Aluminum ring-pull can cover material passivating agent for water-based paint and preparation method of aluminum ring-pull can cover material passivating agent

Abstract

The invention provides an aluminum ring-pull can cover material passivating agent for water-based paint. The aluminum ring-pull can cover material passivating agent is prepared from the following raw materials in percentage by weight: 0.5-5% of a chromium source, 1-5% of a reducing agent, 1.5-6% of a film-forming agent, 1-5% of a silane coupling agent and the balance of deionized water. The invention is applied to water-based paint, the dyne value of a passive film is increased, a surface on which the water-based paint can be quickly wetted and spread is provided, the stability of a passivated film-forming structure is improved, and the abnormal coating performance of the water-based paint caused by the unstable structure of the passive film in the long-term use process is avoided. And the compactness and wear resistance of a passivation film are improved, and the problem that after passivation treatment, a passivation layer is damaged and abraded after the aluminum plate strip passes through a conveying roller and a steering roller is solved. Meanwhile, the passivation film-forming temperature is reduced, and it is guaranteed that a compact passivation film is rapidly formed under the condition that an existing technology is changed and energy consumption is not increased through passivation.

Description

Technical Field

[0001] The invention relates to the field of C09D coating compositions, and in particular to a passivating agent for aluminum can cover materials used for water-based coatings and a preparation method thereof. Background Art

[0002] Aluminum can lids are widely used in the beverage packaging industry. In the manufacturing process of aluminum can lids, aluminum strips are first subjected to surface treatment by coil coating before being stamped and formed. The surface treatment includes cleaning, passivation and coating processes to prevent chemical reactions between the aluminum can lids and beverages or the external environment, and to improve the corrosion resistance and food safety of the aluminum can lids. In order to improve the environmental protection and health of the coating, coatings are increasingly tending to use water-based coatings, which have higher requirements on the surface tension of the substrate to ensure the wettability, spreadability and adsorption of the water-based coating on the surface of the substrate. The passivation film, as a surface in direct contact with the water-based coating, needs to have a higher surface tension. Therefore, it is crucial to develop a high surface tension, corrosion-resistant, and boiling-resistant passivating agent film for use in water-based coatings.

[0003] Chinese invention patent CN201610784509.9 discloses a water-based paint for magnesium-aluminum alloy, a water-based coating for magnesium-aluminum alloy and a preparation method. The passivator is applied to the water-based paint, and through the synergistic effect between the resins and additives in the primer and the topcoat, the primer has the function of not reacting with the magnesium-aluminum alloy material to produce bubbles and has good adhesion, and has the function of adding color and good wetting and dispersibility, but it cannot achieve the effect of boiling water resistance. Chinese invention patent CN202011238138.7 discloses a chemically bonded metal anticorrosive water-based paint and a preparation method thereof. The phosphorus-containing group of the paint can further chemically bond with the metal matrix, thereby having higher anticorrosion performance, resistance to organic solvents, and good corrosion resistance, but the raw materials for the preparation contain certain toxicity and are not suitable for use in beverage packaging. Summary of the invention

[0004] In order to develop a high surface tension, corrosion-resistant, and boiling-resistant passivator for use in water-based coatings, the first aspect of the present invention provides an aluminum can cover material passivator for water-based coatings, and the preparation raw materials include, by weight percentage, 0.5-5% of a chromium source, 1-10% of a reducing agent, 1.5-6% of a film-forming agent, 1-5% of a silane coupling agent, and deionized water is supplemented to 100%.

[0005] As a preferred embodiment, the raw materials for preparation include, by weight percentage, 1.5-4.8% of chromium source, 3.2-8% of reducing agent, 2.7-5.8% of film-forming agent, 1.3-5% of silane coupling agent, and deionized water is added to 100%.

[0006] As a preferred embodiment, the chromium source is selected from at least one of chromic anhydride, chromium trioxide, chromium peroxide, and chromous oxide.

[0007] As a preferred embodiment, the chromium source is chromic anhydride.

[0008] The applicant used chromic anhydride as a chromium source and tartaric acid as a reducing agent during the experiment, and chromic anhydride can be directly reduced to trivalent chromium, which is applied to water-based coatings containing bisphenol A. The leveling speed is slow, the spreading effect is good, and the adhesion is improved while the leveling effect is improved. It is speculated that the possible reason is: chromic anhydride can be directly reduced to trivalent chromium, with less impurities, which improves the structural stability of water-based coatings and is not easy to produce precipitation. And when used in combination with tartaric acid, the redox reaction is gentle, and carbon dioxide is generated after the redox reaction, and no new impurities are introduced, which further ensures the stability of the passivation film structure. And the antioxidant property of tartaric acid can prevent trivalent chromium from being converted into hexavalent chromium during use, and it is safe to use in food packaging. The weight ratio of chromic anhydride and tartaric acid (0.5-5): (1-5) can effectively ensure the thickness of the passivation film is stable, so that the surface tension of the passivation film can be stabilized at a higher value.

[0009] As a preferred embodiment, the reducing agent is selected from at least one of tartaric acid, sodium sulfite, ferrous sulfate, potassium borohydride, lithium aluminum tetrahydride, and sodium borohydride.

[0010] As a preferred embodiment, the reducing agent is tartaric acid.

[0011] As a preferred embodiment, the film-forming agent includes organic phosphoric acid and inorganic zirconic acid, and the weight ratio of the organic phosphoric acid to the inorganic zirconic acid is (0.5-3): (1-3).

[0012] As a preferred embodiment, the weight ratio of the organic phosphoric acid to the inorganic zirconic acid is (0.5-2.8):(2.2-3).

[0013] As a preferred embodiment, the organic phosphate is inositol phosphate, and the inositol phosphate is selected from at least one of inositol diphosphate, inositol triphosphate, inositol tetraphosphate, inositol pentaphosphate and inositol hexaphosphate.

[0014] As a preferred embodiment, the organic phosphate is inositol hexaphosphate (phytic acid).

[0015] As a preferred embodiment, the inorganic zirconic acid is selected from at least one of fluorozirconic acid, chlorozirconic acid, zirconium carbonate, zirconium phosphate and zirconium nitrate.

[0016] As a preferred embodiment, the inorganic zirconic acid is fluorozirconic acid.

[0017] As a preferred embodiment, the silane coupling agent is a vinyl silane coupling agent, and the vinyl silane coupling agent is at least one selected from vinyl trimethoxy silane, vinyl triethoxy silane, and vinyl tri (β-methoxyethoxy) silane.

[0018] As a preferred embodiment, the silane coupling agent is vinyltrimethoxysilane.

[0019] The applicant found during the experiment that the use of phytic acid and fluorozirconic acid as film-forming agents can improve the adhesion of the passivation film to the metal, have a high coating adhesion during use, and the passivation film has a dense structure and good wear resistance. The possible reason is guessed to be: phytic acid and trivalent chromium synergistically improve the compactness and corrosion resistance of the passivation film, and contain rich polar groups to improve the coating adhesion of water-based paint. Phytic acid and tartaric acid can also prevent the passivator from polymerizing and precipitating during storage, prevent the aluminum ions dissolved by trivalent chromium from precipitating during use, and reduce the impact of impurities. The applicant further found that phytic acid and vinyl trimethoxysilane use a weight ratio of (0.5-3): (1-5), which can improve the wear resistance of the passivation film, prevent the stretching during the friction process of the aluminum belt transmission, and avoid the loose structure of the passivation film after stretching, and the generation of gaps will reduce the wetting and spreading effect of the water-based paint. The reason may be that the molecular chain toughness of the passivator is better at the preferred weight ratio of phytic acid and vinyltrimethoxysilane, and the adhesion to the aluminum strip is stronger, which can prevent the aluminum strip from being rubbed off by the transmission roller during the transmission process after passivation.

[0020] The applicant found in the experiment that the use of fluorozirconic acid and phytic acid as film-forming agents, in combination with vinyl trimethoxysilane, can increase the film-forming speed of the passivation film, enhance the water vapor erosion resistance of the passivation film, and improve the high-temperature boiling and acid boiling resistance of the can cover material. The possible reason is that fluorozirconic acid and vinyl trimethoxysilane work together to reduce the film-forming and curing temperature during the film-forming and drying process, accelerate film formation, and cure the film in 1 second at a plate temperature of 60°C. And under the action of fluorozirconic acid, a nano-scale passivation film can be formed to repair the gaps not covered by the trivalent chromium passivation film, so that the water-based paint can quickly penetrate into the surface gaps of the aluminum plate strip, improve the adhesion of the water-based paint, and thus tightly seal the surface of the aluminum plate strip to achieve the effects of water vapor erosion resistance, water boiling resistance, and acid boiling resistance.

[0021] In the existing process, the temperature of the drying board after passivation is generally maintained at about 60-65°C. At this temperature, the moisture in the passivation liquid coated on the board surface is not actually completely evaporated, and the passivation film is not dense enough, which makes the passivation more easily destroyed during the transmission process or even rubbed off by the transmission roller or steering. In addition, due to the limitations of current drying process equipment, site space and production line speed, the board temperature cannot be increased by extending the baking time. The only way is to increase the baking furnace temperature by consuming a large amount of energy. Raising the board temperature to 75-80°C ensures the density of the passivation film. The passivator of the present application lowers the film forming temperature and reduces the process energy consumption.

[0022] The second aspect of the present invention provides a method for preparing a passivating agent for aluminum can cover material for water-based coatings, comprising the following steps:

[0023] S1: dissolving 50 wt% of inorganic zirconic acid in deionized water, controlling the amount of deionized water added to make the pH value 3-3.5, controlling the temperature, starting stirring, adding a silane coupling agent during stirring, continuing stirring for 3-9 hours, cooling to room temperature, and obtaining a mixed solution I for use;

[0024] S2: dissolving 50 wt% of inorganic zirconic acid in 20 wt% of deionized water, adding organic phosphoric acid, and stirring evenly to obtain a mixed solution II;

[0025] S3: adding chromium source to mixed solution II and stirring evenly until the chromium source is dissolved;

[0026] S4, adding a reducing agent to the solution in step S3 while stirring until the solution is completely reduced to trivalent chromium, and cooling to room temperature;

[0027] S5: adding the mixed solution I to the solution in step S4 and stirring evenly;

[0028] S6 Add the remaining deionized water and stir well.

[0029] As a preferred embodiment, the stirring temperature in step S1 is 10-15° C., and the stirring speed is 200-400 r / min.

[0030] The applicant found during the experiment that the reaction can be smoothly carried out only by controlling the stirring temperature. When the temperature is too high and the stirring speed is too fast, the hydrolysis of the silane coupling agent will be too violent, which will cause production danger. When the temperature is too low and the stirring speed is too slow, the hydrolysis speed will be too slow, which will prolong the reaction time and reduce the efficiency.

[0031] As a preferred embodiment, the temperature when the reducing agent is added in step S4 is 38-42°C, the addition is stopped after the temperature reaches 45-48°C, and the stirring speed is 300-500r / min.

[0032] As a preferred embodiment, the temperature of the reducing agent when added in step S4 is 40°C, and the addition is stopped after the temperature reaches 45°C, and the stirring speed is 400r / min.

[0033] The applicant found during the experiment that when the reaction temperature exceeds 45°C, the reaction is too intense and bubbling and spraying are likely to occur. However, when the reaction temperature is too low, the chromic anhydride reduction rate is slow, which will increase the amount of tartaric acid used.

[0034] As a preferred embodiment, in step S4, a diphenylcarbazide solution is used to detect whether the hexavalent chromium is completely reduced to trivalent chromium.

[0035] As a preferred embodiment, in step S5, the stirring speed is 600-700 r / min, and the stirring time is greater than 15 min. In step S6, the stirring time is greater than 15 min.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The aluminum can cover material passivator for water-based coatings of the present invention adopts chromic anhydride as a chromium source and tartaric acid as a reducing agent to form a passivation film with a stable structure, avoid the introduction of impurities, do not produce hexavalent chromium, and is safe to use. In addition, the passivation film has a high thickness and strong corrosion resistance.

[0038] (2) The aluminum can cover material passivator for water-based paint of the present invention comprises phytic acid and fluorozirconic acid as film-forming agents, vinyltrimethoxysilane as silane coupling agent, and phytic acid and silane coupling agent in a weight ratio of (0.5-3): (1-5), thereby improving the adhesion between the passivation film and the metal, having a high coating adhesion during use, and having a dense passivation film structure and good wear resistance.

[0039] (3) In the aluminum can cover material passivator for water-based coatings described in the present invention, the weight ratio of fluorozirconic acid to silane coupling agent is (1-3): (1-5), which increases the film-forming speed of the passivation film, enhances the water vapor corrosion resistance of the passivation film, and improves the high-temperature water boiling and high-temperature acid boiling resistance of the can cover material.

[0040] (4) The aluminum can cover material passivator for water-based paint described in the present invention is applied to water-based paint to increase the dyne value of the passivation film, provide a surface that the water-based paint can quickly wet and spread, and improve the stability of the passivation film structure, thereby avoiding abnormal performance of the water-based paint coating caused by the unstable passivation film structure during long-term use.

[0041] (5) The passivating agent for aluminum can cover material for water-based coatings described in the present invention improves the compactness and wear resistance of the passivation film, and solves the problem that the passivation layer is damaged and worn after the aluminum strip passes through the transmission roller and the steering roller after the passivation treatment.

[0042] (6) The passivating agent for aluminum can lids used for water-based coatings of the present invention reduces the passivation film-forming temperature and ensures that a dense passivation film is quickly formed without changing the existing process and increasing energy consumption. DETAILED DESCRIPTION

[0043] Example 1

[0044] A passivating agent for aluminum can lids used for water-based coatings, the raw materials for preparation are shown in Table 1 by weight percentage:

[0045] Table 1

[0046]

[0047] A method for preparing a passivating agent for aluminum can cover material for water-based coatings comprises the following steps:

[0048] S1: dissolving 50 wt% of inorganic zirconic acid in deionized water, controlling the amount of deionized water added to make the pH value 3-3.5, controlling the temperature, starting stirring, adding silane coupling agent during stirring, continuing stirring for 6 hours, cooling to room temperature, and obtaining mixed solution I for use;

[0049] S2: dissolving 50 wt% of inorganic zirconic acid in 20 wt% of deionized water, adding organic phosphoric acid, and stirring evenly to obtain a mixed solution II;

[0050] S3: adding chromium source to mixed solution II and stirring evenly until the chromium source is dissolved;

[0051] S4, adding a reducing agent to the solution in step S3 while stirring until the solution is completely reduced to trivalent chromium, and cooling to room temperature;

[0052] S5: adding the mixed solution I to the solution in step S4 and stirring evenly;

[0053] S6 Add the remaining deionized water and stir well.

[0054] The stirring temperature in step S1 is 12.5° C. and the stirring speed is 300 r / min.

[0055] The temperature of the reducing agent when added in step S4 is 40° C., and the addition is stopped after the temperature reaches 45° C., and the stirring speed is 400 r / min.

[0056] Comparative Example 1

[0057] A passivating agent for aluminum can lids used for water-based coatings, the raw materials for preparation are shown in Table 2 by weight percentage:

[0058] Table 2

[0059]

[0060]

[0061] A method for preparing a passivating agent for aluminum can cover material for water-based coatings comprises the following steps:

[0062] S1: dissolving 50 wt% of inorganic zirconic acid in deionized water, controlling the amount of deionized water added to make the pH value 3-3.5, controlling the temperature, starting stirring, adding silane coupling agent during stirring, continuing stirring for 6 hours, cooling to room temperature, and obtaining mixed solution I for use;

[0063] S2: dissolving 50 wt% of inorganic zirconic acid in 20 wt% of deionized water, adding organic phosphoric acid, and stirring evenly to obtain a mixed solution II;

[0064] S3: adding chromium source to mixed solution II and stirring evenly until the chromium source is dissolved;

[0065] S4, adding a reducing agent to the solution in step S3 while stirring until the solution is completely reduced to trivalent chromium, and cooling to room temperature;

[0066] S5: adding the mixed solution I to the solution in step S4 and stirring evenly;

[0067] S6 Add the remaining deionized water and stir well.

[0068] The stirring temperature in step S1 is 12.5° C. and the stirring speed is 300 r / min.

[0069] The temperature of the reducing agent when added in step S4 is 40° C., and the addition is stopped after the temperature reaches 45° C., and the stirring speed is 400 r / min.

[0070] Performance Testing

[0071] The passivating agent prepared in the embodiment and the comparative example was diluted 5 times with deionized water, and then roller-coated on the can lid, dried at a plate temperature of 60°C to obtain a passivation film, and then rubbed 60 times with a 10kg-loaded polyurethane rubber roller, with no change. Then, the inside was coated with a special water-based epoxy interior coating (13Q80AG) for Valspar can lid material, and coated with an RDS#12 wire rod, with a curing temperature (PMT) of 241°C and a coating weight of 8 to 10 g / m 2 .

[0072] The test was conducted according to the internal coating requirements of "YS / T726-2010 Aluminum Alloy Sheet and Strip for Can Cover and Ring Pull Materials". The test results are shown in Table 3.

[0073] High temperature sterilization at 121℃, distillation for 30min, the coating is qualified without whitening, gloss loss, peeling or falling off; acid resistance at 121℃, acid etching for 32min, the coating is qualified without whitening, gloss loss, peeling or falling off; sulfur resistance at 121℃, sulfur etching for 31min, the coating is qualified without whitening, gloss loss, peeling or falling off; adhesion level 1 (no peeling or falling off in the 100-grid test of the coating) is qualified.

[0074] Table 3

[0075]

Claims

1. A passivating agent for aluminum can cover material for water-based coating, characterized in that: The raw materials for preparation include 0.5-5% of chromium source, 1-10% of reducing agent, 1.5-6% of film-forming agent, 1-5% of silane coupling agent in weight percentage, and deionized water is added to 100%.

2. The passivating agent for aluminum can cover material for water-based coating according to claim 1, characterized in that: The chromium source is selected from at least one of chromic anhydride, chromium trioxide, chromium peroxide and chromous oxide.

3. The passivating agent for aluminum can cover material for water-based coating according to claim 1, characterized in that: The reducing agent is selected from at least one of tartaric acid, sodium sulfite, ferrous sulfate, potassium borohydride, lithium aluminum tetrahydride, and sodium borohydride.

4. The passivating agent for aluminum can cover material for water-based coating according to claim 1, characterized in that: The film-forming agent comprises organic phosphoric acid and inorganic zirconic acid, and the weight ratio of the organic phosphoric acid to the inorganic zirconic acid is (0.5-3):(1-3).

5. The passivating agent for aluminum can cover material for water-based coating according to claim 4, characterized in that: The organic phosphate is inositol phosphate, and the inositol phosphate is selected from at least one of inositol diphosphate, inositol triphosphate, inositol tetraphosphate, inositol pentaphosphate, and inositol hexaphosphate.

6. The passivating agent for aluminum can cover material for water-based paint according to claim 4, characterized in that: The inorganic zirconic acid is selected from at least one of fluorozirconic acid, chlorozirconic acid, zirconium carbonate, zirconium phosphate and zirconium nitrate.

7. The passivating agent for aluminum can cover material for water-based coating according to claim 4, characterized in that: The silane coupling agent is a vinyl silane coupling agent, and the vinyl silane coupling agent is at least one selected from vinyl trimethoxy silane, vinyl triethoxy silane, and vinyl tri (β-methoxyethoxy) silane.

8. A method for preparing a passivating agent for aluminum can cover material for water-based coating according to any one of claims 4 to 7, characterized in that: The following steps are involved: S1: dissolving 50 wt% of inorganic zirconic acid in deionized water, controlling the amount of deionized water added to make the pH value 3-3.5, controlling the temperature, starting stirring, adding a silane coupling agent during stirring, continuing stirring for 3-9 hours, cooling to room temperature, and obtaining a mixed solution I for use; S2: dissolving 50 wt% of inorganic zirconic acid in 20 wt% of deionized water, adding organic phosphoric acid, and stirring evenly to obtain a mixed solution II; S3: adding chromium source to mixed solution II and stirring evenly until the chromium source is dissolved; S4, adding a reducing agent to the solution in step S3 while stirring until the solution is completely reduced to trivalent chromium, and cooling to room temperature; S5: adding the mixed solution I to the solution in step S4 and stirring evenly; S6 Add the remaining deionized water and stir well.

9. The method for preparing a passivating agent for aluminum can cover material for water-based coating according to claim 8, characterized in that: The stirring temperature in step S1 is 10-15° C., and the stirring speed is 200-400 r / min.

10. The method for preparing a passivating agent for aluminum can cover material for water-based coating according to claim 8, characterized in that: The temperature when the reducing agent is added in step S4 is 38-42° C., and the addition is stopped after the temperature reaches 45-48° C., and the stirring speed is 300-500 r / min.

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