JP2005146111A - Resin-coated aluminum pigment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a resin-coated aluminum pigment especially having excellent chemical resistance and voltage endurance, and also having excellent metallic luster. <P>SOLUTION: This resin-coated aluminum pigment is obtained by coating the surface of a raw material aluminum pigment (A) with a copolymer (B) obtained by polymerizing (a) 80-20 mol% monomer having three or more polymerizable double bonds, (b) 70-5 mol% monomer having one polymerizable double bond and one benzene ring, and (c) 15-0.1 mol% (meth)acrylic acid (with the proviso that the total of them is 100 mol%). A metallic coating material contains the pigment. A method for producing the resin-coated aluminum pigment comprises allowing the raw material monomer mixture comprising the monomers (a), (b) and (c) to coexist with the raw material aluminum pigment in an organic solvent, and reacting them in the presence of a polymerization initiator to precipitate the formed polymer on the surface of the aluminum particles. Preferably, the raw material monomer mixture of 5-25 pts. by mass coexists with the raw material aluminum pigment of 100 pts. by mass in the organic solvent in the production method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a resin-coated aluminum pigment produced by a method such as a ball mill pulverization method, a stamp mill pulverization method, or a vapor deposition pulverization method. More specifically, the present invention relates to an aluminum pigment that is resin-coated on the surface of an aluminum pigment and has excellent chemical resistance, electric shock resistance, and adhesion, a method for producing the same, and use thereof. The present invention also relates to a resin-coated aluminum pigment that satisfies chemical resistance, voltage resistance, adhesion, etc. without impairing the metallic luster when blended in a metallic luster paint, a method for producing the same, and a use thereof.

  In recent years, metallic paint and printing with higher glossiness have been favored for plastic coating, various printed materials, and various cosmetics for household appliances such as radio cassettes, VTRs, TVs, mobile phones, etc., and cosmetics such as nail polish are used. It has become. Resin-coated aluminum pigments are blended in paints, inks, cosmetics, and the like used in these applications as colorants with higher gloss.

  Such resin-coated aluminum pigments are required to have various properties depending on the application.

  For example, when metallic coating is applied to the surface of a plastic molded product or metal, the coated resin aluminum pigment contained in the metallic paint may be required to have chemical resistance. If the chemical resistance of the resin-coated aluminum pigment is poor, the coating resin may be attacked by acid or alkali, and the surface of the aluminum pigment may be discolored to lose the metallic luster of the coating film. Moreover, when an aluminum pigment is blended in an aqueous coating composition or an aqueous ink composition, it reacts with water contained therein to generate hydrogen gas and dissolve it.

  Further, for example, when metallic coating is applied to the surface of a plastic molded article, it is also described in the section “Problems to be solved by the invention” in JP-A-62-81460 (Patent Document 1) described later. As described above, the affinity and adhesion between the resin-coated aluminum pigment in the paint and the binder resin are required. If the adhesion of the metallic paint film coated on the surface of the plastic molded product is poor, the metal powder will be taken off by the cello tape and dropped off from the paint film when the tape is applied to the paint film and rapidly peeled off. The traces are unsightly, and when the characters, numbers, etc. are marked on the coating film by silk screen printing or the like, the characters are lost, and the commercial value of the paint is remarkably impaired.

  In addition, the metal powder itself such as aluminum is electrically conductive. If the insulation of the coating film is insufficient when painting the mask portion of a television cathode ray tube, the high voltage of the cathode ray tube leaks, and if it is touched by a human hand, it will receive an electric shock and in some cases may cause a fatal accident. There is a fear. In electrostatic coating, a high voltage is applied between the spray gun and the object to be coated. However, since the metal powder raw material is electrically conductive, if its concentration is high, a bridging phenomenon occurs and the metal powder passes through. The voltage leaks and the circuit is cut off, making it impossible to paint.

  Further, when a resin-coated aluminum pigment is used as a pigment, various troubles based on the chemical activity of aluminum as a metal may be caused.

  That is, when it comes into contact with other pigments blended in the paint, particularly yellow or red organic pigments, a chemical reaction may occur, causing discoloration or discoloration of those organic pigments. In addition, the binder in the paint may be altered to cause gelation.

  As described above, the resin-coated aluminum pigment is required to have various properties depending on its use. However, many techniques have been disclosed for the resin-coated aluminum pigment used in these various uses.

  For example, Japanese Patent Application Laid-Open No. 62-81460 (Patent Document 1) previously disclosed by the applicant of the present application is coated with a copolymer of trimethylolpropane tri (meth) acrylate and a small amount of (meth) acrylic acid. In this publication, as a manufacturing method thereof, metal powder is dispersed in an organic solvent, an acrylic resin oligomer such as trimethylolpropane tri (meth) acrylate and a small amount of radical polymerizability by a polymerization initiator. A method for producing a synthetic resin-coated metal powder is disclosed in which the surface of a metal powder is coated with an acrylic resin-based polymer by copolymerizing an organic acid having a double bond on the surface of the metal powder.

JP-A-62-253668 (Patent Document 2) discloses radically polymerizable unsaturated carboxylic acid and / or phosphoric acid mono- or diester having a radically polymerizable double bond and 3 radically polymerizable double bonds. A resin-coated metal pigment that has been surface-coated with a resin produced from the above-described monomer is disclosed. Moreover, in this patent document 2, acrylic acid, methacrylic acid, etc. are mentioned as radically polymerizable unsaturated carboxylic acid, and it is used in an amount of 0.01 to 10 parts by weight with respect to 100 parts by weight of the metal pigment. As a phosphate ester monomer having a polymerizable double bond, diphenyl-2-methacryloyloxyethyl phosphate,
Diphenyl-2-acryloyloxyethyl phosphate and the like, and is used in an amount of 0.01 to 30 parts by weight with respect to 100 parts by weight of the metal pigment, and a single molecule having three or more polymerizable double bonds in one molecule. Examples of the monomer include trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, and the like, and it is described that it is used in an amount of 2 to 50 parts by weight with respect to 100 parts by weight of the metal pigment.

  JP-A-2-49076 (Patent Document 3) describes (a) a coating resin and a small amount of JP-A-62-253668 (Patent Document 2) with respect to (a). Resin-coated metal pigment, that is, a resin formed from (b) a radically polymerizable unsaturated carboxylic acid and / or a phosphoric acid mono- or diester having a radically polymerizable double bond and a monomer having three or more radically polymerizable double bonds Discloses a metallic paint comprising a surface-coated resin-coated metal pigment and (c) diluted thinner. Further, it is described that the same monomer as in Patent Document 2 is used in the same amount.

  The paints containing the resin-coated metal powders (pigments) described in Patent Documents 1 to 3 have improved chemical resistance and adhesion to some extent, but satisfy the recent strong demands for high brightness and high gloss aluminum pigments. I can't do it.

  In particular, in Patent Documents 2 and 3, as a phosphoric acid ester monomer having a radical polymerizable double bond, even in an embodiment using diphenyl-2-methacryloyloxyethyl phosphate, diphenyl-2-acryloyloxyethyl phosphate, There is a problem that it is not possible to satisfy the strong demands for light brightness and high gloss aluminum pigments in recent years.

  Japanese Patent Laid-Open No. 58-83033 (Patent Document 4) discloses a metal pigment obtained by coating a surface of a metal powder with a small amount of a polymer obtained by reacting a compound having a polymerizable double bond. A coating composition for plastic coating containing the composition is disclosed, and the metal pigment composition is obtained by polymerizing a compound having a polymerizable double bond in the presence of metal powder.

Japanese Patent Laid-Open No. 2001-115061 (Patent Document 5) discloses a metal having resin protrusions on the surface of metal particles such as aluminum, and a metal particle surface exposed at least at a part between the protrusions. A pigment is disclosed, and its production method includes dispersing metal particles in an organic solvent, having at least one of a radical polymerizable organic acid, a radical polymerizable coupling agent, and three or more radical polymerizable functional groups. A method is disclosed in which a monomer containing at least one monomer is copolymerized on the particle surface with a polymerization initiator.

  However, in the metal pigment compositions or metal pigments described in Patent Documents 4 to 5, although the metallic luster and adhesion are improved to some extent, there is room for further improvement in terms of chemical resistance.

  Thus, it is difficult to achieve both metallic luster and chemical resistance and adhesion, and resin-coated aluminum that provides a well-balanced coating with excellent metallic luster, chemical resistance, and voltage resistance. At present, it is difficult to obtain a pigment.

  For example, when a metallic paint containing a conventional resin-coated aluminum pigment is applied to the surface of plastic or metal, the required chemical resistance and voltage resistance are not sufficient due to the solubility and conductivity of aluminum. In the chemical resistance test, there is a problem that discoloration is large, and in the voltage resistance test, it cannot withstand 6 KV.

Further, the conventional resin-coated aluminum pigment has a problem that the metallic luster of the aluminum pigment is deteriorated by the resin coating.
JP-A-62-81460 Japanese Patent Laid-Open No. 62-253668 JP-A-2-49076 JP 58-83033 A JP 2001-115061 A

  The present invention is intended to solve the problems associated with the prior art as described above, and is excellent in the above-mentioned characteristics, in particular, excellent in chemical resistance and voltage resistance, and excellent in metallic luster. The object is to provide an aluminum pigment.

  Another object of the present invention is to provide an efficient and safe method for producing the above resin-coated aluminum pigment.

  Another object of the present invention is to provide a metallic paint that contains a resin-coated aluminum pigment having the characteristics described above, and that can provide a coating film that is well-balanced in terms of metallic luster, chemical resistance, withstand voltage, and the like. It is said.

  The present invention also includes a resin-coated aluminum pigment having the characteristics described above and an organic solvent, and is used for metallic paints that provide a well-balanced coating film with excellent metallic luster, chemical resistance, and withstand voltage. The object is to provide an aluminum pigment paste.

In the resin-coated aluminum pigment according to the present invention, the surface of the raw material aluminum pigment (A) is
(a) Monomer having 3 or more polymerizable double bonds: 80 to 20 mol%,
(B) Monomer having one polymerizable double bond and one benzene ring: 70 to 5 mol% and (c) (meth) acrylic acid: 15 to 0.1 mol% (provided that (a) + ( b) + (c) = 100 mol%), and is characterized by being coated with a copolymer (B) obtained by polymerization.

  In this invention, it is preferable that the coating amount of the said copolymer (B) is 5-25 mass parts with respect to 100 mass parts of raw material aluminum pigments (A).

In the present invention, the number of moles of monomer (a) having three or more the polymerizable double bond (a _m) and the polymerizable double bond one and the number of moles of monomer (b) having a benzene ring (b _m ) ratio [(
a _m ) :( b _m )] is preferably 1: 1-5.

  In the present invention, the monomer (a) having three or more polymerizable double bonds is preferably trimethylolpropane tri (meth) acrylate.

  In the present invention, the monomer (b) having one polymerizable double bond and one benzene ring is preferably benzyl (meth) acrylate.

  In this invention, it is preferable that the mass of the said (meth) acrylic acid (c) is 0.02-1 mass part with respect to 100 mass parts of raw material aluminum pigments (A).

The method for producing a resin-coated aluminum pigment according to the present invention includes:
Raw material aluminum pigment,
Monomer having three or more polymerizable double bonds (a): 80 to 20 mol%, monomer having one polymerizable double bond and one benzene ring (b): 70 to 5 mol%, and (meth) A raw material monomer mixture consisting of acrylic acid (c): 15 to 0.1 mol% ((a) + (b) + (c) = 100 mol%),
It is characterized in that a polymer produced by coexisting in an organic solvent and reacting in the presence of a polymerization initiator is deposited on the surface of aluminum particles.

  In a preferred embodiment of the production method of the present invention, it is desirable that the raw material monomer mixture is allowed to coexist in the organic solvent in an amount of 5 to 25 parts by mass per 100 parts by mass of the raw material aluminum pigment.

  The metallic paint according to the present invention is characterized by containing any of the above resin-coated aluminum pigments.

  Moreover, the resin-coated aluminum pigment paste according to the present invention is characterized by containing any of the resin-coated aluminum pigments described above and an organic solvent.

  In the present invention, (meth) acrylic acid means acrylic acid and / or methacrylic acid.

  The resin-coated aluminum pigment according to the present invention is less deteriorated in gloss and excellent in chemical resistance and voltage resistance despite the fact that the aluminum pigment is resin-coated.

  According to the method for producing a resin-coated aluminum pigment according to the present invention, the resin-coated aluminum pigment having the above characteristics can be produced efficiently and safely.

According to the metallic paint according to the present invention, it is possible to obtain an excellent coating film with good balance in metallic luster, chemical resistance, withstand voltage, etc. According to the resin-coated aluminum pigment paste according to the present invention, the pigment for the metallic paint, etc. By using as, the coating film of the said characteristic is obtained.

  Hereinafter, the resin-coated aluminum pigment according to the present invention will be specifically described.

[Resin-coated aluminum pigment]
In the resin-coated aluminum pigment according to the present invention, the surface of the raw material aluminum pigment (A) is coated with a specific copolymer (B) as described in detail below, and this copolymer (B) (a) Monomer having three or more polymerizable double bonds: 80 to 20 mol%, (b) Monomer having one polymerizable double bond and one benzene ring: 70 to 5 mol%, and (c) It is a copolymer obtained by polymerizing (meth) acrylic acid: 15 to 0.1 mol% (however, (a) + (b) + (c) = 100 mol%).

  The thickness of the coating resin layer in the resin-coated aluminum pigment is not particularly limited, but is usually 0.02 to 1.0 μm (thickness), preferably 0.05 to 0.5 μm (thickness). It is desirable from the viewpoint of glossiness, and from the viewpoint of voltage resistance, chemical resistance, and adhesion. When the thickness of the coating resin layer is less than the above range, the withstand voltage, chemical resistance, and adhesion tend to deteriorate, and when it exceeds the above range, the metallic luster tends to deteriorate.

  The raw material aluminum pigment to be coated with the resin will be described in detail below.

[Production of resin-coated aluminum pigment]
The resin-coated aluminum pigment according to the present invention precipitates a polymer product formed by coexisting a raw material aluminum pigment and a specific raw material monomer mixture in an organic solvent and reacting them in the presence of a polymerization initiator on the surface of aluminum particles. By doing so, a resin-coated aluminum pigment can be produced.

  Normally, the raw material aluminum pigment is dispersed in an organic solvent, and raw material monomers and a thermal polymerization initiator for forming a resin film are added and heated to conduct a polymerization reaction of the monomers, and the resin film is applied to the surface of the aluminum pigment. It is deposited.

Hereinafter, the raw material aluminum pigment used, the raw material monomer mixture, and the catalyst will be described in detail in this order. <Raw material aluminum pigment>
The raw material aluminum pigment used in the present invention is a conventionally known one, and is produced by a ball milling method, a stamp mill method, or a vapor deposition crushing method. The shape, size, etc. are not particularly limited, but for metallic luster paint, the shape is flaky, the average particle size (D50: cumulative weight 50% particle size) is 5-90 μm, and the thickness is 1 μm. In the following, it is usually about 0.01 μm or more, and the aspect ratio (average particle diameter / thickness) is preferably 20 or more.

  In addition, prior to resin coating of the raw material aluminum pigment, the water resistance of the aluminum pigment as disclosed in Japanese Patent Application Laid-Open No. 2002-88274 and Japanese Patent Application Laid-Open No. 2003-82259 previously proposed by the present applicant is given. The surface treatment to be applied may be performed, and the formation of the resin film of the present invention is not hindered.

The organic solvent for dispersing the raw material aluminum pigment is not particularly limited as long as it can disperse the aluminum pigment and dissolve the raw material monomers. For example, mineral spirit, solvent naphtha, hexane and the like are preferably used. . What is necessary is just to set the usage-amount of an organic solvent so that the density | concentration of an aluminum pigment may be 5-20 mass% normally. If the concentration of the aluminum pigment is lower than the above range, the amount of solvent used increases, which is uneconomical. On the other hand, when the concentration of the aluminum pigment is higher than the above range, it is not preferable because the viscosity of the reaction solution is increased during the polymerization reaction and the aluminum pigment may aggregate.
<Raw material monomer mixture>
As a raw material monomer for forming a resin film, a monomer (a) having three or more polymerizable double bonds, a monomer (b) having one polymerizable double bond and one benzene ring, ) Acrylic acid (c).

  These monomers are usually desirably used as a monomer mixture.

In the present invention, the monomer (a) having 3 or more polymerizable double bonds in the raw material monomer mixture is usually in an amount of 80 to 20 mol%, preferably 70 to 30 mol%. Monomer (b) having one bond and one benzene ring is usually in an amount of 70-5 mol%, preferably 50-20 mol%, and (meth) acrylic acid (c) is usually 15 It is used in an amount of ˜0.1 mol%, preferably 8-1 mol% ((a) + (b) + (c) = 100 mol%).

  When the amount of the monomer (a) is more than the above range, the metallic luster tends to be deteriorated, and when it is less than the above range, the withstand voltage, chemical resistance and adhesion tend to be deteriorated. Further, when the amount of the monomer (b) is larger than the above range, the resin coating does not work well and the withstand voltage and chemical resistance tend to deteriorate, and when it is less than the above range, the chemical resistance tends to deteriorate. Further, when the amount of the monomer (c) is larger than the above range, the chemical resistance tends to be deteriorated, and when it is less than the above range, the resin coating is not performed well and the chemical resistance tends to be deteriorated.

  The total amount ({a) + (b) + (c)} of the amounts used varies depending on the type of aluminum pigment used, and thus cannot be specified unconditionally. It is possible to set the amount (total) of these monomers to be 5 to 25 parts by mass, more preferably 8 to 20 parts by mass, and even more preferably 10.0 to 17.0 parts by mass. This is desirable because a resin-coated aluminum pigment, a coating film, etc. that are excellent in balance in terms of denseness, chemical resistance and the like can be obtained.

  In addition, when the total amount of raw material monomers is less than the above range, the metallic luster is particularly good, but a dense resin film is not formed on the surface of the aluminum pigment, and chemical resistance and the like tend to be insufficient. is there. In addition, when the amount of raw material monomers used is greater than the above range, the amount of resin covering the surface of the aluminum pigment is increased and the chemical resistance and withstand voltage are particularly improved, but the resin is attached to the surface of the aluminum pigment too much, Metal luster tends to be impaired.

  Specifically, when an aluminum pigment called “Sap 616FP” manufactured by Showa Aluminum Powder Co., Ltd. is used, a resin coating is formed in which the total amount of raw material monomers is less than 5 parts by weight with respect to 100 parts by weight of the raw material aluminum pigment. Then, the chemical resistance tends to be insufficient, and when an amount of coating exceeding 25 parts by mass is formed on the aluminum pigment, the coating has excellent chemical resistance and voltage resistance, but the aluminum pigment has Metal luster tends to be impaired.

In the present invention, the number of moles of polymerizable double bonds at least three monomer having (a) and (a _m), the number of moles of monomer (b) having a polymerizable double bond one and benzene rings (b _m ) Ratio [(a _m ) :( b _m )] is 1: 1 to 5 in view of maintaining the metallic luster and chemical resistance of the resulting resin-coated aluminum pigment or the coating film comprising the pigment. To preferred.

Preferred examples of the monomer (a) having three or more polymerizable double bonds include trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate. Used for. Among these, trimethylolpropane triacrylate is more preferable from the viewpoint of metallic luster.

  As the monomer (b) having one polymerizable double bond and one benzene ring, for example, the formula (I):

[In the formula (I), R ¹ represents an alkylene group having 1 to 5 carbon atoms, preferably 1 to 3 carbon atoms,-
One of O—CO— (oxycarbonyl group), ether bond (—O—), and single bond, or a group formed by combining two or more of these groups or bonds is shown. R ² represents H or CH ₃ . Specifically, for example, benzyl methacrylate, benzyl acrylate, styrene, phenoxyethyl acrylate, and the like are preferably used. Among these, a resin-coated aluminum pigment from which benzyl methacrylate is obtained, a metallic gloss such as a coating film, and chemical resistance are more preferable.

Among the above monomers, a combination of trimethylolpropane triacrylate, which is one type of monomer (a), and benzyl methacrylate, which is one type of monomer (b),
It is particularly preferably used from the viewpoint of maintaining metallic luster and chemical resistance.

Furthermore, when these monomers are combined at a specific ratio, there is a tendency that a coating film excellent in chemical resistance and voltage resistance can be formed without impairing the metallic luster. And moles of monomer (a), the ratio of moles of monomer (b) [(a) / (b)], for example, the number of moles of one kind is trimethylol propane triacrylate monomers (a) (a _t ) And, for example, a monomer (
b 1 or a is the number of moles of benzyl methacrylate) (b _b) the molar ratio of the _{[(a t) / (b} b)], preferably 1 to 5, more preferably by 1 to 3, The resulting resin-coated aluminum pigment is particularly preferably used from the viewpoints of metallic luster and chemical resistance of the coating film.

  Moreover, regarding the usage-amount of (meth) acrylic acid (c), 0.02-1 mass part is preferable with respect to 100 mass parts of raw material aluminum pigments, Furthermore, 0.05-0.6 mass part is more preferable. . If the amount of (meth) acrylic acid (c) is larger than the above range, the chemical resistance of the resin-coated aluminum pigment or coating film tends to be lowered. is there.

<Polymerization initiator>
As a polymerization initiator, a general thing can be used, for example, azo compounds, such as azobisisobutyronitrile, and peroxide organic compounds, such as benzoyl peroxide, can be used.

  The amount of the polymerization initiator used is preferably 0.1 to 8.0 parts by mass with respect to 100 parts by mass of the total amount of raw material monomers ((a) + (b) + (c)). Moreover, 1 mass% or less is preferable at the density | concentration in a polymerization reaction liquid. The lower limit is usually about 0.01% by mass in the polymerization reaction solution.

<Polymerization reaction conditions>
The reaction temperature of the polymerization reaction is 60 ° C to 120 ° C, more preferably 80 ° C to 100 ° C, and the reaction time is 1 to 8 hours, more preferably 2 to 4 hours.

  The polymerization reaction is preferably performed in an inert gas atmosphere in order to exclude oxygen that is a polymerization inhibitor.

  The polymerization reaction is carried out with stirring, but a common stirrer may be used, and the stirring speed is preferably a stirring speed at which the aluminum pigment does not settle.

  The obtained resin-coated aluminum pigment can be made into a pigment or a pigment paste through filtration, solvent washing, drying, solid content adjustment, mixing operation, and the like.

  When the resin-coated aluminum pigment obtained by the above method is observed with a high-resolution scanning electron microscope, it is confirmed that fine particles of resin are deposited on the surface of the aluminum pigment to form a film. . Although it is difficult to accurately measure the thickness of the coating, after depositing platinum on the resin-coated aluminum pigment, embedding it with epoxy resin, curing it, and cutting it with a microtome, the cross-section of the resin-coated aluminum pigment is high resolution. According to the method observed with an electron microscope, the film thickness is estimated to be in the range of 20 nm to 1 μm.

[Metallic paint, etc.]
The metallic paint according to the present invention contains the resin-coated aluminum pigment. In addition, a resin component for film formation, a solvent, and various additives, which are components usually contained in a metallic paint, are blended. The resin-coated aluminum pigment is usually contained in an amount of about 5 to 40 parts by mass, preferably about 8 to 35 parts by mass in 100 parts by mass of the solid content (component excluding volatile components such as a solvent) in the metallic paint. It is desirable from the viewpoint of coating formation with excellent metallic luster.

  The resin content is not particularly limited, and examples thereof include acrylic resins, alkyd resins, melamine resins, urethane resins, epoxy resins, lacquers, and mixtures thereof.

Such a metallic paint may be applied one or more times by a conventional method such as brush coating, spray coating, electrostatic coating, or dipping so as to obtain a desired film thickness.

  The resin-coated aluminum pigment paste according to the present invention contains the resin-coated aluminum pigment and an organic solvent. Although there is no restriction | limiting in particular about content of the resin-coated aluminum pigment in this paste, For example, the resin-coated aluminum pigment is often contained in an amount of about 40 to 70 parts by mass in 100 parts by mass of the paste. Such a resin-coated aluminum pigment concentration paste has good dispersibility, solvent affinity, and the like when used in a paint.

[Example]
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these Examples.
<Preparation of resin-coated aluminum pigment>

Showa Aluminum Powder Co., Ltd. aluminum paste “Sap 616FP” (aluminum content 70 mass%) is taken in a glass beaker 64 g, dispersed in mineral spirit 300 g, trimethylolpropane triacrylate (TMP) 4.2 g [0.0141 mol], 1.2 g [0.00681 mol] of benzyl methacrylate (BM), 0.05 g [0.000694 mol] of acrylic acid (AA) and 0.2 g of azobisisobutyronitrile were added. Heat with stirring, continue stirring at 90 ° C for 2 hours, filter after completion of reaction, wash the filter cake (filter cake) with mineral spirit, adjust the concentration with mineral spirit, paste containing 48% by mass of aluminum It was.

  A part of the obtained paste is dried, dissolved in aqua regia, the resin content is filtered, washed with water, and the weight of the resin-coated aluminum pigment obtained by measuring the weight after drying is 100 parts by mass of aluminum. The amount was 11.5 parts by mass (resin yield 95%).

  Showa Aluminum Powder Co., Ltd. aluminum paste “Sap 616FP” (aluminum content 70 mass%) is taken in a glass beaker 64 g, dispersed in 400 g mineral spirit, 4.8 g trimethylolpropane triacrylate (TMP) [0.0162 mol], 2.8 g [0.0159 mol] of benzyl methacrylate (BM), 0.2 g [0.00277 mol] of acrylic acid, and 0.2 g of azobisisobutyronitrile were added. The mixture was heated with stirring and stirred at 90 ° C. for 2 hours. After completion of the reaction, the mixture was filtered, and the filter cake was washed with mineral spirits and then adjusted with mineral spirits to obtain a paste containing 48% by mass of aluminum.

  Moreover, the coating resin amount of the resin-coated aluminum pigment was 16.5 parts by mass (resin yield 95%) per 100 parts by mass of aluminum.

[Comparative Example 1]
In Example 1, except that benzyl methacrylate was not added and the amount of trimethylolpropane triacrylate (TMP) added was 5.4 g [0.0182 mol], the aluminum content was 48 masses in the same manner as in Example 1. % Containing paste was obtained.

  Moreover, the coating resin amount of the resin-coated aluminum pigment was 11.6 parts by mass (resin yield 96%) per 100 parts by mass of aluminum.

[Comparative Example 2]
Example 1 except that the amount of trimethylolpropane triacrylate (TMP) added was 1.2 g [(0.00405 mol) and benzyl methacrylate (BM) 4.2 g [(0.0238 mol]]. In the same manner, a paste containing 48% by mass of aluminum was obtained.

  Further, the coating resin amount of the resin-coated aluminum pigment was 10.8 parts by mass (resin yield 90%) per 100 parts by mass of aluminum.

[Comparative Example 3]
A paste containing 48% by mass of aluminum was obtained in the same manner as in Example 1 except that acrylic acid was changed to 1 g [0.0138 mol].

  Moreover, the coating resin amount of the resin-coated aluminum pigment was 13.5 parts by mass (resin yield 95%) per 100 parts by mass of aluminum.

<Preparation of metallic paint>
[Examples 4-5, Comparative Examples 4-6]
Using the aluminum pigment pastes produced in Examples 1-2 and Comparative Examples 1-3, metallic paints were produced as follows.

Resin-coated aluminum pigment paste 5.8g,
Ethyl acetate 5.8g,
After mixing and dispersing
Origin Electric's “Planet SV Clear” (acrylic lacquer-based clear paint, solid content 31% by mass) 37.5 g,
“Planet thinner # 175” (diluent) (70.0 g) manufactured by Origin Electric Co. was added and stirred for 5 minutes.

<Evaluation method of aluminum pigment>
The metallic paint prepared using the resin-coated aluminum pigment obtained in <Preparation of resin-coated aluminum pigment> in Examples 1-2 and Comparative Examples 1-3 was evaluated by the following method.

(1) Application of metallic paint The metallic paint prepared in Examples 4 to 5 and Comparative Examples 4 to 6 was applied to an ABS resin plate. That is, Iwata's spray gun “WA-100” is attached to an automatic coating machine “Resicoater” manufactured by Kansai Paint Co., Ltd., and spray-coated on an ABS resin plate to a dry film thickness of 15 μm. After being placed, it was dried in an air oven at 60 ° C. for 20 minutes to obtain a test coating plate.

(2) Chemical resistance test A part of the test coating plate obtained by the method of (1) was immersed in a 5% aqueous sodium hydroxide solution or a 10% sulfuric acid aqueous solution at room temperature for 24 hours. The color difference between the immersed part and the non-immersed part was measured with a color difference meter manufactured by Nippon Denshoku. If the color difference ΔE exceeds 0.5, the color change can be visually confirmed, and the chemical resistance is insufficient.

(3) Withstand voltage test Using the test coating plate obtained by the method of (1), using a withstand voltage measuring device ("TW-516" manufactured by Tama Denso Co., Ltd.), breaking current 0.5 mA, electrode interval 10 mm The voltage was increased from 1 kV to 6 kV in 1 kV increments, applied at each voltage for 20 seconds, and the maximum voltage at which the circuit was not destroyed by dielectric breakdown was defined as the withstand voltage.

(4) Gloss The gloss of the test coating plate obtained by the method of (1) was measured using a gloss meter (model number: SZS-90) manufactured by Nippon Denshoku.

  The results of the above evaluation test are shown in Table 1.

* 1: Total amount of monomer for coating resin with respect to 100 parts by mass of aluminum (in parts by mass).
TMP: trimethylolpropane triacrylate.
BM: benzyl methacrylate.
AA: acrylic acid.

[The invention's effect]
According to the present invention, there is provided a resin-coated aluminum pigment that, when blended in a metallic paint, is excellent in chemical resistance, voltage resistance, adhesion, and the like and can provide a coating film with excellent metallic luster.

Claims (10)

The surface of the raw material aluminum pigment (A)
(a) Monomer having 3 or more polymerizable double bonds: 80 to 20 mol%,
(B) Monomer having one polymerizable double bond and one benzene ring: 70 to 5 mol% and (c) (meth) acrylic acid: 15 to 0.1 mol% (provided that (a) + ( a resin-coated aluminum pigment coated with a copolymer (B) obtained by polymerizing (b) + (c) = 100 mol%).   The resin-coated aluminum pigment according to claim 1, wherein the coating amount of the copolymer (B) is 5 to 25 parts by mass with respect to 100 parts by mass of the raw aluminum pigment (A).   The ratio of the number of moles of the monomer (a) having three or more polymerizable double bonds to the number of moles of the monomer (b) having one polymerizable double bond and a benzene ring is 1: 1 to 5. 3. The resin-coated aluminum pigment according to 1 or 2.   The resin-coated aluminum pigment according to any one of claims 1 to 3, wherein the monomer (a) having three or more polymerizable double bonds is trimethylolpropane tri (meth) acrylate.   The resin-coated aluminum pigment according to any one of claims 1 to 4, wherein the monomer (b) having one polymerizable double bond and one benzene ring is benzyl (meth) acrylate.   The resin-coated aluminum pigment according to claim 1, wherein the mass of (meth) acrylic acid (c) is 0.02 to 1 part by mass with respect to 100 parts by mass of the raw material aluminum pigment (A). Raw material aluminum pigment,
Monomer having three or more polymerizable double bonds (a): 80 to 20 mol%, monomer having one polymerizable double bond and one benzene ring (b): 70 to 5 mol%, and (meth) A raw material monomer mixture consisting of acrylic acid (c): 15 to 0.1 mol% ((a) + (b) + (c) = 100 mol%) is present in an organic solvent, and the presence of a polymerization initiator The method for producing a resin-coated aluminum pigment according to any one of claims 1 to 6, wherein a polymer produced by the reaction is precipitated on the surface of aluminum particles.   The method for producing a resin-coated aluminum pigment according to claim 7, wherein the raw material monomer mixture is allowed to coexist in an organic solvent in an amount of 5 to 25 parts by mass per 100 parts by mass of the raw material aluminum pigment.   A metallic paint comprising the resin-coated aluminum pigment according to any one of claims 1 to 6.   A resin-coated aluminum pigment paste comprising the resin-coated aluminum pigment according to claim 1 and an organic solvent.