Preparation method and application of flame-retardant polyurethane elastomer

Abstract

This invention relates to a method for preparing and applying a flame-retardant polyurethane elastomer. The flame-retardant polyurethane elastomer incorporates a network structure, benzene rings, diphenyl phosphate, and silicon-oxygen bonds, increasing the degree of crosslinking and improving mechanical and self-extinguishing properties. Furthermore, the rigid triazine ring structural units effectively enhance the interactions between molecular chains, forming reinforced hard-segment microregions; while the flexible siloxane chains, with their low surface energy, promote microphase separation. This synergistic effect gives the flame-retardant polyurethane elastomer excellent overall performance. The chain extender contains abundant nitrogen and silicon dual flame-retardant elements, which can release non-flammable gases and form a dense silicate layer during combustion, endowing the material with good self-extinguishing ability. The flame-retardant polyurethane elastomer of this invention has excellent recyclability and self-extinguishing properties, can be applied in encapsulation materials, and is environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a method for preparing and applying a flame-retardant polyurethane elastomer. Background Technology

[0002] Polyurethane elastomers have been widely used in numerous fields, including electronic packaging, medical consumables, and aerospace, thanks to their controllable molecular structure, excellent elasticity, and superior abrasion resistance. To date, polyurethane products with excellent mechanical properties and special functions are experiencing explosive growth.

[0003] However, achieving a synergistic improvement in tensile properties (strength and elongation) and optimization for sustainability remains a core bottleneck hindering its breakthrough into high-end applications. Furthermore, with the deepening of the concept of sustainable development, developing high-performance polymer materials that are green, environmentally friendly, and recyclable has become a current research hotspot and challenge. Traditional polyurethane elastomers are highly flammable, potentially leading to rapid combustion and the release of large amounts of heat, while simultaneously producing significant smoke and toxic gases. Therefore, it is crucial to achieve polyurethane materials that combine excellent tensile properties, recyclability, and the ability to suppress combustion risks through effective synthesis processes and chain extension modification of different molecules, introducing strong molecular forces and unique functional structures.

[0004] In conclusion, there is an urgent need to develop a new technical solution to address the problems existing in the current technology. Summary of the Invention

[0005] Based on this, the present invention provides a method for preparing flame-retardant polyurethane elastomers, ultimately forming polyurethane molecules with separated soft and hard microphases and abundant dynamic hydrogen bonds. Therefore, the flame-retardant polyurethane elastomers prepared by the present invention possess excellent mechanical properties, self-extinguishing characteristics, and chemical recyclability.

[0006] The purpose of this invention is to provide a method for preparing a flame-retardant polyurethane elastomer, the method comprising the following steps: S1. Pentaerythritol triacrylate, hydroxyethyl acrylate, butyl acrylate, styrene, diphenyl methacrylate-2-hydroxyethyl phosphate, vinyl silicone oil, and initiator are blended and heated and stirred to obtain an intermediate product. S2. Under an inert atmosphere, the isocyanate, diol, intermediate product and catalyst are mixed and heated and stirred to obtain intermediate 1 mixture. S3. Under an inert atmosphere, the intermediate 1 mixture and the triazine compound chain extender are mixed, heated and stirred to react, and intermediate 2 mixture is obtained. S4. Under an inert atmosphere, the intermediate 2 mixture and the siloxane chain extender are mixed, heated and stirred to react, poured into a mold, and cured to obtain the flame-retardant polyurethane elastomer.

[0007] Furthermore, the isocyanate is selected from one or more of toluene diisocyanate, dicyclohexylmethane isocyanate, hexamethyl diisocyanate, and isophorone diisocyanate.

[0008] Further, in step S1, the molar ratio of pentaerythritol triacrylate, hydroxyethyl acrylate, butyl acrylate, styrene, 2-hydroxyethyl methacrylate diphenyl phosphate, and vinyl silicone oil is (0.1-8):(1-6):(1-6):(1-6):(1-6):(0.5-2).

[0009] Furthermore, in step S1, the heating temperature is 60-100℃.

[0010] Further, the mass ratio of the isocyanate, diol, intermediate product, triazine compound chain extender, and siloxane chain extender is (1-3):(1-10):(1-5):(0.1-2):(0.1-2).

[0011] Furthermore, in step S2, the heating temperature is 60-90℃.

[0012] Furthermore, in step S2, the reaction time is 1-4 hours.

[0013] Furthermore, in step S3, the heating temperature is 65-85°C.

[0014] Furthermore, in step S3, the reaction time is 2-5 hours.

[0015] This invention uses a triazine compound as the first chain extender. The rigid triazine ring structure effectively enhances intermolecular interactions, thereby strengthening the molecular framework. A siloxane is used as the second chain extender; the flexible siloxane chains enhance molecular entanglement, forming a more compact molecular network. Ultimately, a polyurethane with soft and hard segment microphase separation and abundant dynamic hydrogen bonds is formed.

[0016] In the flame-retardant polyurethane elastomer prepared by this invention, triazine compounds are selected as hard segments due to their aromatic rigid structure and high steric hindrance, which promotes the formation of the hard segment skeleton within the elastomer. To further improve mechanical and thermal properties, siloxanes are introduced as secondary chain extenders to enhance the thermal stability of the polyurethane and reduce surface energy, thereby promoting the formation of microphase separation. Microphase separation promotes the formation of aggregated morphologies on the material surface, which can better withstand and disperse stress when subjected to external forces. This invention provides an innovative solution for the preparation of flame-retardant polyurethane elastomers through the synergistic regulation of two chain extenders.

[0017] This invention further expands the other properties of flame-retardant polyurethane elastomers. The chain extender provides abundant hydrogen bonds to the polymer molecules, resulting in excellent recyclability of the flame-retardant polyurethane elastomer. Simultaneously, the chain extender contains abundant nitrogen and silicon dual flame-retardant elements, which release non-flammable gases and form a dense silicate layer during combustion, endowing the material with good self-extinguishing ability. The prepared film has further proven to be an effective encapsulation material for electronic sensors, maintaining sensing accuracy while suppressing flame propagation. Therefore, this work provides a new strategy for enhancing the mechanical properties, recyclability, and self-extinguishing properties of flame-retardant polyurethane elastomers, showing great application potential in electronic sensor encapsulation.

[0018] The present invention has the following beneficial effects: This invention provides a method for preparing and applying a flame-retardant polyurethane elastomer. The flame-retardant polyurethane elastomer is prepared by first blending pentaerythritol triacrylate, hydroxyethyl acrylate, butyl acrylate, styrene, diphenyl methacrylate-2-hydroxyethyl phosphate, and vinyl silicone oil to undergo a polymerization reaction to obtain an intermediate product. Then, isocyanate is blended with diol, the intermediate product, a triazine chain extender, and a siloxane chain extender to obtain the flame-retardant polyurethane elastomer.

[0019] The flame-retardant polyurethane elastomer of this invention incorporates a network structure, benzene rings, diphenyl phosphate, and silicon-oxygen bonds through intermediate products. The network structure increases the degree of crosslinking, improving mechanical properties. The benzene rings possess a rigid structure and steric hindrance, further enhancing mechanical properties. During combustion, diphenyl phosphate promotes polymer dehydration and carbonization, forming a coke layer. This coke layer provides heat and oxygen insulation, preventing the underlying material from continuing to burn, thus improving flame-retardant properties (self-extinguishing properties). The silicon-oxygen bonds in the vinyl silicone oil have high bond energy and can form tighter molecular entanglements, further improving mechanical properties. Attached Figure Description

[0020] Figure 1 The process of recycling Example 1 is shown; Figure 2 The self-extinguishing capability test results of Example 1 are shown; in, Figure 2 (a) Example 1 is shown after the limiting oxygen index test; Figure 2 (b) shows the vertical combustion test procedure of Example 1.

[0021] Figure 3 The packaging test results of the electronic sensor in Example 1 are shown; in, Figure 3(a) shows the current signal results of the packaging test of the electronic sensor in Example 1; Figure 3 (b) shows the self-extinguishing capability test results of the electronic sensor after packaging in Example 1. Detailed Implementation

[0022] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0023] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0024] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0025] The embodiments of the present invention use the following raw materials: Vinyl silicone oil, molecular weight 160, purchased from Nantong Runfeng Petrochemical Co., Ltd.

[0026] Polytetrahydrofuran diol, with a molecular weight of 2000.

[0027] Poly(dimethylsiloxane), bis(3-aminopropyl)-terminated, with a molecular weight of 2500.

[0028] Polybutylene glycol diol, with a molecular weight of 2500.

[0029] Example 1 A method for preparing a flame-retardant polyurethane elastomer, the method comprising the following steps: S1. Using n-butanol as solvent, pentaerythritol triacrylate, hydroxyethyl acrylate, butyl acrylate, styrene, diphenyl methacrylate-2-hydroxyethyl phosphate, vinyl silicone oil, and initiator azobisisobutyronitrile were blended in a molar ratio of 0.5:1:4:2:2:1:0.15, heated to 90°C and stirred for 2.5 h. The solvent was removed, and the mixture was dried to obtain the intermediate product. S2. Under a nitrogen atmosphere, isophorone diisocyanate, polytetrahydrofuran diol, intermediate product, catalyst dibutyltin dilaurate, and solvent anhydrous tetrahydrofuran are mixed in a mass ratio of 2:5.5:1:0.009:12.5 and stirred at 65°C for 2 hours to obtain intermediate 1 mixture. S3. Under a nitrogen atmosphere, the intermediate 1 mixture and the triazine compound chain extender benzomelamine (the mass ratio of benzomelamine to isophorone diisocyanate of S2 is 0.5:2) are mixed and stirred at 65°C for 2.5 h to obtain intermediate 2 mixture. S4. Under a nitrogen atmosphere, the intermediate 2 mixture and the siloxane chain extender 1,3-bis(3-aminopropyl)tetramethyldisiloxane (the mass ratio of 1,3-bis(3-aminopropyl)tetramethyldisiloxane to the isophorone diisocyanate of S2 is 0.2:2) are stirred and reacted at 50°C for 1 hour. The mixture is then poured into a polytetrafluoroethylene mold and placed in a vacuum oven to cure and dry at 80°C for 24 hours to obtain the flame-retardant polyurethane elastomer.

[0030] Example 2 A method for preparing a flame-retardant polyurethane elastomer, the method comprising the following steps: S1. Using n-butanol as solvent, pentaerythritol triacrylate, hydroxyethyl acrylate, butyl acrylate, styrene, diphenyl methacrylate-2-hydroxyethyl phosphate, vinyl silicone oil, and initiator azobisisobutyronitrile were blended in a molar ratio of 0.5:1:4:2:2:1:0.15, heated to 90°C and stirred for 2.5 h. The solvent was removed, and the mixture was dried to obtain the intermediate product. S2. Under a nitrogen atmosphere, isophorone diisocyanate, polytetrahydrofuran diol, intermediate product, catalyst dibutyltin dilaurate, and solvent N,N-dimethylformamide were mixed in a mass ratio of 1:6:1:0.009:25.3 and stirred at 65°C for 2 hours to obtain intermediate 1 mixture. S3. Under a nitrogen atmosphere, the intermediate 1 mixture and the triazine compound chain extender benzomelamine (the mass ratio of benzomelamine to isophorone diisocyanate of S2 is 0.25:1) are mixed and stirred at 65°C for 2.5 h to obtain intermediate 2 mixture. S4. Under a nitrogen atmosphere, the intermediate 2 mixture, the siloxane chain extender poly(dimethylsiloxane), and the bis(3-aminopropyl) end-capped compound (the mass ratio of poly(dimethylsiloxane), bis(3-aminopropyl) end-capped compound, and the isophorone diisocyanate of S2 is 0.5:1) are stirred and reacted at 45°C for 1 hour. The mixture is then poured into a polytetrafluoroethylene mold and placed in a vacuum oven to cure and dry at 80°C for 24 hours to obtain the flame-retardant polyurethane elastomer.

[0031] Example 3 A method for preparing a flame-retardant polyurethane elastomer, the method comprising the following steps: S1. Using n-butanol as solvent, pentaerythritol triacrylate, hydroxyethyl acrylate, butyl acrylate, styrene, diphenyl methacrylate-2-hydroxyethyl phosphate, vinyl silicone oil, and initiator azobisisobutyronitrile were blended in a molar ratio of 0.5:1:4:2:2:1:0.15, heated to 90°C and stirred for 2.5 h. The solvent was removed, and the mixture was dried to obtain the intermediate product. S2. Under a nitrogen atmosphere, toluene diisocyanate, polyethylene glycol diol, intermediate product, catalyst dibutyltin dilaurate, and solvent N,N-dimethylacetamide were mixed in a mass ratio of 1:8.9:1:0.01:29.8 and stirred at 60°C for 3 hours to obtain intermediate 1 mixture. S3. Under a nitrogen atmosphere, the intermediate 1 mixture and the triazine compound chain extender benzomelamine (the mass ratio of benzomelamine to toluene diisocyanate of S2 is 0.3:1) are mixed and stirred at 70°C for 3 hours to obtain intermediate 2 mixture. S4. Under a nitrogen atmosphere, the intermediate 2 mixture and the siloxane chain extender 1,3-bis(3-aminopropyl)tetramethyldisiloxane (the mass ratio of 1,3-bis(3-aminopropyl)tetramethyldisiloxane to the toluene diisocyanate of S2 is 0.1:1) are stirred and reacted at 45°C for 1.5 h. The mixture is then poured into a polytetrafluoroethylene mold and placed in a vacuum oven to cure and dry at 85°C for 36 h to obtain the flame-retardant polyurethane elastomer.

[0032] Example 4 The difference between Example 4 and Example 2 is that the polytetrahydrofuran diol in S2 is replaced with polybutylene glycol ester (molecular weight 3000), and the poly(dimethylsiloxane), bis(3-aminopropyl)-terminated (molecular weight 2500) in S4 is replaced with dihydroxy-terminated polydimethylsiloxane (molecular weight 2000). The remaining components and preparation methods are the same as in Example 2.

[0033] Example 5 The difference between Example 5 and Example 2 is as follows: The mass ratio of isophorone diisocyanate, polytetrahydrofuran diol, intermediate product, catalyst dibutyltin dilaurate, and solvent N,N-dimethylformamide in S2 was modified to 1:4.5:1:0.009:25.3. The triazine chain extender in S3 was replaced with 4,6-diamino-2-hydroxy-1,3,5-triazine, and the mass ratio of 4,6-diamino-2-hydroxy-1,3,5-triazine to isophorone diisocyanate was 0.1:1. The siloxane chain extender in S4 was replaced with α,ω-dihydroxy polydimethylsiloxane (molecular weight 2500), and the mass ratio of α,ω-dihydroxy polydimethylsiloxane to isophorone diisocyanate was 1.3:1.

[0034] The remaining components and preparation methods are the same as in Example 2.

[0035] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that pentaerythritol triacrylate, 2-hydroxyethyl methacrylate diphenyl phosphate, and vinyl silicone oil in step S1 are replaced with butyl acrylate, while the remaining components and preparation methods are the same as in Example 1.

[0036] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that 2-hydroxyethyl phosphate diphenyl methacrylate and vinyl silicone oil in step S1 are replaced with butyl acrylate, while the remaining components and preparation methods are the same as in Example 1.

[0037] Test Example 1 Mechanical properties were tested on the product samples prepared in Examples 1-2 and Comparative Examples 1-2.

[0038] Test method: The product samples were cut into dumbbell shapes with an effective area of ​​20 mm long, 4 mm wide, and 0.5 mm thick. They were stretched using a universal tensile testing machine at a speed of 50 mm / min, and the maximum load and elongation at break were recorded. The tensile strength was calculated using the formula σ = F / S, where σ is the tensile strength (MPa), F is the maximum load before fracture in the tensile test (N), and S is the cross-sectional area of ​​the sample (mm²). 2 ).

[0039] The test results are shown in Table 1.

[0040] Table 1 Mechanical performance test results As shown in Table 1, the samples of Examples 1-2 exhibit better overall performance than those of Comparative Examples 1-2. This is because Comparative Example 1 did not introduce a network structure, diphenyl phosphate, or silicon-oxygen bonds, leading to a decrease in mechanical properties. Similarly, Comparative Example 2, lacking diphenyl phosphate and silicon-oxygen bonds, also experienced a decline in mechanical properties. The results of Examples 1-2 indicate that the short-chain siloxane chain extender in Example 1 can increase the stress of the sample, while the long-chain siloxane chain extender in Example 2 can increase the strain of the sample.

[0041] Test Example 2 The recovery capacity of the product samples prepared in Example 1 and Comparative Examples 1-2 was tested.

[0042] Test method: The shredded sample was dissolved in anhydrous tetrahydrofuran. After complete dissolution, the solution was poured into a polytetrafluoroethylene mold and re-cured into a film. The curing process was the same as S4 in Example 1. The tensile properties of the re-cured film (0.5 mm thick) were tested using the same method as in Example 1.

[0043] Figure 1 The process of recycling Example 1 is shown.

[0044] The test results are shown in Table 2.

[0045] Table 2 Recycling Capacity Test Results As can be seen from Table 2, Example 1 has good recycling ability, and the mechanical properties after recycling are still at a high level, which is better than Comparative Examples 1-2. This is because Comparative Example 1 did not introduce a network structure, diphenyl phosphate, or silicon-oxygen bonds, which caused a decrease in mechanical properties after recycling, thus resulting in a decrease in recycling ability. Similarly, Comparative Example 2 did not introduce diphenyl phosphate or silicon-oxygen bonds, which also caused a decrease in mechanical properties after recycling, resulting in a decrease in recycling ability.

[0046] Test Example 3 The self-extinguishing ability of the product samples prepared in Example 1 and Comparative Examples 1-2 was tested.

[0047] Test method: The limiting oxygen index was tested according to GB / T 2406.2-2009 standard, and the vertical combustion test was conducted according to CB / T 2408-2008 standard. The sample size was 100mm×13mm×3mm (length×width×thickness). The sample was placed vertically 30cm above the absorbent cotton, and the combustion phenomenon was recorded every 10s to evaluate the combustion characteristics of the sample.

[0048] Test results are as follows Figure 2 As shown in Table 3.

[0049] Figure 2 The self-extinguishing capability test results of Example 1 are shown; in, Figure 2 (a) Example 1 is shown after the limiting oxygen index test; Figure 2 (b) shows the vertical combustion test procedure of Example 1.

[0050] Table 3. Results of Self-Extinguishing Capability Test Test results show that the sample of Example 1 has the ability to self-extinguish quickly during combustion. It can only burn in an environment with a minimum oxygen concentration of 28%, and is therefore a self-extinguishing material. In other words, the self-extinguishing ability of Example 1 is better than that of Comparative Examples 1-2. This is because Comparative Example 1 did not introduce a network structure, diphenyl phosphate, or silicon-oxygen bonds, which led to a decrease in self-extinguishing ability. Similarly, Comparative Example 2 did not introduce diphenyl phosphate or silicon-oxygen bonds, which also resulted in a decrease in self-extinguishing ability.

[0051] Test Example 4 The product sample prepared in Example 1 was subjected to packaging tests for electronic sensors.

[0052] Test method: The electronic sensor was encapsulated with a sample, and then objects of different weights, such as glass beads and chestnuts, were applied to the electronic sensor. The mass information of the objects was collected by the acquisition module and converted into different current signals in mA. The changes in the current signals before and after encapsulation were compared. The encapsulated electronic sensor was then subjected to an ignition test. A corner of the encapsulated sensor film was ignited with a high-temperature flame source for 5 seconds and then the flame source was slowly removed to observe its actual self-extinguishing ability.

[0053] The test results of Example 1 are as follows Figure 3 As shown.

[0054] Figure 3 The packaging test results of the electronic sensor in Example 1 are shown; in, Figure 3 (a) shows the current signal results of the packaging test of the electronic sensor in Example 1; Figure 3 (b) shows the self-extinguishing capability test results of the electronic sensor after packaging in Example 1.

[0055] Test results show that the sensor encapsulated in Example 1 does not hinder the conversion process of the current signal. After the quality signal is collected, it is output as a current signal through the electronic module. The reading is basically the same as that of the unencapsulated sensor and can still sensitively display the current signal. Furthermore, after the high-temperature fire source is removed, the flame of the sensor encapsulated in Example 1 is quickly extinguished within 1 second, which can effectively prevent the flame from burning and has good self-extinguishing ability.

[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0057] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a flame-retardant polyurethane elastomer, characterized in that, The preparation method of the flame-retardant polyurethane elastomer includes the following steps: S1. Pentaerythritol triacrylate, hydroxyethyl acrylate, butyl acrylate, styrene, diphenyl methacrylate-2-hydroxyethyl phosphate, vinyl silicone oil, and initiator are blended and heated and stirred to obtain an intermediate product. S2. Under an inert atmosphere, the isocyanate, diol, intermediate product and catalyst are mixed and heated and stirred to obtain intermediate 1 mixture. S3. Under an inert atmosphere, the intermediate 1 mixture and the triazine compound chain extender are mixed, heated and stirred to react, and intermediate 2 mixture is obtained. S4. Under an inert atmosphere, the intermediate 2 mixture and the siloxane chain extender are mixed, heated and stirred to react, poured into a mold, and cured to obtain the flame-retardant polyurethane elastomer.

2. The method for preparing the flame-retardant polyurethane elastomer according to claim 1, characterized in that, The isocyanate is selected from one or more of toluene diisocyanate, dicyclohexylmethane isocyanate, hexamethyl diisocyanate, and isophorone diisocyanate.

3. The method for preparing the flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S1, the molar ratio of pentaerythritol triacrylate, hydroxyethyl acrylate, butyl acrylate, styrene, 2-hydroxyethyl methacrylate diphenyl phosphate, and vinyl silicone oil is (0.1-8):(1-6):(1-6):(1-6):(1-6):(0.5-2).

4. The method for preparing the flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S1, the heating temperature is 60-100℃.

5. The method for preparing the flame-retardant polyurethane elastomer according to claim 1, characterized in that, The mass ratio of the isocyanate, diol, intermediate product, triazine compound chain extender, and siloxane chain extender is (1-3):(1-10):(1-5):(0.1-2):(0.1-2).

6. The method for preparing the flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S2, the heating temperature is 60-90℃.

7. The method for preparing the flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S2, the reaction time is 1-4 hours.

8. The method for preparing the flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S3, the heating temperature is 65-85℃.

9. The method for preparing the flame-retardant polyurethane elastomer according to claim 1, characterized in that, In step S3, the reaction time is 2-5 hours.

10. The application of the flame-retardant polyurethane elastomer prepared by the method of any one of claims 1-9.

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