Preparation method and application of epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion

Abstract

The present invention discloses a preparation method and application of an epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion, belonging to the technical field of polymer waterborne polyurethanes. The present invention first uses castor oil and diisocyanate as base materials to synthesize a castor oil-based aqueous polyurethane prepolymer emulsion, then uses alkali lignin to replace part of the hydrophilic chain extender to carry out a chain extension reaction, and finally uses dihydric fluorinated alcohol and bisphenol A epoxy resin for synergistic modification to produce an epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion. The material prepared by the present invention is environmentally friendly and renewable, and has excellent comprehensive properties such as water resistance, mechanical properties, and thermal stability. The salt spray resistance is particularly significantly improved, with a maximum lifespan of 15 months, and 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 particularly 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. They have obvious shortcomings, 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, water-based polyurethane emulsions prepared with castor oil instead of petroleum are used in water-based coatings, but their performance is still limited. For example, castor oil-based water-based polyurethane emulsions have the disadvantages of poor mechanical properties, poor thermal stability, and poor water resistance, which restricts their practical applications. In the prior art, only castor oil-based water-based 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. Chinese patent document CN109942781B discloses a castor oil-based waterborne polyurethane dispersion, its preparation method, and application. Although the unmodified castor oil-based waterborne polyurethane is stable, its adhesion, thermal stability, and salt spray resistance are poor, resulting in suboptimal overall performance. Chinese patent document CN101967222B discloses a method for preparing an epoxidized castor oil-modified waterborne polyurethane. While the pencil hardness and tensile strength of the epoxy-modified waterborne polyurethane emulsion show a slight improvement, its water resistance and thermal stability still fail to meet industrial production requirements. Summary of the Invention

[0004] The present invention aims to provide a preparation method and application of an epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion. Castor oil is used as a base material, alkali lignin replaces part of the hydrophilic chain extender, and dihydric fluoroalcohol and bisphenol A epoxy resin are synergistically modified to modify the aqueous polyurethane emulsion. While 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:

[0006] (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;

[0007] (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 the mixture to react, thereby obtaining a biomass material modified waterborne polyurethane prepolymer emulsion;

[0008] (3) adding dihydric fluorinated alcohol and conventional chain extender to the biomass material modified waterborne polyurethane prepolymer emulsion, heating and stirring to react, and obtaining a castor oil-based fluorinated modified waterborne polyurethane prepolymer emulsion;

[0009] (4) Add a crosslinking agent and bisphenol A epoxy resin to the castor oil-based fluorine-containing modified waterborne polyurethane prepolymer emulsion, heat and stir to react, and 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.

[0010] Preferably, in step (1), the diisocyanate is one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, aliphatic diisocyanate, xylene diisocyanate, or tetramethyl-m-xylene diisocyanate; and the tin catalyst is one of dibutyltin dilaurate, dibutyltin oxide, dibutyltin diacetate, or monobutyltin oxide.

[0011] Preferably, in step (1), the mass ratio of 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 1.5-3.5h.

[0012] Preferably, in step (2), the hydrophilic chain extender is one of 1,2-propylene glycol-3-sodium sulfonate, 1,4-butanediol-2-sodium sulfonate, dihydroxymethylpropionic acid, or dihydroxymethylbutyric acid; and the polar organic solvent is one of methyl ethyl ketone, methyl formate, ethyl acetate, acetone, butyl acetate, dimethyl sulfoxide, or tetrahydrofuran.

[0013] Preferably, in step (2), the mass ratio of 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 2-4h.

[0014] Preferably, in step (3), the difluoroalcohol is one of 2,3,5,6-tetrafluorophenylenediol or octafluoro-1,6-hexanediol or 2,2,3,3-tetrafluoro-1,4-butanediol or 4,4,4-trifluoro-3-(trifluoromethyl)-1,3-butanediol; and the conventional chain extender is one of 1,3-propylene glycol or 1,4-dihydroxymethylcyclohexane or 1,4-butanediol or diethylene glycol or ethylene glycol or 1,6-hexanediol.

[0015] Preferably, in step (3), the mass ratio of the biomass material modified waterborne polyurethane prepolymer emulsion, dihydric 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 1-3h.

[0016] Preferably, in step (4), the crosslinking agent is one of trimethylolpropane, propylene glycol, pentaerythritol, and isopentaerythritol; the epoxy value of the bisphenol A epoxy resin is 0.35, 0.42, 0.44, 0.51, or 0.55; and the amine neutralizing agent is one of trimethylamine, triethylamine, and tributylamine.

[0017] Preferably, in step (4), the heating reaction temperature is 45-80°C, the heating reaction time is 2-6h; the emulsification time is 10-40min, the emulsification speed is 7500-8500r / min; and the rotary evaporation temperature is 35-55°C.

[0018] On the other hand, the present invention provides an application of the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion prepared by the above preparation method, wherein the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion is applied to an aqueous polyurethane coating.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] 1. In the prior art, when a single compound is used to modify castor oil-based waterborne polyurethane, its salt spray resistance is almost the same as that of unmodified pure castor oil-based waterborne polyurethane, which is at a relatively low level. The technical solution of the present invention introduces dihydric fluoroalcohol and bisphenol A epoxy resin to synergistically modify the castor oil-based waterborne polyurethane emulsion, and the salt spray resistance of the material is greatly improved. In particular, when the epoxy value of the bisphenol A epoxy resin is 0.51, the salt spray resistance of the film can reach up to 15 months, which is significantly improved. Under the premise of moderate emulsion particle size and good stability, the excellent synergistic effect of dihydric fluoroalcohol and bisphenol A epoxy resin is reflected.

[0021] 2. The technical solution of the present invention uses difluoroalcohol and bisphenol A epoxy resin to synergistically modify castor oil-based waterborne polyurethane. The advantages of the two are complementary. The difluoroalcohol makes up for the poor pencil hardness and impact resistance of the film prepared by using bisphenol A epoxy resin to modify the castor oil-based waterborne polyurethane alone. The bisphenol A epoxy resin makes up for the poor adhesion, tensile stress and strain of the film prepared by using difluoroalcohol to modify the castor oil-based waterborne polyurethane alone. The synergistically modified castor oil-based waterborne polyurethane has excellent mechanical properties, with a pencil hardness of up to 4H, a minimum adhesion of level 0, an impact resistance height of up to 80 cm, a tensile stress of up to 30.32 MPa, and a strain of 6.41.

[0022] 3. The technical solution of the present invention uses difluoroalcohol as a modifier to be grafted between the chains of waterborne polyurethane. The difluoroalcohol contains highly water-repellent carbon-fluorine segments, and the fluorine element has self-aggregation properties. The fluorine element is directionally arranged on the surface of the film and synergistically acts with the bisphenol A epoxy resin to reduce the water absorption rate of the castor oil-based waterborne polyurethane film. Its 36h water absorption rate 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.

[0023] 4. The technical solution of the present invention uses bisphenol A epoxy resin as a modifier to be grafted onto the side chain of waterborne polyurethane. Bisphenol A epoxy resin is beneficial to improving the crosslinking degree of the system and helps to improve the thermal stability of the modified waterborne polyurethane film.

[0024] 5. The technical solution of the present invention uses castor oil as the base material and uses alkali lignin to replace part of the hydrophilic chain extender to prepare castor oil-based waterborne polyurethane emulsion. Biomass materials have the advantages of being renewable, widely available, and low in cost. Replacing petroleum-based materials with natural renewable resources can reduce production costs and be more environmentally friendly. Bisphenol A type epoxy resin is grafted onto the side chain of waterborne polyurethane as a modifier, and 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 used to make the waterborne polyurethane emulsion more water-based and more environmentally friendly. The quality of lignin is introduced into the main chain of water-based polyurethane, and through the modification of bisphenol A epoxy resin and difluoroalcohol, the problem of poor basic performance of castor oil-based water-based polyurethane emulsion is compensated. 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 castor oil-based water-based polyurethane prepolymer emulsion is less than or equal to 0.15, the product particle size is moderate, the emulsion is stable, and it has the green, environmentally friendly, degradable and renewable advantages of natural materials. Its basic performance can meet the daily production needs in the field of water-based polyurethane coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a 36h water absorption test chart of the films prepared from the modified aqueous polyurethane emulsions prepared in Example 1 and Comparative Example 1;

[0026] Figure 2 The water contact angle test diagram of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1 and Comparative Examples 4 and 5;

[0027] Figure 3 This is a test chart of particle size and distribution of the modified waterborne polyurethane emulsion prepared in Example 1;

[0028] Figure 4 This is a thermogravimetric test diagram of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1;

[0029] Figure 5This is a salt spray test diagram of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1;

[0030] Figure 6 This is a test chart of the hardness of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1;

[0031] Figure 7 This is a test chart of film adhesion prepared from the modified waterborne polyurethane emulsion prepared in Example 1;

[0032] Figure 8 This is a graph showing the impact test of a film prepared from the modified aqueous polyurethane emulsion prepared in Example 1;

[0033] Figure 9 This is a tensile test diagram of the film prepared from the modified aqueous polyurethane emulsion prepared in Example 1. DETAILED DESCRIPTION

[0034] 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

[0035] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove 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 and stirred at 80 °C and 350 r / min for 2 h to react and generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0036] (2) Add 5.2 g of alkali lignin and 2.0 g of dimethylol propionic acid to the castor oil-based waterborne polyurethane prepolymer emulsion, and at the same time add 40 g of acetone to reduce the viscosity of the system, reduce the stirring speed to 250 r / min, and react at 85 ° C for 3 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion;

[0037] (3) Add 5.6 g of octafluoro-1,6-hexanediol and 1.6 g of 1,4-butanediol to the biomass material modified waterborne polyurethane prepolymer emulsion, maintain stirring at 250 r / min, and continue the reaction at 85°C for 1.5 h to generate a castor oil-based fluorine-modified waterborne polyurethane prepolymer emulsion;

[0038] (4) 1.1 g of trimethylolpropane and 6.25 g of bisphenol A type epoxy resin with an epoxy value of 0.51 were added to the above emulsion, stirred at 200 r / min, and the temperature was reduced to 80°C and the reaction was continued for 2 h to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion. The temperature was reduced to 50°C, and 1.9 g of triethylamine was added to the epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion for neutralization reaction. The temperature was stirred at 120 r / min and the reaction was maintained at 50°C for 1.5 h. 80 g of deionized water was added, and the emulsifier was sheared and emulsified at a speed of 7800 r / min for 20 min. The emulsion was then transferred to a single-necked flask, and the acetone was removed by a rotary evaporator at 42°C to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane emulsion. Example 2

[0039] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove 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 and stirred at 300 r / min for 1.5 h at 60 ° C to react and generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0040] (2) Add 3.02 g of alkali lignin and 1.21 g of 1,2-propylene glycol-3-sulfonate sodium to the castor oil-based waterborne polyurethane prepolymer emulsion, and at the same time add 30.3 g of methyl ethyl ketone to reduce the viscosity of the system, reduce the stirring speed to 200 r / min, and react at 80 ° C for 2 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion;

[0041] (3) Add 1.22 g of 2,3,5,6-tetrafluorophenylenedimethanol and 0.62 g of 1,3-propylene glycol to the biomass material modified waterborne polyurethane prepolymer emulsion, maintain stirring at 200 r / min, and continue the reaction at 70°C for 1 h to generate a castor oil-based fluorine-containing modified waterborne polyurethane prepolymer emulsion;

[0042] (4) 0.91 g of propylene glycol and 1.21 g of bisphenol A type epoxy resin with an epoxy value of 0.35 were added to the above emulsion, stirred at 360 r / min, and the reaction was continued at 70°C for 2.5 h to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion. The temperature was lowered to 45°C, and 1.77 g of trimethylamine was added to the epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion for neutralization reaction. The temperature was stirred at 130 r / min, and the reaction was continued at 45°C for 1.5 h. 72.7 g of deionized water was added, and the emulsifier was sheared and emulsified at a speed of 7500 r / min for 10 min. The emulsion was then 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 fluorinated waterborne polyurethane emulsion. Example 3

[0043] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove 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 and stirred at 70 ° C and 330 r / min for 2.5 h to react and generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0044] (2) 4.23 g of alkali lignin and 1.52 g of 1,4-butanediol-2-sulfonic acid sodium were added to the castor oil-based waterborne polyurethane prepolymer emulsion, and 33.3 g of methyl formate was added to reduce the viscosity of the system to 220 r / min and stirred. The mixture was reacted at 82 °C for 2 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion.

[0045] (3) Add 3.04 g of 2,2,3,3-tetrafluoro-1,4-butanediol and 0.92 g of 1,4-dihydroxymethylcyclohexane to the biomass material modified waterborne polyurethane prepolymer emulsion, increase the stirring speed to 280 r / min, and continue the reaction at 75 ° C for 2 h to generate a castor oil-based fluorine-containing modified waterborne polyurethane prepolymer emulsion;

[0046] (4) 0.98 g of pentaerythritol and 2.43 g of bisphenol A type epoxy resin with an epoxy value of 0.42 were added to the above emulsion, stirred at 330 r / min, and the temperature was reduced to 72°C and the reaction was continued for 3 h to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion. The temperature was reduced to 47°C, and 1.84 g of tributylamine was added to the epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion for neutralization reaction. The temperature was stirred at 140 r / min and the reaction was maintained at 47°C for 1.5 h. 75.8 g of deionized water was added, and the emulsifier was sheared and emulsified at a speed of 8000 r / min for 15 min. The emulsion was then transferred to a single-necked flask, and methyl formate was removed by a rotary evaporator at 40°C to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane emulsion. Example 4

[0047] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove interfering impurities such as air and moisture in the device. 30.7 g of xylene diisocyanate, 30.6 g of castor oil, and 0.00074 g of monobutyltin oxide were poured into the three-necked flask and stirred at 360 r / min for 3 h at 75 ° C to react and generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0048] (2) 6.05 g of alkali lignin and 1.82 g of dihydroxymethylbutyric acid were added to the castor oil-based waterborne polyurethane prepolymer emulsion, and 36.4 g of ethyl acetate was added to reduce the viscosity of the system, and the stirring speed was reduced to 240 r / min. The reaction was carried out at 84 ° C for 3 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion;

[0049] (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 waterborne polyurethane prepolymer emulsion, increase the stirring speed to 320 r / min, and continue the reaction at 80°C for 2.5 h to generate a castor oil-based fluorine-modified waterborne polyurethane prepolymer emulsion;

[0050] (4) 1.04 g of isopentaerythritol and 3.64 g of bisphenol A type epoxy resin with an epoxy value of 0.44 were added to the above emulsion, stirred at 300 r / min, and the temperature was reduced to 75°C and the reaction was continued for 2 h to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion. The temperature was reduced to 48°C, and 1.96 g of triethylamine was added to the epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion for neutralization reaction. The temperature was stirred at 150 r / min and the reaction was maintained at 48°C for 1 h. 78.8 g of deionized water was added, and the emulsifier was sheared and emulsified at a speed of 8200 r / min for 25 min. The emulsion was then transferred to a single-necked flask, and ethyl acetate was removed using a rotary evaporator at 45°C to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane emulsion. Example 5

[0051] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove interfering impurities such as air and moisture in the device. 30.7 g of tetramethyl-m-xylylene diisocyanate, 32.1 g of castor oil, and 0.00086 g of dibutyltin dilaurate were poured into the three-necked flask. The mixture was stirred at 380 r / min at 85 °C for 3.5 h to generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0052] (2) 7.56 g of alkali lignin and 2.18 g of dimethylol propionic acid were added to the castor oil-based waterborne polyurethane prepolymer emulsion, and 38.2 g of butyl acetate was added to reduce the viscosity of the system to 280 r / min. The mixture was stirred at 88 °C for 4 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion.

[0053] (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 the reaction at 88°C for 3 h to generate a castor oil-based fluorine-containing modified waterborne polyurethane prepolymer emulsion;

[0054] (4) 1.16 g of trimethylolpropane and 4.85 g of bisphenol A type epoxy resin with an epoxy value of 0.51 were added to the above emulsion, stirred at 250 r / min, and the temperature was reduced to 78°C and the reaction was continued for 2 h to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion. The temperature was reduced to 52°C, and 2.0 g of trimethylamine was added to the epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion for neutralization reaction. The temperature was stirred at 160 r / min and the temperature was maintained at 52°C for 1.5 h. 81.8 g of deionized water was added, and the emulsifier was sheared and emulsified at a speed of 8300 r / min for 30 min. The emulsion was then transferred to a single-necked flask, and butyl acetate was removed by a rotary evaporator at 50°C to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane emulsion. Example 6

[0055] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove 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 and stirred at 90 °C and 400 r / min for 3.5 h to react and generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0056] (2) 9.07 g of alkali lignin and 2.42 g of 1,2-propylene glycol-3-sodium sulfonate were added to the castor oil-based waterborne polyurethane prepolymer emulsion, and 42.4 g of tetrahydrofuran was added to reduce the viscosity of the system. The stirring speed was reduced to 300 r / min and the mixture was reacted at 90 °C for 4 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion.

[0057] (3) Add 7.3 g of 2,3,5,6-tetrafluorophenylenedimethanol and 1.85 g of ethylene glycol to the biomass material modified waterborne polyurethane prepolymer emulsion, increase the stirring speed to 400 r / min, and continue the reaction at 90 °C for 3 h to generate a castor oil-based fluorine-containing modified waterborne polyurethane prepolymer emulsion;

[0058] (4) 1.22 g of propylene glycol and 7.89 g of bisphenol A type epoxy resin with an epoxy value of 0.55 were added to the above emulsion, stirred at 230 r / min, and the temperature was reduced to 80°C and the reaction was continued for 2 h to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion. The temperature was reduced to 55°C, and 2.03 g of tributylamine was added to the epoxy-modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion for neutralization reaction. The temperature was stirred at 170 r / min and the reaction was maintained at 55°C for 2.5 h. 84.8 g of deionized water was added, and the emulsifier was sheared and emulsified at a speed of 8500 r / min for 40 min. The emulsion was then transferred to a single-necked flask, and tetrahydrofuran was removed using a rotary evaporator at 55°C to obtain an epoxy-modified castor oil-based fluorinated waterborne polyurethane emulsion. Comparative Example 1

[0059] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove 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 and stirred at 80 °C and 350 r / min for 2 h to react and generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0060] (2) Add 5.2 g of alkali lignin and 2.0 g of dimethylol propionic acid to the castor oil-based waterborne polyurethane prepolymer emulsion, and at the same time add 40 g of acetone to reduce the viscosity of the system, reduce the stirring speed to 250 r / min, and react at 85 ° C for 3 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion;

[0061] (3) Add 1.6 g of 1,4-butanediol to the biomass material modified waterborne polyurethane prepolymer emulsion, maintain stirring at 250 r / min, and continue the reaction at 85 °C for 1.5 h to generate a castor oil-based chain-extended modified waterborne polyurethane prepolymer emulsion;

[0062] (4) 1.1 g of trimethylolpropane was added to the above emulsion, and the mixture was stirred at 200 r / min. The temperature was lowered to 80°C and the reaction was continued for 2 h to obtain a cross-linked modified castor oil-based waterborne polyurethane prepolymer emulsion. The mixture was cooled to 50°C and 1.9 g of triethylamine was added to the cross-linked modified castor oil-based waterborne polyurethane prepolymer emulsion for neutralization reaction. The mixture was stirred at 120 r / min and the reaction was maintained at 50°C for 1.5 h. 80 g of deionized water was added and the mixture was emulsified at a speed of 7800 r / min for 20 min. The emulsion was then transferred to a single-necked flask and the acetone was removed by a rotary evaporator at 42°C to obtain a castor oil-based waterborne polyurethane emulsion. Comparative Example 2

[0063] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove interfering impurities such as air and moisture in the device. 30.7 g of isophorone diisocyanate, 30 g of poly(1,4-butylene adipate diol), and 0.0008 g of dibutyltin dilaurate were poured into the three-necked flask and stirred at 80 °C and 350 r / min for 2 h to react and generate a petroleum-based waterborne polyurethane prepolymer emulsion.

[0064] (2) Add 5.2 g of alkali lignin and 2.0 g of dimethylol propionic acid to the petroleum-based waterborne polyurethane prepolymer emulsion, and at the same time add 40 g of acetone to reduce the viscosity of the system, reduce the stirring speed to 250 r / min, and react at 85 ° C for 3 h to generate a biomass material modified petroleum-based waterborne polyurethane prepolymer emulsion;

[0065] (3) Add 1.6 g of 1,4-butanediol to the biomass material modified petroleum-based waterborne polyurethane prepolymer emulsion, maintain stirring at 250 r / min, and continue the reaction at 85°C for 1.5 h to generate a petroleum-based chain-extended modified waterborne polyurethane prepolymer emulsion;

[0066] (4) 1.1 g of trimethylolpropane was added to the above emulsion, and the mixture was stirred at 200 r / min. After the temperature was lowered to 80°C and the reaction was continued for 2 h, a cross-linked modified petroleum-based waterborne polyurethane prepolymer emulsion was obtained. The mixture was cooled to 50°C, and 1.9 g of triethylamine was added to the cross-linked modified petroleum-based waterborne polyurethane prepolymer emulsion for neutralization reaction. The mixture was stirred at 120 r / min and the reaction was maintained at 50°C for 1.5 h. 80 g of deionized water was added, and the emulsifier was sheared and emulsified at a speed of 7800 r / min for 20 min. The emulsion was then transferred to a single-necked flask, and the acetone was removed by a rotary evaporator at 42°C to obtain a petroleum-based waterborne polyurethane emulsion. Comparative Example 3

[0067] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove 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 and stirred at 80 °C and 350 r / min for 2 h to react and generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0068] (2) Add 6 g of alkali lignin and 1.8 g of dimethylol propionic acid to the castor oil-based waterborne polyurethane prepolymer emulsion, and add 40 g of acetone to reduce the viscosity of the system, reduce the stirring speed to 250 r / min, and react at 85 ° C for 3 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion;

[0069] (3) Add 1.6 g of 1,4-butanediol to the biomass material modified waterborne polyurethane prepolymer emulsion, maintain stirring at 250 r / min, and continue the reaction at 85 °C for 1.5 h to generate a castor oil-based chain-extended modified waterborne polyurethane prepolymer emulsion;

[0070] (4) 1.1 g of trimethylolpropane was added to the above emulsion, and the mixture was stirred at 200 r / min. The temperature was lowered to 80°C and the reaction was continued for 2 h to obtain a cross-linked modified castor oil-based waterborne polyurethane prepolymer emulsion. The mixture was cooled to 50°C and 1.9 g of triethylamine was added to the cross-linked modified castor oil-based waterborne polyurethane prepolymer emulsion for neutralization reaction. The mixture was stirred at 120 r / min and the reaction was maintained at 50°C for 1.5 h. 80 g of deionized water was added and the mixture was emulsified at a speed of 7800 r / min for 20 min. The emulsion was then transferred to a single-necked flask and the acetone was removed by a rotary evaporator at 42°C to obtain a castor oil-based waterborne polyurethane emulsion. Comparative Example 4

[0071] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove 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 and stirred at 80 °C and 350 r / min for 2 h to react and generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0072] (2) Add 5.2 g of alkali lignin and 2.0 g of dimethylol propionic acid to the castor oil-based waterborne polyurethane prepolymer emulsion, and at the same time add 40 g of acetone to reduce the viscosity of the system, reduce the stirring speed to 250 r / min, and react at 85 ° C for 3 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion;

[0073] (3) Add 5.6 g of octafluoro-1,6-hexanediol and 1.6 g of 1,4-butanediol to the biomass material modified waterborne polyurethane prepolymer emulsion, maintain stirring at 250 r / min, and continue the reaction at 85°C for 1.5 h to generate a castor oil-based fluorinated waterborne polyurethane prepolymer emulsion;

[0074] (4) 1.1 g of trimethylolpropane was added to the above emulsion, and the mixture was stirred at 200 r / min. The temperature was lowered to 80°C and the reaction was continued for 2 h to obtain a cross-linked modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion. The mixture was cooled to 50°C and 1.9 g of triethylamine was added to the cross-linked modified castor oil-based fluorinated waterborne polyurethane prepolymer emulsion for neutralization reaction. The mixture was stirred at 120 r / min and the reaction was maintained at 50°C for 1.5 h. 80 g of deionized water was added and the mixture was emulsified at a speed of 7800 r / min for 20 min. The emulsion was then transferred to a single-necked flask and the acetone was removed by a rotary evaporator at 42°C to obtain a castor oil-based fluorinated waterborne polyurethane emulsion. Comparative Example 5

[0075] (1) Nitrogen was introduced into the three-necked flask in advance to keep the reaction path filled with inert gas and remove 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 and stirred at 80 °C and 350 r / min for 2 h to react and generate a castor oil-based waterborne polyurethane prepolymer emulsion.

[0076] (2) Add 5.2 g of alkali lignin and 2.0 g of dimethylol propionic acid to the castor oil-based waterborne polyurethane prepolymer emulsion, and at the same time add 40 g of acetone to reduce the viscosity of the system, reduce the stirring speed to 250 r / min, and react at 85 ° C for 3 h to generate a biomass material modified waterborne polyurethane prepolymer emulsion;

[0077] (3) Add 1.6 g of 1,4-butanediol to the biomass material modified waterborne polyurethane prepolymer emulsion, maintain stirring at 250 r / min, and continue the reaction at 85 °C for 1.5 h to generate a castor oil-based chain-extended modified waterborne polyurethane prepolymer emulsion;

[0078] (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, stirred at 200 r / min, and the temperature was reduced to 80°C and the reaction was continued for 2 h to obtain an epoxy-modified castor oil-based waterborne polyurethane prepolymer emulsion. The temperature was reduced to 50°C, and 1.9 g of triethylamine was added to the epoxy-modified castor oil-based waterborne polyurethane prepolymer emulsion for neutralization reaction. The temperature was stirred at 120 r / min and the reaction was maintained at 50°C for 1.5 h. 80 g of deionized water was added, and the emulsifier was sheared and emulsified at a speed of 7800 r / min for 20 min. The emulsion was then transferred to a single-necked flask, and the acetone was removed using a rotary evaporator at 42°C to obtain an epoxy-modified castor oil-based waterborne polyurethane emulsion.

[0079] Test Example 1

[0080] The examples and comparative samples were subjected to film-forming treatment. A polytetrafluoroethylene mold with a specification of 15×8×2 (cm) was cleaned with ethanol, placed in an oven for drying, and then taken out. An appropriate amount of emulsion was poured into the mold groove, and the mold was placed horizontally to make its surface flat and uniform without bubbles. After being dried in a dark environment at 25°C for three days, it was placed in a 45°C oven for drying for 24 hours. After the water was completely evaporated, it was taken out to obtain a film.

[0081] The particle size of the sample emulsions of the examples and comparative examples was tested, and the particle size and distribution of the sample emulsions were tested using a nanoparticle size potentiometer model NanoZS produced by Malvern. The water contact angle of the sample films of the examples and comparative examples was tested using the sessile drop method, and their water resistance was characterized using a DSA100S video contact angle meter.

[0082]

[0083] Table 1 shows the particle size of the latex and the water resistance of the film of the examples and comparative examples. Figure 1 This is a 36h water absorption test chart of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1 and Comparative Example 1. Figure 2The water contact angle test diagram of the film prepared from the modified water-based polyurethane emulsion prepared in Example 1 and Comparative Examples 4 and 5, combined with the above table, can be seen that the water resistance of the sample film of Example 1 is excellent, the water resistance of the sample films of other examples is good, and the water resistance of the sample films of the comparative examples is poor; the castor oil-based water-based polyurethane emulsion is modified in synergistic manner by dihydric fluoroalcohol and bisphenol A type epoxy resin. The dihydric fluoroalcohol contains a highly water-repellent carbon fluorine segment, and the fluorine element has self-aggregation. The fluorine element is oriented on the surface of the film and synergistically acts with the bisphenol A type epoxy resin to reduce the castor oil-based water-based polyurethane emulsion. The water absorption rate of sesame oil-based water-based polyurethane film is greatly reduced (7.71%-7.99%) after 36 hours, and the water contact angle is greatly improved (96.6°-100.8°). Compared with petroleum-based water-based polyurethane, the water resistance of castor oil-based water-based polyurethane is slightly reduced. Compared with Comparative Examples 1 and 2, it can be seen from the embodiment that the introduction of difluoroalcohol and bisphenol A epoxy resin significantly improves the water resistance of epoxy-modified castor oil-based fluorinated water-based polyurethane film, indicating that the synergistic modification effect of difluoroalcohol and bisphenol A epoxy resin on water resistance is good.

[0084] Figure 3 The particle size and distribution test chart of the modified waterborne polyurethane emulsion prepared in Example 1 shows that the introduction of castor oil and alkali lignin into the waterborne polyurethane backbone, through the modification effect of bisphenol A epoxy resin and difluoroalcohol, compensates for the poor basic performance of the castor oil-based waterborne polyurethane emulsion. However, the proportion of alkali lignin should not be too high, otherwise it will affect the stability of the emulsion. As shown in Comparative Example 3, when the alkali lignin content is too high, the emulsion particle size is too high, and precipitation is prone to occur, resulting in an uneven and unstable emulsion. When the mass ratio of alkali lignin to castor oil-based waterborne polyurethane prepolymer emulsion is ≤0.15, the particle size is moderate (124.3-127.0), the emulsion is stable, and it combines the green, environmentally friendly, degradable, and renewable advantages of natural materials. Its basic performance can meet the daily production requirements of the national waterborne polyurethane coating field, reflecting the good synergistic modification effect of difluoroalcohol and bisphenol A epoxy resin on castor oil-based waterborne polyurethane emulsion.

[0085] Test Example 2

[0086] The thermal stability test of the film of the embodiment and the comparative example sample was performed using a TGA thermogravimetric analyzer, with the heating rate set at 15°C / min and the heating range set at 25-550°C. A salt spray test was performed in accordance with the national standard QC / T484-1999 "Paint Coating Industry Standard of the People's Republic of China", with the salt spray being a 5wt% sodium chloride solution.

[0087]

[0088] Table 2 shows the thermal stability and salt spray test of the films of the examples and comparative examples. Figure 4This is a thermogravimetric test diagram of the film prepared from the modified water-based polyurethane emulsion prepared in Example 1. Compared with the comparative example, it can be seen that the increase in the cross-linking degree of bisphenol A epoxy resin and the higher CF bond energy of difluoroalcohol synergistically improve the thermal stability of the modified water-based polyurethane film. When the material is thermally decomposed by 10%, the decomposition temperature can be increased to 320.5°C at most. When the material is thermally decomposed by 50%, the decomposition temperature can be increased to 365.6°C at most.

[0089] Figure 5 The figure shows the salt spray test of the film prepared with the modified waterborne polyurethane emulsion prepared in Example 1. As can be seen from the figure, no obvious rust appears at the intersection of the film, indicating that its salt spray resistance is excellent. Compared with the comparative example, it can be seen that when a single compound is used to modify castor oil-based waterborne polyurethane in the prior art, its salt spray resistance is almost the same as that of the unmodified pure castor oil-based waterborne polyurethane, which is at a lower level. After the technical solution of the present invention introduces dihydric fluoroalcohol and bisphenol A epoxy resin to synergistically modify the castor oil-based waterborne polyurethane emulsion, the salt spray resistance of the material is greatly improved. In particular, when the epoxy value of the bisphenol A epoxy resin is 0.51, the salt spray resistance of the film can reach up to 15 months, which is significantly improved. Under the premise of moderate emulsion particle size and good stability, the excellent synergistic effect of dihydric fluoroalcohol and bisphenol A epoxy resin is reflected.

[0090] Test Example 3

[0091] The film adhesion of the samples of the examples and comparative examples was tested according to the GB-T9286-1998 test standard, which is graded from 0 to 5, with grade 0 being the best and grade 5 being the worst. The pencil hardness was tested according to the GB-T6739-2006 test standard using a pencil hardness tester, with the pencil hardness test scale ranging from 9B to 9H from soft to hard. The pencil hardness test scale range described below includes HB, H, 2H, 3H, 4H, and 5H, with grade 5H being the best and grade HB being the worst. The mechanical properties, including tensile stress and strain, were tested using a 3344 electronic universal material testing machine.

[0092]

[0093] Table 3 shows the mechanical properties of the films of the examples and comparative examples. Figure 6 This is a test chart of the hardness of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1. Figure 7 This is a test chart of film adhesion prepared from the modified waterborne polyurethane emulsion prepared in Example 1. Figure 8 This is the impact test diagram of the film prepared from the modified waterborne polyurethane emulsion prepared in Example 1. Figure 9 The tensile test diagram of the film prepared by the modified waterborne polyurethane emulsion prepared in Example 1 is compared with the comparative example. Figure 6 、 7, 8, 9 It can be seen that the synergistic improvement effect of difluoroalcohol and bisphenol A epoxy resin on the mechanical properties of castor oil-based waterborne polyurethane film is particularly significant, and the two have complementary advantages. Difluoroalcohol makes up for the poor pencil hardness and impact resistance of the film prepared by using bisphenol A epoxy resin to modify castor oil-based waterborne polyurethane alone, and bisphenol A epoxy resin makes up for the poor adhesion, tensile stress and strain of the film prepared by using difluoroalcohol to modify castor oil-based waterborne polyurethane alone. The synergistically modified castor oil-based waterborne polyurethane has excellent mechanical properties, with a pencil hardness of up to 4H, a minimum adhesion of level 0, an impact resistance height of up to 80cm, a tensile stress of up to 30.32MPa, and a strain of 6.41.

[0094] The above-described specific embodiments further illustrate the present invention in detail, but these descriptions should not be construed as limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion, characterized in that: The steps include: (1) Under an inert atmosphere, diisocyanate, castor oil, and a tin catalyst are mixed and heated with stirring to react to obtain a castor oil-based waterborne polyurethane prepolymer emulsion; wherein the mass ratio of diisocyanate, castor oil, and tin catalyst is 1:0.9-1.1:0.00002-0.00003; (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 the mixture to react, thereby obtaining a biomass material modified waterborne polyurethane prepolymer emulsion; wherein the mass ratio of the castor oil-based waterborne polyurethane prepolymer emulsion, the alkali lignin, the hydrophilic chain extender, and the polar organic solvent is 1:0.05-0.15:0.02-0.04:0.5-0.7; (3) Adding difluoroalcohol and conventional chain extender to the biomass material modified waterborne polyurethane prepolymer emulsion, heating and stirring to react, and obtaining a castor oil-based fluorine-containing modified waterborne polyurethane prepolymer emulsion; the mass ratio of the biomass material modified waterborne polyurethane prepolymer emulsion, difluoroalcohol, and conventional chain extender is 1:0.02-0.12:0.01-0.03; the difluoroalcohol is one of 2,3,5,6-tetrafluorophenylenediol, octafluoro-1,6-hexanediol, 2,2,3,3-tetrafluoro-1,4-butanediol, and 4,4,4-trifluoro-3-(trifluoromethyl)-1,3-butanediol; (4) Adding a crosslinking agent and a bisphenol A type epoxy resin to a castor oil-based fluorine-containing modified waterborne polyurethane prepolymer emulsion, heating and stirring the mixture to react, thereby obtaining an epoxy-modified castor oil-based fluorine-containing waterborne polyurethane prepolymer emulsion, then adding an amine neutralizing agent, and finally adding deionized water for emulsification and rotary evaporation to obtain an epoxy-modified castor oil-based fluorine-containing waterborne polyurethane emulsion; wherein the epoxy value of the bisphenol A type epoxy resin is 0.35 or 0.42 or 0.44 or 0.51 or 0.

55.

2. The method for preparing the epoxy-modified castor oil-based fluorinated 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, xylylene diisocyanate, or tetramethyl-m-xylylene diisocyanate; and the tin catalyst is one of dibutyltin dilaurate, dibutyltin oxide, dibutyltin diacetate, or monobutyltin oxide.

3. The method for preparing the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, wherein: In the step (1), the reaction temperature is 60-90°C and the reaction time is 1.5-3.5h.

4. The method for preparing the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, wherein: In the step (2), the hydrophilic chain extender is one of 1,2-propylene glycol-3-sodium sulfonate, 1,4-butanediol-2-sodium sulfonate, dihydroxymethylpropionic acid, or dihydroxymethylbutyric acid; and the polar organic solvent is one of methyl ethyl ketone, methyl formate, ethyl acetate, acetone, butyl acetate, dimethyl sulfoxide, or tetrahydrofuran.

5. The method for preparing the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, wherein: In the step (2), the reaction temperature is 80-90°C and the reaction time is 2-4 hours.

6. The method for preparing the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, wherein: In the step (3), the conventional chain extender is one of 1,3-propylene glycol, 1,4-dihydroxymethylcyclohexane, 1,4-butanediol, diethylene glycol, ethylene glycol, and 1,6-hexanediol.

7. The method for preparing the epoxy-modified castor oil-based fluorine-containing aqueous polyurethane emulsion according to claim 1, wherein: In the step (3), the reaction temperature is 70-90°C and the reaction time is 1-3h.

8. The method for preparing the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion according to claim 1, wherein: In the step (4), the cross-linking agent is one of trimethylolpropane, propylene glycol, pentaerythritol, and isopentaerythritol; and the amine neutralizing agent is one of trimethylamine, triethylamine, and tributylamine.

9. The method for preparing 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 2-6h; the emulsification time is 10-40min, the emulsification speed is 7500-8500r / min; and the rotary evaporation temperature is 35-55°C.

10. An application of the epoxy-modified castor oil-based fluorinated aqueous polyurethane emulsion prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The epoxy-modified castor oil-based fluorine-containing aqueous polyurethane emulsion is applied to an aqueous polyurethane coating.

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