阅读说明：本技术 一种用于氟碳粉末涂料的铝颜料及其制备方法 (Aluminum pigment for fluorocarbon powder coating and preparation method thereof ) 是由 秦昕 黄小尾 曾芳成 周掌叶 赵守元 于 2020-12-29 设计创作，主要内容包括：本发明提供一种用于氟碳粉末涂料的铝颜料及其制备方法,所述方法为：将铝粉与4-6倍铝粉质量的醇类溶液混合,调节pH值至8-9,配置含有硅烷偶联剂和醇类溶液的溶液A以及含有正硅酸乙酯和去离子水的溶液B,匀速滴加溶液A和溶液B 5-7小时,加入的硅烷偶联剂和正硅酸乙酯的量分别为铝粉质量的1-3％和20-35％,重复滴加一次并保持分散4-6小时,干燥后得到粉末C,配置含有丙二醇乙醚、二甲苯和聚甲基丙烯酸丁酯且相当于4-6倍粉末C质量的溶液D,向溶液D中加入7％-10％粉末C质量的聚苯乙烯树脂以及15％-20％粉末C质量的氟碳树脂,分散均匀后与粉末C一起置于反应釜中分散2-4小时,干燥后得到目标铝颜料。(The invention provides an aluminum pigment for fluorocarbon powder coating and a preparation method thereof, wherein the method comprises the following steps: mixing aluminum powder with an alcohol solution 4-6 times of the mass of the aluminum powder, adjusting the pH value to 8-9, preparing a solution A containing a silane coupling agent and the alcohol solution and a solution B containing tetraethoxysilane and deionized water, dropwise adding the solution A and the solution B at a constant speed for 5-7 hours, wherein the added silane coupling agent and tetraethoxysilane account for 1-3% and 20-35% of the mass of the aluminum powder respectively, repeatedly dropwise adding once and keeping the dispersion for 4-6 hours, drying to obtain powder C, preparing a solution D containing propylene glycol ethyl ether, xylene and polybutylmethacrylate and equivalent to 4-6 times of the mass of the powder C, adding 7-10% of polystyrene resin and 15-20% of fluorocarbon resin into the solution D, uniformly dispersing the solution D and the powder C in a reaction kettle for 2-4 hours, and drying to obtain the target aluminum pigment.)

1. A preparation method of an aluminum pigment for fluorocarbon powder coating is characterized by comprising the following steps:

step 1) mixing one part of aluminum powder with an alcohol solution which is 4-6 times of the mass of the aluminum powder to uniformly disperse the aluminum powder;

step 2) adjusting the pH value of the mixture obtained in the step 1) to 8-9;

step 3) preparing a solution A and a solution B, wherein the solution A comprises a silane coupling agent and an alcohol solution, the solution B comprises tetraethoxysilane and deionized water with the molar mass 4-6 times that of the tetraethoxysilane, the solution A and the solution B are simultaneously dripped into the mixture obtained in the step 2) at a constant speed, the addition amount of the silane coupling agent is 1-3% of the mass of the aluminum powder, and the addition amount of the tetraethoxysilane is 20-35% of the mass of the aluminum powder;

step 4) repeating the step 3) at least once, and keeping dispersion after finishing the dripping;

step 5) carrying out filter pressing on the mixture obtained in the step 4), and then carrying out vacuum drying to obtain powder C;

step 6) preparing a solution D, wherein the mass of the solution D is 4-6 times of that of the powder C and comprises propylene glycol ethyl ether, xylene and polybutylmethacrylate, adding polystyrene resin which accounts for 7-10% of the mass of the powder C into the solution D, uniformly dispersing, and keeping stirring for 2-4 hours;

step 7) adding fluorocarbon resin which is 15-20% of the mass of the powder C into the solution obtained in the step 6), uniformly dispersing, and keeping stirring for 2-4 hours;

and 8) adding the powder C obtained in the step 5) into the solution obtained in the step 7), dispersing for 2-4 hours in a reaction kettle, and performing filter pressing and vacuum drying to obtain the target aluminum pigment.

2. The method for preparing an aluminum pigment for fluorocarbon powder coating as set forth in claim 1, wherein the process of dropping the solution a and the solution B is controlled to 5-7 hours in the step 3).

3. A method for preparing an aluminum pigment for fluorocarbon powder coating as claimed in claim 2, characterized in that, in step 3), the silane coupling agent includes at least one of N-aminoethyl-3-aminopropylmethyldimethoxysilane, N- (β -aminoethyl) - γ -aminopropyltrimethoxysilane and 3- (2, 3-glycidoxy) -propyltrimethoxysilane.

4. A method of preparing an aluminum pigment for fluorocarbon powder coating as set forth in claim 3, characterized in that in step 1), said alcohol solution includes at least one of ethanol, ethylene glycol, propylene glycol and isobutanol.

5. A method of preparing an aluminum pigment for fluorocarbon powder coating as set forth in claim 3, wherein in step 3), said alcohol solution includes at least one of ethanol, ethylene glycol, propylene glycol and isobutanol.

6. A method for preparing aluminum pigment for fluorocarbon powder coating as claimed in claim 3, wherein in step 4), the specific operation of maintaining dispersion is to put the mixture after dropping into the reaction kettle and stir for 4-6 hours.

7. A method for preparing aluminum pigments for fluorocarbon powder coatings according to claim 3, characterized in that in step 5) the solid component content in powder C is > 99.6%.

8. The method for preparing an aluminum pigment for fluorocarbon powder coating according to any one of claims 3 to 7, wherein the steps 1) to 4) are all performed at 40 to 60 ℃.

9. An aluminum pigment for fluorocarbon powder coating prepared by the method of any one of claims 3 to 8, wherein the aluminum pigment comprises aluminum sheets, polystyrene resin and fluorocarbon resin, the polystyrene resin serves as an intermediate medium to bond the aluminum sheets and the fluorocarbon resin as a whole, and at least two silicon coating layers are provided on the outer surfaces of the aluminum sheets.

Technical Field

The invention relates to the technical field of coatings, in particular to a preparation method of an aluminum pigment for fluorocarbon powder coating and an aluminum pigment product.

Background

The aluminum pigment is one of the main raw materials for producing fluorocarbon powder coating, and can make the coating show metallic luster after being used and increase visual effect. The existing aluminum pigment for fluorocarbon powder coating has the following defects:

1. when fluorocarbon powder coating is used, an electrostatic spraying process is generally adopted, the electrostatic spraying utilizes the principle of electrostatic attraction, a workpiece to be processed is grounded and serves as an anode, an oil atomizer (namely a spray cup or a spray disk) is connected with high voltage and serves as a cathode, and after the electrostatic spraying is electrified, paint particles with negative electricity move towards the direction of the workpiece with positive electricity and are adsorbed on the surface of the workpiece under the action of an electrostatic field, so that the spraying purpose is realized. In the process, because the aluminum element in the aluminum pigment has strong positive electricity and the fluorine element in the fluorocarbon resin has strong electronegativity, part of negative electricity formed by the oil atomizer can be offset by the positive electricity carried by the aluminum pigment, the negative electricity carried by the fluorocarbon resin can be superposed with the negative electricity of the oil atomizer, and the movement tracks of the aluminum pigment particles and the fluorocarbon resin particles in an electric field are inconsistent, so that the aluminum pigment cannot achieve the expected effect in the fluorocarbon powder coating, and the aluminum pigment is particularly wasted, the metallic luster of the aluminum pigment cannot be well represented, and the like.

The main technical means for solving the problem in the industry at present is bonding, namely adding fluorocarbon resin into a high-speed mixer with a temperature control function, generating heat by utilizing mechanical high-speed rotation friction (the temperature is slightly lower than the glass transition temperature), and then adding aluminum pigment under the protection of nitrogen to bond fluorocarbon resin molecules with aluminum sheets in the aluminum pigment, so that the aluminum pigment and the fluorocarbon resin exist as a whole in the fluorocarbon powder coating instead of being dispersed.

However, strong shearing force is easily generated in the process of high-speed rotation friction, so that an aluminum sheet in the aluminum pigment is bent or deformed, and even a compact silicon coating layer on the surface of the aluminum sheet falls off, so that the quality of the fluorocarbon powder coating is affected.

2. Since aluminum has very active properties and is easily reacted with water, acidic substances, basic substances, and the like in the air, it is necessary to protect the surface of the aluminum pigment. The current mainstream method is to form a compact silicon coating layer on the surface of an aluminum sheet by using a sol-gel method, and because silicon does not react with acid and alkali and is isolated from air, the acid and alkali resistance of the aluminum pigment can be improved.

As far as the current point of view, the service life requirement of customers for fluorocarbon powder coating is usually as long as 20 years, the existing aluminum pigment is difficult to meet the process requirement, and the alkali resistance of the aluminum pigment has a space for further optimization in consideration of the relation between the alkali resistance degree of the aluminum pigment and the compactness and the coating mode of the silicon coating layer.

In view of the above, there is a need to develop a new aluminum pigment product to solve the above problems.

Disclosure of Invention

The invention aims to provide an aluminum pigment which has high acid-base resistance and good performance effect in fluorocarbon powder coating and a preparation method thereof.

In order to achieve the above object, the present invention provides a method for preparing an aluminum pigment for fluorocarbon powder coating, comprising the steps of:

step 1) mixing one part of aluminum powder with an alcohol solution which is 4-6 times of the mass of the aluminum powder to uniformly disperse the aluminum powder;

step 2) adjusting the pH value of the mixture obtained in the step 1) to 8-9;

step 3) preparing a solution A and a solution B, wherein the solution A comprises a silane coupling agent and an alcohol solution, the solution B comprises tetraethoxysilane and deionized water with the molar mass 4-6 times that of the tetraethoxysilane, the solution A and the solution B are simultaneously dripped into the mixture obtained in the step 2) at a constant speed, the addition amount of the silane coupling agent is 1-3% of the mass of the aluminum powder, and the addition amount of the tetraethoxysilane is 20-35% of the mass of the aluminum powder;

step 4) repeating the step 3) at least once, and keeping dispersion after finishing the dripping;

step 5) carrying out filter pressing on the mixture obtained in the step 4), and then carrying out vacuum drying to obtain powder C;

step 6) preparing a solution D, wherein the mass of the solution D is 4-6 times of that of the powder C and comprises propylene glycol ethyl ether, xylene and polybutylmethacrylate, adding polystyrene resin which accounts for 7-10% of the mass of the powder C into the solution D, uniformly dispersing, and keeping stirring for 2-4 hours;

step 7) adding fluorocarbon resin which is 15-20% of the mass of the powder C into the solution obtained in the step 6), uniformly dispersing, and keeping stirring for 2-4 hours;

and 8) adding the powder C obtained in the step 5) into the solution obtained in the step 7), dispersing for 2-4 hours in a reaction kettle, and performing filter pressing and vacuum drying to obtain the target aluminum pigment.

Preferably, in the step 3), the process of dropping the solution A and the solution B is controlled to be 5 to 7 hours.

Preferably, the silane coupling agent includes at least one of N-aminoethyl-3-aminopropylmethyldimethoxysilane, N- (β -aminoethyl) - γ -aminopropyltrimethoxysilane, and 3- (2, 3-glycidoxy) -propyltrimethoxysilane.

Preferably, in step 1), the alcohol solution includes at least one of ethanol, ethylene glycol, propylene glycol, and isobutanol.

Preferably, in step 3), the alcohol solution includes at least one of ethanol, ethylene glycol, propylene glycol, and isobutanol.

Preferably, in the step 4), the dispersion is maintained by placing the mixture after the dropwise addition in a reaction kettle and stirring for 4-6 hours.

Preferably, in step 5), the solid component content in the powder C is > 99.6%.

Preferably, steps 1) to 4) are carried out at 40 to 60 ℃.

The invention also provides an aluminum pigment for fluorocarbon powder coating prepared by the method, wherein the aluminum pigment comprises an aluminum sheet, polystyrene resin and fluorocarbon resin, the polystyrene resin is used as a middle medium to bond the aluminum sheet and the fluorocarbon resin into a whole, and at least two silicon coating layers are arranged on the outer surface of the aluminum sheet.

The technical scheme provided by the invention at least has the following beneficial effects:

1. according to the invention, the aluminum pigment and the fluorocarbon resin are bonded into a whole by adopting a mode of firstly combining the polystyrene resin with the fluorocarbon resin and then combining the polystyrene resin with the aluminum pigment, the polystyrene resin is used as an intermediate medium, so that the defect of poor metal luster during electrostatic spraying is solved, a high-speed mixer is not required, the damage to the structure of the aluminum pigment due to high-speed shearing is avoided, the silicon coating layer is more stable and less prone to falling off compared with the existing bonding scheme, the aluminum pigment is protected, the quality of the aluminum pigment in the finished coating is further improved, and the paint film has better whiteness and metal texture.

2. The invention improves the original silicon coating process, at least two silicon coating layers are formed on the surface of an aluminum sheet by controlling the total adding amount and the dropping time of the silane coupling agent, the protection effect is better, the service time of the pigment is prolonged, the added silane coupling agent is fully utilized, the formed silicon coating layer is more compact, the protection is more comprehensive, and the waste of raw materials is avoided.

Detailed Description

The technical solution of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

An aluminum pigment for fluorocarbon powder coating is prepared by the following steps:

step 1) mixing a part of aluminum powder with an alcohol solution which is 5 times of the mass of the aluminum powder to uniformly disperse the aluminum powder;

step 2) adjusting the pH value of the mixture obtained in the step 1) to 8-9;

step 3) preparing a solution A and a solution B, wherein the solution A comprises a silane coupling agent and an alcohol solution, the solution B comprises tetraethoxysilane and deionized water with the molar mass 5 times that of the tetraethoxysilane, the solution A and the solution B are simultaneously dripped into the mixture obtained in the step 2) at a constant speed, the dripping is completed within 6 hours, the addition amount of the silane coupling agent is 2% of the mass of the aluminum powder, and the addition amount of the tetraethoxysilane is 25% of the mass of the aluminum powder;

step 4) repeating the step 3) once, and after the dropwise addition is finished, placing the mixture in a reaction kettle and stirring for 4 hours;

step 5) carrying out filter pressing on the mixture obtained in the step 4), and then carrying out vacuum drying to obtain powder C, wherein the content of solid components is more than 99.6%;

step 6) preparing a solution D, wherein the mass of the solution D is 5 times of that of the powder C, adding polystyrene resin which accounts for 10% of that of the powder C into the solution D, uniformly dispersing, and keeping stirring for 3 hours;

step 7) adding fluorocarbon resin which is 15 percent of the mass of the powder C into the solution obtained in the step 6), uniformly dispersing, and keeping stirring for 3 hours;

and 8) adding the powder C obtained in the step 5) into the solution obtained in the step 7), dispersing for 3 hours in a reaction kettle, and performing filter pressing and vacuum drying to obtain the target aluminum pigment.

In this embodiment, the alcohol solutions in step 1) and step 3) may be at least one selected from ethanol, ethylene glycol, propylene glycol and isobutanol according to actual conditions. The steps 1) and 4) are all carried out at the temperature of 40-60 ℃. The specific formulations of solution A in step 3) and solution D in step 6) are shown in tables 1 and 2.

TABLE 1 solution A formulation

CAS number	Component name	Mass ratio of
			3069-29-2	N-aminoethyl-3-aminopropylmethyldimethoxysilane	15％
1760-24-3	N- (beta-aminoethyl) -gamma-aminopropyltrimethoxysilane	15％
			2530-83-8	3- (2, 3-epoxypropoxy) -propyltrimethoxysilane	20％
	Alcohol solutions	50％

For the solution A, as the higher the molecular weight of the used silane coupling agent is, the closer the position of the aluminum pigment in the coating is to the substrate after spraying, the metallic texture of the aluminum pigment can be weakened, and the three coupling agents in the table 1 are adopted and matched with a proper mass ratio, so that the aluminum pigment in the coating is close to the surface of the paint film and can meet the requirements of acid and alkali resistance.

TABLE 2 solution D formulation

CAS number	Component name	Mass ratio of
			1569-02-4	Propylene glycol ethyl ether	15％
1330-20-7	Xylene	50％
			9011-15-8	Poly (butyl methacrylate)	35％

For the solution D, because the aluminum pigment contains fluorocarbon resin and polystyrene resin, in order to achieve the better dispersion of the fluorocarbon resin and the polystyrene resin, the invention selects the three components in table 2 as the solvents of the fluorocarbon resin and the polystyrene resin after mixing them according to the corresponding mass ratio, taking into account the polarity of the chemical bond of the molecule and the spatial configuration of the molecule.

In order to verify the effect of the inventive solution on the improvement of the acid and alkali resistance of the aluminum pigment, the following examples and comparative examples were also provided:

example 2 the dropping time of the solution A and the solution B was 7 hours, the amount of the silane coupling agent added was 3% by mass of the powdery aluminum, and the amount of the tetraethoxysilane added was 35% by mass of the powdery aluminum, and the other operations were the same as in example 1.

Example 3 the dropping time of solution A and solution B was 5 hours, the amount of silane coupling agent added was 1% by mass of the powdery aluminum, and the amount of tetraethoxysilane added was 20% by mass of the powdery aluminum, and the other operations were the same as in example 1.

In comparative example 1, the dropping time of the solution A and the solution B was 4 hours, the amount of the silane coupling agent added was 1% by mass of the powdery aluminum, and the other operations were the same as in example 3.

In comparative example 2, the dropping time of the solution A and the solution B was 5 hours, and the amount of the silane coupling agent added was 0.5% by mass of the aluminum powder, and the other operations were the same as in example 3.

The above examples and comparative examples were subjected to an acid and alkali resistance test, in which the aluminum pigment was dispersed in fluorocarbon resin and then electrostatically sprayed on the surface of a workpiece, wherein the alkali resistance test was performed by immersing the workpiece after paint film spraying in a 5% NaOH solution, and the acid test was performed by immersing the workpiece after paint film spraying in a 10% HCl solution, and the specific test data are shown in table 3.

TABLE 3 test data for acid and base resistance

	Results of acid resistance test	Alkali resistance test results
			Example 1	215min later, the surface of the paint film begins to have marks	After 100min, marks begin to appear on the surface of the paint film
Example 2	Marking begins to appear on the surface of the paint film after 225min	After 115min, marks begin to appear on the surface of the paint film
			Example 3	After 180min, marks begin to appear on the surface of the paint film	After 90min, marks begin to appear on the surface of the paint film
Comparative example 1	After 160min, marks begin to appear on the surface of the paint film	After 70min, marks begin to appear on the surface of the paint film
			Comparative example 2	After 115min, marks begin to appear on the surface of the paint film	After 45min, marks begin to appear on the surface of the paint film

The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention, and various modifications and changes may be made by those skilled in the art. Any modification or equivalent substitution made by the present specification, which is directly or indirectly applicable to other related technical fields, within the spirit and principle of the present invention, shall be included in the scope of the present invention.