JP4605534B2 - 1-pack room temperature curable coating composition - Google Patents

Description

  The present invention relates to a one-component room temperature curable coating composition that can be suitably used for metals, particularly galvanized, nonferrous metals such as aluminum, magnesium alloys and stainless steel.

  Conventionally, for coating non-ferrous structures such as galvanized steel and aluminum steel, epoxy resin-based one-component room-temperature curable coating compositions with excellent performance such as adhesion, corrosion resistance, water resistance, impact resistance, and drying properties Things are used. This composition is usually composed of an epoxy resin, which is the main agent, and an amine curing agent, but when used, these two liquids must be weighed and mixed at a predetermined ratio in the field, and the work becomes complicated. In addition, after mixing, the curing reaction proceeds, the viscosity gradually increases, and eventually gelation occurs, so that the pot life is limited. In order to solve such a problem, an epoxy resin-based one-component room temperature curable coating composition using a ketimine compound that is a latent curing agent has been developed (for example, see Patent Document 1). It is not satisfactory in terms of adhesion and hardness. Also, the gloss of the coating film is not sufficient, and dissatisfaction remains in applications where a high design is required.

  In order to dissolve a highly polar epoxy resin or ketimine compound, generally an aromatic hydrocarbon solvent such as xylene or toluene, or a polar solvent such as butyl acetate, butanol or MIBK (methyl isobutyl ketone) (so-called, However, these strong solvents have a unique irritating odor, and have a low boiling point and a low flash point. Therefore, they do not meet today's demand for low VOC. Further, when a paint containing these strong solvents is used as a repair paint, there is a problem in that the old paint film is attacked by the solvent, and the old paint film is lifted from the base. Therefore, it is conceivable to use a solvent (so-called weak solvent) mainly composed of a non-polar aliphatic hydrocarbon compound such as hexane in place of these strong solvents, but a highly polar epoxy resin or ketimine compound. Since it is difficult to melt | dissolve, the problem that the storage stability of a coating composition is inferior has arisen. Although it is conceivable to use an epoxy resin having a low polarity in order to solve such a problem, the adhesion of the coating film to the object to be coated is not sufficient.

JP-A-8-217859

  An object of the present invention is a one-pack room-temperature curable coating composition containing an epoxy resin as a main component and a ketimine compound as a curing agent, and furthermore, excellent adhesion, hardness, and gloss of a coating film to an object are obtained. An object of the present invention is to provide a one-component room temperature curable coating composition. Furthermore, another object of the present invention is to provide a one-component room temperature curable coating composition that suppresses lifting of an old coating film during repeated coating of the coating film and has good storage stability.

  The present applicant has made extensive studies to solve such problems. That is, in the coating composition in which the main agent is a low-polarity epoxy resin and the solvent is the weak solvent, the film performance (adhesion to an object to be coated, particularly hardness, gloss, etc.) is insufficient. In view of the above problem, the idea was to introduce a bulky cyclic structure into the molecule of the epoxy resin. Next, based on the idea, in a low-polar epoxy resin coating composition containing a conventional ketimine compound, by using a rosin glycidyl ester having a bulky hydrophenanthrene nucleus in the molecule as one component of the main agent. The present inventors have found that this problem can be solved and have completed the present invention.

That is, the present invention relates to rosin glycidyl ester (A), a glycidyl ether type epoxy resin of polyhydric alcohol, an alicyclic epoxy resin, and a glycidyl ether type epoxy resin of polyhydric phenol, which are soluble in an aliphatic hydrocarbon solvent. Containing at least one epoxy resin (B) selected from the group consisting of modified epoxy resins obtained by modifying a fatty acid with a fatty acid, a ketimine compound (C), an aliphatic hydrocarbon solvent (D) and a dehydrating agent (E) The one-component room temperature curable coating composition.

  According to the present invention, not only the complicated two-component mixing operation is wiped out, but also excellent adhesion to the object to be coated, corrosion resistance, water resistance, impact resistance, drying property, sufficient hardness and gloss. It is possible to provide a one-component room-temperature-curing coating composition that can provide a coating film having the above-described properties, can suppress lifting of an old coating film during overcoating, and has good storage stability.

  In the one-pack room temperature curable coating composition of the present invention, as described above, the rosin glycidyl ester (A) is indispensably used in order to improve the coating film performance (adhesion, especially hardness and gloss). . The rosin glycidyl ester (A) is generally a reaction product of rosin and epihalohydrin. Specific examples of the rosin include gum rosin, tall oil rosin, wood rosin, disproportionated rosin, hydrogenated rosin and the like, and these can be used alone or in combination of two or more. Of these, disproportionated rosin and hydrogenated rosin are preferred because the resulting coating composition is less colored and discolored. Specific examples of the epihalohydrin include, for example, epifluorohydrin, β-methylepifluorohydrin, epichlorohydrin, β-methylepichlorohydrin, epibromohydrin, β-methylepibromohydrin, Epiiodohydrin, β-methylepiiodohydrin, etc. may be mentioned, and these may be used alone or in combination of two or more. Of these, epichlorohydrin and β-methylepichlorohydrin are preferred because they are easily available.

Soluble in aliphatic hydrocarbon solvent, soluble in aliphatic hydrocarbon solvent, glycidyl ether type epoxy resin of polyhydric alcohol, alicyclic epoxy resin, and glycidyl ether type epoxy resin of polyhydric phenol At least one epoxy resin (B) selected from the group consisting of modified epoxy resins modified with fatty acids (hereinafter referred to as epoxy resin (B)) is the main component of the coating composition according to the present invention. . This has an average of 2 or more, preferably 2 to 5, epoxy groups in one molecule, has an epoxy equivalent of about 200 to 2000, preferably 300 to 1000, and n-butane. , N-hexane, n-heptane, n-octane, isononane, n-decane, n-dodecane, cyclopentane, cyclohexane, cyclobutane and the like can be uniformly dissolved in a non-polar aliphatic hydrocarbon solvent. If the epoxy equivalent is less than 200, the coating strength tends to decrease. If the epoxy equivalent is more than 2000, the viscosity of the coating composition increases and the smoothness of the coating and the coating workability tend to decrease. The epoxy resin (B) and the rosin glycidyl ester (A) both have an epoxy group, but both are clearly distinguished as different concepts.

Examples of the polyhydric alcohol glycidyl ether type epoxy resin include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, neopentyl glycol, butylene glycol, hexanediol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, diglycerin. And a reaction product of any one of sorbitol and epichlorohydrin.

Examples of the alicyclic epoxy resin include (3,4-epoxy-6-methylcyclohexyl) methyl-3,4-epoxy-6-methylcyclohexanecarboxylate, (3,4-epoxycyclohexyl) methyl-3,4-. Epoxy cyclohexane carboxylate, bis (3,4-epoxycyclohexylmethyl) adipate, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, trifunctional alicyclic epoxy resin (manufactured by Daicel Chemical Industries, Ltd., product) Name “Epolide GT300”), tetrafunctional alicyclic epoxy resin (manufactured by Daicel Chemical Industries, Ltd., trade name “Epolide GT400”), polyfunctional alicyclic epoxy resin (manufactured by Daicel Chemical Industries, Ltd., trade name “ EHPE ") and the like.

Examples of the modified epoxy resin (a product obtained by modifying a glycidyl ether type epoxy resin of polyhydric phenol with a fatty acid ) include, for example, a glycidyl ether type epoxy resin obtained by reacting bisphenol A, bisphenol F or the like with epichlorohydrin. And those modified with sebacic acid, dodecanoic acid, dimer acid and the like . Among them, a dimer acid-modified epoxy resin obtained by modifying a glycidyl ether type epoxy resin using bisphenol A with dimer acid and an alkylphenol-modified epoxy resin obtained by modifying the epoxy resin with nonylphenol are storage stability of the coating composition according to the present invention. It is preferably used because of its excellent resistance. Dimer acid is a dimerization of higher unsaturated fatty acids such as purified vegetable oil fatty acids obtained from drying oils and semi-drying oils. Examples of unsaturated fatty acids generally include those having 12 to 24 carbon atoms. The dimer acid may be hydrogenated. The structure of dimer acid is described in, for example, Japanese Patent Publication No. 6-8399.

  In the present invention, when an epoxy resin that is insoluble or hardly soluble in an aliphatic hydrocarbon solvent is used instead of the epoxy resin (B), a stable coating composition cannot be obtained during storage. Examples of such an epoxy resin include a glycidyl ether type epoxy resin obtained by reacting bisphenol A or bisphenol F with epichlorohydrin.

The weight ratio [(A) / (B)] of the rosin glycidyl ester (A) and the epoxy resin (B) is usually about 5/95 to 80/20, preferably 10/90 to 60/40. . If the amount of rosin glycidyl ester (A) is less than the lower limit of the numerical range, the adhesion, hardness and gloss of the coating tend to be insufficient, and if the amount is higher than the upper limit, the coating becomes brittle and adheres to the substrate. Tend to decrease.

  The ketimine compound (C) serves as a curing agent that causes a crosslinking reaction with the rosin glycidyl ester (A) and the epoxy resin (B) to cure the coating film. This is a compound having two or more primary amino groups blocked with a carbonyl compound in one molecule and having no amino group other than the blocked amino group. Here, the “primary amino group blocked with a carbonyl compound” refers to a protected amino group that can be easily hydrolyzed and replaced with a free primary amino group in the presence of moisture, for example. Can be represented by the following general formula.

(In formula, R < ¹ >, R < ² > may be the same or different, and represents a hydrogen atom or a C1-C8 alkyl group, cycloalkyl, or aromatic group which may be branched.)

The ketimine compound (C) is obtained by, for example, reacting a polyamine compound having two or more primary amino groups in one molecule with a carbonyl compound according to various known methods to convert the primary amino group in the polyamine compound. Substantially all can be blocked to obtain a protected amino group represented by the above general formula.

The polyamine compound before blocking may be any of aliphatic, alicyclic and aromatic. The polyamine compound generally has a primary amino group equivalent in the range of about 2000 or less, preferably in the range of about 30 to about 1000, and generally in the range of about 5000 or less, preferably in the range of about 60 to 3000. Having a number average molecular weight of

Specific examples of the polyamine compound include aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, and poly (oxypropylene) diamine; aromatic polyamines such as xylylenediamine, diaminodiphenylmethane, and phenylenediamine; isophorone Examples thereof include alicyclic polyamines such as diamine and 1,3-bisaminomethylcyclohexane.

Examples of the carbonyl compound used for blocking the polyamine compound include ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone; aldehydes such as acetaldehyde and benzaldehyde. Can be mentioned.

The polyamine compound can be ketiminized by blocking with the ketones according to a known method, or can be aldiminated by blocking with the aldehydes. The ketimine compound (C) in the present invention includes both ketimine and aldimine.

In addition, when the total equivalent of each epoxy group of the rosin glycidyl ester (A) and the epoxy resin (B) is 1 equivalent, the total equivalent of active hydrogen in the primary amino group regenerated from (C) is Usually, it is about 0.5 to 1.5, preferably 0.8 to 1.2. Even if it is lower or higher than the lower limit of the numerical range, the coating film is not sufficiently cured.

The aliphatic hydrocarbon solvent (D) is used for the purpose of uniformly dissolving or dispersing each component of the coating composition according to the present invention, adjusting the viscosity, forming a coating film, and the like. Those consisting only of the aromatic cyclic solvent can be preferably used, but a small part thereof may be substituted with a polar solvent such as an aromatic hydrocarbon compound or MIBK. However, if the amount is too large, the old coating film may be lifted when the coating composition according to the present invention is applied over the old coating film, and therefore the aliphatic hydrocarbon solvent (D) is occupied. The amount is usually 30% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less. The amount of the aliphatic hydrocarbon solvent (D) used is determined in consideration of the viscosity of the paint and the workability at the time of painting, and is usually about 20 to 80% by weight in the paint composition according to the present invention. . The coating composition according to the present invention may contain a slight amount of an aromatic solvent derived from the epoxy resin (B).

  Specific examples of the aliphatic hydrocarbon solvent (D) include aliphatic hydrocarbon compounds such as n-butane, n-hexane, n-heptane, n-octane, isononane, n-decane and n-dodecane; Fats such as cyclohexane, methylcyclohexane, ethylcyclohexane, hydrogenated xylene, Ricasolve 900 (“Ricasolve” is a registered trademark of Shin Nippon Rika Co., Ltd.), Swaclin 150 (“Suwakurin” is a registered trademark of Maruzen Petrochemical Co., Ltd.) VM & P naphtha, solvent kerosene, solvent naphtha, mineral spirit, Swazol 310, ("Swazol" is a registered trademark of Cosmo Oil Co., Ltd.), New Solvent A ("New Solvent" is a product of Mitsubishi Oil Corporation) Registered trademark), LAWS, HAWS (manufactured by Shell), IP solvent (Idemitsu Kosan Co., Ltd.) Ltd.), Exxon naphtha, Ekusanoru, manufactured Iasoba (Exxon Corporation) such as so-called weak solvent is used, such as, they may be used in combination alone, or two or more kinds.

The dehydrating agent (E) is blended for the purpose of capturing moisture present in the paint during storage and preventing the regeneration of the primary amine from the ketimine compound (C). It can be used without particular limitation. Specifically, for example, synthetic silica, activated alumina, zeolite, activated carbon, or the like is used as a metal oxide or carbonized material that is powdery and rich in porosity. Examples of calcium compounds having a composition such as CaSO ₄ , CaSO ₄ .1 / 2H ₂ O, and CaO include calcined gypsum, soluble gypsum, and quicklime. Examples of metal alkoxides include aluminum isopropylate, aluminum sec-butyrate, tetraisopropyl titanate, tetra n-butyl titanate, zirconium 2-propylate, zirconium n-butyrate, ethyl silicate, vinyltrimethoxysilane, and the like. Examples of the organic alkoxy compounds include methyl orthoformate, ethyl orthoformate, ethyl orthoacetate, and dimethoxypropane. As monofunctional isocyanates, for example, methyl isocyanate, ethyl isocyanate, propyl isocyanate, additive TI (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name) and the like are used. These dehydrating agents (E) can be used alone or in combination of two or more.

The amount of the dehydrating agent (E) used varies depending on the amount of water contained in the coating composition, the absorption / adsorption capacity of the dehydrating agent and the reactivity with water, but from the viewpoint of storage stability and coating film performance. In general, it is 0.1 to 5.0% by weight, preferably 0.2 to 2.0% by weight, based on the weight (solid content) of the coating composition according to the present invention. . If the value is less than the lower limit of the numerical range, the long-term storage stability of the coating composition tends to decrease. If the value is higher than the upper limit, the reaction between the ketimine compound (C) in the coating film and moisture in the atmosphere occurs. It is hindered, the crosslinking reaction with the epoxy resin is delayed, and it takes a long time for curing.

  The one-component room temperature curable coating composition according to the present invention is obtained by mixing and stirring the above (A) to (E) by a known method such as a sand mill. Pigments, mica, talc and other pigments; additives such as thickeners, plasticizers, fillers and dispersants may be blended.

  The coating method of the coating composition according to the present invention is not particularly limited, and known means such as brush coating, spray coating, and various coater coatings can be used. The coating composition according to the present invention is applied in the range of about 5 to 80 μm, preferably about 10 to 50 μm in dry film thickness per coating, and the coating is usually performed once or twice.

  The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples.

Synthesis of rosin glycidyl ester 300 kg of disproportionated rosin, 600 parts of epichlorohydrin and 0.5 part of trimethylacetate were charged in a reaction vessel equipped with a stirrer, thermometer, nitrogen introduction tube and reflux tube, and heated at 80 ° C. for 3 hours. 40 parts of sodium hydroxide were added. Subsequently, it heated at 120 degreeC and produced | generated water and excess epichlorohydrin were depressurizingly distilled. Thereafter, 400 parts of toluene was added to the residue and the precipitated sodium chloride was filtered, and then toluene was distilled off to obtain a rosin glycidyl ester having an epoxy equivalent of 450.

Synthesis of dimer acid-modified epoxy resin Epicoat 828 (diglycidyl ester of bisphenol A having an epoxy equivalent of 190: manufactured by Japan Epoxy Resin Co., Ltd.) 380 parts and Empol 1061 (dimer acid: Cognis Japan Co., Ltd.) 280 parts) was charged and reacted at 150 ° C. for 8 hours to obtain a dimer acid-modified epoxy resin having an epoxy equivalent of 660.

Example 1-3, Comparative Example 1-4
Each component was mixed in the formulation shown in Table 1 to prepare a one-pack room temperature curable coating composition. Each coating composition obtained was applied to a hot-dip galvanized steel plate and an aluminum plate with a bar coater so that the dry film thickness was 40 μm, and dried at room temperature (23 ± 10 ° C.) for 7 days to obtain a cured film.

(performance test)
(1) Gloss: Measured according to JIS K-5600.
(2) Hardness (pencil hardness): Measured using Mitsubishi Uni in accordance with JIS K-5600.
(3) Adhesion: Cut each test coating plate with a knife until it reaches the substrate, make 100 goby meshes with 2mm spacing, and stick adhesive tape on it, then remain when peeled off rapidly The coating film adhesion was examined by examining the number of gobangs (according to JIS K-5600).
(4) Old coating film compatibility: A synthetic resin blend paint (long oil alkyd acid resin-based paint) applied to an aluminum plate with a film thickness of 30μ, dried at room temperature for 3 months, and then cross-cut scratched with a cutter Was used as a test piece. Each composition obtained in Examples and Comparative Examples was applied to the obtained test plate, and the state of the coating film was observed when left at 23 ° C. and 65% RH.
○: No abnormality ×: Lifting occurred in the coating film

* 1: Epicoat 1001 (epoxy equivalent 450, manufactured by Japan Epoxy Resin Co., Ltd.)
* 2: Diethylenetriamine methyl isobutyl ketone block (active hydrogen equivalent 107, trade name “Epicure H30”, manufactured by Japan Epoxy Resins Co., Ltd.)
* 3: Methyl orthoformate (manufactured by Nichiho Chemical Co., Ltd.)

Claims (5)

The rosin glycidyl ester (A), a polyhydric alcohol glycidyl ether type epoxy resin, an alicyclic epoxy resin, and a polyhydric phenol glycidyl ether type epoxy resin, which are soluble in an aliphatic hydrocarbon solvent, are modified with a fatty acid. One-pack room temperature containing at least one epoxy resin (B) selected from the group consisting of epoxy resins , ketimine compounds (C), aliphatic hydrocarbon solvents (D) and dehydrating agents (E) A curable coating composition. The one-pack room temperature curable coating material according to claim 1, wherein the epoxy resin (B) has 2 to 5 epoxy groups in one molecule and has an epoxy equivalent in the range of 200 to 2000. Composition. The one-component room temperature curable coating composition according to claim 1 or 2, wherein the weight ratio (A) / (B) used between (A) and (B) is 5/95 to 80/20. The total 1 equivalent of the epoxy group of the epoxy groups and (B) of (A), according to claim 1 which is 0.5 to 1.5 equivalents of active hydrogen in the primary amino groups reproduced from the (C) 4. The one-component room temperature curable coating composition according to any one of 3 above. (B) is a modified epoxy resin obtained by modifying a bisphenol A type epoxy resin with a dimer acid, The one-component room temperature curable coating composition according to any one of claims 1 to 4 .