Flame-retardant polyurethane thermoplastic elastomer material based on cage-like phosphate ester micro-crosslinked polymer, and preparation method therefor

Abstract

Disclosed are a flame-retardant polyurethane thermoplastic elastomer material based on a cage-like phosphate ester micro-crosslinked polymer, and a preparation method therefor. The material utilizes a cage-like phosphate ester flame-retardant micro-crosslinked polymer CPFR, and protection of flame-retardant groups is achieved by means of the construction of the micro-crosslinked structure thereof, thereby increasing the water resistance and migration resistance thereof. The flame-retardant TPU material provided by the present invention has excellent transparency, mechanical properties, water resistance, and flame-retardant performance; for the flame-retardant TPU material, taking an addition of 15％wt CPFR as an example, the flame-retardant polyurethane thermoplastic elastomer TPU has transparency, the limiting oxygen index of the flame-retardant TPU material can reach 27.6％, a vertical burning V-0 rating (1.6 mm), and the peak heat release rate is reduced from 1681 MJ / m2 for pure TPU to 325 MJ / m2, a reduction of 80.7％. The flame-retardant TPU provided by the present invention can increase the tensile stress at 300％ from 8.28 MPa to 10.40 MPa, an increase rate of 24.3％, and increase the tensile stress at 500％ from 12.98 MPa to 14.25 MPa, an increase rate of 11.9％; and the TPU can still maintain its original flame-retardant performance after being immersed in hot water at 85℃ for 8 days.

Description

A flame-retardant polyurethane thermoplastic elastomer material based on cage phosphonate micro-crosslinked polymer and a preparation method thereof TECHNICAL FIELD

[0001] The present application belongs to the technical field of high polymer materials, and relates to a halogen-free organic phosphate micro-crosslinked polymer flame-retardant polyurethane thermoplastic elastomer (TPU) composite material and a preparation method thereof, which utilizes a crosslinked structure to construct a high-efficiency halogen-free flame-retardant TPU system with multiple flame-retardant groups. BACKGROUND

[0002] An organic phosphorus-based flame retardant can form an expanded carbon layer during combustion, blocking oxygen and heat, and has extremely high flame-retardant efficiency. When used in combination with other flame retardants, it can play a synergistic flame-retardant and high-efficiency carbonization role. Organic phosphorus-based flame retardants exhibit excellent reactivity due to their participation in various elementary reactions. However, most organic phosphorus-based flame retardants are small molecules, which are prone to migration, resulting in a decrease in flame-retardant performance, changes in polymer appearance, and adverse effects on the environment. To solve the above problems, patent CN201910117619.3 combines phosphorus-containing organic groups within a single molecular unit through a chemical reaction, increases the molecular weight of the organic phosphorus-containing molecule, improves the flame-retardant performance, and reduces the migration of the flame retardant. With the in-depth study of organic phosphorus-based flame retardants, it has been found that when flame-retardant groups with synergistic effects are connected by chemical bonds, they can excite exciting new properties. In the prior art, patents CN202310230588.9 and CN201910352562.5 use a phosphaphenanthrene / siloxane double-base macromolecule in polymers, which not only improves the flame-retardant performance of the polymer material, but also improves the mechanical properties.

[0003] In practical applications, firstly, it is difficult to prepare TPU materials with good flame-retardant effect and excellent halogen-free mechanical properties, and secondly, it is difficult to prepare transparent halogen-free flame-retardant TPU. At the same time, the halogen-free flame-retardant TPU faces the problem that the flame-retardant components have a large hydrolysis migration characteristic in a humid or water-containing environment, and the hydrolysis products are acidic, which causes the TPU to rapidly hydrolyze under this condition, and the physical and mechanical properties of the TPU material deteriorate rapidly.

[0004] To solve the above problems, the present application relates to a cage-like phosphate micro-crosslinked polymer, which has a unique micro-crosslinked structure, giving it excellent migration resistance, insolubility in water and organic solvents. In addition, the cage-like phosphate groups in the polymer can rapidly synergize with another flame-retardant group during combustion, significantly improving the flame-retardant properties of the material. According to the flame-retardant formulation provided by the present application, a 1.6 mm thick vertical combustion sample can achieve a V-0 level of flame-retardant standard, while the peak heat release rate is reduced by more than 75%. More importantly, the formulation can also improve the mechanical properties of TPU and provide an effective solution to the migration and hydrolysis problems of small molecule organic phosphates. SUMMARY

[0005] The main purpose of the present application is to overcome the shortcomings of the prior art, provide a cage-like phosphate micro-crosslinked polymer-based flame-retardant polyurethane thermoplastic elastomer material and a preparation method thereof, which is a transparent, non-migrating, excellent flame-retardant, excellent mechanical property, halogen-free flame-retardant polyurethane thermoplastic elastomer (TPU) material.

[0006] The technical scheme adopted by the present application is as follows:

[0007] A cage-like phosphate flame-retardant micro-crosslinked polymer-based flame-retardant TPU material, by mass percentage, the raw material components include cage-like phosphate micro-crosslinked polymer, phosphorus-nitrogen flame retardant, auxiliary agent, TPU or TPU composite polymer, and the addition amount of each raw material component is as follows:

[0008] The cage-like phosphate micro-crosslinked polymer has a mass fraction of 1-40%;

[0009] The phosphorus-nitrogen flame retardant has a mass fraction of 0%-40%;

[0010] The TPU or TPU composite polymer has a mass fraction of 60%-95%;

[0011] The total addition amount of the other auxiliary agents added is 0%-10% of the TPU or TPU composite polymer.

[0012] The sum of the mass fractions of all components is 100%;

[0013] Preferably, the cage-like phosphate micro-crosslinked polymer is CPFR, which is the ring-opening addition product of a multi-epoxy group compound and a cage-like phosphate containing hydroxyl compound pentaerythritol, and the structure of the cage-like phosphate micro-crosslinked polymer is a mixture of one or more of the following compounds:

[0014] In the formula, R is The continuous part in A3, B3, C3, i.e. the wavy line, is a repeating unit structure, which corresponds to:

[0015] The preparation method of the CPFR is as follows: the polycyclic epoxy group compound and the cage-like phosphoric acid ester of pentaerythritol PEPA are mixed with an organic solvent at 20-150℃, a catalyst is added or not, and the mixture is kept at temperature for 1-48 hours, then the solvent is evaporated under reduced pressure, and the pre-polymer of the reaction is continuously heated to 60-250℃ and kept at temperature for 0.5-48 hours, and the obtained solid material after cooling is the flame retardant CPFR;

[0016] The polycyclic epoxy group compound is usually one or more of 2,4,6-tris(oxirane-2-ylmethoxy)-1,3,5-triazine, tris(oxirane-2-ylmethyl)benzene-1,3,5-tricarboxylate, isocyanuric acid triglycidyl ester, pentaerythritol tetraglycidyl ether, and 1,4-bis[(glycidyloxy)methyl]cyclohexane. The organic solvent is N,N-dimethylformamide DMF, and the mass of DMF is 0-10 times the mass of PEPA. The catalyst can be one or more of triethylamine, aniline, tetraethylammonium bromide, tetrabutylammonium bromide, 4-dimethylamino pyridine, and 4-(aminomethyl)pyridine, and the total molar amount of the catalyst is 0-10% of the molar amount of the epoxy group.

[0017] The feeding ratio of PEPA to the polycyclic epoxy group compound, i.e. the molar ratio n, is 1.0-5.0. The composition of the obtained product is different depending on the polycyclic epoxy group compound used and the feeding ratio of PEPA to the polycyclic epoxy group compound, and is specifically as follows:

[0018] When 2,4,6-tris(oxirane-2-ylmethoxy)-1,3,5-triazine is used as the polycyclic epoxy group compound, A1, A2, and A3 are generated; when tris(oxirane-2-ylmethyl)benzene-1,3,5-tricarboxylate is used as the polycyclic epoxy group compound, B1, B2, and B3 are generated; and when isocyanuric acid triglycidyl ester is used as the polycyclic epoxy group compound, C1, C2, and C3 are generated. In the above three reaction processes, the main products are A3, B3, and C3, respectively. When the feeding ratio n is less than 3, A3, B3, and C3 account for more than 95% of the product; and when 3≤n≤5, A3, B3, and C3 account for more than 70% of the product.

[0019] When pentaerythritol tetraglycidyl ether is used as the polycyclic epoxy group compound, D1 and D2 are generated. When the feeding ratio n is greater than 4, the main product is D1; and when 1≤n≤4, the main product is D2.

[0020] When 1,4-bis[(glycidyloxy)methyl]cyclohexane is used as the polyepoxy compound, E1 and E2 are generated, and when n>2, the main product is E1, and when n≤2, the main product is E2.

[0021] Preferably, the flame-retardant TPU material based on the cage phosphoric ester flame-retardant micro-crosslinked polymer is designed, and the added phosphorus-nitrogen flame retardant is one or a combination of several of the following: piperazine pyrophosphate, melamine polyphosphate, melamine phosphate, ammonium polyphosphate, melamine cyanurate, aluminum diethyl phosphinate, inorganic phosphinate, phosphine compound, phosphine / triazine double-base compound TAD, and phosphine / siloxane double-base macromolecular flame retardant.

[0022] Preferably, the flame-retardant TPU material based on the cage phosphoric ester flame-retardant micro-crosslinked polymer is designed, and the TPU material involved includes a polyurethane thermoplastic elastomer (TPU) used alone or mixed or compounded with other thermoplastic elastomers or polyolefins and the like to form a TPU composite polymer.

[0023] Preferably, the flame-retardant TPU material based on the cage phosphoric ester micro-crosslinked polymer is designed, and the other additives are one or more of the following: antioxidants, anti-dripping agents, lubricants, anti-aging agents, colorants, and hydrolysis stabilizers.

[0024] The preparation of the flame-retardant TPU material is to melt blend the CPFR alone or in combination with the phosphorus-nitrogen flame retardant, or other additives can also be added, and the processing temperature is between 100°C and 300°C. Advantages:

[0025] The cage phosphoric ester flame-retardant micro-crosslinked polymer with a micro-crosslinked structure is used innovatively, which is easy to blend with a polyurethane thermoplastic elastomer (TPU), is resistant to hydrolysis, does not migrate or precipitate, and has a hydroxyl group and an ether bond structure that can be physically and chemically crosslinked with the TPU matrix. The cage phosphoric ester micro-crosslinked polymer flame-retardant TPU has a physical and mechanical performance significantly better than that of a commonly used halogen-free intumescent flame retardant. When the flame-retardant TPU material is added with 15% CPFR, the flame-retardant TPU has a transparent property, the limiting oxygen index of the flame-retardant system can reach 26.9%, the vertical combustion is V-0 level (1.6mm), the peak heat release rate is 1681 MJ / m 2 as low as 325 MJ / m 2, the modulus of elasticity at 300% of the flame-retardant TPU provided by the application is increased from 8.28 MPa of pure TPU to 10.29 MPa, with an increase rate of 24.3%, and the modulus of elasticity at 500% is increased from 12.98 MPa to 14.53 MPa, with an increase of 11.9% compared with pure TPU.

[0026] The small-molecule organic phosphorus flame retardant added into the TPU material has the disadvantages of easy migration and poor water resistance; the application solves the problems of poor durability and easy water absorption of the organic phosphorus flame retardant in the TPU material; when the flame-retardant TPU material is prepared by adding 15% CPFR, the flame-retardant TPU can still maintain the original shape and flame-retardant performance after being soaked in hot water at 85 DEG C for 8 days.

[0027] The flame-retardant formula provided by the application can make the vertical combustion sample with a thickness of 1.6 mm reach the V-0 level of the flame-retardant standard, and the peak value of the heat release rate is reduced to 200 MJ / m 2 In the following, the pure TPU can be reduced by more than 85%; more importantly, the formula can also improve the mechanical properties of the TPU and increase the modulus of elasticity of the TPU material, and the flame-retardant formula provided by the application can reduce the migration of the flame retardant and show better hot water resistance in the hot water soaking experiment. BRIEF DESCRIPTION OF DRAWINGS

[0028] Fig. 1 is a transparent state picture of the sample prepared by different embodiments of the application;

[0029] Fig. 2 is a digital photo of 15% CPFR and 15% PEPA flame-retardant TPU materials soaked in hot water at 85 DEG C for corresponding time; (a) digital photo of CPFR-TPU before and after water boiling; (b) digital photo of PEPA-TPU before and after water boiling; wherein from left to right are the samples when water boiling for 0, 2, 4, 6 and 8 days;

[0030] Fig. 3 is a HRR curve of 15% CPFR flame-retardant TPU material compared with pure TPU; DETAILED DESCRIPTION

[0031] The application will be further described below in combination with examples; the examples are only used for illustrating the application and are not used for limiting the scope of the application; the experimental method without specific conditions in the following example embodiments is usually according to the conventional conditions in the field; the raw materials, reagents and the like used are commercially available raw materials and reagents obtained through commercial channels unless otherwise specified; the raw material amount refers to mass unless otherwise specified; any non-substantial change and replacement made by the person skilled in the art on the basis of the application all belong to the scope of the application claimed.

[0032] Example 1

[0033] The cage phosphate ester micro-crosslinked polymer (CPFR) is crushed, 15% CPFR and 85% polyurethane thermoplastic elastomer (TPU) are melt blended to prepare a flame-retardant TPU material, the material is transparent, the limiting oxygen index is 27.6%, the 1.6mm vertical burning sample passes the V-0 level test, and in the cone calorimeter test, as shown in FIG. 3, the peak heat release rate is reduced to 198MJ / m 2 from 1681MJ / m 2 ; as shown in Table 2, when using CPFR flame-retardant TPU, the modulus of elasticity at 100%, 300%, and 500% is improved compared with the small molecule flame retardant pentaerythritol cage phosphoric acid (PEPA), and is higher than that of pure TPU, while improving the flame retardant performance of the composite material, the mechanical properties are also improved.

[0034] In this example, the CPFR is prepared by ring-opening addition of PEPA and tris (epoxy ethylene-2-ylmethyl) benzene-1, 3, 5-tricarboxylate according to a molar ratio of 2:1, which is a mixture of B1, B2 and B3, wherein the mass fraction of B3 is 95.5%.

[0035] Example 2

[0036] After the CPFR is crushed, 30% CPFR, antioxidant, anti-aging agent and 69.8% TPU are melt blended; other additives are added in an amount of 0.2%, to prepare a flame-retardant TPU material, which has a limiting oxygen index of 32.8%, a 1.6mm vertical burning sample passes the V-0 level test, and the peak heat release rate is reduced to 198MJ / m 2 , which is reduced by 88.2% compared with pure TPU; the modulus of elasticity at 100% deformation is improved to 6.8MPa, which is increased by 1.3MPa compared with pure TPU, and the elongation at break is 340.2%.

[0037] In this example, the CPFR is prepared by ring-opening addition of PEPA and tris (epoxy ethylene-2-ylmethyl) benzene-1, 3, 5-tricarboxylate according to a molar ratio of 2:1, which is a mixture of B1, B2 and B3, wherein the mass fraction of B3 is 99.2%.

[0038] Example 3

[0039] After the CPFR is crushed, CPFR, melamine polyphosphate (MPP) and 85% TPU are melt blended, wherein the total amount of CPFR and MPP is 15%, when CPFR:MPP is 13:2, the limiting oxygen index of the prepared flame-retardant TPU material can reach 27.6%, the 1.6mm vertical burning sample passes the V-0 level test, and the peak heat release rate is reduced to 321MJ / m 2 from 1681MJ / m 2, the residual carbon increased from 8.2% of pure TPU to 21.1%, the carbonization performance was greatly improved, and the flame-retardant TPU composite of this component had good carbonization performance; in addition, the stress at 300% elongation of the flame-retardant composite increased from 8.28 MPa of pure TPU to 9.69 MPa, and the stress at 500% elongation increased from 12.98 MPa to 13.2 MPa. This improved flame-retardant formula not only gave the material excellent flame-retardant performance, but also successfully maintained the original mechanical strength of the material, and even achieved performance improvement in some aspects.

[0040] In this example, the CPFR is prepared by ring-opening addition of PEPA and isocyanuric acid triglycidyl ester according to a molar ratio of 4:1, which is a mixture of C1, C2 and C3, wherein the mass fraction of C3 is 92.7%.

[0041] Example 4

[0042] After the CPFR is crushed, 20% CPFR, 40% TPU and 40% polyolefin thermoplastic elastomer (TPO) are melt blended, and the prepared flame-retardant TPU / TPO composite has a limiting oxygen index of 28.3%, and a 1.6 mm vertical burning sample passes the V-0 level.

[0043] In this example, the CPFR is prepared by ring-opening addition of PEPA and isocyanuric acid triglycidyl ester according to a molar ratio of 4:1, which is a mixture of C1, C2 and C3, wherein the mass fraction of C3 is 90.8%

[0044] Example 5

[0045] After the CPFR is crushed, CPFR, phosphorus hetero-fused triazine double-base compound (TAD) and 85% TPU are melt blended, wherein the total addition amount of CPFR and TAD is 15%; when CPFR:TAD is 11:4, the prepared flame-retardant TPU material has a limiting oxygen index of 26%, and a 1.6 mm vertical burning sample passes the V-0 level test; in addition, the stress at 500% elongation of the flame-retardant TPU increases to 11.29 MPa, and the stress at 300% elongation increases to 8.52 MPa.

[0046] In this example, the CPFR is prepared by ring-opening addition of PEPA and 2,4,6-tris(oxirane-2-ylmethoxy)-1,3,5-triazine according to a molar ratio of 3:1, which is a mixture of A1, A2 and A3, wherein the mass fraction of A3 is 86.9%.

[0047] Example 6

[0048] The CPFR, phosphine triazine double base compound (TAD) and TPU are melt blended after the CPFR is crushed to obtain the flame-retardant TPU material, wherein the total addition amount of the CPFR and the TAD is 15%, when the CPFR:TAD is 13:2, the flame-retardant TPU material is prepared, the oxygen index of which can reach 27.6%, the 1.6mm vertical burning sample passes the V-0 level test; in the cone test, the peak heat release rate is reduced to 321MJ / m 2 ; the modulus of the flame-retardant TPU 500% is increased to 13.2MPa, and the modulus of the flame-retardant TPU 300% is increased to 9.69MPa.

[0049] In this example, the CPFR is obtained by ring-opening addition of PEPA and 2,4,6-tris(oxirane-2-ylmethoxy)-1,3,5-triazine according to a molar ratio of 3:1, which is a mixture of A1, A2 and A3, wherein the mass fraction of A3 is 90.4%.

[0050] Fig. 1 is a picture of the transparent state of different TPU samples, from which it can be seen that the 12CPFR-TPU, 15CPFR-TPU, 13CPFR / 2TAD-TPU and 11CPFR / 4TAD-TPU samples obtained by the method of the present application all have excellent transparency. Table 2 is the test results of the TPU samples of different formulations in Table 1, wherein "-8d" represents the corresponding results after the samples are soaked in hot water at 85℃ for 8 days; it can be seen from Fig. 2 that the samples obtained by the present application have good hot water hydrolysis resistance, can effectively reduce the migration of the flame retardant, and can effectively improve the mechanical properties of the TPU material.

[0051] Table 1. Flame-retardant TPU formulation

[0052] Table 2. Test results of flame-retardant TPU material

Claims

1. A flame retardant polyurethane thermoplastic elastomer material based on a caged phosphate micro-crosslinked polymer, characterized in that, The composition comprises the following components: 1-40% of a cage phosphonate micro-crosslinked polymer; 0-40% of a phosphorus-nitrogen flame retardant; 60-95% of a polyurethane thermoplastic elastomer (TPU) or a TPU composite polymer; 0-10% of an additive, based on the mass of the TPU or the TPU composite polymer; 2. The flame retardant polyurethane thermoplastic elastomer material based on a cagelike phosphate micro-crosslinked polymer according to claim 1, characterized in that, The total mass fraction of all components is 100%.

3. The flame retardant polyurethane thermoplastic elastomer material based on a cagelike phosphate microcrosslinked polymer according to claim 2, characterized in that, The cage-like phosphate micro-crosslinked polymer is one or a mixture of the following compounds: wherein R is The continuous part in A3, B3, C3, i.e. the wavy line, is a repeating unit structure, which corresponds to:

4. The flame retardant polyurethane thermoplastic elastomer material based on a cagelike phosphate microcrosslinked polymer according to claim 1, characterized in that, The cage phosphonate micro-crosslinked polymer is CPFR, which is a ring-opening addition product of a multi-epoxy compound and a cage phosphonate containing hydroxyl groups.

5. The flame retardant polyurethane thermoplastic elastomer material based on a cagelike phosphate microcrosslinked polymer according to claim 1, characterized in that, The phosphorus-nitrogen flame retardant is one or a combination of the following: piperazine pyrophosphate, melamine polyphosphate, melamine phosphate, ammonium polyphosphate, melamine cyanurate, aluminum diethyl phosphinate, inorganic phosphinate, phosphine compound, phosphine / triazine double-base compound TAD, and phosphine / silicone double-base macromolecular flame retardant.

6. The flame retardant polyurethane thermoplastic elastomer material based on a cagelike phosphate microcrosslinked polymer according to claim 1, characterized in that, The TPU composite polymer is a mixture or composite of a polyurethane thermoplastic elastomer (TPU) and other thermoplastic elastomers or polyolefin materials.

7. Process for the preparation of a flame-retardant polyurethane thermoplastic elastomer material based on a caged phosphate micro-crosslinked polymer according to claim 1, characterized in that, The additive is one or more of the following: an antioxidant, an anti-dripping agent, a lubricant, an anti-aging agent, a colorant, and a hydrolysis stabilizer. The composition is prepared by melt blending the CPFR alone or in combination with the phosphorus-nitrogen flame retardant, and other additives, at a processing temperature of 100-300°C.

Images