Heterocyclic onium ion type intrinsic flame-retardant thermoplastic polyurethane and preparation method thereof

Abstract

The invention relates to heterocyclic onium ion type intrinsic flame-retardant thermoplastic polyurethane and a preparation method thereof, and the main method comprises the following steps: by taking heterocyclic onium ion type diol, micromolecular diol and isocyanate group-terminated polyurethane oligomer as raw materials, polymerizing for a certain time in an organic solvent in a nitrogen atmosphere at a certain temperature, thereby obtaining the heterocyclic onium ion type intrinsic flame-retardant thermoplastic polyurethane. The heterocyclic onium ion type intrinsic flame-retardant thermoplastic polyurethane is obtained. The obtained heterocyclic onium ion type intrinsic flame-retardant thermoplastic polyurethane is excellent in mechanical property, the tensile strength is larger than 17 MPa, the flame-retardant limit oxygen index LOI value reaches 27.2%, and the heat release peak value finally reaches 607 kW / m < 2 >. Compared with non-ionic flame-retardant thermoplastic polyurethane, the heterocyclic onium ionic polyurethane has the advantage that the flame retardant property is obviously improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and relates to a preparation method and application of a heterocyclic onium ion type intrinsic flame-retardant thermoplastic polyurethane material. BACKGROUND

[0002] Thermoplastic polyurethane (TPU) is a thermoplastic elastomer, which is a linear polymer of (AB)n, wherein A is a soft segment composed of a relatively high molecular weight polyether or polyester diol, and B is a hard segment composed of a diisocyanate and a low molecular weight diol chain extender. The soft segment and the hard segment can form a block microphase separation structure due to thermodynamic incompatibility, the hard segment microzone is distributed in the soft segment microzone to form a physical crosslinking point, and the polyurethane is endowed with excellent mechanical properties, and is an elastic material between rubber and plastic, and can be processed and recycled like a thermoplastic material. The special structure of TPU endows it with outstanding physical and chemical properties, including wear resistance, good processability, high chemical stability and mechanical properties, and it has been widely used in aviation, biomedical, transportation, military, textile and garment, electronic and electrical, building and other industries. However, like most organic polymers, its flammability, melt dripping characteristics and smoke toxicity limit its application range, and therefore the flame retardant performance of TPU needs to be improved.

[0003] Halogen-based flame retardants and phosphorus-based flame retardants have high flame retardant efficiency. Among them, bromine-based flame retardants have excellent cost performance and excellent flame retardant performance, have little effect on the performance of flame-retardant substrates, and are widely applicable, and so far they are still one of the largest organic flame retardants in the world. At present, most bromine-based flame retardants exert flame-retardant effect on polymers in the form of physical blending, the flame retardant is easy to seep out, and there are problems of persistence, accumulation and biological amplification, and some bromine-based flame retardants (such as decabromodiphenyl ether and tetrabromobisphenol A) are listed as carcinogens or have reproductive toxicity and neurotoxicity, which pose potential threats to the ecological system and human health. In addition, some phosphorus-based flame retardants also have the same problems, and tris (1-chloro-2-propyl) phosphate and dimethyl methylphosphonate have been confirmed to have neurotoxicity, kidney toxicity and biological accumulation hazards. It is crucial to make full use of bromine-based and phosphorus-based flame retardants and to minimize the biological accumulation and non-sustainability of bromine-based and phosphorus-based flame retardants.

[0004] The flame-retardant research of polyurethane includes various ways, and ionic liquids are used to enhance the flame-retardant performance of polyurethane due to their unique and adjustable characteristics. Most of the current researches mix ionic liquids rich in flame-retardant elements into TPU in the form of addition, and there are problems such as migration of ionic liquids. If ionic liquids containing bromine and phosphorus elements are introduced into polymer macromolecular chains through a reaction method, non-additive environmentally friendly polyurethane materials with intrinsic flame-retardant characteristics can be prepared, the flame-retardant molecules can be firmly combined on the polymer chain, migration is not easy, the flame-retardant effect is more durable, and the influence of biological accumulation and non-sustainability of bromine and phosphorus flame retardants can be fundamentally reduced. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a heterocyclic onium ion type intrinsic flame-retardant thermoplastic polyurethane material, which uses imidazole type ionic liquid diol containing bromine and diphenyl phosphate anions as a chain extender, avoids migration of small molecule flame retardants containing bromine and phosphorus elements in the polymer matrix, and improves the flame-retardant performance of the polyurethane elastomer.

[0006] The technical solution adopted to achieve the above-mentioned purpose of the present application includes the following steps:

[0007] The heterocyclic onium ion type diol and the small molecule diol are used as chain extenders to perform polyurethane chain extension reaction on the isocyanate group terminated polyurethane prepolymer in a solvent; after the reaction is completed, the solvent is removed by drying to obtain the heterocyclic onium ion type intrinsic flame-retardant thermoplastic polyurethane.

[0008] In the above technical solution, the molar ratio of the heterocyclic onium ion type chain extender and the small molecule diol chain extender is between 0:6 and 6:0; the content of the heterocyclic onium ion type diol in the final flame-retardant thermoplastic polyurethane is 7wt% to 35wt%.

[0009] In the above technical solution, the heterocyclic onium ion type diol chain extender is one or more of m-benzene bridged bis-imidazolium dibromo diol, m-benzene bridged bis-pyridinium dibromo diol, m-benzene bridged bis-quinolinium dibromo diol, m-benzene bridged bis-thiazolium dibromo diol, m-benzene bridged bis-triazolium dibromo diol, m-benzene bridged bis-pyrrolidinium dibromo diol, m-benzene bridged bis-pyrazinium dibromo diol, m-benzene bridged bis-imidazolium diphenyl phosphate bromine diol, m-benzene bridged bis-pyridinium diphenyl phosphate bromine diol, m-benzene bridged bis-quinoline diphenyl phosphate bromine diol, m-benzene bridged bis-thiazolium diphenyl phosphate bromine diol, m-benzene bridged bis-triazolium diphenyl phosphate bromine diol, m-benzene bridged bis-pyrrolidinium diphenyl phosphate bromine diol, and m-benzene bridged bis-pyrazinium diphenyl phosphate bromine diol.

[0010] In the above technical solution, the isocyanate group terminated polyurethane prepolymer is prepared by reacting diisocyanate and oligomeric diol, and the molar ratio of diisocyanate to oligomeric diol is 8:2.

[0011] In the above technical solution, the small molecule diol chain extender includes but is not limited to 1,4-butanediol, ethylene glycol, and p-benzenediol dihydroxyethyl ether.

[0012] In the above technical solution, the solvent is one or more of N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl pyrrolidone.

[0013] In the above technical solution, the diisocyanate includes but is not limited to one or more of hexamethylene diisocyanate, toluene-2,4-diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, and m-xylylene diisocyanate.

[0014] In the above technical solution, the oligomeric diol includes but is not limited to one or more of polytetrahydrofuran diol, polyethylene glycol, polypropylene glycol, polycaprolactone diol, polybutadiene diol, and polycarbonate diol, and the oligomeric diol has a molecular weight in a range of 1000-4000 g / mol.

[0015] The present application has the following beneficial effects:

[0016] (1) The heterocyclic onium ion type diol chain extender is used as a hard segment structure of the heterocyclic onium ion type polyurethane, and by structural design, a flame-retardant element and a flame-retardant structural unit are introduced into the polyurethane chain, so that the polyurethane is endowed with good flame-retardant performance, use performance, and stability of the flame-retardant structural unit.

[0017] (2) The prepared heterocyclic onium ion type inherently flame-retardant thermoplastic polyurethane has a bromine content of 10.75 wt%, and the limiting oxygen index (LOI) value and the heat release peak value are significantly reduced compared with the non-ionic thermoplastic polyurethane. At the same time, the bromine content is 4.26 wt%, the phosphorus content is 1.63 wt%, the LOI value is 25.0%, and the heat release peak value finally reaches 607 kW / m 2 .

[0018] (3) The heterocyclic onium ion type inherently flame-retardant thermoplastic polyurethane has good mechanical properties, and the tensile strength is greater than 17 MPa. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The heat release rate curve of the cone calorimeter test of the ion type inherently flame-retardant thermoplastic polyurethane prepared for Examples 1-5 and the comparative polyurethane.

[0020] Figure 2 The total heat release curve of the cone calorimeter test of the ion type inherently flame-retardant thermoplastic polyurethane prepared for Examples 1-5 and the comparative polyurethane. DETAILED DESCRIPTION

[0021] For the purpose of better illustrating the object, technical scheme and advantages of the present application, the technical scheme of the present application will be described in detail below in combination with specific examples. The present application can be implemented in different forms, and should not be understood as being limited to the examples set forth herein. On the contrary, these examples are provided so that the present disclosure is thorough and complete, and the concept of the present application will be fully conveyed to those skilled in the art, and the present application will be limited only by the claims.

[0022] In all raw materials used in the present application, unless otherwise specified, can be obtained by commercial purchase.

[0023] In the technical scheme of the present application, the diisocyanate in the polyurethane prepolymer is one or more of 4,4'-diphenyl methane diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene-2,4-diisocyanate (TDI), isophorone diisocyanate (IPDI), 1,5 naphthalene diisocyanate (NDI), m-xylylene diisocyanate (XDI); the oligomeric diol is one or more of polytetrahydrofuran diol (PTMG), polyethylene glycol (PEG), polypropylene glycol (PPG), polycaprolactone diol (PCL), polybutadiene diol (HTPB), polycarbonate diol (PCDL), the molecular weight of the oligomeric diol ranges from 1000 to 4000 g / mol. The small molecule diol is 1,4-butanediol (BDO), ethylene glycol (EG), hydroquinone dihydroxyethyl ether (HQEE). The ionic diol chain extender is 1,3-bis[(1-(2-hydroxyethyl)imidazoliumyl) methyl] benzene dibromide (Br2IL), bromide / diphenyl phosphate (1:1) 1,3-bis[(1-(2-hydroxyethyl)imidazoliumyl) methyl] benzene (BrPIL), the chemical formula is as follows:

[0024]

[0025] The chemical reaction schematic diagram of the synthesized heterocyclic onium ionic intrinsic flame-retardant thermoplastic polyurethane is as follows:

[0026]

[0027] Preparation of heterocyclic onium ionic intrinsic flame-retardant thermoplastic polyurethane in Example 1

[0028] A 250 mL three neck flask equipped with a thermometer and a motor driven stirrer was charged with 4 g of MDI, purged with nitrogen at 80 °C, heated until MDI was melted, then 8 g of PTMG was added, stirred for 1 h to get a polyurethane prepolymer. 0.9 g of BDO and 0.976 g of Br2 IL were dissolved in 21 ml of DMF, added to the polyurethane prepolymer and stirred for 2 h. The product was poured into a Teflon mold and placed in an oven to remove the solvent. The solvent removal method was: the sample was left at room temperature for 12 h, dried in an oven at 30 °C for 48 h, then the temperature was raised to 70 °C until the sample reached a constant weight. A heterocyclic onium ion type inherently flame retardant thermoplastic polyurethane (TPUBr2IL8251) was obtained. The limiting oxygen index value was 23.2%, the heat release peak was 772 kW / m 2 , the total heat release was 89 MJ / m 2 , and the tensile strength was 22.01 MPa.

[0029] Example 2 Preparation of a heterocyclic onium ion type inherently flame retardant thermoplastic polyurethane

[0030] A 250 mL three neck flask equipped with a thermometer and a motor driven stirrer was charged with 4 g of MDI, purged with nitrogen at 80 °C, heated until MDI was melted, then 8 g of PTMG was added, stirred for 1 h to get a polyurethane prepolymer. 0.54 g of BDO and 2.93 g of Br2 IL were dissolved in 23 ml of DMF, added to the polyurethane prepolymer and stirred for 2 h. The product was poured into a Teflon mold and placed in an oven to remove the solvent. The solvent removal method was: the sample was left at room temperature for 12 h, dried in an oven at 30 °C for 48 h, then the temperature was raised to 70 °C until the sample reached a constant weight. A heterocyclic onium ion type inherently flame retardant thermoplastic polyurethane (TPUBr2IL8233) was obtained. The limiting oxygen index value was 24.8%, the heat release peak was 752 kW / m 2 , the total heat release was 82 MJ / m 2 , and the tensile strength was 26.84 MPa.

[0031] Example 3 Preparation of a heterocyclic onium ion type inherently flame retardant thermoplastic polyurethane

[0032] A 250 mL three-neck flask equipped with a thermometer and a motor-driven stirring blade was charged with 4 g of MDI, and heated to 80°C under nitrogen. Then 8 g of PTMG was added, and the prepolymerization was carried out for 1 h. Then 5.856 g of Br2IL was dissolved in 27 mL of DMF, and added to the prepolymerization mixture. The reaction was carried out for 2 h. After the mixture was homogenized, the product was poured into a Teflon mold, and placed in an oven to remove the solvent. The method for removing the solvent was as follows: the sample was left at room temperature for 12 h, and then dried in an oven at 30°C for 48 h. Then the temperature was raised to 70°C until the sample reached a constant weight. A heterocyclic onium ion-containing inherently flame-retardant thermoplastic polyurethane (TPUBr2IL8206) was obtained. The limiting oxygen index value was 27.2%, the heat release peak value was 647 kW / m2, the total heat release value was 70 MJ / m2, and the mechanical tensile strength was 19.85 MPa. 2 2

[0033] Example 4 Preparation of a heterocyclic onium ion-containing inherently flame-retardant thermoplastic polyurethane

[0034] A 250 mL three-neck flask equipped with a thermometer and a motor-driven stirring blade was charged with 4 g of MDI, and heated to 80°C under nitrogen. Then 8 g of PTMG was added, and the prepolymerization was carried out for 1 h. Then 5.856 g of Br2IL was dissolved in 27 mL of DMF, and added to the prepolymerization mixture. The reaction was carried out for 2 h. After the mixture was homogenized, the product was poured into a Teflon mold, and placed in an oven to remove the solvent. The method for removing the solvent was as follows: the sample was left at room temperature for 12 h, and then dried in an oven at 30°C for 48 h. Then the temperature was raised to 70°C until the sample reached a constant weight. A heterocyclic onium ion-containing inherently flame-retardant thermoplastic polyurethane (TPUBr2IL8206) was obtained. The limiting oxygen index value was 27.2%, the heat release peak value was 647 kW / m2, the total heat release value was 70 MJ / m2, and the mechanical tensile strength was 19.85 MPa. 2 2

[0035] Example 5 Preparation of a heterocyclic onium ion-containing inherently flame-retardant thermoplastic polyurethane

[0036] ​​​​A 250 mL three-neck flask equipped with a thermometer and a mechanical stirrer was charged with 4 g of MDI, and heated to 80 °C under nitrogen. Then 8 g of PTMG was added, and the prepolymerization was carried out for 1 h. Then 0.18 g of BDO and 6.58 g of BrPIL were dissolved in 28 mL of DMF, and added to the prepolymerization mixture. The mixture was stirred for 2 h. The product was poured into a Teflon mold, and placed in an oven to remove the solvent. The solvent removal procedure was as follows: the sample was left at room temperature for 12 h, and then placed in an oven at 30 °C for 48 h. The temperature was then increased to 70 °C until the sample reached a constant weight. The resulting intrinsic flame-retardant thermoplastic polyurethane containing onium heterocyclic ions (TPUBrPIL8215) had a limiting oxygen index value of 25.0%, a heat release peak value of 607 kW / m 2 , a total heat release value of 81 MJ / m 2 , and a mechanical tensile strength of 22.17 MPa.

[0037] Preparation of thermoplastic polyurethane of comparative example

[0038] A 250 mL three-neck flask equipped with a thermometer and a mechanical stirrer was charged with 4 g of MDI, and heated to 80 °C under nitrogen. Then 8 g of PTMG was added, and the prepolymerization was carried out for 1 h. Then 1.08 g of BDO was dissolved in 20 mL of DMF, and added to the prepolymerization mixture. The mixture was stirred for 2 h. The product was poured into a Teflon mold, and placed in an oven to remove the solvent. The solvent removal procedure was as follows: the sample was left at room temperature for 12 h, and then placed in an oven at 30 °C for 48 h. The temperature was then increased to 70 °C until the sample reached a constant weight. The resulting thermoplastic polyurethane had a limiting oxygen index value of 20.8%, a heat release peak value of 1026 kW / m 2 , a total heat release value of 103 MJ / m 2 , and a mechanical tensile strength of 39.11 MPa.

[0039] The flame-retardant properties and tensile strength data of the intrinsic flame-retardant thermoplastic polyurethanes containing onium heterocyclic ions prepared in Examples 1-5 and the thermoplastic polyurethane of comparative example are shown in Table 1.

[0040] Table 1. Bromine content, phosphorus content, flame-retardant properties, and mechanical properties of the polyurethanes of Examples 1-5 and comparative example

[0041]

[0042] As shown in Table 1, the heterocyclic onium ion type inherently flame-retardant thermoplastic polyurethane elastomers prepared in Examples 1-5 have good flame-retardant properties. The LOI value of the prepared heterocyclic onium ion type inherently flame-retardant thermoplastic polyurethane can be increased from 20.8% of the non-ion type thermoplastic polyurethane to 27.2% when the bromine content is 10.75wt%, and the heat release peak is reduced by 36.9%; when the bromine content is 4.26wt% and the phosphorus content is 1.63wt% in the presence of bromine and phosphorus, the LOI value is 25.0%, and the heat release peak is reduced by 40.8%.

[0043] The heterocyclic onium ion type inherently flame-retardant thermoplastic polyurethane has good mechanical properties, with a minimum tensile strength of 17.4MPa, meeting the performance requirements.

Claims

1. A process for the preparation of an onium ion type inherently flame retardant thermoplastic polyurethane, characterized in that, The method comprises the following steps: The isocyanate-terminated polyurethane prepolymer is subjected to polyurethane chain extension reaction in a solvent by using heterocyclic onium ion type diol and small molecule diol as chain extender; after the reaction is completed, the solvent is removed by drying to obtain the heterocyclic onium ion type intrinsic flame-retardant thermoplastic polyurethane.

2. The method of claim 1, wherein: The molar ratio of the heterocyclic onium ion type chain extender and the small molecule diol chain extender is 0:6-6:0; the content of the heterocyclic onium ion type diol in the final flame-retardant thermoplastic polyurethane is 7wt%-35wt%.

3. The method of claim 1, wherein: The heterocyclic onium ion type diol chain extender is specifically one or more of m-benzene bisimidazolium dibromine diol, m-benzene bispyridinium dibromine diol, m-benzene bisquinolinium dibromine diol, m-benzene bisthiadiazolium dibromine diol, m-benzene bistriazolium dibromine diol, m-benzene bispyrrolidinium dibromine diol, m-benzene bispyrazinium dibromine diol, m-benzene bisimidazolium diphenyl phosphate bromine diol, m-benzene bispyridinium diphenyl phosphate bromine diol, m-benzene bisquinoline diphenyl phosphate bromine diol, m-benzene bisthiadiazolium diphenyl phosphate bromine diol, m-benzene bistriazolium diphenyl phosphate bromine diol, m-benzene bispyrrolidinium diphenyl phosphate bromine diol, and m-benzene bispyrazinium diphenyl phosphate bromine diol.

4. The method of claim 1, wherein: The isocyanate-terminated polyurethane prepolymer is prepared by reacting diisocyanate and oligomeric diol, and the molar ratio of diisocyanate to oligomeric diol is 8:

2.

5. The method of claim 1, wherein: The small molecule diol chain extender includes but is not limited to 1,4-butanediol, ethylene glycol, and hydroquinone dihydroxyethyl ether.

6. The method of claim 1, wherein: The solvent is one or more of N,N-dimethylformamide, dimethyl sulfoxide, and N-methyl pyrrolidone.

7. The method of claim 4, wherein: The diisocyanate includes but is not limited to one or more of hexamethylene diisocyanate, toluene-2,4-diisocyanate, 4,4'-diphenyl methane diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, and m-xylylene diisocyanate.

8. The method of claim 4, wherein: The oligomeric diol includes but is not limited to one or more of polytetrahydrofuran diol, polyethylene glycol, polypropylene glycol, polycaprolactone diol, polybutadiene diol, and polycarbonate diol, and the molecular weight of the oligomeric diol ranges from 1000g / mol to 4000g / mol.

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