Thermoplastic polyurethane fireproof material and preparation method thereof

Abstract

The invention relates to the technical field of fireproof materials, and discloses a thermoplastic polyurethane fireproof material and a preparation method thereof.The preparation method comprises the steps that 2-chloro-5, 5-dimethyl-1, 3, 2-dioxophosphoryl-2-oxide and hydroxyethyl acrylate are subjected to a substitution reaction under catalysis of triethylamine, and phosphorus-containing acrylate is obtained; the preparation method comprises the following steps: carrying out Mannich reaction on 4, 4 '-(1, 2, 4, 5-tetrazine-3, 6-diyl) diphenylamine, paraformaldehyde and o-allylphenol to obtain divinyl tetrazine benzoxazine; the preparation method comprises the following steps: carrying out a reaction on phosphorus-containing acrylate and divinyl tetrazine benzoxazine under the initiation copolymerization of ammonium persulfate to obtain the poly (phosphate-tetrazine benzoxazine) flame retardant. And finally, blending the poly (phosphate-tetrazine benzoxazine) flame retardant with polyurethane, and carrying out hot pressing to obtain the thermoplastic polyurethane fireproof material. The flame retardant prepared by the preparation method disclosed by the invention is applied to polyurethane and has excellent flame retardant property.

Description

Technical Field

[0001] The present invention relates to the technical field of fireproof materials, and specifically to a thermoplastic polyurethane fireproof material and a preparation method thereof. Background Art

[0002] Polyurethane molecules have repeating urethane segments and have good mechanical properties, weather resistance and other properties, and are widely used in the fields of leather, finishing, etc. Thermoplastic polyurethane has excellent elasticity, toughness, aging resistance and other properties, and is widely used in the fields of shoe materials, sports equipment, leather materials, toys, etc. However, its flame retardancy is poor. Benzoxazine is a new type of thermosetting resin, which refers to the general term of compounds containing N and O six-membered oxazine rings in the structure, and has the characteristics of high modulus, high strength, good heat resistance, low water absorption, etc.

[0003] Flame retardants are divided into organic flame retardants and inorganic flame retardants. The compatibility of inorganic flame retardants with polyurethane is poor. Among the organic flame retardants, nitrogen-phosphorus flame retardants are a widely used type of flame retardant, which are widely used in the fields of plastics, rubbers, textiles, coatings, etc. For example, the patent with the authorization announcement number CN113637151B discloses a preparation method of polybenzoxazine carbonate. Applying it to polyurethane can improve the mechanical properties and thermal stability of polyurethane materials, but its flame retardancy is poor. Summary of the Invention

[0004] (1) Technical Problems to be Solved The present invention aims to provide a thermoplastic polyurethane fireproof material and a preparation method thereof. Based on the traditional nitrogen-phosphorus flame retardant, a flame retardant is obtained through the Mannich reaction, which not only contains nitrogen-phosphorus flame retardant but also has benzoxazine with strong thermal stability. Then, the prepared poly(phosphate-tetrazine benzoxazine) flame retardant is applied to polyurethane materials, and the prepared polyurethane materials have excellent flame retardancy.

[0005] (2) Technical Solutions A preparation method of a thermoplastic polyurethane fireproof material, and the preparation method is as follows: (1) Under nitrogen conditions, add phosphorus-containing acrylate, divinyltetrazine benzoxazine, and sodium dodecylsulfonate to water, heat to 70-90 °C, add ammonium persulfate to it, stir and react for 2-6 h, cool to room temperature, filter, wash with ethanol, and dry to obtain poly(phosphate-tetrazine benzoxazine) flame retardant.

[0006] (2) Put the poly(phosphate-tetrazine benzoxazine) flame retardant and polyurethane into a Haake mixer for mixing, and then put the mixture into a hot press for pressurization and pressure holding to obtain a thermoplastic polyurethane fireproof material.

[0007] Preferably, the mass ratio of each reactant in the step (1) is: phosphorus-containing acrylate: divinyltetrazine benzoxazine: ammonium persulfate = 1: (0.7 - 1.5): (0.012 - 0.018). Preferably, the mass ratio of each reactant in the step (2) is: polyurethane: poly(phosphate - tetrazine benzoxazine) flame retardant = 100: (5 - 25).

[0008] Preferably, the temperature of the hot press in the step (2) is 170 - 190 °C, the pressure is increased to 15 - 20 MPa, and the pressure is maintained for 3 - 6 min.

[0009] Preferably, the preparation method of the phosphorus-containing acrylate in the step (1) is as follows: Under a nitrogen atmosphere, in an ice bath at 0 - 5 °C, dissolve 2-chloro-5,5-dimethyl-1,3,2-dioxaphospholane-2-oxide in dichloromethane solvent, and then add hydroxyethyl acrylate and triethylamine thereto. According to the mass ratio, 2-chloro-5,5-dimethyl-1,3,2-dioxaphospholane-2-oxide: hydroxyethyl acrylate: triethylamine = 1: 0.5 - 0.8: 0.6 - 0.75. React at a temperature of 30 - 50 °C for 6 - 12 h, filter, concentrate the filtrate under reduced pressure, wash with ether, and dry to obtain the phosphorus-containing acrylate. The reaction equation is as follows: .

[0010] Preferably, the preparation method of the divinyltetrazine benzoxazine in the step (1) is as follows: Dissolve 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline, paraformaldehyde, and o-allylphenol in toluene solvent, carry out a reflux reaction, and distill under reduced pressure. Wash successively with sodium hydroxide solution, water, and acetone, and dry to obtain divinyltetrazine benzoxazine. The reaction equation is as follows: .

[0011] Preferably, the mass ratio of each reactant in the step is: 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline: paraformaldehyde: o-allylphenol = 1: 0.4 - 0.6: 1 - 1.15.

[0012] Preferably, the reflux reaction temperature in the step is 100 - 120 °C, and the reflux reaction time is 3 - 6 h.

[0013] (III) Beneficial technical effects 2-Chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane 2-oxide reacts with 2-hydroxyethyl acrylate under the catalysis of triethylamine to undergo a substitution reaction to obtain a phosphorus-containing acrylate; 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline, paraformaldehyde, and o-allylphenol undergo a Mannich reaction to obtain divinyltetrazine benzoxazine; the phosphorus-containing acrylate and divinyltetrazine benzoxazine are copolymerized under the initiation of ammonium persulfate to obtain a poly(phosphate-tetrazine benzoxazine) flame retardant. Finally, the poly(phosphate-tetrazine benzoxazine) flame retardant is blended with polyurethane and hot-pressed to obtain a thermoplastic polyurethane fireproof material.

[0014] Among them, the phosphorus element decomposes when heated to form metaphosphoric acid. At high temperatures, metaphosphoric acid polymerizes to form a polyphosphate vitreous body, which can not only isolate oxygen and heat on the material surface, but also phosphoric acid and metaphosphoric acid have strong dehydrating properties, which can cause the polymer to dehydrate and form carbon, forming a carbonized layer on its surface. The carbonized layer has poor thermal conductivity and isolates the transfer of heat. In addition, the nitrogen element contained therein generates a non-combustible gas when heated, which can dilute the concentration of flammable gases in the air and further achieve the flame retardant effect. The benzoxazine contained therein has a six-membered heterocycle, which can absorb more heat under heating conditions and undergo a ring-opening polymerization reaction to form a network structure similar to phenolic resin. The resulting polymer has high heat resistance. In addition, the main decomposition products of benzoxazine during combustion are non-combustible and non-toxic gases such as NH3 and CO2, which can dilute flammable gases and achieve the flame retardant effect. The nitrogen-phosphorus flame retardant and benzoxazine synergistically assist each other to jointly improve the flame retardant performance of the material. Detailed implementation mode

[0015] The following describes the production and use of the embodiments of the present invention. The embodiments of the present invention provide many suitable inventive concepts and can be widely implemented in various specific backgrounds. The specific embodiments disclosed are only used to illustrate the production and use of the present invention in a specific method and are not used to limit the scope of the present invention.

[0016] Example 1 (1) Under a nitrogen atmosphere and in an ice bath at 0 °C, 3 g of 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane 2-oxide is dissolved in dichloromethane solvent, and 2 g of 2-hydroxyethyl acrylate and 2 g of triethylamine are added thereto. At a temperature of 40 °C, the reaction is carried out for 10 h, filtered, the filtrate is concentrated under reduced pressure, washed with ether, and dried to obtain a phosphorus-containing acrylate.

[0017] (2) Dissolve 6 g of 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline, 3 g of paraformaldehyde, and 6.5 g of o-allylphenol in toluene solvent. Under reflux at 110 °C for 5 h, perform vacuum distillation, and wash successively with sodium hydroxide solution, water, and acetone, then dry to obtain divinyltetrazine benzoxazine.

[0018] (3) Under nitrogen atmosphere, add 12 g of phosphorus-containing acrylate, 15 g of divinyltetrazine benzoxazine, and 0.25 g of sodium dodecylsulfonate to water. Heat to 80 °C, add 0.2 g of ammonium persulfate thereto, stir and react for 5 h, cool to room temperature, filter, wash with ethanol, and dry to obtain poly(phosphate-tetrazine benzoxazine) flame retardant.

[0019] (4) Put 2.5 g of poly(phosphate-tetrazine benzoxazine) flame retardant and 50 g of polyurethane into a Haake mixer for kneading, then put the mixture into a hot press at 180 °C and apply pressure up to 15 MPa, hold the pressure for 6 min to obtain thermoplastic polyurethane fireproof material.

[0020] Example 2 (1) Under nitrogen atmosphere, in an ice bath at 3 °C, dissolve 3 g of 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane-2-oxide in dichloromethane solvent, add 1.9 g of 2-hydroxyethyl acrylate and 2.2 g of triethylamine thereto, and react at 30 °C for 10 h. Filter, concentrate the filtrate under reduced pressure, wash with ether, and dry to obtain phosphorus-containing acrylate.

[0021] (2) Dissolve 6 g of 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline, 2.5 g of paraformaldehyde, and 6 g of o-allylphenol in toluene solvent. Under reflux at 120 °C for 4 h, perform vacuum distillation, and wash successively with sodium hydroxide solution, water, and acetone, then dry to obtain divinyltetrazine benzoxazine.

[0022] (3) Under nitrogen atmosphere, add 12 g of phosphorus-containing acrylate, 15 g of divinyltetrazine benzoxazine, and 0.3 g of sodium dodecylsulfonate to water. Heat to 70 °C, add 0.15 g of ammonium persulfate thereto, stir and react for 5 h, cool to room temperature, filter, wash with ethanol, and dry to obtain poly(phosphate-tetrazine benzoxazine) flame retardant.

[0023] (4) Put 5 g of poly(phosphate-tetrazine benzoxazine) flame retardant and 50 g of polyurethane into a Haake mixer for kneading, then put the mixture into a hot press at 190 °C and apply pressure up to 20 MPa, hold the pressure for 5 min to obtain thermoplastic polyurethane fireproof material.

[0024] Example 3 (1) Under a nitrogen atmosphere, 3 g of 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane 2-oxide was dissolved in dichloromethane solvent in an ice bath at 0 °C. Then, 2 g of 2-hydroxyethyl acrylate and 2.2 g of triethylamine were added thereto. The reaction was carried out at 40 °C for 8 h. After filtration, the filtrate was concentrated under reduced pressure, washed with ether, and dried to obtain a phosphorus-containing acrylate ester.

[0025] (2) 6 g of 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline, 3.5 g of paraformaldehyde, and 6.5 g of o-allylphenol were dissolved in toluene solvent. The reflux reaction was carried out at 100 °C for 4 h. After distillation under reduced pressure, it was washed successively with sodium hydroxide solution, water, and acetone, and dried to obtain divinyltetrazine benzoxazine.

[0026] (3) Under nitrogen conditions, 12 g of the phosphorus-containing acrylate ester, 10 g of divinyltetrazine benzoxazine, and 0.2 g of sodium dodecylsulfonate were added to water. The temperature was raised to 90 °C, and 0.2 g of ammonium persulfate was added thereto. The reaction was stirred for 5 h, cooled to room temperature, filtered, washed with ethanol, and dried to obtain a poly(phosphate ester-tetrazine benzoxazine) flame retardant.

[0027] (4) 7.5 g of the poly(phosphate ester-tetrazine benzoxazine) flame retardant and 50 g of polyurethane were kneaded in a Haake mixer, and then the mixture was placed in a hot press at 180 °C and pressurized to 18 MPa for 4 min to obtain a thermoplastic polyurethane fireproof material.

[0028] Example 4 (1) Under a nitrogen atmosphere, 3 g of 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane 2-oxide was dissolved in dichloromethane solvent in an ice bath at 4 °C. Then, 2.2 g of 2-hydroxyethyl acrylate and 2 g of triethylamine were added thereto. The reaction was carried out at 45 °C for 10 h. After filtration, the filtrate was concentrated under reduced pressure, washed with ether, and dried to obtain a phosphorus-containing acrylate ester.

[0029] (2) 6 g of 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline, 3.5 g of paraformaldehyde, and 6.9 g of o-allylphenol were dissolved in toluene solvent. The reflux reaction was carried out at 100 °C for 4 h. After distillation under reduced pressure, it was washed successively with sodium hydroxide solution, water, and acetone, and dried to obtain divinyltetrazine benzoxazine.

[0030] (3) Under nitrogen conditions, 12 g of the phosphorus-containing acrylate ester, 15 g of divinyltetrazine benzoxazine, and 0.25 g of sodium dodecylsulfonate were added to water. The temperature was raised to 80 °C, and 0.22 g of ammonium persulfate was added thereto. The reaction was stirred for 5 h, cooled to room temperature, filtered, washed with ethanol, and dried to obtain a poly(phosphate ester-tetrazine benzoxazine) flame retardant.

[0031] (4) 10 g of poly(phosphate ester - tetrazine benzoxazine) flame retardant and 50 g of polyurethane were placed in a Haake mixer for mixing, and then the mixture was placed in a hot press at 180 °C and pressurized to 18 MPa, and held under pressure for 6 min to obtain a thermoplastic polyurethane fireproof material.

[0032] Example 5 (1) Under a nitrogen atmosphere and in an ice bath at 0 °C, 3 g of 2 - chloro - 5,5 - dimethyl - 1,3,2 - dioxaphosphorinane - 2 - oxide was dissolved in dichloromethane solvent, and 1.5 g of 2 - hydroxyethyl acrylate and 2.25 g of triethylamine were added thereto. The reaction was carried out at 40 °C for 9 h, filtered, the filtrate was concentrated under reduced pressure, washed with ether, and dried to obtain a phosphorus - containing acrylate.

[0033] (2) 6 g of 4,4'-(1,2,4,5 - tetrazine - 3,6 - diyl)dianiline, 2.5 g of paraformaldehyde, and 6.5 g of o - allylphenol were dissolved in toluene solvent, and the reflux reaction was carried out at 110 °C for 6 h. After vacuum distillation, it was washed successively with sodium hydroxide solution, water, and acetone, and dried to obtain divinyltetrazine benzoxazine.

[0034] (3) Under nitrogen conditions, 12 g of the phosphorus - containing acrylate, 10 g of divinyltetrazine benzoxazine, and 0.3 g of sodium dodecylsulfonate were added to water, heated to 70 °C, 0.15 g of ammonium persulfate was added thereto, and the reaction was stirred for 5 h. After cooling to room temperature, it was filtered, washed with ethanol, and dried to obtain poly(phosphate ester - tetrazine benzoxazine) flame retardant.

[0035] (4) 12.5 g of poly(phosphate ester - tetrazine benzoxazine) flame retardant and 50 g of polyurethane were placed in a Haake mixer for mixing, and then the mixture was placed in a hot press at 180 °C and pressurized to 15 MPa, and held under pressure for 6 min to obtain a thermoplastic polyurethane fireproof material.

[0036] Comparative Example 1 (1) Under a nitrogen atmosphere and in an ice bath at 0 °C, 3 g of 2 - chloro - 5,5 - dimethyl - 1,3,2 - dioxaphosphorinane - 2 - oxide was dissolved in dichloromethane solvent, and 2 g of 2 - hydroxyethyl acrylate and 2 g of triethylamine were added thereto. The reaction was carried out at 40 °C for 10 h, filtered, the filtrate was concentrated under reduced pressure, washed with ether, and dried to obtain a phosphorus - containing acrylate.

[0037] (2) 2.5 g of the phosphorus - containing acrylate and 50 g of polyurethane were placed in a Haake mixer for mixing, and then the mixture was placed in a hot press at 180 °C and pressurized to 15 MPa, and held under pressure for 6 min to obtain a thermoplastic polyurethane fireproof material.

[0038] Comparative Example 2 (1) Dissolve 6 g of 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline, 3 g of paraformaldehyde, and 6.5 g of o-allylphenol in toluene solvent. At 110 °C, reflux for 5 h, then perform vacuum distillation, and wash successively with sodium hydroxide solution, water, and acetone, and dry to obtain divinyltetrazine benzoxazine.

[0039] (2) Place 2.5 g of divinyltetrazine benzoxazine and 50 g of polyurethane in a Haake mixer for mixing, and then place the mixture in a hot press at 180 °C and apply pressure up to 15 MPa, and hold the pressure for 6 min to obtain a thermoplastic polyurethane fireproof material.

[0040] Use a cone calorimeter to measure the heat release rate, peak heat release rate, and total heat release of the material.

[0041] As can be seen from the table, the flame retardant effect of the examples is better than that of the comparative examples. This is because in the examples, poly(phosphate-tetrazine benzoxazine) flame retardant is added, which can achieve a synergistic flame retardant effect of nitrogen and phosphorus. While in Comparative Example 1 and Comparative Example 2, phosphorus-containing acrylate and divinyltetrazine benzoxazine are added respectively, and neither of them achieves a synergistic flame retardant effect of nitrogen and phosphorus; the phosphorus element in poly(phosphate-tetrazine benzoxazine) flame retardant decomposes when heated to form metaphosphoric acid, and at high temperature, it further polymerizes to form a glass layer, which can isolate oxygen and heat on the material surface. Phosphoric acid and metaphosphoric acid have strong dehydration properties, which can cause the polymer to dehydrate and form carbon, forming a carbonized layer on its surface. The carbonized layer has poor thermal conductivity and isolates the transfer of heat. The nitrogen element in it generates a non-flammable gas when heated, which can dilute the concentration of flammable gases in the air and further achieve the flame retardant effect. The benzoxazine in it undergoes a ring-opening polymerization reaction when heated to form a network structure similar to phenolic resin, and the resulting polymer has high heat resistance. The two assist each other and jointly improve the flame retardancy of the material.

[0042] Place the polyurethane material on the horizontal position of the bracket in the smoke density chamber. The specimen burns in the chamber to generate smoke, and record the time to reach the maximum smoke density, the maximum smoke density, and the total smoke release.

[0043] As can be seen from the table, the flame retardant effect of the examples is better than that of the comparative examples, and with the increase of the amount of flame retardant, the time to reach the maximum smoke density increases from 43 s to 54 s, the maximum smoke density decreases from 55% to 40%, and the total smoke release decreases from 18.6 m 2 / m 2 to 16.2 m 2 / m2 The longer the time to reach the maximum smoke density and the smaller the maximum smoke density, the better. Therefore, the flame retardant effect of the examples is better than that of the comparative examples.

[0044] The foregoing description of the specific exemplary embodiments of the present invention is for purposes of illustration and exemplification. These descriptions are not intended to limit the invention to the precise forms disclosed, and obviously, many changes and variations are possible in light of the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical applications, so that those skilled in the art can implement and utilize various different exemplary embodiments of the present invention, as well as various different selections and changes. The scope of the present invention is intended to be defined by the claims and their equivalents.

Claims

1. A preparation method of a thermoplastic polyurethane fireproof material, characterized in that, The preparation method is as follows: (1) Under nitrogen conditions, add phosphorus-containing acrylate, divinyltetrazine benzoxazine, and sodium dodecyl sulfate into water, heat up to 70 - 90 °C, add ammonium persulfate thereto, stir and react for 2 - 6 h, cool to room temperature, filter, wash with ethanol, and dry to obtain a poly(phosphate-tetrazine benzoxazine) flame retardant; (2) Mix the poly(phosphate-tetrazine benzoxazine) flame retardant and polyurethane in a Haake mixer, and then place the mixture in a hot press for pressurization and pressure holding to obtain a thermoplastic polyurethane fireproof material.

2. The preparation method of the thermoplastic polyurethane fireproof material according to claim 1, wherein In the step (1), the mass ratio of each reactant is: phosphorus-containing acrylate: divinyltetrazine benzoxazine: ammonium persulfate = 1: (0.7 - 1.5): (0.012 - 0.018).

3. The preparation method of the thermoplastic polyurethane fireproof material according to claim 1, characterized in that, In the step (2), the mass ratio of each reactant is: polyurethane: poly(phosphate-tetrazine benzoxazine) flame retardant = 100: (5 - 25).

4. The preparation method of the thermoplastic polyurethane fireproof material according to claim 1, characterized in that, In the step (2), the temperature of the hot press is 170 - 190 °C, pressurize to 15 - 20 MPa, and hold the pressure for 3 - 6 min.

5. The preparation method of the thermoplastic polyurethane fireproof material according to claim 1, characterized in that, The preparation method of the phosphorus-containing acrylate in the step (1) is as follows: Under a nitrogen atmosphere, in an ice bath at 0 - 5 °C, dissolve 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane-2-oxide in dichloromethane solvent, add 2-hydroxyethyl acrylate and triethylamine thereto, and according to the mass ratio, 2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane-2-oxide: 2-hydroxyethyl acrylate: triethylamine = 1: 0.5 - 0.8: 0.6 - 0.

75. React at a temperature of 30 - 50 °C for 6 - 12 h, filter, concentrate the filtrate under reduced pressure, wash with ether, and dry to obtain the phosphorus-containing acrylate.

6. The preparation method of the thermoplastic polyurethane fireproof material according to claim 1, characterized in that, The preparation method of the divinyltetrazine benzoxazine in the step (1) is as follows: Dissolve 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline, paraformaldehyde, and o-allylphenol in toluene solvent, reflux and react, distill under reduced pressure, and wash successively with sodium hydroxide solution, water, and acetone, and dry to obtain divinyltetrazine benzoxazine.

7. The preparation method of the thermoplastic polyurethane fireproof material according to claim 6, characterized in that, In the step, the mass ratio of each reactant is: 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dianiline: paraformaldehyde: o-allylphenol = 1: (0.4 - 0.6): (1 - 1.15).

8. The preparation method of the thermoplastic polyurethane fireproof material according to claim 6, characterized in that, The reflux reaction temperature in the step is 100 - 120 °C, and the reflux reaction time is 3 - 6 h.

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