CN110591514B - Powder coating material and method for producing powder coating material - Google Patents

Powder coating material and method for producing powder coating material Download PDF

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CN110591514B
CN110591514B CN201910506260.9A CN201910506260A CN110591514B CN 110591514 B CN110591514 B CN 110591514B CN 201910506260 A CN201910506260 A CN 201910506260A CN 110591514 B CN110591514 B CN 110591514B
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fluororesin
coating material
powder coating
acid value
powder
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CN110591514A (en
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斋藤俊
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AGC Inc
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Asahi Glass Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
    • C08F214/18—Monomers containing fluorine
    • C08F214/24—Trifluorochloroethene
    • C08F214/245—Trifluorochloroethene with non-fluorinated comonomers
    • C08F214/247—Trifluorochloroethene with non-fluorinated comonomers with non-fluorinated vinyl ethers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/03—Powdery paints
    • C09D5/033—Powdery paints characterised by the additives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F216/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical
    • C08F216/12—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical by an ether radical
    • C08F216/14—Monomers containing only one unsaturated aliphatic radical
    • C08F216/1416—Monomers containing oxygen in addition to the ether oxygen, e.g. allyl glycidyl ether
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F216/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical
    • C08F216/12—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical by an ether radical
    • C08F216/14—Monomers containing only one unsaturated aliphatic radical
    • C08F216/16—Monomers containing no hetero atoms other than the ether oxygen
    • C08F216/165—Carbocyclic compounds

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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  • Health & Medical Sciences (AREA)
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Abstract

The invention provides a powder coating material and a method for producing the powder coating material, in particular to a powder coating material capable of forming a coating film in which a fluororesin and a non-fluororesin are uniformly layered and separated, and a method for producing the powder coating material. The powder coating of the present invention comprises: the fluororesin is a resin having a hydroxyl value smaller than the hydroxyl value of the non-fluororesin and having an acid value larger than the acid value of the non-fluororesin, or a resin having an acid value smaller than the acid value of the non-fluororesin and having a hydroxyl value larger than the hydroxyl value of the non-fluororesin, and the content ratio of the fluororesin is 1 to 20% by mass relative to the total mass of the fluororesin and the non-fluororesin.

Description

Powder coating material and method for producing powder coating material
Technical Field
The present invention relates to a powder coating material and a method for producing a powder coating material.
Background
In recent years, in the field of coating materials, attention has been paid to powder coating materials containing no Volatile Organic Compound (VOC) from the viewpoint of environmental protection. Among them, as a coating material for improving weather resistance and the like, a powder coating material containing a fluororesin has been developed.
Further, for the purpose of cost reduction and the like, a mixed powder coating material containing a fluororesin and a non-fluororesin has been proposed. For example, patent document 1 describes a powder coating composition that can obtain a coating film in which a fluororesin and a polyester resin are separated in layers.
Documents of the prior art
Patent document
Patent document 1: japanese patent laid-open publication No. 2011-
Disclosure of Invention
Problems to be solved by the invention
However, the present inventors have found that when the powder coating composition described in patent document 1 is used, unevenness occurs in layer separation of the coating film. Namely, the following were found to exist: the case where the thickness of the layer containing a fluororesin on the surface side of the coating film becomes uneven, or the case where a sea-island structure is formed in the coating film. In this case, the coating film may have uneven weather resistance, which may cause uneven color of the coating film over time.
In view of the above problems, an object of the present invention is to provide a powder coating material capable of forming a coating film in which a fluororesin and a non-fluororesin are uniformly layered, and a method for producing the powder coating material.
Means for solving the problems
The present inventors have conducted extensive studies to solve the above-mentioned problems, and as a result, have found that a desired effect can be obtained when a powder coating composition containing a fluororesin, a non-fluororesin, and a curing agent is used, the acid values and hydroxyl values of the fluororesin and the non-fluororesin are within predetermined ranges, and the content ratio of the fluororesin and the non-fluororesin in the composition is within a predetermined range, and have completed the present invention.
That is, the present inventors have found that the above problems can be solved by the following configuration.
[1] A powder coating material, comprising: the fluororesin is a resin having a hydroxyl value smaller than the hydroxyl value of the non-fluororesin and having an acid value larger than the acid value of the non-fluororesin, or a resin having an acid value smaller than the acid value of the non-fluororesin and having a hydroxyl value larger than the hydroxyl value of the non-fluororesin, and the content ratio of the fluororesin is 1 to 20% by mass relative to the total mass of the fluororesin and the non-fluororesin.
[2] The powder coating material according to [1], wherein an absolute value of a difference between a hydroxyl value of the fluororesin and a hydroxyl value of the non-fluororesin is 5mgKOH/g or more, and an absolute value of a difference between an acid value of the fluororesin and an acid value of the non-fluororesin is 5mgKOH/g or more.
[3] The powder coating material according to item [1] or [2], wherein one of the fluororesin and the non-fluororesin has a hydroxyl value of 20mgKOH/g or more and the other has an acid value of 20mgKOH/g or more.
[4] The powder coating material according to any one of [1] to [3], wherein the fluororesin is a fluororesin having a hydroxyl value of 20mgKOH/g or more and an acid value of 0 to 15mgKOH/g, and the non-fluororesin is a non-fluororesin having an acid value of 20mgKOH/g or more and a hydroxyl value of 0 to 15 mgKOH/g.
[5] The powder coating material according to any one of [1] to [4], wherein a content ratio of fluorine atoms in the powder coating material is 0.01 mass% or more and 10 mass% or less with respect to a total mass of the powder coating material.
[6] The powder coating material according to any one of [1] to [5], comprising: a curing agent having 2 or more isocyanate groups or blocked isocyanate groups in 1 molecule, and a curing agent having 2 or more epoxy groups, carbodiimide groups, oxazoline groups, or β -hydroxyalkylamide groups in 1 molecule.
[7] The powder coating material according to item [6], wherein the content of the curing agent having 2 or more isocyanate groups or blocked isocyanate groups in the 1 molecule in the powder coating material is less than the content of the curing agent having 2 or more epoxy groups, carbodiimide groups, oxazoline groups, or β -hydroxyalkylamide groups in the 1 molecule.
[8] The powder coating material according to any one of [1] to [7], wherein the non-fluororesin is a resin selected from the group consisting of a polyester resin, a (meth) acrylic resin, and a urethane resin.
[9] The powder coating material according to any one of [1] to [8], further comprising an ultraviolet absorber, wherein the ratio of the mass of the ultraviolet absorber to the total mass of the fluororesin and the non-fluororesin is 0.05 to 0.10.
[10] The powder coating material according to any one of [1] to [9], wherein the fluororesin is contained in an amount of 0.1 mass% or more based on the total mass of the powder coating material.
[11] A method for producing a powder coating material, wherein a powder A containing a fluororesin and a powder B containing a non-fluororesin are mixed to obtain the powder coating material according to any one of [1] to [10], wherein the content of the fluororesin in the powder A is larger than the content of the fluororesin in the powder B, and wherein at least one of the powder A and the powder B contains a curing agent.
[12] A method for producing a powder coating material, wherein the powder coating material according to any one of [1] to [10] is obtained by melt-kneading a fluororesin, a non-fluororesin and a curing agent, cooling the mixture, and then pulverizing the mixture.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, a powder coating material capable of forming a coating film in which a fluororesin and a non-fluororesin are uniformly layered and a method for producing the powder coating material can be provided.
Detailed Description
The terms used in the present invention have the following meanings.
The term "(meth) acrylate" refers to a generic name of acrylate and methacrylate, and the term "(meth) acrylic acid" refers to a generic name of acrylic acid and methacrylic acid.
The unit is a generic name of a radical derived from 1 molecule of the monomer directly formed by polymerization of the monomer and a radical obtained by chemically converting a part of the radical. The content (% by mole) of each unit relative to the total units contained in the polymer was determined by analyzing the polymer by nmr spectroscopy.
The average particle diameter of the particles is a 50% particle diameter value obtained by calculating a volume average value from a particle size distribution measured by using a known particle size distribution measuring apparatus (Helos-Rodos, product name, manufactured by Sympatec) using a laser diffraction method as a measurement principle.
The glass transition temperature is an intermediate glass transition temperature measured by a Differential Scanning Calorimetry (DSC) method. The glass transition temperature is also referred to as Tg.
The weight average molecular weight and the number average molecular weight were values measured by gel permeation chromatography using polystyrene as a standard substance. The weight average molecular weight is also referred to as Mw and the number average molecular weight is also referred to as Mn.
The acid value and the hydroxyl value are values measured by the methods in accordance with JIS K0070-3 (1992), respectively.
The film thickness is a value measured using an eddy current type film thickness meter (SANKO DENSHI co., ltd. trade name EDY-5000, etc.).
When the powder coating material of the present invention (hereinafter, also referred to as the present coating material) is used, a coating film can be formed in which a fluororesin is disposed on the surface side of the coating film and a non-fluororesin is disposed on the substrate side of the coating film, the layers of the fluororesin and the non-fluororesin being uniformly separated. The reason is not clear, but is presumed as follows.
In the present coating material, it is considered that since the coating material contains a fluororesin and a non-fluororesin, and one has a hydroxyl value of not less than a predetermined value and the other has an acid value of not more than a predetermined value, a difference in polarity occurs between the fluororesin and the non-fluororesin. Therefore, it is considered that, due to the difference in polarity, the fluororesin is likely to be uniformly disposed on the surface side of the coating film rather than staying in the coating film in the sea-island structure. Further, it is considered that the layer separation further proceeds because the content ratio of the fluororesin to the non-fluororesin in the composition is appropriate.
In the present specification, a coating film in which a fluororesin and a non-fluororesin are uniformly layered means a state in which the fluororesin is disposed on the surface side of the coating film to form a layer, the layer has a uniform thickness, and the sea-island structure of the fluororesin and the non-fluororesin does not substantially exist in the coating film. In the above state, the sea-island structure is allowed to exist by 5% or less in surface area in an arbitrary cross section obtained by cutting the coating film perpendicularly to the surface of the coating film, but the state where the sea-island structure does not exist is preferable.
The fluororesin in the present invention is a resin which has a fluorine atom, has at least one of a hydroxyl value and an acid value, and is solid at ordinary temperature.
The fluororesin may have both a hydroxyl value and an acid value. The fluororesin having no hydroxyl value means a fluororesin having a hydroxyl value of 1mgKOH/g or less, preferably 0mgKOH/g, and the fluororesin having no acid value means a fluororesin having an acid value of 1mgKOH/g or less, preferably 0 mgKOH/g.
The fluororesin in the present invention is preferably a fluoropolymer containing a unit having a fluorine atom and a unit having at least one member selected from the group consisting of a hydroxyl group and a carboxyl group.
The unit having a fluorine atom preferably includes a fluoroolefin-based unit (hereinafter, also referred to as a unit F).
The fluoroolefin is an olefin in which 1 or more hydrogen atoms are substituted with a fluorine atom. 1 or more of the hydrogen atoms in the fluoroolefin not substituted by fluorine atoms may be substituted by chlorine atoms.
Specific examples of the fluoroolefin include CF2＝CF2、CF2＝CFCl、CF2＝CHF、CH2＝CF2、CF2＝CFCF3、CF2＝CHCF3、CF3CH＝CHF、CF3CF＝CH2And formula CH2＝CXf1(CF2)n1Yf1(in the formula, Xf1And Yf1Independently a hydrogen atom or a fluorine atom, and n1 is an integer of 2 to 10. ) Monomers are shown.
As the fluoroolefin, CF is preferable from the viewpoint of weather resistance of a coating film formed from a powder coating material obtained using the present coating material (hereinafter, also referred to as the present coating film)2＝CF2、CH2＝CF2、CF2＝CFCl、CF3CHF, and CF3CF＝CH2More preferably CF2＝CF2And CH2＝CF2Particularly preferred is CF2CFCl. Two or more kinds of the fluoroolefins may be used in combination.
The fluoropolymer in the present invention may contain, as the unit having a fluorine atom, only the unit F, a unit based on a monomer containing a fluorine atom other than a fluoroolefin, and both the unit F.
The content of the unit F is preferably 20 to 100 mol%, more preferably 30 to 70 mol%, and particularly preferably 40 to 60 mol% based on the total units contained in the fluoropolymer, from the viewpoint of weather resistance of the present coating film.
Examples of the unit having at least one selected from the group consisting of a hydroxyl group and a carboxyl group (hereinafter, also referred to as a unit H.) include a unit based on a monomer having at least one selected from the group consisting of a hydroxyl group and a carboxyl group, and a unit in which at least a part of a reactive group of the fluoropolymer in a side chain is converted into a hydroxyl group or a carboxyl group (for example, a unit in which at least a part of a hydroxyl group is converted into a carboxyl group by a polycarboxylic acid or an acid anhydride thereof (such as succinic anhydride), and a unit having a hydroxyl group obtained by deprotecting a protective group such as an alkoxy group). The unit H preferably does not have a fluorine atom from the viewpoint of polymerizability of the fluoropolymer.
Examples of the monomer having a hydroxyl group include hydroxyl-containing vinyl ethers, vinyl esters, allyl ethers, allyl esters, (meth) acrylic acid esters, and allyl alcohols.
Specific examples of the monomer having a hydroxyl group include CH2＝CHO-CH2-cycloC6H10-CH2OH、CH2＝CHCH2O-CH2-cycloC6H10-CH2OH、CH2＝CHOCH2CH2OH、CH2＝CHCH2OCH2CH2OH、CH2＝CHOCH2CH2CH2CH2OH、CH2＝CHCH2OCH2CH2CH2CH2And (5) OH. As the monomer having a hydroxyl group, CH is preferable from the viewpoint of copolymerizability with a fluoroolefin2＝CHCH2OCH2CH2OH and CH2＝CHOCH2CH2CH2CH2OH。
Note that, "-CycloC6H10- "denotes cyclohexenyl," -CycloC6H10The bonding site of the- "is usually 1, 4-.
Examples of the monomer having a carboxyl group include an unsaturated carboxylic acid, (meth) acrylic acid, and a monomer obtained by reacting a hydroxyl group of the monomer having a hydroxyl group with a polycarboxylic acid or an acid anhydride thereof.
As a specific example of the monomer having a carboxyl group,may be exemplified by CH2＝CHCOOH、CH(CH3)＝CHCOOH、CH2＝C(CH3)COOH、HOOCCH＝CHCOOH、CH2＝CH(CH2)n11A monomer represented by COOH (wherein n11 represents an integer of 1-10), and CH2＝CHO(CH2)n12OC(O)CH2CH2A monomer represented by COOH (wherein n12 represents an integer of 1 to 10). The monomer having a carboxyl group is preferably CH from the viewpoint of copolymerizability with a fluoroolefin2＝CH(CH2)n11A monomer represented by COOH.
Two or more monomers having at least one selected from a hydroxyl group and a carboxyl group may be used in combination.
The content of the unit H is preferably 0.5 to 40 mol%, more preferably 3 to 30 mol%, further preferably 5 to 25 mol%, and particularly preferably 5 to 20 mol% based on all units contained in the fluoropolymer.
In order to adjust the coating film properties of the present coating film, the fluoropolymer in the present invention preferably further contains a unit (hereinafter, also referred to as unit D.) based on a monomer (hereinafter, also referred to as monomer D.) having no hydroxyl group and no carboxyl group and having no fluorine atom.
Examples of the monomer D include olefins, vinyl ethers, vinyl esters, allyl ethers, allyl esters, and (meth) acrylic esters. As the monomer D, vinyl ethers and vinyl esters are preferable in view of polymerizability with a monomer having a fluorine atom.
The monomer D may have a crosslinkable group other than a hydroxyl group and a carboxyl group. Examples of such crosslinkable groups include amino groups, alkoxysilyl groups, and epoxy groups.
Specific examples of the monomer D include ethylene, propylene, 1-butene, ethyl vinyl ether, 2-ethylhexyl vinyl ether, vinyl acetate, vinyl versatate and vinyl neodecanoate.
Two or more kinds of the monomer D may be used in combination.
The monomer D is preferably at least partially represented by the formula (VI)Xd1-Zd1Monomer D1 shown.
Xd1Is CH2＝CHC(O)O-、CH2＝C(CH3)C(O)O-、CH2＝CHOC(O)-、CH2＝CHCH2OC(O)-、CH2CHO-or CH2＝CHCH2O-is formed. As Xd1From the viewpoint of polymerizability with a monomer having a fluorine atom, CH is preferable2＝CHOC(O)-、CH2＝CHCH2OC(O)-、CH2CHO-and CH2＝CHCH2O-, particularly preferably CH2CHOC (O) -and CH2＝CHCH2OC(O)-。
Zd1Is of the formula-C (Z)R1)3The alkyl group having 4 to 8 carbon atoms (wherein, 3Z atoms)R1Each independently is an alkyl group having 1 to 5 carbon atoms. ) A C6-10 cycloalkyl group, a C6-10 cycloalkylalkyl group, a C6-10 aryl group, or a C7-12 aralkyl group, and is preferably represented by the formula-C (Z)R1)3The alkyl group having 4 to 8 carbon atoms or the cycloalkyl group having 6 to 10 carbon atoms.
formula-C (Z)R1)3The radicals shown have 3 radicals of the formula Z bonded to the "C (carbon atom)" explicitly shown in the formulaR1The group having a tertiary carbon atom, the above group and the formula Xd1The groups shown are directly bonded. For 3ZR1Preferably 3 are each methyl; or 1 is methyl, and the remaining 2 are each independently an alkyl group having 2 to 5 carbon atoms; or 2 methyl groups and 1 alkyl group having 3 to 5 carbon atoms. When 1 is methyl and the remaining 2 are each independently C2-C5 alkyl groups, 3ZR1The total number of the remaining 2 carbon atoms in (A) is preferably 4 to 6. formula-C (Z)R1)3The group shown is more preferably a tert-butyl group, or a group of the formula ZR12 of the groups are methyl groups and 1 is a tertiary alkyl group of an alkyl group having 3 to 5 carbon atoms.
As the cycloalkyl group, a cyclohexyl group is preferable.
As cycloalkylalkyl group, cyclohexylmethyl group is preferred.
As the aralkyl group, a benzyl group is preferable.
The aryl group is preferably a phenyl group or a naphthyl group, and more preferably a phenyl group.
It is to be noted that hydrogen atoms of the cycloalkyl group, cycloalkylalkyl group, aryl group, and aralkyl group may be substituted with an alkyl group. In this case, the carbon number of the alkyl group as a substituent is not included in the carbon numbers of the cycloalkyl group and the aryl group.
Specific examples of the monomer D1 include vinyl pivalate, vinyl neononanoate, vinyl benzoate, t-butyl vinyl ether, t-butyl (meth) acrylate, and benzyl (meth) acrylate.
Two or more kinds of the monomer D1 may be used in combination.
The content of the unit D in the case where the fluoropolymer contains the unit D is preferably 5 to 60 mol%, and particularly preferably 20 to 50 mol%, based on the total units contained in the fluoropolymer. When the unit D of the fluoropolymer includes the unit based on the monomer D1, the content of the unit based on the monomer D1 is preferably 5 to 60 mol%, and particularly preferably 20 to 50 mol%, based on the total units included in the fluoropolymer, from the viewpoint of increasing Tg of the fluoropolymer.
The Tg of the fluoropolymer in the present invention is preferably 40 to 120 ℃, more preferably 45 to 120 ℃, still more preferably 50 to 100 ℃, and particularly preferably 50 to 80 ℃ from the viewpoint of improving the blocking resistance of the coating material and the surface smoothness of the coating film.
The Mn of the fluoropolymer in the present invention is preferably 8,000 to 50,000 in view of the coating film properties (particularly impact resistance) of the present coating film.
The Mw of the fluoropolymer in the present invention is preferably 20,000 to 80,000 in view of the physical properties (particularly impact resistance) of the coating film of the present invention.
The acid value and the hydroxyl value of the fluoropolymer in the present invention are suitably adjusted in order to appropriately adjust the difference in polarity between the fluoropolymer and the non-fluororesin. The acid value of the fluoropolymer having a carboxyl group is preferably 1 to 150mgKOH/g, more preferably 5 to 50mgKOH/g, and particularly preferably 20 to 40 mgKOH/g. The hydroxyl value of the fluoropolymer having hydroxyl groups is preferably 1 to 150mgKOH/g, more preferably 5 to 50mgKOH/g, and particularly preferably 20 to 40 mgKOH/g.
The fluoropolymer may have both an acid value and a hydroxyl value.
The fluoropolymer in the present invention is preferably a fluoropolymer having no acid value and a hydroxyl value and a fluoropolymer having no hydroxyl value and an acid value, more preferably a fluoropolymer having no acid value and a hydroxyl value of 10 to 150mgKOH and a fluoropolymer having no hydroxyl value and an acid value of 10 to 150mgKOH, and preferably a fluoropolymer having no acid value and a hydroxyl value of 20 to 50mgKOH and a fluoropolymer having no hydroxyl value and an acid value of 20 to 50mgKOH, from the viewpoint of appropriate compatibility with a non-fluororesin and poor polarity described later.
The fluoropolymer in the present invention is produced by a known method. Examples of the method for producing the fluoropolymer include a method of copolymerizing monomers in the presence of a solvent and a radical polymerization initiator, and specific examples thereof include solution polymerization, emulsion polymerization, suspension polymerization, and the like. The reaction temperature, reaction pressure and reaction time in the production may be appropriately adjusted.
The non-fluororesin in the present invention is a resin which is incompatible with the fluororesin, has no fluorine atom, has at least one of a hydroxyl value and an acid value, and is solid at ordinary temperature.
The non-fluororesin may have both a hydroxyl value and an acid value. The non-fluororesin having no hydroxyl value means a non-fluororesin having a hydroxyl value of 1mgKOH/g or less, preferably 0mgKOH/g, and the non-fluororesin having no acid value means a non-fluororesin having an acid value of 1mgKOH/g or less, preferably 0 mgKOH/g.
Examples of the non-fluororesin include a polyester resin, a (meth) acrylic resin, and a urethane resin having at least one of an acid value and a hydroxyl value, and a polyester resin is preferable.
The polyester resin in the present invention is a polymer having a structure in which a polycarboxylic acid-based unit and a polyol-based unit are linked by an ester bond. The polyester resin may contain a hydroxycarboxylic acid-based unit or the like as a unit other than the polycarboxylic acid-based unit and the polyol-based unit.
The polycarboxylic acid is preferably an aromatic carboxylic acid having 8 to 15 carbon atoms. Examples of the polycarboxylic acid include phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, trimellitic acid, pyromellitic acid, and phthalic anhydride. As the polycarboxylic acid compound, isophthalic acid is preferable from the viewpoint of weather resistance.
The polyhydric alcohol is preferably a polyhydric alcohol having 2 to 10 carbon atoms. Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propanediol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol, neopentyl glycol, spiroglycol, 1, 10-decanediol, 1, 4-cyclohexanedimethanol, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, and the like. As the polyhydric alcohol, neopentyl glycol, 1, 2-pentanediol, 1, 5-pentanediol, trimethylolpropane and the like are preferable, and neopentyl glycol and trimethylolpropane are particularly preferable.
The polyester resin is preferably a linear polyester resin in view of the coating film properties (particularly surface smoothness) of the present coating film.
The softening temperature of the polyester resin is preferably 100 to 150 ℃ and particularly preferably 105 to 130 ℃ from the viewpoint of dispersibility when the coating material is made into a paint.
The Tg of the polyester resin is preferably 35 to 150 ℃ and particularly preferably 50 to 100 ℃ from the viewpoint of the blocking resistance of the coating material.
The Mn of the polyester resin is preferably 5,000 or less from the viewpoint of the coating film physical properties (particularly, surface smoothness) of the present coating film. The Mw of the polyester resin is preferably 2,000 to 20,000, particularly preferably 4,000 to 10,000, from the viewpoint of the coating film properties (particularly, surface smoothness) of the coating film.
The polyester resin has at least one group selected from a hydroxyl group and a carboxyl group. The acid value and the hydroxyl value of the polyester resin are appropriately adjusted so as to appropriately differ in polarity from those of the non-fluororesin.
When the polyester resin has a hydroxyl group, the hydroxyl value of the polyester resin is preferably 1 to 300mgKOH/g, more preferably 5 to 200mgKOH/g, still more preferably 20 to 100mgKOH/g, and particularly preferably 30 to 80 mgKOH/g. When the polyester resin has a carboxyl group, the acid value of the polyester resin is preferably 1 to 80mgKOH/g, more preferably 5 to 50mgKOH/g, and particularly preferably 20 to 40 mgKOH/g.
The polyester resin may have both an acid value and a hydroxyl value.
Specific examples of the polyester resin include "CRYLCOAT 4642-3" (hydroxyl value: 3.0mgKOH/g, acid value: 35mgKOH/g), "CRYLCOAT 4842-3" (hydroxyl value: 3.0mgKOH/g, acid value: 36mgKOH/g), "CRYLCOAT 4890-0" (hydroxyl value: 30mgKOH/g, acid value: 0.5mgKOH/g), "U-Pica COAT GV-235" (hydroxyl value: 2.0mgKOH/g, acid value: 39.0mgKOH/g), "U-Pica COAT GV-260" (hydroxyl value: 2.0mgKOH/g, acid value: 77.0 KOH/g), "U-Pica CoGV-3" (hydroxyl value: 50mgKOH/g, acid value: 3mgKOH/g, acid value: 34 g-34 g, etc.) of DAICEL-ALLNEX LTD products, Acid value: 6.0mgKOH/g), "U-Pica Coat GV-110" (hydroxyl value: 49mgKOH/g, acid value: 3mgKOH/g), "BIOMUP" (hydroxyl value: 32mgKOH/g, acid value: 3.5mgKOH/g), and "Uralac 1680" commercially available from DSM (hydroxyl value: 30mgKOH/g, acid value: 3.0mgKOH/g), and "FINEDIC M-8010" commercially available from DIC corporation (hydroxyl value: 24mgKOH/g, acid value: 3.0mgKOH/g), "FINEDIC M-8021" (hydroxyl value: 30mgKOH/g, acid value: 3.0mgKOH/g), "FINEDIC M-8023" (hydroxyl value: 40mgKOH/g, acid value: 6.0mgKOH/g), "FINEDIC M-8842" (hydroxyl value: 3.0mgKOH/g, acid value: 55mgKOH/g), "FINEDIC M-8860" (hydroxyl value: 3.0mgKOH/g, acid value: 36 mgKOH/g).
The (meth) acrylic resin in the present invention is a polymer containing a unit based on an alkyl (meth) acrylate having no hydroxyl group and no carboxyl group and a unit having at least one group selected from the group consisting of a hydroxyl group and a carboxyl group.
Examples of the alkyl (meth) acrylate include alkyl methacrylate (e.g., methyl methacrylate and butyl methacrylate) and alkyl acrylate (e.g., ethyl acrylate).
Examples of the unit having at least one group selected from a hydroxyl group and a carboxyl group include methacrylic acid, acrylic acid, hydroxyalkyl (meth) acrylate (hydroxyethyl methacrylate, etc.), and the like.
The (meth) acrylic resin may further contain units other than those described above (for example, units based on a (meth) acrylate having an epoxy group such as glycidyl methacrylate, and units based on a monomer other than the (meth) acrylate such as styrene).
The Tg of the (meth) acrylic resin is preferably 30 to 60 ℃ from the viewpoint of the blocking resistance of the coating material.
The Mn of the (meth) acrylic resin is preferably 6,000 to 150,000, more preferably 40,000 to 150,000, and particularly preferably 60,000 to 150,000, from the viewpoint of the coating film physical properties (particularly surface smoothness) of the present coating film.
The Mw of the (meth) acrylic resin is preferably 5,000 to 100,000, and particularly preferably 30,000 to 100,000, from the viewpoint of the coating film properties (particularly, surface smoothness) of the coating film.
The acid value and hydroxyl value of the (meth) acrylic resin are appropriately adjusted in order to appropriately adjust the difference in polarity between the (meth) acrylic resin and the non-fluororesin.
When the (meth) acrylic resin has a carboxyl group, the acid value of the (meth) acrylic resin is preferably 1 to 400 mgKOH/g. When the (meth) acrylic resin has a hydroxyl group, the hydroxyl value of the (meth) acrylic resin is preferably 1 to 250 mgKOH/g.
The urethane resin is a mixture of a polyol (acrylic polyol, polyester polyol, polyether polyol, propylene glycol, or the like) and an isocyanate compound, or a resin obtained by reacting the mixture. The urethane resin is preferably a resin obtained by reacting a mixture of powdery polyol (acrylic polyol, polyester polyol, polyether polyol) and powdery isocyanate.
The acid value and the hydroxyl value of the urethane resin are appropriately adjusted so as to appropriately differ in polarity from those of the non-fluororesin.
The non-fluororesin may have both an acid value and a hydroxyl value, and the absolute value of the difference between the acid value and the hydroxyl value is preferably 5mgKOH/g or more, more preferably 10mgKOH/g or more, and particularly preferably 20 to 30 mgKOH/g.
With the present coating, the fluororesin has a hydroxyl value smaller than that of the non-fluororesin and has an acid value larger than that of the non-fluororesin, or has an acid value smaller than that of the non-fluororesin and has a hydroxyl value larger than that of the non-fluororesin. When the acid values and hydroxyl values of the fluororesin and the non-fluororesin satisfy the above conditions, the polarity difference between the fluororesin and the non-fluororesin is appropriate, and the fluororesin is easily and uniformly formed on the surface side of the coating film.
In the case where the fluororesin has a hydroxyl value smaller than that of the non-fluororesin, the fluororesin may not have a hydroxyl value. In the case where the fluororesin has an acid value smaller than that of the non-fluororesin, the fluororesin may not have an acid value.
In the present coating material, from the viewpoint of the difference in polarity between the fluororesin and the non-fluororesin, it is preferable that the absolute value of the difference between the hydroxyl value of the fluororesin and the hydroxyl value of the non-fluororesin is 5mgKOH/g or more (more preferably 10mgKOH/g or more, still more preferably 10mgKOH/g or more, and particularly preferably 25mgKOH/g or more), and the absolute value of the difference between the acid value of the fluororesin and the acid value of the non-fluororesin is 5mgKOH/g or more (more preferably 15mgKOH/g or more, and particularly preferably 25mgKOH/g or more).
However, when the fluororesin or the non-fluororesin has no hydroxyl value, the hydroxyl value is calculated to be 0mgKOH/g, and the same applies to the acid value.
In the present composition, from the viewpoint of the difference in polarity between the fluororesin and the non-fluororesin, it is preferable that one of the fluororesin and the non-fluororesin has a hydroxyl value of 20mgKOH/g or more and the other has an acid value of 20mgKOH/g or more.
In addition, from the viewpoint of the poor polarity of the fluororesin and the non-fluororesin, it is more preferable that one of the fluororesin and the non-fluororesin has a hydroxyl value of 20mgKOH/g or more and an acid value of less than 20mgKOH/g, and the other has an acid value of 20mgKOH/g or more and a hydroxyl value of less than 20 mgKOH/g.
In addition, in the present coating material, from the viewpoint of the poor polarity of the fluororesin and the non-fluororesin, it is more preferable that one of the fluororesin and the non-fluororesin has a hydroxyl value of 20mgKOH/g or more and an acid value of 0 to 15mgKOH/g, and the other has an acid value of 20mgKOH/g or more and a hydroxyl value of 0 to 15 mgKOH/g.
In addition, in the present coating material, from the viewpoint of the poor polarity of the fluororesin and the non-fluororesin, it is particularly preferable that one of the fluororesin and the non-fluororesin has a hydroxyl value of 25mgKOH/g or more and an acid value of 0 to 5mgKOH/g, and the other has an acid value of 25mgKOH/g or more and a hydroxyl value of 0 to 5 mgKOH/g.
In the present coating material, it is preferable that the fluororesin is a resin having an acid value and the non-fluororesin is a resin having a hydroxyl value, because the fluororesin is easily disposed on the surface side of the coating film. That is, in the present composition, it is preferable that the hydroxyl value of the fluororesin is not less than 20mgKOH/g and the acid value of the non-fluororesin is not less than 20mgKOH/g, from the viewpoint of ease of disposing the fluororesin on the surface side of the coating film.
In the present coating material, it is more preferable that the fluororesin has a hydroxyl value of not less than 20mgKOH/g and an acid value of less than 20mgKOH/g, and the non-fluororesin has an acid value of not less than 20mgKOH/g and a hydroxyl value of less than 20mgKOH/g, from the viewpoint of facilitating the disposition of the fluororesin on the surface side of the coating film.
In addition, in the present coating material, from the viewpoint of easy disposition of the fluororesin on the surface side of the coating film, it is more preferable that the fluororesin has a hydroxyl value of 20mgKOH/g or more and an acid value of 0 to 15mgKOH/g, and the non-fluororesin has an acid value of 20mgKOH/g or more and a hydroxyl value of 0 to 15 mgKOH/g.
In addition, in the present coating material, from the viewpoint of easy disposition of the fluororesin on the surface side of the coating film, it is particularly preferable that the fluororesin has a hydroxyl value of 25mgKOH/g or more and an acid value of 0 to 5mgKOH/g, and the non-fluororesin has an acid value of 25mgKOH/g or more and a hydroxyl value of 0 to 5 mgKOH/g.
The content of the fluororesin is 1 to 20% by mass relative to the total mass of the fluororesin and the non-fluororesin. The content ratio is preferably 3 to 17% by mass, more preferably 5 to 15% by mass, and particularly preferably 8 to 12% by mass, in view of the ease of disposing the fluororesin on the surface side of the coating film.
In the present coating material, the total amount of the fluororesin and the non-fluororesin is preferably 10% by mass or more, more preferably 30 to 90% by mass, and particularly preferably 50 to 70% by mass, based on the total mass of the coating material, from the viewpoint of weather resistance of the coating film.
The coating material preferably contains the fluororesin in an amount of 0.1% by mass or more, more preferably 0.5 to 12.0% by mass, and particularly preferably 5.0 to 11.0% by mass, based on the total mass of the coating material, from the viewpoint of weather resistance of the coating film.
The coating contains a curing agent. The curing agent has 2 or more groups reactive with the hydroxyl group or carboxyl group of the fluororesin or non-fluororesin, and can crosslink the fluororesin or non-fluororesin. The curing agent generally has 2 to 30 of the above-mentioned groups capable of reacting with a hydroxyl group or a carboxyl group.
In general, a curing agent having 2 or more isocyanate groups or blocked isocyanate groups in 1 molecule (hereinafter, also referred to as a curing agent 1.) is crosslinked with a resin having a hydroxyl group. In addition, a curing agent having 2 or more epoxy groups, carbodiimide groups, oxazoline groups, or β -hydroxyalkylamide groups in 1 molecule (hereinafter, also referred to as a curing agent 2) is crosslinked with a resin having a carboxyl group.
Examples of the curing agent having 2 or more isocyanate groups in 1 molecule include alicyclic polyisocyanates such as isophorone diisocyanate and dicyclohexylmethane diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, and modified products thereof.
Specific examples of the curing agent having 2 or more blocked isocyanate groups in 1 molecule include compounds obtained by reacting diisocyanate (xylylene diisocyanate, hexamethylene diisocyanate, 4' -methylenebis (cyclohexyl isocyanate), methylcyclohexane diisocyanate, bis (isocyanotomethyl) cyclohexane, isophorone diisocyanate, dimer acid diisocyanate, lysine diisocyanate, etc.) with a blocking agent.
Specific examples of the blocking agent include alcohols, phenols, active methylene groups, amines, imines, amides, lactams, oximes, pyrazoles, imidazoles, imidazolines, pyrimidines, and guanidines.
Specific examples of the curing agent having 2 or more epoxy groups in 1 molecule include triglycidyl isocyanurate (hereinafter, also referred to as TGIC.), TM239 (product name of japanese chemical industry co., ltd.) in which a methylene group is introduced into a glycidyl group portion of TGIC, TEPIC-SP (product name of japanese chemical industry co., ltd.) as an epoxy compound having a triazine skeleton, and PT-910 (product name of HUNTSMAN corporation) as a mixture of glycidyl trimellitate and glycidyl terephthalate.
Specific examples of the curing agent having 2 or more carbodiimide groups in 1 molecule include alicyclic carbodiimide, aliphatic carbodiimide, and aromatic carbodiimide, and multimers and modifications thereof.
Specific examples of the curing agent having 2 or more oxazoline groups in 1 molecule include addition-polymerizable oxazoline having 2-oxazoline groups, and polymers of the addition-polymerizable oxazoline.
Specific examples of the curing agent having a β -hydroxyalkylamide group include N, N '-tetrakis- (2-hydroxyethyl) -adipamide (trade name of Primid XL-552, EMS), and N, N' -tetrakis- (2-hydroxypropyl) -adipamide (trade name of Primid QM 1260, EMS).
The content of the curing agent in the coating material is preferably 1 to 50% by mass, more preferably 1 to 20% by mass, based on the total mass of the fluororesin and the non-fluororesin in the coating material.
Particularly preferably, the curing agent 1 is contained in an amount of 1 to 50 mass% (more preferably 1 to 20 mass%) based on the total mass of the resins having hydroxyl values in the fluororesin and the non-fluororesin, and the curing agent 2 is contained in an amount of 1 to 50 mass% (more preferably 1 to 20 mass%) based on the total mass of the resins having an acid value.
That is, the present coating material preferably contains both the curing agent 1 and the curing agent 2. When the present coating material contains the curing agent 1 and the curing agent 2, the content of the curing agent 1 in the present coating material is preferably smaller than the content of the curing agent 2.
Since epsilon-caprolactam is produced when the curing agent 1 reacts with a hydroxyl group, there are problems such as oven contamination due to the generation of soot (japanese: ヤニ) and coating film quality deterioration due to the adhesion of the generated soot (japanese: ヤニ) to the coating film surface. When the coating material contains a fluororesin having a hydroxyl value and a non-fluororesin having an acid value, and the content of the fluororesin is 20 mass% or less relative to the total mass of the fluororesin and the non-fluororesin, the amount of the curing agent 1 to be used can be reduced, and therefore the environmental burden can be reduced.
The coating may also contain additives. Examples of the additives include catalysts (curing catalysts and the like), fillers (resin beads and the like), pigments (organic pigments, inorganic pigments and the like), light stabilizers, ultraviolet absorbers, delustering agents, surface conditioning agents, degassing agents, heat stabilizers, antistatic agents, rust inhibitors, silane coupling agents, low-pollution treatment agents, plasticizers, adhesives and the like. The present composition preferably contains a light stabilizer and an ultraviolet absorber as additives, and particularly preferably contains an ultraviolet absorber as additives.
Examples of the ultraviolet absorber in the present invention include organic ultraviolet absorbers and inorganic ultraviolet absorbers. The ultraviolet absorber is preferably an organic ultraviolet absorber in that the ultraviolet absorber is not present in the layer containing the fluororesin and thus easily protects the layer containing the non-fluororesin. As the organic ultraviolet absorber, a salicylate-based compound, a benzotriazole-based compound, a benzophenone-based compound, a cyanoacrylate-based compound, a triazine-based compound (particularly, a hydroxyphenyltriazine-based compound), and the like are preferable.
Specific examples of the ultraviolet absorber include trade names "Tinuvin 326", "Tinuvin 405", "Tinuvin 460", "Tinuvin 900", "Tinuvin 928" of BASF corporation, trade names "Sanduvor VSU powder" of Clariant corporation, and "Hastavin PR-25 Gran" of Clariant corporation.
The content of the ultraviolet absorber in the present coating material is preferably 0.01 to 30% by mass, and particularly preferably 1 to 5% by mass, based on the total mass of the present coating material.
In the present invention, the ratio of the mass of the ultraviolet absorber to the total mass of the fluororesin and the non-fluororesin (mass of the ultraviolet absorber/total mass of the fluororesin and the non-fluororesin) is preferably 0.01 to 1, and particularly preferably 0.05 to 0.10. It is considered that when a coating material containing an ultraviolet absorber in the above range is used, the ultraviolet absorber is likely to be unevenly distributed on the surface side of the coating film, and the coating film is excellent in weather resistance, because of the fluororesin and the non-fluororesin satisfying the conditions of the present invention in relation to the acid value and the hydroxyl value.
The light stabilizer in the present invention is preferably a hindered amine compound in view of being likely to be localized in a layer containing a non-fluororesin and suppressing deterioration of the non-fluororesin.
Specific examples of the light stabilizer include trade names "Tinuvin 111 FDL", "Tinuvin 144", "Tinuvin 152" by BASF, trade names "Sanduvor 3051 powder" by Clariant, trade names "Sanduvor 3070 powder" by Clariant, and "VP Sanduvor PR-31".
The content of the light stabilizer in the present coating material is preferably 0.01 to 30% by mass, more preferably 0.05 to 20% by mass, and particularly preferably 1 to 5% by mass, based on the total mass of the present composition.
The present coating may or may not contain a solvent (water, organic solvent, etc.), preferably no solvent. When the present composition contains a solvent, the content is preferably 1% by mass or less based on the total mass of the present coating material.
The content of fluorine atoms in the coating material is preferably 0.01 to 10% by mass, more preferably 0.05 to 7% by mass, and particularly preferably 0.1 to 5% by mass. Since the fluororesin is uniformly disposed on the surface side of the coating film, the coating film has excellent weather resistance despite its low fluorine atom content.
The coating material can be produced by mixing a fluororesin, a non-fluororesin, a curing agent, and additives as required. The fluororesin, the non-fluororesin, the curing agent, the additive and the like to be mixed may be in the form of powder or pellets, which are independent of each other.
One embodiment of the method for producing the coating material is a method in which a powder a containing a fluororesin and a powder B containing a non-fluororesin are mixed to obtain a powder coating material. This method is also called dry mixing, and is a method in which melt kneading is not performed at the time of mixing. The content of the fluororesin in the powder a may be larger than the content of the fluororesin in the powder B, more preferably the content of the non-fluororesin in the powder a is 5 mass% or less with respect to the mass of the fluororesin in the powder a, and the content of the fluororesin in the powder B is 5 mass% or less with respect to the mass of the non-fluororesin in the powder B, and particularly preferably the powder a does not contain the non-fluororesin and the powder B does not contain the fluororesin. At least one of the powder a and the powder B may contain a curing agent.
In addition, as an embodiment of the method for producing a powder coating material in the present invention, there is a method in which a fluororesin, a non-fluororesin, and a curing agent are melt-kneaded, cooled, and then pulverized to obtain a powder coating material. In this case, the fluororesin and the non-fluororesin are contained in the same particle. The coating material is preferably produced by melt kneading. The temperature of the melt kneading is preferably 80 to 130 ℃.
The pulverization can be carried out using a pulverizer such as a pin pulverizer, a hammer mill, or a jet mill. After the pulverization, the pulverized material is classified so that the particle diameters of the obtained powder coating materials are uniform.
The average particle diameter of the powder coating is preferably 1 to 100 μm, more preferably 10 to 80 μm, and particularly preferably 25 to 50 μm.
The coating film is formed by applying the powder coating material of the present invention to a substrate.
Specific examples of the material of the substrate include inorganic materials, organic materials, and organic-inorganic composite materials.
Specific examples of the inorganic substance include concrete, natural stone, glass, and metal (iron, stainless steel, aluminum, copper, brass, titanium, etc.).
Specific examples of the organic material include plastic, rubber, adhesive, and wood.
Specific examples of the organic-inorganic composite material include fiber-reinforced plastics, resin-reinforced concrete, and fiber-reinforced concrete.
The substrate may be subjected to a known surface treatment (chemical conversion treatment or the like). The surface of the substrate may be provided with a resin layer (e.g., a polyester resin layer, an acrylic resin layer, or a silicone resin layer) formed by applying a primer or the like.
Among the above, the material of the substrate is preferably metal, and particularly preferably aluminum. The aluminum base material is excellent in corrosion resistance, light in weight, and suitable for use as a building material such as an exterior member.
The shape, size, and the like of the base material are not particularly limited.
Specific examples of the substrate include building exterior members such as composite panels, curtain wall frames, and window frames, automobile members such as tire rims, scrapers, and automobile exterior members, frames for construction machines and motorcycles.
The thickness of the coating film is preferably 20 to 1,000 μm, more preferably 20 to 500. mu.m. In the applications such as members for high-rise buildings such as aluminum curtain walls, the thickness is preferably 20 to 90 μm. In applications requiring high weather resistance, such as outdoor units of air conditioners installed along the coast, poles of traffic lights, signs, etc., it is preferable that the thickness of the coating is 100 to 200 μm.
The coating film is preferably obtained as follows: the coating composition is obtained by applying the present coating material to a substrate to form a coating layer, and subjecting the obtained coating layer to heat treatment and then cooling.
Examples of the method of forming the coating layer include coating methods such as electrostatic coating, electrostatic blowing, electrostatic dipping, fluidized dipping, and blowing, and electrostatic coating using a powder coating gun is preferred.
Specific examples of the powder coating gun include a corona charging type coating gun and a frictional charging type coating gun. The corona charging type coating gun is a coating gun that performs corona discharge treatment on a powder coating material and blows the powder coating material. The triboelectric coating gun is a coating gun that blows a powder coating material after triboelectric treatment.
The heating temperature in the heat treatment is preferably 120 to 200 ℃. The heating holding time is usually 2 to 60 minutes. After the heating treatment, the mixture is preferably cooled to 20-25 ℃. The coating layer is melted and solidified by heat treatment and cooling, and the coating film is formed.
According to the present invention, since a coating film having more excellent layer separability can be formed as compared with a typical powder coating material containing a fluororesin and a non-fluororesin, even if the content of the fluororesin is small, a coating film having excellent weather resistance can be formed, and a significant cost reduction can be achieved.
Further, according to the present invention, since the fluororesin layer is thin and uniformly laminated with respect to the non-fluororesin layer, the interface between the layers is less disturbed, and the surface smoothness is excellent.
Examples
The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples. Examples 1 to 4 are examples, and examples 5 to 7 are comparative examples.
(names and abbreviations of the components used)
CTFE: chlorotrifluoroethylene
PV: vinyl pivalate
UDA: 10-undecenoic acid
CHVE: cyclohexyl vinyl ether
HBVE: 4-hydroxybutyl vinyl ether
Non-fluororesin 1: polyester resin (DAICEL-ALLNEX LTD. trade name CRYLCOAT 4890-0, hydroxyl value: 30mgKOH/g, acid value: 0.5mgKOH/g)
Non-fluororesin 2: polyester resin (DAICEL-ALLNEX LTD. trade name CRYLCOAT 4642-3, hydroxyl value: 3.0mgKOH/g, acid value: 35mgKOH/g)
Curing agent 1: 1 curing agent having 2 or more blocked isocyanate groups in the molecule (product name of Evonik VESTAGON B1530)
Curing agent 2: 1 curing agent having 2 or more epoxy groups in molecule (triglycidyl isocyanurate)
Ultraviolet absorber: organic ultraviolet absorber (product name Tinuvin 405 from BASF corporation)
Surface conditioner: BYK corporation, BYK-360P
Degassing agent: benzoin
Pigment: titanium oxide pigment (trade name of DuPont Ti-Pure R960, titanium oxide content: 89% by mass)
Curing catalyst: dibutyltin laurate in xylene (100-fold dilution)
[ production of fluoropolymer 1]
Potassium carbonate (12.3g) and Kyowaad KW500SH (trade name, hereinafter, also referred to as an adsorbent, manufactured by Kyowa chemical Co., Ltd.) (4.5g) were charged into an autoclave, and vacuum degassing was performed. Then, xylene (503g), ethanol (142g), CTFE (387g), CHVE (326g) and HBVE (84.9g) were introduced into the autoclave, the temperature was raised, and a 50 mass% xylene solution (20mL) of tert-butyl peroxypivalate as a polymerization initiator was continuously added to carry out polymerization. After 11 hours, the autoclave was water-cooled to stop the polymerization, and the solution in the autoclave was filtered to obtain a solution containing the fluoropolymer 1.
The resulting solution was dried under vacuum at 65 ℃ for 24 hours to remove the solvent, and further dried under vacuum at 130 ℃ for 20 minutes to obtain a block-shaped fluoropolymer 1.
The fluoropolymer 1 is a polymer containing, in order, 50 mol%, 39 mol%, and 11 mol% of units based on CTFE, units based on CHVE, and units based on HBVE, based on all the units contained in the fluoropolymer 1. The fluoropolymer 1 had a Tg of 52 ℃, an Mw of 45,500, an acid value of 0mgKOH/g and a hydroxyl value of 50 mgKOH/g.
[ production of fluoropolymer 2]
An adsorbent (15.1g) was charged into the autoclave, and vacuum degassing was performed. Subsequently, t-butanol (422g), ethanol (106g), Tinuvin 292(15.1g), CTFE (465g), PV (440g), and UDA (103g) were introduced into the autoclave, and the temperature was raised, and a 50 mass% xylene solution (47mL) of t-butylperoxypivalate as a polymerization initiator was continuously added to the autoclave to carry out polymerization. After 11 hours, the autoclave was water-cooled to stop the polymerization, and the solution in the autoclave was filtered to obtain a solution containing a fluoropolymer 2.
The resulting solution was dried under vacuum at 65 ℃ for 24 hours to remove the solvent, and further dried under vacuum at 130 ℃ for 20 minutes to obtain a fluoropolymer 2 in the form of a block.
The fluoropolymer 2 is a polymer containing units based on CTFE, units based on PV, and units based on UDA in the order of 41 mol%, 50 mol%, and 9 mol%, respectively. The fluoropolymer 2 had a Tg of 52 ℃, an Mw of 59,300, an acid value of 33mgKOH/g and a hydroxyl value of 0 mgKOH/g.
[ examples 1 to 7]
The components of the powder coating material described in table 1 were mixed with a high-speed mixer (manufactured by yozaki limited) for 10 to 30 minutes, and then melt-kneaded using a twin-screw extruder (manufactured by Thermo Prism, サーモプリズム, 16mm extruder) at a barrel set temperature of 120 ℃. The resulting kneaded mixture was cooled, pulverized by a pulverizer (product name: Rotor speed mill P14, manufactured by FRITSCH corporation), and classified for 150 mesh to obtain powder coatings each having an average particle diameter of about 40 μm.
(preparation and evaluation of test piece)
One surface of the chromate-treated aluminum substrate was subjected to electrostatic coating using each powder coating material with an electrostatic coating machine (trade name of Onoda Semento Co., Ltd., GX3600C) to form a powder coating layer on the aluminum substrate. The aluminum substrate with the powder coating layer obtained was subjected to heat treatment and cured in an atmosphere at 200 ℃ for 20 minutes, and then cooled to 25 ℃ to obtain aluminum plates with films each having a thickness of 55 to 65 μm. The obtained aluminum plates with coating films were used as test pieces and evaluated. The results are shown in Table 1.
(evaluation method)
< layer separation Property of coating film section >
The test piece was cut perpendicularly to the surface of the coating film, and the cross section of the coating film was observed with a scanning electron microscope under the following measurement conditions, and the determination was made according to the following criteria.
Measurement conditions
Testing machine: JSM-5900LV, manufactured by Nippon electronic Co., Ltd,
Acceleration voltage: 20kV,
Multiplying power: 10,000 times of,
Pretreatment for measurement: platinum was applied to the substrate by an automatic fine coater, JFC-1300, 20mA, 45 seconds, manufactured by Nippon electronics Co., Ltd.
Evaluation criteria
A: the fluoropolymer layer is present on the surface side of the coating film, and the non-fluororesin layer is present on the substrate side of the coating film, and the thickness of the fluoropolymer layer is uniform. In addition, the coating film does not have a sea-island structure of a fluoropolymer and a non-fluororesin.
B: the surface side of the coating film has a layer of a fluoropolymer and the substrate side of the coating film has a layer of a non-fluororesin, but the thickness of the layer of a fluoropolymer is not uniform, or a sea-island structure of a fluoropolymer and a non-fluororesin is present.
< coating Property on coating film surface >
The surface of the coating film of the test piece was subjected to IR analysis at random 5 points using a trade name "FT/IR-600" manufactured by Nippon spectral Co., Ltd to evaluate whether or not the surface of the coating film was uniformly covered with the fluoropolymer. When no peak derived from the non-fluororesin was observed at 5 points of the IR analysis, the coating film surface was evaluated to be uniformly covered with the fluoropolymer.
A: the surface of the coating film is covered with a fluoropolymer.
B: the non-fluororesin is exposed on a part of the surface of the coating film.
< surface smoothness of coating film >
The smoothness of the Coating film on the test piece was determined using a standard plate for visual determination of smoothness based on PCI (Powder Coating Institute). The standard plate has 10 sheets of 1-10, and the smoothness is excellent as the number is increased.
A: the PCI value is 4 or more.
B: the PCI value is less than 4.
< 60 degree specular gloss of coating film >
The 60-degree specular gloss of the coating film surface of the test piece was measured in accordance with JIS K5600-4-7, and evaluated according to the following criteria. For 60 degree specular gloss, a variable angle gloss meter (UGV-6P, 60 degree incident reflection angle, Suga Test Instruments Co., Ltd., product of Ltd.) was used for the measurement.
A: the 60-degree mirror surface glossiness is 90 degrees or more.
B: the 60 degree mirror surface glossiness is less than 90 degrees.
[ Table 1]
Figure BDA0002091908870000241
As described above, it was demonstrated that a powder coating material using the present coating material can form a coating film in which the fluororesin and the non-fluororesin are uniformly separated in layers, although the content of the fluororesin is small.

Claims (11)

1. A powder coating material, comprising: a fluororesin having at least one of a hydroxyl value and an acid value, a non-fluororesin having at least one of a hydroxyl value and an acid value, and a curing agent,
the fluororesin has a hydroxyl value of 20mgKOH/g or more and an acid value of less than 20mgKOH/g, the non-fluororesin has an acid value of 20mgKOH/g or more and a hydroxyl value of less than 20mgKOH/g,
the content of the fluororesin is 1 to 20% by mass relative to the total mass of the fluororesin and the non-fluororesin.
2. A powder coating material according to claim 1, wherein an absolute value of a difference between a hydroxyl value of the fluororesin and a hydroxyl value of the non-fluororesin is 5mgKOH/g or more, and an absolute value of a difference between an acid value of the fluororesin and an acid value of the non-fluororesin is 5mgKOH/g or more.
3. The powder coating material according to claim 1 or 2, wherein the fluororesin is a fluororesin having a hydroxyl value of 20mgKOH/g or more and an acid value of 0 to 15mgKOH/g,
the non-fluororesin has an acid value of 20mgKOH/g or more and a hydroxyl value of 0 to 15 mgKOH/g.
4. The powder coating material according to claim 1 or 2, wherein a content ratio of the fluorine atom in the powder coating material is 0.01 mass% or more and 10 mass% or less with respect to a total mass of the powder coating material.
5. The powder coating material according to claim 1 or 2, comprising: a curing agent having 2 or more isocyanate groups or blocked isocyanate groups in 1 molecule, and a curing agent having 2 or more epoxy groups, carbodiimide groups, oxazoline groups, or β -hydroxyalkylamide groups in 1 molecule.
6. A powder coating material as claimed in claim 5, wherein a content of the curing agent having 2 or more isocyanate groups or blocked isocyanate groups in the 1 molecule in the powder coating material is less than a content of the curing agent having 2 or more epoxy groups, carbodiimide groups, oxazoline groups, or β -hydroxyalkylamide groups in the 1 molecule.
7. A powder coating material according to claim 1 or 2, wherein the non-fluororesin is a resin selected from the group consisting of a polyester resin, (meth) acrylic resin, and a urethane resin.
8. The powder coating material according to claim 1 or 2, further comprising an ultraviolet absorber, wherein the ratio of the mass of the ultraviolet absorber to the total mass of the fluororesin and the non-fluororesin is 0.05 to 0.10.
9. A powder coating material according to claim 1 or 2, comprising a fluororesin in an amount of 0.1% by mass or more based on the total mass of the powder coating material.
10. A method for producing a powder coating material, wherein the powder coating material according to any one of claims 1 to 9 is obtained by mixing a powder A containing a fluororesin and a powder B containing a non-fluororesin,
the content of the fluororesin in the powder A is larger than that in the powder B,
at least one of the powder A and the powder B contains a curing agent.
11. A method for producing a powder coating material, wherein the fluororesin, the non-fluororesin and the curing agent are melt-kneaded, cooled and then pulverized to obtain the powder coating material according to any one of claims 1 to 9.
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