Preparation method and application of epoxy modified castor oil-based fluorine-containing waterborne polyurethane emulsion

Abstract

The invention discloses a preparation method and application of an epoxy modified castor oil-based fluorine-containing waterborne polyurethane emulsion, and belongs to the technical field of macromolecular waterborne polyurethane. The preparation method comprises the following steps: firstly, synthesizing a castor oil-based waterborne polyurethane prepolymer emulsion by taking castor oil and diisocyanate as base materials, then carrying out chain extension reaction by taking alkali lignin instead of part of a hydrophilic chain extender, and finally, carrying out synergistic modification by applying binary fluoroalcohol and bisphenol A epoxy resin, so as to prepare the epoxy modified castor oil-based fluorine-containing waterborne polyurethane emulsion. The material prepared by the invention is environment-friendly and renewable, has excellent comprehensive properties such as water resistance, mechanical property, thermal stability and the like, is particularly remarkably improved in salt spray resistance (up to 15 months at most), and has good practical application value and industrial production prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer waterborne polyurethane, and specifically relates to a preparation method and application of an epoxy-modified castor oil-based fluorine-containing waterborne polyurethane emulsion. Background Art

[0002] At present, water-based polyurethane materials with water as the dispersion medium cannot meet social needs in terms of performance and have obvious disadvantages, such as low water resistance, poor salt spray resistance, poor mechanical properties and thermal stability, which limit their application scope. In addition, most of the base materials for preparing water-based polyurethane come from petroleum raw materials.

[0003] However, in the prior art, castor oil-based waterborne polyurethane emulsions are used instead of petroleum-based waterborne polyurethane emulsions for use in waterborne coatings, but their performance is still limited. For example, castor oil-based waterborne polyurethane emulsions have the disadvantages of poor mechanical properties, poor thermal stability, and poor water resistance, which are limited in practical applications. In the prior art, only castor oil-based waterborne polyurethane modified with difluoroalcohol is used. Although its water resistance is slightly improved, its mechanical properties and thermal stability are still relatively low, making it difficult to achieve large-scale application in industrial production. The Chinese patent document with publication number CN109942781B discloses a castor oil-based waterborne polyurethane dispersion and a preparation method and application thereof. Although the unmodified castor oil-based waterborne polyurethane has a stable emulsion, its adhesion, thermal stability and salt spray resistance are poor, and its overall performance is not good. The Chinese patent document with publication number CN101967222B discloses a preparation method of epoxidized castor oil-modified waterborne polyurethane. The pencil hardness and tensile strength of the epoxy-modified waterborne polyurethane emulsion are slightly improved, but the water resistance and thermal stability are still difficult to meet the needs of industrial production. Summary of the invention

[0004] The invention aims to provide a preparation method and application of an epoxy-modified castor oil-based fluorinated water-based polyurethane emulsion. Castor oil is used as a base material, alkali lignin replaces part of a hydrophilic chain extender, and dihydric fluoroalcohol and bisphenol A type epoxy resin are used to synergistically modify the water-based polyurethane emulsion. Under the premise of maintaining good basic performance of the product, the water resistance, mechanical properties, salt spray resistance and thermal stability of the product are greatly improved.

[0005] In one aspect, the present invention provides a method for preparing an epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion, comprising: (1) Under an inert atmosphere, diisocyanate, castor oil, and a tin catalyst are mixed and heated and stirred to react to obtain a castor oil-based waterborne polyurethane prepolymer emulsion; (2) adding alkali lignin and a hydrophilic chain extender to a castor oil-based waterborne polyurethane prepolymer emulsion, and adding a polar organic solvent, heating and stirring to react, and obtaining a biomass material modified waterborne polyurethane prepolymer emulsion; (3) Add binary fluoroalcohol and conventional chain extender to the biomass material modified aqueous polyurethane prepolymer emulsion, and heat and stir to react to obtain a castor oil-based fluorine-containing modified aqueous polyurethane prepolymer emulsion; (4) Add a crosslinking agent and bisphenol A epoxy resin to the castor oil-based fluorine-containing modified aqueous polyurethane prepolymer emulsion, heat and stir to react to obtain an epoxy-modified castor oil-based fluorine-containing aqueous polyurethane prepolymer emulsion, then add an amine neutralizer, and finally add deionized water for emulsification and rotary evaporation to obtain an epoxy-modified castor oil-based fluorine-containing aqueous polyurethane emulsion.

[0006] Preferably, in step (1), the diisocyanate is one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, aliphatic diisocyanate, benzene diisomethyl diisocyanate, or tetramethyl-m-phenylene diisocyanate; 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 diisocyanate, castor oil, and tin catalyst is 1: 0.9-1.1: 0.00002-0.00003; the reaction temperature is 60-90 °C, and the reaction time is 1.5-3.5 h.

[0008] Preferably, in 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 polar organic solvent is one of methyl ethyl ketone, methyl formate, ethyl acetate, acetone, butyl acetate, dimethyl sulfoxide, or tetrahydrofuran.

[0009] Preferably, in step (2), the mass ratio of the castor oil-based aqueous polyurethane prepolymer emulsion, alkali lignin, hydrophilic chain extender, and polar organic solvent is 1: 0.05-0.15: 0.02-0.04: 0.5-0.7; the reaction temperature is 80-90 °C, and the reaction time is 2-4 h.

[0010] Preferably, in step (3), the binary fluoroalcohol is one of 2,3,5,6-tetrafluoro-p-benzenemethanol, octafluoro-1,6-hexanediol, 2,2,3,3-tetrafluoro-1,4-butanediol, or 4,4,4-trifluoro-3-(trifluoromethyl)-1,3-butanediol; the conventional chain extender is one of 1,3-propanediol, 1,4-bis(hydroxymethyl)cyclohexane, 1,4-butanediol, diethylene glycol, ethylene glycol, or 1,6-hexanediol.

[0011] Preferably, in step (3), the mass ratio of the biomass material modified aqueous polyurethane prepolymer emulsion, binary fluoroalcohol, and conventional chain extender is 1: 0.02-0.12: 0.01-0.03; the reaction temperature is 70-90 °C, and the reaction time is 1-3 h.

[0012] Preferably, in step (4), the crosslinking agent is one of trimethylolpropane, glycerol, pentaerythritol or isopentyltetrol; the epoxy value of bisphenol A epoxy resin is 0.35 or 0.42 or 0.44 or 0.51 or 0.55; the amine neutralizer is one of trimethylamine, triethylamine or tributylamine.

[0013] Preferably, in step (4), the heating reaction temperature is 45 - 80 °C, the heating reaction time is 2 - 6 h; the emulsification time is 10 - 40 min, the emulsification rotation speed is 7500 - 8500 r / min; the rotary evaporation temperature is 35 - 55 °C.

[0014] On the other hand, the present invention provides an application of the epoxy - modified castor oil - based fluorinated water - borne polyurethane emulsion prepared by the above - mentioned preparation method, and applies the epoxy - modified castor oil - based fluorinated water - borne polyurethane emulsion to a water - borne polyurethane coating.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: 1. When a single compound is used to modify castor oil - based water - borne polyurethane in the prior art, its salt spray resistance is almost the same as that of unmodified pure castor oil - based water - borne polyurethane, at a relatively low level. After the technical solution of the present invention introduces binary fluoroalcohol and bisphenol A epoxy resin to synergistically modify the castor oil - based water - borne polyurethane emulsion, the salt spray resistance of the material is greatly improved. In particular, when the epoxy value of bisphenol A epoxy resin is 0.51, the salt spray resistance of its film can reach up to 15 months at most, achieving a significant improvement. On the premise that the emulsion particle size is moderate and the stability is good, it reflects the excellent synergistic effect of binary fluoroalcohol and bisphenol A epoxy resin.

[0016] 2. The technical solution of the present invention uses binary fluoroalcohol and bisphenol A epoxy resin to synergistically modify castor oil - based water - borne polyurethane. They complement each other's advantages. The binary fluoroalcohol makes up for the problems of poor pencil hardness and impact resistance of the film prepared by using bisphenol A epoxy resin alone to modify castor oil - based water - borne polyurethane. Bisphenol A epoxy resin makes up for the problems of poor adhesion, tensile stress and strain of the film prepared by using binary fluoroalcohol alone to modify castor oil - based water - borne polyurethane. The mechanical properties of the synergistically modified castor oil - based water - borne polyurethane are excellent, with a pencil hardness of up to 4H, an adhesion of at least 0 level, an impact resistance height of up to 80 cm at most, a tensile stress of up to 30.32 MPa, and a strain of 6.41.

[0017] 3. In the technical solution of the present invention, a binary fluoroalcohol is grafted between the chains of the waterborne polyurethane as a modifier. The binary fluoroalcohol contains a highly water-repellent fluorocarbon chain segment, and fluorine elements have self-aggregation properties. The fluorine elements are oriented on the surface of the film and act synergistically with bisphenol A epoxy resin, reducing the water absorption rate of the castor oil-based waterborne polyurethane film. Its water absorption rate in 36 hours is only 7.71%, while the water contact angle is as high as 100.8°, indicating that the epoxy-modified castor oil-based waterborne polyurethane film has excellent water resistance.

[0018] 4. In the technical solution of the present invention, bisphenol A epoxy resin is used as a modifier and grafted onto the side chain of the waterborne polyurethane. Bisphenol A epoxy resin is beneficial to improving the crosslinking degree of the system and helps to enhance the thermal stability of the modified waterborne polyurethane film.

[0019] 5. In the technical solution of the present invention, castor oil is used as the base material, and alkali lignin is used to replace part of the hydrophilic chain extender to prepare a castor oil-based waterborne polyurethane emulsion. Biomass materials have the advantages of being renewable, widely available, and low-cost. Replacing petroleum-based materials with natural renewable resources can reduce production costs and is more environmentally friendly. Bisphenol A epoxy resin is used as a modifier and grafted onto the side chain of the waterborne polyurethane, and it has the effect of increasing the crosslinking degree of the system, reducing the use of petroleum-based crosslinking agents, being more environmentally friendly, and reducing production costs. Castor oil and alkali lignin are introduced into the main chain of the waterborne polyurethane. Through the modification of bisphenol A epoxy resin and binary fluoroalcohol, the problem of poor basic properties of the castor oil-based waterborne polyurethane emulsion is solved. However, the proportion of alkali lignin should not be too much, otherwise it will affect the stability of the emulsion. When the mass ratio of alkali lignin to the castor oil-based waterborne polyurethane prepolymer emulsion is less than or equal to 0.15, the product has a moderate particle size, the emulsion is stable, and it also has the advantages of being green, environmentally friendly, degradable, and renewable of natural materials. Its basic properties can meet the daily production requirements in the field of waterborne polyurethane coatings. Description of the Drawings

[0020] Figure 1 It is a test chart of the water absorption rate of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1 and Comparative Example 1 in 36 hours; 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 Comparative Example 4 and Comparative Example 5; Figure 3 It is a test chart of the particle size and distribution of the modified waterborne polyurethane emulsion prepared in Example 1; Figure 4 It is a thermogravimetric test chart of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1; Figure 5 It is a salt spray test chart of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1; Figure 6Hardness test chart of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1; Figure 7 Adhesion test chart of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1; Figure 8 Impact test chart of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1; Figure 9 Tensile test chart of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. Detailed description of the specific implementation

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

[0022] (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. 30.7 g of isophorone diisocyanate, 30 g of castor oil, and 0.0008 g of dibutyltin dilaurate were poured into the three-necked flask. Under the condition of 80 °C, it was stirred at 350 r / min for 2 h to react to form a castor oil-based aqueous polyurethane prepolymer emulsion; (2) 5.2 g of alkali lignin and 2.0 g of dimethylolpropionic acid were added to the castor oil-based aqueous polyurethane prepolymer emulsion. At the same time, 40 g of acetone was added to reduce the viscosity of the system, and the stirring speed was reduced to 250 r / min. The reaction was carried out at 85 °C for 3 h to react to form a biomass material-modified aqueous polyurethane prepolymer emulsion; (3) 5.6 g of octafluoro-1,6-hexanediol and 1.6 g of 1,4-butanediol were added to the biomass material-modified aqueous polyurethane prepolymer emulsion. The stirring was maintained at 250 r / min, and the reaction was continued at 85 °C for 1.5 h to react to form a castor oil-based fluorinated modified aqueous polyurethane prepolymer emulsion; (4) 1.1 g of trimethylolpropane and 6.25 g of bisphenol A epoxy resin with an epoxy value of 0.51 were added to the above emulsion, and it was stirred at 200 r / min. After the temperature was reduced to 80 °C and the reaction was continued for 2 h, an epoxy-modified castor oil-based fluorinated aqueous polyurethane prepolymer emulsion was prepared. The temperature was lowered to 50 °C, 1.9 g of triethylamine was added to the epoxy-modified castor oil-based fluorinated aqueous polyurethane prepolymer emulsion for neutralization reaction, and it was stirred at 120 r / min. The reaction was maintained at 50 °C for 1.5 h, 80 g of deionized water was added, and the emulsion was sheared and emulsified at a speed of 7800 r / min by an emulsifier for 20 min. Then the emulsion was transferred to a single-necked flask, and acetone was removed by a rotary evaporator at 42 °C to obtain an epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion. Example 2

[0023] (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. 30.7 g of toluene diisocyanate, 27.6 g of castor oil, and 0.00062 g of dibutyltin oxide were poured into the three-necked flask. Under the condition of 60 °C, stirring was carried out at 300 r / min for 1.5 h to react to form a castor oil-based waterborne polyurethane prepolymer emulsion; (2) 3.02 g of alkali lignin and 1.21 g of 1,2-propanediol-3-sulfonate were added to the castor oil-based waterborne polyurethane prepolymer emulsion. At the same time, 30.3 g of methyl ethyl ketone was added to reduce the system viscosity. Stirring was reduced to 200 r / min, and the reaction was carried out at 80 °C for 2 h to react to form a biomass material-modified waterborne polyurethane prepolymer emulsion; (3) 1.22 g of 2,3,5,6-tetrafluoroterephthalyl alcohol and 0.62 g of 1,3-propanediol were added to the biomass material-modified waterborne polyurethane prepolymer emulsion. Stirring was maintained at 200 r / min, and the reaction was continued at 70 °C for 1 h to react to form a castor oil-based fluorine-containing modified waterborne polyurethane prepolymer emulsion; (4) 0.91 g of glycerol and 1.21 g of bisphenol A epoxy resin with an epoxy value of 0.35 were added to the above emulsion. Stirring was carried out at 360 r / min, and the reaction was continued at 70 °C for 2.5 h. After that, an epoxy-modified castor oil-based fluorine-containing waterborne polyurethane prepolymer emulsion was prepared. The temperature was lowered to 45 °C, and 1.77 g of trimethylamine was added to the epoxy-modified castor oil-based fluorine-containing waterborne polyurethane prepolymer emulsion for a neutralization reaction. Stirring was carried out at 130 r / min, and the reaction was maintained at 45 °C for 1.5 h. 72.7 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-necked flask, and methyl ethyl ketone was removed by a rotary evaporator at 35 °C to obtain an epoxy-modified castor oil-based fluorine-containing waterborne polyurethane emulsion. Example 3

[0024] (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. 30.7 g of diphenylmethane diisocyanate, 29.1 g of castor oil, and 0.00068 g of dibutyltin diacetate were poured into the three-necked flask. Under the condition of 70 °C, stirring was carried out at 330 r / min for 2.5 h to react to form a castor oil-based waterborne polyurethane prepolymer emulsion; (2) 4.23 g of alkali lignin and 1.52 g of 1,4-butanediol-2-sulfonate were added to the castor oil-based waterborne polyurethane prepolymer emulsion. At the same time, 33.3 g of methyl formate was added to reduce the system viscosity. Stirring was reduced to 220 r / min, and the reaction was carried out at 82 °C for 2 h to react to form a biomass material-modified waterborne polyurethane prepolymer emulsion; (3) Add 3.04 g of 2,2,3,3-tetrafluoro-1,4-butanediol and 0.92 g of 1,4-bis(hydroxymethyl)cyclohexane to the biomass material-modified aqueous polyurethane prepolymer emulsion, increase the stirring speed to 280 r / min, and continue to react at 75 °C for 2 h to obtain a castor oil-based fluorinated modified aqueous polyurethane prepolymer emulsion; (4) Add 0.98 g of pentaerythritol and 2.43 g of bisphenol A epoxy resin with an epoxy value of 0.42 to the above emulsion, stir at 330 r / min, and continue to react at 72 °C for 3 h to obtain an epoxy-modified castor oil-based fluorinated aqueous polyurethane prepolymer emulsion. Cool down to 47 °C, add 1.84 g of tributylamine to the epoxy-modified castor oil-based fluorinated aqueous polyurethane prepolymer emulsion for neutralization reaction, stir at 140 r / min, and keep reacting at 47 °C for 1.5 h. Add 75.8 g of deionized water, shear and emulsify with an emulsifier at a rotation speed of 8000 r / min for 15 min, then transfer the emulsion to a single-neck flask, and remove methyl formate at 40 °C using a rotary evaporator to obtain an epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion. Example 4

[0025] (1) Pre-introduce nitrogen into the three-neck flask to keep the reaction path filled with inert gas, remove interfering impurities such as air and moisture in the device, pour 30.7 g of xylylene diisocyanate, 30.6 g of castor oil, and 0.00074 g of monobutyltin oxide into the three-neck flask, and stir at 75 °C and 360 r / min for 3 h to obtain a castor oil-based aqueous polyurethane prepolymer emulsion; (2) Add 6.05 g of alkali lignin and 1.82 g of dimethylolbutyric acid to the castor oil-based aqueous polyurethane prepolymer emulsion, add 36.4 g of ethyl acetate at the same time to reduce the system viscosity, reduce the stirring speed to 240 r / min, and react at 84 °C for 3 h to obtain a biomass material-modified aqueous polyurethane prepolymer emulsion; (3) Add 4.87 g of 4,4,4-trifluoro-3-(trifluoromethyl)-1,3-butanediol and 1.23 g of diethylene glycol to the biomass material-modified aqueous polyurethane prepolymer emulsion, increase the stirring speed to 320 r / min, and continue to react at 80 °C for 2.5 h to obtain a castor oil-based fluorinated modified aqueous polyurethane prepolymer emulsion; (4) Add 1.04 g of pentaerythritol and 3.64 g of bisphenol A epoxy resin with an epoxy value of 0.44 to the above emulsion, stir at 300 r / min, cool to 75 °C and continue to react for 2 h to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion. Cool to 48 °C, add 1.96 g of triethylamine to the epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion for neutralization reaction, stir at 150 r / min, keep reacting at 48 °C for 1 h, add 78.8 g of deionized water, shear and emulsify with an emulsifier at a rotation speed of 8200 r / min for 25 min, then transfer the emulsion to a single-neck flask, and remove ethyl acetate using a rotary evaporator at 45 °C to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane emulsion. Example 5

[0026] (1) Pre-introduce nitrogen into a three-neck flask, keep the reaction path filled with inert gas, remove interfering impurities such as air and moisture in the device, pour 30.7 g of tetramethyl-m-xylene diisocyanate, 32.1 g of castor oil, and 0.00086 g of dibutyltin dilaurate into the three-neck flask, and stir at 380 r / min at 85 °C for 3.5 h to react to form a castor oil-based waterborne polyurethane prepolymer emulsion. (2) Add 7.56 g of alkali lignin and 2.18 g of dimethylolpropionic acid to the castor oil-based waterborne polyurethane prepolymer emulsion, and at the same time add 38.2 g of butyl acetate to reduce the system viscosity, reduce the stirring speed to 280 r / min, and react at 88 °C for 4 h to react to form a biomass material-modified waterborne polyurethane prepolymer emulsion. (3) Add 6.39 g of octafluoro-1,6-hexanediol and 1.42 g of 1,6-hexanediol to the biomass material-modified waterborne polyurethane prepolymer emulsion, increase the stirring speed to 360 r / min, and continue to react at 88 °C for 3 h to react to form a castor oil-based fluorinated modified waterborne polyurethane prepolymer emulsion. (4) Add 1.16 g of trimethylolpropane and 4.85 g of bisphenol A epoxy resin with an epoxy value of 0.51 to the above emulsion, stir at 250 r / min, cool to 78 °C and continue to react for 2 h to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion. Cool to 52 °C, add 2.0 g of trimethylamine to the epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion for neutralization reaction, stir at 160 r / min, keep reacting at 52 °C for 1.5 h, add 81.8 g of deionized water, shear and emulsify with an emulsifier at a rotation speed of 8300 r / min for 30 min, then transfer the emulsion to a single-neck flask, and remove butyl acetate using a rotary evaporator at 50 °C to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane emulsion. Example 6

[0027] (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. 30.7 g of isophorone diisocyanate, 33.7 g of castor oil, and 0.00092 g of dibutyltin oxide 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 and produce a castor oil-based waterborne polyurethane prepolymer emulsion; (2) 9.07 g of alkali lignin and 2.42 g of 1,2-propanediol-3-sulfonate were added to the castor oil-based waterborne polyurethane prepolymer emulsion. At the same time, 42.4 g of tetrahydrofuran was added to reduce the system viscosity. The stirring speed was reduced to 300 r / min, and the reaction was carried out at 90 °C for 4 h to react and produce a biomass material-modified waterborne polyurethane prepolymer emulsion; (3) 7.3 g of 2,3,5,6-tetrafluoroterephthalyl alcohol and 1.85 g of ethylene glycol were added to the biomass material-modified waterborne polyurethane prepolymer emulsion. The stirring speed was increased to 400 r / min, and the reaction was continued at 90 °C for 3 h to react and produce a castor oil-based fluorine-modified waterborne polyurethane prepolymer emulsion; (4) 1.22 g of glycerol and 7.89 g of bisphenol A epoxy resin with an epoxy value of 0.55 were added to the above emulsion. It was stirred at 230 r / min. After the temperature was reduced to 80 °C and the reaction continued for 2 h, an epoxy-modified castor oil-based fluorine-containing waterborne polyurethane prepolymer emulsion was prepared. The temperature was reduced to 55 °C. 2.03 g of tributylamine was added to the epoxy-modified castor oil-based fluorine-containing waterborne polyurethane prepolymer emulsion for a neutralization reaction. It was stirred at 170 r / min, and the reaction was carried out at 55 °C for 2.5 h. 84.8 g of deionized water was added, and the emulsifier was sheared and emulsified at a rotation speed of 8500 r / min for 40 min. Then the emulsion was transferred to a single-necked flask, and tetrahydrofuran was removed at 55 °C using a rotary evaporator to obtain an epoxy-modified castor oil-based fluorine-containing waterborne polyurethane emulsion. Comparative Example 1

[0028] (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. 30.7 g of isophorone diisocyanate, 30 g of castor oil, and 0.0008 g of dibutyltin dilaurate were poured into the three-necked flask. Under the condition of 80 °C, it was stirred at 350 r / min for 2 h to react and produce a castor oil-based waterborne polyurethane prepolymer emulsion; (2) 5.2 g of alkali lignin and 2.0 g of dimethylolpropionic acid were added to the castor oil-based waterborne polyurethane prepolymer emulsion. At the same time, 40 g of acetone was added to reduce the system viscosity. The stirring speed was reduced to 250 r / min, and the reaction was carried out at 85 °C for 3 h to react and produce a biomass material-modified waterborne polyurethane prepolymer emulsion; (3) Add 1.6 g of 1,4-butanediol to the biomass material-modified aqueous polyurethane prepolymer emulsion, stir at 250 r / min, and continue the reaction at 85 °C for 1.5 h to obtain a castor oil-based chain-extended modified aqueous polyurethane prepolymer emulsion; (4) Add 1.1 g of trimethylolpropane to the above emulsion, stir at 200 r / min, cool to 80 °C and continue the reaction for 2 h to obtain a crosslinked modified castor oil-based aqueous polyurethane prepolymer emulsion. Cool to 50 °C, add 1.9 g of triethylamine to the crosslinked modified castor oil-based aqueous polyurethane prepolymer emulsion for neutralization reaction, stir at 120 r / min, keep the reaction at 50 °C for 1.5 h, add 80 g of deionized water, shear and emulsify with an emulsifier at a speed of 7800 r / min for 20 min, then transfer the emulsion to a single-neck flask, and remove acetone using a rotary evaporator at 42 °C to obtain a castor oil-based aqueous polyurethane emulsion. Comparative Example 2

[0029] (1) Pre-introduce nitrogen into a three-necked flask to keep the reaction path filled with inert gas, remove interfering impurities such as air and moisture in the device. Pour 30.7 g of isophorone diisocyanate, 30 g of poly(1,4-butylene adipate) glycol, and 0.0008 g of dibutyltin dilaurate into the three-necked flask, and stir at 350 r / min at 80 °C for 2 h to obtain a petroleum-based aqueous polyurethane prepolymer emulsion; (2) Add 5.2 g of alkali lignin and 2.0 g of dimethylolpropionic acid to the petroleum-based aqueous polyurethane prepolymer emulsion, add 40 g of acetone at the same time to reduce the system viscosity, reduce the stirring speed to 250 r / min, and react at 85 °C for 3 h to obtain a biomass material-modified petroleum-based aqueous polyurethane prepolymer emulsion; (3) Add 1.6 g of 1,4-butanediol to the biomass material-modified petroleum-based aqueous polyurethane prepolymer emulsion, stir at 250 r / min, and continue the reaction at 85 °C for 1.5 h to obtain a petroleum-based chain-extended modified aqueous polyurethane prepolymer emulsion; (4) Add 1.1 g of trimethylolpropane to the above emulsion, stir at 200 r / min, cool to 80 °C and continue the reaction for 2 h to obtain a crosslinked modified petroleum-based aqueous polyurethane prepolymer emulsion. Cool to 50 °C, add 1.9 g of triethylamine to the crosslinked modified petroleum-based aqueous polyurethane prepolymer emulsion for neutralization reaction, stir at 120 r / min, keep the reaction at 50 °C for 1.5 h, add 80 g of deionized water, shear and emulsify with an emulsifier at a speed of 7800 r / min for 20 min, then transfer the emulsion to a single-neck flask, and remove acetone using a rotary evaporator at 42 °C to obtain a petroleum-based aqueous polyurethane emulsion. Comparative Example 3

[0030] (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. 30.7 g of isophorone diisocyanate, 30 g of castor oil, and 0.0008 g of dibutyltin dilaurate were poured into the three-necked flask. Under the condition of 80 °C, it was stirred at 350 r / min for 2 h to react and produce a castor oil-based waterborne polyurethane prepolymer emulsion; (2) 6 g of alkali lignin and 1.8 g of dimethylolpropionic acid were added to the castor oil-based waterborne polyurethane prepolymer emulsion. At the same time, 40 g of acetone was added to reduce the system viscosity. The stirring speed was reduced to 250 r / min, and the reaction was carried out at 85 °C for 3 h to react and produce a biomass material-modified waterborne polyurethane prepolymer emulsion; (3) 1.6 g of 1,4-butanediol was added to the biomass material-modified waterborne polyurethane prepolymer emulsion. Keeping the stirring speed at 250 r / min, the reaction was continued at 85 °C for 1.5 h to react and produce a castor oil-based chain-extended modified waterborne polyurethane prepolymer emulsion; (4) 1.1 g of trimethylolpropane was added to the above emulsion, and it was stirred at 200 r / min. After the temperature was lowered to 80 °C and the reaction continued for 2 h, a crosslinked modified castor oil-based waterborne polyurethane prepolymer emulsion was prepared. The temperature was lowered to 50 °C, 1.9 g of triethylamine was added to the crosslinked modified castor oil-based waterborne polyurethane prepolymer emulsion for neutralization reaction, and it was stirred at 120 r / min. Keeping the reaction at 50 °C for 1.5 h, 80 g of deionized water was added, and the emulsion was sheared and emulsified at a rotation speed of 7800 r / min for 20 min. Then the emulsion was transferred to a single-necked flask, and acetone was removed using a rotary evaporator under the condition of 42 °C to obtain a castor oil-based waterborne polyurethane emulsion. Comparative Example 4

[0031] (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. 30.7 g of isophorone diisocyanate, 30 g of castor oil, and 0.0008 g of dibutyltin dilaurate were poured into the three-necked flask. Under the condition of 80 °C, it was stirred at 350 r / min for 2 h to react and produce a castor oil-based waterborne polyurethane prepolymer emulsion; (2) 5.2 g of alkali lignin and 2.0 g of dimethylolpropionic acid were added to the castor oil-based waterborne polyurethane prepolymer emulsion. At the same time, 40 g of acetone was added to reduce the system viscosity. The stirring speed was reduced to 250 r / min, and the reaction was carried out at 85 °C for 3 h to react and produce a biomass material-modified waterborne polyurethane prepolymer emulsion; (3) 5.6 g of octafluoro-1,6-hexanediol and 1.6 g of 1,4-butanediol were added to the biomass material-modified waterborne polyurethane prepolymer emulsion. Keeping the stirring speed at 250 r / min, the reaction was continued at 85 °C for 1.5 h to react and produce a castor oil-based fluorinated waterborne polyurethane prepolymer emulsion; (4) Add 1.1 g of trimethylolpropane to the above emulsion, stir at 200 r / min, cool to 80 °C and continue the reaction for 2 h to obtain a crosslinked modified castor oil-based fluorinated aqueous polyurethane prepolymer emulsion. Cool to 50 °C, add 1.9 g of triethylamine to the crosslinked modified castor oil-based fluorinated aqueous polyurethane prepolymer emulsion for neutralization reaction, stir at 120 r / min, maintain the reaction at 50 °C for 1.5 h, add 80 g of deionized water, shear and emulsify with an emulsifier at a speed of 7800 r / min for 20 min, then transfer the emulsion to a single-neck flask and remove acetone using a rotary evaporator at 42 °C to obtain a castor oil-based fluorinated aqueous polyurethane emulsion. Comparative Example 5

[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 30.7 g of isophorone diisocyanate, 30 g of castor oil, and 0.0008 g of dibutyltin dilaurate into the three-neck flask, and stir at 350 r / min at 80 °C for 2 h to react to form a castor oil-based aqueous polyurethane prepolymer emulsion; (2) Add 5.2 g of alkali lignin and 2.0 g of dimethylolpropionic acid to the castor oil-based aqueous polyurethane prepolymer emulsion, add 40 g of acetone at the same time to reduce the system viscosity, reduce the stirring speed to 250 r / min, and react at 85 °C for 3 h to react to form a biomass material-modified aqueous polyurethane prepolymer emulsion; (3) Add 1.6 g of 1,4-butanediol to the biomass material-modified aqueous polyurethane prepolymer emulsion, keep stirring at 250 r / min, and continue the reaction at 85 °C for 1.5 h to react to form a castor oil-based chain-extended modified aqueous polyurethane prepolymer emulsion; (4) Add 1.1 g of trimethylolpropane and 6.25 g of bisphenol A epoxy resin with an epoxy value of 0.51 to the above emulsion, stir at 200 r / min, cool to 80 °C and continue the reaction for 2 h to obtain an epoxy-modified castor oil-based aqueous polyurethane prepolymer emulsion. Cool to 50 °C, add 1.9 g of triethylamine to the epoxy-modified castor oil-based aqueous polyurethane prepolymer emulsion for neutralization reaction, stir at 120 r / min, maintain the reaction at 50 °C for 1.5 h, add 80 g of deionized water, shear and emulsify with an emulsifier at a speed of 7800 r / min for 20 min, then transfer the emulsion to a single-neck flask and remove acetone using a rotary evaporator at 42 °C to obtain an epoxy-modified castor oil-based aqueous polyurethane emulsion. Test Example 1

[0033] 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 being dried in an oven, and an appropriate amount of emulsion was poured into the mold groove. It was placed horizontally to make its surface flat and uniform without bubbles. After being placed in a 25°C environment and dried in the dark for three days, it was put into an oven at 45°C and dried for 24 h. After the water was completely evaporated, it was taken out to obtain a gelatinous film.

[0034] The particle size of the emulsions of the examples and comparative examples was measured. The particle size and distribution of the sample emulsions were measured using a Nano-ZS nano particle size and zeta potential analyzer produced by Malvern. The water contact angle of the gelatinous films of the examples and comparative examples was measured by the sessile drop method, and a DSA100S type video contact angle measuring instrument was used to characterize its water resistance.

[0035]

[0036] Table 1 shows the particle size of the emulsions of the examples and each comparative example and the test of the water resistance performance of the gelatinous films. Figure 1 It is a test chart of the water absorption rate of the gelatinous film prepared from the modified aqueous polyurethane emulsion prepared in Example 1 and Comparative Example 1 for 36 h. Figure 2 It is a test chart of the water contact angle of the gelatinous films prepared from the modified aqueous polyurethane emulsions prepared in Example 1, Comparative Example 4, and Comparative Example 5. Combining the above table, it can be seen that the gelatinous film of the sample in Example 1 has excellent water resistance performance, the gelatinous films of the samples in other examples have good water resistance performance, and the gelatinous films of the comparative example samples have poor water resistance performance; the binary fluoroalcohol and bisphenol A epoxy resin synergistically modify the castor oil-based aqueous polyurethane emulsion. The binary fluoroalcohol contains a highly water-repellent fluorocarbon chain segment, and fluorine has self-aggregation properties. Fluorine is arranged in an oriented manner on the surface of the gelatinous film and acts synergistically with bisphenol A epoxy resin to reduce the water absorption rate of the castor oil-based aqueous polyurethane gelatinous film. The 36 h water absorption rate is greatly reduced (7.71%-7.99%), and the water contact angle is greatly increased (96.6°-100.8°); compared with petroleum-based aqueous polyurethane, the water resistance of castor oil-based aqueous polyurethane decreases slightly. From Example 1 compared with Comparative Example 1 and Comparative Example 2, it can be seen that the introduction of binary fluoroalcohol and bisphenol A epoxy resin significantly improves the water resistance performance of the epoxy-modified castor oil-based fluorinated aqueous polyurethane gelatinous film, indicating that the binary fluoroalcohol and bisphenol A epoxy resin have a good synergistic modification effect on the water resistance performance.

[0037] Figure 3It is a test chart of the particle size and distribution of the modified aqueous polyurethane emulsion prepared in Example 1. It can be seen that by introducing castor oil and alkali lignin into the main chain of aqueous polyurethane and through the modification of bisphenol A epoxy resin and difluoroalcohol, the problem of poor basic properties of castor oil-based aqueous polyurethane emulsion is remedied. However, the proportion of alkali lignin should not be too much, otherwise it will affect the emulsion stability. It can be seen from Comparative Example 3 that when the content of alkali lignin is too much, the emulsion particle size is too high, and precipitation is likely to occur, resulting in uneven and unstable emulsion. When the mass ratio of alkali lignin to castor oil-based aqueous polyurethane prepolymer emulsion ≤ 0.15, the particle size is moderate (124.3 - 127.0), the emulsion is stable, and it also has the advantages of being green, environmentally friendly, degradable, and renewable of natural materials. Its basic properties can meet the daily production requirements in the field of national aqueous polyurethane coatings, reflecting the good synergistic modification effect of difluoroalcohol and bisphenol A epoxy resin on castor oil-based aqueous polyurethane emulsion. Test Example 2

[0038] The thermal stability of the sample films of the examples and comparative examples was tested using a TGA thermogravimetric analyzer. The heating rate was set at 15 °C / min, and the heating range was set at 25 - 550 °C; the salt spray test was carried out in accordance with the national standard QC / T 484-1999 "Industry Standard of Paint Coatings of the People's Republic of China", and the salt spray was a 5wt% sodium chloride solution.

[0039]

[0040] Table 2 shows the thermal stability and salt spray test of the sample films of the examples and each comparative example. Figure 4 It is a thermogravimetric test chart of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. Compared with the comparative example, it can be seen that the improvement of the crosslinking degree of bisphenol A epoxy resin and the relatively high C-F bond energy of difluoroalcohol synergistically improve the thermal stability of the modified aqueous polyurethane film. When the material thermally decomposes by 10%, the decomposition temperature can be increased to a maximum of 320.5 °C, and when the material thermally decomposes by 50%, the decomposition temperature can be increased to a maximum of 365.6 °C.

[0041] Figure 5Salt spray test diagram of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. As can be seen from the figure, there is no obvious rust at the intersection of the film, indicating that its salt spray resistance performance is excellent. Compared with the comparative example, it can be seen that when a single compound is used to modify castor oil-based aqueous polyurethane in the prior art, its salt spray resistance performance is almost the same as that of the unmodified pure castor oil-based aqueous polyurethane, which is at a relatively low level. After the binary fluoroalcohol and bisphenol A epoxy resin are introduced to synergistically modify the castor oil-based aqueous polyurethane emulsion in the technical solution of the present invention, the salt spray resistance performance of the material is greatly improved. In particular, when the epoxy value of bisphenol A epoxy resin is 0.51, the salt spray resistance performance of its film can reach up to 15 months at most, achieving a significant improvement. On the premise that the emulsion particle size is moderate and the stability is good, the excellent synergistic effect of the binary fluoroalcohol and bisphenol A epoxy resin is reflected. Test Example 3

[0042] The adhesion test of the film samples of 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 grade, 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 mechanical properties including tensile stress and strain were tested using a 3344 type electronic universal material testing machine.

[0043]

[0044] Table 3 shows the mechanical property test of the film of the examples and each comparative example sample. Figure 6 Hardness test diagram of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. Figure 7 Adhesion test diagram of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. Figure 8 Impact test diagram of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. Figure 9 Tensile test diagram of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. Compared with the comparative example, combined with Figure 6 、 7As can be seen from 8 and 9, the synergistic improvement effect of binary fluoroalcohol and bisphenol A epoxy resin on the mechanical properties of castor oil-based waterborne polyurethane film is particularly significant. The two complement each other's advantages. The binary fluoroalcohol compensates for the poor pencil hardness and impact resistance of the film prepared by single modification of castor oil-based waterborne polyurethane with bisphenol A epoxy resin. The bisphenol A epoxy resin compensates for the poor adhesion, tensile stress and strain of the film prepared by single modification of castor oil-based waterborne polyurethane with binary fluoroalcohol. The castor oil-based waterborne polyurethane prepared by co-modification has excellent mechanical properties, with a pencil hardness of up to 4H, an adhesion of at least 0 level, an impact resistance height of up to 80 cm, a tensile stress of up to 30.32 MPa, and a strain of 6.41.

[0045] The specific embodiments described above further illustrate the present invention in detail, but these descriptions should not be construed as limiting 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 an epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion, characterized in that, It includes the following steps: (1) Under an inert atmosphere, mix diisocyanate, castor oil, and a tin catalyst, and heat and stir to react to obtain a castor oil-based waterborne polyurethane prepolymer emulsion; (2) Add alkali lignin and a hydrophilic chain extender to the castor oil-based waterborne polyurethane prepolymer emulsion, and add a polar organic solvent, then heat and stir to react to obtain a biomass material-modified waterborne polyurethane prepolymer emulsion; (3) Add a binary fluoroalcohol and a conventional chain extender to the biomass material-modified waterborne polyurethane prepolymer emulsion, and heat and stir to react to obtain a castor oil-based fluorine-modified waterborne polyurethane prepolymer emulsion; (4) Add a crosslinking agent and bisphenol A epoxy resin to the castor oil-based fluorine-modified waterborne polyurethane prepolymer emulsion, heat and stir to react to obtain an epoxy-modified castor oil-based fluorine-containing waterborne polyurethane prepolymer emulsion, then add an amine neutralizer, and finally add deionized water for emulsification and rotary evaporation to obtain an epoxy-modified castor oil-based fluorine-containing waterborne polyurethane emulsion.

2. The preparation method of the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, characterized in that, In the step (1), the diisocyanate is one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, aliphatic diisocyanate, benzylidene diisocyanate, or tetramethylm-benzylidene diisocyanate; the tin catalyst is one of dibutyltin dilaurate, dibutyltin oxide, dibutyltin diacetate, or monobutyltin oxide.

3. The preparation method of the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, characterized in that, In the step (1), the mass ratio of diisocyanate, castor oil, and the tin catalyst is 1:0.9 - 1.1:0.00002 - 0.00003; the reaction temperature is 60 - 90 °C, and the reaction time is 1.5 - 3.5 h.

4. The preparation method of the epoxy-modified castor oil-based fluorinated 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 polar organic solvent is one of methyl ethyl ketone, methyl formate, ethyl acetate, acetone, butyl acetate, dimethyl sulfoxide, or tetrahydrofuran.

5. The preparation method of the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, characterized in that In the step (2), the mass ratio of the castor oil-based waterborne polyurethane prepolymer emulsion, alkali lignin, hydrophilic chain extender, and polar organic solvent is 1:0.05 - 0.15:0.02 - 0.04:0.5 - 0.7; the reaction temperature is 80 - 90 °C, and the reaction time is 2 - 4 h.

6. The preparation method of the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, characterized in that, In the step (3), the binary fluoroalcohol is one of 2,3,5,6-tetrafluoroterephthalyl alcohol, octafluoro-1,6-hexanediol, 2,2,3,3-tetrafluoro-1,4-butanediol, or 4,4,4-trifluoro-3-(trifluoromethyl)-1,3-butanediol; the conventional chain extender is one of 1,3-propanediol, 1,4-dimethylolcyclohexane, 1,4-butanediol, diethylene glycol, ethylene glycol, or 1,6-hexanediol.

7. The preparation method of the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, wherein, In the step (3), the mass ratio of the biomass material-modified waterborne polyurethane prepolymer emulsion, binary fluoroalcohol, and conventional chain extender is 1:0.02 - 0.12:0.01 - 0.03; the reaction temperature is 70 - 90 °C, and the reaction time is 1 - 3 h.

8. The preparation method of the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, characterized in that, In the step (4), the crosslinking agent is one of trimethylolpropane, glycerol, pentaerythritol or isopentaeitol; the epoxy value of bisphenol A epoxy resin is 0.35 or 0.42 or 0.44 or 0.51 or 0.55; the amine neutralizing agent is one of trimethylamine, triethylamine or tributylamine.

9. The preparation method of the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, wherein In the step (4), the heating reaction temperature is 45-80 °C, the heating reaction time is 2-6 h; the emulsification time is 10-40 min, the emulsification rotation speed is 7500-8500 r / min; the rotary evaporation temperature is 35-55 °C.

10. Use of an epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion prepared by the preparation method according to any one of claims 1-9, characterized in that, Apply the epoxy-modified castor oil-based fluorinated waterborne polyurethane emulsion to the waterborne polyurethane coating.

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