JPH06128446A - Curable resin composition, coating composition and coating film forming method - Google Patents

Abstract

PURPOSE:To provide a composition containing a specific amount of a specific polymer having hydroxyl group and carboxyl group, etc., having high crosslinking density and excellent weather resistance, resistance to acid rain and scratch resistance and suitable as an automotive finish coating, etc. CONSTITUTION:The composition contains (A) 5-50wt.% (based on the total solid component of the composition) of a polymer having hydroxyl group and carboxyl group and obtained by the copolymerization of (a) a compound obtained by reacting a hydroxyalkyl (meth)acrylate compound of formula (R is H or methyl; (m) is 2-8; (n) is 3-7; (q) is 0-4) with a compound containing acid anhydride group and (b) a hydroxyalkyl (meth)acrylate compound, (B) 20-60wt.% of a polymer having carboxyl group and carboxylic acid ester group and (C) 30-60wt.% of a polymer having hydroxyl group and epoxy group.

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 which can be suitably used as a topcoat paint for automobiles and a paint for coil coating, and a coating film forming method using the same.

[0002]

2. Description of the Related Art It is common to use a combination of a hydroxyl group-containing polymer and a melamine resin curing agent in a binder used as a top coating for automobiles. However, a cured coating film obtained by using such a melamine resin as a curing agent generally has poor acid resistance. Therefore, such a coating film is particularly likely to be deteriorated by acid rain, which has been a problem in recent years, and causes a defect in appearance.

It is considered that the coating film obtained by using a melamine resin as a curing agent is inferior in acid resistance due to the triazine nucleus in the melamine resin. Therefore, as long as the melamine resin is used as a curing agent, the drawback of poor acid resistance cannot be solved.

In order to solve such a drawback, the present inventors proposed a novel coating composition which does not use a melamine resin in JP-A-2-45577 and JP-A-3-287650. Similar coating compositions are described in U.S. Pat.Nos. 2,977,334 (Zopf et al.) And 3399109 (Zimmerman).
Et al. And No. 3,528,935 (Marion et al.). Since such a coating composition has an ester bond formed by reacting an acid group and an epoxy group as a crosslinking point, it has good acid resistance and also has sufficient weather resistance as a top coating film for automobiles. However, it has a drawback that the brush is easily scratched when the vehicle is washed using a car washing machine or the like. Further, in this curing system, when the crosslink density is increased in order to give the coating film sufficient scratch resistance at the time of car wash, the elongation of the coating film becomes low, and a hard and brittle coating film is easily formed. Since a hard and brittle coating film is easily scratched when rubbed, a coating film merely having an increased crosslink density does not have sufficient scratch resistance even in the case of car washing, etc. Have difficulty.

[0005]

DISCLOSURE OF THE INVENTION The present invention is to solve the above-mentioned conventional problems, and an object thereof is to have a high cross-linking density so that it is excellent in weather resistance, particularly resistance to acid rain, and high. It is an object of the present invention to provide a curable resin composition capable of providing a coating film having excellent elongation and abrasion resistance, and a coating film forming method using the same.

[0006]

The present invention is based on the formulas (a) and (i).

[0007]

[Chemical 3]

[Wherein R is a hydrogen atom or a methyl group, m is an integer of 2 to 8, and n is an integer of 3 to 7,
q is an integer of 0 to 4. ] The hydroxyalkyl (meth) acrylate compound having the structure shown by and the acid anhydride group-containing compound are mixed and reacted at a ratio of the hydroxyl group and the acid anhydride group in a molar ratio of 1 / 0.9 to 1 / 0.5. Carboxyl group-containing ethylenically unsaturated monomer and hydroxyalkyl (meth) obtained by
A hydroxyl group and a carboxyl group, which are obtained by copolymerizing 20 to 100% by weight of a monomer mixture with an acrylate compound, and (ii) 0 to 80% by weight of a copolymerizable ethylenically unsaturated monomer, as necessary. 5 to 50% by weight of polymer (% by weight of polymer is based on the total solid content of the resin composition); (b) (i) (1) acid anhydride group-containing ethylenically unsaturated monomer 15
To 40% by weight and (2) 60 to 85% by weight of another copolymerizable ethylenically unsaturated monomer, an acid anhydride group-containing polymer obtained by copolymerizing (ii) 1 to 12 carbons. It has a carboxyl group and a carboxylic ester group, which are obtained by reacting a hydroxyl group-containing compound containing an atom, an acid anhydride group and a hydroxyl group in a molar ratio of 1 / 1.5 to 1/1. 20 to 60% by weight of a polymer; and (c) (i) 5 to 40% by weight of the hydroxyalkyl (meth) acrylate compound, (ii) 10 to 60% by weight of an epoxy group-containing ethylenically unsaturated monomer, and, if necessary, (iii) A curable resin containing 30 to 60% by weight of a polymer containing a hydroxyl group and an epoxy group, which is obtained by copolymerizing 0 to 85% by weight of another copolymerizable ethylenically unsaturated monomer. To provide a composition, in which Ri the above-mentioned object can be achieved.

The polymer (a) having a hydroxyl group and a carboxyl group used in the curable resin composition of the present invention is a copolymer of at least two kinds of ethylenically unsaturated monomers.

The first ethylenically unsaturated monomer has the formula

[0011]

[Chemical 4]

[Wherein, R is a hydrogen atom or a methyl group, m is an integer of 2 to 8, preferably 2 to 6, and n is 3
Is an integer of -7, preferably 3-5, and q is an integer of 0-4, preferably 0-2. ] A carboxyl group-containing compound obtained by half-esterifying a hydroxyalkyl (meth) acrylate compound having a structure represented by and an acid anhydride group-containing compound in an amount such that a hydroxyl group and an acid anhydride group are equimolar It is an ethylenically unsaturated monomer. This monomer is used for introducing a carboxyl group in the polymer (a) having a hydroxyl group and a carboxyl group used in the present invention.

If the hydroxyalkyl chain of the hydroxyalkyl (meth) acrylate compound usable in the present invention is too short, the flexibility in the vicinity of the cross-linking point will be lost, and it will be too hard. If it is too long, the molecular weight between cross-linking points will be too large. Therefore, it preferably has 4 to 20 carbon atoms, and more preferably 4 to 10 carbon atoms. Specifically, 4-hydroxybutyl (meth) acrylate and (meth)
6-Hydroxyhexyl acrylate, and their ε-
Compounds such as the reaction products with caprolactone are mentioned. Such compounds are commercially available, for example, "4HBA" 4-hydroxybutyl acrylate manufactured by Mitsubishi Kasei Co., Ltd., "Plaxel FM1", "Plaxel FA1" manufactured by Daicel Chemical Industries, Ltd., and the like. To be And 4-hydroxybutyl methacrylate of “4HBMA” and the like. Alternatively, such a compound is (meth) acrylic acid and a large excess of diol (for example, 1,4 butanediol, 1,6 hexanediol).
Can be prepared by esterification.

The acid anhydride group-containing compound that can be used in the present invention is not particularly limited as long as it is a compound having carboxy functionality by reacting with a hydroxyl group under ordinary reaction conditions such as room temperature to 120 ° C. and normal pressure. Here, cyclic (unsaturated or saturated) having 8 to 12 carbon atoms, especially 8 to 10 carbon atoms
It is preferable to use an acid anhydride group-containing compound having a group of. This is because the compatibility of the resin is better when such a compound is used. Specific examples of preferable acid anhydrides include hexahydrophthalic anhydride, phthalic anhydride, 4-methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride and trimellitic anhydride.

The half-esterification reaction between the hydroxyalkyl (meth) acrylate compound and the acid anhydride group-containing compound is carried out at a temperature of room temperature to 120 ° C. according to a conventional method. At this time, it is preferable to use an excess amount of the hydroxyalkyl (meth) acrylate compound in order to prevent the unreacted acid anhydride group from remaining.

As the second ethylenically unsaturated monomer,
In order to prepare the polymer (a) having a hydroxyl group and a carboxyl group, a copolymerizable ethylenically unsaturated monomer (a) (ii) may be used if necessary. Preferred monomer (a) (i
i) is a monomer having 3 to 15 carbon atoms, particularly 2 to 12 carbon atoms, which has one ethylenically unsaturated bond. Further, a hydroxyl group-containing ethylenically unsaturated monomer may be used, and in this case, it is used for introducing a further hydroxyl group into the polymer (a). The hydroxyl group contained in the second monomer is preferably a primary hydroxyl group. This is because it has good reactivity after being made into a paint.

It is also possible to use a mixture of two or more kinds of monomers. This is because it is effective in improving the compatibility between the resins. Specific examples of such a monomer that can be preferably used include ethylenically unsaturated monomers such as styrene, α-methylstyrene, and (meth) acrylic acid ester (e.g., methyl (meth) acrylate, ethyl (meth) acrylate). , Propyl (meth) acrylate, (meth) acrylic acid-n,
i, and t-butyl, 2-ethylhexyl (meth) acrylate and lauryl (meth) acrylate, cyclohexyl (meth) acrylate, etc., VeoVa-9 and VeoVa manufactured by Shell Co.
-10 and the like, and the hydroxyl group-containing ethylenically unsaturated monomer includes 2-hydroxyethyl (meth) acrylate and
4-hydroxybutyl (meth) acrylate may be mentioned. Preferably, a hydroxyalkyl (meth) represented by the formula [I]
An acrylate compound may be used.

Polymerization of a monomer mixture (a) (i) of a carboxyl group-containing ethylenically unsaturated monomer and a hydroxyl group-containing ethylenically unsaturated monomer with a copolymerizable ethylenically unsaturated monomer (a) (ii) It is made by ordinary solution polymerization. It is preferable to carry out polymerization at a temperature of 100 to 150 ° C. for a polymerization time of 3 to 8 hours using an azo or peroxide initiator. At that time, the monomer mixture of the carboxyl group-containing ethylenically unsaturated monomer and the hydroxyl group-containing ethylenically unsaturated monomer (a) (i), and the other monomer (a) (ii), 20-100% by weight, It is preferably copolymerized at a ratio of 40 to 80% by weight / 0 to 80% by weight, preferably 20 to 60% by weight.

If the amount of the monomer mixture (a) (i) of the carboxyl group-containing ethylenically unsaturated monomer and the hydroxyl group-containing ethylenically unsaturated monomer is less than 20% by weight, the curability will be insufficient. Also, when the amount of the other monomer is 60% by weight or more, the amount of the functional group is too low and the curability is insufficient.

Each of the above monomers and radical polymerization initiator
(It may be one usually used in radical polymerization, for example, t
-Butyl peroxy 2-ethylhexanoate, dimethyl
2,2'-azobisisobutyrate and the like can be mentioned. The polymer (a) having a hydroxyl group and a carboxyl group is obtained by radically polymerizing a monomer composition containing (1).

Upon polymerization, a monomer mixture of a carboxyl group-containing ethylenically unsaturated monomer and a hydroxyl group-containing ethylenically unsaturated monomer, and a copolymerizable ethylenically unsaturated monomer are independently mixed in predetermined amounts. However, it is also possible to utilize the hydroxyalkyl (meth) acrylate compound represented by the formula [I] in an excessive amount in the above-mentioned half-esterification step.

That is, when a hydroxyalkyl (meth) acrylate compound is used as the hydroxyl group-containing ethylenically unsaturated monomer, the hydroxyalkyl (meth) acrylate compound is added in an amount required for copolymerization in addition to the amount required for half-esterification. By half-esterifying with an acid anhydride group-containing compound by using an amount added in excess, a monomer mixture of a carboxyl group-containing ethylenically unsaturated monomer and a hydroxyl group-containing ethylenically unsaturated monomer is obtained. In this case, generally, the hydroxyalkyl (meth) acrylate compound and the acid anhydride group-containing compound have a molar ratio of the hydroxyl group and the acid anhydride group of 1 / 0.9 to 1 / 0.5, particularly 1 / 0.8 to 1 / 0.5. It is preferable to mix and react in the amount of the molar ratio. If it is 1 / 0.9 or less, half-esterification may take a long time, and the monomer may gel. On the other hand, if it is 1 / 0.5 or more, the amount of carboxyl groups is too small and curability is insufficient.

The resulting monomer mixture (a) (i) of a carboxyl group-containing ethylenically unsaturated monomer and a hydroxyalkyl (meth) acrylate compound is copolymerized by the same method as described above, or if necessary, The polymer (a) having a hydroxyl group and a carboxyl group of the present invention can be obtained by copolymerizing the above ethylenically unsaturated monomer (a) (ii). When carrying out the polymerization in this way,
Generally, the monomer mixture (a) (i) is from 20 to 100% by weight, preferably 40 to 80% by weight and the ethylenically unsaturated monomer (a) (ii).
0 to 80% by weight, preferably 20 to 60% by weight are used.

If the amount of the monomer mixture (a) (i) is less than 20% by weight, the curability will be insufficient.

Thus, the equation

[0026]

[Chemical 5]

[In the formula, X is a structural unit derived from a radical polymerization initiator, R ₁ is a hydrogen atom or a methyl group,
Y is a residue of an acid anhydride group-containing compound and has 8 to 1 carbon atoms
2, preferably of 8 to 10, Z has the formula _{- (CH 2) m - (} O-CO- (CH 2) n) q - [ wherein, m, n and q are as defined above Is. ] Is an alkylene group represented by

[0028]

[Chemical 6]

[Wherein x, y and z are integers, R ₁ has the same meaning as described above, and R ₂ and R ₄ generally have 2 to 1 carbon atoms.
5, preferably a linear or branched alkyl group having 2 to 12, R ₃ is hydrogen or a linear or branched alkyl group having generally 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms,
The order of each structural unit is arbitrary. ] It has a repeating unit of the structure shown. ] A polymer (a) having a hydroxyl group and a carboxyl group, which can be used in the curable resin composition of the present invention and has a structure shown by This polymer is 1500-20000, especially 2000-5000
It is preferred to have a number average molecular weight Mn of When the number average molecular weight is less than 1500, the number of functional groups per molecule is small and the curability is insufficient, and when it exceeds 20,000, the compatibility with other resins is poor. Also, 30 to 250 mg KOH /
g, especially 25-200 mgKOH / g hydroxyl value and 50-200 mgKOH / g,
It is particularly preferable to have an acid value of 70 to 180 mg KOH / g.
If the hydroxyl value falls below 30 mg KOH / g, the curability will deteriorate, and 250
When it exceeds mgKOH / g, the compatibility becomes poor. Acid value is 50mgKOH / g
If it is below 200 mg, the curability will be poor, and if it exceeds 200 mgKOH / g, the water resistance will be poor due to unreacted acid. The molecular weight of the polymer used in the present invention is determined by the GPC method.

Polymer having a carboxyl group and a carboxylic acid ester group used in the curable resin composition of the present invention
(b) is a half ester group-containing polymer obtained by reacting the acid anhydride group-containing polymer (b) (i) with the hydroxyl group-containing compound (b) (ii).

The acid anhydride group-containing polymer (b) (i) is an acid anhydride group-containing ethylenically unsaturated monomer (b) (i) (1) in an amount of 15 to 40% by weight and another copolymerizable ethylenic group. Unsaturated monomer (b)
It is obtained by copolymerizing (i) (2) with 60 to 85% by weight. Specific examples of the acid anhydride group-containing ethylenically unsaturated monomer include itaconic anhydride, maleic anhydride, citraconic anhydride, and the like. The other copolymerizable ethylenically unsaturated monomer is not particularly limited as long as it does not adversely affect the acid anhydride group, and specifically, a polymer (a) having a hydroxyl group and a carboxyl group is prepared. Therefore, the above-mentioned monomers are mentioned as the "other copolymerizable monomer (a) (ii)", but these do not include a monomer having a hydroxyl group. If styrene is used as the other copolymerizable monomer, it is particularly preferably used in an amount of 5 to 40% by weight.

In the composition of the reactant in the copolymerization reaction, the acid anhydride group-containing ethylenically unsaturated monomer is contained in an amount of 15 to 40% by weight, preferably 15 to 30% by weight, based on the total amount of the component (b) monomer. Used in quantity. If it is less than 15% by weight, the curability will be insufficient, and if it exceeds 40% by weight, it will be too hard and brittle and the weather resistance will be insufficient.

The copolymerization is carried out by a known method such as solution polymerization such as radical polymerization.
It can be carried out at 100 to 150 ° C and a polymerization time of 3 to 8 hours.
As the initiator, an azo type or peroxide type initiator is preferably used. The number average molecular weight of the obtained polymer is preferably 1500 to 20,000, and particularly preferably 2,000 to 10,000. When the number average molecular weight exceeds 20,000, the viscosity of the polymer becomes high, which makes it difficult to prepare a coating composition having a high solid content. If the number average molecular weight is less than 500, the curability of the curable resin composition will be insufficient. The resulting polymer has an average of at least 2 and preferably 2 to 15 acid anhydride groups per molecule. If the number of acid anhydride groups contained in one molecule is less than 2, the curability of the curable resin composition will be insufficient.
If it exceeds 15, it becomes too hard and brittle, and the weather resistance is insufficient.

Then, the obtained polymer is mixed with an acid anhydride group and a hydroxyl group in a molar ratio of 1 / 1.5 to 1/1, preferably 1/1.
A polymer (b) having a carboxyl group and a carboxylic acid ester group is prepared by reacting with a hydroxyl group-containing compound (b) (ii) in an amount of 5 to 1 / 1.3. If it exceeds 1 / 1.5, there is too much alcohol, causing cracking during curing, and if it is less than 1/1, unreacted anhydride groups remain,
Storage stability becomes poor.

Hydroxyl group-containing compound (b) (i) usable in the present invention
i) is a low molecular weight compound having 1 to 12, preferably 1 to 8 carbon atoms. This is because the alcohol volatilizes during heating and is good for regenerating the acid anhydride group. Hydroxyl group-containing compounds that can be suitably used include methanol, ethanol,
Examples thereof include n-propanol, i-propanol, n-butanol, i-butanol, t-butanol, methyl cellosolve, ethyl cellosolve, dimethylaminoethanol, diethylaminoethanol, acetol, allyl alcohol and propargyl alcohol. Particularly preferred are acetol, allyl alcohol, propargyl alcohol and methanol.

The polymer (c) having a hydroxyl group and an epoxy group used in the resin composition of the present invention has an average of preferably 2 to 10 epoxy groups in a molecule, more preferably 3 to 8 epoxy groups.
And, on the average, preferably 2 to 12, more preferably 4 to 10 hydroxyl groups. The epoxy equivalent is preferably 100 to 800, more preferably 200 to 600, and the hydroxy equivalent is preferably 200 to 1,200, more preferably 400.
~ 1,000. When the epoxy equivalent is larger than the above upper limit, the curability of the curable resin composition becomes insufficient. Also, if it is less than the lower limit, it becomes too hard and the coating film becomes brittle, which is not preferable. If the hydroxy equivalent is less than 200, the water resistance of the cured coating film will be insufficient, and if it exceeds 1,200, the curability will not be sufficient, which is not preferable.

Such a polymer (c) is obtained by using a hydroxyalkyl (meth) acrylate compound (c) (i) of the formula [I]
40% by weight, preferably 15-30% by weight, epoxy group-containing ethylenically unsaturated monomer (c) (ii) 10-60% by weight, preferably 15-50% by weight, and optionally other copolymerizable It is obtained by copolymerizing from 0 to 85% by weight, preferably from 10 to 60% by weight, of another ethylenically unsaturated monomer (c) (iii). Hydroxyalkyl (meth) acrylate compound is 5
If it is less than 50% by weight, the curability is insufficient, and if it is more than 40% by weight, the compatibility is insufficient and the reaction does not proceed sufficiently. When the epoxy group-containing ethylenically unsaturated monomer is 10% by weight or less, the curability is insufficient, and when it is 60% by weight or more, it becomes too hard and the weather resistance is insufficient.

The copolymerization is carried out by a known method such as solution polymerization such as radical polymerization.
It can be carried out at 100 to 150 ° C. and a polymerization time of 3 to 8 hours.
As the initiator, peroxide type and azo type initiators are preferably used. Further, the radical polymerization initiator is preferably used in an amount of 3 to 15% by weight based on all monomers.
Other additives such as chain transfer agents may be added to the above-mentioned monomer composition. The polymer obtained has a molecular weight of 500.
It is preferably 20,000, particularly 1,500 to 10,000.

Polymer Having Hydroxyl Group and Epoxy Group
Examples of the monomer (c) (ii) that can be used to prepare (c) include glycidyl (meth) acrylate and 3,4-epoxycyclohexanylmethyl (meth) acrylate. Examples of the monomer (c) (i) include (meth)
Examples thereof include 2-hydroxyethyl acrylate, 4-hydroxybutyl (meth) acrylate, and Praxel FM-1 (ε-caprolactone ring-opening adduct of 2-hydroxyethyl methacrylate (manufactured by Daicel)). Other monomer (c) (ii
Examples of i) include `` other copolymerizable monomer (a) '' for preparing a polymer (a) having a hydroxyl group and a carboxyl group.
(ii) ”includes the monomers described above.

Thus obtained (a) a polymer having a hydroxyl group and a carboxyl group, (b) a polymer having a carboxyl group and a carboxylic acid ester group, and (c)
The curable resin composition of the present invention can be obtained by blending a polymer containing a hydroxyl group and an epoxy group.

The blending is such that the molar ratio of the carboxyl groups contained in the polymers (a) and (b) to the epoxy groups contained in the polymer (c) is from 1 / 1.2 to 1 / 0.6, preferably 1 / 1.0. ~
1 / 0.8 and the carboxyl group or carboxylic acid ester group contained in the polymer (b) (usually the polymer
The carboxyl group and the carboxylic acid ester group in (b) are present in equimolar amounts. And the hydroxyl groups contained in the polymers (a) and (c) are preferably in a molar ratio of 1 / 1.5 to 1 / 0.5.

If the ratio of the carboxyl groups contained in the polymers (a) and (b) to the epoxy groups contained in the polymer (c) exceeds 1 / 0.6, the curability of the obtained resin composition is lowered, If it is less than 1 / 1.2, the coating film turns yellow. When the molar ratio of the carboxyl group or carboxylic acid ester group contained in the polymer (b) to the hydroxyl group contained in the polymers (a) and (c) exceeds 1 / 0.5, the curability of the obtained resin composition is lowered. However, if it is less than 1 / 1.5, the hydroxyl groups become excessive, so that the water resistance decreases.

Such a blending amount can be calculated from the hydroxyl value, acid value and epoxy equivalent of each polymer by a calculation method well known to those skilled in the art. The curable resin composition of the present invention comprises (a) a polymer having a hydroxyl group and a carboxyl group in an amount of 5 to 50% by weight, preferably 5 to 40% by weight, and (b) a polymer having a carboxyl group and a carboxylic acid ester group. ~ 60 wt%, preferably 25-55 wt% and (c) 30-60 wt% polymer containing hydroxyl groups and epoxy groups,
It is preferably obtained by blending in an amount of 35 to 55% by weight. If the amount of the polymer (a) is more than 50% by weight, the coating film becomes too soft and the acid resistance is lowered, and if it is less than 5%, the scratch resistance is deteriorated. If the amount of the polymer (b) is less than 20% by weight, the acid resistance will decrease, and if it exceeds 60% by weight, the coating film will be too hard. Since the polymer (c) is blended in an amount suitable for the total amount of acid groups contained in the system, if it is less than the amount corresponding to the acid groups, the curability will decrease, and if it is too large, the yellowing resistance will deteriorate.

The curing mechanism of the curable resin composition of the present invention thus obtained is as follows.
The carboxyl group and the carboxylic acid ester group therein react with each other to generate an acid anhydride group in the polymer (b), thereby generating a free hydroxyl group-containing low molecular weight compound. The produced low molecular weight compound containing a hydroxyl group is removed from the system by evaporation.
The acid anhydride group formed in the polymer (b) reacts with the hydroxyl group contained in the polymer (a) and the polymer (c) to form a cross-linking point and form an acid group again. The acid group and the carboxyl group contained in the polymer (a) react with the epoxy group contained in the polymer (c) to form a crosslinking point. In this way, the curing proceeds by the mutual reaction of the three types of polymers.

With such a constitution, it is possible to provide a high crosslinking density by reacting the three kinds of polymers with each other. Further, since the hydroxyl group and the carboxyl group of the polymer (a) are separated from the main chain, the degree of freedom of movement near the cross-linking point is high, so the elongation rate is high and it is presumed that performance such as scratch resistance will be exhibited. It

In addition to the above polymers (a), (b) and (c), the curable resin composition of the present invention is usually used in the esterification reaction between an acid such as a quaternary ammonium salt and an epoxy. The curing catalyst used may be included. Specific examples of other catalysts that can be used in the curable resin composition of the present invention include benzyltriethylammonium chloride or bromide, tetrabutylammonium chloride or bromide, salicylate or glycolate, and paratoluenesulfonate. You may mix and use these catalysts. The amount of this catalyst blended is 0 relative to the resin composition solids.
1 to 2.0% by weight is preferable. Further, as described in JP-A-2-151651 and JP-A-2-279713, a tin-based catalyst may be used in combination therewith. Examples of the tin-based catalyst include dimethyltin bis (methylmalate), dimethyltin bis (ethylmalate), dimethyltin bis (butylmalate), dibutyltin bis (butylmalate), and the like. The weight ratio of the curing catalyst to the tin catalyst is preferably 1/4 to 1 / 0.2.

A melamine-formaldehyde resin and / or a blocked isocyanate may be added to the resin composition of the present invention in order to increase the crosslink density and improve the water resistance. Further, in order to improve the weather resistance of the coating film, an ultraviolet absorber, a hindered amine light stabilizer, an antioxidant and the like may be added. Further, crosslinked resin particles as a rheology control agent or a surface conditioner for adjusting the appearance may be added. Furthermore, alcohol-based solvents (for example, methanol, ethanol, propanol, butanol, etc.), hydrocarbon-based solvents, ester-based solvents and the like may be used as diluents for viscosity adjustment and the like.

The resin used in the present invention has an acid group as a functional group. Therefore, by neutralizing with an amine, it is possible to obtain an aqueous resin composition using water as a medium.

The curable resin composition of the present invention is preferably used as a clear coating composition. In this case, a color pigment-containing aqueous paint or a color pigment-containing organic solvent type paint is preferably used as the base paint. At the time of coating, a two-coat / one-bake curing method is preferably used in which the base coating surface is not cured, but a clear coating containing the curable resin composition of the present invention is applied to the surface of the base coating, and then both coatings are cured. To be

However, when an aqueous paint is used,
In order to obtain a good finished coating film, it is preferable to heat the base coat in advance at 60 to 100 ° C. for 2 to 10 minutes before applying the clear paint. As the base paint, those specifically described in US Pat. Nos. 5,151,125 and 5,183,504 can be used. In particular, U.S. Pat.
The water-based coating composition described in No. 4 is most suitable in terms of finish, appearance and performance.

The method for producing the curable resin composition of the present invention is not particularly limited, and any method known to those skilled in the art can be used. For example, in the case of an enamel paint, the compound such as a pigment may be kneaded and dispersed using a kneader or a roll.

The coating composition of the present invention can be applied by spray coating, brush coating, dip coating, roll coating, flow coating and the like. The substrate may be primed or mid-coated if desired. Known undercoat paints and intermediate paints can be used.

The coating composition of the present invention may be advantageously used on any substrate such as wood, metal, glass, cloth, plastics, foams and the like, especially on plastic and metal surfaces such as steel, aluminum and their alloys.

Generally, the film thickness will vary depending on the desired application. In most cases 0.5-3 mils are useful.

After coating the substrate, the coating film is cured. Curing gives a cured coating film with a high degree of crosslinking at 100 to 180 ° C, preferably 120 ° C to 160 ° C. The curing time varies depending on the curing temperature and the like, but curing at 120 ° C to 160 ° C for 10 to 30 minutes is suitable.

[0056]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Unless otherwise specified, the blending amount is indicated by weight.

[0057]

Preparation Examples 1 to 16 Preparation Examples 1 to 16 describe the preparation of the polymer (a) having a hydroxyl group and a carboxyl group used in the curable resin composition of the present invention.

Preparation Examples 1 to 5 describe the preparation of the carboxyl group-containing ethylenically unsaturated monomer (a) (i) which is the precursor thereof.

Preparation Example 1 In a 2 liter reaction vessel equipped with a thermometer, a stirrer, a cooling tube, a nitrogen introducing tube and a dropping funnel, 360 parts of ACOSOLVE PMA (manufactured by Kyowa Yuka Co., Ltd.) solvent, 4-acrylic acid 777 parts of hydroxybutyl, 665 parts of hexahydrophthalic anhydride and 0.48 part of hydroquinone monomethyl ether were charged, and the temperature was raised to 145 ° C. and kept for 20 minutes. Then, it was cooled and taken out from the reaction vessel to obtain a carboxyl group-containing ethylenically unsaturated monomer Ai.

Preparation Examples 2 to 5 Carboxyl group-containing ethylenically unsaturated monomers A-ii to v were obtained in the same manner as in Preparation Example 1 except that the formulations shown in Table 1 below were used.

[0061]

[Table 1]

Preparation Examples 6 to 16 describe the preparation of polymers having a hydroxyl group and a carboxyl group.

Preparation Example 6 A 3 liter reaction vessel equipped with a thermometer, a stirrer, a cooling tube, a nitrogen introducing tube and a dropping funnel was charged with 300 parts of xylene and 200 parts of Arcosolv PMA solvent and heated to 130 ° C. Next, 1300 parts of the carboxyl group-containing ethylenically unsaturated monomer Ai obtained in Preparation Example 1 and 100 parts of t-butylperoxy 2-ethylhexyl hexanoate were added dropwise over 3 hours. After maintaining at 130 ° C for 30 minutes, 10 parts of t-butylperoxy 2-ethylhexanoate and 1 part of xylene
The mixed solution with 00 parts was added dropwise over 30 minutes. 30 minutes at 130 ° C
By cooling after keeping at, and taking out from the container,
A polymer AI having a hydroxyl group and a carboxyl group was obtained. This polymer has a nonvolatile content of 54%, a number average molecular weight of 2000,
Acid value 168mgKOH / g and hydroxyl value 42mgKOH / g
It was a transparent liquid having.

Preparation Examples 7 to 16 Polymers A-II to XI having a hydroxyl group and a carboxyl group were obtained in the same manner as in Preparation Example 6 except that the formulations shown in Table 2 below were used. The properties of these polymers are also shown in Table-2.

[0065]

[Table 2]

[0066]

[Table 3]

[0067]

Preparation Examples 17 to 22 Preparation Examples 17 to 22 describe the preparation of the polymer (b) having a carboxyl group and a carboxylic acid ester group used in the curable resin composition of the present invention.

Preparation Examples 17 to 19 describe the preparation of the precursor polymer (b) (i) having an acid anhydride group.

Preparation Example 17 A 1-liter reaction vessel equipped with a thermometer, a stirrer, a cooling tube, a nitrogen introducing tube and a dropping funnel was charged with 80 parts by weight of xylene and heated to 115 ° C. to prepare 25 parts of styrene and acrylic acid. 21 parts by weight of n-butyl, 95 parts by weight of n-butyl methacrylate, 34 parts by weight of 2-ethylhexyl methacrylate, 50 parts by weight of itaconic anhydride, 100 parts by weight of propylene glycol monomethyl ether acetate and t-butylperoxy 2-ethylhexa A monomer consisting of 10 parts by weight of noate and an initiator solution were added dropwise over 3 hours, and stirring was continued for 2 hours to obtain a polymer Bi having an acid anhydride group having a nonvolatile content of 53% and a number average molecular weight of 5,500.

Preparation Examples 18 and 19 Polymers B-ii and B- having an acid anhydride group were prepared in the same manner as in Preparation Example 17 except that the formulations shown in Table 3 below were used.
got iii.

[0071]

[Table 4]

Preparation Examples 20 to 22 explain the preparation of the polymer (b) having a carboxyl group and a carboxylic acid ester group.

Preparation Example 20 Polymer 1 Bi obtained in Preparation Example 17 was mixed with 385 parts of methanol 1
A polymer having a carboxyl group and a carboxylic acid ester group by adding 8.2 parts and reacting at 65 ° C. for 24 hours
Got BI. It was confirmed by IR that absorption of the acid anhydride group (1785 cm ⁻¹ ) disappeared.

Preparation Examples 21 and 22 Polymers B-II and B-III having a carboxyl group and a carboxylic acid ester group were obtained in the same manner as in Preparation Example 20 except that the formulations shown in Table 4 below were used. . As a result of investigating the obtained polymer by IR, it was confirmed that the absorption of the acid anhydride group had disappeared.

[0075]

[Table 5]

[0076]

Preparation Examples 23 to 25 Preparation Examples 23 to 25 describe the preparation of the polymer (c) containing a hydroxyl group and an epoxy group used in the curable resin composition of the present invention.

Preparation Example 23 500 parts by weight of butyl acetate were charged into a 2 liter reaction vessel equipped with a thermometer, a stirrer, a cooling tube, a nitrogen introducing tube and a dropping funnel, and the temperature was raised to 125 ° C.

50 parts of styrene, 400 parts of glycidyl methacrylate and 350 parts of 4-hydroxybutyl acrylate were placed in a dropping funnel.
Part, 200 parts of 2-ethylhexyl acrylate and 70 parts of t-butylperoxy 2-ethylhexanoate, and an initiator solution were added dropwise over 3 hours. After completion of dropping
After holding at 125 ° C. for 30 minutes, a solution containing 10 parts of t-butylperoxy 2-ethylhexanoate and 250 parts of xylene was added dropwise over 30 minutes. After the dropping was completed, the reaction was continued for another 2 hours at 125 ° C, with a nonvolatile content of 59%, a number average molecular weight of 4,000,
A polymer CI having a hydroxyl group and an epoxy group having a hydroxy equivalent of 411 and an epoxy equivalent of 355 was obtained.

Preparation Examples 24 and 25 A polymer C-having a hydroxyl group and an epoxy group was prepared in the same manner as in Preparation Example 23 except that the formulations shown in Table 5 below were used.
II and C-III were synthesized. The characteristic values of the obtained polymer are shown in Table-5.

[0080]

[Table 6]

[0081]

Examples 1 to 18 Examples 1 to 18 describe coatings containing the curable resin composition of the present invention obtained by using the polymers prepared in Preparation Examples 1 to 25.

Example 1 First, a resin composition was prepared with the formulations shown in the following table.

Ingredients (parts by weight) Polymer AI (Preparation Example 1) 25.0 Polymer BI (Preparation Example 22) 225.0 Polymer CI (Preparation Example 29) 160 Tetrabutylammonium bromide 1.3 Tinuvin-900 2.6 Sanol LS-292 1.3 Total 415.2

Then, the obtained resin composition was treated with butyl acetate.
The coating viscosity was diluted with a solvent consisting of / xylene = 1/1 to obtain a clear coating. A process test board in which a phosphoric acid-treated steel plate is coated with an electrodeposition paint (Power Top U-30 manufactured by Nippon Paint Co., Ltd.) and an intermediate coating (Olga P-2 manufactured by Nippon Paint Co., Ltd.) After applying -90 metallic base, the above clear paint was applied wet-on-wet and baked at 140 ° C for 30 minutes. The effect coating film was evaluated by the following evaluation methods. The results are shown in Table-7. At that time, the dry film thickness of the clear paint was set to 40 μm.

Paint Stability The obtained clear paint was allowed to stand at room temperature for 1 week, and then visually checked for turbidity and separation. When there was no turbidity or separation, it was classified as "no abnormality".

Pencil Hardness The pencil hardness was evaluated according to the method described in JIS K 5400-1979.

Warm water resistance The obtained cured coating film was immersed in warm water at 40 ° C. for 10 days, and then the surface of the coating film was visually evaluated. When no change was observed, it was classified as “no abnormality”.

Alkali resistance The obtained cured coating film was brought into contact with 0.2 ml of 0.1N NaOH aqueous solution at 55 ° C. for 4 hours, and then the coating film surface was visually evaluated.
When no change was observed, it was classified as “no abnormality”.

Acid resistance The obtained cured coating film was added to 0.2 ml of 0.1N H ₂ SO ₄ aqueous solution at 55 to 60 ° C.
After being contacted with each other for 2 hours, the coating film surface was visually evaluated according to the following criteria.

When no change was observed: ⊚ When a trace was slightly observed: ◯ When a trace was clearly observed: Δ

2 × 2 cm flannel cloth coated with 1 g of 50% aqueous dispersion of scratch-resistant cleanser (commercially available from Kao Corporation as New Homing Cleanser; 87% abrasive, 5% surfactant and others) Was attached to a Gakshin type dyeing friction fastness tester (manufactured by Daiei Kagaku Seiki Co., Ltd.). Then, the cured coating film obtained was loaded with 500 g of 10
I rubbed back and forth. The ratio of 20 ° G before and after friction measured with a gloss meter manufactured by Suga Test Instruments Co., Ltd. is shown in%. The correspondence with the visual evaluation is shown below.

> 90 ・ ・ ・ No change 80〜90 ・ ・ ・ Slightly visible but not noticeable 70〜80 ・ ・ ・ Slightly visible 70> ・ ・ ・ Visible

[0093] Except for using an formulations shown in Table 6 of Example 2 to 15 below in the same manner as in Example 1, a clear coating compositions of Examples 2-15 were prepared and evaluated film performance. The evaluation results are shown in Table-7.

Examples 16-18 Examples 1-3 were made as base coating compositions described in US Pat. No. 5,183,504 at column 9, line 16 to column 10, line 6. The phosphoric acid-treated steel sheet was intermediately coated as in Example 1 of the present invention, and then the above-mentioned base paint was spray-coated. 60
After preheating at 5 ° C for 5 minutes, the clear paint of Example 1 was applied and cured at 140 ° C for 30 minutes, and the same evaluation as in Example 1 was performed. The results are shown in Table-7.

[0095] Except for the use of the formulations shown in Table 6 of Comparative Example 1 and 2 below in the same manner as in Example 1 to evaluate coating performance was prepared clear paint Comparative Examples 1 and 2. The evaluation results are shown in Table-7.

[0096]

[Table 7]

[0097]

[Table 8]

[0098]

[Table 9]

[0099]

[Table 10]

As shown in the results of Table 7, Examples 1 to 15
The clear paint of (1) provides a coating film having excellent acid resistance and scratch resistance at high temperature as compared with Comparative Examples.

[0101]

EFFECT OF THE INVENTION A curable resin composition capable of providing a coating film which has a high crosslink density and thus is excellent in weather resistance, particularly resistance to acid rain, and has a high elongation ratio and is also excellent in scratch resistance. sponsored.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location C09D 135/00 PFW 7921-4J 163/00 PJK 8830-4J PKE 8830-4J (72) Inventor Yoshitaka Ide 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd.

Claims (7)

[Claims] 1. A formula of (a) (i): [In the formula, R is a hydrogen atom or a methyl group, and m is 2 to 8
, N is an integer of 3 to 7, and q is an integer of 0 to 4. ] The hydroxyalkyl (meth) acrylate compound having the structure shown by and the acid anhydride group-containing compound are mixed and reacted at a ratio of the hydroxyl group and the acid anhydride group in a molar ratio of 1 / 0.9 to 1 / 0.5. Carboxyl group-containing ethylenically unsaturated monomer and hydroxyalkyl (meth) obtained by
A hydroxyl group and a carboxyl group, which are obtained by copolymerizing 20 to 100% by weight of a monomer mixture with an acrylate compound, and (ii) 0 to 80% by weight of a copolymerizable ethylenically unsaturated monomer, as necessary. 5 to 50% by weight of polymer (% by weight of polymer is based on the total solid content of the resin composition); (b) (i) (1) acid anhydride group-containing ethylenically unsaturated monomer 15
To 40% by weight and (2) 60 to 85% by weight of another copolymerizable ethylenically unsaturated monomer, an acid anhydride group-containing polymer obtained by copolymerizing (ii) 1 to 12 carbons. It has a carboxyl group and a carboxylic ester group, which are obtained by reacting a hydroxyl group-containing compound containing an atom, an acid anhydride group and a hydroxyl group in a molar ratio of 1 / 1.5 to 1/1. 20 to 60% by weight of a polymer; and (c) (i) 5 to 40% by weight of the hydroxyalkyl (meth) acrylate compound, (ii) 10 to 60% by weight of an epoxy group-containing ethylenically unsaturated monomer, and, if necessary, (iii) A curable resin containing 30 to 60% by weight of a polymer containing a hydroxyl group and an epoxy group, which is obtained by copolymerizing 0 to 85% by weight of another copolymerizable ethylenically unsaturated monomer. Composition. 2. The curable resin composition according to claim 1, which contains a quaternary ammonium salt catalyst. 3. The curable resin composition according to claim 1, which contains an organic tin compound. 4. A coating composition containing the curable resin composition according to claim 1, 2 or 3 as a binder component. 5. A step of applying a water-based or solvent-based base coating on an undercoated or intermediate-coated substrate; without curing the base coating, a (a) (i) formula: [In the formula, R is a hydrogen atom or a methyl group, and m is 2 to 8
, N is an integer of 3 to 7, and q is an integer of 0 to 4. ] The hydroxyalkyl (meth) acrylate compound having the structure shown by and the acid anhydride group-containing compound are mixed and reacted at a ratio of the hydroxyl group and the acid anhydride group in a molar ratio of 1 / 0.9 to 1 / 0.5. Carboxyl group-containing ethylenically unsaturated monomer and hydroxyalkyl (meth) obtained by
Hydroxyl group and carboxyl group obtained by copolymerizing 20 to 100% by weight of a monomer mixture with an acrylate compound, and (ii) 0 to 80% by weight of another copolymerizable ethylenically unsaturated monomer, if necessary. 5 to 50% by weight of the polymer having a (based on the total solid content of the resin composition); (b) (i) (1) acid anhydride group-containing ethylenically unsaturated monomer 15
To 40% by weight and (2) 60 to 85% by weight of another copolymerizable ethylenically unsaturated monomer, an acid anhydride group-containing polymer obtained by copolymerizing (ii) 1 to 12 carbons. It has a carboxyl group and a carboxylic ester group, which are obtained by reacting a hydroxyl group-containing compound containing an atom, an acid anhydride group and a hydroxyl group in a molar ratio of 1 / 1.5 to 1/1. 20 to 60% by weight of a polymer; and (c) (i) 5 to 40% by weight of the hydroxyalkyl (meth) acrylate compound, (ii) 10 to 60% by weight of an epoxy group-containing ethylenically unsaturated monomer, and, if necessary, (iii) A curable resin containing 30 to 60% by weight of a polymer containing a hydroxyl group and an epoxy group, which is obtained by copolymerizing 0 to 85% by weight of another copolymerizable ethylenically unsaturated monomer. A composition containing the composition as a binder component. By and heating, curing the base coating film and the clear coating film; step applying the A coating composition coating film-forming method comprising the. 6. The method according to claim 5, wherein the curable resin composition contains a quaternary ammonium salt catalyst. 7. The method according to claim 5, wherein the curable resin composition contains an organotin compound.