JPS6219789B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a binder for water-based paints. More specifically, the present invention relates to a binder for water-based paints that has excellent adhesion to metals, as well as excellent water resistance and corrosion resistance. Traditionally, many paints have been used that contain large amounts of aromatic organic solvents, but in recent years, from the perspective of air pollution and resource conservation, various water-based paints that do not use such solvents have been proposed and some have been put into practical use. It has been done. The performance of such water-based paints mainly depends on the characteristics of the paint resin that is its main component, and the water-based paint resins include emulsion types such as acrylic emulsions, ethylene-vinyl acetate emulsions, polyurethane emulsions, etc. Aqueous solutions have been proposed and put into practical use, such as alkyd resins in which the carboxyl groups in the molecules are neutralized with amines and polyester resins whose main component is diethylene glycol, as disclosed in Japanese Patent Publication No. 47-40873. However, emulsion-type products have the disadvantage of low performance such as water resistance and corrosion resistance because surfactants remain in the coating film, and amine-neutralized aqueous solution-type products have the disadvantage that the amine volatizes during coating film formation. Moreover, in the case of water-soluble polyester resin, the water affinity is too strong, so the water resistance of the coating film is poor, and at the same time, when the coating film dries,
It is well known that it has the disadvantage of consuming a large amount of latent heat of vaporization. For these reasons, there is a strong demand for dispersion-type water-based paints that are excellent in water resistance and corrosion resistance and have a low latent heat of vaporization of water. Generally, in order to uniformly disperse or dissolve a resin in water, it is necessary to introduce a component that imparts some kind of hydrophilicity to the resin, but conversely, after the coating film is formed, this hydrophilic component is This causes a decrease in water resistance and corrosion resistance. It is impossible to develop a practical water-based paint unless the contradictory problems of imparting properties such as imparting hydrophilicity and imparting water resistance and corrosion resistance are overcome. Therefore, the inventors of the present invention conducted extensive research to find a water-based paint with excellent water resistance and corrosion resistance. As a result, polyester resin containing a small amount of hydrophilic component was used in water containing organic compounds that are compatible with small amounts of water. It was discovered that the polyester resin can be uniformly dispersed, and that when used in combination with an amino resin, an excellent coating film that does not deteriorate even when immersed in boiling water is formed, leading to the present invention. That is, the present invention contains 70 to 6% by weight of a polyester resin having the following composition, 0.5 to 28% by weight of an amino resin, and an organic compound compatible with water (provided that the solubility is 20 parts by weight or more per 100 parts by weight of water at 20°C). 1 selected from the group of aliphatic and alicyclic alcohols, ethers, esters and ketones having
More than one species of compound. ) 36-1% by weight and water 24-89
% by weight of a water-based paint binder. Polyester resin: (1) The dicarboxylic acid component is 99.5 to 50 mol% of an aromatic dicarboxylic acid that does not contain a sulfonic acid metal base, 0 to 49.5 mol% of an aliphatic or alicyclic dicarboxylic acid having 4 to 36 carbon atoms, and a sulfonic acid metal. It consists of 0.5 to 7 mol% of a base-containing aromatic dicarboxylic acid, and (2) the glycol component is an aliphatic glycol having 2 to 8 carbon atoms.
100 to 20 mol% and 0 to 80 mol% of an ethylene oxide or propylene oxide adduct of alicyclic glycol having 6 to 15 carbon atoms and/or bisphenol A, and (3) 0 to 10 mol% based on the total carboxylic acid component. % of trivalent or higher polycarboxylic acid and/or polyester resin consisting of 0 to 10 mol % of trivalent or higher polyol based on the total alcohol component. In the present invention, the polyester resin containing a small amount of hydrophilic component is uniformly dispersed in water containing a small amount of water-compatible organic compound, and an amino resin is further used in combination to achieve excellent adhesion to metals. It is possible to obtain a binder for water-based paints which has the following characteristics and also has excellent water resistance and corrosion resistance. Examples of the aromatic dicarboxylic acid containing no sulfonic acid metal base used in the polyester resin of the present invention include terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid. Examples of aliphatic or alicyclic dicarboxylic acids having 4 to 36 carbon atoms include succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, tetrahydrophthalic acid, hexahydrophthalic acid, and hexahydrophthalic acid. Examples include hydroisophthalic acid and hexahydroterephthalic acid. Additionally, P-hydroxybenzoic acid, P-(2-
Hydroxycarboxylic acids such as hydroxyethoxybenzoic acid and hydroxypivalic acid, or cyclic esters such as γ-butyrolactone and ε-caprolactone can also be used within the range of not deteriorating the physical properties of the coating film. The sulfonic acid metal base-containing aromatic dicarboxylic acid used in the polyester resin of the present invention includes:
Examples include metal salts of sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5-[4-sulfophenoxy]isophthalic acid. Metal salts include Li, Na, K, Mg,
Examples include salts of Ca, Cu, Fe, etc., and 5-sodium sulfoisophthalic acid is particularly preferred. Examples of the aliphatic glycol having 2 to 8 carbon atoms used in the polyester resin of the present invention include ethylene glycol, propylene glycol, 1.3
-propanediol, 1,4-butanediol,
Examples include 15-pentanediol, 1,6-hexanediol, neopentyl glycol, and examples of alicyclic glycols having 6 to 15 carbon atoms include 1,4-cyclohexanediol, 1,4-
Examples include cyclohexanedimethanol. The ethylene oxide or propylene oxide adduct of bisphenol A is preferably one in which 2 to 10 moles of ethylene oxide or propylene oxide are added to 1 mole of bisphenol A, particularly preferably 2 to 10 moles of ethylene oxide or propylene oxide.
5 moles were added. In the polyester resin of the present invention, trivalent or higher polycarboxylic acids and/or trivalent or higher polyols can be used, and examples of the trivalent or higher polycarboxylic acids include trimellitic acid,
Examples include aromatic polycarboxylic acids such as pyromellitic acid and benzophenonetetracarboxylic acid, alicyclic polycarboxylic acids such as cyclopentanetetracarboxylic acid, and aliphatic polycarboxylic acids such as butanetetracarboxylic acid. Further, examples of polyols having a valence of 3 or higher include aliphatic polyols such as glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. In the polyester resin of the present invention, the dicarboxylic acid components include 99.5 to 50 mol% of an aromatic dicarboxylic acid containing no sulfonic acid metal base, 0 to 49.5 mol% of an aliphatic or alicyclic dicarboxylic acid having 4 to 36 carbon atoms, and a sulfonic acid. Aromatic dicarboxylic acids containing metal bases
It consists of 0.5 to 7 mol%. Aromatic dicarboxylic acids that do not contain sulfonic acid metal bases are 99.5 to 50 mol%
However, if it exceeds 99.5%, the dispersibility of the polyester resin in water will deteriorate;
If the content of aliphatic or alicyclic dicarboxylic acid having 4 to 36 carbon atoms exceeds 49.5 mol%, the water resistance of the coating film will deteriorate;
Corrosion resistance is greatly reduced. In addition, the aromatic dicarboxylic acid containing sulfonic acid metal base is 0.5 to 7 mol%,
It is preferably within the range of 1 to 4 mol%, but 0.5
If it is less than 7 mol %, the polyester resin will have poor dispersibility in water, and if it exceeds 7 mol %, the water resistance and corrosion resistance of the coating will deteriorate. The polyester resin of the present invention contains 100 to 10 mol% of aliphatic glycol having 2 to 8 carbon atoms, 0 to 80 mol% of alicyclic glycol having 6 to 15 carbon atoms, and/or ethylene oxide or propylene oxide adduct of bisphenol A. Consisting of mole%. 20 mol% aliphatic glycol with 2 to 8 carbon atoms
If the content of the ethylene oxide or propylene oxide adduct of alicyclic glycol and/or bisphenol A exceeds 80 mol %, the polyester resin will have poor dispersibility in water or the aesthetic appearance such as the gloss of the coating film will deteriorate. Furthermore, the ethylene oxide or squid propylene oxide adduct of bisphenol A used in the polyester resin of the present invention is one in which 2 to 10 moles of ethylene oxide or propylene oxide are added per mole of bisphenol.
If it is less than 1 mol %, polymerization becomes difficult using ordinary polyester polymerization methods, and if it exceeds 10 mol %, the water resistance and corrosion resistance of the coating film will decrease. In the polyester resin of the present invention, the use of polyether glycols such as diethylene glycol and polyethylene glycol is not preferable because it reduces water resistance and corrosion resistance, but as long as it is within an acceptable range for coating film performance, that is, within 10 mol% of diethylene glycol. May be used. 5 in polyester resin in the case of polyethylene glycol, especially polyethylene glycol with a molecular weight of 500 or more.
Weight % is the limit. In the polyester resin of the present invention, trivalent or higher polycarboxylic acid is contained within a range of 10 mol% or less based on the total carboxylic acid component, or trivalent or higher polyol is contained within a range of 10 mol% or less based on the total alcohol component. However, if the amount of trivalent or higher polycarboxylic acid and/or polyol exceeds 10 mol %, the appearance of the coating film will deteriorate and the mechanical strength will also decrease. The polyester resin of the present invention has a molecular weight of 1000~
30000, preferably 2500 to 20000, and the molecular weight is
If the molecular weight is less than 1,000, the coating film will lack mechanical strength such as impact resistance, and if the molecular weight exceeds 30,000, the viscosity of the composition will be high and the workability during coating and painting will be poor, making it impractical. . The polyester resin of the present invention is essentially amorphous. Crystalline polyester resins having a distinct crystalline melting point have poor dispersibility in water and easily undergo phase separation during storage, making them unsuitable for practical use. The polyester resin of the present invention can be produced by any known method. Further, if necessary, it may be used without using a solvent or after chain extension with a polyisocyanate compound, polyepoxy compound, etc. in a solvent. The polyester resin of the present invention is used after being dispersed in water containing a water-compatible organic compound.
The water-compatible organic compound used in the present invention is an organic compound having a solubility of 20 parts by weight or more per 100 parts by weight of water at 20°C, such as methanol, ethanol, n-propanol, i-propanol. , n-butanol, i-butanol, Sec
- Alcohols such as butanol, tert-butanol, ethylene glycol, propylene glycol, methyl cellosolve, ethyl cellosolve, n-propyl cellosolve, i-propyl cellosolve, N-butyl cellosolve, tert-butyl cellosolve, ethyl acetate, propyl acetate, butyl acetate, Examples include esters such as methyl cellosolve acetate and ethyl cellosolve acetate, cyclic ethers such as dioxane and tetrahydrofuran, and ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone. Nitrogen-containing organic compounds such as dimethylformamide and pyridine, or sulfur-containing organic compounds such as dimethyl sulfoxide can not be used because they greatly reduce the drying properties of the coating film and impair storage stability. The water-compatible organic compounds used in the present invention can be used alone or in combination of two or more. Examples of the amino resin used in the present invention include formaldehyde adducts of urea, melamine, and benzoguanamine, and alkylated products of these with alcohols having 1 to 4 carbon atoms. The binder for water-based paints of the present invention includes 70 to 6% by weight of the above polyester resin, 0.5 to 28% by weight of amino resin, 36 to 1% by weight of an organic compound compatible with water,
Desirably 18-2% by weight and 24-89% by weight of water,
The content of the polyester resin is preferably 32 to 2% by weight, but if the content exceeds 70% by weight, the viscosity of the binder for water-based paints becomes too high, storage stability deteriorates, and painting workability becomes extremely poor. vice versa,
If the amount is less than 6% by weight, a coating thickness sufficient to maintain corrosion resistance cannot be obtained. On the other hand, if the amino resin content is less than 0.5% by weight, the coating performance such as water resistance and solvent resistance will be poor, and if it exceeds 28% by weight, the aesthetic appearance and mechanical properties such as flexibility will deteriorate. Deteriorate.
If the content of the water-compatible organic compound is less than 1% by weight, the storage stability of the coating material will be reduced, and the coating film appearance will be susceptible to coating defects such as pinholes. On the other hand, if it exceeds 36% by weight, it becomes unsuitable for the resource saving and pollution-free goal of the present invention. In the binder for water-based paints of the present invention, the ratio of amino resin to polyester resin is expressed as a weight ratio.
95-60/5-40, the ratio by weight of organic compounds compatible with water and water is 40-2/60-98, the proportion of polyester resin and amino resin in the aqueous medium is by weight It is 10-70/90-30. The proportion of water is used within the above range, but if the amount of water in the binder for water-based paint exceeds 89% by weight, problems such as difficulty in uniform application to metals may occur in addition to the defects mentioned above. It cannot be put to practical use. The binder for water-based paints of the present invention can be used as it is by applying it to metals, etc., but it can also be used in combination with curing accelerators, various compounding agents, modifiers, pigments, paint additives, etc. For example, curing accelerators include acids such as P-toluenesulfonic acid, dinonylnaphthalenedisulfonic acid, hydrochloric acid, and amine salts of these acids, and compounding agents and modifiers include:
There are dispersions such as acrylic dispersions, epoxy dispersions, urethane dispersions, and aqueous blocked polyisocyanates blocked with sodium hyposulfite, etc. Pigments include organic or inorganic pigments, and paints. Acrylic additives for
Known materials such as silicon-based and fluorine-based materials can be mentioned. The binder for water-based paints of the present invention has excellent adhesion to metals, and also has excellent water resistance and corrosion resistance that cannot be obtained with conventional water-based paints. In particular, it has excellent boiling water resistance, which has traditionally been difficult to achieve with water-based paints, making it ideal for can paints. It can also be used as a baking paint. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples. In the examples, parts simply indicate parts by weight. Further, various properties were measured according to the following methods. (1) Molecular weight: Molecular weight measuring device (manufactured by Hitachi)
115 type) was used for measurement. (2) Adhesion: Compliant with ASTMD-3359. (3) Gloss...Gloss meter (manufactured by Nippon Denshoku Kogyo Co., Ltd., TYPE
-VG107). (4) Water resistance: Compliant with JIS5400. (5) Erichsen value: Based on JIS Z-2247. (6) Corrosion resistance: Compliant with JIS Z-2371. (7) Boiling water resistance...The gloss retention rate was measured after being immersed in boiling water for 1 hour. Production example 1 475 parts of dimethyl terephthalate, 466 parts of dimethyl isophthalate, 44 parts of dimethyl 5-sodium sulfoisophthalate, 409 parts of ethylene glycol
part, 458 parts of neopentyl glycol, zinc acetate
0.44 parts of sodium acetate, 0.02 parts of antimony trioxide, and 0.43 parts of antimony trioxide were charged into a reaction vessel and heated at 140 to 220°C.
The transesterification reaction was carried out over time. Then,
The pressure was reduced to 5 mmHg over 1 hour at 220°C to 260°C, and a polycondensation reaction was further carried out at 260°C under vacuum of 0.1 to 0.2 mmHg for 1 hour to obtain a polyester resin (A-1). Polyester resin (A-1) has a molecular weight of 15,000
The results of composition analysis by NMR etc. are 49 mol% of terephthalic acid, 48 mol% of isophthalic acid, 3 mol% of 5-sodium sulfoisophthalic acid, 45 mol% of ethylene glycol, and 55 mol% of neopentyl glycol.
It was in mol%. Furthermore, polyester resins (A-2) to (A-
9) was obtained.

[Table] Example 1 300 parts of polyester resin (A-1) and 140 parts of n-butyl cellosolve were charged in a melter,
After stirring at 170℃ for about 3 hours to obtain a viscous melt,
Gradually add 560 parts of water while stirring vigorously to make approx.
After a period of time, a homogeneous pale blue-white aqueous dispersion was obtained. Next, 20 parts of Sumimaru M-50W (manufactured by Sumitomo Chemical Industries, Ltd., solid content 80% by weight aqueous solution) as an amino resin was added to 100 parts of this aqueous dispersion to obtain a binder for water-based paints (B-1). The mixing proportions of the polyester resin (A-1), amino resin, organic compound compatible with water, and water in this binder are 25% by weight, 13% by weight, 12% by weight, and 50% by weight of water, respectively. It was %. The obtained binder for water-based paint (B-1) was 0
℃ and 40℃ for one month, but no change was observed in appearance. Next, titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., Taipei R-
40 parts of ethylene glycol dispersion (solid content: 50% by weight) of 930) and 0.5 part of a 50% by weight ethanol solution of paint additive XF-3913 (manufactured by Toshiba Silicon) were added and mixed with thorough stirring to obtain a water-based paint. . This water-based paint was applied to a cold-rolled steel plate treated with zinc phosphate using Bonderite #37 using a bar coater #36 to a film thickness of 20μ, dried at 150℃ for 2 minutes, and then dried at 250℃ for 2 minutes. I did the baking. The resulting coating film has excellent gloss and smoothness, and has a pencil hardness.
2H, Erichsen 7mm or more, adhesion 100/100, water resistance test 300 hours adhesion 100/100, corrosion resistance test 300
Erosion width after 2.5mm, gloss retention after boiling water test
It was 95%. Examples 2 to 4 A binder for water-based paints was prepared using the polyester resins (A-2) to (A-4) amino resins shown in Table 2 and organic compounds compatible with water in the same manner as in Example 1. (B-2) to (B-4) were obtained. These binders for water-based paints (B-2) ~
Paints were manufactured using (B-4) in the same manner as in Example 1, and the results of coating film measurements of these paints are shown in Table 3. Comparative Examples 1 to 8 Binders for water-based paints (B-5) to (B-12) shown in Table 2 were obtained in the same manner as in Example 1. Next, a paint was produced in the same manner as in Example 1, and the measurement results of the resulting paint film are shown in Table 3.

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Claims (1)

[Claims] 1. Polyester resin (A) 70-6 having the following composition
Weight%, amino resin (B) 0.5-28% by weight, water-compatible organic compound (C) 36-1% by weight, and water 24-28% by weight
A binder for water-based paints characterized by containing 89% by weight. (However, (C) is per 100 parts by weight of water at 20℃
One or more compounds selected from the group of aliphatic and alicyclic alcohols, ethers, esters and ketones, having a solubility of 20 parts by weight or more. ) Polyester resin: (1) The dicarboxylic acid component is 99.5 to 50 mol% of aromatic dicarboxylic acid containing no sulfonic acid metal base, 0 to 49.5 mol% of aliphatic or alicyclic dicarboxylic acid having 4 to 36 carbon atoms, and sulfonic acid. It consists of 0.5 to 7 mol% of aromatic dicarboxylic acid containing a metal base, and (2) the glycol component is an aliphatic glycol having 2 to 8 carbon atoms.
100 to 20 mol% and 0 to 80 mol% of an ethylene oxide or propylene oxide adduct of alicyclic glycol having 6 to 15 carbon atoms and/or bisphenol A, and (3) 0 to 10 mol% based on the total carboxylic acid component. % of trivalent or higher polycarboxylic acid and/or polyester resin consisting of 0 to 10 mol % of trivalent or higher polyol based on the total alcohol component.