阅读说明：本技术 粉体涂料、涂覆品及笔记板 (Powder coating material, coated article and note board ) 是由 三枝浩 山中清弘 塩崎启史 江村鹰一朗 于 2019-09-04 设计创作，主要内容包括：一种粉体涂料、涂覆品及笔记板,粉体涂料包含：含有具有碳原子数4以上的烷基及羟基的侧链的丙烯酸树脂；以及固化剂。(A powder coating, a coated article and a note board, the powder coating comprises: an acrylic resin having a side chain having an alkyl group having 4 or more carbon atoms and a hydroxyl group; and a curing agent.)

1. A powder coating comprising:

an acrylic resin having a side chain having an alkyl group having 4 or more carbon atoms and a hydroxyl group; and

and (3) a curing agent.

2. The powder coating material according to claim 1,

the side chain has a hydroxyalkyl group having 3 or more carbon atoms as the hydroxyl group.

3. The powder coating material according to claim 1,

the hydroxyl group in the side chain is a secondary hydroxyl group or a tertiary hydroxyl group.

4. The powder coating material according to claim 1,

the curing agent includes at least one compound selected from the group consisting of a blocked isocyanate compound, an epoxy compound, and an oxetane compound.

5. The powder coating material according to claim 4,

the curing agent comprises a blocked isocyanate compound.

6. A powder coating according to claim 1 further comprising particles.

7. The powder coating material according to claim 6,

the particles comprise inorganic particles.

8. The powder coating material according to claim 6,

the particles comprise organic resin particles.

9. The powder coating material according to claim 8,

the organic resin particles contain organic resin particles containing a gel component.

10. The powder coating material according to claim 8,

the organic resin particles comprise crosslinked resin particles.

11. The powder coating material according to claim 1, further comprising 0.35 mass% or more and 0.88 mass% or less of metal ions with respect to the entire powder particles.

12. A coated article comprising a layer obtained by curing the powder coating material according to claim 1 on an outermost layer thereof.

13. A notebook computer having a layer obtained by curing the powder coating material according to claim 1 on an outermost layer thereof.

14. The note pad of claim 13, which is a projection note pad.

Technical Field

The invention relates to a powder coating, a coated product and a note board.

Background

In recent years, a powder coating technique using a powder coating material has attracted attention in terms of global environment because it discharges a small amount of Volatile Organic Compounds (VOC) in a coating process and recovers and reuses a powder coating material that does not adhere to an object to be coated after coating. Therefore, various studies have been made on powder coating materials.

As conventional projection screens, decorative sheets, or interior wall materials, materials described in patent documents 1 to 3 are known.

Patent document 1 discloses a projection screen including a base material and a coating layer formed on a surface of the base material, wherein the coating layer includes a binder resin, a plurality of particles, and a surface conditioner including at least a silicone polymer having an acrylic group, and an exposed surface of the coating layer on a side opposite to a surface contacting the base material is formed in a concavo-convex shape by the plurality of particles.

Patent document 2 discloses a decorative sheet including: the decorative sheet is characterized in that (1) the surface protective layer contains a resin having an acrylic skeleton as a leveling agent in a proportion of 0.1-4.0 parts by mass relative to 100 parts by mass of an ionizing radiation curable resin, and (2) the structural unit of the resin having an acrylic skeleton is a poly (meth) acrylate containing a (meth) acrylic acid alkyl ester having no hydroxyl group and containing at least one selected from the group consisting of a (meth) acrylic acid hydroxyalkyl ester and an aromatic vinyl compound.

Patent document 3 discloses an interior wall material having a tablet function, which is excellent in stain resistance, throwing power, and anti-glare properties, and which is formed into a clad layer by applying a coating material to an object to be coated and curing the coating material by electron beam irradiation in an environment having an oxygen concentration of 1% or less, wherein the clad layer is formed into a wooden board such as a metal board, a hard fiber board, a particle board, and wood, an asbestos board, a rock board, or the likeThe coating is formed by using oligo (methyl) acrylate as a component 1, using one polyalcohol methacrylate selected from ethylene glycol dimethacrylate, diethylene glycol dimethacrylate and trimethylolpropane trimethacrylate which contains more than 2 methacryloyl groups in 1 molecule and has the equivalent weight of less than 121 as a component 2, wherein the mixing ratio of the component 1 and the component 2 is 1/0.5-1/2 (weight ratio), and the volume of the component 3 is 6.5 × 10 to 100 parts by weight of the total amount of the components⁴μm³1 to 40 parts by mass of the following glass powder, and 1 to 20 parts by mass of aluminum powder and/or stainless steel powder having a radius of 1 to 50 [ mu ] as the 4 th component, wherein the oligo (meth) acrylate is obtained by esterifying three components of tetrahydrophthalic acid, trimethylolpropane, pentaerythritol, and (meth) acrylic acid, each of which contains 2 or more (meth) acryloyl groups in 1 molecule and has a (meth) acryloyl equivalent of 500 or less.

Patent document 1: japanese patent laid-open publication No. 2013-235149

Patent document 2: japanese patent laid-open publication No. 2012-213933

Patent document 3: japanese laid-open patent publication No. 8-253988

Disclosure of Invention

The problem to be solved by the present invention is to provide a powder coating material having an excellent wet feel on the surface of the obtained coating film, as compared with a powder coating material comprising only an acrylic resin having a side chain containing an alkyl group having less than 4 carbon atoms and a hydroxyl group.

The above problems are solved by the following means.

< 1 > a powder coating comprising: an acrylic resin having a side chain having an alkyl group having 4 or more carbon atoms and a hydroxyl group; and a curing agent.

< 2 > the powder coating material according to < 1 >, wherein the side chain has a hydroxyalkyl group having 3 or more carbon atoms as the hydroxyl group.

< 3 > the powder coating according to < 1 > wherein the hydroxyl group in the side chain is a secondary hydroxyl group or a tertiary hydroxyl group.

< 4 > the powder coating material according to < 1 >, wherein the curing agent comprises at least one compound selected from the group consisting of a blocked isocyanate compound, an epoxy compound and an oxetane compound.

< 5 > the powder coating according to < 4 > wherein the curing agent comprises a blocked isocyanate compound.

< 6 > the powder coating according to < 1 > further comprising particles.

< 7 > the powder coating according to < 6 > wherein the particles comprise inorganic particles.

< 8 > the powder coating according to < 6 > wherein the particles comprise organic resin particles.

< 9 > the powder coating material according to < 8 >, wherein the organic resin particles contain organic resin particles containing a gel component.

< 10 > the powder coating material according to < 8 > wherein the organic resin particles comprise crosslinked resin particles.

< 11 > the powder coating material according to < 1 >, further comprising 0.35 mass% or more and 0.88 mass% or less of metal ions with respect to the entire powder particles.

< 12 > A coated article having, on the outermost layer thereof, a layer composed of the powder coating material < 1 >.

< 13 > a note board having a layer consisting of the powder coating < 1 > on the outermost layer.

< 14 > the note board according to < 13 > which is a note board for projection.

Effects of the invention

According to the invention of < 1 > or < 4 >, a powder coating material having a superior wet feel on the surface of the obtained coating film can be provided as compared with a powder coating material comprising only an acrylic resin having a side chain containing an alkyl group having less than 4 carbon atoms and a hydroxyl group.

According to the invention of < 2 >, it is possible to provide a powder coating material having a more excellent wet feel on the surface of the obtained coating film than when the side chain has only a hydroxyalkyl group having less than 3 carbon atoms as the hydroxyl group.

According to the invention of < 3 >, a powder coating material having a more excellent wet feel on the surface of the obtained coating film than when the hydroxyl group in the side chain is a primary hydroxyl group can be provided.

According to the invention of < 5 >, it is possible to provide a powder coating material having a more excellent wet feel on the surface of the obtained coating film than when the curing agent contains only an epoxy compound or an oxetane compound.

According to the invention of < 6 >, < 7 > or < 8 >, the obtained coating film is excellent in durability as compared with the case where only the acrylic resin and the curing agent are contained.

According to the invention of < 9 >, it is possible to provide a powder coating material having a more excellent moist feeling on the surface of the obtained coating film than when the organic resin particles are organic resin particles having a gel content of 0%.

According to the invention of < 10 >, it is possible to provide a powder coating material having a more excellent moist feeling on the surface of the obtained coating film than when the organic resin particles are particles of a linear organic resin.

According to the invention of < 12 >, < 13 > or < 14 >, a coated article or a notebook computer having a coating film with a superior wet feeling on the surface thereof can be provided, as compared with the case where the powder coating material contains only an acrylic resin having a side chain of an alkyl group having less than 4 carbon atoms and a hydroxyl group.

Detailed Description

The present embodiment will be described below. The description and examples are illustrative of the embodiments and do not limit the scope of the embodiments.

In the present embodiment, the numerical range represented by "to" represents a range in which the numerical values described before and after "to" are included as the minimum value and the maximum value, respectively.

In the numerical ranges recited in the present embodiment in stages, the upper limit value or the lower limit value recited in one numerical range may be replaced with the upper limit value or the lower limit value recited in another numerical range recited in stages. In the numerical ranges described in the present embodiment, the upper limit or the lower limit of the numerical range may be replaced with the values shown in the examples.

In the present embodiment, the term "step" includes not only an independent step, but also a step that can achieve the intended purpose of the step even when the step is not clearly distinguished from other steps.

In the present embodiment, when the embodiment is described with reference to the drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. The sizes of the components in the drawings are conceptual, and the relative relationship between the sizes of the components is not limited to this.

In the present specification, "(meth) acrylate" represents both or either one of acrylate and methacrylate, "(meth) acrylic group" represents both or either one of acrylic group and methacrylic group, and "(meth) acryloyl group" represents both or either one of acryloyl group and methacryloyl group.

In the present embodiment, each component may include a plurality of corresponding substances. In the present embodiment, when referring to the amount of each component in the composition, in the case where a plurality of substances corresponding to each component are present in the composition, the total amount of the plurality of substances present in the composition is referred to unless otherwise specified.

(powder coating Material)

The powder coating material according to the present embodiment includes an acrylic resin having a side chain containing an alkyl group having 4 or more carbon atoms and a hydroxyl group, and a curing agent.

The powder coating material according to the present embodiment is suitably used as a powder coating material used for forming a writing surface of a tablet or a projection surface of a projection plate, for example, more suitably used as a powder coating material used for forming a writing surface of a tablet, and particularly suitably used as a powder coating material used for forming a writing surface of a projection plate.

The powder coating material according to the present embodiment may be either a transparent powder coating material (clear coating material) in which the powder particles do not contain a coloring agent or a colored powder coating material in which the powder particles contain a coloring agent, but from the viewpoint of the amount of change in color when forming a coating film and the smoothness of the resulting coating film, for example, a clear powder coating material in which the powder particles do not contain a coloring agent or a white powder coating material in which the powder particles contain a white coloring agent is preferable.

The powder coating material according to the present embodiment is preferably a thermosetting powder coating material, for example.

A coating film using a conventional powder coating material may not have a wet texture (also referred to as a "wet feel") on the surface because the surface of the coating film has large irregularities and glare of reflected light on the surface is large.

The powder coating material according to the present embodiment has excellent wet feeling on the surface of the coating film obtained by the above-described configuration. The reason is assumed to be based on the following reasons, although not clear.

By using an acrylic resin containing a side chain having an alkyl group having 4 or more carbon atoms and a hydroxyl group, the hardness and the water repellency of the coating film are improved, fine irregularities on the surface of the coating film can be controlled, a coating film having an appropriate balance between smoothness and irregularities can be obtained, and the surface of the obtained coating film has an excellent moist feeling.

Further, since the powder coating material according to the present embodiment is improved in hardness and hydrophobicity of the coating film by using the acrylic resin containing the side chain having the alkyl group having 4 or more carbon atoms and the hydroxyl group, when the powder coating material is used for forming a note surface of a note board, the erasing property of a marker (maker) (specifically, a writing tool for a whiteboard), the erasing property with time after leaving a document with the marker at a high temperature, and the durability of repetition of writing and erasing with the marker are also excellent.

The powder coating material according to the present embodiment will be described in detail below.

The powder coating material according to the present embodiment includes powder particles, and preferably includes, for example, powder particles including an acrylic resin having a side chain having an alkyl group having 4 or more carbon atoms and a hydroxyl group, and a curing agent. From the viewpoint of improving fluidity, the powder coating material may have an external additive attached to the surface of the powder particles as necessary.

[ powder particle ]

The powder particles preferably contain, for example, an acrylic resin containing a side chain having an alkyl group having 6 or more carbon atoms and a hydroxyl group, and a curing agent.

< Special acrylic resin >

The powder coating material according to the present embodiment includes an acrylic resin (also referred to as a "specific acrylic resin") having a side chain having an alkyl group having 4 or more carbon atoms and a hydroxyl group, and preferably includes powder particles containing the specific acrylic resin, for example.

The specific acrylic resin may be a resin obtained by polymerizing at least a (meth) acrylic compound, and for example, a resin having 5 to 100% by mass of a structural unit derived from a (meth) acrylic compound (also referred to as a "structural unit formed from a (meth) acrylic compound") is preferable, a resin having 10 to 100% by mass of a structural unit derived from a (meth) acrylic compound is more preferable, a resin having 20 to 100% by mass of a structural unit derived from a (meth) acrylic compound is further preferable, and a resin having 30 to 100% by mass of a structural unit derived from a (meth) acrylic compound is particularly preferable.

Examples of the (meth) acrylic acid compound include an acrylate compound, a methacrylate compound, acrylic acid, methacrylic acid, an acrylamide compound, a methacrylamide compound, an acrylonitrile compound, and a methacrylonitrile compound.

Among these, the specific acrylic resin preferably has at least a structural unit derived from at least one compound selected from the group consisting of an acrylate compound, a methacrylate compound, acrylic acid, and methacrylic acid, and more preferably has a structural unit derived from at least one compound selected from the group consisting of an acrylate compound and a methacrylate compound.

The specific acrylic resin may have the acrylic group and the hydroxyl group having 4 or more carbon atoms in 1 side chain, or may have the acrylic group and the hydroxyl group having 4 or more carbon atoms in each side chain, but from the viewpoints of the wettability of the surface of the obtained coating film, the marker pen cleanability, the cleanability with time after leaving the marking pen at a high temperature, and the repeated durability of the writing and cleaning with the marker pen, for example, it is preferable that each side chain has the acrylic group and the hydroxyl group having 4 or more carbon atoms, and it is more preferable that a structural unit having an alkyl group having 4 or more carbon atoms in the side chain and a structural unit having a hydroxyl group in the side chain are contained.

The structural unit having an alkyl group having 4 or more carbon atoms in a side chain and the structural unit having a hydroxyl group in a side chain are each preferably a structural unit derived from a (meth) acrylate compound, for example.

The structural unit having an alkyl group having 4 or more carbon atoms in a side chain is preferably a structural unit represented by the following formula (a), for example.

[ chemical formula 1]

In the formula (A), R^A1Represents an alkyl group having 4 or more carbon atoms, R^A2Represents a hydrogen atom or a methyl group.

From the viewpoints of the wettability of the surface of the obtained coating film, the erasing properties of the marker, the erasing properties with time after the marking using the marker is left at a high temperature, and the repeated durability of the writing and erasing using the marker, R in the formula (A)^A1For example, the alkyl group is preferably an alkyl group having 6 or more carbon atoms, more preferably an alkyl group having 6 to 20 carbon atoms, still more preferably an alkyl group having 7 to 16 carbon atoms, and particularly preferably an alkyl group having 8 to 12 carbon atoms.

And, said R^A1The alkyl group in (2) may be a straight-chain alkyl group, a branched-chain alkyl group, or an alkyl group having a ring structure, but is preferably a straight-chain alkyl group, for exampleAlkyl or branched alkyl.

As said R^A1Specific examples thereof include n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group, n-dodecyl group, n-tetradecyl group, n-hexadecyl group (cetyl group), and n-octadecyl group (stearyl group).

Among them, from the viewpoint of the moist feeling of the surface of the obtained coating film, the marker pen-removing property, the removing property with time after leaving the marking pen at a high temperature, and the durability of repetition of writing and removing with the marker pen, for example, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, or n-dodecyl is preferable, and 2-ethylhexyl, n-decyl, or n-dodecyl is more preferable.

The specific acrylic resin may have a single structural unit having an alkyl group having 4 or more carbon atoms in a side chain, or may have two or more types.

The content of the structural unit having an alkyl group having 4 or more carbon atoms in the side chain in the specific acrylic resin is, for example, preferably 2% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less, and particularly preferably 10% by mass or more and 30% by mass or less, based on the total mass of the specific acrylic resin, from the viewpoints of the wettability of the surface of the obtained coating film, the cleanability of the coating film with a marker after being left at a high temperature, and the repeated durability of the writing and cleaning with a marker.

In view of the wettability of the surface of the obtained coating film, the marker pen removability, the removability with time after leaving the coating film at a high temperature using a marker pen, and the repeated durability of writing and removability using a marker pen, the specific acrylic resin preferably has a hydroxyalkyl group, for example, a hydroxyalkyl group having 3 or more carbon atoms, more preferably a hydroxyalkyl group having 3 or more carbon atoms and 12 or less carbon atoms, and particularly preferably a hydroxyalkyl group having 4 or more carbon atoms and 8 or less carbon atoms.

The hydroxyl group may be any of primary to tertiary hydroxyl groups, but from the viewpoint of the wettability of the surface of the obtained coating film, the marker pen-erasing property, the erasing property with time after leaving the marking pen at a high temperature, and the repeated durability of the writing and erasing with the marker pen, for example, a secondary hydroxyl group or a tertiary hydroxyl group is preferable, and a secondary hydroxyl group is more preferable.

Examples of the hydroxyl group-containing ethylenically unsaturated compound used for producing the specific acrylic resin include various hydroxyl group-containing (meth) acrylate compounds (e.g., 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, and polypropylene glycol mono (meth) acrylate), addition reaction products of the various hydroxyl group-containing (meth) acrylates with caprolactone, various hydroxyl group-containing vinyl ether compounds (e.g., 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, methyl ethyl ether, ethyl propyl ethyl ether, propyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 5-hydroxypentyl vinyl ether, and 6-hydroxyhexyl vinyl ether), addition reaction products of the various hydroxyl group-containing vinyl ethers and caprolactone, various hydroxyl group-containing allyl ether compounds (e.g., 2-hydroxyethyl (meth) allyl ether, 3-hydroxypropyl (meth) allyl ether, 2-hydroxypropyl (meth) allyl ether, 4-hydroxybutyl (meth) allyl ether, 3-hydroxybutyl (meth) allyl ether, 2-hydroxy-2-methylpropyl (meth) allyl ether, 5-hydroxypentyl (meth) allyl ether, and 6-hydroxyhexyl (meth) allyl ether), and the addition products of the various hydroxyl group-containing allyl ethers and caprolactone Reaction products, and the like.

Among these, for example, a hydroxyl group-containing (meth) acrylate compound is preferable.

The structural unit having a hydroxyl group in a side chain is, for example, preferably a structural unit having a hydroxyalkyl group in a side chain, more preferably a structural unit having a hydroxyalkyl group having 3 or more carbon atoms in a side chain, and particularly preferably a structural unit represented by the following formula (H).

[ chemical formula 2]

In the formula (H), R^H1Represents an alkylene group, R^H2Represents a hydrogen atom or a methyl group.

R of formula (H)^H1The alkylene group in (b) may be linear, branched or cyclic, but is preferably a branched alkylene group or an alkylene group having a cyclic structure, and more preferably a branched alkylene group.

In addition, from the viewpoint of the wettability of the surface of the obtained coating film, the erasing property of the marker, the erasing property with time after the marking using the marker is left at a high temperature, and the repeated durability of the writing and erasing using the marker, R in the formula (H)^HThe number of carbon atoms of 1 is, for example, preferably 2 or more, more preferably 3 or more, further preferably 3 or more and 12 or less, and particularly preferably 4 or more and 8 or less.

In addition, as-R in the formula (H)^H1OH, for example, is preferably 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 2-hydroxybutyl, 3-hydroxybutyl, 4-hydroxybutyl, 2-hydroxypentyl, 5-hydroxypentyl, 2-hydroxyhexyl, 6-hydroxyhexyl, 2-hydroxyheptyl, 7-hydroxyheptyl, 2-hydroxyoctyl or 8-hydroxyoctyl, more preferably 2-hydroxypropyl, 2-hydroxybutyl, 3-hydroxybutyl, 2-hydroxypentyl, 2-hydroxyhexyl, 2-hydroxyheptyl or 2-hydroxyoctyl, from the viewpoints of the wetness sensation on the surface of the obtained coating film, marker removability, removability with time after leaving the marking pen at a high temperature and repeated durability of writing and removal with the marker pen, particularly preferred is 2-hydroxybutyl.

The specific acrylic resin may have a single structural unit having a hydroxyl group in a side chain, or may have two or more types.

The content of the structural unit having a hydroxyl group in the side chain in the specific acrylic resin is, for example, preferably 2% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less, and particularly preferably 10% by mass or more and 30% by mass or less, based on the total mass of the specific acrylic resin, from the viewpoints of the wettability of the surface of the obtained coating film, the cleanability of the coating film with a marker after being left at a high temperature, and the repeated durability of the writing and cleaning with a marker.

The specific acrylic resin preferably further contains a structural unit having an acid group, for example, from the viewpoint of the wettability and dispersibility of the surface of the obtained coating film, particularly the dispersibility in an aqueous medium.

Examples of the acid group include a carboxyl group, a sulfo group, a phosphonic acid group, a phosphoric acid group, and a sulfuric acid group. Among them, for example, a carboxyl group is preferable.

In addition, from the viewpoint of the wet feel and dispersibility of the surface of the obtained coating film, particularly dispersibility in an aqueous medium, the specific acrylic resin preferably further has a structural unit represented by the following formula (AC), for example.

[ chemical formula 3]

In the formula (AC), R^ACRepresents a hydrogen atom or a methyl group.

The specific acrylic resin may have a single structural unit having an acid group, or may have two or more types.

The content of the structural unit having an acid group in the specific acrylic resin is, for example, preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 5% by mass or less, and particularly preferably 0.5% by mass or more and 2% by mass or less, based on the total mass of the specific acrylic resin, from the viewpoints of the wettability and dispersibility of the surface of the obtained coating film, and particularly dispersibility in an aqueous medium.

The specific acrylic resin may be a copolymer obtained by copolymerizing a vinyl compound other than the (meth) acrylic compound.

Examples of the vinyl compound include aromatic vinyl compounds, vinyl ether compounds, vinyl ester compounds, allyl compounds, olefin compounds, and the like, and for example, aromatic vinyl compounds are preferable, styrene compounds are more preferable, and styrene is particularly preferable.

That is, the specific acrylic resin is particularly preferably a styrene-acrylic copolymer, for example.

The specific acrylic resin preferably has a structural unit represented by the following formula (S), for example.

[ chemical formula 4]

From the viewpoint of the wettability of the surface of the obtained coating film, the erasing properties of the marker, the erasing properties with time after the marking using the marker is left at a high temperature, and the repeated durability of the writing and erasing using the marker, the content of the structural unit represented by the formula (S) in the specific acrylic resin is, for example, preferably 10 mass% or more and 95 mass% or less, more preferably 20 mass% or more and 90 mass% or less, further preferably 30 mass% or more and 80 mass% or less, and particularly preferably 50 mass% or more and 75 mass% or less, with respect to the total mass of the specific acrylic resin.

The weight average molecular weight of the specific acrylic resin is, for example, preferably 10,000 to 100,000, more preferably 20,000 to 80,000, and particularly preferably 30,000 to 70,000, from the viewpoint of the wettability of the surface of the obtained coating film, the erasing property of the marking pen, the erasing property with time after the marking pen is left at a high temperature, and the repeated durability of the writing and erasing by the marking pen.

The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the resin were measured by Gel Permeation Chromatography (GPC). The molecular weight measurement based on GPC was carried out in a THF solvent using GPC. HLC-8120GPC manufactured by Tosoh Corporation as a measuring apparatus and using column. TSKgel Super HM-M (15cm) manufactured by Tosoh Corporation. The weight average molecular weight and the number average molecular weight were calculated using a molecular weight calibration curve prepared from the measurement results using a monodisperse polystyrene standard sample.

The powder coating material according to the present embodiment may contain a single specific acrylic resin, or may contain two or more types.

The powder coating material according to the present embodiment may include powder particles containing only one specific acrylic resin, may include powder particles containing two or more specific acrylic resins, or may use powder particles containing different types of specific acrylic resins at the same time.

The content of the specific acrylic resin is, for example, preferably 20% by mass or more and 99% by mass or less, more preferably 30% by mass or more and 95% by mass or less, based on the total mass of the powder coating material, from the viewpoints of the wettability of the surface of the obtained coating film, the erasing property with time after the marking pen is left at a high temperature, and the repeated durability of the writing and erasing with the marking pen.

The content of the specific acrylic resin is, for example, preferably 20 to 99 mass%, more preferably 30 to 95 mass%, based on the total mass of the powder particles, from the viewpoints of the wettability of the surface of the obtained coating film, the marker pen removability, the removability with time after leaving the marking pen at a high temperature, and the repeated durability of writing and removability by the marker pen.

< curing agent >

The powder coating material according to the present embodiment contains a curing agent, and preferably contains powder particles containing a curing agent.

The curing agent is preferably a curing agent having a group that reacts with a hydroxyl group of the specific acrylic resin to cure, for example.

The curing agent is preferably a thermosetting agent, for example.

Here, the heat curing agent is a compound having a functional group capable of reacting with a hydroxyl group of the specific acrylic resin by applying heat.

Examples of the heat-curing agent include various epoxy resins (e.g., polyglycidyl ether of bisphenol a), epoxy group-containing acrylic resins (e.g., glycidyl group-containing acrylic resins), polyglycidyl ethers of various polyols (e.g., 1, 6-hexanediol, trimethylolpropane, trimethylolethane, etc.), polyglycidyl esters of various polycarboxylic acids (e.g., phthalic acid, terephthalic acid, isophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, trimellitic acid, pyromellitic acid, etc.), various alicyclic epoxy group-containing compounds (e.g., bis (3, 4-epoxycyclohexyl) methyladipate, etc.), hydroxyamides (e.g., triglycidyl isocyanurate, β -hydroxyalkylamide, etc.), and the like.

Examples of the heat-curing agent include a blocked isocyanate compound and an aminoplast.

Examples of the blocked isocyanate compound include organic diisocyanates such as various aliphatic diisocyanates (e.g., hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, etc.), various cyclic aliphatic diisocyanates (e.g., xylylene diisocyanate, isophorone diisocyanate, etc.), various aromatic diisocyanates (e.g., tolylene diisocyanate, 4' -diphenylmethane diisocyanate, etc.); adducts of these organic diisocyanates with polyols, low molecular weight polyester resins (e.g., polyester polyols), water, or the like; polymers of these organic diisocyanates with each other (polymers further containing isocyanurate type polyisocyanate compounds); a product obtained by blocking various polyisocyanate compounds such as isocyanate biuret products with a known and conventional blocking agent; self-blocked (self block) polyisocyanate compounds having a uretdione bond as a structural unit, and the like.

Among these, as the curing agent, for example, a blocked isocyanate compound is preferable, and a blocked polyisocyanate compound is more preferable, from the viewpoint of the wettability of the surface of the obtained coating film, the marker pen-clearing property, the erasing property with time after leaving the marking pen at a high temperature, and the repeated durability of the writing and erasing by using the marker pen.

The powder coating material according to the present embodiment may contain one kind of curing agent alone, or may contain two or more kinds.

The powder coating material according to the present embodiment may include powder particles containing only one kind of curing agent, may include powder particles containing two or more kinds of curing agents, or may use powder particles containing different kinds of curing agents at the same time.

The content of the curing agent is, for example, preferably 1% by mass or more and 30% by mass or less, and more preferably 3% by mass or more and 20% by mass or less, based on the content of the specific acrylic resin.

< curing catalyst >

The powder coating material according to the present embodiment contains a curing catalyst in the powder particles, and more preferably contains a curing catalyst in the core portion of the powder particles, from the viewpoint of the curing temperature and the color change at the time of forming a coating film.

The curing catalyst is not particularly limited, but is preferably at least one compound selected from the group consisting of acetylacetone metal and quaternary ammonium salts, for example. When the at least one compound is contained, the decomposition temperature of the heat-curing agent having a uretdione structure can be particularly reduced.

Specific examples of the metal acetylacetonate include aluminum acetylacetonate, chromium acetylacetonate, iron (III) acetylacetonate, zinc (II) acetylacetonate, zirconium (IV) acetylacetonate, and nickel (II) acetylacetonate.

The quaternary ammonium salt is preferably a tetraalkylammonium salt, more preferably a compound selected from the group consisting of tetraethylammonium salts and tetrabutylammonium salts, and still more preferably a compound selected from the group consisting of tetraethylammonium carboxylates, tetraethylammonium chlorides, tetraethylammonium bromides, tetraethylammonium fluorides, tetrabutylammonium carboxylates, tetrabutylammonium chlorides, tetrabutylammonium bromides, and tetrabutylammonium fluorides.

Among these, as the curing catalyst, for example, a compound selected from the group consisting of tetraethylammonium carboxylate and tetrabutylammonium carboxylate is particularly preferable.

The curing catalyst may be used alone or in combination of two or more.

The content of the curing catalyst, preferably the total content of the acetylacetone metal and the quaternary ammonium salt, is, for example, preferably 0.05 mass% to 10 mass%, more preferably 0.1 mass% to 5 mass%, based on the total mass of the powder particles. Within the above range, the color change upon formation of a coating film is less.

< coloring agent >

The powder coating material according to the present invention may contain a coloring agent, but for example, it is preferable that no white coloring agent is contained or a white coloring agent is contained.

Also, the powder particles may contain a colorant, but for example, preferably contain no or a white colorant.

Examples of the colorant include pigments. The colorant may also be a dye used in combination with the pigment.

Examples of the pigment include inorganic pigments such as iron oxide (e.g., iron sesquioxide), titanium oxide, titanium yellow, zinc white, aluminum white, zinc sulfide, lithopone, antimony oxide, cobalt blue, and carbon black; organic pigments such as quinacridone red, phthalocyanine blue, phthalocyanine green, permanent red, hansa yellow, indanthrene blue, bright fast Scarlet (Brilliant First Scarlet), benzimidazolone yellow and the like.

Examples of the pigment include a bright pigment. Examples of the glitter pigment include metallic powders such as pearl pigment, aluminum powder, and stainless steel powder; a metal sheet; glass beads; a glass sheet; mica; scaly iron oxide (MIO), and the like.

The coloring agent may be used alone or in combination of two or more.

The content of the colorant is selected according to the kind of the pigment and the color, brightness, depth, etc. required for the coating film. For example, the content of the colorant is preferably 1% by mass or more and 70% by mass or less, and more preferably 2% by mass or more and 60% by mass or less, with respect to the total resin of the core portion and the resin coating portion.

< other additives >

Examples of the other additives include various additives used in powder coating materials. Specifically, examples of the other additives include a surface conditioner (silicone oil, acrylic oligomer, and the like), a foaming (bubble) inhibitor (e.g., benzoin derivatives, and the like), a curing accelerator (e.g., amine compounds, imidazole compounds, cationic polymerization catalysts, and the like), a plasticizer, a charge control agent, an antioxidant, a pigment dispersant, a flame retardant, a flow imparting agent, and the like.

Further, as the other additive, a resin other than the specific acrylic resin may be contained, but the content thereof is, for example, preferably less than the content of the specific acrylic resin, more preferably 20 parts by mass or less with respect to 100 parts by mass of the content of the specific acrylic resin, still more preferably 10 parts by mass or less with respect to 100 parts by mass of the content of the specific acrylic resin, and particularly preferably 5 parts by mass or less with respect to 100 parts by mass of the content of the specific acrylic resin.

Other constituents of the powder particles

The powder particles may contain a metal capable of being an ion having two or more valences (hereinafter, also simply referred to as "metal ion"). The metal ions are contained in both the core portion and the resin coating portion of the powder particle. When the powder particles contain divalent or higher metal ions, ionic crosslinking based on the metal ions is formed in the powder particles. For example, when a polyester resin is used as the thermosetting resin of the core portion and the resin of the resin coating portion, a carboxyl group or a hydroxyl group of the polyester resin interacts with a metal ion to form an ionic crosslink. The ionic crosslinking can suppress leakage of powder particles, and the storage stability can be easily improved. In addition, the ionomer bonds are broken by heating at the time of thermosetting after the powder coating material is applied, and thus the melt viscosity of the powder particles is reduced, and a coating film having high smoothness is easily formed.

Examples of the metal ion include divalent or more and tetravalent or less metal ions. Specifically, the metal ion includes at least one metal ion selected from the group consisting of an aluminum ion, a magnesium ion, an iron ion, a zinc ion, and a calcium ion.

Examples of the source of the metal ion (the compound contained as the additive in the powder particles) include a metal salt, an inorganic metal salt polymer, and a metal complex. For example, when powder particles are produced by the aggregation and coagulation method, the metal salt and the inorganic metal salt polymer are added to the powder particles as a coagulant.

Examples of the metal salt include aluminum sulfate, aluminum chloride, magnesium sulfate, iron (II) chloride, zinc chloride, calcium chloride, and calcium sulfate.

Examples of the inorganic metal salt polymer include polyaluminum chloride, polyaluminum hydroxide, ferrous (II) polysulfate, calcium polysulfide, and the like.

Examples of the metal complex include metal salts of aminocarboxylic acids. Specific examples of the metal complex include metal salts (for example, calcium salts, magnesium salts, iron salts, and aluminum salts) based on known chelating agents such as ethylenediaminetetraacetic acid, propylenediaminetetraacetic acid, nitrilotriacetic acid, triethylenetetraminehexaacetic acid, and diethylenetriaminepentaacetic acid.

Further, these metal ion supply sources may be added only as additives, not for the purpose of a coagulant.

The higher the valence number of the metal ion, the more easily the network-like ionic crosslink is formed, and is preferable from the viewpoint of, for example, smoothness of the coating film and storage property of the powder coating material. Therefore, as the metal ion, for example, Al ion is preferable. That is, as the supply source of the metal ion, for example, an aluminum salt (for example, aluminum sulfate, aluminum chloride, etc.) and an aluminum salt polymer (for example, polyaluminum chloride, polyaluminum hydroxide, etc.) are preferable. In addition, from the viewpoint of smoothness of the coating film and storage property of the powder coating material, the metal ion supply source is preferably an inorganic metal salt polymer, for example, as compared with the metal salt, even if the valence number of the metal ion is the same. Therefore, as a supply source of the metal ion, an aluminum salt polymer (for example, polyaluminum chloride, polyaluminum hydroxide, or the like) is particularly preferable.

The content of the metal ion is, for example, preferably 0.002 mass% or more and 0.2 mass% or less, and more preferably 0.005 mass% or more and 0.15 mass% or less, with respect to the entire powder particles, from the viewpoint of the smoothness of the coating film and the storage property of the powder coating material.

When the content of the metal ion is 0.002 mass% or more, appropriate ionic crosslinking based on the metal ion is formed, and the leakage of the powder particles is suppressed, so that the storability of the coating material is easily improved. On the other hand, when the content of the metal ion is 0.2 mass% or less, excessive ionic crosslinking by the metal ion is suppressed, and the smoothness of the coating film is easily improved.

Here, when powder particles are produced by the aggregation-coagulation method, the supply source of metal ions (metal salt, metal salt polymer) added as a coagulant contributes to control of the particle size distribution and shape of the powder particles.

Specifically, the higher the valence number of the metal ion, the more preferable is, for example, a narrow particle size distribution. In addition, from the viewpoint of obtaining a narrow particle size distribution, for example, a metal salt polymer is preferable to a metal salt even if the valence number of the metal ion is the same. From these viewpoints, for example, an aluminum salt (for example, aluminum sulfate, aluminum chloride, etc.) and an aluminum salt polymer (for example, polyaluminum chloride, polyaluminum hydroxide, etc.) are also preferable as a source of supplying the metal ion, and an aluminum salt polymer (for example, polyaluminum chloride, polyaluminum hydroxide, etc.) is particularly preferable.

Further, when the coagulant is added so that the content of the metal ion becomes 0.002 mass% or more, the resin particles in the aqueous medium aggregate, contributing to a narrow particle size distribution. Further, the aggregated particles to be the core portion are aggregated with the resin particles to be the resin coating portion, which contributes to the realization of the resin coating portion as a whole on the surface of the core portion. On the other hand, if the aggregating agent is added so that the content of the metal ion becomes 0.2 mass% or less, excessive generation of ionic crosslinks in the aggregated particles is suppressed, and the shape of the produced powder particles tends to be close to a spherical shape when fusion-aggregation is performed. Therefore, from these viewpoints, the content of the metal ion is preferably 0.002 mass% or more and 0.2 mass% or less, and more preferably 0.005 mass% or more and 0.15 mass% or less, for example.

The content of metal ions was measured by quantitative analysis of the fluorescent X-ray intensity of the powder particles. Specifically, for example, first, a resin and a metal ion supply source are mixed to obtain a resin mixture having a known metal ion concentration. Using a tablet former having a diameter of 13mm, a sample of granules was obtained from 200mg of the resin mixture. The mass of the pellet sample was precisely measured, and the fluorescent X-ray intensity of the pellet sample was measured to determine the peak intensity. Similarly, the amount of the metal ion supplied to the particle sample was changed, and a calibration curve was prepared from the results of the measurement. Then, the content of the metal ions in the powder particles to be measured is quantitatively analyzed using the calibration curve.

Examples of the method for adjusting the content of the metal ion include 1) a method of adjusting the amount of a supply source of the metal ion, and 2) a method of adjusting the content of the metal ion by adding a coagulant (for example, a metal salt or a metal salt polymer) as a supply source of the metal ion in an aggregation step, then adding a chelating agent (for example, EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), NTA (nitrilotriacetic acid), or the like) at the end of the aggregation step, forming a complex with the metal ion by the chelating agent, and removing a complex salt formed in a subsequent cleaning step or the like, when powder particles are produced by an aggregation coagulation method.

< granule >

The powder coating material according to the present embodiment preferably further includes particles, for example.

The particles may be contained in powder particles or may be external additives. When the particles are an external additive, the occurrence of aggregation between powder particles is suppressed, and a coating film having high smoothness can be formed with a small amount of the powder coating material.

The particles include, for example, inorganic particles and organic resin particles.

The powder coating material according to the present embodiment preferably contains powder particles further containing particles, for example, and more preferably contains powder particles containing organic resin particles, from the viewpoint of the cleanability with time after the marking pen is left at a high temperature and the repeated durability of the writing and the cleaning with the marking pen.

The powder coating material according to the present embodiment preferably contains, for example, inorganic particles from the viewpoint of repeated durability of writing and erasing with a marker.

As the inorganic particles, SiO can be mentioned₂、TiO₂、Al₂O₃、CuO、ZnO、SnO₂、CeO₂、Fe₂O₃、MgO、BaO、CaO、K₂O、Na₂O、ZrO₂、CaO·SiO₂、K₂O·(TiO₂)_n、Al₂O₃·2SiO₂、CaCO₃、MgCO₃、BaSO₄、MgSO₄And the like.

The surface of the inorganic particle is preferably subjected to, for example, a hydrophobic treatment. The hydrophobization treatment is performed by, for example, immersing the inorganic particles in a hydrophobization agent. The hydrophobizing agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. These may be used alone or in combination of two or more.

The amount of the hydrophobizing agent is preferably, for example, 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the inorganic particles.

The powder coating material according to the present embodiment preferably contains organic resin particles, for example, from the viewpoint of the cleanability with time after the marking pen is left at a high temperature and the repeated durability of the writing and cleaning with the marking pen.

The organic resin particles are preferably organic resin particles containing a gel component, for example, from the viewpoint of repeated durability of writing and erasing using a marker.

From the viewpoint of repeated durability of note taking and erasing with a marker, the organic resin particles preferably contain, for example, 2 mass% or more of the gel component, more preferably 2 mass% or more and 50 mass% or less, and still more preferably 5 mass% or more and 20 mass% or less.

As a method for measuring the content of the gel component, the organic resin particles to be measured were put into an Erlenmeyer flask, and Tetrahydrofuran (THF) heated to 45 ℃ was added, sealed and left to stand for 24 hours. In this case, a constant temperature bath capable of maintaining 45 ℃ may be used. Then, the whole content of the Erlenmeyer flask was transferred to a glass tube for centrifugation, and centrifugation was carried out at 20,000rpm (revolutions per minute) and-10 ℃ for 30 minutes. After the centrifugal separation, all the contents were taken out, and after standing in a constant temperature bath at 45 ℃, the supernatant as a THF-dissolved fraction and a THF-insoluble fraction at 45 ℃ as a precipitate were separated. The THF-insoluble fraction obtained was washed with THF and dried, and the content of the gel fraction was calculated by quantitative analysis.

In view of the long-term cleanability after the marking pen is left at a high temperature, the organic resin particles are preferably crosslinked resin particles, for example.

The method for forming the crosslinked structure in the organic resin particles is not particularly limited, and for example, a method using a known crosslinking agent or the like in the production of a resin is preferable.

Among them, the organic resin particles are particularly preferably crosslinked resin particles having a gel component, for example, from the viewpoint of the removability with time after the marking pen is left at a high temperature and the repeated durability of the writing and removability with the marking pen.

The organic resin in the organic resin particles is not particularly limited, and known organic resins can be used.

Specific examples thereof include acrylic resins, epoxy resins, polyester resins, polyurethane resins, polyurea resins, and polyamide resins.

Among these, acrylic resin particles are preferable as the organic resin particles.

From the viewpoint of the fluidity of the particles, the volume average particle diameter of the particles is, for example, preferably 5nm or more and 1,000nm or less, more preferably 10nm or more and 300nm or less, still more preferably 10nm or more and 200nm or less, and particularly preferably 15nm or more and 100nm or less.

The volume average particle diameter of the particles was measured by the following method.

First, a powder coating material to be measured was observed by a Scanning Electron Microscope (SEM). Then, the equivalent circle diameters of 100 particles to be measured were obtained by image analysis, and the equivalent circle diameter at which the volume standard integration reached 50% from the smaller diameter side in the distribution of the volume standard was defined as the volume average particle diameter.

In image analysis for determining 100 circle-equivalent diameters of particles to be measured, a two-dimensional image having a magnification of 10,000 times was captured by an analyzer (ERA-8900 manufactured by ELIONIX inc., inc.), a projected area was determined under the 0.010000 μm/pixel condition by image analysis software WinROOF (manufactured by MITANI CORPORATION), and the circle-equivalent diameter was 2 × (projected area/. pi): used^1/2The circle equivalent diameter was obtained.

In addition, when the volume average particle diameter of a plurality of external additives is measured from the powder coating material, it is necessary to distinguish the external additives. Specifically, each external additive is distinguished by performing element matching using SEM-EDX (scanning electron microscope with energy dispersive X-ray analysis device) and establishing a correspondence relationship between elements derived from each external additive and the corresponding external additive.

The powder coating material according to the present embodiment may contain one kind of particles alone, or may contain two or more kinds. Further, the inorganic particles and the organic resin particles may be used together.

The content of the particles is, for example, preferably 0.01 mass% or more and 5 mass% or less, and more preferably 0.01 mass% or more and 2.0 mass% or less, based on the total mass of the powder coating material.

< Properties of powder particles and powder coating >

The volume average particle size distribution index GSDv of the powder particles is, for example, preferably 1.50 or less, more preferably 1.40 or less, and particularly preferably 1.30 or less, from the viewpoint of smoothness of the coating film and the storage property of the powder coating material.

The volume average particle diameter D of the powder particles is determined from the viewpoint of forming a coating film having high smoothness with a small amount of the powder coating material_50vFor example, it is preferably 1 μm or more and25 μm or less, more preferably 2 μm or more and 20 μm or less, and particularly preferably 3 μm or more and 15 μm or less.

From the viewpoint of smoothness of the coating film and the storage property of the powder coating material, the average circularity of the powder particles is, for example, preferably 0.95 or more, more preferably 0.96 or more, and particularly preferably 0.97 or more.

Here, the volume average particle diameter D of the powder particles_50vAnd the volume average particle size distribution index GSDv was measured using COULTERMULTISIZER II (manufactured by Beckman Coulter) and the electrolyte was measured using ISOTON-II (manufactured by Beckman Coulter).

In the measurement, a measurement sample of 0.5mg to 50mg is added as a dispersant to 2ml of a 5% by mass aqueous solution of a surfactant (for example, preferably sodium alkylbenzenesulfonate). The electrolyte is added to 100ml to 150ml of the electrolyte.

The electrolyte solution in which the sample was suspended was subjected to dispersion treatment with an ultrasonic disperser for 1 minute, and the particle size distribution of particles having a particle size in the range of 2 μm to 60 μm was measured by a coulter mulisizer II using a pore having a pore diameter of 100 μm. In addition, the number of particles sampled was 50,000.

The cumulative distribution of the volume is plotted from the small diameter side with respect to the particle size range (interval) divided based on the measured particle size distribution, and the particle size at which the cumulative 16% is defined as the volume particle size D_16vThe particle diameter at 50% in total is defined as a volume average particle diameter D_50vThe particle diameter of 84% in total is defined as a volume particle diameter D_84v。

And the volume average particle size distribution index (GSDv) is expressed as (D)_84v/D_16v)^1/2To perform the calculation.

The average circularity of the powder particles was measured by using a flow type particle image analysis device "FPIA-3000 (manufactured by sysmex corporation)". Specifically, 0.1mL to 0.5mL of a surfactant (alkylbenzene sulfonate) as a dispersant, and 0.1g to 0.5g of a measurement sample are added to 100mL to 150mL of water from which impure solids have been removed. The suspension in which the measurement sample is dispersed is subjected to a dispersion treatment with an ultrasonic disperser for 1 minute to 3 minutes, so that the dispersion concentration is 3,000 pieces/. mu.L to 1 ten thousand pieces/. mu.L. The average circularity of the powder particles was measured for the dispersion using a flow type particle image analyzer.

Here, the average circularity of the powder particles is a value obtained by obtaining the circularity (Ci) of each of the n measured particles for the powder particles and then calculating the circularity by the following equation. In the following formula, Ci represents a circularity (i.e., a circumferential length of a circle equal to a projected area of a particle/a circumferential length of a projected image of the particle), and fi represents a frequency of powder particles.

[ numerical formula 1]

The melting temperature of the powder coating material according to the present embodiment in the 1/2 method is, for example, preferably 90 ℃ to 125 ℃, and more preferably 100 ℃ to 115 ℃, from the viewpoint of smoothness of the coating film and reduction in baking temperature.

The softening point of the powder coating material was measured using a flow tester CFT-500D (manufactured by SHIMADZU CORPORATION) which is a flow characteristic evaluation device of a capillary rheometer of a constant load extrusion system, according to the guidelines attached to the device. In the present apparatus, the temperature of the measurement sample filled in the cylinder is raised and melted while applying a constant load from above the measurement sample by the piston, and the melted measurement sample is extruded from the die at the bottom of the cylinder, whereby a flow curve showing the relationship between the amount of piston drop and the temperature at that time can be obtained.

In the present embodiment, "melting temperature in 1/2 method" described in the attached guide to "flow tester CFT-500D" is used as the softening point. The melting temperature in the 1/2 method is a melting temperature calculated as follows. First, 1/2 (x.x ═ Smax-Smin)/2) is obtained as the difference between the piston descent amount Smax at the time when the outflow ends and the piston descent amount Smin at the time when the outflow starts. In the flow curve, the temperature of the flow curve at which the amount of piston descent is the sum of X and Smin is the melting temperature Tm in 1/2 method.

As the measurement sample, a sample of about 1.0g was compression-molded at about 10MPa for about 60 seconds at 25 ℃ for about 60 seconds into a cylindrical shape having a diameter of about 8mm using a tablet molding press (for example, NT-100H, manufactured by NPa SYSTEM co., ltd.).

The CFT-500D was measured under the following conditions.

Test mode: method of raising temperature

Starting temperature: 50 deg.C

Reaching the temperature: 200 deg.C

Measurement interval: 1.0 deg.C

Temperature rise rate: 4.0 ℃/min

Sectional area of piston: 1.000cm²

Test load (piston load): 10.0kgf (0.9807MPa)

Preheating time: 300 seconds

Diameter of the hole of the die: 1.0mm

Length of the die: 1.0mm

The peak temperature of the heat generation peak in the differential scanning calorimetry (DSC measurement) of the powder coating material according to the present embodiment is, for example, preferably in the range of 40 ℃ to 100 ℃, and more preferably in the range of 50 ℃ to 80 ℃ from the viewpoint of smoothness of the coating film and reduction in baking temperature.

The heat generation peak in differential scanning calorimetry (DSC measurement) was measured as follows.

A sample was set in a differential scanning calorimeter (DSC-50 type, manufactured by SHIMADZU CORPORATION) equipped with an automatic tangent processing system, liquid nitrogen was set as a refrigerant, and the sample was heated from 0 ℃ to 200 ℃ at a temperature increase rate of 10 ℃/min to obtain a DSC curve. The peak temperature of the exothermic peak on the obtained DSC curve was obtained as a measured value.

The melting temperature of a mixture of indium and zinc is used for temperature calibration of the detection section of the measuring apparatus, and the heat of fusion of indium is used for heat calibration. The sample was placed on an aluminum pan, and the aluminum pan with the sample and an empty aluminum pan for comparison were set.

[ method for producing powder coating ]

Next, a method for producing a powder coating material according to the present embodiment will be described.

The powder coating material according to the present embodiment is obtained by adding an external additive to powder particles as needed after the powder particles are produced.

The powder particles can be produced by any of a dry process (e.g., kneading and pulverizing process) and a wet process (e.g., aggregation-coagulation process, suspension polymerization process, dissolution-suspension process, etc.). The method for producing the powder particles is not limited to these methods, and a known method may be used.

Among these, for example, powder particles are preferably obtained by aggregation coagulation from the viewpoint of easily controlling the volume average particle size distribution index GSDv and the average circularity in the above ranges.

The details of each step will be described below.

In the following description, a method for producing powder particles containing a colorant will be described, but the colorant is contained as needed.

Respective dispersion preparation procedures

First, each dispersion used in the aggregation coagulation method is prepared. Specifically, a resin particle dispersion liquid in which specific acrylic resin particles are dispersed, a curing agent dispersion liquid in which a curing agent is dispersed, and a colorant dispersion liquid in which a colorant is dispersed are prepared.

Here, the resin particle dispersion liquid is prepared by, for example, dispersing resin particles in a dispersion medium with a surfactant.

Examples of the dispersion medium used in the resin particle dispersion liquid include an aqueous medium.

Examples of the aqueous medium include water such as distilled water and ion-exchanged water; alcohols, and the like. These may be used alone or in combination of two or more.

Examples of the surfactant include cationic surfactants such as sulfate esters, sulfonate salts, phosphate esters, and soaps; cationic surfactants such as amine salt type and quaternary ammonium salt type; nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, cationic surfactants and cationic surfactants are particularly exemplified. The nonionic surfactant may also be used together with the cationic surfactant or the cationic surfactant.

One kind of surfactant may be used alone, or two or more kinds may be used simultaneously.

Examples of a method for dispersing the resin particles in the dispersion medium in the resin particle dispersion include general dispersion methods such as a rotary shear homogenizer, a bead MILL with a medium, a sand MILL, and DYNO-MILL. Depending on the type of the resin particles, the resin particles may be dispersed in the resin particle dispersion liquid by, for example, a phase inversion emulsification method.

The phase inversion emulsification method is a method comprising: the resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, a base is added to the organic continuous phase (O phase) to neutralize the resin, and then an aqueous medium (W phase) is added to convert the resin from W/O to O/W (so-called phase inversion) to form a discontinuous phase, thereby dispersing the resin in the form of particles in the aqueous medium.

Specifically, for example, in the case of an acrylic resin particle dispersion, a raw material monomer is emulsified in water as an aqueous medium, a water-soluble initiator is added, and a chain transfer agent for controlling the molecular weight is added as needed, and the mixture is heated to emulsion-polymerize the mixture, thereby obtaining a resin particle dispersion in which acrylic resin particles are dispersed.

In the case of a polyester resin particle dispersion, a raw material monomer is polycondensed under heating and melting under reduced pressure, the obtained polycondensate is dissolved by adding to a solvent (for example, ethyl acetate), and a weakly alkaline aqueous solution is added to the obtained dissolved product while stirring and phase inversion emulsification are performed, thereby obtaining a resin particle dispersion in which polyester resin particles are dispersed.

In addition, in the case of obtaining a composite particle dispersion, the resin and the thermosetting agent are mixed and dispersed (for example, emulsified by phase inversion emulsification or the like) in a dispersion medium, thereby obtaining the composite particle dispersion.

The volume average particle diameter of the resin particles dispersed in the resin particle dispersion is, for example, preferably 1 μm or less, more preferably 0.01 μm or more and 1 μm or less, still more preferably 0.08 μm or more and 0.8 μm or less, and particularly preferably 0.1 μm or more and 0.6 μm or less.

Further, as for the volume average particle diameter of the resin particles, a particle size distribution obtained by measurement with a laser diffraction type particle size distribution measuring apparatus (for example, LA-700 manufactured by HORIBA, ltd.) is used, and a cumulative distribution is plotted from the small particle diameter side with respect to the volume with respect to the divided particle size range (section), and the cumulative particle diameter of 50% with respect to all the particles is measured as a volume average particle diameter D_50v. The volume average particle diameter of the particles in the other dispersions was also measured in the same manner.

The content of the resin particles contained in the resin particle dispersion is, for example, preferably 5 mass% or more and 50 mass% or less, and more preferably 10 mass% or more and 40 mass% or less.

In addition, in the same manner as the resin particle dispersion, for example, a curing agent dispersion and a coloring agent dispersion are also prepared. That is, the volume average particle diameter of the resin particles in the resin particle dispersion, the dispersion medium, the dispersion method, and the content of the particles are the same for the colorant particles dispersed in the colorant dispersion and the curing agent particles dispersed in the curing agent dispersion.

Aggregate particle formation procedure

Subsequently, the resin particle dispersion liquid, the curing agent dispersion liquid, and if necessary, the coloring agent dispersion liquid are mixed.

Then, the specific acrylic resin particles, the curing agent, and the colorant are agglomerated in the mixed dispersion to form agglomerated particles containing the specific acrylic resin, the curing agent, and the colorant, the agglomerated particles having a diameter close to the diameter of the target powder particles.

Specifically, for example, a coagulant is added to the mixed dispersion, the pH of the mixed dispersion is adjusted to be acidic (for example, pH 2 or more and 5 or less), and after a dispersion stabilizer is added as needed, the mixture is heated to a temperature of not higher than the glass transition temperature of the resin particles (specifically, for example, glass transition temperature of the resin particles is-30 ℃ or higher and glass transition temperature is-10 ℃ or lower) to aggregate the particles dispersed in the mixed dispersion, thereby forming aggregated particles.

In the aggregated particle forming step, a composite particle dispersion liquid containing the specific acrylic resin and the curing agent and a colorant dispersion liquid may be mixed, and the composite particles and the colorant may be aggregated in the mixed dispersion liquid to form aggregated particles.

In the aggregate particle formation step, for example, the flocculant may be added at room temperature (for example, 25 ℃) while the dispersion liquid is stirred and mixed by a rotary shear homogenizer to adjust the pH of the mixed dispersion liquid to acidity (for example, pH 2 or more and 5 or less), and the dispersion stabilizer may be added as necessary, followed by the heating.

Examples of the aggregating agent include a surfactant used as a dispersant to be added to the mixed dispersion liquid, a surfactant of reversed polarity, a metal salt polymer, and a metal complex. When a metal complex is used as the aggregating agent, the amount of the surfactant used can be reduced, and the charging characteristics can be improved.

After completion of aggregation, an additive that forms a complex or a similar bond with the metal ion of the coagulant may be used as needed. As the additive, for example, a chelating agent can be preferably used. By adding the chelating agent, the content of metal ions in the powder particles can be adjusted when an excessive amount of the coagulant is added.

Here, a metal salt polymer, or a metal complex as a coagulant is used as a source of metal ions. Examples of these are as already described.

Examples of the chelating agent include water-soluble chelating agents. Specific examples of the chelating agent include hydroxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA).

The amount of the chelating agent to be added is, for example, preferably 0.01 to 5.0 parts by mass, more preferably 0.1 to less than 3.0 parts by mass, based on 100 parts by mass of the resin particles.

Fusion coagulation procedure-

Next, the aggregated particle dispersion liquid in which the aggregated particles are dispersed is heated, for example, to a temperature equal to or higher than the glass transition temperature of the resin particles (for example, a temperature higher by 10 ℃ to 30 ℃ than the glass transition temperature of the resin particles) to fuse and coagulate the aggregated particles to form powder particles.

The powder particles are obtained through the above procedures.

After the completion of the fusion and coagulation step, the powder particles formed in the dispersion are subjected to a known cleaning step, a solid-liquid separation step, and a drying step to obtain powder particles in a dry state.

In the cleaning step, it is preferable to sufficiently perform substitution cleaning using ion-exchanged water, for example, from the viewpoint of charging properties. The solid-liquid separation step is not particularly limited, but it is preferable to perform suction filtration, pressure filtration, or the like from the viewpoint of productivity. Further, the method of the drying step is not particularly limited, but from the viewpoint of productivity, freeze drying, air-flow drying, fluidized drying, vibration-type fluidized drying, and the like are preferably performed.

The powder coating material according to the present embodiment is produced by, for example, adding and mixing an external additive to the obtained dry powder particles as needed. The mixing is preferably carried out by a V-blender, Henschel mixer, Rodigger mixer, or the like. In addition, coarse particles of the toner may be removed using a vibration sieve, a wind sieve, or the like as necessary.

< coated article/method for producing coated article >

The coated article according to the present embodiment is a coated article having a layer obtained by curing the powder coating material according to the present embodiment, and is preferably a coated article having a layer obtained by curing the powder coating material according to the present embodiment on an outermost layer, for example. The method for producing a coated article according to the present embodiment is a method for producing a coated article coated with the powder coating material according to the present embodiment.

Specifically, the coated article is obtained by applying a powder coating to the coating surface and then heating (baking) the powder coating to form a coating film obtained by curing the powder coating. The application and heating (baking) of the powder coating material may be performed simultaneously.

For application of the powder coating material, known application methods such as electrostatic powder application, triboelectric powder application, fluidized immersion, and the like are used. The thickness of the coating film of the powder coating material is preferably 30 μm or more and 50 μm or less, for example.

The heating temperature (baking temperature) is, for example, preferably 90 ℃ to 250 ℃, more preferably 100 ℃ to 220 ℃, and still more preferably 120 ℃ to 200 ℃. In addition, the heating time (baking time) is adjusted according to the heating temperature (baking temperature).

The object to be coated with the powder coating is not particularly limited, and examples thereof include various metal components, ceramic components, resin components, and the like. These target articles may be unmolded articles before being molded into each article, such as plate-like articles and linear articles, or molded articles for electronic components, road vehicles, building interior and exterior materials, and the like. The target article may be one having a surface treatment such as a primer treatment, a plating treatment, or an electrodeposition coating performed in advance on the surface to be coated.

Among these, as the coating material, from the viewpoint of further exhibiting the effect in the present embodiment such that the wetting feeling of the surface of the coating film is exhibited, for example, a note board or a projection board is preferable, and from the viewpoint of further exhibiting the effect in the present embodiment such that the erasing property of the marker pen, the erasing property with time after the marking pen is left at a high temperature, and the repetition durability of the writing and erasing with the marker pen are excellent, a note board is more preferable, and a projection note board is particularly preferable.

More specifically, the note board or the projection board according to the present embodiment is preferably a note board or a projection board having a layer obtained by curing a powder coating material on the outermost surface thereof, for example, and the projection note board according to the present embodiment is preferably a projection note board having a layer obtained by curing a powder coating material on the outermost surface thereof, for example.

The layer obtained by curing the powder coating material according to the present embodiment in the coated product according to the present embodiment is preferably a colorless transparent layer (colorless layer) or a white layer, for example.

The term "colorless and transparent" in the present embodiment means that the transmittance of light having a wavelength of 400nm to 750nm is 80% or more.