Flame-retardant coating containing nitrogen and phosphorus chitosan modified polyurethane and preparation method of flame-retardant coating

Abstract

The invention relates to the technical field of polyurethane coatings, and discloses a nitrogen and phosphorus-containing chitosan modified polyurethane flame-retardant coating, compared with a pure-phase polyurethane coating, a polyurethane coating using a triazolyl spirocyclophosphoryl chitosan modifier as a modifier has better flame retardance, chitosan is added into the polyurethane coating, and the flame retardance of the polyurethane coating is improved. Chitosan can be used as a carbon source to generate a synergistic effect with a triazolyl nitrogen-containing flame retardant and a spirophosphoryl phosphorus-containing flame retardant, so that the flame retardance of the polyurethane coating is further improved, isocyanate groups in the flame-retardant polyurethane can react with generated substances, a net structure with a high crosslinking degree is generated, and the flame retardance of the polyurethane coating is improved. And matrix substances can be protected, escape of small-molecule volatile substances can be reduced, the smoke generation amount is reduced, and the carbon residue rate is increased.

Description

Technical Field

[0001] The invention relates to the technical field of polyurethane coatings, in particular to a flame retardant coating of nitrogen-phosphorus-containing chitosan-modified polyurethane and a preparation method thereof. Background Art

[0002] As one of the most popular natural textiles, cotton fabric has been widely used in our daily life and has occupied a vast market of textiles. However, despite its many benefits, cotton fabric with an extremely low Limiting Oxygen Index (LOI) of 17%-19% is highly flammable and may cause serious fire hazards. In recent years, the hazards caused by textile combustion have attracted worldwide attention. People are paying more and more attention to improving the flame retardancy of cotton fabrics. Waterborne polyurethane has been widely used in the textile and coating industries.

[0003] The flame retardant modification of urethane coatings has become the focus of current modification, such as the Chinese patent publication number CN107955515B, which discloses flame retardant, light-resistant and low-VOC polyurethane coatings, and the Chinese patent publication number CN106947380A, which discloses an environmentally friendly flame retardant and anti-corrosion coating based on polyurethane. Although both improve the flame retardancy of polyurethane coatings, they still have problems such as high addition amount and poor flame retardant effect. Chitosan is a natural polysaccharide composed of amino-containing 2-deoxyglucan. It has the advantages of non-toxicity, biodegradability and low cost. It is widely used in biotechnology, bio Medical engineering, wastewater treatment, food and cosmetics processing, since its discovery, chitosan is a good green carbonizer. It is reported that chitosan derivatives have been directly used as carbonizers in flame-retardant composite materials. In addition, there are a large number of hydroxyl and amino groups in its structure, which increases the possibility of modification. Halogen-free flame retardants have become one of the most important flame retardants at present. Among them, phosphorus-containing flame retardants have significant advantages, including high flame retardant efficiency, less toxic byproducts produced in flames, and less damage to the environment. Nitrogen compounds can be used as flame retardants alone or as additives to other flame retardant elements (such as phosphorus) to improve their activity.

[0004] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a flame retardant coating of nitrogen-phosphorus-containing chitosan-modified polyurethane and a preparation method thereof, which solves the problem of poor flame retardancy of polyurethane coatings.

[0005] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a flame retardant coating of nitrogen-phosphorus chitosan-modified polyurethane, wherein the preparation method of the flame retardant coating of nitrogen-phosphorus chitosan-modified polyurethane comprises the following steps: (1) Dissolving chitosan and glacial acetic acid in deionized water, then adding the solution to a chloroform solution containing spirocyclic phosphoryl dichloride, stirring evenly, and then adding a catalyst triethylamine (TEA) to react. After the reaction is completed, removing the solvent using a rotary evaporator, washing with ethanol, and obtaining chlorospirocyclic phosphoryl chitosan; (2) dissolving 3-amino-1,2,4-triazole in tetrahydrofuran solvent, stirring evenly, then adding acid-binding agent triethylamine (TEA), continuing stirring and adding glacial acetic acid, deionized water and chloro-spirocyclic phospho-chitosan, heating to the reaction temperature under a nitrogen atmosphere to react, after the reaction is completed, using a rotary evaporator to remove the solvent, washing with deionized water to obtain triazole-based spirocyclic phospho-chitosan; (3) Dissolve waterborne polyurethane, triazole spirocyclic phosphoyl chitosan, 0.8-2% by mass of defoaming agent polyether modified polysiloxane, and 1-3% by mass of leveling agent polydimethylsiloxane in deionized water, and then disperse them in an ultra-speed mixer. Then, add curing agent hexamethylene diisocyanate, stir evenly, and obtain a flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane.

[0006] Preferably, in step (1), the mass ratio of chitosan, glacial acetic acid, deionized water, spirocyclic phosphoryl dichloride, chloroform and triethylamine is 100:8-20:800-2000:50-120:1500-4000:35-80.

[0007] Preferably, in step (1), the reaction temperature is 50-80° C. and the reaction time is 12-36 h.

[0008] Preferably, in step (2), the mass ratio of 3-amino-1,2,4-triazole, tetrahydrofuran, triethylamine, glacial acetic acid, deionized water, and chlorospirophosphoyl chitosan is 25-60:1800-6000:35-80:3-8:300-800:100.

[0009] Preferably, in step (2), the reaction temperature is 60-100° C. and the reaction time is 8-20 h.

[0010] Preferably, in step (3), the mass ratio between the aqueous polyurethane and the triazole-based spirocyclic phosphoinosyl chitosan is 100:6-15.

[0011] 3. Beneficial technical effects Compared with the prior art, the present invention has the following experimental principles and beneficial technical effects: The flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane comprises the following steps: firstly, under the catalytic action of triethylamine, the amino group of chitosan is subjected to substitution reaction with the phosphorus-chlorine bond in spirocyclic phosphoryl dichloride to obtain chloro-spirocyclic phosphoryl chitosan; then, triethylamine is used as an acid-binding agent to further react the chloro-spirocyclic phosphoryl chitosan with the amino group of 3-amino-1,2,4-trinitrogen to obtain triazolyl spirocyclic phosphoryl chitosan; finally, polyurethane is used as a matrix and the triazolyl spirocyclic phosphoryl chitosan modifier is used to prepare the flame retardant chitosan modified polyurethane coating through mechanical blending.

[0012] The flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane has better flame retardancy than pure phase polyurethane coating. Chitosan is added to the polyurethane coating, and chitosan can be used as a carbon source. Chitosan contains a large number of amino and hydroxyl structures, and the molecular skeleton contains rich carbon sources. When heated, the carbon in the molecular skeleton will be converted into a carbon protective layer, and a large amount of non-flammable gases such as carbon dioxide and nitrogen will be generated, and oxygen and other combustion-supporting substances in the air will be diluted. In addition, the triazole nitrogen-containing flame retardant and the spirocyclic phosphorus-containing flame retardant grafted on the chitosan can further increase the flame retardancy of the polyurethane coating, wherein the spirocyclic phosphorus-containing flame retardant decomposes into organic acid films such as phosphoric acid when heated, promotes chitosan to carbonize, and adheres to the surface of the generated protective carbon layer. The surface of the polyurethane coating forms a non-volatile protective film, isolating the combustible substrate from the contact with the combustion-supporting substances in the air, reducing the spread of heat, and increasing the residual rate of the carbon layer. When the triazole-based nitrogen-containing flame retardant decomposes under heat, it not only produces a large amount of non-combustible gases such as ammonia, nitrogen, and water vapor, which dilute the oxygen and other substances in the air, but also conducts a large amount of heat to reduce the temperature of the surface of the body, further increasing the flammability of the polyurethane coating. In addition, the nitrogen-phosphorus flame retardants can produce a synergistic effect to form a PNN bond and a paste-like protective layer of coked carbon, which covers the surface of the body and increases its flame retardancy. The isocyanate groups in the polyurethane can react with the generated substances and generate a highly cross-linked network structure, which can not only protect the matrix substance, but also reduce the escape of small molecular volatile substances, reduce the amount of smoke generated, and increase the residual carbon rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is the reaction formula of chitosan and spirocyclic phosphoryl dichloride; Figure 2 It is the reaction formula of 3-amino-1,2,4-triazole and chlorospirocyclophosphyl chitosan. DETAILED DESCRIPTION

[0014] To achieve the above object, the present invention provides the following specific implementation methods and examples: A flame retardant coating of nitrogen-phosphorus chitosan-modified polyurethane, the preparation method of which comprises the following steps: (1) Dissolve chitosan and glacial acetic acid in deionized water at a mass ratio of 100:8-20:800-2000:50-120:1500-4000:35-80, then add to a chloroform solution containing spirocyclic phosphoryl dichloride, stir evenly, then add catalyst triethylamine (TEA), react at 50-80°C for 12-36h, after the reaction is completed, remove the solvent using a rotary evaporator, remove ethanol and wash to obtain chlorospirocyclic phosphoryl chitosan; (2) Dissolve 3-amino-1,2,4-triazole in tetrahydrofuran solvent at a mass ratio of 25-60:1800-6000:35-80:3-8:300-800:100, stir evenly, then add acid-binding agent triethylamine (TEA), continue stirring and add glacial acetic acid, deionized water and chloro-spirocyclic phospho-chitosan, heat to 60-100°C in a nitrogen atmosphere, react for 8-20 hours, after the reaction is completed, use a rotary evaporator to remove the solvent, wash with deionized water, and obtain triazole-based spirocyclic phospho-chitosan; (3) According to the mass ratio of 100:6-15, waterborne polyurethane, triazole spirocyclic phosphoyl chitosan, 0.8-2% by mass of defoaming agent polyether modified polysiloxane, and 1-3% by mass of leveling agent polydimethylsiloxane are dissolved in deionized water, and then dispersed in an ultra-speed mixer, and then a curing agent hexamethylene diisocyanate is added, and after stirring evenly, a flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane is obtained.

[0015] Example 1

[0016] (1) 4 g of chitosan and 0.32 g of glacial acetic acid were dissolved in 32 g of deionized water, and then 2 g of spirocyclic phosphoryl dichloride and 60 g of chloroform solution were added. After stirring, 1.4 g of catalyst triethylamine (TEA) was added and reacted at 50 °C for 12 h. After the reaction was completed, the solvent was removed by a rotary evaporator, and the mixture was washed with ethanol to obtain chlorospirocyclic phosphoryl chitosan; (2) Dissolve 0.625 g of 3-amino-1,2,4-triazole in 45 g of tetrahydrofuran solvent, stir evenly, then add 0.875 g of acid-binding agent triethylamine (TEA), continue stirring and add 0.075 g of glacial acetic acid, 7.5 g of deionized water and 2.5 g of chloro-spirocyclic phospho-chitosan, heat to 60 ° C in a nitrogen atmosphere and react for 8 h. After the reaction is completed, use a rotary evaporator to remove the solvent, wash with deionized water to obtain triazole-based spirocyclic phospho-chitosan; (3) 5 g of waterborne polyurethane, 0.3 g of triazole spirocyclic phosphoyl chitosan, 0.8% by mass of defoaming agent polyether modified polysiloxane, and 1% by mass of leveling agent polydimethylsiloxane were dissolved in deionized water and then dispersed in an ultra-speed mixer. Then, a curing agent hexamethylene diisocyanate was added and stirred evenly to obtain a flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane.

[0017] Example 2

[0018] (1) Dissolve 4 g of chitosan and 0.4 g of glacial acetic acid in 40 g of deionized water, then add 2.8 g of spirocyclic phosphoryl dichloride and 80 g of chloroform solution, stir evenly, then add 1.8 g of catalyst triethylamine (TEA), react at 6 ° C for 18 h, after the reaction is completed, use a rotary evaporator to remove the solvent, remove ethanol and wash to obtain chlorospirocyclic phosphoryl chitosan; (2) Dissolve 0.8 g of 3-amino-1,2,4-triazole in 60 g of tetrahydrofuran solvent, stir evenly, then add 1 g of acid-binding agent triethylamine (TEA), continue stirring and add 0.01 g of glacial acetic acid, 10 g of deionized water and 2.5 g of chloro-spirocyclic phospho-chitosan, heat to 70 ° C in a nitrogen atmosphere for 10 h, after the reaction is completed, use a rotary evaporator to remove the solvent, wash with deionized water to obtain triazole-based spirocyclic phospho-chitosan; (3) 5 g of waterborne polyurethane, 0.35 g of triazole spirocyclic phosphoyl chitosan, 1% by mass of defoaming agent polyether modified polysiloxane, and 1.5% by mass of leveling agent polydimethylsiloxane were dissolved in deionized water and then dispersed in an ultra-speed mixer. Then, a curing agent hexamethylene diisocyanate was added and stirred evenly to obtain a flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane.

[0019] Example 3

[0020] (1) Dissolve 4 g of chitosan and 0.5 g of glacial acetic acid in 60 g of deionized water, then add 3.2 g of spirocyclic phosphoryl dichloride and 100 g of chloroform solution, stir evenly, then add 2.4 g of catalyst triethylamine (TEA), react at 75 ° C for 24 h, after the reaction is completed, use a rotary evaporator to remove the solvent, remove ethanol and wash to obtain chlorospirocyclic phosphoryl chitosan; (2) Dissolve 1 g of 3-amino-1,2,4-triazole in 100 g of tetrahydrofuran solvent, stir evenly, then add 0.875-2 g of acid-binding agent triethylamine (TEA), continue stirring and add 0.12 g of glacial acetic acid, 12 g of deionized water and 2.5 g of chloro-spirocyclic phospho-chitosan, heat to 80 ° C in a nitrogen atmosphere and react for 14 h. After the reaction is completed, use a rotary evaporator to remove the solvent, wash with deionized water, and obtain triazole-based spirocyclic phospho-chitosan; (3) 5 g of waterborne polyurethane, 0.55 g of triazole spirocyclic phosphoyl chitosan, 1.4% by mass of defoaming agent polyether modified polysiloxane, and 2% by mass of leveling agent polydimethylsiloxane were dissolved in deionized water and then dispersed in an ultra-speed mixer. Then, a curing agent hexamethylene diisocyanate was added and stirred evenly to obtain a flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane.

[0021] Example 4

[0022] (1) Dissolve 4 g of chitosan and 0.64 g of glacial acetic acid in 60 g of deionized water, then add 3.6 g of spirocyclic phosphoryl dichloride and 140 g of chloroform solution, stir evenly, then add 2.4 g of catalyst triethylamine (TEA), react at 65 ° C for 24 h, after the reaction is completed, use a rotary evaporator to remove the solvent, remove ethanol and wash to obtain chlorospirocyclic phosphoryl chitosan; (2) Dissolve 1 g of 3-amino-1,2,4-triazole in 100 g of tetrahydrofuran solvent, stir evenly, then add 1.4 g of acid-binding agent triethylamine (TEA), continue stirring and add 0.014 g of glacial acetic acid, 16 g of deionized water and 2.5 g of chloro-spirocyclic phospho-chitosan, heat to 90 °C in a nitrogen atmosphere and react for 18 h. After the reaction is completed, use a rotary evaporator to remove the solvent, wash with deionized water, and obtain triazole-based spirocyclic phospho-chitosan; (3) 5 g of waterborne polyurethane, 0.65 g of triazole spirocyclic phosphoyl chitosan, 1.8% by mass of defoaming agent polyether modified polysiloxane, and 2.6% by mass of leveling agent polydimethylsiloxane were dissolved in deionized water and then dispersed in an ultra-speed mixer. Then, a curing agent hexamethylene diisocyanate was added and stirred evenly to obtain a flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane.

[0023] Example 5

[0024] (1) Dissolve 4 g of chitosan and 0.8 g of glacial acetic acid in 80 g of deionized water, then add 4.8 g of spirocyclic phosphoryl dichloride and 160 g of chloroform solution, stir evenly, then add 3.2 g of catalyst triethylamine (TEA), react at 80 ° C for 36 h, after the reaction is completed, use a rotary evaporator to remove the solvent, remove ethanol and wash to obtain chlorospirocyclic phosphoryl chitosan; (2) Dissolve 1.5 g of 3-amino-1,2,4-triazole in 150 g of tetrahydrofuran solvent, stir evenly, then add 2 g of acid-binding agent triethylamine (TEA), continue stirring and add 0.2 g of glacial acetic acid, 20 g of deionized water and 2.5 g of chloro-spirocyclic phosphoyl chitosan, heat to 100 ° C in a nitrogen atmosphere and react for 20 h. After the reaction is completed, use a rotary evaporator to remove the solvent, wash with deionized water, and obtain triazole-based spirocyclic phosphoyl chitosan; (3) 5 g of waterborne polyurethane, 0.75 g of triazole spirocyclic phosphoyl chitosan, 2% by mass of defoaming agent polyether modified polysiloxane, and 3% by mass of leveling agent polydimethylsiloxane were dissolved in deionized water and then dispersed in an ultra-speed mixer. Then, a curing agent hexamethylene diisocyanate was added and stirred evenly to obtain a flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane.

[0025] Comparative Example 1 (1) Dissolve 4 g of chitosan and 0.4 g of glacial acetic acid in 50 g of deionized water, then add 3 g of spirocyclic phosphoryl dichloride and 80 g of chloroform solution, stir evenly, then add 2.8 g of catalyst triethylamine (TEA), react at 60 ° C for 36 h, after the reaction is completed, use a rotary evaporator to remove the solvent, remove ethanol and wash to obtain chlorospirocyclic phosphoryl chitosan; (2) 5 g of waterborne polyurethane, 0.5 g of chlorospirocyclic phosphoyl chitosan, 1% by mass of defoaming agent polyether modified polysiloxane, and 1.5% by mass of leveling agent polydimethylsiloxane were dissolved in deionized water and then dispersed in an ultra-speed mixer. Then, a curing agent hexamethylene diisocyanate was added and stirred evenly to obtain a flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane.

[0026] The limiting oxygen index (LOI) of the flame retardant coating of nitrogen and phosphorus chitosan modified polyurethane was tested in accordance with the national standard GB14907-2018.

[0027]

[0028] The carbon residue rate and total smoke generation (TSR) of the flame retardant coating of nitrogen and phosphorus chitosan modified polyurethane were tested in accordance with the national standard GB14907-2018.

[0029]

Claims

1. A flame retardant coating of nitrogen-phosphorus chitosan-modified polyurethane, characterized in that: The preparation method of the flame retardant coating of the nitrogen-phosphorus chitosan modified polyurethane comprises the following steps: (1) dissolving chitosan and glacial acetic acid in deionized water, then adding the mixture into a chloroform solution containing spirocyclic phosphoryl dichloride, stirring evenly, and then adding a catalyst, triethylamine, to react. After the reaction is completed, chlorospirocyclic phosphoryl chitosan is obtained; (2) dissolving 3-amino-1,2,4-triazole in tetrahydrofuran solvent, stirring evenly, then adding acid-binding agent triethylamine, continuing stirring and adding glacial acetic acid, deionized water and chloro-spirocyclic phospho-chitosan, heating to the reaction temperature under a nitrogen atmosphere to react, and after the reaction is completed, obtaining triazole-based spirocyclic phospho-chitosan; (3) Dissolve waterborne polyurethane, triazole spirocyclic phosphoyl chitosan, 0.8-2% by mass of defoaming agent polyether modified polysiloxane, and 1-3% by mass of leveling agent polydimethylsiloxane in deionized water, and then disperse them in an ultra-speed mixer. Then, add curing agent hexamethylene diisocyanate, stir evenly, and obtain a flame retardant coating of nitrogen-phosphorus chitosan modified polyurethane.

2. The flame retardant coating of a nitrogen-phosphorus chitosan-modified polyurethane according to claim 1, characterized in that: In the step (1), the mass ratio of chitosan, glacial acetic acid, deionized water, spirocyclic phosphoryl dichloride, chloroform and triethylamine is 100:8-20:800-2000:50-120:1500-4000:35-80.

3. The flame retardant coating of a nitrogen-phosphorus chitosan-modified polyurethane according to claim 1, characterized in that: In the step (1), the reaction temperature is 50-80°C and the reaction time is 12-36h.

4. The flame retardant coating of a nitrogen-phosphorus chitosan-modified polyurethane according to claim 1, characterized in that: In the step (2), the mass ratio of 3-amino-1,2,4-triazole, tetrahydrofuran, triethylamine, glacial acetic acid, deionized water, and chlorospirophosphoyl chitosan is 25-60:1800-6000:35-80:3-8:300-800:

100.

5. The flame retardant coating of nitrogen-phosphorus chitosan-modified polyurethane according to claim 1, characterized in that: In the step (2), the reaction temperature is 60-100° C. and the reaction time is 8-20 h.

6. The flame retardant coating of nitrogen-phosphorus chitosan-modified polyurethane according to claim 1, characterized in that: In the step (3), the mass ratio between the aqueous polyurethane and the triazole-based spirocyclic phosphoyl chitosan is 100:6-15.

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