Phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of high polymer materials, in particular to phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane as well as a preparation method and application thereof. A preparation method of phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane comprises the following steps: S1, mixing polyisocyanate, a polyol polymer, a hydrophilic chain extender and a catalyst, carrying out heating reaction, and stirring to obtain a reactant A; s2, phosphorus-containing polyol is added into the reactant A for a chain extension reaction, then silicon-containing polyol is added for a chain extension reaction, and a reactant B is obtained; and S3, adding a small molecule chain extender into the reactant B to carry out chain extension reaction. According to the preparation method of phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane, an environment-friendly phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane material with high flame retardance, good thermal stability and good mechanical property is prepared, and the problems that an existing waterborne polyurethane material is inflammable and insufficient in flame retardance are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane, a preparation method thereof, and an application thereof. Background Art

[0002] Waterborne polyurethane has been widely used in coatings, adhesives, textile finishing, and other fields due to its environmental friendliness, good film-forming properties, and mechanical properties. However, polyurethane materials are flammable and release large amounts of toxic fumes when burned, limiting their application in areas requiring high flame retardancy. The development of highly efficient, flame-retardant waterborne polyurethane materials has become a research hotspot. Traditional flame retardant methods rely primarily on halogen flame retardants, but the toxic gases released during combustion and the resulting environmental hazards have prompted researchers to explore more environmentally friendly flame retardant systems. Phosphorus-based flame retardants have been widely studied due to their low toxicity and excellent flame retardant properties, but single phosphorus-based flame retardants are prone to decomposition at high temperatures, resulting in limited flame retardant efficiency and insufficient flame retardant properties. Summary of the Invention

[0003] In response to the problems raised in the background technology, the purpose of the present invention is to propose a method for preparing a phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane, so as to prepare an environmentally friendly phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane material with high flame retardancy, good thermal stability and good mechanical properties, thereby solving the problem that existing waterborne polyurethane materials are flammable and have insufficient flame retardancy.

[0004] Another object of the present invention is to provide the phosphorus-silicon synergistic flame retardant modified waterborne polyurethane prepared by the above-mentioned preparation method, which has the advantages of high flame retardancy, good thermal stability and good mechanical properties.

[0005] Another object of the present invention is to propose the application of the above-mentioned phosphorus-silicon synergistic flame retardant modified waterborne polyurethane in the field of automobile, high-speed rail and aircraft interior materials.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: A method for preparing phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane comprises the following steps: Step S1, mixing a polyisocyanate, a polyol polymer, a hydrophilic chain extender and a catalyst, heating and reacting the mixture, and stirring to obtain a reactant A; Step S2, adding a phosphorus-containing polyol to reactant A to carry out a chain extension reaction, and then adding a silicon-containing polyol to carry out a chain extension reaction to obtain reactant B; Step S3, adding a small molecule chain extender to reactant B to carry out a chain extension reaction, and adding acetone during the chain extension reaction to reduce the viscosity of the system to obtain a prepolymer; Step S4: After cooling, adding a neutralizing agent to the prepolymer for reaction, then adding deionized water for emulsification, and adding a post-chain extender for further chain extension; Step S5: removing the organic solvent from the reaction product obtained in step S4 to obtain phosphorus-silicon synergistic flame retardant modified waterborne polyurethane.

[0007] Further, in step S1, the polyisocyanate is isophorone diisocyanate, the polyol polymer is polycarbonate diol 2000, the hydrophilic chain extender is 2,2-dimethylol propionic acid, and the catalyst is dibutyltin dilaurate; The mass ratio of the polyisocyanate to the polyol polymer is 1:(2-3); The amount of the hydrophilic chain extender is 2 to 6 wt % of the total amount of the polyisocyanate and the polyol polymer; The amount of the catalyst used is 0.5 to 2 wt % of the total amount of the polyisocyanate and the polyol polymer.

[0008] To further illustrate, in step S1, the stirring reaction temperature is 70-100° C., the stirring reaction time is 1-3 h, and the stirring speed is 100-200 rpm.

[0009] To further illustrate, in step S2, the phosphorus-containing polyol is Exolit OP550, and the silicon-containing polyol is diphenylsilanediol; The amount of the phosphorus-containing polyol is 1 to 25 wt% of the total amount of the polyisocyanate and the polyol polymer; The amount of the silicon-containing polyol used is 1 to 5 wt % of the total amount of the polyisocyanate and the polyol polymer.

[0010] To further illustrate, in step S2, the reaction temperature for the chain extension reaction is 60-80° C., and the total reaction time for adding the phosphorus-containing polyol to the reactant A for chain extension reaction and adding the silicon-containing polyol to the reactant A for chain extension reaction is 2-4 hours.

[0011] To further illustrate, in step S3, the small molecule chain extender is 1,4-butanediol, and the amount of the small molecule chain extender is 1 to 5 wt% of the total amount of the polyisocyanate and the polyol polymer. The reaction temperature for the chain extension reaction is 60 to 80° C., and the reaction time is 2 to 4 hours.

[0012] Further, in step S4, the neutralizing agent is triethylamine; The molar ratio of the neutralizing agent to the hydrophilic chain extender is 1:1; In step S4, the reaction temperature of adding the neutralizing agent to the prepolymer is 20 to 50° C., and the reaction time is 5 to 60 minutes; In step S4, the mass ratio of the deionized water to the prepolymer is (2-4):1, the feed rate of the deionized water is 5-20 mL / min, the reaction temperature for emulsification is 10-30° C., and the reaction time for emulsification is 30-60 min; The post-chain extender is anhydrous piperazine, and the amount of the post-chain extender is 1 to 3 wt % of the total amount of the polyisocyanate and the polyol polymer; In step S4, the post-chain extender is first dissolved in 5-20 mL of deionized water to obtain piperazine water, and then the piperazine water is fed into the reaction system at a feeding rate of 2-10 mL / min. The reaction temperature for further chain extension by adding the post-chain extender is 20-50° C., and the reaction time is 30-60 min.

[0013] To further illustrate, in step S5, acetone in the reaction product obtained in step S4 is removed by rotary evaporation under vacuum conditions and a temperature of 30-40°C.

[0014] A phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane is prepared using the method for preparing the phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane.

[0015] The phosphorus-silicon synergistic flame retardant modified waterborne polyurethane is used in the fields of automobile, high-speed rail and aircraft interior materials.

[0016] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: 1. By simultaneously introducing phosphorus-containing polyols and silicon-containing polyols, the flame retardancy and thermal stability of waterborne polyurethane are significantly improved. Silicon forms a stable silicon-carbon layer or silicon dioxide protective layer at high temperatures, effectively isolating the diffusion of heat and oxygen into the material. At the same time, the silicon component inhibits the thermal decomposition and loss of phosphorus-based flame retardants, prolonging the flame retardant efficiency. The two form a synergistic mechanism in the gas phase and condensed phase, and these synergistic effects significantly enhance the flame retardant efficiency of the material. The phosphorus-silicon synergistic flame retardant system combines the advantages of phosphorus-based and silicon-based flame retardants, significantly improving the flame retardant properties of the material through synergistic effects in the gas phase and condensed phase.

[0017] 2. Halogen flame retardants are abandoned and a low-toxic phosphorus-silicon system is adopted, which is in line with the development trend of green materials. The phosphorus-silicon synergistic flame retardant modified waterborne polyurethane of the present invention is superior to traditional flame retardant materials in terms of environmental protection and comprehensive performance.

[0018] 3. Through the synergistic effect of phosphorus and silicon, and combining the advantages of phosphorus and silicon flame retardants, an environmentally friendly phosphorus-silicon synergistic flame retardant modified waterborne polyurethane material with high flame retardancy, good thermal stability and good mechanical properties is prepared. It meets the needs of application fields with high requirements for flame retardant and mechanical properties. It is superior to traditional flame retardant materials in terms of environmental protection and comprehensive performance, has broad application prospects, and solves the problem of flammability and insufficient flame retardant properties of existing waterborne polyurethane materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a preparation process diagram of step S1 in the preparation method of phosphorus-silicon synergistic flame retardant modified waterborne polyurethane according to an embodiment of the present invention.

[0020] Figure 2 This is a diagram of the preparation process of adding phosphorus-containing polyol to carry out chain extension reaction in step S2 of the preparation method of phosphorus-silicon synergistic flame retardant modified waterborne polyurethane in one embodiment of the present invention.

[0021] Figure 3 This is a diagram of the preparation process of adding silicon-containing polyol to carry out chain extension reaction in step S2 of the preparation method of phosphorus-silicon synergistic flame retardant modified waterborne polyurethane in one embodiment of the present invention.

[0022] Figure 4 This is a preparation process diagram of step S3 in the preparation method of phosphorus-silicon synergistic flame retardant modified waterborne polyurethane according to an embodiment of the present invention.

[0023] Figure 5 This is a preparation process diagram of the neutralizing agent addition reaction in step S4 of the preparation method of phosphorus-silicon synergistic flame retardant modified waterborne polyurethane according to one embodiment of the present invention.

[0024] Figure 6 This is a diagram of the preparation process of further chain extension by adding a chain extender in step S4 of the preparation method of phosphorus-silicon synergistic flame retardant modified waterborne polyurethane in one embodiment of the present invention.

[0025] Figure 7 1 is an infrared spectrum of the samples prepared by using Examples 1 to 5 of the present invention.

[0026] Figure 8 3 and 4 are stress-strain test diagrams of the samples prepared in Examples 1 to 5 of the present invention.

[0027] Figure 9 Graphs showing tensile strength and elongation at break of samples prepared in Examples 1 to 5 of the present invention.

[0028] Figure 10 3 and 4 are test graphs of water contact angle and water absorption rate of samples prepared by using Examples 1 to 5 of the present invention.

[0029] Figure 11 This is a thermogravimetric analysis (TGA) test chart of the samples prepared using Examples 1 to 5 of the present invention. DETAILED DESCRIPTION

[0030] A method for preparing phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane comprises the following steps: Step S1, mixing a polyisocyanate, a polyol polymer, a hydrophilic chain extender and a catalyst, heating and reacting the mixture, and stirring to obtain a reactant A; Step S2, adding a phosphorus-containing polyol to reactant A to carry out a chain extension reaction, and then adding a silicon-containing polyol to carry out a chain extension reaction to obtain reactant B; Step S3, adding a small molecule chain extender to reactant B to carry out a chain extension reaction, and adding acetone during the chain extension reaction to reduce the viscosity of the system to obtain a prepolymer; Step S4: After cooling, adding a neutralizing agent to the prepolymer for reaction, then adding deionized water for emulsification, and adding a post-chain extender for further chain extension; Step S5: removing the organic solvent from the reaction product obtained in step S4 to obtain phosphorus-silicon synergistic flame retardant modified waterborne polyurethane.

[0031] Traditional halogen flame retardants are gradually being replaced because they release toxic gases when burned. Although phosphorus-based flame retardants have low toxicity, they are easy to decompose at high temperatures and have limited flame retardant efficiency. Silicon-based flame retardants have good heat and oxygen insulation effects because they can form a stable silicon dioxide protective layer at high temperatures. The present invention significantly improves the flame retardant properties and thermal stability of waterborne polyurethane by simultaneously introducing phosphorus-containing polyols and silicon-containing polyols. Silicon elements can form a stable silicon-carbon layer or silicon dioxide protective layer at high temperatures, effectively isolating the diffusion of heat and oxygen into the material. At the same time, the silicon component can inhibit the thermal decomposition and loss of phosphorus-based flame retardants, prolonging the flame retardant efficiency. The two form a synergistic mechanism in the gas phase and condensed phase, and these synergistic effects significantly improve the flame retardant efficiency of the material. The phosphorus-silicon synergistic flame retardant system combines the advantages of phosphorus-based and silicon-based flame retardants, and significantly improves the flame retardant properties of the material through the synergistic effects of the gas phase and condensed phase.

[0032] Furthermore, the invention abandons halogen flame retardants and adopts a low-toxic phosphorus-silicon system, which is in line with the development trend of green materials. Through the synergistic effect of phosphorus and silicon, the present invention combines the advantages of phosphorus and silicon flame retardants to produce an environmentally friendly phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane material with high flame retardancy, good thermal stability, and excellent mechanical properties. This material meets the needs of applications requiring high flame retardancy and mechanical properties, outperforming traditional flame retardant materials in terms of environmental friendliness and comprehensive performance. It has broad application prospects and solves the problem of existing waterborne polyurethane materials being flammable and insufficient in flame retardancy.

[0033] like Figures 1 to 6 As shown, , n represents the degree of polymerization of the polymer, , further illustrating, in step S1, the polyisocyanate is isophorone diisocyanate, the polyol polymer is polycarbonate diol 2000 (i.e., polycarbonate diol with a molecular weight of 2000), the hydrophilic chain extender is 2,2-dihydroxymethylpropionic acid, and the catalyst is dibutyltin dilaurate; the synthetic monomer raw material polycarbonate diol 2000 used in the present invention has good mechanical properties, and the prepared phosphorus-silicon synergistic flame retardant modified waterborne polyurethane material can have the advantages of high flame retardancy, good thermal stability and good mechanical properties.

[0034] The mass ratio of the polyisocyanate to the polyol polymer is 1:(2-3); The amount of the hydrophilic chain extender is 2 to 6 wt % of the total amount of the polyisocyanate and the polyol polymer; The amount of the catalyst used is 0.5 to 2 wt % of the total amount of the polyisocyanate and the polyol polymer.

[0035] To further illustrate, in step S1, the stirring reaction temperature is 70-100° C., the stirring reaction time is 1-3 h, and the stirring speed is 100-200 rpm.

[0036] To further illustrate, in step S2, the phosphorus-containing polyol is Exolit OP550 (i.e., the phosphorus-containing polyol with the model number Exolit OP550), and the silicon-containing polyol is diphenylsilanediol; The amount of the phosphorus-containing polyol is 1 to 25 wt% of the total amount of the polyisocyanate and the polyol polymer; The amount of the silicon-containing polyol used is 1 to 5 wt % of the total amount of the polyisocyanate and the polyol polymer.

[0037] The present invention uses polycarbonate diol, isophorone diisocyanate, and 2,2-dimethylolpropionic acid as main raw materials, and introduces a phosphorus-based flame retardant (Exolit OP550) and a silicon-containing diol (DPS) to prepare a phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane (Si-P-WPU). The introduction of Exolit OP550 and diphenylsilane diol significantly improves the flame retardancy and thermal stability of the waterborne polyurethane while maintaining good mechanical properties. The silicon element can form a stable silicon-carbon layer or a silicon dioxide protective layer at high temperatures, effectively isolating the diffusion of heat and oxygen into the material. At the same time, the silicon component can inhibit the thermal decomposition and loss of the phosphorus-based flame retardant, thereby extending the flame retardant efficiency. The two form a synergistic mechanism in the gas phase and the condensed phase. These synergistic effects significantly improve the flame retardant efficiency of the material.

[0038] To further illustrate, in step S2, the reaction temperature for the chain extension reaction is 60-80° C., and the total reaction time for adding the phosphorus-containing polyol to the reactant A for chain extension reaction and adding the silicon-containing polyol to the reactant A for chain extension reaction is 2-4 hours.

[0039] Preferably, in step S2, the chain extension reaction is carried out under stirring at a stirring speed of 100 to 200 rpm.

[0040] To further illustrate, in step S3, the small molecule chain extender is 1,4-butanediol, and the amount of the small molecule chain extender is 1 to 5 wt% of the total amount of the polyisocyanate and the polyol polymer. The reaction temperature for the chain extension reaction is 60 to 80° C., and the reaction time is 2 to 4 hours.

[0041] Further, in step S4, the neutralizing agent is triethylamine; The molar ratio of the neutralizing agent to the hydrophilic chain extender is 1:1; In step S4, the reaction temperature of adding the neutralizing agent to the prepolymer is 20 to 50° C., and the reaction time is 5 to 60 minutes; In step S4, the mass ratio of the deionized water to the prepolymer is (2-4):1, the feed rate of the deionized water is 5-20 mL / min, the reaction temperature for emulsification is 10-30° C., and the reaction time for emulsification is 30-60 min; The post-chain extender is anhydrous piperazine, and the amount of the post-chain extender is 1 to 3 wt % of the total amount of the polyisocyanate and the polyol polymer; In step S4, the post-chain extender is first dissolved in 5-20 mL of deionized water to obtain piperazine water, and then the piperazine water is fed into the reaction system at a feeding rate of 2-10 mL / min. The reaction temperature for further chain extension by adding the post-chain extender is 20-50° C., and the reaction time is 30-60 min.

[0042] Preferably, in step S4, the neutralizing agent is added under stirring and the stirring speed is 100 to 200 rpm.

[0043] Preferably, in step S4, deionized water is added under stirring for emulsification, and the stirring speed is 1000-2000 rpm.

[0044] To further illustrate, in step S5, acetone in the reaction product obtained in step S4 is removed by rotary evaporation under vacuum conditions and a temperature of 30-40°C.

[0045] A phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane is prepared using the method for preparing the phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane, and has the advantages of high flame retardancy, good thermal stability and good mechanical properties.

[0046] The phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane is used in the fields of automobile, high-speed rail, and aircraft interior materials. The phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane of the present invention has the advantages of high flame retardancy, good thermal stability and good mechanical properties, and can meet the application needs of automobile, high-speed rail, and aircraft interiors that have high requirements for material flame retardancy and mechanical properties.

[0047] For ease of understanding of the present invention, the present invention will be described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0048] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0049] Example 1 A method for preparing phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane comprises the following steps: Step S1: 5.13 g of polyisocyanate (isophorone diisocyanate), 14 g of polyol polymer (polycarbonate diol 2000, model P909328, manufactured by Shanghai MacLean Biochemical Technology Co., Ltd.), 0.7 g of a hydrophilic chain extender (2,2-dimethylolpropionic acid), and 0.3 g of a catalyst (dibutyltin dilaurate) were placed in a three-necked flask equipped with a stirrer and condenser, the mixture was heated to 85° C., stirred, and reacted for 1 hour at a stirring speed of 150 rpm to obtain reactant A. Step S2: 2 g of phosphorus-containing polyol (Exolit OP550) was added to reactant A for chain extension reaction for 1 hour, and then 0.2 g of silicon-containing polyol (diphenylsilanediol) was added for chain extension reaction for 1 hour. The reaction temperature of the chain extension reaction was 80° C. and the stirring speed was 150 rpm to obtain reactant B; Step S3: adding 0.45 g of a small molecule chain extender (1,4-butanediol) to reactant B for reaction at 80° C. for 2 h. During the chain extension reaction, 10 g of acetone was added to reduce the viscosity of the system, to obtain 22.78 g of a prepolymer; Step S4, after cooling to 30°C, adding 0.53g of a neutralizing agent (using triethylamine) to the prepolymer under stirring at 150rpm for reaction, the reaction temperature for the reaction of adding the neutralizing agent to the prepolymer is 30°C, the reaction time is 10min, adjusting the speed to 1500rpm, slowly adding 50mL of deionized water to the prepolymer for emulsification (the feed rate of deionized water is 20mL / min), the reaction temperature for emulsification is 30°C, the reaction time for emulsification is 30min, and at the same time, adding a post-chain extender (the post-chain extender is anhydrous piperazine, the feeding method is to dissolve 0.2g of anhydrous piperazine in 10mL of water to obtain piperazine water, and the piperazine water is fed into the reaction system at a feed rate of 2mL / min) for further chain extension, and the chain extension reaction is carried out at 30°C for 30min; Step S5: Under vacuum conditions and a temperature of 35° C., remove acetone from the reaction product obtained in step S4 by rotary evaporation to obtain phosphorus-silicon synergistic flame retardant modified waterborne polyurethane.

[0050] Example 2 A method for preparing phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane comprises the following steps: Step S1: 5.13 g of polyisocyanate (isophorone diisocyanate), 14 g of polyol polymer (polycarbonate diol 2000, model P909328, manufactured by Shanghai MacLean Biochemical Technology Co., Ltd.), 0.7 g of a hydrophilic chain extender (2,2-dimethylolpropionic acid), and 0.3 g of a catalyst (dibutyltin dilaurate) were placed in a three-necked flask equipped with a stirrer and condenser, the mixture was heated to 85° C., stirred, and reacted for 1 hour at a stirring speed of 150 rpm to obtain reactant A. Step S2: adding 2 g of phosphorus-containing polyol (Exolit OP550) to reactant A for chain extension reaction for 1 hour, and then adding 0.4 g of silicon-containing polyol (using diphenylsilanediol) for chain extension reaction for 1 hour. The reaction temperature of the chain extension reaction is 80° C. and the stirring speed is 150 rpm to obtain reactant B; Step S3: adding 0.45 g of a small molecule chain extender (1,4-butanediol) to reactant B for reaction at 80° C. for 2 h. During the chain extension reaction, 10 g of acetone was added to reduce the viscosity of the system, to obtain 22.98 g of a prepolymer; Step S4, after cooling to 30°C, adding 0.53g of a neutralizing agent (using triethylamine) to the prepolymer under stirring at 150rpm for reaction, the reaction temperature for the reaction of adding the neutralizing agent to the prepolymer is 30°C, the reaction time is 10min, adjusting the speed to 1500rpm, slowly adding 50mL of deionized water to the prepolymer for emulsification (the feed rate of deionized water is 20mL / min), the reaction temperature for emulsification is 30°C, the reaction time for emulsification is 30min, and at the same time, adding a post-chain extender (the post-chain extender is anhydrous piperazine, the feeding method is to dissolve 0.2g of anhydrous piperazine in 10mL of water to obtain piperazine water, and the piperazine water is fed into the reaction system at a feed rate of 2mL / min) for further chain extension, and the chain extension reaction is carried out at 30°C for 30min; Step S5: Under vacuum conditions and a temperature of 35° C., remove acetone from the reaction product obtained in step S4 by rotary evaporation to obtain phosphorus-silicon synergistic flame retardant modified waterborne polyurethane.

[0051] Example 3 A method for preparing phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane comprises the following steps: Step S1: 5.13 g of polyisocyanate (isophorone diisocyanate), 14 g of polyol polymer (polycarbonate diol 2000, model P909328, manufactured by Shanghai MacLean Biochemical Technology Co., Ltd.), 0.7 g of a hydrophilic chain extender (2,2-dimethylolpropionic acid), and 0.3 g of a catalyst (dibutyltin dilaurate) were placed in a three-necked flask equipped with a stirrer and condenser, the mixture was heated to 85° C., stirred, and reacted for 1 hour at a stirring speed of 150 rpm to obtain reactant A. Step S2: adding 2 g of phosphorus-containing polyol (Exolit OP550) to reactant A for chain extension reaction for 1 hour, and then adding 0.6 g of silicon-containing polyol (diphenylsilanediol) for chain extension reaction for 1 hour. The reaction temperature of the chain extension reaction is 80° C. and the stirring speed is 150 rpm to obtain reactant B; Step S3: adding 0.45 g of a small molecule chain extender (1,4-butanediol) to reactant B for reaction at 80° C. for 2 h. During the chain extension reaction, 10 g of acetone was added to reduce the viscosity of the system, to obtain 23.18 g of a prepolymer; Step S4, after cooling to 30°C, adding 0.53g of a neutralizing agent (using triethylamine) to the prepolymer under stirring at 150rpm for reaction, the reaction temperature for the reaction of adding the neutralizing agent to the prepolymer is 30°C, the reaction time is 10min, adjusting the speed to 1500rpm, slowly adding 50mL of deionized water to the prepolymer for emulsification (the feed rate of deionized water is 20mL / min), the reaction temperature for emulsification is 30°C, the reaction time for emulsification is 30min, and at the same time, adding a post-chain extender (the post-chain extender is anhydrous piperazine, the feeding method is to dissolve 0.2g of anhydrous piperazine in 10mL of water to obtain piperazine water, and the piperazine water is fed into the reaction system at a feed rate of 2mL / min) for further chain extension, and the chain extension reaction is carried out at 30°C for 30min; Step S5: Under vacuum conditions and a temperature of 35° C., remove acetone from the reaction product obtained in step S4 by rotary evaporation to obtain phosphorus-silicon synergistic flame retardant modified waterborne polyurethane.

[0052] Example 4 A method for preparing phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane comprises the following steps: Step S1: 5.13 g of polyisocyanate (isophorone diisocyanate), 14 g of polyol polymer (polycarbonate diol 2000, model P909328, manufactured by Shanghai MacLean Biochemical Technology Co., Ltd.), 0.7 g of a hydrophilic chain extender (2,2-dimethylolpropionic acid), and 0.3 g of a catalyst (dibutyltin dilaurate) were placed in a three-necked flask equipped with a stirrer and condenser, the mixture was heated to 85° C., stirred, and reacted for 1 hour at a stirring speed of 150 rpm to obtain reactant A. Step S2: adding 2 g of phosphorus-containing polyol (Exolit OP550) to reactant A for chain extension reaction for 1 hour, and then adding 0.8 g of silicon-containing polyol (using diphenylsilanediol) for chain extension reaction for 1 hour. The reaction temperature of the chain extension reaction is 80° C. and the stirring speed is 150 rpm to obtain reactant B; Step S3: adding 0.45 g of a small molecule chain extender (1,4-butanediol) to reactant B for reaction at 80° C. for 2 h. During the chain extension reaction, 10 g of acetone was added to reduce the viscosity of the system, to obtain 23.38 g of a prepolymer; Step S4, after cooling to 30°C, adding 0.53g of a neutralizing agent (using triethylamine) to the prepolymer under stirring at 150rpm for reaction, the reaction temperature for the reaction of adding the neutralizing agent to the prepolymer is 30°C, the reaction time is 10min, adjusting the speed to 1500rpm, slowly adding 50mL of deionized water to the prepolymer for emulsification (the feed rate of deionized water is 20mL / min), the reaction temperature for emulsification is 30°C, the reaction time for emulsification is 30min, and at the same time, adding a post-chain extender (the post-chain extender is anhydrous piperazine, the feeding method is to dissolve 0.2g of anhydrous piperazine in 10mL of water to obtain piperazine water, and the piperazine water is fed into the reaction system at a feed rate of 2mL / min) for further chain extension, and the chain extension reaction is carried out at 30°C for 30min; Step S5: Under vacuum conditions and a temperature of 35° C., remove acetone from the reaction product obtained in step S4 by rotary evaporation to obtain phosphorus-silicon synergistic flame retardant modified waterborne polyurethane.

[0053] Example 5 A method for preparing phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane comprises the following steps: Step S1: 5.13 g of polyisocyanate (isophorone diisocyanate), 14 g of polyol polymer (polycarbonate diol 2000, model P909328, manufactured by Shanghai MacLean Biochemical Technology Co., Ltd.), 0.7 g of a hydrophilic chain extender (2,2-dimethylolpropionic acid), and 0.3 g of a catalyst (dibutyltin dilaurate) were placed in a three-necked flask equipped with a stirrer and condenser, the mixture was heated to 85° C., stirred, and reacted for 1 hour at a stirring speed of 150 rpm to obtain reactant A. Step S2: adding 2 g of phosphorus-containing polyol (Exolit OP550) to reactant A for chain extension reaction for 1 h, and then adding 1 g of silicon-containing polyol (diphenylsilanediol) for chain extension reaction for 1 h. The reaction temperature of the chain extension reaction is 80° C. and the stirring speed is 150 rpm to obtain reactant B; Step S3: adding 0.45 g of a small molecule chain extender (1,4-butanediol) to reactant B for reaction at 80° C. for 2 h. During the chain extension reaction, 10 g of acetone was added to reduce the viscosity of the system, to obtain 23.58 g of a prepolymer; Step S4, after cooling to 30°C, adding 0.53g of a neutralizing agent (using triethylamine) to the prepolymer under stirring at 150rpm for reaction, the reaction temperature for the reaction of adding the neutralizing agent to the prepolymer is 30°C, the reaction time is 10min, adjusting the speed to 1500rpm, slowly adding 50mL of deionized water to the prepolymer for emulsification (the feed rate of deionized water is 20mL / min), the reaction temperature for emulsification is 30°C, the reaction time for emulsification is 30min, and at the same time, adding a post-chain extender (the post-chain extender is anhydrous piperazine, the feeding method is to dissolve 0.2g of anhydrous piperazine in 10mL of water to obtain piperazine water, and the piperazine water is fed into the reaction system at a feed rate of 2mL / min) for further chain extension, and the chain extension reaction is carried out at 30°C for 30min; Step S5: Under vacuum conditions and a temperature of 35° C., remove acetone from the reaction product obtained in step S4 by rotary evaporation to obtain phosphorus-silicon synergistic flame retardant modified waterborne polyurethane.

[0054] Weigh 20 g of the phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane in Examples 1 to 5, spread it flat on a surface dish with a diameter of 40 mm, and leave it at room temperature for 48 hours to form a film. They are named Si-P-WPU1, Si-P-WPU2, Si-P-WPU3, Si-P-WPU4, and Si-P-WPU5 respectively.

[0055] Samples Si-P-WPU1, Si-P-WPU2, Si-P-WPU3, Si-P-WPU4, and Si-P-WPU5 were subjected to infrared spectroscopy (FT-IR) testing, stress-strain testing, tensile strength and elongation at break testing, water contact angle and water absorption testing, thermogravimetric analysis (TGA) testing, and flame retardancy testing. The test methods and results are as follows: 1. Infrared spectrum (FT-IR) test: The test was performed using a Nicolet IS10 Fourier transform infrared spectrometer. The sample was evenly applied to a spectral grade potassium bromide sheet using a capillary tube. The infrared absorption spectrum of the potassium bromide sheet after the product was applied was collected, and the wavenumber scanning range was set to 500~4000cm -1 , the average scanning frequency is 32 times, and the resolution is 4cm -1 .

[0056] Figure 7 The infrared spectra of each sample are shown in Figure 1. It can be seen from the figure that there is no hydroxyl compound OH (3428cm -1 ) absorption peak and N=C=O stretching vibration (2270cm -1 ) absorption peak, indicating that the reaction is very complete, and the characteristic absorption is the stretching vibration of the NH bond (3332cm-1 ), stretching vibration of C=O bond in carbamate (1716cm -1 ), stretching vibration of CN bond and bending vibration of NH bond (1530cm -1 ) and antisymmetric stretching vibration (1245cm -1 ), it can be determined that they are all synthesized into waterborne polyurethane, at 1060cm -1 At 1000 cm, we can clearly observe a strong peak, which is the stretching vibration absorption peak of POC, indicating that the phosphorus flame retardant Exolit OP550 has been successfully integrated into the Si-P-WPU molecular chain. -1 ~1100cm -1 A broad peak appears, which is a typical feature of the Si-O bond, indicating that the silicon-containing diol (DPS) has been successfully integrated into the Si-P-WPU molecular chain.

[0057] 2. Stress-strain test: The tensile properties of the cured film were tested using a Shenzhen Sansi UTM 4204 universal testing machine. The film was cut into pieces with a size of 20.0 mm × 10.0 mm × 1.0 mm. The stretching speed was set at 20 mm / min and the testing machine was started until the sample broke. To ensure the accuracy of the experimental results, all samples were tested at least 5 times, and the average value was taken.

[0058] like Figure 8 As shown in the figure, it can be observed that with the gradual increase of silicon-containing glycol (DPS), the stress gradually increases and the strain gradually decreases, with the maximum stress reaching 14.67 MPa and the maximum strain reaching 867.3%. As the silicon-containing glycol content further increases, the aggregation tendency of the siloxane segments increases, which may induce microphase separation or form a locally ordered structure. At the same time, the high bond energy of silicon may limit segment slippage, resulting in increased material rigidity, manifested as a gradual increase in stress and a decrease in strain.

[0059] 3. Tensile strength and elongation at break test: The tensile properties of the cured film were tested using a Shenzhen Sansi UTM 4204 universal testing machine. The film was cut into pieces with a size of 20.0 mm × 10.0 mm × 1.0 mm. The stretching speed was set at 20 mm / min and the testing machine was started until the sample broke. To ensure the accuracy of the experimental results, all samples were tested at least 5 times, and the average value was taken.

[0060] like Figure 9As shown in the figure, it can be observed that as the content of silicon-containing diol (DPS) gradually increases, the tensile strength of the sample gradually increases, while the elongation at break gradually decreases. The maximum tensile strength can reach 14.67 MPa, and the maximum elongation at break can reach 801.826%. As the content of silicon-containing diol further increases, the introduction of silicon-oxygen bonds (Si-O) enhances the rigidity and crosslinking density of the molecular chain, making the molecular chain arrangement more orderly and strengthening the intermolecular force, thereby gradually increasing the tensile strength. However, due to the limited flexibility of the molecular chain, the elongation at break gradually decreases.

[0061] 4. Water contact angle and water absorption test: Cut the prepared film sample into the specified size (10mm×10mm) and accurately weigh its initial mass under dry conditions ( m 0), then soak the film in deionized water. After soaking for 24 hours, take out the film, gently absorb the surface water with filter paper, and immediately weigh its mass after water absorption ( m 1). Calculate corneal water absorption rate according to the following formula ( H ): ; The water contact angle of the cured film was measured using a Powereach JC2000C1 goniometer. The film sample was placed flat on the stage of the measuring instrument. A drop of water was added to the film surface using a microinjector. At the moment the water droplet was formed, a high-speed camera was used to capture the morphological image of the water droplet on the film surface. The contact angle between the water droplet and the film surface was calculated using software analysis.

[0062] like Figure 10 As shown, it can be observed that with increasing silicon-containing diol (DPS) content, the water contact angle of the film gradually increases, while the water absorption rate gradually decreases. The maximum water contact angle can reach 84.79°, and the minimum water absorption rate can reach 33.23%. This is because the addition of silicon-containing diol increases the hydrophobicity of the film. The low surface energy of the silicon-oxygen bond (Si-O) makes it difficult for water molecules to spread on the film surface, resulting in an increase in the water contact angle. At the same time, the introduction of silicon-containing groups changes the molecular structure of the film, reducing the porosity of the film, making it more difficult for water molecules to penetrate the interior of the film, resulting in a decrease in water absorption. The stability of the silicon-oxygen bond also makes it more difficult for the film to undergo structural changes during water absorption, further reducing the water absorption rate.

[0063] 5. Thermogravimetric analysis (TGA) test: The thermal stability of the sample was tested using a Netzsch TG209 FiLibra analyzer. 3 mg of sample was weighed and placed in the instrument's furnace chamber. The sample was tested under the protection of a nitrogen atmosphere with a nitrogen flow rate of 20 ml / min, a temperature range of 30-800°C, and a heating rate of 10°C min. -1 .

[0064] like Figure 11 As shown in the figure, it can be observed that with the increase of the content of silicon-containing diol (DPS), the residual carbon rate also increases from 3.24% to 5.04%. This is because the silicon dioxide generated by the Si group covers the surface of the polymer, plays the role of oxygen and heat insulation, and prevents the degradation of the polymer, thereby increasing the residual carbon rate and improving the flame retardant properties of the Si-P-WPU film.

[0065] 6. Flame Retardancy Test: According to the UL-94 standard, film samples were subjected to a vertical burning test to evaluate their flame retardancy. The film's dripping and burning cotton were observed to assess its grade. The Limiting Oxygen Index (LOI) was also measured. The Limiting Oxygen Index (LOI) refers to the oxygen volume fraction concentration in a polymer in an oxygen and nitrogen mixture that is sufficient to support combustion. The test results are shown in Table 1 below: Table 1 Flame retardant performance test results As shown in Table 1 above, all waterborne polyurethane cured films achieve a V-0 fire rating. As the DPS content increases, the LOI value also rises, and the flame retardant performance is enhanced. This is because silicon can form a stable silicon-carbon layer or silicon dioxide protective layer at high temperatures, effectively isolating the diffusion of heat and oxygen into the material, delaying the combustion process, and enhancing the thermal stability, density, and physical barrier effect of the carbon layer. At the same time, the silicon component can inhibit the thermal decomposition and loss of phosphorus-based flame retardants, prolonging the flame retardant efficiency. The two form a synergistic mechanism in the gas phase and condensed phase, and these synergistic effects significantly improve the flame retardant efficiency of the material.

[0066] In summary, the fire resistance grade of the phosphorus-silicon synergistic flame-retardant modified water-based polyurethane prepared by the present invention reaches V-0, and its LOI value can reach a maximum of 30.1, with good flame retardant performance. While having both flame retardant properties, it also has good mechanical properties, with a maximum tensile strength of 14.67 MPa and a maximum elongation at break of 801.826%.

[0067] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane, characterized in that: The following steps are involved: Step S1, mixing a polyisocyanate, a polyol polymer, a hydrophilic chain extender and a catalyst, heating and reacting the mixture, and stirring to obtain a reactant A; Step S2, adding a phosphorus-containing polyol to reactant A to carry out a chain extension reaction, and then adding a silicon-containing polyol to carry out a chain extension reaction to obtain reactant B; Step S3, adding a small molecule chain extender to reactant B to carry out a chain extension reaction, and adding acetone during the chain extension reaction to reduce the viscosity of the system to obtain a prepolymer; Step S4: After cooling, adding a neutralizing agent to the prepolymer for reaction, then adding deionized water for emulsification, and adding a post-chain extender for further chain extension; Step S5: removing the organic solvent from the reaction product obtained in step S4 to obtain phosphorus-silicon synergistic flame retardant modified waterborne polyurethane.

2. The method for preparing the phosphorus-silicon synergistic flame retardant modified waterborne polyurethane according to claim 1, characterized in that: In step S1, the polyisocyanate is isophorone diisocyanate, the polyol polymer is polycarbonate diol 2000, the hydrophilic chain extender is 2,2-dimethylol propionic acid, and the catalyst is dibutyltin dilaurate; The mass ratio of the polyisocyanate to the polyol polymer is 1:(2-3); The amount of the hydrophilic chain extender is 2 to 6 wt % of the total amount of the polyisocyanate and the polyol polymer; The amount of the catalyst used is 0.5 to 2 wt % of the total amount of the polyisocyanate and the polyol polymer.

3. The method for preparing the phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane according to claim 1, characterized in that: In the step S1, the stirring reaction temperature is 70-100° C., the stirring reaction time is 1-3 hours, and the stirring speed is 100-200 rpm.

4. The method for preparing the phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane according to claim 1, characterized in that: In step S2, the phosphorus-containing polyol is Exolit OP550, and the silicon-containing polyol is diphenylsilanediol; The amount of the phosphorus-containing polyol is 1 to 25 wt% of the total amount of the polyisocyanate and the polyol polymer; The amount of the silicon-containing polyol used is 1 to 5 wt % of the total amount of the polyisocyanate and the polyol polymer.

5. The method for preparing the phosphorus-silicon synergistic flame retardant modified waterborne polyurethane according to claim 1, characterized in that: In step S2, the reaction temperature for the chain extension reaction is 60-80° C., and the total reaction time for adding the phosphorus-containing polyol to the reactant A for chain extension reaction and adding the silicon-containing polyol to the reactant A for chain extension reaction is 2-4 hours.

6. The method for preparing phosphorus-silicon synergistic flame retardant modified waterborne polyurethane according to claim 1, characterized in that: In step S3, the small molecule chain extender is 1,4-butanediol, and the amount of the small molecule chain extender is 1-5 wt% of the total amount of the polyisocyanate and the polyol polymer. The reaction temperature for the chain extension reaction is 60-80° C., and the reaction time is 2-4 hours.

7. The method for preparing phosphorus-silicon synergistic flame retardant modified waterborne polyurethane according to claim 1, characterized in that: In the step S4, the neutralizing agent is triethylamine; The molar ratio of the neutralizing agent to the hydrophilic chain extender is 1:1; In step S4, the reaction temperature of adding the neutralizing agent to the prepolymer is 20 to 50° C., and the reaction time is 5 to 60 minutes; In step S4, the mass ratio of the deionized water to the prepolymer is (2-4):1, the feed rate of the deionized water is 5-20 mL / min, the reaction temperature for emulsification is 10-30° C., and the reaction time for emulsification is 30-60 min; The post-chain extender is anhydrous piperazine, and the amount of the post-chain extender is 1 to 3 wt % of the total amount of the polyisocyanate and the polyol polymer; In step S4, the post-chain extender is first dissolved in 5-20 mL of deionized water to obtain piperazine water, and then the piperazine water is fed into the reaction system at a feeding rate of 2-10 mL / min. The reaction temperature for further chain extension by adding the post-chain extender is 20-50° C., and the reaction time is 30-60 min.

8. The method for preparing phosphorus-silicon synergistic flame retardant modified waterborne polyurethane according to claim 1, characterized in that: In step S5, acetone in the reaction product obtained in step S4 is removed by rotary evaporation under vacuum conditions and a temperature of 30-40°C.

9. A phosphorus-silicon synergistic flame retardant modified waterborne polyurethane, characterized in that: The polyurethane is prepared using the method for preparing the phosphorus-silicon synergistic flame retardant modified waterborne polyurethane as described in any one of claims 1 to 8.

10. Use of the phosphorus-silicon synergistic flame-retardant modified waterborne polyurethane according to claim 9 in the fields of automobile, high-speed rail and aircraft interior materials.

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