Fluororesin

Abstract

To provide a fluororesin having an oxolane ring, which is suppressed in yellowing after heating and melting and which is reduced in coloring especially in the molding of a thick wall product, and a method for producing the same.SOLUTION: Provided is a fluororesin which contains a residue unit represented by the following formula (1) and a terminal group represented by the following formula (2). (In formula (1), Rf1, Rf2, Rf3, and Rf4 each independently represent one selected from the group consisting of a fluorine atom, C1-7 linear perfluoroalkyl groups, C3-7 branched perfluoroalkyl groups, and C3-7 cyclic perfluoroalkyl groups. Rf1, Rf2, Rf3, and Rf4 may be linked to each other to form a ring).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a fluororesin and a method for producing the same.

Background Art

[0002] Fluororesins are used in protective films for electronic components such as semiconductors, water-repellent films for inkjet printer heads, waterproof and oil-repellent coatings for filters, optical members, etc., because they are excellent in heat resistance, electrical properties, chemical resistance, waterproofness, oil-repellency, and optical properties.

[0003] Among them, fluororesins containing an oxolane ring have an amorphous structure due to their bulky ring structure and have high transparency and high heat resistance. In addition, since it is composed only of carbon, fluorine, and oxygen, it has high electrical properties, chemical resistance, waterproofness, and oil-repellency. Furthermore, since it is amorphous, it can be melt-molded.

[0004] Non-Patent Document 1 describes the synthesis and properties of a polymer (polyPFMMD) obtained by polymerizing perfluoro-2-methylene-4-methyl-1,3-dioxolane (PFMMD), which is a type of fluororesin containing an oxolane ring, using perfluorobenzoyl peroxide as a radical polymerization initiator. PolyPFMMD is excellent in heat resistance. According to the studies by the present inventors, the polyPFMMD described in Non-Patent Document 1 showed significant yellowing after heat melt molding, especially in thick molded products. Therefore, there is a strong desire for a technology that can exhibit less coloring and high transparency even in thick molded bodies of polyPFMMD.

[0005] As a method for reducing the coloring of a fluororesin during heating, a method for obtaining a fluororesin having an aliphatic perfluoroalkyl group terminal using an aliphatic perfluorinated initiator is known. For example, Non-Patent Document 2 reports an example in which perfluoro(butenyl vinyl ether) is subjected to bulk polymerization and cyclopolymerization using (CF3CF2CF2COO)2. However, according to the studies of the present inventors, even when the technique described in Non-Patent Document 2 is used for the synthesis of polyPFMMD, it cannot be said that the yellowing of polyPFMMD after heat melt molding is sufficiently reduced. In addition, the yield was extremely poor, the productivity was inferior, and the molecular weight distribution Mw / Mn was large.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made for the purpose of solving problems in a fluororesin containing an oxolane ring. Specifically, an object of the present invention is to provide a fluororesin containing an oxolane ring in which yellowing after heat melting is suppressed, and particularly coloring is reduced even in the molding of thick-walled products, and a method for producing the same.

Means for Solving the Problems

[0008] As a result of intensive studies by the present inventors, it has been found that a fluororesin containing an oxolane ring having a terminal group with a specific structure can solve the above problems, and the present invention has been completed.

[0009] That is, the present invention is a fluororesin containing a residue unit represented by the following formula (1) and a terminal group represented by the following formula (2).

[0010]

Chem.

[0011] (In formula (1), Rf1, Rf2, Rf3, and Rf4 each independently represent one member selected from the group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, and a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Further, Rf1, Rf2, Rf3, and Rf4 may be linked to each other to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an etheric oxygen atom.)

[0012]

Chem.

[0013] (In formula (2), i is an integer from 3 to 20.)

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a fluororesin containing an oxolane ring with suppressed yellowing during melt molding of a thick molded article and a method for producing the same.

Modes for Carrying Out the Invention

[0015] A fluororesin according to one embodiment of the present invention will be described in detail below.

[0016] The fluororesin of the present invention contains a residue unit represented by the following formula (1) and a terminal group represented by the following formula (2).

[0017]

Chem.

[0018] (In formula (1), Rf1, Rf2, Rf3, and Rf4 each independently represent one member selected from the group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Further, Rf1, Rf2, Rf3, and Rf4 may be linked to each other to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an etheric oxygen atom.)

[0019] [Chemical formula]

[0020] (In formula (2), i is an integer of 3 to 20) Since the fluororesin of the present invention has a bulky ring structure contained in a specific formula (1), it is amorphous and has high transparency and high heat resistance. Further, since it is composed only of carbon atoms, fluorine atoms, and oxygen atoms, it has high electrical properties, chemical resistance, waterproofness, and oil and liquid repellency.

[0021] In formula (1), the Rf1, Rf2, Rf3, and Rf4 groups each independently represent one member selected from the group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Further, Rf1, Rf2, Rf3, and Rf4 may be linked to each other to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an etheric oxygen atom.

[0022] Examples of the linear perfluoroalkyl group having 1 to 7 carbon atoms include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, an undecafluoropentyl group, a tridecafluorohexyl group, a pentadecafluoroheptyl group, and the like.

[0023] Examples of the branched perfluoroalkyl group having 3 to 7 carbon atoms include a heptafluoroisopropyl group, a nonafluoroisobutyl group, a nonafluoro sec-butyl group, a nonafluoro tert-butyl group, and the like.

[0024] Examples of the cyclic perfluoroalkyl group having 3 to 7 carbon atoms include a heptafluorocyclopropyl group, a nonafluorocyclobutyl group, a tridecafluorocyclohexyl group, and the like.

[0025] Examples of the linear perfluoroalkyl group which may have an etheric oxygen atom having 1 to 7 carbon atoms include a -CF2OCF3 group, a -(CF2)2OCF3 group, a -(CF2)2OCF2CF3 group, and the like.

[0026] Examples of the cyclic perfluoroalkyl group which may have an etheric oxygen atom having 3 to 7 carbon atoms include a 2-(2,3,3,4,4,5,5,6,6-decafluoro)-pyrinyl group, a 4-(2,3,3,4,4,5,5,6,6-decafluoro)-pyrinyl group, a 2-(2,3,3,4,4,5,5-heptafluoro)-furanyl group, and the like.

[0027] It is preferable that at least one of Rf1, Rf2, Rf3, and Rf4 is a fluororesin which is one kind of the group consisting of a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. Thereby, the fluororesin of the present invention exhibits more excellent heat resistance.

[0028] Specific examples of the residue unit represented by the formula (1) include, for example, the residue unit represented by the following formula (3).

[0029]

Chemical formula

[0030] Among these, a fluororesin containing a residue unit represented by the following formula (4) is preferable because of its excellent heat resistance and moldability, and a fluororesin containing a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit is more preferable.

[0031]

Chemical formula

[0032] The fluororesin of the present invention contains a terminal group represented by the following formula (2). Thereby, yellowing during melt molding of a thick molded product is suppressed.

[0033] Here, the "terminal group" means a group present at the terminal of the main chain of the polymer.

[0034] The terminal group represented by formula (2) preferably has a structure represented by the following formula (5).

[0035]

Chemical formula

[0036] That the fluororesin of the present invention contains a terminal group unit represented by formula (5) can be confirmed, for example, by the following method.

[0037] That is, in the solid 19 19F-NMR spectrum analysis of the fluororesin, when it can be confirmed that peaks showing maxima are present in the ranges of -140 ppm or more and 142 ppm or less, and -143 ppm or more and 145 ppm or less, respectively, it can be determined that the fluororesin of the present invention has a terminal group represented by formula (5). The peaks showing maxima in the ranges of -140 ppm or more and 142 ppm or less, and -143 ppm or more and 145 ppm or less, respectively, are attributed to the -CF2- groups at the 3rd, 4th, and 5th positions of formula (5).

[0038] Incidentally, the solid 19 19F-NMR measurement of the fluororesin is a general 19An F-NMR measuring device may be used. For example, using a VNMRS-400 manufactured by Varian, at a magnetic field strength of 376.18 MHz (19F), using a 1.6 mm FASTMAS probe, by the hahn-echo method, with a pulse width of 1.3 μs, a spectral width of 250 kHz (664.6 ppm), a spectral center: -120 ppm, a waiting time: 10 seconds, an MAS rotation speed: 39 kHz, and an integration number of 2048 times, about 10 mg of a fluororesin is used as a solid with reference to PTFE (-122.0 ppm). 19 A method for performing F-NMR measurement can be exemplified.

[0039] Solid for the fluororesin of the present invention 19 In the solid F-NMR spectrum analysis of the fluororesin of the present invention, the integrated value of the area of the terminal peak (6F) caused by the terminal group showing a maximum in the range of -140 ppm or more and 142 ppm or less, and -143 ppm or more and 145 ppm or less is preferably 0.001 to 10, more preferably 0.01 to 5, and even more preferably 0.05 to 5 with respect to the integrated value of the area of the main chain peak (5F) showing a maximum at the position of -81 ppm, which is 500. Thereby, the yellowing of the fluororesin is further suppressed. Here, the main chain peak (5F) showing a maximum at the position of -81 ppm is attributed to the -CF2O- group and the -CF3 group.

[0040] The fact that the fluororesin of the present invention contains a residue unit represented by the formula (2) or the formula (5) can be confirmed, for example, by performing solid-state 13 13C-NMR measurement on the oligomer of the fluororesin. For example, an oligomer or the like dissolved in a solvent such as zeolora H in the manufacturing process is isolated, and solid-state 13 13C-NMR measurement is performed on the obtained oligomer. At this time, if a peak showing a maximum in the range of 90 to 92 ppm, which is derived from the F atom at the 1-position of the perfluorocycloalkyl group directly bonded to the residue unit represented by the formula (1), is observed, it can be confirmed that the fluororesin contains a terminal group represented by the formula (2) or the formula (5).

[0041] The terminal group represented by the formula (2) or the formula (5) is preferably directly bonded to the residue unit represented by the general formula (1) without passing through other functional groups. Further, the fluororesin of the present invention preferably does not contain a carbonyl group.

[0042] The fluororesin of the present invention has a weight average molecular weight Mw of 5×10 4 ~3×10 5 and is preferably in the range of. When the weight average molecular weight Mw is in this range, it has excellent melt molding processability and degassing property during melting. Further, when the weight average molecular weight Mw is in this range, it has less crack generation during heating and cooling. From the viewpoint of excellent melt molding processability and excellent degassing property during melting, the fluororesin of the present invention is more preferably the weight average molecular weight Mw is 5×10 4 ~2×10 5 and is preferably in the range of.

[0043] The weight average molecular weight Mw of the fluororesin of the present invention can be calculated from the elution time of the sample and the standard sample and the molecular weight of the standard sample by using gel permeation chromatography (GPC), for example, using a standard polymethyl methacrylate with a known molecular weight as a standard sample and a solvent capable of dissolving both the standard sample and the fluororesin as an eluent. Examples of the eluent include Asahiklin AK-225 (manufactured by Asahi Glass Co., Ltd.) added with 1,1,1,3,3,3-hexafluoro-2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.) at 10 wt% with respect to AK-225.

[0044] The molecular weight distribution Mw / Mn, which is the ratio of the weight average molecular weight Mw to the number average molecular weight Mn of the fluororesin of the present invention, is not particularly limited. However, from the viewpoints of suppressing yellowing after heat melting, excellent melt molding processability, excellent defoaming property during melting, and less crack generation during heating and cooling, the molecular weight distribution Mw / Mn is preferably from 1.2 to 8, more preferably from 1.2 to 5, still more preferably from 1.5 to 3, and even more preferably from 2.0 to 3. The number average molecular weight Mn can be measured by the same method as the measurement method of the weight average molecular weight Mw described above, and the molecular weight distribution Mw / Mn can be calculated by dividing the weight average molecular weight Mw by the number average molecular weight Mn.

[0045] The fluororesin of the present invention preferably has a yellowness index (YI) of 10 or less, more preferably 4 or less, and still more preferably 3 or less, as measured in the diameter direction of a thick-walled melt-molded product (a cylindrical molded body with a diameter of 10 mm and a height of about 17 mm, melted and molded by heating at 280 °C for 24 h in a test tube). According to the present inventors, when melt molding a thick molded product in a closed situation as compared with heating in an open environment, the yellowing after heat melting of the fluororesin becomes remarkable. As a method for evaluating the yellowness and coloring of a melt-molded product of a thick molded product, for example, a method of evaluating the yellowness index (YI) measured in the diameter direction of a cylindrical body (diameter 10 mm × height about 17 mm) obtained by melting and molding 3 g of the fluororesin of the present invention by heating at 280 °C for 24 h in a test tube with an outer diameter of 13 mm can be mentioned. Here, the diameter direction is the vertical direction when the test tube is laid horizontally on a desk or the like. The yellowness index is obtained by placing the obtained resin molded product in the test tube and laying the test tube horizontally on white paper, taking a digital photograph from above, reading the RGB values of the molded product from the obtained image by software, and substituting the read RGB values into the following formula X = 0.4124R + 0.3576G + 0.1805B Y = 0.2126R + 0.7152G + 0.0722B Z = 0.0193R + 0.1192G + 0.9505B The tristimulus values X, Y, and Z in the XYZ colorimetric system are obtained, and the yellowness index (YI) under a C light source (auxiliary illuminant C) is calculated according to the method of JIS K7373 from X, Y, and Z, thereby enabling measurement.

[0046] Preferably, the fluororesin of the present invention has a yellowness index (YI) of 1 or less for a thin-film melt-molded product (3 mm thick, melt-molded by heating at 280 °C for 24 h in a petri dish). Examples of the molding method and evaluation method include the methods described in the examples.

[0047] The fluororesin of the present invention may contain other monomer residue units. Examples of other monomer residue units include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), trifluoroethylene, hexafluoroisobutylene, perfluoroalkyl ethylene, fluorovinyl ether, vinyl fluoride (VF), vinylidene fluoride (VDF), perfluoro-2,2-dimethyl-1,3-dioxole (PDD), perfluoro(allyl vinyl ether), and perfluoro(butenyl vinyl ether).

[0048] Although there is no particular limitation on the particle size of the fluororesin of the present invention, since the fluidity of the resin powder is high, continuous supply to a molding processing machine or the like is possible, residual solvents in the resin can be suppressed, the bulk density is large, the filling property is increased, and the handleability during molding processing is excellent, the volume average particle size is preferably 1 to 1000 μm, more preferably 1 to 500 μm, and even more preferably 1 to 300 μm.

[0049] The volume average particle diameter of the fluororesin of the present invention can be evaluated by measuring the particle size distribution (volume distribution) by the laser diffraction scattering method. The particle size distribution by the laser diffraction scattering method can be measured by dispersing resin particles in water or an organic solvent such as methanol and then measuring. As an example of the laser scattering meter, Microtrac manufactured by Microtrac Bell Corporation can be exemplified.

[0050] The volume average particle diameter, also referred to as the Mean Volume Diameter, is the average particle diameter expressed on a volume basis. The particle size distribution is divided for each particle size channel. When the representative particle size value of each particle size channel is d and the percentage on a volume basis for each particle size channel is v, it is represented by Σ(vd) / Σ(v).

[0051] The fluororesin of the present invention is in powder form, and preferably has a volume average particle diameter of 1 to 1000 μm.

[0052] The manufacturing method of the fluororesin, which is one aspect of the present invention, will be described in detail below.

[0053] The fluororesin of the present invention can be manufactured by polymerizing a mixture containing a radical polymerization initiator represented by the following formula (6) and a monomer represented by the following formula (7).

[0054]

Chemical formula

[0055] (In formula (6), j is an integer from 3 to 20)

[0056]

Chemical formula

[0057] (In formula (7), Rf5, Rf6, Rf7, and Rf8 each independently represent one kind of group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Also, Rf5, Rf6, Rf7, and Rf8 may be linked to each other to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an etheric oxygen atom.) Rf5, Rf6, Rf7, and Rf8 in formula (7) have the same meanings as Rf1, Rf2, Rf3, and Rf4 in formula (1), respectively.

[0058] In the method for producing a fluororesin of the present invention, by using a radical polymerization initiator represented by the formula (6), a fluororesin with suppressed yellowing during melt molding of a thick molded article can be obtained. Furthermore, a fluororesin with a narrow molecular weight distribution Mw / Mn can be obtained. By narrowing the molecular weight distribution Mw / Mn, the heat melt moldability is improved. Furthermore, the fluororesin can be obtained with excellent yield and productivity. Also, by using the radical polymerization initiator represented by the formula (6), after the radical polymerization initiator undergoes decarboxylation and is added to the polymer, the resulting polymer contains almost no carbonyl groups, and has a structure in which the end group represented by the formula (2) is directly added to the polymer, which is advantageous for obtaining a fluororesin with suppressed yellowing during melt molding of a thick molded article.

[0059] In the method for producing a fluororesin of the present invention, it is more preferable to use a radical polymerization initiator represented by the following formula (8). By using the radical polymerization initiator represented by the following formula (8), a fluororesin with further suppressed yellowing during melt molding of a thick molded article can be obtained. Furthermore, a fluororesin with a narrow molecular weight distribution Mw / Mn can be obtained. By narrowing the molecular weight distribution Mw / Mn, the heat melt moldability is improved. Furthermore, the fluororesin can be obtained with excellent yield and productivity. In this specification, the radical polymerization initiator represented by the following formula (8) is sometimes referred to as bis(perfluorocyclohexylcarbonyl) peroxide.

[0060] [Chemical formula]

[0061] Bis(perfluorocyclohexylcarbonyl) peroxide can be obtained by the methods described in JP-A-11-49749 and J. Appl. Polym. Sci, 1999, 72, 1101-1108. At that time, as the solvent, instead of AK-225, perfluorohexane (FC-72, manufactured by 3M Japan) or the like can also be used. The bis(perfluorocyclohexylcarbonyl) peroxide of the present invention may be synthesized by a method other than the methods described in the above-mentioned documents. For example, although a method for synthesizing a fluorinated peroxide is described in Chem. Rev, 1996, 96, 1779-1808, examples thereof include a method of reacting an acid fluoride with hydrogen peroxide, a method of reacting an acid chloride with hydrogen peroxide, and a method of reacting an acid anhydride with hydrogen peroxide. At that time, the reaction proceeds by the presence of a base such as sodium hydroxide in the system.

[0062] In the method for producing a fluororesin of the present invention, a chain transfer agent may be used for the purpose of adjusting the molecular weight. Examples of the chain transfer agent include organic compounds having 1 to 20 carbon atoms containing at least one atom selected from the group consisting of a hydrogen atom and a chlorine atom. Specific examples of the chain transfer agent include organic compounds having 1 to 20 carbon atoms containing a hydrogen atom such as toluene, acetone, ethyl acetate, tetrahydrofuran, methyl ethyl ketone, methanol, ethanol, and isopropanol; chloroform, dichloromethane, carbon tetrachloride, chloromethane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, hexachloroethane, benzyl chloride, pentafluorobenzyl chloride, pentafluorobenzoyl chloride, and other organic compounds having 1 to 20 carbon atoms containing a chlorine atom. Among them, from the viewpoint of suppressing yellowing after heat melting, an organic compound having 1 to 20 carbon atoms containing a chlorine atom is preferable, and an organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom is more preferable. The amount of the chain transfer agent is, for example, 0.01 to 50% by weight based on the total of the monomer and the chain transfer agent.

[0063] In the method for producing the resin of the present invention, there is no limitation on the polymerization method, and examples thereof include solution polymerization, precipitation polymerization, bulk polymerization, emulsion polymerization, suspension polymerization and the like.

[0064] In the production method of the present invention, in the step of polymerization, it is preferable to further mix an organic solvent with the mixture.

[0065] In the method for producing the resin of the present invention, since the resin powder has high fluidity, continuous supply to a molding processing machine or the like is possible, residual solvent in the resin can be suppressed, the bulk density is large and the filling property is increased, and a powder excellent in handleability during molding processing can be obtained. Therefore, at least the monomer represented by the formula (7) is dissolved as the organic solvent, and at least a part of the resin produced by polymerization is not dissolved, and it is an organic solvent that causes precipitation of the resin, and the resin produced by the polymerization preferably uses an organic solvent that precipitates as particles in the organic solvent. In the method for producing the resin of the present invention, the organic solvent may be referred to as a "precipitation polymerization solvent". By using the precipitation polymerization solvent, the resin produced by the polymerization reaction can be precipitated as particles having a specific volume average particle diameter, and as a result, resin particles excellent in moldability and filling property can be produced. Further, since polymerization aids such as emulsifiers and dispersants are not used, resin particles not containing emulsifiers and dispersants that cause deterioration of transparency and heat resistance can be produced.

[0066] Here, the precipitation polymerization solvent means a solvent in which resin particles containing the residue unit represented by the formula (1) remain after the resin particles are immersed in the organic solvent for a long time. Specifically, the weight average molecular weight Mw containing the residue unit represented by the general formula (1) is 5 × 10 4 ~70×10 4The resin particles are immersed in an organic solvent at 50 °C for 5 hours or more in an amount 10 times the amount (w / w) of the resin particles. When the remaining resin particles can be visually confirmed in the organic solvent after that, the organic solvent can be regarded as the precipitation polymerization solvent A. The precipitation polymerization solvent A is preferably an organic solvent in which, after immersion at 50 °C for 5 hours or more, the solution is cooled to 25 °C and the resin sample remaining in a solid state is recovered, and the weight loss rate of the resin sample is less than 20% by weight. The weight loss rate of the resin sample is more preferably less than 12% by weight, and even more preferably less than 10% by weight.

[0067] The weight loss rate of the resin can be measured by the following method. After filtering the above-mentioned cooled solution through a filter, the solid on the filter is rinsed with the solvent, washed several times with acetone, dried, and the resin sample on the filter is recovered. The weight of the recovered resin is measured, and the percentage obtained by dividing the value obtained by subtracting the weight of the recovered resin from the amount of resin immersed in the organic solvent by the amount of resin immersed in the organic solvent and multiplying by 100 is taken as the resin reduction rate.

[0068] Examples of the precipitation polymerization solvent include non-halogenated organic solvents such as acetone, methyl ethyl ketone, hexane, and butyl acetate, chlorine-based organic solvents such as dichloromethane and chloroform, and organic solvents containing fluorine atoms in the molecule.

[0069] Furthermore, as the precipitation polymerization solvent, an organic solvent containing a fluorine atom and a hydrogen atom in the molecule is preferable because a chain transfer reaction hardly occurs in radical polymerization, the polymerization yield is excellent, and a high molecular weight polymer is easily obtained. Specific examples of the precipitation polymerization solvent containing a fluorine atom and a hydrogen atom in the molecule include 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoroisopropanol, 1,2,2,3,3,4,4-heptafluorocyclopentane, 1H,1H-pentafluoropropanol, 1H,1H-heptafluorobutanol, 2-perfluorobutylethanol, 4,4,4-trifluorobutanol, 1H,1H,3H-tetrafluoropropanol, 1H,1H,5H-octafluoropropanol, 1H,1H,7H-dodecafluoroheptanol, 1H,1H,3H-hexafluorobutanol, 2,2,3,3,3-pentafluoropropyldifluoromethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethylethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, hexafluoroisopropyl methyl ether, 1,1,3,3,3-pentafluoro-2-trifluoromethylpropyl methyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 2,2,3,4,4,4-hexafluorobutyldifluoromethyl ether, and the like.

[0070] Among them, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoroisopropanol, and 1,2,2,3,3,4,4-heptafluorocyclopentane are preferable. Since they have excellent polymerization yields and are likely to obtain high molecular weight polymers, 1,2,2,3,3,4,4-heptafluorocyclopentane is preferable. As for the ratio of fluorine atoms to hydrogen atoms in the intramolecular structure of the precipitation polymerization solvent, since it has an excellent polymerization yield, the atomic number ratio of fluorine atoms:hydrogen atoms is preferably 1:9 to 9:1, more preferably 1:9 to 7:3, and even more preferably 4:6 to 7:3. As the precipitation polymerization solvent, since it has an excellent polymerization yield, it contains fluorine atoms and hydrogen atoms in the molecule, and the content of hydrogen atoms in the solvent is preferably 1% by weight or more, more preferably 1.5% by weight or more, based on the weight of the solvent molecule. Also, since it has an excellent polymerization yield and is likely to obtain high molecular weight polymers, it is preferably 1% by weight or more and 5% by weight or less, and more preferably 1.5% by weight or more and 4% by weight or less. Further, as the precipitation polymerization solvent, since it has an excellent polymerization yield and is likely to obtain high molecular weight polymers, those that do not contain chlorine atoms in the molecule are preferable.

[0071] Regarding the ratio of the monomer represented by formula (7) to the precipitation polymerization solvent, since particles with excellent productivity and excellent flow characteristics can be obtained, the weight ratio of monomer:precipitation polymerization solvent is preferably 1:99 to 50:50, more preferably 5:95 to 40:60, and even more preferably 5:95 to 30:70.

[0072] In the production method of the present invention, it is preferable that the monomer represented by formula (7) is perfluoro(4-methyl-2-methylene-1,3-dioxolane) represented by the following formula (9), and the residue unit represented by formula (1) is a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit represented by formula (4).

[0073]

Chemical formula

[0074] By manufacturing according to the method of the present invention, a fluororesin with suppressed yellowing during melt molding of a thick molded article can be obtained. Furthermore, a fluororesin with a narrow molecular weight distribution Mw / Mn can be obtained while exhibiting the above characteristics. Furthermore, while exhibiting the above characteristics, the fluororesin can be obtained with excellent yield and productivity.

Examples

[0075] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0076] [Measurement of weight average molecular weight Mw and molecular weight distribution Mw / Mn] Measurement was carried out using gel permeation chromatography equipped with a column TSKgel SuperHZM-M manufactured by Tosoh Corporation and an RI detector. As the eluent, Asahiklin AK-225 (manufactured by Asahi Glass Co., Ltd.) with 10 wt% of 1,1,1,3,3,3-hexafluoro-2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.) added to AK-225 was used. As the standard sample, standard polymethyl methacrylate manufactured by Agilent was used, and the weight average molecular weight Mw and molecular weight distribution Mw / Mn in terms of polymethyl methacrylate were calculated from the elution times of the sample and the standard sample.

[0077] [Solid 19 F-NMR measurement] Using Varian VNMRS-400, at a magnetic field strength of 376.18 MHz (19F), using a 1.6 mm FASTMAS probe, by the hahn-echo method, with a pulse width of 1.3 μs, a spectral width of 250 kHz (664.6 ppm), a spectral center: -120 ppm, a waiting time: 10 seconds, a MAS rotation speed: 39 kHz, and an integration number of 2048 times, using about 10 mg of fluororesin with PTFE (-122.0 ppm) as a reference, solid 19 F-NMR measurement was carried out.

[0078] [Solid 13 C-NMR measurement] Using a Varian VNMRS-400, at a magnetic field strength of 100.55 MHz (13C), with a 4.0 mm MAS probe, by the CP / MAS method, a spectral width of 30.5 kHz, a spectral center: 77.5 ppm, a waiting time: 3 seconds, a MAS rotation speed: 10 kHz, and 4096 integrations, using about 50 mg of fluororesin as a reference to TMS (0 ppm), solid 13 C-NMR measurement was carried out.

[0079] [Measurement of the yellowness index (YI) of the thick-walled melt-molded product (φ10 mm × H17 mm, 24 h at 280 °C in a test tube)] Put 3.0 g of fluororesin into a glass test tube with an outer diameter of φ13 mm and a total length of 100 mm (manufactured by Nippon Electric Glass Co., Ltd., ST-13M), cover the mouth of the test tube with aluminum foil and an aluminum cap (Marumoto, M-1), stand the test tube upright, put it in an oven, heat it at 280 °C for 24 h, and then let it cool to obtain a cylindrical resin molded product in the test tube (diameter: 10 mm, height: about 17 mm). Keep the obtained resin molded product in the test tube, lay the test tube horizontally on white paper, and take a digital photo from above under a white fluorescent lamp using a PowerShot SX620HS (manufactured by Canon), and read the RGB values of the molded product from the obtained image using Paint (Microsoft image processing software). The read RGB values are used in the following formula X = 0.4124R + 0.3576G + 0.1805B Y = 0.2126R + 0.7152G + 0.0722B Z = 0.0193R + 0.1192G + 0.9505B to obtain the tristimulus values X, Y, and Z in the XYZ color system. From X, Y, and Z, according to the method of JIS K7373, the yellowness index (YI) under a C light source (auxiliary illuminant C) was calculated to obtain the yellowness index (YI) of the thick-walled melt-molded product (φ10 mm × H17 mm, 24 h at 280 °C in a test tube).

[0080] [Yellowness index (YI) of the thin-sheet melt-molded product (3 mm thick, 24 h at 280 °C in a petri dish)] Weigh 2.0 g of fluororesin into a petri dish with an inner diameter of 26.4 mm (only the receiver of the set of the lid and receiver of the flat petri dish manufactured by Flat Co., Ltd., with a glass thickness of 1 mm at the bottom of the receiver), place it in an inert oven (DN411I manufactured by Yamato Scientific Co., Ltd.), and leave it standing at room temperature for 30 minutes under an air stream (20 L / min). Then, heat it to 280°C over 30 minutes and heat it at 280°C for 24 hours. After that, while maintaining the air stream (20 L / min), keep the oven door closed, turn off the power of the inert oven, allow it to cool for 12 hours, and take out the sample to obtain a fluororesin heat-melt molded product with a thickness of 3 mm and a diameter of 26.4 mm on the petri dish. At this time, as the air, the air compressed by a compressor and passed through a dehumidifier (dew point temperature of -20°C or lower) was used. The obtained fluororesin heat-melt molded product together with the petri dish was measured for the transmittance at each wavelength at 1 nm intervals in the wavelength range of 200 nm to 1500 nm using a spectrophotometer (U-4100 manufactured by Hitachi High-Tech Science Corporation). From the measured transmittance data, data at 5 nm intervals in the wavelength range of 380 nm to 780 nm were extracted, and the tristimulus values X, Y, and Z in the XYZ colorimetric system were calculated according to the method of JIS Z8701. Furthermore, according to the method of JIS K7373, the yellowness index (YI) under a C light source (auxiliary illuminant C) was calculated, and the yellowness index (YI) of the fluororesin heat-melt molded product including the petri dish was obtained. The yellowness index (YI) of the petri dish alone (only the receiver) was measured, and the yellowness index (YI) of the fluororesin molded product including the petri dish was subtracted from the yellowness index (YI) of the petri dish alone (only the receiver) to obtain the yellowness index (YI) of the fluororesin heat-melt molded product with a thickness of 3 mm. Incidentally, the yellowness index (YI) of the petri dish alone (only the receiver) was 0.21.

[0081] [Measurement of volume average particle size] Using Microtrac MT3000 manufactured by Microtrac Bell Corporation, the volume average particle size (unit: μm) was measured using methanol as the dispersion medium.

[0082] [Example 1] The interior of a 3 L SUS316 autoclave equipped with a paddle-type stirring blade, a nitrogen introduction tube, and a thermometer was purged with nitrogen. A solution prepared by dissolving 2.33 g (0.0036 mol) of bis(perfluorocyclohexylcarbonyl) peroxide, which is an initiator, in 230 g of FC-72 (manufactured by 3M Japan, perfluorohexane), 175 g (0.72 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, and 470 g of FC-72 as a polymerization solvent were put into the autoclave after removing dissolved oxygen, and solution polymerization was carried out by holding at 55 °C for 24 hours with stirring to obtain a viscous liquid in which the resin was dissolved. After cooling to room temperature, the ampule was opened, and the obtained resin solution was poured into 875 g of FC-72 for viscosity adjustment and diluted to prepare a resin-diluted solution. 5250 g of Zeolara H (manufactured by Nippon Zeon Co., Ltd., 1,2,2,3,3,4,4-heptafluorocyclopentane, hydrogen atom content in the solvent molecule: 1.55 wt%, fluorine atom in the solvent molecule: hydrogen atom = 7:3 (number ratio)) was put into a plastic cup equipped with a stirring blade, and the above resin-diluted solution was added to the plastic cup with stirring to precipitate the resin. The precipitated resin was collected by filtration, washed twice with acetone, and dried in vacuo to obtain a powdery perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin (yield: 93%).

[0083] The weight-average molecular weight of the obtained fluororesin was 9.5×10 4 , and the molecular weight distribution Mw / Mn was 3.74. The evaluation results of the fluororesin are shown in Table 1.

[0084] For the obtained fluororesin, solid 19 As a result of performing 19F-NMR measurement, peaks derived from the terminal perfluorocyclohexyl group were confirmed at -140.7 ppm and -143.9 ppm. The integrated value of the peak (6F) derived from the terminal group was 1.46 in total with respect to the integrated value of 500 of the main-chain peak (5F) at -81.3 ppm.

[0085] Also, the filtrate when the resin was precipitated with Zeolara H during the above operation was dried to solid, and the solid was washed with acetone and dried in vacuo to obtain an oligomer.

[0086] For the obtained oligomer, solid 13 As a result of performing 13C-NMR measurement on the obtained oligomer, a peak derived from the F atom at the 1-position of the perfluorocyclohexyl group directly bonded to the end of the polymer was confirmed at 91 ppm. On the other hand, no peak was observed in the carbonyl group region at 130 to 150 ppm.

[0087] [Example 2] The inside of a 3 L SUS316 autoclave equipped with a paddle-type stirring blade, a nitrogen inlet tube, and a thermometer was purged with nitrogen.

[0088] A solution prepared by dissolving 0.80 g (0.0012 mol) of bis(perfluorocyclohexylcarbonyl) peroxide, which is an initiator, in 80 g of FC-72, 300 g (1.23 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, 1120 g of Zeorola-H as a polymerization solvent, and 33.33 g (0.279 mol, amount of chain transfer agent: 10% by weight based on the total of the monomer and the chain transfer agent) of chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) as a chain transfer agent were deoxygenated and placed in the autoclave, and precipitation polymerization was carried out by holding at 40 °C for 24 hours under stirring to obtain a white turbid slurry in which the resin precipitated in the polymerization solvent. The slurry was cooled to room temperature, the produced resin particles were collected by filtration, washed with acetone, and vacuum dried to obtain a powdery perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin (yield: 90%).

[0089] The weight average molecular weight of the obtained fluororesin was 8.8×10 4 , and the molecular weight distribution Mw / Mn was 2.48. Also, the volume average particle diameter of the obtained fluororesin was 26 μm, and it had excellent fluidity of the powder, and was more excellent in the fluidity of the powder than in Example 1.

[0090] [Example 3] The solid of the fluororesin obtained in Example 2 19As a result of F-NMR measurement, peaks derived from the terminal perfluorocyclohexyl group were confirmed at -140.2 ppm and -144.4 ppm. The integral value of the main chain peak (5F) at -81.3 ppm was 500, while the integral value of the peak (6F) derived from the terminal group was a total of 0.23.

[0091] [Comparative Example 1] In a 75mL glass ampoule, 0.173g (0.000410 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide was added as an initiator, 10.0g (0.0410 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) was added as a monomer, and 40.0g of FC-72 was added as a polymerization solvent. The mixture was repeatedly subjected to nitrogen replacement and depressurization by freeze degassing, and then sealed under reduced pressure (monomer / solvent=20 / 80 (wt / wt)). The ampoule was placed in a thermostatic bath at 55°C and held for 24 hours to carry out radical solution polymerization, resulting in a viscous liquid in which the resin was dissolved. After cooling to room temperature, the ampoule was opened, and the resulting resin solution was poured into 50g of FC-72 to adjust the viscosity, and diluted to produce a resin dilution solution. 240 g of Zeorola H was placed in a beaker equipped with a stirrer, and the diluted resin solution was added to the beaker under stirring to precipitate the resin. The precipitated resin was collected by filtration, washed twice with acetone, and vacuum dried to obtain a lump of perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin (yield 94%).

[0092] The weight average molecular weight of the obtained fluororesin was 21 × 10 4 The molecular weight distribution Mw / Mn was 2.8. The obtained fluororesin was in a lump form and had poor powder fluidity. The evaluation results of the fluororesin are shown in Table 1.

[0093] Fluororesin Solid 19 F-NMR measurement did not detect any peaks showing maxima at -140 to 142 ppm or -143 to 145 ppm. The filtrate from the resin precipitated on Zeorora H by the above procedure was dried, the solid was washed with acetone, and dried in vacuum. The obtained oligomer was then solidified. 13When measured by \(^{13}\)C-NMR, no peak was confirmed in the region of 80 to 100 ppm. Also, peaks of carbonyl groups were detected at 139 ppm and 143 ppm.

[0094] [Comparative Example 2] Into a 30-mm diameter glass ampoule equipped with a magnetic stir bar, 0.0865 g (0.000205 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator, 10.0 g (0.0205 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, 40.0 g of Zeorola-H (manufactured by Nippon Zeon Co., Ltd., 1,2,2,3,3,4,4-heptafluorocyclopentane) as a polymerization solvent, and 1.111 g (0.00931 mol) of chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) as a chain transfer agent were placed. After repeating nitrogen substitution by freeze degassing and pressure release, it was sealed under reduced pressure (amount of chain transfer agent: 10% by weight based on the total of the monomer and the chain transfer agent). While stirring the magnetic stir bar with a stirrer in a state where this ampoule was upright, precipitation polymerization was carried out by holding at 55 °C for 24 hours, and a slurry in which it became cloudy and the resin precipitated in the polymerization solvent was obtained. After cooling to room temperature, the ampoule was opened, the liquid containing the produced resin particles was filtered off, washed with acetone, and dried under vacuum to obtain particulate perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin (yield: 82%).

[0095] The weight average molecular weight of the obtained fluororesin was 9.6×10 4 , and the molecular weight distribution Mw / Mn was 2.6.

[0096] [Comparative Example 3] A solution in which 0.52 g (0.0012 mol) of (CF3CF2CF2COO)2 as an initiator was diluted with 52 g of FC-72 was placed in a glass ampoule with a capacity of 75 mL. 30.0 g (0.12 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer was added. After repeating nitrogen substitution by freeze degassing and pressure release, it was sealed under reduced pressure. Radical polymerization was carried out by holding this ampoule at 25 °C for 24 hours. The ampoule was opened, and the contents were put into a beaker containing 600 g of hexane while stirring. After recovering the solid by filtration, it was washed twice with acetone and dried in vacuo to obtain a block-shaped perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin (yield 18%). The evaluation results of the fluororesin are shown in Table 1. The weight average molecular weight of the obtained fluororesin was 86×10 4 , and the molecular weight distribution Mw / Mn was 26.2. The yield was very low, and the molecular weight distribution was very large.

[0097] [Comparative Example 4] Into a glass tube for polymerization equipped with a stirrer, 4.8 g (0.020 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, 3 mL of dichloropentafluoropropane (manufactured by AGC, AK-225) as a solvent, 0.21 g of ammonium perfluorooctanoate as an emulsifier, 0.24 g of Na2HPO4·7H2O as a pH adjuster, 0.15 g of (NH4)2S2O8 as an initiator, and 50 mL of distilled water degassed with N2 as a solvent were charged. After purging the headspace existing above this solution with N2, it was brought to a slightly pressurized state with N2. Next, the contents of this tube were heated at 75 °C for 5 hours while stirring with a stirrer. The resulting reaction mixture was treated with 80 mL of an HCl aqueous solution (6.3 M) to precipitate the polymer. This polymer was washed 3 times with 200 mL of distilled water and then 3 times with 200 mL of acetone. Next, this polymer was placed in a vacuum oven and dried at 150 °C under vacuum (150 mmHg) for 24 hours to obtain a white powdery polymer (yield: 3%). The operations from the above polymerization to drying were carried out separately 2 more times, and the obtained polymers were mixed to obtain a polymer for evaluation. The evaluation results of the obtained polymer are shown in Table 2. The weight average molecular weight of the obtained fluororesin was 34×10 4 , and the molecular weight distribution Mw / Mn was 25. The yield was very low, and the molecular weight distribution was very large. The solid of the fluororesin 19 When 19F-NMR measurement was carried out, peaks showing maxima at -140 to -142 ppm and -143 to -145 ppm were not detected.

[0098] [Comparative Example 5] A glass ampoule with a capacity of 75 mL was charged with 10.0 g (0.041 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, 35 g of AK-225 as a solvent, and 0.02 g of 4,4-bis(t-butylcyclohexyl) peroxydicarbonate (manufactured by NOF Corporation, Peroyl TCP) as an initiator. After repeating nitrogen substitution and pressure release by freeze degassing, it was sealed under reduced pressure. This ampoule was heated at 60 °C for 3 hours with shaking using a constant temperature shaker. The polymer taken out from this ampoule was dried under vacuum (150 mmHg) at 100 °C for 24 hours to obtain a polymer (yield: 76%). The operations from the above polymerization to drying were carried out separately 2 more times, and the obtained polymers were mixed to obtain a polymer for evaluation. The evaluation results of the obtained polymer are shown in Table 2. The weight average molecular weight of the obtained fluororesin was 12×10 4 , and the molecular weight distribution Mw / Mn was 1.8. When solid 19 F-NMR measurement of the fluororesin was performed, peaks showing maxima at -140 to -142 ppm and -143 to -145 ppm were not detected.

[0099] [Comparative Example 6] When solid 19 F-NMR measurement of the fluororesin obtained according to Comparative Example 2 was performed, peaks showing maxima at -140 to -142 ppm and -143 to -145 ppm were not detected.

[0100] [Comparative Example 7] When solid 19 F-NMR measurement of the fluororesin obtained according to Comparative Example 3 was performed, peaks showing maxima at -140 to -142 ppm and -143 to -145 ppm were not detected.

[0101]

Table 1

[0102]

Table 2

[0103] [Reference Example 1] The resin particles obtained in Example 2 were immersed in 10 times the amount of various solvents at 50 °C for 5 hours, and whether the resin particles remained was observed with the naked eye.

[0104] · The organic solvents in which the remaining resin particles were confirmed with the naked eye are as follows: 1,1,2,2 - tetrafluoroethyl - 2,2,2 - trifluoroethyl ether, 2,2,2 - trifluoroethanol, 1,1,1,3,3,3 - hexafluoroisopropanol, 1,2,2,3,3,4,4 - heptafluorocyclopentane, chloroform.

[0105] Thereafter, it was cooled to 25 °C, filtered through a filter, rinsed with the solvent to take out the resin particles, then the resin particles were washed twice with 10 times the amount of acetone and dried in vacuo. When the recovery rate was determined from the dry weight, the recovery rate was 90% or more in all cases. Also, when the filtrate obtained above was distilled off and the solid content in the filtrate was determined, the solid content in the filtrate was less than 10% with respect to the resin particles used. From the above results, it was confirmed that the weight reduction rate of the resin weight was less than 10% by weight.

[0106] As shown in Examples 1 and 2, the fluororesin of the present invention has a smaller yellowness degree of a thick - walled melt - molded product (φ10 mm × H17 mm, 280 °C for 24 h in a test tube) compared to Comparative Examples 1 to 3, and even in a thick - walled molded body, yellowing is suppressed.

[0107] The production method of the fluororesin of the present invention has a higher yield compared to the method of Comparative Example 3. As shown in Examples 1 and 2, the fluororesin can be produced at a yield of 80% or more, and depending on the conditions, at a yield of 85% or more, and further 90% or more.

[0108] The fluororesin obtained by the production method of the fluororesin of the present invention has an improved yellowness degree of a product heated at 280 °C for 24 h in a test tube, and has a narrower molecular weight distribution compared to the method of Comparative Example 3, and a molecular weight distribution Mw / Mn of 5 or less, and depending on the conditions, 4 or less, and further 3 or less of the fluororesin can be produced.

Industrial Applicability

[0109] The fluororesin of the present invention is useful in fields related to fluororesins.

Claims

1. A fluororesin containing a residue unit represented by the following formula (1) and a terminal group represented by the following formula (3). 【Chemical Formula 1】 (In formula (1), Rf １ , Rf ２ , Rf ３ , Rf ４ each independently represents one member of the group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, and the perfluoroalkyl group may have an etheric oxygen atom. Also, Rf １ , Rf ２ , Rf ３ , Rf ４ may be linked to each other to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an etheric oxygen atom) ​

2. Solid １９ The fluororesin according to claim 1, which shows peaks having maxima in the ranges of not less than -142 ppm and not more than -140 ppm, and not less than -145 ppm and not more than -143 ppm, respectively, in F-NMR spectrum analysis.

3. The fluororesin according to claim 1 or 2, wherein the fluororesin is in powder form and has a volume average particle diameter of 1 to 1000 μm.

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