WO2010133119A1 - Salt free, oxidation-resistant zinc cyanamide anticorrosive pigments for environment-friendly mirror back coatings and preparation method thereof - Google Patents

Abstract

Salt free, oxidation-resistant zinc cyanamide anticorrosive pigments for environment-friendly mirror back coatings are disclosed, which are obtained by reacting zinc oxide with cyanamide compounds and adding coupling agents. The method for preparing the pigments comprises the following steps: preparing uniform zinc oxide slurry by completely dispersing highly active zinc oxide into deionized water, slowly adding cyanamide compounds, carrying out exothermic reaction under stirring and dispersing, stirring at high-speed to complete reaction when the temperature lowers, and then adding coupling agents.

Description

 Salt-free, anti-oxidation type cyanamide zinc anticorrosive pigment for environmental protection mirror back coating and production method thereof  Technical field

The invention relates to an anticorrosive pigment and a production method in the chemical industry, in particular to a salt-free and anti-oxidation type cyanamide zinc anticorrosive pigment and a production method thereof for the environmental protection mirror back coating.

Background technique

The silver or aluminum layer on the mirror is protected by a mirror back coating, but it is highly susceptible to corrosion and decomposition when present in the environment, such as moisture, atmospheric pollutants, salt, hydrogen sulfide, ammonia and chloride. Especially in the steel structure heavy anti-corrosion primer, zinc phosphate, aluminum tripolyphosphate and the like are often used as anti-corrosion pigments, but the effect is opposite to the expectation, and does not have a good antiseptic effect in the mirror back coating. It actually has a corrosive effect on the silver or aluminum layer.

The coating used for the mirror back coating is mainly a one-component amino baking varnish cured by a melamine resin, and a metal-containing cyanamide antioxidant pigment can impart an excellent corrosion-resistant mirror back coating.

At present, the method for producing zinc cyanamide has a calcination method in which zinc oxide is calcined together with an excess amount of urea or dicyandiamide under nitrogen or vacuum, first at 135 ° C to 200 ° C, and then at 600 ° C to 800 ° C. In hours, a zinc cyanamide pigment is obtained. The disadvantage of this high energy consumption method is that the resulting product structure is quite "closed", exhibiting a low specific surface area and porosity, and thus reduced reactivity, and does not have the high corrosion protection activity required for the mirror back coating system.

There is also a wet process for preparing zinc cyanamide which is prepared by dissolving a soluble zinc salt in water and precipitating it with an alkali metal hydrocyanamide salt. In order to eliminate by-products, it requires a large amount of water to be washed, thus generating a large amount of waste water. What is more serious is that the soluble salt impurities are not easily removed completely. Therefore, the mirror back coating made of cyanamide zinc by this method has the influence of a trace amount of soluble by-products caused by zinc cyanamide.

It is also possible to first react the dissolved calcium cyanamide with sulfuric acid and carbon dioxide to obtain an aqueous solution of cyanamide hydrogen, and then react the intermediate product with zinc oxide, and then filter and dry the product. Due to the large amount of carbonic acid and sulfuric acid, application in mirror back coatings is limited.

The above various routes for preparing zinc cyanamide have the following disadvantages, and are required to be obtained by excessive cyanamide compound, nitrogen or under vacuum, and at a high temperature; or by precipitation of hydrocyanamide salt; or by preparing cyanide. The amine hydrogen intermediate product is prepared with zinc oxide, has low product activity, high by-products, high water-soluble salt, high energy consumption and complicated process. Therefore, the development of environmentally friendly mirror back coatings for salt-free, anti-oxidant zinc cyanide anti-corrosion pigments is of great significance to improve the corrosion resistance of mirror coatings.

Summary of the invention

The purpose of the invention is to solve the deficiencies of the above-mentioned technologies and to provide a non-environmental mirror-back coating which has less raw materials, low energy consumption, less waste water, less by-products, simple process and good anti-corrosion performance of the pigment. Salt-free, anti-oxidation zinc cyanide anticorrosive pigment and production method.

In order to achieve the above object, the salt-free and oxidation-resistant zinc cyanide anticorrosive pigment for environmentally friendly mirror coatings designed by the present invention is a product obtained by reacting zinc oxide with a cyanamide compound and adding a coupling agent.

The method for producing the salt-free and anti-oxidation type cyanamide anti-corrosion pigment for the environmental protection mirror back coating designed by the invention is to completely disperse the highly active zinc oxide into the deionized water to prepare a uniform zinc oxide slurry, and slowly add the solution. The cyanamide compound starts the exothermic reaction under stirring and dispersion, and when the temperature starts to decrease, it is stirred at a high speed to completely react. Through instrumental observation, it is found that the tiny particles begin to decrease until there is no particles, the water is statically separated, and the separated water is recycled for the next time to obtain the zinc oxide slurry, and the separated zinc cyanamide precipitate is subjected to pressure filtration to remove water. Then dry at 105 ° C until the moisture is less than 0. 1% or less, pulverization is carried out, and the fineness reaches 320 mesh sieve residue less than 0.05% or less to obtain a zinc cyanamide anticorrosive pigment.

 In order to mention the stability of the obtained zinc cyanide anticorrosive pigment, a coupling agent may be added in the reaction of zinc oxide and a cyanamide compound.

In order to save cost and achieve the best reaction effect of the production method designed by the invention, the weight fraction of zinc oxide, deionized water, cyanamide compound and coupling agent in the reaction is 15-25 parts of zinc oxide, respectively. 55-65 parts of ionized water, 18-23 parts of cyanamide compound, and 1.5-2.5 parts of coupling agent. The highly active zinc oxide is ZnO-Xl or ZnO-X2 Or ZnO-Tl or Zn0-T2 or Zn0 -T3 or BA01-05 (type I) or BA01-05 (type II): The cyanamide compound is urea or dicyandiamide or hydrocyanamide or monocyanamide. The coupling agent is 1121# coupling agent or JN-A coupling agent or TYZOR AA-75 coupling agent or KH-550 coupling agent.

 The production method of the salt-free and anti-oxidation type cyanamide anti-corrosion pigment for the environmental protection mirror back coating obtained by the invention is mainly carried out according to the following chemical equation:

Zn0+ H ₂ 0+H ₂ CN ₂ →ZnNCN +H ₂ O

The core part is made of high-activity zinc oxide, reacted with metal cyanamide compound in an aqueous medium, and completely reacted at room temperature by a specific process technology to achieve impurity-free salt impurities. After adding a coupling agent, it is ensured. Stability, through the filtration, water separation, pressure filtration, drying, pulverization production process, to obtain salt-free, antioxidant-type zinc cyanamide pigment. Due to the use of highly active zinc oxide, the reaction rate is improved, especially through specific reaction equipment and process technology, as well as key process control means, so that the content of water-soluble free salts and impurities of zinc cyanamide is less than 0.2%.

 The zinc cyanamide anticorrosive pigment of the present invention has the following advantages:

The product does not contain lead, oil absorption, water soluble free salt and low impurity content, good dispersibility, can inhibit the oxidation of the substrate or metal layer, prevent the saponification of the coating, neutralize the free sulfides and chlorides generated or present during the corrosion process. Ions, save energy, reduce environmental pollution, reduce manufacturing costs, product performance has reached advanced levels in foreign countries, and has good economic benefits.

 detailed description

 The invention is further described below by way of embodiments with reference to the accompanying drawings.

 Example 1:

 In a specific reaction unit equipped with a stirrer and a condenser, 15g-25g ZnO-Tl zinc oxide is put into 55g-65g Dissolve completely in deionized water, prepare a uniform zinc oxide slurry, slowly add 18g-23g of monocyanamide, start the exothermic reaction under stirring and dispersion, and when the temperature begins to drop, stir it at high speed to make it completely react. The instrument observed that the tiny particles began to decrease until no particles were added, adding 1.5g-2.5g. The KH-550 coupling agent is evenly stirred, and the water is separated at rest. The separated water is recycled for the next time to obtain the zinc oxide slurry, and the separated zinc cyanide precipitate is filtered by a plate and frame filter to remove water, and then The stainless steel constant temperature oven is dried at 105 ° C to a moisture content of less than 0.1%, and is transferred to a stainless steel powder machine for pulverization, and the fineness reaches 320 mesh sieve residue of less than 0.05%.

 Example 2:

In a specific reaction device equipped with a stirrer and a condenser, 15g-20g ZnO-Xl zinc oxide is completely dispersed in 50g-65g deionized water to prepare a uniform zinc oxide slurry, and slowly add 15g-20g dicyandiamide Under stirring and dispersion, the exothermic reaction begins. When the temperature begins to decrease, high-speed stirring is carried out to completely react. It is observed by the instrument that the fine particles begin to decrease until no particles are added, and 1.5g-2.0g KH-550 is added. The mixture is stirred evenly, and the water is separated at rest. The separated water is recycled for the next time to obtain the zinc oxide slurry, and the separated zinc cyanide precipitate is filtered by a plate and frame filter to remove water, and then the stainless steel constant temperature oven is used. The medium is dried at 105 ° C to a moisture content of less than 0.1%, and is transferred to a stainless steel powder machine for pulverization, and the fineness reaches 320 mesh sieve residue of less than 0.05%.

 Example 3:

In a specific reaction device equipped with a stirrer and a condenser, 15g-25g of ZnO-Xl zinc oxide is completely dispersed in 55g-60g of deionized water to prepare a uniform zinc oxide slurry, and 18g-20g of dicyandiamide is slowly added. Under stirring and dispersion, the exothermic reaction begins. When the temperature begins to decrease, high-speed stirring is performed to completely react. It is observed by the instrument that the fine particles begin to decrease until no particles are added, and 0.5g-1.5g is added. TYZOR The AA-75 coupling agent is evenly stirred, and the water is separated at rest. The separated water is recycled for the next time to obtain the zinc oxide slurry, and the separated zinc cyanide precipitate is filtered by a plate and frame filter to remove water, and then The stainless steel constant temperature oven is dried at l05 ° C to a moisture content of less than 0.1%, and is transferred to a stainless steel powder machine for pulverization, and the fineness reaches 320 mesh sieve residue of less than 0.05%.

 Example 4:

In a specific reaction device equipped with a stirrer and a condenser, 20g-30g BA01-05 (type II) zinc oxide is completely dispersed in 50g-55g deionized water to prepare a uniform zinc oxide slurry, and slowly add 18g- 25g dicyandiamide, under stirring and dispersion, began to exothermic reaction. When the temperature began to drop, high-speed stirring was carried out to completely react. It was observed by the instrument that the tiny particles began to decrease until no particles were added, and 1.5g-2.0 was added. g TYZOR The AA-75 coupling agent is evenly stirred, and the water is separated at rest. The separated water is recycled for the next time to obtain the zinc oxide slurry, and the separated zinc cyanide precipitate is filtered by a plate and frame filter to remove water, and then The stainless steel constant temperature oven is dried at 105 ° C to a moisture content of less than 0.1%, and is transferred to a stainless steel powder machine for pulverization. The fineness reaches 320 mesh and the residue is less than 0. 05% or less.

 Example 5:

In a specific reaction device equipped with a stirrer and a condenser, 18g-25g BA01-05 (type II) zinc oxide is completely dispersed in 53g-62g deionized water to prepare a uniform zinc oxide slurry, and slowly add 18g- 21g of monocyanamide, under stirring and dispersion, began to exothermic reaction. When the temperature began to drop, high-speed stirring was carried out to completely react. It was observed by the instrument that the tiny particles began to decrease until no particles were added, and 1.5 g was added. 2.2g The KH-550 coupling agent is evenly stirred, and the water is separated at rest. The separated water is recycled for the next time to obtain the zinc oxide slurry, and the separated zinc cyanide precipitate is filtered by a plate and frame filter to remove water, and then The stainless steel constant temperature oven is dried at 105 ° C to a moisture content of less than 0.1%, and is transferred to a stainless steel powder machine for pulverization, and the fineness reaches 320 mesh sieve residue of less than 0.05%.

 The test results of the zinc cyanamide performance in the above 1-5 examples are shown in Table 1.

Table 1: Performance Example 1 Example 2 Example 3 Example 4 Example 5 Exterior White powder White powder White powder White powder White powder Oil absorption value (g/100 g) 12.5 13.5 15 14 16.5 Moisture (%) 0.08 0.05 0.07 0.04 0.08 320 mesh residue (%) 0.02 0.025 0.03 0.01 0.04 No salt (water soluble salt) (%) 0.11 0.25 0.45 0.3 0.7

 The mirror back paint was prepared by the proportion of the coating formulation of the above-mentioned 1-5 examples in the following examples, as shown in Table 2.

Table 2: Performance A1 A2 A3 A4 A5 A6 Epoxy modified alkyd resin 40 40 40 40 40 40 Melamine resin 5.5 5.5 5.5 5.5 5.5 5.5 talcum powder 18 17.5 18 18.5 twenty one 18 Iron red powder 15 16 15.5 16 14 15 Dispersant 0.4 0.4 0.4 0.4 0.4 0.4 Example 1 8.5 Example 2 8.5 Example 3 8.5 Example 4 8.5 Example 5 8.5 Wayne company comparison 8.5 Drier 1.2 1.2 1.2 1.2 1.2 1.2 Xylene 11.4 10.9 10.9 9.9 9.4 11.4 total 100 100 100 100 100 100

 The results of the anti-humidity performance, the anti-neutral salt spray performance, and the optical performance of the mirror-back paint prepared by using the zinc cyanamide in the above 1-5 examples are shown in Table 3.

table 3: Performance A1 A2 A3 A4 A5 A6 Humidity resistance: 55±°C Humidity 90% 400h There is no obvious change in the reflective coating, and the protective coating cannot be bubbled or separated. There is no obvious change in the reflective coating, and the protective coating has no bubbling and separation. Protective coating produces bubbling Reflective coating darkens Large amount of foaming of the coating There is a clear change in the reflective coating, and the protection is separated. A small amount of reflective coating changes, the protective coating is free of bubbles and separation Anti-neutral salt spray performance: According to GB/T1771, the salt spray test chamber is placed for 240h. The reflective layer allows four change points with diameter d≤0.3mm and two protective coating points and edges with diameter d≤2.5mm. The coating loss extends up to 3.5mm inward. The reflective layer has no change point, the protective coating has no change point, and the edge coating loss extends up to 0.13mm. The reflective layer has a small number of change points and the protective coating has no change point. More reflective points with a reflective layer diameter of 0.3 mm or more The protective coating has many points and the edge coating has a large loss. The reflective layer changes a lot and the protective coating begins to fall off. There is no change point in the reflective layer, no change in the protective coating, and the maximum loss of the edge coating extends 0.15mm inward. Optical performance: visible light reflectance ≥ 85% 87.73% 82.55% 75.11% 69% 54.85% 86.99%

Claims (7)

The invention relates to a salt-free and anti-oxidation type zinc cyanide anticorrosive pigment for environmental protection mirror back coating, which is characterized in that the product is obtained by reacting zinc oxide with a cyanamide compound and adding a coupling agent. The invention relates to a method for producing a salt-free and oxidation-resistant zinc cyanide anticorrosive pigment for environmental protection mirror coating according to claim 1, which is characterized in that high-activity zinc oxide is completely dispersed in deionized water to obtain uniform oxidation. Zinc pulp, slowly add cyanamide compound, start stirring reaction under stirring and stirring. When the temperature starts to drop, stir it at high speed to make it completely react. Observe through the instrument, the tiny particles begin to decrease until there is no particle. The water is separated at rest, and the separated water is recycled for the next time to obtain the zinc oxide slurry, and the separated zinc cyanamide precipitate is subjected to pressure filtration to remove water, and then dried at 105 ° C until the water content is less than 0.1%, and is pulverized. The fineness of 320 mesh sieve residue is less than 0.05% to obtain zinc cyanide anticorrosive pigment. The method for producing a salt-free and oxidation-resistant zinc cyanamide anticorrosive pigment for environmentally-friendly mirror coating according to claim 2, wherein a coupling agent is added during the reaction between the zinc oxide and the cyanamide compound. The method for producing a salt-free and oxidation-resistant zinc cyanide anticorrosive pigment for environmentally-friendly mirror coating according to claim 2, wherein the zinc oxide, deionized water and cyanamide compound have a weight fraction of zinc oxide, respectively. 15-25 parts, deionized water 55-65 parts, cyanamide compound 18-23 parts. The method for producing a salt-free and oxidation-resistant zinc cyanamide anticorrosive pigment for environmentally-friendly mirror coating according to claim 3, characterized in that the weight fraction of the zinc oxide, deionized water, cyanamide compound and coupling agent is They are 15-25 parts of zinc oxide, 55-65 parts of deionized water, 18-23 parts of cyanamide compound, and 1.5-2.5 parts of coupling agent. The method for producing a salt-free and oxidation-resistant zinc cyanide anticorrosive pigment for environmentally-friendly mirror coating according to claim 2 or 3 or 4 or 5, wherein the highly active zinc oxide is ZnO-Xl Or ZnO-X2 or ZnO-T1 or ZnO-T2 or ZnO-T3 or BA01-05 (type I) or BA01-05 (type II); the cyanamide compound is urea or dicyandiamide or hydrocyanamide salt Or monocyanamide. The method for producing a salt-free and oxidation-resistant zinc cyanide anticorrosive pigment for environmentally friendly mirror coating according to claim 3 or 5, wherein the coupling agent is a 1121# coupling agent or a JN-A coupling. Agent or TYZOR AA-75 coupling agent or KH-550 coupling agent.