High-solid epoxy zinc-rich coating and preparation method thereof

Abstract

The application discloses a high-solid-content epoxy zinc-rich paint, which comprises a component A and a component B, wherein the component A and the component B are blended according to a weight ratio of (8-10):1; the component A comprises the following raw materials in parts by weight: 3-6 parts of a solvent, 3-15 parts of an epoxy resin, 1-10 parts of a cashew phenol non-active epoxy diluent, 0.1-1 part of an acid-group-containing dispersant, 0.1-1 part of a coupling agent, 0.5-3 parts of an anti-settling agent, 78.5-120 parts of zinc powder and 5-15 parts of a light-aging preventive; the component B comprises the following raw materials in parts by weight: 44-101 parts of a solvent and 60-70 parts of a curing agent; the cashew phenol non-active epoxy diluent is prepared by olefin addition reaction of cashew nut shell oil and a hydrocarbon resin; and the acid-group-containing dispersant is an acid-group-containing block high-molecular polymer. The paint has the characteristics of high solid content and low VOC, can reach 80-120 mu m by one-time film forming, has a smooth paint film and excellent corrosion resistance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of anticorrosive coatings, and more particularly to a high-solid-content epoxy zinc-rich coating and a preparation method thereof. BACKGROUND

[0002] The zinc-rich coating is a rust-proof paint material prepared by mixing a large amount of fine zinc powder and a small amount of base resin. Since the zinc powder content in the zinc-rich coating is generally above 80 wt%, the zinc powder particles maintain good direct contact with each other and with the steel, and the paint film has good electrical conductivity. When the corrosion reaction occurs, the metal zinc is more active than the steel, and the current will flow from the metal zinc to the steel, sacrificing the zinc to protect the steel, thereby achieving the corrosion protection of the steel.

[0003] The zinc-rich coating can be divided into inorganic zinc-rich coating and organic zinc-rich coating according to the characteristics of the base resin. When the dispersion medium of the organic zinc-rich coating is an organic solvent, the solvent-based zinc-rich coating has the characteristics of high surface tolerance, thick film anti-cracking, corrosion resistance, curing environment tolerance and good matching, and is widely used in the fields of marine and industrial heavy corrosion protection, and is the preferred coating product for long-acting heavy corrosion protection matching primer.

[0004] However, the solvent-based zinc-rich coating still has the following problems: first, the solid content in the coating is difficult to exceed 85 wt%. When the solid content of the coating is higher than 85 wt%, the solvent content in the coating is low, and the coating performance is poor, because the zinc powder in the solid component is prone to agglomeration, resulting in large viscosity of the coating system, difficult to level, and rough surface of the paint film. Second, when the zinc powder content is too high, in order to improve the film-forming performance, the solvent content is correspondingly increased, resulting in too high VOC content of the coating during film formation, which is difficult to meet the green and environmental protection requirements. SUMMARY

[0005] In order to solve the above-mentioned problem that the solvent-based zinc-rich coating is difficult to have excellent film-forming performance of the paint film and low VOC content, the application provides a high-solid-content epoxy zinc-rich coating and a preparation method thereof.

[0006] In the first aspect, the application provides a high-solid-content epoxy zinc-rich coating, which adopts the following technical scheme:

[0007] A high-solid-content epoxy zinc-rich coating, which comprises a component A and a component B, and the component A and the component B are blended in a weight ratio of (8-10):1;

[0008] The component A comprises the following raw materials in parts by weight: 3-6 parts of a solvent, 3-15 parts of an epoxy resin, 1-10 parts of a cashew phenol inactive epoxy diluent, 0.1-1 parts of a dispersant containing an acid group, 0.1-1 parts of a coupling agent, 0.5-3 parts of an anti-settling agent, 78.5-120 parts of zinc powder and 5-15 parts of a light aging inhibitor;

[0009] The component B comprises the following raw materials in parts by weight: 44 to 110 parts of solvent and 60 to 70 parts of curing agent;

[0010] The cardanol inactive epoxy diluent is prepared by reacting cashew nut shell oil and hydrocarbon resin through olefin addition reaction; and the acidic group-containing dispersant is a block polymer containing an acidic group.

[0011] Furthermore, the cardanol inactive epoxy diluent is formed by reacting cashew nut shell oil and styrene.

[0012] Furthermore, the acidic group-containing dispersant is formed by ternary copolymerization of acrylic acid, sodium styrene sulfonate and hydroxypropyl acrylate.

[0013] Furthermore, the zinc powder is sieved through a 300-800 mesh sieve.

[0014] Furthermore, the anti-light aging agent is barium sulfate filler.

[0015] Furthermore, the barium sulfate filler is sieved through a 1000-2000 mesh sieve.

[0016] Furthermore, the coupling agent is a coupling agent containing an epoxy group.

[0017] Furthermore, the coupling agent is 3-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0018] Furthermore, the anti-settling agent is organic modified bentonite.

[0019] Furthermore, the organic modified bentonite is organic ammonium modified bentonite.

[0020] Furthermore, the solvent is formed by mixing xylene and n-butanol in a weight ratio of (6-8):(2-4).

[0021] Furthermore, the epoxy resin is bisphenol A epoxy resin.

[0022] Furthermore, the curing agent is a polyamide curing agent.

[0023] In a second aspect, the present application provides a method for preparing a high-solid epoxy zinc-rich coating, which adopts the following technical solution:

[0024] A method for preparing a high-solid epoxy zinc-rich coating comprises the following steps:

[0025] Preparation of Component A: Add solvent, epoxy resin, cardanol inactive epoxy diluent, epoxy coupling agent, anti-settling agent and dispersant according to weight parts, stir and disperse; then add zinc powder and barium sulfate, stir and disperse again to obtain Component A;

[0026] Preparation of the B component: add solvent and curing agent by weight parts, stir to disperse to obtain the B component;

[0027] The A component and the B component are blended according to the weight ratio to obtain the high solid content zinc-rich epoxy coating.

[0028] In summary, the technical scheme of the present application has at least the following advantages:

[0029] First, cashew phenol non-active epoxy diluent can act together with the dispersant containing acidic groups to improve the zinc powder addition amount, and also significantly improve the film forming performance and corrosion resistance of the coating; the reasons are as follows: cashew phenol non-active epoxy diluent is made from cashew nut shell oil and hydrocarbon resin through olefin addition reaction, and contains phenolic hydroxyl and hydrophobic alkyl long chain; the dispersant containing acidic groups is a block polymer containing acidic groups, and contains anchoring groups such as carboxyl and lipophilic segments; the phenolic hydroxyl of cashew phenol non-active epoxy diluent and the acidic groups of the dispersant can have good wetting and dispersing effect on the hydroxyl on the surface of zinc powder through hydrogen bonding. Since cashew phenol non-active epoxy diluent contains alkyl long chain, on the one hand, the phenolic hydroxyl and the acidic groups act as anchoring groups to adsorb zinc powder particles, and the lipophilic segments such as alkyl long chain have large steric hindrance, which can improve the agglomeration problem between zinc powder particles, reduce the overall viscosity of the coating, and improve the film forming performance of the coating; on the other hand, the lipophilic segments are entangled with each other and with the matrix resin such as epoxy resin, so that the zinc powder particles can maintain stable suspension in the coating system, play a compatibilizing role, and enable the inorganic zinc powder particles to be stably dispersed in the coating at a high content, improve the zinc powder addition amount, and the content of zinc in the non-volatile matter can reach 93.15% at most. The thickness of the zinc-rich epoxy coating formed at one time can reach 80-120μm, and at this relatively high film forming thickness, the paint film is level and flat, and the film forming performance is excellent.

[0030] Secondly, cashew phenol non-active epoxy diluent and the dispersant containing acidic groups can not only replace part of the solvent to play a good compatibilizing role for the epoxy resin and reduce the amount of solvent, but also have large molecular weight and are not easy to volatilize, thereby reducing the overall VOC content of the zinc-rich epoxy coating system. It is environmentally friendly.

[0031] Thirdly, the hydrophobic segments of cashew phenol non-active epoxy diluent can play a good waterproof role, solve the defect that high content of zinc powder is easy to absorb moisture, and help the overall coating to have good waterproof performance, thereby greatly improving the corrosion protection performance to the corrosion medium. After salt spray resistance detection, the paint film formed by the coating can withstand more than 1000h of salt spray corrosion, and can achieve the effects of no blistering, no rusting, no cracking, and no peeling.

[0032] Secondly, the coupling agent containing epoxy groups is used in the application, which can work together with the epoxy resin to improve the adhesion of the whole coating; meanwhile, the coupling agent containing epoxy groups can improve the compatibility between the epoxy resin and the zinc powder, further improving the content of the zinc powder. In the application, 3-(2,3-epoxypropoxy) propyl trimethoxysilane is preferred, which can improve the adhesion of the whole coating, and due to the silane chain segment, it can assist the better hydrophobic effect of the cashew phenol non-active epoxy diluent, effectively improving the waterproof performance of the paint film and prolonging the corrosion resistance time of the paint film.

[0033] Thirdly, barium sulfate is used as the light aging inhibitor in the application, which works together with the zinc powder, and the barium sulfate has high reflectivity in the wavelength range of 300-400 μm, which can effectively reduce the light aging possibility caused by the unsaturated double bond contained in the cashew nut shell oil in the cashew phenol non-active epoxy diluent, and improve the corrosion resistance of the paint film. Meanwhile, it can also play the role of filler to improve the strength of the whole paint film.

[0034] Fourthly, the organic bentonite is selected as the anti-settling agent in the application, and after the organic modification of the bentonite, the flaky edges can adsorb the lipophilic long chain of the epoxy resin, so as to have good affinity with the organic resin; meanwhile, the oxygen and hydroxyl groups distributed therein can form hydrogen bonds with the zinc powder, barium sulfate and other solid components to have an anti-settling effect, so that the coating becomes a uniform gel and has a certain viscosity, thereby preventing the solid components from settling. Meanwhile, due to the good dilution and viscosity reduction effect of the cashew phenol non-active epoxy diluent, the thickening problem caused by the addition of the organic bentonite can be effectively improved, so that the zinc powder and other solid components are further fully dispersed, and the coating system still maintains good coating and film forming performance.

[0035] Fifthly, a solvent with a specific proportion is selected in the application, which can have a good solubilizing effect on the epoxy resin at the lowest addition amount, thereby further reducing the VOC content of the coating system. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the application more clear, the technical scheme of the application is further described below in combination with examples.

[0037] Unless otherwise specified, the raw materials in the following examples and comparative examples are as follows:

[0038] Bisphenol A type epoxy resin: grade E51, epoxy functionality 2.5-6;

[0039] Cashew phenol non-active epoxy diluent:

[0040] Grade NX-2021, viscosity 45-75 CPS, purity 87-90%;

[0041] Grade NX-2022, viscosity 40-60CPS, purity≥95%;

[0042] Grade NX-2023, viscosity 40-100CPS, purity≥96%;

[0043] Dispersant containing acid group:

[0044] Acrylic acid, sodium styrene sulfonate and hydroxypropyl acrylate terpolymer, self-made product, monomer molar ratio of acrylic acid, sodium styrene sulfonate and hydroxypropyl acrylate is 3:1:1.5;

[0045] Grade VK.DP2000, amine salt solution of polycarboxylic acid;

[0046] Coupling agent:

[0047] Grade KH-560, 3-(2,3-epoxypropoxy) propyl trimethoxysilane;

[0048] Grade Si-69, bis-[gamma-(triethoxysil) propyl] tetrasulfide;

[0049] Organically modified bentonite: grade FHGEL-979;

[0050] Polyamide curing agent: grade 651, amine value 400-440mgKOH / g.

[0051] Examples

[0052] Examples 1-10

[0053] A high solid content epoxy zinc-rich coating, the specific components corresponding to each example are shown in Table 1:

[0054] Table 1. Specific components of high solid content epoxy zinc-rich coating prepared in Examples 1-10

[0055]

[0056]

[0057] Among them, the zinc powder is passed through a 500 mesh sieve; the barium sulfate is passed through a 1500 mesh sieve;

[0058] Examples 1-10 are prepared according to the following steps:

[0059] In a dry and clean jacketed reaction kettle, solvent, epoxy resin, anti-settling agent, dispersant, cashew phenol non-active epoxy diluent and coupling agent are added, the stirring speed is controlled at 1000r / min, and stirring is carried out for 30min; after uniform stirring, zinc powder and light aging inhibitor are added, the stirring speed is controlled at 1500r / min, and stirring is carried out for 90min, and the mixture is uniformly mixed to obtain component A;

[0060] In a dry and clean jacketed reaction kettle, solvent and curing agent were added, the stirring speed was controlled at 600 r / min, and stirring was carried out for 30 min to obtain component B.

[0061] When needed, component A and component B were taken and mixed uniformly according to the corresponding mass ratio of component A and component B, to obtain the high-solid low-viscosity epoxy zinc-rich coating.

[0062] Examples 11-12

[0063] A high-solid epoxy zinc-rich coating, which is different from example 1 in that the particle size of zinc powder is different, and the specific is as follows:

[0064] In example 11, the zinc powder was passed through a 300 mesh sieve;

[0065] In example 12, the zinc powder was passed through an 800 mesh sieve.

[0066] Examples 13-14

[0067] A high-solid epoxy zinc-rich coating, which is different from example 1 in that the particle size of barium sulfate is different, and the specific is as follows:

[0068] In example 13, the barium sulfate was passed through a 1000 mesh sieve;

[0069] In example 14, the barium sulfate was passed through a 2000 mesh sieve.

[0070] Examples 15-16

[0071] A high-solid epoxy zinc-rich coating, which is different from example 1 in that the weight ratio of solvents in component A and component B is different, and the specific is as follows:

[0072] In example 15, the weight ratio of xylene and n-butanol was 6:4;

[0073] In example 16, the weight ratio of xylene and n-butanol was 8:2.

[0074] Comparative examples

[0075] Comparative example 1

[0076] A high-solid epoxy zinc-rich coating, which is different from example 1 in that the same amount of dispersant acrylic acid, styrene sodium sulfonate and propylene glycol acrylate terpolymer is used instead of cashew phenol inactive epoxy diluent NX-2022.

[0077] Comparative example 2

[0078] A high-solid epoxy zinc-rich coating is different from Example 1 in that an equal mass of cardanol non-reactive epoxy diluent NX-2022 is used instead of the dispersant terpolymer of acrylic acid, sodium styrene sulfonate and hydroxypropyl acrylate.

[0079] Comparative Example 3

[0080] A high-solid epoxy zinc-rich coating is different from Example 1 in that an equal amount of inactive epoxy diluent butyl acetate is used instead of the cardanol inactive epoxy diluent NX-2022.

[0081] Comparative Example 4

[0082] A high-solid epoxy zinc-rich coating is different from Example 1 in that an equal mass of a low molecular weight dispersant phosphate ester is used instead of a dispersant terpolymer of acrylic acid, sodium styrene sulfonate and hydroxypropyl acrylate.

[0083] Performance testing

[0084] 1. VOC content (%): VOC content was tested according to Method 1 in GB / T 23985-2009;

[0085] 2. Metallic zinc content in non-volatile matter (%): Detect the metallic zinc content in non-volatile matter according to the method described in HG / T3688-2020;

[0086] 3. Sample surface condition: record the thickness (μm) of the coating film and the film formation condition;

[0087] 4. Impact resistance (kg): Test the impact resistance according to the method described in HG / T3688-2020;

[0088] 5. Adhesion (MPa): Test the adhesion of the paint film according to the method described in HG / T3688-2020;

[0089] 6. Salt spray resistance time (h): Refer to the method recorded in HG / T3688-2020, with the paint film not blistering, rusting, cracking or falling off as the standard, and record the time the paint film can maintain no blistering, rusting, cracking or falling off.

[0090] Table 2. Properties of coatings prepared in Examples 1-16 and Comparative Examples 1-4 of the present application

[0091]

[0092] According to the test data, in Comparative Example 1, only the dispersant containing an acidic functional group was used to disperse the zinc powder and barium sulfate, and in Comparative Example 2, only cashew phenol inactive epoxy diluent was used to disperse the zinc powder and barium sulfate. According to the inspection data in Table 2, in Comparative Example 1, although the use of only the dispersant containing an acidic group can achieve good dispersion of solid components such as zinc powder and barium sulfate, and reduce the viscosity of the overall coating, the overall coating has too low viscosity, and the one-time film thickness is only 42 μm. At the same time, the proportion of the acidic group contained therein is too high, the acidic group is a hydrophilic group, which is not conducive to the later salt spray corrosion resistance, and the salt spray resistance time can only be maintained for 666 h.

[0093] In Comparative Example 2, only cashew phenol inactive epoxy diluent was used to disperse the zinc powder and barium sulfate, and the surface state of the coating after film formation was poor, indicating that the dispersion ability of cashew phenol inactive epoxy diluent for zinc powder is limited, and the film forming effect is best when it is used with an acidic dispersant. It can ensure that the viscosity of the coating is within a moderate range, the one-time film thickness is more than 80 μm, and the surface of the coating is flat. However, compared with Comparative Example 1, the salt spray corrosion resistance time is improved, and compared with Example 1, the salt spray corrosion resistance time is decreased. The reason is that the hydrophobic segment of the cashew phenol inactive epoxy diluent is beneficial to the improvement of the overall hydrophobicity of the paint film, but the zinc powder in Example 1 is fully dispersed to cooperate with the water resistance of the hydrophobic segment, which can effectively improve the salt spray corrosion resistance of the paint film.

[0094] In Comparative Example 3, a low molecular weight non-active epoxy diluent was used instead of cashew phenol non-active epoxy diluent, and the VOC content of Comparative Example 3 increased sharply. The dispersion effect of the small molecular weight active diluent for zinc powder is poor, the one-time film thickness is only 30 μm, and the film forming effect is poor, and small cracks appear on the surface of the paint film. It shows that although they are both non-active epoxy diluents, the dilution effect of small molecular weight non-active diluents such as butyl acetate is poor, far inferior to that of cashew phenol non-active epoxy diluent.

[0095] In Comparative Example 4, a low molecular weight dispersant containing an acidic group was used, and the VOC content of Comparative Example 4 also increased sharply, which was easy to volatilize during curing. At the same time, the dispersion effect of the low molecular weight dispersant containing an acidic group, phosphate, for zinc powder is limited, and the reason may be that the steric hindrance of phosphate coating zinc powder is limited, and zinc powder is still prone to partial aggregation. Thus, the film forming effect and salt spray corrosion resistance of Comparative Example 4 are poor.

[0096] The content of zinc powder and barium sulfate as solid components in Examples 1-3 is different, and the solid content in the component A in Example 3 can reach 93.51%, and the solid content in the whole coating can be as high as 85wt%, so that the secondary dilution is not needed in the coating process, and the component A and the component B can be blended uniformly and then applied. The application performance of the paint film is better, and the one-time forming thickness of the paint film can reach 117μm, but the adhesion is poor, the paint film is easy to fall off, and the salt spray resistance time is short. Considering various factors, the ratio in Example 1 is the best ratio, which can obtain the high solid content zinc-rich coating and the paint film with excellent salt spray corrosion resistance. The film forming performance of the coating prepared in Example 1 is better, and the film forming thickness of one-time coating is 96μm, and the impact resistance and adhesion are better.

[0097] The difference between Examples 4-5 and Example 1 is that the viscosity of the cashew phenol inactive epoxy diluent and the purity of the cashew phenol are different. The purity of the cashew phenol in the cashew phenol inactive epoxy diluent in Example 4 is low, and the content of the oxidizable impurities in the cashew phenol inactive epoxy diluent is high. Under the adverse factors such as light and air oxidation, oxidation is easy to occur, thereby leading to poor performance of the paint film and affecting the final salt spray test time. The viscosity of the cashew phenol inactive epoxy diluent in Example 5 is high, and the zinc powder in the coating system affects the coating film forming effect and corrosion resistance of the final coating.

[0098] VK.DP2000 containing an acidic group is used as a dispersant in Example 6, and compared with the terpolymer of acrylic acid, sodium styrene sulfonate and hydroxypropyl acrylate, although the dispersibility is better, but the salt spray corrosion resistance of the coating is not good, and the reason may be that the hydrophilicity of VK.DP2000 is good, thereby leading to poor hydrophobicity of the paint film.

[0099] Si-69 is used instead of KH560 as a coupling agent in Example 7, and since the epoxy group is lacking in Si-69, the adhesion and corrosion resistance are decreased compared with Example 1.

[0100] The technical features of the above-described examples can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above-described examples are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the description.

[0101] Moreover, the above-described examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as the limitation of the patent scope. It should be pointed out that for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A high solid content epoxy zinc-rich coating, characterized in that: The method comprises the following steps: comprising mixing component A and component B, wherein component A and component B are mixed in a weight ratio of (8-10):1; The component A comprises the following raw materials in parts by weight: 3 to 6 parts of solvent, 3 to 15 parts of epoxy resin, 1 to 10 parts of cardanol inactive epoxy diluent, 0.1 to 1 part of dispersant containing acidic group, 0.1 to 1 part of coupling agent, 0.5 to 3 parts of anti-settling agent, 78.5 to 120 parts of zinc powder and 5 to 15 parts of anti-light aging agent; The component B comprises the following raw materials in parts by weight: 44 to 101 parts of solvent and 60 to 70 parts of curing agent; The acidic group-containing dispersant is a block polymer containing an acidic group; the cardanol inactive epoxy diluent is formed by the reaction of cashew nut shell oil and styrene; and the acidic group-containing dispersant is formed by the ternary copolymerization of acrylic acid, sodium styrene sulfonate and hydroxypropyl acrylate.

2. The high solid content epoxy zinc-rich coating according to claim 1, characterized in that: The zinc powder is sieved through a 300-800 mesh sieve.

3. The high solid content epoxy zinc-rich coating according to claim 1, wherein: The light aging inhibitor is barium sulfate filler.

4. The high-solid epoxy zinc-rich coating according to claim 3, characterized in that: The barium sulfate filler is passed through a 1000-2000 mesh sieve.

5. The high solid content epoxy zinc-rich coating according to claim 1, characterized in that: The coupling agent is an epoxy-containing coupling agent.

6. The high solid epoxy zinc-rich coating according to claim 1, characterized in that: The anti-settling agent is organic modified bentonite.

7. The high solid epoxy zinc-rich coating according to claim 1, wherein: The solvent is prepared by mixing xylene and n-butanol in a weight ratio of (6-8):(2-4).

8. The method for preparing a high-solid epoxy zinc-rich coating according to any one of claims 1 to 7, characterized in that: The steps include: Preparation of Component A: Add solvent, epoxy resin, cardanol inactive epoxy diluent, epoxy coupling agent, anti-settling agent and acidic group-containing dispersant according to weight parts, stir and disperse; then add zinc powder and light aging inhibitor barium sulfate, stir and disperse again to obtain Component A; Preparation of component B: adding a solvent and a curing agent in parts by weight, stirring and dispersing to obtain component B; blending component A and component B in a weight ratio to obtain a high-solid epoxy zinc-rich coating.

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