JP5036404B2 - Resin composition and powder coating - Google Patents

Description

  The present invention relates to a polyvinyl acetal thermosetting resin composition and a powder coating material.

  There are known thermosetting compositions, in particular adhesive compositions, in which an epoxy compound is blended with a solvent solution of polyvinyl acetal having a carboxyl group, and further fillers such as calcium carbonate and clay are blended with these (patents). Literature 1, Patent Literature 2). However, these are solvent solution-based adhesive compositions, and there is a problem that an environmental load is imposed due to the use of an organic solvent.

  Further, an adhesive composition in which a phenol resin or an epoxy compound is blended with a solvent solution of polyvinyl acetal having a carboxyl group is also known (Patent Document 3). However, this solvent solution-based adhesive composition also has a problem that an environmental load is imposed on the use of an organic solvent.

Japanese Patent Application Laid-Open No. 55-108443 (with claims, upper right column on page 3) JP-A-55-139410 (Claims, page 3, lower right column) JP 50-034389 (claims, page 1, right column, page 2, upper left column)

  The present invention solves the above-mentioned problems of the prior art, and is a thermosetting capable of providing a coating film having no environmental load due to the use of an organic solvent, excellent fluidity, and excellent solvent resistance and smoothness. It is another object of the present invention to provide a thermosetting composition, particularly a powder coating, which can form a coating film excellent in colorability by a pigment when a pigment is used in combination. It is what.

According to the present invention, the object consists of a polyvinyl acetal powder (A) having a reactive functional group and a crosslinking agent (B) powder having a functional group that reacts with the functional group, and satisfies the following conditions: It made reach by the claim 1 the thermosetting resin composition.
(1) The average particle diameter (AD) of (A) is 10 to 250 μm.
(2) The weight ratio of (B) / (A) is 0.1 / 100 to 50/100
(3) The average particle size (BD) of (B) is 2 to 150 μm
(4) | AD-BD | <100 μm

  Furthermore, an object of the present invention is that the polyvinyl acetal (A) having a reactive functional group is a polyvinyl acetal having at least one functional group selected from a carboxyl group, a carboxylate group, an amino group, and a primary hydroxyl group. Is more preferably achieved.

Furthermore, the object of the present invention is more suitably achieved by a thermosetting resin composition that further contains the pigment powder (C) in the resin composition and satisfies the following conditions.
(5) The average particle diameter (CD) of (C) is 2 to 150 μm.
(6) | AD-CD | <100 μm
(7) Weight ratio of (C) / (A) = 0.1 / 100 to 50/100

  Furthermore, the object of the present invention is more preferably achieved by the composition described above being a dry blend composition, particularly a powder coating.

  The thermosetting resin composition of the present invention has no environmental load due to the use of an organic solvent, has excellent fluidity, and can provide a coating film excellent in solvent resistance and smoothness. Furthermore, when a pigment is used in combination, since the polyvinyl acetal is excellent in transparency, a coating film excellent in colorability can be formed at low cost simply by dry blending the polyvinyl acetal with the pigment.

  Here, “excellent solvent resistance” means that a cured product obtained by heat treatment dissolves a polyvinyl acetal powder, such as ethanol, propanol, butanol, methyl ethyl ketone, dioxane, tetrahydrofuran, ethyl acetate, chloroform, dimethylformamide, It means that it is not soluble or difficult to dissolve in dimethyl sulfoxide or the like.

In addition, excellent colorability means that there is no or very little color unevenness, and does not mean whether the dispersion state of the pigment in the coating film is uniform. Moreover, being excellent in smoothness means that the coating film thickness is uniform.
Further, the thermosetting resin composition of the present invention, particularly the powder coating material, does not cause layer separation between the resin powder and the pigment powder, and the fluidity of the powder coating material is excellent. Furthermore, since polyvinyl acetal is excellent in adhesiveness with a base material, it can provide excellent adhesiveness with a base material without any pretreatment with a primer or the like, and has high hardness. A coating film can also be formed.

  In the present invention, the polyvinyl acetal having a reactive functional group preferably includes a polyvinyl acetal having at least one functional group selected from a carboxyl group, a carboxylate group, an amino group, and a primary hydroxyl group. Here, the reactive functional group means a functional group having the ability to react with a crosslinking agent. As the polyvinyl acetal having these reactive functional groups, (1) acetalized polyvinyl alcohol having these reactive functional groups, and (2) acetalized polyvinyl alcohol with an aldehyde containing these functional groups. (3) a compound obtained by reacting a hydroxyl group in polyvinyl acetal with a compound containing these reactive functional groups; (4) graft polymerization of an ethylenic saturated monomer having these functional groups with polyvinyl alcohol; Examples include acetalized ones.

As a polyvinyl alcohol having a carboxyl group or a carboxylate group (carboxylic acid group, carboxylic acid ester group) and a primary hydroxyl group, first, an unsaturated polycarboxylic acid such as an unsaturated monocarboxylic acid or an unsaturated dicarboxylic acid, or those And a vinyl alcohol copolymer using a primary hydroxyl group-containing unsaturated carboxylic acid ester as a comonomer.
As unsaturated monocarboxylic acid or its carboxylate used as a comonomer, (meth) acrylic acid, crotonic acid, oleic acid, and their carboxylates (lithium salt, sodium salt, potassium salt, magnesium salt, calcium) Salt, ammonium salt, etc.). As the unsaturated polyvalent carboxylic acid or its carboxylate used as a comonomer, unsaturated dicarboxylic acid or its salt is particularly suitable. Maleic acid, fumaric acid, itaconic acid, their carboxylate (lithium salt) Sodium salts, potassium salts, magnesium salts, calcium salts, ammonium salts, etc.), unsaturated dicarboxylic acid monoesters (such as alkyl esters such as methyl esters and ethyl esters), unsaturated dicarboxylic acid anhydrides (such as maleic anhydride) Can be mentioned. Examples of the primary hydroxyl group-containing unsaturated carboxylic acid ester used as a comonomer include hydroxyethyl (meth) acrylate.

  The unsaturated monocarboxylic acid ester used as a comonomer includes acrylic acid or a salt thereof, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, acrylic Acrylic acid esters such as i-butyl acid, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, methacrylic acid and salts thereof, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate Methacrylic acid esters such as i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate and octadecyl methacrylate.

  As a method of acetalizing polyvinyl alcohol with an aldehyde containing a reactive functional group, a method of acetalizing polyvinyl alcohol with an aldehyde containing a carboxyl group or a carboxylate group, for example, glyoxylic acid, phthalaldehyde acid, terephthalaldehyde acid , A method of acetalizing polyvinyl alcohol with an aldehyde derivative containing an amino group such as 4-aminobutyraldehyde dimethyl acetal, polyvinyl alcohol as 2-hydroxytetramethylfuran, 2-hydroxytetrahydropyran, 4-methyl-2-hydroxytetrahydro A method of acetalizing with a primary hydroxyl group-containing aldehyde derivative such as pyran is exemplified. Two or more kinds of these aldehydes or derivatives thereof may be used as necessary, or other aldehydes may be used simultaneously.

  Moreover, as a method of reacting a compound containing these reactive functional groups with a hydroxyl group in polyvinyl acetal, for example, a method of reacting a carboxylic anhydride such as maleic anhydride, itaconic anhydride, succinic anhydride, phthalic anhydride or the like , A method of reacting a compound having two or more reactive groups having different reactivities such as itaconic acid, a part of a polyfunctional compound is protected with a protecting group, then reacted with polyvinyl acetal, and then deprotected And a method of adding ethylene oxide, aziridine and the like.

  In addition, as a method of graft polymerizing an ethylenic saturated monomer having a reactive functional group to polyvinyl alcohol and acetalizing it, a carboxyl group or primary hydroxyl group such as (meth) acrylic acid, hydroxyethyl (meth) acrylate, etc. And a method of graft-polymerizing an ethylenically unsaturated monomer having a vinyl alcohol polymer in an aqueous solution of a vinyl alcohol polymer and then acetalizing. Moreover, as a polyvinyl acetal which has a primary hydroxyl group, the method of acetalizing polyvinyl alcohol using hydroxyethyl (meth) acrylate etc. as a comonomer is also mentioned.

  The content of the carboxyl group, carboxylate group, amino group or primary hydroxyl group is preferably 0.1 to 20 mol%, more preferably 0.5 to 10 mol%, relative to the main chain ethylene part of the polyvinyl acetal. It is.

  The polyvinyl acetal constituting the polyvinyl acetal powder used in the present invention is usually produced using a vinyl alcohol polymer as a raw material. The vinyl alcohol polymer can be obtained by a conventionally known method, that is, by polymerizing a vinyl ester monomer and saponifying the obtained polymer. As a method for polymerizing the vinyl ester monomer, a conventionally known method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method can be applied. As the polymerization initiator, an azo initiator, a peroxide initiator, a redox initiator, or the like is appropriately selected depending on the polymerization method. As the saponification reaction, a conventionally known alcoholysis or hydrolysis using an alkali catalyst or an acid catalyst can be applied. Among them, a saponification reaction using methanol as a solvent and a caustic soda (NAOH) catalyst is simple and most preferable.

Examples of vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, and palmitic acid. Examples thereof include vinyl, vinyl stearate, vinyl oleate, vinyl benzoate, and isopropenyl acetate, and vinyl acetate is particularly preferable.
A vinyl alcohol polymer obtained by saponifying a polymer obtained by polymerizing a vinyl ester monomer differs in the content of each unit depending on the degree of saponification. And vinyl ester units corresponding to the monomer. For example, when vinyl acetate is used as the vinyl ester monomer, the vinyl alcohol polymer obtained by the above production method includes a vinyl alcohol unit and a vinyl acetate unit.

  When the vinyl ester monomer is polymerized, other monomers, for example, α-olefins such as ethylene, propylene, n-butene and isobutylene are copolymerized within the range not detracting from the gist of the present invention. You can also.

  It does not specifically limit as an acid catalyst used for acetalization, Any of an organic acid and an inorganic acid can be used, For example, an acetic acid, paratoluenesulfonic acid, nitric acid, a sulfuric acid, hydrochloric acid etc. are mentioned. Of these, hydrochloric acid, sulfuric acid, and nitric acid are more generally used, and hydrochloric acid is particularly preferably used.

  In the present invention, it is preferable to use polyvinyl acetal acetalized with an aldehyde having 2 to 6 carbon atoms. Examples of the aldehyde having 2 to 6 carbon atoms include acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, n-hexylaldehyde, 2-ethylbutyraldehyde, and the like. The above may be used in combination. Of these, aldehydes having 4 to 6 carbon atoms, particularly n-butyraldehyde, are preferably used. By using an aldehyde having 2 to 6 carbon atoms, particularly 4 to 6 carbon atoms, a thermosetting resin composition such as a powder coating material which is an object of the present invention can be suitably obtained.

  The degree of acetalization of the polyvinyl acetal used in the present invention is preferably 40 to 85 mol%, and more preferably 50 to 85 mol%. When the degree of acetalization is in this range, the thermosetting resin such as a powder coating, which is excellent in coloration of the coating film, can give a more uniform coating thickness, and has excellent adhesion to the substrate. A composition is obtained. In order to achieve the object of the present invention more suitably, the content of vinyl ester units of polyvinyl acetal is 0.1 to 30 mol%, and the content of vinyl alcohol units is 10 to 50 mol%. Is preferred.

  Next, what is important in the present invention is that the average particle diameter (AD) of the polyvinyl acetal powder (A) having a reactive crosslinking group satisfies the condition (1) of 10 to 250 μm. By satisfying these conditions, it is possible to impart a coating film having excellent powder flowability and excellent colorability as a powder coating. The average particle size is preferably 150 μm or less, and optimally 100 μm or less. Moreover, about a lower limit, Preferably it is 20 micrometers or more.

  The method for obtaining the average particle diameter of the polyvinyl acetal powder is not particularly limited. For example, an apparatus that can be obtained by measurement by a laser diffraction method and can be used for the measurement is, for example, manufactured by Shimadzu Corporation. It can be measured by a particle size distribution measuring device SALD2200 or the like.

The polyvinyl acetal powder having such a specific particle diameter can be obtained, for example, by the following method.
First, an aqueous solution of vinyl alcohol polymer {concentration 3 to 15% by weight; the concentration is a value calculated by (weight of vinyl alcohol polymer) / (weight of vinyl alcohol polymer aqueous solution) × 100}. Adjust to 80 to 100 ° C., gradually lower the temperature over 10 to 60 minutes, and when the temperature drops to −10 to 30 ° C., add aldehyde and catalyst and keep the temperature constant for 30 to 300 minutes. The reaction proceeds and the temperature is further raised to 40 to 80 ° C. over 30 to 200 minutes, and this temperature is maintained for about 1 to 3 hours. Next, the whole is preferably cooled to room temperature, washed with water, added with a neutralizing agent (alkali, etc.) and dried to obtain the intended polyvinyl acetal powder. Further, although aggregate particles having a maximum particle diameter exceeding 250 μm are hardly generated by the above method, when aggregate particles exceeding the maximum particle diameter of 250 μm are generated, it is preferable to remove them by a filter.

  In the present invention, the degree of polymerization of polyvinyl acetal is preferably 100 to 2000, and more preferably 200 to 1500.

  Next, in the present invention, as the crosslinking agent (B) to be blended with the polyvinyl acetal powder, it is important to have a functional group that reacts with a functional group of polyvinyl acetal, preferably an epoxy group or an isocyanate group. It has a cross-linking agent. A crosslinking agent having two or more of these functional groups is preferred. Examples of the crosslinking agent having an epoxy group include glycidyl type epoxides (bisphenol type epoxides, phenol type epoxides, polyglycol type epoxides, ester type epoxides, etc.). Here, examples of the phenolic epoxide include novolak epoxide, alkylphenol diglycidyl ether, aromatic polyglycidyl, phenolphthalein epoxide, and resorcinol epoxide. Examples of the polyglycol epoxide include glycerin triglycidyl and glycol bisphenol cocondensate. Examples of ester-based epoxides include dimer acid diglycidyl ester, methacrylic acid glycidyl ester, and polymers thereof. Furthermore, as other epoxy compounds, non-glycidyl type epoxide (cyclic fatty acid group epoxide, epoxidized polybutadiene, epoxidized glyceride) and triglycidyl isocyanurate are exemplified. These crosslinker powders having an epoxy group may be used alone or in combination of two or more.

  As the crosslinking agent having an isocyanate group, a blocked isophorone diisocyanate compound is preferably used. Among them, ε-caprolactam blocked isophorone diisocyanate blocked with a blocking agent such as ε-caprolactam, or a uretdione bond type which is a self-blocking type. Isocyanates are preferred. Examples of such ε-caprolactam blocked isophorone diisocyanate include “Vestagon B1530” manufactured by Huls and “Clelan U-1” manufactured by Bayer. Examples of uretdione-bonded isocyanate include “Vestagon BF1540” manufactured by Huls.

  A crosslinking agent (B) can also be used as resin powder (crosslinking agent masterbatch) which contains a crosslinking agent in the inside or the surface. Examples of the resin used for the cross-linking agent master batch include polyvinyl acetal resin, poly (meth) acrylate resin, polystyrene resin, styrene- (meth) acrylate copolymer resin, polyester resin, polyamide resin, polycarbonate resin, Examples thereof include polyolefin resins, and preferable examples include those having good compatibility with the powder (A), and examples thereof include polyvinyl acetal resins. The cross-linking agent master batch is obtained by melt-kneading the cross-linking agent and the master batch resin and pulverizing them. The crosslinking agent is contained in an amount of 0.5 to 95% by weight, preferably 1 to 80% by weight, more preferably 5 to 70% by weight, and most preferably 10 to 60% by weight based on the resin for the masterbatch. The use of a crosslinker masterbatch is often preferred for achieving the purposes of the present invention.

  Furthermore, what is important in the present invention is that the weight ratio (B) / (A) of the condition (2), that is, the polyvinyl acetal powder (A) and the crosslinking agent (B) is 0.1 / 100 to 50/100. Is to satisfy. By satisfying these conditions, a cured product having excellent solvent resistance is obtained, and further excellent fluidity, excellent adhesion to a substrate, and excellent coating film hardness are imparted. The preferred weight ratio (B) / (A) is 1/100 to 30/100, optimally 1.5 / 100 to 25/100. Here, when the crosslinking agent powder (B) is used as a crosslinking agent master batch, the weight of the crosslinking agent powder (B) does not include the weight of the resin for the master batch.

Furthermore, in the present invention, it is a preferred embodiment that the condition (3), that is, the crosslinking agent (B) is a powder and the average particle diameter (BD) satisfies 2 to 150 μm.
When the crosslinking agent powder satisfies this condition, a cured product having excellent solvent resistance can be imparted, and further excellent fluidity can be imparted. The average particle size is preferably 130 μm or less, and optimally 100 μm or less. The lower limit of the average particle diameter is preferably 5 μm or more, and optimally 10 μm or more. The maximum particle size is preferably 250 μm or less. When the crosslinking agent is used as a pulverized product of a crosslinking agent master batch, it is preferable that the particle size of the pulverized product satisfies an average particle size (BD) of 2 to 150 μm.

  In the present invention, it is also a preferable aspect to satisfy the condition (4), that is, | AD-BD | <100 μm. By satisfying this condition, layer separation between the resin powder and the crosslinking agent does not occur, and excellent fluidity is imparted. A more preferable condition is | AD−BD | <80 μm.

  In the present invention, the pigment powder (C) is further blended with the above (A) and (B) so as to satisfy the above (5) to (7). Can be imparted, and further excellent fluidity can be imparted.

  Examples of pigment powder (C) include titanium oxide, iron oxide, red pepper, carbon black, phthalocyanine green, phthalocyanine blue, diazo yellow, quinacridone, aluminum metal and mica, light diffusing agent (glass beads, silicone, polymethyl methacrylate, etc. ), Pigment powders such as barium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, clay, talc, and the like, and it is preferable to use at least one of these powders.

  The pigment powder (C) can also be used as a resin powder (pigment masterbatch) containing a pigment inside or on the surface. The resins used in the pigment masterbatch include polyvinyl acetal resins, poly (meth) acrylate resins, polystyrene resins, styrene- (meth) acrylate copolymer resins, polyester resins, polyamide resins, polycarbonate resins, and polyolefins. Examples thereof include those having good compatibility with the powder (A), such as polyvinyl acetal resin. The pigment master batch is obtained by melt-kneading a pigment and a resin for the master batch and pulverizing them. The pigment is contained in an amount of 0.1 to 99% by weight, preferably 5 to 95% by weight, more preferably 10 to 90% by weight, and most preferably 20 to 80% by weight based on the resin for the masterbatch. The use of a pigment masterbatch is often preferred for achieving the purpose of the present invention.

Next, in the present invention, it is preferable that the average particle diameter (CD) of the pigment powder (C) which is the condition (5) satisfies 2 to 150 μm. When the pigment powder is used as a pulverized product of a pigment master batch, it is preferable that the particle size of the pulverized product satisfies an average particle size (CD) of 2 to 150 μm.
When the pigment powder satisfies this condition, excellent colorability can be imparted to the coating film, and further excellent fluidity can be imparted. The average particle diameter is more preferably 130 μm or less, and most preferably 100 μm or less. The lower limit value of the average particle diameter is preferably 5 μm or more, and optimally 10 μm or more.

  It is also preferable to satisfy the condition (6) | AD-CD | <100 μm. By satisfying these conditions, layer separation between the resin powder and the pigment powder does not occur, and excellent fluidity is imparted. A more preferable condition is | AD-CD | <80 μm.

  Furthermore, the weight ratio (7) (C) / (A) of the polyvinyl acetal powder (A) and the pigment powder (C) satisfying the condition (7) satisfies 0.1 / 100 to 50/100. Is also suitable. By satisfying these conditions, a coating film having excellent colorability can be obtained, and further excellent fluidity, excellent adhesion to a substrate, and excellent coating film hardness can be imparted. The preferred weight ratio (C) / (A) is 1/100 to 30/100, optimally 1.5 / 100 to 25/100. Here, when the pigment powder (C) is used as a pigment master batch, the weight of the pigment powder (C) does not include the weight of the resin for the master batch.

  The thermosetting resin composition of the present invention is preferably obtained by dry blending the polyvinyl acetal powders (A) and (B) or (A), (B) and (C). Examples of the method include a method in which both are uniformly mixed, for example, a method using a drive render, a Henschel mixer, a ball mill, or the like. Thus, the powder obtained by dry blending is suitable as a powder coating material.

  Moreover, in this invention, a crosslinking agent and a pigment can mix | blend a crosslinking agent and a pigment together in resin for masterbatch, melt-knead, grind | pulverize, and can also use this as a crosslinking agent-pigment masterbatch. When used as a pulverized product of a cross-linking agent-pigment masterbatch, the particle size of the pulverized product preferably satisfies an average particle size of 2 to 150 μm.

In the present invention, it is also a preferred aspect to use the polyamide resin powder (D) in combination.
Examples of polyamide-based resins include nylon-6, nylon-6,6, nylon-6 / 6,6 copolymer, nylon-9, nylon-6,10, nylon-11, nylon-12, and the like. 1 type (s) or 2 or more types are used. Among these, nylon-11 and 12 are more preferable. By using these polyamide-based resin powders in combination, it is possible to impart high impact resistance to the coating film, and furthermore, it is possible to obtain a powder coating material that is excellent in fluidity and powder-off properties. Here, “powder-off property” is an evaluation item corresponding to the amount of extra paint adhering to the surface of the base material when the powder paint is applied to the substrate surface, and is determined visually. If the powder coating powder has good powder-off properties, the amount of excess paint is small, or because there is no adhesion of excess paint, coating unevenness of coating is less likely to occur. The amount of the extra paint increases, and coating unevenness of the paint tends to occur.

  More preferably, the polyamide-based resin powder (D) has an average particle size of 10 to 250 μm or less and a maximum particle size of 250 μm. The average particle size of the polyamide resin powder is preferably 150 μm or less, and more preferably 100 μm or less. Moreover, about a lower limit, it is 20 micrometers or more suitably. For example, the polyamide resin powder can be pulverized to a desired particle size. The average particle size and the maximum particle size of the polyamide resin powder (D) are determined by the same method as the average particle size and the maximum particle size of the polyvinyl acetal (A) described above.

  In the present invention, when the polyamide resin powder is used in combination, the polyvinyl acetal powder (A) and the polyamide resin powder (D) are in a weight ratio, and (A) / (D) is 20/100 to 100/5. Preferably it is. Preferably it is 50 / 100-100 / 5, More preferably, it is 50 / 100-100 / 10.

  In the present invention, blending the inorganic fine particles (E) is also a preferred embodiment because it further improves the fluidity of the powder coating material and further improves the adhesion to the substrate and further the hardness. Here, the inorganic fine particles (E) are distinguished from pigments, and examples thereof include silica and aluminum oxide.

It is more preferable that the inorganic particles (E) have an average particle size of 1 μm or less. The average particle diameter of the inorganic particles (E) is preferably 0.5 μm or less, and more preferably 0.1 μm or less. For example, the inorganic fine particles (E) can be pulverized to have a desired particle diameter. The average particle size and the maximum particle size of the inorganic fine particles (E) are determined by the same method as the average particle size and the maximum particle size of the polyvinyl acetal (A) described above. The inorganic fine particles (E) are preferably blended in an amount of 0.0001 to 2 parts by weight, more preferably 100 parts by weight of (A) alone or a total of 100 parts by weight of (A) and (D). Is 0.001 to 1 part by weight.
Furthermore, in the present invention, an additive such as a sagging inhibitor, a surface conditioner, an ultraviolet absorber, a light stabilizer, an antioxidant, and a catalyst for promoting crosslinking can be appropriately added as additives.

  The thermosetting resin composition of the present invention, particularly the powder coating, preferably contains 50% by weight or more of the total of the above (A) and (B), more preferably 70% by weight or more. More preferably, it is 80% or more.

The thermosetting resin composition of the present invention can be applied to various applications because a cured product having excellent solvent resistance can be imparted by heat treatment (about 100 to 300 ° C.). For example, it can be applied to powder coatings, ceramic binders, photosensitive material binders, ink binders, inorganic material binders, glass films for automobiles or buildings, and among these, it is particularly suitable as a powder coating material.
When used for powder coating, it can be used in various powder coating methods. Examples of the powder coating method include a fluid dipping method, an electrostatic coating method, and a thermal spraying method. The coating temperature condition varies depending on the coating method and the MFR of the polyvinyl acetal used, but is preferably about 100 to 300 ° C.

Examples of the base material to be coated with the polyvinyl acetal powder coating of the present invention include metals such as steel pipes, steel plates, baskets, carts, and ceramics, ceramics, glass, plastics, and the like. When powder coating is applied to these metals, the surface of the substrate is degreased, phosphated, or plated as necessary to improve the adhesion to the substrate or the corrosion resistance and appearance of the coating. Alternatively, a primer application treatment such as epoxy resin may be performed.
Moreover, a coating film can also be made into a multilayered structure by apply | coating the powder coating material of this invention on the base material represented by a metal. Here, the multi-layering method is not particularly limited. For example, the method of applying the powder coating of the present invention a plurality of times, the application of the powder coating of the present invention to another powder coating, a predetermined pattern For example, a method of alternately performing a plurality of times, applying a mixture of the powder coating material of the present invention and another powder coating material, and causing phase separation upon melting on the substrate surface due to the difference in affinity between the two. Thus, a method of forming a multi-layered resin layer by a single coating can be used. Among these, the method of applying the powder coating a plurality of times is more preferable because it does not need to consider the affinity between the resins.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. In the following examples, “%” and “part” mean “% by weight” and “part by weight” unless otherwise specified.

Various physical properties of polyvinyl acetal, polyvinyl acetal powder, and pigment powder were measured according to the following methods.
(Vinyl acetate group content of polyvinyl acetal)
It was dissolved in DMSO-d6 at a concentration of 2%, and measured and calculated at 80 ° C. using 1H-NMR (manufactured by JEOL; AL400 type). The amount of modification was calculated relative to the ethylene part of the main chain of polyvinyl butyral.
(Vinyl alcohol group content of polyvinyl acetal)
It was dissolved in DMSO-d6 at a concentration of 2%, and measured and calculated at 80 ° C. using 1H-NMR (manufactured by JEOL; AL400 type). The amount of modification was calculated relative to the ethylene part of the main chain of polyvinyl butyral.
(Polyvinyl acetal modified amount of glyoxylic acid, modified amount of maleic anhydride)
It was dissolved in DMSO-d6 at a concentration of 2%, and measured and calculated at 80 ° C. using 1H-NMR (manufactured by JEOL; AL400 type). The amount of modification was calculated relative to the ethylene part of the main chain of polyvinyl butyral.

(Average particle diameter of polyvinyl acetal powder and pigment powder)
It measured using the particle size distribution analyzer SALD2200 by Shimadzu Corporation.
(Moisture content of polyvinyl acetal powder)
{(Weight of water-containing polyvinyl acetal powder−dry weight of polyvinyl acetal powder) / weight of water-containing polyvinyl acetal powder} × 100. Here, the dry weight of the polyvinyl acetal powder is a weight when the polyvinyl acetal powder is dried in a dryer at 105 ° C. for 3 hours.
(Ethanol resistance test)
A press film having a thickness of 0.2 mm was dried under reduced pressure at room temperature for 24 hours, and then 0.5 g of the press film was immersed in 100 g of ethanol and allowed to stand at 50 ° C. for 2 hours. The press film remaining in ethanol was taken out and weighed. Further, the film taken out was dried at 105 ° C. for 3 hours, and then the weight was measured (the weight of the film after drying), and the residual rate was calculated by the following equation.
(Residual rate) = (weight of film after drying) / (weight of press film before dipping) × 100 (%)
The shape of the press film remaining in ethanol was visually observed and evaluated according to the following criteria.
(Evaluation of the shape of the remaining press film)
○: The shape of the film remains.
X: No film shape remains.

Example 1
(Preparation of polyvinyl butyral)
In a glass container having an internal volume of 2 liters equipped with a reflux condenser, a thermometer and a squid type stirring blade, 1295 g of ion-exchanged water, itaconic acid-modified polyvinyl alcohol (PVA-1: polymerization degree 600, saponification degree 98 mol%, Then, the whole was heated to 95 ° C. to completely dissolve PVA to form an aqueous PVA solution (concentration 7.5% by weight). The formed PVA aqueous solution was gradually cooled to 10 ° C. over about 30 minutes while continuing to stir at a rotational speed of 120 rpm, and then the aqueous solution was added with 53 g of butyraldehyde and an acid catalyst as a butyralization catalyst at a concentration of 20 The butyralization of PVA was started by adding 90 ml of weight% hydrochloric acid. After butyralization was performed for 150 minutes, the whole was heated to 50 ° C. over 60 minutes, held at 50 ° C. for 120 minutes, and then cooled to room temperature. The resin deposited by cooling is filtered, washed with ion exchange water (100 times the amount of ion exchange water relative to the resin), held at 40 ° C. for 15 hours, and then washed again with 100 times the amount of ion exchange water. After dehydration, it was dried at 40 ° C. under reduced pressure for 18 hours to obtain itaconic acid-modified polyvinyl butyral (PVB-1) powder (water content 1.0%). The resulting powder (PVB-1) had a butyralization degree of 68 mol%, a residual acetyl group (content of vinyl acetate units) of 2 mol%, a modification degree of 1.0 mol%, and a residual hydroxyl group (vinyl alcohol unit). The content of was 29 mol%.
(Preparation of polyvinyl butyral powder)
After drying the itaconic acid-modified polyvinyl butyral powder (PVB-1) obtained as described above, using a wire mesh of 60 mesh (aperture 250 μm), particles of 250 μm or more are removed, and polyvinyl butyral powder having an average particle diameter of 85 μm (A-1) was prepared.
100 parts of the powder (A-1) and 10 parts of triglycidyl isocyanurate (TGIC, average particle size 38 μm) were mixed by a drive lender to obtain a resin powder (B-1).
(Preparation of press film)
In a state where 2.5 g of the powder (B-1) was sandwiched between polyimide films and these were further sandwiched between metal plates, using a press machine manufactured by Shinfuji Metal Industry, preheating was performed at 230 ° C. for 5 minutes, and then the temperature was changed to 230 ° C. The sample was pressed at a pressure of 100 kg / cm ² for 10 minutes. The press piece thus obtained was pressed for 2 minutes using a press cooler to obtain a press film having a thickness of 0.2 mm. The results are shown in Table 1.

Example 2
(Preparation of polyvinyl butyral)
In a glass container having an internal volume of 2 liters equipped with a reflux condenser, a thermometer and a squid type stirring blade, 1295 g of ion-exchanged water, itaconic acid-modified polyvinyl alcohol (PVA-1: polymerization degree 600, saponification degree 98 mol%, Then, the whole was heated to 95 ° C. to completely dissolve PVA to form an aqueous PVA solution (concentration 7.5% by weight). The formed PVA aqueous solution was gradually cooled to 10 ° C. over about 30 minutes while continuing to stir at a rotational speed of 120 rpm, and then the aqueous solution was added with 53 g of butyraldehyde and an acid catalyst as a butyralization catalyst at a concentration of 20 The butyralization of PVA was started by adding 90 ml of weight% hydrochloric acid. After butyralization was performed for 150 minutes, the whole was heated to 50 ° C. over 60 minutes, held at 50 ° C. for 120 minutes, and then cooled to room temperature. After filtering the resin deposited by cooling, it was washed with ion-exchanged water (50 times the amount of ion-exchanged water with respect to the resin), then added with 0.3 wt% sodium hydroxide solution for neutralization, and at 40 ° C. After holding for 10 hours, it was washed again with 50 times the amount of ion-exchanged water, dehydrated, dried for 18 hours under reduced pressure at 40 ° C., and itaconic acid-modified polyvinyl butyral (PVB-2) powder (water content) 1.0%). The resulting powder (PVB-2) had a butyralization degree of 68 mol%, a residual acetyl group (content of vinyl acetate units) of 2 mol%, a modification degree of 1.0 mol%, and a residual hydroxyl group (vinyl alcohol unit). The content of was 29 mol%.
(Preparation of polyvinyl butyral powder)
From the powder (PVB-2) obtained as described above, a powder (A-2) having an average particle diameter of 90 μm was prepared in the same manner as in Example 1. 100 parts of the powder (A-2) and 10 parts of triglycidyl isocyanurate (TGIC, average particle size 38 μm) were mixed by a drive lender to obtain a resin powder (B-2).
(Preparation of press film)
In Example 1, it carried out similarly to Example 1 except having used powder (B-2) instead of powder (B-1). The results are shown in Table 1.

Example 3
In a glass container having an internal volume of 2 liters equipped with a reflux condenser, a thermometer, and a squid type stirring blade, 1295 g of ion-exchanged water and 105 g of polyvinyl alcohol (PVA-1: polymerization degree 600, saponification degree 98 mol%). The whole was heated to 95 ° C. to completely dissolve PVA, and an aqueous PVA solution (concentration 7.5% by weight) was prepared. The aqueous PVA solution was gradually cooled to 10 ° C. over about 30 minutes while continuing to stir at a rotational speed of 120 rpm. Then, 2.5 g of glyoxylic acid, 58 g of butyraldehyde, and an acid as a butyralization catalyst were added to the aqueous solution. As a catalyst, 90 ml of hydrochloric acid having a concentration of 20% by weight was added to start butyralization of PVA. After butyralization was performed for 150 minutes, the whole was heated to 50 ° C. over 60 minutes, held at 50 ° C. for 120 minutes, and then cooled to room temperature. After filtering the resin deposited by cooling, it was washed with ion-exchanged water (50 times the amount of ion-exchanged water with respect to the resin), then added with 0.3 wt% sodium hydroxide solution for neutralization, and at 40 ° C. After holding for 10 hours, it was washed again with 50 times the amount of ion-exchanged water, dehydrated, and then dried at 40 ° C. under reduced pressure for 18 hours to obtain a polyvinyl butyral (PVB-3) powder (water content of 1. 0%) was obtained. The resulting powder (PVB-3) had a butyralization degree of 68 mol%, a residual acetyl group (content of vinyl acetate units) of 2 mol%, a modification degree of 2.0 mol%, and a residual hydroxyl group (vinyl alcohol unit). The content of was 28 mol%.
(Preparation of polyvinyl butyral powder)
From the powder (PVB-3) obtained as described above, a powder (A-3) having an average particle diameter of 75 μm was prepared in the same manner as in Example 1. 100 parts of the powder (A-3), 10 parts of triglycidyl isocyanurate (TGIC) and a drive lender were mixed to obtain a resin powder (B-3).
(Preparation of press film)
In Example 1, it carried out like Example 1 except having used powder (B-3) instead of powder (B-1). The results are shown in Table 1. The results are shown in Table 1.

Example 4
(Preparation of polyvinyl butyral porous powder)
In a glass container having an internal volume of 2 liters equipped with a reflux condenser, a thermometer, and a squid type stirring blade, 1295 g of ion-exchanged water and 105 g of polyvinyl alcohol (PVA-1: polymerization degree 600, saponification degree 98 mol%). The whole was heated to 95 ° C. to completely dissolve PVA, and an aqueous PVA solution (concentration 7.5% by weight) was formed. The formed PVA aqueous solution was gradually cooled to 10 ° C. over about 30 minutes while continuing to stir at a rotation speed of 120 rpm, and then the aqueous solution was added with 58 g of butyraldehyde and a concentration of 20 wt. 90 ml of% hydrochloric acid was added to start butyralization of PVA. After butyralization was performed for 150 minutes, the whole was heated to 50 ° C. over 60 minutes, held at 50 ° C. for 120 minutes, and then cooled to room temperature. After filtering the resin deposited by cooling, it was washed with ion-exchanged water (50 times the amount of ion-exchanged water with respect to the resin), then added with 0.3 wt% sodium hydroxide solution for neutralization, and at 40 ° C. After holding for 10 hours, it was washed again with 50 times the amount of ion-exchanged water, dehydrated, and dried at 40 ° C. under reduced pressure for 18 hours to obtain a polyvinyl butyral (PVB-4) powder (water content of 1. 0%) was obtained. The resulting PVB-4 had a butyralization degree of 68 mol%, a vinyl acetate group content of 2 mol%, and a vinyl alcohol group content of 30 mol%.

(Production of crosslinkable polyvinyl butyral porous powder)
Into a 2 L separable flask, 950 g of hexane and 50 g of methyl ethyl ketone (MEK) were added, and 200 g of PVB-4 was added and dispersed while stirring (solid content concentration 17%). 14.7 g of maleic anhydride, 3.0 g of triethylamine, and 0.1 g of 4-methoxyphenol were added, and the reaction was performed in a heterogeneous system at 25 ° C. for 5 hours. After the reaction, the product was filtered, and the obtained powder was washed with 2 L of 0.1 mol / L hydrochloric acid aqueous solution, then washed 5 times with 2 L of distilled water, dried, and modified polyvinyl butyral porous powder (water content) 1.2%). The resulting modified polyvinyl butyral porous powder had a butyralization degree of 68 mol%, a residual acetyl group (vinyl acetate unit content) of 2 mol%, a modification degree of 3.5 mol%, and a residual hydroxyl group (vinyl alcohol unit). The content of was 26.5 mol%.
(Preparation of polyvinyl butyral powder)
A powder (A-4) having an average particle diameter of 67 μm was prepared from the modified polyvinyl butyral porous powder in the same manner as in Example 1. 10 parts of triglycidyl isocyanurate (TGIC, average particle diameter of 38 μm) was mixed with 100 parts of the powder (A-4) by a drive lender to obtain a resin powder (B-4).
(Preparation of press film)
In Example 1, it carried out similarly to Example 1 except having used powder (B-4) instead of powder (B-1). The results are shown in Table 1.

Example 5
100 parts of polyvinyl acetal (manufactured by Kuraray Europe GmBH: Mowital B30H average particle size 98 μm) is mixed with 10 parts of triglycidyl isocyanurate (TGIC) with a drive renderer, kneaded with an extruder, pulverized, and classified with 60 mesh To obtain a powder (MB-1) (crosslinking agent master batch) having an average particle size of 85 μm.
Next, 100 parts of the powder (A-1) was mixed with 20 parts of the powder (MB-1) obtained above by a drive render to obtain a resin powder (A′-1).
(Preparation of press film)
In Example 1, it carried out like Example 1 except having used powder (A'-1) instead of powder (B-1). The results are shown in Table 1.

Example 6
100 g of the powder (B-1) obtained in Example 1 was kneaded with an extruder, then pulverized and classified with 60 mesh to obtain a powder (B′-1) having an average particle diameter of 85 μm.
(Preparation of press film)
In Example 1, it carried out similarly to Example 1 except having used powder (B'-1) instead of powder (B-1). The results are shown in Table 1.

Example 7
100 parts of powder (A-1), 10 parts of triglycidyl diisocyanurate (TGIC) and pigment powder {"Iriodin 100 Silver Pearl" (pearl pigment) manufactured by Merck & Co., Inc. (average particle size 35 μm, 5 parts) (no particles having a particle diameter of 250 μm or more) were mixed by a drive renderer to obtain a powder (C-1).
Coating and coating film evaluation were performed as follows. The results are shown in Table 2 (Coating of base material using powder paint)
The surface of a 0.8 mm (thickness) × 50 mm × 100 mm stainless steel plate (SAS304) was washed with a detergent and degreased, and then thoroughly washed with ion-exchanged water to obtain a substrate. The base material was coated by powder dipping method using powder (C-1). Polyvinyl butyral powder flows into a container equipped with a perforated plate and a cylindrical coating chamber (flow chamber) (height 50 cm, diameter 30 cm), and air is blown into the coating chamber through the perforated plate. I let you. The substrate made of the stainless steel plate is preheated (temperature 230 ° C., 10 minutes), suspended in a fluidized bed of polyvinyl butyral powder, taken out after 10 seconds, and heated at 230 ° C. for 10 minutes. To obtain a painted product.
(Flowability of polyvinyl butyral powder)
The flowability of the polyvinyl butyral powder in the coating chamber was evaluated according to the following criteria. The results are shown in Table 2.
○: Polyvinyl butyral powder flows uniformly.
Δ: The polyvinyl butyral powder flows, but the state is uneven.
X: The whole polyvinyl butyral powder does not flow, and air is ejected from a part of the powder surface.
(Colorability of coating film)
The colorability of the coating film applied to the substrate was visually evaluated according to the following criteria.
○: No unevenness in the colored state.
Δ: Some unevenness is observed.
X: The whole surface is a madara pattern.
(Uniformity of coating thickness)
The uniformity of the thickness of the coating film formed on the surface of the substrate was evaluated according to the following method. The results are shown in Table 2.
For one sample, the thickness of the coating film was measured at five points to determine the average value, and the difference between the maximum value and the minimum value with respect to the average value was expressed in%. The lower the value, the higher the uniformity of the coating thickness.
○: Less than 20% ×: 20% or more (ethanol resistance test of coating film)
The coating film portion of the coated plate was wiped with a cloth moistened with ethanol five times, and the state of the coating film surface was visually evaluated according to the following criteria.
○: No change in coating film surface.
X: The surface of the coating film was dissolved, and there was a change in the coating film (a trace residue, pigment adhesion)

Example 8
To 100 parts of powder (A-1), 10 parts of triglycidyl isocyanurate, 5 parts of pigment {“Toka Carbon # 7100F” (carbon black) manufactured by Tokai Carbon Co., Ltd., average particle size 42 μm} are added, and the drive After mixing with a renderer, the mixture was kneaded and pulverized with an extruder, and classified with a 60 mesh to obtain a powder (C′-1) having an average particle size of 80 μm.
The obtained powder (C′-1) was powder coated in the same manner as in Example 7. Table 2 shows the evaluation results of the obtained coating film.

Example 9
To 100 parts of polyvinyl acetal (manufactured by Kuraray: Mowital B30H average particle size 102 μm), 20 parts of “Toka Carbon # 7100F” (carbon black) manufactured by Tokai Carbon Co., Ltd. is added, mixed by a drive renderer, and then kneaded by an extruder. After pulverization and classification with 60 mesh, a resin powder (MB-2) having an average particle size of 80 μm was obtained.
Next, 10 parts of triglycidyl isocyanurate and 10 parts of the above-obtained powder (MB-2) are mixed with a drive lender to 100 parts of the powder (A-1) to obtain a resin powder (C ′ -2) was obtained.
Powder coating was performed in the same manner as in Example 7 with the obtained powder (C′-2). Table 2 shows the evaluation results of the obtained coating film.

Example 10
In the preparation of the powder coating material of Example 1, powder (B-5) was obtained in the same manner as in Example 1 except that 5 parts of triglycidyl isocyanurate was used instead of 10 parts of triglycidyl isocyanurate.
Powder coating was performed in the same manner as in Example 7 with the obtained powder (B-5). Table 2 shows the evaluation results of the obtained coating film.

Example 11
100 parts of powder (A-2), 10 parts of triglycidyl isocyanurate, and further pigment powder {“Iriodin 100 Silver Pearl” (pearl pigment) (Merck Co., Ltd.) (average particle size 35 μm, particle size 250 μm) 5 parts (without the above particles) were mixed by a drive renderer to obtain a powder (C-2).
Powder coating was performed in the same manner as in Example 7 with the obtained powder (C-2). Table 2 shows the evaluation results of the obtained coating film.

Example 12
10 parts of triglycidyl isocyanurate with respect to 100 parts of powder (A-3), and further pigment powder {"Iriodin 100 Silver Pearl" (pearl pigment) manufactured by Merck & Co., Inc. (average particle size: 35 μm, particle size: 250 μm) 5 parts (without the above particles) were mixed by a drive renderer to obtain a powder paint (C-3).
The obtained powder (C-3) was powder coated in the same manner as in Example 7. Table 2 shows the evaluation results of the obtained coating film.

Example 13
100 parts of powder (A-4), 10 parts of triglycidyl isocyanurate, and pigment powder {“Iriodin 100 Silver Pearl” (pearl pigment) (Merck Co., Ltd.) (average particle size 35 μm, particle size 250 μm) 5 parts (without the above particles) were mixed by a drive renderer to obtain a powder paint (C-4).
Powder coating was performed in the same manner as in Example 7 with the obtained powder (C-4). Table 2 shows the evaluation results of the obtained coating film.

Comparative Example 1
After drying the polyvinyl butyral powder (PVB-4: unmodified) prepared in Example 4, particles of 250 μm or more were removed using a 60-mesh (mesh 250 μm) wire mesh (powder having an average particle diameter of 72 μm ( A-5) was prepared.
A powder (B-6) was obtained in the same manner as in Example 1 except that the powder (A-5) was used instead of the powder (A-1) in Example 1.
The obtained powder coating material was evaluated in the same manner as in Example 1. Table 1 shows the evaluation results of the obtained coating film.

Comparative Example 2
10 parts of triglycidyl isocyanurate obtained in (A-5) obtained in Comparative Example 1 and further pigment powder {“Iriodin 100 Silver Pearl” (pearl pigment) (Merck Co., Ltd.) (average particle size: 35 μm, particle size: 250 μm) 5 parts (without the above particles) were mixed by a drive renderer to obtain a powder paint (C-5).
Powder coating was performed in the same manner as in Example 7 with the obtained powder coating material (C-5). Table 2 shows the evaluation results of the obtained coating film.

Comparative Example 3
A powder (B-6) was prepared in the same manner as in Example 1, except that 55 parts of triglycidyl isocyanurate was used instead of 5 parts of triglycidyl isocyanurate.
Powder coating was performed in the same manner as in Example 7 with the obtained powder (B-6). Table 2 shows the evaluation results of the obtained coating film.

Comparative Example 4
A powder (B-7) was prepared in the same manner as in Example 1, except that 0.05 part of triglycidyl isocyanurate was used instead of 5 parts of triglycidyl isocyanurate. Powder coating was performed in the same manner as in Example 7 with the obtained powder (B-7). Table 2 shows the evaluation results of the obtained coating film.

  The thermosetting resin composition of the present invention can provide a coating film excellent in solvent resistance by heat treatment, and forms a coating film excellent in colorability at low cost by using a pigment in combination. Furthermore, since it has excellent fluidity, it can be used for a wide range of applications. For example, it can be applied to powder coatings, ceramic binders, photosensitive material binders, ink binders, inorganic material binders, glass films for automobiles or buildings, and among these, it is particularly suitable as a powder coating material.

Claims (8)

A thermosetting resin composition comprising a polyvinyl acetal powder having a functional group (A) and a crosslinking agent (B) powder having a functional group that reacts with the functional group, and satisfying the following conditions.
(1) The average particle diameter (AD) of (A) is 10 to 250 μm.
(2) The weight ratio of (B) / (A) is 0.1 / 100 to 50/100
(3) The average particle size (BD) of (B) is 2 to 150 μm
(4) | AD-BD | <100 μm The thermosetting resin according to claim 1, wherein the polyvinyl acetal (A) having a reactive functional group is a polyvinyl acetal having at least one functional group selected from a carboxyl group, a carboxylate group, an amino group, and a primary hydroxyl group. Composition. The thermosetting resin composition according to claim 1 or 2 , wherein the crosslinking agent (B) is a crosslinking agent having an epoxy group or an isocyanate group. The thermosetting resin composition according to any one of claims 1 to 3 , comprising the pigment powder (C) and satisfying the following conditions.
(5) The average particle diameter (CD) of (C) is 2 to 150 μm.
(6) | AD-CD | <100 μm
(7) The weight ratio of (C) / (A) is 0.1 / 100 to 50/100 The thermosetting resin composition according to any one of claims 1 to 4 , wherein the thermosetting resin composition is a dry blend composition. The thermosetting property according to any one of claims 1 to 5 , wherein the polyvinyl acetal constituting (A) is a polyvinyl acetal obtained by acetalizing a vinyl alcohol polymer with an aldehyde having 2 to 6 carbon atoms. Resin composition. The heat according to claim 4 , wherein the pigment powder (C) is at least one selected from titanium oxide, iron oxide, red pepper, carbon black, phthalocyanine green, phthalocyanine blue, diazo yellow, quinacridone, aluminum metal and mica. Curable resin composition. Powder coating made of a thermosetting resin composition according to any one of claims 1-7.