JP7272274B2 - Method for producing powders, powder coatings and laminates - Google Patents

Description

TECHNICAL FIELD The present invention relates to a powder containing fine particles, a powder coating, and a method for producing a laminate.

Fluoropolymers such as copolymers (PFA) having units based on tetrafluoroethylene and units based on perfluoro(alkyl vinyl ether) have a low friction coefficient and excellent properties such as non-stickiness, chemical resistance, and heat resistance. . Therefore, fluoropolymers are widely used for surface finishing of food industrial products, kitchen utensils such as frying pans and pots, household products such as irons, electrical industrial products, mechanical industrial products, and the like.

Patent Literature 1 discloses a method of obtaining a laminate by coating a substrate with a powder coating containing powder composed of fluoropolymer particles and baking the coating to form a fluororesin layer. Patent Document 2 discloses a powder composed of fluoropolymer particles having a functional group such as a carbonyl group-containing group as a powder having excellent adhesiveness to a substrate.

WO2011/048965 WO2016/017801

However, unless the particle diameter of the resin particles constituting the powder is adjusted, irregularities are likely to occur on the surface of the formed fluororesin layer. In particular, the present inventors have found that such a phenomenon becomes remarkable when a powder composed of resin particles containing a fluoropolymer having a high melting point is baked to form a fluororesin layer.
An object of the present invention is to provide a powder that can easily form a fluororesin layer with a smooth surface, a powder coating containing the powder, and a method for producing a laminate using the powder coating.

The present invention has the following aspects.
<1> A powder composed of resin particles containing a fluoropolymer having a unit based on tetrafluoroethylene and having a melting point of 260 to 320° C.,
A powder in which Y/X is 0.3 or less, where X is a volume-based cumulative 50% diameter and Y is a volume-based cumulative 10% diameter.
<2> The powder of <1> having a volume-based cumulative 10% diameter of 4 μm or less and a volume-based cumulative 50% diameter of 15 to 60 μm.
<3> When A is the amount of resin particles with a particle diameter of 4 μm or less contained in the powder, and B is the amount of resin particles with a particle diameter of 15 to 60 μm, A/B is 0.1 or more. Yes, the powder of <2>.
<4> The powder of <2> or <3>, wherein the amount of the resin particles having a particle diameter of 4 μm or less contained in the powder is 5 to 25% by volume.
<5> The powder according to any one of <1> to <4>, wherein the volume-based cumulative 100% diameter is 220 μm or less.
<6> The powder according to any one of <1> to <5>, wherein the fluoropolymer has at least one functional group selected from the group consisting of carbonyl-containing groups, hydroxyl groups, epoxy groups and isocyanate groups.
<7> The powder of <6>, wherein the fluoropolymer has the tetrafluoroethylene-based unit and the functional group-containing unit.
<8> A powder coating containing the powder according to any one of <1> to <7>.
<9> The powder coating of <8>, wherein the amount of the powder contained in the powder coating is 90 to 100% by mass.
<10> A method for producing a laminate having a base material and a fluororesin layer provided on the base material and formed from the powder according to any one of <1> to <7>,
A method for producing a laminate, wherein a powder coating containing the powder is supplied onto the substrate and baked to obtain the fluororesin layer.
<11> The manufacturing method of <10>, wherein the powder coating is baked by heating to a melting point of the fluoropolymer or higher.
<12> The manufacturing method of <10> or <11>, wherein the fluororesin layer has a thickness of 50 to 750 μm.

According to the present invention, a fluororesin layer having a smooth surface can be easily formed.

FIG. 4 is a diagram for explaining state changes when forming a fluororesin layer using the powder of the present invention. It is a figure for demonstrating the state change at the time of forming a fluororesin layer using the conventional powder.

The following term definitions apply throughout the specification and claims.
The term “hot-melt polymer” means a polymer that has a MFR of 0.01 to 1000 g/10 minutes at a temperature 20° C. or more higher than the melting point of the polymer under a load of 49 N.
"Melting point of polymer" means the temperature corresponding to the maximum melting peak of the polymer as measured by differential scanning calorimetry (DSC).
"Polymer MFR" is the melt mass flow rate defined in JIS K 7210-1:2014 (corresponding international standard ISO 1133-1:2011).
"Powder volume-based cumulative 50% diameter (D50)" measures the particle size distribution of powder by a laser diffraction / scattering method, obtains a cumulative curve with the total volume of powder as 100%, and on the cumulative curve It is the particle diameter at the point where the cumulative volume is 50%.
Similarly, "powder volume-based cumulative 10% diameter (D10)", "powder volume-based cumulative 90% diameter (D90)" and "powder volume-based cumulative 100% diameter (D100)" A reference cumulative 10% diameter, a volume-based cumulative 90% diameter, and a volume-based cumulative 100% diameter (maximum particle diameter).
That is, D10, D50, D90 and D100 of the powder are the volume-based cumulative 10% diameter, the volume-based cumulative 50% diameter, the volume-based cumulative 90% diameter and the volume-based cumulative 100% diameter of the particles constituting the powder. .
"A unit based on a monomer" is a general term for an atomic group directly formed by polymerization of one molecule of a monomer and an atomic group obtained by chemically converting a part of this atomic group. In this specification, units based on monomers are also simply referred to as “units”.
"(Meth)acrylate" is a generic term for acrylate and methacrylate. Similarly, "(meth)acrylic acid" is a generic term for acrylic acid and methacrylic acid, and "(meth)acryloyloxy group" is a generic term for acryloyloxy group and methacryloyloxy group.

The resin particles constituting the powder of the present invention are fluoropolymers having units based on tetrafluoroethylene (hereinafter also referred to as “TFE units”) and having a melting point of 260 to 320° C. (hereinafter referred to as “F polymer”). Also referred to as ).
The amount of the F polymer contained in the resin particles is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. By using the powder composed of resin particles containing the F polymer in such an amount, the non-adhesiveness, chemical resistance and heat resistance of the formed fluororesin layer (hereinafter also referred to as "F resin layer") are improved. Two or more F polymers may be used in combination.
Other polymers include fluoropolymers other than F polymer, aromatic polyesters, polyamideimides, and thermoplastic polyimides. Other polymers may be used in combination of two or more.

F polymers include tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylene copolymer, A polymer into which at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxy group, an epoxy group and an isocyanate group (hereinafter also referred to as "adhesive group") is introduced, modified polytetrafluoroethylene is mentioned. Polytetrafluoroethylene can also be used as the F polymer as long as it exhibits thermal melting properties.

Modified polytetrafluoroethylene includes (i) a copolymer of tetrafluoroethylene (hereinafter also referred to as “TFE”) and a very small amount of CH ₂ =CH(CF ₂ ) ₄ F, (ii) the above (i) A copolymer of a copolymer and a monomer having a very small amount of adhesive group (hereinafter also referred to as an "adhesive monomer"), (iii) a copolymer of TFE and a very small amount of an adhesive monomer, (iv) plasma treatment (v) the above copolymer (i) into which an adhesive group is introduced by plasma treatment or the like.

The melting point of the F polymer is 260 to 320°C, preferably 280 to 320°C, more preferably 295 to 315°C, even more preferably 295 to 310°C. If the melting point of the F polymer is equal to or higher than the above lower limit, the heat resistance of the F resin layer is enhanced. If the melting point of the F polymer is equal to or less than the above upper limit, the thermal meltability of the F polymer is improved.
The melting point of the F polymer can be adjusted by the type and ratio of units constituting the F polymer, the molecular weight of the F polymer, and the like. For example, the higher the proportion of TFE units, the higher the melting point of the F polymer tends to be.

The MFR at a temperature 20° C. or more higher than the melting point of the F polymer is preferably 0.1 to 1000 g/10 minutes, more preferably 0.5 to 100 g/10 minutes, still more preferably 1 to 30 g/10 minutes, and 5 to 20 g/10 min is particularly preferred. When the MFR is at least the above lower limit, the heat meltability of the F polymer is further improved, and the appearance of the F resin layer is improved. If the MFR is equal to or less than the above upper limit, the mechanical strength of the F resin layer increases.
The MFR is a measure of the molecular weight of the F polymer. A large MFR indicates a small molecular weight, and a small MFR indicates a large molecular weight. The MFR of the F polymer can be adjusted by the manufacturing conditions of the F polymer. For example, shortening the polymerization time during polymerization of the monomer tends to increase the MFR of the F polymer.

As the adhesive group, a carbonyl group-containing group is preferable from the viewpoint of excellent adhesiveness between the F resin layer and the base material.
Examples of carbonyl group-containing groups include hydrocarbon groups having a carbonyl group between carbon atoms, carbonate groups, carboxy groups, haloformyl groups, alkoxycarbonyl groups, acid anhydride residues (--C(O)--O--C(O) -), polyfluoroalkoxycarbonyl groups, and fatty acid residues.
As the carbonyl group-containing group, a hydrocarbon group having a carbonyl group between carbon atoms, a carbonate group, a carboxy group, a haloformyl group, an alkoxycarbonyl group and an acid Anhydride residues are preferred, carboxy groups and anhydride residues are more preferred.
Examples of the hydrocarbon group in the hydrocarbon group having a carbonyl group between carbon atoms include an alkylene group having 2 to 8 carbon atoms. The number of carbon atoms in the alkylene group does not include the number of carbon atoms forming the carbonyl group.
Haloformyl groups include -C(=O)-F and -C(=O)Cl.
The alkoxy group in the alkoxycarbonyl group includes a methoxy group and an ethoxy group.

The adhesive group may be contained as an adhesive unit in the F polymer, or may be contained as a terminal group at the end of the main chain of the F polymer. In addition, when an adhesive group is included as a terminal group of the main chain, the F polymer may or may not include an adhesive unit.
The F polymer preferably contains TFE units and units based on adhesive monomers (adhesive units).
The number of adhesive groups possessed by the adhesive monomer may be one or two or more. When having two or more adhesive groups, the two or more adhesive groups may be the same or different.

Examples of adhesive monomers include monomers having a carbonyl group-containing group, monomers having a hydroxyl group, monomers having an epoxy group, and monomers having an isocyanate group. As the adhesive monomer, a monomer having a carbonyl group-containing group is preferable from the viewpoint of excellent adhesiveness between the F resin layer and the base material.
Examples of monomers having a carbonyl group-containing group include cyclic monomers having an acid anhydride residue, monomers having a carboxy group, vinyl esters, (meth)acrylates, CF ₂ =CFOR ^f1 CO ₂ X ¹ (where R ^f1 is a perfluoroalkylene group having 1 to 10 carbon atoms, or a perfluoroalkylene group having 2 to 10 carbon atoms having an etheric oxygen atom between carbon atoms, and X ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms ).

Cyclic monomers having acid anhydride residues include unsaturated dicarboxylic acid anhydrides. Examples of unsaturated dicarboxylic anhydrides include itaconic anhydride (hereinafter also referred to as "IAH"), citraconic anhydride (hereinafter also referred to as "CAH"), 5-norbornene-2,3-dicarboxylic anhydride ( Also known as: Himic anhydride (hereinafter also referred to as "NAH"), and maleic anhydride.
Monomers having a carboxy group include unsaturated dicarboxylic acids (itaconic acid, citraconic acid, 5-norbornene-2,3-dicarboxylic acid, maleic acid, etc.), unsaturated monocarboxylic acids (acrylic acid, methacrylic acid, etc.). be done.
Vinyl esters include vinyl acetate, vinyl chloroacetate, vinyl butanoate, vinyl pivalate, vinyl benzoate, and vinyl crotonate.
(Meth)acrylates include (polyfluoroalkyl)acrylates and (polyfluoroalkyl)methacrylates.

As the monomer having a carbonyl group-containing group, a cyclic monomer having an acid anhydride residue is preferable, and IAH, CAH or NAH is more preferable, from the viewpoint of further improving the adhesion between the F resin layer and the base material. The use of IAH, CAH or NAH facilitates the easy preparation of F polymers with anhydride residues. As the monomer having a carbonyl group-containing group, NAH is particularly preferable because the adhesiveness of the F resin layer is likely to increase.

Examples of monomers having a hydroxy group include vinyl esters having a hydroxy group, vinyl ethers having a hydroxy group, allyl ethers having a hydroxy group, (meth)acrylates having a hydroxy group, hydroxyethyl crotonate, and allyl alcohol.
Monomers having an epoxy group include unsaturated glycidyl ethers (allyl glycidyl ether, 2-methylallyl glycidyl ether, vinyl glycidyl ether, etc.) and unsaturated glycidyl esters (glycidyl (meth)acrylate, etc.).
Monomers having an isocyanate group include 2-(meth)acryloyloxyethyl isocyanate, 2-(2-(meth)acryloyloxyethoxy)ethyl isocyanate, and 1,1-bis((meth)acryloyloxymethyl)ethyl isocyanate. be done.
Adhesive monomers may be used in combination of two or more.

Units other than adhesive units and TFE units include units based on perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE") (hereinafter also referred to as "PAVE units"), hexafluoropropylene (hereinafter referred to as Also referred to as "HFP")-based units (hereinafter also referred to as "HFP units"), adhesive monomers, and units based on monomers other than TFE, PAVE and HFP.

PAVE includes CF ₂ =CFOCF ₃ , CF ₂ =CFOCF ₂ CF ₃ , CF ₂ =CFOCF ₂ CF ₂ CF ₃ (hereinafter also referred to as “PPVE”), CF ₂ =CFOCF ₂ CF ₂ CF ₂ CF ₃ , _CF2 =CFO( _CF2 ) _8F is mentioned, with PPVE being preferred.
PAVE may use 2 or more types together.

Other monomers include other fluorine-containing monomers (excluding adhesive monomers, TFE, PAVE and HFP) and other non-fluorine-containing monomers (excluding adhesive monomers).
Other fluorine-containing monomers include vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, CF ₂ ═CFOR ^f3 SO ₂ X ³ (where R ^f3 is a perfluoroalkylene group having 1 to 10 carbon atoms). , or a perfluoroalkylene group having 2 to 10 carbon atoms having an etheric oxygen atom between carbon atoms, and X ³ is a halogen atom or a hydroxy group.), CF ₂ =CF(CF ₂ ) _p OCF=CF ₂ (provided that p is 1 or 2), CH ₂ =CX ⁴ (CF ₂ ) _q X ⁵ (provided that X ⁴ is a hydrogen atom or a fluorine atom, q is an integer of 2 to 10, and X ⁵ is a hydrogen atom or a fluorine atom.) and perfluoro(2-methylene-4-methyl-1,3-dioxolane). Other fluorine-containing monomers may be used in combination of two or more.
As _CH2 = ^CX4 ( _CF2 ) _qX5 , _CH2 =CH( _{CF2 )} ^2F , _CH2 =CH( _CF2 ) _3F , _CH2 =CH( _CF2 ) _4F , _CH2 ═CF(CF ₂ ) ₃ H, CH ₂ ═CF(CF ₂ ) ₄ H, preferably CH ₂ ═CH(CF ₂ ) ₄ F, CH _{2 ═CH} (CF ₂ ) ₂ F.

Other non-fluorine-containing monomers include ethylene and propylene, with ethylene being preferred. Other non-fluorine-containing monomers may be used in combination of two or more.
As other monomers, other fluorine-containing monomers and other non-fluorine-containing monomers may be used in combination.

When the F polymer has an adhesive group as a terminal group at the end of the main chain, the adhesive group is preferably an alkoxycarbonyl group, a carbonate group, a carboxy group, a fluoroformyl group, an acid anhydride residue, or a hydroxy group. Such an adhesive group can be introduced by appropriately selecting a radical polymerization initiator, a chain transfer agent, and the like, which are used in the production of the F polymer.

As the F polymer, from the viewpoint of increasing the heat resistance of the F resin layer, a copolymer having an adhesive unit, a TFE unit and a PAVE unit (hereinafter also referred to as copolymer (A1)), an adhesive unit, a TFE unit and an HFP unit. (hereinafter also referred to as copolymer (A2)) is preferred, and copolymer (A1) is more preferred.

Copolymer (A1) may optionally have at least one of HFP units and other units. That is, copolymer (A1) may be a copolymer comprising adhesive units, TFE units and PAVE units, a copolymer comprising adhesive units, TFE units, PAVE units and HFP units, or a copolymer comprising adhesive units, TFE units and It may be a copolymer having PAVE units and other units, or it may be a copolymer having adhesive units, TFE units, PAVE units, HFP units and other units.
As the copolymer (A1), a copolymer having a unit based on a monomer having a carbonyl group-containing group, a TFE unit and a PAVE unit is preferable from the viewpoint of further increasing the adhesiveness between the F resin layer and the base material, and an acid anhydride. Copolymers having units based on cyclic monomers with residues, TFE units and PAVE units are more preferred.
Preferred specific examples of the copolymer (A1) are copolymers having TFE units, PPVE units and NAH units, copolymers having TFE units, PPVE units and IAH units, copolymers having TFE units, PPVE units and CAH units. mentioned.
The proportion of the adhesive units in the copolymer (A1) is preferably 0.01 to 3 mol %, more preferably 0.05 to 1 mol %, of the total units constituting the copolymer (A1). In this case, it is easy to balance the adhesiveness between the F resin layer and the base material, the heat resistance of the F resin layer, and the color.
The proportion of TFE units in the copolymer (A1) is preferably 90 to 99.89 mol%, more preferably 96 to 98.95 mol%, of the total units constituting the copolymer (A1). In this case, it is easy to balance the heat resistance, chemical resistance, etc. of the F resin layer with the thermal meltability, stress crack resistance, etc. of the copolymer (A1).
The proportion of PAVE units in the copolymer (A1) is preferably 0.1 to 9.99 mol%, more preferably 1 to 9.95 mol%, of the total units constituting the copolymer (A1). In this case, it is easy to adjust the thermal meltability of the fluorocopolymer (A1).
The total amount of adhesive units, TFE units and PAVE units in the copolymer (A1) is preferably 90 mol% or more, more preferably 98 mol% or more. Its upper limit is 100 mol %.

Copolymer (A2) may optionally have PAVE units and/or other monomer units. That is, the copolymer (A2) may be a copolymer comprising adhesive units, TFE units and HFP units, a copolymer comprising adhesive units, TFE units, HFP units and PAVE units, or a copolymer comprising adhesive units, TFE units and It may be a copolymer having HFP units and other monomeric units, or it may be a copolymer having adhesive units, TFE units, HFP units, PAVE units and other units.
The copolymer (A2) is preferably a copolymer having a unit based on a monomer having a carbonyl group-containing group, a TFE unit, and an HFP unit, from the viewpoint of further increasing the adhesiveness between the F resin layer and the base material. Copolymers having units based on cyclic monomers with residues, TFE units and HFP units are more preferred.
Preferred specific examples of the copolymer (A2) are copolymers having TFE units, HFP units and NAH units, copolymers having TFE units, HFP units and IAH units, copolymers having TFE units, HFP units and CAH units. mentioned.

The proportion of the adhesive units in the copolymer (A2) is preferably 0.01 to 3 mol%, more preferably 0.05 to 1.5 mol%, of the total units constituting the copolymer (A2). In this case, it is easy to balance the adhesiveness between the F resin layer and the base material, the heat resistance of the F resin layer, and the color.
The proportion of TFE units in the copolymer (A2) is preferably 90 to 99.89 mol%, more preferably 92 to 96 mol%, of the total units constituting the copolymer (A2). In this case, it is easy to balance the heat resistance, chemical resistance, etc. of the F resin layer with the thermal meltability, stress crack resistance, etc. of the copolymer (A2).
The proportion of HFP units in the copolymer (A2) is preferably 0.1 to 9.99 mol%, more preferably 2 to 8 mol%, of the total units constituting the copolymer (A2). If the proportion of HFP units is within the above range, the thermal meltability of the copolymer (A2) is further enhanced.
The total proportion of the adhesive units, TFE units and HFP units in the copolymer (A2) is preferably 90 mol % or more, more preferably 98 mol % or more. Its upper limit is 100 mol %.
The proportion of each unit in the F polymer is determined by NMR analysis such as fusion nuclear magnetic resonance (NMR) analysis, fluorine content analysis, and infrared absorption spectrum analysis. For example, as described in Japanese Patent Application Laid-Open No. 2007-314720, a method such as infrared absorption spectroscopy can be used to determine the proportion (mol %) of adhesive units in all units constituting the F polymer.

Methods for producing the F polymer include (i) a method of polymerizing adhesive monomers and TFE, and optionally PAVE, FEP, and other monomers; A method of heating a fluorine-containing copolymer having a unit and a TFE unit to thermally decompose a functional group to generate an adhesive group (e.g., a carboxy group), (iii) adding an adhesive monomer to the fluorine-containing copolymer having a TFE unit and the method (i) is preferred.
The polymerization method (bulk polymerization method, solution polymerization method, suspension polymerization method, emulsion polymerization method, etc.) is not particularly limited and can be set as appropriate. Also, the amounts and types of the solvent, polymerization initiator, and chain transfer agent used in the polymerization can be appropriately set. Moreover, the polymerization conditions (temperature, pressure, time, etc.) can also be appropriately set according to the type of monomer used.

In the powder of the present invention, when D50 is X and D10 is Y, Y/X is 0.3 or less. That is, the powder of the present invention includes resin particles having a medium particle size (hereinafter also referred to as "moderate particles") and resin particles having a sufficiently small particle size with respect to the medium particles (hereinafter referred to as "microscopic particles"). Also referred to as "particles").
The F resin film is formed by supplying powder onto a substrate to form a powder layer and then firing the powder layer. At this time, as shown in FIG. 1(a), gaps are formed between medium-sized particles in the powder layer, and these gaps are filled with fine particles. For this reason, when firing the powder layer, as shown by the thick line in FIG. An F resin layer is likely to be formed.

On the other hand, when fine particles are not contained, as shown in FIG. 2(a), there are many voids formed between medium-sized particles in the powder layer. Therefore, when firing the powder layer, as shown by the thick line in FIG. An F resin layer having unevenness reflected on the surface is easily formed.
An F polymer having an adhesive group that is preferably used in the present invention tends to have a higher MFR than an F polymer having no adhesive group. Therefore, even if the F polymer having an adhesive group is melted during baking, it becomes difficult to flow, and irregularities tend to remain on the surface of the F resin layer. In such a case, the effect of the present invention using powder containing microparticles is particularly high.

In the present invention, Y/X is preferably 0.25 or less, more preferably 0.15 to 0.2. If Y/X is within the above range, voids formed between medium-sized particles in the powder layer can be more reliably filled with fine particles. As a result, an F resin layer having a smoother surface is formed. Y/X is a value obtained by dividing Y by X.
Specifically, it is preferable that D10 is 4 μm or less and D50 is 15 to 60 μm. By adjusting the D10 and D50 of the powder within the above range, a thin F resin layer with a smooth surface can be easily formed regardless of whether the F polymer has an adhesive group or not.

D10 of the powder is more preferably 0.5 to 3.9 μm, still more preferably 2 to 3.9 μm. When D10 is equal to or less than the above upper limit, an F resin layer having a smoother surface can be easily formed. If D10 is at least the above lower limit, the powder is less likely to adhere to the nozzle when applying a powder coating containing powder, and workability during coating is improved.
D50 of the powder is more preferably 17 to 50 μm, still more preferably 20 to 40 μm. When D50 is at least the above lower limit, it is easy to form a thinner F resin layer. When D50 is equal to or less than the above upper limit, it is easy to form an F resin layer having a smoother surface.

D100 of the powder is preferably 220 μm or less, more preferably 100 to 210 μm, even more preferably 140 to 205 μm. If D100 is equal to or less than the above upper limit, the powder does not contain resin particles (hereinafter also referred to as "coarse particles") whose particle diameter is too large for medium particles, so the F resin layer has a smoother surface. is easy to form. When D100 is at least the above lower limit, it is easy to form an F resin layer having a sufficient thickness.

Further, when A is the amount of resin particles having a particle diameter of 4 μm or less in the powder and B is the amount of resin particles having a particle diameter of 15 to 60 μm, A/B is preferably 0.1 or more, and 0 .2 or more is more preferable. A/B is preferably 0.5 or less, more preferably 0.4 or less. If A/B satisfies the above range, voids formed between medium-sized particles in the powder bed can be filled with fine particles at a higher density. Note that A/B is a value obtained by dividing A by B.
A specific amount of resin particles having a particle diameter of 4 μm or less contained in the powder is preferably 5 to 25% by volume, more preferably 10 to 20% by volume. If resin particles having a particle diameter of 4 μm or less are contained in such an amount, it is easy to form an F resin layer having a smooth surface even when the powder contains coarse particles.

Such powder can be obtained by (i) obtaining F polymer by solution polymerization, suspension polymerization or emulsion polymerization, removing the organic solvent or aqueous medium to obtain powder, and then classifying the powder; ii) It can be produced by a method of melt-kneading the F polymer and, if necessary, other components, pulverizing the kneaded product, and, if necessary, classifying the pulverized product.
Alternatively, the powder can be produced by mixing the first powder having D50 of X and the second powder having D50 of Y at a predetermined ratio. The first powder and the second powder can be produced by the method (i) or (ii) above.

D10 and D50 of the powder can be adjusted by the type of pulverization method and pulverization conditions.
Examples of the pulverizing method include methods using pulverizers such as rotor mills, pin mills, hammer mills, freeze hammer mills, edge runner mills, screen mills, vibration mills, sand mills, eddy mills, ball mills and basket mills. Among them, a method using a rotor mill or a pin mill is preferable because it is easy to adjust the D10 and D50 of the powder to the above ranges.
D10 and D50 tend to increase when the number of revolutions of the grinder is low. D10 and D50 tend to be small when the number of revolutions of the grinder is high and the grinding time is long.

The powder coating of the present invention is a powder coating containing the powder of the present invention.
In the method for producing a laminate of the present invention, a powder coating containing the powder of the present invention is supplied onto a substrate and baked to form an F resin layer. As a result, a laminate having the base material and the F resin layer formed on the base material and formed from the powder coating is obtained.
Powder coatings may contain other components than the powder of the present invention, if necessary. Other ingredients include pigments, carbon fibers and graphite.
The amount of the powder of the present invention contained in the powder coating is preferably 90% by mass or more, more preferably 95% by mass or more. The upper limit of the amount of the powder of the invention contained in the powder coating is 100% by mass.

Substrates include household items such as frying pans, pots, and irons, as well as factory piping.
Materials for the substrate include metals such as stainless steel and iron, resins, glass, and ceramics.
Electrostatic coating is suitable as a method of supplying the powder coating.

Baking of the powder coating is preferably carried out by heating to the melting point of the F polymer or higher. A specific firing temperature is preferably 350 to 380°C, more preferably 350 to 375°C, and even more preferably 350 to 370°C. When the baking temperature is at least the above lower limit, it is easy to form an F resin layer with a smooth surface, and the adhesion between the F resin layer and the substrate is enhanced.
On the other hand, if the firing temperature is equal to or lower than the above upper limit, the F polymer in the present invention has a melting point of 260 to 320° C., so that generation of gas due to thermal decomposition of the F polymer can be prevented. Therefore, the occurrence of foaming and cracking in the F resin layer can be suppressed, and a laminate with high safety and excellent appearance can be easily obtained. In other words, when F polymer with a melting point of 260 to 320° C. is used, the sintering temperature cannot be extremely increased, and the powder layer must be sintered at a relatively low temperature. Since the powder of the present invention contains microparticles, it is easy to obtain an F resin layer having a smooth surface even when fired at a relatively low temperature.

The firing time is preferably 1 to 20 minutes, more preferably 1 to 15 minutes. When the baking time is at least the above lower limit, it is easy to form an F resin layer having a smooth surface. When the baking time is equal to or less than the above upper limit, it is easier to suppress the occurrence of foaming and cracks in the F resin layer.

In the present invention, the operation of supplying the powder coating material onto the base material and baking the coating material may be repeated two or more times.
In this case, the firing temperature and firing time in each firing step may be different or the same. In this case, the total baking time is preferably 3 to 60 minutes, more preferably 4 to 60 minutes, even more preferably 5 to 45 minutes, and particularly preferably 10 to 30 minutes. If the total firing time is equal to or less than the above upper limit, it is easy to suppress the occurrence of foaming and cracks in the F resin layer. If the total baking time is at least the above lower limit, it is easy to form an F resin layer with a smooth surface, and the adhesion between the F resin layer and the substrate is further enhanced.

The thickness of the F resin layer to be formed is preferably 50-750 μm, more preferably 100-500 μm. If the thickness of the F resin layer is at least the above lower limit, the productivity of the laminate is improved. If the thickness of the F resin layer is equal to or less than the above upper limit, the chemical resistance of the F resin layer is high.

The peel strength between the F resin layer and the substrate is preferably 14 N/cm or more, more preferably 15 to 100 N/cm, even more preferably 16 to 90 N/cm, and particularly preferably 16 to 85 N/cm. When the peel strength between the F resin layer and the substrate is equal to or higher than the above lower limit, it indicates that the adhesion between the F resin layer and the substrate is high, and the F resin layer is difficult to peel off from the substrate.

Although the method for manufacturing the powder and laminate of the present invention has been described above, the present invention is not limited to the configurations of the above-described embodiments.
For example, the powder of the present invention may be added to any other configuration in the configurations of the above-described embodiments, or may be replaced with any configuration that exhibits similar functions.
In addition, the method for manufacturing a laminate of the present invention may additionally have other arbitrary steps in the configuration of the above-described embodiment, or may be replaced with arbitrary steps that produce similar effects.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these.

1. Production of Raw Material Powder [Production Example 1]
Raw material powder (A1) composed of F polymer (1) was produced using NAH, TFE and PPVE according to the procedure described in paragraph [0123] of WO 2016/017801.
The proportions (mol %) of NAH units, TFE units and PPVE units contained in F polymer (1) were 0.1, 97.9 and 2.0 in this order. Polymer F (1) had a melting point of 300° C., an MFR of 17.6 g/10 min, and a raw material powder (A1) of D50 of 1554 μm.

[Production Example 2]
Raw material powder (A2) composed of F polymer (2) was obtained in the same manner as in Production Example 1, except that 0.5 kg of methanol was used as the chain transfer agent.
The proportions (mol %) of NAH units, TFE units and PPVE units contained in F polymer (2) were 0.1, 97.9 and 2.0 in this order. F polymer (2) had a melting point of 300° C., an MFR of 25.0 g/10 min, and a D50 of raw material powder (A2) of 1570 μm.

[Production Example 3]
Raw material powder (A3) composed of F polymer (3) was obtained in the same manner as in Production Example 1, except that 0.35 kg of methanol was used as the chain transfer agent.
The proportions (mol%) of NAH units, TFE units and PPVE units contained in F polymer (3) were 0.1, 97.9 and 2.0 in this order. The melting point of F polymer 3 was 300° C., the MFR was 8.2 g/10 min, and the D50 of raw material powder (A3) was 1490 μm.
The ratio of each unit contained in the F polymer was measured by the method described in WO2016/017801.
The melting point was measured using a differential scanning calorimeter (DSC-7020) manufactured by Seiko Instruments Inc. The heating rate of F polymer was 10° C./min.
MFR is measured by using a melt indexer manufactured by Technoseven Co., Ltd. under a load of 49 N at 372° C. and measuring the mass (g) of F polymer that flows out from a nozzle with a diameter of 2 mm and a length of 8 mm for 10 minutes (unit time). and asked.
The D50 of the raw material powder was obtained by the following procedure.
From top to bottom, 2.000 mesh sieve (opening 2.400 mm), 1.410 mesh sieve (opening 1.705 mm), 1.000 mesh sieve (opening 1.205 mm), 0.710 mesh sieve (opening 1.205 mm) 0.855 mm opening), 0.500 mesh sieve (0.605 mm opening), 0.250 mesh sieve (0.375 mm opening), 0.149 mesh sieve (0.100 mm opening), and a saucer were stacked.
The raw material powder was placed in the top sieve and sieved with a shaker for 30 minutes. Measure the mass of the raw material powder remaining on each sieve, graph the cumulative total of passing mass for each mesh opening value, determine the particle diameter at which the cumulative passing mass is 50%, and determine the D50 of the raw material powder. bottom.
2. Manufacture of powders and laminates [Example 1]
First, using a rotor mill (rotor speed mill P-14 manufactured by Fritsch), the raw material powder (A1) was pulverized at a rotation speed of 1700 rpm to obtain a pulverized powder.
Next, the pulverized powder was classified using a circular vibrating sieve machine (manufactured by Seishin Enterprise Co., Ltd., model KGO-1000, sieve opening 212 μm) to obtain powder (B1).
The powder (B1) has a D10 of 3.8 μm, a D50 of 22.2 μm, a D90 of 100.6 μm, and a D100 of 200.5 μm, a loosely packed bulk density of 0.491 g/mL, and a close packed bulk density of It was 0.646 g/mL.

First, a steel plate made of SUS304 having a length of 40 mm, a width of 150 mm, and a thickness of 2 mm was prepared.
Next, the surface of the steel plate was sandblasted using 60-mesh alumina particles so as to have a surface roughness Ra of 5 to 10 μm.
After that, the surface of the steel plate was cleaned with ethanol to prepare a substrate.
After electrostatically coating the surface of the base material with a powder coating material comprising the powder (B1), the operation of firing at a firing temperature of 350° C. for a firing time of 4 minutes was repeated 10 times to obtain a laminate.
The thickness of the F resin layer formed on the substrate was 314 μm.

[Example 2]
First, using a pin mill (manufactured by Seishin Enterprise Co., Ltd., Model M-4), the raw material powder (A2) was pulverized at a rotation speed of 5000 rpm to obtain a pulverized powder.
Next, the pulverized powder was classified using a circular vibrating sieve machine (manufactured by Seishin Enterprise Co., Ltd., model KGO-1000, sieve opening 212 μm) to obtain powder (B2).
The powder (B2) has a D10 of 3.6 μm, a D50 of 21.1 μm, a D90 of 99.4 μm, and a D100 of 181.9 μm, a loosely packed bulk density of 0.524 g/mL, and a close packed bulk density of It was 0.695 g/mL.
Next, after electrostatically coating the surface of the substrate prepared in the same manner as in Example 1 with the powder coating material (B2), the operation of firing at a firing temperature of 350° C. and a firing time of 6 minutes is repeated twice. to obtain a laminate.
The thickness of the F resin layer formed on the substrate was 330 μm.

[Example 3]
A powder (B3) was obtained in the same manner as in Example 2, except that the raw powder (A3) was used instead of the raw powder (A2).
The powder (B3) has a D10 of 3.9 μm, a D50 of 24.4 μm, a D90 of 78.2 μm, and a D100 of 169.9 μm, a loosely packed bulk density of 0.525 g/mL, and a close packed bulk density of It was 0.699 g/mL.
Next, after electrostatically coating the surface of the base material prepared in the same manner as in Example 1 with the powder coating material (B3), the operation of firing at a firing temperature of 350° C. and a firing time of 4 minutes was repeated five times. Furthermore, after electrostatically coating the above powder coating, an operation of firing at a firing temperature of 350° C. for a firing time of 6 minutes was performed once to obtain a laminate.
The thickness of the F resin layer formed on the substrate was 330 μm.

[Example 4]
A powder (B4) was obtained in the same manner as in Example 2 except that the number of revolutions of the pin mill was changed to 2100 rpm and the classification was not performed.
The powder (B4) had a D10 of 10.6 μm, a D50 of 94.4 μm, a D90 of 260.1 μm, and a D100 of 340.1 μm, with a loosely packed bulk density of 0.729 g/mL and a densely packed bulk density of It was 0.835 g/mL.
Next, a laminate was obtained in the same manner as in Example 3, except that a powder coating composed of powder (B4) was used.
The thickness of the F resin layer formed on the substrate was 330 μm.

[Example 5]
A powder (B5) was obtained in the same manner as in Example 2 except that the rotation speed of the pin mill was changed to 2100 rpm.
The powder (B5) had a D10 of 10.6 μm, a D50 of 82.1 μm, a D90 of 186.5 μm, and a D100 of 212.0 μm, with a loosely packed bulk density of 0.511 g/mL and a densely packed bulk density of It was 0.672 g/mL.
Next, a laminate was obtained in the same manner as in Example 3, except that a powder coating made of powder (B5) was used.
The thickness of the F resin layer formed on the substrate was 330 μm.

[Example 6]
A powder (B6) was obtained in the same manner as in Example 2 except that the rotation speed of the pin mill was changed to 3000 rpm.
The powder (B6) has a D10 of 9.2 μm, a D50 of 56.9 μm, a D90 of 131.6 μm, and a D100 of 203.2 μm, a loosely packed bulk density of 0.529 g/mL, and a close packed bulk density of It was 0.691 g/mL.
Next, a laminate was obtained in the same manner as in Example 3, except that a powder coating composed of powder (B6) was used.
The thickness of the F resin layer formed on the substrate was 330 μm.

[Example 7 (comparative example)]
A powder (B7) and a laminate were obtained in the same manner as in Example 2 except that the rotation speed of the pin mill was changed to 4000 rpm.
The powder (B7) had a D10 of 8.3 μm, a D50 of 25.5 μm, a D90 of 120.6 μm, and a D100 of 191.3 μm, with a loosely packed bulk density of 0.503 g/mL and a densely packed bulk density of It was 0.657 g/mL.
Further, the thickness of the F resin layer formed on the substrate was 330 μm.

The particle size and amount of the resin particles constituting the powder, loosely packed bulk density and densely packed bulk density were measured as follows.
(Measurement of particle size and amount of resin particles)
Using a laser diffraction/scattering particle size distribution analyzer (LA-920 measuring instrument) manufactured by Horiba, Ltd., the powder was dispersed in water, the particle size distribution was measured, and D10, D50, D90 and D100 were calculated.
Also, from the obtained particle size distribution graph, the amount of resin particles with a particle size of 4 μm or less and the amount of resin particles with a particle size of 15 to 60 μm were determined.
(loosely packed bulk density and close packed bulk density)
The loosely packed bulk density and the closely packed bulk density of the powder were measured using the methods described in [0117] and [0118] of WO 2016/017801, respectively.

3. Measurement and evaluation 3-1. Peel Strength First, from the surface side of the F resin layer of the laminate obtained in each example, cuts were made at intervals of 10 mm using a cutter knife.
Next, part of the F resin layer was peeled off and fixed to a chuck of a tensile tester.
Thereafter, the peel strength (N/cm) was measured when the F resin layer was peeled from the substrate at a pulling speed of 50 mm/min and 90°.

3-2. Appearance Evaluation In each example, 100 laminates were produced, the surface of the F resin layer of each laminate was visually confirmed, and the appearance was evaluated according to the following evaluation criteria.
<Evaluation Criteria>
A: No unevenness was observed on the surface of the F resin layer in any of the laminates.
Good: Unevenness was observed on the surface of the F resin layer in laminates of 5 or less.
Δ: Unevenness was observed on the surface of the F resin layer in 6 to 10 laminates.
x: Unevenness was observed on the surface of the F resin layer in more than 10 laminates.
Table 1 shows the above results together with the powder production conditions, particle diameters (D10, D50, D90, D100) and amounts, and the laminate production conditions.

As shown in Table 1, in Examples 1 to 6 using powders having a relationship between D10 and D50 within the range defined by the present invention, the adhesion between the substrate and the F resin layer was excellent.
In Examples 1 to 3 using powder with a small D50, an F resin layer with a smooth surface is formed, whereas in Examples 4 to 6 using a powder with a large D50, unevenness occurs on the surface of the F resin layer. showed a trend.
In Example 7, in which the powder having the relationship between D10 and D50 deviated from the range defined by the present invention, unevenness was observed on the surface of the F resin layer. In addition, there was a tendency for the adhesion between the base material and the F resin layer to decrease.

The powder of the present invention is suitable for powder coatings used for powder coating, and particularly suitable for powder coatings that form a thick fluororesin layer with a smooth surface.
The entire contents of the specification, claims, abstract and drawings of Japanese Patent Application No. 2017-235350 filed on December 07, 2017 are cited here and incorporated as disclosure of the specification of the present invention. It is.

Claims (10)

A powder composed of resin particles containing a fluoropolymer having a unit based on tetrafluoroethylene and having a melting point of 260 to 320 ° C.,
The volume-based cumulative 100% diameter is 220 μm or less,
The volume-based cumulative 10% diameter is 4 μm or less and the volume-based cumulative 50% diameter is 15 to 60 μm,
A powder in which Y/X is 0.3 or less, where X is a volume-based cumulative 50% diameter and Y is a volume-based cumulative 10% diameter. A/B is 0.12 or more, where A is the volume of resin particles with a particle diameter of 4 μm or less contained in the powder, and B is the volume of resin particles with a particle diameter of 15 to 60 μm. , the powder of claim 1. 3. The powder according to claim 1, wherein the amount of resin particles having a particle diameter of 4 μm or less contained in the powder is 5 to 25% by volume. The powder according to any one of claims 1 to 3, wherein the fluoropolymer has at least one functional group selected from the group consisting of carbonyl-containing groups, hydroxy groups, epoxy groups and isocyanate groups. 5. The powder according to claim 4, wherein the fluoropolymer has units based on the tetrafluoroethylene and units having the functional group. A powder coating comprising the powder according to any one of claims 1 to 5. The powder coating according to claim 6, wherein the amount of said powder contained in said powder coating is 90-100% by mass. A method for producing a laminate having a substrate and a fluororesin layer formed on the substrate and formed from the powder according to any one of claims 1 to 5,
A method for producing a laminate, wherein a powder coating containing the powder is supplied onto the substrate and baked to obtain the fluororesin layer. 9. The manufacturing method according to claim 8, wherein the powder coating is baked by heating to the melting point of the fluoropolymer or higher. 10. The manufacturing method according to claim 8, wherein the fluororesin layer has a thickness of 50 to 750 μm.

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