KR20170130933A - Heat and Corrosion resistant Ceramic Composites Coating Composition And Manufacturing Methods For The Same - Google Patents

Abstract

The present invention relates to a heat and corrosion resistant ceramic-based coating composition for protecting the surface of metals. The present invention provides a heat and corrosion resistant ceramic-based composite wet coating agent for protecting the surface of metals, which comprises: 40 to 50 wt% of a hydrophobic surface-treated liquid nano-colloidal sol; 25 to 45 wt% of an organosilane compound; 5 to 10 wt% of an organic solvent; 0.01 to 1 wt% of other additives; and 10 to 15 wt% of an active metal filler containing at least one metal selected from a group consisting of Al, Si, Ti, Zr, Cr and B. According to the present invention, it is possible to provide the coating composition having good adhesion to the metal surface of a corrosive material such as carbon steel, imparting heat resistance and corrosion resistance, and suppressing cracking of a coating film.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a ceramic-based composite wet-

TECHNICAL FIELD The present invention relates to a coating composition coated on a metal surface to provide heat resistance and corrosion resistance, and more particularly, to a ceramic heat-resistant and corrosion-resistant coating composition for protecting a metal surface.

Ceramic coating agents used in various industrial products such as boilers, heat exchangers, steam pipes, ovens, gas ranges, irons and household appliances, displays for high temperature environments, and architectural products require various performance such as heat resistance, corrosion resistance and adhesion.

In particular, for the production of high-temperature and high-pressure steam, the development of coating materials for boiler pipe material and boiler pipe has been progressed.

The problem with conventional boilers is that when coal is burned, about 10% of coal ash is generated. In order to reduce fuel cost, the amount of coal ash is increasing while blending low grade and high grade coal. Most of them float in the furnace with fly ash or flooring, and some of them adhere to the water surface of the wall of the furnace wall and interfere with heat exchange, which is a function as a boiler tube. In addition, since the fuel with a lot of alkaline components such as Na and K is burned and becomes molten at high temperature, it becomes firm and grows as a large clinker and falls into overload and damages the lower sloping water pipe of the boiler, . Also, the adhered material lowers the heat exchange performance and causes direct economic loss.

Therefore, the boiler tube is thinned by the combination of sulfur corrosion, high temperature corrosion due to high temperature environment, erosion by friction with soft material, steam for removing attached soft material and high pressure air spray .

In order to solve this problem, conventionally, an inner type high hardness metal coating and a heat resistant high hardness ceramic coating have been used. However, as the size of the boiler is increased and the use temperature is increased, the use of the metal coating is limited. The heat conduction which is the main function of the heat transfer tube is interfered with and the heat transfer tube is weakly impacted.

In this regard, Korean Patent Laid-Open No. 10-2004-0018570 relates to a composition for sol-gel coating, a method for producing the same, and a surface treatment method using the same, and it relates to a method for improving durability, heat resistance, stain resistance, Gel coating composition, that is, an organosilane compound having a predetermined functional group, is heated to dissolve the alcohol-removed product in an appropriate solvent to prepare a coating composition. The coating composition is free from cracks and mechanical Thereby forming a coating film having excellent strength.

However, the sol-gel coating composition has a pencil hardness of about 6H and has a limitation in that it can not satisfy the mechanical properties at a high temperature of 1000 ° C or more to be applied in the present invention.

KR 2004-0018570 A

In order to solve the problems of the prior art, it is an object of the present invention to provide a ceramic composite coating agent having excellent heat resistance, corrosion resistance and mechanical properties at high temperatures.

Another object of the present invention is to provide a surface protective coating composition having good adhesion to metal surfaces such as carbon steel.

Another object of the present invention is to provide a method for producing the above-mentioned coating composition.

According to an aspect of the present invention, there is provided a hydrophobic surface-treated liquid nano-colloidal sol comprising 40 to 50% by weight; 25 to 45% by weight of an organosilane compound; 5 to 10% by weight of an organic solvent; 0.01 to 1% by weight of other additives; And 10 to 15% by weight of an active metal filler containing at least one metal selected from the group consisting of Al, Si, Ti, Zr, Cr and B.

In the present invention, at least a part of the organosilane compound may be coupled to the surface of the liquid nano-colloidal sol.

In addition, the organosilane compound preferably includes a silane hydrolyzate. At this time, the organosilane compound may be prepared from at least two silanes.

In the present invention, the silane compound may include at least two kinds of silane compounds selected from the group consisting of MTMS, TEOS and GPTMS.

According to another aspect of the present invention, there is provided a method for preparing a liquid nanocloid sol comprising: providing a hydrophobic surface-treated liquid nanocolloidal sol; Aging a mixed solution obtained by mixing a first silane with the liquid nano-colloid sol in an organic solvent; Mixing the aged mixed solution with a second silane and distilled water to hydrolyze and polycondense the silane compound; And a step of adding an active metal filler to the mixed solution through the polycondensation step. The present invention also provides a method for manufacturing a ceramic-based composite wet coating agent for metal surface protection.

In this case, in the ceramic-based composite wet coating agent, the hydrophobic surface-treated liquid nano-colloidal sol is 40 to 50% by weight, the first and second silanes are 15 to 25% by weight, the organic solvent is 5 to 10% 15 to 20% by weight of the additive, 0.01 to 1% by weight of the additive, and 10 to 15% by weight of the active metal filler.

In addition, the hydrophobic surface treatment of the liquid nanocolloid sol may include: providing a water-dispersed liquid nanocolloid sol; Removing moisture of the liquid nano-colloidal sol by a decompression apparatus and introducing an organic solvent; And adding a distilled water and a silane coupling agent to the liquid nano-colloidal sol and hydrolyzing the liquid nano-colloidal sol.

At this time, the silane coupling agent may include at least one silane selected from the group consisting of an alkyl silane, an acryl silane, and an epoxy silane.

According to the present invention, it becomes possible to provide a coating composition which has good adhesion to a metal surface of a corrosive material such as carbon steel, imparts heat resistance and corrosion resistance, and can suppress cracking of the coating film.

The ceramic-based composite wet coating composition according to the present invention is particularly effective in preventing corrosion of a surface of a heat exchanger in a boiler water tube, which is in contact with the surrounding corrosive material, and adhesion of foreign matter, thereby improving thermal efficiency and purifying operation. .

Further, the ceramic-based composite wet coating agent having excellent resistance to corrosion and corrosion of the present invention has an advantage that an outer coating of a boiler water pipe having a clinker adhesion inhibiting function, which inhibits adhesion of coal ash and the like, is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart illustrating a method of surface-treating an inorganic nanocolloidal sol according to an embodiment of the present invention. FIG.
FIG. 2 is a schematic diagram illustrating a method of manufacturing a composite wet coating agent according to an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to the preferred embodiments of the present invention with reference to the drawings.

The ceramic-based composite wet coating material for protecting a metal surface of the present invention comprises 40 to 50% by weight of a hydrophobic surface-treated liquid nano-colloidal sol, 25 to 45% by weight of an organic silane compound, 5 to 10% by weight of an organic solvent, 10 to 15% by weight of an active metal filler comprising at least one metal selected from the group consisting of Al, Si, Ti, Zr, Cr and B.

The liquid nano-colloidal sol may be at least one inorganic nano-colloidal sol selected from the group consisting of silica sol, alumina sol, titania sol, and zirconia sol. Preferably, the liquid nano-colloidal sol is alumina sol. Alumina is chemically stable and has a high melting point, which is advantageous in terms of physical properties such as mechanical strength and hardness. Alumina is one of neutral refractories and does not cause erosion of various materials and can maintain its properties even at a high temperature of 1000 ° C or higher. In addition, alumina sol has a capability of forming a film, and a good film is produced by drying. Although it is an inorganic substance, the sol particle has a fibrous structure and also has flexibility.

In the present invention, since inorganic nanocolloidal sol such as alumina sol has a hydroxy group on the surface of the particle, it is preferable that the particle surface is surface-modified from hydrophilic to hydrophobic in order to improve reactivity, compatibility and dispersibility.

According to the embodiment of the present invention, it is preferable to use an organosilane compound in order to modify the hydrophilic particles of the inorganic nanocolloidal sol to hydrophobicity.

A method of surface-treating an inorganic nano-colloidal sol in the present invention will be described with reference to Fig.

Referring to FIG. 1, a water-dispersed liquid alumina sol is first prepared to remove water from the alumina sol (S110). For removing moisture, for example, decompression equipment can be used. Subsequently, an organic solvent having a content (weight) corresponding to the amount of water removed is introduced to replace the water with an organic solvent (S120). As the organic solvent, an alcohol-based, ether-based, ketone-based, or acetate-based organic solvent may be used.

Next, water and a silane coupling agent are added to the alumina sol solution (S130), and hydrolysis condensation polymerization is performed (S140).

At this time, the silane coupling agent is used for the purpose of achieving adhesion or affinity of both of them by a compound bond in a complex system with inorganic, organic or metallic materials. That is, the silane coupling agent plays an important role in improving various properties such as mechanical strength, heat resistance, weather resistance and the like, which improves adhesion of the material.

As the silane coupling agent in the present invention, an organic silane compound such as an alkyl silane, an acryl silane or an epoxy silane may be used either singly or in combination of two or more.

In the present invention, it is preferable that the liquid nano-colloidal sol surface treated with hydrophobicity includes 40 to 50% by weight based on the coating composition. Outside of the above range, the performance such as heat resistance and corrosion resistance of the coating agent deteriorates.

In addition, the ceramic-based composite wet coating agent for metal surface protection of the present invention includes an organosilane compound.

The organosilane compound acts as a binder of the ceramic-based composite coating agent. Specifically, the organosilane compound undergoes hydrolysis and polycondensation with a hydrophobic surface-treated nanocolloidal sol to improve stability, durability and adhesion at high temperatures. In the present invention, it is preferable that the organic silane compound is contained in an amount of 25 to 45% by weight.

In one embodiment of the present invention, methyltrimethoxysilane (MTMS), tetraethoxysilane (TEOS), and 3- (2-ethylhexyl) silane, which are hydrolyzable by water and have three or more alkyl groups, And at least two of glycidol oxypropyl-trimethoxysilane (GPTMS) may be used in combination. According to an embodiment of the present invention, the combination of the MTMS and TEOS is preferable.

The organosilane compound may be prepared by hydrolyzing and condensing a silane such as MTMS and TEOS with water. At this time, the silane as a raw material for the production of the organosilane compound is preferably contained in the composite wet coating agent in an amount of 15 to 25% by weight. In addition, it is preferable that the distilled water for hydrolysis of the silane is contained in an amount of 15 to 20% by weight. Preferably, the weight ratio of silane to distilled water is preferably maintained in the range of 1: 0.8 to 1: 1.5.

The MTMS for the preparation of the organosilane compound is a chemical monomer that constitutes silanetriol and methanol by reacting with water and is used to prevent the inorganic surface from being easily absorbed in water and has excellent dispersibility with other silane.

The TEOS generates silica bonds and silanol by hydrolysis and polycondensation, and when the coating film is cured, all of the remaining silanol is converted into a silica bond, thereby increasing the hardening density and improving the strength of the finally formed coating film. Accordingly, heat resistance and durability are provided in the coating film, which is advantageous for preventing cracking of the coating film.

In the present invention, the content of silane for preparing the organosilane compound can be appropriately controlled. For example , the ratio of MTMS to TEOS is preferably in the range of 1: 1 to 1: 2.

If the amount of MTMS is smaller than the above ratio, the proportion of the organic material of the MTMS in the binder component constituting the coating film may be lowered and the adhesive strength may be lowered or the dispersibility with other silane may be lowered. In addition, when the MTMS is excessive, gelation of the coating agent may occur during the condensation polymerization reaction with the hydrophobic surface-modified alumina sol. On the other hand, when the TEOS is used in a small amount, the content of the inorganic component in the binder component constituting the coating film is lowered, and the hardness is lowered because the effect of increasing the curing density is low. In addition, when the MTMS is excessive, there is a problem that adhesion due to stress due to curing shrinkage is deteriorated or cracks are generated due to residual silanol in which the condensation reaction is not progressed at the time of curing.

In the present invention, distilled water is added for hydrolysis and condensation polymerization of the organosilane compound. As described above, it is preferable that the distilled water is maintained at a weight ratio of silane and water as raw materials for the production of the organosilane compound in the range of 1: 0.8 to 1: 1.5. If it is out of the above range, detachment from high temperature may occur due to deterioration of binding force between the silane compound and the hydrophobic surface treated liquid nano colloid sol.

The composite wet coating agent of the present invention also includes an organic solvent.

The organic solvent serves to disperse or adjust the viscosity of each component of the composite wet coating agent appropriately. In particular, since the organosilane compound is produced by condensation polymerization during the production of the binder by the sol-gel process, it is preferable to use at least one organic solvent such as an alcohol-based, ether-based or ketone-based organic solvent.

In the present invention, the organic solvent is preferably included in the range of 5 to 10% by weight. When the amount of the organic solvent is less than 5% by weight, the viscosity of the composite wet coating agent is increased to make it difficult to form a coating film. When the organic solvent is more than 10% by weight, shrinkage of the coating film occurs in a process of forming a coating film and drying.

Of course, the organic solvent may be the same as the organic solvent used for the surface modification of the hydrophobic liquid nano-colloidal sol described above.

Further, in the present invention, the composite wet coating agent may further include additives. For example, a surfactant may be used as the additive in the present invention. Surfactants connect hydrophobic surface-treated nanocolloidal sol and silane hydrolyzate to each other. In addition, they improve the leveling property of the coating surface and defects such as pinholes, crater phenomena Generation can be prevented. In the composite wet coating agent of the present invention, the surfactant is preferably contained in an amount of 0.01 to 1.0% by weight.

On the other hand, the composite wet coating agent of the present invention may comprise the active metal filler. The active metal filler compensates for pores and cracks in the coating film at high temperatures. Preferably, the active metal filler is in powder form.

In the present invention, various kinds of materials may be used as the active metal filler depending on temperature and application field. For example, at least one metal selected from the group consisting of Al, Si, Ti, Zr, Cr and B may be used. Illustratively, Si with excellent corrosion resistance at high temperatures can be used as the active metal filler.

In the present invention, the active metal filler is preferably contained in an amount of 10 to 15 wt% of the composite wet coating agent. A content exceeding the above range may cause material swelling at high temperatures.

The composite wet coating agent of the present invention described above can be prepared by various methods. A uniform coating film can be formed by a conventional wet coating method such as flow coating, spin coating, bar coating, dip coating and spray coating. Of course, the coating method can be appropriately selected depending on the type and shape of the material and the desired coating film thickness.

The coating film formed by a suitable method is dried at room temperature for 10 minutes or more and then cured by heat treatment at 150 to 200 DEG C for 1 hour or more. Such a heat treatment gives sufficient hardness to the coating film.

2 is a flow chart illustrating a method of manufacturing a composite wet coating agent according to an embodiment of the present invention.

Referring to FIG. 2, a hydrophobic treated liquid nano colloid sol is provided (S210). The hydrophobic surface-treated liquid nano-colloidal sol can be prepared by the method described in connection with Fig. Of course, anyone of ordinary skill in the art will recognize that other methods than this method can be used.

The liquid nano-colloidal sol of Step 210 and the first silane are mixed in the organic solvent and the mixed solution is aged (S220). Subsequently, the silane compound is hydrolyzed and condensed by mixing the aged mixed solution with the second silane and distilled water (S230). The complex wet coating agent of the present invention can be obtained by adding an active metal filler to the mixed solution through the condensation polymerization step (S240).

Hereinafter, an experimental example of the present invention will be described.

<Production example of alumina sol>

In order to prepare hydrophobic surface treated alumina sol, the water-dispersed alumina sol was first subjected to removal of water using a vacuum device, and then replaced with an organic solvent having the same weight as the weight of the alumina sol. Next, a hydrolytic condensation reaction was carried out in order to modify the surface of the alumina sol contained in the solution substituted with the organic solvent from hydrophilic to hydrophobic. To this end, 2 moles of water per mole of alumina sol is added, and the content of the silane coupling agent is 25 to 35 parts by weight based on 100 parts by weight of alumina sol, and the reaction is carried out at 65 DEG C for 4 hours or more, .

&Lt; Example 1 >

(Step 1)

40% by weight of alumina sol surface-treated with hydrophobicity and 10% by weight of IPA as an organic solvent are mixed, and 5% by weight of methyltrimethoxysilane is mixed and reacted at 65 ° C for 4 hours or more, and aged at room temperature for 12 hours or more.

(Step 2)

15 wt% of tetraethoxysilane was mixed with the coating solution prepared in step 1, 19 wt% of distilled water was added as a catalyst, and the mixture was mixed for 4 hours or more. Then, 1 wt% of a surfactant and 10 wt% For 2 hours or more.

&Lt; Examples 2 to 6 >

The composite wet coating agent was prepared in the same manner as in Example 1, except that the amounts of alumina sol and silane surface-treated with hydrophobicity were changed as shown in Table 1 below.

&Lt; Comparative Examples 1 to 4 >

The ceramic composite wet coating agent having excellent resistance to corrosion resistance was prepared in the same manner as in Example 1. As shown in Table 1, the compounding ratio was different from that in Examples.

<Test Example>

(1) Coating condition after curing

The state of the coating film was evaluated at the time of curing in a drying oven at 200 ° C for 1 hour and then at room temperature to see whether cracks or bubbles occurred visually. ?, When cracks or bubbles were not observed,? When cracks occurred in a thick part of the coating film,? When no cracks occurred in the inside, or when bubbles spread over the entire surface and the coating film was not clear.

(2) Pencil hardness

The pencil hardness was obtained as a mean value measured three times at a load of 9.8N based on KS M ISO 15184.

(3) Adhesiveness

Adhesive strength is measured with ASTM D 3359-02 as cross-cut after cross-cut, 5B if not peeled off, 4B if peeled less than 5% of total lattice, 5 ~ 15% peel off 3B, 1B when pulled off by 15 to 35%, 2B when pulled off, 0B when pulled off by 35 to 65%, and 0B when pulled off by 65% or more.

(4) Heat resistance

After one hour at 1000 占 폚, it was evaluated whether the blisters or cracks were visually observed.

(5) High temperature corrosion characteristics

The test pieces were immersed in 5% CH ₃ COOH at 1000 ° C for 24 hours, and the corrosion of the coating film was visually evaluated.

The results obtained through the above test are shown in Table 2.

As shown in Table 2, in Comparative Examples 3 and 4, a coating film was not formed due to a crack in the coating film, so that performance evaluation was impossible.

Further, as shown in Table 2, it can be seen that the composite wet coating agent according to the embodiment of the present invention is superior in heat resistance and high temperature corrosion resistance to those of Comparative Examples 1 and 2. Also, as in Examples 1 to 6, the content of alumina sol surface-treated with hydrophobicity of the ceramic-based composite coating material excellent in resistance to thermal corrosion resistance was excellent at 40 wt%, but 45 to 55 wt% was most effective. In the case of less than 40% by weight or more than 55% by weight, cracks occurred in the external appearance of the coating film as in Comparative Examples 1 and 2, and problems were also found in other performance. In addition, as in Comparative Examples 3 and 4, evaluation of performance of silane hydrolyzate alone without addition of hydrophobic surface-treated alumina sol resulted in swelling and cracking from the curing process, There was no.

It can be seen that it is preferable to use a hydrophobic surface treated alumina sol in order to obtain a ceramic-based composite wet coating agent having excellent heat resistance, corrosion resistance and other mechanical properties even at a high temperature of 1000 캜 or higher. It is also understood that when the active metal filler is mixed with the hydrophobic surface treated alumina sol, the problems of pores and cracks occurring at high temperatures can be solved.

Claims (9)

40 to 50 wt.% Liquid nano-colloidal sol surface treated with hydrophobicity;
25 to 45% by weight of an organosilane compound;
5 to 10% by weight of an organic solvent;
0.01 to 1% by weight of other additives; And
10 to 15% by weight of an active metal filler comprising at least one metal selected from the group consisting of Al, Si, Ti, Zr, Cr and B; The method according to claim 1,
Wherein at least a part of the organosilane compound is coupled to the surface of the liquid nano-colloidal sol. The method according to claim 1,
Wherein the organosilane compound comprises a silane hydrolyzate. &Lt; RTI ID = 0.0 &gt; 8. &lt; / RTI &gt; The method according to claim 1,
Wherein the organosilane compound is prepared from at least two silanes. 5. The method of claim 4,
Wherein the silane compound comprises at least two selected from the group consisting of MTMS, TEOS and GPTMS. Providing a hydrophobic surface-treated liquid nano-colloidal sol;
Aging a mixed solution obtained by mixing a first silane with the liquid nano-colloid sol in an organic solvent;
Mixing the aged mixed solution with a second silane and distilled water to hydrolyze and polycondense the silane compound; And
And adding an active metal filler to the mixed solution through the condensation polymerization step. The method according to claim 6,
In the ceramic-based composite wet coating agent,
The hydrophobic surface-treated liquid nano-colloidal sol contains 40 to 50% by weight,
15 to 25% by weight of the first and second silanes,
5 to 10% by weight of an organic solvent,
15 to 20% by weight of distilled water,
0.01 to 1% by weight of an additive,
Wherein the active metal filler is added in an amount of 10-15 wt%. The method according to claim 6,
The step of providing the hydrophobic surface-treated liquid nanocolloid sol may include:
Providing a water-dispersed liquid nano-colloidal sol;
Removing moisture of the liquid nano-colloidal sol by a decompression apparatus and introducing an organic solvent; And
And adding a distilled water and a silane coupling agent to the liquid nano-colloidal sol and hydrolyzing the liquid nano-colloidal sol. 9. The method of claim 8,
Wherein the silane coupling agent comprises at least one silane selected from the group consisting of alkyl silane, acryl silane and epoxy silane.

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