JP2012241088A - Active energy ray-curable water-containing coating material - Google Patents

Abstract

The present invention provides a coating composition using a hydrous solvent as a diluting solvent in order to reduce the amount of an organic solvent used in coating in a molded article having low scratch resistance, which exhibits a surface that is difficult to be damaged after coating.
An active energy ray-curable water-containing coating material comprising an active energy ray-curable compound containing ethylene oxide-modified glycerin tri (meth) acrylate and a diluting solvent containing water.
[Selection figure] None.

Description

  The present invention relates to an active energy ray-curable water-containing coating material.

  From the viewpoint of productivity and energy saving, UV curable paints are widely used, and in particular, they are put into practical use in a wide range of fields such as hard coating materials for plastic molded products, coating materials for woodwork, and inks. Many of these use a diluting solvent to improve workability during coating, and an organic solvent is used. Organic solvents are required to reduce emissions from the viewpoints of environmental protection and prevention of air pollution. In such a social environment, the use of water as a diluting solvent has been studied, and water-based or water-containing paints are used as woodwork paints. Has been put to practical use in fields such as paper glossy ink. (Patent Document 1)

JP-A-6-136015

When the technique disclosed in this document is applied to a hard coat material for a plastic molded product, the scratch resistance of the formed coating film is low, and the performance as a hard coat is insufficient.
Accordingly, an object of the present invention is to provide a coating composition that can form a coating film that is difficult to be damaged after coating, and that uses a hydrous solvent as a diluent solvent in order to reduce the amount of organic solvent used during coating.

  The present invention relates to an active energy ray-curable water-containing coating material (hereinafter referred to as “the present coating material”) comprising an active energy ray-curable compound containing ethylene oxide-modified glycerin tri (meth) acrylate and a diluent solvent containing water. It is.

  The active energy ray-curable water-containing coating composition of the present invention can form a highly scratch-resistant coating film on a plastic molded article having low scratch resistance, and reduces the amount of organic solvent discharged during coating. Therefore, it is suitable as a coating material for forming a hard coat layer for protecting the surface of a mobile phone, a cosmetic container or the like.

Hereinafter, the present invention will be described in detail.
In the present invention, ethylene oxide-modified glycerin tri (meth) acrylate (hereinafter referred to as “component (A)”) is one of the components of the active energy ray-curable compound (hereinafter referred to as “curable compound”) contained in the coating composition. In the compound, the content is preferably 25 to 75% by mass, more preferably 30 to 67% by mass. In the present invention, ethylene oxide-modified glycerin tri (meth) acrylate is represented by the formula:
_{CH 2 O- (C 2 H 4} O) l -C (= O) -CR = CH 2
｜
CHO— (C ₂ H ₄ O) _m —C (═O) —CR═CH ₂ (1)
｜
_{CH 2 O- (C 2 H 4} O) n -C (= O) -CR = CH 2
The compound represented by these is shown. In the above formula, R is a hydrogen atom or a methyl group. In this specification, “(meth) acrylate” refers to at least one selected from “acrylate” and “methacrylate”. The component (A) is excellent in compatibility with water as well as an organic solvent used as a diluting solvent, and is a suitable component for reducing the organic solvent that is the object of the present invention. In addition, many of the curable compounds having high hydrophilicity tend to lower the physical properties of the coating film after curing, particularly the hardness, and are therefore unsuitable as coating materials for plastic molded articles and the like used in the present invention. Among them, it was found that the component (A) exhibits good hardness in order to protect the surface of the molded product. Further, as the component (A), compounds different in the number of moles modified with ethylene oxide are known, and the ethylene oxide structure has an average of about 3 to 20 moles per molecule (that is, l + m + n = about 3 in the above formula (1)). The compound added up to about 20) can be obtained by purchasing a commercial product or by a known synthesis method. Among them, the number of modified moles of ethylene oxide is an average of 9 moles per molecule (that is, 1 + m + n = about 9 in the above formula (1)), and it may be used from the viewpoint of the curability and hardness of the coating material from which the modified compound is obtained. More preferred.

  In carrying out the present invention, the proportion of the component (A) in the curable compound is adjusted according to the purpose of use of the coating material, but preferably 25 to 75% by mass in the curable compound contained in the coating material. More preferably, the content is 30 to 67% by mass from the viewpoints of the stability of the coating material and the hardness of the cured coating film.

  The curable compound other than the component (A) in the coating composition is polymerized by active energy rays such as ultraviolet rays and electron beams alone or by the action of a photopolymerization initiator described later, and has been conventionally used. Known compounds can be used. For example, urethane (meth) acrylates, epoxy (meth) acrylates, polyester (meth) acrylates, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, tri Methylolpropane tri (meth) acrylate, tris (2-acryloyloxyethyl) isocyanurate, polyethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate , Neopentyl glycol di (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, tetra Rofurufuriru (meth) acrylate, 2-hydroxyethyl (meth) acrylate of (meth) acrylates. These may be used alone or in combination of two or more.

  Of these, dipentaerythritol hexa (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and the like that have high reactivity and good coating film hardness are preferred.

  Moreover, it becomes possible to reduce the amount of the organic solvent which volatilizes in air | atmosphere by containing water as a dilution solvent, but it is preferable to use the ratio of the water in a dilution solvent in the range of 20-60 mass%. . The higher the proportion of water, the lower the amount of organic solvent used. However, the solvent drying step after coating tends to be longer, and it is preferably used in the above-mentioned range. The water to be used is preferably pure water, but any water quality that is industrially used such as tap water or well water can be used. As the organic solvent to be used, ester solvents, ketone solvents, aromatic solvents, and the like can be used. Although not particularly limited, propyl alcohol, butyl alcohol, and methoxypropanol having high compatibility with water are used. Alcohol solvents such as are preferred because of their high coating stability.

  The dilution solvent may be used at an arbitrary ratio so as to have a viscosity suitable for the method of coating the coating material. For example, when the spray coating method is used, 50 to 200 parts by mass with respect to 100 parts by mass of the curable compound. It is preferable to use parts.

  In order to cure the coating paint, it is preferable to use ultraviolet rays as active energy rays from the viewpoint of productivity and energy saving, and it is effective to contain a photopolymerization initiator in the coating paint.

  Examples of the photopolymerization initiator include benzoin monomethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzophenone, p-methoxybenzophenone, diethoxyacetophenone, benzyldimethyl ketal, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone. Methylphenylglyoxylate, ethylphenylglyoxylate, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-ethylanthraquinone, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide. Can be mentioned. These may be used alone or in combination of two or more. It is effective to use these in the range of 0.5 to 10 parts by mass with respect to 100 parts by mass of the curable compound.

  Among these, benzophenone and 1-hydroxycyclohexyl phenyl ketone are preferable in terms of excellent curability.

  In addition, the coating paint may contain a polymer resin such as an acrylic resin, a polyester resin or an alkyd resin for the purpose of improving the adhesion and flexibility with the base material, a leveling agent, an antifoaming agent or an anti-settling agent. Additives such as lubricants, abrasives, rust inhibitors, antistatic agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors and the like can be added.

  This coating material is particularly useful for, for example, ABS resin, ASA resin, AS resin, polycarbonate resin, or a resin molded product obtained by molding these alloy resins.

  Examples of the method for applying the coating material to a resin molded product include publicly known methods such as brush coating, spray coating, dip coating, spin coating, and flow coating. However, application workability, smoothness of coating film, uniformity, etc. From this point, the spray coating method is preferable.

The curing method of the applied coating paint will be described in sequence. First, after applying this coating material, the dilution solvent contained in this material is volatilized. Examples of the method for volatilizing the diluting solvent include a method in which the solvent is volatilized under conditions of 40 to 130 ° C. and 1 to 20 minutes by heating with an infrared heater or warm air. Then, as a method of obtaining a cured coating film, the method of hardening by active energy ray irradiation is mentioned, for example. Examples of the active energy rays include ultraviolet rays and electron beams. As the irradiation condition of the active energy ray, for example, when a high-pressure mercury lamp is used, the irradiation energy amount is preferably about 500 to 4,000 mJ / cm ² .

  As for the film thickness when this coating material is applied and cured, the film thickness after curing is preferably about 3 to 40 μm.

  This coating material is used as a protective coating for the purpose of protecting molded articles from scratches and dirt. Alternatively, it can be used as an undercoat or a topcoat when a metal thin film layer such as aluminum or chromium is laminated after the molded product is coated and a metal decoration process is performed. The metal decoration process is a thin film formation process in which a metal thin film layer is formed by a known technique such as a vacuum deposition method, an ion plating method, or a sputtering method, and these decorated molded products are used for lighting, light, etc. It can be used in various applications such as reflectors, reflector parts, home appliances such as mobile phones, and cosmetic containers.

  Hereinafter, the present invention will be described with reference to examples. In the following, “part” means “part by mass”, and “%” means “mass%”. Various evaluations of the coating material were carried out by the following methods.

Scratch resistance A test piece of an ABS resin molded product having a width of 5 cm, a length of 9 cm and a thickness of 3 mm was held horizontally, and the coating paint was spray-coated so that the film thickness after curing was 10 μm. After that, after the test piece of the resin molded product thus coated is kept in a hot air drier at 60 ° C. under room humidity for 5 minutes to evaporate the diluting solvent containing water, in the air, using a high-pressure mercury lamp, An active energy ray having a wavelength of 340 to 380 nm and an integrated light quantity of 1,000 mJ / cm ² was irradiated to form a cured coating film. After that, grasp steel wool (# 0000, manufactured by Bonstar Co., Ltd.) with your thumb and forefinger, rub the surface of the cured coating film 5 times with a load of about 1 kg, and visually observe the condition of the scratch on the surface. The scratch resistance was evaluated.
“◎”: There is no scar.
“◯”: There is a slight scar.
“△”: A scar remains clearly.
“×”: Many scars remain.

[Example 1]
The raw materials having the composition shown in the table were put into a stainless steel container and stirred for about 30 minutes until the whole became uniform to prepare an active energy ray-curable water-containing coating material. The results of evaluating the scratch resistance of this coating paint are shown in the table.

Ａ−ＧＬＹ−３Ｅ：エチレンオキサイド３モル変性グリセリントリアクリレート（式（１）中でｌ＋ｍ＋ｎ＝３のもの、新中村化学工業（株）製、商品名：ＮＫエステル（商標）Ａ−ＧＬＹ−３Ｅ）
Ａ−ＧＬＹ−９Ｅ：エチレンオキサイド９モル変性グリセリントリアクリレート（式（１）中でｌ＋ｍ＋ｎ＝９のもの、新中村化学工業（株）製、商品名：ＮＫエステル（商標）Ａ−ＧＬＹ−９Ｅ）
ＤＴＭＰＴＡ：ジトリメチロールプロパンテトラアクリレート（東亞合成（株）製、商品名：アロニックス（商標）Ｍ−４０８）
ＤＰＨＡ：ジペンタエリスリトールヘキサアクリレート（日本化薬（株）製、商品名：ＫＡＹＡＲＡＤ（商標） ＤＰＨＡ）ＤＡ−３１４：グリセリントリエポキシアクリレート（ナガセケムテックス（株）製、商品名：デナコールアクリレート ＤＡ−３１４）
ＡＣＭＯ：アクリロイルモルフォリン（興人（株）製、商品名：ＡＣＭＯ（商標））
ＨＣＰＫ：１−ヒドロキシシクロヘキシルフェニルケトン（チバスペシャリティーケミカル（株）製、商品名：イルガキュアー（商標）１８４）
水：水道水
ＩＰＡ：イソプロピルアルコール
ＰＭ：メトキシプロパノール [Examples 2-5, Comparative Examples 1-2]
An active energy ray-curable water-containing coating composition was obtained in the same manner as in Example 1 except that the composition shown in the table was used. The evaluation results of the scratch resistance of the obtained coating paint are shown in the table.

A-GLY-3E: Ethylene oxide 3 mol-modified glycerin triacrylate (in formula (1), l + m + n = 3, manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK ester (trademark) A-GLY-3E)
A-GLY-9E: Ethylene oxide 9 mol-modified glycerin triacrylate (in formula (1), l + m + n = 9, manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK ester (trademark) A-GLY-9E)
DTMPTA: Ditrimethylolpropane tetraacrylate (manufactured by Toagosei Co., Ltd., trade name: Aronix (trademark) M-408)
DPHA: dipentaerythritol hexaacrylate (manufactured by Nippon Kayaku Co., Ltd., trade name: KAYARAD (trademark) DPHA) DA-314: glycerin triepoxy acrylate (manufactured by Nagase ChemteX Corporation, trade name: Denacol acrylate DA- 314)
ACMO: Acryloyl morpholine (trade name: ACMO (trademark), manufactured by Kojin Co., Ltd.)
HCPK: 1-hydroxycyclohexyl phenyl ketone (manufactured by Ciba Specialty Chemicals Co., Ltd., trade name: Irgacure (trademark) 184)
Water: Tap water IPA: Isopropyl alcohol PM: Methoxypropanol

  Since the active energy ray-curable water-containing coating materials of Examples 1 to 5 are composed of the components and ratios shown in the claims, a cured coating film having high scratch resistance is formed on the surface of the molded product while being a water-containing coating material. It can be done.

  Since the active energy ray-curable water-containing coating materials of Comparative Examples 1 and 2 lack the components shown in the claims, the resulting cured coating films have low scratch resistance.

Claims (2)

  An active energy ray-curable water-containing coating composition comprising an active energy ray-curable compound containing ethylene oxide-modified glycerin tri (meth) acrylate and a diluting solvent containing water.   The paint according to claim 1, wherein the active energy ray-curable compound contains 25 to 75% by mass of the ethylene oxide-modified glycerol tri (meth) acrylate.