JPH10140075A - Composition for coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating composition, comprising a specific graft copolymer prepared by compolymerizing a specified macromonomer with a silicone-based macromonomer and a free radical-polymerizable monomer and a cross-linking agent and excellent in drying properties and fouling resistance without sticking an oil-based ink thereto. SOLUTION: This composition comprises a graft copolymer, obtained by copolymerizing a macromonomer having a free radical-polymerizable group at one terminal of a vinyl polymer having 40-160 deg.C Tg with a silicone-based macromonomer and other free radical-polymerizable monomers, having hydroxyl groups and containing (A) a hydroxyalkyl (meth)acrylate unit and (B) a monomer unit represented by formula I [R<1> is H or methyl; (i) is 2 or 3; (j) is 2-60] or formula II [R<3> is H or methyl; R<4> is a 2-4C alkylene; (k) is 1-50] as essential constituent units at (0.5-10):1 molar ratio of the units A:B and having 80-150 KOHmg/g hydroxyl value and a cross-linking agent reactive with the hydroxyl groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition containing a silicone-based graft copolymer as a main component, and the coating composition is contained as a branch polymer in the graft copolymer. It has stain resistance derived from silicone.

[0002]

2. Description of the Related Art Coating agents applied to buildings, building materials, structures, automobiles, vehicles, electric and precision equipment, etc. include:
In addition to imparting a beautiful appearance to the base material, a stain resistance as described below is required. That is,
Generally, it is difficult to adhere to air pollutants such as carbon fine particles, or it can be easily wiped off even if it adheres, or it can easily erase graffiti etc. with oil or water-based ink. Is referred to as stain resistance. Conventionally, it has been known to use a polymer composed of silicone as one of the typical technical means for imparting stain resistance to a coating film.

[0003] Among the stain-resistant coating agents or paints using a silicone-containing polymer, a silicone-based graft copolymer having an alkyl acrylate-based polymer as a main polymer is preferred because of its excellent adhesion to a substrate. Many proposals have been made to use it. For example, JP-A-61-151272 discloses a silicone-based graft copolymer obtained by copolymerizing a radically polymerizable silicone macromonomer and an alkyl (meth) acrylate. It has been proposed for use in paints.

However, conventional silicone-based graft copolymer coatings still have insufficient stain resistance.
For example, graffiti or the like written with oil-based ink on the film often occurs after a long time, and it is not easy to wipe it without a trace. In addition, in the case of the conventional silicone-based graft copolymer, the time from application of the coating agent solution to drying of the film is shorter than that of a general-purpose alkyl acrylate copolymer-free coating agent containing no silicone. There was a problem that it was long.

As a means for solving the above problems, a graft copolymer using a polylactone as a branch polymer in combination with silicone has been proposed (JP-A-3-281516). Although the stain resistance of the ink was improved, the drying speed of the coating was just one step away. In addition, we have found that Tg4
A crosslinked coating film composed of a graft copolymer having a vinyl polymer having a hydroxyl group at 0 to 160 ° C. as a branch polymer and a vinyl polymer having a hydroxyl group as a trunk polymer is excellent in both stain resistance and drying property of the coating film. And filed a patent application for a composition containing the graft copolymer as a component (Japanese Patent Application No. 8-263484).

[0006]

DISCLOSURE OF THE INVENTION The present invention has a property of hardly adhering dust in the air, dirt by rainwater, graffiti or sticking paper, that is, stain resistance and weather resistance, and is used for building, tanks, and highways. An object of the present invention is to provide a coating composition suitable for a top coat of a bridge or a train.

[0007]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the above-mentioned Japanese Patent Application No. Hei.
In the graft copolymer obtained by using only hydroxyalkyl (meth) acrylate as a monomer for introducing a hydroxyl group for crosslinking used in the invention according to the application No. 63484, the hydroxyl group concentration in the polymer is at a certain level. It was found that when the temperature was higher than the above, it was difficult to react stoichiometrically with the crosslinking agent.
Thereafter, as a result of further studies, when the graft copolymer is obtained, it is represented by the following formula 3 or 4 together with a hydroxyalkyl (meth) acrylate as a monomer into which a hydroxyl group for crosslinking is to be introduced ( By using (meth) acrylic acid ester and in combination, it was found that the crosslink density could be further increased, thereby obtaining a cured film having excellent physical properties which could not be obtained conventionally, and completed the present invention. .

That is, the present invention is obtained by copolymerizing a macromonomer having a radical polymerizable group at one end of a vinyl polymer having a Tg of 40 to 160 ° C., a silicone-based macromonomer and other radical polymerizable monomers. A graft copolymer having a hydroxyl group and a crosslinking agent reactive with the hydroxyl group, wherein the graft copolymer is (a) a hydroxyalkyl (meth) acrylate monomer unit derived from the other radical polymerizable monomer And (b)
Or a monomer unit represented by Chemical formula 4 as an essential constituent unit,
The proportions thereof are (a) monomer unit: (b) monomer unit = (0.5 to 10): 1 and the hydroxyl value is 80.
It is a coating composition of up to 150 KOH mg / g.

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[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. In the present invention, in order to improve the drying property of the graft copolymer as the main component of the coating composition, Tg
A branch component derived from a macromonomer having a radical polymerizable group at one end of a vinyl polymer at 40 to 160 ° C. is defined as one constituent unit of the graft copolymer. When the Tg of the vinyl polymer serving as the skeleton of the macromonomer is lower than 40 ° C., the resulting graft copolymer is inferior in drying property.
If the temperature exceeds ℃, the impact resistance of the coating is inferior. The more preferred Tg of the vinyl polymer is from 90 to 160C. The preferred number average molecular weight of the macromonomer having a radical polymerizable group at one end of the vinyl polymer having a Tg of 40 to 160 ° C (hereinafter sometimes referred to as a vinyl polymer macromonomer) in the present invention is determined by gel permeation chromatography. The number average molecular weight in terms of polystyrene by
It is 1,000 to 30,000, and as the radical polymerizable group in the macromonomer, a (meth) acryloyl group or a styryl group is preferable.

The monomers forming the polymer skeleton in the macromonomer include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. (Meth) acrylic acid alkyl esters such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate;
Styrene derivatives such as styrene, α-methylstyrene and p-methylstyrene; hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, hydroxy (meth) acrylate Hydroxyalkyl (meth) acrylates such as butyl; N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N
N- such as isobutoxymethyl (meth) acrylamide
Alkoxymethyl (meth) acrylamide; (meth) acrylonitrile, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, and the like. These may be used alone or in combination of two or more. Can be used.

Preferred monomers forming the skeleton of the macromonomer are methyl methacrylate, ethyl methacrylate,
Alkyl methacrylates such as butyl methacrylate, cyclohexyl methacrylate and 2-ethylhexyl methacrylate, wherein the alkyl methacrylate monomer unit is 60% by weight of all monomer units constituting the macromonomer skeleton
More preferably, it is included. When the content of the alkyl methacrylate unit is less than 60% by weight, the obtained coating may have insufficient weather resistance.

The preferred ratio of the branch component based on the macromonomer in the graft copolymer is 3 to 30% by weight based on the total amount of all the constituent units of the graft copolymer.
And a more desirable ratio is 5 to 20% by weight. When the proportion of the branch component based on the macromonomer is less than 3% by weight, the coating tends to have insufficient stain resistance and drying properties.

[0013] A preferred silicone which forms the skeleton of the silicone-based macromonomer is a polyorganosiloxane represented by polydimethylsiloxane, polydiethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane and the like. Examples of the functional group include a (meth) acryloyl group and a styryl group. The preferred number average molecular weight of the silicone-based macromonomer is from 1,000 to 30,000. The number average molecular weight of the silicon-based macromonomer is
If it is less than 1,000, the lubricity and water repellency of the coating tend to be insufficient, while if it exceeds 30,000, it is difficult to obtain a transparent graft polymer solution.

As a method for synthesizing the silicone-based macromonomer, a dimethylpolysiloxane living polymer having a predetermined molecular weight is synthesized by an anionic polymerization method, and then reacted with a halogenated alkyl (meth) acrylate to form a terminal polymer. (Meth) acryloyl group is introduced, or γ-methacryloxypropyl triamine is added to polydimethylsiloxane having a silanol structure at both ends in an organic solvent such as toluene or xylene in the presence of a catalyst such as sulfuric acid or p-toluenesulfonic acid. A method in which methoxysilane is subjected to an addition reaction (JP-A-58-167606).

The preferred ratio of the branch component based on the silicone-based macromonomer in the graft copolymer is based on the total amount of all the structural units of the graft copolymer.
It is 0.5% by weight or more, and more preferably 1 to 20% by weight. If the proportion of the branch component of the silicone-based macromonomer is less than 0.5% by weight, the lubricity of the film is reduced and the property of repelling oil-based ink tends to be insufficient, while if it exceeds 20% by weight, the hardness of the film is reduced. Contaminants are more likely to adhere.

In the present invention, the graft copolymer is obtained by copolymerizing the above vinyl weight-based macromonomer and silicone-based macromonomer with another radical weight monomer (hereinafter, referred to as a copolymer monomer). To manufacture. As the comonomer, a monomer represented by the following formula (5) or (6) and a monomer for the polymer skeleton of the vinyl polymer-based macromonomer described above can be used. Satisfies the following requirements,
It is necessary to select the type and amount of the monomer. A preferred copolymer monomer is a monomer mixture satisfying the above requirements and mainly containing a methacrylic ester having an alkyl group having 4 to 8 carbon atoms.

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As described above, the graft copolymer is required to satisfy (a) a hydroxyalkyl (meth) acrylate monomer unit and (b) a monomer unit represented by the following formula (5) or (6). (A) monomer and (b) monomer are collectively referred to as hydroxyl group-introducing monomer] as essential structural units;
The molar ratio thereof is (a) monomer unit: (b) monomer unit = (0.5 to 10): 1, and the hydroxyl value is 80 to 150 KOH mg / g. is there. In the above proportional formula, if the ratio of the monomer units (a) is less than 0.5, the hardness of the coating film is poor. On the other hand, if it exceeds 10, the cross-linking of the graft copolymer is insufficient and the oiliness in the coating film is low. The ink soaks, ie the coating does not repel oil-based inks. When the hydroxyl value of the graft copolymer is 80 KOH mg / g, the degree of crosslinking of the coating is insufficient and oily ink permeates into the coating.
If it exceeds 50 KOH mg / g, the impact strength and workability of the coating will be poor.

The monomer represented by the above formula (5) can be synthesized by an addition reaction between (meth) acrylic acid and an alkylene oxide, and commercially available products such as Blemmer PE (Nippon Oil & Fats Co., Ltd., trade name) can also be used. . The monomer represented by Chemical formula 6 can be synthesized by ring-opening polymerization of ε-caprolactone in the presence of hydroxyethyl (meth) acrylate, and can be synthesized by Praxel FM or Praxel FA [both from Daicel Chemical Industries, Ltd. ), Trade names] and the like.

In the present invention, the above-mentioned polymerizable components, ie, the vinyl polymer-based macromonomer, the silicone-based macromonomer, and the copolymerized monomer are used in an amount of 3 to 30% by weight based on the total amount of the polymerizable components. %, Silicone macromonomer 0.5-20% by weight
It is preferable that the copolymerization is carried out at a ratio of 50 to 96.5% by weight of the comonomer. Each of the components copolymerized at the above ratios is polymerized at a polymerization rate of almost 100% by a solution polymerization method or the like, the outline of which is described below, to form a graft copolymer having a configuration corresponding to the charged ratio. I do. That is, polymerization is carried out at 60 to 150 ° C. using a hydrocarbon solvent such as toluene or xylene as a polymerization solvent and a radical generating compound such as azobisisobutyronitrile or benzoyl peroxide as a polymerization initiator. Also, if necessary, n-dodecyl mercaptan, mercaptoacetic acid,
The molecular weight of the obtained graft copolymer can be adjusted by using an appropriate amount of a chain transfer agent such as thiomalic acid, mercaptoethanol and mercaptopropionic acid. The molecular weight of the graft copolymer was 8,000 in weight average molecular weight.
0-40,000, or 2,000- in number average molecular weight
20,000 is preferred.

By the above polymerization, an organic solvent solution of the graft copolymer used as one component of the coating composition of the present invention is obtained. The polymer solution can be used for forming a film as it is, but if necessary, a solution obtained by replacing a solvent with butyl acetate, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, or the like can be used for forming a film. The concentration of the graft copolymer in the polymer solution used for forming a coating film is usually preferably from 30 to 60% by weight.

In the present invention, the crosslinking agent used together with the above graft copolymer is a crosslinking agent comprising a compound reactive with a hydroxyl group.
Examples include polyisocyanate and amino resin.
Examples of the polyisocyanate include diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and hexamethylene diisocyanate, and polyisocyanates such as isocyanurate type and burette type. The amount of the polyisocyanate to be used is preferably 0.5 to 1.5 equivalents of an isocyanate group per 1 equivalent of the hydroxyl value in the graft copolymer.
The curing reaction can be usually performed at room temperature, and an organotin compound such as dibutyltin dilaurate may be used as a catalyst for the curing reaction.

Examples of the amino resin include alkyl etherified melamine, alkyl etherified urea resin and alkyl etherified benzoguanamine. More preferably, alkyl etherified melamine, for example,
Fully alkyl etherified melamine such as hexamethoxymethylol melamine and hexabutoxymethylol melamine, or partially alkyl etherified melamine having an alkyl etherification degree of 5 or less can be used. Also, multimers such as dimers and trimers of alkyl etherified melamine can be used. The preferred amount of the amino resin used is 15 to 50 parts by weight per 100 parts by weight of the graft copolymer. The curing reaction is carried out at 110 to 220 ° C. for about 1 to 30 minutes. As a catalyst, paratoluenesulfonic acid or phosphoric acid may be used.

The coating composition of the present invention can be used as a clear without adding pigments, dyes and other additives, or as a colored enamel with added pigments. Any of concrete and plastic may be used.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The following abbreviations used in each example are the following compounds, respectively. AA-6 polymethyl methacrylate macromonomer [manufactured by Toagosei Co., Ltd., methacryloxy type at one end, number average molecular weight 6000] The Tg of polymethyl methacrylate is 105 ° C. AK-32 @ polydimethylsiloxane macromonomer [manufactured by Toagosei Co., Ltd., methacryloxy type at one end, number average molecular weight 20,000]

Flaxel FM1 (a compound represented by the following formula 7 [manufactured by Daicel Chemical Industries, Ltd.])

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PE-350 {Compound represented by the following formula 8 [manufactured by NOF CORPORATION]

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MMA────methyl methacrylate IBMA───isobutyl methacrylate 2-EHMA エ チ ル 2-ethylhexyl methacrylate St───styrene HA───2-ethylhexyl acrylate HEMA───hydroxyethyl methacrylate

[0028]

EXAMPLE 1 Using the compounds shown in Table 1, a graft copolymer was produced. That is, a stirrer, a reflux condenser,
In a glass flask equipped with two dropping funnels, a gas inlet tube and a thermometer, AK-32; 2.0 g and xylene 4
9.8 g was charged and the temperature was raised to 140 ° C. Next, a mixture of monomers other than AK-32 shown in Table 1 was dropped from one dropping funnel over 3 hours, and simultaneously, 2,2 ′ azobis (2-methylbutyro) was dropped from the other dropping funnel. A polymerization initiator solution in which 0.95 g of nitrile (hereinafter referred to as ABN-E) was dissolved in 24.9 g of xylene was added dropwise over 3 hours.

Thereafter, 8.8 g of a xylene solution containing 0.47 g of ABN-E was added dropwise over 1 hour, and the reaction was further continued for 30 minutes, after which the polymerization was terminated. The obtained graft copolymer had a weight average molecular weight (weight average molecular weight in terms of polystyrene measured by gel permeation chromatography) of 16,600 and a hydroxyl value (KOHmg / g) of 120. The obtained graft copolymer xylene solution and polyisocyanate (trade name: Coronate HX, manufactured by Nippon Polyurethane Co., Ltd.) were mixed at a ratio of 1.1 equivalents of isocyanate groups per equivalent of hydroxyl groups in the graft copolymer. A coating composition was obtained. To the obtained coating composition, butyltin dilaurate was added as a catalyst, and a coating film having a thickness of 20 μm was formed on an aluminum test plate with a bar coater. The physical properties described in Table 2 were measured for the coating film. .

[0030]

Example 2 and Comparative Examples 1-2 In the same manner as in Example 1, the monomers shown in Table 1 were polymerized to obtain a xylene solution of the graft copolymer having the following properties. Further, in the same manner as in Example 1, a coating film was formed on an aluminum plate using polyisocyanate in combination, and the physical properties of the film were measured. (Example 2) Weight average molecular weight──17400 hydroxyl value (KOHmg / g) ──99 (Comparative Example 1) Weight average molecular weight──16000 Hydroxyl value (KOHmg / g) ──120 (Comparative Example 2) Weight average molecular weight {16500 hydroxyl value (KOHmg / g)} 120 The evaluation results of the film properties of each of the above examples are as shown in Table 2.

[0031]

[Table 1]

[0032]

[Table 2]

The physical properties of the coatings in Table 2 are evaluated by the following methods. B) Oil-resistant ink contamination a. Initial cissing was evaluated by the cissing of the ink when marked on the coating with a red oil-based ink pen. The judgment is
When remarkably repelled; 、, when slightly repelled; b. After 12 hours: The coated plate (even if the initial repelling was ○ but the ink was still mottled) was further cured at 25 ° C for 12 hours.
After leaving for a while, the tissue was wiped off with a tissue paper, and the ink was not soaked at all;

(B) Quick drying The coated plate was put into an oven at 60 ° C., taken out at regular intervals, and strongly touched with a fingertip until the tack was eliminated. C) Hardness of coating film: pencil hardness specified in JIS K 5400. D) Stain resistance ── After the coated plate was immersed in boiling water for 8 hours, the stain test of the above item a) was performed to evaluate the repellency of the oil-based ink. E) Adhesion test: A cross cut test specified in JIS K5400.

[0035]

Industrial Applicability The coating composition of the present invention is excellent in the property of not adhering oil-based ink as compared with the conventional type of stain-resistant coating agent of the type containing a silicone-containing copolymer as a main component. The drying property is also remarkably excellent.

Claims (2)

[Claims] 1. A graft having a hydroxyl group obtained by copolymerizing a macromonomer having a radical polymerizable group at one end of a vinyl polymer having a Tg of 40 to 160 ° C., a silicone macromonomer and another radical polymerizable monomer. The graft copolymer comprises a copolymer and a crosslinking agent reactive with a hydroxyl group, and the graft copolymer is composed of (a) a hydroxyalkyl (meth) acrylate monomer unit derived from the other radical polymerizable monomer and (b) The monomer units represented by the following chemical formulas 1 or 2 are defined as essential constituent units, and their ratio is a molar ratio of (a) monomer unit: (b) monomer unit = (0.5)
-10): 1 and a hydroxyl value of 80 to 150 KOH mg / g
A coating composition which is: Embedded image Embedded image 2. Tg 40-1 in the graft copolymer
The unit based on the macromonomer having a radical polymerizable group at one end of the vinyl polymer at 60 ° C. and the unit based on the silicone-based macromonomer are 3 to 30% by weight and 0%, respectively, based on the total amount of all the constituent units. The coating composition according to claim 1, wherein the amount is from 0.5 to 20% by weight.