Zinc silicate primer and preparation method thereof

Abstract

The invention discloses a zinc silicate primer and a preparation method thereof, and relates to the technical field of zinc silicate primer. A preparation method of zinc silicate primer comprises the following steps: (1) adding ethyl silicate, water, organic solvent A and oxalic acid into a closed container, adding a co-catalyst under an inert atmosphere for reaction, washing and drying the obtained product after purification, and obtaining an adhesive; (2) adding a thickener, an organic solvent B and zinc powder into the adhesive, and mixing them uniformly to obtain the zinc silicate primer; in step (1), the mass ratio of ethyl silicate, water, organic solvent A and oxalic acid is (8-12): 1: (8-12): (0.1-0.2). The present invention adopts degradable oxalic acid to replace inorganic acid, and chloride ions are not introduced in the preparation process, which effectively reduces the corrosion of chloride ions on the metal surface and prolongs the service life of the primer.

Description

Technical Field

[0001] The invention relates to the technical field of zinc silicate primers, in particular to a zinc silicate primer and a preparation method thereof. Background Art

[0002] Inorganic zinc silicate primer is widely used on metal surfaces as a transition layer material to enhance the adhesion of paint on metal surfaces. Due to the presence of zinc powder, inorganic zinc silicate primer has cathodic protection and anti-rust properties. It also has the advantages of good heat resistance, good low-temperature curing, good impact resistance and compatibility with most coating systems. Inorganic zinc silicate primer is a two-component coating consisting of two components: an inorganic binder and dusty / flaky metallic zinc. When used, the two are mixed and applied to the surface of the metal substrate with a spray gun or brush. It can be cured and formed at room temperature and humidity. The inorganic binder is obtained by hydrolysis of ethyl silicate, and then colored with silica, clay or other inert fillers.

[0003] In the hydrolysis process of inorganic adhesives, inorganic acids (mainly hydrochloric acid) are required as catalysts in industrial production. However, the introduction of hydrochloric acid will cause harm to the environment and human health. It is corrosive to human skin, mucous membranes, etc., and careless use will cause serious burns to body parts. At the same time, the chloride ions in hydrochloric acid will accelerate the corrosion of metals, reduce the mechanical and electrical properties of the metal surface, shorten its service life, and pose a huge safety hazard. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a zinc silicate primer and a preparation method thereof. The present invention uses degradable oxalic acid to replace inorganic acid, and no chloride ions are introduced during the preparation process, which effectively reduces the corrosion of chloride ions on the metal surface and prolongs the service life of the primer.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, the present invention provides a method for preparing a zinc silicate primer, comprising the following steps:

[0007] (1) adding ethyl silicate, water, organic solvent A, and oxalic acid into a sealed container, adding a co-catalyst to react under an inert atmosphere, purifying the obtained product, washing, and drying the product to obtain an adhesive;

[0008] (2) adding a thickener, an organic solvent B and zinc powder to the adhesive, and mixing them evenly to obtain a zinc silicate primer;

[0009] In the step (1), the mass ratio of ethyl silicate, water, organic solvent A and oxalic acid is (8-12):1:(8-12):(0.1-0.2).

[0010] The present invention adopts oxalic acid as a main catalyst to catalyze the hydrolysis of ethyl silicate to prepare zinc silicate primer. Chloride ions are not introduced in the preparation process, which effectively reduces the corrosion of chloride ions on the metal surface and prolongs the service life of the primer. The addition of a co-catalyst is conducive to promoting the polymerization reaction of ethyl silicate. If the water content is too little, insufficient hydrolysis is likely to occur, thereby reducing the strength of the paint film; if the water content is too much, excessive hydrolysis is likely to occur, and gelation is likely to occur. In addition, too high or too low oxalic acid content will affect the hydrolysis process of ethyl silicate. Therefore, the present invention controls the mass ratio of water to ethyl silicate and organic solvent A within the above range, so that the hydrolysis process of ethyl silicate is not easily affected, thereby improving the performance of the adhesive.

[0011] Preferably, the purification in step (1) is performed by replacing the solvent of the product with an organic solution of polyethyl silicate containing terminal hydroxyl groups and ethoxy groups.

[0012] The invention adds polyethyl silicate to carry out solvent replacement on the product, which is beneficial to purify the hydrolyzate of ethyl silicate and further improve the performance of the adhesive.

[0013] Preferably, the organic solvent A in step (1) is at least one of ethylene glycol ethyl ether, butyl acetate and butanol.

[0014] Preferably, the co-catalyst in step (1) is at least one of ammonium hydroxide, sodium hydroxide and yttrium chloride.

[0015] More preferably, the co-catalyst in step (1) is ammonium hydroxide.

[0016] Since ammonium hydroxide is a weak catalyst, it can promote the polymerization reaction of ethyl silicate, so that the adhesive has a higher degree of curing and adhesion.

[0017] Preferably, after the solvent replacement in step (1), a mixed solution of trimethylchlorosilane and n-hexane is added for modification treatment.

[0018] The invention adds trimethylchlorosilane to carry out surface hydrophobic modification on the product, which is beneficial to reducing the water content in the adhesive. The n-hexane provides a channel for the trimethylchlorosilane during gel modification, which is beneficial to shortening the modification time and improving the modification efficiency.

[0019] More preferably, the volume ratio of trimethylchlorosilane to n-hexane is (8-12):(86-94).

[0020] The present invention uses trimethylchlorosilane and n-hexane in a specific ratio to perform surface modification on the product, which is beneficial to reducing the usage of trimethylchlorosilane, thereby reducing the number of solvent replacements after gel modification, shortening the aerogel preparation cycle and reducing production costs.

[0021] Preferably, the thickener in step (2) is at least one of silicon dioxide and bentonite.

[0022] Preferably, the organic solvent B in step (2) is at least one of benzophenone, isopropanol and o-xylene.

[0023] Preferably, in step (2), the mass ratio of the adhesive, the thickener, the organic solvent B, and the zinc powder is (42-47): (20-24): (33-37): (60-70).

[0024] In the present invention, by controlling the mass ratio of the adhesive, the thickener, the organic solvent B, and the zinc powder, the emulsion is dispersed evenly, and the filler is prevented from sinking, which is beneficial for storage and painting. Since the zinc powder has the functions of cathode protection and rust prevention, by controlling the amount of the zinc powder, the adhesion of the primer is further improved.

[0025] Preferably, in step (2), a 50-70 mesh filter is used for screening.

[0026] The invention adopts a filter screen with a specific mesh number for sieving, and can remove components with larger particle sizes in the primer.

[0027] In a second aspect, the present invention also provides a zinc silicate primer prepared by the above method.

[0028] The zinc silicate primer prepared by the invention has excellent adhesion and mechanical properties and can be used as a high-quality transitional connecting layer material to enhance the adhesion of the coating on the metal surface.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention uses oxalic acid to catalyze the hydrolysis of ethyl silicate to prepare the zinc silicate primer, and no chloride ions are introduced during the preparation process, which effectively reduces the corrosion of chloride ions on the metal surface and prolongs the service life of the primer. In addition, the zinc silicate primer prepared by the present invention can be used as a high-quality transitional connecting layer material to enhance the adhesion of the coating on the metal surface. DETAILED DESCRIPTION

[0031] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the protection scope and implementation methods of the present invention are not limited thereto.

[0032] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0033] name factory model Ethyl silicate Chengfeng Chemical ZQ-342-Si28 Ethylene glycol ether Shandong Taixi Chemical / oxalic acid Weifang Huabo Chemical / Ethyl Polysilicate Hubei Tosoh Chemical Si-40 Trimethylchlorosilane Wuhan Jixinyibang /

[0034] Example 1

[0035] A method for preparing a zinc silicate primer comprises the following steps:

[0036] (1) Using a peristaltic pump, 21 g of ethyl silicate, 2.5 g of water and 21 g of ethylene glycol ethyl ether were sequentially poured into a four-necked round-bottom flask equipped with a thermometer, a titration funnel and a condenser, and nitrogen was introduced into the flask, and the mixture was mixed and stirred at room temperature for 40 min; then 0.3 g of oxalic acid was added, and nitrogen was continued to be introduced, and the mixture was stirred for 15 min, and dried for 18 h in a nitrogen atmosphere; then 0.5 g of ammonium hydroxide was added, and nitrogen was continued to be introduced, and the mixture was stirred for 12 h, and dried for 18 h in a nitrogen atmosphere; the dried product was dispersed in an organic solvent of polyethyl silicate containing terminal hydroxyl groups and ethoxy groups, and the solvent was replaced once every 12 h as a sol, and the solvent was replaced twice in total; after the replacement was completed, the sample was immersed in a mixed solution of trimethylchlorosilane and n-hexane with a volume ratio of 1:9 for modification; the modified sample was washed with n-hexane; the washed sample was dried at 150° C. for 3 h to obtain an adhesive;

[0037] (2) Weigh 45 g of an adhesive into a round-bottom flask, then add 22 g of silicon dioxide (particle size 15-50 nm), 2 g of benzophenone, 13 g of isopropanol, and 20 g of o-xylene, stir for 30 min, during which nitrogen is continuously introduced to maintain an inert environment, and mix well to obtain a colored adhesive;

[0038] (3) Mix the colored adhesive and zinc powder in a mass ratio of 40:60, slowly add the zinc powder into the adhesive while stirring; after the mixture is evenly stirred, filter with a 60-mesh filter to obtain a zinc silicate primer.

[0039] When spraying zinc silicate primer, the zinc silicate primer should be stirred continuously to prevent the performance of the zinc silicate primer from deteriorating due to aluminum powder precipitation.

[0040] In this embodiment, the mass ratio of ethyl silicate, water, ethylene glycol ethyl ether and oxalic acid in step (1) is 8.4:1:8.4:0.12.

[0041] Example 2

[0042] The difference from Example 1 is that the mass ratio of ethyl silicate, water, ethylene glycol ethyl ether and oxalic acid in step (1) is 8:1:8:0.12, and the other steps are the same as Example 1.

[0043] Example 3

[0044] The difference from Example 1 is that the mass ratio of ethyl silicate, water, ethylene glycol ethyl ether and oxalic acid in step (1) is 12:1:12:0.12, and the other steps are the same as Example 1.

[0045] Example 4

[0046] The difference from Example 1 is that the mass ratio of ethyl silicate, water, ethylene glycol ethyl ether and oxalic acid in step (1) is 8.4:1:8.4:0.2, and the other steps are the same as Example 1.

[0047] Comparative Example 1

[0048] The difference from Example 1 is that in step (1), an equal mass of hydrochloric acid is used instead of oxalic acid, and the other steps are the same as in Example 1.

[0049] Comparative Example 2

[0050] The difference from Example 1 is that in step (1), an equal amount of acetic acid is used instead of oxalic acid, and the other steps are the same as in Example 1.

[0051] Comparative Example 3

[0052] The difference from Example 1 is that an equal amount of lactic acid is used instead of oxalic acid in step (1), and the other steps are the same as those in Example 1.

[0053] Comparative Example 4

[0054] The difference from Example 1 is that an equal amount of citric acid is used instead of oxalic acid in step (1), and the other steps are the same as those in Example 1.

[0055] Comparative Example 5

[0056] The difference from Example 1 is that the mass ratio of ethyl silicate, water, ethylene glycol ethyl ether and oxalic acid in step (1) is 5:1:8:0.12, and the other steps are the same as Example 1.

[0057] Comparative Example 6

[0058] The difference from Example 1 is that the mass ratio of ethyl silicate, water and ethylene glycol ethyl ether in step (1) is 1:1:3:0.12, and the other steps are the same as Example 1.

[0059] Comparative Example 7

[0060] The difference from Example 1 is that the mass ratio of ethyl silicate, water, ethylene glycol ethyl ether and oxalic acid in step (1) is 8.4:1:8.4:0.04, and the other steps are the same as Example 1.

[0061] Comparative Example 8

[0062] The difference from Example 1 is that the mass ratio of ethyl silicate, water, ethylene glycol ethyl ether and oxalic acid in step (1) is 8.4:1:8.4:0.32, and the other steps are the same as Example 1.

[0063] experiment

[0064] The adhesives prepared in Examples 1-4 and Comparative Examples 1-8 were respectively subjected to hydrolysis degree test, service life test, and film-forming ability test. The primers prepared in Examples 1-4 and Comparative Examples 1-8 were respectively subjected to mechanical property test. The test results are shown in Tables 1, 2, and 3.

[0065] Degree of hydrolysis of ethyl silicate: Since the degree of hydrolysis is proportional to the amount of silica formed by hydrolysis of ethyl silicate, the degree of hydrolysis is measured by the percentage of silica formed. The test method is carried out in accordance with "ASTM D 2369-07". The acidity is measured by the pH determination method.

[0066] The surface drying and thorough drying time tests are carried out in accordance with "ASTM D 1640", the hardness test is carried out in accordance with "GB / T 6739-2006", the adhesion test is carried out in accordance with "GB / T 9286-1998", and the abrasion resistance test is carried out in accordance with "ASTM D 4145".

[0067] Table 1

[0068] Acidity / kPa Silicon dioxide content / % Example 1 1.27 28.00 Example 2 1.27 28.03 Example 3 1.27 27.98 Example 4 1.27 28.12 Comparative Example 1 -8 29.00 Comparative Example 2 3.15 22.48 Comparative Example 3 3.86 19.38 Comparative Example 4 4.76 18.8 Comparative Example 5 1.27 36.25 Comparative Example 6 1.27 44.72 Comparative Example 7 1.27 13.56 Comparative Example 8 1.27 35.26

[0069] Table 2

[0070]

[0071]

[0072] Table 3

[0073]

[0074]

[0075] From the comparison of Comparative Examples 1-4 with Example 1 in Table 1 and Table 2, it can be seen that after mixing with zinc powder, the sol of the acetic acid and lactic acid catalyst system gelled immediately, while the primer coating obtained by mixing zinc powder with the sol of the oxalic acid and citric acid catalyst system has good stability, which is similar to the hydrochloric acid catalyst system. The primers of the acetic acid and lactic acid catalyst systems have a shorter service life and instability, which can be attributed to the higher acid value of the acid. In the process of hydrolyzing the binder, the generated SiO 2For the hydrochloric acid and oxalic acid catalytic systems, sol particles can only be observed after 30 days of hydrolysis, and the size of both sols increases at a very slow rate, which makes the adhesive prepared by the method of the present invention have a long shelf life and can be used for industrial applications.

[0076] According to the comparison between comparative examples 5-8 in Table 1 and the embodiments, the mass ratio of ethyl silicate, water, ethylene glycol ethyl ether, and oxalic acid is not within the scope of the present invention, and gelation or silicon dioxide precipitation and the like will occur, and the coating cannot form a film. Therefore, only by controlling the mass ratio of ethyl silicate, water, ethylene glycol ethyl ether, and oxalic acid within the scope defined by the present invention can the primer coating have a hard film with excellent adhesion, and also have excellent mechanical properties, and can be used as a high-quality transitional connecting layer material for enhancing the adhesion of the coating on the metal surface.

[0077] From the comparison between Example 1 and Comparative Example 1 in Table 3, it can be seen that at 25°C, the surface drying time and actual drying time of the primer at different relative humidity decrease with the increase of relative humidity, and the drying speed of the oxalic acid system is slightly slower than that of the hydrochloric acid system; in the hardness test, the primers all passed the 7H pencil hardness test; from the adhesion test, it can be seen that the adhesion of the oxalic acid system on the steel substrate is better than that of the hydrochloric acid system; from the wear resistance test, it can be seen that no delamination or detachment of the coating at the edge and in the square lattice was observed. Therefore, the oxalic acid system has equally excellent mechanical properties compared to the traditional hydrochloric acid system.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a zinc silicate primer, It is characterized in that The following steps are involved: (1) adding ethyl silicate, water, organic solvent A, and oxalic acid into a sealed container, adding a co-catalyst to react under an inert atmosphere, purifying the obtained product, washing, and drying the product to obtain an adhesive; (2) adding a thickener, an organic solvent B and zinc powder to the adhesive, and mixing them evenly to obtain a zinc silicate primer; In the step (1), the mass ratio of ethyl silicate, water, organic solvent A and oxalic acid is (8-12):1:(8-12):(0.1-0.2).

2. The method for preparing the zinc silicate primer according to claim 1, It is characterized in that The purification in step (1) is as follows: using an organic solvent of polyethyl silicate containing terminal hydroxyl groups and ethoxy groups to replace the solvent of the product.

3. The preparation method of zinc silicate primer as claimed in claim 2, It is characterized in that After the solvent replacement in step (1), a mixed solution of trimethylchlorosilane and n-hexane is added for modification.

4. The method for preparing the zinc silicate primer according to claim 1, It is characterized in that In the step (1), the organic solvent A is at least one of ethylene glycol ethyl ether, butyl acetate and butanol.

5. The preparation method of zinc silicate primer according to claim 1, It is characterized in that The co-catalyst in step (1) is at least one of ammonium hydroxide, sodium hydroxide and yttrium chloride.

6. The method for preparing the zinc silicate primer according to claim 3, It is characterized in that The volume ratio of trimethylchlorosilane to n-hexane is (8-12):(86-94).

7. The preparation method of the zinc silicate primer according to claim 1, It is characterized in that The thickener in step (2) is at least one of silicon dioxide and bentonite.

8. The method for preparing the zinc silicate primer according to claim 1, It is characterized in that In the step (2), the organic solvent B is at least one of benzophenone, isopropanol and o-xylene.

9. The method for preparing the zinc silicate primer according to claim 1, It is characterized in that In the step (2), the mass ratio of the adhesive, the thickener, the organic solvent B, and the zinc powder is (42-47): (20-24): (33-37): (60-70).

10. The zinc silicate primer prepared by the method for preparing the zinc silicate primer according to any one of claims 1 to 9.

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