JPH04292675A - Polyurethane based coating composition - Google Patents

Abstract

PURPOSE:To obtain one-pack type polyurethane coating composition having low cross-linking temperature and excellent compatibility, weather resistance and yellowing resistance. CONSTITUTION:A coating composition obtained by blending a polyol having 10--300 hydroxyl value based on resin content with a blocked isocyanate obtained by blocking an isocyanate group of an aliphatic polyisocyanate having isocyanurate structure with an oxime based compound or lactam based compound, etc., at a molar ratio of the blocked isocyanate group to hydroxyl group in polyol of 0.4:1 to 2:1 and containing one or two or more kinds of curing accelerators selected from chelate compounds of cobalt, zinc, nickel, tin, manganese and copper at an amount of 0.5-5wt.% based on the resin solid content.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to thermosetting coating compositions using blocked isocyanates.

0002

[Prior Art] Conventionally, polyurethane resin paints have very excellent abrasion resistance, chemical resistance, and stain resistance. has even better weather resistance, and its demand is on the rise.

However, since polyurethane resin paints are generally two-component, their use has been extremely inconvenient. That is, ordinary urethane resin paints consist of two components, polyol and polyisocyanate, which must be stored separately and mixed at the time of coating. Furthermore, once mixed, the current situation is that the paint gels in a short period of time and becomes unusable. This makes it extremely difficult to perform automatic painting in the field of line painting such as automobiles or weak electric painting.

Furthermore, since it is necessary to thoroughly clean the coating machine and coating tank at the end of the work, the work efficiency is significantly reduced. In order to improve the above-mentioned drawbacks, it has been proposed to use blocked isocyanates in which all active isocyanate groups are blocked with blocking agents. This blocked isocyanate does not react with the polyol at room temperature, but at high temperatures it dissociates the blocking agent and regenerates the active isocyanate group, which reacts with the polyol and causes a crosslinking reaction, thus improving the above-mentioned drawbacks. I can do it.

However, the above-mentioned crosslinking reaction requires a high baking temperature. High baking temperatures not only increase energy costs but also increase air pollution associated with them, and are a fatal drawback when coating materials that are sensitive to heat such as plastics. Therefore, in the field of polyurethane resin paints, there has been a demand for a one-component polyurethane resin paint that has excellent weather resistance and has a low baking temperature.

Several proposals have been made to lower the crosslinking temperature. In Japanese Patent Publication Nos. 44-18877, 53-138434, 56-84714, and 57-8217, a specific organic tin compound is added as a catalyst. In JP-A-62-199609, a lead compound and an inorganic zinc compound are added as catalysts.

[0007]

[Problems to be Solved by the Invention] However, the crosslinking temperature of paints using blocked isocyanate, in which the isocyanate groups of polyisocyanate are masked, as a curing agent is not so low, and the applications thereof have been limited. An object of the present invention is to provide a coating composition that lowers the crosslinking temperature of a coating using a blocked isocyanate in which the isocyanate groups of a polyisocyanate having an isocyanurate structure are masked as a curing agent.

[0008]

[Means for Solving the Problems] As a result of intensive studies by the present inventors, by combining a specific blocked isocyanate and a specific organometallic compound, the crosslinking temperature of a paint using a blocked isocyanate as a curing agent is reduced. The present invention was achieved by successfully achieving this goal. That is, in the present invention, the resin has a hydroxyl value of 10 to
300 polyol, blocked isocyanate that blocks the isocyanate group of aliphatic polyisocyanate having an isocyanurate structure, and one or more types selected from chelate compounds of cobalt, zinc, nickel, tin, manganese, and copper. This is a coating composition characterized by containing a curing accelerator as a main component.

The blocked isocyanate used in the present invention is a blocked isocyanate obtained by blocking the isocyanate groups of a polyisocyanate having an isocyanurate structure with a blocking agent. Polyisocyanates having an isocyanurate structure are obtained by cyclic trimerization of aliphatic diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate as raw materials. Polyisocyanates having this isocyanurate structure are disclosed in JP-A-57-47321 and JP-A-61-11137.
It may be urethane modified using the technique disclosed in No. 1 et al. In this case, urethane modification is performed using hydroxyl compounds, such as methanol, ethanol, isopropanol, monohydroxy compounds such as phenol, ethylene glycol, propylene glycol, 1,3-butanediol, pentanediol, hexanediol, cyclohexanediol, neopentyl glycol. ,2,2,4
-Dihydroxyl compounds such as trimethyl 1,3-pentanediol and the like. Even when used alone, these
More than one species may be used in combination.

By using a material having this isocyanurate structure, the compatibility with polyols, especially acrylic polyols, is improved, and an excellent non-yellowing paint can be obtained. The isocyanate groups of the polyisocyanate described above are blocked with a blocking agent to form a blocked isocyanate. Blocking agents include phenol-based, alcohol-based, active methylene, mercaptan-based, acid amide-based, acid imide-based, imidazole-based, urea-based, oxime-based, amine-based, and imide-based compounds, and these may be used alone or May be used in combination. More specific examples of blocking agents are shown below. (1) Phenols: phenol, cresol, ethylphenol, butylphenol, etc. (2) Alcohols: butyl cellosolve, propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol,
Methanol, ethanol, 2-ethylhexanol, etc.
(3) Active methylene type; dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, etc.; (4) Mercaptan type; butyl mercaptan, dodecyl mercaptan, etc.; (5) Acid amide type; acetanilide, acetate amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc., (6) acid imide series; succinimide, maleic acid imide, etc., (7) imidazole series; imidazole, 2-methylimidazole, etc., (8) urea series; Urea, thiourea, ethylene urea, etc. (9
) Oxime series: formaldoxime, acetaldoxime, acetone oxime, methyl ethyl ketoxime, cyclohexanone oxime, etc., (10) amine series: diphenylamine, aniline, carbazole, etc., (12)
Imine type: ethyleneimine, polyethyleneimine, etc., oxime type and acid amide type are preferred, and acetone oxime, methyl ethyl ketoxime, and lactam are particularly preferred.

[0011] In the present invention, a polyol is a compound having at least two hydroxyl groups in one molecule, and examples of such compounds include aliphatic hydrocarbon polyols,
Examples include polyether polyols, polyester polyols, epoxy resins, and acrylic polyols. Specific examples of aliphatic hydrocarbon polyols include:
Examples include polybutadiene with terminal hydroxyl groups and hydrogenated products thereof. Examples of polyether polyols include polyether polyols obtained by adding alkylene oxides such as ethylene oxide and propylene oxide alone or as a mixture to polyhydric alcohols such as glycerin and propylene glycol, and polytetra Polyether polyols obtained by reacting methylene glycols and alkylene oxides with polyfunctional compounds such as ethylenediamine and ethanolamine, and so-called polymer polyols obtained by polymerizing acrylamide etc. using these polyethers as a medium. etc. are included.

Examples of the polyester polyols include dibasic acids selected from the group of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid. or polyester polyol resins and e.g. Examples include polycaprolactones obtained by ring-opening polymerization of caprolactone using a polyhydric alcohol.

Examples of fluorine polyols include copolymers of fluoroolefins, cyclohexyl vinyl ethers, hydroxyalkyl vinyl ethers, monocarboxylic acid vinyl esters, etc. disclosed in JP-A-57-34107, JP-A-61-275311, etc. etc. Epoxy resins include, for example, novolak type, β-methylepicro type, cyclic oxirane type, glycidyl ether type, glycol ether type, epoxy type of aliphatic unsaturated compounds, epoxidized fatty acid ester type, polycarboxylic acid ester type, amino Epoxy resins such as glycidyl type, halogenated type, and resorcin type are mentioned.

Examples of the acrylic polyol include acrylic esters having active hydrogen such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate, or acrylic monoester of glycerin. Alternatively, methacrylic acid monoester, trimethylolpropane acrylic acid monoester is used singly or in combination with methacrylic acid monoester, methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid-n-
Acrylic acid esters such as butyl, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, and methacrylates such as lauryl methacrylate. Acrylic acid, singly or in mixtures selected from the group of acid esters;
Unsaturated carboxylic acids such as methacrylic acid, maleic acid, itaconic acid, unsaturated amides such as acrylamide, N-methylolacrylamide, diacetone acrylamide, glycidyl methacrylate, styrene, vinyltoluene,
Examples include acrylic polyol resins obtained by polymerizing in the presence or absence of other polymerizable monomers such as vinyl acetate and acrylonitrile, either alone or in a mixture.

Particularly preferred among these polyols are acrylic polyols. In the present invention, the polyol preferably has a resin hydroxyl value of 10 to 300. If the resin hydroxyl value is less than 10, the crosslinking density of the urethane due to the reaction with the isocyanate component will decrease, and the urethane bond function will not be exerted, and the resin hydroxyl value will be less than 30.
If it exceeds 0, on the contrary, the crosslinking density will increase and the mechanical properties of the coating film will deteriorate, which is undesirable, and in some cases, the hydroxyl group and the isocyanate group will not react completely.

In the thus obtained blocked isocyanate and polyol, the molar ratio of the blocked isocyanate groups in the blocked isocyanate to the hydroxyl groups in the polyol is in the range of 0.4:1 to 2:1. is suitable. The curing accelerator used in the present invention will be described. The metal chelate compound used in the present invention includes cobalt,
It is a chelate compound of zinc, nickel, tin, manganese, copper, and organic compounds of these metals.

In these organometallic compounds, at least one metal atom is an alkoxy group having 1 to 14 carbon atoms, such as methoxy, ethoxy, n-propoxy,
Isopropoxy, n-butoxy, isobutoxy, sce
-butoxy, n-pentoxy, isoamyloxy, n-
Compounds such as heptyloxy, n-octyloxy, n-stearyloxy, or alkoxyalkoxy groups having 2 to 10 carbon atoms, such as methoxymethoxy, methoxyethoxy, ethoxybutoxy, butoxypentoxy, etc., are preferred. .

The remaining groups bonded to the above-mentioned metals include, for example, alkyl groups having 1 to 8 carbon atoms, such as methyl, ethyl, n-butyl, isobutyl, sec.
-Butyl, tert-butyl, amyl group, etc., aryl group such as phenyl group, tolyl group, etc., alkenyl group such as vinyl, allyl group, etc., alkyl group having 1 to 8 carbon atoms substituted with mercapto group or amino group, such as γ- These include mercaptopropyl, aminoethyl, aminopropyl, aminobutyl groups, and the like.

Examples of the chelating agent include lower alkanolamines such as triethanolamine, diethanolamine, dimethylaminoethanol and dimethylaminoethanol, acetoacetic esters such as methyl acetoacetate and ethyl acetoacetate, and diketone alcohols such as diacetone alcohol. diketones such as acetylacetone, glycols such as ethylene glycol and octylene glycol, oxycarboxylic acids such as lactic acid and tartaric acid, dicarboxylic acids or their esters such as maleic acid and ethyl malonate, other salicylic acid, catechol, and pyrogallol. Among them, diketones and acetoacetic esters are preferred.

Typical examples of the metal compounds used in the present invention include dibutyl bis(acetylacetone)tin,
Butyl tris(acetylacetonate)tin, dipropyl bis(acetylacetonate)tin, propyl tris(acetylacetonate)tin, dioctyl bis(acetylacetonate), dibutyl bis(ethylacetoacetate)tin, propyl・Tris (ethylacetoacetate) tin, propoxy tris (ethylacetoacetate) tin, bis (acetylacetone) zinc, bis (ethylacetoacetate) zinc, dipropoxy bis (acetylacetonate) cobalt, dipropoxy bis (ethylacetoacetate) ) cobalt, bis(acetylacetone) cobalt, bis(acetylacetone) nickel,
Bis(ethylacetoacetate)nickel may be mentioned. These may be used alone or in combination of two or more. Preferably it is a bis(acetylacetone) salt. The amount added is not particularly limited, but is usually 0.01 to 10% by weight, preferably 0.5 to 10% by weight based on the resin solid content.
It is 5% by weight.

[0021] The composition of the present invention can also be used as a powder coating, and if necessary, a suitable solvent such as benzene, toluene, xylene, cyclohexane, mineral spirit may be used when mixing the components. , hydrocarbons such as naphtha, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, acetic acid-n-
It can also be used as a solvent-based paint by appropriately selecting from the group of esters such as butyl and cellosolve acetate depending on the purpose and use. These solvents may be used alone or in combination of two or more. Further, antioxidants, ultraviolet absorbers, pigments, etc. may be added as necessary.

[0022]

EXAMPLES The present invention will be explained in more detail below based on examples, but the present invention is not limited to the following examples. All formulations in Examples and Comparative Examples are expressed by weight. Evaluation was performed according to the following. (Gel fraction) The coating film after hardening by baking is soaked in acetone at 20°C.
When the weight of the undissolved portion after immersion for 24 hours is less than 50% of the weight before immersion, ×, 50 to less than 85%, △, 85%
The above items were evaluated as ○. (Coating film haze value) A coating film with a film thickness of 30 μ applied to a 1 mm thick transparent glass plate was measured using a direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. The value was 1.
．． Less than 0 was evaluated as ○, and 1.0 or more was evaluated as ×.

[0023]

[Reference Example-1] (Production of isocyanurate-based blocked isocyanate) A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen blowing tube was made into a nitrogen atmosphere, and an isocyanurate structure using HDI as a raw material was prepared. 100 parts of a polyisocyanate compound (Duranate TPA-100, manufactured by Asahi Kasei Industries, Ltd.) and 37 parts of ethyl acetate were added and thoroughly mixed. 48 parts of butanone oxime was added dropwise over 2 hours while maintaining the temperature inside the flask at 40 to 50°C. It was confirmed that the absorption of isocyanate groups in the infrared spectrum had disappeared.

[0024]

[Reference Example-2] (Manufacture of buret-based blocked isocyanate) Using the same apparatus as in Reference Example-1, after creating a nitrogen atmosphere in the flask, a polyisocyanate having a burette structure made from HDI (Asahi Kasei Corporation 100 parts of Duranate 24A-100) and 37 parts of ethyl acetate were added and mixed thoroughly. The temperature inside the flask is 40-5.
While maintaining the temperature at 0°C, 49 parts of butanone oxime was added dropwise over 2 hours. It was confirmed that the absorption of isocyanate groups in the infrared spectrum had disappeared.

[0025]

[Reference Example-3] (Production of isocyanurate-based blocked isocyanate) Using the same equipment as in Reference Example-1, after creating a nitrogen atmosphere in the flask, a polyurethane-modified isocyanurate structure using HDI as a raw material was produced. Isocyanate (Asahi Kasei Co., Ltd.) Duranate THA-100
) and 36 parts of ethyl acetate were added and thoroughly mixed. 44 parts of butanone oxime was added dropwise over 2 hours while maintaining the temperature inside the flask at 40 to 50°C. It was confirmed that the absorption of isocyanate groups in the infrared spectrum had disappeared.

[0026]

[Reference Example 4] (Production of isocyanurate-based blocked isocyanate) After creating a nitrogen atmosphere in the flask, 100 parts of a polyisocyanate compound (Duranate TPA-100 manufactured by Asahi Kasei Industries, Ltd.) was added. While keeping the temperature inside the flask at 80-90℃, add butyl acetate 4.
1 part and 63 parts of ε-caprolactam were added dropwise over 2 hours. The temperature during the reaction period was maintained until the absorption of isocyanate groups in the infrared spectrum disappeared.

[0027]

[Examples 1 to 9] Using the blocked isocyanate synthesized in the reference example, the mixtures were blended as shown in Table 1 and coated with an applicator. After setting for 30 minutes at room temperature, 120
Baking was performed at ℃ for 30 minutes. Table 1 shows the results of the above evaluation method.

[0028]

[Comparative Examples 1 to 5] Using the blocked isocyanate synthesized in the reference example, the compositions were blended as shown in Table 2 and coated with an applicator. After setting for 30 minutes at room temperature, 120
Baking was performed at ℃ for 30 minutes. Table 2 shows the results of the above evaluation method.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

Effects of the Invention According to the present invention, compared to conventional one-component polyurethane paints mainly composed of polyol and blocked isocyanate, it not only becomes possible to cure at a lower temperature.
In particular, coating film properties excellent in compatibility, weather resistance, and yellowing resistance can be obtained.

Claims (1)

[Claims] Claim 1: A polyol with a resin hydroxyl group value of 10 to 300, a blocked isocyanate obtained by blocking the isocyanate groups of an aliphatic polyisocyanate having an isocyanurate structure, and a chelate of cobalt, zinc, nickel, tin, manganese, and copper. One or two selected from compounds
A coating composition characterized by containing at least one curing accelerator as a main component.