CN112300657A

CN112300657A - Water-based corrosion-resistant composition suitable for color coating production line and manufacturing and using methods thereof

Info

Publication number: CN112300657A
Application number: CN202010629117.1A
Authority: CN
Inventors: 朱丹青; 陆海涛; 俞威; 曾建峰
Original assignee: Shanghai Xingsaier Surface Material Co ltd
Current assignee: Shanghai Xingsaier Surface Material Co ltd
Priority date: 2020-07-02
Filing date: 2020-07-02
Publication date: 2021-02-02

Abstract

The invention provides a water-based corrosion-resistant composition suitable for a color coating production line and a manufacturing and using method thereof. The composition comprises a water-based resin and a curing agent thereof; at least one hydrolyzed silsesquioxane oligomer containing active organic functional groups, at least one environment-friendly corrosion inhibitor particle, a single-wall or multi-wall carbon nanotube, at least one dispersion aid of the carbon nanotube, filling powder and a functional aid. The aqueous corrosion resistant composition of the present invention can be directly coated on a metal substrate without using a chemical pretreatment. By shortening the production process, the invention is beneficial to realizing the purpose of environmental protection and cost reduction of the color coating line. The invention also discloses a manufacturing method and a using method of the corrosion-resistant composition.

Description

Water-based corrosion-resistant composition suitable for color coating production line and manufacturing and using methods thereof

Technical Field

The invention relates to the field of anticorrosive coatings, in particular to a water-based corrosion-resistant composition suitable for a color coating production line and a manufacturing and using method thereof.

Background

The products of a coil coating (or color coating) line are called pre-coated sheet(s). The base plates capable of being color coated are various, and the most common base plates are galvanized alloy plates and aluminum alloy plates. Color-coated sheets have a wide range of industrial applications: such as the building industry for indoor and outdoor applications, the automotive and transportation industry, household appliances, office furniture, heating and air conditioning outer panels and air ducts, commercial equipment, vending machines, food service equipment and cooling and beverage cans, etc.

The color coating process comprises the following steps: (1) cleaning a belt material, (2) chemically pretreating, (3) drying, (4) coating primer on one side or two sides, (5) passing through a first curing oven, (6) cooling, (7) coating finish on one side or two sides, (8) passing through a second curing oven. Chemical pretreatments currently used in color coating lines include hexavalent chromium treatments, fluorotitanic acid or fluorozirconic acid treatments, and the like. These pretreatments serve to ensure excellent adhesion between the primer and the substrate, i.e., the primer provides intercoat adhesion between the pre-treated film and the topcoat, thereby improving the corrosion resistance of the overall coating system. In addition, the composition of the primer varies depending on the type of topcoat used, and the primer needs to be compatible with various pretreatment and topcoat systems. Topcoats provide primarily weatherability, abrasion resistance, and other properties. The types of topcoats and primers used on color coating lines include polyester, polyurethane, polyvinylidene fluoride (PVDF), epoxy, plastisol and laminated films. It is to be noted that, although the hexavalent chromium treatment solution contains hexavalent chromium ions, which are highly carcinogenic and polluting to the environment, it is still currently applied to a color coating line due to its excellent coating and corrosion resistance properties.

Disclosure of Invention

The object of the present invention is to provide an aqueous corrosion-resistant composition free of hexavalent chromium compounds, which can be used in color-coated lines. The composition can be directly applied to clean metal surfaces without the use of any chemical pretreatment. Therefore, the invention not only completely eliminates the danger of using hexavalent chromium products, but also realizes the purpose of reducing the cost of the color coating production line by omitting the pretreatment process.

The invention also aims to provide a preparation method of the composition.

The purpose of the invention is realized by the following technical scheme:

the water-based corrosion-resistant composition for the color coating line is characterized by comprising the following components in percentage by weight:

30-70% of organic resin aqueous dispersoid and curing agent thereof;

1-10% hydrolyzed silsesquioxane oligomer containing reactive organic functional groups;

5-30% of environment-friendly corrosion inhibitor particles;

0.05-5% of carbon nano tube;

0.01-3% of dispersing auxiliary agent of the carbon nano tube;

10-30% of filling powder;

0.01-2% of functional auxiliary agent;

the balance being deionized water.

Further, the organic resin aqueous dispersion in the organic resin aqueous dispersion and the curing agent is one or more of acrylic acid aqueous dispersion, polyurethane aqueous dispersion and epoxy aqueous dispersion. The particle size of the organic resin aqueous dispersion is in the range of 0.01 to 1 μm. The solid content is 40-60%. The acrylic aqueous dispersion is preferably

AVE 191; the epoxy aqueous dispersion is preferably a bisphenol A epoxy resin aqueous dispersion, such as Epi-rez 5522-WY-55, Epi-rez 3540, and corresponding polyamine-based curing agents.

Further, the hydrolyzed silsesquioxane oligomer having a reactive organic functional group is an amino group-containing siloxane oligomer, an aminopropyl silsesquioxane oligomer, a methylsilsesquioxane oligomer, and a 3 ((2-aminoethyl) aminopropyl) silanetriol homopolymer. The molecular weight of the water-soluble silicone oligomer should be between 250 and 650, preferably greater than 500.

The active silsesquioxane oligomer has a self-crosslinking function, and can further compact an organic resin coating and improve water resistance. And simultaneously, the adhesive has condensation reaction with the metal substrate to form firm adhesion to the substrate. The silsesquioxane represents a kind of three-dimensional structure with more or less order, and the empirical formula is RSiO_3/2. The silsesquioxane had an O/Si ratio of 1.5, between siloxane (O/Si ═ 1) and silica (O/Si ═ 2). A typical structure of a silsesquioxane is shown in fig. 1. The formation of silsesquioxanes involves two distinct steps that occur simultaneously in the hydrolytic condensation reaction of silanes. First, the organosilane is hydrolyzed to produce silanol (Si-OH). These silanols are then condensed with each other to form an oligomeric siloxane intermediate. These oligomeric siloxane intermediates contain unreacted hydroxyl groups and further undergo intermolecular/intramolecular bonding and eventually undergo rearrangement reactions to give different types of silsesquioxanes. A typical structure of a silsesquioxane is as follows:

furthermore, the environment-friendly corrosion inhibitor particles are slightly water-soluble particles with the effect of inhibiting metal corrosion, and comprise at least one of zinc phosphate particles, aluminum triphosphate particles, barium metaborate particles and barium phosphosilicate particles, and the particle size of the particles is 5-15 mu m. The selected environment-friendly corrosion inhibitor particles and the organic resin aqueous dispersion have good compound property and good dispersibility.

Further, the carbon nanotube is at least one of Single Wall Carbon Nanotubes (SWCNTs) and Multi Wall Carbon Nanotubes (MWCNTs) and surface-treated Single wall or Multi wall nanotubes. Single-walled nanotubes (SWCNTs) are graphene tubes that are terminated at the ends. They have a single cylindrical wall. Multi-walled carbon nanotubes (MWCNTs) can be considered as coaxial cylindrical tubes. The interlayer distance is close to the distance between graphene layers in graphite. The nanotubes have an inner diameter and an outer diameter. The inner diameter is in the range of about 0.5-20nm, while the outer diameter may be in the range of 1-80 nm. The nanotubes may have an aspect ratio of, for example, about 1-10000. These nanotubes may also be surface modified, physically or chemically, prior to use to enhance their bonding strength to the organic matrix. The carbon nanotubes are used to fill the voids in the organic coating layer and further densify the structure of the organic coating layer, thereby improving the water resistance of the coating layer.

Further, effective carbon nanotube dispersing aids for use in the present invention include polyvinylpyrrolidone, sodium lauryl sulfate, ethoxylated tristyrylphenol. The dispersing assistant is dissolved in water and then added into the carbon nano tube. And (3) forming the aqueous dispersion of the carbon nano tube by ultrasonic dispersion treatment. The aqueous dispersion of the produced carbon nanotubes is then added to the coating material in a stirred state. The content of the dispersing auxiliary agent in the carbon nano tube water dispersion liquid is 0.1-3%.

Furthermore, the filling powder is at least one of taibai powder, silicon dioxide, quartz powder, calcium carbonate, barium sulfate and talcum powder, and the particle size of the filling powder is 10-15 mu m. The selected filling powder has uniform particles, good compounding property with the organic resin aqueous dispersion and good dispersibility.

Further, the functional auxiliary agent is at least one of a wetting agent, a thickening agent, a dispersing agent and a defoaming agent. The selection of the type and amount of such adjuncts is within the knowledge and skill of those skilled in the art and is made without undue experimental validation.

The preparation of the aqueous corrosion-resistant composition comprises the following steps:

1) adding a dispersing agent and part of the defoaming agent into part of the organic resin aqueous dispersoid in a stirring state, and uniformly stirring;

2) adding corrosion inhibition particles and filling powder under the stirring condition, and uniformly stirring by adopting a high-speed dispersion method;

3) adding the carbon nano tube aqueous dispersion under the stirring condition, and uniformly stirring;

4) under the condition of stirring, adding the silsesquioxane oligomer, the residual organic resin aqueous dispersion and water, and uniformly stirring;

5) before coating, adding the curing agent under the condition of stirring, and uniformly stirring.

The application method of the aqueous corrosion-resistant composition can coat the prepared composition on the metal surface by a spraying or rolling method. Methods of use the composition is preferably applied to the metal surface using a stainless steel coating bar. The using conditions are as follows:

1) degreasing and cleaning the metal surface, washing with water, and drying for later use;

2) uniformly coating a certain amount of the composition on the surface of the metal by using a stainless steel coating rod at normal temperature;

3) putting the mixture into a drying box, and drying for 15-120 seconds at the plate temperature of not lower than 240 ℃;

in the specific process, the metal surface does not need to be chemically pretreated.

The invention has the following beneficial effects:

1) the water-based corrosion-resistant composition does not contain hexavalent chromium compounds, and is an environment-friendly coating;

2) the paint has excellent comprehensive properties including salt spray corrosion resistance, coating property and adhesion to a substrate;

3) the aqueous corrosion resistant composition can be directly coated on a metal substrate without any chemical pretreatment of the substrate. Thus, the risk of using hexavalent chromium products is completely eliminated;

4) the chemical pretreatment process is omitted, and the purposes of environmental protection and cost reduction of the color coating line are facilitated.

The aqueous corrosion-resistant composition of the present invention is suitable for galvanized sheets and aluminum alloy sheets. Galvanized sheets include electrogalvanized or hot-dip galvanized and alloy galvanized steels such as pure zinc sheet (GI), aluminum zinc sheet (GL), zinc-aluminum-magnesium, zinc-iron alloy, electrogalvanized, etc. The aluminum alloy plate includes aluminum copper alloy, aluminum magnesium alloy, aluminum silicon alloy, aluminum zinc alloy and the like.

Drawings

Fig. 1 shows a comparison of the low-frequency alternating impedance values (f ═ 0.1Hz) for different compositions (electrolyte: 3.5% NaCl solution, pH 6.5).

Detailed Description

The present invention will be further described with reference to the following examples.

Examples 1 to 3

Table 1 lists 3 composition formulations. The order of formulation of these formulations was:

1) adding a dispersant (DISPERBYK 191) into a part of the epoxy resin aqueous dispersion (Epi-rez 5522-WY-55) in a stirring state, and uniformly stirring;

2) adding zinc phosphate particles and titanium dioxide under the stirring condition, and uniformly stirring by adopting a high-speed dispersion method;

3) adding 3% multiwall carbon nanotube (MWCNT) aqueous dispersion under stirring, and uniformly stirring;

4) adding the silsesquioxane oligomer containing amino, the residual organic resin aqueous dispersion and water under the stirring condition, and uniformly stirring;

5) before coating, polyamine curing agent (Epi-rez 8290-WY-60) is added under stirring condition, and is stirred uniformly.

TABLE 1 formulation of compositions containing multiwall carbon nanotubes (MWCNT) (in weight percent)

A Galvanized (GI) sample plate (10cm X15 cm X0.09 cm) is cleaned by spraying an alkaline degreasing agent for 15 seconds at the temperature of 55 ℃, washed by tap water for 15 seconds and dried by hot air. The formulated composition was applied down to the surface of the panel using a #20 stainless steel coating bar on the clean panel. And (3) putting the mixture into a drying box, and drying the mixture for 120 seconds at the plate temperature of not lower than 240 ℃, wherein the thickness of the coating after drying is 15 mu m. Table 2 shows the test results.

TABLE 2 results of Performance tests on galvanized plates

Content of test	Example 1	Example 1	Example 3
				500 hours salt fog (scratch fork)	Severe peeling of paint film	Severe peeling of paint film	No film peeling
Adhesion to substrate	No film peeling	No film peeling	No film peeling
				Bonding force with finish paint	No film peeling	No film peeling	No film peeling

An aluminum-copper alloy (A12024-T3) sample plate (10cm X15 cm X0.09 cm) is sprayed and cleaned for 15 seconds by using an alkaline degreasing agent at the temperature of 55 ℃, washed for 15 seconds by using tap water and dried by using hot air. Examples 1-3 were coated down on the surface of the panel using a #20 stainless steel coating bar on the clean panel. And (3) putting the mixture into a drying box, and drying the mixture for 120 seconds at the plate temperature of not lower than 240 ℃, wherein the thickness of the coating after drying is 15 mu m. Table 3 shows the test results.

TABLE 3 results of Performance tests on aluminum-copper alloy plates

Content of test	Example 1	Example 2	Example 3
				500 hours salt fog (scratch fork)	Severe peeling of paint film	Slight peeling of the paint film	No film peeling
Adhesion to substrate	No film peeling	No film peeling	No film peeling
				Bonding force with finish paint	No film peeling	No film peeling	No film peeling

The Galvanized (GI) panels were cleaned and coated in the manner described in example 1. The dried coated panels (without cross-hatching) were exposed for 2 weeks in a cyclic corrosion chamber and tested according to the general automobile company cyclic corrosion test (GM 9540P). Before and after the prototype test, Electrochemical Impedance Spectroscopy (EIS) was used to determine the water resistance (or corrosion resistance) of the coating. Fig. 1 shows the measured low frequency alternating impedance values (f ═ 0.1Hz) for each type of coating.

As can be seen from the results of fig. 1, the low frequency alternating impedance value of the coating before the test decreased with the increase in the amount of MWCNTs. This indicates that the conductivity of the coating increases with the addition of MWCNTs. After 2 weeks of testing in the cyclic corrosion test chamber, the low frequency crossover resistance values of example 1 (formulation #1) (0% MWCNT) and example 2 (formulation #2) (0.9% MWCNT) both tended to decrease, with the decrease being most pronounced for example 1 (formulation # 1). The decrease in low frequency alternating impedance values resulting from the corrosion test was associated with the penetration of the corrosive medium (e.g., brine) into the coating, indicating that formulation #1, which did not contain MWCNTs, was not structurally dense enough to allow the corrosive medium (e.g., brine) to penetrate easily and therefore had poor water resistance. The low frequency alternating impedance value of example 3 (formulation #3) (1.9% MWCNT) was unchanged after the test, which indicates that the 1.9% MWCNT significantly enhances the compactness of the coating structure, greatly slows down the penetration of corrosive media, and improves the water resistance of the coating.

Examples 4 to 6

The Galvanized (GI) panels were cleaned in the manner described in example 1, coated with the composition formulations listed in table 4, and dried. Example 1 (without CNTs) in table 1 was used as a control. The content of SWCNTs in the dried coating was about: 0.9% (example 4), 1.8% (example 5), 2.3% (example 6)

TABLE 4 composition formula (weight percent) containing single-walled carbon nanotubes (SWCNT)

TABLE 5 results of Performance tests on galvanized plates

Content of test	Example 1	Example 4	Example 5	Example 6
					500 hours salt fog	Severe peeling of paint film	Slight peeling of the paint film	No film peeling	No film peeling
Adhesion to substrate	No film peeling	No film peeling	No film peeling	No film peeling
					Bonding force with finish paint	No film peeling	No film peeling	No film peeling	No film peeling

From the test results, it can be seen that the aqueous corrosion-resistant composition for color-coated lines according to the present invention can provide excellent corrosion resistance, adhesion to a substrate, and adhesion to a topcoat without performing a chemical pretreatment process.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any description in the claims should not be construed as limiting the claim concerned. Furthermore, it is obvious that the word "comprising" does not exclude other elements or steps, and the singular does not exclude the plural.

Claims

1. The water-based corrosion-resistant composition suitable for the color coating production line is characterized by comprising the following components in percentage by weight: 30-70% of organic resin aqueous dispersoid and curing agent thereof; 1-10% hydrolyzed silsesquioxane oligomer containing reactive organic functional groups; 5-30% of environment-friendly corrosion inhibitor particles; 0.05-5% of carbon nano tube; 0.01-3% of dispersing auxiliary agent of the carbon nano tube; 10-30% of filling powder; 0.01-2% of functional auxiliary agent; the balance being deionized water.

2. The aqueous corrosion-resistant composition suitable for color coating production line according to claim 1, wherein the aqueous organic resin dispersion and the curing agent thereof are one or more of acrylic aqueous dispersion, polyurethane aqueous dispersion and epoxy aqueous dispersion.

3. The aqueous corrosion resistant composition suitable for use in a color coating line of claim 2 wherein said curing agent is a polyamine curing agent.

4. The aqueous corrosion resistant composition suitable for use in a color coating line of claim 1 wherein said hydrolyzed reactive organofunctional group containing silsesquioxane oligomer is one or more of an amino group siloxane oligomer, an aminopropyl silsesquioxane oligomer, a methyl silsesquioxane oligomer and a 3 ((2-aminoethyl) aminopropyl) silanetriol homopolymer.

5. The aqueous corrosion resistant composition suitable for use in a color coating line of claim 4 wherein said hydrolyzed reactive organofunctional silsesquioxane oligomer has a molecular weight of between 250 and 650, preferably greater than 500.

6. The aqueous corrosion resistant composition for use in a color coating line according to claim 1, wherein the corrosion inhibitor particles are sparingly water-soluble particles having a metal corrosion inhibiting effect, and comprise one or more of zinc phosphate particles, aluminum triphosphate particles, barium metaborate particles, and barium phosphosilicate particles.

7. The aqueous corrosion-resistant composition for color coating line according to claim 6, wherein the corrosion inhibitor particles are slightly water-soluble particles having metal corrosion inhibiting effect and have a particle size of 5-15 m.

8. The aqueous corrosion resistant composition suitable for use in a color coating line of claim 1, wherein the carbon nanotubes are one or more of single-walled carbon nanotubes and multi-walled carbon nanotubes and surface treated single-walled or multi-walled nanotubes.

9. The carbon nanotube dispersing aid of claim 1, comprising one or more of polyvinylpyrrolidone, sodium lauryl sulfate, ethoxylated tristyrylphenol.

10. The aqueous corrosion-resistant composition for use in a color coating line according to claim 1, wherein said powder filler is one or more of titanium dioxide, silica, quartz powder, calcium carbonate, barium sulfate, and talc.

11. The aqueous corrosion resistant composition suitable for use in a color coating line of claim 10 wherein said powder filler has a particle size of between 10 and 15 m.

12. The aqueous corrosion resistant composition suitable for use in a color coating line of claim 1 wherein said functional additives are one or more of wetting agents, thickeners, dispersants and defoamers.

13. A method of making an aqueous corrosion resistant composition suitable for use in a color coating line according to claim 1, comprising the steps of:

(1) adding a dispersing agent and part of the defoaming agent into part of the organic resin aqueous dispersoid in a stirring state, and uniformly stirring;

(2) adding corrosion inhibition particles and filling powder under the stirring condition, and uniformly stirring by adopting a high-speed dispersion method;

(3) under the condition of stirring, adding the carbon nano tube aqueous dispersion, and uniformly stirring;

(4) under the condition of stirring, adding the silsesquioxane oligomer, the residual organic resin aqueous dispersion and water, and uniformly stirring;

(5) before coating, adding the curing agent under the condition of stirring, and uniformly stirring.

14. A method of coating a metal surface with the aqueous corrosion-resistant composition suitable for use in a color coating line of claim 1, wherein the metal surface does not require chemical pretreatment prior to coating.

15. A method of coating a metal surface according to claim 14, wherein the aqueous corrosion resistant composition suitable for use in a color coating line is applied to the metal surface using a stainless steel coating bar.