KR20230031052A - Low temperature hardening water based coating composition comprising zinc-aluminum flake - Google Patents

Abstract

The present invention relates to a low-temperature cured water-based coating composition including zinc-aluminum flakes. The coating composition includes a first composition and a second composition, and the first composition and the second composition are mixed before coating to form the coating composition. The coating composition includes: 20 to 40% by weight of a metal component including zinc dust, zinc flakes and aluminum flakes; and 10 to 20% by weight of an epoxy silane oligomer. The first composition includes the metal component, and the second composition includes the epoxy silane oligomer.

Description

Low temperature hardening water based coating composition comprising zinc-aluminum flake}

The present invention relates to a low-temperature curing water-based zinc-aluminum flake coating composition.

Typically, the material of the brake disc is gray cast iron. When cast iron is injected into a mold to manufacture a brake disc, a large amount of pores and rust are generated in the disc due to exposure to atmospheric moisture and oxygen. For this reason, brake discs are generally surface treated with a zinc-aluminum flake coating.

Zinc-aluminum flake coating is composed of organic/inorganic binders that chemically bond with metal flakes such as zinc and aluminum. Zinc and aluminum have a higher ionization tendency than iron, preventing corrosion by oxidizing instead of iron.

In the case of the water-based zinc-aluminum flake coating currently applied to the surface treatment of automobile brake discs, curing is performed at a high temperature of 330 ° C. or higher, which causes material deformation.

If a brake disc with a deformed material is installed and driving continues at a certain speed or more, uneven wear of the brake disc occurs, which causes a change in the thickness of the brake disc, which is the main cause of vibration and noise. Severe vibrations and abnormal noises can lead to serious problems such as causing complaints from consumers, so a fundamental problem solution is required.

Therefore, if a product with a lower curing temperature than the current one is applied, it is possible to improve the quality of brake discs by minimizing material deformation, as well as to improve costs through energy savings due to reduced gas or electricity consumption, and environmental improvement through reduction of CO ₂ emission. there is.

Korean Patent Publication No. 10-2018-0114800, published on October 19, 2018

It is an object of the present invention to provide a low-temperature curable water-based zinc-aluminum flake coating composition.

An object of the present invention is a low-temperature curing, water-based coating composition comprising zinc-aluminum flake, wherein the coating composition includes a first composition and a second composition, wherein the first composition and the second composition are prior to coating. mixed to form the coating composition, wherein the coating composition includes 20 to 40% by weight of a metal component including zinc dust, zinc flake and aluminum flake and 10 to 20% by weight of an epoxy silane oligomer, the first composition The metal component is included, and the second composition is achieved by including the epoxy silane oligomer.

The second composition may further include at least one of 0.5 to 5% by weight of a modified acrylic resin and 1 to 6% by weight of acidic colloidal silica.

The second composition may further include 1 to 3% by weight of a modified acrylic resin and 2 to 4% by weight of acidic colloidal silica.

The zinc dust may be 3 to 8% by weight, the zinc flakes may be 10 to 25% by weight, and the aluminum flakes may be 5 to 13% by weight.

The zinc flakes may include first zinc flakes and second zinc flakes having different average particle diameters.

The average particle diameter of the zinc dust is 1 to 3㎛, the average particle diameter of the first zinc flake is 8 to 12㎛, the average particle diameter of the second zinc flake is 10 to 16㎛, and the average particle diameter of the aluminum flake is 7 to 11㎛ ㎛, the average particle diameter of the second zinc flakes is greater than the average particle diameter of the first zinc flakes, and the weight ratio between the first zinc flakes and the second zinc flakes may be 1:1 to 1:2.

The first composition further includes 12 to 17% by weight of glycols, 2 to 4% by weight of a wetting and dispersing agent, and 0.3 to 0.7% by weight of an antifoaming agent, and the second composition contains 18 to 30% by weight of deionized water and 3 to 7% by weight of glycols. % by weight, 1 to 3% by weight of organotitanate, 0.3 to 0.7% by weight of an amine neutralizing agent, and 0.3 to 0.7% by weight of a leveling agent may be further included.

The first composition and the second composition are mixed in a weight ratio of 1:0.8 to 1:1.2, and the coating composition may be cured at 220 to 250 °C.

According to the present invention, a low-temperature curable water-based zinc-aluminum flake coating composition is provided.

The present invention relates to a low-temperature curing, water-based coating composition comprising zinc-aluminum flakes.

The coating composition of the present invention may be used to improve automobile brake disk durability and prevent corrosion, but is not limited thereto.

The curing temperature of the coating composition may be 200 to 270 °C or 220 to 250 °C.

The coating composition is formed by mixing the first composition and the second composition, and is used by mixing before coating.

The first composition includes a metal component including zinc dust, zinc flake, and aluminum flake, and may further include glycols, a wetting and dispersing agent, and an antifoaming agent.

The second composition includes an epoxy silane oligomer, and may further include deionized water, glycols, organic titanate, an amine neutralizing agent, and a leveling agent. In addition, the second composition may further include a modified acrylic resin and/or acidic colloidal silica.

Some of the components of the first composition may be divided into the second composition or included only in the second composition. Conversely, some of the components of the second composition may be included separately in the first composition or included only in the first composition.

The first composition and the second composition may be mixed in a weight ratio of 1:0.6 to 1:1.6 or 1:0.8 to 1:1.2.

The metal component may be 25 to 35% by weight or 20 to 40% by weight. 3 to 8% by weight or 3 to 6% by weight of zinc dust, 14 to 22% by weight or 10 to 25% by weight of zinc flakes, and 7 to 11% by weight or 5 to 13% by weight of aluminum flakes.

The average particle diameter of zinc dust may be 1 to 3 μm or 1 to 5 μm, the average particle diameter of zinc flake may be 5 to 20 μm, and the average particle diameter of aluminum flake may be 7 to 15 μm or 5 to 15 μm. . When the average particle diameter of the flakes is 20 μm or more, there is a high possibility that the particles are vertically arranged during spray coating. This not only causes non-uniformity of the coating film but also lowers corrosion resistance.

Deionized water and glycols are used as the main solvents. Deionized water may be included in 18 to 30% by weight in the second composition, and glycols may be included in 12 to 17% by weight in the first composition and 3 to 7% by weight in the second composition. The weight ratio of deionized water to glycols may be 3:1 to 1:1.

The wet dispersant is 2 to 4% by weight, and is effective in stably dispersing metal flakes, but as the content increases, the physical properties of the coating film may deteriorate, so it should not be used in excess of a certain amount.

Organic titanates are used in an amount of 1 to 3% by weight, and enhance adhesion and corrosion resistance when forming a coating film. However, if more than the appropriate amount is used, the storage stability of the coating agent may be deteriorated.

The epoxy silane oligomer having an epoxy functional group is included in an amount of 10 to 20% by weight or 12 to 18% by weight. Epoxy silane oligomers have three or more epoxy groups and are used as a major binder that greatly improves the adhesive strength and mechanical properties of coating films when cured.

The modified acrylic resin is used in an amount of 0.5 to 5% by weight or 1 to 3% by weight. Modified acrylic resin has a structure in which silicate is partly mixed, and its pH is close to neutral, so it is easy to use and strengthens the bonding force between the coating layers. However, when used excessively, heat resistance deteriorates.

Acidic colloidal silica is used at 1 to 6% or 2 to 4% by weight. Acidic colloidal silica contributes to corrosion resistance by strengthening the abrasion resistance of the coating film and imparting hydrophobicity.

The amine neutralizing agent is used in an amount of 0.3 to 0.7% by weight. Amine neutralizing agents are used as pH adjusting agents.

Other additives are used in an amount of 0.3 to 0.7% by weight as a leveling agent. The leveling agent is a surface conditioner having a polysiloxane structure, and is effective in flowability, antifoaming, and anti-creating.

The weight ratio of zinc dust to zinc flakes may be 1:2 to 1:5. A mixture of zinc flakes having a small average particle diameter and a relatively large one is used, and the weight ratio may be about 1:1 to 1:2. The average particle diameter of zinc flakes having a small average particle diameter may be 8 to 12 μm, and the average particle diameter of zinc flakes having a large average particle diameter may be 10 to 16 μm. The aluminum flake may be of leafing type.

Glycols may be used alone or in combination with propylene glycol or dipropylene glycol monomethyl ether. Glycols, as co-solvents, affect the workability of coating agents such as smoothness, atomization and volatility of the coating film. The boiling point of the co-agent may be lower than that of the coating composition.

In terms of liquid stability, it is preferable to use a mixture of at least two nonionic types having different HLB values as the wet dispersant.

Organic titanates may be used alone or in combination with butylisopropyl titanate, tetra n-butyl titanate, or titanium chelate.

As the epoxy silane oligomer, a compound in which three or more epoxy groups are condensed may be used. Monomeric epoxy silane is mainly used as an organic-inorganic coupling agent and serves as a binder through hydrolysis and condensation reactions during thermal curing. Monomeric epoxy silane has a structure of silane and an epoxy functional group. Silane is hydrolyzed to silanol and mainly contributes to adhesion by thermally bonding to the metal surface, and the epoxy functional group improves physical properties through chemical bonding with organic materials. A fatal disadvantage of monomeric epoxy silanes when used with water is that the hydrolysis and condensation reactions are difficult to control. This is because in an aqueous solution state, stability may decrease due to ring opening of epoxy, which is a major functional group of the monomer, and gelation may occur due to crosslinking of hydrolyzed silanol groups. The epoxy silane oligomer can have a stable material, excellent adhesion, and a fast curing structure in a state in which a certain portion of the hydrolysis and condensation reaction of the silane epoxy monomer is controlled in advance using a small amount of a catalyst. In addition, hydrophilicity and hydrophobicity can coexist depending on the shape of the silane end group, and physical or chemical properties are excellent. Unlike monomeric epoxy silane, a part of the silane compound is already present as a silanol group, which reacts quickly on the metal surface and is advantageous in forming an initial coating film. It has a curing structure.

The modified acrylic resin is a mixture of some silicate in a vinyl copolymer composed of acrylic acid and methacrylic acid and can be used alone. In general, the durability of the coating film of the coating deteriorates due to internal and external factors over time, and aging progresses. In particular, defects such as discoloration, swelling, falling off, and abrasion of the coating film appear due to external factors such as ultraviolet rays, heat, humidity, or moisture. Applying modified acrylic resin can improve the durability and weather resistance of the coating film. In detail, different types of acrylic monomers can show different characteristics. Using an acrylic monomer with a low Tg gives flexibility to the coating film and greatly enhances the adhesive force, and using a methacrylic monomer with a high Tg increases the hardness and durability of the coating film. Excellent weatherability. In addition, when silicate is mixed, it helps to improve the hardness of the coating film and has high heat resistance.

Unlike general colloidal silica, acidic colloidal silica has excellent compatibility with glycols because alkali salts are removed, so it can be used alone. Colloidal silica has a large number of -OH groups on the surface and has a siloxane structure inside, greatly enhancing adsorption, mechanical strength and heat resistance. When acidic colloidal silica is applied, it is advantageous to form a hard coating film with high hardness.

The amine neutralizing agent may be used alone or in combination with triethanolamine or dimethylethanolamine.

The leveling agent has a polysiloxane structure and may be used in combination with those having excellent compatibility with deionized water or glycols.

The material of the brake disc is gray cast iron, and a large amount of pores exist in the metal at the time of manufacture. A large amount of pores is considered to be the biggest cause of lowering the corrosion resistance of gray cast iron. Corrosion resistance can be greatly improved if metal flakes are properly sprayed and penetrated into internal pores to completely cover them. Zinc dust has a small average particle diameter and is easy to penetrate into pores, which is advantageous for build up. Zinc flakes are advantageous in blocking moisture and other corrosive factors after a coating film is formed in the form of a lamella. Therefore, in order to enhance the corrosion resistance of gray cast iron, it is preferable to use a mixture of zinc dust and zinc flakes.

Zinc-aluminum flake coatings are generally high temperature curing systems of about 330 °C or higher. The main reason is that most of the zinc-aluminum flake coatings on the market use an epoxy silane monomer having one epoxy functional group as a core binder. They form chemical bonds as hydrolysis and condensation reactions occur. However, since it exists as a monomer, high-temperature energy is required for chemical bonding.

This problem can be solved by preparing the epoxy silane monomer as an oligomer as in the present invention. Epoxy silane oligomers have at least 3 or 3 to 5 or 3 to 10 epoxy functional groups in a state where a certain portion of the hydrolysis and condensation reaction is controlled in advance, so that they can be chemically bonded even at a low curing temperature.

The present invention will be described in detail through experimental examples below.

Preparation of coating composition

The formulations of Examples and Comparative Examples are shown in Tables 1 and 2.

Blending ratio of the coating agent according to the embodiment

<Table 1>

Comparative Example Blending ratio of coating agent

<Table 2>

One) Zinc dust: TNC Co., Ltd., ZD-13, average particle size of about 2㎛

2) Zinc flake 1: Eckart, Zinc flake G, average particle size about 10㎛

3) Zinc flake 2: Eckart, Zinc flake GTT, average particle size about 13㎛

4) Aluminum flakes: Eckart, STAPA 15 Aluminum Paste, average particle diameter of about 9㎛

5) Glycols: Samjeon Pure Medicine, Propylene glycol 99%

6) Wetting and dispersing agent: Hannong Chemical, Koreamul-OA 5, Koreamul-OA 14

7) Defoamer: Evonik, TEGO Foamex 810

8) deionized water

9) Glycols: Samjeon Pure Chemical, Dipropylene glycol monomethyl Ether

10) Organotitanic acid chelating agent: Borica, Tytan CX200

11) Epoxy Silanes: Momentive, A-187

12) Epoxy Silane Oligomer: Momentive, CoatOSil MP200

13) Amine neutralizer: Samjeon Pure Medicine, Triethanolamine 99%

14) Leveling agent: Evonik, TEGO GLIDE 450K

15) Modified acrylic resin: Samjihwaseong, SAP-7148

16) Acidic colloidal silica: SKemtech Co., Ltd., SS-SOL 30A

In the present invention, the coating composition is composed of a two-component type, and when used, the first composition and the second composition are mixed and stirred for a predetermined time to undergo a dry bath process (make up).

The manufacturing method of the first composition and the second composition is as follows.

In the preparation of the first composition, after adding 4 to 7 times in order to the mixing container, it was stirred for 10 minutes at 600 to 800 rpm with a dissolver. Thereafter, steps 1 to 3 were carefully added in order and stirred at 1000 to 1200 rpm for about 1 hour. After stirring for about 1 hour, the dissolver was stopped and aged to stabilize the mixture from exothermic heat or a large amount of bubbles.

In the manufacturing process of the second composition, 8 to 9 times were sequentially added to another mixing container, stirred at 600 to 800 rpm with a dissolver, and then slowly added 10 times over 60 minutes. At this time, the temperature of the mixing container was maintained at 20°C. After stirring at about 600-800 rpm for about 60 minutes, No. 11 or No. 12 was slowly added. After stirring at 600-800 rpm for about 30 minutes and adding 13 to 14 times in order, the mixture was stirred for about 60 minutes. In the case of Example 2-4, 15 to 16 times were further added and then stirred for about 30 minutes. Finally, after filtering through 325 mesh, the second composition was stored.

In the case of the dry bath process, while the first composition is stirred at 800 to 1000 rpm with a dissolver, half of the second composition is added and sufficiently mixed. Thereafter, the remaining amount of the second composition was additionally added and thoroughly mixed. The drying time was 12 hours.

Physical property test of coating composition

In the case of a test piece, a cast plate (100x100mm) made of cast iron or a cold-rolled steel plate is degreased with acetone and applied by spraying to a coating thickness of 6-8㎛. It was cured in a hot air oven at 230°C for 20 minutes.

The test evaluation method is as follows.

1)Adhesion: In accordance with MS 619-07 or ISO 2409, 100 checkerboard eyes at 1mm intervals are drawn with a knife so that they penetrate the coating and reach the substrate, and then completely adhere the 24mm cellophane adhesive tape with 9.6±1N adhesive strength to the tape. The peeling state of the coating film when pulled off instantaneously in a taut state is determined.

2) Salt spray resistance: In general, high-temperature frictional heat is generated due to the contact between the disc and the pad when the brake is applied while driving. This can cause the brake disc to overheat, which also affects the coated film. Therefore, in the method of evaluating brake disc salt spray resistance, there is an additional test method called after thermal shock, which evaluates salt spray resistance by baking at 300 ° C for 1 hour. Neutral salt spray test is conducted in accordance with MS 619-07 or ISO 9227, and 144 hours must be satisfied before and after thermal shock (300℃, 1 hour baking).

3) Combined Cycle Corrosion Test: Must satisfy the CCT-A Mode test conditions of MS600-66, the test standard for Hyundai-Kia Motors. Test conditions are 1Cycle=12hr (1. Salt spray-35℃,95%RH,5hr 2.Dry-70℃,30%RH,2hr 3.Wet-50℃,95%RH,3hr 4.Dry-60℃ ,30%RH,2hr), and must satisfy 6Cycle.

4) Flexibility: After bending the coated cold-rolled steel sheet at 180°, the 24mm cellophane adhesive tape with 9.6±1N adhesive force was completely adhered to it, and the peeling state of the coating film was determined when the tape was momentarily pulled off in a taut state.

5) Impact resistance: Evaluate drop resistance of the coating film using a DuPont type drop impact tester. After fixing the test piece between the punch and the die, a weight is dropped from a certain height to determine whether or not the coating film is peeled off due to impact deformation.

R1/2¨, 500g, 30cm, 1 drop condition was carried out.

The evaluation results are summarized in Tables 3 and 4.

Example Test item evaluation result of coating composition

<Table 3>

* ◎: very good, ○: good, ◐: normal, △: bad, X: very bad

Comparative Example Test Item Evaluation Results of Coating Compositions

<Table 4>

Comparative Example 1 was cured at 230 ° C. for 20 minutes, but was cured at 230 ° C. for 20 minutes for comparative evaluation with the previous formulation. The results of the salt spray resistance test before thermal shock and the combined cycle corrosion test were very poor because the cross-linking density of the binder was not dense due to insufficient curing temperature. In addition, the salt spray resistance after thermal shock was relatively better than before thermal shock because the heat source was sufficiently supplied during the baking process at 300 ° C for 1 hour to increase the crosslinking density of the binder. This means that the binder of Comparative Example 1 is not suitable for a curing system at a lower temperature of 230 to 250 ° C. than before.

Comparing Comparative Example 1 and Example 1, when the epoxy silane oligomer was applied, relatively better results were obtained than epoxy silanes in terms of salt spray resistance and combined cycle corrosion. This is because the oligomer form of the compound enables chemical bonding at a lower temperature than that of the monomer, thereby increasing the crosslinking density.

Comparing Comparative Example 1 and Example 2, Example 2 in which spherical zinc dust and zinc flakes were mixed obtained relatively better results than Comparative Example 1 in which zinc flakes were applied alone in salt spray resistance and combined cycle corrosion tests. This is because zinc dust and flakes having a small average particle diameter can effectively defend a large number of pores existing inside cast iron. Similar results can be obtained by comparing Example 1 with Example 3.

Comparative Example 2 not using zinc dust and Comparative Example 3 not using epoxy silane oligomer had no excellent test items. In Comparative Example 4 in which organic titanate was not used, adhesion was very poor. It is known that organic titanates affect adhesion and corrosion resistance.

Example 2 is a composition in which the modified acrylic resin in Example 1, the acidic colloidal silica in Example 3, and the modified acrylic resin and the acidic colloidal silica in Example 4 are added. It can be seen that the addition of the modified acrylic resin enhances the adhesion and flexibility of the coating agent, and the addition of acidic colloidal silica enhances the impact resistance of the coating agent.

Overall, looking at the above results, the epoxy silane oligomer is capable of chemical bonding at a temperature 80 to 110 ° C lower than the composition using the monomer, and zinc dust and flakes with a small average particle diameter effectively defend the pores inside the brake disc cast iron. It improves corrosion resistance, and organic titanates affect adhesion and corrosion resistance. In addition, the modified acrylic resin and acidic colloidal silica help to improve the physical properties and durability of the coating agent.

Claims (8)

In the low-temperature curing, water-based coating composition comprising zinc-aluminum flakes,
The coating composition includes a first composition and a second composition,
The first composition and the second composition are mixed before coating to form the coating composition,
The coating composition,
20 to 40% by weight of metal components including zinc dust, zinc flakes and aluminum flakes, and
Contains 10 to 20% by weight of an epoxy silane oligomer,
The first composition includes the metal component,
The second composition is a coating composition comprising the epoxy silane oligomer. According to claim 1,
The second composition,
A coating composition further comprising at least one of 0.5 to 5% by weight of a modified acrylic resin and 1 to 6% by weight of acidic colloidal silica. According to claim 1,
The second composition,
A coating composition further comprising 1 to 3% by weight of a modified acrylic resin and 2 to 4% by weight of acidic colloidal silica. According to any one of claims 1 to 3,
The zinc dust is 3 to 8% by weight, the zinc flake is 10 to 25% by weight, the aluminum flake is 5 to 13% by weight of the coating composition. According to claim 4,
The coating composition of claim 1, wherein the zinc flakes include first zinc flakes and second zinc flakes having different average particle diameters. According to claim 5,
The average particle diameter of the zinc dust is 1 to 3㎛,
The average particle diameter of the first zinc flake is 8 to 12 μm,
The average particle diameter of the second zinc flake is 10 to 16 μm,
The average particle diameter of the aluminum flake is 7 to 11 μm,
The average particle diameter of the second zinc flakes is greater than the average particle diameter of the first zinc flakes,
The coating composition of claim 1, wherein the weight ratio of the first zinc flake and the second zinc flake is 1:1 to 1:2. According to claim 6,
The first composition further comprises 12 to 17% by weight of glycols, 2 to 4% by weight of a wetting and dispersing agent, and 0.3 to 0.7% by weight of an antifoaming agent,
The second composition further comprises 18 to 30% by weight of deionized water, 3 to 7% by weight of glycols, 1 to 3% by weight of organotitanate, 0.3 to 0.7% by weight of an amine neutralizing agent, and 0.3 to 0.7% by weight of a leveling agent. composition. According to claim 7,
The first composition and the second composition are mixed in a weight ratio of 1:0.8 to 1:1.2,
The coating composition is a coating composition that is cured at 220 ~ 250 ℃.