Aqueous surface treatment solution for galvanized steel sheets, self-lubricating galvanized steel sheet, and method for manufacturing the same.

Abstract

The present invention discloses an aqueous surface treatment solution for galvanized steel sheets comprising deionized water and solids, wherein the solids comprise the following: an aqueous cationic polymer resin A, comprising 25 to 65 parts by weight of the solids; a composite organic silane coupling agent B, comprising 30 to 65 parts by weight of the solids; a composite lubricating particle C, comprising 3 to 10 parts by weight of the solids; wherein the composite lubricating particle C comprises at least one unsaturated bond-containing organic silane coupling agent C1 and a mixture of an oxidized polyethylene wax emulsion and a polytetrafluoroethylene wax emulsion; a water-soluble fluorine-containing compound D, comprising 1.5 to 5.3 parts by weight of fluorine in the solids; a water-soluble phosphorus-containing compound E, comprising 1 to 3 parts by weight of phosphorus in the solids; and a water-soluble group VIII iron-containing salt compound F, comprising 0.2 to 0.6 parts by weight of group VIII iron in the solids.

Description

[Technical Field]

[0001] The present invention relates to a surface treatment liquid, and more particularly to a surface treatment liquid for galvanized steel sheets. [Background technology]

[0002] Galvanized steel sheets are widely used in light industry, construction, home appliances, and automobiles. However, many galvanized steel sheets require press forming for use in industries such as home appliances and automobile manufacturing. Due to friction between the die and the steel sheet, the plating layer is prone to problems such as powder shedding and blackening during forming. This not only affects the appearance quality, dimensional accuracy, and corrosion resistance of the formed parts, but also accelerates die wear and shortens their service life.

[0003] To improve the surface wear resistance and workability of galvanized steel sheets, self-lubricating galvanized steel sheets were developed. These sheets not only offer improved processing and forming performance, but also eliminate the need to apply rust-preventive oil to prevent rust during transportation and storage, simplifying the packaging process and reducing production and transportation costs.

[0004] The self-lubricating properties of self-lubricating galvanized steel sheets are imparted by an organic-inorganic composite coating applied to the steel sheet surface. The typical thickness of this coating is 1-3 μm, and the main component forming the composite coating is a resin-silane composite. Furthermore, to ensure high lubricity, a considerable amount of lubricating additives, usually mainly lubricating fine wax, polyolefin emulsified wax, nano MoS2, and graphene, must be added. These lubricating additives typically remain unevenly distributed on the coating surface, contacting the mold surface before the coating itself during processing. Their relative sliding action acts like a lubricant, mitigating wear and abrasion of the coating and the galvanized layer of the steel sheet during processing. However, these lubricating additives all possess low surface energy and low cohesive strength, affecting the spread and leveling of subsequent paints on the surface. They also tend to cause delamination, reducing the adhesion of the coating to the substrate, making them unsuitable for further painting of processed parts. Therefore, self-lubricating galvanized steel sheet products are generally not recommended for use after painting.

[0005] However, in the process of using galvanized steel sheets, a considerable portion of the product's functionality (such as aesthetic appearance and corrosion resistance protection) must be achieved through subsequent painting. Therefore, attention must be paid to the painting process of processed parts. Typically, the painting procedure is as follows: After press forming, the parts are briefly treated with alkaline degreasing to remove oil and dirt from the surface. Products produced on the same line as galvanized raw materials or cold-rolled sheets may also undergo phosphate (or vitrification) treatment, and finally, electrostatic powder spray coating and heat curing are performed. Furthermore, from the perspective of cost reduction, many parts are painted only on one side, the exterior surface. In this process, the pH value of the alkaline degreasing solution is usually 9-11, and the pH value of the acidic phosphate (or vitrification) treatment solution is usually 2-5. In addition, a high-temperature firing curing process of 180-240°C is required for curing. All of these factors destroy the surface coating on the unpainted side of the galvanized steel sheet, causing phenomena such as yellowing, which affects the appearance of the coating, subsequent corrosion resistance, and performance. Therefore, in the painting process, there are extremely high requirements for the paintability, acid and alkali resistance, and high-temperature resistance of the surface treatment coating of galvanized steel sheets, and it is difficult to meet these requirements with existing self-lubricating galvanized steel sheet products.

[0006] A Chinese patent document with publication number CN104451638A, published on March 25, 2015, and titled "Chromium-Free Self-Lubricating Passivating Agent and Method for Producing the Same," discloses a method using stearate and ethylene / vinyl acetate wax as lubricants. However, while the softening point of stearate and ethylene / vinyl acetate wax-based lubricants is usually below 70°C, the surface temperature of continuous press dies exceeds 70°C in the parts processing processes of the OA product, home appliance, and automotive parts industries. As a result, the lubricating function of these lubricants is significantly reduced, and they are unable to exert sufficient lubrication.

[0007] A Chinese patent document with publication number CN105255338A, published on January 20, 2016, and titled "Zinc-plated steel sheet and aqueous surface treatment liquid with excellent surface wear resistance, corrosion resistance, and acid / alkali resistance" describes a lubricant system formed by combining composite lubricating particles, which are a mixture of polytetrafluoroethylene particles and surface-modified high-density polyethylene particles, with graphene oxide. [Overview of the project] [Problems that the invention aims to solve]

[0008] The object of the present invention is to provide an aqueous surface treatment liquid for galvanized steel sheets that can be applied to the surface of galvanized steel sheets and, by forming an organic-inorganic composite coating on the surface of the galvanized steel sheet, provides surface-treated galvanized steel sheet products with excellent lubricity and wear resistance without reducing the paintability of the coating. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides an aqueous surface treatment liquid for galvanized steel sheets comprising deionized water and solids, wherein the solids are as follows: Aqueous cationic polymer resin A, its weight in the solids content is 25 to 65 parts; The composite organic silane coupling agent B has a weight of 30 to 65 parts in the solid content; however, the composite organic silane coupling agent B is formed by hydrolyzing a mixture of at least one epoxy functional group-containing organic silane coupling agent B1 and at least one amino functional group-containing organic silane coupling agent B2, and the molar ratio of epoxy functional groups to amino functional groups in the epoxy functional group-containing organic silane coupling agent B1 and the amino functional group-containing organic silane coupling agent B2 is 2 to 5. The composite lubricating particles C comprise 3 to 10 parts by weight of the solid content; however, the composite lubricating particles C comprise at least one unsaturated bond-containing organic silane coupling agent C1 and a mixture of an oxidized polyethylene wax emulsion and a polytetrafluoroethylene wax emulsion. For water-soluble fluorine-containing compound D, the weight of fluorine in the solid content is 1.5 to 5.3 parts; Water-soluble phosphorus-containing compound E contains 1 to 3 parts by weight of phosphorus in its solid content; Water-soluble group VIII iron-containing salt compound F contains 0.2 to 0.6 parts by weight of group VIII iron-containing elements in its solid content.

[0010] The aqueous surface treatment solution for galvanized steel sheets according to the present invention is an environmentally friendly, weakly acidic aqueous surface treatment solution that can be manufactured stably.

[0011] However, the dispersion form of aqueous cationic polymer resin A in water may be aqueous solution, water dispersion, or emulsion.

[0012] If the amount of water-based cationic polymer resin A is less than 25 parts by weight, the adhesion of the formed organic-inorganic composite coating may decrease. However, if the amount of water-based cationic polymer resin A exceeds 65 parts by weight, the relative ratio of the silane skeleton formed by the composite organic silane coupling agent B, which is responsible for the electrochemical corrosion protection of the galvanized steel sheet surface, decreases in the organic-inorganic composite coating, affecting the corrosion resistance of the self-lubricating galvanized steel sheet material. Therefore, in this invention, the amount of water-based cationic polymer resin A is controlled to be between 25 and 65 parts by weight.

[0013] If the amount of composite organic silane coupling agent B is less than 30 parts by weight, the corrosion resistance of the organic-inorganic composite coating may decrease. However, if it exceeds 65 parts, the relative proportion of aqueous cationic polymer resin A, which plays a role in enhancing the flexibility of the organic-inorganic composite coating, decreases, affecting the T-bending performance, cupping performance, and corrosion resistance after molding of the organic-inorganic composite coating. Therefore, in this invention, the amount of composite organic silane coupling agent B is set to 30 to 65 parts by weight. In some embodiments, the amount of composite organic silane coupling agent B in the solid content is set to 30 to 60 parts by weight.

[0014] During the hydrolysis process, epoxy and amino functional groups in different organic silane coupling agents undergo ring-opening reactions to form a silane skeleton network. However, since one amino functional group can usually undergo ring-opening reactions with two epoxy functional groups, if the molar ratio of epoxy to amino functional groups falls below 2, amino functional groups remain. The active hydrogen in these amino functional groups then reacts further with aqueous cationic polymer resin A, disrupting the charge equilibrium of aqueous cationic polymer resin A, causing resin aggregation and affecting the stability of the coating. Therefore, in this invention, the molar ratio of epoxy to amino functional groups in epoxy-functional group-containing organic silane coupling agents and amino-functional group-containing organic silane coupling agents is limited to 2 to 5. It should be explained that a slightly excessive amount of epoxy-functional group-containing organic silane coupling agent can improve the adhesion between the final organic-inorganic composite coating and the zinc-plated substrate, while simultaneously improving the paintability of the composite coating. On the other hand, if the molar ratio of epoxy functional groups to amino functional groups exceeds 5, the relative proportion of silane skeletons that can be formed in the composite organic silane coupling agent B decreases, affecting the corrosion resistance of the final organic-inorganic composite coating.

[0015] If the weight of the composite lubricating particles C is less than 3 parts, the lubricity and wear resistance of the coating will be insufficient. However, if it exceeds 10 parts, the presence of excessive solid lubricating particles in the film will significantly reduce the cohesive force of the coating, potentially causing delamination between coatings. Furthermore, the corrosion resistance and chemical resistance of the coating will also decrease. Therefore, in this invention, the weight of the composite lubricating particles C is set to 3 to 10 parts.

[0016] In the present invention, the oxidized polyethylene wax emulsion in the composite lubricating particles C is a commercially available lubricating emulsion additive. This additive undergoes catalytic oxidation modification to form a certain amount of oxygen-containing polar functional groups such as carboxyl groups, hydroxyl groups, and carbonyl groups in the surface molecular chains, resulting in good compatibility with the aqueous cationic polymer resin A. It mainly exerts an internal lubrication effect in the final organic-inorganic composite coating, that is, it reduces intermolecular friction of the composite coating and exerts a plasticizing effect, thereby improving the heat generated during the wear process of pressing the coating and the coating's fluidity. The polytetrafluoroethylene wax emulsion is also a commercially available lubricating emulsion additive. This lubricating additive is characterized by high temperature resistance (high softening point), low surface energy, high hardness, and high lubricity. It rapidly migrates to the coating surface during the firing and solidification process of the coating, mainly exerts an external lubrication effect during the friction process of pressing, and improves the friction between the organic-inorganic composite coating and the high-temperature metal mold surface during the pressing process, thereby achieving the objective of enhancing the press molding performance of the coating.

[0017] If the weight of fluorine element is less than 1.5 parts, that is, if there is a small amount of fluorine compound, the corrosion resistance of the formed organic-inorganic composite coating may decrease. However, if the weight of fluorine element exceeds 5.3 parts, that is, if there is an excess of fluorine compound, due to the water-soluble nature of fluorine compound, residual fluorine compound that did not sufficiently react with the zinc-plated interface may reduce the water resistance of the composite coating and affect performance such as humidity and heat resistance. Therefore, in this invention, the weight of fluorine element in the water-soluble fluorine-containing compound D is set to 1.5 to 5.3 parts. In some embodiments, the weight of fluorine element in the water-soluble fluorine-containing compound D is set to 1.5 to 5.0 parts.

[0018] If the amount of phosphorus by weight is less than 1 part, that is, if there is a small amount of phosphorus-containing compound, the additive effect will be lost and the corrosion resistance of the composite coating may decrease. However, if the amount of phosphorus by weight exceeds 3 parts, that is, if there is an excess of acidic phosphorus-containing compound, the stability of the water treatment solution may decrease. Therefore, in this invention, the amount of phosphorus by weight of the water-soluble phosphorus-containing compound E is set to 1 to 3 parts.

[0019] In the present invention, the water-soluble Group VIII iron-based element-containing salt compound F plays a role in balancing the potential of the zinc plating layer on the surface of the zinc-plated steel sheet, and prevents galvanic corrosion caused by potential imbalance at the interface between the zinc plating layer on the surface of the zinc-plated steel sheet and the composite coating. When the parts by weight of the Group VIII iron-based element are less than 0.2 parts, that is, when the content of the water-soluble Group VIII iron-based element-containing salt compound is low, the addition effect disappears, and the corrosion resistance of the composite coating may decrease. However, when the parts by weight of the Group VIII iron-based element exceed 0.6 parts, that is, when the water-soluble Group VIII iron-based element-containing salt compound is excessive, a large amount of Group VIII iron-based metal formed by the substitution reaction is unevenly distributed on the surface of the zinc plating layer, reducing the adhesion between the composite coating and the zinc plating layer. Moreover, when the acidic Group VIII iron-based element-containing salt compound is excessive, the stability of the water treatment liquid also decreases. Therefore, the parts by weight of the Group VIII iron-based element in the solid content are set to 0.2 to 0.6 parts.

[0020] Furthermore, the parts by weight of the aqueous cationic polymer resin A may be controlled to be 35 to 45 parts, and the parts by weight of the composite organic silane coupling agent B may be controlled to be 40 to 50 parts.

[0021] Furthermore, in the aqueous surface treatment liquid according to the present invention, the weight ratio of the deionized water to the solid content is 3.5 to 10.

[0022] When the weight ratio of the deionized water to the solid content is less than 3.5, that is, when the ratio of the solid content in the aqueous surface treatment liquid is too high, the storage stability of the aqueous surface treatment liquid decreases. On the other hand, when the weight ratio of the deionized water to the solid content exceeds 10, that is, when the ratio of the solid content in the aqueous surface treatment liquid is too low, it is disadvantageous for forming an organic-inorganic composite coating with a sufficient film weight on the surface of the zinc-plated steel sheet by single application.

[0023] Of course, in some other embodiments of the present invention, the weight ratio of the deionized water to the solid content may be less than 3.5, for example, 3. In some embodiments, the weight ratio of the deionized water to the solid content is 3 to 10.

[0024] Furthermore, the aqueous surface treatment liquid according to the present invention further contains a leveling agent. Furthermore, the weight ratio of the deionized water to the leveling agent is 19 to 45.

[0025] In this embodiment, when the weight ratio of the deionized water to the leveling agent is less than 19, that is, when the ratio of the leveling agent in the aqueous surface treatment liquid is too high, defective defects such as pinholes are likely to occur during the process of applying and curing the aqueous surface treatment liquid on the surface of the galvanized steel sheet. However, when the weight ratio of the deionized water to the leveling agent exceeds 45, that is, when the ratio of the leveling agent in the aqueous surface treatment liquid is too low, problems such as poor wetting and poor leveling are likely to occur during the process of applying the aqueous surface treatment liquid on the surface of the galvanized steel sheet. As a result, defects such as coating leakage and diffraction fringes due to edge shrinkage occur on the surface coating of the galvanized steel sheet after curing.

[0026] Furthermore, in the aqueous surface treatment liquid according to the present invention, the leveling agent is at least one selected from the group consisting of ethylene glycol butyl ether, ethylene glycol methyl ether, dipropylene glycol butyl ether, diethylene glycol monobutyl ether, and isopropanol.

[0027] Furthermore, in the aqueous surface treatment liquid according to the present invention, the electrical conductivity of the deionized water is ≦10 μs / cm.

[0028] In such an embodiment, limiting the electrical conductivity of the deionized water to ≦10 μs / cm is to further ensure the storage stability of the aqueous surface treatment liquid. In some embodiments, the electrical conductivity of the deionized water is 3 to 10 μs / cm.

[0029] Furthermore, in the aqueous surface treatment liquid according to the present invention, the aqueous cationic polymer resin A is at least one selected from the group consisting of 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 at least one selected from the group consisting of aqueous acrylic resin, aqueous epoxy resin, aqueous alkyd resin, and copolymer-modified resins of aqueous polyurethane resin. In some embodiments, the copolymer-modified resin of aqueous polyurethane resin is polycarbonate-modified polyurethane, and its molecular weight is preferably 8000 to 10000.

[0030] Furthermore, in the aqueous surface treatment solution according to the present invention, the number average molecular weight of the aqueous cationic polymer resin A is 5000 or more, the pH value is 3.5 to 7, the 100% modulus of the formed resin dry film is 50 to 600 MPa, and the elongation at break is 100 to 400%. In some embodiments, the molecular weight of the aqueous cationic polymer resin A according to the present invention is 5000 to 100000. In some embodiments, the molecular weight of the aqueous cationic polymer resin A according to the present invention is 5000 to 80000.

[0031] In this text, the 100% modulus of elasticity and elongation at break of the resin-dried film were measured in accordance with GB 13022 "Test Method for Tensile Performance of Plastic Films," where the 100% modulus of elasticity refers to the tensile strength when the elongation is 100%.

[0032] In this embodiment, by limiting the molecular weight of the aqueous cationic polymer resin A to 5000 or more, the pH value to 3.5 to 7, the 100% modulus of the formed resin dry film to 50 to 600 MPa, and the elongation at break to 100 to 400%, it is possible to further improve the technical effects of the present invention.

[0033] However, if the molecular weight of aqueous cationic polymer resin A falls below 5000, the water resistance, solvent resistance, and scratch resistance of the dried resin film may decrease.

[0034] When the pH value of aqueous cationic polymer resin A falls below 3.5, the hydrolysis and self-polymerization rates of the composite organic silane coupling agent B in the paint are accelerated, affecting the paint's stability. However, when the pH value exceeds 7, the acidic hydrolyzed solution of the composite organic silane coupling agent B undergoes a neutralization reaction with aqueous cationic polymer resin A, disrupting the charge equilibrium of aqueous cationic polymer resin A, making resin aggregation more likely, and thus affecting the paint's stability.

[0035] The 100% modulus of elasticity of the resin-dried film formed with the aqueous cationic polymer resin A is 50 to 600 MPa, and the elongation at break is 100 to 400%, thereby achieving a good balance of hardness and flexibility in the final organic-inorganic composite coating. If the 100% modulus of elasticity of the resin-dried film is too high, the T-bending performance and cupping performance of the final organic-inorganic composite coating will decrease, but if it is too low, the solvent resistance and abrasion resistance of the final organic-inorganic composite coating will decrease. Also, if the elongation at break is too low, the corrosion resistance of the final organic-inorganic composite coating after molding will decrease, but if it is too high, the solvent resistance and resistance to chemical media of the composite coating will decrease. In some embodiments, the 100% modulus of elasticity of the resin-dried film formed with the aqueous cationic polymer resin A according to the present invention may be 50 to 500 MPa. In some embodiments, the elongation at break of the resin-dried film formed with the aqueous cationic polymer resin A according to the present invention may be 100 to 320%.

[0036] In some embodiments, the aqueous cationic polymer resin A according to the present invention is (1) an aqueous polyurethane copolymer modified resin having a molecular weight of 8000 to 10000, a pH value of 4.8 to 5.2, a 100% modulus of elasticity of the formed resin dry film of 150 to 230 MPa, and an elongation at break of 280 to 350%; (2) an aqueous polycarbonate modified polyurethane having a molecular weight of 6000 to 80000, a pH value of 3.5 to 4.0, and a 100% modulus of elasticity of the formed resin dry film of 280 to 320 MPa. (3) an aqueous acrylic resin with a breaking elongation of 100-150%; (4) an aqueous epoxy resin with a molecular weight of 10,000-15,000, a pH of 6.2-6.7, a 100% modulus of elasticity of the formed resin dry film of 450-550 MPa, and a breaking elongation of 100-150%; and (5) an aqueous alkyd resin with a molecular weight of 5,000-8,000, a pH of 6.5-7.0, a 100% modulus of elasticity of the formed resin dry film of 50-100 MPa, and a breaking elongation of 280-320%.

[0037] Furthermore, in the aqueous surface treatment solution according to the present invention, the epoxy functional group-containing organic silane coupling agent B1 is at least one selected from the group consisting of 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropylmethyldimethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Preferably, the epoxy functional group-containing organic silane coupling agent B1 is at least one selected from the group consisting of 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane.

[0038] Furthermore, in the aqueous surface treatment solution according to the present invention, the amino functional group-containing organic silane coupling agent B2 is at least one selected from the group consisting of 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 group-containing organic silane coupling agent B2 is at least one selected from the group consisting of 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropyltriethoxysilane, and bis(3-triethoxysilylpropyl)amine.

[0039] Furthermore, in the aqueous surface treatment solution according to the present invention, the unsaturated bond in the unsaturated bond-containing organic silane coupling agent C1 is one or more of a vinyl group, an acetoxy group, a vinyloxy group, and a methacryloxy group. Preferably, the unsaturated bond-containing organic silane coupling agent C1 is at least one selected from the group consisting of vinyltriethoxysilane, 3-acetoxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane.

[0040] Furthermore, in the aqueous surface treatment liquid according to the present invention, 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 to 0.3.

[0041] In this embodiment, the unsaturated bonds of the organic silane coupling agent form crosslinks or intermolecular interactions with oxygen-containing functional groups such as carboxyl groups, hydroxyl groups, and carbonyl groups, as well as residual vinyl groups, on the surface of the polyethylene oxide wax, while the other alkoxy groups (methoxy groups, ethoxy groups) of the organic silane, after hydrolysis, form crosslinks with the composite organic silane coupling agent B, coupling the polyethylene oxide wax to the organic-inorganic composite coating. However, if the weight ratio falls below 0.05, the relative content of at least one unsaturated bond-containing organic silane coupling agent becomes low, and the polyethylene oxide wax The organic-inorganic composite coating cannot be effectively coupled, and as a result, the appearance, wear resistance, and surface coating properties of the self-lubricating galvanized steel sheet coated with this organic-inorganic composite coating after press working are affected. However, if the weight ratio exceeds 0.3, the brittle organic silane coupling agent due to crosslinking polymerization increases the surface friction coefficient of the organic-inorganic composite coating, affecting the processing lubrication performance. Therefore, 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 limited to 0.05 to 0.3.

[0042] Furthermore, the weight ratio of at least one unsaturated bond-containing organosilane coupling agent C1 to the mixture of oxidized polyethylene wax emulsion and polytetrafluoroethylene wax emulsion may be 0.05 to 0.1.

[0043] Furthermore, in the aqueous surface treatment solution according to the present invention, the acid value of the oxidized polyethylene wax is in the range of 10 to 30, and the particle size is 50 to 1500 nm.

[0044] In this application, the particle size distribution is measured using a laser particle size analyzer, and the measurement method is as described in GB / T 19077 "Particle Size Distribution: Laser Diffraction Method".

[0045] Acid value is a method for measuring the degree of oxidation of oxidized polyethylene wax. Acid value increases with increasing degree of oxidation of the oxidized wax, increase in oxygen-containing functional groups such as carboxyl groups, hydroxyl groups, and carbonyl groups, and decrease in carbon chain length, molar mass, viscosity, and hardness.

[0046] In this embodiment, if the acid value of the oxidized polyethylene wax falls below 10, the degree of oxidation becomes insufficient, reducing the coupling and compatibility with the organic silane coupling agent and polymer resin. This reduces the bonding strength between the oxidized polyethylene wax and the coating matrix, making delamination more likely during friction and wear. Corrosive media also penetrate more easily into the coating through the gaps between the oxidized polyethylene wax and the coating matrix, affecting the wear resistance and corrosion resistance of the organic-inorganic composite coating. However, if the acid value of the oxidized polyethylene wax exceeds 30, the carbon chain length, molar mass, viscosity, and hardness decrease, causing a rapid increase in the coefficient of friction under high temperature and high load conditions, affecting the wear resistance of the organic-inorganic composite coating. Therefore, the acid value of the oxidized polyethylene wax is kept within the range of 10 to 30.

[0047] In some embodiments of the present invention, if the particle size (median diameter) of the polyethylene oxide wax is less than 50 nm, the polyethylene oxide wax is too small, making it difficult to achieve significant reductions in the coefficient of dynamic friction and improvements in the wear resistance of the film in the final organic-inorganic composite coating. However, if it exceeds 1500 nm, the polyethylene oxide wax particles are too large, preventing the composite coating from completely enclosing them. This makes it easier for the polyethylene oxide wax exposed in large quantities on the surface to peel off during the press friction process, affecting the processing lubrication performance and wear resistance of the organic-inorganic composite coating. Therefore, the particle size (median diameter) of the polyethylene oxide wax is limited to 50 to 1500 nm. Furthermore, the particle size (median diameter) of the polyethylene oxide wax may also be controlled within the range of 100 to 300 nm. In some embodiments, the particle size (median diameter) of the polyethylene oxide wax is within the range of 200 to 1500 nm.

[0048] Furthermore, in the aqueous surface treatment liquid according to the present invention, the particle size of the polytetrafluoroethylene wax emulsion is 50 to 1000 nm. In some embodiments, in the aqueous surface treatment liquid according to the present invention, the particle size of the polytetrafluoroethylene wax emulsion is 50 to 150 nm, preferably 90 to 110 nm.

[0049] In some embodiments of the present invention, if the particle size (median diameter) of the polytetrafluoroethylene wax is less than 50 nm, the polytetrafluoroethylene wax particles are too small, and the effect of improving the wear resistance of the composite coating becomes less significant. However, if it exceeds 1000 nm, the polytetrafluoroethylene wax particles are too large, and the composite coating cannot effectively enclose the polytetrafluoroethylene wax particles. Furthermore, the bonding force with the coating matrix is ​​weak, making it easier for relative sliding and peeling to occur even under low load conditions. As a result, self-lubricating galvanized steel sheets transported in a coiled state are prone to loosening and collapse of the steel coil due to relative sliding between the coatings during transport and storage. In the case of friction of the sheet surface coating under low load conditions such as unwinding and stripping, a large amount of polytetrafluoroethylene wax particles on the surface peel off, making it easy for phenomena such as "powder shedding" and "film detachment" to occur. Therefore, the particle size (median diameter) of the polytetrafluoroethylene wax is limited to the range of 50 to 1000 nm.

[0050] Furthermore, in the aqueous surface treatment liquid according to the present invention, the weight ratio of the oxidized polyethylene wax emulsion to the polytetrafluoroethylene wax emulsion is 1 to 5.

[0051] In this embodiment, when the weight ratio of the polyethylene oxide wax emulsion to the polytetrafluoroethylene wax emulsion is less than 1, that is, when there is more polytetrafluoroethylene wax which is responsible for the external lubrication, the polytetrafluoroethylene wax has the characteristics of low surface energy and weak cohesive force between particles. Therefore, a large amount of polytetrafluoroethylene wax forms a loose polytetrafluoroethylene layer on the composite coating surface. However, because the bonding force between the polytetrafluoroethylene wax and the coating matrix is ​​weak, relative sliding and peeling are more likely to occur even under low load conditions. As a result, self-lubricating galvanized steel sheets transported in a coiled state are prone to loosening and collapse of the steel coil due to relative sliding between the coatings during the transport and storage process, and under low load conditions such as unwinding and stripping... Even in the case of friction with the plate surface coating, a large amount of polytetrafluoroethylene wax particles on the surface tend to peel off, making phenomena such as "powder shedding" and "film detachment" more likely. Furthermore, the low surface energy and weak cohesive force of the polytetrafluoroethylene layer are unfavorable for subsequent painting, film application, and printing of self-lubricating galvanized steel plate parts to which the composite coating is applied. However, if the ratio exceeds 5, that is, if there is too little polytetrafluoroethylene, the polytetrafluoroethylene cannot form a good external lubrication effect on the coating surface. In particular, during the friction process with metal molds at high temperatures, the oxide polyethylene wax, which has a low softening point, cannot provide sufficient lubrication, resulting in insufficient wear resistance of the coating and affecting press molding performance. Therefore, the weight ratio of oxide polyethylene wax emulsion to polytetrafluoroethylene wax emulsion should be limited to 1 to 5.

[0052] Furthermore, in the aqueous surface treatment solution according to the present invention, the water-soluble fluorine-containing compound D comprises at least one of a fluorine-containing metallic acid, a fluorine metal salt, 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.

[0053] In some embodiments, the water-soluble fluorine-containing compound D may be, for example, one or more of the following: fluorotitanic acid, fluorozirconium acid, fluorosilicic acid, ammonium fluorotitanic acid, sodium fluorotitanic acid, potassium fluorotitanic acid, ammonium fluorozirconate, sodium fluorozirconate, potassium fluorozirconate, sodium fluorosilicate, sodium fluoride, ammonium fluoride, and potassium fluoride.

[0054] Furthermore, in the aqueous surface treatment solution according to the present invention, the water-soluble phosphorus-containing compound E includes hydrogen phosphate and / or phosphorus-containing acids.

[0055] In some embodiments, the water-soluble phosphorus-containing compound E may be one or more of ammonium dihydrogen phosphate, zinc dihydrogen phosphate, manganese dihydrogen phosphate, phosphoric acid, phytic acid, and hydroxiecylidene diphosphonic acid. Preferably, the water-soluble phosphorus-containing compound E may be one or more of ammonium dihydrogen phosphate, phytic acid, and hydroxiecylidene diphosphonic acid.

[0056] Furthermore, in the aqueous surface treatment solution according to the present invention, the water-soluble group VIII iron-containing salt compound F is at least one iron-based metal salt selected from the group consisting of cobalt nitrate, nickel nitrate, iron nitrate, cobalt acetate, nickel acetate, iron acetate, cobalt citrate, and iron citrate.

[0057] Another objective of the present invention is to provide a self-lubricating galvanized steel sheet that has excellent surface paintability, corrosion resistance, and surface abrasion resistance, and that satisfies the environmental friendliness, surface abrasion resistance, press formability, paintability, and degreasing phosphate treatment resistance that users in various fields require of galvanized steel sheets, and further possesses good resistance to various chemical media, such as resistance to wiping with organic solvents.

[0058] Specifically, surface coating properties include steel plate surface energy, epoxy powder coating adhesion, alkyd resin coating adhesion, and precision ink printing adhesion; surface abrasion resistance includes appearance after high-load, high-temperature sliding friction, and appearance after repeated friction with different materials such as polyurethane gaskets and corrugated cardboard; corrosion resistance includes flat plate corrosion resistance, post-molding corrosion resistance, corrosion resistance after cross-line breakage, and corrosion resistance after degreasing and phosphate treatment; resistance to various chemical media includes acid and alkali resistance (i.e., resistance to alkaline degreasing agents, acidic phosphate treatment solutions, and vitrification treatment solutions), and organic solvent wiping resistance (appearance after withstanding multiple wipes with gauze soaked in 80% ethanol solution and butanone solution).

[0059] Through their research, the inventors discovered that the above-mentioned objective of the invention can be achieved by applying the above-mentioned aqueous surface treatment solution to the surface of a galvanized steel sheet and curing it. The galvanized steel sheet to which the present invention can be applied may be any type or model of galvanized steel sheet that is well known in the art.

[0060] Based on this, the present invention further provides a self-lubricating galvanized steel sheet, wherein the surface of the galvanized steel sheet has a composite coating formed by applying the above-mentioned aqueous surface treatment liquid. The thickness of the galvanized steel sheet may be 0.1 to 10 mm, preferably 0.4 to 1.0 mm. The weight of the zinc layer on one side of the galvanized steel sheet is 20 to 100 g / m². 2 Preferably 50-70 g / m² 2 The weights of the zinc layers on both sides of the galvanized steel sheet may be the same or different. In the self-lubricating galvanized steel sheet according to the present invention, the composite coating has a single-layer structure.

[0061] Furthermore, in the self-lubricating galvanized steel sheet according to the present invention, the film weight on one side of the composite coating is 0.5 to 2 g / m². 2 That is the case.

[0062] In this embodiment, the film weight of the composite coating is 0.5 g / m². 2If the coating thickness falls below 2 g / m², the coating may be too thin, potentially reducing its abrasion resistance, corrosion resistance, and acid / alkali resistance. 2 If the coating thickness exceeds this, not only will the surface treatment cost per unit area increase, but the coating's cohesive strength will decrease due to its thickness, potentially reducing its abrasion resistance. Therefore, the film weight of the composite coating should be kept between 0.5 and 2 g / m². 2 Control it.

[0063] Another objective of the present invention is to provide a method for manufacturing self-lubricating galvanized steel sheets. Based on the above-described objectives of the invention, the method for manufacturing a self-lubricating galvanized steel sheet provided by the present invention includes the following steps: The aqueous surface treatment solution is applied to the surface of the galvanized steel sheet; A composite coating is formed on the surface of a galvanized steel sheet by curing an aqueous surface treatment solution.

[0064] In the manufacturing method according to the present invention, the method of applying the aqueous surface treatment solution to the surface of the galvanized steel sheet may include roll coating, dipping, or spraying.

[0065] In the manufacturing method according to the present invention, the method for curing the aqueous surface treatment solution applied to the surface of the galvanized steel sheet is not particularly strictly limited, and a heating method such as hot air heating, induction heating, infrared heating, or a combination thereof may be employed.

[0066] The aqueous surface treatment solution may be applied to one or both sides of the galvanized steel sheet. Furthermore, in the manufacturing method according to the present invention, the curing temperature is set to 80 to 180°C.

[0067] In this embodiment, within a temperature range of 80 to 180°C, the solvent water and low-boiling point additives in the aqueous surface treatment solution volatilize, promoting the crosslinking of the aqueous cationic polymer resin A and the composite organic silane coupling agent B. However, if the solidification temperature falls below 80°C, the crosslinking of the organic-inorganic composite coating formed by solidifying the surface treatment solution becomes insufficient, potentially reducing the adhesion of the coating to the surface of the galvanized steel sheet. On the other hand, if the curing temperature exceeds 180°C, not only does the energy cost of surface treatment of the steel sheet increase, but the degree of crosslinking of some silanes in the composite coating increases with rising temperature, adversely affecting the corrosion resistance and paintability after coating deformation. Therefore, a temperature of 80 to 180°C is selected to solidify the aqueous surface treatment solution. [Effects of the Invention]

[0068] The aqueous surface treatment liquid for galvanized steel sheets and the self-lubricating galvanized steel sheets according to the present invention have the following features and beneficial effects: This invention employs an aqueous cationic polymer resin and a composite organic silane coupling agent as the matrix of a composite coating, thereby achieving both physical penetration prevention of corrosive media and suppression of electrochemical corrosion, and imparting excellent corrosion resistance and acid / alkali resistance to the formed composite coating. This invention also employs composite lubricating particles to simultaneously provide external and internal lubrication to the composite coating. Specifically, when a certain amount of oxygen-containing polar functional groups such as carboxyl groups, hydroxyl groups, and carbonyl groups are formed on the surface molecular chains of oxidized polyethylene wax particles, after appropriate silane coupling modification, good compatibility is achieved with the silane skeleton formed by the aqueous cationic polymer resin A and the composite organic silane coupling agent B, allowing the oxidized polyethylene wax particles to be uniformly dispersed in the coating and firmly bonded to the coating. This provides internal lubrication to the coating without reducing the cohesive bonding strength of the coating itself.

[0069] The aqueous surface treatment solution according to the present invention does not contain chromium and is an environmentally friendly surface treatment agent. When applied to galvanized steel sheets, it imparts excellent paintability, corrosion resistance, and surface abrasion resistance to the surface of the galvanized steel sheets.

[0070] In this invention, a certain amount of polytetrafluoroethylene wax particles are dispersed on the coating surface, exerting an external lubricating effect and improving friction between the composite coating and the high-temperature metal mold surface during the pressing process.

[0071] In a more preferable technical solution, by rationally controlling the weight ratio of polytetrafluoroethylene wax to polyethylene oxide wax, it becomes possible to provide excellent lubricity and wear resistance without reducing the paintability of the coating.

[0072] In a more favorable technical solution, by selecting an aqueous cationic polymer resin system that simultaneously possesses high elastic modulus and high elongation, such as aqueous cationic polycarbonate-modified polyurethane, flexibility and hardness can be achieved in the coating, improving the problem of poor abrasion resistance and corrosion resistance after processing deformation in zinc-plated surface treatment coatings of this system.

[0073] In a more preferred technical solution, the composite organic silane coupling agent enhances the density of the silane skeleton in the composite coating through pre-crosslinking with epoxy functional group-containing and amino functional group-containing organic silane coupling agents, and the slightly excess epoxy functional group-containing organic silane coupling agent migrates to the interface between the coating surface and the zinc plating layer, thereby improving the corrosion resistance, adhesion, and paintability of the coating. [Modes for carrying out the invention]

[0074] The following interpretation and explanation will be based on specific examples and will further describe the aqueous surface treatment liquid for galvanized steel sheets, the self-lubricating galvanized steel sheet, and the method for manufacturing the same according to the present invention. However, this interpretation and explanation will not unduly limit the technical solutions of the present invention.

[0075] Examples 1-38 and Comparative Examples 1-6 To verify the technical effects of the present invention, the inventors prepared aqueous surface treatment solutions according to Examples 1 to 38 and surface treatment solutions according to Comparative Examples 1 to 6.

[0076] The composition and content of solids in the aqueous surface treatment solutions for Examples 1-38 and Comparative Examples 1-6, as well as the type and content of leveling agents, are shown in Tables 1-1 and 1-2.

[0077] [Table 1-1-1]

[0078] [Table 1-1-2]

[0079] [Table 1-2-1]

[0080] [Table 1-2-2]

[0081] [Table 1-2-3]

[0082] [Table 1-2-4]

[0083] remarks: A1 is an aqueous polycarbonate-modified polyurethane copolymer resin with a molecular weight of 8000-10000, a pH of 5, a 100% modulus of elasticity of the formed resin dry film of 200 MPa, and an elongation at break of 320%; A2 is an aqueous acrylic resin with a molecular weight of 6000-80000, a pH of 3.5, a 100% modulus of elasticity of the formed resin dry film of 300 MPa, and an elongation at break of 120%; A3 is an aqueous epoxy resin with a molecular weight of 10000-15000, a pH of 6.5, a 100% modulus of elasticity of the formed resin dry film of 500 MPa, and an elongation at break of 100%; A4 is an aqueous alkyd resin with a molecular weight of 5000-8000, a pH of 7, a 100% modulus of elasticity of the formed resin dry film of 50 MPa, and an elongation at break of 300%; 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; C1-1 is vinyltriethoxysilane, C1-2 is 3-acetoxypropyltrimethoxysilane, C1-3 is 3-methacryloxypropyltriethoxysilane, C2 represents an 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, any polytetrafluoroethylene wax emulsion with a particle size of 50 to 1000 nm can be applied.

[0084] D1 is fluorotitanium acid, D2 is ammonium fluorotitaniumate, and D3 is ammonium fluorozirconate; E1 is ammonium dihydrogen phosphate, E2 is phytic acid, and E3 is hydroxiecylidene diphosphonic acid; F1 is cobalt nitrate, F2 is nickel nitrate, and F3 is cobalt citrate.

[0085] In Comparative Examples 3 and 6, the asterisk (*) indicates that tap water was used instead of deionized water. Furthermore, although only four types of aqueous cationic polymer resin A (A1, A2, A3, and A4) were provided in the above embodiments, other aqueous cationic polymer resins may be selected in other embodiments, such as aqueous polyurethane resin, aqueous polyester resin, aqueous acrylic resin, aqueous epoxy resin, copolymer-modified resin of aqueous polyester resin and aqueous alkyd resin, and combinations of all of these substances.

[0086] The galvanized steel sheets were treated using the aqueous surface treatment solutions described in each of the above examples and comparative examples by the following steps: (1) For Examples 1 to 38 and Comparative Examples 1 to 6, a 0.6 mm galvanized steel sheet was used as the base material, and the weight of the zinc layer on both sides of the galvanized steel sheet was 60 g / m². 2 The following procedure was followed: A solvent degreasing method was employed for the steel plate surface. First, the steel plate surface was wiped with a thin gauze soaked in heptane to remove the rust-preventive oil. Next, it was ultrasonically cleaned in an ethanol solution for 20 minutes, and finally washed with pure water to remove any remaining organic solvent components from the surface. After drying, it was prepared for use.

[0087] (2) The aqueous surface treatment solutions according to Examples 1-38 and Comparative Examples 1-6 were applied to the surface of a galvanized steel sheet, cured at 80-180°C, and dried, resulting in a film weight of 0.5-2 g / m² on the surface of the galvanized steel sheet. 2 A composite coating was formed.

[0088] It is important to explain that the present invention focuses on the superior performance of composite coatings formed with a specially designed aqueous surface treatment solution. The zinc-plated substrate used is not particularly limited, and those skilled in the art may select the necessary zinc-plated steel sheet according to their specific needs in actual application processes.

[0089] Table 2 shows the curing temperature and film weight of the self-lubricating galvanized steel sheets used in Examples 1-38 and Comparative Examples 1-6.

[0090] [Table 2]

[0091] To verify the excellent performance of this aqueous surface treatment solution designed according to the present invention, samples were taken from self-lubricating galvanized steel sheets produced in Examples 1-38 and Comparative Examples 1-6, cut into standard-sized sample plates, and the following tests were conducted to obtain test data for evaluating each performance. The specific test items and test methods were as follows: 1) Corrosion resistance of flat plates: A salt spray test was performed on a flat plate in accordance with the ASTM-B117 standard, with a test duration of 168 hours, and the evaluation criteria were: ◎: White rust area ratio is less than 5% ○: White rust area ratio is over 5% and less than 10% △: White rust area ratio exceeds 10% but is less than 50% ×: White rust area ratio exceeds 50% 2) Corrosion resistance after molding: An 8mm cupping test was performed using an Erichsen cupping test machine, and a salt spray test was conducted on the cupping site. The test standard was ASTM B117, the test duration was 96 hours, and the evaluation criteria were: ◎: White rust area percentage in cupping areas is less than 5% ○: The percentage of white rust in the cupping area is more than 5% but less than 10%. △: The percentage of white rust area in the cupping area is more than 10% but less than 50%. ×: The percentage of white rust on the cupping area exceeds 50%. 3) Corrosion resistance after drawing: A cross line was drawn using a surgical scalpel, with a length of 60 mm and an intersection angle of 60°. The line penetrated the passivation layer but not the metal plating layer. A salt spray test was performed on the flat plate sample after the line drawing, using ASTM-B177 as the test standard, with a test duration of 96 hours, and the evaluation criteria were: ◎: White rust area ratio is less than 5% ○: White rust area ratio is over 5% and less than 10% △: White rust area ratio exceeds 10% but is less than 50% ×: White rust area ratio exceeds 50% 4) Corrosion resistance after alkaline cleaning: The surface was cleaned with a moderately alkaline degreasing agent (pH: 9-11), rinsed at 50°C for 2 minutes, and then washed with deionized water. A salt spray test was then performed, using ASTM-B177 as the test standard, with a test duration of 96 hours, and the evaluation criteria were: ◎: White rust area ratio is less than 5% ○: White rust area ratio is over 5% and less than 10% △: White rust area ratio exceeds 10% but is less than 50% ×: White rust area ratio exceeds 50% 5) Press formability: Using a homemade plated steel sheet high-temperature sliding friction performance testing apparatus (publication number: CN114813421A), the experimental conditions were: load 1000kN, temperature setting: 80℃, indenter material: SKD mold steel (R0.5), indenter length: 4mm, friction distance: 50mm, speed: 200mm / s, and the evaluation criteria were: ◎: No change in appearance ○: There are a small number of black spots on the exterior. △: Has many prominent black stripes on its exterior. ×: The exterior will be completely blackened. 6) Abrasion resistance: Using the Esri multi-functional abrasion resistance tester, the friction material was (1) polyurethane gasket and (2) corrugated cardboard. The test load was 50g, the stroke distance was 30mm, the test speed was 50 cycles / min, and the abrasion cycle was repeated 50 times. The evaluation criteria were: ◎: No change in coating ○: There is a small amount of damage to the coating. △: The coating has numerous damages. ×: The coating completely peels off. 7) Resistance to organic solvent wiping: (1) Using gauze moistened with an 80% ethanol aqueous solution, wipe the surface of the steel plate back and forth 30 times. The evaluation criteria are: ◎: No change in appearance ○: There are slight traces on the exterior. Δ: The exterior is clearly discolored, and the coating is partially dissolved. ×: The coating is completely dissolved. (2) Using gauze moistened with butanone, wipe the surface of the steel plate back and forth 20 times, and the evaluation criteria are: ◎: No change in appearance ○: There are slight traces on the exterior. Δ: The exterior is clearly discolored, and the coating is partially dissolved. ×: The coating is completely dissolved. 8) Acid and alkali resistance: (1) Alkali resistance: Immerse in a 1 wt% room temperature NaOH solution for 10 minutes, rinse with water, and then visually observe the change in surface appearance. The evaluation criteria are: ◎: No change in appearance ○: There are slight traces on the exterior. Δ: The exterior is clearly discolored, and the coating is partially dissolved. ×: The coating is completely dissolved. (2) Acid resistance: Immerse in a 1 wt% room temperature HCl solution for 10 minutes, rinse with water, and then visually observe any changes in the surface appearance. The evaluation criteria are: ◎: No change in appearance ○: There are slight traces on the exterior. Δ: The exterior is clearly discolored, and the coating is partially dissolved. ×: The coating is completely dissolved. 9) Paintability: A surface-treated galvanized steel sheet was rinsed for 2 minutes in an alkaline degreasing agent (pH: 9-11) at 50°C, the surface was washed with deionized water, and then dried in a 140°C oven for 15 minutes. After painting under the following conditions, a paint adhesion test was performed, with the test conditions being: (1) Alkyd white paint (product of Shanghai Zhenhua Paint Factory, product number: A-09), applied with a 22# bar, baking conditions: baked at 140 °C for 40 min; (2) Epoxy powder paint (product of Akzo Nobel, product number: EA05BH), powder coating layer thickness is 70 - 80 μm, baking conditions: baked at 200 °C for 10 min; (3) Ink (product of Nippon Seiko Ink, product number: 1300EX type), applied with a 12# bar, dry film thickness is 10 - 12 μm, baking conditions: baked at 120 °C for 20 min; After applying the above-mentioned paint or ink, the surface of the coating film was cut into 100 checkerboard patterns with an Erichsen 295 cross cutter knife, and the size was 1 mm 2 in depth, reaching the steel plate surface through the coating film layer. After pasting and peeling off a 3M610 tape, the damage of the coating film and the remaining number of checkerboard patterns were observed, and the evaluation criteria were: ◎: The cutting edge is completely smooth, and none of the checkerboard patterns fall off ○: There is slight coating peeling at the intersection of the cut, but the affected cross-sectional area of the intersection cut shall not clearly exceed 5% Δ: There is coating peeling along the intersection of the cut and / or the cut edge, and the affected cross-sectional area of the intersection cut clearly exceeds 5%, but shall not clearly exceed 15% ×: There is coating peeling along the intersection of the cut and / or the cut edge, and the affected cross-sectional area of the intersection cut clearly exceeds 15% The relevant performance parameters of the self-lubricating zinc-plated steel sheets according to Examples 1 - 38 and Comparative Examples 1 - 6 after undergoing the above tests are shown in Table 3.

[0092]

Table 3-1

[0093]

Table 3-2

[0094] As can be seen from Table 3 above, the galvanized steel sheets of Examples 1 to 38 all received "◎" and "○" in evaluation results after undergoing the above tests, and showed particularly good paintability to various paints and printing media such as alkyd-based paints, epoxy powders and inks. This indicates that the galvanized steel sheets coated with the aqueous surface treatment solution of the present invention possess overall performance such as excellent surface paintability, corrosion resistance (flat sheet, after forming, after drawing, after alkaline cleaning), abrasion resistance and solvent resistance, in addition to the press formability of self-lubricating steel sheets.

[0095] As can be seen by combining Table 1 and Table 3, Comparative Example 1, compared to Examples 1 to 38, has a very low content of aqueous cationic resin A in the surface treatment solution, resulting in inferior film formation, corrosion resistance, and paintability after drying of the applied surface treatment solution.

[0096] Comparative Example 2 suffers from poor adhesion, corrosion resistance, press formability, and overall coating durability because the content of the composite organic silane coupling agent B in the surface treatment solution is too low, and the firing curing temperature is also too low.

[0097] In Comparative Example 3, unreacted amino functional groups were present in the composite organic silane coupling agent B, affecting the performance of the aqueous cationic resin A. As a result, the film-forming properties, corrosion resistance, overall durability of the coating, and paintability of the applied surface treatment solution after drying were all inferior.

[0098] Comparative Example 4 suffers from inferior corrosion resistance and overall durability of the coating because the skeletal network cannot be effectively formed due to the silane blending ratio in the composite organic silane coupling agent B.

[0099] Comparative Examples 5 and 6 do not satisfy the requirements of the present invention because the content of composite lubricating particles C does not allow for good coordination between internal and external lubrication, resulting in poor press workability and wear resistance of the coating.

[0100] As can be seen from the above, the self-lubricating galvanized steel sheet formed by applying the aqueous surface treatment solution according to the present invention to the surface of a galvanized steel sheet has excellent surface paintability, corrosion resistance, surface abrasion resistance, and overall resistance such as chemical solvent resistance and acid / alkali resistance, meeting the requirements of users in multiple fields for environmental compatibility of raw materials, intensive green processability (press workability, paintability), and excellent usability (corrosion resistance and overall resistance) for galvanized steel sheets.

[0101] It should be noted that the embodiments described above are merely specific examples of the present invention. The present invention is not limited to the embodiments described above, and it is clear that any similar changes or modifications that a person skilled in the art can directly derive from the disclosure of the present invention or readily conceive are also covered within the scope of the present invention.

Claims

1. An aqueous surface treatment liquid for galvanized steel sheets containing deionized water and solids, wherein the solids include the following: Aqueous cationic polymer resin A, its weight in the solids is 25 to 65 parts; The composite organic silane coupling agent B has a weight of 30 to 65 parts in the solid content; however, the composite organic silane coupling agent B is formed by hydrolyzing a mixture of at least one epoxy functional group-containing organic silane coupling agent B1 and at least one amino functional group-containing organic silane coupling agent B2, and the molar ratio of epoxy functional groups to amino functional groups in the epoxy functional group-containing organic silane coupling agent B1 and the amino functional group-containing organic silane coupling agent B2 is 2 to 5; The composite lubricating particles C comprise 3 to 10 parts by weight of the solid content; however, the composite lubricating particles C comprise at least one unsaturated bond-containing organic silane coupling agent C1 and a mixture of an oxidized polyethylene wax emulsion and a polytetrafluoroethylene wax emulsion; Water-soluble fluorine-containing compound D contains 1.5 to 5.3 parts by weight of fluorine in its solid content; Water-soluble phosphorus-containing compound E, the amount of phosphorus element in the solid content is 1 to 3 parts by weight; and In the water-soluble group VIII iron-containing salt compound F, the weight of group VIII iron elements in the solid content is 0.2 to 0.6 parts.

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

3. The aqueous surface treatment liquid according to claim 1, further comprising a leveling agent; preferably, the leveling agent is at least one selected from the group consisting of 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 to 45.

4. The aqueous surface treatment liquid according to claim 1, characterized in that the electrical 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 at least one selected from the group consisting of 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; and / or the aqueous cationic polymer resin A has a molecular weight of 5000 or more, a pH value of 3.5 to 7, a 100% modulus of elasticity of the formed resin dry film of 50 to 600 MPa, and an elongation at break of 100 to 400%.

6. The aqueous surface treatment liquid according to claim 1, characterized in that the epoxy functional group-containing organic silane coupling agent B1 is at least one selected from the group consisting of 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 group-containing organic silane coupling agent B2 is at least one selected from the group consisting of 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 unsaturated bond in the unsaturated bond-containing organic silane coupling agent C1 is one or more of a vinyl group, an acetoxy group, a vinyloxy group, and a methacryloxy group; preferably, the unsaturated bond-containing organic silane coupling agent C1 is at least one selected from the group consisting of vinyltriethoxysilane, 3-acetoxypropyltrimethoxysilane, and 3-methacryloxypropyltriethoxysilane, as described in claim 1.

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 polyethylene oxide wax emulsion and polytetrafluoroethylene wax emulsion is 0.05 to 0.3; and / or the weight ratio of polyethylene oxide wax emulsion to polytetrafluoroethylene wax emulsion is 1 to 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 to 30 and the particle size is 50 to 1500 nm; and / or the particle size of the polytetrafluoroethylene wax emulsion is 50 to 1000 nm.

11. The aqueous surface treatment liquid according to claim 1, wherein the water-soluble fluorine-containing compound D comprises at least one of a fluorine-containing metallic acid, a fluorine metal salt, and a fluoride; preferably, the fluorine-containing compound D is one or more of fluorotitanic acid, fluorozirconium 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, wherein the water-soluble phosphorus-containing compound E comprises hydrogen phosphate and / or phosphorus-containing acids; preferably, the water-soluble phosphorus-containing compound E is one or more of ammonium dihydrogen 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 group VIII iron-containing salt compound F is at least one selected from the group consisting of cobalt nitrate, nickel nitrate, iron nitrate, cobalt acetate, nickel acetate, iron acetate, cobalt citrate, and iron citrate.

14. A self-lubricating galvanized steel sheet, wherein the surface of the galvanized steel sheet has a coating formed by applying an aqueous surface treatment solution according to any one of claims 1 to 13; preferably, the film weight of one side of the coating is 0.5 to 2 g / m². ２ A self-lubricating galvanized steel sheet characterized by the following:

15. A method for manufacturing a self-lubricating galvanized steel sheet according to claim 14, characterized by including the following steps. The aqueous surface treatment solution is applied to the surface of the galvanized steel sheet; By curing the aqueous surface treatment solution, a composite coating is formed on the surface of the galvanized steel sheet; Preferably, the curing temperature is set to 80 to 180°C.

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