CN1986648A - Preparing method of coated aluminium powder pigment - Google Patents

Abstract

The invention discloses a coated aluminum powder pigment and a preparation method thereof. In this method, aluminum powder pigment and solvent alcohol are mixed; then organosiloxane, water and acidic catalyst are added, and heated in a water bath to react to obtain aluminum powder pigment initially coated with organosiloxane; then the temperature of the reaction system is raised to 65-120°C , add one or more monomers and initiators containing polymerizable groups, react to obtain organosiloxane and polymer-coated aluminum powder pigments; finally cool, filter, wash, and dry to obtain coated aluminum powder Pigment products. The product organosiloxane first forms the first coating layer on the surface of the aluminum powder pigment, and then the polymer forms the second coating layer on the surface of the aluminum powder pigment. Coated aluminum powder pigments have good acid and alkali resistance on the basis of maintaining good metallic luster, and are suitable for water-based paints. It better solves the problem of "gassing" during the use and storage of traditional aluminum powder pigments, and lays the foundation for the safe use of aluminum powder pigments.

Description

A kind of preparation method of coated aluminum powder pigment

technical field

The invention relates to the technical field of surface treatment of metal pigments, in particular to a method for preparing coated aluminum powder pigments.

Background technique

Aluminum powder pigment is one of the important metal pigments, the main application areas are industrial coatings, automotive coatings, printing inks and plastic processing industry. The reason why aluminum powder pigments have many application fields is that they have characteristics different from other pigments: (1) "angle-dependent" effect or "two-color" effect. That is, when the coating containing aluminum powder is observed from different angles, the color of the coating will change with the angle. The coating color is very bright when viewed from the front and darkens when viewed from the side. Aluminum powder pigments are widely used in decorative paints because of this effect. (2) Aluminum powder pigments have good ability to reflect light and reflect heat. Aluminum powder pigments can form a continuous metal film when forming a film, which can reflect visible light, ultraviolet light and infrared light. The reflection of the full spectrum of visible light is silvery white, which makes it have good decorative properties; the reflection of infrared light makes it have anti-heat insulation performance; and the reflection of ultraviolet light can protect the coating from being damaged by ultraviolet rays and aging. Extends the life of the coating. Therefore it is used in petroleum industry, chemical industry and transport vehicles, pipelines. In some hot areas abroad, aluminum powder pigments are widely used in roof asphalt paint to brush roofs, which effectively reduces the indoor temperature. (3) Aluminum powder pigments have a covering ability that varies within a wide range. The technical index to express the performance of aluminum powder pigment is the hiding power of the water surface. One gram of aluminum powder can cover the water surface in the range of 1000-30000cm ² . Aluminum powder pigments are tiny aluminum flakes that have a certain ratio between their diameter and thickness. Varieties with small thickness and little difference in diameter have relatively large water surface covering ability. This feature is not only economical, but also has the function of gloss change.

Most of the products such as paints and paints are weakly acidic or weakly alkaline. During storage or use, the color of aluminum powder pigments in paints and paints will gradually change from bright metallic to metallic due to corrosion by acid or alkaline substances. Off-white, which seriously affects the performance of the product. In addition, restricted by environmental factors, the paint and paint industry is moving towards the direction of reducing volatile organic compounds, and water-based coatings are a better choice to solve this problem. When aluminum powder pigments are used in water-based coatings, many adverse effects will occur, such as: dispersion stability, etc. However, the most important thing is that most of the water-based paints are formulated under alkaline conditions, and the aluminum powder pigments are easily corroded. As a result, the aluminum powder pigments will gradually lose their metallic luster, and a large amount of H ₂ will be generated, which is prone to explosion. Therefore, it is necessary to carry out surface treatment on aluminum powder pigments.

At present, there are two main methods of surface treatment of aluminum powder pigments: physical protection method and chemical protection method. The physical protection method is to brush a layer of transparent resin on the surface of the aluminum powder as a protective layer. Because the adhesion between the resin and the surface of the aluminum powder is weak, the resin is easy to fall off from the surface of the aluminum powder, thereby losing the protective effect on the aluminum powder. Chemical protection methods are mainly divided into passivation method, additive method and coating method. The passivation method is the earliest chemical protection method, which is to treat the aluminum powder with a passivation agent to form a passivation film on the surface. The most effective passivating agent is chromate, but because hexavalent chromium ions are extremely harmful to the environment and are carcinogenic, new alternatives are being sought. The additive method is to add substances that can inhibit the corrosion of aluminum powder pigments in coatings and other systems. The protective effect of additives on aluminum powder pigments lies in their ability to adsorb on the surface of aluminum powder pigments. However, due to this weak adsorption, and additives cannot completely Insulate aluminum powder pigments from contact with corrosive media, therefore, the protective effect of additives on aluminum powder pigments is also very limited. The coating method is to coat one or more layers of relatively transparent substances on the surface of the aluminum powder pigment. This method can effectively protect the aluminum powder pigment from corrosion because it can isolate the aluminum powder pigment from contact with the corrosive medium. In addition, since the coating layer is a transparent substance, it can better maintain the unique gloss of the aluminum powder pigment. Therefore, the coating method is the most promising method among the surface treatment methods of the aluminum powder pigment. However, it is difficult for the existing coating technology to form a dense protective layer on the surface of the aluminum powder pigment or the protective layer is easy to fall off from the surface of the aluminum powder pigment, which does not have a good protective effect on the aluminum powder pigment.

Contents of the invention

The object of the present invention is to provide a method for preparing coated aluminum powder pigments in order to solve the deficiencies in the prior art. The aluminum powder pigment prepared by the method has acid and alkali resistance, good gloss, good dispersibility in water-based and solvent-based systems, and good compatibility with organic matter such as resins.

Another object of the present invention is to provide the coated aluminum powder pigment prepared by the above method.

The purpose of the present invention is achieved through the following technical solutions.

A preparation method of coated aluminum powder pigment, comprising the following steps and process conditions:

The first step is to add 2 to 10 parts of aluminum powder pigment and 50 to 90 parts of solvent alcohol into the reaction vessel in parts by mass, and stir at room temperature for 0.5 to 2 hours;

In the second step, add 1 to 10 parts of organosiloxane, 4 to 15 parts of water, and 2 to 8 parts of acidic catalyst to the reaction vessel described in the first step, heat in a water bath, and react for 2 to 10 hours under stirring. at 30-60°C, and adjust the pH value to 4-6 to obtain aluminum powder pigments initially coated with organosiloxane; the organosiloxane is Si(OR) ₄ and/or R'Si(OR) ₃ , Wherein, OR is a hydrolyzable alkoxy group, R' is an organic functional group or a carbon chain containing an organic functional group;

The third step is to raise the temperature of the reaction system described in the second step to 65-120°C, add 3-20 parts of one or more monomers containing polymerizable groups, and 0.01-8 parts of initiator, and react for 2-2 hours under stirring. In 10 hours, the aluminum powder pigment coated with organosiloxane and polymer was obtained; the monomer containing polymerizable groups included monomers containing polymerizable double bonds and benzene rings, esters containing polymerizable double bonds, containing Acids with polymerizable double bonds, acid anhydrides containing polymerizable double bonds;

The fourth step is to cool the aluminum powder and pigment suspension obtained in the third step to room temperature, then filter, wash the filter residue with alcohol solvent, then wash with distilled water and filter, then dry the obtained filter residue, the drying temperature does not exceed 50°C, The drying time is 2-10 hours, and the coated aluminum powder pigment product is obtained.

The hydrolyzable alkoxy group is methoxy or ethoxy; the R' is aminopropyl, vinyl or epoxy.

The organosiloxane is tetraethoxysilane, aminopropyltriethoxysilane, vinyltrimethoxysilane or epoxytrimethoxysilane.

The monomer containing a polymerizable double bond and a benzene ring is styrene or divinylbenzene; the ester containing a polymerizable double bond is methyl acrylate, methyl methacrylate or butyl methacrylate; the The acid containing a polymerizable double bond is acrylic acid or methacrylic acid; the acid anhydride containing a polymerizable double bond is maleic anhydride or norbornene dioic anhydride.

The solvent alcohol used in the first step is methanol, ethanol, propanol or isopropanol. The acid catalyst used is hydrochloric acid, phosphoric acid, sulfuric acid or hydrofluoric acid. The aluminum powder pigment used is in the form of flakes with a particle size of 100nm-50μm.

The initiator used in the third step is azobisisobutyronitrile, potassium persulfate or ammonium persulfate.

The coated aluminum pigment prepared by the above method uses the aluminum pigment as the core, and organosiloxane and polymer successively form the first and second coating layers on the surface of the aluminum pigment.

The aluminum powder prepared by the present invention can be made into aluminum paste or directly used as an aluminum pigment, has excellent storage stability, and has good performance in the fields of industrial coatings, metal coatings, automotive coatings, etc. When used in water-based coatings, it has good oxidation and corrosion resistance and metallic luster retention.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. In the preparation process of the present invention, an organosiloxane is firstly used to form a coating layer on the surface of the aluminum powder pigment, and the binding force between the coating layer and the surface of the aluminum powder pigment is relatively strong.

2. In the preparation process of the present invention, on the basis of the initial coating of the aluminum powder pigment by the organosiloxane, polymerizable monomers are used to polymerize with the organosiloxane to form a second coating layer, that is, the polymer coating cladding.

3. The two-layer cladding layer formed by organosiloxane and polymer is relatively dense, which effectively isolates the contact between aluminum powder pigment and other corrosive media, such as oxygen, water, acid and alkali, so the coated aluminum prepared by the present invention Powder pigment has good acid and alkali resistance and water resistance.

4. The coated aluminum powder pigment prepared by the present invention also has better metallic luster.

5. The coated aluminum powder pigment prepared by the present invention has good compatibility with organic matter such as resin in the coating system.

Detailed ways

In order to better understand the present invention, the present invention will be further described in detail below in conjunction with the examples, but the protection scope of the present invention is not limited to the range indicated by the examples.

Example 1

In the first step, in parts by mass, 2 parts of aluminum powder pigment and 50 parts of solvent methanol are added to the reaction vessel, and stirred at room temperature for 0.5 hours;

In the second step, add 1 part of aminopropyltriethoxysilane, 4 parts of water, and 2 parts of acidic catalyst hydrochloric acid into the reaction vessel described in the first step, heat in a water bath, and react for 2 hours under stirring. The reaction temperature is 30 ° C. The pH value is 5, and the aluminum powder pigment initially coated with organosiloxane is obtained;

The third step is to raise the temperature of the reaction system described in the second step to 65°C, add 3 parts of styrene, 0.01 part of initiator azobisisobutyronitrile, and react for 2 hours under stirring to obtain organosiloxane and polymer coating Aluminum powder pigment;

The fourth step is to cool the aluminum powder pigment suspension obtained in the third step to room temperature, and then filter. The filter residue was first washed three times with an alcohol solvent, then washed three times with distilled water and then filtered, and then the obtained filter residue was dried at a drying temperature of 40° C. for 2 hours to obtain the final product.

Example 2

In the first step, in parts by mass, 6 parts of aluminum powder pigment and 70 parts of solvent ethanol are added to the reaction vessel, and stirred at room temperature for 1 hour;

In the second step, add 5.5 parts of tetraethoxysilane, 9.5 parts of water, and 5 parts of acid catalyst sulfuric acid into the reaction vessel described in the first step, heat it in a water bath, and react for 6 hours under stirring. The reaction temperature is 45 °C and the pH value is 4. Obtain the aluminum powder pigment initially coated with organosiloxane;

In the third step, the temperature of the reaction system described in the second step is raised to 92.5°C, 5 parts of styrene, 6.5 parts of divinylbenzene, and 4.005 parts of initiator potassium persulfate are added, and the reaction is carried out under stirring for 6 hours to obtain organosiloxane and Polymer-coated aluminum powder pigments;

The fourth step is to cool the aluminum powder pigment suspension obtained in the third step to room temperature, and then filter. The filter residue was first washed three times with an alcohol solvent, then washed three times with distilled water and then filtered, and then the obtained filter residue was dried at a drying temperature of 40° C. for 6 hours to obtain the final product.

Example 3

In the first step, in parts by mass, 10 parts of aluminum powder pigment and 90 parts of solvent propanol are added to the reaction vessel, and stirred at room temperature for 2 hours;

In the second step, add 6 parts of epoxytrimethoxysilane, 10 parts of water, and 8 parts of acidic catalyst hydrofluoric acid into the reaction vessel described in the first step, heat in a water bath, and react for 10 hours under stirring, and the reaction temperature is 60°C , the pH value is 6, and the aluminum powder pigment initially coated with organosiloxane is obtained;

In the third step, the temperature of the reaction system described in the second step is raised to 120°C, 5 parts of methyl methacrylate, 5 parts of butyl methacrylate and 10 parts of methyl acrylate, and 8 parts of initiator ammonium persulfate are added, and stirred React for 10 hours to obtain the aluminum powder pigment coated with organosiloxane and polymer;

The fourth step is to cool the aluminum powder pigment suspension obtained in the third step to room temperature, and then filter. The filter residue was first washed three times with an alcohol solvent, then washed three times with distilled water and then filtered, and then the obtained filter residue was dried at a drying temperature of 30° C. for 10 hours to obtain the final product.

Example 4

In the first step, in parts by mass, 5 parts of aluminum powder pigment and 85 parts of solvent isopropanol are added to the reaction vessel, and stirred at room temperature for 1 hour;

In the second step, add 5 parts of tetraethoxysilane, 4 parts of water, and 3 parts of acidic catalyst phosphoric acid into the reaction vessel described in the first step, heat it in a water bath, and react for 6 hours under stirring. The reaction temperature is 50 ° C, and the pH value is 5. Obtain an aluminum powder pigment initially coated with organosiloxane;

The third step is to raise the temperature of the reaction system described in the second step to 85°C, add 4 parts of acrylic acid and 4 parts of methacrylic acid, and 4 parts of initiator ammonium persulfate, and react for 4 hours under stirring to obtain organosiloxane and polymer Coated aluminum powder pigments;

The fourth step is to cool the aluminum powder pigment suspension obtained in the third step to room temperature, and then filter. The filter residue was first washed three times with alcohol solvent, then washed three times with distilled water and then filtered, and then the obtained filter residue was dried at a drying temperature of 50° C. for 4 hours to obtain the final product.

Example 5

In the first step, in parts by mass, 8 parts of aluminum powder pigment and 65 parts of solvent methanol are added to the reaction vessel, and stirred at room temperature for 0.5 hours;

In the second step, add 6 parts of tetraethoxysilane, 6 parts of water, and 4 parts of acid catalyst sulfuric acid into the reaction vessel described in the first step, heat it in a water bath, and react for 6 hours under stirring. The reaction temperature is 50°C, and the pH value is 4. Obtain the aluminum powder pigment initially coated with organosiloxane;

The third step is to raise the temperature of the reaction system described in the second step to 85°C, add 10 parts of polymerizable monomer maleic anhydride, 1 part of initiator ammonium persulfate, and react for 4 hours under stirring to obtain organosiloxane and polymer Material-coated aluminum powder pigment;

The fourth step is to cool the aluminum powder pigment suspension obtained in the third step to room temperature, and then filter. The filter residue was first washed three times with alcohol solvent, then washed three times with distilled water and then filtered, and then the obtained filter residue was dried at a drying temperature of 50° C. for 4 hours to obtain the final product.

Example 6

In the first step, in parts by mass, 3 parts of aluminum powder pigment and 75 parts of solvent propanol are added to the reaction vessel, and stirred at room temperature for 1 hour;

In the second step, add 10 parts of tetraethoxysilane, 8 parts of water, and 5 parts of acidic catalyst hydrochloric acid into the reaction vessel described in the first step, heat in a water bath, and react for 6 hours under stirring. The reaction temperature is 50°C, and the pH value is 4. Obtain the aluminum powder pigment initially coated with organosiloxane;

The third step is to raise the temperature of the reaction system described in the second step to 85°C, add 5 parts of styrene, 5 parts of methacrylic acid and 5 parts of methyl methacrylate, and 4 parts of initiator ammonium persulfate, and react for 4 hours under stirring , to obtain organosiloxane and polymer-coated aluminum powder pigment;

The fourth step is to cool the aluminum powder pigment suspension obtained in the third step to room temperature, and then filter. The filter residue was first washed three times with an alcohol solvent, then washed three times with distilled water and then filtered, and then the obtained filter residue was dried at a drying temperature of 40° C. for 6 hours to obtain the final product.

Example 7

In the first step, in parts by mass, 7 parts of aluminum powder pigment and 80 parts of solvent isopropanol are added to the reaction vessel, and stirred at room temperature for 2 hours;

In the second step, add 7 parts of tetraethoxysilane, 12 parts of water, and 3 parts of acid catalyst hydrofluoric acid to the reaction vessel described in the first step, heat in a water bath, and react for 9 hours under stirring. The reaction temperature is 55 ° C, pH Value is 6, obtains the aluminum powder pigment of organosiloxane primary coating;

The third step is to raise the temperature of the reaction system described in the second step to 110°C, add 3 parts of divinylbenzene, 5 parts of acrylic acid, 10 parts of norbornene dioic anhydride, 4 parts of initiator potassium persulfate, and react for 4 hours under stirring , to obtain organosiloxane and polymer-coated aluminum powder pigment;

The fourth step is to cool the aluminum powder pigment suspension obtained in the third step to room temperature, and then filter. The filter residue was first washed three times with an alcohol solvent, then washed three times with distilled water and then filtered, and then the obtained filter residue was dried at a drying temperature of 35° C. for 10 hours to obtain the final product.

Example 8

The coated aluminum powder pigment of the present invention is compared with the aluminum powder pigment currently on the market for alkali resistance, and the result is: the coated aluminum powder pigment prepared in Examples 1-7 is in the water-based coating system with pH=9 , when the storage period at room temperature is six months, no hydrogen is generated, and the color of the pigment does not change; while the aluminum powder pigments sold on the market have a storage period of 15 days at room temperature in a water-based paint system with pH=9 That is, a large amount of hydrogen gas is released, and the color of the pigment gradually becomes off-white. It is proved that the coated aluminum powder pigment of the present invention has good alkali resistance and good storage stability in the alkaline water-based paint system with pH=9. In addition, it also shows that the coating layer on the surface of the coated aluminum powder pigment of the present invention is relatively dense, which can better protect the aluminum powder pigment.

Example 9

The coated aluminum powder pigment of the present invention is compared with the aluminum powder pigment currently on the market for alkali resistance, and the result is: the coated aluminum powder pigment prepared in Examples 1-7 is in the water-based coating system with pH=11 , when the storage period at room temperature is 1 month, no hydrogen gas is produced, and the color of the pigment does not change; the aluminum powder pigments sold on the market are in a water-based paint system with pH=11, and the storage period at room temperature is 7 days. A large amount of hydrogen gas is released, and the color of the pigment gradually becomes off-white. It is proved that the coated aluminum powder pigment of the present invention has good alkali resistance and good storage stability in the alkaline water-based paint system with pH=11.

Example 10

The coated aluminum powder pigment of the present invention is compared with the aluminum powder pigment currently on the market for acid resistance, and the result is: the coated aluminum powder pigment prepared in Examples 1-7 is in a water-based coating system with pH=5, When the storage period at room temperature is 6 months, no hydrogen gas is generated, and the color of the pigment does not change; the aluminum powder pigments sold in the market are in the water-based paint system with pH=5, and the storage period at room temperature is 5 days. A large amount of hydrogen gas is evolved. It is proved that the coated aluminum powder pigment of the present invention has good acid resistance and good storage stability in the acidic water-based paint system with pH=5.

Example 11

The coated aluminum powder pigment of the present invention is compared with the aluminum powder pigment before coating: the glossiness of the coated aluminum powder pigment prepared in Examples 1 to 7 is higher than the gloss of the aluminum powder pigment before coating degree is slightly reduced, and the glossiness of the coated aluminum pigment of the present invention is 90% to 100% of the glossiness of the aluminum powder pigment before coating (related to the preparation conditions and the thickness of the coating layer), which proves that the coated aluminum pigment of the present invention The coated aluminum powder pigment can better maintain the glossiness of the original aluminum powder raw material.

Example 12

The coated aluminum powder pigments prepared in Examples 1 to 7 were placed in distilled water, then vibrated on an electric oscillator for 15 days, the oscillation frequency was 200 times/min, and the oscillation amplitude was 20mm. As a result, no change in the color of the aluminum powder was found. It proves that the coating layer of the coated aluminum powder pigment of the present invention is not easy to fall off from the surface of the aluminum powder pigment.

Example 13

In the weather resistance test of the coated aluminum pigments prepared in Examples 1 to 7, no changes in color, gloss and brightness were found after one year, which proves that the coated aluminum pigments of the present invention have better weather resistance sex.

Claims (10)

1. the preparation method of a coated aluminium powder pigment is characterized in that comprising the steps and processing condition:

The first step adds 2～10 parts of aluminium powder pigments and 50～90 parts of solvent alcohols in mass fraction in reaction vessel, stirred under the room temperature 0.5～2 hour;

Second step added 1～10 part of organo-siloxane, 4～15 parts of water, 2～8 parts of an acidic catalysts again in the described reaction vessel of the first step, heating in water bath stirs reaction down 2～10 hours, and temperature of reaction is 30～60 ℃, regulating the pH value is 4～6, obtains the preliminary aluminium powder pigment that coats of organo-siloxane; Described organo-siloxane is Si (OR) ₄And/or R ' Si (OR) ₃, wherein, OR is hydrolyzable alkoxyl group, R ' is organo-functional group or the carbochain that contains organic functional group;

The 3rd step was warming up to 65～120 ℃ with described reaction system of second step, add 3～20 parts one or more contain the monomer of polymerizable groups, 0.01～8 parts of initiators stir reaction down 2～10 hours, obtain the aluminium powder pigment of organo-siloxane and polymer overmold; The described monomer that contains polymerizable groups comprises monomer, the ester that contains polymerizable double bond, the acid that contains polymerizable double bond that contains polymerizable double bond and phenyl ring, the acid anhydrides that contains polymerizable double bond;

The aluminium powder pigment suspension of the 4th step with the 3rd step gained is cooled to room temperature, filters then, and filter residue is washed with alcoholic solvent earlier, use the distilled water wash after-filtration then, again with the gained filter residue and drying, drying temperature is no more than 50 ℃, be 2～10 hours time of drying, gets the coated aluminium powder pigment product.

2. according to the preparation method of claim 1 described a kind of coated aluminium powder pigment, it is characterized in that described hydrolyzable alkoxyl group is a methoxy or ethoxy.

3. according to the preparation method of claim 1 described a kind of coated aluminium powder pigment, it is characterized in that described R ' is aminopropyl, vinyl or epoxy group(ing).

4. according to the preparation method of claim 1 described a kind of coated aluminium powder pigment, it is characterized in that described organo-siloxane is tetraethoxysilane, aminopropyl triethoxysilane, vinyltrimethoxy silane or epoxy group(ing) Trimethoxy silane.

5. according to the preparation method of claim 1 described a kind of coated aluminium powder pigment, it is characterized in that the described monomer that contains polymerizable double bond and phenyl ring is vinylbenzene or Vinylstyrene; The described ester that contains polymerizable double bond is methyl acrylate, methyl methacrylate or butyl methacrylate; The described acid that contains polymerizable double bond is acrylic or methacrylic acid; The described acid anhydrides that contains polymerizable double bond is maleic anhydride or norbornene dicarboxylic anhydride.

6. according to the preparation method of claim 1 described a kind of coated aluminium powder pigment, it is characterized in that the used solvent alcohol of the first step is methyl alcohol, ethanol, propyl alcohol or Virahol.

7. according to the preparation method of claim 1 described a kind of coated aluminium powder pigment, it is characterized in that the used an acidic catalyst of the first step is hydrochloric acid, phosphoric acid, sulfuric acid or hydrofluoric acid.

8. according to the preparation method of claim 1 described a kind of coated aluminium powder pigment, it is characterized in that used initiator of the 3rd step is Diisopropyl azodicarboxylate, Potassium Persulphate or ammonium persulphate.

9. according to the preparation method of claim 1 described a kind of coated aluminium powder pigment, it is characterized in that the used aluminium powder pigment of the first step is laminar, particle diameter is 100nm～50 μ m.

10. by a kind of coated aluminium powder pigment of any described method preparation of claim 1～9, it is characterized in that with the aluminium powder pigment being nuclear, organo-siloxane and polymkeric substance form first, second layer coating layer on the aluminium powder pigment surface successively.