JPH06220397A - Two-pack type urethane coating composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition having both excellent acid resistance and scratch resistance by blending a specific acrylic resin with a specific oligoester and an isocyanate prepolymer in a specific ratio. CONSTITUTION:This coating composition comprises (A) an acrylic resin having 0-50 deg.C glass transition temperature, 140-280 hydroxyl number and 5,00-20,000 weight-average molecular weight, (B) an oligoester having >=80 hydroxyl number and 400-2,000 weight-average molecular weight and (C) an isocyanate prepolymer as essential components and has the blending ratio of 20-80 pts.wt. of the component A and 20-60 pts.wt. of the component B and the ratio of NCO group in the component C to hydroxyl group in the components A and B of 0.8-1.3. The component A is preferably obtained by adding epsilon-caprolactone to a hydroxyl group-containing monomer such as alpha-hydroxyethyl (meth)acrylate and copolymerizing the monomer. The component B, for example, is obtained by reacting a reactional product of an acid anhydride and a polyhydric alcohol with a monofunctional epoxy compound.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a two-pack urethane coating composition containing an isocyanate prepolymer.

[0002]

2. Description of the Related Art In recent years, a two-pack type urethane coating composition having excellent acid resistance as compared with a commonly used melamine coating and having a strong resistance to acid rain has been used outdoors. It has been proposed to use it for paints for many automobiles. For example, as disclosed in JP-A-62-30160, in a two-pack type urethane coating comprising a polyol component and a polyisocyanate component, a predetermined tertiary amine catalyst is added to either of the polyol component or the polyisocyanate component. Is included.

[0003]

The above-mentioned two-component urethane paint has excellent adhesion, water resistance, hardness and acid resistance, but has a shorter pot life (usable time) than melamine paint. There is a problem that the cross-linking of the resin is insufficient and the scratch resistance of the coating film is low.

Therefore, in the coating material disclosed in the above publication, by containing a predetermined tertiary amine catalyst,
I try to lengthen the pot life. But,
Even with the paint disclosed in the above publication, the scratch resistance of the coating film cannot be sufficiently improved, and development of a two-component urethane paint composition in which this point is improved has been desired.

The present invention has been made in view of the above points, and an object thereof is to provide a two-component urethane coating composition having excellent properties in both acid resistance and scratch resistance.

[0006]

The present invention comprises 40 to 80 parts of an acrylic resin having a glass transition temperature of 0 to 50 ° C., a hydroxyl value of 140 to 280 and a weight average molecular weight of 5,000 to 20,000. The first component and the hydroxyl group are 80
As described above, 20 to 60 parts of the second component consisting of the oligoester having a weight average molecular weight in the range of 400 to 2000 and the ratio of the isocyanate group to the hydroxyl group contained in these first and second components are 0.8. A two-component urethane coating composition containing, as an essential component, a third component consisting of an isocyanate prepolymer within the range of 1.3 to 1.3.

The two-component urethane coating composition of the present invention will be described in more detail below. Here, the acrylic resin that constitutes the first component is prepared by using the following hydroxyl group-containing monomer as a raw material.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, polyoxyalkylene glycol (meth) acrylate, 3-hydroxypropyl (meth) acrylate and 2,3-dihydroxypropyl (meth) acrylate. (Meth) acrylates such as, vinyl ethers such as hydroxyethyl vinyl ether and hydroxybutyl vinyl ether, and allyl compounds such as hydroxyethyl allyl ether.

Then, 1 to 6 mol of ε-caprolactone is added to the above hydroxyl group-containing monomer to copolymerize the monomer, or
Alternatively, by adding ε-caprolactone to the hydroxyl group of the copolymerized resin, the acrylic resin that constitutes the first component is synthesized.

Typical examples of the monomer copolymerizable with the above-mentioned monomer include an alkyl (meth) acrylate which is an ester compound of an alkyl group having 1 to 22 carbon atoms and (meth) acrylic acid. , Styrene, vinyltoluene, ter-butylstyrene, glycidyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate,
Unsaturated carboxylic acids such as (meth) acrylonitrile cyclohexyl (meth) acrylate, (meth) acrylic acid, maleic acid, fumaric acid and itaconic acid, maleic acid or fumaric acid and monohydric alcohols having 1 to 22 carbon atoms Ester and diester, (meth) acrylamide, (meth) diacrylamide, N, N-dialkylaminoalkyl (meth) acrylate, phosphoric acid group-containing (meth) acrylate such as phosphonooxyethyl (meth) acrylate, vinyl acetate, hexa There are compounds such as α-olefins such as fluoropropylene and tetrafluoroethylene, and perfluorovinyl ethers such as trifluoromethyltrifluorovinyl ether.

The glass transition temperature of the first component made of the acrylic resin is limited to the range of 0 to 50 ° C.
The temperature is preferably within the range of 40 ° C. The glass transition temperature of the first component is set within the above range because when the glass transition temperature is lower than 0 ° C, the coating film is likely to be softened and the acid resistance is lowered. This is because the coating film is easily penetrated and the coating film is easily damaged. Further, if the glass transition temperature is higher than 50 ° C., the viscosity of the coating material becomes too high and the coating work becomes difficult, and the appearance of the coating film tends to deteriorate.

The hydroxyl value of the first component is 140
It is limited to within the range of 280 to 280, and is preferably within the range of 168 to 224. The reason why the hydroxyl value of the first component is limited to the above range is that when the hydroxyl value is less than 140, the coating composition is insufficiently crosslinked and the chemical resistance is lowered. Further, if the hydroxyl value exceeds 280, the viscosity of the coating material becomes too high, which impairs the coating workability.

Furthermore, the weight average molecular weight of the first component is limited to the range of 5,000 to 20,000, and 600
It is preferably in the range of 0 to 10,000. The weight average molecular weight of the first component is limited to the above range,
This is because if the weight average molecular weight is less than 5,000, the cross-linking of the coating material becomes insufficient and the chemical resistance decreases. Further, if the weight average molecular weight exceeds 20,000, the viscosity of the coating material becomes too high, and the workability of coating is impaired.

The second component composed of the above oligoester is
For example, a compound (c) obtained by reacting an acid anhydride compound (a) such as phthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride or succinic anhydride with a polyhydric alcohol (b) It can be obtained by reacting a monofunctional epoxy (d) or by reacting the polyhydric alcohol (b) with ε-capkratone in an amount of 1 to 6 mol per 1 mol of a hydroxyl group.

Examples of the polyhydric alcohol compound (b) that reacts with the acid anhydride compound (a) include ethylene glycol, propylene glycol, dipropylene glycol, 1,3 butylene glycol, and 1,4 butylene glycol. And diols such as cyclohexanedimethanol, triols such as glycerin, trimethylolethane, trimethylolpropane, and trishydroxymethylaminomethane, and tetrafunctional or higher-functional polyols such as pentaerythritol.

The monofunctional epoxy compound (d) to be reacted with the compound (c) obtained by reacting the acid anhydride compound (a) with the alcohol compound (b) is, for example, a trade name of Showa Shell Sekiyu KK "Currager E10", "Pes 10", Daicel Chemical Industries' trade name "AOEX
24 "etc.

And a second one consisting of the above oligoester
The hydroxyl value of the component is limited to 80 or more. The reason why the hydroxyl value of the second component is limited to 80 or more is that, when the hydroxyl value is less than 80, the cross-linking of the paint becomes insufficient and the scratch resistance of the coating film cannot be improved. Is.

The weight average molecular weight of the second component is
Limited to the range of 400-2000, 400-100
It is preferably within the range of 0. The weight average molecular weight of the second component is limited to the above range, when the weight average molecular weight is less than 400, the coating workability of the paint is deteriorated, and when it exceeds 2000, the effect of improving the scratch resistance is obtained. Because you will not be able to.

The mixing ratio of the first component composed of the acrylic resin and the second component composed of the oligoester is in the range of 40 to 80 parts for the first component and 20 to 60 parts for the second component. Limited. This is because if the first component is less than 40 parts and the second component is more than 60 parts, the acid resistance of the coating composition will be poor. In addition, the first component is 40
When the second component is less than 60 parts while exceeding the parts,
This is because the effect of improving the scratch resistance of the paint cannot be expected.

Examples of the isocyanate prepolymer as the third component include, for example, hexahydrodiisocyanate, xylene diisocyanate, hydrogenated xylene diisocyanate, aliphatic isocyanate such as isophorone diisocyanate, isocyanurate body of alicyclic isocyanates, and trimethylol. Examples thereof include a propane adduct body and a burette body.

The above-mentioned isocyanate prepolymer functions as a curing agent that reacts with the hydroxyl groups of the above-mentioned first component and second component. Specifically, the trade name "Sumijour N3500" manufactured by Sumitomo Bayer Urethane Co., Ltd. This is the case. The ratio of the isocyanate group contained in the third component composed of the isocyanate prepolymer to the hydroxyl group contained in the first and second components is limited to the range of 0.8 to 1.3. If this ratio is less than 0.8, the isocyanate groups remaining in the coating film after the reaction will cause deterioration of weather resistance, and the above ratio will be 1.3.
If it exceeds, the hydroxyl group remaining in the coating film causes a decrease in water resistance.

As the curing catalyst used when the first component composed of the acrylic resin and the second component composed of the oligoester are reacted with the third component composed of the isocyanate prepolymer to cure, phosphoric acid ester and dodecylbenzene are used. Examples thereof include organic acids such as sulfonic acid and p-toluenesulfonic acid and their amine acids, and organic tin compounds such as dibutyl susdilaurate and dibutyl tin malate and chelate compounds thereof.

Furthermore, when the above-mentioned first component and second component are reacted to form a coating material, various resins, solvents and colorants such as pigments or dyes, as well as other flow regulators and ultraviolet light absorbers are used. Needless to say, various conventionally known additives such as agents, light stabilizers, and silane coupling agents are added as necessary.

[0024]

According to the two-component urethane coating composition having the above-mentioned structure, the first composition is made of the acrylic resin mixed in a predetermined ratio.
By mixing the third component composed of the isocyanate prepolymer with the second component composed of the component and the oligoester, the hydroxyl group in the first and second components and the third component
The resin reacts with the isocyanate groups of the components to properly crosslink the resin.

[0025]

EXAMPLES Next, examples of the present invention will be described in comparison with comparative examples. In the following, all parts and% are based on weight unless otherwise specified.

(1) Synthesis of acrylic resin (first component) First, 40 parts of xylene was placed in a four-necked flask equipped with a stirrer, an inert gas inlet, a thermometer and a cooler.
After the temperature was raised to 30 ° C., 31.9 parts of “Plaxel FM-2”, trade name of Daicel Chemical Industries, Ltd., and styrene 13.
3 parts, 3.1 parts of ethylhexyl methacrylate and 2 parts
-Hydroxyethyl methacrylate 11.7 parts, ter
A mixture of 0.7 parts of butyl peroxy 2-ethylhexanoate is added dropwise over 3 hours. Further, 4 parts of xylene and 0.1 part of 2-hydroxyethyl methacrylate were added, and the mixture was kept at the above temperature for 3 hours to react,
An acrylic resin solution having a nonvolatile content of 60% is synthesized. As a result, a first example (molecular weight 7200) of the first component constituting the coating composition according to the present invention is obtained.

Similarly, by mixing the components in the composition ratios shown in Table 1 below, the glass transition temperature becomes 0.
Examples 2 to 9 of the first component (acrylic resin) having a hydroxyl value of 140 to 280 and a weight average molecular weight of 5,000 to 20,000 are obtained at -50 ° C.

[0028]

[Table 1]

Further, the acrylic resins according to Comparative Examples 1 to 5 were synthesized by synthesizing the respective components in the composition ratios shown in Table 2 below. In Comparative Example 1, the glass transition temperature is 0 ° C.
And the glass transition temperature is 50 ° C. in Comparative Example 2.
Is over. In Comparative Example 3, the hydroxyl value is 140
And the weight average molecular weight is 2000 in Comparative Example 5.
The value exceeds 0, and in Comparative Example 4, the weight average molecular weight is less than 5,000.

[0030]

[Table 2]

(2) Synthesis of oligoester (second component) Into the four-necked flask, a solvent of butyl acetate 200 was added.
Parts, 222 parts of an acid anhydride compound (a) composed of methylhexahydrophthalic anhydride, and 631 parts of a polyhydric alcohol (b) composed of glycerin, and heated to 130 ° C. and reacted for about 2 hours Then, the compound (c) is synthesized. After that, a monofunctional epoxy compound (d) 51 consisting of "Curular E10" under the trade name of Showa Shell Sekiyu KK
A tenth example (weight average molecular weight 808) of an oligoester which is the second component of the present invention is synthesized by adding 4.9 parts and 2 parts of dimethylimidazole and reacting for 2 hours.

Similarly, by mixing the respective components in the composition ratios shown in Table 3 below, the weight average molecular weight was 4
Example 11 of the second component in the range of 00-2000
In addition to synthesizing the oligoester of No. 14, Comparative Example 6 having a weight average molecular weight of less than 400 and Comparative Examples 7 and 8 of the oligoester having a weight average molecular weight of more than 2000 are synthesized.

[0033]

[Table 3]

(3) Preparation of Base Coat Resin 20 parts of xylene and 10 parts of butyl isoacetate were placed in the four-necked flask and stirred at 130 ° C. to obtain 20 parts of butyl acrylate and 10 parts of 2-hydroxyl ethyl methacrylate. Part, 20 parts of methyl metaarylate, 10 parts of butyl methacrylate, 0.05 part of the trade name "Perbutyl O" of NOF CORPORATION, and 0.05 part of the same "Perbutyl A", a monomer mixture for 3 hours. And let it drip.

After completion of the dropping, the mixture was stirred for 1 hour, 0.05 part of trade name "Perbutyl A" manufactured by NOF CORPORATION was added, and 10 parts of xylene was added after stirring for 2 hours to give a resin solution having a solid content of 60%. To get

(4) Preparation of Base Coat 50 parts of the base coat resin obtained as described above, and 5 parts of Asahi Kasei's trade name "Aluminum paste CR601S"
Mitsui Toatsu Chemicals Inc. product name "Uban 122" 21.5 parts, xylene 15 parts, butyl acetate 15 parts, Big Chemie product name "BYK307" 0.5 parts, Eastman product name " A base coat is prepared by mixing and stirring 5 parts of CAB531-1 "and 20 parts of toluene.

(5) Preparation of clear paint Examples 1 to 9 and Comparative Examples 1 to 5 of the above acrylic resin
And oligoester Examples 10-14 and Comparative Example 1
To 3 and a prescribed curing agent, curing catalyst and solvent were blended as shown in Tables 4 to 6 below to prepare clear coating materials A to Y by a conventional method. In addition, in Tables 4 to 6, Sumidule N3500 is a trade name of a curing agent (isocyanate prepolymer) manufactured by Sumitomo Bayer Urethane Co., Ltd. Further, in Tables 4 to 6, NCO / OH represents the ratio of the isocyanate group contained in the third component (isocyanate prepolymer) to the hydroxyl group contained in the first component (acrylic resin) and the second component (oligoester). Shows.

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

(6) Preparation of coated plate Xylene 50 is applied to the plate coated with electrodeposition and intermediate coating.
Parts of the above base coat diluted with FC (Ford Cup) # 4 for 12 seconds in a mixed solvent of 50 parts and 50 parts of butyl acetate. Then, after standing for 10 minutes, the two-pack type urethane coating composition consisting of the above clear coatings A to Y is treated with FC (Ford cup) # 4 for 18 seconds with a solvent consisting of xylene-sixahexynone (weight ratio = 60/40). After adjusting the viscosity as described above, the solution was applied on the plate and left for 10 minutes, and then dried at a temperature of 140 ° C. for 15 minutes.

(7) Comparison and Evaluation The coated plate on which the finished coating films of the clear coating materials A to Y were formed as described above was fixed to the ceiling of the automobile, and the car was washed repeatedly by the car washer. Then, the scratches produced on the coating film by the rubbing of the car wash brush were visually observed, and the scratch resistance was evaluated according to the state of the scratches. The evaluation results shown in Table 7 below were obtained. The number of car washes was 20 each.

Further, 1 cc of sulfuric acid having a concentration of 5% was dripped onto the coated surfaces of the clear coatings A to Y and dried at a temperature of 50 ° C., and then the state of the coated surfaces was visually observed to confirm that the coating film had an acid resistance. And the above-mentioned clear paints A to Y
By visually observing the skin of the coated surface of No. 3, the quality of the work made by coating was evaluated, and the evaluation results shown in Table 7 below were obtained.

[0044]

[Table 7]

As can be seen from Table 7, the acrylic resins of Examples 1 to 9 (first component) and the oligoesters of Examples 10 to 14 (second component) blended in a predetermined ratio,
In the coating materials A to P according to the present invention using the curing agent (Sumijour N3500) made of the isocyanate prepolymer, scratches were scarcely generated. On the other hand, the acrylic resins of Comparative Examples 1 to 5 and Comparative Examples 6 to 8
In the coating materials Q to Y according to the comparative examples using the oligoesters, the occurrence of noticeable scratches was observed.

A paint using the oligoester according to Comparative Example 6, that is, a paint using the oligoester having a weight average molecular weight of 256 as shown in Table 3 and having an extremely small molecular weight as compared with the examples of the present invention. In V, the solvent was vaporized before the coating was applied, and it could not be used as a coating.

In the coating materials A to P according to the present invention,
While the acid resistance and workability were both good, it was confirmed that the paint Q using the acrylic resin according to Comparative Example 1 and the oligoester according to Comparative Example 7 had poor acid resistance. It was In addition, a paint R using the acrylic resin according to Comparative Example 2 and the oligoester according to Comparative Example 7
Then, it was confirmed that the workability of the painting was poor, as it was a little defective.

As described above, the two-component urethane coating composition according to this embodiment contains the first component made of a specific acrylic resin and the second component made of an oligoester in a predetermined ratio, and both of them are mixed. A two-component urethane coating having excellent acid resistance because it is configured to cure the coating by using a third component composed of an isocyanate prepolymer containing a predetermined proportion of isocyanate groups that react with the hydroxyl groups of the component. It can be seen that the scratch resistance of the coating film can be effectively improved and the workability of the coating can be maintained in a good state without impairing the characteristics of 1.

[0049]

As described above, according to the present invention, 40 to 80 parts of the first component made of a specific acrylic resin, 20 to 60 parts of the second component made of a specific oligoester, and hydroxyl groups thereof are included. Isocyanate group ratio is 0.8
A two-component urethane coating composition having excellent acid resistance, since it is a two-component urethane coating composition containing as an essential component a third component consisting of an isocyanate prepolymer within the range of 1.3 to 1.3. Without damaging the characteristics of
There are advantages that the scratch resistance of the coating film can be effectively improved and the coating workability can be maintained in a good state.

That is, the glass transition temperature of the first component is set to 0 to 50 ° C., the hydroxyl value is set to 140 to 280, the weight average molecular weight is set to 5,000 to 20,000, and the hydroxyl group of the second component is set to 80 or more. Weight average molecular weight is 4
Since it is set within the range of 00 to 2000, it is possible to prevent the viscosity of the coating material from becoming unnecessarily high and prevent the coating workability of the coating material from being lowered. Further, it is possible to properly crosslink the first component and the second component with the curing agent composed of the third component to improve the scratch resistance thereof and to maintain the acid resistance of the coating film in a good state. it can.

Claims (1)

[Claims] 1. The following first to third components are contained as essential components, and the second component is added to 20 to 80 parts of the first component.
20 to 60 parts of the component is blended, and the ratio of the isocyanate group of the third component to the hydroxyl group contained in the first component and the second component is set within the range of 0.8 to 1.3. Two-component urethane coating composition. First component: glass transition temperature 0 to 50 ° C., hydroxyl value 1
40 to 280, weight average molecular weight of 5,000 to 20,000
Acrylic resin in the range of 2nd component: hydroxyl value is 80 or more, weight average molecular weight is 4
Oligoester in the range of 00 to 2000 Third component: Isocyanate prepolymer