Preparation method of additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer

Abstract

The application discloses a preparation method of an added type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer, and the polyurethane elastomer is prepared by compounding isocyanate as a hard segment, polybutylene glycol as a soft segment, a phosphorus-nitrogen flame retardant and lanthanum carbonate; the preparation method is simple, the process is easy to control, and when the prepared polyurethane elastomer is burned, the phosphorus-nitrogen flame retardant forms a blocking layer by isolating oxygen free radicals, the lanthanum coordination bond is broken to generate lanthanum oxide to consume oxygen and cover the surface of the polyurethane, and the carbonate is decomposed to release carbon dioxide to dilute oxygen, so that the three are synergistically combined to prevent the polyurethane from burning, the limiting oxygen index reaches 35.2, and the commercial standard and UL-94 V-0 flame-retardant grade requirements of the flame-retardant material are met; in addition, the polyurethane elastomer also has good mechanical properties, and the tensile strength can reach 27.9 MPa.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high polymer materials, and relates to a preparation method of an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer. BACKGROUND

[0002] As a new type of thermoplastic polymer, polyurethane elastomer (TPU) has good wear resistance, flexibility and environmental resistance, and is widely used in the fields of electric wires and cables, buildings, automobiles, furniture and the like. However, due to the fact that the polyurethane elastomer is rich in organic elements such as carbon, hydrogen, oxygen and nitrogen, it is extremely flammable, and a large amount of heat and toxic smoke is released during the combustion process, which poses a threat to personnel and the environment, and this seriously restricts its use in related fields. Therefore, the development of flame-retardant polyurethane elastomer has become the focus of the industry.

[0003] The traditional flame-retardant polyurethane is added with a halogen-based flame-retardant system, which has high efficiency (15-20% can reach V-0 level), but releases toxic substances and corrosive gases during combustion, and has been limited by regulations such as the European Union RoHS. The phosphorus-nitrogen intumescent flame retardant (such as ammonium polyphosphate APP / pentaerythritol PER system) is easy to absorb moisture and migrate in TPU, and the carbon layer is loose and porous during combustion, which is difficult to effectively isolate oxygen and heat. In addition, lanthanide compounds have been confirmed to have excellent flame-retardant synergistic effect in recent years due to their unique electronic layer structure (4f orbit not filled with electrons) and Lewis acidity. However, when the lanthanide compound is used alone as a polyurethane flame retardant, 20 wt.% is needed to have a certain flame-retardant effect. However, adding too much rare earth compound not only makes the polyurethane elastomer difficult to be formed, but also makes the mechanical properties seriously decreased.

[0004] Based on this, the application aims to provide a polyurethane elastomer with good flame-retardant effect, and the prepared polyurethane elastomer can be applied to various industries, which has excellent flame-retardant effect and also maintains high tensile strength. SUMMARY

[0005] In view of the above technical problems, the application aims to provide a preparation method of an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer. The polyurethane elastomer is prepared by compounding isocyanate as a hard segment, polybutylene glycol as a soft segment, a phosphorus-nitrogen flame retardant and lanthanum carbonate. The preparation method is simple and the process is easy to control. When the prepared polyurethane elastomer burns, the phosphorus-nitrogen flame retardant forms a blocking layer by isolating oxygen free radicals, the lanthanum coordination bond breaks to generate lanthanum oxide to consume oxygen and cover the surface of the polyurethane, and the carbonate decomposes to release carbon dioxide to dilute oxygen, so that the three synergistically prevent the polyurethane from burning. The limiting oxygen index reaches 35.2, which meets the commercial standards and UL-94 V-0 flame-retardant grade requirements of flame-retardant materials. In addition, the polyurethane elastomer also has good mechanical properties, and the tensile strength can reach 27.9 MPa.

[0006] To achieve the above object, the technical scheme adopted by the present application is:

[0007] A preparation method of an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer, which is sequentially carried out according to the following steps:

[0008] S1, preparation of an additive type phosphorus-nitrogen flame retardant

[0009] In a glass flask, 50 mL of tetrahydrofuran solution was added, then cystamine dihydrochloride and triethylamine were added, and stirring was carried out until complete dissolution, then diphenyl phosphinic chloride was slowly added dropwise under ice bath condition at 0℃, and stirring reaction was carried out for 6 h, then the reaction mixture was quenched with water, 100 mL of ethyl acetate and 30 mL of water were added for extraction, and the obtained organic phase was dried with 5 g of anhydrous sodium sulfate, filtered, and then rotary evaporation was carried out under reduced pressure at 55℃ for 1 h to obtain a phosphorus-nitrogen flame retardant;

[0010] S2, preparation of a polyurethane prepolymer

[0011] 20 g of polybutylene glycol was placed in a dry glass container, and heated to 120℃, then the glass container was vacuumed to remove residual moisture, and argon gas was filled as a protective gas, then the temperature of the reaction system was reduced to 80℃, 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added to the system, and stirring was carried out under argon gas environment for 5 h to obtain a polyurethane prepolymer;

[0012] S3, preparation of an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer

[0013] The phosphorus-nitrogen flame retardant and lanthanum carbonate were dispersed in a round-bottom flask, 5 mL of N,N-dimethylformamide was added under nitrogen protection, and stirring was carried out for 20-30 min to obtain a composite solution; the temperature of the polyurethane prepolymer was adjusted to 55℃, the composite solution and 0.9 g of 1,4-butanediol were added, stirring was carried out for 1-2 min, 0.6 g of triethylamine was added to obtain a polymer emulsion, which was then poured into a polytetrafluoroethylene mold, and placed in an oven for reaction and curing to obtain an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer.

[0014] As a limitation of the preparation method of the present application, in step S1, the molar ratio of cystamine dihydrochloride, triethylamine and diphenyl phosphinic chloride is 5:20:10.

[0015] As a second limitation of the preparation method of the present application, in step S1, the dropwise addition rate of diphenyl phosphinic chloride is 1 mL / min.

[0016] In the present application, the dropwise addition rate of diphenyl phosphinic chloride will affect the yield and purity of the phosphorus-nitrogen flame retardant, thus affecting its flame retardant effect. When the dropwise addition rate is 1 mL / min, the amino group of cystamine dihydrochloride and the chlorine element of diphenyl phosphinic chloride will just combine to form hydrogen chloride, thus maximizing the yield of the phosphorus-nitrogen flame retardant; when the dropwise addition rate is less than 1 mL / min, the diphenyl phosphinic chloride will volatilize rapidly, thus causing incomplete reaction of the cystamine dihydrochloride, resulting in too low yield and purity of the phosphorus-nitrogen flame retardant, and ultimately leading to reduced flame retardant effect; when the dropwise addition rate is greater than 1 mL / min, the cystamine dihydrochloride cannot fully react with the diphenyl phosphinic chloride, resulting in residual diphenyl phosphinic chloride. The residual diphenyl phosphinic chloride will further undergo a hydrolysis side reaction with moisture in the air, producing impurities, resulting in too low yield and purity of the phosphorus-nitrogen flame retardant, and ultimately leading to reduced flame retardant effect.

[0017] As a third limitation of the preparation method of the present application, in step S3, the molar ratio of the phosphorus-nitrogen flame retardant to lanthanum carbonate is 3:1.

[0018] In the present application, the molar ratio of the phosphorus-nitrogen flame retardant to lanthanum carbonate will affect the flame retardant effect and mechanical properties of the polyurethane elastomer. When the molar ratio is as such, the phosphorus-oxygen double bond of the phosphorus-nitrogen flame retardant will just form a coordination bond with the lanthanum carbonate, maximizing the flame retardant effect and mechanical properties; when the molar ratio is greater than this, there will be too much phosphorus-nitrogen flame retardant, causing the phosphorus-nitrogen flame retardant to be distributed between the hard segment and the soft segment, and its polarity to interact with the hard segment or the soft segment, acting as a "compatibilizer" or "diluent" between the two, reducing the incompatibility between the hard segment and the soft segment, hindering the ordered aggregation and formation of the hard segment microzone, causing the physical crosslinking network to be weakened and become imperfect, thus leading to a decrease in the mechanical properties of the polyurethane elastomer; when the molar ratio is less than this, there will be too much lanthanum carbonate, which will also cause the lanthanum carbonate to be distributed between the hard segment and the soft segment, causing the physical crosslinking network to be weakened and become imperfect, thus leading to a decrease in the mechanical properties of the polyurethane elastomer.

[0019] As a fourth limitation of the preparation method of the present application, in step S3, the addition amount of the phosphorus-nitrogen flame retardant is 5% of the total volume of the polyurethane prepolymer.

[0020] In the present application, the addition amount of phosphorus-nitrogen flame retardant is crucial, when the addition amount of phosphorus-nitrogen flame retardant is 5% of the total volume of polyurethane prepolymer, the phosphorus-nitrogen flame retardant will be embedded in the high molecular chain segment of the polyurethane elastomer, so that the mechanical properties and flame retardant properties of the polyurethane elastomer are maximized; when the addition amount of phosphorus-nitrogen flame retardant is greater than 5% of the total volume of polyurethane, too much phosphorus-nitrogen flame retardant will cause the remaining phosphorus-nitrogen flame retardant not to be embedded in the high molecular chain segment of the polyurethane elastomer, resulting in the crosslinking point of polybutylene glycol and isophorone diisocyanate being destroyed, so that the mechanical properties of the polyurethane elastomer are greatly reduced; when the addition amount of phosphorus-nitrogen flame retardant is less than 5% of the total volume of polyurethane prepolymer, too little phosphorus-nitrogen flame retardant will cause the flame retardant properties of the polyurethane elastomer to decrease.

[0021] As a fifth limitation of the preparation method of the present application, in step S3, the temperature during the reaction and curing in the oven is 80-85℃, and the time is 45-48 h.

[0022] As the last limitation of the preparation method of the present application, in step S1, the structural formula of the phosphorus-nitrogen flame retardant prepared is:

[0023] .

[0024] The present application embeds the additive phosphorus-nitrogen flame retardant and lanthanum carbonate into the polyurethane elastomer network through chemical reaction. During the reaction, lanthanum ions can form coordination bonds with the phosphorus-oxygen double bond (P=O) in the phosphorus-nitrogen flame retardant molecule. This coordination bond, as a weak bond, will quickly break down during combustion, releasing a large amount of lanthanum ions. These lanthanum ions quickly react with oxygen to form lanthanum oxide (La2O3), not only quickly consuming oxygen, but also forming a dense insulating layer on the surface of the polyurethane, forming a dense insulating layer. At the same time, the decomposition of carbonate ions releases carbon dioxide, which can effectively dilute the oxygen concentration and inhibit combustion. In addition, the phosphorus-nitrogen flame retardant can capture oxygen radicals in the gas phase during combustion, interrupting the chain reaction, thereby forming a blocking layer in the gas phase, achieving a dual flame-retardant effect in the gas and condensed phases.

[0025] The above technical solutions of the present application are closely related and interact with each other as a whole, which together determine the morphology and performance of the product.

[0026] The above technical solutions have the following advantages or beneficial effects:

[0027] 1、The limiting oxygen index value of the polyurethane elastomer prepared by the present application reaches 35.2, and the UL-94 test reaches V-0 flame retardant grade; and the polyurethane elastomer has good flame retardant properties while maintaining high tensile strength, the tensile strength can reach 27.9 MPa;

[0028] 2. During the combustion process, the polyurethane elastomer prepared by this invention captures oxygen free radicals in the air, isolating the combustible material from oxygen free radicals, thereby forming a blocking layer. At the same time, the coordination bond formed by lanthanum ions and phosphorus-oxygen double bonds breaks rapidly, releasing lanthanum ions that combine with oxygen to form lanthanum oxide. This not only rapidly consumes oxygen, but the generated lanthanum oxide, as a non-combustible substance, covers the surface of the polyurethane, forming a blocking layer. Carbonate ions form carbon dioxide during combustion, thereby diluting the oxygen and further preventing the combustion of polyurethane.

[0029] 3. The preparation method of the present invention is simple, the process is easy to control, the preparation cycle is short, and the cost is low.

[0030] This invention is applicable to the preparation of additive nitrogen, phosphorus, and lanthanum synergistic flame-retardant polyurethane elastomers.

[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0032] Figure 1 The structure characterization diagram of the phosphorus-nitrogen flame retardant prepared in step S1 of Example 1 of the present invention is shown in the figure. (A) is the elemental analysis test diagram of the phosphorus-nitrogen flame retardant, (B) is the elemental analysis simulation diagram of the phosphorus-nitrogen flame retardant, (C) is the high-resolution mass spectrum of the phosphorus-nitrogen flame retardant, and (D) is the infrared spectrum of the phosphorus-nitrogen flame retardant.

[0033] Figure 2 The images shown are infrared images of the polyurethane elastomers prepared in Examples 1-3 of the present invention and scanning electron microscope (SEM) images of the polyurethanes in Examples 1 and 1 and Comparative Example 1 after combustion, wherein: (A) is an SEM image of Example 1 after combustion, (B) is an SEM image of Comparative Example 1 after combustion, and (C) is an infrared image of the polyurethane elastomers prepared in Examples 1-3.

[0034] Figure 3 The images show the LOI test results of the polyurethane elastomer prepared in Example 1 of this invention, wherein: (A) is the LOI test result at 0 s after ignition, (B) is the LOI test result at 5 s after ignition, and (C) is the LOI test result at 10 s after ignition.

[0035] Figure 4 The images shown are LOI test diagrams of the polyurethane elastomer prepared in Example 2 of the present invention, wherein: (A) is the LOI test diagram at 0 s after ignition, (B) is the LOI test diagram at 5 s after ignition, and (C) is the LOI test diagram at 10 s after ignition.

[0036] Figure 5LOI test plots for the polyurethane elastomer prepared for Inventive Example 3, where: (A) is the LOI test plot at 0 s of ignition, (B) is the LOI test plot at 5 s of ignition, and (C) is the LOI test plot at 10 s of ignition;

[0037] Figure 6 LOI test plots for the polyurethane elastomer prepared for Inventive Example 3, where: (A) is the LOI test plot at 0 s of ignition, (B) is the LOI test plot at 5 s of ignition, and (C) is the LOI test plot at 10 s of ignition;

[0038] Figure 7 LOI test plots for the polyurethane elastomer prepared for Inventive Example 3, where: (A) is the LOI test plot at 0 s of ignition, (B) is the LOI test plot at 5 s of ignition, and (C) is the LOI test plot at 10 s of ignition;

[0039] Figure 8 LOI test plots for the polyurethane elastomer prepared for Inventive Example 3, where: (A) is the LOI test plot at 0 s of ignition, (B) is the LOI test plot at 5 s of ignition, and (C) is the LOI test plot at 10 s of ignition;

[0040] Figure 9 LOI test plots for the polyurethane elastomer prepared for Inventive Example 3, where: (A) is the LOI test plot at 0 s of ignition, (B) is the LOI test plot at 5 s of ignition, and (C) is the LOI test plot at 10 s of ignition;

[0041] Figure 10 LOI test plots for the polyurethane elastomer prepared for Inventive Example 3, where: (A) is the LOI test plot at 0 s of ignition, (B) is the LOI test plot at 5 s of ignition, and (C) is the LOI test plot at 10 s of ignition;

[0042] Figure 11 LOI test plots for the polyurethane elastomer prepared for Inventive Example 3, where: (A) is the LOI test plot at 0 s of ignition, (B) is the LOI test plot at 5 s of ignition, and (C) is the LOI test plot at 10 s of ignition;

[0043] Figure 12 Vertical burn test plots for the polyurethane elastomer prepared for Inventive Example 1, where: (A) is the vertical burn test plot at 0 s of ignition, (B) is the vertical burn test plot at 5 s of ignition, and (C) is the vertical burn test plot at 10 s of ignition;

[0044] Figure 13Vertical burn test photographs of the polyurethane elastomer prepared in accordance with Example 2 of the present invention, wherein: (A) is a vertical burn test photograph at 0 s of ignition, (B) is a vertical burn test photograph at 5 s of ignition, and (C) is a vertical burn test photograph at 10 s of ignition;

[0045] Figure 14 Vertical burn test photographs of the polyurethane elastomer prepared in accordance with Example 3 of the present invention, wherein: (A) is a vertical burn test photograph at 0 s of ignition, (B) is a vertical burn test photograph at 5 s of ignition, and (C) is a vertical burn test photograph at 10 s of ignition;

[0046] Figure 15 Vertical burn test photographs of the polyurethane elastomer prepared in accordance with Comparative Example 1 of the present invention, wherein: (A) is a vertical burn test photograph at 0 s of ignition, (B) is a vertical burn test photograph at 5 s of ignition, and (C) is a vertical burn test photograph at 10 s of ignition;

[0047] Figure 16 Vertical burn test photographs of the polyurethane elastomer prepared in accordance with Comparative Example 2 of the present invention, wherein: (A) is a vertical burn test photograph at 0 s of ignition, (B) is a vertical burn test photograph at 5 s of ignition, and (C) is a vertical burn test photograph at 10 s of ignition;

[0048] Figure 17 Vertical burn test photographs of the polyurethane elastomer prepared in accordance with Comparative Example 3 of the present invention, wherein: (A) is a vertical burn test photograph at 0 s of ignition, (B) is a vertical burn test photograph at 5 s of ignition, and (C) is a vertical burn test photograph at 10 s of ignition;

[0049] Figure 18 Vertical burn test photographs of the polyurethane elastomer prepared in accordance with Comparative Example 4 of the present invention, wherein: (A) is a vertical burn test photograph at 0 s of ignition, (B) is a vertical burn test photograph at 5 s of ignition, and (C) is a vertical burn test photograph at 10 s of ignition;

[0050] Figure 19 Vertical burn test photographs of the polyurethane elastomer prepared in accordance with Comparative Example 5 of the present invention, wherein: (A) is a vertical burn test photograph at 0 s of ignition, (B) is a vertical burn test photograph at 5 s of ignition, and (C) is a vertical burn test photograph at 10 s of ignition;

[0051] Figure 20 Vertical burn test photographs of the polyurethane elastomer prepared in accordance with Comparative Example 6 of the present invention, wherein: (A) is a vertical burn test photograph at 0 s of ignition, (B) is a vertical burn test photograph at 5 s of ignition, and (C) is a vertical burn test photograph at 10 s of ignition. DETAILED DESCRIPTION

[0052] The following examples are merely illustrative of some embodiments of the application and do not limit the scope of the application as there are many alternatives for the embodiments besides those explicitly described. The following detailed description of the embodiments of the application is not intended to limit the scope of the application as claimed, but merely to provide a selected embodiment of the application.

[0053] In the present application, all the equipment and raw materials, etc. can be purchased from the market or commonly used in the industry, unless otherwise specified. The methods in the following examples are all conventional methods in the art, unless otherwise specified. Example 1

[0054] This example prepares an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer, and the preparation process and steps are as follows:

[0055] S1, preparation of an additive type phosphorus-nitrogen flame retardant

[0056] In a glass flask, 50 mL of tetrahydrofuran solution was added, 5 mol of cystamine dihydrochloride and 20 mol of triethylamine were added, and stirring was carried out at 400 rpm until complete dissolution. 10 mol of diphenyl phosphinic chloride was added dropwise at a rate of 1 mL / min at 0°C, and the reaction was stirred at 400 rpm for 6 h. The reaction mixture was quenched with water, and 100 mL of ethyl acetate and 30 mL of water were added for extraction. The obtained organic phase was dried with 5 g of anhydrous sodium sulfate, filtered, and then rotary evaporated at 55°C under reduced pressure for 1 h to obtain a phosphorus-nitrogen flame retardant;

[0057] S2, preparation of polyurethane prepolymer

[0058] 20 g of polybutylene glycol with a molecular weight of 2500 was placed in a 80°C air drying oven for 2 h to remove water, and was placed in a dry glass container and heated to 120°C. The glass container was then evacuated to remove residual water and filled with argon as a protective gas. The temperature of the reaction system was then reduced to 80°C, 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added, and the system was stirred at 600 rpm under argon for 5 h to obtain a polyurethane prepolymer.

[0059] S3, preparation of an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer

[0060] 3 mmol phosphorus-nitrogen flame retardant and 1 mmol lanthanum carbonate were dispersed in a round-bottom flask, 5 mL N,N-dimethylformamide was added under nitrogen protection, and stirring was carried out at 400 rpm for 30 min to obtain a composite solution; the temperature of the polyurethane prepolymer system was adjusted to 55℃ (the addition amount of the phosphorus-nitrogen flame retardant added to the polyurethane prepolymer was 5% of the mass of the polyurethane prepolymer), the composite solution and 0.9 g of 1,4-butanediol were added, stirring was carried out at 600 rpm for 1 min, 0.6 g of triethylamine was added, a polymer emulsion was obtained, and then it was poured into a polytetrafluoroethylene mold, and reaction and curing were carried out in an 80℃ oven for 48 h to obtain an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer. Example 2

[0061] An additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer was prepared in this example, and the preparation process and steps were as follows:

[0062] S1, preparation of an additive type phosphorus-nitrogen flame retardant

[0063] In a glass flask, 50 mL of tetrahydrofuran solution was added, then 5 mol of cystamine dihydrochloride and 20 mol of triethylamine were added, stirring was carried out at 400 rpm until complete dissolution, 10 mol of diphenyl phosphinic chloride was added dropwise at a rate of 1 mL / min at 0℃, and stirring was carried out at 400 rpm for 6 h, then the reaction mixture was quenched with water, 100 mL of ethyl acetate and 30 mL of water were added for extraction, the obtained organic phase was dried with 5 g of anhydrous sodium sulfate, filtered, and then rotary evaporation was carried out at 55℃ under reduced pressure for 1 h to obtain a phosphorus-nitrogen flame retardant;

[0064] S2, preparation of a polyurethane prepolymer

[0065] 20 g of polybutylene glycol with a molecular weight of 2500 was placed in a 80℃ air-drying oven for 2 h to remove water, and then it was placed in a dry glass container and heated to 120℃, then the glass container was vacuumed to remove residual water, and then argon was filled as a protective gas, then the temperature of the reaction system was reduced to 80℃, 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added, and stirring was carried out at 600 rpm under argon for 5 h to obtain a polyurethane prepolymer;

[0066] S3, preparation of an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer

[0067] 3 mmol phosphorus-nitrogen flame retardant and 1 mmol lanthanum carbonate were dispersed in a round-bottom flask, 5 mL N,N-dimethylformamide was added under nitrogen protection, and stirring was carried out at 400 rpm for 20 min to obtain a composite solution; the temperature of the polyurethane prepolymer system was adjusted to 55°C (the addition amount of the phosphorus-nitrogen flame retardant added to the polyurethane prepolymer was 5% of the volume of the polyurethane prepolymer), the composite solution and 0.9 g of 1,4-butanediol were added, stirring was carried out at 600 rpm for 1.5 min, 0.6 g of triethylamine was added, a polymer emulsion was obtained, and then it was poured into a polytetrafluoroethylene mold, and reaction and curing were carried out in an oven at 83°C for 45 h to obtain an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer. Example 3

[0068] In this example, an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer was prepared, and the preparation process and steps were as follows:

[0069] S1, preparation of an additive type phosphorus-nitrogen flame retardant

[0070] In a glass flask, 50 mL of tetrahydrofuran solution was added, 5 mol of cystamine dihydrochloride and 20 mol of triethylamine were added, and stirring was carried out at 400 rpm until complete dissolution. 10 mol of diphenyl phosphinic chloride was added dropwise at a rate of 1 mL / min at 0°C, and stirring was carried out at 400 rpm for 6 h. The reaction mixture was quenched with water, 100 mL of ethyl acetate and 30 mL of water were added for extraction, and the obtained organic phase was dried with 5 g of anhydrous sodium sulfate, filtered, and then rotary evaporated at 55°C under reduced pressure for 1 h to obtain a phosphorus-nitrogen flame retardant;

[0071] S2, preparation of a polyurethane prepolymer

[0072] 20 g of polybutylene glycol with a molecular weight of 2500 was placed in a 80°C air-drying oven for 2 h to remove water, and then it was placed in a dry glass container and heated to 120°C. The glass container was then evacuated to remove residual water and filled with argon as a protective gas. The temperature of the reaction system was then reduced to 80°C, 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added, and stirring was carried out at 600 rpm under argon for 5 h to obtain a polyurethane prepolymer;

[0073] S3, preparation of an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer

[0074] 3 mmol phosphorus-nitrogen flame retardant and 1 mmol lanthanum carbonate were dispersed in a round-bottom flask, 5 mL N,N-dimethylformamide was added under nitrogen protection, and stirring was carried out at 400 rpm for 25 min to obtain a composite solution; the temperature of the polyurethane prepolymer system was adjusted to 55°C (the addition amount of the phosphorus-nitrogen flame retardant added to the polyurethane prepolymer was 5% of the volume of the polyurethane prepolymer), the composite solution and 0.9 g of 1,4-butanediol were added, stirring was carried out at 600 rpm for 2 min, 0.6 g of triethylamine was added, a polymer emulsion was obtained, and then it was poured into a polytetrafluoroethylene mold, and reaction and curing were carried out in an oven at 85°C for 47 h to obtain a nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer. Comparative Example

[0075] In order to explore the influence of adding different substances or using different parameters in the preparation process of the present application on the performance of the product of the present application, the following comparative experiments were carried out, and different polyurethane elastomers were prepared in the following comparative examples:

[0076] Comparative Example 1

[0077] A polyurethane elastomer was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that no phosphorus-nitrogen flame retardant and lanthanum carbonate were added in step S3.

[0078] Comparative Example 2

[0079] A polyurethane elastomer was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that no lanthanum carbonate was added in step S3.

[0080] Comparative Example 3

[0081] A polyurethane elastomer was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that no phosphorus-nitrogen flame retardant was added in step S3.

[0082] Comparative Example 4

[0083] A polyurethane elastomer was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that the rate of adding diphenyl phosphinic chloride was 2 mL / min in step S1.

[0084] Comparative Example 5

[0085] A polyurethane elastomer was prepared in this comparative example, and the preparation process was similar to that of Example 1, except that the mass ratio of phosphorus-nitrogen flame retardant to polyurethane elastomer was 3% in step S3.

[0086] Comparative Example 6

[0087] A polyurethane elastomer was prepared in the same manner as in Example 1, except that in step S3, the molar ratio of phosphorus-nitrogen flame retardant to lanthanum carbonate was 2:1.

[0088] Performance test

[0089] The polyurethane elastomers prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to relevant performance tests, and the specific test results are as follows:

[0090] As Figure 1 is the structure characterization diagram of the phosphorus-nitrogen flame retardant prepared in step S1 of Example 1 of the present application, wherein: (A) is the elemental analysis test diagram of the phosphorus-nitrogen flame retardant, (B) is the elemental analysis simulation diagram of the phosphorus-nitrogen flame retardant, (C) is the high-resolution mass spectrum diagram of the phosphorus-nitrogen flame retardant, and (D) is the infrared diagram of the phosphorus-nitrogen flame retardant; from Figure 1 (A) and (B) can be seen that the proportions of N, C, H, and S of the organically synthesized phosphorus-nitrogen flame retardant are 5.01%, 59.64%, 5.68%, and 11.73%, respectively, which is basically the same as the elemental simulation proportion of the phosphorus-nitrogen flame retardant structure formula, which preliminarily indicates that the phosphorus-nitrogen flame retardant is synthesized; from Figure 1 (C) can be seen that the relative molecular mass of the organically synthesized phosphorus-nitrogen flame retardant is 552, which meets the M+1 criterion, further indicating that the phosphorus-nitrogen flame retardant is synthesized; from Figure 1 (D) can be seen that the -NH2 and P-Cl peaks on the ligand of the organically synthesized phosphorus-nitrogen flame retardant disappear, and a P-N peak appears at 920 cm -1 and a -NH peak appears at 3320 cm -1 , indicating that the phosphorus-nitrogen flame retardant is synthesized.

[0091] As Figure 2 is the infrared diagram of the polyurethane elastomers prepared in Examples 1-3 and the scanning electron microscope diagram of the polyurethane after combustion of Example 1 and Comparative Example 1, wherein: (A) is the scanning electron microscope diagram of Example 1 after combustion, (B) is the scanning electron microscope diagram of Comparative Example 1 after combustion, and (C) is the infrared diagram of the polyurethane elastomers prepared in Examples 1-3; from Figure 2 (A) can be seen that the surface layer of the polyurethane after combustion is more compact after adding the phosphorus-nitrogen flame retardant and lanthanum carbonate, indicating that the organically synthesized phosphorus-nitrogen flame retardant and lanthanum carbonate form a flame-retardant layer, which achieves the effect of separating air combustible gas, thereby achieving better flame-retardant effect; from Figure 2 (B) can be seen that the residual carbon layer after combustion of the pure polyurethane has a loose and porous structure, and its compactness is significantly different from the compact flame-retardant carbon layer obtained in Example 1; from Figure 2As can be seen in (C), after the phosphorus-nitrogen flame retardant and lanthanum carbonate, the position of P=O peak is shifted backward, indicating that lanthanum ion forms a coordination bond with the P=O of the ligand of the organic synthetic phosphorus-nitrogen flame retardant.

[0092] Figures 3 to 11 The LOI test figures of the polyurethane elastomers prepared in Examples 1-3 and Comparative Examples 1-6 of the present application; as can be seen from the figures, the flame retardant effect is not obvious when only the phosphorus-nitrogen flame retardant or the lanthanum carbonate is added; when the phosphorus-nitrogen flame retardant and the lanthanum carbonate are added together, the LOI of the polyurethane is obviously improved.

[0093] Figures 12 to 20 The vertical combustion test figures of the polyurethane elastomers prepared in Examples 1-3 and Comparative Examples 1-6 of the present application; as can be seen from the figures, the polyurethane elastomer in which only the phosphorus-nitrogen flame retardant or the lanthanum carbonate is added has a serious dripping phenomenon, and the dripped drops ignite the absorbent cotton below; when the phosphorus-nitrogen flame retardant and the lanthanum carbonate are added, there is no obvious dripping phenomenon, and the V-0 level is reached.

[0094] The polyurethane materials prepared in Examples 1-3 and Comparative Examples 1-6 are subjected to flame retardant performance and mechanical property tests, and the specific test results are shown in the following table:

[0095] .

[0096] As can be seen from the above table, compared with Comparative Example 1-6, the added-type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer prepared by using the technical solution of the present application has improved flame retardancy while still maintaining high mechanical properties.

[0097] Finally, it should be noted that: the above only describes the preferred embodiments of the present application and is not used to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced equivalently. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the claims of the present application.

Claims

1. A process for the preparation of a synergistic flame retardant polyurethane elastomer with additive nitrogen phosphorus lanthanum characterized in that, The following steps are carried out in sequence: S1, preparation of additive phosphorus-nitrogen flame retardant In a glass flask, 50 mL of tetrahydrofuran solution was added, then cystamine dihydrochloride and triethylamine were added, stirred until completely dissolved, and then diphenyl phosphinic chloride was slowly added dropwise at 0°C, and the reaction was stirred for 6 h. The reaction mixture was quenched with water, extracted with 100 mL of ethyl acetate and 30 mL of water, and the obtained organic phase was dried with 5 g of anhydrous sodium sulfate, filtered, and then rotary evaporated at 55°C under reduced pressure for 1 h to obtain the phosphorus-nitrogen flame retardant; S2, preparation of polyurethane prepolymer 20 g of polybutylene glycol was placed in a dry glass container and heated to 120°C, then the glass container was vacuumed to remove residual moisture and filled with argon as a protective gas, then the temperature of the reaction system was reduced to 80°C, 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added, and stirred for 5 h under argon atmosphere to obtain the polyurethane prepolymer; S3, preparation of additive nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer The phosphorus-nitrogen flame retardant and lanthanum carbonate were dispersed in a round-bottom flask, 5 mL of N,N-dimethylformamide was added under nitrogen protection, and stirred for 20-30 min to obtain a composite solution; the temperature of the polyurethane prepolymer was adjusted to 55°C, the composite solution and 0.9 g of 1,4-butanediol were added, stirred for 1-2 min, 0.6 g of triethylamine was added to obtain a polymer emulsion, which was then poured into a polytetrafluoroethylene mold and placed in an oven for reaction and curing to obtain the additive nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer.

2. The preparation method of the additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S1, the molar ratio of cystamine dihydrochloride to triethylamine to diphenyl phosphinic chloride is 5:20:

10.

3. The preparation method of the additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S1, the dropwise addition rate of diphenyl phosphinic chloride is 1 mL / min.

4. The preparation method of the additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S3, the molar ratio of the phosphorus-nitrogen flame retardant to lanthanum carbonate is 3:

1.

5. The method for preparing the additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S3, the addition amount of the phosphorus-nitrogen flame retardant is 5% of the total volume of the polyurethane prepolymer.

6. The method for preparing the additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S3, the temperature for reaction and curing in the oven is 80-85°C, and the time is 45-48 h.

7. The preparation method of the additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer according to any one of claims 1-3, characterized in that, In step S1, the structure of the prepared phosphorus-nitrogen flame retardant is: 。

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