JP2012188498A - Coating method of metal base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method of a metal base material to provide a coating layer having good adhesivity to the metal base material and having durability such as adhesivity maintenance even under severer conditions.SOLUTION: The coating method of a metal base material includes: coating a solventless coating agent composition containing a urethane (meth)acrylate-based compound (A), a phosphoric acid group-containing ethylenic unsaturated compound (B), and an ethylenically unsaturated compound (C) having ≥2 ethylenic unsaturated groups (excluding the (A) component and the (B) component) on the surface of the metal base material; heating the resultant at 70 to 130°C for 0.5 to 20 min; and thereafter irradiating the resultant with an active energy rays.

Description

  The present invention relates to a method for coating a metal substrate for forming a coating layer on the surface of the metal substrate by performing active energy ray irradiation.

  Active energy ray-curable resin compositions are widely used as coating agents, adhesives, anchor coating agents, and the like on various substrates because curing is completed by irradiation with radiation for a very short time.

  However, regarding coating agents and paints for forming a cured film on the surface of a metal-based substrate, the coating agents and paints using the active energy ray-curable resin composition are inferior in adhesion to the metal-based substrate. Therefore, it has been difficult to obtain sufficient products, and various developments have been made to improve metal adhesion.

  In addition, the curable resin composition containing an organic solvent has manufacturing defects such as environmental pollution caused by solvent volatilization and the need for equipment to prevent the contamination, and a solvent-free curable resin composition. Things are sought.

  For example, in Patent Document 1, a composition for a coating material containing, as a component of a composition, an organic phosphate ester having a polymerizable unsaturated group capable of reacting with active energy rays in its molecule is used as a metal substrate. It describes that it has excellent adhesiveness.

  However, in the disclosed technology of Patent Document 1, although the adhesion to the metal substrate is recognized to some extent by using the organic phosphate ester, it is still difficult to say that it is practically sufficient. In addition, the coated metal substrate is often bent during processing and production, or immersed in water or exposed to high temperature conditions. Therefore, in consideration of these, development of a coating layer having good adhesion and having durability such as adhesion maintenance under more severe conditions such as substrate processing and immersion in water is required. It was.

JP 58-219272 A

  The present invention has been made in view of the above circumstances, and its purpose is to have good adhesion to a metal substrate, and adhesion even under more severe conditions (during immersion or bending). The object is to provide a method for coating a metal substrate to obtain a coating layer having durability such as maintenance.

  However, as a result of intensive studies, the inventor has obtained a urethane (meth) acrylate compound (A), a phosphoric acid group-containing ethylenically unsaturated compound (B), and an ethylenic group containing two or more ethylenically unsaturated groups. After applying to the surface of the metal substrate using a solventless coating composition containing the unsaturated compound (C) (excluding the component (A) and the component (B)), the active energy is applied. In the coating method of the metal base material that performs the radiation irradiation, the metal adhesion promoting effect of the coating layer is expressed by adopting an appropriate preheating step after coating and before the active energy ray irradiation at the time of coating film formation. As a result, the present invention has been completed.

  That is, the present invention relates to a urethane (meth) acrylate compound (A), a phosphoric acid group-containing ethylenically unsaturated compound (B), and an ethylenically unsaturated compound (C) containing two or more ethylenically unsaturated groups. (However, the component (A) and the component (B) are excluded.) The present invention relates to a method for coating a metal substrate, characterized by performing active energy ray irradiation after heating for a minute.

  According to the method for coating a metal substrate of the present invention, a coating layer having good adhesion properties can be obtained for a metal substrate that is usually not sufficiently adhered, and the coating layer is By including a structural portion derived from the urethane (meth) acrylate-based compound (A), good flexible film properties can be obtained. Therefore, it has an excellent effect that the coating film is hardly peeled off or the appearance is hardly changed even when the metal base material after coating is bent or boiled.

The present invention is described in detail below.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate.

[Urethane (meth) acrylate compound (A)]
The urethane (meth) acrylate compound (A) in the present invention is obtained by reacting a hydroxyl group-containing (meth) acrylate compound (a1) and a polyvalent isocyanate compound (a2). In addition to the above (a1) and (a2), it is obtained by further reacting a polyol compound (a3).

Examples of the hydroxyl group-containing (meth) acrylate compound (a1) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth). Acrylates, hydroxyalkyl (meth) acrylates such as 6-hydroxyhexyl (meth) acrylate, 2- (meth) acryloyloxyethyl-2-hydroxypropyl phthalate, caprolactone-modified 2-hydroxyethyl (meth) acrylate, dipropylene glycol ( (Meth) acrylate, fatty acid-modified glycidyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3- (meth) a Liloyloxypropyl (meth) acrylate, glycerin di (meth) acrylate, 2-hydroxy-3-acryloyl-oxypropyl methacrylate, pentaerythritol tri (meth) acrylate, caprolactone modified pentaerythritol tri (meth) acrylate, ethylene oxide modified pentaerythritol Examples include tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, caprolactone-modified dipentaerythritol penta (meth) acrylate, ethylene oxide-modified dipentaerythritol penta (meth) acrylate, and the like.
Among these, a hydroxyl group (meth) acrylate compound having one ethylenically unsaturated group is preferable, and hydroxyalkyl (meth) acrylate, particularly 2-hydroxyethyl (meth) acrylate is particularly used for reactivity and general purpose. It is preferable at the point which is excellent in property.
Moreover, these can be used 1 type or in combination of 2 or more types.

Examples of the polyvalent isocyanate compound (a2) include aromatics such as tolylene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate. Aliphatic polyisocyanates such as polyisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, lysine triisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, 1,3-bis (Isocyanatomethyl) Cycloaliphatic polyisocyanates such as hexane, trimer compounds or multimeric compounds of these polyisocyanates, allophanate type polyisocyanates, burette type polyisocyanates, water-dispersed polyisocyanates (for example, manufactured by Nippon Polyurethane Industry Co., Ltd.) "Aquanate 100", "Aquanate 110", "Aquanate 200", "Aquanate 210", etc.).
Among these, cycloaliphatic polyisocyanate compounds are preferably used, and in particular, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated xylylene diisocyanate have less yellowing of the cured coating film and less curing shrinkage. It is further preferably used in terms of points.

  Examples of the polyol compound (a3) include polyether polyols, polyester polyols, polycarbonate polyols, polyolefin polyols, polybutadiene polyols, (meth) acrylic polyols, polysiloxane polyols, and the like.

  Examples of polyether polyols include polyether polyols containing alkylene structures such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol, and polyhexamethylene glycol, and random or block copolymers of these polyalkylene glycols. Is mentioned.

Examples of the polyester-based polyol include a condensation polymer of a polyhydric alcohol and a polycarboxylic acid; a ring-opening polymer of a cyclic ester (lactone); a polyhydric alcohol, a polycarboxylic acid, and a cyclic ester. And reactants.
Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylene diol, 1,3-tetramethylene diol, 2-methyl-1,3-trimethyl. Methylene diol, 1,5-pentamethylene diol, neopentyl glycol, 1,6-hexamethylene diol, 3-methyl-1,5-pentamethylene diol, 2,4-diethyl-1,5-pentamethylene diol, glycerin , Trimethylolpropane, trimethylolethane, cyclohexanediols (such as 1,4-cyclohexanediol), bisphenols (such as bisphenol A), and sugar alcohols (such as xylitol and sorbitol).
Examples of the polyvalent carboxylic acid include aliphatic dicarboxylic acids such as malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; -Cycloaliphatic dicarboxylic acids such as cyclohexanedicarboxylic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylene dicarboxylic acid, trimellitic acid, and the like.
Examples of the cyclic ester include propiolactone, β-methyl-δ-valerolactone, and ε-caprolactone.

Examples of the polycarbonate-based polyol include a reaction product of a polyhydric alcohol and phosgene; a ring-opening polymerization product of a cyclic carbonate (such as alkylene carbonate).
Examples of the polyhydric alcohol include polyhydric alcohols exemplified in the description of the polyester-based polyol, and examples of the alkylene carbonate include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, hexamethylene carbonate, and the like. It is done.
In addition, the polycarbonate polyol should just be a compound which has a carbonate bond in a molecule | numerator, and the terminal is a hydroxyl group, and may have an ester bond with a carbonate bond.

  Examples of the polyolefin-based polyol include those having a saturated hydrocarbon skeleton having a homopolymer or copolymer such as ethylene, propylene and butene, and having a hydroxyl group at the molecular end.

Examples of the polybutadiene-based polyol include those having a butadiene copolymer as a hydrocarbon skeleton and having a hydroxyl group at the molecular end.
The polybutadiene-based polyol may be a hydrogenated polybutadiene polyol in which all or part of the ethylenically unsaturated groups contained in the structure thereof are hydrogenated.

  Examples of the (meth) acrylic polyol include those having at least two hydroxyl groups in the molecule of the polymer or copolymer of the (meth) acrylic acid ester. , For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, (meth) acrylic acid Examples include 2-ethylhexyl, (meth) acrylic acid decyl, (meth) acrylic acid dodecyl, (meth) acrylic acid alkyl esters such as octadecyl (meth) acrylic acid, and the like.

  Examples of the polysiloxane polyol include dimethyl polysiloxane polyol and methylphenyl polysiloxane polyol.

  Among these, polyester-based polyols and polyether-based polyols are preferable, and polyester-based polyols are particularly preferable in terms of excellent mechanical properties such as flexibility during curing.

  As a molecular weight of the polyol type compound (a3) used by this invention, 100-8000 are preferable normally, Especially preferably, it is 300-5000, More preferably, it is 600-3000. If the molecular weight of the polyol (a3) is too large, mechanical properties such as coating film hardness tend to be reduced during curing, and if it is too small, curing shrinkage tends to be large and stability tends to be lowered.

  In the present invention, the urethane (meth) acrylate compound (A) is a urethane (meth) acrylate compound (A-1) represented by the following general formula (1) and used for various applications. In particular, it is preferable in that the required physical properties are easily provided.

[Wherein, R ¹ is a urethane bond residue of a polyvalent isocyanate compound, R ² is a urethane bond residue of a hydroxyl group-containing (meth) acrylate compound, and a is an integer of 2 to 50. ]

  In the general formula (1), a may be an integer of 2 to 50, preferably 2 to 20, particularly preferably 2 to 10.

  The urethane (meth) acrylate (A-1) represented by the general formula (1) (hereinafter sometimes abbreviated as “urethane (meth) acrylate compound (A-1)”) is a hydroxyl group-containing (meth). It is obtained by reacting an acrylate compound and a polyvalent isocyanate compound.

  Examples of the hydroxyl group-containing (meth) acrylate compound include those exemplified as the hydroxyl group-containing (meth) acrylate compound (a1) in the description of the urethane (meth) acrylate (A). It is done. Examples of the polyvalent isocyanate compound are the same as those exemplified as the polyvalent isocyanate compound (a2) in the description of the urethane (meth) acrylate (A), or polyvalent isocyanate. What reacted the system compound (a2) and the polyol system compound (a3) is mentioned.

  What is necessary is just to manufacture the manufacturing method of the urethane (meth) acrylate type compound (A) in this invention according to the manufacturing method of a well-known general urethane (meth) acrylate type compound. For example, the hydroxyl group-containing (meth) acrylate compound (a1) and the polyvalent isocyanate compound (a2) may be charged or reacted together in a reactor.

The reaction molar ratio between the polyvalent isocyanate compound (a2) and the hydroxyl group-containing (meth) acrylate compound (a1) is, for example, that the polyisocyanate compound (a2) has two isocyanate groups and the hydroxyl group-containing (meth). When the acrylate compound (a1) has one hydroxyl group, the polyvalent isocyanate compound (a2): hydroxyl group-containing (meth) acrylate compound (a1) is about 1: 2 to 3, When the compound (a2) has three isocyanate groups and the hydroxyl group-containing (meth) acrylate compound (a1) has one hydroxyl group, the polyvalent isocyanate compound (a2): hydroxyl group-containing (meth) acrylate compound (A1) is about 1: 3-4.
In the addition reaction between the polyvalent isocyanate compound (a2) and the hydroxyl group-containing (meth) acrylate compound (a1), the reaction is terminated when the residual isocyanate group content in the reaction system is 0.5% by weight or less. By making it, a urethane (meth) acrylate type compound (A) is obtained.

  Moreover, when manufacturing a urethane (meth) acrylate type compound (A) from a hydroxyl-containing (meth) acrylate type compound (a1), a polyvalent isocyanate type compound (a2), and a polyol type compound (a3), usually a hydroxyl group containing ( Although the meth) acrylate compound (a1), the polyvalent isocyanate compound (a2), and the polyol compound (a3) may be charged into the reactor or reacted separately, the polyol compound (a3) and the polyvalent isocyanate are allowed to react. It is useful in terms of reaction stability and reduction of by-products to react a hydroxyl group-containing (meth) acrylate compound (a1) with a reaction product obtained by reacting the compound (a2) in advance. It is.

  For the reaction between the polyol compound (a3) and the polyvalent isocyanate compound (a2), known reaction means can be used. At that time, for example, the molar ratio of the isocyanate group in the polyvalent isocyanate compound (a2) to the hydroxyl group in the polyol compound (a3) is usually about 2n: (2n-2) (n is an integer of 2 or more). Thus, after obtaining the terminal isocyanate group-containing urethane (meth) acrylate compound having the isocyanate group remaining, the addition reaction with the hydroxyl group-containing (meth) acrylate compound (a1) is made possible.

  The addition reaction of the reaction product obtained by reacting the polyol compound (a3) and the polyvalent isocyanate compound (a2) in advance with the hydroxyl group-containing (meth) acrylate compound (a1) is also a known reaction. Means can be used.

The reaction molar ratio between the reaction product and the hydroxyl group-containing (meth) acrylate compound (a1) is, for example, that the polyisocyanate compound (a2) has two isocyanate groups and the hydroxyl group-containing (meth) acrylate compound (a1). ) Has one hydroxyl group, the reaction product: hydroxyl group-containing (meth) acrylate compound (a1) is about 1: 2, and the polyisocyanate compound (a2) has three isocyanate groups. When the hydroxyl group-containing (meth) acrylate compound (a1) has one hydroxyl group, the reaction product: hydroxyl group-containing (meth) acrylate compound (a1) is about 1: 3.
In the addition reaction between the reaction product and the hydroxyl group-containing (meth) acrylate compound (a1), the reaction is terminated when the residual isocyanate group content in the reaction system is 0.5% by weight or less. A (meth) acrylate compound (A) is obtained.

  The reaction between the polyol compound (a3) and the polyvalent isocyanate compound (a2), the reaction product with the hydroxyl group-containing (meth) acrylate compound (a1), and the above (a1) to (a3) ), It is also preferable to use a catalyst for the purpose of accelerating the reaction. Examples of such a catalyst include organometallic compounds such as dibutyltin dilaurate, trimethyltin hydroxide, and tetra-n-butyltin; zinc octoate , Metal salts such as tin octoate, cobalt naphthenate, stannous chloride, stannic chloride; triethylamine, benzyldiethylamine, 1,4-diazabicyclo [2,2,2] octane, 1,8-diazabicyclo [5, 4,0] undecene, N, N, N ′, N′-tetramethyl-1,3-butanediamine, N-ethylmorpholine, etc. Amine-based catalysts; inorganic bismuth compounds such as bismuth nitrate, bismuth bromide, bismuth iodide and bismuth sulfide; organic bismuth compounds such as dibutyl bismuth dilaurate and dioctyl bismuth dilaurate; bismuth 2-ethylhexanoate and bismuth naphthenate Salts, bismuth isodecanoate, bismuth neodecanoate, bismuth laurate, bismuth maleate, bismuth stearate, bismuth oleate, bismuth linoleate, bismuth acetate, bismuth bisneodecanoate, disalicylic acid Examples thereof include bismuth catalysts such as bismuth salts and organic acid bismuth salts such as bismuth digallate, among which dibutyltin dilaurate and 1,8-diazabicyclo [5,4,0] undecene are suitable.

  The reaction between the polyol compound (a3) and the polyvalent isocyanate compound (a2), the reaction product with the hydroxyl group-containing (meth) acrylate compound (a1), and the above (a1) to (a3). ), An organic solvent having no functional group that reacts with an isocyanate group, for example, esters such as ethyl acetate and butyl acetate; ketones such as methyl ethyl ketone and methyl isobutyl ketone; aromatics such as toluene and xylene Organic solvents, such as a kind, can be used.

  Moreover, reaction temperature is 30-90 degreeC normally, Preferably it is 40-80 degreeC, and reaction time is 2 to 10 hours normally, Preferably it is 3 to 8 hours.

The urethane (meth) acrylate compound (A) used in the present invention preferably has 20 or less ethylenically unsaturated groups, and preferably has 10 or less ethylenically unsaturated groups. Is more preferable, and further having 4 or less ethylenically unsaturated groups is more preferable in terms of the hardness of the cured coating film.
Moreover, the minimum of the ethylenically unsaturated group which a urethane (meth) acrylate type compound (A) contains is 1 normally, Preferably it is two.

  The weight average molecular weight of the obtained urethane (meth) acrylate compound (A) is preferably 700 to 50,000, more preferably 2,000 to 40,000, particularly 4,000 to 30,000. Preferably there is. If the weight average molecular weight is too small, the cured coating film tends to be brittle, and if it is too large, the viscosity tends to be high and difficult to handle.

In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, a column: Shodex GPC KF-806L (high-performance liquid chromatography (the Showa Denko company make, "Shodex GPC system-11 type | mold")). Exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plate / piece, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm) Measured by using this series.

The viscosity of the urethane (meth) acrylate compound (A) at 60 ° C. is preferably 500 to 150,000 mPa · s, particularly 500 to 120,000 mPa · s, more preferably 1,000 to 100,000 mPa · s. It is preferable. When the viscosity is out of the above range, the coatability tends to be lowered.
The viscosity is measured with an E-type viscometer.

[Phosphoric group-containing ethylenically unsaturated compound (B)]
Examples of the phosphoric acid group-containing ethylenically unsaturated compound (B) in the present invention include 2- (meth) acryloyloxyethyl phosphate, ethylene (meth) acrylate, trimethylene (meth) acrylate, and phosphoric acid 1 -Phosphoric acid group-containing ethylenically unsaturated compound having one ethylenically unsaturated group such as chloromethylethylene (meth) acrylate, bis (2- (meth) acryloyloxyethyl) phosphate, ethylene oxide-modified phosphoric acid diacrylate And phosphoric acid group-containing ethylenically unsaturated compounds having two or more ethylenically unsaturated groups such as ethylene oxide-modified phosphoric acid di (meth) acrylate and ethylene oxide-modified phosphoric acid tri (meth) acrylate. These phosphate group-containing ethylenically unsaturated compounds (B) may be used alone or in combination of two or more.
Among them, it is preferable to use a compound having two or more ethylenically unsaturated groups from the viewpoint of scratch resistance, and bis (2- (meth) acryloyloxyethyl) phosphate is particularly preferable, and bis (2-methacrylic acid) is particularly preferable. Loyloxyethyl) phosphate is preferred in terms of substrate adhesion.

  The content of the phosphoric acid group-containing ethylenically unsaturated compound (B) is preferably 0.01 to 100 parts by weight, particularly 100 parts by weight of the urethane (meth) acrylate compound (A). Preferably it is 0.05-50 weight part, More preferably, it is 0.1-25 weight part, Especially preferably, it is 0.2-10 weight part. If the content of the phosphoric acid group-containing ethylenically unsaturated compound (B) is too small, the adhesion tends to decrease. If the content is too large, the substrate is corroded, and mechanical properties such as scratch resistance and hardness are reduced. There is a tendency to decrease.

[Ethylenically unsaturated compound (C) containing two or more ethylenically unsaturated groups]
The ethylenically unsaturated compound (C) in the present invention is an ethylenically unsaturated monomer having two or more ethylenically unsaturated groups in one molecule, which is a urethane (meth) acrylate compound (A) and phosphoric acid. It is an ethylenically unsaturated monomer excluding the group-containing ethylenically unsaturated compound (B), and examples thereof include a bifunctional monomer and a trifunctional or higher functional monomer.

  The bifunctional monomer may be any monomer containing two ethylenically unsaturated groups. For example, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol Di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, ethylene oxide Modified bisphenol A type di (meth) acrylate, propylene oxide modified bisphenol A type di (meth) acrylate, 1,6-hexanediol di (meth) acrylate 1,6-hexanediol ethylene oxide modified di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) Examples include acrylate, diglycidyl phthalate di (meth) acrylate, hydroxypivalic acid-modified neopentyl glycol di (meth) acrylate, isocyanuric acid ethylene oxide-modified diacrylate, and tricyclodecane dimethanol di (meth) acrylate.

  The tri- or higher functional monomer may be any monomer containing three or more ethylenically unsaturated groups. For example, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) Acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, tri (meth) acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly (meth) acrylate, isocyanuric acid ethylene oxide modified triacrylate, ethylene Oxide-modified dipentaerythritol penta (meth) acrylate, ethylene oxide-modified dipentaerythritol hexa (meth) acrylate, ethylene Side modified pentaerythritol tri (meth) acrylate, ethylene oxide modified pentaerythritol tetra (meth) acrylate, caprolactone modified dipentaerythritol penta (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate, caprolactone modified pentaerythritol tri (meth) ) Acrylate, caprolactone-modified pentaerythritol tetra (meth) acrylate, succinic acid-modified pentaerythritol tri (meth) acrylate, and the like.

  These ethylenically unsaturated compounds (C) may be used alone or in combination of two or more.

  Preferably, it is a trifunctional or higher functional monomer containing 3 or more ethylenically unsaturated groups. Specifically, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate Dipentaerythritol hexa (meth) acrylate is preferable for obtaining a coating film having high hardness.

  In addition, a monofunctional monomer may be mixed. The monofunctional monomer may be any monomer containing one ethylenically unsaturated group, and a compound that does not volatilize in the preheating process after coating or a compound that has low volatility is preferable. By mixing a monofunctional monomer, the viscosity of the paint is reduced and the coatability is improved.

  As content of an ethylenically unsaturated compound (C), it is 1-1000 with respect to a total of 100 weight part of a urethane (meth) acrylate type compound (A) and a phosphoric acid group containing ethylenically unsaturated compound (B). It is preferably part by weight, particularly preferably 5 to 500 parts by weight, particularly preferably 1 to 200 parts by weight. If the content of the ethylenically unsaturated compound (C) is too small, the surface hardness tends to decrease, and if it is too large, the curing shrinkage becomes too large at the time of active energy ray irradiation and tends to inhibit the adhesion to the substrate. There is.

  In the present invention, in addition to the urethane (meth) acrylate compound (A), the phosphoric acid group-containing ethylenically unsaturated compound (B), and the ethylenically unsaturated compound (C), the photopolymerization initiator (D) is further added. It is preferable that it is contained in that the effect of the present invention is exhibited.

  Examples of the photopolymerization initiator (D) include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 4- (2-hydroxyethoxy) phenyl- (2- Hydroxy-2-propyl) ketone, 1-hydroxycyclohexylphenylketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholino) Acetophenones such as phenyl) butanone and 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propanone oligomer; benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether Benzoin etc. Benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, 2, 4,6-trimethylbenzophenone, 4-benzoyl-N, N-dimethyl-N- [2- (1-oxo-2-propenyloxy) ethyl] benzenemethananium bromide, (4-benzoylbenzyl) trimethylammonium chloride, etc. Benzophenones: 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2- (3-dimethylamino-2-hydroxy)- 3,4- Thioxanthones such as methyl-9H-thioxanthone-9-one mesochloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphos Acylphosphine oxides such as fin oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide; In addition, as for these photoinitiators (D), only 1 type may be used independently and 2 or more types may be used together.

  These auxiliary agents include triethanolamine, triisopropanolamine, 4,4′-dimethylaminobenzophenone (Michler ketone), 4,4′-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, 4-dimethylaminobenzoic acid. Ethyl, 4-dimethylaminobenzoic acid (n-butoxy) ethyl, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone Etc. can be used in combination.

  Among these, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, benzoyl isopropyl ether, 4- (2-hydroxyethoxy) -phenyl (2-hydroxy-2-propyl) ketone, 2-hydroxy-2-methyl-1- It is preferable to use phenylpropan-1-one.

  The content of the photopolymerization initiator (D) is preferably 0.1 to 20 parts by weight, particularly preferably 0 when the total of the above components (A) to (C) is 100 parts by weight. 0.5 to 15 parts by weight, particularly preferably 1 to 10 parts by weight. If the content of the photopolymerization initiator (D) is too small, curing tends to be poor, and if it is too large, active energy rays are absorbed only on the surface of the coating film, and the curability at the deep part of the coating film tends to decrease. Tend to cause embrittlement and coloring problems.

  In the present invention, in addition to the components (A) to (D), a surface conditioner, a leveling agent, a polymerization inhibitor and the like can be further added as necessary.

The surface conditioner is not particularly limited, and examples thereof include a cellulose-based additive and an alkyd resin.
Such a cellulose-based additive and alkyd resin have an effect of imparting a film-forming property at the time of coating and an effect of increasing the adhesion to a metal vapor deposition surface. The cellulose-based additive is preferably a high-molecular-weight product having a number average molecular weight of 15000 or more in order to reduce fluidity. Examples of such a cellulose-based additive include cellulose-acetate-butyrate resin.

  As the leveling agent, a known general leveling agent can be used as long as it has a wettability imparting action to the base material of the coating liquid and a surface tension reducing action. For example, a silicone-modified resin, a fluorine-modified resin, An alkyl-modified resin or the like can be used.

  Examples of the polymerization inhibitor include p-benzoquinone, naphthoquinone, tolquinone, 2,5-diphenyl-p-benzoquinone, hydroquinone, 2,5-di-t-butylhydroquinone, methylhydroquinone, hydroquinone monomethyl ether, mono-t- Examples thereof include butyl hydroquinone and pt-butyl catechol.

  In addition, the coating agent composition includes organic fine particles, inorganic fine particles, dyes, pigments, oils, antioxidants, flame retardants, antistatic agents, fillers, stabilizers, reinforcing agents, matting agents, if necessary. It is also possible to mix an abrasive or the like.

  Thus, a solventless coating composition containing at least the urethane (meth) acrylate compound (A), the phosphoric acid group-containing ethylenically unsaturated compound (B), and the ethylenically unsaturated compound (C) is obtained.

In producing a solvent-free coating agent composition, urethane (meth) acrylate compound (A), phosphoric acid group-containing ethylenically unsaturated compound (B), ethylenically unsaturated compound (C), photopolymerization initiator ( The mixing method of D) is not particularly limited, and can be mixed by various methods. For example, a method in which the components (A) to (D) are charged all together, a method in which the components (A) and (B) are mixed, (C) is added, and then (D) is preferably used.
Moreover, you may use an ethylenically unsaturated compound (C) as a dilution monomer at the time of manufacture of a urethane (meth) acrylate type compound (A).

[Coating process on the surface of metal substrate]
The solventless coating agent composition (hereinafter also referred to as paint) is applied to the surface of a metal substrate. Such a metal substrate is preferably a substrate containing at least one element selected from aluminum, zinc, iron, magnesium, tin, chromium, nickel, copper, and silver. For example, an aluminum substrate, SUS304, SUS304BA, Examples thereof include a Zn-plated steel plate and an AL / Zn alloy plate.

  In coating, general coating (coating) means can be employed, for example, by a coating apparatus accompanied by coating equipment such as a bar coater, a blade coater, a knife coater, a comma coater, a lip coater, and a die coater. Coating, spray painting, etc. can be employed.

  The coating film thickness is usually 1 to 300 μm, preferably 3 to 100 μm, and more preferably 5 to 50 μm. In coating, the coating can usually be performed at room temperature (room temperature), but it is also possible to use it by heating to lower the viscosity of the coating. However, the temperature for heating is set to a temperature at which the photopolymerization initiator (D) does not react or volatilize, for example, about 80 ° C. If the coating is left in a state where the heating temperature is too high, the photopolymerization initiator will react, and this tends to be unfavorable in terms of the stability of the coating, and it may volatilize depending on the type of the photopolymerization initiator (D). Therefore, it tends to be difficult to obtain uniform physical properties as a cured coating film after coating.

[Preheating process]
In the present invention, it is important to perform preheating at a stage between the coating step and the later-described curing step. The drying furnace system used for preheating is not particularly limited as long as it is an apparatus that can heat the coating substrate, and examples thereof include known systems represented by a hot air circulation type and an infrared type.

  The temperature required for preheating is 70 to 130 ° C, preferably 70 to 120 ° C, more preferably 80 to 110 ° C. If the temperature is too low, it tends to be difficult to obtain the expected metal adhesion within the process time considering productivity. Moreover, when the temperature is too high, the photopolymerization initiator (D) starts to react even in a preheating process in a short time of about several minutes, and there is a tendency that a problem arises in uniformity of curing by irradiation with active energy rays. . Moreover, since there exists what volatilizes depending on the kind of photoinitiator (D), there exists a tendency for the expected cured coating film to become difficult to be obtained. The above temperature is the temperature of the furnace environment (atmosphere).

  The heating time required for preheating is required to be 0.5 to 20 minutes, preferably 1 to 15 minutes, and more preferably 2 to 10 minutes. If the heating time is too short, it is difficult to uniformly heat the whole coated substrate, resulting in uneven performance, and it is difficult to obtain the expected metal adhesion effect. On the other hand, if the heating time is too long, the expected metal adhesion physical properties can be expressed, but the productivity tends to decrease in the line process.

  Note that the coating process, the preheating process, and the curing process described below do not need to be strictly distinguished, and the preheating temperature condition may be satisfied in a part of the coating process or the curing process. For example, after heating for preheating, the curing process may be performed in a temperature environment that satisfies the preheating temperature condition.

[Curing process by irradiation with active energy rays]
As active energy rays used in the curing process, far ultraviolet rays, ultraviolet rays, near ultraviolet rays, infrared rays and other electromagnetic waves, X rays, γ rays and other electromagnetic waves, electron beams, proton rays, neutron rays, etc. can be used. In view of the availability of the irradiation device and the price, curing by ultraviolet irradiation is advantageous. The required wavelength of ultraviolet rays is related to the type of photopolymerization initiator (D), but any device may be used as long as it is generally used in an ultraviolet curing device. Examples include metal halide lamps, high pressure mercury lamps, ultra high pressure mercury lamps, carbon arc lamps, xenon lamps, chemical lamps, electrodeless discharge lamps, UV-LED lamps, and the like. In addition, when performing electron beam irradiation, it can harden | cure even without using a photoinitiator (D).

The amount of UV irradiation as the curing condition varies depending on the content of the photopolymerization initiator (D), etc., but generally conforms to the conditions handled in a series of lines as a general UV curing process. Usually, it is about 200 to 2,500 mj / cm ² . When the irradiation amount is too small, a complete cross-linked structure is not formed, so that there is a tendency that sufficient hardness as a coating film after ultraviolet curing cannot be obtained. Moreover, when there is too much irradiation amount, the advantage commensurate with irradiation amount will not be acquired, but it will use excessive energy and there exists a tendency which is unpreferable industrially. The time required for curing depends on the exposure amount, that is, the lamp intensity (illuminance), and a desired coating film can be obtained in a short time if the lamp has a large output.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to a following example, unless the summary is exceeded. In the examples, “parts” and “%” mean weight basis unless otherwise specified.

[Urethane (meth) acrylate compound (A-1) composition]
In a four-necked flask equipped with a thermometer, a stirrer, a water-cooled condenser, and a nitrogen gas inlet, 66.7 g of tricyclodecane dimethanol diacrylate (C-1) and hydrogenated xylylene diisocyanate 32.3 (0.3. 17 mol), neopentyl glycol (hydroxyl value 1077.5 mg KOH / g) 11.6 g (0.11 mol), hydroquinone methyl ether 0.02 g as a polymerization inhibitor, and dibutyltin dilaurate 0.01 g as a reaction catalyst were charged at 60 ° C. At the end of the theoretical reaction of the isocyanate group and the hydroxyl group, 49.6 g (0.028 mol) of a bifunctional polyester polyol (hydroxyl value 62.8 mgKOH / g) was charged and reacted at 60 ° C. for 1 hour. It was. Furthermore, 6.5 g (0.056 mol) of 2-hydroxyethyl acrylate was added at the reaction theoretical end point of isocyanate group and hydroxyl group, and reacted at 60 ° C. for 4 hours. When the residual isocyanate group reached 0.5%, The reaction was terminated to obtain a composition of a bifunctional urethane (meth) acrylate compound (A-1) (weight average molecular weight Mw = 8,200, E-type viscometer viscosity 25,000 mPa · s at 60 ° C.). It was.

The following were prepared as the phosphoric acid group-containing ethylenically unsaturated compound (B).
(B-1) bis (2-methacryloyloxyethyl) phosphate (light ester P-2M: manufactured by Kyoeisha Chemical Co., Ltd.)

The following were prepared as the ethylenically unsaturated compound (C) containing two or more ethylenically unsaturated groups.
(C-1) Tricyclodecane dimethanol diacrylate (NK ester A-DCP: manufactured by Shin-Nakamura Chemical Co., Ltd.)
(C-2) Dipentaerythritol hexaacrylate (KAYARAD DPHA: manufactured by Nippon Kayaku Co., Ltd.)

The following were prepared as monofunctional monomers.
・ Phenoxypolyethylene glycol acrylate (Light acrylate P-200A: manufactured by Kyoeisha Chemical Co., Ltd.)

The following were prepared as the photopolymerization initiator (D).
1-hydroxy-cyclohexyl-phenyl-ketone (Irg184: manufactured by BASF)

[Example 1]
Urethane (meth) acrylate compound (A-1) composition [urethane (meth) acrylate compound (A-1) 100 parts, tricyclodecane dimethanol diacrylate (C-1) 66.7 parts. ), 4.2 parts of bis (2-methacryloyloxyethyl) phosphate (B-1), 23.6 parts of dipentaerythritol hexaacrylate (C-2), 83.3 parts of phenoxypolyethylene glycol acrylate (monofunctional monomer) 1-hydroxycyclohexyl phenyl ketone (D) (11.1 parts) was blended to obtain a solventless coating agent composition.

The coating agent composition obtained above was applied onto an aluminum substrate (JIS H 4000, A1050P) using an applicator so that the film thickness after UV curing was 25 μm. After preheating at 80 ° C for 4 minutes, using a high pressure mercury lamp lamp 80W and one lamp, UV irradiation (cumulative irradiation amount 800mJ / cm ² ) is performed at a conveyor speed of 2.0m / min from a height of 18cm. A cured coating film (coating layer) was formed. The following evaluation was performed about the obtained cured coating film.

<Base material adhesion>
The cured coating film was evaluated by a cross-cut tape method according to JIS K 5400 (1990 edition).
(Evaluation)
○: All the coating films were in close contact with the substrate even after the tape test (100/100).
(Triangle | delta): Even after a tape test, all the coating films are closely_contact | adhered to a base material (100/100), but there exists stickiness on the coating-film surface.
X: The coating film has peeled off from the base material after the tape test (less than 100/100).

<Waterproof substrate adhesion>
The cured coating film was immersed in purified water for 48 hours, and then evaluated by a cross-cut tape method according to JIS K 5400 (1990 edition).
(Evaluation)
○: All the coating films were in close contact with the substrate even after the tape test (100/100).
(Triangle | delta): Even after a tape test, all the coating films are closely_contact | adhered to a base material (100/100), but there exists a stickiness on the coating-film surface and it is accompanied by the appearance defect (whitening).
X: The coating film has peeled off from the base material after the tape test (less than 100/100).

<Flexibility>
Bending resistance according to JIS K 5600-5-1: 1999 (cylindrical mandrel method) after leaving the aluminum base material (test piece) on which the above-mentioned cured coating film was formed for 48 hours in an environment of 23 ° C. and 50% RH. The test was conducted by a test on the property (tested with a type 1 test apparatus under a mandrel diameter of 2 mm, a bending time of 2 seconds, and an environment of 23 ° C. and 50%).
(Evaluation)
○: There is no coating film cracking even when bent 180 °.
X: The coating film breaks at less than 180 °.

[Example 2]
In Example 1, a cured coating film (coating layer) was formed on an aluminum substrate in the same manner except that the temperature of the heating chamber was changed to 100 ° C. The obtained cured coating film was evaluated for substrate adhesion, water-resistant substrate adhesion and flexibility in the same manner as in Example 1.

[Comparative Example 1]
In Example 1, after coating a coating agent composition on an aluminum substrate, a cured coating film (coating layer) was formed by ultraviolet irradiation without preheating. The obtained cured coating film was evaluated for substrate adhesion, water-resistant substrate adhesion and flexibility in the same manner as in Example 1.

[Comparative Example 2]
In Example 1, a cured coating film (coating layer) was formed on an aluminum substrate in the same manner except that the temperature of the heating chamber was changed to 60 ° C. The obtained cured coating film was evaluated for substrate adhesion, water-resistant substrate adhesion and flexibility in the same manner as in Example 1.

[Comparative Example 3]
In Example 1, a cured coating film (coating layer) was formed on an aluminum substrate in the same manner except that the temperature of the heating chamber was changed to 140 ° C. The obtained cured coating film was evaluated for substrate adhesion, water-resistant substrate adhesion and flexibility in the same manner as in Example 1.

  The evaluation results of Examples 1 and 2 and Comparative Examples 1 to 3 are summarized in Table 1 below.

  In the coating method of the metal substrate of Examples 1 and 2 in which preheating was performed at the specific temperature and time after application to the metal substrate, all of the substrate adhesion, water-resistant substrate adhesion, and flexibility were achieved. An excellent metal coating layer was obtained.

On the other hand, it can be seen that Comparative Example 1 in which preheating was not performed and Comparative Example 2 in which the preheating temperature was low were inferior in substrate adhesion and water-resistant substrate adhesion.
Further, in Comparative Example 3 where the preheating temperature is high, although the adhesion to the metal substrate is excellent, the surface of the metal coating layer becomes sticky due to poor coating curing due to volatilization of the photopolymerization initiator, Furthermore, when evaluating the water-resistant substrate adhesion, the appearance was whitened by excessively infiltrated moisture.

  The present invention is a coating method useful for coating a metal substrate, particularly an aluminum substrate, using a solvent-free coating agent composition.

Claims (4)

Urethane (meth) acrylate compound (A),
Phosphoric acid group-containing ethylenically unsaturated compound (B) and ethylenically unsaturated compound (C) containing two or more ethylenically unsaturated groups (excluding the component (A) and the component (B)). )
A metal substrate characterized in that a solvent-free coating agent composition containing a coating is applied to the surface of a metal substrate, heated at 70 to 130 ° C. for 0.5 to 20 minutes, and then irradiated with active energy rays. Material coating method.   The content of the phosphoric acid group-containing ethylenically unsaturated compound (B) is 0.01 to 100 parts by weight with respect to 100 parts by weight of the urethane (meth) acrylate compound (A). 2. The method for coating a metal substrate according to 1.   Content of the ethylenically unsaturated compound (C) containing two or more ethylenically unsaturated groups is a total of 100 of the urethane (meth) acrylate compound (A) and the phosphoric acid group-containing ethylenically unsaturated compound (B). The metal substrate coating method according to claim 1 or 2, wherein the amount is 1 to 1000 parts by weight with respect to parts by weight.   The metal base material according to claim 1, wherein the metal base material contains at least one element selected from aluminum, zinc, iron, magnesium, tin, chromium, nickel, copper, and silver. Coating method.