JP3339629B2 - Aqueous dispersion and resin composition for aqueous paint using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous dispersion containing a polyurethane resin as an active ingredient, and more particularly to a polyurethane having both high bending workability, coin scratch resistance, and corrosion resistance, and particularly suitable as a primer for a pre-coated steel sheet. The present invention relates to an aqueous dispersion of a resin and a resin composition for an aqueous paint using the same.

[0002]

2. Description of the Related Art Organic solvents have been used in large amounts in the fields of paints, inks, coatings, adhesives, and various processing agents such as textiles and paper. The use of organic solvents is becoming more difficult year by year due to the enforcement of organic solvent emission regulations such as RACT, restrictions on organic solvents due to the revision of the Fire Service Law, and strengthening of regulations on working environment concentration.

There are various methods, for example, (1) high solid type, (2) non-aqueous dispersion type,
(3) Aqueous dispersion, (4) Emulsion type, (5) Solventless type and the like have been proposed and many of them have already been implemented. Among these, the aqueous dispersion type is considered to be the most versatile and promising because of its easy handling.

On the other hand, in recent years, so-called pre-coated steel sheets have been widely used in the fields of roofing materials, building materials and home appliances in place of the post-coating method from the viewpoint of economy and productivity. Pre-coated steel sheets have drawbacks in that they are easily scratched in the manufacturing process and are inferior to post-coats in the corrosion resistance of the bent portions. The generation of scratches in the processing step is a cause of corrosion of the steel sheet base, and is a major cause of the deterioration of the corrosion resistance of the steel sheet such as the occurrence of cracks in the bending step. The solution of the above two points in the expansion of the field of application of the precoated steel sheet, that is, the improvement of coin scratch resistance and the improvement of bending workability, are currently the biggest issues in the industry.

[0005] Solvent-type epoxy resins or copolymerized polyester resins are currently used as primers for precoated steel sheets. Solvent type epoxy resin is excellent in adhesion to steel sheet, coin scratch property, corrosion resistance,
Cracks are formed during the bending process, and satisfactory requirements for high bending processability have not been obtained. In addition, there is also a problem that the adhesion between the layers and the polyester-based topcoat for high processing is not good.

Further, when a solvent-type copolymerized polyester resin is used as a primer, the bendability is extremely good, but the coin scratching property is inferior, causing scratches in the processing step, resulting in poor appearance and reduced corrosion resistance. There is a drawback to wake up.

As a solvent type resin, a polyurethane resin described in Japanese Patent Application No. 1-305961 has been proposed to solve these problems.

[0008] On the other hand, in consideration of making the primer for pre-coated steel sheet water-soluble, the resin used for the primer, as described above, is required to have a high degree of corrosion resistance and is therefore particularly strong in hydrophobicity. Is a major issue. Another important issue is how to impart water resistance, corrosion resistance, and the like to a coating film formed from a resin that has been made water-soluble. These technical solutions are of high difficulty regardless of the type of resin, and have not been put to practical use.

[0009]

As described above, an aqueous resin having both high processability, coin scratchability and corrosion resistance and a resin composition for an aqueous paint using the same have not been developed yet. It is strongly desired.

[0010]

In view of the above situation, the present inventors have considered an aqueous dispersion excellent in bending workability, coin scratchability and corrosion resistance, and a resin for aqueous paint using the same. As a result of intensive studies on the composition, the present invention has been achieved.

That is, the present invention relates to (A) two of the acid components
A polyester diol (a), an organic diisocyanate compound (b) containing 10 to 70% by weight of a repeating unit of any of bisphenol A, bisphenol F and cyclohexane skeleton, wherein 0 to 100 mol% is an aromatic dicarboxylic acid; Urethane obtained by reacting a chain extender (c) having a molecular weight of less than 500 at a ratio represented by the formula 1)
Group concentration of 300-5,000 equivalent / 10 ⁶ g, reduced viscosity
Is 0.2 to 1.5 dl / g, and the acid value is 50 equivalent / 10
⁶ g or more of polyurethane resin, (B) boiling point is 250
(A), (B), (C) and (D), containing a water-soluble organic compound having a temperature of not more than 0 ° C., (C) water, and (D) a neutralizing agent.
Satisfy the compounding ratios of the formulas 2), 3) and 4).
It is an aqueous dispersion to be characterized. Formula 1) 0.8 <(b) / ((a) + (c)) ≦ 1 (equivalent ratio) Formula 2) A / B / C = 1 to 70/0 to 69/9 to 99 (weight ratio) Formula 3) B / (B + C) = 0 to 0.7 (weight ratio) Formula 4) D / (acid value of A) = 0.1 to 20 (equivalent ratio)

When the aqueous dispersion of the present invention and the resin composition for water-based paint using the same are used as a primer for a precoated steel sheet, the water-based dispersion and the solvent-based epoxy resin of the prior art are higher in water but are more sophisticated. It has scratching properties, and is remarkably excellent in bending workability and interlayer adhesion with an overcoat. Further, as compared with a solvent-type copolyester resin, it has a bending property equal to or higher than that of the solvent-type copolyester resin, and is remarkably excellent in coin scratch property and corrosion resistance.

In the polyester diol (a) used in the present invention, 20 to 100 mol% of the acid component is an aromatic dicarboxylic acid. Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, orthophthalic acid, 2,6
-Naphthalenedicarboxylic acid, diphenyl-p, p'-dicarboxylic acid, diphenyl-m, m'-dicarboxylic acid, diphenylmethane-p, p'-dicarboxylic acid, 2,2'-
Examples thereof include bis (4-carboxyphenyl) propane and indene dicarboxylic acid, and one or two or more of these are used in combination. These aromatic dicarboxylic acids can be arbitrarily selected from coating film properties and economics, but it is preferable to use terephthalic acid and isophthalic acid in combination from the viewpoint of coating film properties, particularly mechanical properties and solubility. More preferably, terephthalic acid is in the range of 40 to 60 mol% of the acid component. Further, a tri- or higher functional carboxylic acid such as trimellitic anhydride may be used in a range of 10 mol% or less.

The polyester diol (a) used in the present invention may contain succinic acid, glutaric acid, etc. in an amount of less than 80 mol%, preferably 60 mol% or less of the acid component, if necessary.
Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanedioic acid and dimer acid or alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, tetrahydrophthalic acid and hexahydroisophthalic acid can be used. As the aliphatic dicarboxylic acid, adipic acid is used as one of the acid components in consideration of physical properties of the coating film and economy.
It is preferable to use it at 0 mol% or less.

If necessary, a dicarboxylic acid containing a metal sulfonic acid base such as 5-sodium sulfoisophthalic acid, 5-potassium sulfophthalic acid or sodium sulfophthalic acid may be contained in an amount of not more than 10 mol% as a part of the acid component. May be used. Further, a hydroxycarboxylic acid such as 2-hydroxyethoxybenzoic acid or p-hydroxybenzoic acid may be used.

The glycol component used in the polyester diol (a) used in the present invention is ethylene.
Glycol , propylene glycol, 1,3-propanediol, 1,4-butanediol, 3-methyl-1,
5-pentanediol, 2-ethyl-2-butylpropanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, dimethylol heptane, dimethylol pentane, diethylene glycol, triethylene glycol, cyclohexane dimethanol , TCD glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, bisphenol A ethylene oxide or propylene oxide derivatives, bisphenol S ethylene oxide or propylene oxide derivatives, bisphenol F ethylene oxide or propylene oxide derivatives, and the like. Of these, bisphenol A or bisphenol F ethylene oxide 2
It is preferable to use an adduct of 6 to 6 mol or cyclohexanedimethanol at 30 mol% or more of the glycol component. In the polyester diol (a), it is necessary that any one of bisphenol A, bisphenol F and a cyclohexane skeleton has a repeating unit content of 10 to 70% by weight.

Further, glycols containing a metal sulfonate such as 2-sodium sulfo-1,4-butanediol and 2-potassium sulfo-1,4-butanediol are used in an amount of 10 mol% or less based on all glycol components. You can also.

Further, a trifunctional or higher functional glycol such as glycerin, trimethylolpropane or pentaerythritol may be used in a range of 10 mol% or less.

Other components of the polyester diol (a) other than the above include dicarboxylic acids and glycols containing a metal base of a known acidic phosphorus compound.

The molecular weight of the polyester diol (a) is 5
00 to 15,000, preferably 1,000 to 5,000
It is in the range of 0. If the molecular weight is less than 500, the characteristics of the polyester resin are not exhibited, and the bending property is deteriorated. In addition, in order to obtain a polyurethane resin having a reduced viscosity described later, the urethane group concentration becomes extremely high, and the solubility, water dispersibility and bending property are reduced. Adversely affect sex. In addition, the molecular weight is 15,000.
If it exceeds 0, the urethane group concentration after the urethane conversion is 300
The equivalent weight is less than 10 ⁶ g, and good coin scratch property cannot be obtained.

The organic diisocyanate compound (b) used in producing the polyurethane resin (A) of the present invention includes tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate and the like. Aromatic diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, 4,4 '
-Aliphatic and alicyclic diisocyanates such as diisocyanate cyclohexylmethane, hydrogenated diphenylmethane diisocyanate and hydrogenated xylylene diisocyanate.

When producing a polyurethane resin, the chain extender (c) having a molecular weight of less than 500, which is used if necessary, is a compound having two or more functional groups having high reactivity with isocyanate groups. Preferably, these functional groups are two, but three or more compounds may be used in combination.

These chain extenders increase the urethane group concentration in the polyurethane resin, improve coin scratchability,
In addition, there is an effect of imparting toughness specific to the polyurethane resin.

Among the chain extenders, those containing a carboxyl group are required to be 50 equivalents / 1 required for the polyurethane resin of the present invention.
It is necessary in order to impart 0 ⁶ g or more acid number. The acid value is necessary to obtain good water dispersibility, coin scratchability and corrosion resistance. The preferred acid value is 150 to 600 equivalent / 10 ⁶ g, and if it is less than 50 equivalent / 10 ⁶ g, good water dispersibility cannot be obtained.

Specific examples of the chain extender include ethylene glycol, propylene glycol, tetramethylene glycol, 1,6-hexanediol, cyclohexanedimethanol, diethylene glycol, neopentyl glycol, 3-methyl-1,5-pentanediol. Glycols such as monoethanolamine, amino alcohols such as N-methylethanolamine, diamines such as hexamethylenediamine, isophoronediamine, 4,4-diaminodiphenylmethane, and diaminodiphenylether; carboxyls such as dimethylolpropionic acid and tartaric acid Group-containing glycols and the like.

Among these, preferred are neopentyl glycol, 1,6-hexanediol, and dimethylolpropionic acid suitable for imparting an acid value.

The polyurethane resin (A) of the present invention is prepared by mixing the polyester diol (a) described above with a molecular weight of 5 if necessary.
A method of dissolving a chain extender (c) of less than 00 in an organic solvent, and then charging the organic isocyanate compound (b) at a ratio shown in the formula 1) and reacting the mixture at 60 to 90 ° C. A known method such as a method of reacting the isocyanate compound (b) with an equivalent excess at 60 to 90 ° C., then charging the chain extender (c) at the ratio shown in the formula 1), and further reacting to complete the polymerization. Are synthesized.

As the organic solvent used for synthesizing the polyurethane resin (A) of the present invention, any known organic solvent can be used. However, since it is necessary to substitute water as described later, it has a low boiling point. Most preferred is methyl ethyl ketone, which is soluble and has good affinity for water.

Further, (A) the polyurethane resin of the present invention preferably has a urethane group of 300 to 5,000 equivalent / 1.
0 ⁶ g (tons), more preferably 1,500～3,00
0 equivalent / 10 ⁶ g, and the acid value is preferably 50 equivalent / 10 ⁶ g or more, more preferably 250-600 equivalent /
10 ⁶ g, and and a reduced viscosity of preferably 0.2 to
1.5 dl / g, more preferably 0.5 to 1.0 dl / g
g. In addition, the glass transition temperature is preferably from 40 to 90 ° C. from the physical properties of the coating film.

If the urethane group concentration is less than 300 equivalents / 10 ⁶ g, good coin scratching properties may not be obtained. If the acid value is less than 50 equivalents / 10 ⁶ g, good water dispersibility may not be obtained. 0.2d reduced viscosity
If it is less than 1 / g, good bending workability may not be obtained, and if it exceeds 1.5 dl / g, the viscosity of the solution may be significantly increased, which is not preferable.

The polyurethane resin (A) of the present invention can be used alone or in combination of two or more.

The (B) water-soluble organic compound used in the present invention is used for the purpose of increasing the affinity of the polyurethane resin for water which has been consciously lowered, and assisting the dispersibility in water. That is, a good aqueous dispersion can be obtained in a state where the polyurethane resin of the present invention, the water-soluble organic compound and water coexist.

The water-soluble organic compound (B) used in the present invention is an organic compound having a solubility of 20 g or more in 1 liter of water at 20 ° C., specifically, aliphatic and alicyclic alcohols, ethers and esters. And ketone compounds. For example, methanol, ethanol, n
-Propanol, i-propanol, n-butanol,
monohydric alcohols such as i-butanol, sec-butanol, tert-butanol, ethylene glycol,
Glycols such as propylene glycol, methyl cellosolve, ethyl cellosolve, ethylene glycol alkyl ethers such as butyl cellosolve and acetates thereof, ethyl carbitol, diethylene glycol alkyl ethers such as butyl carbitol and acetates thereof, propylene glycol alkyl ethers and Examples thereof include acetates, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate, and ketones such as acetone, methyl ethyl ketone, cyclohexanone, cyclooctanone, cyclodecanone, and isophorone. Particularly preferred are butyl cellosolve, butyl carbitol, propylene glycol monoethyl ether and the like.

These water-soluble organic compounds can be used alone or
More than one species can be used in combination. The boiling point of these water-soluble organic compounds needs to be 250 ° C. or lower. If the boiling point exceeds 250 ° C., good drying properties cannot be obtained after applying the obtained aqueous dispersion.

When the polyurethane resin of the present invention is dispersed in water, it is necessary to neutralize the carboxyl group added by the above method with a neutralizing agent to dissociate the carboxyl group. Without alkali neutralization, the carboxyl groups do not dissociate and good water dispersibility cannot be obtained.

(D) As a neutralizing agent, aqueous ammonia, methylethanolamine, diethylethanolamine, N
-Methyl-diethanolamine, bis-hydroxypropyl-methylamine, tri-n-butylamine, triethylamine, bis-2-hydroxypropylamine, N
-Methyl-ethanolamine, aminomethylpropanol, 3-amino-1-propanolamine, isopropanolamine, 2-amino-2-hydroxymethyl 1-
Amines such as 3-propanediol, aminomethyl-propanediol, cyclohexylamine and t-butylamine; salts of weak acids and strong bases such as sodium carbonate and potassium carbonate; and hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide. Things and the like. If these neutralizing agents remain in the coating film after drying and curing, they adversely affect the physical properties of the coating film. Therefore, low-boiling amines such as aqueous ammonia and dimethylethanolamine that volatilize and do not remain after drying and curing are preferable.

The aqueous dispersion of the present invention is prepared by previously mixing (A) a polyurethane resin solution synthesized in an organic solvent, (B) a water-soluble organic compound, (C) water, and (D) a neutralizing agent. Alternatively, it is produced by a known method such as a method of distilling off an organic solvent at normal pressure.

In any production method, (A) a polyurethane resin, (B) a water-soluble organic compound, (C) water,
And (D) the compounding ratio of the neutralizing agent is an important factor for maintaining the performance of the aqueous dispersion, and the formulas 2), 3), and
It is preferable to satisfy the compounding ratio of 4) . Formula 2) A / B / C = 1-70 / 0-69 / 9-99 (weight ratio) Formula 3) B / (B + C) = 0-0.7 (weight ratio) Formula 4) Acid of D / A Value = 0.1 to 20 (equivalent ratio)

When the mixing ratio of the polyurethane resin (A) contained in the aqueous dispersion is less than 1% by weight based on the total amount of (A) + (B) + (C), the viscosity of the aqueous dispersion becomes too low. ,
Repelling easily occurs during coating. On the other hand, if it exceeds 70% by weight, the viscosity is undesirably too high.

When (B) a water-soluble organic compound is blended, when (B) is 5% by weight or more in the blending ratio of (B) the water-soluble organic compound and (C) water, excellent water dispersibility and transparency are obtained. , And the coating film is excellent in appearance due to its excellent coating properties. If it exceeds 70% by weight, problems such as lowering of the flash point of the system occur.

The compounding amount of the neutralizing agent is (D) neutralizing agent / (A) acid value of the polyester resin = 0.1 to 20 (equivalent ratio), preferably 1.0 to 2.0 (equivalent ratio). Range. If this ratio is less than 0.1 (equivalent ratio), the carboxyl group cannot be sufficiently dissociated, and good water dispersibility cannot be obtained. Also, 20
Exceeding the (equivalent ratio) causes adverse effects such as remaining in the coating film after drying to lower the water resistance and hydrolyzing the polyester resin during storage of the aqueous dispersion.

Although the aqueous dispersion of the present invention can be used as it is, 1 to 60 parts by weight of a curing agent capable of reacting with 100 parts by weight (solid part) of the aqueous dispersion is blended to form a resin composition for coating. It can also be used as an object. As a typical curing agent, one or more compounds selected from the group consisting of an amino resin, an epoxy compound and an isocyanate compound can be used in combination.

Examples of the amino resin include formaldehyde adducts such as urea, melamine and benzoguanamine;
Further, there may be mentioned alkyl ether compounds of alcohols having 1 to 6 carbon atoms. Specifically, methoxylated methylol urea, methoxylated methylol N,
N-ethylene urea, methoxylated methylol dicyandiamide, methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, butoxylated methylol benzoguanamine and the like, preferably methoxylated methylol melamine, butoxylated methylol melamine, and methylolated Benzoguanamine, which can be used alone or in combination.

As the epoxy compound, bisphenol A
Diglycidyl ethers and oligomers thereof, diglycidyl ethers of hydrogenated bisphenol A and oligomers thereof, diglycidyl orthophthalate, diglycidyl isophthalate, diglycidyl terephthalate, diglycidyl p-oxybenzoate, tetrahydrophthalate Acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol di Glycidyl ether, 1,6-hexanediol diglycidyl ether and polyalkylene glycol diglycidyl ethers, Triglycidyl citrate, triglycidyl isocyanurate, 1,4-diglycidyloxybenzene, diglycidyl propylene urea, glycerol triglycidyl ether, trimethylol ethane triglycidyl ether, trimethylol propane triglycidyl ether, pentaerythritol tetraglycidyl ether And glycerol alkylene oxide adduct triglycidyl ether.

Further, as the isocyanate compound, there are aromatic and aliphatic diisocyanates and trivalent or higher valent polyisocyanates, and either low molecular weight compounds or high molecular weight compounds may be used. For example, tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate or trimers of these isocyanate compounds, and excess of these isocyanate compounds And the amount of low molecular active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, triethanolamine or various polyester polyols, polyether polyols, polyamides Anti-polymer active hydrogen compounds It includes terminal isocyanate group-containing compounds obtained by.

The isocyanate compound may be a blocked isocyanate. As the isocyanate blocking agent, for example, phenol, thiophenol,
Phenols such as methylthiophenol, ethylthiophenol, cresol, xylenol, resorcinol, nitrophenol, chlorophenol, acetoxime, methylethylketoxime, cyclohexanone oxime and its oximes, alcohols such as methanol, ethanol, propanol and butanol, ethylene chlorohydroxide Phosphorus, halogen-substituted alcohols such as 1,3-dichloro-2-propanol, t-butanol, t-
Tertiary alcohols such as pentanol, ε-caprolactam, δ-valerolactam, γ-butyrolactam,
lactams such as β-propyl lactam; and other active amines such as aromatic amines, imides, acetylacetone, acetoacetate, and malonic acid ethyl ester; mercaptans, imines, ureas, and diaryl compounds. Sodium bisulfite and the like are also included. The blocked isocyanate can be obtained by subjecting the above isocyanate compound, isocyanate compound and isocyanate blocking agent to an addition reaction by a conventionally known appropriate method.

A curing agent or an accelerator can be used in combination with these crosslinking agents. As a method of compounding the cross-linking agent, there are (A) a method of mixing with a polyurethane resin, and (B) a method of dissolving or dispersing in a mixture with a water-soluble organic compound or (C) water in advance. You can choose.

The aqueous dispersion of the present invention can be used by blending a pigment, a dye and various additives, and is particularly suitable for a primer coating by blending a coating agent for a precoated steel sheet or a rust preventive pigment. Spray painting is also possible.

[0049]

The present invention will be specifically described below with reference to examples. In the examples, “part (s)” means “part (s) by weight”.

Each measurement item was in accordance with the following method.

(1) Reduced viscosity ηsp / c (dl / g) A sufficiently dried polyurethane resin (0.10 g) was mixed with a phenol / tetrachloroethane (volume ratio 6/4) mixed solvent 25.
cc and measured at 30 ° C.

(2) Number average molecular weight Measured by gel permeation chromatography (GPC) and expressed in terms of polystyrene.

(3) Acid value 0.2 g of a sufficiently dried sample was precisely weighed and dissolved in 20 ml of chloroform. Then, it was determined by titration with 0.01 N potassium hydroxide (ethanol solution). Phenolphthalein was used as the indicator.

(4) Glass transition temperature Measured at a heating rate of 20 ° C./min using a differential scanning calorimeter (DSC). The sample was prepared by placing 5 mg of the sample in an aluminum holding lid type container and crimping it.

(5) Composition analysis of polyester diol The polyester diol was analyzed by NMR (nuclear magnetic resonance method) or the like.

(6) Urethane Group Concentration Calculated from the charged amount of the organic diisocyanate compound in the total charged amount, and expressed as equivalent / ton.

(7) Coinscratchability The coated steel plate coating film was strongly scraped with a 10-yen coin, and the peeling state of the coating film was visually determined. ：: The primer hardly peeled off from the substrate (steel plate), the interlayer adhesion between the primer and the top coat was good, and only the top coat was cohesively broken. ：: The primer is slightly peeled off from the substrate, but the interlayer adhesion between the primer and the overcoat is good. Δ: The primer is hardly peeled off from the substrate, but the interlayer adhesion between the primer and the overcoat is poor, and the overcoat is easily peeled. ×: The top coat is peeled off from the substrate together with the primer. Poor adhesion of primer to substrate. XX: The overcoat is remarkably peeled from the substrate together with the primer.

(8) Workability (T-bend method) After leaving the coated steel sheet in a constant temperature room at 5 ° C. for 1 hour or more, it is bent from 4T to 0T sequentially, and the crack generated in the bent portion is observed and judged with a 15-fold loupe. did. For example, when three steel plates of the same thickness are sandwiched and bent in the bent portion and no crack occurs when the two steel plates are similarly bent when sandwiched and bent, the workability is said to be 3T by T-bend, Therefore, the smaller the T-bend number, the better the workability.

(9) Boiling Water Resistance The coated steel sheet was immersed in ion-exchanged water, boiled for 8 hours, taken out, and the coating film was observed and judged. ：: no blister, adhesion: 100/100 △: blister generation ×: remarkable blister generation

(10) Corrosion resistance The coated steel plate was cross-cut with a cutter knife,
After performing a salt spray test for 500 hours according to SK-5400, the cross cut portion was subjected to cellotape stripping, and the strip width was evaluated. ：: Stripping width of less than 2 mm ○: 〃 2 mm or more and less than 3 mm △: 〃 3 mm or more and less than 4 mm ×: 〃 4 mm or more

(11) Preparation of Primer Coating (in the case of aqueous system) In a glass bottle, 100 solid parts of an aqueous dispersion, Sumimar M as an alkyl etherified aminoformaldehyde resin
40W (manufactured by Sumitomo Chemical Co., Ltd.) 10 solid parts, 0.25 part of paratoluenesulfonic acid as a curing accelerator, 30 parts of zinc chromate as a rust preventive pigment, 50 parts of titanium oxide,
250 parts of glass beads (5 mm in diameter) were blended, stirred, shaken with a paint shaker for 4 hours, and dispersed to obtain a primer coating.

(12) Preparation of primer paint (in the case of a solvent system) 100 solid parts of a solvent-based comparative resin in a glass bottle, 10 solid parts of Sumimar M40S (manufactured by Sumitomo Chemical Co., Ltd.) as an alkyl etherified aminoformaldehyde resin, curing acceleration 0.25 parts of paratoluenesulfonic acid as an agent, 30 parts of zinc chromate as a rust preventive pigment, 50 parts of titanium oxide
And 250 parts of glass beads (diameter 5 mm) were mixed and shaken and dispersed with a paint shaker for 4 hours after stirring to obtain a primer paint.

(13) Preparation of Topcoat (I) Byron 20 which is a copolymerized polyester resin in a glass bottle
0 (manufactured by Toyobo Co., Ltd.), 80 parts byron 500 (manufactured by Toyobo Co., Ltd.), 25 solid parts of Cymel 325 (manufactured by Mitsui Cyanamid Co., Ltd.) as an alkyl etherified aminoformaldehyde resin, paratoluene sulfone as a curing accelerator Acid 0.25 part, titanium oxide 125 parts, leveling agent MK Conc (manufactured by Kyoeisha Yushi Kagaku Kogyo) 0.5
Part, 400 parts of cyclohexanone, glass beads (diameter 5
mm) 250 parts were blended, stirred and then painted with a paint shaker.
The mixture was shaken and dispersed for a time to obtain a top coat (I).

(14) Preparation of Painted Steel Sheet and Evaluation of Physical Properties of Coated Film The above-mentioned primer paint was applied to a 0.5 mm-thick electrogalvanized steel sheet which had been subjected to a chromate treatment by a bar coater so that the dry film thickness became 5 μm. Baked at 220 ° C. for 50 seconds. Then, after cooling, the above-mentioned top coat (I) is applied on the primer coating film by a bar coater so that the dry film thickness becomes 25 μm, set at 70 ° C. for 10 minutes, and baked at 235 ° C. for 60 seconds to obtain a coated steel sheet. Was prepared. The obtained coated steel sheet was evaluated by the method described above.

(15) Synthesis Example of Polyester Diol Synthesis of Polyester Diol (a) 4 equipped with a stirrer, thermometer and Vigreux fractionating tube
291 parts of dimethyl terephthalate, 291 parts of dimethyl isophthalate, ethylene glycol 26
6 parts, 240 parts of neopentyl glycol and 0.3 part of tetrabutyl titanate as a catalyst were charged.
While distilling the methanol produced at 230 ° C out of the system,
The transesterification was carried out for 5 hours. Then, the Vigreux fractionation tube was removed and the reaction system was set to 5 mmHg over 30 minutes.
The pressure was reduced to 210 ° C. during this time. further,
A polycondensation reaction was performed at 0.3 mmHg and 210 ° C. for 30 minutes to obtain a polyester diol (a). The obtained polyester diol (a) was subjected to composition analysis by NMR to show that terephthalic acid / isophthalic acid // ethylene glycol / ne
Opentyl glycol = 50/50 // 48/52 (molar ratio), pale yellow transparent resin having a reduced viscosity of 0.23 dl / g, a number average molecular weight of 2,200, and an acid value of 8.7 equivalent / 10 ⁶ g. Met.

Synthesis of Polyester Diols (b) to (d) In the same manner as in the synthesis example of polyester diol (a), polyester diols (b) to
(D) was synthesized. Composition analysis and measurement of resin properties were performed in the same manner as the polyester diol (a). Table 1 shows the results.

[0067]

[Table 1]

Example of synthesizing polyurethane resin

Synthesis of Polyurethane Resin (e) 100 parts of polyesterdiol (b), 4 parts of neopentyl glycol as a chain extender, and 153 parts of methyl ethyl ketone were charged into a four-necked flask equipped with a cooling tube.
The mixture was heated and dissolved at 0 ° C. Then cooled to 60 ° C,
39 parts of 4'-diphenylmethane diisocyanate was charged and stirred for 10 minutes. Then, the mixture was heated to 80 ° C., and 0.04 part of dibutyltin dilaurate as an accelerator was added and reacted for 1 hour. Further, dimethylolpropionic acid 10
The resulting mixture was reacted at 80 ° C. for 3 hours to obtain a polyurethane resin (e). The obtained polyurethane resin (e) was a pale yellow transparent liquid having a reduced viscosity of 0.66 dl / g, an acid value of 498 equivalents / 10 ⁶ g (ton), and a urethane group concentration of 2,039 equivalents / 10 ⁶ g.

Synthesis of Polyurethane Resins (g) to (p) Light yellow transparent polyurethane resins (f) to (i) whose compositions are shown in Table 2 were synthesized in the same manner as the polyurethane resin (e). Composition analysis and measurement of resin properties were performed in the same manner as the polyurethane resin (e). Table 2 shows the results.

[0071]

[Table 2]

Example 1 70 parts (35 solid parts) of polyurethane resin (e), water 57
And 2.1 parts of 28% aqueous ammonia were charged into a 2 L flask equipped with a Vigreux fractionating tube and heated to 60 ° C. with stirring. Then, the pressure was gradually reduced by an aspirator to completely remove methyl ethyl ketone, and then cooled to obtain an aqueous dispersion. The resulting aqueous dispersion was stable, translucent and good.

Next, when the physical properties and corrosion resistance of the predetermined coating film were evaluated, the coin scratch property was remarkably better than that of the conventional solvent-based polyester resin or epoxy resin, and the workability and corrosion resistance were improved. It was significantly better than the epoxy resin. Table 3 shows the results.

Next, when the physical properties and corrosion resistance of a predetermined coating film were evaluated, the coin scratch property was remarkably better as compared with the solvent-based polyester resin or epoxy resin of the prior art, and the workability and corrosion resistance were improved. It was significantly better than the epoxy resin. Table 3 shows the results.

[0075]

[Table 3]

Examples 2 to 5 For the polyurethane resins (f) to (i), the dispersion compositions shown in Table 3 were evaluated in the same manner as in Example 1. Table 3 shows the results.

COMPARATIVE EXAMPLES 1-2 Comparative polyurethane resins (j)-(k) were used in Example 1.
Evaluation was performed using the dispersion compositions shown in Table 3 in the same manner as in the above. Table 3 shows the results.

Comparative Examples 3 and 4 For comparison with a conventional solvent system, polyester diol (d) and epoxy resin Epicoat 1007 (manufactured by Yuka Shell Epoxy Co., Ltd.) were added to cyclohexanone / solvesso 1
50 = 50/50 (weight ratio) It was dissolved in a mixed solvent, and the physical properties of the coating film were evaluated. Table 4 shows the results.

[0079]

[Table 4]

As apparent from Tables 1 to 4, the aqueous dispersion of the present invention is excellent in its dispersion stability, and is also excellent in its coating film properties such as coin scratchability, processability and corrosion resistance.

[0081]

The aqueous dispersion of the present invention has very good water dispersibility even with only a carboxyl group, and an aqueous dispersion having good transparency can be obtained. For this reason, it is excellent in both water dispersibility and water resistance, which are conventionally contradictory, and thus is useful as a paint, a coating agent, a binder, an adhesive, a fiber and a paper treating agent, and is particularly suitable for a PCM primer. Further, the aqueous dispersion of the present invention is superior in coin scratch property and corrosion resistance as compared with the conventional solvent-based polyester resin, and is superior in bending workability as compared with the conventional solvent-based epoxy resin. Further, since the aqueous dispersion of the present invention has a low viscosity, it can be made into a high solid, and spray coating is also possible.

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C09D 175/06 C09D 175/06 (56) References JP-A-53-110649 (JP, A) JP-A-57-165420 (JP) , A) JP-A-63-179987 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 18/00-18/87 C08L 75/04-75/12 C09D 5/00 , 5/02 C09D 175/04-175/12

Claims (2)

(57) [Claims] 1. A polyester diol in which (A) 20 to 100 mol% of an acid component is an aromatic dicarboxylic acid and 10 to 70% by weight of a repeating unit of any of bisphenol A, bisphenol F and cyclohexane skeleton. (A), an organic diisocyanate compound (b) and, if necessary, a chain extender (c) having a molecular weight of less than 500 reacted at a ratio shown in the formula 1) to form a urethane group.
Is 300 to 5,000 equivalent / 10 ⁶ g, and the reduced viscosity is 0.1 .
2 to 1.5 dl / g and an acid value of 50 equivalents / 10 ⁶ g or more
And (B) a water-soluble organic compound having a boiling point of 250 ° C. or lower, (C) water, and (D) a neutralizing agent, and (A), (B), (C) and (D). ) Is the expression
Characterized by satisfying the compounding ratio of 2), 3) and 4)
Aqueous dispersion. Formula 1) 0.8 <(b) / ((a) + (c)) ≦ 1 (equivalent ratio) Formula 2) A / B / C = 1 to 70/0 to 69/9 to 99 (weight ratio) Formula 3) B / (B + C) = 0 to 0.7 (weight ratio) Formula 4) D / (acid value of A) = 0.1 to 20 (equivalent ratio) 2. An aqueous system comprising 100 parts by weight (solid part) of the aqueous dispersion according to claim 1 and 1 to 60 parts by weight of a curing agent capable of reacting with the aqueous dispersion. Resin composition for paint.