JP3385648B2 - Coating composition and method for producing liquid resin used therein - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin coating composition which can be applied without using a solvent and a method for producing a liquid resin used therein.

[0002]

2. Description of the Related Art Conventionally, metal, plastic film cans,
Paints containing organic solvents have been used for coating containers and the like. This conventional paint disperses a large amount of organic solvent in the painting process and the curing and drying process. With increasing interest in the global environment and the working environment, restrictions on the use of such paints have come to be imposed. As one of the methods, there are water-based paints and powders. However, it is hard to say that the water-based paints also contain some organic solvents from the viewpoint of improving the paintability, and the odor in the working environment is removed.
In addition to the incineration of the released organic solvent, investment is required for wastewater treatment. Although a paint factory equipped with a large-scale exhaust gas treatment facility can suppress the release of organic solvents into the atmosphere,
Small-scale factories that do not have such equipment have the problem that they cannot treat wastewater even if they can treat organic solvents. Further, in the case of powder coating, the method is significantly different from the conventional coating equipment, and it is necessary to introduce new equipment.

In order to solve the above problems, high solidification of paints, improvement of water-based paints and the like are being carried out, and it is considered that the efforts will further reduce the usage of solvent-based paints in the future. To be However, as a fundamental solution, there is a strong demand for the development of a solvent-free paint which is free from problems such as pollution, safety and hygiene, ignition and explosion, can be applied in a wide range, and is easy to apply. Such a solvent-free coating material is disclosed in JP-A-57-171. This technique uses a liquid resin based on an acrylic monomer, but the obtained resin is an oligomer, contains a low molecular weight component in the composition, and uses an amine type or an isocyanate type hardener having strong skin irritation. Due to the necessity, further improvement is required in terms of safety and health. In terms of physical properties, it is known that it is difficult to control the physical properties of the coating film after curing in the case of a coating composed of a resin in the oligomer region (Soichi Muroi, "1992 Adhesion and Painting Microscope Society Lecture"). Abstracts of lectures, P4, 1993), there is a demand for a coating material using a resin capable of increasing the molecular weight while maintaining a low viscosity.

[0004]

DISCLOSURE OF THE INVENTION The present invention does not contaminate the working environment of the coating process with the organic solvent that scatters and does not discharge the organic solvent into the atmosphere, and thus does not require special exhaust gas treatment equipment. Further, the present invention provides a paint which can be applied by a conventionally used coating method, for example, a roll coater or a knife coater, and which does not dissipate the solvent even when the conventional heating and drying is performed.

[0005]

Means for Solving the Problems The present invention provides (A): 35 to 90% of a monomer represented by the following formula (1), CH ₂ = C (R ¹ ) COOR ² (1) (in the formula, R ¹ is H or CH ₃ , and R ² is a hydrocarbon group having 10 to 20 carbon atoms. ) (B): Polymerizable unsaturated carboxylic acid 3 to 35% by weight (C): containing an alkoxy group or a hydroxyl group Polymerizable unsaturated monomer 5 to 60% by weight (D): Other polymerizable vinyl compound 0 to 40% by weight as a constituent component and number average molecular weight of 10,000 to 200,
000 and the viscosity is 500 cps to 30,000 cps
It relates to a coating composition comprising a liquid resin of (50 ° C.).

Further, the present invention provides the above (A) to (D).
The present invention relates to a method for producing the above liquid resin, which comprises radically polymerizing the components in a water-miscible solvent which may contain water.

[0007] monomer (A) of the present invention, is used a copolymer as a component for a liquid, e.g., decyl
(Meth) acrylate, undecyl (meth) acrylate
Todo, dodecyl (meth) acrylate, tridecyl (meth)
A) acrylate, tetradecyl (meth) acrylate
G, pentadecyl (meth) acrylate, hexadecyl
(Meth) acrylate, heptadecyl (meth) acryl
, Octadecyl (meth) acrylate, nonadecyl
(Meth) acrylate, icosyl (meth) acrylate
Etc.

The amount of the monomer (A) used is 35 to 90% by weight, preferably 50 to 90% by weight, based on the liquid resin which is a copolymer.
When the amount of the monomer (A) in the copolymer is less than 50% by weight, particularly less than 35% by weight, the copolymerization cannot maintain a liquid state. If it is too large, a hard coating film cannot be obtained, which is not preferable.

The polymerizable unsaturated carboxylic acid (B) of the present invention is used for introducing a crosslinking component into the copolymer together with the component (C), and examples thereof include maleic acid, fumaric acid, itaconic acid, citraconic acid, or , These alkyl or alkenyl monoesters, phthalic acid β- (meth) acryloxyethyl monoester, isophthalic acid β- (meth)
Acryloxyethyl monoester, terephthalic acid β-
(Meth) acryloxyethyl monoester, succinic acid β
-(Meth) acryloxyethyl monoester, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid and the like.

The amount of the polymerizable unsaturated carboxylic acid (B) used is 3 to 35% by weight, preferably 5 to 20% by weight, based on the liquid resin which is a copolymer. ) When the content of the component is less than 5% by weight, particularly less than 3% by weight, it becomes difficult to obtain a hard coating film.
If the amount is larger, the viscosity of the liquid resin becomes higher and the coating becomes difficult, which is not preferable.

Examples of the polymerizable unsaturated monomer (C) having an alkoxy group or a hydroxyl group of the present invention include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate. , Glycerol mono (meth) acrylate, diethylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, polyethylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, and these A plurality of groups may be used.

The amount of the polymerizable unsaturated monomer (C) containing an alkoxy or hydroxyl group used is 5 to 60% by weight, preferably 7 to 40% by weight, based on the liquid resin which is a copolymer. If the content of the component (B) in the composition is less than 7% by weight, especially less than 5% by weight, the liquid resin cannot be cured, and conversely
If the amount is more than 60% by weight, the water resistance is lowered, which is not preferable.

Examples of the polymerizable vinyl compound (D) of the present invention include aromatic monomers such as styrene and vinyltoluene, and (meth) acrylates having an alkyl group having 3 or less carbon atoms such as methylmethacrylate and ethylmethacrylate. Such a compound (D) can be used for improving the water resistance and hardness of the coating film.

The liquid resin of the present invention has a number average molecular weight of the copolymer of 10,000 to 200,000, preferably 1
It is 5,000 to 150,000. If the number average molecular weight is smaller than the above value, it is difficult to isolate the resin component from the polymerization solution, mechanical properties such as flexibility are deteriorated, and solvent resistance, boiling water resistance, and other coating film physical properties are It is not preferable because it lowers, and when it is larger than the above value, the resin cannot maintain a coatable viscosity, which is not preferable.

The liquid resin of the present invention can be produced by radical polymerization by dissolving a mixture of the above monomers in a solution in the presence of a known radical polymerization initiator, or by dropping a mixture of the monomers. it can. As the solvent used,
Although water-immiscible organic solvents such as ethyl acetate, toluene, methyl ethyl ketone, benzene, sec-butanol, tert-butanol, isobutanol, methyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, and diacetone alcohol can be used, When a water-miscible solvent such as dioxane, n-propanol, methanol, isopropanol, tetrahydrofuran, n-butanol, butyl cellosolve, methyl carbitol, ethyl carbitol is used, water is added to isolate the resin component from the reaction solution. It is good because it is good. It is also possible to use water in a water-miscible solvent as long as it does not precipitate the above-mentioned monomer. The viscosity of the obtained resin is 500 to 30,000 cp at 50 ° C.
s, preferably 800-10,000 cps liquid.

The coating composition of the present invention comprises a liquid resin itself comprising a copolymer of the above monomers and can be used as a substantially solvent-free coating. However, a small amount of water, an organic solvent or the like may be added in order to improve the coatability of the paint. The amount that can be blended is up to 5% by weight based on the liquid resin. The coating composition of the present invention may contain a curing agent resin such as an amino resin or a phenol resin in order to enhance the curability of the coating composition. Further, titanium white, colorants such as various pigments, lubricants and the like may be added.

The coating composition of the present invention is applied to a substrate such as various steel plates, metal plates such as aluminum plates and plastic films for 3 to 30 μm, and cured by heating at 150 to 250 ° C. for 5 to 25 minutes. You can Examples of the coating method include a roll coater and a knife coater.

[0018]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

(Prototype Example-1) In a 500 ml four-necked round bottom flask equipped with a stirrer, a nitrogen introducing tube, a temperature sensor, and a condenser, isopropyl alcohol (IPA) 200 ml water 50 ml n-lauryl methacrylate 45 g succinic acid β-methacryloxyethyl monoester 10 g methoxydiethylene glycol methacrylate 8 g AIBN 1 g was charged, and the temperature inside the flask was raised to 65 ° C. in a water bath. The system became more opaque as the polymerization reaction proceeded. The reaction is continued for 4 hours as it is, and then 50 ml of water is added to the obtained polymer solution to precipitate the resin. When settling started, while swirling, transfer the contents of the flask to a 500 ml beaker, remove the upper layer liquid, and leave at 60 ° C.
It was transferred to a vacuum oven of No. 2 and dried under reduced pressure overnight while maintaining 5 mmHg. The yield was 95%. The obtained resin was an odorless viscous liquid, and had a number average molecular weight of 27,000 as measured by GPC (in terms of styrene).
When the viscosity was measured at 50 ° C. using a rotational vibration type viscometer (Yamaichi Denki Co., Ltd. VM-100), it was 15,000.
It showed 0 cps.

(Prototype Example-2) With the prescription of (Prototype Example-1),
A similar reaction was carried out with a charged amount of water of 25 ml and an charged amount of IPA of 225 ml.

The yield of the obtained resin was 97%, the number average molecular weight was 32,000, and the viscosity was 18,000 at 50 ° C.
It was cps.

Comparative Example-1 A 500 ml four-neck round bottom flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a condenser was charged with isopropyl alcohol (IPA) 200 ml water 60 ml n-lauryl methacrylate 15 g succinic acid. β-methacryloxyethyl monoester 23 g methoxydiethylene glycol methacrylate 28 g AIBN 1 g is charged, and the temperature inside the flask is raised to 65 ° C. in a water bath. The reaction is continued for 4 hours as it is, and 500 ml of diethyl ether is added to the obtained polymer solution to precipitate the resin. Dioxane (100 ml) was added to the solution obtained by removing the upper layer solution, and reprecipitation was performed again with diethyl ether. The upper layer solution was removed, and the mixture was transferred to a vacuum oven at 60 ° C. as it was at 5 mmHg.
While maintaining the above, vacuum drying was performed overnight. The yield of the obtained resin was 90%, and the molecular weight was measured by GPC (in terms of styrene).
The number average molecular weight was 38,000, but at room temperature (25
(° C), it was a solid, and the viscosity could not be measured even when heated to 90 ° C.

Comparative Example 2 In a 500 ml four-necked round bottom flask equipped with a stirrer, nitrogen inlet tube, temperature sensor, and condenser, isopropyl alcohol (IPA) 150 ml water 100 ml n-lauryl methacrylate 45 g succinic acid β -Methacryloxyethyl monoester 10 g methoxydiethylene glycol methacrylate 8 g AIBN 5 g are charged, and the temperature inside the flask is raised to 65 ° C in a water bath. The reaction is continued for 4 hours, and 100 ml of water is added to the obtained polymer solution. Put this in a centrifuge tube,
The resin content is separated from the polymer solution by a centrifuge set at 5,000 times / minute. After removing the liquid of the upper layer, IPA is poured and dissolved, and then a mixed solvent of water / methanol = 5: 2 is poured to reprecipitate. The liquid in the upper layer was removed, the mixture was transferred to a vacuum oven at 60 ° C. as it was, and dried under reduced pressure overnight while maintaining 5 mmHg. The yield was 60%. The obtained resin was a viscous liquid and had a number average molecular weight of 3,000 as measured by GPC (in terms of styrene). When the viscosity was measured at 50 ° C. using a rotary vibration type viscometer, it was 2,000.
It showed cps.

(Prototype Example-3) In a 500 ml four-necked round bottom flask equipped with a stirrer, a nitrogen introducing tube, a temperature sensor, and a condenser, IPA 200 ml water 50 ml n-lauryl methacrylate 45 g succinic acid β-meta acid. Acryloxyethyl monoester 10 g Diethylene glycol methacrylate 7 g AIBN 1 g is charged and the temperature inside the flask is raised to 65 ° C. in a water bath. The reaction is continued as it is for 3 hours, and 50 ml of water is added to the obtained polymer solution to precipitate the resin. When settling started, while swirling, the contents of the flask were transferred to a 500 ml beaker, the upper layer liquid was removed, 300 ml of dioxane was added here to redissolve the resin, and 100 ml of methanol was added to reprecipitate the supernatant. Except,
Vacuum drying was performed at 50 ° C. overnight. The resin yield was 95%. The obtained resin was an odorless viscous liquid and had a number average molecular weight of 24,000. When the viscosity was measured at 50 ° C., it was 16,000 cps.

(Prototype Example 4) IPA 220 ml water 60 ml n-pentadecylmethacrylate 55 g g phthalate β in a 500 ml four-necked round bottom flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a condenser. -Methacryloxyethyl monoester 7 g methoxytetraethylene glycol methacrylate 7.5 g AIBN 1 g were charged, and the temperature inside the flask was raised to 65 ° C. in a water bath,
The reaction was continued for 4 hours as it was. The resin yield was 96%. The obtained resin was an odorless viscous liquid and had a number average molecular weight of 20,000. When the viscosity was measured at 50 ° C., it showed 16,500 cps.

(Prototype Example-5) 50 equipped with a stirrer, a nitrogen introducing pipe, a temperature sensor, a dropping funnel and a condenser
A 0 ml four-necked round bottom flask was charged with IPA 200 ml, water 25 ml, stearyl acrylate 40 g, maleic acid 5 g, methacrylic acid 3 g, 4-hydroxybutyl acrylate 10 g, styrene 3 g and AIBN 0.6 g. Raise the temperature to 65 ° C. The reaction was continued for 4 hours as it was. Resin yield is 93%
Met. The obtained resin was an odorless viscous liquid and had a number average molecular weight of 13,000. When the viscosity was measured at 50 ° C., it was 23,000 cps.

(Example-1) The copolymer synthesized in (Prototype Example-1) was hung on a hard aluminum plate on a hot plate kept at 80 ° C and coated using a 1 mil applicator. During coating, there was no odor of low molecular weight organic compounds such as residual monomers. After coating, no cissing was observed on the coating film, and this was placed in an electric oven at 200 ° C. for 15 minutes to obtain a smooth cured coating film. An attempt was made to tack the finger on the surface of the coating film, but there was no tack. In the cross-cut peeling test, the coating film residual rate was 100%. The aluminum plate was cut into a piece having a width of 2 cm, placed in tetrahydrofuran, and allowed to stand at room temperature for 1 day, but no whitening or the like was observed. Similarly, the aluminum piece was kept in boiling water for 1 hour, but whitening and peeling of the coating film did not occur, and solvent resistance and water resistance were good.

(Example-2) The copolymer synthesized in (Comparative Example-2) was dropped on a hard aluminum plate on a hot plate at 80 ° C. and applied using a 1 mil applicator.
After coating, no cissing was observed on the coating film, and this was placed in an electric oven at 200 ° C. for 15 minutes to obtain a smooth cured coating film. However, during heating, there was an odor, which was probably due to thermal decomposition of the resin. An attempt was made to tack the finger on the surface of the coating film, but there was no tack. In the cross-cut peeling test, the coating film residual rate was 70%. When the aluminum plate was cut into a piece having a width of 2 cm, placed in tetrahydrofuran, and allowed to stand at room temperature for 1 day, some whitening was observed. Similarly, when the aluminum pieces were kept in boiling water for 1 hour, whitening occurred partially.

Table 1 collectively shows Examples 1 to 7 and Comparative Example 2 performed on the copolymers obtained in Prototype Examples 1 to 5.

[0030]

[Table 1]

Explanation of symbols ◯: No tack (tack), no whitening (solvent resistance, boiling water resistance) Δ: Some tack (tack), slightly cloudy (solvent resistance,
Water resistance (boiling resistance) X: With tack (tack), whitening (solvent resistance, resistance to boiling water) The numerical value in the adhesion column in the table indicates the coating film residual rate in the cellophane tape peeling test.

[0032]

The coating composition having a molecular weight in the conventional oligomer region can be applied at a temperature slightly higher than the coating temperature, and the residual low molecular weight monomer is removed during the resin synthesis step. It is possible to suppress the scattering of particles and monomers and improve the working environment.

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Claims (2)

(57) [Claims] 1. (A): 35 to 90% of a monomer represented by the following formula (1), CH ₂ = C (R ¹ ) COOR ² (1) (wherein R ¹ is H or CH ₃ , R ² represents a hydrocarbon group having 10 to 20 carbon atoms.) (B): polymerizable unsaturated carboxylic acid 3 to 35% by weight (C): polymerizable unsaturated monomer containing an alkoxy group or a hydroxyl group 5 -60% by weight (D): Other polymerizable vinyl compound 0-40% by weight as a constituent, and the number average molecular weight is 10,000-200,
000 and the viscosity is 500 cps to 30,000 cps
A coating composition comprising a liquid resin (50 ° C.). 2. The method for producing a liquid resin according to claim 1, wherein the components (A) to (D) are radically polymerized in a water-miscible solvent which may contain water.