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

Abstract

The invention discloses a preparation method of an additive type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer, which is prepared by compounding isocyanate as a hard segment and polybutylene glycol as a soft segment with a phosphorus-nitrogen flame retardant and lanthanum carbonate, the preparation method is simple, the process is easy to control, when the prepared polyurethane elastomer burns, the phosphorus-nitrogen flame retardant isolates oxygen free radicals to form a blocking layer, lanthanum coordination bonds break to generate lanthanum oxide to consume oxygen and cover the surface of polyurethane, carbonate is decomposed to release carbon dioxide to dilute oxygen, and the phosphorus-nitrogen flame retardant, the lanthanum oxide and the carbonate synergistically prevent polyurethane from burning, so that the flame-retardant performance of the polyurethane elastomer is improved. The limit oxygen index of the flame-retardant material reaches 35.2, and the commercial standard of the flame-retardant material and the UL-94 V-0 flame-retardant grade requirement are met; in addition, the polyurethane elastomer also has good mechanical properties, and the tensile strength of the polyurethane elastomer can reach 27.9 MPa.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials and relates to a method for preparing an additive nitrogen, phosphorus and lanthanum synergistic flame-retardant polyurethane elastomer. Background Art

[0002] Polyurethane elastomer (TPU), a new thermoplastic polymer, offers excellent wear resistance, flexibility, and environmental resistance, making it widely used in industries such as wire and cable, construction, automobiles, and furniture. However, due to its inherent richness in organic elements such as carbon, hydrogen, oxygen, and nitrogen, it is highly flammable, releasing large amounts of heat and toxic fumes during combustion, posing a threat to both personnel and the environment. This severely restricts its use in related fields. Consequently, the development of flame-retardant polyurethane elastomers has become a focus of industry attention.

[0003] Traditional flame-retardant polyurethanes are made by adding halogen-based flame retardants. While this is highly effective (a 15-20% addition can achieve V-0 rating), it releases highly toxic substances and corrosive gases during combustion, restricting its use under regulations such as the EU RoHS. Phosphorus-nitrogen intumescent flame retardants (such as the ammonium polyphosphate (APP) / pentaerythritol (PER) system) are susceptible to moisture absorption and migration in TPU, and the resulting porous char layer during combustion makes it difficult to effectively isolate oxygen and heat. Furthermore, lanthanide rare earth compounds, due to their unique electron shell structure (unfilled 4f orbitals) and Lewis acidity, have recently been shown to exhibit excellent flame retardant synergy. However, when used alone as polyurethane flame retardants, 20 wt.% is required to achieve a reasonable flame retardant effect. Excessive addition of rare earth compounds not only makes polyurethane elastomers difficult to mold but also significantly degrades mechanical properties.

[0004] Based on this, the present invention aims to provide a polyurethane elastomer with good flame retardant effect. The prepared polyurethane elastomer can be applied to various industries. While having excellent flame retardant effect, it can also maintain high tensile strength. Summary of the Invention

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

[0006] To achieve the above object, the technical solution adopted by the present invention is: A method for preparing an additive nitrogen, phosphorus and lanthanum synergistic flame-retardant polyurethane elastomer is carried out in the following steps in sequence: S1. Preparation of additive phosphorus-nitrogen flame retardant 50 mL of tetrahydrofuran solution was added to a glass flask, followed by cystamine dihydrochloride and triethylamine, and the mixture was stirred until completely dissolved. Diphenylphosphinyl chloride was slowly added dropwise in an ice bath at 0°C, and the mixture was stirred 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 over 5 g of anhydrous sodium sulfate, filtered, and then vacuum rotary evaporated at 55°C for 1 h to obtain a 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. The container was then evacuated to remove residual moisture and filled with argon as a protective gas. The temperature of the reaction system was then lowered to 80°C. 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added to the system, and the mixture was stirred under argon for 5 h to obtain a polyurethane prepolymer. S3. Preparation of added nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer The phosphorus-nitrogen flame retardant and lanthanum carbonate were dispersed in a round-bottom flask, and 5 mL of N,N-dimethylformamide was added under nitrogen protection. The mixture was stirred for 20-30 minutes to obtain a composite solution. The temperature of the polyurethane prepolymer was adjusted to 55°C, and the composite solution and 0.9 g of 1,4-butanediol were added. The mixture was stirred for 1-2 minutes, and 0.6 g of triethylamine was added to obtain a polymer emulsion. The emulsion was then poured into a polytetrafluoroethylene mold and placed in an oven for reaction and curing to obtain an additive nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer.

[0007] As a limitation of the preparation method of the present invention, in step S1, the molar ratio of cystamine dihydrochloride to triethylamine and diphenylphosphinyl chloride is 5:20:10.

[0008] As a second limitation of the preparation method of the present invention, in step S1, the dropping rate of the diphenylphosphinic chloride is 1 mL / min.

[0009] In the present invention, the addition rate of diphenylphosphinoyl chloride affects the yield and purity of the synthesis of the phosphorus-nitrogen flame retardant, thereby affecting its flame retardant effect. When the addition rate is 1 mL / min, the amino group of cystamine dihydrochloride and the chlorine element of diphenylphosphinoyl chloride will just combine to form hydrogen chloride, thereby maximizing the yield of the synthesis of the phosphorus-nitrogen flame retardant; when the addition rate is less than 1 mL / min, the diphenylphosphinoyl chloride will volatilize rapidly, resulting in the incomplete reaction of cystamine dihydrochloride, making the yield and purity of the synthesis of the phosphorus-nitrogen flame retardant too low, and ultimately resulting in a reduction in the flame retardant effect; when the addition rate is greater than 1 mL / min, the cystamine dihydrochloride will not be able to fully react with the diphenylphosphinoyl chloride, resulting in residual diphenylphosphinoyl chloride. The residual diphenylphosphinoyl chloride then undergoes a hydrolysis side reaction with moisture in the air to produce impurities, resulting in too low a yield and low purity of the synthesis of the phosphorus-nitrogen flame retardant, ultimately resulting in a reduction in the flame retardant effect.

[0010] As a third limitation of the preparation method of the present invention, in step S3, the molar ratio of the phosphorus-nitrogen flame retardant to lanthanum carbonate is 3:1.

[0011] In the present invention, the molar ratio of the phosphorus-nitrogen flame retardant to lanthanum carbonate affects the flame retardant effect and mechanical properties of the polyurethane elastomer. When this molar ratio is reached, the phosphorus-oxygen double bond of the phosphorus-nitrogen flame retardant forms a coordination bond with the lanthanum carbonate, maximizing the flame retardant effect and mechanical properties. When the molar ratio is greater than this, the phosphorus-nitrogen flame retardant is excessive, resulting in the phosphorus-nitrogen flame retardant being distributed between the hard segment and the soft segment. Its polarity interacts 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 orderly aggregation and formation of hard segment microdomains, and causing the physical crosslinking network to be weakened and imperfect, thereby reducing the mechanical properties of the polyurethane elastomer. When the molar ratio is less than this, the lanthanum carbonate is excessive, which also causes the lanthanum carbonate to be distributed between the hard segment and the soft segment, resulting in the physical crosslinking network to be weakened and imperfect, thereby reducing the mechanical properties of the polyurethane elastomer.

[0012] As a fourth limitation of the preparation method of the present invention, in step S3, the amount of the phosphorus-nitrogen flame retardant added is 5% of the total volume of the polyurethane prepolymer.

[0013] In the present invention, the amount of phosphorus-nitrogen flame retardant added is crucial. When the amount of phosphorus-nitrogen flame retardant added is 5% of the total volume of the polyurethane prepolymer, the phosphorus-nitrogen flame retardant will be just embedded in the polymer chain segments of the polyurethane elastomer, so that the mechanical properties and flame retardant properties of the polyurethane elastomer are maximized; when the amount of phosphorus-nitrogen flame retardant added is greater than 5% of the total volume of the polyurethane, the phosphorus-nitrogen flame retardant will be excessive, resulting in the remaining phosphorus-nitrogen flame retardant not being embedded in the polymer chain segments of the polyurethane elastomer, causing the cross-linking points of polybutylene glycol and isophorone diisocyanate to be destroyed, resulting in a significant decrease in the mechanical properties of the polyurethane elastomer; when the amount of phosphorus-nitrogen flame retardant added is less than 5% of the total volume of the polyurethane prepolymer, the phosphorus-nitrogen flame retardant is too insufficient, resulting in a decrease in the flame retardant properties of the polyurethane elastomer.

[0014] As a fifth limitation of the preparation method of the present invention, in step S3, the temperature during the reaction and curing in the oven is 80-85° C., and the time is 45-48 h.

[0015] As the last limitation of the preparation method of the present invention, in step S1, the structural formula of the phosphorus-nitrogen flame retardant prepared is: .

[0016] The present invention embeds an additive phosphorus-nitrogen flame retardant and lanthanum carbonate into a polyurethane elastomer network through a chemical reaction. During the reaction, lanthanum ions form coordination bonds with the phosphorus-oxygen double bonds (P=O) in the phosphorus-nitrogen flame retardant molecules. These weak coordination bonds rapidly break during combustion, releasing a large number of lanthanum ions. These lanthanum ions react rapidly with oxygen to form lanthanum oxide (La2O3), which not only rapidly consumes oxygen but also coats the polyurethane surface with the non-flammable lanthanum oxide, forming a dense insulating layer. Simultaneously, the carbon dioxide released by the decomposition of carbonate ions effectively dilutes the oxygen concentration and suppresses combustion. Furthermore, during combustion, the phosphorus-nitrogen flame retardant captures oxygen free radicals in the gas phase, interrupting the chain reaction and forming a blocking layer in the gas phase, achieving a dual flame retardant effect in both the gas and condensed phases.

[0017] The above technical solution of the present invention is taken as a whole, and the various steps are closely related and influence each other, which jointly determine the morphological characteristics and performance of the product.

[0018] The above technical solution has the following advantages or beneficial effects: 1. The polyurethane elastomer prepared by the present invention has a limiting oxygen index value of 35.2 and a flame retardancy rating of V-0 according to the UL-94 test. Furthermore, the polyurethane elastomer has good flame retardancy while maintaining a high tensile strength of 27.9 MPa. 2. During the combustion process of the polyurethane elastomer prepared by the present invention, the phosphorus-nitrogen flame retardant captures oxygen free radicals in the air, isolating the combustibles from the oxygen free radicals, thereby forming a blocking layer. At the same time, the coordination bond formed by the lanthanum ion and the phosphorus-oxygen double bond is rapidly broken, releasing the lanthanum ion to combine with oxygen to form lanthanum oxide. This not only quickly consumes oxygen, but the generated lanthanum oxide, as a non-combustible substance, covers the surface of the polyurethane to form a blocking layer. Carbonate ions form carbon dioxide during the combustion process, thereby achieving the effect of diluting oxygen and further preventing the combustion of the polyurethane. 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.

[0019] The invention is suitable for preparing added nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Figure 1 is a structural representation of the phosphorus-nitrogen flame retardant prepared in step S1 of Example 1 of the present invention, wherein: (A) is an elemental analysis test diagram of the phosphorus-nitrogen flame retardant, (B) is an elemental analysis simulation diagram of the phosphorus-nitrogen flame retardant, (C) is a high-resolution mass spectrum of the phosphorus-nitrogen flame retardant, and (D) is an infrared image of the phosphorus-nitrogen flame retardant; Figure 2 These are infrared images of the polyurethane elastomers prepared in Examples 1-3 of the present invention and scanning electron micrographs of the polyurethanes of Example 1 and Comparative Example 1 after combustion, wherein: (A) is a scanning electron micrograph of Example 1 after combustion, (B) is a scanning electron micrograph of Comparative Example 1 after combustion, and (C) is an infrared image of the polyurethane elastomers prepared in Examples 1-3; Figure 3 LOI test graphs of the polyurethane elastomer prepared in Example 1 of the present invention, wherein: (A) is the LOI test graph at 0 s after ignition, (B) is the LOI test graph at 5 s after ignition, and (C) is the LOI test graph at 10 s after ignition; Figure 4 LOI test graphs of the polyurethane elastomer prepared in Example 2 of the present invention, wherein: (A) is the LOI test graph at 0 s after ignition, (B) is the LOI test graph at 5 s after ignition, and (C) is the LOI test graph at 10 s after ignition; Figure 5 LOI test graphs of the polyurethane elastomer prepared in Example 3 of the present invention, wherein: (A) is the LOI test graph at 0 s after ignition, (B) is the LOI test graph at 5 s after ignition, and (C) is the LOI test graph at 10 s after ignition; Figure 6LOI test graphs of the polyurethane elastomer prepared in Comparative Example 1 of the present invention, wherein: (A) is the LOI test graph at 0 s after ignition, (B) is the LOI test graph at 5 s after ignition, and (C) is the LOI test graph at 10 s after ignition; Figure 7 LOI test graphs of the polyurethane elastomer prepared in Comparative Example 2 of the present invention, wherein: (A) is the LOI test graph at 0 s after ignition, (B) is the LOI test graph at 5 s after ignition, and (C) is the LOI test graph at 10 s after ignition; Figure 8 LOI test graphs of the polyurethane elastomer prepared in Comparative Example 3 of the present invention, wherein: (A) is the LOI test graph at 0 s after ignition, (B) is the LOI test graph at 5 s after ignition, and (C) is the LOI test graph at 10 s after ignition; Figure 9 LOI test graphs of the polyurethane elastomer prepared in Comparative Example 4 of the present invention, wherein: (A) is the LOI test graph at 0 s after ignition, (B) is the LOI test graph at 5 s after ignition, and (C) is the LOI test graph at 10 s after ignition; Figure 10 LOI test graphs of the polyurethane elastomer prepared in Comparative Example 5 of the present invention, wherein: (A) is the LOI test graph at 0 s after ignition, (B) is the LOI test graph at 5 s after ignition, and (C) is the LOI test graph at 10 s after ignition; Figure 11 LOI test graphs of the polyurethane elastomer prepared in Comparative Example 6 of the present invention, wherein: (A) is the LOI test graph at 0 s after ignition, (B) is the LOI test graph at 5 s after ignition, and (C) is the LOI test graph at 10 s after ignition; Figure 12 The vertical combustion test graphs of the polyurethane elastomer prepared in Example 1 of the present invention are shown, wherein: (A) is the vertical combustion test graph at 0 s after ignition, (B) is the vertical combustion test graph at 5 s after ignition, and (C) is the vertical combustion test graph at 10 s after ignition; Figure 13 The vertical combustion test graphs of the polyurethane elastomer prepared in Example 2 of the present invention are shown, wherein: (A) is the vertical combustion test graph at 0 s after ignition, (B) is the vertical combustion test graph at 5 s after ignition, and (C) is the vertical combustion test graph at 10 s after ignition; Figure 14 The vertical combustion test graphs of the polyurethane elastomer prepared in Example 3 of the present invention are shown, wherein: (A) is the vertical combustion test graph at 0 s after ignition, (B) is the vertical combustion test graph at 5 s after ignition, and (C) is the vertical combustion test graph at 10 s after ignition; Figure 15 The vertical combustion test graphs of the polyurethane elastomer prepared in Comparative Example 1 of the present invention are shown, wherein: (A) is the vertical combustion test graph at 0 s after ignition, (B) is the vertical combustion test graph at 5 s after ignition, and (C) is the vertical combustion test graph at 10 s after ignition; Figure 16 The vertical combustion test graphs of the polyurethane elastomer prepared in Comparative Example 2 of the present invention are shown, wherein: (A) is the vertical combustion test graph at 0 s after ignition, (B) is the vertical combustion test graph at 5 s after ignition, and (C) is the vertical combustion test graph at 10 s after ignition; Figure 17 The vertical combustion test graphs of the polyurethane elastomer prepared in Comparative Example 3 of the present invention are shown, wherein: (A) is the vertical combustion test graph at 0 s after ignition, (B) is the vertical combustion test graph at 5 s after ignition, and (C) is the vertical combustion test graph at 10 s after ignition; Figure 18 The vertical combustion test graphs of the polyurethane elastomer prepared in Comparative Example 4 of the present invention are shown, wherein: (A) is the vertical combustion test graph at 0 s after ignition, (B) is the vertical combustion test graph at 5 s after ignition, and (C) is the vertical combustion test graph at 10 s after ignition; Figure 19 The vertical combustion test graphs of the polyurethane elastomer prepared in Comparative Example 5 of the present invention are shown, wherein: (A) is the vertical combustion test graph at 0 s after ignition, (B) is the vertical combustion test graph at 5 s after ignition, and (C) is the vertical combustion test graph at 10 s after ignition; Figure 20 These are vertical combustion test diagrams of the polyurethane elastomer prepared in Comparative Example 6 of the present invention, wherein: (A) is the vertical combustion test diagram at 0 s after ignition, (B) is the vertical combustion test diagram at 5 s after ignition, and (C) is the vertical combustion test diagram at 10 s after ignition. DETAILED DESCRIPTION

[0022] The following embodiments are merely some of the embodiments of the present invention, rather than all of them. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. All other embodiments derived by those skilled in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0023] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art. Example 1

[0024] This embodiment prepares an additive nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastic material, and the preparation process and steps are as follows: S1. Preparation of additive phosphorus-nitrogen flame retardant 50 mL of tetrahydrofuran solution was added to a glass flask, followed by 5 mol of cystamine dihydrochloride and 20 mol of triethylamine. The mixture was stirred at 400 rpm until completely dissolved. 10 mol of diphenylphosphinyl chloride was added dropwise at a rate of 1 mL / min at 0°C, and the mixture 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 over 5 g of anhydrous sodium sulfate, filtered, and then subjected to reduced pressure rotary evaporation at 55°C for 1 h to obtain a phosphorus-nitrogen flame retardant. S2. Preparation of polyurethane prepolymer 20 g of polybutylene glycol (2500 molecular weight) was placed in a forced air drying oven at 80°C for 2 h to remove moisture, placed in a dry glass container, and heated to 120°C. The glass container was then evacuated to remove residual moisture and filled with argon as a protective gas. The temperature of the reaction system was then lowered to 80°C, 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added to the system, and the mixture was stirred at 600 rpm under an argon atmosphere for 5 h to obtain a polyurethane prepolymer. S3. Preparation of added nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer 3 mmol of phosphorus-nitrogen flame retardant and 1 mmol of lanthanum carbonate were dispersed in a round-bottom flask. Under nitrogen protection, 5 mL of N,N-dimethylformamide was added, and the mixture was stirred at 400 rpm for 30 min to obtain a composite solution. The temperature of the polyurethane prepolymer system was adjusted to 55°C (the amount of phosphorus-nitrogen flame retardant added to the polyurethane prepolymer was 5% of the mass of the polyurethane prepolymer), and the composite solution and 0.9 g of 1,4-butanediol were added. The mixture was stirred at 600 rpm for 1 min, and 0.6 g of triethylamine was added to obtain a polymer emulsion. The emulsion was then poured into a polytetrafluoroethylene mold and reacted and cured in an 80°C oven for 48 h to obtain an additive-type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer. Example 2

[0025] This embodiment prepares an additive nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastic material, and the preparation process and steps are as follows: S1. Preparation of additive phosphorus-nitrogen flame retardant 50 mL of tetrahydrofuran solution was added to a glass flask, followed by 5 mol of cystamine dihydrochloride and 20 mol of triethylamine. The mixture was stirred at 400 rpm until completely dissolved. 10 mol of diphenylphosphinyl chloride was added dropwise at a rate of 1 mL / min at 0°C, and the mixture 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 over 5 g of anhydrous sodium sulfate, filtered, and then subjected to reduced pressure rotary evaporation at 55°C for 1 h to obtain a phosphorus-nitrogen flame retardant. S2. Preparation of polyurethane prepolymer 20 g of polybutylene glycol (2500 molecular weight) was placed in a forced air drying oven at 80°C for 2 h to remove moisture, placed in a dry glass container, and heated to 120°C. The glass container was then evacuated to remove residual moisture and filled with argon as a protective gas. The temperature of the reaction system was then lowered to 80°C, 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added to the system, and the mixture was stirred at 600 rpm under an argon atmosphere for 5 h to obtain a polyurethane prepolymer. S3. Preparation of added nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer 3 mmol of phosphorus-nitrogen flame retardant and 1 mmol of lanthanum carbonate were dispersed in a round-bottom flask. Under nitrogen protection, 5 mL of N,N-dimethylformamide was added, and the mixture was stirred at 400 rpm for 20 min to obtain a composite solution. The temperature of the polyurethane prepolymer system was adjusted to 55°C (the amount of phosphorus-nitrogen flame retardant added to the polyurethane prepolymer was 5% of the polyurethane prepolymer volume), and the composite solution and 0.9 g of 1,4-butanediol were added. The mixture was stirred at 600 rpm for 1.5 min, and 0.6 g of triethylamine was added to obtain a polymer emulsion. The emulsion was then poured into a polytetrafluoroethylene mold and reacted and cured in an 83°C oven for 45 h to obtain an additive-type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer. Example 3

[0026] This embodiment prepares an additive nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastic material, and the preparation process and steps are as follows: S1. Preparation of additive phosphorus-nitrogen flame retardant 50 mL of tetrahydrofuran solution was added to a glass flask, followed by 5 mol of cystamine dihydrochloride and 20 mol of triethylamine. The mixture was stirred at 400 rpm until completely dissolved. 10 mol of diphenylphosphinyl chloride was added dropwise at a rate of 1 mL / min at 0°C, and the mixture 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 over 5 g of anhydrous sodium sulfate, filtered, and then subjected to reduced pressure rotary evaporation at 55°C for 1 h to obtain a phosphorus-nitrogen flame retardant. S2. Preparation of polyurethane prepolymer 20 g of polybutylene glycol (2500 molecular weight) was placed in a forced air drying oven at 80°C for 2 h to remove moisture, placed in a dry glass container, and heated to 120°C. The glass container was then evacuated to remove residual moisture and filled with argon as a protective gas. The temperature of the reaction system was then lowered to 80°C, 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added to the system, and the mixture was stirred at 600 rpm under an argon atmosphere for 5 h to obtain a polyurethane prepolymer. S3. Preparation of added nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer 3 mmol of phosphorus-nitrogen flame retardant and 1 mmol of lanthanum carbonate were dispersed in a round-bottom flask. Under nitrogen protection, 5 mL of N,N-dimethylformamide was added, and the mixture was stirred at 400 rpm for 25 min to obtain a composite solution. The temperature of the polyurethane prepolymer system was adjusted to 55°C (the amount of phosphorus-nitrogen flame retardant added to the polyurethane prepolymer was 5% of the polyurethane prepolymer volume), and the composite solution and 0.9 g of 1,4-butanediol were added. The mixture was stirred at 600 rpm for 2 min, and 0.6 g of triethylamine was added to obtain a polymer emulsion. The emulsion was then poured into a polytetrafluoroethylene mold and reacted and cured in an 85°C oven for 47 h to obtain an additive-type nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer. Comparative Example

[0027] In order to explore the effects of adding different substances or using different parameters in the preparation process of the present invention on the performance of the product of the present invention, the following comparative experiments were conducted. Different polyurethane elastomers were prepared in the following comparative examples, as follows: Comparative Example 1 In this comparative example, a polyurethane elastomer is prepared. The preparation process is similar to that of Example 1, except that in step S3, no phosphorus-nitrogen flame retardant and lanthanum carbonate are added.

[0028] Comparative Example 2 In this comparative example, a polyurethane elastomer is prepared. The preparation process is similar to that of Example 1, except that lanthanum carbonate is not added in step S3.

[0029] Comparative Example 3 In this comparative example, a polyurethane elastomer is prepared. The preparation process is similar to that of Example 1, except that no phosphorus-nitrogen flame retardant is added in step S3.

[0030] Comparative Example 4 In this comparative example, a polyurethane elastomer was prepared. The preparation process was similar to that of Example 1, except that in step S1, the rate of adding diphenylphosphine chloride was 2 mL / min.

[0031] Comparative Example 5 In this comparative example, a polyurethane elastomer is prepared. The preparation process is similar to that of Example 1, except that in step S3, the mass ratio of the phosphorus-nitrogen flame retardant to the polyurethane elastomer is 3%.

[0032] Comparative Example 6 In this comparative example, a polyurethane elastomer is prepared. The preparation process is similar to that of Example 1, except that in step S3, the molar ratio of the phosphorus-nitrogen flame retardant to lanthanum carbonate is 2:1. Performance Testing

[0033] The polyurethane elastomers prepared in Examples 1-3 of the present invention and Comparative Examples 1-6 were subjected to relevant performance tests, and the specific test results are as follows: like Figure 1 , which are structural characterization diagrams of the phosphorus-nitrogen flame retardant prepared in step S1 of Example 1 of the present invention, wherein: (A) is an elemental analysis test diagram of the phosphorus-nitrogen flame retardant, (B) is an elemental analysis simulation diagram of the phosphorus-nitrogen flame retardant, (C) is a high-resolution mass spectrum diagram of the phosphorus-nitrogen flame retardant, and (D) is an infrared diagram of the phosphorus-nitrogen flame retardant; from Figure 1 As can be seen from Figure (A) and Figure (B), the ratios of N, C, H, and S in the organically synthesized phosphorus-nitrogen flame retardant are 5.01%, 59.64%, 5.68%, and 11.73%, respectively, which are basically the same as the element simulation ratios of the phosphorus-nitrogen flame retardant structure, preliminarily indicating that the phosphorus-nitrogen flame retardant has been synthesized; Figure 1 As can be seen from (C), 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 has been synthesized; Figure 1 As can be seen in (D), the -NH2 and P-Cl peaks on the organically synthesized phosphorus-nitrogen flame retardant ligands disappear, and the peak at 920 cm -1 There is a PN peak at 3320 cm -1 The -NH peak appeared at , indicating that phosphorus-nitrogen flame retardant was synthesized.

[0034] like Figure 2 , are infrared images of the polyurethane elastomers prepared in Examples 1-3 of the present invention and scanning electron microscope images of the polyurethanes of Example 1 and Comparative Example 1 after combustion, wherein: (A) is a scanning electron microscope image of Example 1 after combustion, (B) is a scanning electron microscope image of Comparative Example 1 after combustion; (C) is an infrared image of the polyurethane elastomers prepared in Examples 1-3; from Figure 2 As can be seen from (A), the surface of the polyurethane with added phosphorus-nitrogen flame retardant and lanthanum carbonate is denser after combustion, indicating that the organically synthesized phosphorus-nitrogen flame retardant and lanthanum carbonate form a flame-retardant layer, which achieves the effect of isolating the combustible gas from the air, thereby achieving a better flame retardant effect; Figure 2As can be seen from (B), the residual carbon layer after the combustion of pure polyurethane is loose and porous, and its density is significantly different from the dense flame-retardant carbon layer obtained in Example 1; Figure 2 As can be seen in (C), after the addition of phosphorus-nitrogen flame retardant and lanthanum carbonate, the position of the P=O peak shifts backward, indicating that the lanthanum ion forms a coordination bond with the P=O of the organic synthetic phosphorus-nitrogen flame retardant ligand.

[0035] Figures 3 to 11 The LOI test graphs of the polyurethane elastomers prepared in Examples 1-3 of the present invention and Comparative Examples 1-6 are shown respectively. As can be seen from the graph, the flame retardant effect of only adding the phosphorus-nitrogen flame retardant or lanthanum carbonate is not obvious. When the phosphorus-nitrogen flame retardant and lanthanum carbonate are added together, the LOI of the polyurethane is significantly improved.

[0036] Figures 12 to 20 This is a vertical combustion test diagram of the polyurethane elastomer prepared by Examples 1-3 of the present invention and Comparative Examples 1-6. As can be seen from the figure, the polyurethane elastomer to which only the phosphorus-nitrogen flame retardant or lanthanum carbonate was added had severe dripping, and the dripping droplets ignited the absorbent cotton below. When the phosphorus-nitrogen flame retardant and lanthanum carbonate were added, there was no obvious dripping phenomenon, and the V-0 grade was achieved.

[0037] The polyurethane materials prepared in Examples 1-3 and Comparative Examples 1-6 were subjected to flame retardancy and mechanical property tests. The specific test results are shown in the following table: .

[0038] It can be seen from the above table that, compared with comparative examples 1-6, the added nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer prepared using the technical solution of the present invention has improved flame retardancy while still maintaining high mechanical properties.

[0039] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an additive nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer, characterized in that: Follow the steps below in order: S1. Preparation of additive phosphorus-nitrogen flame retardant Add 50 mL of tetrahydrofuran solution to a glass flask, then add cystamine dihydrochloride and triethylamine, stir until completely dissolved, slowly add diphenylphosphinyl chloride dropwise at 0°C, stir and react for 6 h, quench the reaction mixture with water, add 100 mL of ethyl acetate and 30 mL of water for extraction, dry the obtained organic phase with 5 g of anhydrous sodium sulfate, filter, and evaporate under reduced pressure at 55°C for 1 h to obtain a 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. The container was then evacuated to remove residual moisture and filled with argon as a protective gas. The temperature of the reaction system was then lowered to 80°C. 3.34 g of isophorone diisocyanate and 0.002 g of butyltin dilaurate were added to the system, and the mixture was stirred under argon for 5 h to obtain a polyurethane prepolymer. S3. Preparation of added nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer A phosphorus-nitrogen flame retardant and lanthanum carbonate were dispersed in a round-bottom flask, and 5 mL of N,N-dimethylformamide was added under nitrogen protection. The mixture was stirred for 20-30 minutes to obtain a composite solution. The temperature of the polyurethane prepolymer was adjusted to 55°C, and the composite solution and 0.9 g of 1,4-butanediol were added. The mixture was stirred for 1-2 minutes, and 0.6 g of triethylamine was added to obtain a polymer emulsion. The emulsion was then poured into a polytetrafluoroethylene mold and placed in an oven for reaction and curing to obtain an additive nitrogen-phosphorus-lanthanum synergistic flame-retardant polyurethane elastomer.

2. The method for preparing an additive nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer according to claim 1, characterized in that: In step S1, the molar ratio of cystamine dihydrochloride to triethylamine and diphenylphosphinyl chloride is 5:20:

10.

3. The method for preparing an additive nitrogen, phosphorus and lanthanum synergistic flame retardant polyurethane elastomer according to claim 1, characterized in that: In step S1, the dropwise addition rate of diphenylphosphine chloride is 1 mL / min.

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

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

7. The method for preparing an additive nitrogen, phosphorus and lanthanum synergistic flame-retardant polyurethane elastomer according to any one of claims 1 to 3, characterized in that: In step S1, the structural formula of the prepared phosphorus-nitrogen flame retardant is: 。

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