Alkaline water-washing-free surface treatment agent

Abstract

The application discloses a kind of alkaline water-washing-free surface treatment agent, which is composed of the following components by mass percentage: 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid 10%, cosolvent 6-8%, alcohol amine 5-8%, bactericide 1%, and deionized water in remainder amount. The surface treatment agent forms a film on the surface of metal workpieces using a quasi-covalent bond, achieving a bridging role in the surface treatment technology before painting. On the one hand, the quasi-covalent bond structure it possesses can be firmly combined with the metal substrate, and on the other hand, the amino functional group it contains can crosslink with the epoxy functional group in the powder coating, thereby effectively improving the adhesion of the coating to the metal substrate.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of basic water-washing-free surface treatment agent. BACKGROUND

[0002] In manufacturing, metal parts usually need to be surface treated, and then powder coated to obtain the expected appearance and high corrosion resistance. The existing surface treatment technology is ceramization technology, but because it uses liquid acid, metal parts are prone to re-rust during use, which causes the decline of coating quality. At the same time, ceramization technology requires more processing stations (usually 7 stations) because water rinsing is needed after ceramization treatment to ensure coating quality. In order to meet the needs of users for fewer equipment stations (usually 4 stations), many water-washing-free silane-based surface treatment products have been developed. This type of product can be directly dried and powder sprayed after treatment without water rinsing, thereby reducing the number of required stations. At the same time, because the product is alkaline, it can effectively prevent the occurrence of metal part re-rust during production.

[0003] During the surface treatment process before coating, a film layer needs to be formed between the metal and the paint. On the one hand, it forms a firm film layer with the metal surface, and on the other hand, it forms a strong bond with the paint, ultimately achieving the purpose of high adhesion and corrosion resistance of the coating after coating. The existing water-washing-free silane-based product uses the silicon hydroxyl generated by the hydrolysis of silane coupling agent in the product to form a film layer on the metal surface. However, the film layer formed by the silicon hydroxyl generated by the hydrolysis of silane coupling agent on the metal surface is combined by hydrogen bond, and the bonding force is weak, which can easily cause peeling after coating and ultimately affect the coating quality. SUMMARY

[0004] The purpose of the present application is to provide a basic water-washing-free surface treatment agent that can form a film layer on the surface of a metal substrate after treatment. This film layer can effectively improve the bonding force between the coating and the metal substrate.

[0005] Technical solution: The basic water-washing-free surface treatment agent according to the present application is composed of the following components in mass percentage: 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid (product model: CAS 760127-60-4) 10%, cosolvent 6-8%, alcohol amine 5-8%, bactericide 1%, and deionized water in remainder.

[0006] The structural formula of 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid is as follows:

[0007] The film forming mechanism of the surface treatment agent on the metal surface is that the carboxyl and the benzene ring of 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid form a covalent bond film layer on the metal surface, and the amino group at the other end crosslinks with the epoxy group in the coating, so that the metal substrate and the coating are firmly combined together.

[0008] The cosolvent is ethanol or butyl ether.

[0009] The alcohol amine is monoethanolamine or triethanolamine; the alcohol amine can play a cosolvent effect and adjust the pH value of the treatment agent.

[0010] The bactericide is non-formaldehyde-releasing bactericide BIT or BBIT, and the addition of the bactericide can ensure that the treatment agent avoids bacterial growth during use.

[0011] The surface treatment agent is prepared into a working solution with a mass fraction of 5-6% by using deionized water.

[0012] The pH of the working solution is 9.0-9.7.

[0013] The preparation method of the above-mentioned alkaline water-washing-free surface treatment agent is as follows: first, the formula amount of 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid is added to the cosolvent and stirred for at least 10 min; then, the formula amount of deionized water is added and stirred for at least 5 min; then, the formula amount of alcohol amine is added and stirred for at least 10 min; finally, the formula amount of bactericide is added and stirred for at least 10 min.

[0014] Advantages: compared with the prior art, the surface treatment agent of the present application has the following significant progress: after the metal workpiece is treated by the surface treatment agent, it can be directly dried after powder spraying without water rinsing, thereby reducing the number of required workstations; at the same time, since the surface treatment agent is alkaline, it can effectively avoid the occurrence of rusting of the metal workpiece during production; in addition, the surface treatment agent of the present application forms a film on the surface of the metal workpiece by using a covalent bond, thereby playing a bridging role in the surface treatment technology before coating, on the one hand, the covalent bond structure can be firmly combined with the metal substrate, and on the other hand, the amino functional group can crosslink with the epoxy functional group in the powder coating, thereby effectively improving the adhesion (long-term adhesion) of the coating to the metal substrate, and the longer the salt spray resistance time is, the better the long-term adhesion of the coating to the metal substrate is. DETAILED DESCRIPTION

[0015] Example 1

[0016] The alkaline non-rinse surface treatment agent of the present application is composed of the following components in mass percentage: 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid 10%, ethanol (purity 99%) 8%, monoethanolamine 8%, BIT 1%, and deionized water 73%.

[0017] After the preparation is completed, a working solution with a mass fraction of 5% is prepared using deionized water, and the pH of the working solution is 9.7.

[0018] Example 2

[0019] The alkaline non-rinse surface treatment agent of the present application is composed of the following components in mass percentage: 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid 10%, ethanol (purity 99%) 8%, triethanolamine 5%, BBIT 1%, and deionized water 76%.

[0020] After the preparation is completed, a working solution with a mass fraction of 5% is prepared using deionized water, and the pH of the working solution is 9.0.

[0021] Example 3

[0022] The alkaline non-rinse surface treatment agent of the present application is composed of the following components in mass percentage: 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid 10%, butyl ether (purity 99%) 6%, triethanolamine 5%, BBIT 1%, and deionized water 78%.

[0023] After the preparation is completed, a working solution with a mass fraction of 5% is prepared using deionized water, and the pH of the working solution is 9.0.

[0024] Comparative Example 1

[0025] A surface treatment agent is composed of the following components in mass percentage: tyrosine 10%, ethanol (purity 99%) 8%, monoethanolamine 8%, BIT 1%, and deionized water 73%.

[0026] After the preparation is completed, a working solution with a mass fraction of 5% is prepared using deionized water, and the pH of the working solution is 9.7.

[0027] Comparative Example 2

[0028] A surface treatment agent is composed of the following components in mass percentage: 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid 10%, propanol 8%, monoethanolamine 8%, BIT 1%, and deionized water 73%.

[0029] After the preparation is completed, a working solution with a mass fraction of 5% is prepared using deionized water, and the pH of the working solution is 9.7.

[0030] Comparative Example 3

[0031] A surface treatment agent is composed of the following components in mass percentage: 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid 10%, ethanol (purity 99%) 8%, KOH 0.5%, BIT 1%, and deionized water 81.5%.

[0032] After the preparation is completed, deionized water is used to prepare a working solution with a mass fraction of 5%, and the pH of the working solution is 9.7.

[0033] The plate preparation process is as follows: commercially available Q235 cold-rolled steel plates (produced by Shanghai Baosteel) with a specification of (170mm x 100mm x 0.8mm) are used as test samples for the embodiments of the present application; seven steel plates are first immersed in a commonly used alkaline cleaner (50°C) for about 6 minutes, and then rinsed with flowing tap water for about 30 seconds. Among them, the test plates of the control example are hung at room temperature for 1 minute, then placed in a 120°C oven for drying for 10 minutes, then sprayed with tiger powder, and cured at 180°C for 20 minutes, with the coating thickness controlled at 40-50μm. The remaining six test plates are immediately immersed in the working solutions prepared by the surface treatment agents of Examples 1-3 and Comparative Examples 1-3, respectively, for 5 minutes, then immediately rinsed with deionized water for about 30 seconds, and then hung at room temperature for 1 minute. The dried test plates are then placed in a 120°C oven for drying for 10 minutes, then sprayed with tiger powder, and cured at 180°C for 20 minutes, with the coating thickness controlled at 40-50μm.

[0034] The adhesion of the coating on the seven steel plates (referring to standard GB 9286-2021) and the neutral salt spray resistance (referring to standard GBT 1771-2007) are tested, and the test results are shown in Table 1. According to industry technical requirements, the adhesion immediately after the coating is applied is 0 level, which is qualified, and the neutral salt spray test is judged by the time experienced when the single-sided etching width at the scratch line is less than or equal to 2mm.

[0035] Table 1

[0036] Test performance index Comparative example Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Adhesion 0 level 0 level 0 level 0 level 0 level 0 level 0 level Resistance to neutral salt spray, hours 236 384 360 336 268 294 248

[0037] From the comparison of the data in Table 1, the short-term adhesion of all test panels can reach the standard (0 level), but the neutral salt spray test result of the control example test panel without surface treatment is the worst, which shows that surface treatment is needed before coating to improve the adhesion between the coating and the metal substrate. From the comparison of Example 1 and Example 2, higher pH value is beneficial to improve the anti-flash rust ability of the film before drying, and finally improves the corrosion resistance of the coating; from the comparison of Example 2 and Example 3, different additives have different effects on the dispersion and film forming of the film-forming main agent 3-(4-(6-aminohexanoyloxy)phenyl)propanoic acid, and better additives can better play the film forming quality of the film-forming main agent to some extent to improve the salt spray resistance of the film after coating.

[0038] From the comparison of Example 1 and Comparative Example 1, different film-forming main agents, even if similar in structure, such as most amino acids, have amino and carboxyl groups, but due to their short molecular chains, they will show weak adsorption ability and film forming quality, and finally reflect the large difference in corrosion resistance of the coating; from the comparison of Example 1 and Comparative Example 2, different dispersion abilities of the additive to the film-forming main agent, weaker dispersion will have a greater impact on the film forming quality of the film-forming main agent; from the comparison of Example 1 and Comparative Example 3, using inorganic compounds to adjust the pH value, it is easy to form more residues on the surface of the metal substrate, which will have an adverse effect on the long-term corrosion resistance of the subsequent coating.

Claims

1. An alkaline no-rinse surface treatment agent, characterized by comprising: The surface treatment agent is prepared from the following components with the following mass percentages: 3-(4-(6-aminohexanoyloxy)phenyl)propionic acid 10%, a cosolvent 6-8%, an alcohol amine 5-8%, a bactericide 1%, and deionized water in the balance; the cosolvent is ethanol or butyl ether; the alcohol amine is monoethanolamine or triethanolamine; the surface treatment agent is prepared into a working solution with a mass fraction of 5-6% by using deionized water, and the pH of the working solution is 9-9.

7.

2. The alkaline no-rinse surface treatment agent according to claim 1, characterized by: The bactericide is BIT20 or BBIT, which is a non-formaldehyde-releasing bactericide.