Water-based surface treatment fluid for galvanized steel sheet, self-lubricating galvanized steel sheet and manufacturing method therefor

Abstract

Disclosed in the present invention is a water-based surface treatment fluid for a galvanized steel sheet. The water-based surface treatment fluid comprises deionized water and solid components. The solid components comprise: a water-based cationic polymer resin A, the parts by weight of which in the solid components is 25-65 parts; a compound organosilane coupling agent B, the parts by weight of which in the solid components is 30-65 parts; compound lubricating particles C, the parts by weight of which in the solid components is 3-10 parts, the compound lubricating particles C comprising at least one unsaturated-bond-containing organosilane coupling agent C1 and a mixture of an oxidized polyethylene wax emulsion and a polytetrafluoroethylene wax emulsion; a water-soluble fluorine-containing compound D, the parts by weight of fluorine in the solid components being 1.5-5.3 parts; a water-soluble phosphorus-containing compound E, the parts by weight of phosphorus in the solid components being 1-3 parts; and a water-soluble compound F containing a salt of a group-VIII iron family element, the parts by weight of the group-VIII iron family element in the solid components being 0.2-0.6 parts.

Description

Aqueous surface treatment liquid for galvanized steel sheet, self-lubricating galvanized steel sheet and manufacturing method thereof Technical Field

[0001] The invention relates to a surface treatment liquid, in particular to a surface treatment liquid for galvanized steel plates. Background Art

[0002] Galvanized steel sheets are widely used in light industry, construction, home appliances, and automotive applications. Most applications in these sectors require stamping. Due to friction between the die and the steel sheet, the coating is prone to powdering and blackening during forming. This not only affects the appearance, dimensional accuracy, and corrosion resistance of the formed parts, but also increases die wear and reduces die life.

[0003] In order to improve the surface wear resistance and processability of galvanized steel sheets, self-lubricating galvanized steel sheets have been developed. In addition to improving the processing and forming performance, self-lubricating galvanized steel sheets do not need to be coated with anti-rust oil to prevent galvanized steel sheets from rusting during transportation and storage, which can simplify the packaging process and reduce production and transportation costs.

[0004] The self-lubricating properties of self-lubricating galvanized steel sheet are imparted by an organic-inorganic composite coating applied to the surface of the steel sheet. The coating is generally 1-3 μm thick and is primarily composed of a resin-silane complex. Furthermore, to ensure the coating's high lubricity, a considerable amount of lubricating additives is typically added, primarily lubricating micronized wax, polyolefin emulsified wax, nano-MoS2, and graphene. These lubricating additives typically accumulate on the coating surface and come into contact with the mold surface before the coating bulk during processing. Through their relative sliding motion, they act like lubricants, alleviating wear and tear on the coating and the galvanized layer of the steel sheet during processing. However, these lubricating additives are substances with low surface energy and low cohesive strength, which can affect the spreading and leveling of subsequent coatings. They are also prone to interlayer delamination, reducing the coating's adhesion to the substrate and hindering the further coating of processed parts. Therefore, post-coating of self-lubricating galvanized steel sheet products is generally not recommended.

[0005] However, during the use of galvanized steel sheets, a considerable portion relies on subsequent coating to achieve product functionality, such as decorative appearance and corrosion protection. Therefore, attention should be paid to the coating processing of processed parts. The usual coating processing steps are as follows: After stamping and forming, the parts are subjected to a short period of alkaline degreasing to remove grease and contamination on the surface of the parts. Some production lines that are co-produced with galvanized bare sheets or cold-rolled sheets will also perform phosphating (or ceramic treatment), and finally electrostatic powder spraying and heat curing. In addition, from the perspective of cost saving, many parts are only coated on one side of the exterior. However, the pH value of the alkaline degreasing agent solution in this treatment process is generally 9-11, and the pH value of the acidic phosphating (or ceramic treatment) solution is generally 2-5. In addition, the curing requires high-temperature baking at 180-240°C, which will damage the surface coating of the galvanized steel sheet on the uncoated side, causing yellowing and other phenomena, thereby affecting the appearance of the coating, subsequent corrosion resistance and service performance. Therefore, the coating process places extremely high demands on the coatability, acid and alkali resistance, and high temperature resistance of the surface treatment coating of the galvanized steel sheet, and existing self-lubricating galvanized sheet products are difficult to meet the requirements.

[0006] A Chinese patent document, CN104451638A, published on March 25, 2015, and titled "A Chromium-Free Self-Lubricating Passivator and Its Preparation Method," discloses the use of stearates and ethylene / vinyl acetate waxes as lubricants. However, the softening points of these lubricants are typically below 70°C. During the continuous stamping die processing of parts for OA products, home appliances, and automotive parts, the surface temperature can exceed 70°C, significantly reducing the lubricating properties of these lubricants and rendering them ineffective.

[0007] The Chinese patent document with publication number CN105255338A, published on January 20, 2016, and titled "A galvanized steel sheet and aqueous surface treatment liquid with excellent surface wear resistance, corrosion resistance, and acid and alkali resistance" uses composite lubricating particles blended with polytetrafluoroethylene particles and surface-modified high-density polyethylene particles and graphene oxide to form a lubricant system.

[0008] Summary of the Invention

[0009] The object of the present invention is to provide an aqueous surface treatment liquid for galvanized steel sheets, which can be applied to the surface of the galvanized steel sheets and form an organic-inorganic composite coating on the surface of the galvanized steel sheets, so that the galvanized steel sheet products after surface treatment have excellent lubricity and wear resistance without reducing the coating's paintability.

[0010] In order to achieve the above object, the present invention provides an aqueous surface treatment solution for galvanized steel sheets, which comprises deionized water and a solid component; wherein the solid component comprises:

[0011] Aqueous cationic polymer resin A, having an amount of 25-65 parts by weight in the solid content;

[0012] A composite organic silane coupling agent B, comprising 30-65 parts by weight of the solid content; wherein the composite organic silane coupling agent B is formed by mixing and hydrolyzing at least one organic silane coupling agent B1 containing an epoxy functional group and at least one organic silane coupling agent B2 containing an amino functional group, and the molar ratio of the epoxy functional group to the amino functional group in the organic silane coupling agent B1 containing an epoxy functional group and the organic silane coupling agent B2 containing an amino functional group is 2-5;

[0013] Compound lubricating particles C, whose weight parts in the solid content are 3-10 parts; wherein the compound lubricating particles C include: at least one organic silane coupling agent C1 containing an unsaturated bond; and a mixture of an oxidized polyethylene wax emulsion and a polytetrafluoroethylene wax emulsion;

[0014] A water-soluble fluorine-containing compound D, wherein the weight portion of fluorine element in the solid content is 1.5-5.3 parts;

[0015] A water-soluble phosphorus-containing compound E, wherein the weight portion of phosphorus in the solid content is 1-3 parts;

[0016] The water-soluble salt compound F containing the Group VIII iron series element has a weight portion of the Group VIII iron series element in the solid content of 0.2-0.6 parts.

[0017] The aqueous surface treatment liquid for galvanized steel sheets of the present invention is an environmentally friendly weakly acidic aqueous surface treatment liquid that can be stably manufactured.

[0018] The dispersion form of the aqueous cationic polymer resin A in water can be either an aqueous solution type, a water dispersion type or an emulsion type.

[0019] In the present invention, the weight proportion of the aqueous cationic polymer resin A is controlled within the range of 25-65 parts because, when the weight proportion of the aqueous cationic polymer resin A is less than 25 parts, the adhesion of the formed organic-inorganic composite coating may decrease, and when the weight proportion of the aqueous cationic polymer resin A is greater than 65 parts, the relative proportion of the silane skeleton formed by the composite organic silane coupling agent B in the organic-inorganic composite coating, which plays an electrochemical anti-corrosion role on the surface of the galvanized steel sheet, will decrease, thereby affecting the corrosion resistance of the self-lubricating galvanized steel sheet material.

[0020] In the present invention, the weight of the compounded organosilane coupling agent B is 30-65 parts because: when the weight of the compounded organosilane coupling agent B is less than 30 parts, the corrosion resistance of the organic-inorganic composite coating may decrease. When the weight of the compounded organosilane coupling agent B is greater than 65 parts, the relative proportion of the aqueous cationic polymer resin A in the organic-inorganic composite coating, which increases the coating's flexibility, decreases, affecting the T-bend and cupping properties of the organic-inorganic composite coating and the corrosion resistance after molding. In some embodiments, the weight of the compounded organosilane coupling agent B is 30-60 parts in the solid content.

[0021] In the present invention, the molar ratio of epoxy to amino groups in the epoxy- and amino-containing organosilane coupling agents is limited to 2-5. This is because, during the hydrolysis process, the epoxy and amino groups on the different organosilane coupling agents undergo a ring-opening reaction to form a silane backbone network. Typically, one amino group can undergo a ring-opening reaction with two epoxy groups. Therefore, when the molar ratio of epoxy to amino groups is less than 2, amino groups may remain. The active hydrogens on the amino groups may further react with the waterborne cationic polymer resin A, disrupting the charge balance of the waterborne cationic polymer resin A, causing resin agglomeration and affecting the stability of the coating. It should be noted that a slight excess of the epoxy-containing organosilane coupling agent can improve the adhesion of the final organic-inorganic composite coating to the galvanized substrate and enhance the coatability of the composite coating. When the molar ratio of the epoxy functional group to the amino functional group is greater than 5, the relative proportion of the silane skeleton that can be formed in the composite organic silane coupling agent B will decrease, affecting the corrosion resistance of the final organic-inorganic composite coating.

[0022] In the present invention, the weight proportion of the compound lubricating particles C is 3-10 parts because: if it is less than 3 parts, the lubricity and wear resistance of the coating are insufficient; if it is greater than 10 parts, too many solid lubricating particles are present in the film, which significantly reduces the cohesion of the coating and may lead to delamination between the coatings. In addition, the corrosion resistance and chemical resistance of the coating are reduced.

[0023] In the present invention, the oxidized polyethylene wax emulsion in the compounded lubricating particles C is a commercial lubricating emulsion additive. After catalytic oxidation modification, this type of additive forms a certain amount of oxygen-containing polar functional groups such as carboxyl, hydroxyl and carbonyl groups in the surface molecular chain, which can form good compatibility with the aqueous cationic polymer resin A. In the final organic-inorganic composite coating, it mainly plays the role of internal lubrication, that is, it reduces the intermolecular friction of the composite coating and plays a plasticizing role, thereby improving the heat generated by the coating during the stamping wear process and the coating fluidity. Polytetrafluoroethylene wax emulsion is also a commercial lubricating emulsion additive. This type of lubricating additive has the characteristics of high temperature resistance (high softening point), low surface energy, high hardness and high lubricity. It quickly migrates to the coating surface during the coating baking and curing process, and mainly plays the role of external lubrication during the stamping friction process, improving the friction between the organic-inorganic composite coating and the hot metal mold surface during the stamping process, thereby achieving the purpose of strengthening the stamping forming performance of the coating.

[0024] In the present invention, the weight of the water-soluble fluorine-containing compound D is 1.5-5.3 parts by weight, calculated as elemental fluorine. This is because: if the weight of the fluorine element is less than 1.5 parts, that is, if the fluorine compound is too low, the corrosion resistance of the formed organic-inorganic composite coating may decrease. If the weight of the fluorine element is greater than 5.3 parts, that is, if the fluorine compound is too high, due to the water solubility of the fluorine compound, the residual fluorine compound that has not fully reacted with the galvanized interface may deteriorate the water resistance of the composite coating and affect properties such as moisture and heat resistance. In some embodiments, the weight of the water-soluble fluorine-containing compound D is 1.5-5.0 parts by weight, calculated as elemental fluorine.

[0025] In the present invention, the weight portion of the water-soluble phosphorus-containing compound E calculated as phosphorus element is 1-3 parts, because: if the weight portion of phosphorus element is less than 1 part, that is, when the phosphorus-containing compound is small, there is no adding effect, and the corrosion resistance of the composite coating may decrease; if the weight portion of phosphorus element is greater than 3 parts, that is, there are too many acidic phosphorus-containing compounds, which may cause the stability of the water treatment liquid to deteriorate.

[0026] In the present invention, the water-soluble salt compound F containing an element of Group VIII iron serves to balance the potential of the zinc coating on the surface of the galvanized steel sheet, thereby preventing galvanic corrosion caused by potential imbalance at the interface between the zinc coating on the surface of the galvanized steel sheet and the composite coating. The weight percentage of the element of Group VIII iron in the solid content is 0.2-0.6 parts because: if the weight percentage of the element of Group VIII iron is less than 0.2 parts, that is, if the water-soluble salt compound containing an element of Group VIII iron is low, the addition effect is lost, and the corrosion resistance of the composite coating may deteriorate. If the weight percentage of the element of Group VIII iron is greater than 0.6 parts, that is, if the water-soluble salt compound containing an element of Group VIII iron is excessive, a large amount of the element of Group VIII iron is enriched on the surface of the galvanized layer due to a substitution reaction, which reduces the adhesion between the composite coating and the galvanized layer. In addition, an excessive amount of the acidic salt compound containing an element of Group VIII iron may also lead to poor stability of the water treatment solution.

[0027] Furthermore, the weight proportion of the aqueous cationic polymer resin A can be controlled to be 35-45 parts, and the weight proportion of the compounded organic silane coupling agent B can be controlled to be 40-50 parts.

[0028] Furthermore, in the aqueous surface treatment liquid of the present invention, the weight ratio of the deionized water to the solid content is 3.5-10.

[0029] When the weight ratio of deionized water to solids is less than 3.5, the solid content in the aqueous surface treatment solution is too high, which will reduce the storage stability of the aqueous surface treatment solution. When the weight ratio of deionized water to solids is greater than 10, the solid content in the aqueous surface treatment solution is too low, which is not conducive to forming a sufficient film weight of the organic-inorganic composite coating on the surface of the galvanized steel sheet in a single coating.

[0030] Of course, in some other embodiments of the present invention, the weight ratio of deionized water to solids may also be less than 3.5, such as 3. In some embodiments, the weight ratio of deionized water to solids is 3-10.

[0031] Furthermore, the aqueous surface treatment liquid of the present invention also includes a leveling agent.

[0032] Furthermore, the weight ratio of the deionized water to the leveling agent is 19-45.

[0033] In this embodiment, when the weight ratio of deionized water and the leveling agent is less than 19, that is, the proportion of the leveling agent in the aqueous surface treatment liquid is relatively high, it is easy for the aqueous surface treatment liquid to have defects such as shrinkage holes during the coating and curing process on the galvanized steel plate surface. When the weight ratio of deionized water and the leveling agent is greater than 45, that is, the proportion of the leveling agent in the aqueous surface treatment liquid is relatively low, it is easy for the aqueous surface treatment liquid to have problems such as poor wetting and poor leveling during the coating on the galvanized steel plate surface, thereby causing defects such as edge shrinkage, missing coating, and diffraction stripes on the surface coating of the galvanized steel plate after curing.

[0034] Furthermore, in the aqueous surface treatment liquid of the present invention, the leveling agent is selected from at least one of the following: ethylene glycol butyl ether, ethylene glycol methyl ether, dipropylene glycol butyl ether, diethylene glycol monobutyl ether and isopropyl alcohol.

[0035] Furthermore, in the aqueous surface treatment liquid of the present invention, the conductivity of the deionized water is ≤10 μs / cm.

[0036] In this embodiment, the conductivity of the deionized water is limited to ≤10 μs / cm in order to further ensure the storage stability of the aqueous surface treatment liquid. In some embodiments, the conductivity of the deionized water is 3-10 μs / cm.

[0037] Furthermore, in the aqueous surface treatment liquid of the present invention, the aqueous cationic polymer resin A is selected from at least one of the following: aqueous acrylic resin, aqueous epoxy resin, aqueous polyurethane resin, aqueous polyester resin, aqueous alkyd resin, and copolymer-modified resins of aqueous acrylic resin, aqueous epoxy resin, aqueous polyurethane resin, aqueous polyester resin, and aqueous alkyd resin. In some embodiments, the aqueous cationic polymer resin A is selected from at least one of the following: copolymer-modified resins of aqueous acrylic resin, aqueous epoxy resin, aqueous alkyd resin, and aqueous polyurethane resin. In some embodiments, the copolymer-modified resin of the aqueous polyurethane resin is a polycarbonate-modified polyurethane, preferably having a molecular weight of 8,000 to 10,000.

[0038] Furthermore, in the aqueous surface treatment liquid of the present invention, the aqueous cationic polymer resin A has a number average molecular weight greater than or equal to 5,000, a pH value of 3.5-7, and a 100% modulus of the formed resin dry film of 50-600 MPa and an elongation at break of 100-400%. In some embodiments, the molecular weight of the aqueous cationic polymer resin A of the present invention is 5,000-100,000. In some embodiments, the molecular weight of the aqueous cationic polymer resin A of the present invention is 5,000-80,000.

[0039] In this paper, the 100% modulus and elongation at break of the resin dry film are tested according to GB 13022 “Test method for tensile properties of plastic films”, wherein the 100% modulus is the tensile strength when the elongation is 100%.

[0040] In this embodiment, limiting the molecular weight of the aqueous cationic polymer resin A to be greater than or equal to 5000, the pH value to be 3.5-7, the 100% modulus of the formed resin dry film to be 50-600Mp, and the elongation at break to be 100-400% is conducive to further improving the technical effect of this case.

[0041] When the molecular weight of the aqueous cationic polymer resin A is less than 5,000, the water resistance, solvent resistance, and scratch resistance of the resin dry film may be reduced.

[0042] When the pH value of the water-based cationic polymer resin A is less than 3.5, the hydrolysis and self-polymerization rate of the compounded organic silane coupling agent B in the coating will be accelerated, affecting the stability of the coating. When the pH value is greater than 7, the acidic hydrolyzate of the compounded organic silane coupling agent B will react with the water-based cationic polymer resin A to neutralize it, destroying the charge balance of the water-based cationic polymer resin A, easily causing resin agglomeration, and affecting the stability of the coating.

[0043] The 100% modulus of the dry film formed by the aqueous cationic polymer resin A is 50-600 MPa, and the elongation at break is in the range of 100-400%, which can achieve a good balance between hardness and flexibility in the final organic-inorganic composite coating. A 100% modulus of the dry film formed by the aqueous cationic polymer resin A is too high, which can reduce the T-bend and cupping properties of the final organic-inorganic composite coating; a 100% modulus of the dry film formed by the aqueous cationic polymer resin A is too low, which can reduce the solvent resistance and abrasion resistance of the final organic-inorganic composite coating. A 100% modulus of the dry film formed by the aqueous cationic polymer resin A is too high, which can reduce the corrosion resistance of the final organic-inorganic composite coating after molding; a 100% modulus of the dry film formed by the aqueous cationic polymer resin A is too high, which can reduce the solvent resistance and chemical resistance of the composite coating. In some embodiments, the 100% modulus of the dry film formed by the aqueous cationic polymer resin A of the present invention can be 50-500 MPa. In some embodiments, the elongation at break of the dry film formed by the aqueous cationic polymer resin A of the present invention is 100-320%.

[0044] In some embodiments, the aqueous cationic polymer resin A of the present invention is selected from: (1) aqueous polycarbonate modified polyurethane, which is a copolymer modified resin of aqueous polyurethane resin, having a molecular weight of 8000-10000, a pH value of 4.8-5.2, a 100% modulus of the formed resin dry film of 150-230 MPa, and an elongation at break of 280-350%; (2) aqueous acrylic resin, having a molecular weight of 6000-80000, a pH value of 3.5-4.0, and a 100% modulus of the formed resin dry film of 2 (3) waterborne epoxy resin having a molecular weight of 10,000-15,000, a pH of 6.2-6.7, a 100% modulus of the formed resin dry film of 450-550 MPa, and an elongation at break of 100-150%; and (4) waterborne alkyd resin having a molecular weight of 5,000-8,000, a pH of 6.5-7.0, a 100% modulus of the formed resin dry film of 50-100 MPa, and an elongation at break of 280-320%.

[0045] Furthermore, in the aqueous surface treatment liquid of the present invention, the epoxy-functional organic silane coupling agent B1 is selected from at least one of the following: 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Preferably, the epoxy-functional organic silane coupling agent B1 is selected from at least one of the following: 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

[0046] Furthermore, in the aqueous surface treatment liquid of the present invention, the amino-functional organic silane coupling agent B2 is selected from at least one of the following: 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane, and bis(3-triethoxysilylpropyl)amine. Preferably, the amino-functional organic silane coupling agent B2 is selected from at least one of the following: 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, and bis(3-triethoxysilylpropyl)amine.

[0047] Furthermore, in the aqueous surface treatment liquid of the present invention, the unsaturated bond in the unsaturated bond-containing organosilane coupling agent C1 is one or more of a vinyl group, an acetoxy group, a vinylacyloxy group, and a methacryloxy group. Preferably, the unsaturated bond-containing organosilane coupling agent C1 is selected from at least one of the following: vinyltriethoxysilane, 3-acetoxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0048] Furthermore, in the aqueous surface treatment liquid of the present invention, the weight ratio of the unsaturated bond-containing organic silane coupling agent C1 to the mixture of the oxidized polyethylene wax emulsion and the polytetrafluoroethylene wax emulsion is 0.05-0.3.

[0049] In this embodiment, the weight ratio of the unsaturated bond-containing organosilane coupling agent C1 to the mixture of the oxidized polyethylene wax emulsion and the polytetrafluoroethylene wax emulsion is limited to 0.05-0.3 because: the unsaturated bonds on the organosilane coupling agent will crosslink or form intermolecular forces with oxygen-containing functional groups such as carboxyl, hydroxyl and carbonyl groups and residual vinyl groups on the surface of the oxidized polyethylene wax, and other alkoxy groups (methoxy, ethoxy) on the organosilane will form crosslinks with the compounded organosilane coupling agent B after hydrolysis to couple the oxidized polyethylene wax to the organic-inorganic composite coating. When the weight ratio is lower than 0.05, the relative content of the at least one unsaturated bond-containing organosilane coupling agent is low, and the oxidized polyethylene wax cannot be effectively coupled to the organic-inorganic composite coating, thereby affecting the appearance, wear resistance and surface paintability of the self-lubricating galvanized steel sheet covered with the organic-inorganic composite coating after stamping. When the weight ratio is greater than 0.3, the cross-linked and polymerized organic silane coupling agent becomes brittle, which increases the surface friction coefficient of the organic-inorganic composite coating and affects the processing lubrication performance.

[0050] Furthermore, the weight ratio of the at least one unsaturated bond-containing organic silane coupling agent C1 to the mixture of the oxidized polyethylene wax emulsion and the polytetrafluoroethylene wax emulsion can be 0.05-0.1.

[0051] Furthermore, in the aqueous surface treatment liquid of the present invention, the acid value of the oxidized polyethylene wax is in the range of 10-30, and the particle size is 50-1500 nm.

[0052] In this application, the particle size distribution is detected by a laser particle size analyzer, and the test method refers to GB / T 19077 "Particle size distribution laser diffraction method".

[0053] Acid value is a method to test the degree of oxidation of oxidized polyethylene wax. As the degree of oxidation of the oxidized wax increases, the acid value increases, the oxygen-containing functional groups such as carboxyl, hydroxyl and carbonyl increase, and the length of the carbon chain as well as the molar mass, viscosity and hardness decrease.

[0054] In this embodiment, the acid value of the oxidized polyethylene wax is within the range of 10-30 because: when the acid value of the oxidized polyethylene wax is less than 10, the degree of oxidation is insufficient, and the coupling and compatibility with the organosilane coupling agent and polymer resin are reduced, resulting in a reduced bonding strength between the oxidized polyethylene wax and the coating substrate, which is prone to flaking during friction and wear. Corrosive media are also more likely to penetrate into the coating through the gap between the oxidized polyethylene wax and the coating substrate, affecting the wear and corrosion resistance of the organic-inorganic composite coating. When the acid value of the oxidized polyethylene wax is greater than 30, the carbon chain length, molar mass, viscosity, and hardness are reduced. Under high temperature and high load conditions, the friction coefficient will increase rapidly, affecting the wear resistance of the organic-inorganic composite coating.

[0055] In some embodiments of the present invention, limiting the polyethylene oxide wax particle size (median diameter) at 50-1500nm is because: if less than 50nm, the polyethylene oxide wax is on the small side, which is not conducive to playing a significant role in reducing the coefficient of kinetic friction and improving the wear resistance of the film in the final organic-inorganic composite coating, and if greater than 1500nm, the polyethylene oxide wax particles are too large, and the composite coating cannot completely coat the polyethylene oxide wax particles, and a large amount of polyethylene oxide wax exposed to the surface is prone to peeling during the stamping friction process, affecting the processing lubrication and wear resistance of the organic-inorganic composite coating. Further, the polyethylene oxide wax particle size (median diameter) can be controlled in the scope of 100-300nm. In some embodiments, the polyethylene oxide wax particle size (median diameter) is in the scope of 200-1500nm.

[0056] Furthermore, in the aqueous surface treatment liquid of the present invention, the particle size of the polytetrafluoroethylene wax emulsion is 50-1000 nm. In some embodiments, in the aqueous surface treatment liquid of the present invention, the particle size of the polytetrafluoroethylene wax emulsion is 50-150 nm, preferably 90-110 nm.

[0057] In some embodiments of the present invention, the particle size (median diameter) of the polytetrafluoroethylene wax is limited to the range of 50-1000 nm because: if it is less than 50 nm, the polytetrafluoroethylene wax particles are too small and the wear resistance of the composite coating is not significantly improved; if it is greater than 1000 nm, the polytetrafluoroethylene wax particles are too large and the composite coating cannot effectively cover the polytetrafluoroethylene wax particles. In addition, the weak bonding force between the polytetrafluoroethylene wax particles and the coating substrate causes relative sliding and peeling under low load conditions, which can easily cause the self-lubricating galvanized steel sheets transported in rolls to loosen and collapse due to relative sliding between the coatings during transportation and storage. In the case of low-load plate surface coating friction such as uncoiling and slitting, the surface polytetrafluoroethylene wax particles are also prone to large-scale peeling, resulting in "powdering" or "de-coating" phenomena.

[0058] Furthermore, in the aqueous surface treatment liquid of the present invention, the weight ratio of the oxidized polyethylene wax emulsion to the polytetrafluoroethylene wax emulsion is 1-5.

[0059] In this embodiment, the weight ratio of the oxidized polyethylene wax emulsion to the polytetrafluoroethylene wax emulsion is limited to 1-5 because: if it is less than 1, that is, more polytetrafluoroethylene wax is used for external lubrication. Due to the low surface energy and weak cohesion between the polytetrafluoroethylene wax particles, a large amount of polytetrafluoroethylene wax will form a loose polytetrafluoroethylene layer on the surface of the composite coating. Due to the weak bonding between the polytetrafluoroethylene wax and the coating substrate, relative sliding and peeling will occur under low load conditions. This can easily cause the self-lubricating galvanized steel sheet transported in rolls to loosen or collapse due to relative sliding between the coating layers during transportation and storage. In low-load conditions such as unwinding and slitting, the friction of the plate surface coating can also easily cause large amounts of surface polytetrafluoroethylene wax particles to peel off, resulting in "dusting" or "de-coating". In addition, the low surface energy and weak cohesion of the polytetrafluoroethylene layer are not conducive to the subsequent painting, lamination, and printing of the self-lubricating galvanized steel sheet coated with the composite coating. If it is greater than 5, that is, the polytetrafluoroethylene is too low, the polytetrafluoroethylene cannot form a good external lubrication effect on the coating surface, especially during the friction with the hot metal mold, the oxidized polyethylene wax with a lower softening point cannot provide sufficient lubrication, which will lead to insufficient wear resistance of the coating and affect the stamping performance.

[0060] Furthermore, in the aqueous surface treatment fluid of the present invention, the water-soluble fluorine-containing compound D comprises at least one of a fluorine-containing metal acid, a fluorometallate, and a fluoride. In some embodiments, the metal is selected from titanium and zirconium. In some embodiments, the salt is a sodium salt, an ammonium salt, or a potassium salt.

[0061] In some embodiments, illustratively, the water-soluble fluorine-containing compound D can be one or more of: fluorotitanic acid, fluorozirconic acid, fluorosilicic acid, ammonium fluorotitanate, sodium fluorotitanate, potassium fluorotitanate, ammonium fluorozirconate, sodium fluorozirconate, potassium fluorozirconate, sodium fluorosilicate, sodium fluoride, ammonium fluoride and potassium fluoride.

[0062] Furthermore, in the aqueous surface treatment liquid of the present invention, the water-soluble phosphorus-containing compound E includes: hydrogen phosphate and / or phosphoric acid.

[0063] In some embodiments, illustratively, the water-soluble phosphorus-containing compound E can be one or more of ammonium dihydrogen phosphate, zinc dihydrogen phosphate, manganese dihydrogen phosphate, phosphoric acid, phytic acid, and hydroxyethylidene diphosphonic acid. Preferably, the water-soluble phosphorus-containing compound E can be one or more of ammonium dihydrogen phosphate, phytic acid, and hydroxyethylidene diphosphonic acid.

[0064] Furthermore, in the aqueous surface treatment liquid described in the present invention, the water-soluble salt compound F containing Group VIII iron-based elements is an iron-based metal salt, which is selected from at least one of the following: cobalt nitrate, nickel nitrate, iron nitrate, cobalt acetate, nickel acetate, iron acetate, cobalt citrate and iron citrate.

[0065] Another object of the present invention is to provide a self-lubricating galvanized steel sheet having excellent surface paintability, corrosion resistance and surface wear resistance, which can meet the requirements of users in multiple fields for environmental protection, surface wear resistance, stamping formability, paintability and resistance to degreasing and phosphating treatment of galvanized steel sheets. The self-lubricating galvanized steel sheet also has good resistance to various chemical media, such as resistance to wiping with organic solvents.

[0066] Specifically, surface coating properties include steel plate surface energy, epoxy powder coating adhesion, alkyd resin coating adhesion and precision ink printing adhesion; surface wear resistance includes the appearance after high-load and high-temperature sliding friction and the appearance after multiple friction of different materials such as polyurethane gaskets and corrugated paper; corrosion resistance includes flat plate corrosion resistance, corrosion resistance after molding, corrosion resistance after scratching and damage, and corrosion resistance after degreasing and phosphating; resistance to various chemical media includes acid and alkali resistance, that is, resistance to alkaline degreasing agents and acidic phosphating solutions and ceramic treatment solutions, resistance to organic solvent wiping, that is, resistance to 80% ethanol solution and butanone solution after multiple wiping with gauze.

[0067] Through research, the inventors found that the above-mentioned object of the invention can be achieved by coating and curing the aqueous surface treatment solution as described above on the surface of the galvanized steel sheet. The galvanized steel sheet applicable to the present invention can be any type and model of galvanized steel sheet known in the art.

[0068] Based on this, the present invention also provides a self-lubricating galvanized steel sheet, wherein the surface of the galvanized steel sheet has a composite coating formed by coating the aqueous surface treatment liquid as described above. The thickness of the galvanized steel sheet can be 0.1-10 mm, preferably 0.4-1.0 mm. The weight of the zinc layer on one side of the galvanized steel sheet is 20-100 g / m 2 , preferably 50-70g / m 2 The weight of the zinc layer on both sides of the galvanized steel sheet can be the same or different. In the self-lubricating galvanized steel sheet of the present invention, the composite coating is a single-layer structure.

[0069] Furthermore, in the self-lubricating galvanized steel sheet of the present invention, the single-side film weight of the composite coating is 0.5-2 g / m 2 .

[0070] In this embodiment, the film weight of the composite coating is controlled to be 0.5-2 g / m 2 Because: when less than 0.5g / m 2When the coating is thin, the wear resistance, corrosion resistance and acid and alkali resistance of the coating may decrease. The coating thickness exceeds 2g / m 2 On the one hand, the surface treatment cost per unit area will increase; on the other hand, due to the thicker coating, the coating cohesion and wear resistance may decrease.

[0071] Another object of the present invention is to provide a method for manufacturing a self-lubricating galvanized steel sheet.

[0072] Based on the above invention objectives, the present invention also provides a method for manufacturing a self-lubricating galvanized steel sheet, comprising the steps of:

[0073] Applying the aqueous surface treatment liquid on the surface of the galvanized steel sheet;

[0074] The aqueous surface treatment liquid is cured to form a composite coating on the surface of the galvanized steel sheet.

[0075] In the manufacturing method of the present invention, the method of coating the aqueous surface treatment liquid on the galvanized steel sheet may include roller coating, dipping or spraying.

[0076] In the manufacturing method described in the present invention, there is no particularly strict restriction on the curing method of the aqueous surface treatment liquid coated on the surface of the galvanized steel plate, and hot air heating, induction heating, infrared heating or combined heating can be used.

[0077] The water-based surface treatment liquid can be applied to one or both sides of the galvanized steel sheet.

[0078] Furthermore, in the manufacturing method of the present invention, the curing temperature is 80-180°C.

[0079] In this embodiment, the aqueous surface treatment liquid is cured at a temperature of 80-180°C because: 80-180°C can volatilize the solvent water and low-boiling point additives in the aqueous surface treatment liquid, promote the cross-linking film formation of the aqueous cationic polymer resin A and the compounded organic silane coupling agent B, when the curing temperature is lower than 80°C, the organic-inorganic composite coating formed by the curing of the surface treatment liquid is not sufficiently cross-linked, which may lead to a decrease in the adhesion of the coating on the surface of the galvanized steel plate, and when the curing temperature is higher than 180°C, on the one hand, the energy consumption cost of the surface treatment of the steel plate will increase, and on the other hand, the cross-linking degree of the silane in some composite coatings increases with temperature, which has an adverse effect on the corrosion resistance and paintability of the coating after deformation.

[0080] The aqueous surface treatment liquid for galvanized steel sheets and the self-lubricating galvanized steel sheets of the present invention have the following characteristics and beneficial effects:

[0081] The present invention uses a water-based cationic polymer resin and a compounded organic silane coupling agent as the matrix of the composite coating to achieve the effects of preventing the physical penetration of corrosive media and inhibiting the occurrence of electrochemical corrosion, so that the formed composite coating has excellent corrosion resistance and acid and alkali resistance. The present invention uses compounded lubricating particles to simultaneously provide external and internal lubrication for the composite coating. That is, a certain amount of oxygen-containing polar functional groups such as carboxyl, hydroxyl, and carbonyl groups are formed in the molecular chains of the surface of the oxidized polyethylene wax particles. After appropriate silane coupling modification, they can simultaneously form good compatibility with the silane skeleton formed by the water-based cationic polymer resin A and the compounded organic silane coupling agent B, so that the oxidized polyethylene wax particles are uniformly dispersed in the coating and form a strong bond with the coating. While providing internal lubrication for the coating, the internal cohesive bonding strength of the coating itself is not reduced.

[0082] The aqueous surface treatment liquid of the present invention does not contain chromium and is an environmentally friendly surface treatment agent. After surface treatment of the galvanized steel sheet, the surface of the galvanized steel sheet has excellent paintability, corrosion resistance and surface wear resistance.

[0083] In the present invention, a certain amount of polytetrafluoroethylene wax particles are distributed on the coating surface to play the role of external lubrication, thereby improving the friction between the composite coating and the hot metal mold surface during the stamping process.

[0084] In a further preferred technical solution, by reasonably controlling the weight ratio of polytetrafluoroethylene wax to oxidized polyethylene wax, it is possible to achieve excellent lubrication and wear resistance without reducing the coatability of the coating.

[0085] In a further preferred technical solution, a water-based cationic polymer resin system with both high modulus and high elongation is selected, such as water-based cationic polycarbonate modified polyurethane, so that the coating has both flexibility and hardness, thereby improving the problems of poor wear resistance and corrosion resistance after processing deformation of such galvanized surface treatment coatings.

[0086] In a further preferred technical solution, the compounded organosilane coupling agent increases the density of the silane skeleton in the composite coating by pre-crosslinking with organosilane coupling agents containing epoxy functional groups and amino functional groups, and a slightly excessive amount of organosilane coupling agent containing epoxy functional groups migrates to the surface of the coating and the interface with the galvanized layer, thereby enhancing the corrosion resistance, adhesion and paintability of the coating. DETAILED DESCRIPTION

[0087] The aqueous surface treatment liquid for galvanized steel sheets, the self-lubricating galvanized steel sheets and the manufacturing method thereof described in the present invention will be further explained and illustrated below in conjunction with specific embodiments. However, such explanation and illustration do not constitute an undue limitation to the technical solution of the present invention.

[0088] Examples 1-38 and Comparative Examples 1-6

[0089] In order to verify the technical effects of the present invention, the inventors prepared aqueous surface treatment liquids of Examples 1-38 and surface treatment liquids of Comparative Examples 1-6.

[0090] Tables 1-1 and 1-2 list the components and contents of the solids in the aqueous surface treatment liquids of Examples 1-38 and Comparative Examples 1-6, as well as the types and contents of the leveling agents.

[0091] Table 1-1.

[0092] Table 1-2.

[0093] Note:

[0094] A1 is a waterborne polycarbonate modified polyurethane, which is a copolymer modified resin of a waterborne polyurethane resin, with a molecular weight of 8000-10000, a pH of 5, and a 100% modulus of 200 MPa and an elongation at break of 320% for the formed resin dry film; A2 is a waterborne acrylic resin, with a molecular weight of 6000-80000, a pH of 3.5, and a 100% modulus of 300 MPa and an elongation at break of 120% for the formed resin dry film; A3 is a waterborne epoxy resin, with a molecular weight of 10000-15000, a pH of 6.5, and a 100% modulus of 500 MPa and an elongation at break of 100% for the formed resin dry film; A4 is a waterborne alkyd resin, with a molecular weight of 5000-8000, a pH of 7, and a 100% modulus of 50 MPa and an elongation at break of 300% for the formed resin dry film;

[0095] B1-1 is 3-glycidyloxypropyltriethoxysilane, B1-2 is 3-glycidyloxypropylmethyldiethoxysilane, B1-3 is 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane; B2-1 is 3-aminopropyltriethoxysilane, B2-2 is 3-aminopropylmethyldimethoxysilane, B2-3 is N-2-aminoethyl-3-aminopropyltriethoxysilane, and B2-4 is bis(3-triethoxysilylpropyl)amine;

[0096] C1-1 is vinyltriethoxysilane, C1-2 is 3-acetoxypropyltrimethoxysilane, C1-3 is 3-methacryloyloxypropyltriethoxysilane, C2 represents oxidized polyethylene wax emulsion, C2-1 is an oxidized polyethylene wax emulsion with a median diameter of 200 nm and an acid value of 30, C2-2 is an oxidized polyethylene wax emulsion with a median diameter of 1500 nm and an acid value of 10, and C3 is a polytetrafluoroethylene wax emulsion with a median diameter of 100 nm; of course, in other embodiments, polytetrafluoroethylene wax emulsions with a particle size of 50-1000 nm are feasible.

[0097] D1 is fluorotitanic acid, D2 is ammonium fluorotitanate, and D3 is ammonium fluorozirconate; E1 is ammonium dihydrogen phosphate, E2 is phytic acid, and E3 is hydroxyethylidene diphosphonic acid; F1 is cobalt nitrate, F2 is nickel nitrate, and F3 is cobalt citrate.

[0098] The “*” in Comparative Examples 3 and 6 indicates that tap water was used instead of deionized water.

[0099] In addition, although only four aqueous cationic polymer resins A, A1, A2, A3, and A4, are provided in the above embodiments, other aqueous cationic polymer resins may be selected, for example, aqueous polyurethane resins, aqueous polyester resins, copolymer-modified resins of aqueous acrylic resins, aqueous epoxy resins, aqueous polyester resins, and aqueous alkyd resins, as well as combinations of all these substances.

[0100] The galvanized steel sheets were treated using the aqueous surface treatment solutions of the above embodiments and comparative examples according to the following steps:

[0101] (1) The substrates of Examples 1-38 and Comparative Examples 1-6 are all 0.6 mm thick galvanized steel sheets, and the weight of the zinc layer on both sides of the galvanized steel sheets is 60 g / m 2 The steel plate surface was degreased by solvent. First, the steel plate surface was wiped with gauze soaked in heptane to remove the anti-rust oil on the steel plate surface. Then, it was ultrasonicated in ethanol solution for 20 minutes. Finally, it was washed with pure water to remove the residual organic solvent components on the surface and dried for later use.

[0102] (2) The aqueous surface treatment liquids of Examples 1-38 and Comparative Examples 1-6 were applied to the surface of the galvanized steel sheet and cured and dried at 80-180° C. to form a film with a weight of 0.5-2 g / m2 on the surface of the galvanized steel sheet. 2 composite coating.

[0103] It should be noted that the present invention focuses on the excellent performance of the composite coating formed by the designed aqueous surface treatment liquid. There is no special limitation on the galvanized substrate used. In actual application, technicians in this field can select the required galvanized steel plate according to specific needs.

[0104] Table 2 lists the curing temperature and film weight of the self-lubricating galvanized steel sheets of Examples 1-38 and Comparative Examples 1-6.

[0105] Table 2.

[0106] In order to verify the superior performance of the aqueous surface treatment solution designed by the present invention, the self-lubricating galvanized steel sheets prepared in Examples 1-38 and Comparative Examples 1-6 were sampled and cut into standard-sized samples and subjected to the following tests to obtain test data for evaluating various properties. The specific test items and test methods are as follows:

[0107] 1) Flat plate corrosion resistance:

[0108] According to the requirements of ASTM-B117, the flat plate was subjected to a salt spray test for 168 hours. The evaluation criteria were:

[0109] ◎: White rust area ratio is less than 5%

[0110] ○: White rust area ratio is greater than 5% and less than 10%

[0111] Δ: White rust area ratio is greater than 10% and less than 50%

[0112] ×: White rust area ratio is greater than 50%

[0113] 2) Corrosion resistance after forming:

[0114] Use the Ericsson cupping instrument to perform an 8mm cupping test, and conduct a salt spray test on the cupping area. The test standard is ASTM-B177, the test time is 96 hours, and the evaluation criteria are:

[0115] ◎: The white rust area ratio of the cupping part is less than 5%

[0116] ○: The white rust area ratio of the cupping part is greater than 5% and less than 10%

[0117] Δ: The white rust area ratio of the cupping part is greater than 10% and less than 50%

[0118] ×: The white rust area ratio of the cupping part is greater than 50%

[0119] 3) Corrosion resistance after scribing:

[0120] Use a surgical blade to cross-scribe with a length of 60 mm and a cross angle of 60°, scratching through the passivation layer but not the metal coating. The scribed flat sample is subjected to a salt spray test according to ASTM-B177 for 96 hours. The evaluation criteria are:

[0121] ◎: White rust area ratio is less than 5%

[0122] ○: White rust area ratio is greater than 5% and less than 10%

[0123] Δ: White rust area ratio is greater than 10% and less than 50%

[0124] ×: White rust area ratio is greater than 50%

[0125] 4) Corrosion resistance after alkali washing:

[0126] Use a medium alkalinity degreasing agent (pH: 9-11) for cleaning, spray the degreasing agent at 50℃ for 2 minutes, and then clean the surface with deionized water and conduct a salt spray test. The test standard is ASTM-B177 and the test time is 96 hours. The evaluation criteria are:

[0127] ◎: White rust area ratio is less than 5%

[0128] ○: White rust area ratio is greater than 5% and less than 10%

[0129] Δ: White rust area ratio is greater than 10% and less than 50%

[0130] ×: White rust area ratio is greater than 50%

[0131] 5) Stamping formability:

[0132] A self-made high-temperature sliding friction performance test device for coated steel plates (publication number: CN114813421A) was used. Experimental conditions: load 1000 kN, temperature setting: 80°C, indenter material: SKD die steel (R0.5), indenter length: 4 mm, friction distance: 50 mm, speed: 200 mm / s, evaluation criteria:

[0133] ◎: No change in appearance

[0134] ○: A few black spots on the surface

[0135] Δ: More obvious black stripes on the surface

[0136] ×: The appearance is completely black

[0137] 6) Wear resistance:

[0138] Use the Esrui multifunctional abrasion tester, friction pair materials: ① polyurethane gasket and ② corrugated paper, test load: 50g, travel distance: 30mm, test speed: 50 times / min, repeated wear 50 times, evaluation criteria:

[0139] ◎: No change in coating

[0140] ○: Slight scratches on the coating

[0141] Δ: Multiple scratches on the coating

[0142] ×: The coating is completely peeled off

[0143] 7) Resistance to organic solvent wiping:

[0144] ① Use gauze moistened with 80% alcohol solution to rub the surface of the steel plate back and forth 30 times. Evaluation criteria:

[0145] ◎: No change in appearance

[0146] ○: Slight marks on the exterior

[0147] Δ: The appearance is obviously whitened and the coating is partially dissolved

[0148] ×: The coating is completely dissolved

[0149] ② Use gauze moistened with butanone to rub the surface of the steel plate back and forth 20 times. Evaluation criteria:

[0150] ◎: No change in appearance

[0151] ○: Slight marks on the exterior

[0152] Δ: The appearance is obviously whitened and the coating is partially dissolved

[0153] ×: The coating is completely dissolved

[0154] 8) Acid and alkali resistance:

[0155] ①Alkali resistance: Soak in a 1wt% NaOH solution at room temperature for 10 minutes, rinse with water and visually observe the changes in surface appearance. Evaluation criteria:

[0156] ◎: No change in appearance

[0157] ○: Slight marks on the exterior

[0158] Δ: The appearance is obviously whitened and the coating is partially dissolved

[0159] ×: The coating is completely dissolved

[0160] ② Acid resistance: Soak in a 1wt% HCl solution at room temperature for 10 minutes, rinse with water, and visually observe the changes in surface appearance. Evaluation criteria:

[0161] ◎: No change in appearance

[0162] ○: Slight marks on the exterior

[0163] Δ: The appearance is obviously whitened and the coating is partially dissolved

[0164] ×: The coating is completely dissolved

[0165] 9) Paintability:

[0166] The surface treated galvanized steel sheet was sprayed with a medium alkalinity degreasing agent (pH: 9-11) at 50°C for 2 minutes, the surface was cleaned with deionized water, and then dried in an oven at 140°C for 15 minutes. After coating according to the following conditions, the coating adhesion test was performed. Test conditions:

[0167] ① Alkyd white paint (product of Shanghai Zhenhua Paint Factory, brand: A-09), 22# rod coating, baking conditions: 140℃ baking for 40min;

[0168] ②Epoxy powder coating (Akzo Nobel product, brand: EA05BH), powder coating thickness 70-80μm, baking conditions: 200℃ baking for 10min;

[0169] ③ Ink (Japan Seiko ink, brand: 1300EX), 12# rod coating, dry film 10-12μm, baking conditions: 120℃ baking for 20min;

[0170] After applying the above coating and ink, use Erichsen295 cross-hatch knife to cut 100 small grids with a size of 1mm on the surface of the coating film. 2 The depth should penetrate the paint film layer to reach the steel plate surface. After applying and peeling with 3M610 tape, observe the damage of the paint film and the number of remaining grids. Evaluation criteria:

[0171] ◎: The cutting edge is completely smooth, without any falling off

[0172] ○: There is a little coating peeling off at the intersection of the cut, but the cross-cut area affected cannot be significantly greater than 5%

[0173] Δ: Coating peels off at the intersection of the cuts and / or along the edges of the cuts. The affected cross-cut area is significantly greater than 5%, but not significantly greater than 15%.

[0174] ×: Coating peeled off at the intersection of the cuts and / or along the edges of the cuts, and the affected cross-cut area was significantly greater than 15%.

[0175] Table 3 lists the relevant performance parameters of the self-lubricating galvanized steel sheets of Examples 1-38 and Comparative Examples 1-6 after the above tests.

[0176] Table 3.

[0177] It can be seen from Table 3 above that after the galvanized steel sheets in Examples 1-38 were subjected to the above tests, their evaluation results were all "◎" and "○", especially they had good coatability for various coatings and printing media such as alkyd coatings, epoxy powders and inks, indicating that the galvanized steel sheets coated with the aqueous surface treatment liquid of the present invention not only have the stamping formability of self-lubricating steel sheets but also have excellent comprehensive properties such as surface coatability, corrosion resistance (flat plate, after forming, after scribing and after alkali washing), wear resistance and solvent resistance.

[0178] Combining Table 1 and Table 3, it can be seen that compared with Examples 1-38, since the content of aqueous cationic resin A in the surface treatment liquid of Comparative Example 1 is too low, the film-forming property, corrosion resistance and coatability of the surface treatment liquid after drying are poor.

[0179] In Comparative Example 2, since the content of the compounded organic silane coupling agent B in the surface treatment liquid is too low and the baking and curing temperature is too low, the adhesion, corrosion resistance, stamping formability and comprehensive resistance of the coating are all poor.

[0180] In Comparative Example 3, the presence of incompletely reacted amino functional groups in the composite organic silane coupling agent B affected the performance of the water-based cationic resin A. Therefore, the film-forming property, corrosion resistance, comprehensive resistance and coatability of the applied surface treatment liquid after drying were poor.

[0181] In Comparative Example 4, the corrosion resistance and comprehensive resistance of the coating were poor because the composite organic silane coupling agent B failed to form an effective skeleton network due to the silane ratio problem.

[0182] Since the content of the compound lubricating particles C in Comparative Examples 5 and 6 does not meet the requirements of the present invention, a good internal and external lubrication coordination cannot be formed, resulting in poor stamping processability and wear resistance of the coating.

[0183] From this, it can be seen that the self-lubricating galvanized steel sheet formed by coating the aqueous surface treatment liquid of the present invention on the surface of the galvanized steel sheet has excellent surface paintability, corrosion resistance, surface wear resistance and comprehensive resistance to chemical solvents and acids and alkalis, and can meet the requirements of users in many fields for environmentally friendly raw materials of galvanized steel sheets, intensive and green processing (stamping processability, paintability) and excellent service performance (corrosion resistance and comprehensive resistance).

[0184] It should be noted that the above embodiments are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith that can be directly derived from or easily associated with the contents disclosed by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. An aqueous surface treatment solution for galvanized steel sheets, comprising deionized water and solids; characterized in that: The solid content includes: Aqueous cationic polymer resin A, the weight portion of which in the solid content is 25-65 parts; A composite organic silane coupling agent B, whose weight part in the solid content is 30-65 parts; wherein the composite organic silane coupling agent B is formed by mixing and hydrolyzing at least one organic silane coupling agent B1 containing an epoxy functional group and at least one organic silane coupling agent B2 containing an amino functional group, and the molar ratio of the epoxy functional group to the amino functional group in the organic silane coupling agent B1 containing an epoxy functional group and the organic silane coupling agent B2 containing an amino functional group is 2-5; Compound lubricating particles C, whose weight parts in the solid content are 3-10 parts; wherein the compound lubricating particles C include: at least one organic silane coupling agent C1 containing unsaturated bonds; and a mixture of oxidized polyethylene wax emulsion and polytetrafluoroethylene wax emulsion; A water-soluble fluorine-containing compound D, wherein the weight portion of fluorine element in the solid content is 1.5-5.3 parts; A water-soluble phosphorus-containing compound E, wherein the weight portion of phosphorus in the solid content is 1-3 parts; and The water-soluble salt compound F containing the eighth group iron series element, wherein the weight portion of the eighth group iron series element in the solid content is 0.2-0.6 parts.

2. The aqueous surface treatment liquid according to claim 1, characterized in that The weight ratio of the deionized water to the solid content is 3.5-10.

3. The aqueous surface treatment liquid according to claim 1, characterized in that It also includes a leveling agent; preferably, the leveling agent is selected from at least one of the following: ethylene glycol butyl ether, ethylene glycol methyl ether, dipropylene glycol butyl ether, diethylene glycol monobutyl ether and isopropanol; preferably, the weight ratio of the deionized water to the leveling agent is 19-45.

4. The aqueous surface treatment liquid according to claim 1, characterized in that The conductivity of the deionized water is ≤10 μs / cm.

5. The aqueous surface treatment liquid according to claim 1, characterized in that The aqueous cationic polymer resin A is selected from at least one of the following: aqueous acrylic resin, aqueous epoxy resin, aqueous polyurethane resin, aqueous polyester resin and aqueous alkyd resin, and copolymer-modified resins of aqueous acrylic resin, aqueous epoxy resin, aqueous polyurethane resin, aqueous polyester resin and aqueous alkyd resin; and / or the aqueous cationic polymer resin A has a molecular weight greater than or equal to 5000, a pH value of 3.5-7, a 100% modulus of the formed resin dry film of 50-600 MPa, and an elongation at break of 100-400%.

6. The aqueous surface treatment liquid according to claim 1, characterized in that The epoxy-functional organic silane coupling agent B1 is selected from at least one of the following: 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

7. The aqueous surface treatment liquid according to claim 1, characterized in that The amino-functional organic silane coupling agent B2 is selected from at least one of the following: 3-aminopropylmethyldimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, N-(n-butyl)-3-aminopropyltrimethoxysilane and bis(3-triethoxysilylpropyl)amine.

8. The aqueous surface treatment liquid according to claim 1, characterized in that The unsaturated bond in the unsaturated bond-containing organic silane coupling agent C1 is one or more of vinyl, acetoxy, vinyl acyloxy and methacryloxy groups; preferably, the unsaturated bond-containing organic silane coupling agent C1 is selected from at least one of the following: vinyl triethoxysilane, 3-acetoxypropyl trimethoxysilane and 3-methacryloxypropyl triethoxysilane.

9. The aqueous surface treatment liquid according to claim 1, characterized in that: The weight ratio of the unsaturated bond-containing organic silane coupling agent C1 to the mixture of oxidized polyethylene wax emulsion and polytetrafluoroethylene wax emulsion is 0.05-0.3; and / or the weight ratio of the oxidized polyethylene wax emulsion to polytetrafluoroethylene wax emulsion is 1-5.

10. The aqueous surface treatment liquid according to claim 1, characterized in that The acid value of the oxidized polyethylene wax is in the range of 10-30, and the particle size is 50-1500nm; and / or the particle size of the polytetrafluoroethylene wax emulsion is 50-1000nm.

11. The aqueous surface treatment liquid according to claim 1, characterized in that The water-soluble fluorine-containing compound D includes: at least one of a fluorine-containing metal acid, a fluorine metal salt and a fluoride; preferably, the fluorine-containing compound D is selected from one or more of fluorotitanic acid, fluorozirconic acid, fluorosilicic acid, ammonium fluorotitanate, sodium fluorotitanate, potassium fluorotitanate, ammonium fluorozirconate, sodium fluorozirconate, potassium fluorozirconate, sodium fluorosilicate, sodium fluoride, ammonium fluoride and potassium fluoride.

12. The aqueous surface treatment liquid according to claim 1, characterized in that The water-soluble phosphorus-containing compound E includes: hydrogen phosphate and / or phosphoric acid; preferably, the water-soluble phosphorus-containing compound E is selected from one or more of diammonium phosphate, zinc dihydrogen phosphate, manganese dihydrogen phosphate, phosphoric acid, phytic acid and hydroxyethylidene diphosphonic acid.

13. The aqueous surface treatment liquid according to claim 1, characterized in that: The water-soluble salt compound F containing the eighth group iron series element is selected from at least one of the following: cobalt nitrate, nickel nitrate, iron nitrate, cobalt acetate, nickel acetate, iron acetate, cobalt citrate and iron citrate.

14. A self-lubricating galvanized steel sheet, characterized in that: The surface of the galvanized steel sheet has a coating formed by coating the aqueous surface treatment liquid as described in any one of claims 1 to 13; preferably, the single-sided film weight of the coating is 0.5-2 g / m 2 .

15. The method for manufacturing a self-lubricating galvanized steel sheet according to claim 14, characterized in that: Includes steps: Applying the aqueous surface treatment liquid on the surface of the galvanized steel sheet; curing the aqueous surface treatment liquid to form a composite coating on the surface of the galvanized steel sheet; Preferably, the curing temperature is 80-180°C.

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