Long-acting waterborne epoxy zinc-rich primer and preparation method thereof

Abstract

According to the long-acting waterborne epoxy zinc-rich primer and the preparation method thereof, zinc powder with the surface grafted with a polymer chain and carboxyl functionalized graphene oxide are combined, on one hand, the polymer chain is grafted on the surface of the zinc powder, so that the zinc powder is easily dispersed in a water-free epoxy system and is not easily deposited in a component A; on the other hand, the polymer grafted on the surface of the zinc powder can be combined with carboxyl of the carboxyl functionalized graphene oxide to form a complex and staggered connection network structure, the isolated connection state among zinc powder particles in the coating is improved, a conductive network is optimized, and the coating can form long-acting corrosion-resistant protection; and on the other hand, the carboxyl functionalized graphene oxide has good hydrophilicity and lipophilicity, and after the component A and the component B are mixed, the carboxyl functionalized graphene oxide can be quickly connected with the zinc powder of which the surface is grafted with a polymer chain and drive the zinc powder to be uniformly dispersed, so that the zinc powder is better dispersed, the coating is more uniform and compact, and the flexibility and the impact strength of the coating are improved.

Description

Technical Field

[0001] The invention relates to the technical field of anti-corrosion coatings, and in particular to a long-acting water-based epoxy zinc-rich primer and a preparation method thereof. Background Art

[0002] With the implementation and promotion of national infrastructure construction, more and more steel structures are used. Solvent-based epoxy zinc-rich primer has excellent corrosion resistance, making it the most common and important primer for protecting steel. However, its VOC content is high and it seriously pollutes the atmospheric environment. In the current situation where the country strictly enforces environmental protection and prevents air pollution, water-based epoxy zinc-rich primer came into being. It has the advantages of low VOC content, safety and environmental friendliness. However, the salt spray resistance, mechanical properties, long-term anti-corrosion performance, anti-settling and anti-sagging performance of water-based epoxy zinc-rich primer are still not comparable to those of traditional solvent-based epoxy zinc-rich primer.

[0003] Generally speaking, the zinc powder content determines the anti-corrosion performance of water-based epoxy zinc-rich primers. A higher zinc powder content often enables the coating to obtain better corrosion protection performance. However, a high zinc powder content will also bring a series of problems, such as being environmentally unfriendly, having a larger mass, having a higher cost, and being prone to serious bottoming during storage. In the early stage of coating protection, the epoxy zinc-rich primer mainly acts as a cathodic protection. After being immersed in the corrosive medium for 168 hours, part of the zinc powder is oxidized into a non-conductive zinc salt, which weakens the interconnectivity between the zinc powders and reduces the efficiency of the zinc powder to a certain extent. At this time, the coating protection is mainly shielding.

[0004] Therefore, developing a new water-based epoxy zinc-rich primer that fully utilizes zinc powder, has excellent performance, and is green and environmentally friendly has become a trend in the current era. Summary of the invention

[0005] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a long-acting water-based epoxy zinc-rich primer, which is used to solve the problems of low zinc powder utilization, easy precipitation of zinc powder and poor corrosion resistance in the water-based epoxy zinc-rich primer in the prior art. At the same time, the present invention will also provide a preparation method of the long-acting water-based epoxy zinc-rich primer.

[0006] In order to achieve the above-mentioned object and other related objects, the present invention provides the following technical solutions: In a first aspect of the present invention, a long-lasting waterborne epoxy zinc-rich primer is provided, comprising component A and component B in a mass ratio of (3-5):1. Wherein, the A component includes the following components in mass percentage:

[0007] The B component includes the following components in mass percentage:

[0008] In the present invention, the polymer grafted in the zinc powder grafted with a polymer chain is selected from polyvinyl amide or polyvinyl alcohol, and the zinc powder grafted with a polymer chain is zinc powder grafted with polyvinyl amide or zinc powder grafted with polyvinyl alcohol.

[0009] When the zinc powder of the grafted polymer chain is zinc powder grafted with polyvinyl amide, the zinc powder grafted with polyvinyl amide is obtained by the following preparation method: the pretreated zinc powder is uniformly dispersed in water, vinylamide monomer is added during stirring, an initiator is added after sufficient mixing, a precipitate is obtained after heating reaction for a period of time, and the precipitate is washed, dried and crushed to obtain the zinc powder grafted with polyvinyl amide.

[0010] Wherein, the mass ratio of zinc powder to vinylamide monomer is 100:(10-50), preferably 100:(15-30); The initiator includes azobisisobutyronitrile (AIBN) or persulfate; The reaction temperature is 60-80°C and the reaction time is 2-6h.

[0011] During the polymerization reaction, the present invention firstly allows the polymerization monomer to fully cover the dispersed zinc powder, and then adds the initiator to stimulate the reaction, so that the polymer chains grafted on the surface of the zinc powder are more uniform and consistent, and the dispersibility of the zinc powder is also better.

[0012] When the zinc powder of the grafted polymer chain is zinc powder grafted with polyvinyl alcohol, the zinc powder grafted with polyvinyl alcohol is obtained by the following preparation method: dissolving polyvinyl alcohol powder in hot water, uniformly dispersing the pretreated zinc powder in the polyvinyl alcohol solution, adding a crosslinking agent during stirring, standing at room temperature for a period of time, and then washing, drying and crushing the precipitate to obtain the zinc powder grafted with polyvinyl alcohol.

[0013] Wherein, the cross-linking agent is selected from glutaraldehyde or glyceraldehyde; Due to the addition of cross-linking agent, in order to avoid excessive coating of polymer, the standing time is 1-3h; The hot water temperature is 70-90℃; The mass ratio of zinc powder to polyvinyl alcohol is 100:(5-20).

[0014] Furthermore, the zinc powder is spherical or flake, and has a size of 500 mesh, 800 mesh, 1000 mesh or 1200 mesh.

[0015] Furthermore, the pretreatment of the zinc powder includes: washing the zinc powder, soaking it in a solution containing an activator, stirring and activating it for a period of time, and drying it to obtain the pretreated zinc powder. The activation treatment can promote the grafting reaction of the polymer chain.

[0016] Furthermore, the activator includes a silane coupling agent or an isocyanate; the activator is preferably triethoxysilane 3-methylpropanoate.

[0017] The invention grafts polymer chains on the surface of zinc powder so that the zinc powder is easily dispersed in a water-free epoxy system and is not easily deposited in component A. Moreover, when component A and component B are mixed, the polyvinyl amide grafted on the surface of the zinc powder can be combined with the carboxyl group of carboxyl functionalized graphene oxide through an amine group to form an amide bond, or the polyvinyl alcohol grafted on the surface of the zinc powder can be bonded with the carboxyl group of carboxyl functionalized graphene oxide through a hydroxyl group to form an ester bond, and there is also covalent bonding, hydrogen bonding or π-π interaction between the polymer chain and the carboxyl functionalized graphene oxide, so that a complex and staggered network structure is formed between the zinc powder particles and the graphene oxide particles through the polymer chain and the carboxyl group, the isolated connection state between the zinc powder particles in the coating is improved, the conductive network is optimized, and the coating can form a long-term protection; at the same time, because the carboxyl functionalized graphene oxide is connected to the zinc powder particles, the hydrophilicity of the carboxyl group makes the zinc powder particles easy to be evenly dispersed in the water phase and not easy to agglomerate in the coating.

[0018] In the present invention, carboxyl functionalized graphene oxide is obtained by the following preparation method: graphene oxide is uniformly dispersed in deionized water, hydrobromic acid is added and stirred for a period of time, then oxalic acid is added and stirred for reaction, and the carboxyl functionalized graphene oxide is obtained after centrifugation, washing and freeze-drying.

[0019] Furthermore, the mass ratio of the graphene oxide, hydrobromic acid and oxalic acid is 1: (50-150): (10-30).

[0020] The present invention greatly improves the hydrophilicity and dispersibility of graphene oxide by carboxyl modification. Not only can it be evenly dispersed in the water-containing component B, but after the component A is mixed with the component B, it can quickly act on the polymer chain grafted on the surface of the zinc powder to drive the dispersion of the zinc powder, overcome the poor dispersion of the zinc powder, and enable the zinc powder to be evenly dispersed in the water-based epoxy system.

[0021] Furthermore, the graphene oxide is prepared by the Hummers method, which specifically includes the following steps: mixing natural flake graphite and sodium nitrate solid evenly, adding concentrated sulfuric acid while stirring, then adding potassium peroxide while stirring, stirring in an ice water bath for a period of time, and then stirring in a 35°C water bath for a period of time, and then adding deionized water, while raising the water bath temperature to 95°C, keeping stirring, and then quickly adding deionized water dropwise, and then adding hydrogen peroxide, filtering while hot, washing, centrifuging, and drying to obtain graphene oxide.

[0022] In the present invention, the dispersant is a high molecular polymer dispersant, such as dispersant BYK191 or Additol VXW6208 / 60 from Allnex, USA.

[0023] In the present invention, the co-solvent is selected from at least one of propylene glycol butyl ether (PNB) and dipropylene glycol butyl ether (DPNB).

[0024] In the present invention, the defoamer is selected from silicone defoamers, alkyl aryl phosphate defoamers or alkyl benzene sulfonate defoamers.

[0025] In the present invention, the thickener is selected from aqueous thickeners, such as aqueous polyurethane thickeners.

[0026] In the present invention, the adhesion promoter is selected from silane coupling agents and multifunctional acrylate promoters.

[0027] In the present invention, the substrate wetting agent is selected from a nonionic surfactant or an organic fluorine-modified wetting agent.

[0028] In the present invention, the filler wetting agent is selected from a phosphate wetting agent or a polycarboxylic acid wetting agent.

[0029] In the present invention, the flash rust inhibitor is selected from flash rust inhibitor C4E or flash rust inhibitor FRI1030.

[0030] The second aspect of the present invention provides a method for preparing a long-acting waterborne epoxy zinc-rich primer, comprising the following steps: (1) Preparation of component A: Add epoxy resin, dispersant, cosolvent, substrate wetting agent and zinc powder grafted with polymer chains in proportion to each other in a dispersion tank, stir them evenly, then add organic bentonite, filler wetting agent, defoamer, adhesion promoter and thickener, and stir them evenly; (2) Preparation of component B: Add water-based polyamide epoxy curing agent, carboxyl functionalized graphene oxide, anti-flash rust agent and water in a dispersion tank in proportion and stir well; (3) Mix component A and component B in a mass ratio of (3-5):1 and let it stand for a while.

[0031] As described above, the long-acting waterborne epoxy zinc-rich primer and the preparation method thereof of the present invention have the following beneficial effects: 1. The present invention grafts polymer chains on the surface of zinc powder. On the one hand, the zinc powder grafted with polymer chains is easily dispersed in a water-free epoxy system and is not easy to deposit in component A. On the other hand, the polymer grafted on the surface of the zinc powder can combine with the carboxyl group of carboxyl-functionalized graphene oxide to form a complex and staggered connection network structure, thereby improving the isolated connection state between zinc powder particles inside the coating, optimizing the conductive network, making full use of the zinc powder, and enabling the coating to form long-term corrosion protection. On the other hand, since the zinc powder is spaced apart by the carboxyl-functionalized graphene oxide, the zinc powder is better dispersed, and the coating is more uniform and dense, so the flexibility and impact strength of the coating are improved.

[0032] 2. The carboxyl functionalized graphene oxide prepared by the present invention has excellent hydrophilicity and lipophilicity. It can not only be evenly dispersed in the aqueous component B, but also can quickly connect the zinc powder with the surface grafted polymer chain after the component A is mixed with the component B and drive the uniform dispersion of the zinc powder, thus overcoming the poor dispersion characteristic of the zinc powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a graph showing the salt spray resistance test results of the long-lasting waterborne epoxy zinc-rich primer prepared in Example 1 of the present invention.

[0034] Figure 2 This is a graph showing the salt spray resistance test results of the long-lasting waterborne epoxy zinc-rich primer prepared in Example 2 of the present invention.

[0035] Figure 3 This is a graph showing the salt spray resistance test results of the waterborne epoxy zinc-rich primer prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0037] A carboxyl functionalized graphene oxide, the preparation method of which comprises the following steps: Graphene oxide was prepared by the Hummers method. 3.75 g of graphene oxide was dissolved in 1 L of deionized water and ultrasonically dispersed for 2 h. 200 mL of hydrobromic acid was added and stirred for 12 h. Then 50 g of oxalic acid solution was added and stirred for 4 h. After centrifugation, washing, and freeze-drying, a carboxyl-functionalized graphene oxide was obtained.

[0038] Example 1 A zinc powder grafted with polyvinyl amide, the preparation method of which comprises the following steps: 100g of zinc powder (800 mesh, 1:1 of spheres and flakes) was washed and immersed in a 1% ethanol solution of 3-aminopropyltriethoxysilane, and activated by stirring for 2h. After being taken out and dried, the zinc powder was evenly dispersed in 2L of deionized water, and ultrasonically dispersed for 2h. 20g of vinylamide monomer was added during stirring, and ultrasonically dispersed for 1h. Then, 0.2g of ammonium persulfate was added, and the temperature was raised to 70°C, and the reaction was carried out at a constant temperature for 6h. After washing, drying and crushing the precipitate, a zinc powder grafted with polyvinyl amide was obtained.

[0039] A long-lasting water-based epoxy zinc-rich primer, comprising component A and component B in a mass ratio of 3.5:1. Wherein, the A component includes the following components in mass percentage:

[0040] The B component includes the following components in mass percentage:

[0041] Example 2 A long-lasting water-based epoxy zinc-rich primer, comprising component A and component B in a mass ratio of 3.5:1. Wherein, the A component includes the following components in mass percentage:

[0042] The B component includes the following components in mass percentage:

[0043] Example 3 A zinc powder grafted with polyvinyl amide, the preparation method of which comprises the following steps: 100g of zinc powder (800 mesh, 1:1 spherical and flake) was washed and immersed in a 1% isocyanate chlorobenzene solution, stirred and activated for 2h, taken out and dried, and then the zinc powder was evenly dispersed in 2L of deionized water. After ultrasonic dispersion for 2h, 20g of vinylamide monomer was added during stirring, ultrasonic dispersion for 1h, and then 0.2g of azobisisobutyronitrile was added. The temperature was raised to 70°C and the reaction was carried out at a constant temperature for 6h. The precipitate was washed, dried and crushed to obtain a zinc powder grafted with polyvinyl amide.

[0044] A long-lasting water-based epoxy zinc-rich primer, comprising component A and component B in a mass ratio of 3.5:1. Wherein, the A component includes the following components in mass percentage:

[0045] The B component includes the following components in mass percentage:

[0046] Example 4 A zinc powder grafted with polyvinyl alcohol, the preparation method of which comprises the following steps: 100g of zinc powder (800 mesh, 1:1 sphere and flake) was washed and immersed in a 1% isocyanate toluene solution, stirred and activated for 2h, taken out and dried to obtain pretreated zinc powder; 15g of polyvinyl alcohol powder was dissolved in 1L of hot water at a temperature of 80°C, and the pretreated zinc powder was evenly dispersed in the polyvinyl alcohol solution. 0.1g of glutaraldehyde was added during stirring, mixed evenly, and allowed to stand at room temperature for 2h, and then the precipitate was washed, dried, and crushed to obtain the zinc powder grafted with polyvinyl alcohol.

[0047] A long-lasting water-based epoxy zinc-rich primer, comprising component A and component B in a mass ratio of 3.5:1. Wherein, the A component includes the following components in mass percentage:

[0048] The B component includes the following components in mass percentage:

[0049] Example 5 A long-lasting water-based epoxy zinc-rich primer, comprising component A and component B in a mass ratio of 3:1. Wherein, the A component includes the following components in mass percentage:

[0050] The B component includes the following components in mass percentage:

[0051] Comparative Example 1 A water-based epoxy zinc-rich primer comprises a component A and a component B in a mass ratio of 3.5:1. Wherein, the A component includes the following components in mass percentage:

[0052] The B component includes the following components in mass percentage:

[0053] The performance tests were conducted on the long-acting waterborne epoxy zinc-rich primers prepared in Examples 1-5 and the waterborne epoxy zinc-rich primers prepared in Comparative Example 1. The test results are shown in Table 1. Figure 1-3 The following are photos of the salt spray resistance test results of Example 1, Example 2 and Comparative Example 1.

[0054] Table 1 Performance test results of waterborne epoxy zinc-rich primers of Examples 1-5 and Comparative Example 1

[0055] According to the test results, the combination of modified zinc powder and modified graphene oxide has almost no effect on the hardness of the coating. For the flexibility, impact resistance and adhesion of the coating, the combination of modified zinc powder and modified graphene oxide is better than unmodified zinc powder and graphene, and the performance is better as the amount added increases. This result can be understood as the polymer grafted on the surface of zinc powder can combine with the carboxyl group of carboxyl functionalized graphene oxide to form a complex, staggered connection network structure, making the coating more uniform and dense, and the zinc powder is better dispersed, so the flexibility and impact resistance of the coating are improved. Adhesion refers to the ability of the coating and the surface of the substrate to bond to each other through physical or chemical effects. The modified zinc powder and graphene oxide are more compatible with the system due to the effect of their grafts, and can fully fill the space between the interfaces, so the adhesion is also improved.

[0056] According to the salt spray resistance test results, the corrosion resistance of the coating is significantly improved after adding zinc powder with surface grafted polymer chains and carboxyl functionalized graphene oxide. However, referring to Example 1 and Example 2, as the amount of modified zinc powder and modified graphene oxide added increases, although the corrosion is further improved, the coating surface becomes slightly rough, so the amount of modified zinc powder and modified graphene oxide added should be controlled to balance the corrosion resistance effect and coating performance.

[0057] In summary, the present invention combines zinc powder with surface grafted polymer chains and carboxyl functionalized graphene oxide. On the one hand, by grafting polymer chains on the surface of zinc powder, the zinc powder with grafted polymer chains is easily dispersed in a water-free epoxy system and is not easy to deposit in component A; on the other hand, the polymer grafted on the surface of zinc powder can be combined with the carboxyl group of carboxyl functionalized graphene oxide to form a complex and staggered connection network structure, improve the state of isolated connection between zinc powder particles inside the coating, optimize the conductive network, and enable the coating to form a long-term corrosion protection; on the other hand, carboxyl functionalized graphene oxide has good hydrophilicity and lipophilicity. After component A and component B are mixed, the zinc powder with surface grafted polymer chains can be quickly connected and the zinc powder can be uniformly dispersed, so that the zinc powder is better dispersed, the coating is more uniform and dense, and therefore the flexibility and impact strength of the coating are improved. Therefore, the present invention effectively overcomes the various shortcomings in the prior art and has a high industrial utilization value.

[0058] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A long-lasting waterborne epoxy zinc-rich primer, characterized in that: It includes component A and component B in a mass ratio of (3-5):

1. Wherein, the A component includes the following components in mass percentage: The B component includes the following components in mass percentage: 。 2. The long-acting waterborne epoxy zinc-rich primer according to claim 1, characterized in that: The zinc powder grafted with polymer chains is zinc powder grafted with polyvinyl amide or zinc powder grafted with polyvinyl alcohol.

3. The long-acting waterborne epoxy zinc-rich primer according to claim 2, characterized in that: The zinc powder grafted with polyvinyl amide is obtained by the following preparation method: pretreated zinc powder is uniformly dispersed in water, vinylamide monomer is added during stirring, initiator is added after sufficient mixing, a precipitate is obtained after heating reaction for a period of time, and the precipitate is washed, dried and crushed to obtain the zinc powder grafted with polyvinyl amide.

4. The long-acting waterborne epoxy zinc-rich primer according to claim 2, characterized in that: The zinc powder grafted with polyvinyl alcohol is obtained by the following preparation method: dissolving polyvinyl alcohol powder in hot water, uniformly dispersing pretreated zinc powder in the polyvinyl alcohol solution, adding a crosslinking agent during stirring, standing at room temperature for a period of time, and then washing, drying and crushing the precipitate to obtain the zinc powder grafted with polyvinyl alcohol.

5. The long-acting waterborne epoxy zinc-rich primer according to claim 4, characterized in that: The cross-linking agent is selected from glutaraldehyde or glyceraldehyde.

6. The long-acting waterborne epoxy zinc-rich primer according to claim 3 or 4, characterized in that: The pretreatment of zinc powder includes: washing the zinc powder, soaking it in a solution containing an activator, stirring and activating it for a period of time, filtering it out, and drying it to obtain the pretreated zinc powder.

7. The long-acting waterborne epoxy zinc-rich primer according to claim 6, characterized in that: The activator includes a silane coupling agent or an isocyanate.

8. The long-acting waterborne epoxy zinc-rich primer according to claim 1, characterized in that: The carboxyl functionalized graphene oxide is obtained by the following preparation method: graphene oxide is uniformly dispersed in deionized water, hydrobromic acid is added and stirred for a period of time, then oxalic acid is added and stirred for reaction, and the carboxyl functionalized graphene oxide is obtained after centrifugation, washing and freeze drying.

9. The long-acting waterborne epoxy zinc-rich primer according to claim 8, characterized in that: The mass ratio of the graphene oxide, hydrobromic acid and oxalic acid is 1: (50-150): (10-30).

10. A method for preparing a long-acting waterborne epoxy zinc-rich primer as claimed in any one of claims 1 to 9, characterized in that: The following steps are involved: (1) Preparation of component A: Add epoxy resin, dispersant, cosolvent, substrate wetting agent and zinc powder grafted with polymer chains in proportion to each other in a dispersion tank, stir them evenly, then add organic bentonite, filler wetting agent, defoamer, adhesion promoter and thickener, and stir them evenly; (2) Preparation of component B: Add water-based polyamide epoxy curing agent, carboxyl functionalized graphene oxide, anti-flash rust agent and water in a dispersion tank in proportion and stir well; (3) Mix component A and component B in a mass ratio of (3-5):1 and let it stand for a while.

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