Triazinyl flame-retardant chain extender as well as preparation method and application thereof

Abstract

The invention discloses a triazinyl flame-retardant chain extender as well as a preparation method and application thereof, relates to the field of intrinsic flame-retardant thermoplastic polyurethane materials, and aims at solving the problems that the existing intrinsic flame-retardant thermoplastic polyurethane is difficult to polymerize, relatively low in mechanical property and relatively low in flame-retardant efficiency. The triazinyl flame-retardant chain extender is 2, 4-hydroxyethylamino-6-chloro-1, 3, 5-triazine, and the method comprises the following steps: 1, adding cyanuric chloride and acetone into a reaction device, dissolving to obtain a cyanuric chloride solution, mixing ethanolamine and sodium hydroxide, adding water, dissolving to obtain a mixed solution A, and dropwise adding the mixed solution A into the reaction device; 2, mixing ethanolamine and sodium hydroxide, and adding water for dissolving to obtain a mixed solution B; dropwise adding the mixed solution B into the reaction device, simultaneously removing the ice-salt bath device, continuously reacting after dropwise adding, recovering the reaction solution to room temperature, carrying out suction filtration, and finally drying a product obtained by suction filtration, thereby obtaining the product. The triazinyl flame-retardant chain extender disclosed by the invention is used for preparing intrinsic flame-retardant thermoplastic polyurethane.

Description

Technical Field

[0001] The invention relates to the field of intrinsic flame-retardant thermoplastic polyurethane materials, and in particular to a triazine-based flame-retardant chain extender and a preparation method and application thereof. Background Art

[0002] As an emerging polymer material, thermoplastic polyurethane (TPU) is widely used in various fields such as rail transportation, communication cables, building materials, aerospace, etc. due to its many advantages such as high wear resistance, good flexibility, chemical corrosion resistance and easy processing. However, traditional TPU is flammable, with an LOI of only 19%, and releases a large amount of toxic gases during combustion, posing a serious threat to human life and property safety. Therefore, in the actual application process, TPU must be subjected to necessary flame retardant modification.

[0003] At present, the flame retardant modification methods commonly used in thermoplastic polyurethane are mainly divided into two types: additive flame retardant and intrinsic flame retardant. Among them, the additive flame retardants used for TPU flame retardancy mainly include halogen, metal hydroxide, nitrogen, phosphorus and phosphorus nitrogen flame retardants. Although additive flame retardants can give TPU a certain flame retardant efficiency, the introduction of flame retardant additives destroys the hydrogen bonding effect of the TPU material matrix itself, and some additive flame retardants have strong molecular polarity and are easy to absorb moisture and migrate under humid conditions, resulting in a significant reduction in the comprehensive properties of flame retardant TPU materials such as mechanics.

[0004] Intrinsic flame-retardant thermoplastic polyurethane is a product that introduces flame-retardant groups or elements into the chain segments of TPU molecules through chemical reactions, thereby giving TPU a certain flame-retardant property. However, due to the introduction of a large number of heteroelements into the intrinsic flame-retardant TPU monomer, the reaction monomer itself has poor reactivity, and the synthesis is difficult and costly. In recent years, there have been few reports on its use in flame-retardant TPU materials. The small amount of research currently reported on intrinsic flame-retardant thermoplastic polyurethanes mainly focuses on the introduction of highly polymerized phosphorus-containing polyesters, aromatic chain extenders and phosphorus-containing diols. The acid value of this type of flame-retardant group is high and the molecular polarity is large. The introduction of chain extenders often makes TPU materials difficult to polymerize and seriously damages the intermolecular hydrogen bonding, resulting in reduced material processing performance and mechanical properties, and the flame retardant efficiency of intrinsic flame-retardant TPU materials is low. Summary of the invention

[0005] The invention aims to solve the problems of difficult polymerization, low mechanical properties and low flame retardant efficiency of existing intrinsic flame retardant thermoplastic polyurethane, and provides a triazine-based flame retardant chain extender and a preparation method and application thereof.

[0006] The triazine-based flame retardant chain extender of the present invention is 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine, and its chemical structural formula is as follows:

[0007]

[0008] The preparation method of the triazine-based flame retardant chain extender 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine of the present invention comprises the following steps:

[0009] 1. Add cyanuric chloride and acetone to a reaction device, dissolve to obtain a cyanuric chloride solution, and reduce the temperature to -5 to 0°C by an ice-salt bath device; mix ethanolamine and sodium hydroxide, add water to dissolve to obtain a mixed solution A, and then drop the mixed solution A into the reaction device;

[0010] 2. Ethanolamine and sodium hydroxide are mixed, and water is added to dissolve to obtain a mixed solution B; the mixed solution B is then added dropwise to the reaction device, and the ice-salt bath device is removed at the same time, and the pH of the reaction system is controlled to be 7-9. After the addition is completed, the reaction is continued for 2-2.5 hours, and then the reaction solution is restored to room temperature and filtered, and finally the product obtained by filtration is dried to obtain 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine (HECT).

[0011] Furthermore, in step 1, the mass ratio of cyanuric chloride to acetone is 1:3-6.

[0012] Furthermore, in step 1, the molar ratio of ethanolamine to sodium hydroxide is 1:1.

[0013] Furthermore, in step 1, the molar ratio of cyanuric chloride to ethanolamine is 1:1.

[0014] Furthermore, the mixed solution in step 1 is added dropwise to the reaction device within 30 to 45 minutes.

[0015] Furthermore, in step 2, the molar ratio of ethanolamine to sodium hydroxide is 1:1.

[0016] Furthermore, the mixed solution B in step 2 is equal to the mixed solution A in step 1.

[0017] The triazine-based flame retardant chain extender of the invention is used for preparing intrinsic flame retardant thermoplastic polyurethane.

[0018] Furthermore, the preparation method of the intrinsic flame retardant thermoplastic polyurethane is:

[0019] Add the dried tetrahydrofuran homopolyether (PTMG) and 4,4'-diphenylmethane diisocyanate (MDI) into the reaction device, and perform N2 protection, and then stir the reaction at 75°C for 1.5 to 2.5 hours at a stirring speed of 300 to 600 r / min;

[0020] According to the molar ratio of -NCO and -OH in the reaction system of (1-1.04):1, BDO and HECT are weighed and added to the reaction system. After stirring for 10-20 minutes, the reactants are poured into a polytetrafluoroethylene mold at a stirring speed of 500-800 r / min. The polytetrafluoroethylene mold is placed in a vacuum oven at 100°C, aged for 12-24 hours, and then placed on a flat vulcanizer for hot pressing.

[0021] Furthermore, the molar ratio of tetrahydrofuran homopolyether to 4,4'-diphenylmethane diisocyanate is 1:2.

[0022] Beneficial effects of the present invention:

[0023] The present invention uses a nitrogen-rich triazine structure as a starting material, retains a chlorine-containing group with a free radical capture effect in the gas phase in the structure, and synthesizes a reactive chain extender 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine (HECT) containing a triazine structure and a hydroxyethyl terminal. The triazine-based chain extender is introduced into a TPU material to prepare an intrinsic flame-retardant TPU material. The structure of the hydroxyethyl terminal of the triazine-based chain extender has high reactivity in the TPU preparation process. Under the condition of introducing a relatively low amount, the intrinsic TPU material can be endowed with excellent flame retardant properties, and has broad prospects in the emerging application fields of TPU materials.

[0024] Compared with traditional flame retardant chain extenders, the hydroxyethyl structure of the triazine-based flame retardant chain extender HECT of the present invention has high reactivity with isocyanate, thus overcoming the problem of difficulty in polymerization of intrinsic flame retardant TPU materials.

[0025] The 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine (HECT) molecule of the present invention contains a nitrogen-rich triazine ring group, which releases a large amount of non-flammable gas (such as NH3 and N2) during the cracking process, so that the concentration of the intrinsic flame-retardant TPU is diluted during the combustion, delaying the combustion process of the material. The retention of part of the C-Cl in the HECT structure is introduced into the molecular chain segment of TPU. During the combustion of the intrinsic flame-retardant TPU material, the chlorine-containing free radicals generated by it effectively capture the H·, O· and HO· active free radicals generated by the pyrolysis of the material, play an excellent free radical capture role in the gas phase, and improve the flame retardant efficiency.

[0026] The triazine-based flame retardant chain extender HECT of the present invention is introduced into the TPU molecular segment. Due to the presence of the triazine ring structure in HECT, not only the high-temperature thermal stability and mechanical properties of the material are improved, but also the anti-ultraviolet aging performance of the TPU material is improved.

[0027] The flame retardant chain extender of the present invention is not only applicable to polyurethane, but also applicable to the intrinsic flame retardancy of high polymers such as polyester. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 FTIR spectra of raw materials cyanuric chloride, ethanolamine and product HECT;

[0029] Figure 2 For the product (HECT) 13 C NMR;

[0030] Figure 3 For the product HECT 1 H NMR;

[0031] Figure 4 This is the thermogravimetric analysis curve of the product HECT. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any combination of the specific implementation modes.

[0033] Specific implementation method 1: The triazine-based flame retardant chain extender in this implementation method is 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine, and its chemical structure is as follows:

[0034]

[0035] Part of the C-Cl in the molecular structure of 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine (HECT) of the present invention is retained. When it is introduced into the molecular segment of TPU, the chlorine-containing free radicals generated during the combustion of the intrinsic flame-retardant TPU material effectively capture the H·, O· and HO· active free radicals generated by the pyrolysis of the material, play an excellent free radical capture role in the gas phase, and give the intrinsic flame-retardant TPU a higher efficiency. On the other hand, the aromatic groups and C-Cl-containing compounds generated by the decomposition of HECT accelerate the formation of the condensed coating. The flame retardant efficiency is improved through the synergistic effect of gas phase inhibition of N / Cl and carbonization of the condensed phase.

[0036] The triazine-based flame retardant chain extender HECT of the present invention is introduced into the TPU molecular chain segment. Since the Cl atom exhibits a stronger electrostatic attraction, the hydrogen bond interaction between molecules and the π-π conjugation of the triazine ring are further strengthened, which not only improves the high-temperature thermal stability and mechanical properties of the material, but also improves the anti-ultraviolet aging performance of the TPU material.

[0037] Specific embodiment 2: The preparation method of the triazine-based flame retardant chain extender of this embodiment is 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine, comprising the following steps:

[0038] 1. Add cyanuric chloride and acetone to a reaction device, dissolve to obtain a cyanuric chloride solution, and reduce the temperature to -5 to 0°C by an ice-salt bath device; mix ethanolamine and sodium hydroxide, add water to dissolve to obtain a mixed solution A, and then drop the mixed solution A into the reaction device;

[0039] 2. Ethanolamine and sodium hydroxide are mixed, and water is added to dissolve to obtain a mixed solution B; the mixed solution B is then added dropwise to the reaction device, and the ice-salt bath device is removed at the same time, and the pH of the reaction system is controlled to be 7-9. After the addition is completed, the reaction is continued for 2-2.5 hours, and then the reaction solution is restored to room temperature and filtered, and finally the product obtained by filtration is dried to obtain 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine (HECT).

[0040] Specific implementation method 3: In step 1 of this implementation method, the mass ratio of cyanuric chloride to acetone is 1:3 to 6. Other steps and parameters are the same as those in specific implementation method 2.

[0041] Specific embodiment 4: In step 1 of this embodiment, the molar ratio of ethanolamine to sodium hydroxide is 1: 1. Other steps and parameters are the same as those of specific embodiment 2 or 3.

[0042] Specific implementation method 5: In step 1 of this implementation method, the molar ratio of cyanuric chloride to ethanolamine is 1: 1. Other steps and parameters are the same as those of specific implementation methods 2 to 4.

[0043] Specific implementation method 6: In step 1 of this implementation method, the mixed solution is added dropwise to the reaction device within 30 to 45 minutes. The other steps and parameters are the same as those of specific implementation methods 2 to 5.

[0044] Specific embodiment 7: In step 2 of this embodiment, the molar ratio of ethanolamine to sodium hydroxide is 1: 1. Other steps and parameters are the same as those of specific embodiments 2 to 6.

[0045] Specific implementation eight: In this implementation, the mixed solution B in step two is equal to the mixed solution A in step one. The other steps and parameters are the same as those in specific implementations two to seven.

[0046] Specific embodiment 9: In this embodiment, the triazine-based flame retardant chain extender is used to prepare intrinsic flame retardant thermoplastic polyurethane.

[0047] Specific embodiment 10: The preparation method of the intrinsic flame retardant thermoplastic polyurethane described in this embodiment is:

[0048] Add the dried tetrahydrofuran homopolyether (PTMG) and 4,4'-diphenylmethane diisocyanate (MDI) into the reaction device, and perform N2 protection, and then stir the reaction at 75°C for 1.5 to 2.5 hours at a stirring speed of 300 to 600 r / min;

[0049] According to the molar ratio of -NCO and -OH in the reaction system of (1-1.04):1, BDO and HECT are weighed and added to the reaction system, and the reactants are poured into a polytetrafluoroethylene mold after stirring for 10-20 minutes at a stirring speed of 500-800 r / min. The polytetrafluoroethylene mold is placed in a vacuum oven at 100°C, and after aging for 12-24 hours, it is placed on a flat vulcanizer for hot pressing. The other steps and parameters are the same as those in the seventh embodiment.

[0050] Specific embodiment eleven: In this embodiment, the molar ratio of tetrahydrofuran homopolyether to 4,4'-diphenylmethane diisocyanate is 1:2. Other steps and parameters are the same as those in specific embodiment ten.

[0051] The embodiments of the present invention are described in detail below. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation schemes and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0052] Embodiment 1:

[0053] The synthesis method of the triazine-based flame retardant chain extender (HECT) of this embodiment comprises the following steps:

[0054] Step 1: Synthesis of intermediate 2-hydroxyethylamino-4,6-chloro-1,3,5-triazine

[0055] Install a thermometer, a stirrer, a spherical condenser and a constant pressure dropping funnel on the fully dried four-necked bottle. Add 0.10 mol of cyanuric chloride to a 500 mL four-necked bottle, and add 100 mL of acetone to dissolve it to obtain a cyanuric chloride solution, and then reduce the reaction temperature to 0 ° C through an ice-salt bath device. Weigh 0.10 mol of ethanolamine and 0.10 mol of sodium hydroxide in a beaker, add 20 mL of water to fully dissolve them, and obtain a mixed solution A; then transfer the mixed solution A to a constant pressure dropping funnel, and then slowly add it dropwise to the four-necked bottle, and complete the addition within 30 minutes. As the reaction proceeds, the reaction solution in the four-necked bottle gradually changes from the initial white turbid liquid to a transparent solution, which is the intermediate. The synthesis route of the intermediate is as follows.

[0056]

[0057] Step 2: Synthesis of the product 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine (HECT)

[0058] After the reaction of step 1 is completed, weigh 0.10 mol ethanolamine and 0.10 mol sodium hydroxide in a beaker, add water to fully dissolve, and obtain a mixed solution B. Slowly add the mixed solution B to the reaction system through a constant pressure dropping funnel, and complete the addition within 30 minutes. At the same time, remove the ice salt bath device, control the pH of the reaction system to 7, and continue the reaction for 2 hours after the addition is completed. After the reaction is completed, the reaction solution is cooled to room temperature, the product is filtered out, and the product is placed in a vacuum oven at 80°C for drying to obtain the final target product 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine (HECT), and the product synthesis route is shown below.

[0059]

[0060] The triazine-based flame retardant chain extender (HECT) prepared in this example was subjected to the following experiment:

[0061] (I) Product structure characterization

[0062] The infrared spectra of cyanuric chloride (CNC), ethanolamine (ETA) and the product HECT are shown in Figure 1 The upper curve represents the product HECT, the middle curve represents CNC, and the lower curve represents ETA. The infrared spectrum of the raw material CNC shows that at 1563cm -1 The absorption peak at 846 cm corresponds to the stretching vibration of the triazine ring in the cyanuric chloride molecule. -1 is the C-Cl stretching vibration on the triazine ring; at the same time, the infrared spectrum of the raw material ETA is at 3108cm -1 and 3276cm -1 The absorption peak at 2864cm is the stretching vibration of -NH- and -OH in its structure. -1 The stretching vibration of CH is at 3108cm -1 )、CH(2864cm -1 ) and triazine ring (1247cm -1 ) is clearly retained. In addition, at 1247cm -1 A new CN stretching vibration is formed at 871 cm -1 The intensity of the corresponding C-Cl stretching vibration peak was significantly reduced, indicating that CNC and ETA reacted successfully and the triazine-based flame retardant chain extender (HECT) was successfully synthesized.

[0063] Synthetic product HECT 13 C NMR spectrum Figure 2As shown. From the HECT carbon nuclear magnetic spectrum, it can be seen that the peak at δ167.55-168.30ppm is the peak of the carbon atom of the triazine ring, the peak at δ165.11-165.69ppm is the peak of the carbon atom b connected to the triazine ring and ethanolamine, and the peaks at δ59.80 and δ43.16ppm correspond to the peaks of the carbon atoms d and c on the ethanolamine, respectively. 13 CNMR analysis data proved that cyanuric chloride and ethanolamine reacted successfully.

[0064] Synthetic product HECT 1 H NMR spectrum Figure 3 As shown. 1 It can be seen from the H NMR spectrum that the peak at δ7.86-7.39ppm is the peak of the a hydrogen atom on the N atom connecting ethanolamine to the triazine ring, the peak at δ4.68ppm is the peak of the d hydrogen atom of the hydroxyl group in ethanolamine, and the peaks at δ3.70 and δ3.38ppm are the peaks of the c and b hydrogen atoms on ethanolamine, respectively. 13 C and 1 The analysis results of the H NMR spectrum show that the structure of the synthesized product is consistent with that of the target product, proving that the flame retardant chain extender HECT was successfully synthesized.

[0065] Thermogravimetric analysis curve of triazine flame retardant chain extender (HECT) is as follows Figure 4 As shown, the black curve represents TG and the blue curve represents DTG. Figure 4 Thermogravimetric analysis (TGA) tests show that the initial thermal decomposition temperature of HECT is 201°C, which meets the synthesis temperature requirements of most polyester materials such as TPU. At 800°C, the residual carbon content of HECT is 18wt%, which indicates that the synthesized triazine-based flame retardant chain extender (HECT) has good self-carbonization performance, which has a positive significance for improving the flame retardant properties of TPU.

[0066] Example 2: Preparation of intrinsic flame retardant thermoplastic polyurethane

[0067] Tetrahydrofuran homopolyether (PTMG) and 4,4'-diphenylmethane diisocyanate (MDI) were placed in a vacuum oven at 100°C to remove moisture.

[0068] 0.06 mol MDI and 0.03 mol PTMG were added to a four-necked bottle, and N2 protection was applied to the bottle, and then stirred at 75°C for 2 h. The temperature was kept at 75°C, and 0.030 mol 1,4-butanediol (BDO) was quickly added to the reaction system, and stirred for 20 min to obtain a mixture, which was then poured into a polytetrafluoroethylene mold.

[0069] The polytetrafluoroethylene mold was then placed in a vacuum oven at 100°C for aging for 24 hours and placed on a flat vulcanizer for hot pressing at a temperature of 180°C and a pressure of 10 MPa to obtain a thermoplastic polyurethane (TPU1).

[0070] Example 3: Preparation of intrinsic flame retardant thermoplastic polyurethane

[0071] Tetrahydrofuran homopolyether (PTMG) and 4,4'-diphenylmethane diisocyanate (MDI) were placed in a vacuum oven at 100°C to remove moisture.

[0072] 0.06 mol MDI and 0.03 mol PTMG were added to a four-necked bottle, and N2 protection was applied to the bottle, followed by stirring and reacting at 75° C. for 2 h. While maintaining the temperature at 75° C., 0.021 mol BDO and 0.009 mol HECT prepared in Example 1 were quickly added to the reaction system, stirred for 20 min, and a mixture was obtained, which was then poured into a polytetrafluoroethylene mold.

[0073] The polytetrafluoroethylene mold was then placed in a vacuum oven at 100°C for aging for 24 hours and placed on a flat vulcanizer for hot pressing at a temperature of 180°C and a pressure of 10 MPa to obtain an intrinsic flame retardant thermoplastic polyurethane (TPU2).

[0074] The synthesis route of the intrinsic flame retardant thermoplastic polyurethane of this embodiment is as follows.

[0075]

[0076] Example 4: Preparation of intrinsic flame retardant thermoplastic polyurethane

[0077] Tetrahydrofuran homopolyether (PTMG) and 4,4'-diphenylmethane diisocyanate (MDI) were placed in a vacuum oven at 100°C to remove moisture.

[0078] 0.06 mol MDI and 0.03 mol PTMG were added to a four-necked bottle, and N2 protection was applied to the bottle, followed by stirring and reacting at 75° C. for 2 h. While maintaining the temperature at 75° C., 0.015 mol BDO and 0.015 mol HECT prepared in Example 1 were quickly added to the reaction system, stirred for 20 min, and a mixture was obtained, which was then poured into a polytetrafluoroethylene mold.

[0079] The polytetrafluoroethylene mold was then placed in a vacuum oven at 100°C for aging for 24 hours and placed on a flat vulcanizer for hot pressing at a temperature of 180°C and a pressure of 10 MPa to obtain an intrinsic flame retardant thermoplastic polyurethane (TPU3).

[0080] Example 5: Preparation of intrinsic flame retardant thermoplastic polyurethane

[0081] Tetrahydrofuran homopolyether (PTMG) and 4,4'-diphenylmethane diisocyanate (MDI) were placed in a vacuum oven at 100°C to remove moisture.

[0082] 0.06 mol MDI and 0.03 mol PTMG were added to a four-necked bottle, and N2 protection was applied to the bottle, followed by stirring and reacting at 75° C. for 2 h. While maintaining the temperature at 75° C., 0.009 mol BDO and 0.021 mol HECT prepared in Example 1 were quickly added to the reaction system, stirred for 20 min, and a mixture was obtained, which was then poured into a polytetrafluoroethylene mold.

[0083] The polytetrafluoroethylene mold was then placed in a vacuum oven at 100°C for aging for 24 hours and placed on a flat vulcanizer for hot pressing at a temperature of 180°C and a pressure of 10 MPa to obtain an intrinsic flame retardant thermoplastic polyurethane (TPU4).

[0084] The intrinsic flame retardant TPU samples prepared in Examples 2 to 5 were cut into standard strips and subjected to performance tests. Table 1 shows the data of the intrinsic flame retardant TPU materials tested by vertical combustion (UL-94) and limiting oxygen index (LOI) tests. As shown in Table 1, once TPU1 (pure TPU) prepared in Example 2 is ignited, it burns rapidly until it is burned out, and the oxygen index is only 19.0%. As HECT is introduced into the TPU molecular segment instead of part of the chain extender BDO, the flame retardant properties of the intrinsic thermoplastic polyurethane material are improved. When the amount of HECT introduced is 0.009 mol, the oxygen index of the TPU2 material is increased from 19.0% to 27.8%, and the intrinsic flame retardant thermoplastic polyurethane TPU2 achieves the effect of self-extinguishing from the fire. As the amount of HECT introduced is further increased to 0.021 mol, the oxygen index of the intrinsic flame retardant thermoplastic polyurethane TPU4 is increased to 29.0%, and the average burning time of the TPU material after 2 ignitions is significantly shortened. This shows that with the introduction of triazine-based flame retardant chain extender HECT, the TPU material has obtained excellent flame retardant properties. In Table 1, the mechanical properties of TPU1 and intrinsic flame retardant thermoplastic polyurethane were analyzed by a universal mechanical testing machine. Compared with TPU1, with the increase in the amount of triazine-based flame retardant chain extender HECT introduced, the mechanical properties of the intrinsic flame retardant thermoplastic polyurethane are improved. This is because the introduction of the triazine-based flame retardant chain extender HECT enhances the hydrogen bonding effect and structural rigidity in the TPU main chain, thereby giving TPU intrinsic flame retardant properties while obtaining more excellent mechanical properties.

[0085] Table 2 shows the UV aging test data of TPU1-TPU4 materials. As the UV irradiation time increases, the tensile strength of the TPU sample drops sharply. After 720 hours of UV irradiation, the tensile strength of TPU1 decreased by 24.00% compared with the unirradiated sample. Similarly, the tensile strength of the TPU2 sample after 720 hours of UV irradiation decreased by 8.43% compared with the unirradiated sample. As the introduction of HECT increases, the reduction in tensile strength is smaller, which means that the addition of HECT gives TPU materials excellent UV resistance and can be used as UV shielding materials required in various fields of human production and life.

[0086] Table 1 Vertical combustion and limiting oxygen index test data of intrinsic flame retardant TPU materials

[0087]

[0088] Table 2 UV aging test data of intrinsic flame retardant TPU materials

[0089]

[0090] Note: UV intensity (0.89W / m 2 / nm), fluorescent lamp (UVA-340)

[0091] Compared with traditional intrinsic flame retardant chain extenders, the triazine-based flame retardant chain extender HECT synthesized in the present invention has the following advantages: 1) The raw materials for preparing HECT are easy to obtain, the synthesis process is simple, the yield is high, and the solvent can be recycled, which is conducive to its industrial production; 2) Compared with traditional flame retardant chain extenders, the hydroxyethyl structure of the triazine-based flame retardant chain extender HECT itself has high reactivity with isocyanate, which overcomes the problem of difficulty in polymerization of intrinsic flame retardant TPU materials; 3) HECT molecules contain nitrogen-rich triazine ring groups, which release a large amount of non-flammable gases (such as NH3 and N2) during the cracking process, so that the intrinsic flame retardant TPU is diluted during combustion. 4) The concentration of combustible gas is reduced, delaying the combustion process of the material; 5) The triazine-based flame retardant chain extender HECT is introduced into the molecular chain segment of TPU. The triazine-based flame retardant chain extender HECT is introduced into the molecular chain segment of TPU. Due to the presence of the triazine ring structure in HECT, it not only improves the high-temperature thermal stability and mechanical properties of the material, but also improves the anti-ultraviolet aging performance of the TPU material. Therefore, compared with traditional TPU, the introduction of the triazine-based flame retardant chain extender HECT significantly improves the flame retardancy, mechanical and anti-ultraviolet aging performance of the intrinsic TPU, which has important application value for expanding the application of TPU in emerging fields.

Claims

1. A triazine-based flame retardant chain extender, characterized in that: The triazine-based flame retardant chain extender is 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine, and its chemical structure is as follows:

2. The method for preparing a triazine-based flame retardant chain extender according to claim 1, characterized in that: The method comprises the following steps:

1. Add cyanuric chloride and acetone to a reaction device, dissolve to obtain a cyanuric chloride solution, and reduce the temperature to -5 to 0°C by an ice-salt bath device; mix ethanolamine and sodium hydroxide, add water to dissolve to obtain a mixed solution A, and then drop the mixed solution A into the reaction device; 2. Mix ethanolamine and sodium hydroxide, add water to dissolve, and obtain a mixed solution B; then add the mixed solution B dropwise to the reaction device, remove the ice-salt bath device, and control the pH of the reaction system to be 7-9. After the addition is completed, continue the reaction for 2-2.5 hours, then restore the reaction solution to room temperature and filter it, and finally dry the product obtained by filtration to obtain 2,4-hydroxyethylamino-6-chloro-1,3,5-triazine.

3. The method for preparing a triazine-based flame retardant chain extender according to claim 2, characterized in that: In step 1, the mass ratio of cyanuric chloride to acetone is 1:3-6.

4. The method for preparing a triazine-based flame retardant chain extender according to claim 2 or 3, characterized in that: In step 1, the molar ratio of ethanolamine to sodium hydroxide is 1:

1.

5. The method for preparing a triazine-based flame retardant chain extender according to claim 4, characterized in that: In step 1, the molar ratio of cyanuric chloride to ethanolamine is 1:

1.

6. The method for preparing a triazine-based flame retardant chain extender according to claim 5, characterized in that: The mixed solution in step 1 is added dropwise to the reaction device within 30 to 45 minutes.

7. The method for preparing a triazine-based flame retardant chain extender according to claim 6, characterized in that: The mixed solution B in step 2 is equal to the mixed solution A in step 1.

8. Use of the triazine-based flame retardant chain extender as claimed in claim 1 in the preparation of intrinsic flame retardant thermoplastic polyurethane.

9. The use according to claim 8, characterized in that: The preparation method of the intrinsic flame retardant thermoplastic polyurethane is: Add the dried tetrahydrofuran homopolyether and 4,4'-diphenylmethane diisocyanate into the reaction device and perform N2 protection, then stir and react at 75°C for 1.5 to 2.5 hours at a stirring speed of 300 to 600 r / min; According to the molar ratio of -NCO and -OH in the reaction system of (1-1.04):1, BDO and HECT are weighed and added to the reaction system. After stirring for 10-20 minutes, the reactants are poured into a polytetrafluoroethylene mold at a stirring speed of 500-800 r / min. The polytetrafluoroethylene mold is placed in a vacuum oven at 100°C, aged for 12-24 hours, and then placed on a flat vulcanizer for hot pressing.

10. The use according to claim 9, characterized in that: The molar ratio of the tetrahydrofuran homopolyether to 4,4'-diphenylmethane diisocyanate is 1:2.

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