KR20200043834A - Method for modifying surfaces using rare earth metal oxide solution mixed with binder - Google Patents

Abstract

The present invention provides a surface modification method using a rare earth metal oxide solution mixed with a binder. Particularly, the surface modification method is a hydrophobic coating method which includes the steps of: a) dissolving a rare earth metal precursor in ethanol; b) adding aqueous hydroxide solution to the solution to form a rare earth metal oxide; c) adding a binder to the rare earth metal oxide solution; and d) coating the rare earth metal oxide and binder solution onto a substrate. The method uses a polymer binder to increase the adhesion between the substrate and the rare metal oxide layer. Polyacrylic acid (PAA) is used as polymer binder and the carboxyl groups present in the PAA binder forms binder-binder hydrogen bonding, and thus the strong cohesion of the hydrogen bonding causes binding of the nanoparticles used herein with the binder, thereby forming a hydrophobic coating layer having high adhesion.

Description

METHOD FOR MODIFYING SURFACES USING RARE EARTH METAL OXIDE SOLUTION MIXED WITH BINDER

The present invention relates to a surface modification method using a rare earth metal oxide solution mixed with a binder, specifically, a) dissolving a rare earth metal precursor in ethanol; b) preparing a rare earth metal oxide by adding an aqueous hydroxide solution to the solution; c) adding a binder to the rare earth metal oxide solution; and d) coating the rare earth metal oxide and binder solution on a substrate.

Hydrophobicity in various fields such as hot plate, glassware, kitchenware and household goods, various finishing materials, water pipes, piping, semiconductor, construction, display screen, aviation and metal wiring. There is an increasing demand for water repellency materials.

To this end, attempts have been made to modify the surface of a hydrophilic substrate with hydrophobicity, and products, for example, having a hydrophilic surface hydrophobicized using an organic polymer modifier have been commercially available.

However, the conventional organic polymer material having hydrophobic properties is vulnerable to heat and deteriorates when heated to a high temperature and loses its hydrophobic properties. The poor thermal stability of these existing polymer modifiers has become a major obstacle to application in industrial fields where heat resistance is particularly required.

Rare Earth Oxide (REO) is a ceramic material that is not only resistant to heat and has excellent durability, but also has stable hydrophobicity due to its unique electronic structure, and can be applied to not only cooking utensils, kitchen utensils, but also semiconductor components.

However, in order to apply rare earth metal oxides to appropriate applications, coating technology is essential. When a rare earth metal oxide nanoparticle is synthesized based on a sol-gel process as a prior study, and the desired surface is coated using spin coating or spray coating, the adhesion between the substrate and the coating layer is poor, so that the coating layer is easily removed. Cons were identified.

This is not only a problem of rare earth metal oxides, but is a disadvantage that is generally observed in spin coating or spray coating.

Korean Registered Patent No. 10-1617396

The present invention is to solve the problems of the prior art as described above, by mixing a binder and a rare earth metal oxide and coating it on a substrate, with excellent hydrophobicity, thermal stability and durability in a simple coating method, between the coating layer and the substrate surface It is a technical problem to provide a new surface modification method capable of improving adhesion.

In order to solve the above technical problem, the present invention comprises a) dissolving a rare earth metal precursor in ethane or isopropyl alcohol; b) preparing a rare earth metal oxide by adding an aqueous hydroxide solution to the solution; c) adding a binder to the rare earth metal oxide solution; and d) coating the rare earth metal oxide and binder solution on a substrate; provides a method for surface modification using a rare earth metal oxide solution containing a binder.

In one embodiment of the present invention, the rare earth metal precursor is samarium (Sm), praseodymium (Pr), europium (Eu), gadolinium (Gd), lanthanum (La), terbium (Tb), dysprosium (Dy), Characterized in that it is a nitrate or chloride containing at least one rare earth metal selected from the group consisting of holmium (Ho), erbium (Er), tolium (Tm) and ruthenium (Lu), and is preferable. Preferably, it is either cerium nitrate hexahydrate ((Ce (NO ₃ )) ₃ · 6H ₂ O) or cerium chloride (Cerium Chloride, CeCl ₃ ), most preferably cerium nitrate hexahydrate, (Ce (NO ₃ )) ₃ · 6H ₂ O).

The cerium nitrate hexahydrate ((Ce (NO ₃ )) ₃ · 6H ₂ O) is decomposed into cerium ions (Ce ³⁺ ) in an ethanol solution, and hydroxyl groups (or hydroxyl groups; OH-) are added later. It is combined with and is formed in the form of cerium hydroxide (Ce-OH). In addition, cerium hydroxide forms cerium oxide (CeO ₂ ) while H ₂ O is decomposed again through a condensation reaction.

As the organic solvent, isopropyl alcohol (IPA), which is an alcohol-based alcohol, may be used instead of ethanol.

The hydroxide may be at least one selected from NaOH and KOH or a mixture thereof. In addition, the aqueous hydroxide solution may be dissolved in water at a predetermined concentration and used in the form of an aqueous solution. As the aqueous hydroxide solution, an aqueous solution having a concentration of hydroxide of 0.01 to 1M may be used, and preferably, an aqueous solution of 0.1M is used. The aqueous hydroxide solution is insufficient in the formation of cerium hydroxide when the concentration of the hydroxide is too low.

The hydroxide is introduced into the precursor solution to supply a hydroxyl group to the ions of the precursor so that the precursor has the form of a hydroxide. In addition, the precursor hydroxide is later formed of an oxide through a condensation reaction. Thus, the hydroxide acts as a source of oxygen needed to form the electrolyte oxide from the precursor.

In one embodiment of the present invention, the binder is characterized in that it is a polymer containing a carboxyl group, preferably one or more selected from the group consisting of polyacrylic acid, polyaspartic acid, and polyglutamic acid, more preferably poly It is characterized by being acrylic acid.

The polymer binder serves as an adhesive between the coating layer and the surface, thereby compensating for the limitation of the existing weak adhesiveness. The carboxyl group in the polymer binder forms a hydrogen bond between the binder and the binder. Due to this strong cohesion of hydrogen bonding, CeO ₂ particles used in the invention can be combined with a binder to form a hydrophobic coating layer with high adhesion.

In the case of the polyacrylic acid (Polyacrylic acid, PAA), since the thermal decomposition temperature is 120 ° C or higher, there is no great problem in the safety of the polymer during the sintering process. In addition, the hydrogen bond between polymer molecules of the PAA binder can play a role in connecting linear bonds, which can show stronger bonds than simple one-dimensional linear polymers, thereby improving adhesion between the coating layer and the substrate.

In one embodiment of the present invention, steps a) and b) are performed at a temperature of 100 to 140 ° C., the coating is performed by a spin coating method, and spin coating is performed at 1000 rpm 60 seconds as 1 cycle 3 It is desirable to perform ~ 12 cycles. When agitation is performed under an allowable temperature range (100 to 140 ° C.), sufficient energy for bonding may not be supplied, and thus formation of CeO ₂ particles may be insufficient. In addition, when stirring over the allowable temperature range, the bonding strength becomes strong, and the size of the CeO ₂ particles increases, so that a successful hydrophobic surface cannot be formed later.

In one embodiment of the present invention, after the step d), may further include the step of sintering at 80 ℃ for 24 hours.

The present invention relates to a technique using a polymer binder to increase the adhesion between the substrate and the rare earth metal oxide layer, the polymer binder used polyacrylic acid (PAA) and the carboxyl group in the PAA binder forms a hydrogen bond between the binder and the binder, , Due to the strong cohesion of hydrogen bonding, CeO ₂ nanoparticles used in the invention can be combined with a binder to form a hydrophobic coating layer with high adhesion.

In addition, since it is coated by mixing PAA binder and rare earth metal oxide, it has the advantage of simple coating and large-scale coating is possible because it uses a wet method.

1 is a view showing the hydrogen structure of the polyacrylic acid and the chemical structure (left) of the polyacrylic acid (PAA) binder according to the present invention.
2 is a view showing the coating structure of the mixed CeO ₂ nanoparticles and a polyacrylic acid (PAA) binder.
3 is a view showing a contact angle of a Si substrate coated with CeO ₂ nanoparticles and PAA binder according to Examples 1 to 4 of the present invention.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only for the understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

Example 1

First, cerium nitrate hexahydrate, sodium hydroxide, ethanol, and polyacrylic acid binders were prepared.

After dissolving 0.06M of cerium nitrate rapidly in ethanol at 120 ° C, a 0.10M sodium hydroxide solution was slowly added thereto, followed by stirring at 120 ° C for 1 hour and 30 minutes.

After cooling the solution to room temperature for 30 minutes, the final particles are washed three times with ethanol. In addition, the CeO ₂ nanoparticles thus obtained were dispersed in ethanol for further analysis.

10 ml of the CeO ₂ nanoparticle solution thus obtained is mixed with 0.001 g of a polyacrylic acid (PAA) binder.

The CeO ₂ nanoparticle solution and the PAA binder mixture solution (CeO ₂ / PAA binder solution) were coated on a silicon substrate through spin coating at 1000 rpm for 60 seconds, and this was performed three times. After the coating was completed, the film was sintered at 80 ° C. for 24 hours to form a film on the substrate.

Si wafer was used as the substrate, and the substrate was washed with acetone, isopropyl alcohol (IPA), and distilled water.

Example 2

It was the same as in Example 1, except that the coating was performed 6 times.

Example 3

It was the same as in Example 1, except that the coating was performed 9 times.

Example 4

It is the same as in Example 1, except that the coating was performed 12 times.

Experimental Example: Measurement of contact angle

The contact angles of the deionized water droplets on the surfaces coated by Examples 1 to 4 were measured and are shown in Table 1 and FIG. 3 below. The contact angle was measured using a contact angle analyzer (SDL200TEZD, FEMTOFA) by dropping 1.4 to 2 µl droplets onto the coated substrate.

Example 1 Example 2 Example 3 Example 4 Contact angle (CA) 92.2 ° 90.1 ° 96.2 ° 104.4 °

Referring to [Table 1], a substrate coated with a CeO ₂ / PAA binder solution according to the present invention was measured to have a contact angle of 90 ° or more in all examples, and it was confirmed that the substrate successfully exhibited hydrophobicity.

Also, as the number of spin coatings increased, hydrophobicity tended to increase.

Claims (12)

a) dissolving the rare earth metal precursor in ethanol;
b) preparing a rare earth metal oxide by adding an aqueous hydroxide solution to the solution;
c) adding a binder to the rare earth metal oxide solution; and
d) coating the rare earth metal oxide and binder solution on a substrate; including, surface modification method using a rare earth metal oxide solution mixed with a binder.
The rare earth metal precursor is nitrate or chloride containing at least one rare earth metal selected from the group consisting of Sm, Pr, Eu, Gd, La, Tb, Dy, Ho, Er, Tm and Lu Characterized in that, the surface modification method using a rare earth metal oxide solution mixed with a binder.
According to claim 2,
The rare earth metal precursor is any one of cerium nitrate (Cerium nitrate hexahydrate, (Ce (NO ₃ )) ₃ · 6H ₂ O) or cerium chloride (Cerium Chloride, CeCl ₃ ), a rare earth metal mixed with a binder Method of surface modification using oxide solution.
According to claim 1,
The binder is characterized in that the polymer containing a carboxyl group, surface modification method using a rare earth metal oxide solution mixed with a binder.
According to claim 4,
The carboxyl group-containing polymer is polyacrylic acid, poly aspartic acid, and polyglutamic acid, characterized in that one or more selected from the group consisting of, surface modification method using a rare earth metal oxide solution mixed with a binder.
According to claim 1,
The hydrophilic inorganic substrate is a silicon (Si) substrate, a silica (SiO ₂ ) substrate or a platinum (Pt) substrate, characterized in that the surface modification method using a rare earth metal oxide solution mixed with a binder.
The hydroxide aqueous solution is characterized in that the NaOH or KOH aqueous solution having a concentration of 0.01 ~ 1M, surface modification method using a rare earth metal oxide solution mixed with a binder.
According to claim 1,
The step a) and step b) is characterized in that is performed at a temperature of 100 ~ 140 ℃, surface modification method using a rare earth metal oxide solution mixed with a binder.
According to claim 1,
The coating is characterized by being performed by a spin coating method, a surface modification method using a rare earth metal oxide solution mixed with a binder.
The method of claim 9,
The spin coating is characterized in that made for 60 seconds at 1000 rpm, surface modification method using a rare earth metal oxide solution mixed with a binder.
The method of claim 9,
The spin coating is performed 3 to 12 times, characterized in that the surface modification method using a rare earth metal oxide solution mixed with a binder.
According to claim 1,
After the step d), characterized in that it further comprises the step of sintering for 24 hours at 80 ℃, surface modification method using a rare earth metal oxide solution mixed with a binder.

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