Method for producing fluorine-containing copolymer, method for producing powder coating material, and method for producing coated article

Abstract

Provided are a method for producing a fluorine-containing copolymer, a method for producing a powder coating material, and a method for producing a coated article, with which it is possible to produce a fluorine-containing copolymer having excellent thermal stability, excellent glossiness of a coating film when used to form the coating film, and further suppressed coloring of the coating film. The method for producing a fluorine-containing copolymer according to the present invention produces a fluorine-containing copolymer containing a chlorotrifluoroethylene-based unit and a vinyl ether-based unit, the method comprising: using a radical polymerization initiator, a piperidinyl group-containing compound, and hydrotalcite; a fluorine-containing copolymer is produced by polymerizing monomers containing chlorotrifluoroethylene and vinyl ether, the ratio of the molar amount of piperidinyl groups in a piperidinyl-containing compound to the molar amount of the total amount of monomers being 0.0032-0.010, the mass ratio of the amount of hydrotalcite to the amount of the piperidinyl-containing compound being 0.3 or more but less than 4.6, and after the polymerization is started, the amount of the vinyl ether is less than 0.3% by mass, and the amount of the vinyl ether is less than 0.3% by mass. Chlorotrifluoroethylene and vinyl ether are continuously or intermittently supplied into the reaction system.

Description

Technical Field

[0001] The present invention relates to a method for producing a fluorine-containing copolymer, a method for producing a powder coating material, and a method for producing a coated article. Background Art

[0002] A coating containing a fluorinated copolymer can form a coating film having excellent weather resistance. As a method for producing such a fluorinated copolymer, Patent Document 1 discloses a method in which a fluorinated copolymer is obtained by using a fluoroolefin, a monomer having a crosslinking group, and a monomer having no fluorine atom and a crosslinking group in the presence of a piperidinyl-containing compound and an organic solvent.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2014 / 054545 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] There is a demand for further improvement in thermal stability of fluorinated copolymers used as coating materials so that the molecular weight does not increase due to heat. There is also a demand for further improvement in glossiness and coloring of the resulting coating film.

[0008] The present inventors evaluated the fluorinated copolymer described in Patent Document 1 and found that there is room for improvement in the thermal stability of the fluorinated copolymer and the gloss and coloring of the formed coating film.

[0009] The present invention aims to provide a method for producing a fluorinated copolymer which is excellent in thermal stability, has excellent glossiness when used to form a coating film, and further suppresses the coloring of the coating film. In addition, the present invention aims to provide a method for producing a powder coating containing the fluorinated copolymer and a method for producing a coated article using the powder coating.

[0010] Solutions for solving problems

[0011] The present inventors have conducted intensive studies on the above-mentioned problems and have found that, in a method for producing a fluorinated copolymer comprising units based on chlorotrifluoroethylene and units based on vinyl ether by polymerizing monomers comprising chlorotrifluoroethylene and vinyl ether using a radical polymerization initiator, a piperidinyl group-containing compound and a hydrotalcite, the molar ratio of the piperidinyl group in the piperidinyl group-containing compound to the molar ratio of the total amount of the monomers used is 0.0032 to 0.010, the mass ratio of the amount of the hydrotalcite to the amount of the piperidinyl group-containing compound used is 0.3 or more and less than 4.6, and chlorotrifluoroethylene and vinyl ether are continuously or intermittently supplied to the reaction system after the start of polymerization, thereby obtaining a fluorinated copolymer having excellent thermal stability, excellent glossiness of a coating film when used to form a coating film, and further suppressed coloring of the coating film when used to form a coating film, thereby completing the present invention.

[0012] That is, the inventors have found that the above-mentioned problems can be solved by the following configuration.

[0013] [1] A method for producing a fluorinated copolymer comprising units based on chlorotrifluoroethylene and units based on vinyl ether, wherein the fluorinated copolymer is produced by polymerizing monomers comprising chlorotrifluoroethylene and vinyl ether using a radical polymerization initiator, a piperidinyl-containing compound and hydrotalcite, wherein the molar amount of the piperidinyl group in the piperidinyl-containing compound relative to the molar amount of the total amount of the monomers is 0.0032 to 0.010, and the mass ratio of the amount of the hydrotalcite relative to the amount of the piperidinyl-containing compound is 0.30 or more and less than 4.60, and after the start of the polymerization, the chlorotrifluoroethylene and the vinyl ether are continuously or intermittently supplied to the reaction system.

[0014] [2] The method for producing a fluorinated copolymer according to [1], which is a method for producing a fluorinated copolymer in which the polymerization is carried out in a reactor, wherein a solvent and the monomers are present in the reactor before the polymerization is started, and the ratio of the total molar amount of the monomers to the molar amount of the solvent in the reactor before the polymerization is started is 0.30 or more.

[0015] [3] The method for producing a fluorinated copolymer according to [1] or [2], wherein the vinyl ether contains at least a vinyl ether having a crosslinkable group.

[0016] [4] The method for producing a fluorinated copolymer according to [3], wherein the crosslinkable group is a hydroxyl group or a carboxyl group.

[0017] [5] The process for producing a fluorinated copolymer according to [3], wherein the amount of the vinyl ether having a crosslinkable group used is 1 to 20 mol % based on the total amount of the monomers used.

[0018] [6] The method for producing a fluorinated copolymer according to [1] or [2], wherein the vinyl ether comprises a vinyl ether having a crosslinkable group and a vinyl ether having no crosslinkable group, and the amount of the vinyl ether having no crosslinkable group is 1 to 70 mol % based on the total amount of the monomers used.

[0019] [7] The process for producing a fluorinated copolymer according to [1] or [2], wherein the molar ratio of the amount of the chlorotrifluoroethylene used is 30 to 70 mol % based on the total amount of the monomers used.

[0020] [8] The method for producing a fluorinated copolymer according to [1] or [2], wherein the fluorinated copolymer has a weight average molecular weight of 10,000 to 60,000.

[0021] [9] A method for producing a powder coating material, comprising producing the powder coating material using a fluorinated copolymer produced by the method for producing a fluorinated copolymer according to [1] or [2].

[0022]

[10] A method for producing a coated article, characterized in that a powder coating produced by the method for producing a powder coating according to [9] is applied to a surface of a substrate to form a coating layer, and the coating layer is melted and solidified to form a coating film.

[0023] Effects of the Invention

[0024] According to the present invention, there can be provided a method for producing a fluorinated copolymer which is capable of producing a fluorinated copolymer having excellent thermal stability, excellent glossiness of a coating film when used to form a coating film, and further suppressed coloring of the coating film. In addition, there can be provided a method for producing a powder coating material containing the fluorinated copolymer, and a method for producing a coated article using the powder coating material. DETAILED DESCRIPTION

[0025] The meanings of the terms in the present invention are as follows.

[0026] The numerical range represented by "~" refers to a range containing the numerical values ​​recorded before and after "~" as the lower limit and the upper limit. In the numerical range recorded in stages in this specification, the upper limit or lower limit recorded in a certain numerical range can be replaced by the upper limit or lower limit of the numerical range recorded in other stages. In addition, in the numerical range recorded in this specification, the upper limit or lower limit recorded in a certain numerical range can be replaced by the value shown in the embodiment.

[0027] In this specification, each component may be used alone or in combination of two or more thereof. Here, when two or more substances are used in combination, the content of the component refers to the total content of the substances used in combination unless otherwise specified.

[0028] In the present specification, a combination of two or more preferred aspects is a more preferred aspect.

[0029] Unit refers to the general term for the atomic group based on one molecule of the above monomer directly formed by polymerization of the monomer and the atomic group obtained by chemical conversion of a part of the above atomic group. The content (mol %) of each unit relative to all units contained in the polymer is obtained by analyzing the polymer using nuclear magnetic resonance spectroscopy, and can also be determined by the input amount of the components used in the production of the polymer.

[0030] (Meth)acrylic acid is a general term for acrylic acid and methacrylic acid.

[0031] The hydrolyzable silyl group refers to a group that can undergo a hydrolysis reaction to form a silanol group.

[0032] The acid value and the hydroxyl value are values ​​measured by the method according to JIS K 0070-3 (1992), respectively.

[0033] The glass transition temperature (Tg) is the midpoint glass transition temperature of a polymer as measured by differential scanning calorimetry (DSC).

[0034] The melt viscosity is a value of the melt viscosity of a sample at 170° C. when the temperature is increased from 130° C. to 200° C. using a rotational rheometer at a temperature increase rate of 10° C. / min.

[0035] The number average molecular weight (Mn) and the weight average molecular weight (Mw) are values ​​measured by size exclusion chromatography (gel permeation chromatography) using polystyrene as a standard substance. In addition, the ratio of Mw to Mn represents the molecular weight distribution and is also referred to as Mw / Mn.

[0036] The average particle size of the particles is a value of 50% particle size obtained by calculating the volume average from particle size distribution measured using a known particle size distribution measuring apparatus (Sympatec trade name Helos-Rodos, etc.) based on the measurement principle of laser diffraction.

[0037] The film thickness is a value measured using an eddy current film thickness meter (SANKO ELECTRONIC LABORATORY CO., LTD., trade name EDY-5000, etc.).

[0038] The method for producing a fluorinated copolymer of the present invention (hereinafter also referred to as the present production method) is a method for producing a fluorinated copolymer comprising units based on chlorotrifluoroethylene and units based on vinyl ether, wherein: a free radical polymerization initiator, a piperidinyl-containing compound and hydrotalcite are used to polymerize monomers comprising chlorotrifluoroethylene and vinyl ether to produce the fluorinated copolymer, the ratio of the molar amount of the piperidinyl group in the piperidinyl-containing compound to the molar amount of the total amount of the monomers used is 0.0032 to 0.010, the mass ratio of the amount of the hydrotalcite to the amount of the piperidinyl-containing compound used is 0.30 or more and less than 4.60, and chlorotrifluoroethylene and vinyl ether are continuously or intermittently supplied to the reaction system after the start of polymerization.

[0039] In addition, the monomer in this specification refers to both an embodiment including only one monomer and an embodiment including two or more monomers.

[0040] Hereinafter, the fluorinated copolymer produced by the present production method will be described, and then the present production method will be described.

[0041] The fluorinated copolymer produced by the present production method (hereinafter also referred to as a specific fluorinated copolymer) comprises units based on chlorotrifluoroethylene (CF2=CFCl) and units based on vinyl ether.

[0042] The content of the units based on chlorotrifluoroethylene is preferably 30 to 70 mol %, more preferably 40 to 60 mol %, further preferably 45 to 55 mol %, based on the total repeating units of the specific fluorinated copolymer, from the viewpoint that the weather resistance of a coating film obtained by using the specific fluorinated copolymer is more excellent.

[0043] The vinyl ether may be a vinyl ether having a crosslinkable group or a vinyl ether not having a crosslinkable group.

[0044] The vinyl ether preferably has a crosslinkable group from the viewpoint of further improving the hardness of a coating film obtained by using the specific fluorinated copolymer.

[0045] Specific examples of the crosslinking group include at least one group selected from the group consisting of a hydroxyl group, an amino group, an epoxy group, an oxetane group, a hydrolyzable silyl group, a sulfo group, and a carboxyl group. From the perspective of further improving the hardness of the coating film obtained by using the specific fluorinated copolymer, a hydroxyl group or a carboxyl group is preferred, and a hydroxyl group is more preferred. It should be noted that the sulfo group and the carboxyl group can be ionized to form -SO3 - or -COO - , or it can form salts with cations to become -SO3 - Na + or -COO - Na+ wait.

[0046] The number of crosslinkable groups may be 1 or 2 or more. Two or more crosslinkable groups may be used in combination.

[0047] Two or more kinds of vinyl ethers may be used in combination, and among them, a mode in which a vinyl ether having a crosslinkable group and a vinyl ether having no crosslinkable group are used in combination is preferred.

[0048] Vinyl ether may or may not have a fluorine atom, but preferably does not have a fluorine atom.

[0049] Two or more types of the vinyl ethers having a crosslinkable group may be used in combination.

[0050] As the vinyl ether having a crosslinkable group, a vinyl ether having a hydroxyl group or a vinyl ether having a carboxyl group is preferred, and a vinyl ether having a hydroxyl group is more preferred, since the hardness of a coating film obtained by using the specific fluorinated copolymer can be further improved.

[0051] Two or more types of vinyl ethers having no crosslinkable group may be used in combination.

[0052] Specific examples of vinyl ethers having a hydroxyl group include CH2=CHO-CH2-cycloC6H 10 -CH2OH, CH2=CHOCH2CH2OH, CH2=CHOCH2CH2CH2CH2OH.

[0053] It should be noted that "-cycloC6H 10 -" refers to cyclohexylene, "-cycloC6H 10 -" is usually a 1,4-bonding site.

[0054] Two or more types of vinyl ethers having a hydroxyl group may be used in combination.

[0055] Specific examples of vinyl ethers having a carboxyl group include CH2=CHO(CH2) n12 A monomer represented by OC(O)CH2CH2COOH (wherein n12 represents an integer from 1 to 10).

[0056] Two or more types of vinyl ethers having a carboxyl group may be used in combination.

[0057] Specific examples of the vinyl ether having no crosslinkable group include ethyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, and cyclohexyl methyl vinyl ether.

[0058] The content of the units derived from vinyl ether is preferably from 1 to 80 mol %, more preferably from 10 to 70 mol %, further preferably from 20 to 60 mol %, based on all repeating units of the specific fluorinated copolymer.

[0059] In a case where the units based on vinyl ether include units based on vinyl ether having a crosslinkable group, the content of the units based on vinyl ether having a crosslinkable group is preferably 1 to 20 mol %, more preferably 3 to 20 mol %, further preferably 5 to 15 mol % based on the total repeating units of the specific fluorinated copolymer, from the viewpoint of further improving the hardness of a coating film obtained using the specific fluorinated copolymer.

[0060] In a case where the units based on vinyl ether include units based on vinyl ether having no crosslinking group, the content of the units based on vinyl ether having no crosslinking group is preferably 1 to 70 mol %, more preferably 5 to 60 mol %, further preferably 10 to 50 mol % based on the total repeating units of the specific fluorinated copolymer, from the viewpoint of further improving the smoothness of a coating film obtained using the specific fluorinated copolymer.

[0061] The specific fluorinated copolymer may contain units other than the units based on chlorotrifluoroethylene and the units based on vinyl ether (hereinafter also referred to as other units), but preferably contains substantially no other units from the viewpoint that a coating film obtained by using the specific fluorinated copolymer has more excellent weather resistance.

[0062] Here, substantially containing no other units means that the content of other units is at most 0.1 mol % based on all repeating units of the specific fluorinated copolymer.

[0063] Specific examples of other units include units based on fluoroolefins other than chlorotrifluoroethylene and units based on vinyl esters.

[0064] The specific fluorinated copolymer preferably has no carboxyl group from the viewpoint that the hardness of the coating film obtained by using the specific fluorinated copolymer can be further improved. In this case, the specific fluorinated copolymer preferably has a hydroxyl group.

[0065] The specific fluorinated copolymer preferably comprises units based on chlorotrifluoroethylene, units based on vinyl ether having a crosslinkable group and units based on vinyl ether having no crosslinkable group, and is more preferably a fluorinated copolymer composed only of units based on chlorotrifluoroethylene, units based on vinyl ether having a crosslinkable group and units based on vinyl ether having no crosslinkable group.

[0066] In the specific fluorinated copolymer, the units based on chlorotrifluoroethylene, the units based on vinyl ether having a crosslinkable group and the units based on vinyl ether not having a crosslinkable group are preferably contained in an amount of 30 to 70 mol%, 1 to 20 mol% and 1 to 70 mol%, respectively, based on all the units contained in the specific fluorinated copolymer, and more preferably 45 to 55 mol%, 5 to 15 mol% and 10 to 50 mol%, respectively.

[0067] The Tg of the specific fluorinated copolymer is preferably 30 to 60°C, more preferably 35 to 60°C, further preferably 40 to 55°C, from the viewpoint of further improving the anti-blocking property of the powder coating material comprising the specific fluorinated copolymer and the surface smoothness of a coating film obtained using the powder coating material.

[0068] The melt viscosity of the specific fluorinated copolymer at 170°C is preferably from 10 to 450 Pa·s, more preferably from 30 to 450 Pa·s, further preferably from 40 to 400 Pa·s.

[0069] When the specific fluorinated copolymer has a hydroxyl value, the hydroxyl value of the specific fluorinated copolymer is preferably higher than 0 mgKOH / g and lower than 150 mgKOH / g, more preferably 5 to 100 mgKOH / g, further preferably 15 to 70 mgKOH / g, particularly preferably 30 to 60 mgKOH / g.

[0070] When the specific fluorinated copolymer has an acid value, the acid value of the specific fluorinated copolymer is preferably more than 0 mgKOH / g and less than 10 mgKOH / g, more preferably 2 to 8 mgKOH / g, further preferably 3 to 7 mgKOH / g.

[0071] From the viewpoint of more excellent effects of the present invention, the Mw of the specific fluorinated copolymer is preferably from 10,000 to 60,000, more preferably from 15,000 to 55,000, further preferably from 20,000 to 50,000.

[0072] From the viewpoint of more excellent effects of the present invention, Mn of the specific fluorinated copolymer is preferably from 5,000 to 20,000, more preferably from 6,000 to 18,000, further preferably from 7,000 to 16,000.

[0073] From the viewpoint of more excellent effects of the present invention, Mw / Mn (molecular weight distribution) of the specific fluorinated copolymer is preferably from 2.0 to 3.5, more preferably from 2.3 to 3.3, further preferably from 2.5 to 3.2.

[0074] As an example of a method for adjusting the Mw / Mn of the specific fluorinated copolymer, in the present production method, there can be mentioned a method of adjusting the amounts of the piperidinyl group-containing compound and the hydrotalcite, and a method of continuously or intermittently supplying chlorotrifluoroethylene and vinyl ether into the reaction system after the start of polymerization of the monomers containing chlorotrifluoroethylene and vinyl ether.

[0075] The specific fluorinated copolymer can be used as a component of a coating. The coating prepared from the specific fluorinated copolymer can be any of a solvent-based coating in which the specific fluorinated copolymer is dissolved in an organic solvent, an aqueous coating in which the specific fluorinated copolymer is dispersed in water, and a powder coating containing powder of the specific fluorinated copolymer, preferably a powder coating.

[0076] As described above, the present production method is a method for producing a fluorinated copolymer, wherein monomers containing chlorotrifluoroethylene and vinyl ether are polymerized using a radical polymerization initiator, a piperidinyl group-containing compound and hydrotalcite to produce a fluorinated copolymer containing units based on chlorotrifluoroethylene and units based on vinyl ether.

[0077] In the present production method, the ratio of the molar amount of the piperidinyl group in the piperidinyl group-containing compound to the molar amount of the total amount of the monomers (hereinafter, also referred to as the ratio Pg / M.) is 0.0032 to 0.010, the mass ratio of the amount of hydrotalcite to the amount of the piperidinyl group-containing compound (hereinafter, also referred to as the ratio H / Pc.) is 0.30 or more and less than 4.60, and chlorotrifluoroethylene and vinyl ether are continuously or intermittently supplied to the reaction system after the start of polymerization, thereby being able to produce a fluorinated copolymer having excellent thermal stability, excellent glossiness of the coating film when used to form a coating film, and further suppressed coloring of the coating film when used to form a coating film. The reason for this may not be clear, but it is considered to be as follows.

[0078] It is presumed that by making the ratio Pg / M equal to or more than the lower limit, the change in molecular weight (increase in molecular weight) of the fluorinated copolymer, which is one of the factors causing gelation of the fluorinated copolymer, can be suppressed even in a high temperature environment, thereby improving the thermal stability of the fluorinated copolymer.

[0079] It is presumed that by making the ratio Pg / M equal to or less than the upper limit value, coloring derived from the piperidinyl group-containing compound in a coating film formed using the fluorinated copolymer is suppressed.

[0080] It is presumed that by setting the ratio H / Pc within the above range, undesirable side reactions in the polymerization of the monomers are suppressed, the molecular weight of the fluorinated copolymer becomes more uniform, and a fluorinated copolymer in which the generation of foreign matter is suppressed when the fluorinated copolymer is used to form a coating film is produced, resulting in improved glossiness of the coating film.

[0081] It is also presumed that the molecular weight of the fluorinated copolymer becomes more uniform and the glossiness of a coating film formed using the fluorinated copolymer is improved by continuously or intermittently supplying chlorotrifluoroethylene and vinyl ether into the reaction system after the start of polymerization of the monomers containing chlorotrifluoroethylene and vinyl ether.

[0082] The components used for producing the specific fluorinated copolymer in the present production method will be described.

[0083] In the present production method, at least a monomer containing chlorotrifluoroethylene and vinyl ether, a radical polymerization initiator, a piperidinyl group-containing compound, and hydrotalcite are used.

[0084] Chlorotrifluoroethylene and vinyl ether used in the present production method are as described in the above-mentioned specific fluorinated copolymer, respectively, and suitable embodiments thereof are also the same.

[0085] The preferred amount of chlorotrifluoroethylene used relative to the total amount of monomers used in the present production method is the same as the preferred amount of the content of units based on chlorotrifluoroethylene relative to the total repeating units of the above-mentioned specific fluorinated copolymer. That is, the amount of chlorotrifluoroethylene used relative to the total amount of monomers used is preferably 30 to 70 mol%, more preferably 40 to 60 mol%, and further preferably 45 to 55 mol%.

[0086] In addition, suitable embodiments of the amount of vinyl ether used, the amount of vinyl ether having a crosslinkable group used, and the amount of vinyl ether not having a crosslinkable group used relative to the total amount of monomers used in the present production method are the same as suitable embodiments of the content of units based on vinyl ether, the content of units based on vinyl ether having a crosslinkable group, and the content of units based on vinyl ether not having a crosslinkable group, respectively, relative to all repeating units of the above-mentioned specific fluorinated copolymer.

[0087] In the present production method, monomers other than chlorotrifluoroethylene and vinyl ether may be used. However, from the viewpoint of achieving more excellent effects of the present invention, it is preferred to use only chlorotrifluoroethylene and vinyl ether as monomers.

[0088] In the present production method, preferably a monomer containing chlorotrifluoroethylene, a vinyl ether having a crosslinkable group, and a vinyl ether having no crosslinkable group is used, and more preferably a monomer containing only chlorotrifluoroethylene, a vinyl ether having a crosslinkable group, and a vinyl ether having no crosslinkable group is used.

[0089] The preferred embodiment of the respective amounts of chlorotrifluoroethylene, the vinyl ether having a crosslinkable group, and the vinyl ether having no crosslinkable group to be used relative to the total amount of the monomers to be used is the same as the preferred embodiment of the respective contents of the units based on chlorotrifluoroethylene, the units based on the vinyl ether having a crosslinkable group, and the units based on the vinyl ether having no crosslinkable group to be contained in the above-mentioned specific fluorinated copolymer.

[0090] In the present production method, a piperidinyl group-containing compound is used. The piperidinyl group-containing compound refers to a compound having a piperidinyl group or a piperidinyl group having a substituent. As the piperidinyl group-containing compound, a compound having a piperidinyl group having a substituent is preferred.

[0091] The piperidinyl group having a substituent is preferably a tetra-substituted piperidinyl group, and more preferably a 2,2,6,6-tetra-substituted piperidinyl group.

[0092] The piperidinyl group-containing compound is preferably a piperidinyl group-containing compound having two or more piperidinyl groups or a piperidinyl group having a substituted group in one molecule.

[0093] Two or more piperidinyl group-containing compounds may be used, and preferably two or more piperidinyl group-containing compounds are used.

[0094] The piperidinyl group-containing compound is preferably a compound represented by the following formula (a compound having a 2,2,6,6-tetrasubstituted piperidinyl group).

[0095] [Chemistry 1]

[0096]

[0097] R 11 ~R 14 Each is independently an alkyl group having 1 to 18 carbon atoms (such as methyl, ethyl, propyl, dodecyl, and stearyl), a cycloalkyl group (such as cyclopentyl and cyclohexyl), a substituted alkyl group (such as 2-hydroxyethyl, 2-methoxycarbonylethyl, and 3-hydroxypropyl), an aryl group (such as phenyl and naphthyl), or an aralkyl group (such as phenethyl and benzyl), R 11 and R 12 , or R 13 and R 14 It can form an aliphatic ring having 3 to 6 carbon atoms. 11 ~R 14 In view of price and availability, an alkyl group having 1 to 18 carbon atoms is preferred, and a methyl group is more preferred.

[0098] R 15It is a hydrogen atom, an alkyl group (methyl, ethyl, propyl, butyl, dodecyl, stearyl, etc.), a substituted alkyl group (2-hydroxyethyl, 2-methoxycarbonylethyl, 2-acetoxyethyl, 2-(3-methoxycarbonylpropionyloxy)ethyl, 3-hydroxypropyl, etc.), an aryl group (phenyl, naphthyl, hydroxyphenyl, etc.), an aralkyl group (phenethyl, benzyl, hydroxyphenylalkyl, etc.) or a cycloalkyl group (cyclohexyl, etc.).

[0099] R 16 is a hydrogen atom, a hydroxyl group, an alkyl group (methyl, ethyl, propyl, butyl, dodecyl, stearyl, etc.), a substituted alkyl group (2-hydroxyethyl, 2-methoxycarbonylethyl, 2-acetoxyethyl, 2-(3-methoxycarbonylpropionyloxy)ethyl, 3-hydroxypropyl, etc.), an aryl group (phenyl, naphthyl, etc.), an aralkyl group (phenethyl, benzyl, etc.), a group containing an ester bond (acetoxy, propionyloxy, butyryloxy, lauroyloxy, substituted alkylcarbonyloxy, benzoyloxy, substituted benzoyloxy, etc.), a group containing an amino group (alkoxycarbonylamino, N-monoalkylcarbamoylamino, N,N-dialkylcarbamoylamino, etc.), or a group containing a 2,2,6,6-tetrasubstituted piperidinyl group. For R 16 , these groups may be combined with two or more.

[0100] Specific examples of the piperidinyl group-containing compound include 2,2,6,6-tetramethylpiperidine, 1,2,2,6,6-pentamethylpiperidine, 4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, 1-ethyl-2,2,6,6-tetramethylpiperidine, 1-ethyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-butyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-dodecyl-2,2,6,6-tetramethylpiperidine, 1-phenyl-2,2,6,6-tetramethylpiperidine, 1-(2-hydroxyethyl)-2,2,6,6-tetramethylpiperidine, 1-(6-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-acetoxy -1,2,2,6,6-pentamethylpiperidine, 1-(2-acetoxyethyl)-4-acetoxy-2,2,6,6-tetramethylpiperidine, 1-(2-benzoyloxyethyl)-4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 4-ethyl-2,2,6,6-tetramethylpiperidine, 4-ethyl-1,2,2,6,6-pentamethylpiperidine, 4-butyl-2,2,6,6 -tetramethylpiperidine, 4-octyl-2,2,6,6-tetramethylpiperidine, 4-dodecyl-2,2,6,6-tetramethylpiperidine, 4-stearyl-2,2,6,6-tetramethylpiperidine, 4-stearyl-1,2,2,6,6-pentamethylpiperidine, methyl 1,2,2,6,6-pentamethyl-4-piperidinyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate.

[0101] As R 16 Examples of the piperidinyl group-containing compound which is a group containing a 2,2,6,6-tetrasubstituted piperidinyl group include piperidinyl group-containing compounds having two or more 2,2,6,6-tetramethylpiperidinyl groups in one molecule obtained by reacting 2,2,6,6-tetramethylpiperidine (4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-(2-hydroxyethyl)-2,2,6,6-tetramethylpiperidine, etc.) having a hydroxyl group with a polybasic acid (succinic acid, adipic acid, sebacic acid, azelaic acid, decane-1,10-dicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, malonic acid, substituted malonic acid, etc.). Specifically, examples include compounds represented by the following formula.

[0102] Here, n3 is an integer from 1 to 20.

[0103] [Chemistry 2]

[0104]

[0105] In the present production method, the ratio of the molar amount of the piperidinyl group in the piperidinyl group-containing compound to the molar amount of the total amount of the monomers used (the total molar amount of all monomers used in the polymerization) (ratio Pg / M) is 0.0032 to 0.010. In terms of the more excellent effect of the present invention, the ratio Pg / M is preferably 0.0040 to 0.0090, and more preferably 0.0050 to 0.0080.

[0106] In the present production method, hydrotalcite is used. Hydrotalcite refers to a layered composite hydroxide represented by the following formula.

[0107] [Mg 2+ 1-x Al 3+ x (OH)2] x+ [CO3 2 -x / 2 ·mH2O] x-

[0108] Wherein, x is 0.2~0.33, and m is 0~2.

[0109] From the perspective of excellent chloride ion adsorption and easy availability, the hydrotalcite is preferably Mg6Al2(OH) 16 CO3·4H2O (in the above formula representing hydrotalcite, x=0.25, m=0.5), or Mg 4.5 Al2(OH) 13 CO3·3.5H2O (in the above formula representing hydrotalcite, x=0.308, m=0.538).

[0110] Two or more types of hydrotalcites may be used.

[0111] The particle size of the hydrotalcite is preferably 5 to 500 μm, more preferably 5 to 110 μm. When the particle size of the hydrotalcite is 5 μm or more, it is easy to remove by filtration. When the particle size of the hydrotalcite is 500 μm or less, the surface area per unit mass is large, and the effect of the hydrotalcite is further exerted.

[0112] The particle size of the hydrotalcite is measured in accordance with JIS K 0069 "Sieve Test Methods for Chemicals".

[0113] In the present production method, the mass ratio of the amount of hydrotalcite used to the total amount of monomers used (the total amount of all monomers used in polymerization) is preferably 0.001 to 0.050, more preferably 0.003 to 0.030. When the above ratio is within the above range, the molecular weight distribution of the obtained fluorinated copolymer can be further reduced.

[0114] In the present production method, the mass ratio of the amount of hydrotalcite used to the amount of the piperidinyl-containing compound used (ratio H / Pc) is 0.30 or more and less than 4.60. In terms of more excellent effects of the present invention, the ratio H / Pc is preferably 0.50 to 2.00, more preferably 0.80 to 1.50.

[0115] In the present production method, a radical polymerization initiator is used for polymerization of the monomers.

[0116] Examples of the radical polymerization initiator include peroxide-based initiators and azo-based initiators.

[0117] Specific examples of the peroxide-based initiator include cyclohexanone peroxide, tert-butyl hydroperoxide, dibenzoyl peroxide, di-tert-butyl peroxide, 2,2-di(tert-butylperoxy)butane, tert-butyl peroxypivalate, and diisopropyl peroxydicarbonate.

[0118] Specific examples of the azo initiator include 2,2'-azobisisobutyronitrile, 1,1'-azobiscyclohexane-1-carbonitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), and 2,2'-azobis(2-methylbutyronitrile).

[0119] Two or more radical polymerization initiators may be used in combination.

[0120] In the present production method, the molar ratio of the polymerization initiator to the total molar amount of the monomers used is preferably 0.05 to 1.5, more preferably 0.1 to 1.0.

[0121] Examples of the polymerization method of the monomer in the present production method include solution polymerization, emulsion polymerization, suspension polymerization, etc., and solution polymerization is preferred. Therefore, in the present production method, it is preferred to use a solvent (polymerization solvent) in the polymerization of the monomer.

[0122] Examples of the solvent include organic solvents, water and mixed solvents thereof, and organic solvents are preferred since the production of the fluorinated copolymer is easy.

[0123] The organic solvent is preferably one or more organic solvents selected from the group consisting of aromatic hydrocarbon solvents, ketone solvents, ester solvents, alcohol solvents, and ether ester solvents.

[0124] Specific examples of aromatic hydrocarbon solvents include toluene, xylene, ethylbenzene, aromatic naphtha, tetralin, and turpentine. Commercially available aromatic hydrocarbon solvents may be used, such as SOLVESSO (registered trademark) #100 (manufactured by ExxonMobil Corporation), SOLVESSO (registered trademark) #150 (manufactured by ExxonMobil Corporation), and the like.

[0125] Specific examples of the ketone solvent include acetone, methyl ethyl ketone, methyl amyl ketone, methyl isobutyl ketone, ethyl isobutyl ketone, diisobutyl ketone, cyclohexanone, and isophorone.

[0126] Specific examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, isobutyl acetate, and tert-butyl acetate.

[0127] Specific examples of the alcohol solvent include ethanol, tert-butyl alcohol, and isopropyl alcohol.

[0128] Specific examples of the ether ester solvent include ethyl 3-ethoxypropionate, propylene glycol monomethyl ether acetate, and methoxybutyl acetate.

[0129] Two or more organic solvents may be used in combination.

[0130] In the present production method, after the polymerization of monomers containing chlorotrifluoroethylene and vinyl ether is started, chlorotrifluoroethylene and vinyl ether are continuously or intermittently supplied into the reaction system.

[0131] Thereby, the concentrations of chlorotrifluoroethylene and vinyl ether in the reaction system can be easily kept constant during the polymerization reaction, so that a fluorinated copolymer having a more uniform molecular weight and more excellent effects of the present invention can be produced.

[0132] In the present production method, the type of vinyl ether present before the start of polymerization is the same as the type of vinyl ether added to the reaction system after the start of polymerization.

[0133] The reaction system refers to a system containing chlorotrifluoroethylene and vinyl ether and in which a polymerization reaction occurs, and exists in, for example, a reactor.

[0134] The polymerization start time may be the time when the temperature of a reactor containing chlorotrifluoroethylene, vinyl ether and a radical polymerization initiator is raised to the 10-hour half-life temperature of the radical polymerization initiator, or the time when the temperature of a reactor containing chlorotrifluoroethylene and vinyl ether but no radical polymerization initiator is raised to the 10-hour half-life temperature of the radical polymerization initiator and the radical polymerization initiator is added to the reactor while maintaining the temperature.

[0135] In the present production method, after the polymerization of the monomers starts, a mixture of chlorotrifluoroethylene and vinyl ether may be supplied to the reaction system, or chlorotrifluoroethylene and vinyl ether may be supplied to the reaction system separately. In addition, after the polymerization of the monomers starts, monomers other than chlorotrifluoroethylene and vinyl ether may be supplied to the reaction system in the form of a mixture with at least one of chlorotrifluoroethylene and vinyl ether, or separately from chlorotrifluoroethylene and vinyl ether.

[0136] In this specification, monomers including chlorotrifluoroethylene and vinyl ether which are continuously or intermittently supplied after the start of polymerization of the monomers are also collectively referred to as "additional monomers".

[0137] In the present production method, continuously supplying the additional monomer to the reaction system means a method of adding the additional monomer without interruption within a predetermined period, and means a method of not adding the additional monomer outside the predetermined period.

[0138] In the present production method, intermittently supplying additional monomers means adding additional monomers intermittently in batches, which means that periods of adding additional monomers and periods of not adding additional monomers are repeated alternately, and the period of adding additional monomers is repeated two or more times.

[0139] In the present production method, for example, monomers including chlorotrifluoroethylene and vinyl ether, a piperidinyl group-containing compound, hydrotalcite, and a radical polymerization initiator are introduced into a reactor, and then polymerization is initiated.

[0140] The amount of chlorotrifluoroethylene added before the start of polymerization (hereinafter also referred to as the initial stage) is a part of the total amount of chlorotrifluoroethylene used in the polymerization reaction, and the remainder is used for continuous or intermittent supply to the reaction system after the start of polymerization (hereinafter also referred to as continuous addition). Similarly, the amount of vinyl ether added initially is a part of the total amount of vinyl ether used in the polymerization reaction, and the remainder is used for continuous addition after the start of polymerization.

[0141] In the present production method, the molar ratio (Mm / Ma) of the total molar amount Mm of chlorotrifluoroethylene and vinyl ether initially charged to the total amount Ma of chlorotrifluoroethylene and vinyl ether used in the production of the specific fluorinated copolymer is preferably 0.30 or more, more preferably 0.45 or more, and further preferably 0.55 or more. When the molar ratio (Mm / Ma) is at least the above lower limit, the anti-blocking property of the coating becomes good and the glossiness when the coating film is formed improves.

[0142] The molar ratio (Mm / Ma) is preferably 1.00 or less, more preferably 0.90 or less, and further preferably 0.85 or less. When the molar ratio (Mm / Ma) is below the upper limit value, the melt viscosity of the coating material becomes good, the smoothness of the coating film becomes good, and thus the glossiness of the coating film is improved.

[0143] In the present production method, the molar ratio A of the amount of vinyl ether initially charged to the amount of chlorotrifluoroethylene initially charged is preferably 0.5 to 1.5, more preferably 0.7 to 1.3, and further preferably 0.9 to 1.1.

[0144] The molar ratio B of the amount of vinyl ether in the additional monomer continuously added to the reaction system relative to the amount of chlorotrifluoroethylene is preferably 0.7 to 2.0, more preferably 0.8 to 1.4, and even more preferably 0.9 to 1.1.

[0145] Furthermore, the ratio (A / B) of the molar ratio A to the molar ratio B is preferably 0.5 to 1.5, more preferably 0.7 to 1.3, and still more preferably 0.9 to 1.1. When the ratio (A / B) is within the above range, the amount of low molecular weight components contained in the obtained fluorinated copolymer decreases. As a result, the molecular weight distribution of the fluorinated copolymer can be narrowed, and the glossiness of the coating film formed using the fluorinated copolymer can be improved.

[0146] The piperidyl-containing compound may be initially added to the total amount used in the present manufacturing method, or may be initially added to a portion of the total amount used in the present manufacturing method and the remainder may be added to the reaction system after the polymerization starts. The piperidyl-containing compound is preferably initially added to the total amount. When the piperidyl-containing compound is added to the reaction system after the polymerization starts, it may be added continuously or at one time.

[0147] The hydrotalcite may be initially added in the total amount used in the present production method, or a part of the total amount used in the present production method may be initially added and the remainder may be added to the reaction system after the polymerization starts. The hydrotalcite is preferably initially added in total amount. When the hydrotalcite is added to the reaction system after the polymerization starts, it may be added continuously or all at once.

[0148] The radical polymerization initiator may be initially charged in the total amount used in the polymerization of the monomers, or may be initially charged in a portion of the total amount used in the polymerization of the monomers and the remainder added to the reaction system after the polymerization starts. The radical polymerization initiator is preferably initially charged in a portion of the total amount used in the polymerization of the monomers and the remainder added to the reaction system after the polymerization starts, more preferably initially charged in a portion of the total amount used in the polymerization of the monomers and the remainder continuously added to the reaction system after the polymerization starts.

[0149] In the present production method, when a solvent is used in the polymerization of the monomers, it is preferred that the solvent is charged into the reactor together with the monomers before the start of the polymerization, and the polymerization of the monomers is carried out in the reactor.

[0150] When a solvent is used in the polymerization of the monomer, the ratio (Mm / Ms) of the total molar amount Mm of the monomers present in the reactor before the start of the polymerization to the molar amount Ms of the solvent present in the reactor before the start of the polymerization is preferably 0.30 or more, more preferably 0.50 or more, and further preferably 0.65 or more. By making the ratio (Mm / Ms) in the above range, the polymerization is started while the concentration of the monomers in the reactor is kept high, so that the polymer chain is well elongated and the amount of low molecular weight components contained in the obtained fluorinated copolymer is reduced. As a result, the molecular weight distribution of the fluorinated copolymer can be narrowed, and the glossiness of the coating film formed using the fluorinated copolymer can be improved.

[0151] From the viewpoint of smoothness of the coating film, the ratio (Mm / Ms) is preferably 1.50 or less, more preferably 1.45 or less, and further preferably 1.00 or less.

[0152] In the present production method, the temperature in the reactor during polymerization of the monomers (polymerization temperature) is preferably 50 to 90° C., more preferably 60 to 80° C. The polymerization temperature is the temperature in the reaction system at the start of polymerization, and is the temperature in the reaction system when the monomers are polymerized while continuously adding additional monomers after the start of polymerization.

[0153] The pressure in the reaction system when additional monomers including chlorotrifluoroethylene and vinyl ether are continuously added after the start of polymerization (hereinafter also referred to as polymerization pressure) is preferably 0.3 to 0.8 MPa, more preferably 0.4 to 0.7 MPa.

[0154] The polymerization time from the start of polymerization of the monomer to the completion of polymerization of the monomer to which the additional monomer is continuously added is preferably 0.5 to 30 hours, more preferably 1 to 5 hours.

[0155] In the present production method, after the polymerization of the monomers is completed, a mixed liquid containing insoluble components derived from the hydrotalcite in addition to the specific fluorinated copolymer is obtained. The present production method may further include a step of removing the insoluble components from the mixed liquid.

[0156] Specific examples of the method for removing the insoluble component include solid-liquid separation treatment such as filtration.

[0157] In the present production method, when a solvent is used in the polymerization of the monomers, a mixed solution containing the fluorinated copolymer and the solvent may be obtained after the completion of the polymerization of the monomers. In this case, the present production method may further include a step of removing the solvent from the mixed solution.

[0158] Specific examples of the method for removing the solvent from the mixed liquid include heating and distillation.

[0159] In the present production method, components such as a chain transfer agent, a polymerization inhibitor, and a stabilizer may be used as necessary.

[0160] In the present production method, the monomers are polymerized according to the above steps to obtain a composition comprising the specific fluorinated copolymer and the piperidinyl group-containing compound (hereinafter also referred to as the present composition).

[0161] The content of the specific fluorinated copolymer contained in the present composition is preferably from 5 to 99.5 mass %, more preferably from 10 to 99 mass %, based on the total mass of the present composition.

[0162] The piperidinyl group-containing compound contained in the present composition is preferably the piperidinyl group-containing compound exemplified in the above-mentioned method for producing the fluorinated copolymer.

[0163] The content of the piperidinyl group-containing compound is preferably from 0.3 to 2.6 mass%, more preferably from 0.8 to 2.0 mass%, based on the total mass of the specific fluorinated copolymer.

[0164] The present composition may contain a solvent.

[0165] The solvent may be the polymerization solvent used for polymerization of the specific fluorinated copolymer, may be a solvent other than the polymerization solvent, or may be a mixed liquid of the polymerization solvent and a solvent other than the polymerization solvent.

[0166] Specific examples of the solvent include the solvents exemplified in the above-mentioned method for producing the fluorinated copolymer.

[0167] When the present composition contains a solvent, the content of the solvent is preferably 10 to 95% by mass, more preferably 20 to 90% by mass, based on the total mass of the present composition.

[0168] The present composition may contain an insoluble component derived from hydrotalcite, but preferably contains substantially no hydrotalcite.

[0169] Here, substantially containing no hydrotalcite means that the content of the hydrotalcite is 0.05 mass % or less relative to the total mass of the present composition.

[0170] The present composition may contain ingredients other than those described above.

[0171] The specific fluorinated copolymer is preferably used for producing a powder coating material.

[0172] When the composition containing the specific fluorinated copolymer contains a solvent, it may be used for the production of a powder coating material after removing the solvent.

[0173] The powder coating material of the present invention (hereinafter also referred to as the present coating material) contains a specific fluorinated copolymer.

[0174] The content of the specific fluorinated copolymer is preferably from 30 to 100 mass %, more preferably from 40 to 100 mass %, based on the total mass of the coating material.

[0175] The present coating material may contain a piperidinyl group-containing compound. The piperidinyl group-containing compound is preferably the piperidinyl group-containing compound exemplified in the method for producing the fluorinated copolymer.

[0176] When the present coating material contains a piperidinyl group-containing compound, the content of the piperidinyl group-containing compound is preferably 0.1 to 2.6% by mass, more preferably 0.15 to 2.0% by mass, based on the total mass of the present coating material.

[0177] The coating may further contain additives.

[0178] Specific examples of additives include pigments, curing agents, catalysts (curing catalysts, etc.), polymers other than the above (for example, polyester resins, (meth) acrylic resins, epoxy resins), fillers (resin beads, etc.), light stabilizers, ultraviolet absorbers, matting agents, surface conditioners, degassing agents, flow agents, heat stabilizers, antistatic agents, rust inhibitors, silane coupling agents, low-pollution treatment agents, plasticizers, adhesives, etc.

[0179] The coating may contain a solvent (water, organic solvent, etc.) or may not contain a solvent (water, organic solvent, etc.), preferably not containing a solvent. The content of the solvent is preferably less than 1% by mass, more preferably less than 1% by mass, and further preferably 0% by mass relative to the total mass of the coating.

[0180] The coating material can be produced by mixing the specific fluorinated copolymer and, if necessary, the additives. The mixed specific fluorinated copolymer and the additives may be in the form of independent powders or pellets.

[0181] One embodiment of the method for producing the present coating material includes a method in which the specific fluorinated copolymer and the additives used as required are melt-kneaded, cooled, and then pulverized to obtain a powder coating material. The melt-kneading temperature is preferably 80 to 130°C.

[0182] In addition, as one aspect of the method for producing the present coating, there can be mentioned a method in which a powder containing a specific fluorinated copolymer and a powder of an additive used as required are mixed to obtain a powder coating. This method is also called dry mixing and is a method in which melt kneading is not performed during mixing.

[0183] The pulverization can be performed using a pulverizer such as a pin mill, a hammer mill, or a jet mill. The pulverized product is preferably classified after pulverization so that the particle size of the obtained powder coating is uniform. The average particle size of the powder coating is preferably 1 to 100 μm, more preferably 10 to 80 μm.

[0184] The coating film of the present invention (hereinafter, also referred to as the present coating film) is formed by applying the present coating material to a substrate.

[0185] Furthermore, the coated article of the present invention comprises a substrate and a coating film formed of the present coating material and disposed on the substrate.

[0186] Specific examples of the material of the substrate include inorganic substances, organic substances, and organic-inorganic composite materials.

[0187] Specific examples of inorganic substances include concrete, natural stone, glass, and metals (iron, stainless steel, aluminum, copper, brass, titanium, etc.).

[0188] Specific examples of organic substances include plastics, rubber, adhesives, and wood.

[0189] Specific examples of the organic-inorganic composite material include fiber-reinforced plastics, resin-reinforced concrete, and fiber-reinforced concrete.

[0190] The substrate may be subjected to a known surface treatment (chemical conversion treatment, etc.) Alternatively, the substrate may have a resin layer (polyester resin layer, acrylic resin layer, silicone resin layer, etc.) formed by applying a primer or the like on the surface of the substrate in advance.

[0191] The material of the substrate is preferably metal, more preferably iron, an alloy containing iron (eg, carbon steel, stainless steel), or aluminum.

[0192] Specific examples of the shape of the substrate include a flat plate shape, a spherical shape, and a rod shape.

[0193] The film thickness of the present coating film is preferably 20 to 1000 μm, more preferably 20 to 500 μm.

[0194] The coated article of the present invention is preferably produced by applying (coating) the coating material to the surface of a substrate to form a coating layer, heating the obtained coating layer, and then cooling it.

[0195] Examples of the method for forming the coating layer include electrostatic coating, electrostatic spraying, electrostatic dipping, fluidized dipping, and spraying. Electrostatic coating using a powder coating gun is preferred.

[0196] Specific examples of powder coating guns include corona charging type coating guns and friction charging type coating guns. A corona charging type coating gun is a coating gun that performs corona discharge treatment on powder coating and blows it. A friction charging type coating gun is a coating gun that performs friction charging treatment on powder coating and blows it.

[0197] The heating temperature during the heat treatment is preferably 120 to 250° C. The heating maintenance time is usually 2 to 60 minutes. After the heat treatment, it is preferably cooled to 20 to 25° C. The coating layer melts and solidifies (melt solidification) by the heat treatment and cooling to form the present coating film.

[0198] Example

[0199] Hereinafter, examples are given to explain the present invention in detail. Examples 1 to 9 are embodiments, and Examples 10 to 14 are comparative examples. However, the present invention is not limited to these examples. It should be noted that the blending amount of each component in the table described below represents a mass standard unless otherwise specified.

[0200] (Example 1)

[0201] Into a stainless steel pressure-resistant reactor having an internal volume of 2500 ml equipped with a stirrer, 20 g of a piperidyl group-containing compound (manufactured by BASF, trade name "TINUVIN 292", a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (mass ratio 3:1)), 20 g of hydrotalcite (manufactured by Kyowa Chemical Industry Co., Ltd., trade name "KW500", particle size 45 μm or less: 38%, 45 to 75 μm: 35%, 75 to 106 μm: 21%, 106 to 500 μm: 6%), 679 g of xylene, 118 g of 4-hydroxybutyl vinyl ether (hereinafter also referred to as HBVE), and 453 g of cyclohexyl vinyl ether (hereinafter also referred to as CHVE) were charged, and dissolved oxygen in the liquid was removed by degassing with nitrogen. Furthermore, 536 g of chlorotrifluoroethylene (hereinafter referred to as CTFE) was introduced into the above reactor and the temperature was raised. When the temperature in the reactor reached 65° C., the pressure showed 0.59 MPaG. Thereafter, 2 ml of a 5% xylene solution of tert-butyl peroxypivalate (hereinafter referred to as PBPV) was added to the reactor to start the reaction.

[0202] While maintaining the pressure as the pressure decreased, additional monomers of CTFE 110 g, CHVE 93 g, and HBVE 24 g were continuously added to the reactor, and PBPV 5% xylene solution as a free radical polymerization initiator was intermittently added to the reactor to allow polymerization to proceed. After the start of polymerization, the total amount of PBPV 5% xylene solution intermittently added to the reactor was 55 ml. After 16 hours, the reactor was water-cooled to stop the reaction.

[0203] After the reaction solution is cooled to room temperature, the unreacted monomers are purged, the insoluble components of the obtained reaction solution are removed by filtration, and then an appropriate amount of xylene is added to obtain a fluorinated copolymer solution (A-1) having a solid content concentration of 65%. The fluorinated copolymer solution (A-1) contains a fluorinated copolymer, a piperidinyl-containing compound and xylene.

[0204] The composition of the fluorinated copolymer contained in the fluorinated copolymer solution (A-1) is CTFE / CHVE / HBVE (mol%) = 50 / 39 / 11. In the case where CTFE / CHVE / HBVE (mol%) = XX / YY / ZZ, the numerical values ​​represented by XX, YY and ZZ respectively refer to the molar ratios (percentages) of the structural units derived from CTFE, the structural units derived from CHVE and the structural units derived from HBVE relative to all the structural units of the fluorinated copolymer.

[0205] (Example 2)

[0206] In a stainless steel pressure-resistant reactor with an internal volume of 2500 ml equipped with a stirrer, 22 g of a piperidyl group-containing compound (manufactured by BASF, trade name "TINUVIN292", a mixture of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidinyl sebacate (mass ratio 3:1)), 22 g of hydrotalcite (manufactured by Kyowa Chemical Industry Co., Ltd., trade name "KW500", particle size 45 μm or less: 38%, 45 to 75 μm: 35%, 75 to 106 μm: 21%, 106 to 500 μm: 6%), 726 g of xylene, 79 g of HBVE, and 303 g of CHVE were introduced, and dissolved oxygen in the liquid was removed by degassing with nitrogen. Furthermore, 357 g of CTFE was introduced into the reactor and the temperature was raised. When the temperature in the reactor reached 75° C., the pressure showed 0.55 MPaG. Then, 6 ml of a 20% xylene solution of PBPV was added to the reactor to start the reaction.

[0207] While maintaining the pressure as the pressure decreased, additional monomers of 350 g of CTFE, 297 g of CHVE, and 78 g of HBVE were continuously added to the reactor, and a 20% xylene solution of PBPV as a free radical polymerization initiator was intermittently added to the reactor to allow polymerization to proceed. After the start of polymerization, the total amount of the 20% xylene solution of PBPV intermittently added to the reactor was 25 ml. After 16 hours, the reactor was water-cooled to stop the reaction.

[0208] After the reaction solution is cooled to room temperature, the unreacted monomers are purged, the insoluble components of the obtained reaction solution are removed by filtration, and then an appropriate amount of xylene is added to obtain a fluorinated copolymer solution (A-2) having a solid content concentration of 65%. The fluorinated copolymer solution (A-2) contains a fluorinated copolymer, a piperidinyl-containing compound and xylene.

[0209] The composition of the fluorinated copolymer contained in the fluorinated copolymer solution (A-2) was CTFE / CHVE / HBVE (mol %)=50 / 39 / 11.

[0210] (Example 3~Example 5)

[0211] The amounts of the components and the polymerization temperatures were as shown in Table 1. Fluorinated copolymer solutions (A-3) to (A-5) were obtained in the same manner as in Example 2. Fluorinated copolymer solutions (A-3) to (A-5) all contained fluorinated copolymers, piperidinyl-containing compounds, and xylene. The compositions of the fluorinated copolymers contained in the fluorinated copolymer solutions (A-3) to (A-5) were all CTFE / CHVE / HBVE (mol%) = 50 / 39 / 11.

[0212] (Example 6~Example 9)

[0213] The amounts of the components and the polymerization temperatures were as shown in Table 1. Fluorinated copolymer solutions (A-6) to (A-9) were obtained in the same manner as in Example 1. Fluorinated copolymer solutions (A-6) to (A-9) all contained fluorinated copolymers, piperidinyl-containing compounds, and xylene. The compositions of the fluorinated copolymers contained in the fluorinated copolymer solutions (A-6) to (A-9) were all CTFE / CHVE / HBVE (mol%) = 50 / 39 / 11.

[0214] (Example 10)

[0215] In a stainless steel pressure-resistant reactor with an internal volume of 2500 ml equipped with a stirrer, 12.4 g of a piperidyl-containing compound (manufactured by BASF, trade name "TINUVIN144", bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate), 929 g of xylene, 212 g of ethyl vinyl ether (hereinafter also referred to as EVE), 132 g of HBVE, and 214 g of CHVE were placed, and the dissolved oxygen in the liquid was removed by degassing with nitrogen. Furthermore, 677 g of CTFE was introduced into the above reactor and the temperature was raised. When the temperature in the reactor reached 65° C., 2.5 ml of a PBPV 27.9% xylene solution was added to the reactor to start polymerization.

[0216] After the polymerization started, PBPV 27.9% xylene solution was intermittently added to the reactor to allow the polymerization to proceed. The total amount of PBPV 27.9% xylene solution intermittently added to the reactor after the polymerization started was 50 ml. After 10 hours, the reactor was water-cooled to stop the reaction.

[0217] After the reaction solution was cooled to room temperature, the unreacted monomers were purged, the insoluble components of the obtained reaction solution were removed by filtration, and an appropriate amount of xylene was further added to the obtained filtrate to obtain a fluorinated copolymer solution (A-10) having a solid content concentration of 60.7%. The fluorinated copolymer solution (A-10) contains a fluorinated copolymer, a piperidinyl-containing compound and xylene.

[0218] The composition of the fluorinated copolymer contained in the fluorinated copolymer solution (A-10) was CTFE / EVE / CHVE / HBVE (mol %)=50 / 25 / 15 / 10.

[0219] (Example 11~Example 13)

[0220] The amounts of the components and the polymerization temperatures were as shown in Table 1. Fluorinated copolymer solutions (A-11) to (A-13) were obtained in the same manner as in Example 1. Fluorinated copolymer solutions (A-11) to (A-13) all contained fluorinated copolymers, piperidinyl-containing compounds, and xylene. The compositions of the fluorinated copolymers contained in the fluorinated copolymer solutions (A-11) to (A-13) were all CTFE / CHVE / HBVE (mol%) = 50 / 39 / 11.

[0221] (Example 14)

[0222] The fluorinated copolymer solution (A-14) was obtained in the same manner as in Example 10 except that the amounts of the components and the polymerization temperature were as shown in Table 1. The fluorinated copolymer solution (A-14) contained a fluorinated copolymer, a piperidinyl-containing compound and xylene. The composition of the fluorinated copolymer contained in the fluorinated copolymer solution (A-14) was CTFE / CHVE / HBVE (mol %) = 50 / 39 / 11.

[0223] (Determination of Molecular Weight of Fluorinated Copolymer)

[0224] Tetrahydrofuran (hereinafter also referred to as THF) was added to the fluorinated copolymer solution of each example to obtain a solution diluted to a concentration of 1 mass % of the fluorinated copolymer. The obtained solution was filtered through a hydrophilic PTFE membrane filter with a pore size of 0.45 μm, and 1.5 ml of the filtered solution (measurement solution) was filled into a transparent glass vial with a capacity of 2 ml.

[0225] Next, the elution curve (chromatogram) of the specific fluorinated copolymer obtained from the elution time and the detection intensity based on the RI (differential refractive index detector) was obtained by gel permeation chromatography. Then, the Mw, Mn, and Mw / Mn of the fluorinated copolymer were obtained from the retention time of the obtained elution curve using a polystyrene standard curve. The results are shown in Table 1. In addition, the measurement conditions of the gel permeation chromatography are shown below.

[0226] <Measurement conditions based on gel permeation chromatography>

[0227] Device: HLC-8320GPC (manufactured by Tosoh Corporation)

[0228] Analytical column: Two Shodex GPC KF-806M (manufactured by Showa Denko K.K.) and one Shodex GPC KF-802 (manufactured by Showa Denko K.K.) connected and used

[0229] Column oven: 40°C

[0230] Pump box: 40℃

[0231] Eluent: Tetrahydrofuran

[0232] Flow rate: 1.0ml / min

[0233] Detector: RI

[0234] Standard curve sample: EasiCal PS-1 (polystyrene, manufactured by Agilent)

[0235] Standard curve molecular weight range: 580~570000

[0236] (Thermal stability)

[0237] 50 g of the fluorinated copolymer solution of each example was placed in a heat-resistant container and placed in an oven set at 70° C. The heat-resistant container was taken out of the oven 14 days after being placed in the oven. THF was added to the fluorinated copolymer solution after the heating test to prepare a solution diluted to a concentration of 1% by mass of the fluorinated copolymer, and the molecular weight of the fluorinated copolymer was measured according to the above-mentioned measurement method.

[0238] The ratio of the weight average molecular weight (Mw2) of the fluorinated copolymer after the heating test to the weight average molecular weight (Mw1) of the fluorinated copolymer before the heating test was calculated as the Mw change rate (=Mw2 / Mw1). The thermal stability of the fluorinated copolymer was evaluated according to the following evaluation criteria based on the calculated Mw change rate. The evaluation results are shown in Table 1.

[0239] ○: Mw change rate is less than 1.3.

[0240] △: The Mw change rate is 1.3 or more and less than 1.5.

[0241] ×: The Mw change rate is 1.5 or more.

[0242] (Manufacturing of powder coatings)

[0243] The fluorinated copolymer solution of each example was kept at 65°C for 3 hours under reduced pressure and heating in a vacuum dryer, and then kept at 130°C for 20 minutes under reduced pressure and heating to remove volatile components to obtain the fluorinated copolymer composition of each example. The obtained fluorinated copolymer composition of each example was made into powder using a pulverizer.

[0244] Next, a powdery mixture was prepared using the powdery fluorinated copolymer composition of each example according to the following procedure. To 100 parts by mass of the powdery fluorinated copolymer composition, 67 parts by mass of titanium oxide (Ti-Pure (registered trademark) R960 manufactured by Dupont), 25 parts by mass of a blocked isocyanate curing agent (VESTAGON (registered trademark) B1530 manufactured by Evonik), 0.012 parts by mass of a xylene solution of dibutyltin dilaurate (10,000 times diluted product) as a curing catalyst, 0.8 parts by mass of benzoin as a deaerator, and 2 parts by mass of a surface conditioner (BYK (registered trademark)-360P manufactured by BYK Corporation) were added, and mixed for about 10 to 30 minutes using a high-speed mixer (manufactured by Yusaki Co., Ltd.) to obtain a powdery mixture.

[0245] Next, the powdered mixture was melt-kneaded at a barrel setting temperature of 120° C. using a twin-screw extruder (manufactured by Thermo Fisher Scientific Inc., 16 mm extruder) to obtain pellets. The obtained pellets were pulverized at room temperature using a pulverizer (manufactured by FRITSCH, Rotor speed mill P14) and classified using a 150-mesh sieve to obtain a powder coating composition having an average particle size of about 40 μm.

[0246] (Production of a substrate with a coating)

[0247] Each powder coating composition was electrostatically coated on one side of an aluminum plate treated with chromate using an electrostatic coating machine (GX3600C manufactured by Onoda Cement Co., Ltd.) and maintained in an atmosphere at 200° C. for 20 minutes. After heating, the aluminum plate with a coating layer corresponding to each example was placed and cooled to room temperature to obtain an aluminum plate with a coating film (cured film) having a film thickness of 55 to 65 μm.

[0248] (Evaluation of glossiness of coating film)

[0249] The 20° gloss value of the surface of the coating film was measured 24 hours after the production of the aluminum plate with the coating film using a gloss meter (manufactured by Nippon Denshoku Industries, Ltd., PG-1M). The glossiness of the coating film was evaluated based on the obtained gloss value according to the following evaluation criteria. The evaluation results are shown in Table 1.

[0250] 0: 20° gloss value is 40 or more.

[0251] ×: The 20° gloss value is less than 40.

[0252] (Evaluation of coloration of coating film)

[0253] The b* value of the surface of the coating film was measured 24 hours after the production of the aluminum plate with the coating film using a colorimeter (SE-7700 manufactured by Nippon Denshoku Industries Co., Ltd.). It should be noted that the b* value is one of the color coordinates in the L*a*b* colorimetric system specified in JIS Z8729. The coloration of the coating film was evaluated based on the following evaluation criteria using the measured b* value. The evaluation results are shown in Table 1.

[0254] ○: b* value is less than 1.6.

[0255] ×: b* value is 1.6 or more.

[0256] In the following tables, Pg / M represents the ratio of the molar amount of the piperidinyl group in the piperidinyl group-containing compound to the molar amount of the total amount of the monomers used.

[0257] In the following table, H / Pc represents the mass ratio of the amount of hydrotalcite used to the amount of the piperidinyl group-containing compound used.

[0258] In the following table, Mm / Ms represents the ratio of the total molar amount Mm of all monomers in the reactor before the start of polymerization to the molar amount Ms of the solvent.

[0259] In the following table, the numerical values ​​shown in the composition 1 column represent the molar ratios (percentages) of the structural units derived from CTFE, the structural units derived from CHVE, and the structural units derived from HBVE, respectively, from the left side of the paper, relative to the total structural units of the fluorinated copolymer produced in each example. The numerical values ​​shown in the composition 2 column represent the molar ratios (percentages) of the structural units derived from CTFE, the structural units derived from EVE, the structural units derived from CHVE, and the structural units derived from HBVE, respectively, from the left side of the paper, relative to the total structural units of the fluorinated copolymer produced in each example.

[0260] [Table 1]

[0261]

[0262] As shown in Table 1, it was confirmed that in a method for producing a fluorinated copolymer in which a monomer containing CTFE and a vinyl ether is polymerized using a radical polymerization initiator, a piperidinyl-containing compound and a hydrotalcite to produce a fluorinated copolymer, if the ratio of the molar amount of the piperidinyl group in the piperidinyl-containing compound to the molar amount of the total amount of the monomers used is 0.0032 to 0.010, the mass ratio of the amount of the hydrotalcite used to the amount of the piperidinyl-containing compound used is 0.30 or more and less than 4.60, and chlorotrifluoroethylene and vinyl ether are continuously or intermittently supplied to the reaction system after the start of polymerization, a fluorinated copolymer having excellent thermal stability, excellent glossiness of a coating film when used for forming a coating film, and further suppressed coloring of the coating film when used for forming a coating film can be produced.

[0263] It should be noted that the entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2022-108313 filed on Jul. 5, 2022 are incorporated herein as a disclosure of the specification of the present invention.

Claims

1. A method for producing a fluorinated copolymer, characterized in that: The method for producing a fluorinated copolymer comprising units based on chlorotrifluoroethylene and units based on vinyl ether, wherein: The fluorine-containing copolymer is produced by polymerizing monomers containing chlorotrifluoroethylene and vinyl ether using a free radical polymerization initiator, a piperidinyl-containing compound and hydrotalcite, The ratio of the molar amount of the piperidinyl group in the piperidinyl group-containing compound to the molar amount of the total amount of the monomer is 0.0032 to 0.010, The mass ratio of the amount of the hydrotalcite to the amount of the piperidinyl-containing compound is greater than 0.30 and less than 4.60, After the polymerization is started, the chlorotrifluoroethylene and the vinyl ether are continuously or intermittently supplied to the reaction system.

2. The method for producing a fluorinated copolymer according to claim 1, which is a method for producing a fluorinated copolymer in which the polymerization is carried out in a reactor, wherein: The solvent and the monomer are present in the reactor before starting the polymerization, In the reactor before starting the polymerization, the ratio of the total molar amount of the monomers to the molar amount of the solvent is 0.30 or more.

3. The method for producing a fluorinated copolymer according to claim 1 or 2, wherein The vinyl ether contains at least a vinyl ether having a crosslinkable group.

4. The method for producing a fluorinated copolymer according to claim 3, wherein The crosslinking group is a hydroxyl group or a carboxyl group.

5. The method for producing a fluorinated copolymer according to claim 3, wherein The amount of the vinyl ether having a crosslinkable group used is 1 to 20 mol % relative to the total amount of the monomers used.

6. The method for producing a fluorinated copolymer according to claim 1 or 2, wherein The vinyl ether includes a vinyl ether having a crosslinkable group and a vinyl ether not having a crosslinkable group. The amount of the vinyl ether having no crosslinking group used is 1 to 70 mol % relative to the total amount of the monomers used.

7. The method for producing a fluorinated copolymer according to claim 1 or 2, wherein The molar ratio of the amount of chlorotrifluoroethylene used relative to the total amount of the monomers used is 30 to 70 mol%.

8. The method for producing a fluorinated copolymer according to claim 1 or 2, wherein The weight average molecular weight of the fluorine-containing copolymer is 10,000 to 60,000.

9. A method for producing a powder coating, characterized in that: A powder coating material is produced using the fluorinated copolymer produced by the method for producing a fluorinated copolymer according to claim 1 or 2.

10. A method for producing a coated article, characterized in that: The powder coating material produced by the method for producing a powder coating material according to claim 9 is applied to the surface of a substrate to form a coating layer, and the coating layer is melted and solidified to form a coating film.

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