JPH1180289A - Curable resin composition which forms hydrophilic film surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silicate-condensate-free composition which forms a hydrophilic film surface by including a polyoxyethylene/vinyl block copolymer (A) comprising an acrylic monomer and an F- or Si-containing ethylenically unsaturated monomer or the like, a film-forming resin (B) capable of reacting with the crosslinkable functional groups copolymer A and a curing agent (C). SOLUTION: Copolymer A is obtained by copolymerizing a crosslinkable- functional-group-containing acryl monomer with an F- or Si-containing ethylenically unsaturated monomer and an ethylenically unsaturated monomer copolymerizable therewith in the presence of a macro-initiator containing a plurality of polyoxymethylene chains each terminated with a 2,2-azobisnitrile group at each end. Resin B contains functional groups crosslinkable with a curing agent which is the same as the crosslinkable functional group of copolymer A or reactive with the functional groups. Curing agent C is reactive with resin B. The amount of copolymer A used is 0.5-10 pts.wt. per 100 pts.wt. total solids of resin B and curing agent C.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curable resin composition for a coating which forms a hydrophilic film surface.

[0002] The surface of a coating film applied to a substrate used outdoors such as a building material and an automobile is contaminated by various pollutants such as exhaust gas, iron powder, and dust.

[0003] Although the reason is not clear, generally, if the surface of the coating film is hydrophilic (water contact angle of 70 ° or less), water is more likely to adhere to the coating film than the dirt component. It is believed to be more easily washed away.

[0004] On the basis of such an idea, there has been proposed in the prior art a coating material for forming a hydrophilic low-contamination film surface.
Among these, the coating disclosed in Japanese Patent Application Laid-Open No. HEI 8-12942 uses a mixture of a silicate condensate and an alkoxysilyl group-containing polymer as a film-forming component, and is disclosed in WO96 / 26254.
Discloses a coating composition containing a silicate condensate having a fluorine-containing organic group. After the silicate condensate used in these coating compositions is concentrated on the surface of the coating film, the alkoxysilyl groups remaining in the condensate are gradually hydrolyzed into hydrophilic silanol groups, thereby hydrophilizing the film surface.

[0005] However, when the hydrolysis reaction proceeds in the paint, the paint gels, particularly when an acid or base serving as a catalyst is present in the paint, and cannot be stored for a long time.
Further, silanol groups formed on the coating film are dehydrated and condensed with each other, so that the performance of the coating film may be deteriorated such as cracking of the coating film. Further, it is preferable that a component forming a hydrophilic film surface contains a silicone or a fluorine-containing component which helps the coating film surface to be concentrated to a high concentration and contributes to making the coating film non-tacky. It is economically disadvantageous, if not impossible, to bond these non-sticky components to the silicate condensate, which requires special raw materials.

Furthermore, this type of coating using a silicate condensate has the disadvantage that its hydrophilizing function decreases over time due to its hydrophilizing mechanism.

It is an object of the present invention to provide a curable resin composition for a coating which forms a hydrophilic film surface without using a silicate condensate, which can overcome the disadvantages of the prior art composition. .

Solutions It is well known that polyoxyethylene chains are hydrophilic, for example, incorporated into the hydrophilic block of a nonionic surfactant. In the present invention, a polyoxyethylene containing a polyethoxyethylene block in the molecule is used.
The vinyl block copolymer is used as a resin component for forming a hydrophilic film surface.

This block copolymer has the function of an azo radical initiator and is obtained by polymerizing a vinyl monomer mixture by a conventional method in the presence of a macroinitiator containing a polyoxyethylene chain. Can be The monomer mixture must include an ethylenically unsaturated monomer having a crosslinkable functional group in order to fix the block copolymer to the main binder resin by crosslinking. The monomer mixture also contains an ethylenically unsaturated monomer containing fluorine or silicone to help the block copolymer float or migrate to the surface portion of the coating.

[0010] The composition of the present invention is prepared by crosslinking the above block copolymer with a functional group which can be crosslinked by the same crosslinking agent as the functional group of the block copolymer, or which reacts with the functional group of the block copolymer. With the main binder resin that you have,
It contains at least a curing agent that reacts with the main binder resin.

Preferred Embodiments The azo polyoxyethylene macroinitiators used in the present invention are known. The azo initiator itself is composed of two molecules of nitrile bonded by an azo group between carbons at position 2,
2′-azobisnitrile and its derivatives. In order to covalently bond to a polyoxyethylene chain which is a hydrophilic block, an azo initiator having a carboxyl group, for example, 4,4′-azobis (4-cyanovaleric acid) is used as a reactive derivative, and for example, acid chloride And bonded to the polyethylene glycol by an ester bond. Such a polyoxyethylene macroinitiator and a block copolymerization method using the same are described in, for example, JP-A-1-254780, JP-A-6-306155, and JP-A-8-134118.

A macroinitiator having a repeating unit in which 4,4'-azobis (4-cyanovaleric acid) is bonded to polyethylene glycol is a VP such as VPE-0201.
It is commercially available as E series from Wako Pure Chemical Industries, Ltd.
Polyethylene glycol 400, 600, 1000, 2
A polyoxyethylene block derived from polyethylene glycol having an average degree of polymerization of 9 to 50, such as 000.
Macroinitiators containing 2 to 20 in the molecule are preferred.

At least one of the monomers forming the vinyl polymer of the block copolymer is an acrylic monomer having a crosslinkable functional group.

[0014] Such monomers are well known in the coatings art and include, but are not limited to:

Hydroxy group-containing monomers: 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl methacrylate Adduct of ε-caprolactone with 1: 1 (Placel FM-1), 2-
1: 1 adduct of hydroxyethyl acrylate and ε-caprolactone (Placcel FA-1), adduct of 2-hydroxyethyl (meth) acrylate and neopentyl glycol carbonate, and the like.

Epoxy group-containing monomers: glycidyl (meth) acrylate, α-methylglycidyl (meth) acrylate, methacrylate having an alicyclic epoxy group (Cyclomer M-100, manufactured by Daicel Chemical Industries, Ltd.), etc. .

Carboxyl group-containing monomer: acrylic acid,
Methacrylic acid, itaconic acid, maleic acid and its anhydrides and half esters.

Active methylene group-containing monomers: 2-acetoacetoxyethyl (meth) acrylate, 2-ethoxymalonyloxyethyl (meth) acrylate and the like.

Alkoxysilyl group-containing monomers: 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyldimethoxymethylsilane and the like.

The monomers for the vinyl block of the block copolymer also include ethylenically unsaturated monomers containing fluorine or silicone.

Typical fluorine-containing monomers are acrylic or methacrylic acid esters of alkyl groups having 2 or more carbon atoms which are substituted by fluorine, for example, 2,2,2-trifluoroethyl (meth) acrylate, 2,2 2,3,3-
Tetrafluoropropyl (meth) acrylate, 1H,
1H, 5H-octafluoropentyl (meth) acrylate, 1H, 1H, 2H, 2H-heptadecafluorodecyl (meth) acrylate, and the like.

A typical example of a silicone-containing ethylenically unsaturated monomer is a terminal methacryloyloxy-based silicone macromonomer in which methacrylic acid is bonded to polydimethylsiloxane by an ester bond. Such macromonomer is available from Chisso Co., Ltd.
0711, FM-0721, and FM-0725.

The monomer for the vinyl block may optionally contain an ethylenically unsaturated monomer other than the above-mentioned monomers. Examples of such monomers include, but are not limited to:

Aromatic monomers such as styrene, p-methylstyrene and t-butylstyrene.

Methyl (meth) acrylate, ethyl (meth) acrylate, isobutyl (meth) acrylate,
n-butyl (meth) acrylate, t-butyl (meth)
(Meth) acrylates such as acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and cyclohexyl (meth) acrylate.

(Meth) acrylamide, dimethyl (meth) acrylamide: other monomers such as (meth) acrylonitrile and vinyl acetate.

The ratio of each monomer in the monomer mixture is 99 to 10 parts by weight, especially 60 to 30 parts by weight, of a monomer having a crosslinkable functional group, and 1-80 parts by weight of silicone-containing monomer, especially 5-
It is preferred that 60 parts by weight and the balance be other monomers.

The polymerization can be carried out by a conventional bulk polymerization method or a solution polymerization method using a macroinitiator. The ratio of the macroinitiator and the vinyl monomer is generally from 95: 5 to 5:95 when the total of both is 100 parts by weight.
Parts by weight, preferably in the range of 80:20 to 20:80.

In the case of solution polymerization, ethers such as tetrahydrofuran, dioxane and cellosolves, petroleum ethers, hydrocarbons such as n-hexane, cyclohexane, toluene and xylene, ethyl acetate, butyl acetate and ethylene glycol or propylene glycol monomethyl are used as solvents. Esters such as ether acetate, alcohols such as methanol, ethanol, isopropanol and butanol, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, and other substances such as acetonitrile, N, N-dimethylformamide, dimethyl sulfoxide, etc., alone or mixed Can be used.

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

The obtained block copolymer has 1 to 3
It is a mixture of a copolymer containing two vinyl polymer blocks and one or two polyoxyethylene blocks.

[0032] Film-forming binder resins and curing agents that are cured by a crosslinking reaction with a curing agent are well known in the coatings art. These resins have hydroxyl, epoxy,
It has crosslinkable functional groups such as amino groups, active methylene groups, and alkoxysilyl groups. The resin type is preferably an acrylic resin or a polyester resin (including alkyd).

Since the block copolymer is mainly intended to improve the hydrophilicity of the coating film by adding a small proportion to the existing room temperature or thermosetting paint, the main binder resin is used as described below. The main binder resin may be a known one, except that special consideration is required for the combination of the above.

In the present invention, the block copolymer must be fixed to the binder resin by crosslinking.
There are two ways to achieve this. The first method is
The combination is such that both have a functional group that can be crosslinked by a common curing agent. For example, a block copolymer having a hydroxyl group and a binder resin can be cured by a melamine resin or a polyisocyanate crosslinking agent.

The copolymer having an epoxy group and the binder resin can be cured with a curing agent having a carboxyl group or an amino group. Conversely, when the resin has a carboxyl group, it can be cured with a curing agent having an epoxy group. Can be.

Both components having an alkoxysilyl group can be cured by a curing agent having a hydroxyl group or a melamine resin.

Both components having an active methylene group include α, β
-It can be cured using a Michael addition reaction of a compound having an unsaturated carbonyl group, for example, an aliphatic polyhydric alcohol with poly (meth) acrylate.

A second method is to combine the components so that they have functional groups that can react with each other, in other words, combine one component so as to function as the other curing agent. Examples of combinations of functional groups that react with each other are:
And the combination of an epoxy group and a carboxyl group, and the combination of an alkoxysilyl group and a hydroxyl group. Both the first method and the second method may include a plurality of combinations.

The amount of the block copolymer to be added should be determined according to the desired degree of hydrophilicity and the like. Generally, when the total solid content of the binder resin and the curing agent is 100 parts by weight, 0 0.5 to 10 parts by weight.

As mentioned above, since the block copolymer is intended to be used as a hydrophilic additive, the coating of the present invention may be the same as a conventional curable coating except for this point. In the case of colored paints, coloring pigments such as titanium dioxide, carbon black, iron oxide, cyanine blue and cyaning ray, and extenders such as calcium carbonate, clay and barium sulfate can be added. The paint may contain other conventional additives, such as anti-sagging agents, leveling agents, UV absorbers, antioxidants, etc. A sulfonic acid based catalyst such as dodecylbenzene sulfonic acid blocked with an amine can be included.

The coating of the present invention is particularly suitable for applications requiring a persistent stain resistance function, for example, coatings applied to substrates used outdoors such as automotive topcoats and precoat metal coatings.

Examples of the preparation of the block copolymer and examples of the composition to which the block copolymer is added are shown below.

The macro initiator used was VPE-0201 manufactured by Wako Pure Chemical Industries, Ltd.

The test method is as follows. Measurement of water contact angle: The water contact angle of the coating film was measured using an automatic contact angle meter (CA-Z manufactured by Kyowa Interface Science Co., Ltd.) after forming a droplet and 30 seconds had elapsed.

Production Example 1 Propylene glycol monomethyl ether acetate (PMAc) 6 was placed in a 300 ml flask equipped with a stirrer, nitrogen inlet tube, cooling condenser, dropping funnel and thermometer.
5 g was charged and heated to 120 ° C. under a nitrogen atmosphere.

A solution of 50.2 g of the macroinitiator (VPE-0201) dissolved in 40 g of PMAc and 29.8 g of 2-hydroxyethyl methacrylate was added separately to PMA.
A solution of 20 g of 1H, 1H, 2H, 2H-heptadecafluorodecyl acrylate dissolved in 45 g of c.
It was dropped over time. Thereafter, heating was continued at 120 ° C. for 2 hours to obtain a target block copolymer A. The standard polystyrene-equivalent molecular weight obtained using GPC is Mn =
9550, Mw = 16500, Mw / Mn = 1.73. Resin solids 35%

Production Example 2 In the same apparatus as in Production Example 1, 65 g of PMAc was charged and heated to 120 ° C. under a nitrogen atmosphere. Macro initiator (VPE-0201) 70.1 dissolved in 76 g of PMAc
g, 14.9 g of 2-hydroxyethyl methacrylate, and 1H, 1H, 2 separately dissolved in 45 g of PMAc
H, 2H-heptadecafluorodecyl acrylate 15
g of solution was simultaneously added dropwise over 3 hours. Then 12
Heating was continued at 0 ° C. to obtain a target block copolymer B. Mn = 8300, Mw = 14600, Mw / Mn =
1.76, resin solid content 24%

Production Example 3 The same apparatus as in Production Example 1 was charged with 65 g of PMAc and heated to 120 ° C. under a nitrogen atmosphere. A solution of 50.2 g of a macroinitiator (VPE-0201) dissolved in 40 g of PMAc and 29.8 g of 2-hydroxyethyl methacrylate, and Thyraplane FM separately dissolved in 45 g of PMAc
A solution of -0711 (terminal methacryloyloxy polydimethylsiloxane manufactured by Chisso Corporation) (20 g) was simultaneously added dropwise over 3 hours. Thereafter, heating was continued at 120 ° C. for 2 hours to obtain a target block copolymer C. Mn = 7520,
Mw = 15300, Mw / Mn = 2.03, resin solid content 32%

Production Example 4 (Comparative) 80 g of PMAc was charged into the same apparatus as in Production Example 1, and heated to 120 ° C. in a nitrogen atmosphere. 50.2 g of macro initiator (VPE-0201) dissolved in 70 g of PMAc,
A solution of 29.8 g of 2-hydroxyethyl methacrylate and 20 g of methyl methacrylate was added dropwise over 3 hours. Thereafter, heating was continued at 120 ° C. for 2 hours to obtain a target block copolymer D. Mn = 9220, Mw = 1660
0, Mw / Mn = 1.80, resin solid content 33%

Examples 1 to 3 and Comparative Examples 1 to 2 Curable acrylic resin compositions (Macflow O, manufactured by Nippon Paint Co., Ltd.) having a curing mechanism of the interaction between block and non-block carboxylic acid groups, epoxy groups and hydroxyl groups. -280) 5 parts by weight of the block copolymers of Production Examples 1 to 4 were added as solids per 100 parts by weight of the resin solids, and this was added to a tin plate with a dry film thickness of 30 to 4 parts.
It was spray-coated so as to have a thickness of 0 μm and baked at 140 ° C. for 20 minutes. In Comparative Example 2 (blank), no block copolymer was added.

For the obtained coated plate, the initial water contact angle (30)
Second) and the following results were obtained:

Table 1 Example Comparative Example 1 2 3 1 2 Block Copolymer A BC D Additive Water Contact Angle (degree) 66 32 70 86 85

Examples 4 to 5 and Comparative Examples 3 to 4 Resin solid content of 100% by weight of an acrylic urethane resin composition (Mighty Rack GII-295 manufactured by Nippon Paint Co., Ltd.) obtained by curing an acrylic resin having a hydroxyl group with polyisocyanate 5 parts by weight of the block copolymers A, B, and D were added as solids per part, and spray-coated on a tin plate to a dry film thickness of 30 to 40 μm, and 80 ° C. × 2
Bake for 0 minutes. In Comparative Example 4 (blank), no block copolymer was added.

The initial water contact angle of the obtained coated plate was measured, and the following results were obtained.

Table 2 Example Comparative Example 4 5 3 4 Block Copolymer A BD No Addition Water Contact Angle (degree) 62 48 93 95

Example 6 and Comparative Example 5 A block of 0.5 part by weight as a solid content per 100 parts by weight of the resin solid content of a polyester resin composition (Flexcoat 100HQ manufactured by Nippon Paint Co., Ltd.) which is a melamine-curable system was used. Polymers B and D were added, and this was applied to a tin plate with a dry coat thickness of 80 μm using a bar coater.
Baking was performed at 60 ° C. for 60 seconds.

The initial water contact angle of the obtained coated plate was measured, and the following results were obtained.

[0058]

The results in Tables 1 to 3 show that the block copolymers A, B, and C have the function of making the coating film surface hydrophilic, but do not contain fluorine or silicone components. Indicates that the same addition level gives a water contact angle that is almost the same as the blank value. This is because alignment of hydrophilic polyoxyethylene chains on the film surface hardly occurs.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08L 51/08 C08L 51/08 C09D 151/08 C09D 151/08

Claims (6)

[Claims] (1) In the presence of a macroinitiator containing a plurality of polyoxyethylene chains having both ends linked to a 2,2'-azobisnitrile group, (i) having a crosslinkable functional group At least one acrylic monomer, (ii) an ethylenically unsaturated monomer containing fluorine or silicone, and (iii) other ethylenically unsaturated monomers optionally copolymerizable with these monomers. (B) crosslinkable by the same curing agent as the crosslinkable functional group of the block copolymer (a), or A film-forming resin having a reactive functional group, and (c) a curable agent for forming a hydrophilic film surface, comprising at least a curing agent that reacts with the film-forming resin (b). Resin group Thing. 2. The composition according to claim 1, wherein the proportion of the block copolymer (a) in the composition is such that the film-forming resin (b) and the curing agent (c)
2. The composition according to claim 1, wherein the amount is 0.5 to 10 parts by weight per 100 parts by weight of the total solid content. 3. The macroinitiator according to claim 1, wherein the macroinitiator has a repeating unit in which 2,2′-azobisnitrile having a carboxyl group at each end is bonded to a terminal hydroxyl group of polyethylene glycol by an ester bond. Composition. 4. The composition according to claim 1, wherein the crosslinkable functional group of the acrylic monomer is a hydroxyl group, an epoxy group, a carboxyl group, an active methylene group, or an alkoxysilyl group. 5. The ethylenically unsaturated monomer containing fluorine or silicone is an alkyl fluoride (meth)
The composition according to any one of claims 1 to 4, which is a silicone macromonomer having an acrylate or (meth) acryloyl group. 6. A paint containing the resin composition according to claim 1 as a vehicle component.