JP2003292886A - Urethane paint composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-liquid urethane-type low VOC (volatile organic chemicals) paint containing a high solid-type polyol as a binder. <P>SOLUTION: The paint composition comprises (a) an acrylic polyol with a hydroxy group value of 80-200, a number average molecular wt. of 1,500-3,000, a wt. average molecular wt. of 2,500-6,000, a solid component ratio of 65-85 wt.% and viscosity of Z or less determined with a bubble viscometer at 25°C and (b) an isocyanate curing agent. The above acrylic polyol is prepared by polymerization of a monomer mixture consisting of 5-60 wt.% isobornyl(meth) acrylate, 35-60 wt.% ethylenic unsaturated monomer containing a hydroxy group and 0.1-5 wt.% ethylenic unsaturated monomer containing a carboxy group with an equivalent ratio of (a) the acrylic polyol to (b) the isocyanate curing agent is 1/0.2-to 1/1.8. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a urethane coating composition, and more particularly to a high solid type urethane coating composition.

[0002]

2. Description of the Related Art Volatile organic compounds (V
Attempts have been made to reduce OC). Since most of VOCs in paints are solvents, paints containing a high solid type resin having the same viscosity and a high solid content are attracting attention as low VOC paints. In order to achieve low VOCs in the 2-liquid urethane type coatings that are usually used for coating substrates with low heat resistance such as plastics and automobile repairs, it is important to make the polyol, which is the binder, high solid. Come on.

On the other hand, a polymer obtained from isobornyl (meth) acrylate, which is an acrylic monomer having an alicyclic hydrocarbon group, has a high glass transition temperature,
It is known that high drying properties can be obtained by using it as a binder for paints. Japanese Unexamined Patent Publication No. 2000-273393 discloses that a copolymer obtained from this isobornyl (meth) acrylate and styrene is contained,
A coating composition capable of forming a coating film having high gloss and excellent abrasiveness is disclosed. However, since the copolymer contained in this coating composition is not of high solid type, low V
It is difficult to achieve OC.

[0004]

The object of the present invention is to include a high solid type polyol as a binder.
It is to provide a liquid urethane type low VOC paint.

[0005]

The urethane coating composition of the present invention comprises (a) a hydroxyl value of 80 to 200 and a number average molecular weight of 1
500-3000, weight average molecular weight 2500-600
A coating composition containing 0, an acrylic polyol having a solid content of 65 to 85% by weight, a viscosity measured at 25 ° C. using a bubble viscometer of Z or less, and (b) an isocyanate curing agent, wherein a) A monomer mixture in which the acrylic polyol comprises 5 to 60% by weight of isobornyl (meth) acrylate, 35 to 60% by weight of a hydroxyl group-containing ethylenically unsaturated monomer, and 0.1 to 5% by weight of a carboxyl group-containing ethylenically unsaturated monomer. Is obtained by polymerizing the above, wherein the equivalent ratio of the above (a) acrylic polyol and (b) isocyanate curing agent is 1 / 0.2 to 1 / 1.8.

The polymerization of the monomer mixture for obtaining the above-mentioned (a) acrylic polyol may be carried out at 150 to 200 ° C., or may be carried out using a reactor capable of keeping the reaction system in a closed state.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The urethane coating composition of the present invention comprises:
It contains (a) a high solid type acrylic polyol and (b) an isocyanate curing agent.

The (a) acrylic polyol has a hydroxyl value of 80 to 200, a number average molecular weight of 1500 to 3000, a weight average molecular weight of 2500 to 6000, and a solid content of 65 to 85.
It has a special value that the viscosity measured by weight% at 25 ° C. using a bubble viscometer is Z or less.

If the hydroxyl value is less than 80, curing will not proceed sufficiently, and if it exceeds 200, the water resistance of the coating film obtained will be poor.
When the number average molecular weight and the weight average molecular weight are less than the lower limits, it is difficult to produce and the coating film performance is poor, and when the upper limits are exceeded, high solidification is difficult. If the solid content is less than 65% by weight, high solidification is achieved, and if the solid content exceeds 85% by weight, it is produced by a usual method.
Each is difficult. A preferable solid content is 70 to 80% by weight. The solid content can be determined, for example, from the change in weight when heated at 105 ° C. for 3 hours.

The (a) acrylic polyol is
The viscosity measured at 25 ° C. using a bubble viscometer is Z or less. The high solid type means one satisfying the conditions of the solid content and the viscosity.

The above-mentioned (a) high solid type acrylic polyol includes isobornyl (meth) acrylate 5 to
60% by weight, hydroxyl group-containing ethylenically unsaturated monomer 35
It is obtained by polymerizing a monomer mixture consisting of ˜60% by weight and 0.1 to 5% by weight of a carboxyl group-containing ethylenically unsaturated monomer. The above ratio is based on the total weight of each component.

The above-mentioned isobornyl (meth) acrylate is used to increase the hardness of the obtained coating film. If the amount is less than 5% by weight, the object cannot be achieved, and if it exceeds 60% by weight, the target acrylic polyol may not be obtained. A preferred range is 25 to 45% by weight.

The hydroxyl group-containing ethylenically unsaturated monomer is for introducing a hydroxyl group that reacts with an isocyanate curing agent described later. If the amount is less than 35% by weight, the curing will be insufficient, and if it exceeds 60% by weight, the water resistance of the resulting coating film may be poor. The preferred range is 40
˜55 wt%. Specific examples of the hydroxyl group-containing ethylenically unsaturated monomer include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, allyl alcohol,
Methacrylic alcohol, an adduct of hydroxyethyl (meth) acrylate and ε-caprolactone can be mentioned. Among these, preferred are hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, and adducts of hydroxyethyl (meth) acrylate with ε-caprolactone.

On the other hand, the carboxyl group-containing ethylenically unsaturated monomer is used to impart a catalytic function to the acrylic polyol to accelerate the curing reaction. If the amount is less than 0.1% by weight, the curability is insufficient and the amount is 5% by weight.
If it exceeds, the water resistance of the coating film deteriorates and the pot life of the urethane coating composition becomes shorter. The preferred range is 0.5 to
It is 1.5% by weight. Specific examples of the carboxyl group-containing ethylenically unsaturated monomer include acrylic acid, methacrylic acid, acrylic acid dimer, crotonic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl succinic acid, and ω-carboxy-polycaprolactone. Mono (meth) acrylate, isocrotonic acid, α-hydro-ω-((1-oxo-2-propenyl) oxy) poly (oxy (1-oxo-1,6-hexanediyl)),
Maleic acid, fumaric acid, itaconic acid, 3-vinylsalicylic acid, 3-vinylacetylsalicylic acid and the like can be mentioned. Among these, preferred is acrylic acid,
Methacrylic acid and acrylic acid dimer.

The above-mentioned monomer mixture contains the above-mentioned three kinds of ethylenically unsaturated monomers within the range of the respective contents, and does not adversely affect various properties such as the curing reactivity of the resulting acrylic polyol. May be further included. Examples of the other monomer include (meth) acrylic acid esters (for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate,
T-Butyl (meth) acrylate, (meth) acrylic acid 2
-Ethylhexyl, lauryl methacrylate, phenyl acrylate, cyclohexyl methacrylate, t-butylcyclohexyl (meth) acrylate, dicyclopentadienyl (meth) acrylate, dihydrodicyclopentadienyl (meth) acrylate, etc.), Polymerizable amide compound (for example, (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N , N
-Dioctyl (meth) acrylamide, N-monobutyl (meth) acrylamide, N-monooctyl (meth) acrylamide 2,4-dihydroxy-4'-vinylbenzophenone, N- (2-hydroxyethyl) acrylamide, N- (2- Hydroxyethyl) methacrylamide, etc.), polymerizable aromatic compounds (eg, styrene, α-
Methyl styrene, vinyl ketone, t-butyl styrene,
Parachlorostyrene and vinylnaphthalene etc.), polymerizable nitrile (eg acrylonitrile, methacrylonitrile etc.), α-olefin (eg ethylene, propylene etc.), vinyl ester (eg vinyl acetate, vinyl propionate etc.), diene (Eg, butadiene, isoprene, etc.), polymerizable aromatic compound, polymerizable nitrile,
Mention may be made of α-olefins, vinyl esters and dienes.

The above-mentioned polymerization can be carried out by radical polymerization in a well-known solution, but in order to obtain a polymer having a molecular weight in the above range, the polymerization temperature is 130-.
It is necessary to raise the temperature to 140 ° C., which is higher than usual, to increase the number of initiators such as azo type and peroxide type, and to use chain transfer agents such as mercapto compounds and halogenated compounds together. However, since the acrylic polyol usually obtained under these conditions has a solid content of less than 65% by weight,
In order to obtain the acrylic polyol having the desired solid content, the step of distilling off the solvent is further required. When a solvent having a relatively high boiling point is used to increase the polymerization temperature, a large amount of energy is required for distilling off the solvent, and the evaporation rate of the solvent at the time of forming the coating film becomes slow. Have a point. Further, increasing the amount of the initiator or the chain transfer agent is not preferable in terms of cost, and the above-mentioned method by radical polymerization in a well-known solution is not efficient.

Therefore, by carrying out the above polymerization at 150 to 200 ° C., the acrylic polyol having a solid content of 65% by weight or more can be obtained in one step without distilling off the solvent. In addition, since the boiling point is not easily restricted by the selection of the polymerization solvent, it is possible to select a solvent having an appropriate volatilization rate at the time of forming the coating film. In order to carry out the above polymerization at 150 to 200 ° C., it is preferable to use a reactor capable of keeping the reaction system in a closed state. When a solvent having a boiling point lower than the polymerization reaction temperature is selected by using a reactor capable of sealing the reaction system, the pressure in the reaction vessel is necessarily atmospheric pressure or higher during the polymerization, but the pressure is It does not affect the properties of the acrylic polyol thus obtained.

When the above polymerization is carried out at 150 to 200 ° C.,
Examples of the initiator include azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide, para. Chlorobenzoyl peroxide, di (t-amyl) peroxide, di (t-butyl) peroxide, t-amyl peroxyacetate, t-butyl peroxyacetate,
Lauroyl peroxide, t-amyl peroxy-2
-Ethyl hexanoate, t-butyl peroxy-2-
Ethyl hexanoate and the like can be used. The amount used is, for example, based on the above monomer mixture.
It is 0.5 to 10% by weight. When a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer are used, an amount corresponding to 5 to 10% by weight of the above monomer mixture can be used.

As the solvent used for the polymerization, various types such as hydrocarbon type, ester type, ketone type alcohol type and ether type can be used. However, when the polymerization temperature is taken into consideration, it has a boiling point of 100 ° C. or higher. It is preferable to use a solvent. In addition, these solvents can be used in combination of 2 or more types.

Polymerization is carried out, for example, for 2 to 9 hours in the above temperature range, whereby the acrylic polyol can be obtained in one step.

As the (b) isocyanate curing agent, which is another component contained in the urethane coating composition of the present invention, those which are generally used as curing agents for urethane coatings can be used.

Aliphatic diisocyanates such as lysine diisocyanate, hexamethylene diisocyanate and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4 (or 2,6)
-Cyclic aliphatic diisocyanates such as diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate) and 1,3- (isocyanatomethyl) cyclohexane; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate and diphenylmethane diisocyanate Examples: trivalent or higher polyisocyanates such as lysine triisocyanate and the like.
In addition to isocyanurate and biuret type adducts which are multimers of these isocyanate compounds, those added to polyhydric alcohol or low molecular weight polyester resin can also be used. Further, a so-called blocked isocyanate in which a part or all of the isocyanate group of the above isocyanate curing agent is blocked with an active hydrogen compound such as an alcohol type, a phenol type, a lactam type, an oxime type and an active methylene type can also be used.

In the urethane coating composition of the present invention, the equivalent ratio of (a) acrylic polyol to (b) isocyanate curing agent is 1 / 0.2 to 1 / 1.8. Outside of these ranges, curing may be inadequate.

The urethane coating composition of the present invention contains, in addition to the above-mentioned components, pigments, curing catalysts, additives usually added to coatings, such as surface conditioners, thickeners, antioxidants, and UV inhibitors. It may contain other ingredients.

The urethane coating composition of the present invention is obtained by mixing the above components and other components.
When the above (b) isocyanate curing agent is not blocked, it is preferable to use a two-pack type coating composition in which the above (a) acrylic polyol and (b) isocyanate curing agent are separated, and to mix both at the time of use. At that time, the above-mentioned other components are generally mixed in (a) the acrylic polyol.

The urethane coating composition of the present invention can be applied to various substrates. Examples of the base material include metals such as iron, aluminum, copper or alloys thereof; inorganic materials such as glass, cement and concrete; polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, polyamide resin, acrylic resin,
Examples thereof include resins such as vinylidene chloride resin, polycarbonate resin, polyurethane resin, and epoxy resin, and various plastic materials such as FRP; natural and synthetic materials such as wood and fiber materials (paper, cloth, etc.). Further, a coating film made of another paint may be formed on these base materials.

The urethane coating composition of the present invention can be applied using various coating methods, for example, a dry film thickness of 10
A coating film can be obtained by coating the coating film at about 80 μm and then drying at room temperature to about 90 ° C.

[0028]

EXAMPLES Production Example Production of Acrylic Polyol 24 parts of butyl acetate was placed in a pressure resistant vessel equipped with a stirrer, a thermometer, a reflux condenser, and a dropping pump, and under a nitrogen atmosphere,
The temperature was raised to 100 ° C. with stirring. The reaction vessel was sealed at 100 ° C. and the temperature was raised to 170 ° C., 41 parts of isobornyl (meth) acrylate, 38 parts of a hydroxyl group-containing monomer obtained by adding 1 mol of ε-caprolactone to hydroxyethyl methacrylate, and 14 parts of hydroxyethyl methacrylate.
Part, 100 parts of a monomer mixture consisting of 6 parts of styrene and 1 part of methacrylic acid, and a mixed solution of 4 parts of di (t-amyl) peroxide and 7 parts of butyl acetate were added dropwise using a dropping pump over 3 hours. . 170 ℃ after dropping
The heating was continued for 30 minutes. Furthermore, di (t-amyl)
A mixed solution of 0.4 parts of peroxide and 3 parts of butyl acetate was added dropwise and heated for 1 hour to complete the polymerization reaction. The acrylic polyol thus obtained has a hydroxyl value of 15
0, number average molecular weight 1960, weight average molecular weight 3160,
It was a uniform transparent solution having a solid content of 73% by weight and a viscosity of U measured at 25 ° C. using a Gardner bubble viscometer.

Example Preparation of Urethane Coating Composition 86.3 parts of the acrylic polyol obtained in the preparation example, 0.5 part of tin catalyst, 1.5 parts of UV absorber, 0.8 parts of light stabilizer.
Parts, surface conditioning agent 1.4 parts, N-methylpyrrolidone 9.5
Desmodur N3600 (Sumitomo Bayer Urethane Co., Ltd., nurate type isocyanate curing agent, solid content 100%) was added to the mixture of the mixture and the parts so that the equivalent ratio of hydroxyl group / isocyanate group was 1/1. Using a thinner for dilution, Ford Cup No. The viscosity was adjusted at 20 ° C. so that it was 4 seconds and 20 seconds to obtain a urethane coating composition.

Measurement of VOC Value It is defined as the gram weight of volatile components contained in 1 liter of a paint, and 400 g / l or less is acceptable. here,
It was determined by multiplying 980 g of 1 liter of the paint by volatile component content obtained by heating at 105 ° C. for 3 hours. The urethane coating composition thus obtained had a VOC value of 376 g / l. Further, the VOC value of the conventional two-pack type urethane coating composition containing an acrylic polyol which is not a high solid type was 477 g / l.

Evaluation of Coating Film The above urethane coating composition and a conventional two-pack type urethane coating composition were spray-coated on a test panel so that a dry film thickness was 30 μm. This was dried at 80 ° C. for 35 minutes to obtain a test plate. The test plate thus obtained,
When the following respective items were evaluated, both the above urethane coating composition and the conventional two-pack type urethane coating composition satisfied the acceptance criteria for all the items.
The mirror gloss of the urethane coating composition was 89.
0, the conventional two-component urethane coating composition was 89.1, and the polishability was 60,
The conventional two-component urethane coating composition was 58.

<Adhesion> 11 pieces of vertical and horizontal cuts having a width of 2 mm were made on the test plate in the shape of scoring, and then the presence or absence of scoring when the scoring tape was peeled off was evaluated. Those without peeling are acceptable.

<Water resistance> After immersing the test plate in warm water of 40 ° C. for 24 hours, the visual evaluation and the above-mentioned adhesion evaluation were performed by visual observation. The appearance evaluation is passed if no abnormality is recognized.

<Moisture resistance> The test plate was tested at 50 ° C. and a relative humidity of 95.
%, After standing for 240 hours, the visual evaluation and the adhesiveness evaluation were performed visually. The appearance evaluation is passed if no abnormality is recognized.

<Alkali resistance> A drop of an aqueous solution of sodium hydroxide having a concentration of 0.1 mol / l was dropped on a test plate using a spoid. After leaving at 55 ° C. for 4 hours, the drops were wiped off, and it was visually confirmed whether or not a mark remained. If there are no traces left, it passes.

<Acid resistance> One drop of sulfuric acid having a concentration of 0.1 mol / l was dropped on a test plate by using a spoid. After leaving at room temperature for 24 hours, the droplets were wiped off and it was visually confirmed whether or not there were marks. If there are no traces left, it passes.

<Specular glossiness> The glossiness was measured by a 20 degree method using a gloss meter. Eighty-five or more pass.

<Impact resistance> A weight of 3 kg is used for 60 at room temperature.
cm, the one which is dropped from a height of 40 cm at −30 ° C. and has no crack in the coating film is acceptable.

<Polishability> The test plate was sanded with No. 1500 sandpaper, the compound was applied, and the gloss when buffing was performed with a polisher was measured. 50 or more are acceptable.

[0040]

EFFECT OF THE INVENTION Since the urethane coating composition of the present invention contains a high solid type acrylic polyol, it is possible to reduce the VOC of the coating. Further, by performing the polymerization reaction under pressure, the high solid type acrylic polyol can be efficiently obtained. Further, since the acrylic polyol contains a predetermined amount of isobornyl (meth) acrylate, it is possible to obtain a coating film which is stiffer than its molecular weight, and is useful for applications such as automobile repair. Further, since the urethane coating composition of the present invention can be cured at room temperature, it is useful for substrates having low heat resistance such as plastics.

Continued front page    F-term (reference) 4J034 BA03 DA01 DA05 DB03 DB08                       DC07 DC12 DC43 DP03 DP18                       HA07 HA08 HC03 HC12 HC16                       HC17 HC22 HC46 HC54 HC61                       HC64 HC67 HC71 HC73 MA01                       MA21 QA02 QA03 QA05 QA07                       RA07                 4J038 DG191 MA14 MA15                 4J100 AD03P AJ01R AJ02R AJ08R                       AJ09R AL08P AL08Q AL08R                       AL09P BA03P BA16R BA21P                       BC07Q BC43R CA05 DA01                       DA09 DA30 FA28 FA29 FA47                       JA01

Claims (3)

[Claims] (A) Hydroxyl value 80-200, number average molecular weight 1500-3000, weight average molecular weight 2500-60.
00, a solid content of 65 to 85% by weight, a coating composition containing an acrylic polyol having a viscosity of Z or less measured at 25 ° C. using a bubble viscometer and (b) an isocyanate curing agent, a) A monomer mixture in which the acrylic polyol comprises 5 to 60% by weight of isobornyl (meth) acrylate, 35 to 60% by weight of a hydroxyl group-containing ethylenically unsaturated monomer, and 0.1 to 5% by weight of a carboxyl group-containing ethylenically unsaturated monomer. A urethane coating composition obtained by polymerizing the above, wherein the equivalent ratio of the (a) acrylic polyol and the (b) isocyanate curing agent is 1 / 0.2 to 1 / 1.8. object. 2. The urethane coating composition according to claim 1, wherein the polymerization of the monomer mixture for obtaining the acrylic polyol (a) is carried out at 150 to 200 ° C. 3. The urethane coating composition according to claim 2, wherein the polymerization of the monomer mixture for obtaining the (a) acrylic polyol is carried out using a reactor capable of keeping a reaction system in a closed state.