CN111372976A

CN111372976A - Powder, powder coating material, and method for producing laminate

Info

Publication number: CN111372976A
Application number: CN201880075908.5A
Authority: CN
Inventors: 细田朋也; 诹佐等; 寺田达也
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2017-12-07
Filing date: 2018-12-06
Publication date: 2020-07-03
Anticipated expiration: 2038-12-06
Also published as: CN111372976B; JPWO2019112017A1; JP7272274B2; TW201927936A; WO2019112017A1; TWI798306B

Abstract

The invention provides a powder capable of easily forming a fluororesin layer with a smooth surface, and a method for manufacturing a laminated body using a powder coating material containing the powder. The powder of the present invention is a powder composed of resin particles containing a fluoropolymer having units based on tetrafluoroethylene and a melting point of 260 to 320 ℃, and when D50 is X and D10 is Y, the ratio of Y/X is 0.3 or less. Further, D10 is preferably 4 μm or less and D50 is preferably 15 to 60 μm.

Description

Powder, powder coating material, and method for producing laminate

Technical Field

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

Background

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

Patent document 1 discloses a method of applying a powder coating material containing a powder composed of fluoropolymer particles to a substrate and firing the powder coating material to form a fluororesin layer, thereby obtaining a laminate. Patent document 2 discloses a powder composed of fluoropolymer particles having a functional group such as a carbonyl group as a powder having excellent adhesion to a substrate.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2011/048965

Patent document 2: international publication No. 2016/017801

Disclosure of Invention

Technical problem to be solved by the invention

However, if the particle diameter of the resin particles constituting the powder is not adjusted, unevenness is likely to occur on the surface of the fluororesin layer to be formed. The present inventors have found that the above phenomenon becomes remarkable particularly when a powder composed of resin particles containing a fluoropolymer having a high melting point is fired to form a fluororesin layer.

The purpose of the present invention is to provide a powder capable of easily forming a fluororesin layer having a smooth surface, a powder coating material containing the powder, and a method for producing a laminate using the powder coating material.

Technical scheme for solving technical problem

The present invention has the following aspects.

[ 1] A powder comprising resin particles comprising a fluoropolymer having units based on tetrafluoroethylene and having a melting point of 260-320 ℃, wherein Y/X is 0.3 or less when the volume-based cumulative 50% diameter is X and the volume-based cumulative 10% diameter is Y.

<2> the powder according to <1>, wherein the cumulative 10% by volume diameter is 4 μm or less and the cumulative 50% by volume diameter is 15 to 60 μm.

<3> the powder according to <2>, wherein A/B is 0.1 or more, where A represents the amount of the resin particles having a particle diameter of 4 μm or less contained in the powder and B represents the amount of the resin particles having a particle diameter of 15 to 60 μm.

<4> the powder according to <2> or <3>, wherein the resin particles having a particle diameter of 4 μm or less are contained in an amount of 5 to 25 vol%.

<5> the powder according to any one of <1> to <4>, wherein the cumulative 100% diameter on a volume basis 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 a carbonyl group, a hydroxyl group, an epoxy group and an isocyanate group.

<7> the powder according to <6>, wherein the fluoropolymer has the tetrafluoroethylene-based unit and the unit having the functional group.

<8> a powder coating material comprising the powder according to any one of <1> to <7 >.

<9> the powder coating material according to <8>, wherein the amount of the powder contained in the powder coating material is 90 to 100% by mass.

<10> a method for producing a laminate comprising a base material and a fluororesin layer formed from the powder according to any one of <1> to <7> and provided on the base material, wherein the fluororesin layer is obtained by supplying a powder coating material containing the powder onto the base material and firing the powder coating material.

<11> the production method according to <10>, wherein the powder coating material is fired by heating to a temperature not lower than the melting point of the fluoropolymer.

<12> the production method according to <10> or <11>, wherein the fluororesin layer has a thickness of 50 to 750 μm.

ADVANTAGEOUS EFFECTS OF INVENTION

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

Drawings

Fig. 1 is a diagram for explaining a state change when a fluororesin layer is formed using the powder of the present invention.

Fig. 2 is a diagram for explaining a state change when a fluororesin layer is formed using a conventional powder.

Detailed Description

The following definitions of terms apply to the present description and claims.

The "heat-fusible polymer" is a polymer having MFR of 0.01 to 1000g/10 min at a temperature higher than the melting point of the polymer by 20 ℃ or more under a load of 49N.

"melting point of a polymer" refers to the temperature corresponding to the maximum of the melting peak of the polymer as determined by Differential Scanning Calorimetry (DSC).

"MFR of the polymer" is a melt flow rate specified in JIS K7210-1: 2014 (corresponding to International Standard ISO 1133-1: 2011).

"volume-based cumulative 50% diameter (D50) of the powder" is a particle diameter at a point where the cumulative volume reaches 50% on a cumulative curve obtained by measuring the particle size distribution of the powder by a laser diffraction scattering method and assuming that the total volume of the powder is 100%.

Similarly, "the volume-based cumulative 10% diameter of the powder (D10)", "the volume-based cumulative 90% diameter of the powder (D90)" and "the volume-based cumulative 100% diameter of the powder (D100)" are the volume-based cumulative 10% diameter, the volume-based cumulative 90% diameter and the volume-based cumulative 100% diameter (maximum particle diameter).

In other words, 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.

The "monomer-based unit" is a generic name of a radical formed directly by polymerization of 1 molecule of a monomer and a radical obtained by chemically converting a part of the radical. In the present specification, the monomer-based unit is also abbreviated as "unit".

"(meth) acrylate" is a generic term for both acrylates and methacrylates. Similarly, "(meth) acrylic acid" is a general term for acrylic acid and methacrylic acid, and "(meth) acryloyloxy" is a general term for acryloyloxy and methacryloyloxy.

The resin particles constituting the powder of the present invention include a fluoropolymer (hereinafter also referred to as "F polymer") having tetrafluoroethylene-based units (hereinafter also referred to as "TFE units") and having a melting point of 260 to 320 ℃.

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, further preferably 90% by mass or more, and particularly preferably 100% by mass. When the powder composed of the resin particles containing the F polymer in the above-mentioned amount is used, the non-tackiness, chemical resistance and heat resistance of the formed fluororesin layer (hereinafter also referred to as "F resin layer") are improved. The F polymer may be used in combination of 2 or more.

Examples of the other polymer include a fluoropolymer other than the polymer F, an aromatic polyester, a polyamide-imide, and a thermoplastic polyimide. The other polymers may be used in combination of 2 or more.

Examples of the polymer F include a tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, an ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, an ethylene-chlorotrifluoroethylene copolymer, a polymer obtained by introducing at least one functional group selected from a carbonyl group-containing group, a hydroxyl group, an epoxy group and an isocyanate group (hereinafter, also referred to as "adhesive group"), and a modified polytetrafluoroethylene. Further, polytetrafluoroethylene may be used as the F polymer as long as it exhibits thermal fusibility.

The modified polytetrafluoroethylene may, for example, be (i) tetrafluoroethylene (hereinafter also referred to as "TFE") or a very small amount of CH₂＝CH(CF₂)₄A copolymer of F, (ii) a copolymer of the copolymer of (i) above, and further a monomer having an extremely small amount of an adhesive group (hereinafter also referred to as "adhesive monomer"), (iii) a copolymer of TFE and an extremely small amount of an adhesive monomer, (iv) polytetrafluoroethylene having an adhesive group introduced thereto by plasma treatment or the like, and (v) a copolymer of (i) above having an adhesive group introduced thereto by plasma treatment or the like.

The melting point of the F polymer is 260-320 ℃, preferably 280-320 ℃, more preferably 295-315 ℃, and further preferably 295-310 ℃. If the melting point of the F polymer is not less than the lower limit, the heat resistance of the F resin layer is improved. If the melting point of the F polymer is not more than the above upper limit, the F polymer will have improved heat-fusibility.

The melting point of the F polymer can be adjusted by the kind and proportion of the units constituting the F polymer, the molecular weight of the F polymer, and the like. For example, the melting point of the F polymer tends to increase as the proportion of TFE units increases.

The MFR of the F polymer at a temperature higher than the melting point by 20 ℃ or higher is preferably 0.1 to 1000g/10 min, more preferably 0.5 to 100g/10 min, still more preferably 1 to 30g/10 min, particularly preferably 5 to 20g/10 min. When the MFR is not less than the lower limit value, the heat-fusibility of the F polymer is further improved, and the appearance of the F resin layer is good. If the MFR is not more than the above upper limit, the mechanical strength of the F resin layer is improved.

MFR is an index of the molecular weight of the F polymer, and 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 depending on the production conditions of the F polymer. For example, if the polymerization time during the polymerization of the monomer is shortened, the MFR of the F polymer tends to be increased.

The adhesive group is preferably a carbonyl group, from the viewpoint of excellent adhesion between the F resin layer and the substrate.

Examples of the carbonyl group-containing group include a hydrocarbon group having a carbonyl group between carbon atoms, a carbonate group, a carboxyl group, a haloformyl group, an alkoxycarbonyl group, an acid anhydride residue (-C (O) -O-C (O) -), a polyfluoroalkoxycarbonyl group and a fatty acid residue.

The carbonyl group-containing group is preferably a hydrocarbon group having a carbonyl group between carbon atoms, a carbonate group, a carboxyl group, a haloformyl group, an alkoxycarbonyl group, and an acid anhydride residue, and more preferably a carboxyl group and an acid anhydride residue, from the viewpoint of further improving the adhesion between the F resin layer and the substrate.

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. In addition, the number of carbons of the alkylene group does not include the number of carbons constituting the carbonyl group.

Examples of the haloformyl group include-C (═ O) -F and-C (═ O) Cl.

Examples of the "alkoxy" group in the "alkoxycarbonyl" group may include a methoxy group and an ethoxy group.

The adhesive group may be contained in the F polymer as an adhesive unit, or may be contained as a terminal group at a terminal of the main chain of the F polymer. When the terminal group as the main chain contains an adhesive group, the F polymer may or may not contain an adhesive unit.

The F polymer preferably contains a TFE unit and a unit based on an adhesive monomer (adhesive unit).

The number of the adhesive groups of the adhesive monomer may be 1, or 2 or more. In the case of having 2 or more adhesive groups, the 2 or more adhesive groups may be the same or different, respectively.

Examples of the adhesive monomer include a monomer having a carbonyl group, a monomer having a hydroxyl group, a monomer having an epoxy group, and a monomer having an isocyanate group. The adhesive monomer is preferably a monomer having a carbonyl group, from the viewpoint of excellent adhesion between the F resin layer and the substrate.

Examples of the monomer having a carbonyl group include a cyclic monomer having an acid anhydride residue, a monomer having a carboxyl group, a vinyl ester, (meth) acrylic acid ester, and CF₂＝CFOR^f1CO₂X¹(wherein, R^f1Is a C1-10 perfluoroalkylene group or a C2-10 perfluoroalkylene group having an etheric oxygen atom between carbon atoms, X¹Is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms).

The cyclic monomer having an acid anhydride residue may, for example, be an unsaturated dicarboxylic anhydride. Examples of the unsaturated dicarboxylic acid anhydride include itaconic anhydride (hereinafter, also referred to as "IAH"), citraconic anhydride (hereinafter, also referred to as "CAH"), 5-norbornene-2, 3-dicarboxylic anhydride (also referred to as nadic anhydride, hereinafter, also referred to as "NAH"), and maleic anhydride.

Examples of the monomer having a carboxyl group include unsaturated dicarboxylic acids (itaconic acid, citraconic acid, 5-norbornene-2, 3-dicarboxylic acid, maleic acid, etc.) and unsaturated monocarboxylic acids (acrylic acid, methacrylic acid, etc.).

Examples of the vinyl ester include vinyl acetate, vinyl chloroacetate, vinyl butyrate, vinyl pivalate, vinyl benzoate, and vinyl crotonate.

Examples of the (meth) acrylic acid ester include (polyfluoroalkyl) acrylate and (polyfluoroalkyl) methacrylate.

The monomer having a carbonyl group is preferably a cyclic monomer having an acid anhydride residue, and more preferably IAH, CAH or NAH, from the viewpoint of further improving the adhesion between the F resin layer and the substrate. If IAH, CAH or NAH is used, the F polymer having an acid anhydride residue can be easily produced. As the monomer having a carbonyl group, NAH is particularly preferable in view of easily increasing the adhesiveness of the F resin layer.

Examples of the monomer having a hydroxyl group include vinyl esters having a hydroxyl group, vinyl ethers having a hydroxyl group, allyl ethers having a hydroxyl group, (meth) acrylic esters having a hydroxyl group, hydroxyethyl crotonate and allyl alcohol.

Examples of the monomer 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.).

Examples of the monomer having an isocyanate group include 2- (meth) acryloyloxyethyl isocyanate, 2- (2- (meth) acryloyloxyethoxy) ethyl isocyanate, and 1, 1-bis ((meth) acryloyloxymethyl) ethyl isocyanate.

The adhesive monomers may be used in combination of 2 or more.

Examples of the units other than the adhesive unit and TFE unit include a unit based on perfluoro (alkyl vinyl ether) (hereinafter also referred to as "PAVE unit"), a unit based on hexafluoropropylene (hereinafter also referred to as "HFP unit"), and a unit based on an adhesive monomer, TFE, PAVE, and other monomers other than HFP.

As PAVE, CF is mentioned₂＝CFOCF₃、CF₂＝CFOCF₂CF₃、CF₂＝CFOCF₂CF₂CF₃(hereinafter also referred to as "PPVE"), CF₂＝CFOCF₂CF₂CF₂CF₃、CF₂＝CFO(CF₂)₈F, preferably PPVE.

More than 2 PAVEs can be used simultaneously.

Examples of the other monomer include other fluorine-containing monomers (excluding the adhesive monomer, TFE, PAVE, and HFP) and other non-fluorine-containing monomers (excluding the adhesive monomer).

Examples of the other fluorine-containing monomer include vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, and CF₂＝CFOR^f3SO₂X³(wherein, R^f3Is a C1-10 perfluoroalkylene group or a C2-10 perfluoroalkylene group having an etheric oxygen atom between carbon atoms, X³Is a halogen atom or a hydroxyl group), CF₂＝CF(CF₂)_pOCF＝CF₂(wherein p is 1 or 2), CH₂＝CX⁴(CF₂)_qX⁵(it isIn, X⁴Is a hydrogen atom or a fluorine atom, q is an integer of 2 to 10, X⁵Hydrogen atom or fluorine atom), perfluoro (2-methylene-4-methyl-1, 3-dioxolane). The other fluorine-containing monomers may be used in combination of 2 or more.

As CH₂＝CX⁴(CF₂)_qX⁵Can be exemplified by CH₂＝CH(CF₂)₂F、CH₂＝CH(CF₂)₃F、CH₂＝CH(CF₂)₄F、CH₂＝CF(CF₂)₃H、CH₂＝CF(CF₂)₄H, preferably CH₂＝CH(CF₂)₄F、CH₂＝CH(CF₂)₂F。

Examples of the other non-fluorine-containing monomer include ethylene and propylene, and ethylene is preferred. The other non-fluorine-containing monomers may be used in combination of 2 or more.

As other monomers, other fluorine-containing monomers and other non-fluorine-containing monomers may be used together.

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 carboxyl group, a fluoroformyl group, an acid anhydride residue, or a hydroxyl group. The adhesive group can be introduced by appropriately selecting a radical polymerization initiator, a chain transfer agent, and the like used in the production of the F polymer.

The F polymer is preferably a copolymer having an adhesive unit, a TFE unit, and a PAVE unit (hereinafter also referred to as copolymer (a1)), or a copolymer having an adhesive unit, a TFE unit, and an HFP unit (hereinafter also referred to as copolymer (a2)), and more preferably a copolymer (a1), from the viewpoint of improving the heat resistance of the F resin layer.

The copolymer (a1) may further have at least one of HFP unit and other unit as necessary. That is, the copolymer (a1) may be a copolymer having an adhesive unit, a TFE unit, and a PAVE unit, a copolymer having an adhesive unit, a TFE unit, a PAVE unit, and an HFP unit, a copolymer having an adhesive unit, a TFE unit, a PAVE unit, and other units, or a copolymer having an adhesive unit, a TFE unit, a PAVE unit, an HFP unit, and other units.

From the viewpoint of further improving the adhesion between the F resin layer and the substrate, the copolymer (a1) is preferably a copolymer having a unit based on a monomer having a carbonyl group, a TFE unit, and a PAVE unit, and more preferably a copolymer having a unit based on a cyclic monomer having an acid anhydride residue, a TFE unit, and a PAVE unit.

Preferred specific examples of the copolymer (a1) include a copolymer having TFE units, PPVE units, and NAH units, a copolymer having TFE units, PPVE units, and IAH units, and a copolymer having TFE units, PPVE units, and CAH units.

The proportion of the adhesive unit in the copolymer (a1) in the total units constituting the copolymer (a1) is preferably 0.01 to 3 mol%, more preferably 0.05 to 1 mol%. In this case, the adhesiveness between the F resin layer and the substrate and the heat resistance and color tone of the F resin layer are easily balanced.

The proportion of TFE units in the copolymer (a1) in the total units constituting the copolymer (a1) is preferably 90 to 99.89 mol%, and more preferably 96 to 98.95 mol%. In this case, the heat resistance, chemical resistance, and the like of the F resin layer are easily balanced with the heat fusion property, stress crack resistance, and the like of the copolymer (a 1).

The proportion of the PAVE units in the copolymer (a1) in the total units constituting the copolymer (a1) is preferably 0.1 to 9.99 mol%, more preferably 1 to 9.95 mol%. In this case, the thermal fusibility of the fluorocopolymer (a1) can be easily adjusted.

The total amount of the adhesive unit, the TFE unit, and the PAVE unit in the copolymer (a1) is preferably 90 mol% or more, and more preferably 98 mol% or more. The upper limit is 100 mol%.

The copolymer (a2) may further have at least one of a PAVE unit and another monomer unit as required. That is, the copolymer (a2) may be a copolymer having an adhesive unit, a TFE unit, and an HFP unit, a copolymer having an adhesive unit, a TFE unit, an HFP unit, and a PAVE unit, a copolymer having an adhesive unit, a TFE unit, an HFP unit, and another monomer unit, or a copolymer having an adhesive unit, a TFE unit, an HFP unit, a PAVE unit, and another unit.

From the viewpoint of further improving the adhesion between the F resin layer and the substrate, the copolymer (a2) is preferably a copolymer having a unit based on a monomer having a carbonyl group, a TFE unit, and an HFP unit, and more preferably a copolymer having a unit based on a cyclic monomer having an acid anhydride residue, a TFE unit, and an HFP unit.

Preferred specific examples of the copolymer (a2) include a copolymer having a TFE unit, an HFP unit, and an NAH unit, a copolymer having a TFE unit, an HFP unit, and an IAH unit, and a copolymer having a TFE unit, an HFP unit, and a CAH unit.

The proportion of the adhesive unit in the copolymer (a2) in the total units constituting the copolymer (a2) is preferably 0.01 to 3 mol%, more preferably 0.05 to 1.5 mol%. In this case, the adhesiveness between the F resin layer and the substrate and the heat resistance and color tone of the F resin layer are easily balanced.

The proportion of TFE units in the copolymer (a2) in the total units constituting the copolymer (a2) is preferably 90 to 99.89 mol%, and more preferably 92 to 96 mol%. In this case, the heat resistance, chemical resistance, and the like of the F resin layer are easily balanced with the heat fusion property, stress crack resistance, and the like of the copolymer (a 2).

The proportion of HFP units in the copolymer (a2) in the total units constituting the copolymer (a2) is preferably 0.1 to 9.99 mol%, and more preferably 2 to 8 mol%. If the proportion of HFP units is within the above range, the copolymer (A2) has further improved heat fusibility.

The total ratio of the adhesive unit, the TFE unit, and the HFP unit in the copolymer (a2) is preferably 90 mol% or more, and more preferably 98 mol% or more. The upper limit is 100 mol%.

The proportion of each unit in the F polymer can be determined by NMR analysis such as melt Nuclear Magnetic Resonance (NMR) analysis, fluorine content analysis, and infrared absorption spectrum analysis. For example, the proportion (mol%) of the adhesive unit in the total units constituting the F polymer can be determined by a method such as infrared absorption spectrum analysis as described in Japanese patent laid-open No. 2007-314720.

The method for producing the polymer F may, for example, be: (i) a method of polymerizing an adhesive monomer, TFE, and, if necessary, PAVE, FEP, and other monomers; (ii) a method in which a fluorocopolymer having a unit having a functional group which generates an adhesive group by thermal decomposition and a TFE unit is heated to thermally decompose the functional group to generate an adhesive group (e.g., a carboxyl group); (iii) the method of graft-polymerizing an adhesive monomer onto a fluorocopolymer having a TFE unit is preferably the method (i) described above.

The polymerization method (bulk polymerization method, solution polymerization method, suspension polymerization method, emulsion polymerization method, etc.) is not particularly limited, and may be appropriately set. Further, the amounts and kinds of the solvent, polymerization initiator, and chain transfer agent used in the polymerization may be appropriately set. The polymerization conditions (temperature, pressure, time, etc.) may be appropriately set according to the kind of the 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 an intermediate particle size (hereinafter also referred to as "intermediate particles") and resin particles having a particle size sufficiently smaller than that of the intermediate particles (hereinafter also referred to as "fine particles").

The F resin film is formed by supplying powder onto a substrate to form a powder layer, and then firing the powder layer. In this case, as shown in fig. 1(a), voids may be formed between the medium-sized particles in the powder layer, but the voids are filled with fine particles. Therefore, when the powder layer is fired, as shown by the thick line in fig. 1(b), the surface of the powder layer (medium-sized particles and fine particles) starts to melt substantially uniformly, and an F resin layer having a smooth surface is easily formed.

On the other hand, if fine particles are not contained, many voids formed between the medium-sized particles exist in the powder layer as shown in fig. 2 (a). Therefore, when the powder layer is fired, as shown by the thick line in fig. 2(b), the surface of the powder layer starts to melt along the shape of the medium particle, and an F resin layer having irregularities reflecting the shape of the medium particle on the surface is easily formed.

The F polymer having an adhesive group preferably used in the present invention tends to have an increased MFR as compared with an F polymer having no adhesive group. Therefore, the F polymer having an adhesive group is not likely to flow even when melted during firing, and the uneven shape is likely to remain on the surface of the F resin layer. In this case, the effect of the present invention using the powder containing fine particles is particularly high.

In the present invention, Y/X is preferably 0.25 or less, more preferably 0.15 to 0.2. When Y/X is in the above range, the voids formed between the medium-sized particles can be more reliably filled with fine particles in the powder layer. As a result, an F resin layer having a smoother surface can be formed. Y/X is a value obtained by dividing Y by X.

Specifically, D10 is preferably 4 μm or less and D50 is preferably 15 to 60 μm. When the powder D10 and D50 are adjusted to fall within the above range, an F resin layer having a smooth and thin surface can be easily formed regardless of whether the F polymer has an adhesive group.

The D10 of the powder is more preferably 0.5 to 3.9 μm, and still more preferably 2 to 3.9 μm. If D10 is not more than the above upper limit, an F resin layer having a smoother surface can be easily formed. When D10 is not less than the lower limit value, the powder is less likely to adhere to the nozzle when the powder coating material containing the powder is applied, and workability in application is improved.

The D50 content of the powder is more preferably 17 to 50 μm, and still more preferably 20 to 40 μm. If D50 is not less than the lower limit value, a thinner F resin layer can be easily formed. If D50 is not more than the above upper limit, an F resin layer having a smoother surface can be easily formed.

The D100 of the powder is preferably 220 μm or less, more preferably 100 to 210 μm, and further preferably 140 to 205 μm. If D100 is not more than the above upper limit, the powder does not contain resin particles having a particle size too large for the medium-sized particles (hereinafter, also referred to as "coarse particles"), and therefore an F resin layer having a smoother surface can be easily formed. If D100 is not less than the lower limit, an F resin layer having a sufficient thickness can be easily formed.

When the amount of resin particles having a particle diameter of 4 μm or less in the powder is denoted as A and the amount of resin particles having a particle diameter of 15 to 60 μm is denoted as B, A/B is preferably 0.1 or more, more preferably 0.2 or more. A/B is preferably 0.5 or less, more preferably 0.4 or less. If A/B satisfies the above range, the voids formed between the medium-sized particles can be filled with fine particles at a higher density in the powder layer. Further, a/B is a value obtained by dividing a by B.

The specific amount of the resin particles having a particle diameter of 4 μm or less contained in the powder is preferably 5 to 25 vol%, more preferably 10 to 20 vol%. If the resin particles having a particle diameter of 4 μm or less are contained in this amount, an F resin layer having a smooth surface can be easily formed even if the powder contains coarse particles.

Such a powder can be produced by the following method: (i) a method of obtaining an F polymer by a solution polymerization method, a suspension polymerization method or an emulsion polymerization method, removing an organic solvent or an aqueous medium to obtain a powder, and then classifying the powder; (ii) a method comprising melt-kneading the polymer F and, if necessary, other components, pulverizing the kneaded product, and classifying the pulverized product, if necessary.

The powder may be produced by mixing a first powder in which D50 is X and a second powder in which D50 is Y at a predetermined ratio. The first powder and the second powder can be produced by the method (i) or (ii) described above.

The D10 and D50 contents of the powder can be adjusted depending on the type of the pulverization method and the pulverization conditions.

Examples of the method of pulverization include a method using a pulverizer such as a rotor mill, pin mill, hammer mill, freeze hammer mill, wheel mill, screen mill, vibration mill, sand mill, eddy current mill, ball mill, basket sand mill, etc. Among them, a rotor mill or a pin mill is preferably used in view of easy adjustment of the powder amounts of D10 and D50 within the above ranges.

If the rotation speed of the pulverizer is low, D10 and D50 tend to increase. If the rotational speed of the pulverizer is high and the pulverizing time is long, D10 and D50 tend to be small.

The powder coating material of the present invention is a powder coating material containing the powder of the present invention.

The method for producing a laminate of the present invention comprises supplying a powder coating material comprising the powder of the present invention onto a substrate, and firing the powder coating material to form an F resin layer. Thereby, a laminate having a substrate and an F resin layer formed of a powder coating material provided on the substrate was obtained.

The powder coating material may contain other components than the powder of the present invention as required. Examples of the other component include pigments, carbon fibers, and graphite.

The amount of the powder of the present invention contained in the powder coating material is preferably 90 mass% or more, and more preferably 95 mass% or more. The upper limit of the amount of the powder of the present invention contained in the powder coating material is 100 mass%.

Examples of the base material include household goods such as frying pans, pots, and irons, and pipes in factories.

Examples of the material of the substrate include metals such as stainless steel and iron, resins, glass, and ceramics.

As a method of supplying the powder coating material, electrostatic coating is preferable.

The powder coating material is preferably fired by heating to a temperature not lower than the melting point of the F polymer. The firing temperature is preferably 350 to 380 ℃, more preferably 350 to 375 ℃, and still more preferably 350 to 370 ℃. When the firing temperature is not lower than the above lower limit, the F resin layer having a smooth surface is easily formed, and the adhesion between the F resin layer and the base material is improved.

On the other hand, if the firing temperature is not more than the above upper limit, the melting point of the F polymer in the present invention is 260 to 320 ℃, and therefore, the generation of gas due to thermal decomposition of the F polymer can be prevented. Therefore, a laminate which can suppress the occurrence of foaming or cracking in the F resin layer, has high safety, and has excellent appearance can be easily obtained. In other words, when an F polymer having a melting point of 260 to 320 ℃ is used, the firing temperature cannot be raised extremely, and the powder layer must be fired at a relatively low temperature. The powder of the present invention contains fine particles, and therefore, an F resin layer having a smooth surface can be easily obtained even when fired at a relatively low temperature.

The firing time is preferably 1 to 20 minutes, more preferably 1 to 15 minutes. If the firing time is not less than the lower limit, an F resin layer having a smooth surface is easily formed. If the firing time is not more than the above upper limit, the occurrence of foaming and cracks in the F resin layer can be more easily suppressed.

In the present invention, the operation of supplying and baking the powder coating material onto the substrate may be repeated 2 or more times.

In this case, the firing temperature and the firing time in each firing step may be different or the same. In this case, the total firing time is preferably 3 to 60 minutes, more preferably 4 to 60 minutes, further preferably 5 to 45 minutes, and particularly preferably 10 to 30 minutes. If the total of the firing times is not more than the upper limit value, the occurrence of foaming and cracks in the F resin layer is easily suppressed. If the total of the firing times is not less than the lower limit, the F resin layer having a smooth surface is easily formed, and the adhesion between the F resin layer and the base material is further improved.

The thickness of the F resin layer to be formed is preferably 50 to 750 μm, more preferably 100 to 500 μm. If the thickness of the F resin layer is not less than the lower limit, the productivity of the laminate is improved. If the thickness of the F resin layer is not more than the above upper limit, the F resin layer has high chemical resistance.

The peel strength between the F resin layer and the substrate is preferably 14N/cm or more, more preferably 15 to 100N/cm, still more preferably 16 to 90N/cm, and particularly preferably 16 to 85N/cm. When the peel strength between the F resin layer and the substrate is not less than the lower limit, the adhesion between the F resin layer and the substrate is high, and the F resin layer is less likely to peel from the substrate.

The powder and the method for producing a laminate of the present invention have been described above, but the present invention is not limited to the configuration of the above embodiment.

For example, the powder of the present invention may be configured in any other way in the above-described embodiments, or may be replaced with any other way to achieve the same function.

In the method for producing a laminate according to the present invention, in the configuration of the above embodiment, any other steps may be added, or any other steps may be substituted to perform the same function.

Examples

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

1. Production of raw material powder

Production example 1

A raw powder (A1) comprising the F polymer (1) was produced by using NAH, TFE and PPVE in accordance with the procedure described in paragraph [0123] of International publication No. 2016/017801.

The proportions (mol%) of the NAH unit, TFE unit, and PPVE unit contained in the F polymer (1) were 0.1, 97.9, and 2.0 in this order. The melting point of the F polymer (1) was 300 ℃ and the MFR was 17.6g/10 min, and the D50 of the raw material powder (A1) was 1554 μm.

Production example 2

A raw material powder (A2) composed of the F polymer (2) was obtained in the same manner as in production example 1, except that the chain transfer agent was changed to 0.5kg of methanol.

The proportions (mol%) of the NAH unit, TFE unit, and PPVE unit contained in the F polymer (2) were 0.1, 97.9, and 2.0 in this order. The melting point of the F polymer (2) was 300 ℃ and the MFR was 25.0g/10 min, and the D50 of the raw material powder (A1) was 1570. mu.m.

Production example 3

A raw material powder (A3) composed of the F polymer (3) was obtained in the same manner as in production example 1, except that the chain transfer agent was changed to 0.35kg of methanol.

The proportions (mol%) of the NAH unit, TFE unit, and PPVE unit contained in the F polymer (3) were 0.1, 97.9, and 2.0 in this order. The melting point of the F polymer (3) was 300 ℃ and the MFR was 8.2g/10 min, and the D50 of the raw material powder (A3) was 1490. mu.m.

The proportion of each unit contained in the F polymer was measured by the method described in international publication No. 2016/017801.

The melting point was measured by using a differential scanning calorimeter (DSC-7020) manufactured by Seiko instruments K.K. (セイコーインスツル Co.). The temperature rising rate of the polymer F was set to 10 ℃ per minute.

The MFR was determined by measuring the mass (g) of the F polymer flowing out from a nozzle having a diameter of 2mm and a length of 8mm in 10 minutes (unit time) at 372 ℃ under a load of 49N using a melt index apparatus manufactured by Techno7 K.K. (テクノセブン Co.).

The raw material powder D50 was obtained by the following procedure.

2.000 mesh sieves (with the sieve aperture of 2.400mm), 1.410 mesh sieves (with the sieve aperture of 1.705mm), 1.000 mesh sieves (with the sieve aperture of 1.205mm), 0.710 mesh sieves (with the sieve aperture of 0.855mm), 0.500 mesh sieves (with the sieve aperture of 0.605mm), 0.250 mesh sieves (with the sieve aperture of 0.375mm), 0.149 mesh sieves (with the sieve aperture of 0.100mm) and a receiving vessel are sequentially stacked from top to bottom.

The raw material powder was put into the uppermost sieve and sieved with an oscillator for 30 minutes. The mass of the raw material powder remaining on each sieve was measured, and the cumulative mass passing through each sieve aperture value was plotted on a graph, and the particle diameter at which the cumulative mass passing through each sieve aperture value was 50% was determined as D50 of the raw material powder.

2. Production of powder and laminate

[ example 1]

First, a raw material powder (A1) was pulverized at a rotation speed of 1700rpm by a rotor mill (ロータースピードミル P-14, manufactured by Friez corporation, フリッチュ Co.) to obtain a pulverized powder.

Next, the pulverized powder was classified by using a circular vibrating screen (model KGO-1000, sieve size 212 μm, manufactured by QINGXINGKOKU Co., Ltd. (セイシン corporation )) to obtain powder (B1).

The D10 of the powder (B1) was 3.8. mu.m, D50 was 22.2. mu.m, D90 was 100.6. mu.m, D100 was 200.5. mu.m, the bulk density was 0.491g/mL for loose packing, and the bulk density was 0.646g/mL for dense packing.

First, a SUS304 steel plate having a length of 40mm, a width of 150mm and a thickness of 2mm was prepared.

Then, the surface of the steel sheet is subjected to sand blasting using 60 mesh alumina particles under the condition that the surface roughness Ra is 5 to 10 μm.

Then, the surface of the steel sheet was cleaned with ethanol to prepare a substrate.

After a powder coating material comprising the powder (B1) was electrostatically applied to the surface of the substrate, the firing was repeated 10 times under the condition of a firing temperature of 350 ℃ to × ℃ for 4 minutes to obtain a laminate.

The thickness of the F resin layer formed on the substrate was 314. mu.m.

[ example 2]

First, a raw material powder (A2) was pulverized at 5000rpm using a pin mill (model M-4, manufactured by freshening industries, Ltd.) to obtain a pulverized powder.

Next, the pulverized powder was classified by using a circular vibrating screen (model KGO-1000, sieve diameter 212 μm, manufactured by QINGKOKAI Co., Ltd.) to obtain powder (B2).

The D10 of the powder (B2) was 3.6. mu.m, D50 was 21.1. mu.m, D90 was 99.4. mu.m, D100 was 181.9. mu.m, the bulk density for bulk filling was 0.524g/mL, and the bulk density for dense filling was 0.695 g/mL.

Next, a powder coating material composed of the powder (B2) was electrostatically applied to the surface of the substrate prepared in the same manner as in example 1, and then firing was repeated 2 times under the conditions of a firing temperature of 350 ℃ and a firing time of × for 6 minutes, to obtain a laminate.

The thickness of the F resin layer formed on the substrate was 330 μm.

[ example 3]

Powder (B3) was obtained in the same manner as in example 2, except that raw material powder (A3) was used in place of raw material powder (a 2).

The D10 of the powder (B3) was 3.9 μm, D50 was 24.4 μm, D90 was 78.2 μm, D100 was 169.9. mu.m, the bulk density for bulk filling was 0.525g/mL, and the bulk density for dense filling was 0.699 g/mL.

Next, a powder coating material comprising a powder (B3) was electrostatically applied to the surface of the substrate prepared in the same manner as in example 1, and then the firing at a firing temperature of 350 ℃ to × for 4 minutes was repeated 5 times, and further, after the above powder coating material was electrostatically applied, firing at a firing temperature of 350 ℃ to × for 6 minutes was performed 1 time, to obtain a laminate.

The thickness of the F resin layer formed on the substrate was 330 μm.

[ example 4]

Powder (B4) was obtained in the same manner as in example 2, except that the rotational speed of the pin mill was changed to 2100rpm and classification was not performed.

The D10 of the powder (B4) was 10.6. mu.m, D50 was 94.4. mu.m, D90 was 260.1. mu.m, D100 was 340.1. mu.m, the bulk density for bulk filling was 0.729g/mL, and the bulk density for dense filling was 0.835 g/mL.

Next, a laminate was obtained in the same manner as in example 3, except that the powder coating material composed of the powder (B4) was used.

The thickness of the F resin layer formed on the substrate was 330 μm.

[ example 5]

Powder (B5) was obtained in the same manner as in example 2, except that the rotational speed of the pin mill was changed to 2100 rpm.

The D10 of the powder (B5) was 10.6. mu.m, D50 was 82.1. mu.m, D90 was 186.5. mu.m, D100 was 212.0. mu.m, the bulk density for bulk filling was 0.511g/mL, and the bulk density for dense filling was 0.672 g/mL.

Next, a laminate was obtained in the same manner as in example 3, except that the powder coating material composed of the powder (B5) was used.

The thickness of the F resin layer formed on the substrate was 330 μm.

[ example 6]

Powder (B6) was obtained in the same manner as in example 2, except that the rotational speed of the pin mill was changed to 3000 rpm.

The D10 of the powder (B6) was 9.2 μm, D50 was 56.9 μm, D90 was 131.6 μm, D100 was 203.2 μm, the bulk density was 0.529g/mL for loose packing, and the bulk density was 0.691g/mL for dense packing.

Next, a laminate was obtained in the same manner as in example 3, except that the powder coating material composed of the powder (B6) was used.

The thickness of the F resin layer formed on the substrate was 330 μm.

Example 7 (comparative example)

Powder (B7) and a laminate were obtained in the same manner as in example 2, except that the rotational speed of the pin mill was changed to 4000 rpm.

The D10 of the powder (B7) was 8.3 μm, D50 was 25.5 μm, D90 was 120.6 μm, D100 was 191.3. mu.m, the bulk density was 0.503g/mL for loose packing, and the bulk density was 0.657g/mL for dense packing.

The thickness of the F resin layer formed on the substrate was 330 μm.

The particle diameter and amount of the resin particles constituting the powder, the bulk density of loose packing, and the bulk density of dense packing were measured as follows.

(measurement of particle diameter and amount of resin particles)

The powder was dispersed in water using a laser diffraction scattering particle size distribution measuring device (LA-920 measuring instrument) manufactured by horiba japan, ltd, and measured for particle size distribution, and D10, D50, D90, and D100 were calculated.

The amount of resin particles having a particle diameter of 4 μm or less and the amount of resin particles having a particle diameter of 15 to 60 μm were determined from the obtained particle size distribution map.

(bulk and dense pack bulk Density)

The bulk density and the dense bulk density of the powder were measured by the methods described in [0117] and [0118] of International publication No. 2016/017801, respectively.

3. Measurement and evaluation

3-1. peel strength

First, cuts were made with a dicing blade at intervals of 10mm from the surface side of the F resin layer of the laminate obtained in each example.

Next, a part of the F resin layer was peeled off and fixed to a chuck of a tensile tester.

Then, the peel strength (N/cm) was measured when the F resin layer was peeled from the substrate at a tensile speed of 50 mm/min at 90 ℃.

3-2. evaluation of appearance

In each example, 100 laminates were produced, and the surface of the F resin layer of each laminate was visually observed and evaluated for appearance according to the following evaluation criteria.

< evaluation criteria >

◎ No unevenness was observed on the surface of the F resin layer in any of the laminates.

○ in the laminate of 5 or less, irregularities were observed on the surface of the F resin layer.

△ unevenness was observed on the surface of the F resin layer in the 6-10 laminates.

× unevenness was observed on the surface of the F resin layer in the laminate of more than 10.

The results described above, as well as the production conditions of the powder, the particle diameters (D10, D50, D90, and D100), the amounts, and the production conditions of the laminate are shown in table 1.

[ Table 1]

As shown in table 1, in examples 1 to 6 using the powder in which the relationship between D10 and D50 was within the range specified in the present invention, the adhesion between the substrate and the F resin layer was excellent.

Examples 1 to 3 using the powder having a small D50 size showed a tendency to form a smooth F resin layer on the surface, while examples 4 to 6 using the powder having a large D50 size showed a tendency to form irregularities on the surface of the F resin layer.

In example 7 in which the powder having a relationship between D10 and D50 out of the range specified in the present invention was used, irregularities were observed on the surface of the F resin layer. Further, the adhesiveness between the base material and the F resin layer tends to be reduced.

Possibility of industrial utilization

The powder of the present invention is suitable for a powder coating material used for powder coating, and particularly suitable for a powder coating material for forming a thick fluororesin layer having a smooth surface.

In addition, the entire contents of the specification, claims, abstract and drawings of japanese patent application No. 2017-235350 filed on 12/7/2017 are cited herein as disclosures of the present specification.

Claims

1. A powder comprising resin particles comprising a fluoropolymer having units based on tetrafluoroethylene and having a melting point of 260 to 320 ℃, wherein when the volume-based cumulative 50% diameter is X and the volume-based cumulative 10% diameter is Y, the ratio of Y/X is 0.3 or less.

2. The powder according to claim 1, wherein the volume-based cumulative 10% diameter is 4 μm or less and the volume-based cumulative 50% diameter is 15 to 60 μm.

3. The powder according to claim 2, wherein A/B is 0.1 or more, where A represents an amount of resin particles having a particle diameter of 4 μm or less contained in the powder and B represents an amount of resin particles having a particle diameter of 15 to 60 μm.

4. The powder according to claim 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 vol%.

5. The powder according to any one of claims 1 to 4, wherein the volume-based cumulative 100% diameter is 220 μm or less.

6. The powder according to any one of claims 1 to 5, wherein the fluoropolymer has at least one functional group selected from the group consisting of a carbonyl group-containing group, a hydroxyl group, an epoxy group and an isocyanate group.

7. The powder according to claim 6, wherein the fluoropolymer has the tetrafluoroethylene-based unit and the unit having the functional group.

8. A powder coating material comprising the powder according to any one of claims 1 to 7.

9. A powder coating material as claimed in claim 8, wherein the amount of the powder contained in the powder coating material is 90 to 100% by mass.

10. A method for producing a laminate comprising a base material and a fluororesin layer formed of the powder according to any one of claims 1 to 7 provided on the base material, wherein the fluororesin layer is obtained by supplying a powder coating material containing the powder onto the base material and firing the powder coating material.

11. The production method according to claim 10, wherein the powder coating material is fired by heating to a temperature not lower than the melting point of the fluoropolymer.

12. The method according to claim 10 or 11, wherein the fluororesin layer has a thickness of 50 to 750 μm.