JP2000212474A - Curing resin composition for water repellent coating and coated matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a curing resin composition for water repellent coatings which lasts water repellency and exerts excellent water repellency and coated matter coated with the same. SOLUTION: This curing resin composition for water repellent coatings comprises (A) a silicone acrylic block polymer obtained by polymerizing (a1) an acrylic monomer having a cross-linkable functional group or a mixture of (a1) the acrylic monomer and (a2) another ethylenically unsaturated monomer in the presence of an azo group-containing silicone macro initiator, (B) a curing agent which reacts with (A) the silicone acrylic block polymer and (C) a power of an inorganic oxide subjected to a hydrophobic treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curable resin composition for a water-repellent coating, and an object to which the composition is applied.

[0002]

2. Description of the Related Art In order to prevent accidents and obstacles due to icing and snow, structures such as power transmission lines and steel towers laid in snowfall areas are
Surface treatment with a substance having water repellency has been performed. In addition, a heat exchanger for an outdoor unit of an air heat source type heat pump air conditioner is also subjected to the same surface treatment in order to prevent frost which is a cause of a decrease in cooling / heating capacity.

In general, water repellency can be evaluated by a contact angle, which is an angle formed by a liquid and a gas on a solid. The larger the value of the contact angle that water exhibits on a substrate, the higher the water repellency. Represents It is known that the contact angle depends on the molecular structure of the surface and the surface morphology.

[0004] The molecular structure of the solid surface, which is one of the factors affecting the water repellency, includes, for example, CF bond and C
Compounds containing many -H bonds exhibit water repellency as a result of low surface free energy due to low polarizability of these bonds. As materials for imparting water repellency, fluorine-based and silicone-based resin compounds have been conventionally used. JP-A-7-331122 discloses that a mixture of a fluorocopolymer resin and an acrylic resin is
There is disclosed an anti-icing and snow-preventive coating composition obtained by mixing a specific hydrophobic compound such as a silicon resin powder.

Regarding the surface morphology of a solid, which is another factor affecting the water repellency, for example, as in the case of a protruding villi of a lotus leaf, apparent contact with water is affected by surface irregularities and the like. The higher the angle, the higher the water repellency. This phenomenon is described by Wenzel in the formula: cos θ ′ = r × cos θ (where θ is the true water contact angle, r is the real surface area with respect to the apparent surface area, and θ ′ is the apparent water contact angle). It is reported that the water repellency is improved by roughening the surface.

Japanese Patent Application Laid-Open No. 7-328532 discloses that after a resin is applied to a substrate, the contact angle with water having an average particle size of 1 nm to 1 mm is 90 when the coating film is in an uncured or semi-cured state.
Discloses a water-repellent coating obtained by adhering fine particles having a temperature of at least 90 °. This technique shows higher water repellency due to the unevenness of hydrophobic fine particles adhered later.

JP-A-3-259975 discloses a water-repellent solution comprising a solution comprising a silicone-based or fluorine-based resin compound and an inorganic powder whose surface has been subjected to a hydrophobic treatment by gas phase adsorption of a substance having a hydrophobic group. A coating composition is disclosed. JP-A-3-244680 discloses a repellent solution comprising a solution comprising a silicone-based or fluorine-based resin compound and an inorganic powder having a surface having a specific surface area of 50 m ² / g or more and an average particle diameter of 4 μm or less subjected to hydrophobic treatment. Aqueous coating compositions are disclosed. In addition to these technologies, the surface is made water-repellent by a water-repellent resin,
Since fine irregularities are formed on the surface, they exhibit high water repellency.

[0008] However, these techniques may be insufficient in water repellency depending on the environmental conditions in which they are used, or may decrease with time. Also,
In terms of coating film adhesion and dispersibility of fine particles added to improve water repellency, binding with the fine particles, and the like,
Although the silicone resin compound is superior to the fluorine resin composition, the silicone is poorly compatible with the coating resin, so that a sufficient amount of silicone is required to exhibit a desired level of water repellency. Was difficult. Furthermore,
When a silicone resin compound and a curing agent are used in combination, there are also problems such as poor compatibility with the curing agent.

By the way, the silicone-vinyl block copolymer has properties such as excellent heat resistance, cold resistance, water repellency, release property, slipping property and weather resistance of a silicone resin such as an organosiloxane. This is expected to find use in the fields of plastics, paints, adhesives, release agents, and the like.

Such a silicone-vinyl block copolymer is prepared by a living anionic polymerization method (M. Morton).
et al. , J. et al. Appl. Polym. Sc
i. , 8, 2707 (1964)) and the hydrosilylation method (P. Chaumount et al., Polyme).
r, 22 (5), 663 (1981)), but it has been known for some time that both methods require strict control of polymerization conditions. Furthermore, applicable vinyl monomers are limited, and only aprotic monomers such as styrene can be applied. Therefore, since it cannot be directly applied to the synthesis of a block copolymer having a crosslinkable functional group such as 2-hydroxyethyl (meth) acrylate, the polymerization is carried out after protecting the hydroxyl group of the monomer with a protecting group in advance. However, an economically disadvantageous method such as deprotection after polymerization had to be taken.

Japanese Patent Publication No. Hei 2-33053 discloses 4,
There is disclosed a macroinitiator in which an azo radical initiator such as 4'-azobis (4-cyanovaleric acid) is covalently bonded to a polysiloxane, without limiting the applicable vinyl monomer. The silicone-vinyl block copolymer could be produced efficiently. JP-A-7-18139 discloses a silicone-vinyl chloride block copolymer obtained by using the above-mentioned macroinitiator as a polymerization initiator for the purpose of improving the processability of a vinyl chloride resin. A resin composition added to a system resin is disclosed.

[0012]

SUMMARY OF THE INVENTION In view of the above situation, the present invention provides a curable resin composition for a water-repellent paint, which has a long-lasting water-repellent function and exhibits excellent water repellency, and a coating material coated with the same. The purpose is to provide a coating.

[0013]

According to the present invention, there is provided an acrylic monomer (a1) having a crosslinkable functional group in the presence of an azo group-containing silicone macroinitiator, or the above acrylic monomer (a1) and A silicone acrylic block polymer (A) obtained by polymerizing a mixture of other ethylenically unsaturated monomers (a2), a curing agent (B) that reacts with the silicone acrylic block polymer (A), and a hydrophobic agent. A curable resin composition for a water-repellent coating, comprising a powder (C) of an inorganic oxide subjected to a hydrophobizing treatment. Hereinafter, the present invention will be described in detail.

The curable resin composition for a water-repellent coating of the present invention comprises a silicone acrylic block polymer (A), a curing agent (B) which reacts with the silicone acrylic block polymer (A), and a hydrophobic treatment. It is composed of the applied inorganic oxide powder (C).

The silicone acrylic block polymer (A) is an acrylic monomer (a) having a crosslinkable functional group in the presence of an azo group-containing silicone macroinitiator.
1) or a polymer obtained by polymerizing a mixture of the acrylic monomer (a1) and another ethylenically unsaturated monomer (a2).

Examples of the azo group-containing silicone macroinitiator include the following compounds described in JP-B-2-33053 and JP-A-7-18139.

[0017]

Embedded image

(In the formula, R ₁ is the same or different and represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a nitrile group. R ₂ is the same or different and represents a hydrogen atom or 1 carbon atom.
Represents an alkyl group of 1 to 6. R ₃ is the same or different,
Represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group or a phenyl group. p and q are the same or different and represent an integer of 0-6. m represents an integer of 0 to 200. And azo group-containing polysiloxane amide comprising a repeating unit represented by formula (1).

The azo group-containing silicone macroinitiator can be synthesized, for example, by reacting a diamine having a polysiloxane segment with an azo group-containing dibasic acid dihalide.

As the azo group-containing silicone macroinitiator, those obtained by bonding 4,4'-azobis (4-cyanovaleric acid) to a polydimethylsiloxane chain via an amide bond are commercially available from Wako Pure Chemical Industries as VPS series. It is possible to use this.

The acrylic monomer (a1), which is a monomer component of the silicone acrylic block polymer (A)
Has a crosslinkable functional group. When only a monomer having no reactive functional group such as vinyl chloride, styrene and methyl methacrylate is used as a monomer component of the silicone acrylic block polymer (A), the water repellency of the obtained coating film is not sufficient. In the present invention, an acrylic monomer (a1) having a crosslinkable functional group is used.

The crosslinkable functional groups include a hydroxyl group,
It is preferably at least one selected from the group consisting of an epoxy group, a carboxyl group, an active methylene group and an alkoxyl group.

Examples of the acrylic monomer (a1) having a crosslinkable functional group include, for example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1: 1 adduct of 2-hydroxyethyl methacrylate and ε-caprolactone (Placel FM-1), 2-
Hydroxyl-containing monomers such as 1: 1 adduct of hydroxyethyl acrylate and ε-caprolactone (Placcel FA-1), adduct of 2-hydroxyethyl (meth) acrylate and neopentyl glycol; glycidyl (meth) acrylate, α -Epoxy group-containing monomers such as methyl glycidyl (meth) acrylate and methacrylic acid ester having an alicyclic epoxy group (Cyclomer M-100: manufactured by Daicel Chemical Industries, Ltd.); acrylic acid, methacrylic acid, itaconic acid, and maleic acid And carboxyl group-containing monomers such as anhydrides and half esters thereof;
Active methylene group-containing monomers such as acetoacetoxyethyl (meth) acrylate and 2-ethoxymalonyloxyethyl (meth) acrylate; alkoxysilyls such as 3-methacryloyloxypropyltrimethoxysilane and 3-methacryloyloxypropyldimethoxymethylsilane Examples include a group-containing monomer. The acrylic monomers (a1) can be used alone or in combination of two or more.

The monomer component of the silicone acrylic block polymer (A) includes the acrylic monomer (a)
In addition to 1), it may contain another ethylenically unsaturated monomer (a2).

The other ethylenically unsaturated monomer (a2)
Is not particularly limited, and examples thereof include aromatic monomers such as styrene, p-methylstyrene, and t-butylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, isobutyl (meth) acrylate, and n-butyl ( Meth) acrylate, t-butyl (meth) acrylate,
(Meth) such as 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and cyclohexyl (meth) acrylate
Acrylic acid esters; fluoroalkyl (meth) acrylates such as perfluoroethylmethyl (meth) acrylate; and other monomers such as acrylamide, dimethyl (meth) acrylamide, (meth) acrylonitrile, and vinyl acetate. The other ethylenically unsaturated monomers (a2) can be used alone or in combination of two or more.

The other ethylenically unsaturated monomer (a2)
Is preferably 95% by weight or less of the total amount of the monomer components of the silicone acrylic block polymer (A). If it exceeds 95% by weight, the amount of the acrylic monomer (a1) having a crosslinkable functional group is too small, and the water repellency of the resulting coating film may decrease over time. More preferably, it is at most 80% by weight.

As a method for producing the silicone acrylic block polymer (A), the acrylic monomer (a1) having a crosslinkable functional group in the presence of the azo group-containing silicone macroinitiator or the acrylic monomer Monomer (a1) and the above-mentioned other ethylenically unsaturated monomer (a2)
Can be obtained by polymerization by a conventional bulk polymerization method or a solution polymerization method.

The above-mentioned monomer component, that is, the acrylic monomer (a1) or a mixture of the acrylic monomer (a1) and another ethylenically unsaturated monomer (a2), and the silicone macroinitiator Is preferably in the range of 95: 5 to 5:95 in terms of weight ratio when the total of both is 100 parts by weight. Even if the ratio is more than 95: 5 or less than 5:95, the silicone acrylic block polymer (A)
, A good water-repellent function cannot be obtained, and the compatibility with other components may be poor.

When the above polymerization method is a solution polymerization method, the solvent is not particularly limited, and for example, tetrahydrofuran,
Ethers such as dioxane; hydrocarbon solvents such as petroleum ether, n-hexane, cyclohexane, toluene and xylene; esters such as ethyl acetate and butyl acetate; alcohols such as methanol, ethanol, isopropanol and butanol; acetone and methyl ethyl ketone , Methyl isobutyl ketone, ketones such as cyclohexanone;
Acetonitrile, N, N-dimethylformamide, dimethylsulfoxide and the like can be mentioned. The above solvents can be used alone or as a mixture.

In the above polymerization, if necessary, the molecular weight can be adjusted by using a chain transfer agent such as n-dodecyl mercaptan. When the residual unreacted monomer component is not desirable, an initiator such as an azo initiator may be further added during the reaction to complete the polymerization.

In the present invention, the azo group-containing silicone macroinitiator is heated or irradiated with light to obtain nitrogen (N
₂ ) is generated and decomposed to generate a radical species, whereby the acrylic monomer (a1) or the acrylic monomer (a1) is generated.
And a mixture of the other ethylenically unsaturated monomers (a2) undergoes polymerization, while at the same time radical fragments having polysiloxane segments formed from the silicone macroinitiator are introduced into the acrylic polymer to form polysiloxane segments ( [(A1) (A2)] composed of A1) and an acrylic polymer segment (A2) or _n- type or [(A1) (A2)
(A1)] type silicone acrylic block polymer (A) can be produced.

The silicone acrylic block polymer (A) contains one to two acrylic polymer blocks in the chain, and the number average molecular weight is usually on the order of tens of thousands.

In the present invention, the curable resin composition for a water-repellent paint contains a curing agent (B) which reacts with the silicone acrylic block polymer (A). The curing agent (B) can react with and crosslink with a crosslinkable functional group derived from the acrylic monomer (a1) contained in the silicone acrylic block polymer (A) to form a strong coating film. It is possible to maintain the water repellent function of the coating film.

The curing agent (B) reacts with the silicone acrylic block polymer (A).
It has a crosslinkable functional group such as a hydroxyl group, an epoxy group, a carboxyl group, an amino group, an active methylene group and an alkoxysilyl group. The resin type of the above curing agent is acrylic resin or polyester resin (including alkyd resin)
Is preferred.

The curing agent (B) is not particularly restricted but includes, for example, melamine resin (Cymel-211), blocked isocyanate (MEK oxime block HMDI)
Nurate), polyisocyanate crosslinking agents (IPDI Nurate; Takenate D-140N, HMDI Nurate; Coronate HX, MDI; Coronate 2041) and the like.

In the present invention, the curing agent (B) is
Those which react with the silicone acrylic block polymer (A) and are integrated in the coating film by crosslinking are selected. For example, when the silicone acrylic block polymer (A) has a hydroxyl group, the curing agent (B) can use a melamine resin or a polyisocyanate crosslinking agent. The above silicone acrylic block polymer (A)
Has an epoxy group, a curing agent (B) having a carboxyl group or an amino group can be used. Conversely, when the silicone acrylic block polymer (A) has a carboxyl group, As the curing agent (B), those having an epoxy group can be used. When the silicone acrylic block polymer (A) has an alkoxysilyl group, the curing agent (B) may be a compound having a hydroxyl group or a melamine resin. When the silicone acrylic block polymer (A) has an active methylene group, the curing agent (B) has α,
A compound having a β-unsaturated carbonyl group, for example, a Michael addition reaction of an aliphatic polyhydric alcohol with poly (meth) acrylate can be used. The curing agent (B) can be used alone or in combination of two or more.

The curable resin composition for a water-repellent coating of the present invention contains a powder (C) of an inorganic oxide subjected to a hydrophobic treatment. The inorganic oxide powder (C) must not react with other components, and should exist as particles in the coating film after forming the coating film. By mixing the inorganic oxide powder (C), fine irregularities are imparted to the surface after the coating film is cured, the apparent contact angle with water is increased, and higher water repellency can be exhibited.

Examples of the inorganic oxide of the powder (C) include silica fine powder and titania fine powder.
Preferably, it is a silica fine powder.

The powder (C) of the inorganic oxide has been subjected to a hydrophobic treatment. As the above-mentioned hydrophobization treatment, a method of performing treatment so as to have a hydrophobic group such as a lower alkyl group such as a methyl group or an ethyl group or a fluorinated alkyl group on the powder surface of the inorganic oxide, or a silicone oil A surface treatment method by vapor-phase adsorption can be used. As the inorganic oxide powder (C), silica treated by vapor-phase adsorption of silicone oil is preferable, and as commercial products, R202 and RY manufactured by Nippon Aerosil Co., Ltd.
-200 and the like.

The inorganic oxide powder (C) preferably has an average primary particle size of 40 nm or less. If it exceeds 40 nm, the surface irregularities of the obtained coating film may become too large, and the water repellency may decrease. The inorganic oxide powder (C) preferably has a BET specific surface area of 50 m ² / g or more. If it is less than 50 m ² / g, the water repellency of the resulting coating film may decrease.

The curable resin composition for a water-repellent coating of the present invention comprises the above-mentioned silicone acrylic block polymer (A), the above-mentioned curing agent (B), and the above-mentioned hydrophobized inorganic oxide powder (C). It consists of

The compounding amount of the curing agent (B) is, for example, 5 to 100 parts by weight in terms of solids based on 100 parts by weight of the solids in the silicone acrylic block polymer (A). . If the amount is less than 5 parts by weight, the crosslinking may be insufficient. If the amount exceeds 100 parts by weight, the water repellency of the resulting coating film may decrease due to the decrease in the amount of the silicone acrylic block polymer (A).

The amount of the inorganic oxide powder (C) subjected to the hydrophobic treatment is preferably from 20 to 60% by weight based on the total weight of the solid content of the curable resin composition for water-repellent paint. . If the amount is less than 20% by weight, the apparent water contact angle of the obtained coating film is not increased and the water repellency is poor, and the effect of adding the inorganic oxide powder (C) subjected to the above-mentioned hydrophobic treatment cannot be expected. . If it exceeds 60% by weight, not only the water repellency of the obtained coating film does not change, but also mechanical properties such as coating film adhesion may be poor. More preferably, 30 to 55
% By weight.

The curable resin composition for a water-repellent paint of the present invention may further contain a film-forming resin (D). The film-forming resin (D) comprises the silicone acrylic block polymer (A) and / or the curing agent (B)
And are integrated in the coating film. Therefore, the film-forming resin (D) is a curing agent (B)
Functional groups that can be cross-linked by an acrylic monomer (a
The one having a functional group which reacts with the functional group of 1) is used. By further adding the film-forming resin (D), mechanical properties such as hardness and coating film adhesion of the obtained coating film can be improved.

Examples of the functional group which can be crosslinked by the curing agent (B) or the functional group which reacts with the functional group of the acrylic monomer (a1) include a hydroxyl group, an epoxy group,
Examples thereof include a carboxyl group, an active methylene group, and an alkoxyl group.

When a resin having a functional group which can be crosslinked by a curing agent (B) is used as the film-forming resin (D), the film-forming resin (D) and the silicone acrylic block polymer (A) Crosslinking is carried out by the common curing agent (B). On the other hand, when a resin having a functional group that is mutually reactive with the functional group of the acrylic monomer (a1) is used as the film-forming resin (D), the film-forming resin (D) and the silicone acrylic block weight may be used. The coalescence (A) reacts with each other and crosslinks.

The film-forming resin (D) can be selected in the same manner as described above as a method for selecting the curing agent (B). For example, the curing agent (B) may be a melamine resin or a melamine resin. When a polyisocyanate crosslinking agent,
As the film-forming resin (D), those having a hydroxyl group can be used.

The resin of the film-forming resin (D) is not particularly limited, but is preferably an acrylic resin or a polyester resin (including alkyd). The curing agent (B) can be used alone or in combination of two or more.

The amount of the film-forming resin (D) to be compounded is as follows.
It is preferable that the solid content is 40 parts by weight or less based on 100 parts by weight of the solid content. If it exceeds 40 parts by weight, excellent water repellency may not be exhibited.

The curable resin composition for a water-repellent coating composition of the present invention can contain additives such as an anti-sagging agent, a leveling agent, an ultraviolet absorber, and an antioxidant. Normal coloring pigments; may also include extender pigments. Further, in the case of a urethane curing system, a tin catalyst such as dibutyltin dilaurate; in the case of a melamine curing system, a sulfonic acid catalyst such as dotesylbenzenesulfonic acid blocked with an amine may be included.

The curable resin composition for a water-repellent paint of the present invention can be prepared by mixing and stirring each component to obtain a water-repellent metal, plastic, glass, woody material or the like. The material can be coated on the surface by a conventional coating method such as spray coating, brush coating, roller coating and the like.

The curable resin composition for a water-repellent coating of the present invention is applied so that the dry film thickness is usually 10 to 100 μm. The method for curing the coating film is a conventionally known method, for example, 110 to 180 C. for 5 to 30 minutes. An object to be coated formed by applying the curable resin composition for a water-repellent paint of the present invention is also one of the present invention. In the coated object of the present invention, the apparent water contact angle is 135 to 155 °, preferably 145 to 155 °.
Is obtained.

In the curable resin composition for a water-repellent coating of the present invention, the silicone acrylic block polymer (A) itself has good water repellency, and the silicone acrylic block polymer (A) further comprises Since it is crosslinked by the curing agent (B), the water repellency of the coating film does not decrease with time. Further, since the hydrophobic oxide-treated inorganic oxide powder (C) is added, the apparent water contact angle of the resulting coating film can be greatly increased, and excellent water repellency can be exhibited. .

The substrate to which the curable resin composition for a water-repellent paint of the present invention is applied is not particularly limited, but articles requiring water repellency, such as automobile bodies, building exteriors and rooftops, Examples thereof include outdoor structures such as electric wires and steel towers, and fins of a heat exchanger for an outdoor unit for an air heat source type heat pump air conditioner. The curable resin composition for a water-repellent coating of the present invention has an extremely excellent effect, and among the above-mentioned objects to be coated, particularly, a power transmission line and a steel tower for laying in a snowfall area, and an air heat source type heat pump air conditioner. The fins of the outdoor unit heat exchanger are preferred. When the curable resin composition for a water-repellent coating of the present invention is applied to a transmission line for a snowfall zone, it will exhibit hard-to-adhere ice and snow, so the curable resin composition for a water-repellent paint of the present invention is: When it becomes a hard-to-ice and snow coating composition and the curable resin composition for a water-repellent coating of the present invention is applied to fins of a heat exchanger, it becomes a frost prevention coating composition. In particular, it can be applied as a hard-to-ice and snow coating composition.
This is one of the most suitable application examples of the curable resin composition for a water-repellent coating of the present invention.

[0055]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Synthesis Example 1 In a 300 mL glass container equipped with a stirring blade, a nitrogen introducing tube, a cooling condenser, and a dropping funnel, 90 parts of butyl acetate was added.
g and heated to 120 ° C. in a nitrogen atmosphere. 20 g of an azo group-containing silicone amide (VPS-0501; manufactured by Wako Pure Chemical Industries) dissolved in 60 g of butyl acetate,
9.1 g of n-butyl methacrylate, 56.0 g of ethyl methacrylate and 14.9 g of 2-hydroxyethyl methacrylate were dropped at a constant rate over 3 hours. Then 1
The solution was kept at 20 ° C. for 0.5 hour, and 0.2 g of azobisisobutyronitrile dissolved in 5 g of butyl acetate was dropped at a constant speed in 30 minutes. Further, by continuing heating at 120 ° C. for 1.5 hours, a target block copolymer was obtained. The azo group-containing silicone amide (VPS-0501) has the following structure.

[0056]

Embedded image

For the synthesized block copolymer, GP
The value of the molecular weight in terms of standard polystyrene obtained using C is Mn = 15500, Mw = 62800, Mw / Mn =
4.04. The resin solids was 37%.

Synthesis Example 2 In Synthesis Example 1, after the dropwise addition at a constant speed, the temperature was maintained at 120 ° C. for 0.5 hour, and 0.2 g of azobisisobutyronitrile dissolved in 5 g of butyl acetate was dropped at a constant speed in 30 minutes. , And 12
Instead of continuing heating at 0 ° C. for 1.5 hours,
Synthesis was performed in the same manner as in Synthesis Example 1 except that the target block copolymer was obtained by continuing to heat at 120 ° C. for 2 hours. The values of the molecular weight in terms of standard polystyrene obtained using GPC are Mn = 18900, Mw = 692
00, Mw / Mn = 3.65. 3 resin solids
4%.

Synthesis Example 3 Using the same apparatus as in Example 1, 78 g of butyl acetate was added, and the mixture was heated to 120 ° C. under a nitrogen atmosphere. Te in the container
rt-butyl peroxy 2-ethylhexanoate2.
5 g, butyl acetate 20 g, n-butyl methacrylate 1
1.4 g, 70.0 g of ethyl methacrylate and 18.6 g of 2-hydroxyethyl methacrylate were dropped at a constant speed over 3 hours. Thereafter, the temperature is maintained at 120 ° C. for 0.5 hour,
0.5 g of tert-butyl peroxy 2-ethylhexanoate dissolved in 5 g of butyl acetate was dropped at a constant speed in 30 minutes. Further, heating was continued at 120 ° C. for 1 hour to obtain an acrylic resin solution. The value of the molecular weight in terms of standard polystyrene obtained using GPC is Mn = 6860, Mw = 15
000, Mw / Mn = 2.18. The resin solids was 49%.

Examples 1 to 4 Resin solution of Synthesis Example 1, melamine resin (curing agent; Cymel-211, solid content 80%; manufactured by Mitsui Toatsu Chemicals, Inc.), isopropanol dodecylbenzenesulfonate solution (Nacu)
re5225; active content 25%; manufactured by Kusumoto Kasei Co., Ltd., silica surface-treated with dimethyl silicone oil (Aeros)
il R-202; average diameter of primary particles is about 14 nm, BE
(T specific surface area: 100 m ² / g; manufactured by Nippon Aerosil Co., Ltd.) and ethyl acetate were mixed and stirred in parts by weight shown in Table 1 to prepare a coating composition. It is applied on an aluminum plate using an applicator and baked at 140 ° C. for 20 minutes to obtain a film thickness of about 4
A coating of 0 μm was obtained.

The water contact angle of the coating film was determined using an automatic contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., CA-Z) to form a droplet having a diameter of about 3 mm, and the water contact angle after 30 seconds had elapsed. . Table 1 shows the results. In Table 1, PWC represents the weight percentage (%) of the inorganic particles in the total solid content of the resin composition.

Example 5 Water of a coating film obtained in the same manner as in Example 1 except that 4.1 parts by weight of the resin solution of Synthesis Example 3 was added and the amount of silicone-treated silica was changed to the amount shown in Table 1. The contact angle was measured. Table 1 shows the results.

Comparative Example 1 A water contact angle of a coating film obtained in the same manner as in Example 1 except that no silicone-treated silica was used was measured. Table 1 shows the results.

Comparative Example 2 Silicone-treated silica (Aerosil R-202)
Instead of untreated silica (Aerosil 20)
0; average particle diameter of primary particles: about 12 nm; manufactured by Nippon Aerosil Co., Ltd.), except that the same amount was used. The film could not be formed.

[0065]

[Table 1]

Examples 6 to 8 Resin solution of Synthesis Example 2, methyl isobutyl ketone / butyl cellosolve solution of isocyanate obtained by blocking hexamethylene diisocyanate with methyl ketone oxime (solid content: 80%), 3-aminopropyltriethoxysilane (KBE- 903; manufactured by Shin-Etsu Chemical Co., Ltd.), dibutyltin dilaurate, butyl acetate and silica treated with dimethyl silicone oil (Aerosil R-202)
Was mixed and stirred in the amount shown in Table 2 to prepare a coating composition. It was applied on an aluminum plate using an applicator and baked at 160 ° C. for 20 minutes to obtain a coating having a thickness of about 40 μm. The water contact angle of the coating film was measured in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 3 A water contact angle of a coating film obtained in the same manner as in Example 6 except that no silicone-treated silica was used was measured. Table 2 shows the results.

Comparative Example 4 Instead of siliconized silica, a finely powdered highly crosslinked silicone resin (Trefil R-902A; average particle size 8 μm)
m; manufactured by Dow Corning Toray Silicone Co., Ltd.), and a coating film was prepared in the same manner as in Example 6 using the compounding amounts shown in Table 2, and the water contact angle was measured. Table 2 shows the results.

[0069]

[Table 2]

[0070]

Since the curable resin composition for a water-repellent coating of the present invention has the above-mentioned constitution, the water-repellent function of the resulting coating film can be maintained and excellent water-repellency can be exhibited. For this reason, it can be applied to a transmission line for a snowfall area to obtain a hard-to-ice and snow coating composition, and applied to a fin of a heat exchanger to obtain a frost prevention coating composition.

Continued on the front page F-term (reference) 4H020 BA32 4J038 DL151 DL152 GA02 GA03 GA06 GA08 HA216 HA446 KA03 KA14 KA20 NA07 PB05 PC02

Claims (5)

[Claims] An acrylic monomer (a) having a crosslinkable functional group in the presence of an azo group-containing silicone macroinitiator.
1) or a silicone acrylic block polymer (A) obtained by polymerizing a mixture of the acrylic monomer (a1) and another ethylenically unsaturated monomer (a2); A curable resin composition for a water-repellent coating, comprising: a curing agent (B) that reacts with A); and a powder (C) of an inorganic oxide subjected to a hydrophobic treatment. 2. A film-forming resin (D) having a functional group which can be crosslinked by a curing agent (B) or a functional group which reacts with a functional group of an acrylic monomer (a1). 2. The curable resin composition for a water-repellent coating according to 1. 3. The average primary particle diameter of the inorganic oxide powder (C) subjected to the hydrophobic treatment is 40 nm or less.
Or the curable resin composition for a water-repellent coating according to 2. 4. The water-repellent coating according to claim 1, wherein the crosslinkable functional group is at least one selected from the group consisting of a hydroxyl group, an epoxy group, a carboxyl group, an active methylene group and an alkoxyl group. Curable resin composition. 5. An article to be coated, wherein the curable resin composition for a water-repellent coating according to claim 1, 2, 3, or 4 is applied.