Method for preparing durable flame-retardant cotton fabric through double processes

Abstract

According to the double-process flame-retardant finishing method for the cotton fabric, a'rolling and baking process' and a'coating process' are combined, and the cotton fabric is endowed with durability and flame retardance. The cotton fabric treated by the method disclosed by the invention still has a good flame-retardant effect after being washed at high temperature for 50 hours, so that the cotton fabric can be combusted vertically without afterflame, and the smoldering time is lt; 5 s, the damaged length lt; and the requirement of 10cm is met.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant cotton fabrics, and particularly relates to a method for preparing durable flame retardant cotton fabrics through double-process flame retardant finishing of cotton fabrics. Background Art

[0002] Cotton fabric is widely used because of its good softness, comfort, air permeability and moisture permeability, and its wide source and renewable nature. It has a large output, which makes it occupy an important position in the textile industry. However, the only drawback is that cotton fabric is a very flammable material, and its limiting oxygen index (LOI) is only about 18%. Therefore, the flame retardant finishing of cotton fabric has become the focus of researchers. The main component of cotton fiber is cellulose, with a cellulose content of up to 94%. Cellulose is a macromolecular polysaccharide composed of multiple β-D-glucose connected by 1,4-glycosidic bonds. The molecular formula is (C6H 10 O5) n , with cellobiose as the repeating unit structure, the degree of polymerization n of cotton fiber is generally above 2000. The specific structure of cotton fiber is as follows Figure 1 As shown in the figure. From the molecular structure of cellulose, it can be seen that the secondary hydroxyl groups at C2 and C3 and the primary hydroxyl group at C6 on each sugar unit in the cellulose molecule have high activity, especially the primary hydroxyl group at C6 has less steric hindrance than the secondary hydroxyl groups at C2 and C3, and has higher reaction activity and reaction capacity than the secondary hydroxyl groups at C2 and C3. The hydroxyl groups can be used to undergo many derivatization reactions, such as esterification, etherification, oxidation and graft copolymerization.

[0003]

[0004] Common flame retardant finishing agents for cotton fabrics include N-hydroxymethyl-3-dimethoxyphosphoryl propionamide flame retardants (trade name Pyrovatex CP) designed and synthesized by Swiss Ciba Fine Chemicals and Proban cotton durable flame retardants developed by British Aowei Company. The main ingredients are organic phosphonates, such as tetramethylol flame retardants (THPC or THPOH). Pyrovatex CP is a reactive flame retardant with a molecular structure of N-hydroxymethyl-3-dimethoxyphosphoryl propionamide. The molecule contains a highly reactive N-CH2-OH group, which can preferentially react with the primary alcohol hydroxyl group at the C6 position in cotton cellulose under high temperature conditions to form an ether bond, which is grafted onto the molecular structure of cotton fabrics in the form of covalent bonds, giving cotton fabrics durable flame retardancy. Since there is only one N-CH2-OH group in the molecular structure of Pyrovatex CP, in order to increase the grafting rate of flame retardant and cotton fabric, crosslinking agents such as melamine (MA), trimethylol melamine (TMM), hexamethylol melamine (HMMM) are usually added to the system to jointly improve the durability of flame retardant cotton fabric. Studies have shown that the limiting oxygen index (LOI) of cotton fabric treated with Pyrovatex CP can reach more than 30%, and the LOI of the finished cotton fabric is only more than 26% after 50 home machine washings. The flame retardant performance of the cotton fabric after washing has a significant decline, which is also a defect in the application process, and it cannot be completely durable and flame retardant.

[0005] The Chinese patent with publication number CN 112796105 A discloses a production process of pure cotton CP flame-retardant fabrics, using CP flame retardant to prepare flame-retardant finishing liquid, and using a rolling baking process alone to perform flame-retardant finishing on cotton fabrics. The inventor also used CP flame retardant to perform a rolling baking process on cotton fabrics, and then washed them with 5g / L Na2CO3 at 60°C for 1h, washed them with hot water to remove impurities and residual Na2CO3 on the surface of FR1-C cotton fabrics, and then washed them with 2% strong detergent at 60°C for 50h, and finally washed them with hot water to remove the residues on the surface of the flame-retardant treated cotton fabrics, and dried them to obtain flame-retardant cotton fabrics. After the vertical burning test, the no afterburning requirement could not be met, and the flame-retardant requirement was not met. Based on this, the original process was optimized, and a dual flame-retardant process was selected to prepare durable flame-retardant cotton fabrics. The present invention has certain innovations in method selection. In addition, it also has certain innovations in the compounding of flame retardants in the coating process. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for flame retardant finishing of cotton fabrics by dual processes, which combines the "rolling baking process" with the "coating process" to give the cotton fabrics durable flame retardancy. The cotton fabrics treated by the method of the present invention still have good flame retardant effects after 50 hours of high temperature washing, and meet the requirements of vertical combustion without after-flaming, smoldering time <5s, and damaged length <10cm.

[0007] The present invention adopts the following technical solutions:

[0008] A method for preparing a durable flame-retardant cotton fabric comprises a pad baking step, a coating step, an alkali washing step and a washing step:

[0009] The rolling and baking step comprises:

[0010] The flame retardant finishing liquid is prepared by a two-immersion and two-rolling soaking process, wherein the two-immersion and two-rolling soaking process comprises placing the cotton fabric in the flame retardant finishing liquid for soaking, and then rolling it once after it is completely soaked, and then soaking it once again, and then rolling it once again; the treated cotton fabric is dried at 80°C-110°C, and then baked at a high temperature of 150°C-180°C for 2min-5min to obtain a one-step flame retardant cotton fabric FR1-C cotton fabric;

[0011] Preferably, the flame retardant of the flame retardant liquid is Pyrovatex CP;

[0012] Preferably, the rolling rate of the double dipping and double rolling method is 100%-120%;

[0013] Preferably, the weight gain rate of the FR1-C cotton fabric is 30%-45%;

[0014] The coating step comprises:

[0015] After the compound flame retardant is stirred evenly, it is scraped on the FR1-C cotton fabric, and after drying, a two-step flame retardant cotton fabric FR2-C cotton fabric is obtained, wherein the compound flame retardant is an organic-inorganic flame retardant compound;

[0016] Preferably, the scraping is single-sided scraping;

[0017] Preferably, the composite flame retardant is based on polyurethane resin, and its organic components are selected from: diethyl phosphinate, melamine polyphosphate, melamine phosphate, melamine cyanurate (MCA), ammonium polyphosphate (APP), melamine (MA), piperazine pyrophosphate (PPAP); the inorganic components are selected from: aluminum hydroxide, magnesium hydroxide, magnesium sulfate, decabromodiphenylethane, antimony trioxide, zinc borate (ZB); the diethyl phosphinate is selected from: aluminum diethyl phosphinate (ADP), zinc diethyl phosphinate (ZDP);

[0018] The alkali washing step comprises:

[0019] The FR2-C cotton fabric is washed in hot alkali solution for at least 1 hour, and then washed with hot water for at least 3 times to remove impurities and residues on the surface of the FR2-C cotton fabric, and dried at above 100° C. until the mass is reduced by 25%-30%.

[0020] Preferably, the alkali solution is a 5 g / L Na2CO3 solution;

[0021] Preferably, the temperature of the hot alkali solution is 60°C.

[0022] The washing step comprises:

[0023] The FR2-C cotton fabric after alkali washing is continuously washed in hot detergent for 40-60 hours, and then washed with hot water for at least 3 times to remove the residue on the surface of the cotton fabric, and dried above 105°C until the mass is reduced by 5%-10%, thereby obtaining a durable flame retardant cotton fabric. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a vertical combustion test diagram of Comparative Example 1;

[0025] Figure 2 This is a diagram of the vertical combustion experiment of Example 1. DETAILED DESCRIPTION

[0026] Example 1

[0027] Prepare a flame retardant finishing liquid of Pyrovatex CP, the specific formula is Pyrovatex CP flame retardant 350g / L~400g / L, crosslinking agent 60g / L~80g / L, softener 20g / L~30g / L, 85wt% phosphoric acid 18g / L~20g / L, penetrant 1g / L, and the rest is water. Stir the flame retardant finishing liquid evenly and perform two-immersion and two-rolling treatment. The specific method is to fully immerse the cotton fabric in the flame retardant finishing liquid, and after it is completely soaked, perform a rolling, and then immerse again, and then press and roll once, that is, complete the two-immersion and two-rolling, and prepare flame retardant FR1-C cotton fabric. ADP and melamine are compounded in a ratio of 4:2, added to the polyurethane resin substrate, mechanically stirred evenly, and then coated on the surface of FR1-C cotton fabric on one side, and dried to obtain FR2-C cotton fabric. Then, the FR2-C cotton fabric was washed in 5g / L Na2CO3 at 60℃ for 1h, washed with hot water three times, and dried in a blast drying oven at 105℃ for 1h; then it was washed in a 2% strong detergent solution at 60℃ for 50h, washed with hot water three times, and dried at 105℃, thus obtaining a durable flame-retardant cotton fabric that can withstand 50h washing. The vertical burning test showed that there was no afterflaming time, the smoldering time was <5s, and the damaged length was <10cm. See Table 1 for specific data.

[0028] Example 2

[0029] The flame retardant finishing liquid of Pyrovatex CP was prepared with reference to Example 1, and flame retardant FR1-C cotton fabric was prepared after two dipping and two rolling. ADP and aluminum hydroxide were compounded in a ratio of 4:2, added to the polyurethane resin substrate, mechanically stirred evenly, and coated on one side on the surface of FR1-C cotton fabric, and dried to obtain FR2-C cotton fabric. Subsequently, the FR2-C cotton fabric was washed in 5g / L Na2CO3 at 60°C for 1h, washed with hot water three times, and placed in a blast drying oven at 105°C for 1h; then it was placed in a 2% strong detergent solution at 60°C for continuous washing for 50h, washed with hot water three times, and dried at 105°C, to obtain a durable flame retardant cotton fabric that can withstand 50h washing. According to the vertical burning test, the afterflaming time is 0, the smoldering time is <5s, and the damaged length is <10cm.

[0030] Example 3

[0031] The flame retardant finishing liquid of Pyrovatex CP was prepared with reference to Example 1, and flame retardant FR1-C cotton fabric was prepared after two dipping and two rolling. ADP and MCA were compounded in a ratio of 4:2, added to the polyurethane resin substrate, mechanically stirred evenly, and coated on one side on the surface of FR1-C cotton fabric, and dried to obtain FR2-C cotton fabric. Subsequently, the FR2-C cotton fabric was washed in 5g / L Na2CO3 at 60°C for 1h, washed with hot water three times, and placed in a blast drying oven at 105°C for 1h; then it was placed in a 2% strong detergent solution at 60°C for continuous washing for 50h, washed with hot water three times, and dried at 105°C, to obtain a durable flame retardant cotton fabric that can withstand 50h washing. According to the vertical burning test, the afterflaming time is 0, the smoldering time is <5s, and the damaged length is <10cm.

[0032] Example 4

[0033] The flame retardant finishing liquid of Pyrovatex CP was prepared with reference to Example 1, and flame retardant FR1-C cotton fabric was prepared after two dipping and two rolling. Decabromodiphenylethane and antimony trioxide were compounded in a ratio of 4:2, added to the polyurethane resin substrate, mechanically stirred evenly, and coated on one side on the surface of FR1-C cotton fabric, and dried to obtain FR2-C cotton fabric. Subsequently, the FR2-C cotton fabric was washed in 5g / L Na2CO3 at 60°C for 1h, washed with hot water three times, and placed in a blast drying oven at 105°C for 1h; then placed in a 2% strong detergent solution at 60°C for continuous washing for 50h, washed with hot water three times, and dried at 105°C, to obtain a durable flame retardant cotton fabric that can withstand 50h washing. According to the vertical burning test, the afterburning time is 0 and the damaged length is <10cm.

[0034] Comparative Example 1

[0035] The flame retardant finishing liquid of Pyrovatex CP was prepared with reference to Example 1, and flame retardant FR1-C cotton fabric was prepared after two dipping and two rolling. After alkali washing with 5g / L Na2CO3 at 60℃ for 1h, hot water washing three times, and drying at 105℃ in a blast drying oven for 1h; then it was placed in a 2% strong detergent solution at 60℃ for continuous washing for 50h, hot water washing three times, and drying at 105℃ to obtain a one-step flame retardant treated cotton fabric. According to the vertical burning test, there is after-flaming and smoldering time, and the damaged length is >10cm, which does not meet the flame retardant requirements. Specific data are shown in Table 1.

[0036] Table 1:

[0037]

Claims

1. A method for preparing a durable flame-retardant cotton fabric, comprising a pad baking step, a coating step, an alkali washing step and a washing step: The rolling and baking step comprises: The flame retardant finishing liquid is prepared by a two-immersion and two-rolling soaking process, wherein the two-immersion and two-rolling soaking process comprises placing the cotton fabric in the flame retardant finishing liquid for soaking, and then rolling it once after it is completely soaked, and then soaking it once again, and then rolling it once again; the treated cotton fabric is dried at 80°C-110°C, and then baked at a high temperature of 150°C-180°C for 2min-5min to obtain a one-step flame retardant cotton fabric FR1-C cotton fabric; The coating step comprises: After the compound flame retardant is stirred evenly, it is scraped on the FR1-C cotton fabric, and after drying, a two-step flame retardant cotton fabric FR2-C cotton fabric is obtained, wherein the compound flame retardant is an organic-inorganic flame retardant compound; The alkali washing step comprises: The FR2-C cotton fabric is washed in hot alkali solution for at least 1 hour, and then washed with hot water for at least 3 times to remove impurities and residues on the surface of the FR2-C cotton fabric, and dried at a temperature above 100° C. until the mass is reduced by 25% to 30%; The washing step comprises: The FR2-C cotton fabric after alkali washing is continuously washed in hot detergent for 40-60 hours, and then washed with hot water for at least 3 times to remove the residue on the surface of the cotton fabric, and dried above 105°C until the mass is reduced by 5%-10%, thereby obtaining a durable flame retardant cotton fabric.

2. The preparation method according to claim 1, characterized in that The flame retardant of the flame retardant liquid is Pyrovatex CP.

3. The preparation method according to claim 1, characterized in that: The rolling rate of the double dipping and double rolling method is 100%-120%.

4. The preparation method according to claim 1, characterized in that: The weight gain rate of the FR1-C cotton fabric is 30%-45%.

5. The preparation method according to claim 1, characterized in that: The scraping is single-sided scraping.

6. The preparation method according to claim 1, characterized in that: The composite flame retardant is based on polyurethane resin, and its organic components are selected from: diethyl phosphinate, melamine polyphosphate, melamine phosphate, melamine cyanurate, ammonium polyphosphate, melamine, and piperazine pyrophosphate; the inorganic components are selected from: aluminum hydroxide, magnesium hydroxide, magnesium sulfate, decabromodiphenylethane, antimony trioxide, and zinc borate; the diethyl phosphinate is selected from: aluminum diethyl phosphinate and zinc diethyl phosphinate.

7. The preparation method according to claim 1, characterized in that: The alkali solution is a 5g / L Na2CO3 solution.

8. The preparation method according to claim 1, characterized in that: The temperature of the hot alkali solution is 60°C.

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