Preparation and application of high-performance polyacrylonitrile carbon fiber sizing agent

Abstract

The invention discloses preparation and application of a high-performance polyacrylonitrile carbon fiber sizing agent. The technological process comprises the following four steps: step A, carrying out graft polymerization on bisphenol S type epoxy resin and an acrylic monomer to obtain polyacrylic acid water-borne epoxy resin rich in hydrophilic groups; step B, synthesizing a polysiloxane copolymer containing a functional group from a silane coupling agent and dimethyl diethoxy silane; step C, carrying out graft polymerization on the reaction product in the step A and the reaction product in the step B to prepare polyacrylic acid and polysiloxane modified waterborne epoxy resin; d, reacting the prepared product with a curing agent, and curing at high temperature to obtain a modified epoxy resin cured film; the product provided by the invention has good epoxy reaction activity and storage stability, strong adhesive force, better carbon fiber flexibility, flame retardance, thermal oxidation resistance and other mechanical properties, and the compatibility between the carbon fiber and a polymer is improved; and a three-dimensional cross-linked structure formed by curing can improve the tensile strength and the water resistance of the carbon fiber.

Description

Technical Field

[0001] This patent relates to the field of organic synthesis, specifically to the preparation and application of a high-performance polyacrylonitrile carbon fiber sizing agent. Background Art

[0002] As one of the most important reinforcing materials, carbon fiber has been widely used in aerospace, sports and leisure products, automobiles, civil engineering, electronic products, medical equipment and other fields.

[0003] Carbon fiber needs to be sizing in its application. The sizing agent forms a protective film on the surface of the carbon fiber to protect the surface of the carbon fiber, reduce the phenomenon of lint and single filament breakage, make the carbon fiber easy to bundle, and also improve the wettability of the carbon fiber and the resin matrix, thereby increasing the bonding strength between the fiber and the resin, improving the processability and increasing the interface shear strength between the fiber and the matrix resin.

[0004] Traditional carbon fiber sizing agents use epoxy resins and polyurethanes as sizing agents. Sized carbon fibers are mainly used in composite materials used at low temperatures. However, when used in high-temperature composite materials, traditional sizing agents are prone to degradation at high processing temperatures (>300°C) and high operating temperatures, affecting the cross-sectional bonding of the composite material and thus reducing the mechanical properties of the composite material at high temperatures.

[0005] Publication (Announcement) No.: CN102660874A, Inventors: Liu Wenbo, Wang Rongguo, Zhang Shu, etc. invented "A thermoplastic sizing agent for carbon fiber and its preparation and use method", specifically: a thermoplastic resin, an organic solvent A and an additive are mixed and stirred evenly to obtain a thermoplastic sizing agent. When used, the carbon fiber is impregnated in the thermoplastic sizing agent, and then the sized carbon fiber is subjected to a squeegee treatment. Thereafter, the squeegee-treated carbon fiber is impregnated in an organic solvent B, and finally the carbon fiber is dried; This type of sizing agent has a high solvent content, which causes many small molecules to volatilize during the curing process, thus having a negative impact on the properties of the cured product; at the same time, the epoxy resin has high internal stress and is brittle, which has a great impact on the function of carbon fiber; flammable, explosive, and toxic organic solvents such as aromatic hydrocarbons and ketones cause great pollution to the environment.

[0006] Publication (Announcement) No.: CN114263043A, inventors Zhong Jingcheng, Li Yuyi, Zhou Zhengjun, Lin Shengxun, Zhang Yijuan, Zhou Jianxu, and Huang Longtian, "A sizing agent for carbon fiber," comprising 2 to 30 parts by weight of a resin base (A) of at least one epoxy compound, 2 to 30 parts by weight of a resin base (B) of at least one acrylate compound, 0.5 to 15 parts by weight of a surfactant (C), and 0.01 to 0.5 parts by weight of a hindered phenolic agent (D), wherein the particle size of the sizing agent is between 0.01 and 0.5 μm. This type of emulsion sizing agent uses non-ionic or anionic emulsified epoxy resin, polyacrylic resin, etc. In order to improve the storage stability of the epoxy resin emulsion, a large amount of non-ionic or anionic emulsifier is used. Since the emulsifier is extremely hydrophilic, the emulsifier often migrates to the surface of the carbon fiber after sizing during the drying process, resulting in the carbon fiber surface having very strong moisture absorption, causing the carbon fiber to harden in the cold winter after sizing, affecting the storage stability of the carbon fiber and the subsequent preparation of composite materials and the mechanical properties of the composite materials.

[0007] In summary, it is difficult to improve the mechanical properties of carbon fiber composites such as interfacial adhesion, flexibility, impact resistance, thermal stability, especially interlaminar shear strength after the above-mentioned sizing agents are applied to the carbon fiber surface. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the present invention synthesizes a water-based epoxy resin modified with polyacrylic acid and polysiloxane, and provides a preparation and application of a high-performance polyacrylonitrile carbon fiber sizing agent.

[0009] The second purpose of the present invention is to provide a polyacrylonitrile carbon fiber sizing agent that does not require the use of emulsifiers and solvents and can greatly improve the mechanical properties of carbon fiber interface adhesion, flexibility, impact resistance, thermal stability, shear strength, etc.

[0010] Technical Solution

[0011] The present invention adopts a chemical modification method, which is divided into four steps: Step A: Synthesis of polyacrylic acid modified epoxy resin rich in hydrophilic groups In an organic solvent, bisphenol S epoxy resin, acrylic comonomer and initiator are added in proportion and heated to react, so that the methylene groups in the epoxy resin molecules become active points and initiate free radical graft polymerization of acrylic monomers to generate polyacrylic acid modified epoxy resin rich in hydrophilic groups. Step B: Synthesis of functional group-containing polysiloxane copolymers A silane coupling agent, dimethyldiethoxysilane, anhydrous ethanol and deionized water in proportion are added to an enameled reactor, stirring is started, and the temperature is raised for preheating. When the temperature reaches 60-100° C., an acidic catalyst is added, and reflux reaction is carried out for 1-5.5 hours. After the reaction is completed, the hydrolysis product is removed, and an alkaline neutralizing agent is added dropwise to neutralize it to neutrality. The product is then pumped into a rotary evaporator, and vacuum is applied to recover ethanol and water respectively, thereby forming a transparent polysiloxane copolymer containing functional groups with a certain viscosity. Step C: Synthesis of polyacrylic acid and polysiloxane modified waterborne epoxy resin The reaction product of step B is added to the reaction product of step A, heated, stirred, reacted at 70-100° C. for 2-5 hours, vacuumed to remove the solvent, cooled to room temperature, diluted to a specified concentration by adding deionized water, and then neutralized to a pH of 7-9 by adding an alkaline neutralizer to obtain a waterborne epoxy resin modified with polyacrylic acid and polysiloxane. Step D: Application Method In a sizing tank, the product prepared by the present invention and a water-based epoxy resin curing agent are respectively added to the sizing tank according to a proportion, fully stirred and mixed, and then impregnated on the polyacrylonitrile carbon fiber pulled by a traction machine, and then pulled into a hot air drying oven, protected by nitrogen, and cured at 120-180° C. for 5-30 minutes. After curing is completed, the yarn cake is collected by a winding device.

[0012] In step A, the organic mixed solvent is n-butanol, acetone, ethylene glycol monobutyl ether, toluene, xylene, mineral oil, etc.; preferably, the solvent is a mixture of two of n-butanol, acetone, and ethylene glycol monobutyl ether; specifically, the mixture is prepared by mixing n-butanol and ethylene glycol monobutyl ether in a ratio of 1:1 to 3:1 or n-butanol and acetone in a ratio of 1:1 to 3:1, and the amount of the mixed solvent used is 1:1 to 2:1 to the total amount of reactants.

[0013] In step A, the bisphenol S epoxy resin is a high-temperature resistant epoxy resin obtained by polycondensation of bisphenol S and epichlorohydrin under alkaline conditions. This type of resin has better bonding properties, thermal stability, toughness and chemical stability than bisphenol A epoxy resin.

[0014] Further, the solid bisphenol S type epoxy resin includes low relative molecular weight solid bisphenol S type epoxy resin and high relative molecular weight solid bisphenol S type epoxy resin; preferably, the low relative molecular weight solid bisphenol S type epoxy resin has an epoxy equivalent of 160 to 195 g / mol, a softening point of 155 to 180°C, an average degree of polymerization between 1.0 and 3.0, and a content of ≥99.5%.

[0015] The acrylic copolymerization comprises three monomers with different functions: acrylic acid, methacrylic acid and methylene succinic acid which make the copolymer water-soluble and improve adhesion; methyl methacrylate, ethyl methacrylate, styrene and acrylonitrile which improve hardness; and ethyl acrylate, n-butyl acrylate, lauryl acrylate and 2-ethylhexyl acrylate which improve flexibility and promote film-forming properties.

[0016] Specifically, the present invention selects one of three acrylic copolymer monomers with different functions and mixes them in a molar ratio of 1:1:1. The total amount of the monomer mixture accounts for 10-60% of the mass of the bisphenol S epoxy resin.

[0017] The initiator in step A is one of benzoyl peroxide, tert-butylbenzoyl peroxide, and azobisisobutyronitrile, or a mixture of any two thereof, and the amount of the initiator used is 0.2-2.0% of the total mass of the reactants.

[0018] The step A: the heating polymerization grafting reaction: the heating temperature is controlled at 80-130° C., and the reaction time is 2-5 hours.

[0019] The step B: hydrolyzing and polycondensing the functional group-containing siloxane co-condensate with a silane coupling agent and dimethyldiethoxysilane under acidic catalysis.

[0020] In the step B, the silane coupling agent is methyltrichlorosilane (MTS), aminosilane (AMO), vinylsilane (VTS), epoxysilane (EPS), or allyltrimethoxysilane (VTMS); in the present invention, aminosilane coupling agent is preferably used.

[0021] Specifically, the aminosilane coupling agent is selected from one of Y-aminopropyltriethoxy (KH550), Y-(2,3-epoxypropyloxy)propyltrimethoxysilane (KH560), vinyltriethoxysilane (A151), or a mixture of the two in any proportion.

[0022] In step B, the acidic catalyst is one of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid or a mixture of two of them in any proportion, and the amount used is 1-15% of the total reactant weight.

[0023] In step B, the alkaline neutralizing agent is one of N,N-dimethylethanolamine, diethanolamine, and triethylamine, or a mixture of two of them in any proportion. Preferably, N,N-dimethylethanolamine or triethylamine is used, or a mixture of several of them in any proportion.

[0024] The method comprises the following steps: adding a silane coupling agent and dimethyldiethoxysilane in a mass ratio of 1:1 to 5:1; using an acidic catalyst in an amount of 2 to 6.5% of the total mass of the reactants; using ethanol in an amount of 5 to 40% of the mass of the reactants; using deionized water in an amount of 10 to 50% of the mass of the reactants; maintaining a system reaction temperature of 60 to 100° C. and a reaction time of 1 to 5.5 hours; controlling the dehydration and alcoholization temperature at 70 to 100° C. and the dealcoholization water pressure at 0.05 to 0.01 MPa.

[0025] In step C, the synthesis of the water-based epoxy resin modified with polyacrylic acid and polysiloxane is carried out by chemical modification of the functional group-containing siloxane co-condensate and the polyacrylic acid-modified epoxy resin. That is, the functional group-containing polysiloxane contains amino groups -NH2, and the primary amine -NH2 has two active hydrogens, which can undergo a ring-opening reaction with the epoxy end groups in the epoxy resin to form cross-linking groups.

[0026] The step C is: adding a functional group-containing siloxane co-condensation polymer to the polypropylene-modified waterborne epoxy resin for grafting reaction, with the addition ratio being 10:1 to 2:1 by mass.

[0027] In step C, the alkaline neutralizing agent is one of N,N-dimethylethanolamine, diethanolamine, and triethylamine, or a mixture of two of them in any proportion. Preferably, N,N-dimethylethanolamine or triethylamine is used, or a mixture of several of them in any proportion.

[0028] In the step C, the deionized water is ultrapure water with a resistivity of ≥18.2 MΩ·cm (25° C.).

[0029] The step C: diluting the modified epoxy resin with deionized water to control the solid content to 20-50%.

[0030] The waterborne epoxy resin curing agent in step D is one or a mixture of any two of polyamide-modified amines, polyamine adducts, thermosetting phenolic resins, silane coupling agents, and photoinitiators, preferably a polyamine adduct curing agent.

[0031] Specifically, the polyamine adduct curing agent uses a compound system of dicyandiamide and hydrazide with a mass ratio of 1:1 to 1:5, and the mass ratio of polyacrylic acid and polysiloxane modified water-based epoxy resin to curing agent is 2:1 to 4:1.

[0032] In the step D, the product of the present invention and the water-based epoxy resin curing agent are stirred and mixed uniformly in a sizing tank, and then the mixture is pulled by a traction machine and evenly coated on the polyacrylonitrile carbon fiber. The traction machine sends the carbon fiber to a hot air furnace and cures it at 120-180° C. under nitrogen protection for 5-30 minutes. After curing, the fiber cake is collected by a winding device.

[0033] Beneficial effects of the present invention

[0034] It has good epoxy reaction activity and storage stability, high adhesion, improves the compatibility between carbon fiber and polymer, does not require the addition of solvents and emulsifiers during use, and is environmentally friendly.

[0035] It can greatly improve the mechanical properties of carbon fiber, such as bending strength, tensile strength, impact strength and elastic modulus, and improve the flexibility, flame retardancy, thermal oxidation resistance, tensile strength and water resistance of the coated carbon fiber. DETAILED DESCRIPTION

[0036] Example 1

[0037] The present invention adopts a chemical modification method, which is divided into four steps: Step A: Synthesis of a polyacrylic acid-modified epoxy resin rich in hydrophilic groups (I) Preparation of raw materials: 70 kg of a mixed solvent of n-butanol and ethylene glycol monobutyl ether in a mass ratio of 3:1, 27 kg of a bisphenol S epoxy resin with an epoxy equivalent of 170 g / mol, 9 kg of a mixed monomer of methacrylic acid, methyl methacrylate, and styrene in a ratio of 1:1:0.5, 0.15 kg of benzophthalene peroxide, and 0.06 kg of azobisisobutyronitrile. (2) First, 27 kg of bisphenol S epoxy resin was added to the reactor, and 1 / 3 of the total amount of the mixed solvent was added through a liquid separator. The reactor jacket was steam-heated, stirring was started, and the temperature was raised to about 95° C. Within 20 to 30 minutes, 1 / 3 of the total amount of methacrylic acid mixed monomers, 1 / 3 of benzophthalene peroxide, and 1 / 3 of the mixed solvent were added through the liquid separator bucket. The reaction was continued for 20 minutes. The remaining methacrylic acid mixed monomers, the remaining benzophthalene peroxide, and the remaining mixed solvent were added through the liquid separator within 30 minutes. The reaction was continued for 2.5 hours. Finally, 0.06 kg of azobisisobutyronitrile was added and the reaction was continued for 30 minutes to complete the reaction. Step B: Synthesis of functional group-containing polysiloxane copolymers 47 kg of γ-aminopropyltriethoxy, 23 kg of dimethyldiethoxysilane, 7 kg of anhydrous ethanol, and 21 kg of deionized water were added to an enameled reactor respectively, stirring was started, and the interlayer was steam heated. While heating, 5.5 kg of acidic catalyst hydrochloric acid was added. After hydrolysis reaction at 80° C. for 3 hours, the hydrolyzate was removed, and 0.5 to 1.0 kg of alkaline neutralizer N, N-dimethylethanolamine was added through a liquid separator. The pH value was controlled at 7.0 to 8.5. The product was then transferred to a rotary evaporator, heated to 85 to 100° C., and vacuumed to 0.03 to 0.05 MPa to remove ethanol and water respectively to obtain a transparent functional group-containing polysiloxane copolymer with a certain viscosity. Step C: Synthesis of a polyacrylic acid and polysiloxane modified waterborne epoxy resin: 14 kg of the reaction product of step B is metered into 70 kg of the reaction product of step A, and the mixture is heated to 85° C. with stirring. After reacting for 3 hours, the mixture is poured into a desolventizing kettle, vacuumed to 0.05 MPa, and heated to 160° C. to recover n-butanol and ethylene glycol monobutyl ether solvents. After the solvent is removed, the mixture is cooled to 80° C., 260 kg of deionized water is added while stirring, and the mixture is diluted to a solid content of 25-30%. The temperature is controlled at 60° C., 1-1.5 kg of N,N-dimethylethanolamine is added, and the pH value is adjusted to 7-8.5. The mixture is then cooled to 40° C. and discharged to obtain a polyacrylic acid and polysiloxane modified waterborne epoxy resin. Step D: Application Method In the carbon fiber sizing tank, 100 kg of water-based epoxy resin modified by polyacrylic acid and polysiloxane and 25 kg of curing agent prepared by dicyandiamide and hydrazide in a mass ratio of 1:1 are respectively added in proportion, mixed and stirred evenly, and applied to the polyacrylonitrile carbon fiber filaments pulled by a traction machine, and then put into a hot air drying oven, protected by nitrogen, and cured at about 160 ° C for 15 minutes. After the resin cured film is formed, it is collected into a silk cake by a winding device.

[0038] Example 2

[0039] The present invention adopts a chemical modification method, which is divided into four steps: Step A: Synthesis of polyacrylic acid modified epoxy resin rich in hydrophilic groups (1) Preparation of raw materials: prepare 60 kg of mixed solvent with n-butanol and ethylene glycol monobutyl ether in a mass ratio of 1:1, 25 kg of bisphenol S epoxy resin with an epoxy equivalent of 190 g / mol, 10 kg of mixed monomers of methacrylic acid, methyl methacrylate and styrene in a ratio of 1.5:1:0.5, 0.25 kg of tert-butylbenzoyl peroxide, and 0.1 kg of azobisisobutyronitrile. (2) First, 25 kg of bisphenol S epoxy resin was added to the reactor, and 1 / 3 of the total amount of the mixed solvent was added through a liquid separator. The reactor jacket was steam-heated, stirring was started, and the temperature was raised to about 90° C. Within half an hour, 1 / 3 of the total amount of methacrylic acid mixed monomers, 1 / 3 of the total amount of tert-butylbenzoyl peroxide, and 1 / 3 of the total amount of the mixed solvent were added through the liquid separator bucket. The reaction was continued for half an hour. The remaining methacrylic acid mixed monomers, the remaining tert-butylbenzoyl peroxide, and the remaining mixed solvent were added through the liquid separator within 30 minutes. The reaction was continued for 2.5 hours. Then, 0.1 kg of azobisisobutyronitrile was added, and the aging reaction was continued for 25 minutes before termination. Step B: Synthesis of functional group-containing polysiloxane copolymers 45 kg of vinyltriethoxysilane (A151), 25 kg of dimethyldiethoxysilane, 15 kg of anhydrous ethanol, and 16 kg of deionized water were added to an enameled reactor respectively, stirring was started, and the interlayer was steam heated. While heating, 4.5 kg of acidic catalyst sulfuric acid was added. After hydrolysis reaction at 90°C for 5 hours, the hydrolyzate was removed, and 0.5-1.5 kg of triethylamine was added through a liquid separator. The pH value was adjusted to 7.0-7.5. The mixture was then transferred to a rotary evaporator, heated to 80-95°C and the pressure was 0.01-0.05 MPa. The ethanol and water were removed respectively to obtain a transparent functional group-containing polysiloxane copolymer with a certain viscosity. Step C: Synthesis of a polyacrylic acid and polysiloxane modified waterborne epoxy resin: 25 kg of the reaction product of step B is metered into 65 kg of the reaction product of step A, and the mixture is heated to 85° C. with stirring and reacted for 3 hours. The mixture is then pumped into a desolventizing kettle at a pressure of 0.05 MPa and 160° C. to recover n-butanol and ethylene glycol monobutyl ether solvents. After recovery, the mixture is cooled to 80° C., 290 kg of deionized water is added while stirring to dilute the mixture to a solid content of 25-30%, 1-1.5 kg of triethylamine is added at 60° C., the pH value is adjusted to 7-8.5, and the mixture is cooled to 40° C. to obtain a polyacrylic acid and polysiloxane modified waterborne epoxy resin. Step D: Application Method In the carbon fiber sizing tank, 80 kg of water-based epoxy resin modified by polyacrylic acid and polysiloxane, and 30 kg of curing agent prepared by dicyandiamide and hydrazide in a mass ratio of 1:3 are respectively added in proportion, mixed and stirred evenly, and applied to the polyacrylonitrile carbon fiber filaments pulled by a traction machine, and then put into a hot air drying oven, protected by nitrogen, and cured at about 180 ° C for 10 minutes. After the resin cured film is formed, it is collected into a silk cake by a winding device.

[0040] Comparative Example 1 The comparative example 1 is a polyacrylonitrile carbon fiber precursor sizing agent produced by Mitsui Chemicals, Japan.

[0041] Comparative Example 2 The comparative example 2 is a polyacrylonitrile carbon fiber precursor sizing agent produced by SGL Carbon of Germany.

[0042] Polyacrylonitrile carbon fiber precursors with a single filament count of 6000 per bundle and a tensile strength of 4.5 GPa were sized with the above four sizing agents respectively. The drying temperature after sizing was 160°C for curing for 15 minutes. The samples were tested for wear resistance, tensile strength, hair reduction rate and fiber opening. Wear resistance was evaluated by the number of frictions when the fiber was broken under a certain friction medium. Fiber opening was evaluated by measuring the width of the fiber after passing through four groups of guide rollers with a diameter of 150 mm. Other indicators were tested according to national standards. The results are shown in Table 1.

[0043] Test results table 1: index Comparative Example 1 Example 1 Example 2 Comparative Example 2 Friction resistance (times) 3685 3898 3881 3612 Spreading width (mm) 5.6 6.3 6.6 5.8 Tensile strength (GPa) 5.73 5.87 5.83 5.79 Hair reduction rate (%) 88.5 89.3 89.8 88.8 As can be seen from the above table, the abrasion resistance, tensile strength, fiber width and lint reduction rate of Example 1 and Example 2 are all better than those of Comparative Example 1 and Comparative Example 2.

[0044] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. Preparation and application of a high-performance polyacrylonitrile carbon fiber sizing agent, characterized by: The process uses chemical modification and is divided into four steps: Step A: Synthesis of a polyacrylic acid-modified epoxy resin rich in hydrophilic groups: Bisphenol S epoxy resin, acrylic acid comonomer, and initiator are added in appropriate proportions to an organic solvent and heated to react, thereby making the methylene groups in the epoxy resin molecules active sites and initiating free radical graft polymerization of the acrylic acid monomers to produce a polyacrylic acid-modified epoxy resin rich in hydrophilic groups; Step B: Synthesis of a functional group-containing polysiloxane copolymer: A silane coupling agent, dimethyldiethoxysilane, anhydrous ethanol, and deionized water are added to an enameled reactor in a proportional amount, stirred, and preheated to 60-100° C., followed by addition of an acidic catalyst and reflux reaction for 1-5.5 hours. After the reaction is complete, the hydrolyzed product is removed and dropwise neutralized with an alkaline neutralizer until neutral. The product is then placed in a rotary evaporator and vacuumed to recover ethanol and water, thereby forming a transparent, viscous polysiloxane copolymer containing a functional group. Step C: Synthesis of a polyacrylic acid and polysiloxane modified waterborne epoxy resin: The reaction product of step B is metered into the reaction product of step A, the temperature is increased, stirring is started, and the reaction is carried out at 70-100° C. for 2-5 hours. The solvent is removed by vacuuming, the temperature is lowered to room temperature, and deionized water is added to dilute to a specified concentration. An alkaline neutralizer is then added to neutralize to a pH of 7-9 to obtain a polyacrylic acid and polysiloxane modified waterborne epoxy resin; Step D: Application method: In the sizing tank, the product prepared by the present invention and the water-based epoxy resin curing agent are respectively added to the sizing tank according to a proportion, and after being fully stirred and mixed, they are impregnated on the polyacrylonitrile carbon fiber pulled by the traction machine, and then pulled into a hot air drying oven, protected by nitrogen, and cured at 120-180°C for 5-30 minutes. After curing is completed, it is collected into a silk cake by a winding device.

2. The process according to claim 1, wherein: The step A synthesizes a polypropylene-modified epoxy resin rich in hydrophilic groups, wherein the organic mixed solvent is n-butanol, acetone, ethylene glycol monobutyl ether, toluene, xylene, and mineral oil; preferably, the organic solvent is a mixture of two of n-butanol, acetone, and ethylene glycol monobutyl ether; specifically, the organic solvent is prepared by mixing n-butanol:ethylene glycol monobutyl ether in a ratio of 1:1 to 3:1 or n-butanol:acetone in a ratio of 1:1 to 3:1; and the amount of the mixed solvent used: the total amount of reactants is 1:1 to 2:

1.

3. The process according to claim 1, wherein: The step A synthesizes a polypropylene modified epoxy resin rich in hydrophilic groups, wherein the bisphenol S epoxy resin is a low relative molecular weight solid bisphenol S epoxy resin with an epoxy equivalent of 160 to 195 g / mol, a softening point of 155 to 180° C., an average degree of polymerization between 1.0 and 3.0, and a content of ≥99.5%.

4. The process according to claim 1, wherein: The step A synthesizes a polypropylene modified epoxy resin rich in hydrophilic groups, wherein the initiator is one or a mixture of any two of benzophthalide peroxide (BPO), tert-butylbenzophthalide peroxide, and azobisisobutyronitrile (AIBN), and the amount of the initiator is 0.2-2.0% of the amount of the monomer.

5. The process according to claim 1, wherein: The step A synthesizes a polypropylene-modified epoxy resin rich in hydrophilic groups. The acrylic copolymer contains three monomers with different functions: acrylic acid, methacrylic acid, and methylene succinic acid to make the copolymer water-soluble and improve adhesion; methyl methacrylate, ethyl methacrylate, styrene, and acrylonitrile to improve hardness; and ethyl acrylate, n-butyl acrylate, lauryl acrylate, and 2-ethylhexyl acrylate to improve flexibility and promote film-forming properties. Specifically, one of the three acrylic copolymer monomers with different functions is selected and mixed in a molar ratio of 1:1:1, and the total amount of the monomer mixture used accounts for 10-60% of the mass of the bisphenol S epoxy resin.

6. The process according to claim 1, wherein: In step B, a polysiloxane copolymer containing functional groups is synthesized. A silane coupling agent and dimethyldiethoxysilane are added in a mass ratio of 1:1 to 5:

1. The amount of the acidic catalyst used is 2 to 6.5% of the total mass of the reactants. The amount of ethanol used is 5 to 40% of the total mass of the reactants. The amount of deionized water used is 10 to 50% of the total mass of the reactants. The reaction temperature of the system is 60 to 100° C., and the reaction time is 1 to 5.5 hours.

7. The process according to claim 1, wherein: In step B, a functional group-containing polysiloxane copolymer is synthesized, and the silane coupling agent is an aminosilane coupling agent, specifically one of γ-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), and vinyltriethoxysilane (A151), or a mixture of the two in any proportion.

8. The process according to claim 1, wherein: In the step C, a waterborne epoxy resin modified with polyacrylic acid and polysiloxane is synthesized, and a functional group-containing siloxane co-condensate is added to the waterborne epoxy resin modified with polypropylene, with the addition ratio being 10:1 to 2:1 by weight.

9. The process according to claim 1, wherein: In step C, a waterborne polypropylene resin and a polysiloxane-modified epoxy resin are synthesized. The alkaline neutralizer is selected from one of N,N-dimethylethanolamine, diethanolamine, and triethylamine, or a mixture of two of them in any proportion; specifically, N,N-dimethylethanolamine or triethylamine is selected. The alkaline neutralization requires the product pH value to be between 7 and 9.

10. The process according to claim 1, wherein: In the application method of step D, a polyamine adduct curing agent is selected as the water-based epoxy resin curing agent, specifically a compound system of dicyandiamide and hydrazide with a mass ratio of 1:1 to 1:5 is selected, the mass ratio of the water-based epoxy resin modified by polyacrylic acid and polysiloxane to the curing agent is 2:1 to 4:1, the curing film forming temperature is 120 to 180° C., and the curing time is 5 to 30 minutes.