JP2006088045A - Cured coating film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cured coating film forming method by which a coating film having a high film thickness and a mirror finished surface is obtained on the surface of a base material using a grooved roll coater. <P>SOLUTION: This cured coating film forming method includes: a 1st coating step for applying a 1st coating material composition on the surface of the base material using the roll coater; a 2nd coating step for applying a 2nd coating material composition by a wet-on-wet system using the grooved roll coater successively; and a step for making the surface of the base material be irradiated with an active energy ray. The 1st and the 2nd coating material compositions are active energy curable coating material compositions containing one or more kinds of oligomer components and having 90-100 mass% non-volatile portion and the coating is carried out under a condition that viscosity of the 1st coating material composition is higher than that of the 2nd coating material composition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming a cured coating film of an active energy ray-curable coating composition.

  Conventionally, the surface of base materials such as paper, plastic, glass, metal, wood, and ceramic has been coated to protect the surface by adding various functions and design features such as high hardness and stain resistance. Yes. In recent years, the demand for active energy ray-curable coatings has been expanding in response to environmental problems. Under such circumstances, in the field of building materials, there has been a demand for painted building materials for various uses such as ceiling materials, wall materials, floor materials, etc., having a cured coating film of an active energy ray-curable coating material. Among them, in the case of products laid on the floor such as flooring, the coating film is required to have a high film thickness and a mirror-like surface in order to give a high-class feeling.

  Conventionally, in order to obtain a mirror-like coating film with a high film thickness, it has been common to paint using a flow coater, but painting with a flow coater lacks stability and yields in the painting process are poor. It was expensive. In recent years, as a new technology that replaces the flow coater, a method of coating using a roll coater using a roll called a grooved roll in which a groove is cut in a roll of an ordinary roll coater has been proposed (see, for example, Patent Document 1). ).

  However, the use of the grooved roll can relatively easily obtain a high film thickness, but it is easy to generate streaks, bubbles, etc. derived from the groove on the roll surface, and it is difficult to obtain a mirror-like coating film. there were.

JP 2003-71372 A

  The object of the present invention is to solve such problems of the prior art, and while taking advantage of the use of a grooved roll coater, a high-thickness and mirror-like coating is applied to the substrate surface. The object is to provide a method for forming a cured coating film for obtaining a film.

  As a result of various studies on the means for solving the above problems, the present inventors combined coating with a natural roll coater and coating with a grooved roll coater, coating with a wet-on-wet method, The present inventors have found that a coating film having a high film thickness and a good mirror surface can be obtained by adjusting the composition of the coating material used in the process and the viscosity at the time of coating.

  That is, the present invention provides a first coating step in which a first coating composition is applied to the surface of a substrate using a roll coater, followed by a wet-on-wet method using a grooved roll coater. A method of forming a cured coating film comprising a second coating step of coating the coating composition and a step of irradiating active energy rays, wherein the first and second coating compositions are one or more oligomer components. An active energy ray-curable coating composition having a non-volatile content of 90 to 100% by mass, wherein the first coating composition has a viscosity greater than that of the second coating composition. The present invention provides a method for forming a cured coating film.

  According to this invention, the cured coating film which has a mirror-like surface with a high film thickness can be obtained by adjusting the viscosity of each coating material using a natural roll and a grooved roll.

  The present invention provides a first coating process in which a first coating composition is applied to the surface of a substrate using a roll coater, followed by a second roll-on-wet method using a grooved roll coater. A cured coating film forming method comprising a second coating step of coating a coating composition and a step of irradiating active energy rays, wherein the first and second coating compositions comprise an oligomer component as an essential component It is an active energy ray-curable coating composition having a nonvolatile content of 90 to 100% by weight, and is applied under conditions where the viscosity of the first coating composition is greater than the viscosity of the second coating composition. Provided is a method for forming a cured coating film.

  A natural roll coater is particularly preferably used as the roll coater used in the first coating step. When a natural roll coater is used, the viscosity at the time of coating of the coating material to be used is preferably about 320 to 720 mPa · s at a coating temperature of 40 ° C.

  The viscosity at the time of application of the first coating composition in the first coating step described above is the second coating composition at the time of coating using a grooved roll coater in the second coating step. It needs to be higher than the viscosity at the time of coating. The paint used for the grooved roll coater in the second coating process preferably has a relatively low viscosity, and it is appropriate for the same viscosity as the paint suitable for the natural roll coater in the first coating process. Therefore, the second coating composition is required to have a low viscosity at the time of coating compared to the first coating composition.

As for the coating amount in a 1st coating process, 10-40 g / m < ² > is preferable. A more preferable coating amount may vary depending on the number of grooves and the coating amount of the grooved roll coater used in the second coating step. For example, when the number of grooves of the grooving roll coater in the second coating process is 20 / cm and the application amount is 20 g / m ² , the proper coating in the first coating process is performed. The work amount is more preferably about 10 to 30 g / m ² .

  The second coating process is a wet-on-wet method after applying the first coating composition with the natural roll coater, which is the first coating process, and the second coating composition with a grooved roll coater. It is a process of applying an object.

  A grooved roll coater is a coater having a plurality of kerfs on the roll surface. Examples of the material of the roll include urethane rubber, butyl rubber, and ethylene / propylene rubber. Examples of the shape of the cut groove include groove shapes such as a square shape, a trapezoidal shape, a V shape, and a U shape. The kerf may be parallel to the roll rotation direction or may be spiral.

  As a grooved roll used in the present invention, a grooved roll having longitudinal grooves having a number of grooves of 5 to 40 / cm, a groove width of 0.5 to 2.0 mm, and a groove depth of about 0.1 to 1.0 mm. A roll coater can be used.

As for the coating amount in a 2nd coating process, 10-40 g / m < ² > is preferable. The number of grooves of the grooved roll coater used is often different depending on the target coating amount. For example, when an object of coating weight of 15 to 30 g / ^{m 2,} a number of grooves is approximately 15-25 present / cm of grooving roll coater used, if an object of coating amount of 10~18g / ^{m 2} The number of grooves of the grooved roll coater to be used is preferably about 25 to 40 / cm.

  The coating speed depends on the properties of the object to be coated, but is preferably about 10 to 100 m / min in order to obtain a high film thickness of about 30 to 50 μm with a wooden substrate.

  The first coating process may be an undercoating process that is applied directly to the substrate, or may be a coating as an intermediate coating process after the undercoating process.

  If the coating substrate is a substrate with many irregularities on the surface, such as a wooden substrate, bubbles will easily occur due to the paint flowing into the irregularities of the substrate, making it difficult to obtain a good mirror surface. It is preferable to provide an undercoat step as a pre-step of the first coating step.

  When an undercoat process is provided before the first coating process, it is preferable to use a natural reverse coater or a sponge reverse coater. When using a natural reverse coater, the viscosity when applying the paint used is about 1500 to 3000 mPa · s at a paint temperature of 40 ° C. When using a sponge reverse coater, the viscosity when applying the paint used is About 25 to 400 mPa · s is preferable at a coating temperature of 40 ° C.

  The undercoat paint used in the natural reverse coater and the sponge reverse coater is an active energy ray curable paint composition described later, and the composition is the first and second coating processes used in the first coating process and the second coating process. The coating composition may be the same or different. Moreover, there may be another process after these processes.

  In the coating composition used in the present invention, the first coating composition and the second coating composition both have an active component having a nonvolatile content of 90 to 100% by mass containing an active energy ray-polymerizable oligomer component as an essential component. It is an energy ray curable coating composition. It is preferable to have a common active energy ray polymerizable component composition because a leveling defect or the like is likely to occur when coatings having different active energy ray polymerizable component compositions are used in the first and second coating steps. . In particular, the oligomer components contained in the first and second coating compositions are preferably the same oligomer component.

  The compositions of the first coating composition and the second coating composition are those in which an active energy ray polymerizable oligomer component is essential, and an active energy ray polymerizable monomer component is added as necessary. It is preferable that the oligomer component used for each is the same. Other oligomer components may or may not be mixed, but it is more preferable to contain only the same oligomer component.

  Among the active energy ray polymerizable monomers that can be used in the first and second coating compositions having active energy ray curability used in the method for forming a cured coating film of the present invention, as the monofunctional monomer, 2- Hydroxyethyl acrylate, 2-hydroxypropyl acrylate, lauryl acrylate, stearyl acrylate, tetrahydrofurfuryl acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, isobornyl acrylate, benzyl acrylate, phenyl acrylate, phenoxyethyl Acrylate, phenoxydiethylene glycol acrylate, phenoxytetraethylene glycol acrylate, nonylphenoxyethyl acrylate, Nylphenoxytetraethylene glycol acrylate, methoxydiethylene glycol acrylate, ethoxydiethylene glycol acrylate, butoxyethyl acrylate, butoxytriethylene glycol acrylate, 2-ethylhexyl polyethylene glycol acrylate, nonylphenyl polypropylene glycol acrylate, methoxydipropylene glycol acrylate, glycidyl acrylate, glycerol acrylate, Polyethylene glycol acrylate, polypropylene glycol acrylate, epichlorohydrin (hereinafter abbreviated as ECH) modified butyl acrylate, ECH modified phenoxy acrylate, ethylene oxide (hereinafter abbreviated as EO) modified phthalic acid acrylate, EO modified succinic acid acrylate , Caprolactone-modified 2-hydroxyethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, morpholinoethyl acrylate, EO-modified phosphoric acid acrylate. The monomer expressed as acrylate may be (meth) acrylate.

  Examples of the bifunctional monomer include trimethylolpropane diacrylate, 1,3-butanediol diacrylate, 1,4-butanediol diacrylate, neopentanediol diacrylate, 1,6-hexanediol diacrylate, and 1,9-nonane. Diol diacrylate, ethylene glycol diacrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, tripropylene glycol diacrylate, EO modified neopentyl glycol diacrylate, propylene oxide (hereinafter abbreviated as PO) modified neopentyl glycol diacrylate Bisphenol A diacrylate, EO modified bisphenol A diacrylate, ECH modified bisphenol A diacrylate, EO modified bisphenol S di Chryrate, hydroxypivalate ester neopentyl glycol diacrylate, caprolactone modified hydroxypivalate ester neopentyl glycol diacrylate, neopentyl glycol modified trimethylolpropane diacrylate, stearic acid modified pentaerythritol diacrylate, dicyclopentenyl diacrylate, EO modified Examples include dicyclopentenyl diacrylate and diacryloyl isocyanurate. The monomer expressed as acrylate may be (meth) acrylate.

  The trifunctional or higher polyfunctional monomers include trimethylolpropane triacrylate, pentaerythritol triacrylate, EO-modified trimethylolpropane triacrylate, PO-modified trimethylolpropane triacrylate, ECH-modified trimethylolpropane triacrylate, ECH-modified glycerol triacrylate , Tris (acryloyloxyethyl) isocyanurate, ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol monohydroxypentaacrylate, alkyl-modified dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, caprolactone-modified dipentaerythritol hexaacrylate Etc. The monomer expressed as acrylate may be (meth) acrylate.

  These monomers can be used by 1 type, or 2 or more types of mixed systems.

  As the active energy ray-polymerizable oligomer used as an essential component by the first and second coating compositions having active energy ray curability used in the present invention, conventionally known ones can be used. Examples include bisphenol A type, novolak type, polyhydric alcohol type, polybasic acid type, polybutadiene type epoxy (meth) acrylate, polyester type, polyether type urethane (meth) acrylate, etc. It can be used in a seed or a mixed system of two or more.

  Among them, it is particularly preferable to use epoxy acrylate, urethane acrylate, polyether acrylate, or the like in order to obtain performance such as hardness and heat resistance required in recent years and to obtain a good coating film.

  Other active energy ray polymerizable compounds that can be used in the present invention include, for example, N-vinylpyrrolidone, N-vinylcarbazole, styrene, 4-methylstyrene, α-methylstyrene, 1,4-divinylbenzene, diallyl phthalate. And maleimide compounds described in JP-A-11-124403 and JP-A-11-124404, which can be used as necessary.

  Further, in the first and second coating compositions having active energy ray curability used in the present invention, as a hydrogen abstraction type polymerization initiator used as a polymerization initiator, conventionally known benzophenone, acetophenone, diethoxyacetophenone, benzyl , Benzoylbenzoic acid, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone and the like.

  Other examples of the polymerization initiator that can be used in the present invention include photocleavable types such as benzoin ethyl ether, benzyl dimethyl ketal, hydroxycyclohexyl phenyl ketone, and 2-hydroxy-2-methylphenyl ketone. Among these hydrogen abstraction type and photocleavage type polymerization initiators, one or two or more types can be used in combination.

  The blending ratio of the polymerization initiator in the resin composition comprising the active energy ray polymerizable monomer and oligomer component and the polymerization initiator is preferably 1 to 15% by mass in the resin composition.

  In addition, these polymerization initiators can be used in combination with known and commonly used photosensitizers. When using together, it is preferable that it is 1-15 mass% in a resin composition.

  The first and second coating compositions having active energy ray curability used in the present invention are further provided with various functions within a range not departing from the object of the present invention, if necessary. Additives such as pigments, lubricants, plasticizers, antifoaming agents, antioxidants, coupling agents, organic solvents and chelating agents can be added.

  Manufacture of the 1st and 2nd coating composition which has active energy ray curability used for this invention can be implemented by a conventionally well-known method. As an example, active energy ray polymerizable monomers and oligomers, polymerization initiators, extender pigments, and, if necessary, coating additives can be prepared in this order by mixing, stirring, and the like.

  The volatile matter of the coating composition in the present invention is a component that volatilizes at room temperature or by heating from the paint before curing, except for the components involved in polymerization by the initiator and active energy rays in the coating composition. This component is called a non-volatile component.

  The first and second coating compositions having active energy ray curability used in the present invention have a nonvolatile content of 90 to 100% by mass. If a paint having a large amount of volatile components is used, it is advantageous in terms of finish, but it cannot cope with environmental problems such as VOC emission. The present invention is a cured coating film forming method for obtaining a coating film having a high-thickness film and a mirror-like surface, using a highly nonvolatile coating composition that can cope with environmental problems.

  The active energy rays used in the active energy ray irradiation step of the present invention are ionizing radiation, electromagnetic waves, etc. such as ultraviolet rays, electron rays and γ rays, but ultraviolet rays are preferred as the active energy rays in the general irradiation step.

  When irradiating with ultraviolet rays, a known ultraviolet irradiating device including a high pressure mercury lamp, an excimer lamp, a metal halide lamp, or the like can be used.

  There may or may not be a setting zone after the second coating step until the step of irradiating the active energy ray, but it is preferable that there is a setting zone of 10 to 60 seconds.

  The active energy ray irradiation is preferably performed at a material temperature of 30 to 80 ° C.

  The coated substrate used in the method for forming a cured coating film of the present invention is not particularly limited as long as it is an object that is generally coated with a cured coating film. Specifically, plastic, metal, paper, wood, inorganic board, Or what printed these, the thing which stuck printing layers, such as gravure ink, with adhesives etc. are mentioned. In particular, it is effective for exhibiting a high film thickness and specular design on a wooden substrate.

  EXAMPLES Next, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to these. In the following, unless otherwise specified, the numbers in the table represent parts by mass.

  It mix | blends using the active energy ray curable composition of the composition of following Table 1, and mixes with a dispersion stirrer, a coating material (A1), a coating material (A2), a coating material (A3), a coating material (B1), a coating material ( B2) and paint (B3) were prepared.

  Unidic V-5508 (a bifunctional epoxy acrylate oligomer manufactured by Dainippon Ink & Chemicals, Inc.) was used for each of the paints A1, A2, and A3. As paints B1, B2, and B3, Unidick V-4007 (a trifunctional urethane acrylate oligomer manufactured by Dainippon Ink and Chemicals) was used. Trimethylolpropane diacrylate was used as the bifunctional monomer in Table 1, and 2-hydroxyethyl methacrylate was used as the monofunctional monomer. Irgacure 184 (manufactured by Ciba Specialty Chemicals) was used as a polymerization initiator. Further, 0.1 part of an antifoaming agent was added.

The plywood prepared by applying these paints was coated at the coating amount shown in Table 2 under the conditions that the rotation speed of the feed roll of the roll coater and the rotation speed of the coating roll was 40 m / min, and the rotation speed of the doctor roll was 15 m / min. . Each ultraviolet irradiation was cured at a room temperature of 25 ° C. with an ultraviolet irradiation amount of 160 mJ / cm ² . For each of the resulting cured coating films, a finished feeling (smoothness, feeling of flesh) was confirmed. In Table 2, A represents the paint (A), and (15 g) represents the coating amount per square meter. “Yes” in “UV presence / absence” after the first coating means that the first coating composition is cured before the second coating, and “No” means that the second coating is cured. It means that the first coating composition is not cured before, the second coating composition is applied by a wet-on-wet method, and then UV-cured.

  From the results in Table 2, it can be seen that it is preferable to use a paint having the same oligomer component. It can also be seen that even with a combination of paints having the same oligomer component, a good coating film cannot be obtained unless a paint having a lower viscosity is used in the second step. Moreover, it turns out that the balance of an appropriate viscosity is required also in a 1st process and a 2nd process.

To the coating field to protect the surface while adding various functions and design features such as high hardness, high gloss, and stain resistance to the surface of base materials such as paper, plastic, glass, metal, wood and ceramic. Is expected.

Claims (9)

The first coating process in which the first coating composition is applied to the substrate surface using a roll coater, and then the second coating composition is applied in a wet-on-wet system using a grooved roll coater. A cured coating film forming method having a second coating step of coating and a step of irradiating active energy rays, wherein the first and second coating compositions contain at least one oligomer component and have a nonvolatile content A cured coating composition comprising an active energy ray-curable coating composition of 90 to 100% by mass, wherein the first coating composition is applied under a condition where the viscosity is higher than that of the second coating composition. Film forming method. The method for forming a cured coating film according to claim 1, wherein the oligomer component described above is one or more selected from a urethane acrylate oligomer, an epoxy acrylate oligomer, and a polyether acrylate oligomer. The first coating composition has a viscosity of 320 to 720 mPa · s at a coating temperature of 40 ° C., and the second coating composition has a viscosity of 50 to 320 mPa · s at a coating temperature of 40 ° C. The cured coating film forming method according to claim 1, wherein coating is performed in a range. The first coating amount in the coating step is 10 to 40 g / m ^2, a cured coating film forming method according to claim 1 coating amount in the second coating step is 10 to 40 g / m ² . The method for forming a cured coating film according to claim 1, wherein the oligomer component contained in the first coating composition and the oligomer component contained in the second coating composition are the same oligomer component. The method for forming a cured coating film according to claim 1, wherein the step of irradiating active energy rays is performed at a material temperature of 30 to 80 ° C. The grooved roll coater is a grooved roll coater having longitudinal grooves with 5 to 40 grooves / cm, a groove width of 0.5 to 2.0 mm, and a groove depth of 0.1 to 1.0 mm. The method for forming a cured coating film according to claim 1. The method for forming a cured coating film according to claim 1, wherein the roll coater used in the first coating step is a natural roll coater. The method for forming a cured coating film according to claim 1, wherein the active energy ray is ultraviolet rays.