An aluminum silver paste and its preparation method

Abstract

This application belongs to the field of metallic pigment technology, and particularly relates to an aluminum silver paste and its preparation method. The preparation method of this application is as follows: methyl methacrylate, a crosslinking agent, and an oil-soluble initiator are mixed and dissolved to obtain a polymethyl methacrylate solution; an oil-based aluminum silver paste and an alcohol solvent are mixed and dispersed to obtain an oil-based aluminum silver paste dispersion; under a protective atmosphere, the oil-based aluminum silver paste dispersion and an olefinic carboxylic acid monomer are mixed and heated to obtain a modified aluminum silver paste mixture system; the polymethyl methacrylate solution is added dropwise to the modified aluminum silver paste mixture system and mixed, then heated to react, and filtered to obtain the aluminum silver paste. This application uses PMMA monomer, after polymerization, to deposit on the surface of aluminum sheets to coat the sheet-like aluminum silver paste, effectively preventing it from directly contacting water in an aqueous system and causing corrosion. PMMA has high light transmittance and low impact on the surface gloss and hiding power of the aluminum silver paste. Simultaneously, the high polarity of PMMA results in good compatibility and adhesion between the aluminum silver paste and the resin.

Description

Technical Field

[0001] This application belongs to the field of metallic pigment technology, and in particular relates to an aluminum silver paste and its preparation method. Background Technology

[0002] Aluminum silver paste is a mixture of flake-shaped metallic aluminum and organic solvents. It is a pigment with a silvery-gray metallic luster, possessing excellent floating properties, hiding power, and shielding properties, making it widely used in the modern pigment and coating industries. The production process of aluminum silver paste is generally a wet process, which involves spreading sprayed aluminum powder into flake structures of suitable size and aspect ratio under solvent oil protection conditions. Then, it undergoes grading, solid-liquid separation, and surface treatment to produce metallic pigment products of various specifications and models.

[0003] The aluminum silver paste obtained by the above method is easily chemically corroded in corrosive environments. This is because aluminum powder has high surface activity and can react with water to release hydrogen gas, which not only affects the surface gloss of the aluminum silver paste, but also makes the production, storage and transportation of water-based coatings unsafe.

[0004] To meet the needs of water-based systems and prevent corrosion of the aluminum silver paste surface, surface modification is required. For example, conventional coating materials can be used to coat the aluminum sheet surface with a dense film to prevent corrosion. However, existing coating materials may reduce the gloss and hiding power of the aluminum silver paste or have poor compatibility with resins, resulting in reduced adhesion of the aluminum silver paste after coating. Summary of the Invention

[0005] To address the shortcomings of current processes, this application uses polymethyl methacrylate (PMMA) monomer, deposited onto the surface of an aluminum sheet after polymerization to coat it with flake-like aluminum silver paste. A precipitation polymerization method is employed to coat the aluminum sheet with a cross-linked PMMA film, effectively preventing direct contact with water in aqueous systems and thus avoiding corrosion. PMMA has high light transmittance, minimizing its impact on the surface gloss and hiding power of the aluminum silver paste. Furthermore, PMMA's high polarity ensures good compatibility and adhesion between the aluminum silver paste and the resin.

[0006] The first aspect of this application provides a method for preparing aluminum silver paste, comprising the following steps:

[0007] Step 1: Mix and dissolve methyl methacrylate, crosslinking agent and oil-soluble initiator to obtain polymethyl methacrylate solution;

[0008] Oily aluminum silver paste and alcohol solvent are mixed and dispersed to obtain an oily aluminum silver paste dispersion;

[0009] Step 2: Under a protective atmosphere, the oily aluminum silver paste dispersion and the olefinic carboxylic acid monomer are mixed and heated to react, thereby obtaining a modified aluminum silver paste mixture system.

[0010] Step 3: Add the polymethyl methacrylate solution dropwise to the modified aluminum silver paste mixing system, mix, then heat and react, and filter to obtain aluminum silver paste.

[0011] In another embodiment, in step 1, the crosslinking agent is selected from one or more of allyl methacrylate, trimethylolpropane triacrylate, triallyl isocyanurate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, ethylene glycol dimethacrylate, and diethylene glycol dimethacrylate, preferably trimethylolpropane triacrylate.

[0012] In another embodiment, in step 1, the oil-soluble initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, 2-ethylhexyl peroxide dicarbonate, dicyclohexyl peroxide dicarbonate, diphenoxyethyl peroxide dicarbonate, bis(3,5,5-trimethylacetyl) peroxide, and cumyl peroxide, preferably azobisisobutyronitrile and benzoyl peroxide.

[0013] Specifically, the amount of oil-soluble initiator added is 0.5% to 1% of the total mass of methyl methacrylate monomers.

[0014] In another embodiment, in step 1, the alcohol solvent is selected from one or more of methanol, ethanol, isopropanol and n-butanol, preferably isopropanol.

[0015] In another embodiment, in step 2, the solid content of the oily aluminum silver paste dispersion is 70-80%.

[0016] In another embodiment, in step 2, the olefinic carboxylic acid monomer is selected from acrylic acid and / or methacrylic acid.

[0017] In another embodiment, the amount of methyl methacrylate added is 5% to 35% of the mass of the pure oily aluminum silver paste, preferably 15% to 25%.

[0018] In another embodiment, the amount of crosslinking agent added is 0.5% to 1.5% of the mass of methyl methacrylate, preferably 0.8% to 1%.

[0019] In another embodiment, the amount of alcohol solvent added is 3 to 10 times the mass of the pure oily aluminum silver paste, preferably 5 to 6 times.

[0020] In another embodiment, the amount of the olefinic carboxylic acid monomer added is 0.1% to 1% of the mass of the pure oily aluminum silver paste, preferably 0.7% to 0.8%.

[0021] In another embodiment, in step 2, the temperature of the heating reaction is 60–90°C, the heating reaction time is 1–5 h, and the protective atmosphere is nitrogen.

[0022] In another embodiment, in step 3, the dripping time is 1 to 5 hours, preferably 3 to 4 hours; the dripping and mixing temperature is 60°C to 80°C, preferably 65°C to 70°C.

[0023] In another embodiment, in step 3, the temperature of the heating reaction is 80℃~90℃, preferably 85℃~90℃, and the heating reaction time is 1~5h, preferably 3~4h.

[0024] A second aspect of this application provides an aluminum silver paste, including the aluminum silver paste prepared by the aforementioned preparation method.

[0025] This application provides an aluminum silver paste and its preparation method. Polymethyl methacrylate (PMMA) monomer is deposited onto the surface of an aluminum sheet after polymerization to coat the sheet with the aluminum silver paste. A precipitation polymerization method is used to coat the aluminum sheet with a cross-linked PMMA film, effectively preventing direct contact with water in an aqueous system and thus preventing corrosion. PMMA has high light transmittance, minimizing its impact on the surface gloss and hiding power of the aluminum silver paste. Simultaneously, the high polarity of PMMA ensures good compatibility and adhesion between the aluminum silver paste and the resin. Detailed Implementation

[0026] This application provides an aluminum silver paste and its preparation method, which solves the technical defects of conventional coating materials used in the prior art that reduce the gloss and hiding power of aluminum silver paste or have poor compatibility with resin, resulting in reduced adhesion of the coated aluminum silver paste.

[0027] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] In the following examples, all raw materials or reagents used are commercially available or self-made.

[0029] In the embodiments of this application, the tests for each physical property are performed using the following methods:

[0030] (1) Gloss test

[0031] Take 1g of PMMA resin-coated aluminum silver paste sample, add 1g of toluene solvent, then add 10g of acrylic resin, and stir evenly. Then, apply the paste evenly to a specially made iron plate using a 50μm wire rod. After drying, use a gloss meter to test the gloss of the coating at 60°.

[0032] (2) Adhesion test

[0033] Take 1g of PMMA resin-coated aluminum silver paste sample, add 1g of toluene solvent, then add 10g of acrylic resin, and stir evenly. Then, apply the paste evenly to a specially made iron plate using a 50μm wire bar. After drying, conduct a paint film adhesion test according to the national standard GB / T9286-1998 "Paints and Varnishes - Cross-cut Test of Paint Films". The test results are divided into 0 to 5 grades, with grade 0 being the best and grade 5 being the worst.

[0034] Example 1

[0035] This application provides an aluminum silver paste, the specific preparation method of which includes:

[0036] In a 1L flask equipped with a stirrer, thermometer, and reflux condenser, 50g of oily aluminum silver paste and 300g of isopropanol solvent were added and stirred until homogeneous to obtain an oily aluminum silver paste dispersion. 0.5g of acrylic acid was added to the oily aluminum silver paste dispersion, nitrogen gas was introduced, the temperature was raised to 70℃, and maintained at this temperature for 1 hour to obtain a modified aluminum silver paste mixture.

[0037] 12.5 g of methyl methacrylate, 0.063 g of azobisisobutyronitrile, 0.025 g of benzoyl peroxide, and 0.063 g of trimethylolpropane triacrylate were weighed and mixed thoroughly to obtain a polymethyl methacrylate solution. This polymethyl methacrylate solution was added dropwise to a flask containing a modified aluminum silver paste mixture over 4 hours at a temperature of 65°C, with continuous stirring throughout the addition. After the addition was complete, the polymer was matured by gradually increasing the temperature: 75°C for 1 hour, 80°C for 1 hour, 85°C for 1 hour, and finally 90°C for 1 hour. After the reaction was complete, the temperature was lowered to room temperature, and the product was filtered to obtain the PMMA resin-coated aluminum silver paste, which is the aluminum silver paste of Example 1.

[0038] Example 2

[0039] This application provides an aluminum silver paste, the specific preparation method of which includes:

[0040] In a 1L flask equipped with a stirrer, thermometer, and reflux condenser, 50g of oily aluminum silver paste and 300g of isopropanol solvent were added and stirred until homogeneous to obtain an oily aluminum silver paste dispersion. 0.5g of acrylic acid was added to the oily aluminum silver paste dispersion, nitrogen gas was introduced, the temperature was raised to 70℃, and maintained at this temperature for 1 hour to obtain a modified aluminum silver paste mixture.

[0041] 7.5 g of methyl methacrylate, 0.038 g of azobisisobutyronitrile, 0.015 g of benzoyl peroxide, and 0.038 g of trimethylolpropane triacrylate were weighed and mixed thoroughly to obtain a polymethyl methacrylate solution. This polymethyl methacrylate solution was added dropwise to a flask containing a modified aluminum silver paste mixture over 4 hours at a temperature of 70°C, with continuous stirring throughout the addition. After the addition was complete, the polymer was matured by gradually increasing the temperature: 75°C for 1 hour, 80°C for 1 hour, 85°C for 1 hour, and finally 90°C for 1 hour. After the reaction was complete, the temperature was lowered to room temperature, and the product was filtered to obtain the PMMA resin-coated aluminum silver paste, which is the aluminum silver paste of Example 2.

[0042] Comparative Example 1

[0043] This application provides an aluminum silver paste as a comparative example, the specific preparation method of which includes:

[0044] In a 1L flask equipped with a stirrer, thermometer, and reflux condenser, 50g of oily aluminum silver paste and 300g of isopropanol solvent were added and stirred until homogeneous to obtain an oily aluminum silver paste dispersion. 0.5g of acrylic acid was added to the oily aluminum silver paste dispersion, nitrogen gas was introduced, the temperature was raised to 70℃, and maintained at this temperature for 1 hour to obtain a modified aluminum silver paste mixture.

[0045] 2.5 g of methyl methacrylate, 0.013 g of azobisisobutyronitrile, 0.005 g of benzoyl peroxide, and 0.013 g of trimethylolpropane triacrylate were weighed and mixed thoroughly to obtain a polymethyl methacrylate solution. This polymethyl methacrylate solution was added dropwise to a flask containing a modified aluminum silver paste mixture over 4 hours at a temperature of 65°C, with continuous stirring throughout the addition. After the addition was complete, the polymer was matured by gradually increasing the temperature: 75°C for 1 hour, 80°C for 1 hour, 85°C for 1 hour, and finally 90°C for 1 hour. After the reaction was complete, the temperature was lowered to room temperature, and the product was filtered to obtain the PMMA resin-coated aluminum silver paste, which is the aluminum silver paste of Comparative Example 1.

[0046] Comparative Example 2

[0047] This application provides an aluminum silver paste as a comparative example, the specific preparation method of which includes:

[0048] In a 1L flask equipped with a stirrer, thermometer, and reflux condenser, 50g of oily aluminum silver paste and 300g of isopropanol solvent were added and stirred until homogeneous to obtain an oily aluminum silver paste dispersion. 0.5g of acrylic acid was added to the oily aluminum silver paste dispersion, nitrogen gas was introduced, the temperature was raised to 70℃, and maintained at this temperature for 1 hour to obtain a modified aluminum silver paste mixture.

[0049] 20g of methyl methacrylate, 0.1g of azobisisobutyronitrile, 0.04g of benzoyl peroxide, and 0.1g of trimethylolpropane triacrylate were weighed and mixed thoroughly to obtain a polymethyl methacrylate solution. This polymethyl methacrylate solution was added dropwise to a flask containing a modified aluminum silver paste mixture over 4 hours at a temperature of 70°C, with continuous stirring throughout the addition. After the addition was complete, the polymer was matured by gradually increasing the temperature: 75°C for 1 hour, 80°C for 1 hour, 85°C for 1 hour, and finally 90°C for 1 hour. After the reaction was complete, the temperature was lowered to room temperature, and the product was filtered to obtain the PMMA resin-coated aluminum silver paste, which is the aluminum silver paste of Comparative Example 2.

[0050] Comparative Example 3

[0051] This application provides an aluminum silver paste as a comparative example, the specific preparation method of which includes:

[0052] In a 1L flask equipped with a stirrer, thermometer, and reflux condenser, 50g of oily aluminum silver paste and 300g of isopropanol solvent were added and stirred until homogeneous to obtain an oily aluminum silver paste dispersion. 0.5g of acrylic acid was added to the oily aluminum silver paste dispersion, nitrogen gas was introduced, the temperature was raised to 70℃, and maintained at this temperature for 1 hour to obtain a modified aluminum silver paste mixture.

[0053] 12.5 g of styrene, 0.063 g of azobisisobutyronitrile, 0.025 g of benzoyl peroxide, and 0.063 g of trimethylolpropane triacrylate were weighed and mixed thoroughly to obtain a polystyrene solution. This polystyrene solution was added dropwise to a flask containing a modified aluminum silver paste mixture over 4 hours at a temperature of 65°C, with continuous stirring throughout the addition. After the addition was complete, the polymer was matured by gradually increasing the temperature: 75°C for 1 hour, 80°C for 1 hour, 85°C for 1 hour, and finally 90°C for 1 hour. After the reaction was complete, the temperature was lowered to room temperature, and the product was filtered to obtain the aluminum silver paste of Comparative Example 3.

[0054] Comparative Example 4

[0055] This application provides an aluminum silver paste as a comparative example, the specific preparation method of which includes:

[0056] In a 1L flask equipped with a stirrer, thermometer, and reflux condenser, 50g of oily aluminum silver paste and 300g of isopropanol solvent were added and stirred until homogeneous to obtain an oily aluminum silver paste dispersion. 0.5g of acrylic acid was added to the oily aluminum silver paste dispersion, nitrogen gas was introduced, the temperature was raised to 70℃, and maintained at this temperature for 1 hour to obtain a modified aluminum silver paste mixture.

[0057] 3.1 g of acrylonitrile, 9.4 g of styrene, 0.063 g of azobisisobutyronitrile, 0.025 g of benzoyl peroxide, and 0.063 g of trimethylolpropane triacrylate were weighed and mixed thoroughly to obtain a SAN (styrene-acrylonitrile copolymer) solution. This SAN solution was added dropwise to a flask containing a modified aluminum silver paste mixture over 4 hours at a temperature of 70°C, with continuous stirring throughout the addition. After the addition was complete, the polymer was matured by gradually increasing the temperature: 75°C for 1 hour, 80°C for 1 hour, 85°C for 1 hour, and finally 90°C for 1 hour. After the reaction was complete, the temperature was lowered to room temperature, and the product was filtered to obtain the aluminum silver paste of Comparative Example 4.

[0058] The gloss and adhesion of Examples 1-2, Comparative Examples 1-4, and uncoated PMMA resin-modified aluminum silver paste were tested, and the test results are shown in Table 1.

[0059] Table 1

[0060]

[0061]

[0062] Note: "-" in the table above indicates that it cannot be measured.

[0063] The experimental results above show that as the amount of methyl methacrylate monomer increases, the gloss decreases, but the adhesion increases. When the methyl methacrylate monomer content is too high, such as in Comparative Example 2 where the methyl methacrylate monomer content is 40% of the aluminum silver paste, it cannot disperse properly during synthesis, causing the aluminum sheets to stick together through the resin, leading to synthesis failure. If the methyl methacrylate content is too low, as shown in Comparative Example 1, it cannot adequately coat the aluminum silver paste, resulting in poor adhesion. When other polymers are used for coating, such as polystyrene in Example 3 and SAN (styrene-acrylonitrile copolymer) in Example 4, the adhesion is not as good as that of PMMA coating.

[0064] Taking all factors into consideration, the synthesis of aluminum silver paste with a methyl methacrylate monomer dosage of 25% (Example 1) is stable, and both gloss and adhesion meet the requirements. Although the gloss is reduced compared to unmodified aluminum silver paste, the adhesion to the substrate is greatly improved. If other common plastic polymers are coated, the adhesion of the aluminum silver paste will be significantly reduced.

[0065] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for preparing aluminum silver paste, characterized in that, Includes the following steps: Step 1: Mix and dissolve methyl methacrylate, crosslinking agent and oil-soluble initiator to obtain polymethyl methacrylate solution; An oil-based aluminum silver paste and an alcohol solvent are mixed and dispersed to obtain an oil-based aluminum silver paste dispersion; the alcohol solvent is selected from one or more of methanol, ethanol, isopropanol, and n-butanol. Step 2: Under a protective atmosphere, the oily aluminum silver paste dispersion and the olefinic carboxylic acid monomer are mixed and heated to react, resulting in a modified aluminum silver paste mixture system. Step 3: The polymethyl methacrylate solution is added dropwise to the modified aluminum silver paste mixing system and mixed at a temperature of 60℃~80℃ for 1~5h. After the addition is complete, the polymer is matured by gradually increasing the temperature at a temperature of 80℃~90℃ for 1~5h. The reaction product is filtered to obtain aluminum silver paste.

2. The preparation method according to claim 1, characterized in that, In step 1, the crosslinking agent is selected from one or more of allyl methacrylate, trimethylolpropane triacrylate, triallyl isocyanurate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, ethylene glycol dimethacrylate, and diethylene glycol dimethacrylate.

3. The preparation method according to claim 1, characterized in that, In step 1, the oil-soluble initiator is one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, 2-ethylhexyl peroxide dicarbonate, dicyclohexyl peroxide dicarbonate, diphenoxyethyl peroxide dicarbonate, bis(3,5,5-trimethylacetyl peroxide), and cumyl peroxide.

4. The preparation method according to claim 1, characterized in that, In step 2, the solid content of the oily aluminum silver paste dispersion is 70-80%.

5. The preparation method according to claim 1, characterized in that, In step 2, the olefinic carboxylic acid monomer is selected from acrylic acid and / or methacrylic acid.

6. The preparation method according to claim 1, characterized in that, The amount of methyl methacrylate added is 5% to 35% of the mass of the oily aluminum silver paste; the amount of crosslinking agent added is 0.5% to 1.5% of the mass of methyl methacrylate; the amount of alcohol solvent added is 3 to 10 times the mass of the oily aluminum silver paste; and the amount of olefinic carboxylic acid monomer added is 0.1% to 1% of the mass of the oily aluminum silver paste.

7. The preparation method according to claim 1, characterized in that, In step 2, the heating temperature is 60~90℃ and the heating time is 1~5h.

8. The aluminum silver paste prepared by the method of any one of claims 1 to 7.

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