherein the 5th to 8th tanks contain sodium metabisulfite and soap powder, wherein the mass concentrations of sodium metabisulfite in the 5th to 8th tanks are 2%, 1%, 1% and 1%, respectively; the mass concentrations of soap powder in the 5th to 8th tanks are 1%, 1%, 1% and 1%, respectively; squeeze drying; and then rinsing with running water in the 9th to 10th tanks at 25°C for 2 minutes, and squeeze drying. Change the water in tanks 1 to 8 every time you wash 1 ton of cloth.

[0066] When the cotton fabric is a knitted fabric, the washing steps are as follows: first, soap washing in a solution containing soda ash, hydrogen peroxide and soap powder at 50°C for 10 minutes, wherein the soda ash mass concentration is 3%, the hydrogen peroxide mass concentration is 2%, and the soap powder mass concentration is 1%, and the sewage is drained; then, at 60°C, washing in a solution containing sodium metabisulfite and soap powder for 10 minutes, wherein the sodium metabisulfite mass concentration is 1%, and the soap powder mass concentration is 1%, spin drying, and finally, rinsing with running water at 25°C for 1 minute on a splay machine and rolling dry; timing starts after the fabric is completely put into the vat.

[0067] Step 4: shaping and drying to obtain flame-retardant finished cotton fabric.

[0068] According to the flame retardant finishing method of cotton fabric, the present invention specifically adopts the flame retardant shown in formula (61) for flame retardant finishing, and obtains 205g of the finished woven fabric, which is then subjected to performance testing and compared with the performance of woven fabrics treated with flame retardants commonly used internationally, with reference to the standard GB / T 17951-2025. The results are shown in Table 3. The Nissen 007 flame retardant in Table 3 is the flame retardant product obtained by the present invention.

[0069] Table 3 Comparison of the properties of the woven fabric treated with the present invention and other flame retardant products Among them, the color change comparison of the flame retardant products in Table 3 is as follows: Figure 3 As shown, Figure 3 The flame retardant of 007 is the color change of the product of the present invention. Figure 4 As shown, the tearing strength is Figure 5 The corresponding experimental report is shown in Figure 6It can be seen that compared with the woven fabrics treated with flame retardants commonly used in the world, the woven fabric treated with the present invention has the advantages of high color fastness to sunlight, high strength, and no color difference after treatment.

[0070] The flame retardant properties and the detection comparison of its production wastewater are shown in Table 4 and Table 5, respectively. Sample NS-ZR-007 in Table 4 and Table 5 is the sample of the present invention.

[0071] Table 4 Comparative data of performance of different flame retardant products Table 5 Wastewater testing data generated by different production processes Flame retardant test results after 100 washes Figure 7 As shown in the figure, the flame retardant effect is still very good after 100 times of water washing. The vertical burning carbon length in 12 seconds is only 2-3cm, which is much lower than the US standard of 10cm and the national standard of 15cm. Figure 8 As shown. The antibacterial effect after 100 washes is as follows Figure 9 As shown. The antiviral effect after 100 washes is as follows Figure 10 shown.

[0072] The above test results indicate that the cotton fabric finishing process of the present invention is environmentally friendly and odorless, and the process is simple and convenient to use, requiring no special processing equipment, significantly reducing process costs and operational difficulty. The product is washable, non-toxic, pollution-free, and has unobstructed import and export. It produces little smoke and is odorless when exposed to an open flame. It automatically extinguishes after the fire source is removed, without smoldering, salt stains, or moisture retention. It is very suitable for natural fiber fabrics such as cotton, linen, and silk, and is also suitable for nylon-cotton blended fabrics, which other flame retardants cannot achieve. It is an excellent choice for bed sheets, quilt covers, children's bedding, clothing, military uniforms, and special work clothes.

[0073] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications of the present invention fall within the scope of the claims and their equivalents, such changes and modifications are also intended to be included.

Claims

1. A flame retardant finishing method for cotton fabric, characterized in that: The following steps are involved: Mixing the flame retardant, carboxyl acid catalyst and penetrant in water to prepare a flame retardant finishing liquid; The cotton fabric is immersed in a flame retardant finishing liquid, and after padding, pre-baking, baking, washing, setting and drying, a flame retardant finished cotton fabric is obtained; The structure of the flame retardant is shown below: , wherein R is hydroxy or methoxy.

2. The flame retardant finishing method for cotton fabric according to claim 1, characterized in that: The preparation method of the flame retardant comprises the following steps: Under a protective gas atmosphere, the compound of formula (1) is dissolved in methanol, and then a sodium methoxide methanol solution and acrylamide represented by formula (2) are added to prepare a compound of formula (3) through an addition reaction; Using a mixture of water and THF as solvent, at a pH of 2-3, the compound of formula (3) and glyoxylic acid undergo a nucleophilic addition-dehydration reaction to generate an intermediate of formula (4); adjusting the pH to 5-6, adding sodium cyanoborohydride, which selectively reduces the C=N double bond to generate a compound of formula (5); Under a protective gas atmosphere, LiAlH4 is placed in anhydrous ether, and then a THF solution of the compound of formula (5) is added. LiAlH4 reduces the carboxyl group to a hydroxymethyl group to prepare the compound of formula (6); The synthetic route is as follows: ； Wherein, R is hydroxyl or methoxy.

3. The flame retardant finishing method for cotton fabric according to claim 2, characterized in that: The molar ratio of the compound of formula (1) to acrylamide is 1:1, the mass concentration of the sodium methoxide methanol solution is 27%~31%, the amount ratio of the sodium methoxide methanol solution to acrylamide is 13mL~14mL:1mol, the temperature of the addition reaction is room temperature, and the time is 2h~3h.

4. The flame retardant finishing method for cotton fabric according to claim 2, characterized in that: The molar ratio of the compound of formula (3) to glyoxylic acid is 2:3~4, and the reaction temperature is 3°C~5°C during the nucleophilic addition-dehydration reaction. When sodium cyanoborohydride selectively reduces the C=N double bond, the reaction temperature is 5°C~10°C, and the molar ratio of sodium cyanoborohydride to the compound of formula (3) is 1:

1.

5. The flame retardant finishing method for cotton fabric according to claim 2, characterized in that: The mass ratio of LiAlH4 to the compound of formula (5) is 1:7~9, and the reaction is carried out at room temperature for 2h~2.5h.

6. The flame retardant finishing method for cotton fabric according to claim 1, characterized in that: In the flame retardant finishing liquid, the mass concentration of the flame retardant is 30%~50%, the mass ratio of the flame retardant to the carboxyl acid catalyst is 6.25:1, the mass concentration of the penetrant is 1%~3%, and the temperature of the flame retardant finishing liquid is 10℃~35℃.

7. The flame retardant finishing method for cotton fabric according to claim 1, characterized in that: During padding, the liquid rolling rate is 70%~75%, the pre-baking temperature is 90℃~125℃, the pre-baking time is 30s~170s, and the moisture content is retained after pre-baking at 5%~15%.

8. The flame retardant finishing method for cotton fabric according to claim 1, characterized in that: The baking temperature is 150℃~190℃, and the time is 150s~210s.

9. The flame retardant finishing method for cotton fabric according to claim 1, characterized in that: When the cotton fabric is woven, the washing steps are as follows: soap washing in the first to fourth tanks at 75°C to 85°C, wherein the first to fourth tanks contain soda ash, hydrogen peroxide and soap powder, and rolling drying; soap washing in the fifth to eighth tanks at 60°C to 70°C, wherein the fifth to eighth tanks independently contain sodium metabisulfite or sodium bisulfite and soap powder, and rolling drying; and then rinsing with running water in the ninth to tenth tanks at 25-35°C and rolling drying.

10. The flame retardant finishing method for cotton fabric according to claim 1, characterized in that: When the cotton fabric is a knitted fabric, the washing steps are as follows: first, soap wash in a solution containing soda ash, hydrogen peroxide and soap powder at 50℃~60℃ for 5min~15min, drain the sewage, then wash in a solution containing sodium metabisulfite or sodium bisulfite and soap powder at 50℃~60℃ for 5min~15min, spin dry, and finally rinse with running water at 25℃~35℃ on a splay machine for 1min~2min and squeeze dry.

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