Preparation method and application of fluoroalcohol modified waterborne polyurethane emulsion

Abstract

The invention discloses a preparation method and application of a fluoroalcohol modified waterborne polyurethane emulsion, and belongs to the technical field of macromolecular waterborne polyurethane. The preparation method comprises the following steps: firstly synthesizing a waterborne polyurethane prepolymer emulsion by using diisocyanate and dihydric alcohol as base materials, then modifying the waterborne polyurethane prepolymer emulsion by using binary fluoroalcohol in a chain extension manner, and finally carrying out end capping reaction synergistic modification by using monohydric fluoroalcohol to prepare the waterborne polyurethane emulsion synergistically modified by the monohydric fluoroalcohol and the binary fluoroalcohol. According to the technical scheme, due to the surface aggregation of fluorine, the water resistance and the salt spray resistance of the material are remarkably improved, and the thermal stability and the mechanical property of the material are remarkably improved due to the high bond energy of a fluorocarbon bond. According to the prepared material, on the premise that good basic performance is guaranteed, the synergistic effect of the unitary fluoroalcohol and the binary fluoroalcohol is outstanding, and the material has good practical application value and industrial production prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of high molecular waterborne polyurethane, and specifically relates to a preparation method and application of a fluoroalcohol modified waterborne polyurethane emulsion. Background Art

[0002] At present, the performance of water-based polyurethane emulsions with water as the dispersion medium cannot meet the application needs in various fields of society. Due to the introduction of hydrophilic groups, the existing pure water-based polyurethane emulsions have low water resistance, poor salt spray resistance, poor mechanical properties and thermal stability, which limits the wide application of water-based polyurethane emulsions and restricts the application scope of water-based polyurethane emulsions. In order to make water-based polyurethane emulsions meet complex application scenarios, they need to be optimized and modified.

[0003] In the prior art, the thermal stability and tensile strength of waterborne polyurethane modified with a single fluorine alcohol are slightly improved, but its mechanical properties and water resistance are still relatively low, making it difficult to achieve large-scale industrial application. A Chinese patent document with publication number CN112250825A discloses an organic fluorine-modified waterborne polyurethane emulsion and a preparation method thereof. The waterborne polyurethane emulsion modified by grafting reaction only shows a slight improvement in tensile strength, while the mechanical properties, water resistance, thermal stability, etc. are relatively poor, and the overall performance is poor. Summary of the invention

[0004] The purpose of the present invention is to provide a preparation method and application of a fluoroalcohol-modified waterborne polyurethane emulsion, by which the waterborne polyurethane is synergistically modified by chain extension of a divalent fluoroalcohol and end-capping of a monovalent fluoroalcohol, thereby greatly improving the water resistance, mechanical properties, salt spray resistance and thermal stability of the product while maintaining good basic performance of the product.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In one aspect, the present invention provides a method for preparing a fluoroalcohol-modified aqueous polyurethane emulsion, comprising the following steps: (1) In an inert atmosphere, diisocyanate, diol, and tin catalyst are mixed and heated and stirred to react to obtain a waterborne polyurethane prepolymer emulsion; (2) adding a hydrophilic chain extender, a difluoroalcohol, and a polar organic solvent to an aqueous polyurethane prepolymer emulsion, heating and stirring to react, and obtaining an aqueous polyurethane prepolymer emulsion modified by a difluoroalcohol chain extender; (3) Add a crosslinking agent, a conventional chain extender, and a monofluoroalcohol to the waterborne polyurethane prepolymer emulsion modified by the difluoroalcohol chain extender, heat and stir to react, and obtain a monofluoroalcohol and difluoroalcohol synergistically modified waterborne polyurethane prepolymer emulsion, then add an amine neutralizing agent, and finally add deionized water for emulsification and rotary evaporation to obtain a fluoroalcohol modified waterborne polyurethane emulsion.

[0006] Preferably, in step (1), the diisocyanate is one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, aliphatic diisocyanate, xylylene diisocyanate, or tetramethylxylylene diisocyanate; the diol is one of polyethylene glycol, polypropylene glycol, polycaprolactone diol, or poly(1,4-butylene adipate) diol; and the tin catalyst is one of dibutyltin dilaurate, dibutyltin oxide, dibutyltin diacetate, or monobutyltin oxide.

[0007] Preferably, in step (1), the mass ratio of the diol, diisocyanate, and tin catalyst is 1: 0.4 - 0.6: 0.0001 - 0.0002.

[0008] Preferably, in step (1), the reaction temperature is 70 - 90 °C and the reaction time is 2 - 4 h.

[0009] Preferably, in step (2), the hydrophilic chain extender is one of sodium 3-sulphonato-1,2-propanediol, sodium 2-sulphonato-1,4-butanediol, dimethylolpropionic acid, or dimethylolbutyric acid; the difluoroalcohol is one of perfluoroalkane diol, 2,2,3,3-tetrafluoro-1,4-butanediol, octafluoro-1,6-hexanediol, 4,4,4-trifluoro-3-(trifluoromethyl)-1,3-butanediol, or 2,3,5,6-tetrafluoroterephthalyl alcohol; and the polar organic solvent is one of methyl ethyl ketone, methyl formate, ethyl acetate, acetone, butyl acetate, dimethyl sulfoxide, or tetrahydrofuran.

[0010] Preferably, in step (2), the mass ratio of the aqueous polyurethane prepolymer emulsion, polar organic solvent, hydrophilic chain extender, and difluoroalcohol is 1: 0.2 - 0.4: 0.04 - 0.07: 0.02 - 0.12.

[0011] Preferably, in step (2), the reaction temperature is 80 - 90 °C and the reaction time is 2 - 3 h.

[0012] Preferably, in step (3), the crosslinking agent is one of trimethylolpropane, glycerol, pentaerythritol, or isopentaeitol; the conventional chain extender is one of ethylene glycol, 1,4-butanediol, diethylene glycol, 1,6-hexanediol, 1,3-propanediol, or 1,4-bis(hydroxymethyl)cyclohexane; the monohydric fluoroalcohol is one of perfluorohexylethanol, perfluorooctylethanol, 3-perfluorooctylpropanol, octafluoropentanol, 3,3,4,4,5,5,5-heptafluoro-1-pentanol, perfluorodecanol, or pentafluoropropanol; the amine neutralizer is one of trimethylamine, triethylamine, triethanolamine, or tributylamine; the mass ratio of the waterborne polyurethane prepolymer emulsion modified by the dihydric fluoroalcohol chain extender, the crosslinking agent, the conventional chain extender, the monohydric fluoroalcohol, and the amine neutralizer is 1:0.02 - 0.03:0.025 - 0.035:0.024 - 0.124:0.03 - 0.05, and the mass ratio of the waterborne polyurethane prepolymer emulsion modified by the dihydric fluoroalcohol chain extender and deionized water is 1:1.2 - 1.8.

[0013] Preferably, in step (3), the heating reaction temperature is 40 - 90 °C, and the heating reaction time is 1.5 - 4 h; the emulsification time is 5 - 60 min, and the emulsification rotation speed is 7000 - 9000 r / min; the rotary evaporation temperature is 30 - 50 °C.

[0014] On the other hand, the present invention provides an application of the fluoroalcohol-modified waterborne polyurethane emulsion prepared by the above preparation method, and the fluoroalcohol-modified waterborne polyurethane emulsion is used for a waterborne polyurethane coating.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: 1. The technical solution of the present invention synergistically modifies waterborne polyurethane by end-capping with monohydric fluoroalcohol and chain-extending with dihydric fluoroalcohol to prepare a fluoroalcohol-modified waterborne polyurethane emulsion. The synergistically modified waterborne polyurethane emulsion has excellent basic properties. Compared with the waterborne polyurethane emulsion modified by a single fluoroalcohol in the prior art, the particle size of the waterborne polyurethane emulsion modified by the synergistic action of monohydric fluoroalcohol and dihydric fluoroalcohol prepared by the present invention is smaller, the viscosity is moderate, the solid content is higher, and the emulsion stability is stronger. Its basic properties can meet the daily production requirements in the field of waterborne polyurethane coatings, reflecting the good synergistic modification effect of monohydric fluoroalcohol and dihydric fluoroalcohol on the basic properties of the modified waterborne polyurethane emulsion.

[0016] 2. The technical solution of the present invention synergistically modifies waterborne polyurethane by using monofluorinated alcohol for end-capping and difluorinated alcohol for chain extension. The monofluorinated alcohol is grafted onto the end of the main chain of waterborne polyurethane as an end-capping modifier. Due to the strong water repellency of the carbon-fluorine chain segment in the monofluorinated alcohol and the self-aggregation property of fluorine element, when the waterborne polyurethane emulsion modified synergistically is made into a film, the fluorine element is arranged in an oriented manner on the surface of the film, and together with the difluorinated alcohol, it reduces the water absorption rate of the film. The water absorption rate within 24 hours is only 5.01%, while the water contact angle of the film is as high as 103.4°, greatly improving the water resistance of the film.

[0017] 3. The technical solution of the present invention synergistically modifies waterborne polyurethane by using monofluorinated alcohol for end-capping and difluorinated alcohol for chain extension. Since the fluorine-containing carbon chain is grafted onto the main chain of waterborne polyurethane, the distribution of carbon-fluorine bonds at the chain ends and between the chains is uniform, which significantly improves the thermal stability and salt spray resistance of the waterborne polyurethane emulsion. When it is made into a film and its properties are tested, it is found that the thermal decomposition temperature of the film is as high as 393.6 °C, and the salt spray resistance performance lasts for 12 months.

[0018] 4. The technical solution of the present invention synergistically modifies waterborne polyurethane by using monofluorinated alcohol for end-capping and difluorinated alcohol for chain extension. The difluorinated alcohol is grafted onto the main chain of waterborne polyurethane as a chain extension modifier, which has the effect of increasing the crosslinking degree of the system, reducing the usage amount of crosslinking agent, lowering the production cost, and being more environmentally friendly; the improvement of the crosslinking degree of the modified waterborne polyurethane and the relatively high carbon-fluorine bond energy synergistically improve the mechanical properties of the film. The tensile stress of the film is as high as 31.63 MPa, the elongation at break is as high as 10.33, it has good wear resistance, a relatively high solid content, and has good practical application value and industrial production prospects.

[0019] 5. In the prior art, the adhesion and pencil hardness properties of waterborne polyurethane modified with a single fluorinated alcohol are almost the same as those of unmodified pure waterborne polyurethane, at a relatively low level. Compared with the prior art, the technical solution of the present invention uses a waterborne polyurethane emulsion modified synergistically with monofluorinated alcohol and difluorinated alcohol to prepare a film, and the adhesion and pencil hardness properties of the film are significantly improved. Especially when the content of monofluorinated alcohol is 6 wt% and the content of difluorinated alcohol is 8 wt%, the adhesion of its film can reach grade 0 at most, and the pencil hardness is as high as 5H, reflecting the excellent synergistic effect of monofluorinated alcohol and difluorinated alcohol. Brief Description of the Drawings

[0020] Figure 1 It is a test chart of the particle size and distribution of the modified waterborne polyurethane emulsion prepared in Example 1; Figure 2 It is a test chart of the water contact angle of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1 and each comparative example; Figure 3 It is a thermogravimetric test chart of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1; Figure 4Salt spray test diagram of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1; Figure 5 Tensile test diagram of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. Detailed implementation manners

[0021] The present invention will be described in detail below in conjunction with examples and comparative examples, but the present invention is not limited thereto. Example 1

[0022] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas, removing interfering impurities such as air and moisture in the device. 40 g of poly(1,4-butylene adipate) diol, 21.5 g of isophorone diisocyanate, and 0.0008 g of dibutyltin dilaurate were poured into the three-necked flask. Under the condition of 85 °C, stirring was carried out at 300 r / min for 3 h to react to form an aqueous polyurethane prepolymer emulsion; (2) 3.5 g of dimethylolpropionic acid and 5.65 g of 2,2,3,3-tetrafluoro-1,4-butanediol were added to the aqueous polyurethane prepolymer emulsion. At the same time, 20 g of acetone was added to reduce the viscosity of the system. Stirring was continued at 300 r / min and the reaction was carried out at 85 °C for 2.5 h to react to form a binary fluoroalcohol chain-extended modified aqueous polyurethane prepolymer emulsion; (3) 1.7 g of 1,4-butanediol, 1.3 g of trimethylolpropane, and 4.58 g of 3-perfluorooctylpropanol were added to the emulsion obtained in the above step (2). Stirring was carried out at 300 r / min and the reaction was continued at 85 °C for 2 h. After that, a synergistically modified aqueous polyurethane prepolymer emulsion with a monofluoroalcohol and a difluoroalcohol was prepared. The temperature was lowered to 45 °C, 2.5 g of triethylamine was added to the synergistically modified aqueous polyurethane prepolymer emulsion for neutralization reaction, stirring was carried out at 150 r / min, and the reaction was carried out at 45 °C for 1 h. 100 g of deionized water was added, and the emulsion was sheared and emulsified at a speed of 8000 r / min for 15 min. Then the emulsion was transferred to a single-necked flask, and acetone was removed by a rotary evaporator at 38 °C to obtain a fluoroalcohol-modified aqueous polyurethane emulsion. Example 2

[0023] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas, removing interfering impurities such as air and moisture in the device. 40 g of polyethylene glycol, 18.3 g of toluene diisocyanate, and 0.00053 g of dibutyltin oxide were poured into the three-necked flask. Under the condition of 70 °C, stirring was carried out at 200 r / min for 2 h to react to form an aqueous polyurethane prepolymer emulsion; (2) Add 2.46 g of sodium 1,2 - propanediol - 3 - sulfonate and 1.26 g of perfluoroalkane diol to the water - borne polyurethane prepolymer emulsion. At the same time, add 20 g of methyl ethyl ketone to reduce the system viscosity. Continue stirring at 200 r / min and react at 80 °C for 2 h to obtain a water - borne polyurethane prepolymer emulsion modified by binary fluoroalcohol chain extension. (3) Add 1.52 g of ethylene glycol, 1.24 g of glycerol, and 1.49 g of perfluorohexyl ethanol to the emulsion obtained in the above step (2). Stir at 200 r / min and continue to react at 70 °C for 1.5 h to obtain a water - borne polyurethane prepolymer emulsion synergistically modified by monofluoroalcohol and binary fluoroalcohol. Cool down to 40 °C, add 1.83 g of trimethylamine to the synergistically modified water - borne polyurethane prepolymer emulsion for neutralization reaction. Stir at 100 r / min and keep reacting at 40 °C for 1 h. Add 73.6 g of deionized water, and shear - emulsify with an emulsifier at a rotation speed of 7000 r / min for 5 min. Then transfer the emulsion to a single - neck flask and remove methyl ethyl ketone at 30 °C using a rotary evaporator to obtain a fluoroalcohol - modified water - borne polyurethane emulsion. Example 3

[0024] (1) Pre - introduce nitrogen into a three - neck flask to keep the reaction path filled with inert gas, remove interfering impurities such as air and moisture in the device. Pour 40 g of polypropylene glycol, 19.2 g of diphenylmethane diisocyanate, and 0.00059 g of dibutyltin diacetate into the three - neck flask. Stir at 230 r / min at 73 °C for 2.5 h to obtain a water - borne polyurethane prepolymer emulsion. (2) Add 2.64 g of sodium 1,4 - butanediol - 2 - sulfonate and 1.88 g of octafluoro - 1,6 - hexanediol to the water - borne polyurethane prepolymer emulsion. At the same time, add 20 g of methyl formate to reduce the system viscosity. Continue stirring at 230 r / min and react at 82 °C for 2.5 h to obtain a water - borne polyurethane prepolymer emulsion modified by binary fluoroalcohol chain extension. (3) Add 1.58 g of diethylene glycol, 1.36 g of pentaerythritol, and 2.1 g of perfluorooctyl ethanol to the emulsion obtained in the above step (2). Stir at 250 r / min and continue to react at 75 °C for 2.5 h to obtain a water - borne polyurethane prepolymer emulsion synergistically modified by monofluoroalcohol and binary fluoroalcohol. Cool down to 43 °C, add 2.01 g of triethanolamine to the synergistically modified water - borne polyurethane prepolymer emulsion. Stir at 120 r / min and keep reacting at 43 °C for 1 h. Add 79.8 g of deionized water, and shear - emulsify with an emulsifier at a rotation speed of 7500 r / min for 10 min. Then transfer the emulsion to a single - neck flask and remove methyl formate at 35 °C using a rotary evaporator to obtain a fluoroalcohol - modified water - borne polyurethane emulsion. Example 4

[0025] (1) Nitrogen was pre-introduced into the three-necked flask to keep the reaction path filled with inert gas, removing interfering impurities such as air and moisture in the device. 40 g of polycaprolactone diol, 20.1 g of xylylene diisocyanate, and 0.00064 g of monobutyltin oxide were poured into the three-necked flask. Under the condition of 76 °C, stirring was carried out at 250 r / min for 3.5 h to generate an aqueous polyurethane prepolymer emulsion; (2) 2.82 g of dimethylolbutyric acid and 2.51 g of 4,4,4-trifluoro-3-(trifluoromethyl)-1,3-butanediol were added to the aqueous polyurethane prepolymer emulsion. At the same time, 20 g of ethyl acetate was added to reduce the viscosity of the system. Stirring was continued at 270 r / min, and the reaction was carried out at 84 °C for 3 h to generate an aqueous polyurethane prepolymer emulsion modified by chain extension with binary fluoroalcohol; (3) 1.64 g of 1,6-hexanediol, 1.42 g of isopentanetetraol, and 2.72 g of octafluoropentanol were added to the emulsion obtained in the above step (2). Stirring was carried out at 320 r / min, and the reaction was continued at 80 °C for 3 h. Then, an aqueous polyurethane prepolymer emulsion synergistically modified by monofluoroalcohol and binary fluoroalcohol was prepared. The temperature was lowered to 47 °C. 2.26 g of tributylamine was added to the synergistically modified aqueous polyurethane prepolymer emulsion, and stirring was carried out at 140 r / min. The reaction was maintained at 47 °C for 1 h. 85.9 g of deionized water was added, and the emulsifier was sheared and emulsified at a rotation speed of 8500 r / min for 30 min. Then, the emulsion was transferred to a single-necked flask, and ethyl acetate was removed by a rotary evaporator at 40 °C to obtain a fluoroalcohol-modified aqueous polyurethane emulsion. Example 5

[0026] (1) Nitrogen was pre-introduced into the three-necked flask to keep the reaction path filled with inert gas, removing interfering impurities such as air and moisture in the device. 40 g of 1,4-butanediol adipate diol, 22.9 g of tetramethylxylylene diisocyanate, and 0.00069 g of dibutyltin dilaurate were poured into the three-necked flask. Under the condition of 80 °C, stirring was carried out at 280 r / min for 4 h to generate an aqueous polyurethane prepolymer emulsion; (2) 3.07 g of dimethylolpropionic acid and 3.77 g of 2,3,5,6-tetrafluoroterephthalyl alcohol were added to the aqueous polyurethane prepolymer emulsion. At the same time, 20 g of butyl acetate was added to reduce the viscosity of the system. Stirring was continued at 320 r / min, and the reaction was carried out at 86 °C for 2 h to generate an aqueous polyurethane prepolymer emulsion modified by chain extension with binary fluoroalcohol; (3) Add 1.82 g of 1,3 - propanediol, 1.55 g of trimethylolpropane, and 3.34 g of 3,3,4,4,5,5,5 - heptafluoro - 1 - pentanol to the emulsion obtained in the above step (2), stir at 350 r / min, continue the reaction at 90 °C for 3.5 h, then prepare a waterborne polyurethane prepolymer emulsion modified by the synergistic effect of monofluoroalcohol and difluoroalcohol. Cool down to 50 °C, add 2.38 g of triethylamine to the synergistically modified waterborne polyurethane prepolymer emulsion, stir at 160 r / min, keep the reaction at 50 °C for 1 h, add 92 g of deionized water, shear - emulsify with an emulsifier at a rotation speed of 9000 r / min for 60 min, then transfer the emulsion to a single - neck flask, and remove butyl acetate using a rotary evaporator at 50 °C to obtain a fluoroalcohol - modified waterborne polyurethane emulsion. Example 6

[0027] (1) Pre - introduce nitrogen into a three - neck flask to keep the reaction path filled with inert gas, remove interfering impurities such as air and moisture in the device. Pour 40 g of polyethylene glycol, 23.8 g of isophorone diisocyanate, and 0.00075 g of dibutyltin oxide into the three - neck flask, stir at 330 r / min at 83 °C for 2 h to react and generate a waterborne polyurethane prepolymer emulsion. (2) Add 3.25 g of 1,2 - propanediol - 3 - sulfonate and 5.02 g of perfluoroalkane diol to the waterborne polyurethane prepolymer emulsion, and at the same time add 20 g of dimethyl sulfoxide to reduce the system viscosity. Continue to stir at 340 r / min and react at 87 °C for 2.5 h to generate a waterborne polyurethane prepolymer emulsion modified by difluoroalcohol chain extension. (3) Add 1.88 g of 1,4 - dimethylolcyclohexane, 1.61 g of glycerol, and 3.96 g of perfluorodecanol to the emulsion obtained in the above step (2), stir at 200 r / min, continue the reaction at 70 °C for 1.5 h, then prepare a waterborne polyurethane prepolymer emulsion modified by the synergistic effect of monofluoroalcohol and difluoroalcohol. Cool down to 40 °C, add 2.62 g of trimethylamine to the synergistically modified waterborne polyurethane prepolymer emulsion, stir at 100 r / min, keep the reaction at 40 °C for 1 h, add 98.2 g of deionized water, shear - emulsify with an emulsifier at a rotation speed of 7000 r / min for 5 min, then transfer the emulsion to a single - neck flask, and remove dimethyl sulfoxide using a rotary evaporator at 30 °C to obtain a fluoroalcohol - modified waterborne polyurethane emulsion. Example 7

[0028] (1) Pre - introduce nitrogen into a three - neck flask to keep the reaction path filled with inert gas, remove interfering impurities such as air and moisture in the device. Pour 40 g of polypropylene glycol, 24.7 g of toluene diisocyanate, and 0.00085 g of dibutyltin diacetate into the three - neck flask, stir at 350 r / min at 87 °C for 2.5 h to react and generate a waterborne polyurethane prepolymer emulsion. (2) 3.68 g of sodium 1,4 - butanediol - 2 - sulfonate and 6.28 g of octafluoro - 1,6 - hexanediol were added to the water - borne polyurethane prepolymer emulsion. At the same time, 20 g of tetrahydrofuran was added to reduce the viscosity of the system. Stirring continued at 360 r / min, and the reaction was carried out at 88 °C for 3 h to produce a water - borne polyurethane prepolymer emulsion modified by binary fluoroalcohol chain extension. (3) 1.94 g of 1,4 - butanediol, 1.67 g of pentaerythritol, and 5.2 g of pentafluoropropanol were added to the emulsion obtained in step (2) above. Stirring was carried out at 250 r / min, and the reaction continued at 75 °C for 2.5 h. Then, a water - borne polyurethane prepolymer emulsion modified synergistically by monofluoroalcohol and binary fluoroalcohol was prepared. The temperature was lowered to 43 °C, 2.74 g of triethanolamine was added to the synergistically modified water - borne polyurethane prepolymer emulsion, and stirring was carried out at 120 r / min. The reaction was maintained at 43 °C for 1 h. 101.2 g of deionized water was added, and the emulsion was sheared and emulsified at a speed of 7500 r / min by an emulsifier for 10 min. Then, the emulsion was transferred to a single - neck flask, and tetrahydrofuran was removed at 35 °C using a rotary evaporator to obtain a fluoroalcohol - modified water - borne polyurethane emulsion. Example 8

[0029] (1) Nitrogen was introduced into the three - neck flask in advance to keep the reaction path filled with inert gas, removing interfering impurities such as air and moisture in the device. 40 g of polycaprolactone diol, 26.1 g of diphenylmethane diisocyanate, and 0.00096 g of monobutyltin oxide were poured into the three - neck flask. Under the condition of 88 °C, stirring was carried out at 380 r / min for 3 h to produce a water - borne polyurethane prepolymer emulsion. (2) 3.99 g of dimethylolbutyric acid and 6.91 g of 4,4,4 - trifluoro - 3 - (trifluoromethyl) - 1,3 - butanediol were added to the water - borne polyurethane prepolymer emulsion. At the same time, 20 g of acetone was added to reduce the viscosity of the system. Stirring continued at 380 r / min, and the reaction was carried out at 89 °C for 2 h to produce a water - borne polyurethane prepolymer emulsion modified by binary fluoroalcohol chain extension. (3) 2 g of 1,6 - hexanediol, 1.8 g of isopentaeitol, and 6.19 g of 3 - perfluorooctylpropanol were added to the emulsion obtained in step (2) above. Stirring was carried out at 320 r / min, and the reaction continued at 80 °C for 3 h. Then, a water - borne polyurethane prepolymer emulsion modified synergistically by monofluoroalcohol and binary fluoroalcohol was prepared. The temperature was lowered to 47 °C, 2.93 g of tributylamine was added to the synergistically modified water - borne polyurethane prepolymer emulsion, and stirring was carried out at 140 r / min. The reaction was maintained at 47 °C for 1 h. 104.3 g of deionized water was added, and the emulsion was sheared and emulsified at a speed of 8500 r / min by an emulsifier for 30 min. Then, the emulsion was transferred to a single - neck flask, and acetone was removed at 40 °C using a rotary evaporator to obtain a fluoroalcohol - modified water - borne polyurethane emulsion. Example 9

[0030] (1) Nitrogen was pre-introduced into a three-necked flask to keep the reaction path filled with inert gas, removing interfering impurities such as air and moisture in the device. 40 g of poly(butylene adipate) diol, 27.4 g of xylylene diisocyanate, and 0.00107 g of dibutyltin dilaurate were poured into the three-necked flask. Under the condition of 90 °C, it was stirred at 400 r / min for 3.5 h to react to form an aqueous polyurethane prepolymer emulsion; (2) 4.3 g of dimethylolpropionic acid and 7.53 g of 2,3,5,6-tetrafluoroterephthalyl alcohol were added to the aqueous polyurethane prepolymer emulsion. At the same time, 20 g of acetone was added to reduce the viscosity of the system. Stirring continued at 400 r / min, and the reaction was carried out at 90 °C for 3 h to react to form an aqueous polyurethane prepolymer emulsion modified by binary fluoroalcohol chain extension; (3) 2.125 g of 1,3-propanediol, 1.86 g of trimethylolpropane, and 7.67 g of perfluorohexyl ethanol were added to the emulsion obtained in the above step (2). Stirring was carried out at 350 r / min, and the reaction was continued at 90 °C for 3.5 h. Then, an aqueous polyurethane prepolymer emulsion synergistically modified by monofluoroalcohol and binary fluoroalcohol was prepared. The temperature was lowered to 50 °C, 3.05 g of triethylamine was added to the synergistically modified aqueous polyurethane prepolymer emulsion, and stirring was carried out at 160 r / min. The reaction was maintained at 50 °C for 1 h. 110.4 g of deionized water was added, and the emulsion was sheared and emulsified at a speed of 9000 r / min by an emulsifier for 60 min. Then, the emulsion was transferred to a single-necked flask, and acetone was removed by a rotary evaporator at 50 °C to obtain a fluoroalcohol-modified aqueous polyurethane emulsion. Comparative Example 1

[0031] (1) Nitrogen was pre-introduced into a three-necked flask to keep the reaction path filled with inert gas, removing interfering impurities such as air and moisture in the device. 40 g of poly(butylene adipate) diol, 21.5 g of isophorone diisocyanate, and 0.0008 g of dibutyltin dilaurate were poured into the three-necked flask. Under the condition of 85 °C, it was stirred at 300 r / min for 3 h to react to form an aqueous polyurethane prepolymer emulsion; (2) 3.5 g of dimethylolpropionic acid was added to the aqueous polyurethane prepolymer emulsion. At the same time, 20 g of acetone was added to reduce the viscosity of the system. Stirring continued at 300 r / min, and the reaction was carried out at 85 °C for 2.5 h to react to form an aqueous polyurethane prepolymer emulsion containing hydrophilic groups; (3) Add 1.7 g of 1,4-butanediol and 1.3 g of trimethylolpropane to the above emulsion, stir at 300 r / min, continue the reaction at 85 °C for 2 h, then cool down to 45 °C, add 2.5 g of the amine neutralizer triethylamine, stir at 150 r / min, keep the reaction at 45 °C for 1 h, add 100 g of deionized water, shear and emulsify with an emulsifier at a rotation speed of 8000 r / min for 15 min, and then transfer the emulsion to a single-neck flask. Remove acetone using a rotary evaporator at 38 °C to obtain a pure waterborne polyurethane emulsion. Comparative Example 2

[0032] (1) Pre-introduce nitrogen into a three-neck flask to keep the reaction path filled with inert gas, remove interfering impurities such as air and moisture in the device. Pour 40 g of poly(1,4-butylene adipate) diol, 21.5 g of isophorone diisocyanate, and 0.0008 g of dibutyltin dilaurate into the three-neck flask, stir at 300 r / min at 85 °C for 3 h to react to form an aqueous polyurethane prepolymer emulsion. (2) Add 3.5 g of dimethylolpropionic acid to the aqueous polyurethane prepolymer emulsion, and at the same time add 20 g of acetone to reduce the system viscosity, continue to stir at 300 r / min, and react at 85 °C for 2.5 h to react to form an aqueous polyurethane prepolymer emulsion containing hydrophilic groups. (3) Add 1.7 g of 1,4-butanediol, 1.3 g of trimethylolpropane, and 4.58 g of 3-perfluorooctylpropanol to the above emulsion, stir at 300 r / min, continue the reaction at 85 °C for 2 h to obtain a monofluorinated alcohol-terminated modified aqueous polyurethane prepolymer emulsion. Cool down to 45 °C, add 2.5 g of the amine neutralizer triethylamine to the monofluorinated alcohol-terminated modified aqueous polyurethane prepolymer emulsion, stir at 150 r / min, keep the reaction at 45 °C for 1 h, add 100 g of deionized water, shear and emulsify with an emulsifier at a rotation speed of 8000 r / min for 15 min, and then transfer the emulsion to a single-neck flask. Remove acetone using a rotary evaporator at 38 °C to obtain a monofluorinated alcohol-terminated modified aqueous polyurethane emulsion. Comparative Example 3

[0033] (1) Pre-introduce nitrogen into a three-neck flask to keep the reaction path filled with inert gas, remove interfering impurities such as air and moisture in the device. Pour 40 g of poly(1,4-butylene adipate) diol, 21.5 g of isophorone diisocyanate, and 0.0008 g of dibutyltin dilaurate into the three-neck flask, stir at 300 r / min at 85 °C for 3 h to react to form an aqueous polyurethane prepolymer emulsion. (2) 3.5 g of dimethylolpropionic acid and 5.65 g of 2,2,3,3-tetrafluoro-1,4-butanediol were added to the waterborne polyurethane prepolymer emulsion. Meanwhile, 20 g of acetone was added to reduce the viscosity of the system. Stirring continued at 300 r / min, and the reaction was carried out at 85 °C for 2.5 h to generate a binary fluoroalcohol chain-extended modified waterborne polyurethane prepolymer emulsion; (3) 1.7 g of 1,4-butanediol and 1.3 g of trimethylolpropane were added to the above emulsion. Stirring was carried out at 300 r / min, and the reaction continued at 85 °C for 2 h. Then, the temperature was lowered to 45 °C, 2.5 g of the amine neutralizer triethylamine was added, and stirring was carried out at 150 r / min. The reaction was maintained at 45 °C for 1 h. 100 g of deionized water was added, and the emulsifier was sheared and emulsified at a rotation speed of 8000 r / min for 15 min. Then, the emulsion was transferred to a single-neck flask, and acetone was removed at 38 °C using a rotary evaporator to obtain a binary fluoroalcohol chain-extended modified waterborne polyurethane emulsion. Test Example 1

[0034] The particle size of the sample emulsions of the examples and comparative examples was measured. The particle size and distribution of the sample emulsions were measured using a NanoZS nanosizer produced by Malvern. For the viscosity measurement, an NDJ-5S digital rotary viscometer with a 31# rotor was used to measure the viscosity of the sample emulsions. The test results refer to the standard GB / T7198-1987. In the stability test, 5 mL of the emulsion was weighed and placed in a test tube. The centrifuge speed was set at 3000 r / min, and the sample was centrifuged for 20 min. If the sample did not separate or precipitate, it indicated that the sample emulsion had good stability.

[0035]

[0036] Table 1 shows the performance test of the sample emulsions. The basic performance of the sample emulsion of Example 1 was excellent, the performance of the sample emulsions of other examples was good, and the performance of the sample emulsion of the comparative example was poor. Figure 1 It is a test chart of the particle size and distribution of the modified waterborne polyurethane emulsion prepared for Example 1. Combining the above table, it can be seen that compared with the single fluoroalcohol modification of the waterborne polyurethane emulsion in the comparative example, in the example, a synergistic modification of the waterborne polyurethane emulsion was carried out using a monofluoroalcohol and a difluoroalcohol. The sample had a smaller particle size (72.8 - 81.9 nm), a moderate viscosity (108.8 - 128.2 mPa·s), a higher solid content (26.6% - 29.8%), stronger emulsion stability, and its basic performance could meet the daily production requirements in the national waterborne polyurethane coating field, reflecting the good synergistic modification effect of the monofluoroalcohol and the difluoroalcohol on the basic performance of the emulsion. Test Example 2

[0037] The samples of the examples and comparative examples were subjected to film-forming treatment. A polytetrafluoroethylene mold with specifications of 15×8×2 (cm) was washed with ethanol, taken out after drying in an oven, and an appropriate amount of emulsion was poured into the mold groove. It was placed horizontally to make its surface flat, uniform, and bubble-free. After being placed in a dark environment at 25°C for three days of drying, it was put into an oven at 45°C for 24 hours of drying. After the water was completely evaporated, it was taken out to obtain a gelatinous film.

[0038] The sessile drop method was used to measure the water contact angle of the gelatinous films of the examples and comparative examples, and a DSA100S type video contact angle measuring instrument was used to characterize its water resistance; the salt spray test was carried out in accordance with the national standard QC / T484-1999 "Industry Standard of Paint Coatings of the People's Republic of China", and the salt spray was a 5wt% sodium chloride solution; a TGA thermogravimetric analyzer was used for the thermal stability test, the heating rate was set at 15°C / min, and the heating range temperature was set at 25-550°C.

[0039]

[0040] Table 2 shows the test of the water resistance, heat resistance and salt spray resistance of the gelatinous films of the samples. Figure 2 It is the test diagram of the water contact angle of the gelatinous film prepared from the modified aqueous polyurethane emulsion prepared in Example 1 and each comparative example. It can be seen that the water resistance of the gelatinous film of the example sample has been significantly improved. Compared with the comparative example, the water contact angle of the gelatinous film of the example is excellent. Due to the water repellency of the fluorocarbon chain segment and the self-aggregation of fluorine elements, they are arranged in an orderly manner on the surface of the gelatinous film. The water contact angle of the gelatinous film of the example can reach up to 103.4°, and the water absorption rate is only 5.01% at the lowest, indicating that the introduction of monofluorohydrin and difluorohydrin has greatly improved the water resistance of the gelatinous film, and the surface aggregation of fluorine elements has greatly improved the problem of poor water resistance of the gelatinous film, and the synergistic effect is prominent.

[0041] Figure 3 It is the thermogravimetric test diagram of the gelatinous film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. Due to the high bond energy of the C-F bond, the fluorocarbon-containing graft chain reacts onto the main chain of the aqueous polyurethane, and the C-F bonds at the chain ends and between the chains are evenly distributed. The thermal decomposition temperature of the gelatinous film of the example has increased. When 10% of the gelatinous film decomposes, the decomposition temperature is 312.3°C. When 50% of the gelatinous film decomposes, the decomposition temperature is 393.6°C. Compared with the comparative example, there is a significant increase, which proves the good synergistic effect of monofluorohydrin and difluorohydrin; Figure 4 It is the salt spray test diagram of the gelatinous film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. There is no obvious rust at the intersection of the gelatinous film within 12 months, indicating that its salt spray resistance is excellent, and there is a significant improvement compared with the aqueous polyurethane modified with a single fluorohydrin. Test Example 3

[0042] The adhesion test of the sample film for the examples and comparative examples was carried out according to the test standard of GB-T9286-1998. It can be classified into grades 0-5 according to the level, with grade 0 being the best and grade 5 being the worst; the pencil hardness test was carried out according to the test standard of GB-T6739-2006, and a pencil hardness tester was used for the test. The pencil hardness test grades range from soft to hard as 9B-9H. The pencil hardness test grade range described below includes HB, H, 2H, 3H, 4H, 5H. Among them, grade 5H is the best and grade HB is the worst; the 3344 type electronic universal material testing machine was used to test its mechanical properties, including tensile stress and strain; the abrasion resistance test was carried out according to the test standard of GB / T23988-2009.

[0043]

[0044] Table 3 shows the test data of the mechanical properties of the film. Figure 5 It is the tensile test diagram of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. It can be seen that, compared with the comparative example, the improvement of the crosslinking degree and the relatively high C-F bond energy synergistically improve the mechanical properties of the synergistically modified aqueous polyurethane film. The maximum tensile stress of the aqueous polyurethane film synergistically modified by monofluorohydric alcohol and difluorohydric alcohol can reach 31.63 MPa, and the maximum elongation at break can reach 10.33. The minimum abrasion resistance is only 3.1 mg, and the mechanical properties are significantly improved; in particular, when using a single fluorohydric alcohol to modify aqueous polyurethane, its adhesion and pencil hardness properties are almost the same as those of unmodified pure aqueous polyurethane and are at a relatively low level. After introducing the synergistic modification of monofluorohydric alcohol and difluorohydric alcohol into the aqueous polyurethane emulsion, the synergistic effect enables the adhesion of the modified aqueous polyurethane film to reach grade 0 at most, and the pencil hardness to reach 5H at most, achieving a significant improvement, reflecting the excellent synergistic effect of monofluorohydric alcohol and difluorohydric alcohol, which is an effect that cannot be achieved by using a single fluorohydric alcohol to modify aqueous polyurethane emulsion, and their synergistic effect is prominent.

[0045] The specific embodiments described above have further elaborated on the present invention, but these descriptions should not be construed as limitations on the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a fluoroalcohol-modified aqueous polyurethane emulsion, characterized in that, It includes the following steps: (1) Under an inert atmosphere, a diisocyanate, a diol, and a tin catalyst are mixed and heated with stirring for reaction to obtain an aqueous polyurethane prepolymer emulsion; (2) A hydrophilic chain extender, a difluoroalcohol, and a polar organic solvent are added to the aqueous polyurethane prepolymer emulsion, and the mixture is heated with stirring for reaction to obtain an aqueous polyurethane prepolymer emulsion modified by difluoroalcohol chain extension; (3) A crosslinking agent, a conventional chain extender, and a monofluoroalcohol are added to the aqueous polyurethane prepolymer emulsion modified by difluoroalcohol chain extension, and the mixture is heated with stirring for reaction to prepare an aqueous polyurethane prepolymer emulsion synergistically modified by monofluoroalcohol and difluoroalcohol. Then, an amine neutralizer is added, and finally deionized water is added for emulsification and rotary evaporation to obtain a fluoroalcohol-modified aqueous polyurethane emulsion.

2. The preparation method of the fluoroalcohol-modified aqueous polyurethane emulsion according to claim 1, wherein, In the step (1), the diisocyanate is one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, aliphatic diisocyanate, benzene diisomethylene diisocyanate, or tetramethyl-m-phenylene diisocyanate; the diol is one of polyethylene glycol, polypropylene glycol, polycaprolactone diol, or poly(1,4-butylene adipate) glycol; and the tin catalyst is one of dibutyltin dilaurate, dibutyltin oxide, dibutyltin diacetate, or monobutyltin oxide.

3. The preparation method of the fluoroalcohol-modified aqueous polyurethane emulsion according to claim 1, wherein, In the step (1), the mass ratio of the diol, the diisocyanate, and the tin catalyst is 1: 0.4 - 0.6: 0.0001 - 0.0002.

4. The preparation method of the fluoroalcohol-modified aqueous polyurethane emulsion according to claim 1, wherein In the step (1), the reaction temperature is 70 - 90 °C, and the reaction time is 2 - 4 h.

5. The preparation method of the fluoroalcohol-modified aqueous polyurethane emulsion according to claim 1, characterized in that, In the step (2), the hydrophilic chain extender is one of sodium 1,2 - propanediol - 3 - sulfonate, sodium 1,4 - butanediol - 2 - sulfonate, dimethylolpropionic acid, or dimethylolbutyric acid; the difluoroalcohol is one of perfluoroalkane diol, 2,2,3,3 - tetrafluoro - 1,4 - butanediol, octafluoro - 1,6 - hexanediol, 4,4,4 - trifluoro - 3 - (trifluoromethyl) - 1,3 - butanediol, or 2,3,5,6 - tetrafluoroterephthalyl alcohol; and the polar organic solvent is one of methyl ethyl ketone, methyl formate, ethyl acetate, acetone, butyl acetate, dimethyl sulfoxide, or tetrahydrofuran.

6. The preparation method of the fluoroalcohol-modified aqueous polyurethane emulsion according to claim 1, wherein, In the step (2), the mass ratio of the aqueous polyurethane prepolymer emulsion, the polar organic solvent, the hydrophilic chain extender, and the difluoroalcohol is 1: 0.2 - 0.4: 0.04 - 0.07: 0.02 - 0.

12.

7. The preparation method of the fluoroalcohol-modified aqueous polyurethane emulsion according to claim 1, wherein In the step (2), the reaction temperature is 80 - 90 °C, and the reaction time is 2 - 3 h.

8. The preparation method of the fluoroalcohol-modified aqueous polyurethane emulsion according to claim 1, characterized in that, In the step (3), the crosslinking agent is one of trimethylolpropane, glycerol, pentaerythritol or isopentaerythritol; the conventional chain extender is one of ethylene glycol, 1,4-butanediol, diethylene glycol, 1,6-hexanediol, 1,3-propanediol or 1,4-bis(hydroxymethyl)cyclohexane; the monohydric fluoroalcohol is one of perfluorohexylethanol, perfluorooctylethanol, 3-perfluorooctylpropanol, octafluoropentanol, 3,3,4,4,5,5,5-heptafluoro-1-pentanol, perfluorodecanol or pentafluoropropanol; the amine neutralizer is one of trimethylamine, triethylamine, triethanolamine or tributylamine; the mass ratio of the waterborne polyurethane prepolymer emulsion modified by the dihydric fluoroalcohol chain extender, the crosslinking agent, the conventional chain extender, the monohydric fluoroalcohol and the amine neutralizer is 1: 0.02-0.03: 0.025-0.035: 0.024-0.124: 0.03-0.05, and the mass ratio of the waterborne polyurethane prepolymer emulsion modified by the dihydric fluoroalcohol chain extender and deionized water is 1: 1.2-1.

8.

9. The preparation method of the fluoroalcohol-modified aqueous polyurethane emulsion according to claim 1, characterized in that, In the step (3), the heating reaction temperature is 40-90 °C, and the heating reaction time is 1.5-4 h; the emulsification time is 5-60 min, and the emulsification rotation speed is 7000-9000 r / min; the rotary evaporation temperature is 30-50 °C.

10. Use of a fluoroalcohol-modified aqueous polyurethane emulsion prepared by the preparation method according to any one of claims 1-9, characterized in that, Apply the fluoroalcohol-modified waterborne polyurethane emulsion to the waterborne polyurethane coating.

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