Preparation and application of a green and environmentally friendly inorganic / organic composite plating solution for tinplate

Abstract

The present invention relates to the preparation and application of a green and environmentally friendly inorganic / organic composite plating solution for tinplate, and belongs to the field of food packaging. The present invention provides a method for preparing a green and environmentally friendly inorganic / organic composite plating solution for tinplate, comprising adding tetramethyl caged silane and glycidyloxypropyl cyclotetrasiloxane to anhydrous ethanol and stirring; then adding phosphoric acid and continuing to stir to react to form a clear solution A; then adding fluorotitanate, fluorozirconate, manganese acid phosphate, and methionine and slowly stirring to completely dissolve them to obtain a solution B; mixing solution A, solution B, and phosphoric acid and allowing to stand to obtain a transparent green and environmentally friendly plating solution. The present invention also provides a method for using the plating solution. The plating solution can form a nano-scale coating on the surface of the tinplate, has excellent bonding strength with polymer coatings, and is corrosion-resistant, acid-resistant, and anti-yellowing, and has excellent welding properties, meeting the application performance requirements of the tinplate.

Description

Technical Field

[0001] The invention belongs to the field of food packaging, and in particular relates to the preparation and application of a green and environmentally friendly inorganic / organic composite plating solution for tinplate. Background Art

[0002] Tinplate, commonly known as tinplate, is a corrosion-resistant material made by coating a thin, low-carbon steel plate with a protective layer of pure tin. During the tinplate production process, the surface of the tinplate, after electroplating and reflow treatment, requires a final passivation treatment. Currently, chromate passivation is the primary method used for this purpose. Typically, this chromate passivation process utilizes dichromate, or sodium dichromate. This contains the highly toxic carcinogen hexavalent chromium, which severely pollutes the environment and poses a significant health risk. The health risks of chromate passivation are particularly significant for tinplate used in the food and beverage industry, and with the increasing focus on environmental protection, it is inevitable that this process will be phased out. Therefore, adopting a green, chromium-free passivation process, replacing the chromium passivation process, has become an inevitable choice for the tinplate manufacturing industry.

[0003] In the prior art, patent CN111172524A proposes a plating solution composed of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropyloxy)propyltrimethoxysilane, ammonium dihydrogen phosphate, zinc dihydrogen phosphate, and manganese nitrate. CN102066612A contains one or more water-soluble compounds of at least one atom of elemental titanium and / or zirconium, and one or more water-soluble compounds containing at least one fluorine atom. Patent CN110373661A proposes a plating solution composed of fluorotitanate, fluorozirconate, permanganate, hydrofluoric acid, phosphate, and organosilane. Patent CN115896769A proposes a plating solution formed by reacting sodium glucoheptonic acid with L-cysteine, vitamins, zirconium oxychloride, chitosan, organic carboxylic acid, and ferric nitrate. Patent CN1416478A proposes a chemical solution containing phosphate ions, tin ions, and an epoxy silane coupling agent, which achieves excellent coating adhesion, corrosion resistance, and processability through impregnation or electrolysis. Patent CN115261842A proposes a system consisting of a water-based epoxy resin, an organic corrosion inhibitor, nanoparticles, and a water-based organic cosolvent to meet corrosion resistance and other requirements. Summary of the Invention

[0004] The present invention aims to provide a method for preparing and using a green, environmentally friendly inorganic / organic composite plating solution for tinplate. This solution can produce a coating with excellent corrosion resistance, excellent adhesion to polymer coatings, acid resistance, yellowing resistance, and excellent weldability, meeting the application performance requirements of tinplate. The specific technical solution is as follows:

[0005] The invention provides a green and environmentally friendly inorganic / organic composite plating solution for tinplates. The green and environmentally friendly inorganic / organic composite plating solution for tinplates consists of tetramethylsilane, glycidyloxypropylcyclotetrasiloxane, fluorotitanate, fluorozirconate, manganese acid phosphate, methionine and phosphoric acid.

[0006] A method for preparing a green and environmentally friendly inorganic / organic composite plating solution for tinplate comprises the following steps:

[0007] Step 1: Tetramethylsilane and glycidyloxypropyl cyclotetrasiloxane are added to a solvent and mechanically stirred until uniformly mixed, and then phosphoric acid is added and slowly stirred to obtain solution A;

[0008] Step 2: Add fluorotitanate, fluorozirconate, manganese acid phosphate, and methionine to deionized water and slowly stir to fully dissolve them to obtain solution B;

[0009] Step 3: Add solution B and phosphoric acid obtained in step 2 to solution A obtained in step 1, stir and allow to stand to obtain a transparent green and environmentally friendly plating solution;

[0010] The green and environmentally friendly inorganic / organic composite plating solution can form a nano-scale coating on the surface of tinplate, which is the main raw material for making food cans and beverage cans;

[0011] Furthermore, in step 1, the tetramethylsilane is tetramethylsilane containing a cage structure, the glycidyloxypropylcyclotetrasiloxane is a propylsilane containing four epoxy groups, the solvent is anhydrous ethanol, and the phosphoric acid is a 1 mol / L aqueous solution;

[0012] Furthermore, in step 1, the stirring time is 60 to 120 minutes;

[0013] Furthermore, in step 1, the volume ratio of tetramethylsilane to glycidyloxypropylcyclotetrasiloxane is 1:(1-1.1), the volume ratio of tetramethylsilane to anhydrous ethanol is (0.03-0.08):1, and the volume of added phosphoric acid is 3%-6% of the tetramethylsilane.

[0014] Furthermore, in step 2, in solution B, the concentration of fluorotitanate is 0.2-0.5 g / L, the concentration of fluorozirconic acid is 0.1-0.5 g / L, the concentration of manganese acid phosphate is 0.5-1 g / L, and the concentration of methionine is 0.03-0.1 g / L;

[0015] Furthermore, in step 3, the volume ratio of solution A to solution B is 1:(1-1.5), and the volume ratio of solution A to phosphoric acid is 1:(0.3-0.8);

[0016] Furthermore, in step 3, the standing time is 12 to 24 hours.

[0017] The present invention also provides a method for using the green and environmentally friendly inorganic / organic composite plating solution for tinplate, comprising the following steps:

[0018] (1) preparing a working solution of a green and environmentally friendly inorganic / organic composite plating solution for tinplate using deionized water and a green and environmentally friendly inorganic / organic composite plating solution for tinplate;

[0019] (2) using a pressure atomizing nozzle or a siphon atomizing nozzle to evenly apply the working liquid of the green and environmentally friendly inorganic / organic composite plating solution to the surface of the tinplate, and then using a metal roller coating device to homogenize the surface droplets to obtain a continuous and uniform coating;

[0020] (3) The tinplate is heated to cause the liquid film to react with the tin layer and solidify to obtain a tinplate coating.

[0021] Furthermore, in step (1), the volume ratio of the deionized water to the green and environmentally friendly plating solution is 20:(1-8);

[0022] Furthermore, in step (3), the heating method is any one or a combination of hot air, infrared and electromagnetic induction; the heating temperature is 90-140°C, and the obtained tinplate coating weight is 2-18 mg / m 2 .

[0023] Beneficial effects of the present invention:

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The green and environmentally friendly inorganic / organic composite plating solution for tinplate prepared by the method of the present invention has a cross-linked and dense network film skeleton structure formed by organic silane and titanium salt zirconium salt, has high density on the surface of the tinplate and has good corrosion protection effect; phosphoric acid is used as a pH value regulator and can also increase the phosphorus content in the chromium-free plating solution, which is beneficial to improving the corrosion resistance and antioxidant properties of the chromium-free passivated tinplate; acidic manganese phosphate is used as an oxidant to accelerate the film formation process and improve the passivation efficiency; methionine contains hydroxyl, thiol and amino groups that can react and chelate with the carbon chain structure to chelate titanium and zirconium ions in the plating solution.

[0026] The green and environmentally friendly inorganic / organic composite plating solution for tinplate prepared by the method of the present invention is green, safe and environmentally friendly, uses water as the main medium, does not contain toxic and harmful organic solvent components, and solves the technical problem of chromium-containing in existing chromate plating solutions through chromium-free passivation. It meets the special packaging requirements of tinplate, reduces the burden of wastewater treatment and environmental pollution, and meets the requirements of RoHS and REACH directives.

[0027] The green and environmentally friendly inorganic / organic composite plating solution for tinplate prepared by the method of the present invention can form a nano-level passivation film on the surface of the tinplate, and has little effect on the performance of the tin layer on the surface of the tinplate;

[0028] The chromium-free passivated tinplate prepared by the method of the present invention using a green and environmentally friendly inorganic / organic composite plating solution has a salt spray resistance grade, porosity, acid resistance and adhesion that reach or exceed the level of tinplate produced by the chromate passivation process.

[0029] The tinplate prepared by the method described in the present invention is passivated using a green and environmentally friendly inorganic / organic composite plating solution, eliminating the need for electrolytic passivation and directly employing atomization and roller coating. Compared to electrolytic passivation, this process significantly saves energy, is easy to control, produces no wastewater, and is environmentally friendly. Compared to dipping or spraying methods, this method offers advantages in controlling film thickness and uniformity. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to specific implementation cases, but the present invention is not limited to these embodiments.

[0031] Commercially available analytically pure tetramethyl caged silane, glycidyl ether oxypropyl cyclotetrasiloxane, fluorotitanate, fluorozirconate, manganese acid phosphate, methionine and phosphoric acid are selected for preparation.

[0032] Example 1

[0033] Preparation of green and environmentally friendly inorganic / organic composite plating solution for tinplate:

[0034] 800 μL of tetramethyl caged silane and 800 μL of glycidyloxypropyl cyclotetrasiloxane were pipetted into 16.8 g of anhydrous ethanol and mechanically stirred for 10 min to form a uniform mixed solution. The pH was adjusted with 30 μL of 1 mol / L H3PO4 and the reaction was continued for 1 h to obtain a colorless and transparent solution A.

[0035] Solution B was composed of: 0.3 g fluorotitanate, 0.1 g fluorozirconate, 0.5 g manganese acid phosphate, 0.05 g methionine, and 1 L deionized water;

[0036] 4 mL of solution A, 4 mL of solution B, and 2.0 mL of 1 mol / L H3PO4 were mixed evenly and allowed to stand for 12 h to obtain a green and environmentally friendly inorganic / organic composite plating solution.

[0037] The method for passivating a tinplate steel sheet using the green and environmentally friendly inorganic / organic composite plating solution for tinplate comprises the following steps:

[0038] (1) diluting the green and environmentally friendly inorganic / organic composite plating solution with deionized water at a volume ratio of 6% and allowing it to stand for 12 hours to obtain a working solution of the green and environmentally friendly inorganic / organic composite plating solution for tinplate;

[0039] (2) Using an atomizing nozzle device to evenly disperse the droplets of the working liquid onto the surface of the tinplate, and then using a roller coating device to homogenize the droplets to obtain a continuous and uniform liquid film;

[0040] (3) The tinplate is heated by hot air to obtain a plate temperature (PMT = 125°C), so that the liquid film reacts with the tin layer and solidifies to obtain a coating; the obtained coating weight is 10 mg / m 2 .

[0041] The above treatment can form a colorless coating on the surface of the tinplate in this embodiment. According to QB / T2763-2006 "Coated Tin (Chromium) Thin Steel Sheet" for adhesion test, the adhesion is excellent; according to ISV (GB / T22316 Test Method for Corrosion Resistance of Electroplated Tin Steel Sheet), the corrosion resistance reaches the level of chromium film; the acid resistance test (3% acetic acid solution, 121°C × 60min) shows that the coating has no bubbles, no peeling, no discoloration, and no whitening; the yellowing resistance test (hot air drying oven, 200°C × 20min) shows that there is no yellowing after iron printing and coating baking, and other excellent comprehensive performance.

[0042] Example 2

[0043] Preparation of green and environmentally friendly inorganic / organic composite plating solution for tinplate:

[0044] 680 μL of tetramethyl caged silane and 680 μL of glycidyloxypropyl cyclotetrasiloxane were pipetted into 15.2 g of anhydrous ethanol and mechanically stirred for 10 min to form a uniform mixed solution. The pH was adjusted with 30 μL of 1 mol / L H3PO4 and the reaction was continued for 40 min to obtain a colorless and transparent solution A.

[0045] The composition of solution B is: 0.3 g of fluorotitanate, 0.4 g of fluorozirconate, 0.5 g of manganese acid phosphate, 0.06 g of methionine, and 1 L of deionized water.

[0046] 4 mL of solution A, 4 mL of solution B, and 1.5 mL of 1 mol / L H3PO4 were mixed evenly and allowed to stand for 12 h to obtain a green and environmentally friendly inorganic / organic composite plating solution.

[0047] The method for passivating a tinplate steel sheet using the green and environmentally friendly inorganic / organic composite plating solution for tinplate comprises the following steps:

[0048] (1) diluting the green and environmentally friendly inorganic / organic composite plating solution for tinplate with deionized water at a volume ratio of 7% and allowing to stand for 12 hours to obtain a working solution of the green and environmentally friendly inorganic / organic composite plating solution for tinplate;

[0049] (2) Using an atomizing nozzle device to evenly disperse the droplets of the working liquid onto the surface of the tinplate, and then using a roller coating device to homogenize the droplets to obtain a continuous and uniform liquid film;

[0050] (3) The tinplate is heated by hot air to obtain a plate temperature (PMT = 140°C), so that the liquid film reacts with the tin layer and solidifies to obtain a coating; the obtained coating weight is 9 mg / m 2 .

[0051] The above treatment can form a colorless coating on the surface of the tinplate in this embodiment. According to QB / T2763-2006 "Coated Tin (Chromium) Thin Steel Sheet" for adhesion test, the adhesion is excellent; according to ISV (GB / T22316 Test Method for Corrosion Resistance of Electroplated Tin Steel Sheet), the corrosion resistance reaches the level of chromium film; the acid resistance test (3% acetic acid solution, 121°C × 60min) shows that the coating has no bubbles, no peeling, no discoloration, and no whitening; the yellowing resistance test (hot air drying oven, 200°C × 20min) shows that there is no yellowing after iron printing and coating baking, and other excellent comprehensive performance.

[0052] Example 3

[0053] Preparation of green and environmentally friendly inorganic / organic composite plating solution for tinplate:

[0054] 940 μL of tetramethyl caged silane and 940 μL of glycidyloxypropyl cyclotetrasiloxane were pipetted into 19.0 g of anhydrous ethanol and mechanically stirred for 10 min to form a uniform mixed solution. The pH was adjusted with 30 μL of 1 mol / L H3PO4 and the reaction was continued for 1.5 h to obtain a colorless and transparent solution A.

[0055] The composition of solution B is: 0.3 g of fluorotitanate, 0.4 g of fluorozirconate, 0.6 g of manganese acid phosphate, 0.04 g of methionine, and 1 L of deionized water.

[0056] 4 mL of solution A, 4 mL of solution B, and 3.0 mL of 1 mol / L H3PO4 were mixed evenly and allowed to stand for 12 h to obtain a green and environmentally friendly inorganic / organic composite plating solution.

[0057] The method for passivating a tin-plated steel sheet using the green and environmentally friendly inorganic / organic composite plating solution comprises the following steps:

[0058] (1) diluting the green and environmentally friendly inorganic / organic composite plating solution with deionized water at a volume ratio of 9% and allowing it to stand for 12 hours to obtain a working solution of the green and environmentally friendly inorganic / organic composite plating solution for tinplate;

[0059] (2) Using an atomizing nozzle device to evenly disperse the droplets of the working liquid onto the surface of the tinplate, and then using a roller coating device to homogenize the droplets to obtain a continuous and uniform liquid film;

[0060] (3) The tinplate is heated by hot air to obtain a plate temperature (PMT = 145°C), so that the liquid film reacts with the tin layer and solidifies to obtain a coating; the obtained coating weight is 12 mg / m 2 .

[0061] The above treatment can form a colorless coating on the surface of the tinplate in this embodiment. According to QB / T2763-2006 "Coated Tin (Chromium) Thin Steel Sheet" for adhesion test, the adhesion is excellent; according to ISV (GB / T22316 Test Method for Corrosion Resistance of Electroplated Tin Steel Sheet), the corrosion resistance reaches the level of chromium film; the acid resistance test (3% acetic acid solution, 121°C × 60min) shows that the coating has no bubbles, no peeling, no discoloration, and no whitening; the yellowing resistance test (hot air drying oven, 200°C × 20min) shows that there is no yellowing after iron printing and coating baking, and other excellent comprehensive performance.

[0062] Table 1 Performance parameters of tinned steel sheets after passivation treatment according to the present invention

[0063] index Salt tolerance grade / level Acid-resistant / grade Adhesion / Grade Example 1 1 1 1 Example 2 1 1 1 Example 3 1 1 1 .

Claims

1. A method for preparing a green and environmentally friendly inorganic / organic composite plating solution for tinplate, characterized in that: The following steps are included: Step 1: Tetramethylsilane and glycidyloxypropyl cyclotetrasiloxane are added to a solvent and mechanically stirred until uniformly mixed, and then phosphoric acid is added and slowly stirred to obtain solution A; Step 2: Add fluorotitanate, fluorozirconate, manganese acid phosphate, and methionine to deionized water and slowly stir to fully dissolve them to obtain solution B; Step 3: Add solution B and phosphoric acid obtained in step 2 to solution A obtained in step 1, stir and let stand to obtain a transparent green and environmentally friendly plating solution.

2. The method for preparing the green and environmentally friendly inorganic / organic composite plating solution for tinplate according to claim 1, characterized in that: In the step 1, the tetramethylsilane is tetramethylsilane containing a cage structure, the glycidyloxypropylcyclotetrasiloxane is propylsilane containing four epoxy groups, the solvent is anhydrous ethanol, and the phosphoric acid is a 1 mol / L aqueous solution.

3. The method for preparing the green and environmentally friendly inorganic / organic composite plating solution for tinplate according to claim 2, characterized in that: The volume ratio of tetramethylsilane to glycidyloxypropylcyclotetrasiloxane is 1:(1-1.1), the volume ratio of tetramethylsilane to anhydrous ethanol is (0.03-0.08):1, and the volume of added phosphoric acid is 3%-6% of the tetramethylsilane.

4. The method for preparing the green and environmentally friendly inorganic / organic composite plating solution for tinplate according to claim 1, characterized in that: In step 2, in the solution B, the concentration of fluorotitanate is 0.2-0.5 g / L, the concentration of fluorozirconic acid is 0.1-0.5 g / L, the concentration of manganese acid phosphate is 0.5-1 g / L, and the concentration of methionine is 0.03-0.1 g / L.

5. The method for preparing the green and environmentally friendly inorganic / organic composite plating solution for tinplate according to claim 1, characterized in that: In step 3, the volume ratio of solution A to solution B is 1:(1-1.5), and the volume ratio of solution A to phosphoric acid is 1:(0.3-0.8).

6. The method for preparing the green and environmentally friendly inorganic / organic composite plating solution for tinplate according to claim 1, characterized in that: In step 3, the standing time is 12 to 24 hours.

7. A method for using a green and environmentally friendly inorganic / organic composite plating solution for tinplate, characterized in that: The green and environmentally friendly inorganic / organic composite plating solution for tinplate is prepared by the method for preparing the green and environmentally friendly inorganic / organic composite plating solution for tinplate according to claim 1, comprising the following steps: A working solution of a green and environmentally friendly inorganic / organic composite plating solution for tinplate is prepared by using deionized water and a green and environmentally friendly inorganic / organic composite plating solution for tinplate; Use a pressure atomizing nozzle or a siphon atomizing nozzle to evenly apply the working liquid of the green and environmentally friendly inorganic / organic composite plating solution to the surface of the tinplate, and then use a metal roller coating device to homogenize the surface droplets to obtain a continuous and uniform coating; The tinplate is heated to cause the liquid film to react with the tin layer and solidify to obtain the tinplate coating.

8. The method of use according to claim 7, characterized in that: In step (1), the volume ratio of the deionized water to the green and environmentally friendly plating solution is 20:(1-8).

9. The method of use according to claim 7, characterized in that: In step (3), the heating method is any one or a combination of hot air, infrared and electromagnetic induction; the heating temperature is 90~140℃, and the obtained tinplate coating weight is 2~18 mg / m 2 .