JPH0671217A - Coating method - Google Patents

Abstract

PURPOSE:To easily obtain a coating film excellent in mirror finishing property and surface hardness by hardening a coating material applied on articles by irradiating with active energy beam, grinding the obtained coating film then, hardening the obtained coating film by a method except the irradiation of active energy beam. CONSTITUTION:In a coating method for articles with the coating material hardenable by a hardening means with active energy beam (UV) and by a hardening means except UV, the following three processes are successively executed. The 1st process is to harden a coating film formed by applying the coating material on the parts by irradiating with UV. The 2nd process to grind the coating film obtained in the 1st process. The 3rd process is to harden the coating film obtained in the 2nd process by the method except hardening with the irradiation of UV. By the constitution, the hardened coated film easy to grind is formed by irradiating with UV in the 1st process and after the grinding is finished, the coated film is hardened by the hardening method different from that of the 1st process to finally obtain a coated material having high hardness and excellent mirror finishing property.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for forming a coating film having high hardness and smoothness on the surface of a building material, a table, a member, etc., which is cured by irradiation with active energy rays (hereinafter abbreviated as UV) .

[0002]

2. Description of the Related Art In recent years, UV-curable paints have been used for painting tabletops made of rubber laminated wood or wood, kitchen counters made by wrapping vinyl chloride resin on MDF (medium fiberboard) equipment, and housing materials. It has been used well.

For such equipment, the surface is smooth and
It has a mirror finish with a high pencil hardness of H or higher, and in order to obtain its specularity, polishing the coating after the final clear coating will cause small distortions and large undulations that occur on the surface of the coating. Need to take.

Conventionally used as paints for these coatings are thermosetting paints represented by two-component urethane-based paints having isocyanate as a functional group, unsaturated polyester type resins with peroxides and metal catalysts. Redox type curable coatings and the like that are mixed, polymerized, and accelerated are often used.

Since these curable paints take a relatively long time to completely cure the coating film, after removing the solvent and the like,
The present situation is that the above-mentioned surface treatment is performed at the time when the coating film is hardened to a hardness that facilitates surface treatment (pencil hardness of about F to 3H), and the process takes a long time.

On the other hand, in the case of forming a high-hardness, mirror-like coating film on equipment by using a UV-curable coating, UV curing proceeds in a short time of 0.001 to 1 sec. Therefore, the cured state of the coating film is controlled. It is difficult to do so, and when trying to obtain a hardness of 4H or more as the pencil hardness of the coating film,
Because of the hardness, it becomes difficult to polish the formed coating film, so that only a coating surface having a hardness of 3H or less can be obtained, or the polishing agent is successively fined and polished many times. It is the current situation that the coating surface is smoothed by applying the process and labor of.

[0007]

In view of the above-mentioned circumstances, the present invention provides a cured coating film having high hardness and high smoothness, which can be easily obtained by curing with UV and curing coating film other than UV. Regarding the painting method.

That is, the inventor of the present invention uses a coating material which is cured by at least one kind of curing means of UV curing means and other curing means, and by the curing means of the first stage, the coating film is easily cured by polishing. It was found that a coating film having a high hardness and a high specularity can be finally obtained by forming a coating film and curing the coating film by a curing means different from the first step at the end of the polishing. Reached

[0009]

The present invention is a method for coating an article with a coating material which can be cured by a curing means using an active energy ray and a curing means other than the active energy ray. The present invention relates to a coating method characterized by being performed. First step: a step of applying a coating material to an article and then irradiating it with an active energy ray to cure the coating film. Second step: a step of polishing the coating film obtained in the first step. Third step: a step of curing the coating film obtained in the second step by a curing method using active energy rays.

Furthermore, the present invention is characterized in that the following three steps are sequentially carried out in a method of coating an article with a coating material which can be cured by a curing means using active energy rays and a curing means other than active energy rays. The coating method First step: a step of coating the article with a coating material and then curing the coating film by a method other than curing with active energy rays. Second step: a step of polishing the coating film obtained in the first step. Third step: a step of irradiating the coating film obtained in the second step with an active energy ray to cure the coating film.

As the paint used in the present invention, any paint satisfying the above conditions can be used, and the number of components involved in the above may be either single or plural and is arbitrary. However, it is more advantageous to satisfy the above requirements with a plurality of constituent components than to use them alone, from the viewpoint of ease of designing the paint. Therefore, a normal UV curable paint and a paint that is cured by a curing means other than UV curing are used. It is better to use paint that is a combination of and.

Further, the paint of the present invention may be designed by arbitrarily combining two or more kinds of paints which are hardened by a hardening method other than UV hardening. Further, the curing of the coating film usually means a crosslinking reaction of the coating film forming component, and in the lacquer type coating composition, such a chemical reaction is not involved, but only by volatilization of the solvent component coexisting with the coating film forming component, it is physically Although the coating film forming component merely exhibits an apparent hardness (pencil hardness), a lacquer type coating material is defined as a coating material that is cured by a curing method other than UV curing in the present invention.

Therefore, more preferably, the present invention is
(1) A coating containing 5% by weight or more of a coating that crosslinks by a curing means other than UV curing on a UV-curable coating is applied to an article, cured by UV, and then polished, and then UV cured. A coating method characterized by obtaining a cured coating film by a crosslinking means other than (2) a coating material selected from the group of (2) UV-curable coating material and lacquer-type coating material and coating material curable by a method other than UV-curing The present invention relates to a coating method characterized by obtaining a cured coating film by coating a coating material containing 5% by weight or more on an article, polishing it after curing other than UV curing, and then irradiating the coated surface with UV. .

The UV-curable coating material which can be used in the present invention and which can be cured in combination with other curing methods may be a resin consisting of a single component having such a function, if it is available. As described above, it is easier to adjust the hardness of the present invention by designing the process of the present invention with a plurality of mechanism components having different curing methods. Therefore, a resin that causes a curing reaction by UV irradiation and a UV curing that includes a lacquer. It is convenient to use a mixture with a resin component that causes curing other than as the coating material of the present invention.

The resin which causes a curing reaction by being irradiated with UV is, for example, (1) bisphenol A type,
Epoxy (meth) acrylate resin derived from epoxy resin such as bisphenol S type, bisphenol F type, epoxidized oil type, phenol novolac type, or alicyclic type, (2) polyurethane (meth) acrylate resin,
(3) Polyester (meth) acrylate resin, (4)
Examples thereof include polyol (meth) acrylate resins, (5) unsaturated acrylic side chain-containing silicone resins, and (6) unsaturated polyester resins. These resins can be used alone or as a mixture. Further, for the purpose of decreasing the viscosity of the coating composition and other purposes, monomers and oligomers having an unsaturated group, for example, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, propyl (meth) acrylate. , 2-ethylhexyl (meth) acrylate, (meth) acrylic acid, dimethylaminomethyl (meth) acrylate, polyethylene glycol di (meth)
Acrylate (average molecular weight 300), trimethylolpropane tri (meth) acrylate, triallyl isocyanurate, triallyl trimate and the like may be used in combination.

Examples of curing means other than crosslinking by UV include urethane crosslinking type curing, crosslinking type curing utilizing radicals generated by methods other than UV irradiation, epoxy crosslinking type curing, melamine resin crosslinking type curing and the like. .

Urethane cross-linking type curing Photopolymerizable oligomer having at least one unsaturated double bond such as acryloyl group, methacryloyl group, allyl group and vinyl group at the molecular end and in the molecular chain and at least one of the above functional groups. A UV-curable coating composition (hereinafter UV) in which a photoinitiator is added to the above monomers alone or a mixture thereof.
Examples of the paint) include a mixture of an isocyanate compound and a polyol resin, a UV paint containing an isocyanate group in the molecular chain, and a mixture of a UV paint and a polyol resin. This is a method of utilizing UV curing and urethane curable crosslinking with isocyanate in the form of the coating material as described above.

Isocyanate compounds include, for example, tolylene diisocyanate, xylylene diisocyanate,
Hexamethylene diisocyanate, diphenylmethane-
4,4′-diisocyanate, isophorone diisocyanate, 1,4-tetramethylene diisocyanate, and the like, or adducts of these isocyanate compounds with trimethylolpropane, triethylene glycol, and the like can be mentioned.

Examples of the polyol resin include acrylic resin polyol, polyester polyol, polyether polyol, polycarbonate polyol, polyurethane polyol and the like.

Crosslinking type curing using radicals generated by methods other than UV irradiation Polymerization is carried out by utilizing radicals generated by heating such as peroxides such as benzoyl peroxide and thermal decomposition of azobisisobutyronitrile. And a method of curing at room temperature using an oxidation-reduction reaction (redox reaction) using a metal catalyst or the like, and a mixture of a resin having an unsaturated double bond, for example, an unsaturated polyester resin and the above catalysts. Is mentioned.

Since the redox reaction and the UV curing reaction are both reactions by radicals, the same resin can be used, and a peroxide and a metal catalyst and a photoinitiator are used together in the resin. It is necessary to control the radical concentration during the reaction to control the curing state by changing the addition amount and the temperature during the reaction.

The peroxides used include, for example, benzoyl peroxide, parachlorobenzoyl peroxide, acetyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, and the like.
Examples of the catalyst include metal soaps such as cobalt naphthenate, amines such as dimethylaniline and N, N-dimethylparatoluidine, and β-diketones used in combination with a cobalt accelerator.

Epoxy cross-linking type curing: Room temperature cross-linking by mixing a bisphenol A type or novolak type epoxy resin with a primary diamine, an epoxy resin containing a basic catalyst such as a tertiary amine, and a resin having a carboxylic acid at the end. Crosslinking with resins such as acrylic copolymers and resins with methylol groups is applicable.

Crosslinking curing of melamine resin Other resins containing hydroxyl group, carboxyl group and amide group (eg acrylic resin, polyester resin, urethane resin)
It utilizes the cross-linking reaction between melamine resin and melamine resin, and accelerates the curing reaction under a basic catalyst.

Incidentally, a lacquer type (thermoplastic) resin, which does not undergo a crosslinking reaction but forms and cures a coating film by volatilizing a solvent, can be used in combination. This lacquer type resin has acrylic resin, nitrocellulose,
Examples thereof include CAB (cellulose acetate butyrate) and polyvinyl chloride. The Tg of the resin used is 50 ° C
The above is desirable, and the higher the molecular weight, the more stable the coating film,
It is necessary to select the properties according to the painting method used.

Although the typical crosslinking means and lacquer type coating film forming means have been described above, the crosslinking means used in combination with UV curing is not necessarily limited to these cases, and resins such as resins used for these crosslinking means are not limited to these examples. The materials must not interfere with the UV curing reaction.

When the UV-curable resin and the other cured resin including lacquer are mixed, the mixing ratio is
The range of coating film hardness at the end of the first stage is 2B to 4 in terms of pencil hardness.
The range of H is desirable, and it is more desirable to select it so as to be in the range of HB to 3H. Further, in order to improve the reproducibility of the coating film hardness and the reliability of the paint design, the above mixing ratio (weight ratio) Is preferably selected within the range of 5/95 to 95/5.

The coating composition of the present invention may further contain fillers and additives if necessary. Examples of the filler include fillers such as silica, carion, clay, feldspar powder and barite, and pigments such as titanium oxide, zinc sulfide, phthalocyanine, iron oxide and carbon. Examples of the additive include a flow regulator, a defoaming agent, a dispersant, a dye, a solvent, an ultraviolet absorber and a light stabilizer.

The coating material of the present invention is uniformly kneaded by a conventional method for preparing a coating material, for example, a dispersion stirrer, three rolls, mixing by a kneader, mixing by a ball mill, dyno mill, and mixing by a paint shaker. .

Various methods may be used to apply the coating composition of the present invention depending on the purpose. Specific examples thereof include air (airless) spray coating, electrostatic spray coating, roll coater coating, flow coater coating, brush coating, vacuum coating, and dipping.

The article to be coated may be a plate or sheet of wood, plastic, metal, stone or the like.

The UV curing may be carried out in air, but when the coating is cured by irradiating it with UV in an inert gas, the physical properties of the surface coating can be remarkably improved. Thus, a UV curable coating material containing a photopolymerization initiator in an amount of 3% by weight or less can be used.

As a light source for generating UV, a known active light source such as carbon arc, mercury vapor arc, xenon arc, or the like may be used.

As the (active energy ray), an electron beam having an acceleration energy of 0.1 to 3 Mev may be used, and in that case, for example, Cockcroft type, Van de Graaff type, Dynamitron type, high frequency type, electro curtain type Electron beam accelerators such as linear type, insulated core transformer type, etc. can be used.

The curing time in the crosslinking means other than UV or the heating time and temperature in the curing of the lacquer type resin vary depending on the kind of the coating material and the coating object to be used, but the coating object is polyvinyl chloride. In this case, it is desirable to set the heating temperature to 60 ° C or lower, and in the case of wood, to 100 ° C or lower. Moreover, a sufficiently cured coating film can be obtained. The heating method is not particularly limited, but widely used methods such as drying with hot air, heating with far infrared rays, and dielectric heating can be used.

[0036]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. All parts are parts by weight, and hardness is (JI
It means the pencil hardness of SK 5400-8.4).

Example 1 A coating composition was prepared by thoroughly agitating the compounding mixture of the following UV curable composition and CAB lacquer with a dispersion stirrer.

This paint is sprayed on a veneer plywood that has been pre-sealed to a thickness of about 125 μm,
The solvent is volatilized with a dryer (70 ° C, 10 minutes) and the hardness is HB.
After forming the coating film of, the surface processing of buffing was performed.

Further, using a high pressure mercury lamp of 80 W / cm 2 lamp (line speed 5 m / sec, which corresponds to light energy of 320 mj), the coating film was cured by irradiation from a distance of 15 cm above the plate surface. A mirror coating having a hardness of 4H could be obtained.

Acrylic urethane hard coat resin 30 parts (Arakawa Chemical Co., Ltd. beam set 570) Cellulose acetate butyrate 10 parts (Eastman Chemical CAB381-20) Benzoin ether photopolymerization initiator 3 parts (Ciba Geigy) Irger cure 184) Acrylic resin leveling agent 0.3 part (LC-951 manufactured by Kusumoto Kasei Co., Ltd.) Ethyl acetate 57 parts

Example 2 A UV curable resin composition having the following composition was mixed with an organic peroxide, and sprayed on a veneer plywood that had been subjected to a sealing treatment in a thickness of about 125 μm, and 80 W / cm 2 high-pressure mercury lamp (line speed 5 m / sec or 320
mj) was irradiated from a distance of 15 cm from the plate surface to cure the coating film.

The hardness of the obtained coating film was measured and buffing was performed. After heating at 90 ° C for 30 minutes, leave it overnight,
Next day, the coating film surface hardness of that portion was measured.

57 parts of unsaturated polyester oligomer (Diovar CN-75 manufactured by Dainippon Ink and Chemicals, Inc.)
2) Styrene monomer 25 parts Benzyl dimethyl ketal 3 parts (Ciba-Geigy Irger Cure 651) Diallyl peroxide 15 parts (Nippon Oil & Fat Co., Ltd. Niper BO)

As a result of the measurement under the above conditions, the coating film immediately after UV curing had a hardness of H, and the hardness measured the next day had a hardness of 5H, and the specularity by polishing was sufficient.

Example 3 A UV curable resin composition having the following composition was mixed with isocyanate, and sprayed on a veneer plywood that had been pre-sealed to a thickness of 125 μm, and a high pressure of 80 W / cm 2 lamps was applied. Mercury lamp (line speed 5 m / sec, ie 320 m
Using j), the coating film was cured by irradiation from a distance of 15 cm from the plate surface. When the hardness of the obtained coating film was measured, the hardness was H.

After that, buffing is performed, and further at room temperature (25
After being left for 3 days at a temperature of 3 ° C., the hardness of the coated surface was measured and found to be 4H.

60 parts of urethane acrylate oligomer (Unidick V421 manufactured by Dainippon Ink and Chemicals, Inc.
0) Benzoin ether type photoinitiator 3 parts (Ciba Geigy Irger Cure 184) Ethyl acetate 20 parts MDI isocyanate 17 parts (Mitsubishi Kasei Dow Co., Ltd. Papi 135)

[0048]

The coating method of the present invention is a cross-linking and curing method which is a combination of cross-linking by UV irradiation and curing other than that. Therefore, at the end of the first step, the coating film can be easily surface-treated (buffed). It is possible to easily obtain a coating material with high hardness of 4H or more, which is difficult to achieve in the past, that is, a coating film excellent in both specularity and surface hardness. Is.

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Claims (2)

[Claims] 1. A method for coating an article using a coating material that can be cured by a curing means using active energy rays and a curing means other than active energy rays, characterized in that the following three steps are sequentially performed: . First step: a step of applying a coating material to an article and then irradiating it with an active energy ray to cure the coating film. Second step: a step of polishing the coating film obtained in the first step. Third step: a step of curing the coating film obtained in the second step by a method other than curing with active energy rays. 2. A method for coating an article using a coating material which can be cured by a curing means using active energy rays and a curing means other than active energy rays, characterized in that the following three steps are carried out in sequence. . First step: a step of curing the coated film by a method other than curing with active energy rays after coating the article with the coating material. Second step: a step of polishing the coating film obtained in the first step. Third step: a step of irradiating the coating film obtained in the second step with an active energy ray to crosslink the coating film.