Flame-retardant polyurethane thermoplastic elastomer material based on caged phosphate micro-crosslinked polymer and preparation method of flame-retardant polyurethane thermoplastic elastomer material

Abstract

The invention discloses a flame-retardant polyurethane thermoplastic elastomer material based on a caged phosphate micro-crosslinked polymer and a preparation method of the flame-retardant polyurethane thermoplastic elastomer material. According to the material, a caged phosphate flame-retardant micro-cross-linked polymer CPFR is utilized, protection of flame-retardant groups is achieved through construction of a micro-cross-linked structure, and the water resistance and migration resistance of the material are improved; the flame-retardant TPU material provided by the invention has excellent transparency, mechanical properties, water resistance and flame retardance; when the flame-retardant TPU material is used, by taking 15 wt% of CPFR as an example, the flame-retardant thermoplastic polyurethane elastomer TPU has transparency, the limit oxygen index of the flame-retardant TPU material can reach 27.6%, the vertical combustion level is V-0 (1.6 mm), the heat release rate peak value is reduced to 325 MJ / m < 2 > from 1681 MJ / m < 2 > of pure TPU and is reduced by 80.7%, the stress at definite elongation of 300% of the flame-retardant TPU provided by the invention can be improved to 10.40 MPa from 8.28 MPa, the improvement rate reaches 24.3%, and the flame-retardant TPU material has excellent flame retardance and flame retardance. When the tensile stress is 500%, the tensile stress is increased to 14.25 MPa from 12.98 MPa, and the increase rate reaches 11.9%; and after being soaked in hot water at 85 DEG C for 8 days, the flame retardant can still maintain the original flame retardant property.

Description

Technical Field

[0001] The invention belongs to the technical field of 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, and utilizes a crosslinked structure to construct a multi-flame-retardant group high-efficiency halogen-free flame-retardant TPU system. Background Art

[0002] Organophosphorus flame retardants can form an expanded carbon layer during the combustion process, blocking oxygen and heat, and have extremely high flame retardant efficiency. When used in combination with other flame retardants, they can play a synergistic flame retardant and efficient carbonization role. Organophosphorus flame retardants exhibit excellent reactivity due to their participation in a variety of elementary reactions. However, most organophosphorus flame retardants are small molecular structures, which are prone to migration, resulting in a decrease in flame retardant properties, changes in the appearance of polymers, and adverse effects on the environment. To solve the above problems, patent CN201910117619.3 combines phosphorus-containing organic groups in a molecular unit through chemical reactions, increases the molecular weight of organic phosphorus-containing molecules, achieves improved flame retardant properties, and reduces the migration of flame retardants. With the deepening of research on organophosphorus flame retardants, people have found that when flame retardant groups with synergistic effects are connected by chemical bonds, they can inspire exciting new properties. In the prior art, patents CN202310230588.9 and CN201910352562.5 construct phosphaphenanthrene / siloxane dibasic macromolecules and use them in polymers, which can not only improve the flame retardant properties of polymer materials, but also improve 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; secondly, it is difficult to prepare transparent halogen-free flame retardant TPU. At the same time, halogen-free flame retardant TPU faces the problem that the flame retardant components have large hydrolysis migration characteristics in a humid or water-containing environment, and their hydrolysis products are acidic, which causes TPU to hydrolyze rapidly under this condition, and the physical and mechanical properties of TPU materials deteriorate sharply.

[0004] To solve the above problems, the present invention relates to a caged phosphate micro-crosslinked polymer, which has a unique micro-crosslinked structure, giving it excellent migration resistance and insolubility in water and organic solvents. In addition, the caged phosphate group in the polymer can quickly synergize with another flame retardant group during the combustion process, significantly improving the flame retardant properties of the material. According to the flame retardant formula provided by the present invention, a 1.6 mm thick vertical burning sample can meet the V-0 flame retardant standard, and the peak heat release rate is reduced by more than 75%. More importantly, the formula 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 of the invention

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

[0006] The technical solution adopted by the present invention is as follows:

[0007] A flame retardant TPU material based on a caged phosphate flame retardant micro-crosslinked polymer, wherein the raw material components thereof include, by mass percentage, a caged phosphate micro-crosslinked polymer, a phosphorus-nitrogen flame retardant, an additive, TPU or a TPU composite polymer, and the addition amount of each raw material component is as follows:

[0008] Caged phosphate micro-crosslinked polymer, the mass fraction of which is 1-40%;

[0009] Phosphorus-nitrogen flame retardant, with a mass fraction of 0%-40%;

[0010] TPU or TPU composite polymer, the mass fraction of which is 60%-95%;

[0011] The total amount of the other additives 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 caged phosphate micro-crosslinked polymer is CPFR, which is a ring-opening addition product of a polyepoxy compound and a hydroxyl-containing compound, pentaerythritol caged phosphate, and the structure of the caged phosphate micro-crosslinked polymer is a mixture of one or more of the following compounds:

[0014]

[0015]

[0016]

[0017] Among them, R is The continuous part in A3, B3, and C3, i.e., the wavy line, is a repeated unit structure, and the unit structures correspond to:

[0018]

[0019] The preparation method of the CPFR is as follows: after uniformly mixing a polyepoxy compound and pentaerythritol caged phosphate PEPA together with an organic solvent at 20-150° C., adding a catalyst or not adding a catalyst, keeping the temperature for 1-48 hours, then evaporating the solvent under reduced pressure, and continuing to heat the prepolymer to 60-250° C. and keeping the temperature for 0.5-48 hours. After cooling, the solid material obtained is the flame retardant CPFR;

[0020] The polyepoxy compound is usually one or more of 2,4,6-tri(oxirane-2-ylmethoxy)-1,3,5-triazine, tri(oxirane-2-ylmethyl)benzene-1,3,5 tricarboxylate, triglycidyl isocyanurate, pentaerythritol tetraglycidyl ether, 1,4-bis[(glycidyloxy)methyl]cyclohexane. The organic solvent is N,N-dimethylformamide DMF, and the mass of DMF is 0 to 10 times the mass of PEPA. The catalyst can be one or more of triethylamine, aniline, tetraethylammonium bromide, tetrabutylammonium bromide, 4-dimethylaminopyridine, and 4-(aminomethyl)pyridine, and the total molar amount of the catalyst added is 0-10% of the molar amount of the epoxy group.

[0021] The feed ratio of PEPA to the polyepoxy compound, i.e. the ratio of the amount of substance n, is 1.0-5.0. The composition of the obtained product varies depending on the polyepoxy compound used and the feed ratio of PEPA to the polyepoxy compound, specifically:

[0022] When 2,4,6-tri(oxiran-2-ylmethoxy)-1,3,5-triazine is used as the polyepoxy compound, A1, A2 and A3 are generated; when tri(oxiran-2-ylmethyl)benzene-1,3,5 tricarboxylate is used as the polyepoxy compound, B1, B2 and B3 are generated; when triglycidyl isocyanurate is used as the polyepoxy compound, C1, C2 and C3 are generated; in the above three reaction processes, the main products are A3, B3 and C3 respectively, among which, when the feed ratio n is less than 3, A3, B3 and C3 account for more than 95% of the products, and when 3≤n≤5, A3, B3 and C3 account for more than 70%;

[0023] When pentaerythritol tetraglycidyl ether is used as the polyepoxy compound, D1 and D2 are generated. When the feed ratio n>4, the main product is D1. When the feed ratio 1≤n≤4, D2 is mainly generated.

[0024] When 1,4-bis[(glycidyloxy)methyl]cyclohexane is used as the polyepoxy compound, E1 and E2 are generated. When n>2, the main product is E1, and when n≤2, the main product is E2.

[0025] Preferably, the flame retardant TPU material based on caged phosphate flame retardant micro-cross-linked polymer designed by the present invention, the added phosphorus-nitrogen flame retardant is one or a combination of several of piperazine pyrophosphate, melamine polyphosphate, melamine phosphate, ammonium polyphosphate, melamine cyanurate, diethyl aluminum hypophosphite, inorganic hypophosphite, phosphaphenanthrene compounds, phosphaphenanthrene / triazine dibasic compound TAD, phosphaphenanthrene / siloxane dibasic macromolecular flame retardant.

[0026] Preferably, the present invention designs a flame retardant TPU material based on caged phosphate flame retardant micro-crosslinked polymer, and the TPU material involved includes a polyurethane thermoplastic elastomer (TPU) used alone or mixed or compounded with other thermoplastic elastomers or polyolefins to form a TPU composite polymer.

[0027] Preferably, the present invention relates to a flame retardant TPU material based on a caged phosphate micro-crosslinked polymer, wherein the other additives are one or more of an antioxidant, an anti-dripping agent, a lubricant, an antioxidant, a colorant, a hydrolysis stabilizer, and the like.

[0028] The flame retardant TPU material is prepared by mixing CPFR alone or with a phosphorus nitrogen flame retardant, or adding other additives, and performing melt blending processing at a processing temperature between 100°C and 300°C.

[0029] Beneficial effects:

[0030] The invention innovatively uses a caged phosphate flame retardant micro-crosslinked polymer with a micro-crosslinked structure, which is easy to blend with a polyurethane thermoplastic elastomer (TPU), and is resistant to hydrolysis, non-migrating, and non-precipitating; at the same time, the hydroxyl group and ether bond structure contained in the caged phosphate micro-crosslinked polymer can be physically and chemically crosslinked with the TPU matrix, and while the caged phosphate micro-crosslinked polymer flame retards TPU, the physical and mechanical properties of TPU are significantly better than those of the commonly used halogen-free intumescent flame retardants; when the flame retardant TPU material is added, taking 15% CPFR as an example, the flame retardant TPU has a transparent characteristic, the limiting oxygen index of the flame retardant system can reach 26.9%, the vertical combustion V-0 level (1.6mm), and the peak heat release rate is increased from 1681MJ / m of pure TPU 2 Will be as low as 325MJ / m 2 , reduced by 80.7%. The flame-retardant TPU provided by the present invention can increase the elongation stress at 300% from 8.28MPa of pure TPU to 10.29MPa, with an increase rate of 24.3%. The elongation stress at 500% is increased from 12.98MPa to 14.53MPa, which is 11.9% higher than that of pure TPU. .

[0031] Small molecule organophosphorus flame retardants added to TPU materials have the disadvantages of easy migration and poor water resistance; the present invention solves the problems of poor durability and easy water absorption of organophosphorus flame retardants in TPU materials; when the flame retardant TPU material is added, taking the addition of 15% CPFR as an example, the flame retardant TPU can still maintain its original shape and flame retardant properties after being immersed in 85°C hot water for 8 days.

[0032] The flame retardant formula provided by the present invention can achieve the V-0 flame retardant standard for a 1.6 mm thick vertical burning sample, and the peak value of the heat release rate is reduced to 200 MJ / m 2 The following can be reduced by more than 85% compared with pure TPU; more importantly, the formula can also improve the mechanical properties of TPU, increase the tensile stress of TPU materials, and the flame retardant formula provided by the present invention can reduce the migration of flame retardants and show better thermal hydrolysis resistance in hot water immersion experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Pictures of transparent states of samples obtained in different embodiments of the present invention;

[0034] Figure 2 Digital photos of 15% CPFR and 15% PEPA flame-retardant TPU materials immersed in 85°C hot water for corresponding time periods; (a) Digital photos of CPFR-TPU before and after boiling; (b) Digital photos of PEPA-TPU before and after boiling; from left to right are samples after 0, 2, 4, 6, and 8 days of boiling;

[0035] Figure 3 HRR curve of 15% CPFR flame retardant TPU material compared with pure TPU; DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with examples; these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention; the experimental methods in the following examples without specifying specific conditions are usually based on conventional conditions in the art; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets; unless otherwise specified, the amount of raw materials used refers to mass; any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention belong to the scope of protection claimed by the present invention.

[0037] Example 1

[0038] After the caged phosphate micro-crosslinked polymer (CPFR) was crushed, 15% CPFR and 85% polyurethane thermoplastic elastomer (TPU) were melt-blended to obtain a flame-retardant TPU material. The material was transparent and had a limiting oxygen index of 27.6%. The 1.6 mm vertical burning sample passed the V-0 test. In the cone calorimetry test, Figure 3 The peak heat release rate of pure TPU is 1681MJ / m 2 Reduced to 325MJ / m 2 As shown in Table 2, when CPFR flame retardant TPU is used, its tensile stress at 100%, 300%, and 500% is improved compared with the small molecule flame retardant pentaerythritol caged phosphate (PEPA), and is higher than that of pure TPU, which improves the flame retardant properties of the composite material while improving its mechanical properties.

[0039] In this example, the CPFR is prepared by ring-opening addition of PEPA and tri(epoxyethylene-2-ylmethyl)benzene-1,3,5-tricarboxylate according to a molar ratio of 2:1, and is a mixture of B1, B2, and B3, wherein the mass fraction of B3 is 95.5%.

[0040] Example 2

[0041] After CPFR was crushed, 30% CPFR, antioxidant, anti-aging agent and 69.8% TPU were melt blended; the addition amount of other additives was 0.2%, and the flame retardant TPU material was obtained, whose limiting oxygen index was 32.8%, and the 1.6mm vertical burning sample passed the V-0 level, and its peak heat release rate was reduced to 198MJ / m 2 , which is 88.2% lower than that of pure TPU; its tensile stress at 100% deformation is increased to 6.8MPa, which is 1.3MPa higher than that of pure TPU, and its elongation at break is 340.2%.

[0042] In this example, the CPFR is prepared by ring-opening addition of PEPA and tri(epoxyethylene-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%.

[0043] Example 3

[0044] After CPFR was crushed, CPFR, melamine polyphosphate (MPP) and 85% TPU were melt-blended, wherein the total addition amount of CPFR and MPP was 15%. When CPFR:MPP was 13:2, the flame-retardant TPU material obtained had a limiting oxygen index of 27.6%, and a 1.6 mm vertical burning sample passed the V-0 test, and its peak heat release rate increased from 1681 MJ / m of pure TPU to 27.6% of the original material. 2 Reduced to 321MJ / m 2, decreased by 80.9%, and the residual carbon increased from 8.2% of pure TPU to 21.1%, and the carbon-forming performance was greatly improved. The flame-retardant TPU composite material of this component has good carbon-forming property; in addition, the tensile stress of the flame-retardant composite material at 300% was increased from 8.28MPa of pure TPU to 9.69MPa, and the tensile stress at 500% was increased from 12.98MPa to 13.2MPa. This improved flame-retardant formula not only gives the material excellent flame-retardant properties, but also successfully maintains the original mechanical strength of the material, and even achieves performance improvements in some aspects.

[0045] In this example, the CPFR is prepared by ring-opening addition of PEPA and triglycidyl isocyanurate according to a molar ratio of 4:1, and is a mixture of C1, C2, and C3, wherein the mass fraction of C3 is 92.7%.

[0046] Example 4

[0047] After CPFR was crushed, 20% CPFR, 40% TPU and 40% polyolefin thermoplastic elastomer (TPO) were melt-blended to obtain a flame-retardant TPU / TPO composite material with a limiting oxygen index of 28.3% and a 1.6 mm vertical burning sample passing the V-0 grade.

[0048] In this example, the CPFR is prepared by ring-opening addition of PEPA and triglycidyl isocyanurate 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%.

[0049] Example 5

[0050] After CPFR is crushed, CPFR, phosphaphenanthrene / triazine dibase 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 flame retardant TPU material obtained has a limiting oxygen index of 26%, and the 1.6mm vertical burning sample passes the V-0 level test; in addition, the tensile stress at 500% of the flame retardant TPU is increased to 11.29MPa, and the tensile stress at 300% is increased to 8.52MPa.

[0051] In this example, the CPFR is prepared by ring-opening addition of PEPA and 2,4,6-tri(oxirane-2-ylmethoxy)-1,3,5-triazine according to a molar ratio of 3:1, and is a mixture of A1, A2, and A3, wherein the mass fraction of A3 is 86.9%.

[0052] Example 6

[0053] After CPFR was crushed, CPFR, phosphaphenanthrene / triazine dibasic compound (TAD) and TPU were melt-blended to obtain flame-retardant TPU material, wherein the total addition amount of CPFR and TAD was 15%. When CPFR:TAD was 13:2, flame-retardant TPU material was prepared, and its oxygen index could reach 27.6%. The 1.6mm vertical burning sample passed the V-0 level test; in the cone test, its heat release rate peak was reduced to 321MJ / m 2 The tensile stress at 500% of flame retardant TPU is increased to 13.2MPa, and the tensile stress at 300% is increased to 9.69MPa.

[0054] In this example, the CPFR is prepared by ring-opening addition of PEPA and 2,4,6-tri(oxirane-2-ylmethoxy)-1,3,5-triazine according to a molar ratio of 3:1, and is a mixture of A1, A2, and A3, wherein the mass fraction of A3 is 90.4%.

[0055] Figure 1 The transparent state pictures of different TPU samples show that the 12CPFR-TPU, 15CPFR-TPU, 13CPFR / 2TAD-TPU and 11CPFR / 4TAD-TPU samples obtained by the method of the present invention all have excellent transparency. Table 2 shows the test results of TPU samples with different formulas in Table 1, where "-8d" means the corresponding results after the samples were soaked in hot water at 85°C for 8 days; Figure 2 It can be seen that the sample obtained by the present invention has good thermal hydrolysis resistance, can effectively reduce the migration of flame retardants, and can effectively improve the mechanical properties of TPU materials.

[0056] Table 1. Flame retardant TPU formulation

[0057]

[0058]

[0059] Table 2. Test results of flame retardant TPU materials

[0060]

Claims

1. A flame retardant polyurethane thermoplastic elastomer material based on a caged phosphate micro-crosslinked polymer, characterized in that: Includes the following components: Caged phosphate micro-crosslinked polymer, the mass fraction of which is 1-40%; Phosphorus-nitrogen flame retardant, with a mass fraction of 0%-40%; polyurethane thermoplastic elastomer TPU or TPU composite polymer, with a mass fraction of 60%-95%; Additives, the total amount added is 0%-10% of the mass of TPU or TPU composite polymer; The sum of all component mass fractions is 100%.

2. The flame retardant polyurethane thermoplastic elastomer material based on caged phosphate micro-crosslinked polymer according to claim 1, characterized in that: The caged phosphate micro-crosslinked polymer is CPFR, which is a ring-opening addition product of a polyepoxy compound and a hydroxyl-containing compound, pentaerythritol caged phosphate.

3. The flame retardant polyurethane thermoplastic elastomer material based on caged phosphate micro-crosslinked polymer according to claim 2, characterized in that: The caged phosphate micro-crosslinked polymer is a mixture of one or more of the following compounds: Among them, R is The continuous part in A3, B3, and C3, i.e., the wavy line, is a repeated unit structure, and the unit structures correspond to:

4. The flame retardant polyurethane thermoplastic elastomer material based on caged phosphate micro-crosslinked polymer according to claim 1, characterized in that: The phosphorus-nitrogen flame retardant is one or a combination of piperazine pyrophosphate, melamine polyphosphate, melamine phosphate, ammonium polyphosphate, melamine cyanurate, diethyl aluminum hypophosphite, inorganic hypophosphite, phosphaphenanthrene compounds, phosphaphenanthrene / triazine dibasic compound TAD, and phosphaphenanthrene / siloxane dibasic macromolecular flame retardant.

5. The flame retardant polyurethane thermoplastic elastomer material based on caged phosphate micro-crosslinked polymer according to claim 1, characterized in that: The TPU composite polymer is a mixture or composite of polyurethane thermoplastic elastomer TPU and other thermoplastic elastomers or polyolefin materials.

6. The flame retardant polyurethane thermoplastic elastomer material based on caged phosphate micro-crosslinked polymer according to claim 1, characterized in that: The auxiliary agent is one or more of an antioxidant, an anti-dripping agent, a lubricant, an antioxidant, a colorant, and a hydrolysis stabilizer.

7. The method for preparing the flame-retardant polyurethane thermoplastic elastomer material based on caged phosphate micro-crosslinked polymer according to claim 1, characterized in that: The method comprises the following steps: CPFR is mixed alone or with a phosphorus-nitrogen flame retardant, or other additives are added, and melt-blended at a processing temperature between 100° C. and 300° C.

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