Trifluoromethyl-containing polyurethane material as well as preparation method and application thereof

Abstract

The invention discloses a trifluoromethyl-containing polyurethane material as well as a preparation method and application thereof, trifluoromethyl TDI (toluene diisocynate) obtained by introducing trifluoromethyl into TDI (toluene diisocynate) is polymerized with different polymers containing dihydroxyl to prepare the polyurethane material; through trifluoromethylation, the mechanical property of polyurethane can be effectively improved, so that the service life of the polyurethane is prolonged. Compared with TDI, the prepared polyurethane has high tensile strength, high toughness, good uniformity and excellent comprehensive performance, has higher reliability and longer service life, and has important significance and development value for widening the application range of polyurethane materials in the fields of aerospace, automobiles, textiles, buildings, medical treatment, intelligent detection and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane materials and relates to a trifluoromethyl-containing polyurethane material and a preparation method thereof. Background Art

[0002] Solid propellant is the power source for solid rockets and missiles, and is an important material basis for achieving long-range strikes. At the same time, solid propellant is the basic technology, key technology and core technology of rockets, missiles and other weapons and equipment. The performance of solid propellant directly affects the maneuvering speed and capability of rocket and missile systems, and determines their survivability and combat effectiveness. Among them, composite solid propellant is a dense material that can burn regularly and produce high-temperature and high-pressure gas without relying on oxygen in the atmosphere. It is mainly composed of three parts: binder, oxidant and high-performance fuel. In the formula of composite solid propellant, the binder system (including additives such as polymer prepolymers, curing agents, chain extenders and cross-linking agents) accounts for about 10% of the mass fraction of the entire formula. It acts as a matrix or continuous phase in the composite solid propellant, allowing other components to be evenly dispersed therein, playing the role of bonding and carrying solid filler components, and acting as a fuel to provide energy for the propellant, which is different from the generally mentioned adhesive. The latter is a substance that connects two structural components of the same or different materials through adhesion, also known as glue. The performance of the binder system often directly determines the performance of the composite solid propellant. It is an important reference indicator for the formulation design, process preparation, and long-term storage of solid propellants, as well as the main indicator of renewal. Therefore, the binder for composite solid propellants must meet the performance requirements of high energy, low viscosity, low glass transition temperature, excellent mechanical properties and thermal stability, and good compatibility with other components.

[0003] Binders are the basis of the comprehensive performance of composite solid propellants, and directly determine the mechanical properties, storage properties, combustion properties, and insensitivity of composite solid propellants. Composite solid propellants are subjected to various mechanical and environmental loads during production, transportation, use, and long-term storage, which causes various periodic stresses and strains inside the grain. If these changes exceed the allowable range of their corresponding properties (such as tensile strength and elongation at break), the grain of the composite solid propellant will be excessively deformed or even ruptured, seriously threatening the safety performance of the storage and use of the propellant. Composite solid propellants with excellent mechanical properties can absorb the energy of various mechanical and environmental loads, thereby reducing the risk and sensitivity of composite solid propellant grain damage. Therefore, improving the mechanical properties of propellants is one of the important tasks in the research of composite solid propellants. With the continuous development of new high-performance weapon equipment systems, higher requirements are put forward for the mechanical properties of composite propellants, and further improvement is urgently needed. Among them, polyurethane (PU) adhesive is a commonly used adhesive system in composite propellants.

[0004] Polyurethane is a general term for polymers with urethane binding groups. It is formed by the chemical reaction of isocyanate groups and compounds with active hydrogen such as hydroxyl groups. It was produced by Bayer and others in 1937. Polyurethane mainly includes two major categories: polyester type and polyether type. It can be made into polyurethane plastics (mainly foam plastics), polyurethane fibers (spandex), polyurethane rubber and elastomers. Polyurethane appeared in the 1930s. After nearly 80 years of technological development, it has been widely used in defense, aerospace, light industry, chemical industry, petroleum, textile, transportation, automobile, medical and other fields. Polyurethane has both the elasticity of rubber and the strength and excellent processing properties of plastic. It has advantages that other synthetic materials cannot match in terms of heat insulation, sound insulation, wear resistance, oil resistance, elasticity, etc. It is the sixth largest plastic after polyethylene, polyvinyl chloride, polypropylene, polystyrene and polyacrylonitrile-butadiene-styrene resin (ABS), and has become an indispensable emerging material for economic development and people's lives.

[0005] At present, the way to introduce fluorine into the polyurethane structure can be divided into hard segment fluorine modification and soft segment fluorine modification. There are three main methods: one is to fluorine-modify the isocyanate monomer, the second is to use fluorine-containing diols as small molecule chain extenders, and the third is to fluorine-modify the soft segment polymer polyol. The most reported is the synthetic modification of fluorine-containing polyether polyols. From the overall preparation technology of fluorine-containing polyethers, there are generally problems such as long preparation routes, harsh process conditions, and high costs. So far, it is still difficult to industrialize. There are few reports on fluorine-containing modification of polyester polyols. First, the monomers of fluorine-containing dibasic acids and fluorine-containing diols that can be used for polymerization are relatively expensive. Second, the monomer activity is low, the polymer structure and molecular weight are difficult to control, and the batch stability is poor. It can only be prepared by solvent method. The subsequent removal of solvent not only increases the complexity of the process and the product cost, but also harms the human body and the environment. Therefore, although the performance of polyurethane elastomers of fluorine-containing polyesters is far better than that of polyurethane elastomers of fluorine-containing polyethers, it is also difficult to industrialize on a large scale. The fluorine-containing modification of isocyanate monomers, although the fluorine content in polyurethane materials is not too high, the tensile strength of the polyurethane materials produced can be improved while maintaining the original elongation performance. At present, common diisocyanates include toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), dicyclohexylmethane diisocyanate (HMDI), hexamethylene diisocyanate (HDI), etc. Among them, TDI material has the characteristics of simple structure, easy modification, multiple modification sites, rich series of derived products, and excellent performance.

[0006] Since the performance of polyurethane elastomers made from TDI is difficult to further improve and the reaction rate is uncontrollable, its application range is limited, resulting in its market share facing the pressure of a sharp decline. Therefore, it is particularly necessary to modify TDI with fluorine atoms, improve the performance of TDI materials, and solve the difficulties faced by TDI. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a trifluoromethyl-containing polyurethane material and a preparation method and application thereof, so as to solve the technical problems such as limited improvement in mechanical properties and narrow application scenarios of TDI-based polyurethane materials.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0009] A method for preparing a trifluoromethyl polyurethane material, the reaction equation is:

[0010]

[0011] in, Diol polymers, including HTPB, GAP and HTPE;

[0012] The structural formulas of HTPB, GAP and HTPE are as follows:

[0013]

[0014] The present invention also includes the following technical features:

[0015] Specifically, the method uses diol polymer and trifluoromethyl TDI as reaction raw materials, performs polymerization reaction in an organic solvent with a catalyst under stirring, drains the reaction solvent, puts the reactants into a polytetrafluoroethylene mold, degasses at room temperature, performs a curing reaction, and demolds.

[0016] Specifically, the catalyst is one of dibutyltin dilaurate, dimethylcyclohexylamine, and triphenylbismuth.

[0017] Specifically, the organic solvent is one of dichloromethane, tetrahydrofuran and ethyl acetate.

[0018] Specifically, the curing reaction temperature is 25 to 80° C., and the time is 72 to 120 hours.

[0019] Specifically, the molar ratio of the diol polymer, trifluoromethyl TDI, and the catalyst is 1:(0.8-1.2):0.01.

[0020] A trifluoromethyl-containing polyurethane material is prepared by adopting the preparation method of the trifluoromethyl-containing polyurethane material.

[0021] The trifluoromethyl polyurethane material is used as a binder for composite solid propellants.

[0022] Compared with the prior art, the present invention has the following technical effects:

[0023] (I) The method of the present invention is the first to perform trifluoromethylation modification on polyurethane, which expands the types of polyurethane materials and realizes the simple preparation of polyurethane materials, which is consistent with the preparation process of propellants and lays a material foundation for material application.

[0024] (II) The curing reaction rate is easy to control during the curing process of the present invention, the strip has a smooth appearance, good uniformity, and a controllable rate.

[0025] (III) Compared with TDI materials, the trifluoromethyl TDI material prepared by the present invention has improved tensile strength or elongation at break, and exhibits higher tensile strength and toughness than TDI, better uniformity, and excellent comprehensive performance, and has higher reliability and longer service life.

[0026] (IV) The fluorine-containing polyurethane material prepared by the present invention can effectively block the penetration of air and water as a protective layer, delay the oxidation of Al powder in the composite propellant, and stimulate the pre-ignition exothermic reaction on the surface of the aluminum oxide shell layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Dumbbell-shaped specimen for mechanical properties testing.

[0028] Figure 2 It is a comparison diagram of the films of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0029] The present invention provides a trifluoromethyl-containing polyurethane material and a preparation method and application thereof, wherein the fluorine atom has strong electronegativity, high CF bond energy (540 kJ / mol), the smallest van der Waals radius except for hydrogen, and the shielding and protective effect of fluorine on the carbon chain, which endows the fluorine-containing polymer with excellent thermal stability, weather resistance and chemical inertness, as well as unique properties such as low surface free energy, low friction coefficient, low refractive index, low dielectric constant and low power consumption factor, and the low surface energy and low friction coefficient of the fluorine-containing polymer make it have outstanding hydrophobic and oleophobic and anti-adhesion properties. Introducing fluorine-containing groups into polyurethane can combine the excellent mechanical properties and two-phase microstructure characteristics of polyurethane, and can greatly improve the surface properties and overall properties of polyurethane. This is mainly because: ① Due to the particularity of the CF bond, it will affect the physical and chemical properties of organic molecules; ② The C-F bond strength is relatively high, so the metabolism of the fluorinated active site is inhibited; ③ The strong electronegativity of fluorine will greatly affect the properties of other functional groups in the molecule. Compared with conventional polyurethane, fluorinated polyurethane can improve the new structure in terms of heat resistance, water resistance, radiation resistance, chemical resistance, low friction coefficient and other aspects while maintaining the original polyurethane performance due to the introduction of fluorine elements, thus greatly expanding the application field of new structure polyurethane, especially in some high-end military and pharmaceutical industries. At the same time, the introduction of fluorine atoms can increase the molecular force between polyurethane chains and improve the mechanical properties of the material, providing a new idea for improving the mechanical properties and stability of composite propellants.

[0030] The preparation method of the trifluoromethyl polyurethane material of the present invention has the following reaction formula:

[0031]

[0032] in, Diol polymers, including HTPB, GAP and HTPE;

[0033] The structures of HTPB, GAP and HTPE are shown below:

[0034]

[0035] The method uses diol polymer and trifluoromethyl TDI as reaction raw materials, conducts polymerization reaction in an organic solvent with stirring in the presence of a small amount of catalyst, drains the reaction solvent, puts the reactants into a polytetrafluoroethylene mold, degasses at room temperature for 20 minutes, cures at a certain temperature for a certain time, demolds, and cuts dumbbell-shaped specimens for mechanical property testing.

[0036] The catalyst is one of dibutyltin dilaurate, dimethylcyclohexylamine and triphenylbismuth;

[0037] The organic solvent is one of dichloromethane, tetrahydrofuran and ethyl acetate;

[0038] The curing reaction temperature is 25-80°C and the time is 72-120h.

[0039] The molar ratio of the diol polymer, trifluoromethyl TDI and the catalyst is 1:(0.8-1.2):0.01.

[0040] Application of trifluoromethyl polyurethane materials as binders for composite solid propellants.

[0041] The synthesis method of the raw material trifluoromethyl TDI of the present invention is: trifluoromethyl DNT is used as a reaction raw material, and under the action of a transition metal catalyst and a ligand, a one-step reaction is carried out with an isocyanate raw material under certain conditions, and trifluoromethyl TDI is obtained by recrystallization and distillation. The reaction equation is:

[0042]

[0043] Specifically, the following steps are included: under nitrogen protection, trifluoromethyl DNT, isocyanate raw materials, transition metal catalysts, ligands and bases are added to a reaction vessel, and the reaction is vacuumed and filled with nitrogen three times; solvents are added using a syringe, and oil bath heating is performed. After the reaction, the reaction is cooled to room temperature, monitored by TLC, and filtered to obtain TDI products by distillation separation. The transition metal catalyst is Pd(acac) 2 、Pd(OAc) 2 , Pd 2 (dba) 3 、Pd(TFA) 2 , Pd 2 (allyl) 2 Cl 2 、Ni(COD) 2 、NiCl 2 (PCy 3 ) 2 Any one of the following. The ligand is BrettPhos, IPr, IMes, SIMes, XPhos, RuPhos, DPPF, PCy 3 , BINAP. Isocyanate raw materials are NaOCN, KOCN, AgOCN, NH 4One of OCN. The solvent is any one of toluene, xylene, dioxane, and trifluorotoluene. The base is any one of potassium tert-butoxide, lithium tert-butoxide, sodium ethoxide, anhydrous potassium phosphate, potassium carbonate, cesium carbonate, potassium acetate, potassium pivalate, and cesium fluoride. The reaction temperature is 80-150°C and the time is 12-48h. The mass ratio of isocyanate raw material, catalyst, and ligand is 1: (0.01-0.5): (0.01-0.8). Preferably, the synthesis method of trifluoromethyl TDI comprises: under nitrogen protection, adding 0.5mmol trifluoromethyl DNT, 2mmol NaOCN, 10mol% Pd 2 (allyl) 2 Cl 2 , 25 mol% RuPhos, 1.5 mmol potassium acetate, evacuate and fill with nitrogen three times; add 3 mL of dioxane using a syringe, heat the oil bath to 150°C, and react for 24 hours; cool to room temperature, monitor by TLC, filter, and separate by distillation to obtain light yellow solid trifluoromethyl TDI.

[0044] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0045] Embodiment 1:

[0046] This embodiment provides a trifluoromethyl-containing polyurethane material and a preparation method thereof. 15 g HTPB, 1.21 g trifluoromethyl TDI and 10 mL dichloromethane or tetrahydrofuran or ethyl acetate are added to a 100 mL beaker for dissolution, 0.0015 g dibutyltin dilaurate or dimethylcyclohexylamine or triphenylbismuth is added, stirred for 15 min, vacuumed to remove the solvent and bubbles, poured the reactants into a polytetrafluoroethylene mold, vacuumed for 30 min, and then cured in a 70° C. oven for 3 days. After demolding, dumbbell-shaped specimens are cut with a cutter and mechanical properties are tested according to GB / T 528-2009.

[0047] Embodiment 2:

[0048] This embodiment provides a trifluoromethyl-containing polyurethane material and a preparation method thereof. 15 g of GAP, 1.59 g of trifluoromethyl TDI and 10 mL of dichloromethane or tetrahydrofuran or ethyl acetate are added to a 100 mL beaker for dissolution, 0.0015 g of dibutyltin dilaurate or dimethylcyclohexylamine or triphenylbismuth is added, stirred for 15 min, vacuumed to remove the solvent and bubbles, poured the reactants into a polytetrafluoroethylene mold, vacuumed for 30 min, and then cured in a 50° C. oven for 5 days. After demolding, dumbbell-shaped specimens are cut with a cutter and mechanical properties are tested according to GB / T 528-2009.

[0049] Embodiment 3:

[0050] This embodiment provides a trifluoromethyl-containing polyurethane material and a preparation method thereof. 15g HTPE, 1.60g trifluoromethyl TDI and 10mL dichloromethane or tetrahydrofuran or ethyl acetate are added to a 100mL beaker for dissolution, 0.0015g dibutyltin dilaurate or dimethylcyclohexylamine or triphenylbismuth is added, stirred for 15 minutes, vacuumed to remove the solvent and bubbles, poured the reactants into a polytetrafluoroethylene mold, vacuumed for 30 minutes, and then cured in a 50°C oven for 5 days. After demolding, dumbbell-shaped specimens are cut with a cutter and mechanical properties are tested according to GB / T 528-2009.

[0051] Comparative Example 1:

[0052] Add 15g HTPB, 0.87g TDI and 10mL dichloromethane or tetrahydrofuran or ethyl acetate to a 100mL beaker to dissolve, add 0.0015g dibutyltin dilaurate or dimethylcyclohexylamine or triphenylbismuth, stir for 15min, vacuum to remove solvent and bubbles, pour the reactants into a polytetrafluoroethylene mold, vacuum exhaust for 30min, and then cure in a 70℃ oven for 3 days. After demolding, use a cutter to cut dumbbell-shaped specimens for mechanical property testing according to GB / T 528-2009.

[0053] Comparative Example 2:

[0054] Add 15g HTPB, 0.96g 4-FTDI and 10mL dichloromethane or tetrahydrofuran or ethyl acetate to a 100mL beaker for dissolution, add 0.0015g dibutyltin dilaurate or dimethylcyclohexylamine or triphenylbismuth, stir for 15min, vacuum to remove solvent and bubbles, pour the reactants into a polytetrafluoroethylene mold, vacuum exhaust for 30min, and then cure in a 70℃ oven for 3 days. After demolding, use a cutter to cut dumbbell-shaped specimens for mechanical property testing according to GB / T 528-2009.

[0055] Comparative Example 3:

[0056] Add 15g GAP, 1.14g TDI and 10mL dichloromethane or tetrahydrofuran or ethyl acetate to a 100mL beaker for dissolution, add 0.0015g dibutyltin dilaurate or dimethylcyclohexylamine or triphenylbismuth, stir for 15min, vacuum to remove solvent and bubbles, pour the reactants into a polytetrafluoroethylene mold, vacuum exhaust for 30min, and then cure in a 50℃ oven for 5 days. After demolding, use a cutter to cut dumbbell-shaped specimens for mechanical property testing according to GB / T 528-2009.

[0057] Comparative Example 4:

[0058] Add 15g GAP, 1.26g 4-FTDI and 10mL dichloromethane or tetrahydrofuran or ethyl acetate to a 100mL beaker for dissolution, add 0.0015g dibutyltin dilaurate or dimethylcyclohexylamine or triphenylbismuth, stir for 15min, vacuum to remove solvent and bubbles, pour the reactants into a polytetrafluoroethylene mold, vacuum exhaust for 30min, and then cure in a 50℃ oven for 5 days. After demolding, use a cutter to cut dumbbell-shaped specimens for mechanical property testing according to GB / T 528-2009.

[0059] Comparative Example 5:

[0060] Add 15g HTPE, 1.15g TDI and 10mL dichloromethane or tetrahydrofuran or ethyl acetate to a 100mL beaker for dissolution, add 0.0015g dibutyltin dilaurate or dimethylcyclohexylamine or triphenylbismuth, stir for 15min, vacuum to remove solvent and bubbles, pour the reactants into a polytetrafluoroethylene mold, vacuum exhaust for 30min, and then cure in a 50℃ oven for 5 days. After demolding, use a cutter to cut dumbbell-shaped specimens for mechanical property testing according to GB / T 528-2009.

[0061] Comparative Example 6:

[0062] Add 15g HTPE, 1.27g 4-FTDI and 10mL dichloromethane or tetrahydrofuran or ethyl acetate to a 100mL beaker for dissolution, add 0.0015g dibutyltin dilaurate or dimethylcyclohexylamine or triphenylbismuth, stir for 15min, vacuum to remove solvent and bubbles, pour the reactants into a polytetrafluoroethylene mold, vacuum exhaust for 30min, and then cure in a 50℃ oven for 5 days. After demolding, use a cutter to cut dumbbell-shaped specimens for mechanical property testing according to GB / T 528-2009.

[0063] Mechanical properties test

[0064] The mechanical properties of the cut specimens were tested using a CMT 6303 electronic universal testing machine. The test standard was GB / T 528-2009. The specimens were dumbbell-shaped. Figure 1 As shown, the test section size is 25mm*6mm*2mm. The specific mechanical properties results are shown in Table 1 below. Figure 2 It is a comparison diagram of the films of Example 1 (left) and Comparative Example 1 (right). From the film comparison, it can be seen that the polyurethane prepared based on trifluoromethyl TDI is smoother and more uniform, and is less likely to produce bubbles, indicating that the polymerization process reaction is more stable and the rate is controllable.

[0065] Table 1 Mechanical properties results

[0066]

Claims

1. A method for preparing a trifluoromethyl polyurethane material, characterized in that: The reaction equation is: in, Diol polymers, including HTPB, GAP and HTPE; The structural formulas of HTPB, GAP and HTPE are as follows:

2. The method for preparing a trifluoromethyl-containing polyurethane material according to claim 1, characterized in that: The method uses diol polymer and trifluoromethyl TDI as reaction raw materials, performs polymerization reaction in an organic solvent with a catalyst under stirring, drains the reaction solvent, puts the reactants into a polytetrafluoroethylene mold, degasses at room temperature, performs a curing reaction, and demolds.

3. The method for preparing a trifluoromethyl-containing polyurethane material according to claim 2, characterized in that: The catalyst is one of dibutyltin dilaurate, dimethylcyclohexylamine and triphenylbismuth.

4. The method for preparing a trifluoromethyl-containing polyurethane material according to claim 2, wherein: The organic solvent is one of dichloromethane, tetrahydrofuran and ethyl acetate.

5. The method for preparing a trifluoromethyl-containing polyurethane material according to claim 2, characterized in that: The curing reaction temperature is 25-80° C. and the time is 72-120 hours.

6. The method for preparing a trifluoromethyl-containing polyurethane material according to claim 2, characterized in that: The molar ratio of the diol polymer, trifluoromethyl TDI and the catalyst is 1:(0.8-1.2):0.

01.

7. A trifluoromethyl polyurethane material, characterized in that: The polyurethane is prepared by the method for preparing the trifluoromethyl-containing polyurethane material according to any one of claims 1 to 6.

8. Use of the trifluoromethyl polyurethane material according to claim 7 as a binder for composite solid propellants.

Images