JP2011046854A - Photocurable paint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain paint used for coating of outer walls of a building, forming a paint film with excellent stain resistance while having elasticity. <P>SOLUTION: The photocurable paint contains a photocurable resin and a pigment. The glass transition point (Tg) of the photocurable resin is -50 to 35°C, and a contrast ratio of the paint film with a dried film thickness of 80 μm formed from the photocurable paint is 50% or more. The photocurable paint may contain a photopolymerization initiator. The pigment volume concentration (PVC) of the photocurable paint is preferably 20-40%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a paint using a photocurable resin. This paint is mainly used for painting the outer wall of a building. And the coating film formed with this coating material has elasticity and is excellent in stain resistance.

Here, the description will focus on the coating on the outer wall of the building, but the coating of the present invention can also be applied to the inner wall, ceiling, etc. of the building. It is also possible to paint on an object to be painted such as a civil engineering structure.
It can also be used to paint building materials attached to buildings and civil engineering structures.

In this specification, the term “elastic coating” refers to a coating formed by a paint having an elongation rate of 120% or more as a result of an elongation test (elongation test at 20 ° C.) of JIS A6909: 2003. It is.
In addition, the “elasticity” of the coating film is a performance showing an elongation rate of 120% or more in the elongation test (elongation test at 20 ° C.).

  Conventionally, as a paint using a photocurable resin, there has been a paint described in Patent Document 1. However, these paints were premised on curing using an ultraviolet irradiation device. And the paint which is painted on the outer wall of the building and cured by sunlight has not been sufficiently studied.

On the other hand, the paint which forms an elastic coating film may be used for the coating of the outer wall of a building. The elastic coating film has elongation performance, can follow displacement due to cracks or the like of the object to be coated, and can exhibit an effect of preventing water from entering the substrate.
Examples of the paint having such performance include “waterproof outer wall synthetic resin emulsion-based thin finish coating material” and “waterproof outer wall synthetic resin emulsion-based multilayer coating material” defined in JIS A6909: 2003. Is mentioned.

However, the elastic coating film has a problem that it is difficult to obtain sufficient contamination resistance. That is, when the elasticity of the coating film is increased, the surface of the coating film tends to become soft, so that contaminants are likely to adhere to the coating film. Further, since the surface of the coating film is soft, it is difficult to remove the contaminants once attached to the coating film from the coating film surface.
For this reason, the surface of the elastic coating film may be coated with a top coating to prevent contamination.

JP 2002-3560 A ("Claims" etc.)

  The present invention solves the problems of the above-described elastic coating film, and uses a photocurable resin to provide a coating material that can form a coating film having excellent resistance to contamination while having elasticity. The purpose is to obtain.

The photocurable paint of the present invention is a photocurable paint containing a photocurable resin and a pigment, wherein the photocurable resin has a glass transition point (Tg) of −50 to 35 ° C. and the light. It is a photocurable paint characterized in that the concealment ratio of a coating film having a dry film thickness of 80 μm formed by a curable paint is 50% or more.

The photocurable coating material may contain a photopolymerization initiator.

Moreover, it is preferable that the pigment volume concentration (PVC) of the said photocurable coating material is 20 to 40%.

Moreover, it is preferable to contain the polymer nanoparticle with an average particle diameter of 1-50 nm in the said photocurable coating material.

By coating the photocurable paint of the present invention on the outer wall of a building, it is possible to obtain a coating film having excellent resistance to contamination while having elasticity.

The photocurable paint of the present invention is dried and cured to form an elastic coating film. Thereafter, the surface of the formed elastic coating film is cross-linked with resin molecules on the surface of the coating film by a crosslinking reaction (hereinafter also referred to as photocrosslinking) by irradiating sunlight onto the surface of the coating film surface. Increased hardness. Thereby, an elastic coating film whose coating film surface is harder than the inside of the coating film is formed.

  The photocurable paint contains a photocurable resin and a pigment. Moreover, it is preferable to contain a photopolymerization initiator in order to promote photocrosslinking of the photocurable resin.

  In addition, when the exterior wall of a building is coated with a photocurable paint, the light applied to the coating film is mainly sunlight, so that the photocurable paint starts a crosslinking reaction by sunlight. It is preferable to use what to do. Or when a photocurable resin does not carry out sufficient crosslinking reaction with sunlight, it is preferable to utilize the photoinitiator which generate | occur | produces active species with sunlight with a photocurable resin.

Moreover, as light irradiated to a coating film, light irradiation apparatuses, such as an ultraviolet irradiation apparatus using an ultraviolet lamp other than sunlight, can also be used, for example.

  An elastic coating film formed from a photocurable coating has a high crosslinking density on the surface of the coating film due to photocrosslinking, and the hardness of the coating film surface increases, so that contaminants are less likely to adhere to the coating film surface. Moreover, it becomes easy to remove the contaminants once adhered. On the other hand, although the surface of the coating film is photocrosslinked, the elasticity of the coating film is not impaired because the inside of the coating film is difficult to reach sunlight and is not photocrosslinked like the coating film surface.

  The photocurable resin is a resin composition that starts a crosslinking reaction when irradiated with light. Specifically, the photocurable resin is a resin composition having a photopolymerizable functional group in the molecular skeleton. In addition, a photopolymerizable functional group is a functional group which can start a crosslinking reaction by light irradiation and can form a crosslinking bond between molecules of the photocurable resin.

The photopolymerizable functional group may be one in which the photocurable resin is directly activated by light irradiation to cause a crosslinking reaction, or the photopolymerizable functional group is light when irradiated with light in the coexistence of the photocurable resin and the photopolymerization initiator. The crosslinking reaction of the photocurable resin may be initiated and promoted by the action of active species generated from the polymerization initiator.

Examples of the photopolymerizable functional group include those having radical photopolymerization reactivity such as unsaturated double bonds (typically ethylenic double bonds) and light such as cyclic ether groups such as epoxy groups. Examples thereof include those having cationic polymerization reactivity, those having photoanion polymerization reactivity, those having photodimerization reactivity, and the like. Among them, it is preferable to use a photocurable resin having a photopolymerizable functional group having photoradical polymerization reactivity from the viewpoint of easy synthesis and low cost.

The photopolymerizable functional group having photoradical polymerization reactivity is preferably a carbonyl group or a nitrile group. A photocurable resin having a carbonyl group or a nitrile group is excellent in crosslinking reactivity and can further increase the hardness of the coating film surface.

Further, the pre-photocurable resin preferably has 1 to 10 photocrosslinkable functional groups per 1000 molecular weight of the resin. By using such a photocurable resin for the photocurable coating, the crosslink density on the coating film surface can be further increased.

The photocurable resin is preferably one that initiates a crosslinking reaction upon irradiation with sunlight, and more preferably one that initiates a crosslinking reaction with ultraviolet light having a wavelength of 280 to 400 nm, which is contained in a large amount of sunlight. By using such a photocurable resin, a crosslinking reaction of the photocurable resin can be quickly performed by sunlight.

When blending these photocurable resins into the photocurable paint, the photocurable resin may be used alone, or may be copolymerized and used in combination of two or more. You can also. Further, as a form for blending the resin into the photocurable paint, a resin dissolved in a solvent or a water-dispersed emulsion can be used.

In addition, the photocurable coating material of this invention forms an elastic coating film by drying and hardening, and the said photocurable resin uses what forms an elastic coating film by drying and hardening. Specifically, the photocurable resin preferably has a glass transition point (Tg) of −50 to 35 ° C. (more desirably −40 to 0 ° C., particularly desirably −30 to −5 ° C.). When the Tg of the photocurable resin is −50 ° C. or lower, the coating film formed with the photocurable resin is likely to be dirty, and the stain resistance may not be sufficient. Moreover, when Tg of photocurable resin is 35 degreeC or more, the elasticity of the coating film formed with this photocurable resin is not enough, and it may be unable to fully follow the displacement of a to-be-coated object.
When the Tg of the photocurable resin is −50 to 35 ° C., a coating film having excellent stain resistance and sufficient elasticity can be obtained. Further, the stain resistance and elasticity of the coating film are more excellent when Tg is −40 to 20 ° C., and particularly excellent when Tg is −30 to 5 ° C.

The pigments are color pigments and extender pigments. The pigment content is preferably a pigment volume concentration (PVC) of 20 to 40% (more desirably 25 to 35%). If the PVC is too small, sufficient stain resistance may not be obtained even with a coating film photocrosslinked with a photocurable resin. Conversely, if the PVC is too large, it is difficult to obtain a coating film having sufficient elasticity. When the PVC is in the above-described range, the coating film formed from the photocurable coating has sufficient contamination resistance and has excellent elasticity.
The PVC is a percentage of the volume of the pigment (sum of the volume of the colored pigment and the volume of the extender pigment) in the total volume of the dry coating film formed by the paint.
In addition, what is necessary is just to adjust the kind and addition amount of the said pigment in order to obtain the photocurable coating material whose concealment rate of the coating film with a dry film thickness of 80 micrometers is 50% or more. Since the concealability of the coating film varies depending on the type of pigment used or the degree of dispersion of the pigment, the addition amount cannot be described in general, but the concealment rate is increased by increasing the addition amount of the color pigment among the pigments. be able to. A photo-curable paint having a coating film thickness of 80 μm in dry film thickness of 50% or more when the color pigment is 15 parts by mass or more, preferably 25 parts by mass or more with respect to 100 parts by mass of the photo-curable resin. Easy to get.

  Examples of the color pigment include titanium oxide, zinc oxide, yellow lead, zinc white, yellow iron oxide, bengara, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue and other inorganic pigments, azo pigments , Diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, isoindolinone pigments, selenium pigments, perylene pigments, perinone pigments, dioxane pigments and other organic pigments, aluminum pigments, pearl pigments Etc.

  Examples of the extender pigment include talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, aluminum hydroxide, silica powder, silica sand, cold water sand, alumina white, diatomaceous earth, resin beads, glass beads, hollow balloons, and the like. Can be mentioned.

  The photopolymerization initiator generates an active species that initiates and / or accelerates the crosslinking reaction of the photocurable resin by light irradiation. As the photopolymerization initiator, one that generates appropriate active species according to the difference in the reaction mode of the photocurable resin is used. That is, a photo radical polymerization initiator has photo radical polymerization reactivity, a photo radical polymerization initiator has photo radical polymerization reactivity, and a photo cationic polymerization initiator has photo cationic polymerization reactivity. A photoanionic polymerization initiator is used for the resin.

Examples of the radical photopolymerization initiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, α-methylbenzoin, α-phenylbenzoin, anthraquinone, methylanthraquinone, acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetone, benzyldiacetylacetophenone, benzophenone, p-chlorobenzophenone, 2-hydroxy-2-methylpropiophenone, diphenyldisulfide, tetramethylthiuram sulfide, α-chloromethylnaphthalene, anthracene, hexachloro Butadiene, pentachlorobutadiene, Michler's ketone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzyldimethyl Luketal, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1,2-hydroxy-2-methyl- Examples include 1-phenylpropan-1-one and 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one.

Examples of the photocationic polymerization initiator include aromatic diazonium salts, aromatic iodonium salts, aromatic sulfonium salts, aromatic phosphonium salts, mixed ligand metal salts, and the like.

Examples of the photoanionic polymerization initiator include 1,10-diaminodecane, 4,4′-trimethylenedipiperidine, carbamates and derivatives thereof, cobalt-amine complexes, aminooxyiminos, ammonium borates and the like. Can be mentioned.

The photopolymerization initiator preferably generates active species by irradiation with sunlight, and more preferably generates active species by ultraviolet rays having a wavelength of 280 to 400 nm, which are contained in a large amount of sunlight. By using such a photopolymerization initiator, active species can be quickly generated by sunlight.

Moreover, in order to improve the storage stability of a coating material, you may mix | blend a polymerization inhibitor with the said photocurable coating material. Examples of the polymerization inhibitor include phenols such as hydroquinone, t-butylhydroquinone, catechol and hydroquinone monomethyl ether; quinones such as benzoquinone and diphenylbenzoquinone; phenothiazines; copper and the like. The polymerization inhibitor is preferably blended at a ratio of 0.1 to 10% by weight with respect to the total solid content of the photocurable resin composition.

In addition, the photocurable paint may contain a resin component other than the photocurable resin. By containing a resin component other than the photocurable resin, the properties of the paint before drying and the physical properties of the coating film after drying and curing can be adjusted. For example, it may be blended for the purpose of adjusting the elongation performance, adhesion performance, weather resistance and the like of the coating film after drying and curing.
As the resin component, a resin generally used for a paint may be used. In order to contain such a resin in the coating material, a resin dissolved in a solvent or an emulsion dispersed in water is used.

  In addition, various additives used for ordinary paints can be appropriately added as additives to the photocurable paint. For example, surfactants such as dispersants and wetting agents, thickeners such as methylcellulose, polyacrylic acid and bentonite, film forming aids, pH adjusting agents, antifoaming agents, antiseptics, antioxidants, etc. may be used. it can.

  It is preferable that the photocurable paint obtained by the above configuration does not easily reach the inside of the coating film when the coating film formed by the coating material is irradiated with sunlight. When sunlight reaches the inside of the coating film, curing due to photocrosslinking proceeds even inside the coating film, so that the entire coating film becomes hard when irradiated with sunlight, and the elasticity of the coating film may decrease. Conversely, by making it difficult for sunlight to reach the inside of the coating film, even if photocrosslinking proceeds near the surface of the coating film and the coating film near the surface becomes hard, photocrosslinking is suppressed inside the coating film. Since elasticity is maintained, the elasticity of the entire coating film is maintained.

In order to make it difficult for sunlight to reach the inside of the coating film, the concealment rate of the coating film having a dry film thickness of 80 μm formed by the photocurable coating is 50% or more (more preferably 60% or more, particularly preferably 70). % Or more). When the coating ratio is less than 50%, when the coating film is exposed to sunlight for a long period of time, the curing by photocrosslinking tends to proceed to the inside of the coating film, so that the elasticity of the coating film cannot be maintained for a long time. There is a case. On the contrary, if the concealment ratio is 50% or more, the curing of the coating film by photocrosslinking stays in the vicinity of the surface of the coating film, and the elasticity inside the coating film is not impaired. The coating film has elasticity. Moreover, if the concealment rate is 60% or more, it is possible to obtain a coating film having excellent elasticity even after being irradiated with sunlight. If the concealment rate is 70% or more, the elasticity is maintained. A particularly excellent coating film can be obtained. In addition, the said maintainability is the value which remove | divided the elongation rate of the coating film after irradiating sunlight with the elongation rate of the coating film before irradiating sunlight, and it becomes maintainability, so that the value is close to 1. It is evaluated as excellent.
In addition, the measuring method of the said concealment rate is based on the method B (test method with concealment rate test paper) described in JIS K5600-4-1: 1999. However, the thickness of the coating film is 80 μm in terms of dry film thickness.

Moreover, it is preferable that the said photocurable coating material contains a polymer nanoparticle with an average particle diameter of 1-50 nm (more desirably 1-30 nm). The polymer nanoparticles are non-coating-forming polymer particles that do not form a film by themselves. When polymer nanoparticles are blended with the photocurable paint, the polymer nanoparticles are densely arranged on the surface layer of the coating film formed by the photocurable paint.
The glass transition point (Tg) of the polymer nanoparticles used in the photocurable coating of the present invention is 20 ° C. or higher (more desirably 50 ° C. or higher), and from the Tg of the photocurable resin blended in the photocurable coating. Larger ones are preferred. By using the polymer nanoparticles of Tg, the polymer nanoparticles are arranged on the surface layer of the coating film formed by the photo-curable paint, and the damage resistance, contamination resistance, decontamination property, etc. of the coating film are improved. To do.

As said polymer nanoparticle, what is shown by Unexamined-Japanese-Patent No. 2007-224318, the thing shown by Unexamined-Japanese-Patent No. 2004-162006, etc. can be used, for example.

  Next, the usage method of the said photocurable coating material is demonstrated.

The substrate on which the photocurable paint is applied is not particularly limited, and concrete, mortar, siding board, extrusion board, calcium silicate board, gypsum board, metal, glass, plastic, wood, plywood, etc. It can be used for various substrates used in the field or civil engineering field.

The applied film thickness of the photocurable paint is preferably 0.5 to 15 mm (more preferably 0.8 to 10 mm, and particularly preferably 1 to 7 mm) as the thickness of the dry coating film. If the construction film thickness is too thin, even the elastic coating film cannot sufficiently follow the displacement of the object to be coated, and the coating film is easily damaged. On the other hand, when the construction film thickness is too thick, the drying of the coating film is slow, which may not be suitable as a coating for an outer wall of a building. Moreover, when the said construction film thickness is too thick, a wrinkle and a crack may generate | occur | produce in a coating film at the time of drying, and a defect may arise in a coating film. When the coating amount is in the above-described range, it is possible to obtain a coating film that has excellent drying properties and can follow the displacement of the object to be coated.

  Moreover, what is necessary is just to apply the coating method of the said photocurable coating material using commonly used coating instruments and coating machines, such as a roller, a brush, an air spray, an air gun, an airless spray, an airless gun.

Example 1
Acrylic resin emulsion having a photopolymerizable functional group as a photocurable resin (Tg: −15 ° C., solid content: 50% by mass), titanium oxide as a color pigment, calcium carbonate as an extender, and photopolymerization as other additives Using an initiator (benzophenone), a dispersant, a thickener, an antifoaming agent, a film forming aid, and water, these were mixed in the following proportions to produce a photocurable coating.
Formulation: 400 parts by mass of a photocurable resin (solid content), 130 parts by mass of a coloring pigment, 400 parts by mass of an extender pigment, 100 parts by mass of other additives, and water as appropriate.
The produced photocurable coating material had a solid content of 50% by mass and PVC of 31%, and the concealment ratio of the dry coating film having a thickness of 80 μm was 77%.

(Examples 2-3, Comparative Examples 1-2)
In the formulation shown in Example 1, only the blending amount of the color pigment and the extender pigment was adjusted to produce a photocurable paint having a concealment ratio of a dry coating film having a solid content, PVC, and a thickness of 80 μm shown in Table 1. Examples 2-3 and Comparative Examples 1-2 were used.

(Comparative Example 3)
In addition, in the formulation shown in Example 1, a paint having a formulation in which the photocurable resin is replaced with an acrylic resin emulsion having no photopolymerizable functional group (Tg: −15 ° C., solid content: 50% by mass) is manufactured. Comparative Example 3 was obtained. Table 1 shows the solid content, PVC, and concealment ratio of the dry coating film having a thickness of 80 μm.

Example 4
Example 4 was obtained by adding 50% by mass of polymer nanoparticles to the formulation of Example 1. Table 1 shows the solid content, PVC, and concealment ratio of the dry coating film having a thickness of 80 μm.

  The paints of Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to an elongation test (immediately after formation of the coating film and after irradiation with sunlight) and a contamination test in the following procedure.

The elongation test (immediately after the formation of the coating film) was performed according to the test method of the elongation test (elongation test at 20 ° C.) of JIS A6909: 2003. However, the test specimens were cured in a dark place without light irradiation. In addition, two sheets with a dry film thickness of 1 mm prepared according to JIS A6909 were prepared using each paint, and one of them was used for this test, and the remaining one was an elongation test (after outdoor exposure). Used for.

The test specimen for the elongation test (after sunlight irradiation) was affixed to a stainless steel plate with a dry film thickness 1 mm sheet prepared according to the above JIS A6909, and the plate was subjected to the test method of JIS K5600-7-6: 2002. Similarly, after the outdoor exposure (for 6 months), the sheet removed from the stainless steel plate was used.
Using this sheet as a test body, a test was conducted according to the test method of the elongation test (elongation test at 20 ° C.) of JIS A6909: 2003.

As a contamination test, the contamination of the specimen exposed outdoors was confirmed. First. Outdoor exposure was performed according to the test method of JIS K5600-7-6: 2002. And the grade of the stain | pollution | contamination of the test body after 6 months passed from the start of outdoor exposure was evaluated according to the following criteria.
First, the degree of dirt of Comparative Example 3 was set as Δ, and the following scoring was performed according to the degree of dirt of each specimen.
A: The dirt is not particularly noticeable compared to the specimen of Comparative Example 3.
○: Stain is less noticeable than the specimen of Comparative Example 3.
(Triangle | delta): The thing dirty as much as the test body of the comparative example 3.
X: It is dirty from the specimen of Comparative Example 3.

The results of each test are shown in Table 2.
The significant number of the result of the elongation test was 2 digits.

  Looking at the results of the elongation test, the difference between the elongation immediately after formation of the coating and the elongation after irradiation with sunlight is smaller the greater the concealment rate of the coating film with a dry film thickness of 80 μm in the paint using the photocurable resin. The difference tends to increase as the concealment rate decreases. Moreover, the difference became particularly large when the concealment rate was less than 50%.

From the result of the contamination test, it can be seen that the paint using the photocurable resin is difficult to get dirty. This is apparent from the results of Example 1 and Comparative Example 3 in which only the resin used is different.
Moreover, the coating film by the coating material of Example 4 using a polymer nanoparticle was especially hard to get dirty.

Claims (4)

A photocurable paint containing a photocurable resin and a pigment, wherein the photocurable resin has a glass transition point (Tg) of −50 to 35 ° C., and the photocurable paint has a film thickness of 80 μm. A photocurable coating material having a film concealment ratio of 50% or more. Furthermore, a photoinitiator is contained, The photocurable coating material of Claim 1 characterized by the above-mentioned. The photocurable paint according to claim 1 or 2, wherein the pigment volume concentration (PVC) is 20 to 40%. The photocurable paint according to any one of claims 1 to 3, comprising polymer nanoparticles having an average particle diameter of 1 to 50 nm.