Softening auxiliary agent for methanesulfonic acid tin plating and preparation method of softening auxiliary agent

Abstract

The invention provides a softening and melting auxiliary agent for tin plating with methanesulfonic acid, which comprises the following components in parts by mass: 1-10 parts of sulfur-containing aromatic salt compound, 1-10 parts of sulfur-containing aromatic hydrocarbon compound, 5-10 parts of oxyacid, 1-3 parts of surfactant and 1-3 parts of benzenediol.

Description

Technical Field

[0001] The invention relates to a treatment agent for steel plates and a treatment method thereof, in particular to a treatment agent for methanesulfonic acid tin-plated steel plates and a treatment method thereof. Background Art

[0002] Tinplate, commonly known as tinplate, is a cold-rolled thin steel plate with a double-sided electroplated tin layer, mostly used to make food cans and beverage cans. There are two commonly used production processes for electroplated tin steel strips: one is the phenolsulfonic acid (PSA) plating solution system, which is used in most tinning lines; the other is a halide-based plating solution system. As the electroplating tin industry pays more attention to environmental protection, the production process of electroplated tin steel strips has undergone tremendous changes. A methylsulfonate (MSA) tinning process with special additives has developed rapidly. In recent years, domestic tinplate manufacturers have gradually adopted this more environmentally friendly process to replace the PSA process. As the users of tinplates have increasing requirements for low costs, products are gradually developing towards low tin plating amounts, 1.1g / m 2 There are more and more thin tinplate products with even lower tin plating amount.

[0003] After 10 years of production practice, it was found that the fluxing and reflowing process of the methanesulfonate tinning process has a great influence on the corrosion resistance of the thin coating. In addition, different fluxes will also affect other surface characteristics of the tinplate after passivation. Since methanesulfonate and its additives themselves do not have the fluxing effect of traditional plating solutions, the tinplate needs to be immersed in the flux for fluxing before reflowing. Common fluxes are divided into two categories: organic solutions and inorganic salt solutions. The flux has many functions in the soft melting process: (1) removes oxides on the surface of the strip after electroplating; (2) utilizes the fluidity of the flux to promote the flow of liquid tin on the surface of the tinplate and improve the leveling effect; (3) the flux decomposes or volatilizes during the soft melting process, which can absorb the heat on the surface of the tinplate and help the melting and crystallization process of the tinplate surface; (4) the flux (especially organic flux) decomposes under high temperature conditions, and the process of generating carbon dioxide and water needs to absorb oxygen on the surface of the tinplate, thereby reducing the formation of oxides on the surface of the tinplate; (5) when the tin layer is quenched after soft melting, the flux can provide crystal nuclei for the secondary crystallization process of metallic tin and refine the tin grains.

[0004] A Chinese patent document with publication number CN1381532 and publication date November 27, 2002, entitled "Non-chromate metal surface treatment agent, surface treatment method and treated steel material", discloses a non-chromate metal surface treatment agent suitable for metal substrates. In the technical solution disclosed in the patent document, the non-chromate surface treatment agent includes a silane coupling agent and / or a hydrolysis condensation product thereof, a zirconium compound and / or a titanium compound, and / or a thiocarbonyl-containing compound and / or a water-soluble acrylic resin, and the surface treatment method adopts a coating treatment agent.

[0005] A Chinese patent document entitled "A Metal Surface Treatment Composition and Its Preparation Method and Use" with publication number CN1986885 and publication date June 27, 2007 discloses a metal surface treatment composition and its preparation method and use. In the technical solution disclosed in the patent document, the composition used for surface treatment of tin-plated steel sheets contains a fluorine complex of metal elements selected from titanium, zirconium and silicon, a zirconium-aluminum bimetallic organic complex, Mg, Al metal ions and a water-soluble acrylic resin polymer compound.

[0006] The Chinese patent document with publication number CN 109913782 A and publication date June 21, 2019, entitled "A Softening Aid for Tin-plated Steel Sheet and Surface Treatment Method for Tin-plated Steel Sheet" discloses a softening aid for tin-plated steel sheet. In the technical solution disclosed in the patent document, the mass percentage of the components of the softening aid is: 0.5-3% inorganic phosphate; 1-5% organic carboxylic acid; 0.05-0.5% water-soluble divalent tin salt; 0.1-1% water-soluble rare earth salt containing at least one of lanthanum and cerium; the balance is water. The surface treatment method is to apply a treatment agent after soft melting. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a soft fluxing aid for methanesulfonic acid tin plating. When the soft fluxing aid is used for tin-plated steel plates, it can be well adsorbed on the surface of the tin-plated plates, improve the corrosion resistance of the tin-plated plates, and reduce the porosity of the surface of the tin-plated plates.

[0008] The technical problem to be solved can be implemented through the following technical solutions.

[0009] A reflow aid for methanesulfonic acid tin plating, characterized in that, by mass ratio, the reflow aid is a mixture comprising the following components: 1 to 10 parts of sulfur-containing aromatic salt compounds, 1 to 10 parts of sulfur-containing aromatic hydrocarbon compounds, 5 to 10 parts of oxygen-containing acids, 1 to 3 parts of surfactants and 1 to 3 parts of hydroquinone.

[0010] The paired electrons in the sulfur aromatic salt compounds and sulfur-containing aromatic hydrocarbon compounds in the solution form a coordination effect with the empty orbits of the tin metal, which can form tin-oxygen bonds and adsorb on the surface of the tin layer to form a monomolecular adsorption layer adsorbed on the surface of the fresh tin-plated plate to prevent the oxidation of tin in the reflow process. The oxygen-containing acid in the solution can remove the tin oxide SnO formed at high temperature. The hydroquinone in the solution can prevent the oxidation of tin in the reflow furnace.

[0011] Furthermore, the general structural formula of the sulfur-containing aromatic salt compound is:

[0012]

[0013] Wherein, in the general structural formula, R1 is located at position 1, 2, 3, 4, 5 or 6, R2 is located at position 1, 2, 3, 4, 5 or 6, the sulfonate substituent is located at position 2, 3, 4, 5 or 6, and the positions of R1, R2 and the sulfonate substituent do not overlap. Wherein, R1 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy; R2 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy; Y in the sulfonate substituent is selected from alkali metal ions, alkaline earth metal ions, transition metal ions or ammonium ions.

[0014] Furthermore, the general structural formula of the sulfur aromatic hydrocarbon compound is:

[0015]

[0016] Wherein, in the general structural formula, R1 is located at position 1, 2, 3, 4, 5 or 6, and R2 is located at position 1, 2, 3, 4, 5 or 6. Wherein, R1 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy; R2 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy.

[0017] Preferably, the catechol is selected from catechol, resorcinol or hydroquinone.

[0018] Preferably, the oxygen-containing acid is selected from sulfuric acid, nitric acid, salicylic acid or dithiophenecarboxylic acid.

[0019] The flux (soft fluxing aid) proposed in the present invention can be adsorbed on the surface of the tinplate through polar groups. The polar groups contain elements such as S and O. These elements contain lone pairs of electrons with large electronegativity, which can change the double electric layer structure of the metal surface, increase the activation energy of the corrosion reaction, and inhibit the progress of the corrosion reaction. After the tinplate is immersed in the flux for a period of time, when the concentration and temperature of each component of the flux are appropriate, it will be adsorbed on the surface of the tinplate as a corrosion inhibitor, thereby improving the corrosion resistance of the tinplate, thereby providing a certain protection for the tinplate.

[0020] Another technical problem to be solved by the present invention is to provide a method for preparing the aforementioned reflow aid, the method comprising the following steps:

[0021] (1) weighing an appropriate amount of a sulfur-containing aromatic salt compound and a sulfur-containing aromatic hydrocarbon compound according to a ratio and dissolving them in deionized water to prepare a solution A;

[0022] (2) Weighing an appropriate amount of oxygen-containing acid according to the ratio and adding it to solution A to prepare solution B;

[0023] (3) Weighing an appropriate amount of surfactant and hydroquinone and adding them to solution B to prepare solution C;

[0024] (4) The solution C is heated and continuously stirred until the sulfur-containing aromatic salt compound and the sulfur-containing aromatic hydrocarbon compound are completely dissolved to obtain a flux.

[0025] Furthermore, in step (4), the heating temperature is 55°C to 65°C.

[0026] After soaking the tinplate in flux for a period of time, the tinplate is reflowed. The result of reflow is that part of the tin reacts with the strip steel to form an intermetallic compound FeSn2 (i.e., a tin-iron alloy layer). The tin-iron alloy layer can make the tin layer have good adhesion on the strip steel and improve the corrosion resistance of the tinplate. During the reflow process, the organic components of the flux absorb oxygen and decompose, and form a highly soluble compound Sn(OH) with the oxide on the surface of the tin layer. x , thereby inhibiting the generation of oxides in the tin layer during the reflow process. In addition, the flux has good fluidity, which can promote the flow of liquid tin on the surface of the tinplate during reflow and improve the leveling effect. The flux decomposes or volatilizes during the reflow process, which can absorb the heat on the surface of the tinplate and help the melting and crystallization process of the tinplate surface. Moreover, when the tin layer is quenched after reflow, the flux can provide crystal nuclei for the secondary crystallization process of the metallic tin and refine the tin grains. This can make the tinplate after reflow more dense and reduce the porosity of the tinplate after reflow, thereby greatly improving the corrosion resistance of the tinplate after reflow.

[0027] Through the above-mentioned surface treatment method, the soft fluxing agent proposed in the present invention can be successfully adsorbed on the surface of the tinplate. The adsorption behavior of the flux on the surface of the tinplate is closely related to the elements such as O and S in its molecular structure. The polar groups with O and S as the central atoms contain lone pairs of electrons or unsaturated bonds, have a certain electron-donating ability, and can form coordination bonds with the tinplate for chemical adsorption. Factors such as the spatial structure of the flux, the number of active center groups, the surface roughness of the tinplate, and the charge density of the tinplate surface will have a great influence on the adsorption behavior of the metal surface. DETAILED DESCRIPTION

[0028] The invention provides a soft fluxing aid for methanesulfonic acid tin plating, which comprises 1 to 10 parts of sulfur-containing aromatic salt compounds, 1 to 10 parts of sulfur-containing aromatic hydrocarbon compounds, 5 to 10 parts of oxygen-containing acid, 1 to 3 parts of surfactant and 1 to 3 parts of hydroquinone.

[0029] In the above ratio, the general structural formula of the sulfur-containing aromatic salt compound is:

[0030]

[0031] In the general structural formula, R1 is located at position 1, 2, 3, 4, 5 or 6, R2 is located at position 1, 2, 3, 4, 5 or 6, the sulfonate substituent is located at position 2, 3, 4, 5 or 6, and the positions of R1, R2 and the sulfonate substituent do not overlap. Wherein, R1 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy; R2 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy; Y in the sulfonate substituent is selected from alkali metal ion, alkaline earth metal ion, transition metal ion or ammonium ion.

[0032] In the above ratio, the general structural formula of the sulfur aromatic hydrocarbon compound is:

[0033]

[0034] In the general structural formula, R1 is located at position 1, 2, 3, 4, 5 or 6, and R2 is located at position 1, 2, 3, 4, 5 or 6. R1 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy; R2 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy.

[0035] In the above ratio, the catechol is selected from catechol, resorcinol or hydroquinone; hydroquinone is particularly preferred.

[0036] In the above ratio, the oxygen-containing acid is selected from sulfuric acid, nitric acid, salicylic acid or dithiophenecarboxylic acid; sulfuric acid is particularly preferred.

[0037] For further understanding of the present invention, the present invention is further described in detail below in conjunction with embodiments, but this should not be construed as limiting the scope of the present invention to the following embodiments.

[0038] Example 1

[0039] A soft fluxing aid for methanesulfonic acid tin plating has the following composition ratios: 10 parts of 2.5-dihydroxybenzenesulfonate calcium, 8 parts of 3-hydroxy-4-hydroxybenzenesulfonic acid, 8 parts of sulfuric acid, and 1 part of a surfactant and 1 part of hydroquinone.

[0040] The preparation method of the above-mentioned soft fluxing aid is as follows:

[0041] (1) weighing appropriate amounts of 2,5-dihydroxybenzenesulfonate calcium and 3-hydroxy-4-hydroxybenzenesulfonic acid according to a ratio and dissolving them in deionized water to prepare a solution A;

[0042] (2) Weigh an appropriate amount of concentrated sulfuric acid according to the ratio and add it to solution A to prepare solution B;

[0043] (3) Weigh a small amount of surfactant and hydroquinone and add them to solution B to prepare solution C;

[0044] (4) Solution C is heated to 55° C. and stirred continuously until the 2,5-dihydroxybenzenesulfonic acid calcium and 3-hydroxy-4-hydroxybenzenesulfonic acid are completely dissolved to obtain a flux.

[0045] Example 2

[0046] A soft fluxing aid for methanesulfonic acid tin plating has the following composition ratios: 10 parts of 4-hydroxybenzenesulfonic acid zinc salt, 10 parts of 4-hydroxybenzenesulfonic acid, 8 parts of salicylic acid, and further 1 part of a surfactant and 2 parts of catechol.

[0047] The preparation method of the above-mentioned soft fluxing aid is as follows:

[0048] (1) weighing appropriate amounts of 4-hydroxybenzenesulfonic acid zinc salt and 4-hydroxybenzenesulfonic acid according to a ratio and dissolving them in deionized water to prepare a solution A;

[0049] (2) Weigh an appropriate amount of concentrated sulfuric acid according to the ratio and add it to solution A to prepare solution B;

[0050] (3) Weigh a small amount of surfactant and hydroquinone and add them to solution B to prepare solution C;

[0051] (4) Solution C is heated to 60° C. and stirred continuously until the 4-hydroxybenzenesulfonic acid zinc salt and 4-hydroxybenzenesulfonic acid are completely dissolved to obtain a flux.

[0052] Example 3

[0053] A soft fluxing aid for methanesulfonic acid tin plating has the following composition ratios: 8 parts of sodium 2-formyl-5-hydroxybenzenesulfonate, 8 parts of 3-hydroxy-4-hydroxybenzenesulfonic acid, 10 parts of dithiophene carboxylic acid, and 3 parts of a surfactant and 1 part of resorcinol.

[0054] The preparation method of the above-mentioned soft fluxing aid is as follows:

[0055] (1) weighing appropriate amounts of sodium 2-formyl-5-hydroxybenzenesulfonate and 3-hydroxy-4-hydroxybenzenesulfonic acid according to a ratio and dissolving them in deionized water to prepare a solution A;

[0056] (2) Weigh an appropriate amount of concentrated sulfuric acid according to the ratio and add it to solution A to prepare solution B;

[0057] (3) Weigh a small amount of surfactant and hydroquinone and add them to solution B to prepare solution C;

[0058] (4) Solution C is heated to 65° C. and stirred continuously until the sodium 2-formaldehyde-5-hydroxybenzenesulfonate and the 3-hydroxy-4-hydroxybenzenesulfonic acid are completely dissolved to obtain a flux.

[0059] The soft fluxing aids obtained in Examples 1-3 can all be well adhered to the surface of the tinplate, significantly increasing the corrosion resistance of the tinplate and reducing the porosity of the surface of the tinplate.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A soft fluxing aid for methanesulfonic acid tin plating, characterized in that: The composition ratio by mass ratio is: 1 to 10 parts of sulfur-containing aromatic salt compounds, 1 to 10 parts of sulfur-containing aromatic hydrocarbon compounds, 5 to 10 parts of oxygen-containing acids, 1 to 3 parts of surfactants and 1 to 3 parts of hydroquinone.

2. The reflow aid for methanesulfonic acid tin plating according to claim 1, characterized in that: The general structural formula of the sulfur-containing aromatic salt compound is: Wherein, in the general structural formula, R1 is located at position 1, 2, 3, 4, 5 or 6, R2 is located at position 1, 2, 3, 4, 5 or 6, the sulfonate substituent is located at position 2, 3, 4, 5 or 6, and the positions of R1, R2 and the sulfonate substituent do not overlap.

3. The reflow aid for methanesulfonic acid tin plating according to claim 2, characterized in that: R1 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy; R2 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy; Y in the sulfonate substituent is selected from alkali metal ion, alkaline earth metal ion, transition metal ion or ammonium ion.

4. The reflow aid for methanesulfonic acid tin plating according to claim 1, characterized in that: The general structural formula of the sulfur aromatic hydrocarbon compound is: Wherein, in the general structural formula, R1 is located at position 1, 2, 3, 4, 5 or 6, and R2 is located at position 1, 2, 3, 4, 5 or 6.

5. The reflow aid for methanesulfonic acid tin plating according to claim 4, characterized in that: R1 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy; R2 is selected from H, carboxyl, halogen, C1-C3 alkyl, substituted C1-C3 alkyl, cyano, nitro, amino or epoxy.

6. The reflow aid for methanesulfonic acid tin plating according to claim 1, characterized in that: The catechol is selected from catechol, resorcinol or hydroquinone.

7. The reflow aid for methanesulfonic acid tin plating according to claim 1, characterized in that: The oxygen-containing acid is selected from sulfuric acid, nitric acid, salicylic acid or dithiophenecarboxylic acid.

8. A method for preparing the soft flux aid according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) weighing an appropriate amount of a sulfur-containing aromatic salt compound and a sulfur-containing aromatic hydrocarbon compound according to a ratio and dissolving them in deionized water to prepare a solution A; (2) Weighing an appropriate amount of oxygen-containing acid according to the ratio and adding it to solution A to prepare solution B; (3) Weighing an appropriate amount of surfactant and hydroquinone and adding them to solution B to prepare solution C; (4) The solution C is heated and continuously stirred until the sulfur-containing aromatic salt compound and the sulfur-containing aromatic hydrocarbon compound are completely dissolved to obtain a flux.

9. The preparation method according to claim 8, characterized in that: In step (4), the heating temperature is 55°C to 65°C.

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