JP2002265853A - Normal-temperature curable coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a normal-temperature curable coating composition capable of forming a coating film having excellent antifogging properties and water resistance on a plastic substrate. SOLUTION: This normal-temperature curable coating composition is characterized in that coating composition is a copolymer comprises (a) 25-70 pts.wt. of at least one kind of a quaternary ammonium salt-containing (meth)acrylic acid ester, (b) 30-75 pts.wt. of a (meth)acrylic acid ester monomer and (c) 0.1-10 pts.wt. of a vinyl ester-based monomer containing methoxysilane or ethoxysilane, (b) the (meth)acrylic acid ester monomer is composed of two or more kinds of monomer components, the monomer components are each composed of a hard segment having >=30 deg.C glass transition temperature as a homopolymer and a soft segment having a glass transition temperature lower than 30 deg.C and the weight ratio of the segments is 10:90 to 90:10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a room temperature-curable coating composition capable of forming a film having excellent antifogging properties and water resistance.

[0002]

2. Description of the Related Art Plastic materials are widely used as transparent substrates in place of glass because of their productivity, price, and excellent physical properties. However, a drawback of such general-purpose plastics is that the surface is so hydrophobic that fogging occurs when the surface temperature falls below the dew point of the environment.

As a means for overcoming such disadvantages, a study has been made on a coating material for forming a film having excellent antifogging properties on the surface of a plastic transparent material.
5317, JP-A-8-253654, JP-A-8-2
No. 69387 and Japanese Patent Publication No. 3-74248.

However, Japanese Patent Application Laid-Open No. 8-253654
In Japanese Patent Application Laid-Open No. Hei 8-269387, heating is required to obtain a crosslinked structure, and in Japanese Patent Publication No. 3-74248, ultraviolet irradiation is required, which is problematic in terms of productivity and equipment costs.

The inventors of the present invention have conducted intensive studies on a coating material for forming a film having excellent antifogging properties.
-295317 was confirmed to be excellent at low cost in terms of productivity and equipment. However, in Japanese Patent Application Laid-Open No. 5-295317, when the coating is left for a long time under the condition of the dew point or less, there are disadvantages that the coating contains moisture and sags or the coating dissolves and disappears. .

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a coating composition capable of obtaining a coating having excellent antifogging properties and water resistance by a room temperature curing method which is advantageous in productivity and equipment cost. To provide things.

[0007]

Relative invention of JP-A No. 5-295317 has excellent anti-fogging properties while being relatively simple composition SUMMARY OF THE INVENTION, the present inventors in order to impart good water resistance intensive Study result, as a means of imparting water resistance to the invention of JP-a-5-295317, the antifogging by improved adhesion to plastic material as an adherend, and introducing a crosslinked structure without lowering it was found to improve the water resistance.

That is, (a) 25 to 70 parts by weight of a (meth) acrylate monomer containing at least one quaternary ammonium salt, (b) 30 to 75 parts by weight of a (meth) acrylate monomer, and ( c) a copolymer composed of 0.1 to 10 parts by weight of a vinyl ester monomer having methoxysilane or ethoxysilane, wherein (b) the (meth) acrylate monomer is at least two types of monomer components The monomer component comprises a hard segment having a glass transition temperature of 30 ° C. or higher as a homopolymer and a soft segment having a glass transition temperature of less than 30 ° C. as a homopolymer, and has a weight ratio of 10:90. The present invention provides a cold-curable coating composition characterized by having a ratio of about 90:10.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When the coating composition is coated on a plastic substrate, silanol groups, which are hydrolysates of methoxysilane or ethoxysilane, undergo a polycondensation reaction to form a cross-linked structure, thereby improving water resistance. Will have.
On the other hand, the adhesiveness to the plastic substrate is reduced due to the curing shrinkage caused by having the crosslinked structure, but the (meth) acrylate monomer is composed of two or more monomer components, and the Tg of homopolymer of monomer and hard segment whose glass transition temperature (hereinafter referred to as Tg) of homopolymer is 30 ° C or higher
Is less than 30 ° C and the weight ratio to the soft segment is 10:
By setting the ratio to 90 to 90:10, the adhesion to the plastic substrate is ensured.

[0010] The anti-fog property of a coating is closely related to hydrophilicity, and a hydrophilic coating becomes a coating film having good anti-fog properties.
It is essential that the coating composition of the present invention contains a (meth) acrylate monomer containing at least one quaternary ammonium salt in order to impart antifogging property.

This is because, in combination with a hydrophobic monomer to be copolymerized, a monomer containing a quaternary ammonium salt as a functional group is suitable for balancing antifogging property and water resistance. As for the tendency of the contained functional groups to become hydrophilic, there is a theory of Davies in the surfactant handbook, a new edition published by Kogaku Tosho Co., Ltd. (described on pages 234 to 236). -OSO ₄ Na, -SO ₃ Na ≧ ^{N +} · Cl ⁻ >
_{-OPO 3 Na 2, -COONa »-OH} , -O- is described. In the present invention, the functional group
It is preferable to use a quaternary ammonium salt.While the tendency toward hydrophilicity becomes stronger, the antifogging property is excellent, but the water resistance becomes poor, and conversely, when the tendency toward hydrophilicity becomes weaker than the quaternary ammonium salt, the water resistance becomes higher. Although it is excellent, it is difficult to obtain a product having satisfactory antifogging property.

The (meth) acrylate monomers containing a quaternary ammonium salt include dimethylaminoethyl acrylate hydrochloride, dimethylaminoethyl acrylate methyl chloride, dimethylaminoethyl acrylate benzyl chloride, and dimethylaminoethyl acrylate. Dimethyl sulfate, dimethylaminoethyl acrylate diethyl sulfate, dimethylaminomethyl acrylate hydrochloride, dimethylaminomethyl acrylate methyl chloride, dimethylaminomethyl acrylate benzyl chloride, dimethylaminomethyl acrylate dimethyl sulfate, dimethyl Aminomethyl acrylate diethyl sulfate, dimethylaminoethyl acrylate halide, dimethylaminoethyl acrylate quaternary ammonium Hydride, etc.
Among them, methyl chloride salt of dimethylaminoethyl methacrylate is particularly preferred.

The proportion of the monomer for imparting anti-fogging property in the copolymer component is 25 to 70 parts by weight.
When the ratio is lower than 25 parts by weight, satisfactory anti-fog performance cannot be obtained, and when the ratio is higher than 70 parts by weight, the water resistance decreases.

The methacrylate or acrylate monomer forming a hard segment having a Tg of 30 ° C. or higher in the present invention includes, for example, methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate , T-butyl methacrylate, t-butyl acrylate and the like. These monomers are used for improving the water resistance of the coating and ensuring the resin strength, that is, the cohesive strength of the coating.

On the other hand, as a methacrylate or acrylate monomer forming a soft segment having a Tg of less than 30 ° C., for example, n-methacrylate
Butyl, n-butyl acrylate, 2-ethylhexyl methacrylate, 2-ethylhexyl acrylate, lauryl methacrylate, stearyl methacrylate, isobutyl methacrylate and the like. These are used for improving the water resistance of the coating and ensuring the adhesion to the plastic substrate.

The methacrylate or acrylate monomer forming a hard segment having a Tg of 30 ° C. or more and the methacrylate or acrylate monomer forming a soft segment having a Tg of less than 30 ° C. have a composition ratio of 10: 90-90: 1
0, preferably 10:90 to 60:40.
If the ratio of the methacrylate or acrylate monomer forming a hard segment having a Tg of 30 ° C. or more is higher than this range, the adhesion to a plastic substrate is reduced, and a soft segment having a Tg of less than 30 ° C. is formed. When the ratio of the methacrylic acid ester or the acrylic acid ester monomer is increased, the cohesive force of the coating film is reduced, and the adhesion of dirt resulting from the lowered Tg is liable to occur.

The coating composition of the present invention is characterized by forming a crosslinked structure by room temperature curing which does not require special equipment in order to have antifogging properties and to improve water resistance. Therefore, in order to form a crosslinked structure by room temperature curing, a silanol group is formed by hydrolysis, and the silanol group forms a crosslinked structure by a siloxane bond by a polycondensation reaction. It is characterized by being copolymerized with a monomer component having a property.

The vinyl ester monomer having methoxysilane or ethoxysilane in the present invention includes γ-acryloxypropyltrimethoxysilane and γ-acryloxypropyltrimethoxysilane.
Methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, vinyltriacetoxysilane, γ-
Diallylaminopropyltrimethoxysilane, and the like.

The copolymerization ratio of the vinyl ester monomer having methoxysilane or ethoxysilane in the coating composition is in the range of 0.1 to 10 parts by weight. If the copolymerization ratio of the vinyl ester monomer having methoxysilane or ethoxysilane is too low, a sufficient crosslinked structure cannot be obtained and the water resistance becomes insufficient. On the other hand, if the copolymerization ratio of the vinyl ester monomer having methoxysilane or ethoxysilane is higher than this, the shrinkage force due to cross-linking becomes too large, and cracks occur on the coating surface.

The coating composition of the present invention can be produced by a known method such as bulk polymerization, solution polymerization, and emulsion polymerization. Preferably, for example, (a) a (meth) acrylate monomer containing at least one quaternary ammonium salt, (b) a (meth) acrylate monomer, and (c) methoxysilane or ethoxysilane A conventional amount of a polymerization catalyst such as azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile) is added to a monomer comprising a vinyl ester monomer having 70 ° C to 120 ° C
It is obtained by performing solution polymerization under polymerization conditions at 6 ° C. for 6 to 12 hours.

As a method for forming a film using the coating composition of the present invention, a dipping method, a spray method, a roller method, and a flow coating method can be used. Depending on the method of forming the film, it may be better to dilute the coating composition with a solvent before use. As the solvent used in this case,
Lower alcohols such as methanol, ethanol, propanol and butanol, cellosolve solvents such as butyl cellosolve, ester solvents such as ethyl acetate and butyl acetate,
Examples thereof include ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone, and these can be used alone or as a mixed solvent.

In forming a film on the surface of a plastic with the coating composition of the present invention, silicon-based or fluorine-based leveling is included in the coating composition so as not to impair the surface smoothness which is a characteristic of the moldability of the plastic. The agents can be added in conventional amounts. In order to further improve the weather resistance of the coating, an ultraviolet absorber, an antioxidant, a light stabilizer (HAL
S) or the like may be added customary amount.

After the coating composition of the present invention is applied to the surface of a plastic, a hard coating is formed by the reaction with moisture in the air upon drying and standing at room temperature. Therefore, room temperature is sufficient for the drying step, but a heating step may be added during drying for the purpose of accelerating the reaction.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 (1) Polymerization of coating composition 200 equipped with a stirrer, thermometer, nitrogen inlet tube and cooling tube
In a 0 ml three-necked flask, dimethylaminoethyl methacrylate methyl chloride salt (manufactured by Mitsubishi Rayon Co., Ltd.,
Trade name, acrylester DMC) 270 g, methyl methacrylate (MMA) 72 g, n-butyl methacrylate (n-BMA) 150 g, 2-ethylhexyl methacrylate (2-EHA) 90 g, γ-methacryloxypropyltrimethoxysilane (Toray) 18 g of Silicone (trade name, SZ-6030), 447 g of methyl ethyl ketone, 447 g of methanol, and 5.35 g of azobisisoethylonitrile as a polymerization initiator were mixed with stirring. Thereafter, nitrogen was added at a rate of 20 ml / min under stirring for 30 minutes, and the reaction was carried out for 8 hours while maintaining the temperature of the contents at 70 to 73 ° C. Thereafter, the mixture was cooled to obtain a polymer as the coating composition of the present invention.

(2) Coating 20 g of the above polymer, 35 g of isopropyl alcohol,
After mixing and stirring 5 g of cyclohexanone and 40 g of propylene glycol monomethyl ether to form a uniform mixture,
The mixture was applied on a polycarbonate plate by a spray method so that the dry film thickness was 5 μm. Apply this coated plate to 20
It was left for 1 week under the conditions of ° C and 65% RH.

(3) Coating test On a beaker containing hot water maintained at 80 ° C., the coating surface of the polycarbonate plate coated above was brought into contact with steam generated from the hot water, and the coating was clouded. Was observed and the antifogging property was evaluated. After maintaining this state for 10 minutes, the polycarbonate plate was allowed to stand upright so as not to come into contact with steam generated from warm water, and the surface state of the coating was observed to evaluate the water resistance.

Comparative Examples 1 to 5 The amounts of methyl chloride salt of dimethylaminoethyl methacrylate, methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate and γ-methacryloxypropyltrimethoxysilane in Example 1 are shown in Table 1. A polymer as a coating composition was obtained in the same manner as in Example 1, except that the procedure was as described above. Further, the coating and coating tests were performed in the same manner as in Example 1.

[0029]

[Table 1]

The coatings after the test were evaluated as follows, and the results are shown in Table 2. 1. 1. Anti-fogging property 〇: No fogging occurs even after contact with steam for 10 minutes ×: Fogging starts immediately after contact with steam Water resistance 〇: There is no change in the coating ×: The coating contains moisture and the dripping phenomenon occurs

[0031]

[Table 2]

[0032]

The coating composition of the present invention can be formed into a cured film at room temperature, and the cured film film has excellent antifogging property on the surface of a base material such as various plastic materials and the like, It has adhesiveness.

Claims (2)

[Claims] (A) a (meth) acrylic acid ester monomer containing at least one quaternary ammonium salt
A copolymer composed of 70 parts by weight, (b) 30 to 75 parts by weight of a (meth) acrylate monomer, and (c) 0.1 to 10 parts by weight of a vinyl ester monomer having methoxysilane or ethoxysilane. Wherein (b) the (meth) acrylic acid ester monomer is composed of two or more types of monomer components, the monomer components comprising a hard segment having a glass transition temperature of 30 ° C. or higher as a homopolymer, and a hard segment as a homopolymer. A cold-setting coating composition comprising a soft segment having a glass transition temperature of less than 30 ° C and a weight ratio of 10:90 to 90:10. 2. The cold-setting coating according to claim 1, wherein (a) the (meth) acrylate monomer containing at least one quaternary ammonium salt is a methyl chloride salt of dimethylaminoethyl methacrylate. Composition.