JPH0684487B2 - Resin composition for urethane paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a pigment dispersibility which is a characteristic of a polyester resin,
The present invention relates to a urethane coating composition that provides an excellent coating film having both flexibility and quick drying characteristics, hardness, weather resistance, and stain resistance, which are characteristics of acrylic resins.

(Conventional Technology and Problems) In the paint industry, from the viewpoint of energy saving, a room temperature or low temperature curable paint is demanded.

Conventionally, urethane coatings made of isocyanate compounds for acrylic resins have been generally used for applications requiring weather resistance, and the drying performance, hardness, and stain resistance were generally at satisfactory performance levels. However, the acrylic resin has a drawback that it has poor dispersibility for pigments having a large oil absorption property such as carbon black and organic pigments, and thus problems such as pigment dispersion during storage tend to occur. In addition, in applications where flexibility is required, there is an example in which the glass transition point of acrylic resin is designed to be low (for example, around 0 ° C), but in this case, drying property, hardness, stain resistance Is poor, and it is difficult to balance the two.

On the other hand, a urethane coating composed of a polyester resin and an isocyanate compound has satisfactory performance in terms of pigment dispersion and flexibility, but has a slow drying property and is poor in weather resistance and stain resistance as compared with an acrylic resin type.

The present invention aims to provide a urethane coating which does not have such drawbacks.

(Means for Solving Problems) The inventors of the present invention have diligently studied a hybrid resin composition of both systems that makes use of the excellent characteristics of both polyester and acrylic coatings, and as a result, make both resins react with each other. According to the present invention, it was found that a resin composition capable of forming a uniform solution even when dissolved in a solvent can be obtained, whereby a urethane coating material having the excellent features of both systems can be obtained, and the present invention was reached.

That is, the present invention is that when 5 to 95 parts by weight of a polyester resin having a hydroxyl value of 5 to 200 KOHmg / g and 95 to 5 parts by weight of an acrylic resin having a hydroxyl value of 5 to 200 KOHmg / g are reacted with each other and dissolved in a solvent. A resin composition for urethane coatings, which comprises a resin composition (A) forming a uniform solution and a curing agent (B) which is an isocyanate compound.

The polyester resin used in the present invention must have a hydroxyl value of 5 to 200 KOHmg / g, and a hydroxyl value of 20 to 150 KOHmg.
It is preferably / g. If the hydroxyl value is less than 5 KOHmg / g, the reaction with the acrylic resin does not proceed sufficiently, the compatibility is poor, the resin solution becomes cloudy, and phase separation occurs. Also, the hydroxyl value is 200KOHmg
If it exceeds / g, the reaction with the acrylic resin will proceed rapidly and gelation tends to occur, which makes it difficult to control the reaction. Further, gelation will occur partially and a uniform solution cannot be obtained. The hydroxyl groups other than those involved in the reaction with the acrylic resin act as a cross-linking reaction group with the curing agent.

Such polyester resins include, for example, terephthalic acid, isophthalic acid, phthalic anhydride, naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, 1,10-decanedicarboxylic acid, cyclohexanedicarboxylic acid and tricarboxylic acid as carboxylic acid components. Meritic acid, maleic acid,
Polyvalent carboxylic acids such as fumaric acid and lower alcohol esters thereof, hydroxycarboxylic acids such as paraoxybenzoic acid and monovalent carboxylic acids such as benzoic acid can be used.

Further, as the alcohol component, for example, ethylene glycol, diethylene glycol, 1,3-propanediol,
1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 3-methyl-pentanediol, 2,2'-
Diethyl-1,3-propanediol, 2-ethyl 1,3-hexanediol, neopentyl glycol, trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, ethylene oxide adduct of bisphenol A, propylene oxide addition of bisphenol A Compounds, hydrogenated bisphenol A propylene oxide adducts, and the like can be used.

Further, it is a matter of course that flaxseed oil, tung oil, safflower oil, dehydrated castor oil, cottonseed oil, coconut oil and fatty acids thereof can be used if necessary.

Such a polyester resin can be obtained by a general transesterification method or a direct esterification reaction of one or more kinds of the above-mentioned carboxylic acid component and one or more kinds of the above-mentioned alcohol component.

The number average molecular weight of the polyester resin measured by the GPC method is preferably 500 to 10,000.

The acrylic resin used in the present invention has a hydroxyl value of 5 to 5.
It is necessary to be 200 KOHmg / g, preferably 20 to 150 KOHmg / g. If the hydroxyl value is less than 5 KOHmg / g, the reaction with the polyester resin does not proceed sufficiently, the compatibility is poor, and the resin solution becomes turbid and phase separates. Also, the hydroxyl value is 200KOHmg
If it exceeds / g, the reaction with the polyester resin will rapidly proceed, gelation tends to occur, the reaction control is difficult, and gelation will occur partially, and a uniform solution cannot be obtained.

For such acrylic resin, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 1,4-butanediol (meth) acrylate and the like can be used as the hydroxyl group-containing monomer.

(Meth) acrylic acid, itaconic acid,
Maleic acid, fumaric acid and itaconic acid, maleic acid, lower alcohol-modified monoalkyl esters of fumaric acid and methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl ( (Meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, tridecyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, Glycidyl (meth) acrylate, α-methylglycidyl (meth)
Esters of acrylic acid and methacrylic acid such as acrylate, β-methylglycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate can be used. Other copolymerizable monomers include styrene and α-
Methyl styrene, vinyl toluene, acrylonitrile,
Methacrylonitrile, vinyl acetate, vinyl propionate, acrylamide, methacrylamide, methylol acrylamide, methylol methacrylamide, vinyl chloride, propylene, ethylene, C ₄ -C ₂₀ α-olefins and the like can be mentioned.

Such an acrylic resin can be produced by any known polymerization method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method and an emulsion polymerization method. At that time, as a polymerization initiator, azobisisobutyronitrile, 4,4′-azobis (4-cyanopentanoic acid), benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, cumene hydroperoxide, Potassium persulfate, hydrogen peroxide, 2,2'-azobis [2-methyl-N- (2-hydroxyethyl) propioamide] and the like can be used,
Further, if necessary, dodecyl mercaptan, mercaptoethanol, etc. can be used as a chain transfer agent.

The number average molecular weight of the acrylic resin measured by the GPC method is 500.
~ 20,000 is preferred.

The resin composition (A) of the present invention is a composition in which the polyester resin and the acrylic resin react with each other. When the polyester resin is more than 95 parts by weight or the acrylic resin is less than 5 parts by weight in this composition, only the characteristics of the polyester resin are emphasized and the features of both resins, which are the object of the present invention, are emphasized. It is impossible to form an excellent coating film having both Conversely, if the acrylic resin is more than 95 parts by weight or the polyester resin is less than 5 parts by weight,
Only the characteristics of the acrylic resin are emphasized and the object of the present invention cannot be achieved.

The resin composition (A) of the present invention is a polyester resin 5 to 95.
180 parts by weight and acrylic resin 95-5 parts by weight are mixed.
10 minutes to 5 hours at a temperature of 80 ° C, preferably 30 minutes to 3 hours,
It can be produced by reacting the ester group and the hydroxyl group present in both resins with each other under the condition that the transesterification reaction can be carried out. The transesterification reaction does not necessarily have to proceed completely, and only a part thereof may have reacted. Then, a suitable solvent can be added to obtain a resin solution, and further, butylated melamine, methylated melamine, butylated urea, amino resins such as methylated urea, or hexamethylene diisocyanate, isophorone diisocyanate, toluene diisocyanate, xylylene diisocyanate. Isocyanates or their polyaddition compounds such as water adducts, trimethylolpropane adducts, isocyanurates, etc. are allowed to react with each other by reacting 0.1 to 5% by weight of the resin solid content to bond the hydroxyl groups remaining in the acrylic resin and polyester resin to each other. It is also possible to proceed with the reaction.

As the solvent of the resin composition (A) of the present invention, toluene,
Aromatic solvent such as xylene, ester solvent such as ethyl acetate, butyl acetate or cellosolve acetate, ketone solvent such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ether solvent such as dioxane and tetrahydrofuran, chlorine solvent such as tetrachloroethane The solvents can be used alone or as a mixture.

The resin composition (A) in which the polyester resin and the acrylic resin of the present invention partially react with each other becomes a uniform resin solution when dissolved in the above-mentioned solvent, and does not undergo phase separation even when left standing and stored. . When the phases are separated to form a non-uniform solution, a coating film having a smooth and excellent gloss cannot be obtained when it is used as a paint.

Further, in the present invention, an isocyanate compound is used as the curing agent (B). As the isocyanate compound,
A polyvalent isocyanate such as a polyvalent isocyanate, a polymer of a polyvalent isocyanate, an adduct of a polyvalent isocyanate and a polyvalent alcohol, or the like can be used.

As the polyvalent isocyanate, tolylene diisocyanate, metaphenylene diisocyanate, naphthylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, dicyclohexyl propane diisocyanate, trimethylpentane diisocyanate, etc. aromatic, aliphatic or alicyclic Group polyvalent isocyanates are exemplified.

The isocyanate compound used in the present invention has an unblocked free isocyanate group.
Blocked materials require heating during curing, which is not preferable.

The isocyanate compound used in the present invention is a curing agent component that causes a cross-linking reaction with the hydroxyl group in the resin composition (A) during curing of the coating material to form a coating film.

The mixing ratio of the resin composition (A) and the isocyanate compound in the coating composition is such that the hydroxyl groups contained in the resin composition (A) and the isocyanate groups in the isocyanate compound are equivalent to the former 1 equivalent and the latter 0.5. It is desirable to be ~ 2.0 equivalents. In this equivalent ratio because the isocyanate group is less than 0.5 equivalents the cross-linking density of the cured coating is not sufficient, chemical resistance, solvent resistance, various physical properties of the coating such as water resistance are not sufficient,
If it exceeds 2.0 equivalents, the cured coating film becomes extremely hard and is not practicable due to poor flexibility, bending property and the like.

The urethane coating composition of the present invention can obtain a uniform resin solution by additionally adding an acrylic resin and / or a polyester resin in addition to the resin composition (A) and a curing agent which is an isocyanate compound, These additional uses are also possible. It is considered that this is because the resin composition (A) partially improved the compatibility with both resins due to the mutual reaction of both resins.

In addition, as various materials generally used for paints, coloring pigments such as titanium oxide, carbon black and red iron oxide, and extender pigments such as clay and calcium carbonate,
Barium sulfate, talc, alumina, silica, silica powder, etc. can be blended and used.

In addition, fibrin derivatives, petroleum resins, phenolic resins, ketone resins, synthetic rubbers, unsaturated polyester resins, natural resins such as rosin, synthetic resins, leveling agents, anti-sagging agents, defoaming agents, surfactants, and curing accelerators. Various auxiliaries such as agents can also be used.

The coating composition of the present invention can be prepared by a method known per se. For example, each of the above-mentioned components together with an organic solvent is mixed and dispersed by a steel mill, a pepper mill, an attritor, a sand mill, a bladed high speed agitator, or the like. It can be adjusted by charging the mixture into a mixture and uniformly mixing and dispersing. Examples of the organic solvent used at that time include hydrocarbons such as xylene and solvent naphtha, ketones such as methyl isobutyl ketone and cyclohexanone, ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol. Examples thereof include those used in ordinary coating compositions such as esters such as monobutyl ether acetate and ethers.

The amount of the total solvent can be selected in an appropriate range depending on the coating method used, and is generally 10 to 90% by weight in the total coating composition.

The coating composition of the present invention can be coated on metals, plastics, inorganic materials, inorganic-organic composites or woodworking products by a conventional coating method such as spray coating, brush coating or roll coating. The method for curing the coating film is usually at room temperature, but at 40-150 ° C
It is also possible to heat for a minute to 60 minutes.

(Examples) Next, the present invention will be specifically described with reference to Reference Examples, Examples and Comparative Examples. All parts and% are based on weight unless otherwise specified.

Reference Example 1 (Preparation Example of Polyester Resin) A raw material shown in Table 1 was charged into a four-necked flask equipped with a stirrer, a thermometer, a condenser with a stack din, and a nitrogen introducing tube, and the temperature was about 10 at 220 ° C in a nitrogen stream. The reaction is carried out while distilling off the reaction product to produce polyester resin A-1.
~ A-5 was obtained.

Reference Example 2 (Preparation example of acrylic resin) 100 parts of xylene was charged into a four-necked flask equipped with a stirrer, a thermometer, and a condenser, and heated to 100 ° C. The raw materials shown in Table 2 were dropped therein for 4 hours and then kept at the same temperature for 6 hours to obtain acrylic resins B-1 to B-5 having a solid content of 50%.

Reference Example 3 (Preparation Example of Resin Composition (A)) The polyester resin and acrylic resin shown in Table 3 were placed in a four-necked flask equipped with a stirrer, a thermometer, and a condenser with a stack Din, heated and heated to xylene. The temperature was raised to 220 ° C while distilling off the reaction product, followed by reaction at the same temperature for 1 hour, and after cooling, the solvent shown in Table 3 was added to the resin solution C-1 to C-3 having a solid content of 50%. And C-6 and C-9 were obtained.

Further, the reaction conditions are as follows:
-4 was obtained. C-5 was obtained in the same manner except that the reaction condition was 180 ° C. for 3 hours.

Example 1 C-1 of the resin composition (A) shown in Table 3 and the pigments shown in Table 4 were dispersed in a ball mill for 4 hours, then a curing agent was added with stirring, and 70 parts of xylene and acetic acid were further added. Dilute with a mixed solvent consisting of 20 parts of ethyl and 10 parts of cellosolve acetate.
The viscosity was adjusted to 15 seconds / 25 ° C with rd Cup # 4 to obtain a paint. This was applied to an object to be coated (bonderite # 144 zinc phosphate-treated steel sheet) by air spray and dried at 30 ° C. for 7 days to obtain a test plate. The coating performance is shown in Table-4.

Examples 2 to 5 and Comparative Examples 1 to 4 The coating materials were adjusted in the proportions shown in Table 4 in the same manner as in Example 1, and test plates were obtained by the same method. The coating performance is shown in Table-4.

1) Olester NP-1000: Aliphatic polyisocyanate (manufactured by Mitsui Toatsu Chemicals, Inc.) solid content 75%, NCO content 17%.

2) Rubycron 500RG: Red organic pigment (manufactured by Toyo Soda Co., Ltd.) 3) Drying time: After spray painting, touch the finger gently with the finger until the paint does not adhere to the finger (touch) and with a finger I watched the time (curing) until it was pressed and no trace was left. If both of them show a short time, the drying property becomes good.

4) Appearance of coating film: The finish of the coating film was visually observed, and a smooth and uniform coating film was evaluated as ⊚, slightly inferior as ○, and inferior in uniformity as ×.

5) Flexibility: When the coating film was bent with a curvature of 3 mmφ and the film was not bent, ⊚ was evaluated, ∘ was slightly generated and ∘ was marked.

6) Contamination resistance: A line was drawn with a magic ink, and after 24 hours, it was evaluated as ⊚ for those that did not remain at all, as ∘ for those that remained slightly, and as x for most that remained depending on the degree of contamination after wiping with methanol.

7) Weather resistance: The gloss retention rate after 1000 hours of testing with a sunshine weather meter was displayed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08G 18/64 NER 8620-4J (56) Reference JP-A-49-98499 (JP, A) Special features Kai 50-71728 (JP, A) JP 55-131067 (JP, A) JP 59-157275 (JP, A) JP 61-28518 (JP, A)

Claims (1)

[Claims] 1. When dissolved in a solvent by reacting 5 to 95 parts by weight of a polyester resin having a hydroxyl value of 5 to 200 KOHmg / g and 95 to 5 parts by weight of an acrylic resin having a hydroxyl value of 5 to 200 KOHmg / g. A resin composition for urethane coating, comprising a resin composition (A) which is a uniform solution and a curing agent (B) which is an isocyanate compound.