KR20220046402A - Composition for flexible coating film with high surface hardness and method of forming coating film using the same - Google Patents

Abstract

A conventional UV-curable coating composition or thermosetting coating composition has problems in that process costs are high and long process times are required to form a coating film using the same. To solve the above problems, the present invention provides a method for forming a coating film, comprising: a mixed solution step of making a mixed solution by mixing an acidic first solution containing an OH group-containing polymer or oligomer and a basic second solution containing an OH group-containing polymer or oligomer; an application step of applying the mixed solution to an object to be coated; and a curing step of curing the applied mixed solution. Accordingly, process costs can be reduced.

Description

A composition for a flexible coating film having high surface hardness and a method for forming a coating film using the same

The present invention relates to a coating composition and a method for forming a coating film for forming a coating film that imparts high hardness and chemical resistance to the surface of an object requiring a protective function by being exposed to the outside, such as packaging materials and iron plates, and more particularly, acid and basic It relates to a coating composition consisting of a polymer or oligomer solution and a method for forming a coating film using the same.

A method of forming a coating film using a liquid coating composition is widely used to protect vinyl, metal plate, glass, etc., which are often used as conventional packaging materials. In general, a method of curing a liquid coating composition by applying UV or the like after applying it to an object to be protected, or a method of curing by increasing the temperature is widely used.

However, in the case of a UV-curable coating composition cured by using UV, the use of an oil-soluble solvent having high solubility inevitably causes many environmental pollution problems, and the demand for changing the solvent to alcohol or water is increasing. In addition, in the case of a thermosetting type coating composition mainly used for metal coating, a high temperature is required for curing. , a device for applying a high temperature is additionally required, which is disadvantageous in terms of cost.

Conventional UV curable coating composition or thermosetting coating composition has a problem in that the process cost is high and a long process time is required in order to form a coating film using the same.

In the present invention, in order to solve the above problems, a mixed solution is prepared by mixing a first solution that is acidic while containing a polymer or oligomer containing an OH group and a second solution that is basic while containing a polymer or oligomer containing an OH group. It provides a coating film forming method comprising a mixed solution step, a coating step of applying the mixed solution to a coating object, and a curing step of curing the applied mixed solution.

The coating composition and coating method that can be provided in the present invention not only have high hardness and chemical resistance, but also have flexible properties. In particular, the coating film can be formed at room temperature without UV irradiation or additional heating. can be reduced and a coating film can be formed on various objects, so that it is possible to broaden the scope of the object to be coated.

1 is a flowchart of a coating method according to an embodiment of the present invention.
2 is a flowchart of a coating method according to an embodiment of the present invention.
3 is a flowchart of a coating method according to an embodiment of the present invention.
4 is a flowchart of a coating method according to an embodiment of the present invention.
5 is a flowchart of a coating method according to an embodiment of the present invention.

Hereinafter, the configuration and operation of the embodiment of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, when a part 'includes' a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

The present invention provides a coating composition comprising a first solution containing a polymer or oligomer containing an OH group and being acidic, and a second solution containing a polymer or oligomer containing an OH group and being basic.

In order to solve the problems of the prior art, the inventors of the present invention paid attention to the fact that, in the case of a material having a large number of OH groups attached to the terminal, a polycondensation reaction occurs with a material such as an acid or a base, and is cured while being polymerized. In general, the reaction occurs very rapidly even at room temperature, and an addition reaction may occur as an exothermic reaction generating heat.

However, in the case of general acids or bases, exact equivalent calculation is required, and if the amounts are not balanced, what remains may affect the basic properties and cause problems. Accordingly, in the present invention, acids and bases having a hydroxyl group in a branch while being an oligomer or a polymer were used to solve this problem. In this way, the above problem was solved by inhibiting the addition reaction and allowing the remaining acid or base to form a coating film by itself after participating in the reaction.

In particular, it is advantageous to be able to form a coating film at room temperature without an additional heat source because it can be cured quickly through this stable reaction of acid and base. Here, the room temperature is a temperature that appears in a general indoor working environment and means a temperature in a state in which there is no additional heat source. Therefore, considering the summer and winter temperatures in Korea, it may be in the range of 5 to 40 °C, and may be in the range of 10 to 30 °C. Although it is the greatest advantage of the present invention that it is a room temperature curable coating composition, the composition and method for curing by increasing the temperature using a heat source also fall within the scope of the present invention.

In addition, since the coating film is formed through curing of the composition containing the polymer or oligomer, the coating film has flexible properties, so that even if the coating film is formed on the flexible material, the coating film is not damaged according to the movement of the flexible material.

On the other hand, the polymer or oligomer used in the present invention was designed to be dissolved in alcohol or water as well as in general organic solvents to solve environmental problems in operation.

Here, the acidic first solution may have a pH range of 3 to 6, more preferably 4 to 5.

In addition, the basic second solution may have a pH range of 8 to 11, more preferably 9 to 10.

In addition, in the present invention, the polymer or oligomer of the first solution or the second solution may be a silane-based solution.

The silane-based polymer or oligomer has a chain-like molecular structure while including silicon, and thus has fluidity in appearance. Since the coating film formed by curing the liquid material having such fluidity has high hardness and chemical stability due to the silicone contained therein, it is suitable for protecting the object to be coated.

In addition, in the present invention, the acidic first solution may include epoxy silane, and the basic second solution may provide a coating composition containing amino silane.

This is because, in general, epoxy silane is advantageous for maintaining acidity and amino silane for maintaining basicity.

In the present invention, M1/M2, which is the ratio of the weight M1 of the epoxy silane of the first solution and the amount M2 of the amino silane of the second solution, is preferably in the range of 0.8 to 1.2, more preferably in the range of 0.9 to 1.1 .

This is because, as the weight ratio of the epoxy silane and the amino silane to each other is closer to 1, the curing speed becomes faster, and through this, the curing speed can be controlled.

In addition, the precursor for making the acidic first solution in the present invention may provide a coating composition comprising TEOS (Tetraethyl orthosilicate).

Compared to epoxy silane, TEOS has a higher content of inorganic silicon and, conversely, lower organic content. Therefore, by using TEOS as a precursor, the coating film made through it may have a higher content of inorganic substances and thus may have higher hardness and may be suitable for use in fields where the content of organic substances must be low.

In addition, the present invention can provide a coating film forming method comprising the steps of applying and curing the first solution and the second solution described above to the coating object alternately with each other in the present invention.

As described above, when the acidic and basic solutions meet each other, a polycondensation reaction occurs and is cured while being polymerized. Curing occurs stably and in a short time by this, and a coating film can be formed even at room temperature. For faster curing, additional heat may be applied to achieve curing.

When applied to the object to be coated, either the first solution or the second solution may be applied first to form a coating film. Therefore, as in FIG. 1, after applying the first solution as a lower film to the object to be coated, the second solution is applied on the lower film to form an upper film to form a final coating film, and the second solution as shown in FIG. A final coating film may be formed by coating as a lower film and applying the first solution as an upper film thereon.

In addition, as shown in FIG. 3, after each coating film is applied, a drying process may be added to remove the solvent. By adding a drying process, it is possible to eliminate the flow of the lower film to be advantageous in forming a uniform coating film. The drying process may be performed through wind at room temperature or hot air for rapid solvent volatilization.

In addition, the film by the first solution and the film by the second solution may be alternately applied a plurality of times to form a final coating film. After the first solution is applied, the second solution is applied, and then the first solution is applied thereon, 2 The solution may be applied to form a final coating film (see FIG. 4 ). When applying a plurality of coatings as described above, it may be advantageous to control the reaction between the acid and the base if the first solution and the second solution have the same number of applications, but if curing is possible, the number of applications may not be the same.

In the present invention, a coating film forming method comprising a mixed solution step of making a mixed solution by mixing the above-described first solution and the second solution, an application step of applying the mixed solution to a coating object, and curing the mixed solution provides

In addition, the method may further include diluting each of the first solution and the second solution with a solvent before the mixed solution step.

When the first solution and the second solution are alternately coated, at least two coating operations are required for this, which takes a lot of process time and cost.

To solve this, the first solution and the second solution are mixed and applied to the coating object at once. Each solution can be diluted in a solvent to prevent curing immediately when mixed. It is possible to reduce the process time and cost by applying and curing the mixed solution to the coating object at once (see FIG. 5 ).

Here, the curing may be performed at room temperature as described above, and additional heat may be applied for faster curing to be cured. In the present invention, room temperature means that there is no additional heat source for raising the temperature of the applied mixed solution, and the range of room temperature may be in the range of 5 to 40 °C, or 10 to 30 °C, which is the room temperature in a general working space. As such, since the curing is performed at room temperature without an additional heat source, the process cost can be reduced. In addition to the heat source, a process such as UV irradiation to increase the additional reaction rate is not required.

In order to volatilize the solvent before curing, a drying process may be added through wind or hot air at room temperature.

The solvent for the dilution may be any one or more of methyl ethyl ketone, ethyl acetate, ethanol, methanol, and water.

In particular, since water can be used, it can be an environmentally friendly coating process.

The ratio of the solvent in the diluted first solution and the second solution may be 30 to 80% by volume.

If the ratio of solvent is high, the curing speed is slow, and if the ratio of solvent is low, the curing speed is fast.

In particular, this coating process can be made through a continuous coating process, which is a process that can efficiently form a thin film on the surface of a flexible material such as glass or film, and is generally a roll-to-roll process The process is being developed by various methods such as slit coater, gravure offset, reverse offset, imprint, screen printing, and inkjet printing.

By applying the coating composition provided in the present invention to such a continuous coating process, it is possible to reduce process time and cost, thereby increasing the efficiency of the process.

Hereinafter, preferred embodiments of the present invention will be described in order to fully understand the present invention.

The embodiments of the present invention are provided to more completely explain the present invention to those of ordinary skill in the art, and the following examples can be modified in various other forms, and the scope of the present invention is not limited It is not limited to the following examples. Rather, these examples are provided so that this disclosure will be more thorough and complete, and will fully convey the spirit of the invention to those skilled in the art.

[Example 1]

<Preparation of the first solution>

140.5 g of 3-Glycidoxypropyltrimethoxysilane, 100.5 g of tetraethoxysilanes, and 200 g of isopropanol were put into a three-neck flask equipped with a heating device and stirred while stirring, 0.01 mole A solution of 2 ml of nitric acid / liter concentration and 52 ml of pure water was added dropwise from a funnel installed in the flask to a filter paper for 30 minutes.

After the temperature of the flask contents reached 50° C. or less, a reflux condenser was installed and refluxed at atmospheric pressure for 12 hours while heating to obtain an acidic first solution.

This solution was collected, diluted with tetrahydrofuran, and the weight average molecular weight was measured using tetrahydrofuran as a carrier and a gel permeation chromatography apparatus equipped with a refractive index detector. As a result, it was measured to be about 2,000.

<Preparation of second solution>

Put 230.22 g of 3-aminopropyltriethoxysilane and 200 g of isopropanol in a three-neck flask equipped with a heating device, and while stirring, pour 90 ml of pure water from a funnel installed in the flask using filter paper. It was dripped over 30 minutes.

After the temperature of the flask contents reached 50° C. or less, a reflux condenser was installed and refluxed for 6 hours at atmospheric pressure while heating to obtain a basic second solution.

This solution was collected, diluted with tetrahydrofuran, and the weight average molecular weight was measured using tetrahydrofuran as a carrier and a gel permeation chromatography apparatus equipped with a refractive index detector. As a result, it was measured to be about 1,500.

<Manufacture of coating film>

Using Bar Coater No. 12, coat the first solution on the PET film, apply a transparent thin film of about 0.7 to 1 μm, dry it to form a lower film, and then coat the second solution on the lower film in the same way to approximately 0.5 to 0.8 A ㎛ upper film was formed and cured. The time required for curing was less than 1 minute. It was confirmed that a film with a total thickness of 1 to 2 μm was formed by combining the upper and lower layers.

[Example 2]

<Preparation of the first solution>

Except for tetraethoxysilane in the input monomer of Example 1, only 240.2 g of 3-glycidoxypropyltrimethoxysilane was used for the reaction, and the rest was synthesized under the same conditions as in Example 1.

This solution was collected, diluted with tetrahydrofuran, and the weight average molecular weight was measured using tetrahydrofuran as a carrier and a gel permeation chromatography apparatus equipped with a refractive index detector. As a result, it was measured to be about 2,100.

<Preparation of second solution>

It proceeded in the same manner as in Example 1.

<Manufacture of coating film>

It proceeded in the same manner as in Example 1.

[Example 3]

<Preparation of the first solution>

The same procedure as in Example 1 was performed except that the added monomer was changed to 30.12 g of 3-glycidoxypropyltrimethoxysilane, 85.5 g of tetraethoxysilane, and 90 g of methyltriethoxysilane.

This solution was collected, diluted with tetrahydrofuran, and the weight average molecular weight was measured using tetrahydrofuran as a carrier and a gel permeation chromatography apparatus equipped with a refractive index detector. As a result, it was measured to be about 1,800.

<Preparation of second solution>

It proceeded in the same manner as in Example 1.

<Manufacture of coating film>

It proceeded in the same manner as in Example 1.

[Example 4]

<Preparation of the first solution>

TEOS (Tetraethyl orthosilicate) 210.05g and isopropyl alcohol 200g are put into a three-neck flask equipped with a heating device, and while stirring, a solution of 2ml of 0.01 mol/liter nitric acid and 52ml of pure water is filtered through a funnel installed in the flask. It was dripped for 30 minutes using paper.

After the temperature of the flask contents reached 50° C. or less, a reflux condenser was installed and refluxed for 12 hours at atmospheric pressure while heating to obtain a first solution.

This solution was collected, diluted with tetrahydrofuran, and the weight average molecular weight was measured using tetrahydrofuran as a carrier and a gel permeation chromatography apparatus equipped with a refractive index detector. As a result, it was measured to be about 3,000.

<Preparation of second solution>

It proceeded in the same manner as in Example 1.

<Manufacture of coating film>

It proceeded in the same manner as in Example 1.

[Example 5]

<Preparation of the first solution>

It proceeded in the same manner as in Example 1.

<Preparation of second solution>

It proceeded in the same manner as in Example 1.

<Preparation of mixed solution>

A diluted first solution was prepared by mixing 500 ml of the first solution and 500 ml of ethanol. Similarly, 500 ml of the second solution and 500 ml of ethanol were mixed to prepare a diluted second solution. A mixed solution was prepared by mixing the diluted first solution and the second diluted solution thus prepared.

<Manufacture of coating film>

Using Bar Coater No. 12, the mixed solution was coated on the PET film, a transparent thin film of about 1 to 2 μm was applied, dried to form a coating film, and then cured at room temperature. The time required for curing was less than 2 minutes. It was confirmed that a coating film having a thickness of 1 to 2 μm was formed.

[Comparative Example 1]

<Preparation of the first solution>

It proceeded in the same manner as in Example 1.

<Preparation of second solution>

230.22 g of 3-aminopropyltriethoxysilane and 200 g of isopropanol were put into a three-neck flask equipped with a heating device, and while stirring, 90 ml of formic acid at a concentration of 0.01 mol/liter was added to the flask and the filter paper was removed from the funnel. was added dropwise for 30 minutes.

After the temperature of the flask contents reached 50° C. or less, a reflux condenser was installed and refluxed for 6 hours at atmospheric pressure while heating to obtain a second solution.

This solution was collected, diluted with tetrahydrofuran, and the weight average molecular weight was measured using tetrahydrofuran as a carrier and a gel permeation chromatography apparatus equipped with a refractive index detector. As a result, it was measured to be about 1,700.

<Manufacture of coating film>

It proceeded in the same manner as in Example 1.

[Comparative Example 2]

<Preparation of the first solution>

It proceeded in the same manner as in Example 1.

<Preparation of second solution>

It proceeded in the same manner as in the first acidic solution of Example 2.

<Manufacture of coating film>

It proceeded in the same manner as in Example 1.

[Comparative Example 3]

<Preparation of the first solution>

It proceeded in the same manner as in the second solution of Example 1.

<Preparation of second solution>

It proceeded in the same manner as the second solution of Example 1

<Manufacture of coating film>

It proceeded in the same manner as in Example 1.

For evaluation of the coating films made in Examples and Comparative Examples, the film thickness was measured at 9 locations using a micrometer. Pencil hardness was measured with a pencil hardness tester with a working load of 500 g, and chemical resistance was measured by dropping Methyl Ethyl Ketone (MEK) and rubbing it 50 times with Kimwipes.

Such Examples and Comparative Examples are summarized in [Table 1] and [Table 2] below.

Example 1 Example 2 Example 3 Example 4 Example 5 Molecular Weight
<bottom film>
<Upper film>
2000
1500
2100
1500
1800
1500
1200
1500 film thickness 1~2㎛ 1~2㎛ 1-2㎛ 1-2㎛ 1-2㎛ pH
<bottom film>
<Upper film>
4-5
9-10
4-5
9-10
4-5
9-10
3.5~4.5
9-10 pencil hardness 5H 5H 6H 7H 5H MEK rubbing test OK OK OK OK OK membrane transparency OK OK 20% Haze OK OK upper film drying time 20 seconds 30 seconds 1 hours 2 minutes 2 hours

Comparative Example 1 Comparative Example 2 Comparative Example 3 Molecular Weight
<bottom film>
<Upper film>
1800
1700
2000
2100
1500
1500 film thickness 1-2㎛ 1-2㎛ 1-2㎛ pH
<bottom film>
<Upper film>
4-5
6-7
4-5
4-5
9-10
9-10 pencil hardness 4H B or less 2H MEK rubbing test OK Recording during MEK Drop Peel off after about 30 times membrane transparency 50% haze OK OK upper film drying time 1 day 2 days 1 day

As can be seen from the above, it was confirmed that when the acidic polymer or oligomer and the basic polymer or oligomer were sequentially coated, a mutual reaction occurred to maintain a fast drying time and transparency of the film. However, when the acid polymer or oligomer was overlapped and coated, and when the basic polymer or oligomer was overlapped and coated, the hardness of the film was significantly lowered or chemical resistance was lowered, so it was confirmed that sufficient curing did not occur. In addition, it was confirmed that a stable curing reaction occurs even when an acidic polymer or oligomer solution and a basic solution or an oligomer solution are mixed and then applied and cured to form a coating film with excellent hardness and chemical resistance.

Claims (11)

A first solution containing a polymer or oligomer containing an OH group and being acidic and a second solution containing a polymer or oligomer containing an OH group being basic, the polymer or oligomer of the first solution or the second solution is silane (silane) based, coating composition. The method of claim 1,
wherein the acidic first solution has a pH in the range of 3-6. The method of claim 1,
The second solution, which is basic, has a pH in the range of 8 to 11, the coating composition. The method of claim 1,
wherein the first solution comprises an epoxy silane and the second solution comprises an amino silane. 5. The method of claim 4,
The ratio of M1, which is the weight of the epoxy silane of the first solution, and M2, which is the weight of the amino silane of the second solution, M1/M2 is in the range of 0.8 to 1.2, the coating composition. The method of claim 1,
The silane-based precursor for making the first solution comprises TEOS (Tetraethyl orthosilicate), the coating composition. A mixed solution step of making a mixed solution by mixing the first solution and the second solution according to any one of claims 1 to 7;
an application step of applying the mixed solution to the object to be coated; and
A method of forming a coating film, comprising a curing step of curing the applied mixed solution. 8. The method of claim 7,
Further comprising the step of diluting the first solution and the second solution with a solvent before the mixed solution step, the coating film forming method. 9. The method of claim 8,
The solvent is methyl ethyl ketone, ethyl acetate, ethanol, methanol, and any one or more of water, the coating film forming method. 9. The method of claim 8,
The ratio of the solvent in the diluted first solution and the second solution is 30 to 80% by volume, the coating film forming method. 11. The method according to any one of claims 7 to 10,
The curing step is made at room temperature without an additional heat source, the coating film forming method.

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