JPS645626B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to coating compositions curable by ultraviolet or electron beam irradiation and heating. Conventionally, methods for coating various substrates include a method in which a coating composition is applied to the substrate and heated to cause a crosslinking reaction and hardening, and a method in which a reaction is caused by ultraviolet or electron beam irradiation to cause curing. There is. The heat curing method involves, for example, crosslinking and curing a resin having hydroxyl groups, carboxyl groups, or amide groups using methylolmethylated melamine resin, but in order to obtain a sufficiently cured film, long-term heating is required or high temperatures are required. It is necessary to do it. It is often difficult to apply this method to base materials such as plastics and paper that cannot be heated sufficiently due to heat-induced deformation. On the other hand, methods of curing the coating composition with ultraviolet light or electron beams allow for short-time curing and therefore can also be applied to substrates that cannot be heated or cannot be heated for long periods of time. Various studies have been conducted for these reasons, and some have already been put into practical use. However, it is often difficult to form a satisfactory cured film on pigment-containing systems and thick coatings where sufficient hardness is difficult to obtain and ultraviolet rays or electron beams do not pass through sufficiently. As a result of various studies aimed at solving these problems, the present inventors discovered that a coating composition that can be cured by ultraviolet or electron beam irradiation and heating solves these problems all at once, and completed the present invention. I came to the conclusion. That is, the present invention provides (A) an alkoxymethylated melamine resin, an α,β-ethylenically unsaturated compound having at least one hydroxyl group, and a polyol having at least two hydroxyl groups or at least one hydroxyl group. Ultraviolet rays or ultraviolet rays containing a mixture of melamine acrylate having at least 0.5 or more alkoxy groups per melamine nucleus obtained by reaction with higher fatty acid ester, (B) a photopolymerization initiator, and (C) an amino resin curing catalyst. The present invention relates to a curable coating composition that can be cured by electron beam irradiation and heating, and an object of the present invention is to form a coating with excellent hardness by applying ultraviolet rays or electron beams after application and further heating. The object of the present invention is to provide a curable coating composition that obtains a curable coating composition. That is, the melamine acrylate (A) used in the present invention is an α,β-
It has an alkoxy group, a methylol group, etc. that can react with an ethylenically unsaturated group by heating, and has the characteristic that it can be cured by either ultraviolet irradiation or electron beam irradiation and heating. In order to make these characteristics of the melamine acrylate most effective, the present invention attempts to form a coating having excellent hardness by irradiating a composition containing the melamine acrylate with ultraviolet or electron beam irradiation and heating. . The present invention will be explained in detail below. Examples of the alkoxymethylated melamine resin used in the present invention include methoxymethylated melamine resin and butoxymethylated melamine resin, but methoxymethylated melamine resin is preferred. More preferred is hexamethoxymethylmelamine. Further, these may be a mixture or co-condensate with an alkoxymethylated urea resin or benzoguanamine resin. The α,β-ethylenically unsaturated compound having at least one hydroxyl group used in the present invention includes ethylene glycol monoacrylate, diethylene glycol monoacrylate,
Polyethylene glycol monoacrylate, propylene glycol monoacrylate, dipropylene glycol monoacrylate, polypropylene glycol monoacrylate, glycerin mono- or diacrylate, trimethylolpropane mono- or diacrylate, pentaerythritol mono- or di- or triacrylate, N-methylol acrylamide, etc. be. These may be used alone or in combination of two or more. Preferred are ethylene glycol monoacrylate and propylene glycol monoacrylate. Further, the polyol having at least two or more hydroxyl groups in the present invention is a compound having alcoholic or phenolic hydroxyl groups. Examples of compounds having alcoholic hydroxyl groups include ethylene glycol,
Diethylene glycol, triethylene glycol, tetraethylene glycol and other polyethylene glycols, propylene glycol, dipropylene glycol, tripropylene glycol,
Other polypropylene glycols, 1,3-propanediol, 1,4-butanediol, 1,
Polyhydric alcohols such as 3-butanediol, 1,5-pentanediol, neopentylglycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbinol, or etherified condensates thereof, as well as bisphenols and hydrogenated Bisphenols, halogenated bisphenols, polyether polyols produced by the reaction of the polyhydric alcohol and alkylene oxide, and polyester polyols produced by the reaction of the polyhydric alcohol and polybasic acid are included. Examples of compounds having a phenolic hydroxyl group include bisphenols, hydrogenated bisphenols, halogenated bisphenols, and resorcinol. Furthermore, methylolated products obtained by reacting various phenols, xylene, the above-mentioned bisphenols, etc. with formaldehyde may also be used. Further, in the present invention, higher fatty acid esters having at least one hydroxyl group are alcoholysis reaction products between fats and oils and polyhydric alcohols, partial esterification reaction products between higher fatty acids and polyhydric alcohols, and higher fatty acids or active hydrogen. It is an addition reaction product between a higher fatty acid ester having atoms and an epoxy compound. Examples of fats and oils include drying oils such as tung oil, linseed oil, eno oil, soybean oil, and dehydrated castor oil; semi-drying oils such as castor oil, cottonseed oil, sesame oil, corn oil, rapeseed oil, safflower oil, and tall oil; olive oil; Non-drying oils such as camellia oil, coconut oil, cacao oil, sardine oil,
Examples include vegetable oils and fats such as squid oil and whale oil, and animal fats and oils. Higher fatty acids include fatty acids contained in the above-mentioned fats and oils, such as eleostearic acid, linoleic acid, linolenic acid, ricinoleic acid, oleic acid,
Unsaturated fatty acids such as elaidic acid, stearic acid, palmitic acid, myristic acid, lauric acid,
Examples include saturated fatty acids such as caprylic acid, as well as dimer acids and trimer acids derived from unsaturated higher fatty acids. Furthermore, resin acids such as abietic acid contained in rosin may also be used. In addition, polyhydric alcohols include dihydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, hexanediol, and neopentyl glycol, glycerin, trimethylolethane, and trimethylolpropane. , pentaerythritol, sorbitol, or their etherified condensates. Further, oils and fatty acids having hydroxyl groups such as castor oil, castor oil fatty acids, ricinoleic acid, and dioxystearic acid can also be used. These may be used alone or as a mixture. Examples of the photopolymerization initiator in the present invention include benzoin methyl ether, benzoin ethyl ether,
Benzoins such as benzoin isopropyl ether, ketones such as benzophenone and Michler's ketone, azos such as azobisisobutyronitrile, and quinones such as anthraquinone can be used. Moreover, various combinations of these may also be used. The amount of photoinitiator added in the present invention is preferably 0.1 to 10% by weight, more preferably 1 to 7% by weight, based on the melamine acrylate (A) in the present invention. If it is less than 0.1% by weight, the coating will not have sufficient hardness, and if it is more than 10% by weight, the storage stability of the coating composition will tend to decrease, which is not preferable. The amino resin curing catalyst used in the present invention is one that is generally used in amino resin coating compositions. For example, P-toluenesulfonic acid,
Acids are produced by thermal decomposition of free acids such as oxalic acid, amine salts of free acids, acid anhydrides, P-toluenesulfonic acid esters, phosphoric acid esters, sulfuric esters, acid amides, imidodisulfonic acids, nitrilosulfonates, etc. Examples include things.
Particularly preferred are P-toluenesulfonic acid esters such as P-toluenesulfonic acid methyl ester and P-toluenesulfonic acid ethyl ester, which provide excellent storage stability of the coating composition. The amount of the amino resin curing catalyst added is preferably 0.1 to 10% by weight, more preferably 0.2 to 5% by weight, based on the melamine acrylate (A) in the present invention. 0.1
If it is less than 10% by weight, it is difficult to obtain a sufficient effect on curability, and if it is more than 10% by weight, it tends to reduce the storage stability of the coating composition, which is not preferable. Furthermore, ethylenically unsaturated monomers commonly used for the purpose of viscosity adjustment or crosslinking may be added. Such unsaturated monomers include, for example, styrene, vinyl acetate, 2-vinylpyridine, N
-vinylpyrrolidone, N-vinylcarbazole,
Methyl acrylate, ethyl acrylate, butyl acrylate, lauryl acrylate, stearyl acrylate, benzyl acrylate, hydroxyethyl acrylate, cyclohexyl acrylate, ethylene glycol diacrylate,
Diethylene glycol diacrylate, triethylene glycol diacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate , triethylene glycol dimethacrylate, 1,6
-hexanediol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, etc., and these may be used alone or in combination of two or more. Furthermore, pigments, colorants, plasticizers, solvents, etc. may be used in combination with the composition as long as they do not impair the characteristics of the present invention. The coating composition of the present invention may be applied to a substrate by a conventional method, first cured by ultraviolet rays or electron beam irradiation, and then thermally cured by heating. By heating with a method such as an external lamp, a coating having satisfactory hardness can be formed. EXAMPLES The present invention will be explained in detail below using Examples, but the present invention is not limited to these Examples. Synthesis Example 1 390 g of Sumimaru M-100 (hexakismethoxymethylmelamine, trade name of Sumitomo Chemical) and 45 g of 1,4-butanediol were placed in a stirrer, a thermometer, a pressure reducing device, and a cooling condenser connected to a cooled trap. A flask was charged, 0.25 ml of 85% phosphoric acid was added, and the mixture was reacted at 110°C to 120°C, and methanol was distilled off under atmospheric pressure. 35℃ when distilled amount reaches 31g
0.6g of 2-methylhydroquinone,
Add 580 g of ethylene glycol monoacrylate and 1.2 g of P-toluenesulfonic acid and heat to 80°C.
Methanol was distilled off under reduced pressure of about 45 mmHg while reacting at ~95°C. When the total distillate amount reached 190 g, the pressure was returned to normal and the mixture was cooled. The reaction product (hereinafter referred to as resin a) was a colorless and transparent liquid. Synthesis example 2 Soybean oil 453g, glycerin 96g and lead oxide 1.2
g was placed in a flask equipped with a stirrer, a thermometer, a cooling condenser, and a nitrogen gas blowing device, and the temperature was raised to 220° C. while blowing nitrogen gas. After being maintained at the same temperature for 4 hours, it was cooled to obtain a pale yellow and transparent alcoholysis reaction product. 390 g of Sumimaru M-100 and 5.28 g of the alcoholysis reaction product synthesized above were placed in a flask equipped with a cooling condenser connected to a stirrer, a thermometer, a pressure reducing device, and a cooled trap, and 3.5 ml of 85% phosphoric acid was added. While reacting at 110 to 130°C, methanol was distilled off under reduced pressure of about 50 mmHg. When the distilled amount reached 75 g, the pressure was returned to normal and cooled. Then 0.4 g of 2-methylhydroquinone, 390 g of propylene glycol monoacrylate and 0.8 g of P-toluenesulfonic acid.
was added and reacted at 80°C to 95°C, and methanol was distilled off under reduced pressure of about 50 mmHg. Total distillation amount is 160g
When this occurred, the pressure was returned to normal and the mixture was cooled. The reaction product (hereinafter referred to as resin b) was a pale yellow transparent liquid. Examples 1 to 4 A coating composition was prepared using the resin (a) or resin (b) synthesized in the synthesis example according to the recipe shown in Table 1, and coated on a tin plate that had been degreased with acetone using a bar coater #10. After that, the film was irradiated with an 80 W/cm mercury lamp at a belt conveyor speed of 5 m/min, and then baked in hot air drying at 180°C for 5 minutes, and the pencil hardness was measured. Comparative Examples 1 to 3 A coating composition was prepared using the resin (a) or resin (b) synthesized in the synthesis example according to the recipe shown in Table 1, and coated on a tin plate that had been degreased with acetone using a bar coater #10. After irradiation with a mercury lamp of 80 W/cm at a belt conveyor speed of 5 m/min, the pencil hardness was measured. These results are shown in Table 1. Comparative Examples 4 to 8 A coating composition was prepared using the resin (a) or resin (b) synthesized in the synthesis example according to the recipe shown in Table 1, and coated on a tin plate that had been degreased with acetone using a bar coater #10. Afterwards, it was baked for 5 minutes in hot air drying at 180°C, and the pencil hardness was measured. These results are shown in Table 1.

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Claims (1)

[Claims] 1 (A) an alkoxymethylated melamine resin, an α,β-ethylenically unsaturated compound having at least one hydroxyl group, and a polyol having at least two hydroxyl groups or a higher fatty acid ester having at least one hydroxyl group; A mixture consisting of a melamine acrylate having at least 0.5 or more alkoxy groups per melamine nucleus obtained by the reaction of A curable coating composition that can be cured by ultraviolet rays or electron beam irradiation and heating.