JP2024023453A - Fluororesin - Google Patents

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

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

Fluororesin has excellent heat resistance, electrical properties, chemical resistance, waterproofness, oil repellency, and optical properties, so it is used as a protective film for semiconductors and other electronic components, a water-repellent film for inkjet printer heads, and a water-repellent film for filters. Used in oil coatings, optical components, etc.

Among them, fluororesins containing an oxolane ring have a bulky ring structure and therefore are amorphous and have high transparency and high heat resistance. Also, because it is composed only of carbon, fluorine, and oxygen, it has high electrical properties, chemical resistance, waterproofness, and oil and liquid repellency. Furthermore, since it is amorphous, it can be melt-molded.

Non-Patent Document 1 describes perfluoro-2-methylene-4-methyl-1,3-dioxolane (PFMMD), which is a type of fluororesin containing an oxolane ring, and perfluorobenzoyl peroxide as a radical polymerization initiator. There are descriptions regarding the synthesis and properties of the polymer (polyPFMMD) obtained by polymerization using the method. Poly PFMMD has excellent heat resistance. According to the studies conducted by the present inventors, the poly PFMMD described in Non-Patent Document 1 showed significant yellowing after hot melt molding, and yellowing was particularly significant in thick molded products. Therefore, there is a strong need for a technology that can exhibit high transparency with less coloration even in the case of thick molded products of poly PFMMD.

As a method for reducing coloring of a fluororesin during heating, a method is known in which a fluororesin having an aliphatic perfluoroalkyl group terminal is obtained using an aliphatic perfluorinated initiator. For example, Non-Patent Document 2 reports an example of cyclization polymerization of perfluoro(butenyl vinyl ether) using (CF ₃ CF ₂ CF ₂ COO) ₂ by bulk polymerization. However, according to the studies of the present inventors, even if the technique described in Non-Patent Document 2 is used for the synthesis of polyPFMMD, it cannot be said that the yellowing of polyPFMMMD after heat melt molding is sufficiently reduced. Met. Furthermore, the yield was extremely poor, the productivity was poor, and the molecular weight distribution Mw/Mn was large.

Macromolecules 2005, 38, 4237-4245 Journal of the Chemical Society of Japan 2001, No. 12, 659-668

The present invention was made with the aim of solving the problems associated with fluororesins containing oxolane rings. Specifically, the object of the present invention is to provide a fluororesin containing an oxolane ring that suppresses yellowing after heating and melting, and in particular reduces coloring even when molding thick-walled products, and a method for producing the same.

As a result of extensive studies, the present inventors have found that a fluororesin containing an oxolane ring having a terminal group with a specific structure can solve the above problems, and have completed the present invention.

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).

(In formula (1), Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, and a branched chain having 3 to 7 carbon atoms. Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ may be linked to each other to form a ring having 4 to 8 carbon atoms, and the ring may contain an etheric oxygen atom.)

(In formula (2), i is an integer from 3 to 20)

According to the present invention, it is possible to provide a fluororesin containing an oxolane ring in which yellowing during melt molding of a thick molded product is suppressed, and a method for producing the same.

The fluororesin that is one embodiment of the present invention will be described in detail below.

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

(In formula (1), Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, and a branched perfluoroalkyl group having 3 to 7 carbon atoms. Represents one of the group consisting of a perfluoroalkyl group or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms, the perfluoroalkyl group may have an ether oxygen atom, and Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ may be linked to each other to form a ring having 4 or more and 8 or less carbon atoms, and the ring may contain an ether oxygen atom.)

(In formula (2), i is an integer from 3 to 20)
Since the fluororesin of the present invention has a bulky ring structure included in the specific formula (1), it is amorphous and has high transparency and high heat resistance. Furthermore, 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.

In formula (1), Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ groups each independently represent a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, or a branched chain having 3 to 7 carbon atoms. This refers to one of the group consisting of a perfluoroalkyl group having a cyclic shape or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an ether oxygen atom. Furthermore, Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ may be linked to each other to form a ring having 4 or more and 8 or less carbon atoms, and the ring may contain an etheric oxygen atom.

Examples of the linear perfluoroalkyl group having 1 to 7 carbon atoms include trifluoromethyl group, pentafluoroethyl group, heptafluoropropyl group, nonafluorobutyl group, undecafluoropentyl group, tridecafluorohexyl group, Examples include pentadecafluoroheptyl group.

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

Examples of the cyclic perfluoroalkyl group having 3 to 7 carbon atoms include heptafluorocyclopropyl group, nonafluorocyclobutyl group, and tridecafluorocyclohexyl group.

Examples of the linear perfluoroalkyl group which may have an etheric oxygen atom having 1 to 7 carbon atoms include -CF ₂ OCF ₃ group, -(CF ₂ ) ₂ OCF ₃ group, -(CF ₂ ) ₂ OCF ₂ CF ₃ groups and the like.

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

At least one of Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ is a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a carbon number A fluororesin that is one of the group consisting of 3- to 7-cyclic perfluoroalkyl groups is preferred. As a result, the fluororesin of the present invention exhibits better heat resistance.

Specific examples of the residue unit represented by formula (1) include, for example, the residue unit represented by formula (3) below.

Among these, a fluororesin containing a residue unit represented by the following formula (4) is preferable because it has excellent heat resistance and moldability, and perfluoro(4-methyl-2-methylene-1,3-dioxolane) More preferred are fluororesins containing residue units.

The fluororesin of the present invention includes a terminal group represented by the following formula (2). As a result, yellowing during melt molding of a thick molded product is suppressed.

Here, the term "terminal group" means a group present at the end of the main chain of the polymer.

The terminal group represented by formula (2) preferably has a structure represented by formula (5) below.

It can be confirmed, for example, by the following method that the fluororesin of the present invention contains the terminal group unit represented by formula (5).

That is, in the solid ^19F -NMR spectrum analysis of the fluororesin, if it is confirmed that peaks exhibiting maxima in the ranges of -140 ppm to 142 ppm and -143 ppm to 145 ppm are confirmed to be the fluororesin of the present invention. It can be determined that it has a terminal group represented by formula (5). The peaks showing maxima in the ranges of -140 ppm to 142 ppm and -143 ppm to 145 ppm are assigned to the -CF ₂ - group at the 3rd, 4th, and 5th positions of formula (5).

Note that a general ¹⁹ F-NMR measuring device may be used for solid ¹⁹ F-NMR measurement of the fluororesin. For example, using a VNMRS-400 manufactured by Varian, a magnetic field strength of 376.18 MHz (19F), a 1.6 mm FASTMAS probe, a pulse width of 1.3 μs, a spectral width of 250 kHz (664.6 ppm), and a spectrum using the hahn-echo method. Center: -120 ppm, waiting time: 10 seconds, MAS rotation speed: 39 kHz, integration number of 2048 times, solid ¹⁹ F-NMR measurement is performed using PTFE (-122.0 ppm) as a reference and approximately 10 mg of fluororesin. Can give examples of methods.

In the solid ^19F -NMR spectrum analysis of the fluororesin of the present invention, the integrated value of the area of the terminal peak (6F) due to the terminal group showing maximum in the range of -140 ppm to 142 ppm and -143 ppm to 145 ppm is , the integral value of the area of the main chain peak (5F) showing the maximum at the position of -81 ppm is 500, the total is preferably 0.001 to 10, more preferably 0.01 to 5, and 0. More preferably, it is between .05 and .05. This further suppresses yellowing of the fluororesin. Here, the main chain peak (5F) showing a maximum at the position of -81 ppm is assigned to the -CF ₂ O- group and the -CF ₃ group.

The fact that the fluororesin of the present invention contains the residue unit represented by formula (2) or formula (5) can also be confirmed, for example, by solid-state ¹³ C-NMR measurement of the oligomer of the fluororesin. For example, an oligomer or the like dissolved in a solvent such as Zeorola H during the production process is isolated, and the obtained oligomer is subjected to solid ¹³ C-NMR measurement. At this time, if a peak with a maximum in the range of 90 to 92 ppm is observed, which originates from the F atom at position 1 of the perfluorocycloalkyl group directly bonded to the residue unit represented by formula (1), then fluorine It can be confirmed that the resin contains the terminal group represented by formula (2) or formula (5).

It is preferable that the terminal group represented by formula (2) or formula (5) is directly bonded to the residue unit represented by general formula (1) without intervening another functional group. Moreover, it is preferable that the fluororesin of the present invention does not contain a carbonyl group.

The fluororesin of the present invention preferably has a weight average molecular weight Mw in the range of 5×10 ⁴ to 3×10 ⁵ . When the weight average molecular weight Mw is within this range, melt molding processability and defoaming property during melting are excellent. Furthermore, when the weight average molecular weight Mw is within this range, cracks are less likely to occur during heating and cooling. The fluororesin of the present invention preferably has a weight average molecular weight Mw of 5×10 ⁴ to 2×10 ⁵ from the viewpoint of excellent melt molding processability and excellent defoaming properties during melting.

The weight average molecular weight Mw of the fluororesin of the present invention can be determined using gel permeation chromatography (GPC), for example, by using a standard polymethyl methacrylate with a known molecular weight as a standard sample, and using an eluent that can dissolve both the standard sample and the fluororesin. It can be calculated from the elution time of the sample and standard sample and the molecular weight of the standard sample using a solvent. The solution includes Asahiklin AK-225 (manufactured by Asahi Glass Co., Ltd.) and 10 wt% of 1,1,1,3,3,3-hexafluoro-2-propanol (Wako Pure Chemical Industries, Ltd.) based on AK-225. (Industrial products) can be added.

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, but it suppresses yellowing after heating and melting, has excellent melt moldability, and The molecular weight distribution Mw/Mn is preferably 1.2 to 8, more preferably 1.2 to 5, from the viewpoint of excellent defoaming properties during heating and less cracking during heating and cooling. , 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 in the same manner as the method for measuring 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.

The fluororesin of the present invention has a yellowness index (YI) of 10 when measured in the diameter direction of a thick melt-molded product (cylindrical molded product with a diameter of 10 mm and a height of about 17 mm, heated and melted in a test tube at 280°C for 24 hours). It is preferably at most 4, more preferably at most 4, even more preferably at most 3. According to the present inventors, when a thick molded product is melt-molded in a closed environment, yellowing of the fluororesin after heating and melt-molding becomes more significant than when heating in an open environment. As a method for evaluating the yellowness and coloring of a thick melt-molded product, for example, 3 g of the fluororesin of the present invention is heated at 280°C for 24 hours in a test tube with an outer diameter of 13 mm, and then melted and molded. A method for evaluating the yellowness index (YI) of a cylindrical body (diameter 10 mm x height approximately 17 mm) measured in the diameter direction can be mentioned. Here, the diametrical direction is the vertical direction when the test tube is placed horizontally on a desk or the like. To determine the degree of yellowness, place the resin molded product in the test tube sideways on a piece of white paper, take a digital photograph from above, and use software to determine the degree of yellowness of the molded product. Read the RGB values and calculate the read RGB values using the following formula: X=0.4124R+0.3576G+0.1805B
Y=0.2126R+0.7152G+0.0722B
Z=0.0193R+0.1192G+0.9505B
Calculate the tristimulus values X, Y, and Z of the XYZ color system using be able to.

The fluororesin of the present invention preferably has a yellowness index (YI) of 1 or less in a flaky melt-molded product (3 mm thick, molded by heating and melting in a petri dish at 280° C. for 24 hours). As the molding method and evaluation method, the methods described in Examples can be mentioned.

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

Although there is no particular limitation on the particle size of the fluororesin of the present invention, the resin powder has high fluidity, enables continuous supply to molding machines, etc., suppresses residual solvent in the resin, and has a large bulk density. The volume average particle size is preferably from 1 to 1000 μm, preferably from 1 to 500 μm, and more preferably from 1 to 300 μm, since the filling properties are increased and the handling properties during molding are excellent. .

The volume average particle size of the fluororesin of the present invention can be evaluated by particle size distribution measurement (volume distribution) using a laser diffraction scattering method. The particle size distribution by laser diffraction scattering can be measured by dispersing resin particles in water or an organic solvent such as methanol. As a laser scatterometer, Microtrac manufactured by Microtrac Bell Co., Ltd. can be exemplified.

The volume average particle diameter, also called Mean Volume Diameter, is the average particle diameter expressed on a volume basis.The particle diameter distribution is divided into each particle diameter channel, and the representative particle diameter value of each particle diameter channel is d, and each It is expressed as Σ(vd)/Σ(v), where v is the volume-based percentage for each particle size channel.

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

A method for producing a fluororesin, which is one embodiment of the present invention, will be described in detail below.

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

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

(In formula (7), Rf ₅ , Rf ₆ , Rf ₇ , and Rf ₈ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, and 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 ether oxygen atom, and Rf ₅ , Rf ₆ , Rf ₇ , and Rf ₈ may be linked to each other to form a ring having 4 to 8 carbon atoms, and the ring may contain an etheric oxygen atom.)
Rf ₅ , Rf ₆ , Rf ₇ , and Rf ₈ in formula (7) have the same meanings as Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ in formula (1), respectively.

In the method for producing a fluororesin of the present invention, by using a radical polymerization initiator represented by formula (6), a fluororesin with suppressed yellowing during melt molding of a thick molded product is obtained. be able to. Furthermore, a fluororesin having a narrow molecular weight distribution Mw/Mn can be obtained. By narrowing the molecular weight distribution Mw/Mn, heat melt moldability is improved. Furthermore, fluororesin can be obtained with excellent yield and productivity. In addition, by using a radical polymerization initiator represented by formula (6), the radical polymerization initiator is decarboxylated and then added to the polymer, so that the resulting polymer contains almost no carbonyl groups, and the radical polymerization initiator is decarboxylated and then added to the polymer. It has a structure in which the terminal group represented by (2) is directly added to the polymer, which is advantageous in obtaining a fluororesin in which yellowing is suppressed during melt molding of thick molded products.

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), it is possible to obtain a fluororesin in which yellowing during melt molding of a thick molded product is further suppressed. Furthermore, a fluororesin having a narrow molecular weight distribution Mw/Mn can be obtained. By narrowing the molecular weight distribution Mw/Mn, heat melt moldability is improved. Furthermore, 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.

Bis(perfluorocyclohexylcarbonyl) peroxide is disclosed in JP-A No. 11-49749 and J. App. Polym. Sci, 1999, 72, 1101-1108. At this time, perfluorohexane (FC-72, manufactured by 3M Japan) or the like may be used instead of AK-225 as a solvent. The bis(perfluorocyclohexylcarbonyl) peroxide of the present invention may be synthesized by a method other than the method described in the above-mentioned literature, for example, Chem. Rev, 1996, 96, 1779-1808 describes a method for synthesizing fluorinated peroxides, in addition to the method of reacting acid fluoride with hydrogen peroxide, the method of reacting acid chloride with hydrogen peroxide, and the method of reacting acid anhydride. Examples include a method of reacting a substance with hydrogen peroxide. At this time, the reaction proceeds due to the presence of a base such as sodium hydroxide in the system.

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

In the method for producing the resin of the present invention, there are no limitations on the polymerization method, but examples include methods such as solution polymerization, precipitation polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization.

In the production method of the present invention, it is preferable that an organic solvent is further mixed into the mixture in the polymerization step.

In the resin manufacturing method of the present invention, the resin powder has high fluidity and can be continuously supplied to a molding machine, etc., the residual solvent in the resin can be suppressed, the bulk density is large, the filling property is increased, Since a powder with excellent handling properties during molding processing is obtained, at least the monomer represented by formula (7) is dissolved as an organic solvent, and at least a part of the resin produced by polymerization is not dissolved. It is preferable to use an organic solvent that causes precipitation of the resin, and in which the resin produced by the polymerization precipitates in the form of particles in the organic solvent. In the method for producing a 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 with excellent moldability and fillability can be produced. . Furthermore, since polymerization aids such as emulsifiers and dispersants are not used, resin particles can be produced that do not contain emulsifiers and dispersants that cause deterioration of transparency and heat resistance.

Here, the precipitation polymerization solvent means a solvent in which resin particles remain after immersing resin particles containing the residue unit represented by formula (1) in the organic solvent for a long time. Specifically, resin particles containing residue units represented by the general formula (1) and having a weight average molecular weight Mw of 5×10 ⁴ to 70×10 ⁴ were added in an amount 10 times (w/w) to the resin particles. If residual resin particles can be seen with the naked eye in the organic solvent after being immersed in the organic solvent at 50°C for 5 hours or more, the organic solvent can be regarded as precipitation polymerization solvent A. Precipitation polymerization solvent A is After cooling the solution to 25 °C after immersion at 5 hours or more at °C, the resin sample remaining in a solid state is recovered, and the organic solvent is preferably an organic solvent in which the weight loss rate of the resin sample is less than 20% by weight.Resin The weight loss rate of the sample is more preferably less than 12% by weight, even more preferably less than 10% by weight.

The rate of decrease in resin weight can be measured by the following method. After the cooled solution is filtered, the solid on the filter is rinsed with the solvent, washed multiple times with acetone and dried, and the resin sample on the filter is collected. Measure the weight of the recovered resin, and calculate the resin reduction rate by dividing the value obtained by subtracting the recovered resin weight from the amount of resin immersed in the organic solvent by the amount of resin immersed in the organic solvent. do.

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

Further, 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 is difficult to occur in radical polymerization, the polymerization yield is excellent, and a high molecular weight product is easily obtained. Specific examples of precipitation polymerization solvents containing fluorine atoms and hydrogen atoms in the molecule include 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,2-trifluoroethyl ether, and 2,2,2-trifluoroethyl ether. Fluoroethanol, 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-dodecafluorohepta alcohol, 1H,1H,3H-hexafluorobutanol, 2,2,3,3,3-pentafluoropropyl difluoromethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2 -tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl ethyl 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-hexafluoropropylethyl ether, 2,2,3,4,4,4-hexafluorobutyl difluoromethyl ether, and the like.

Among them, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoro Isopropanol, 1,2,2,3,3,4,4-heptafluorocyclopentane are preferred, and 1,2,2,3,3,4, 4-Heptafluorocyclopentane is preferred. The ratio of fluorine atoms to hydrogen atoms in the molecule of the precipitation polymerization solvent is preferably fluorine atoms:hydrogen atoms=1:9 to 9:1 in terms of the number ratio of atoms, since the polymerization yield is excellent. The ratio is more preferably 9 to 7:3, and even more preferably 4:6 to 7:3. The precipitation polymerization solvent preferably contains a fluorine atom and a hydrogen atom in its molecule, and the content of hydrogen atoms in the solvent is preferably 1% by weight or more based on the weight of the solvent molecule, since it has an excellent polymerization yield.1. More preferably, the amount is 5% by weight or more. Further, since the polymerization yield is excellent and it is easy to obtain a high molecular weight product, the amount is preferably 1% by weight or more and 5% by weight or less, and preferably 1.5% by weight or more and 4% by weight or less. Further, as the precipitation polymerization solvent, one that does not contain a chlorine atom in the molecule is preferable because it has an excellent polymerization yield and is easy to obtain a high molecular weight product.

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

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

By manufacturing according to the method of the present invention, it is possible to obtain a fluororesin in which yellowing during melt molding of a thick molded product is suppressed. Furthermore, a fluororesin having a narrow molecular weight distribution Mw/Mn can be obtained while exhibiting the above characteristics. Furthermore, the fluororesin can be obtained with excellent yield and productivity while exhibiting the above characteristics.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[Measurement of weight average molecular weight Mw and molecular weight distribution Mw/Mn]
The measurement was performed using a gel permeation chromatography equipped with a column TSKgel SuperHZM-M manufactured by Tosoh Corporation and an RI detector. As an eluent, Asahiklin AK-225 (manufactured by Asahi Glass Co., Ltd.) was added with 10 wt% of 1,1,1,3,3,3-hexafluoro-2-propanol (manufactured by Wako Pure Chemical Industries, Ltd.) relative to AK-225. was used. Using standard polymethyl methacrylate manufactured by Agilent as a standard sample, 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.

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

[Solid ^13C -NMR measurement]
Using VNMRS-400 manufactured by Varian, magnetic field strength 100.55 MHz (13C), 4.0 mm MAS probe, CP/MAS method, spectral width 30.5 kHz, spectral center: 77.5 ppm, waiting time: 3 seconds , MAS rotation speed: 10 kHz, integration number of 4096 times, solid ¹³ C-NMR measurement was performed using TMS (0 ppm) as a reference using about 50 mg of fluororesin.

[Measurement of yellowness index (YI) of thick melt-molded product (φ10 mm x H17 mm, in test tube at 280°C for 24 hours)]
Put 3.0 g of fluororesin into a glass test tube (Nichiden Rika Glass, ST-13M) with an outer diameter of 13 mm and a total length of 100 mm, and cover the mouth of the test tube with aluminum foil and an aluminum cap (Maruem, M-1). It was placed in a test tube stand, placed in an oven, heated at 280° C. for 24 hours, and then allowed to cool to obtain a cylindrical resin molded product inside the test tube (diameter: 10 mm, height: approximately 17 mm). With the resulting resin molded product still in the test tube, place the test tube sideways on a piece of white paper, and take a digital photo from above under white fluorescent light using PowerShotSX620HS (manufactured by Canon Inc.). The RGB values of the molded article were read from the obtained image using Paint (image processing software manufactured by Microsoft). The read RGB values are calculated using 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 of the XYZ color system were determined. Calculate the yellowness (YI) at light source C (auxiliary illuminant C) from X, Y, and Z according to the method of JIS K7373, and calculate the yellowness (YI) of the thick melt-molded product (φ10mm x H17mm, 280°C in a test tube for 24 hours). YI) was calculated.

[Yellowness index (YI) of thin flake melt-molded product (3 mm thickness, 280°C in Petri dish for 24 hours)]
Weighed 2.0 g of fluororesin into a Petri dish with an inner diameter of 26.4 mm (of the flat petri dish lid and receiver set manufactured by Flat Co., Ltd., the glass thickness at the bottom of the receiver is 1 mm), and placed it in an inert oven (Yamato Scientific Co., Ltd.). DN411I) and left to stand at room temperature for 30 minutes under an air stream (20 L/min), then heated to 280°C over 30 minutes, and then heated at 280°C for 24 hours. After that, while maintaining the air flow (20 L/min), keep the oven door closed, turn off the power to the inert oven, let it cool for 12 hours, then take out the sample and place it on a Petri dish with a thickness of 3 mm. A fluororesin heat-melted molded product with a diameter of 26.4 mm was obtained. At this time, the air used was air compressed by a compressor and passed through a dehumidifier (dew point temperature -20°C or lower). Using a spectrophotometer (U-4100, manufactured by Hitachi High-Tech Science Co., Ltd.), the transmittance at each wavelength of the obtained fluororesin heat-melted molded product was measured at 1 nm intervals in a wavelength range of 200 nm to 1500 nm, using a petri dish. Data at 5 nm intervals at a wavelength of 380 nm to 780 nm was extracted from the measured transmittance data, and tristimulus values X, Y, and Z of the XYZ color system were calculated according to the method of JIS Z8701. Further, according to the method of JIS K7373, the yellowness index (YI) in the 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 determined. By measuring the yellowness (YI) of the Petri dish alone (receiver only) and subtracting the yellowness (YI) of the Petri dish alone (receiver only) from the yellowness (YI) of the fluororesin molded product including the Petri dish, the thickness can be determined. The yellowness index (YI) of a 3 mm thick fluororesin heat-melted molded product was determined. The yellowness index (YI) of the petri dish alone (receiver only) was 0.21.

[Measurement of volume average particle diameter]
The volume average particle diameter (unit: μm) was measured using Microtrac MT3000 manufactured by Microtrac Bell Co., Ltd. and methanol as a dispersion medium.

[Example 1]
The inside of a 3L SUS316 autoclave equipped with a paddle-type stirring blade, a nitrogen introduction tube, and a thermometer was purged with nitrogen. A solution in which 2.33 g (0.0036 mol) of bis(perfluorocyclohexyl carbonyl) peroxide as an initiator was dissolved in 230 g of FC-72 (manufactured by 3M Japan Co., Ltd., perfluorohexane), with perfluoro as a monomer. (4-Methyl-2-methylene-1,3-dioxolane): 175 g (0.72 mol) and FC-72: 470 g as a polymerization solvent were placed in an autoclave after removing dissolved oxygen, and heated at 55°C for 24 hours with stirring. Solution polymerization was carried out by holding for a certain period of time, and a viscous liquid in which the resin was dissolved was obtained. After cooling to room temperature, the ampoule was opened, and the resulting resin solution was poured into 875 g of FC-72 to adjust the viscosity and diluted to prepare a diluted resin solution. In a plastic cup equipped with stirring blades, Zeorola H (manufactured by Nippon Zeon Co., Ltd., 1,2,2,3,3,4,4-heptafluorocyclopentane, hydrogen atom content in solvent molecules: 1.55 weight) %, fluorine atoms:hydrogen atoms in solvent molecules = 7:3 (number ratio)), and the resin was precipitated by adding the above diluted resin solution to the plastic cup while stirring. The precipitated resin was collected by filtration, washed twice with acetone, and vacuum-dried to obtain a powdered perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin. rate: 93%).

The weight average molecular weight of the obtained fluororesin was 9.5×10 ⁴ , and the molecular weight distribution Mw/Mn was 3.74. Table 1 shows the evaluation results for the fluororesin.

As a result of performing solid ¹⁹ F-NMR measurement on the obtained fluororesin, peaks derived from the terminal perfluorocyclohexyl group were confirmed at -140.7 ppm and -143.9 ppm. While the integral value of the main chain peak (5F) at -81.3 ppm was 500, the integral value of the peak derived from the terminal group (6F) was 1.46 in total.

Moreover, the filtrate obtained when the resin was precipitated with Zeorola H during the above operation was dried to solidity, and the solid was washed with acetone and vacuum-dried to obtain an oligomer.

As a result of performing solid ¹³ C-NMR measurement on the obtained oligomer, a peak originating from the F atom at the 1st 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 between 130 and 150 ppm.

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

A solution of 0.80 g (0.0012 mol) of bis(perfluorocyclohexylcarbonyl) peroxide as an initiator dissolved in 80 g of FC-72, perfluoro(4-methyl-2-methylene-1, 3-dioxolane): 300 g (1.23 mol), Zeolola-H as a polymerization solvent: 1120 g, chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) as a chain transfer agent: 33.33 g (0.279 mol), amount of chain transfer agent: (10% by weight based on the total of polymer and chain transfer agent) was placed in an autoclave after removing dissolved oxygen, and maintained at 40°C for 24 hours with stirring to perform precipitation polymerization, and the resin became a cloudy polymerization solvent. A slurry was obtained. The slurry is cooled to room temperature, the generated resin particles are collected by filtration, washed with acetone, and vacuum dried to obtain powdered perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin. (yield: 90%).

The weight average molecular weight of the obtained fluororesin was 8.8×10 ⁴ , and the molecular weight distribution Mw/Mn was 2.48. Further, the volume average particle diameter of the obtained fluororesin was 26 μm, and the powder had excellent fluidity, which was better than that of Example 1.

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

[Comparative example 1]
A glass ampoule with a capacity of 75 mL contained 0.173 g (0.000410 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator and perfluoro(4-methyl-2 as a monomer). - Methylene-1,3-dioxolane): 10.0 g (0.0410 mol) and FC-72: 40.0 g as a polymerization solvent were added, and after repeated nitrogen substitution and depressurization by freeze degassing, melting was carried out under reduced pressure. It was sealed (monomer/solvent = 20/80 (wt/wt)). This ampoule was placed in a constant temperature bath at 55° C. and maintained for 24 hours to perform radical solution polymerization to obtain 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 50 g of FC-72 to adjust the viscosity and diluted to prepare a diluted resin solution. Zeorola H: 240 g was placed in a beaker equipped with a stirrer, and the resin was precipitated by adding the diluted resin solution to the beaker while stirring. The precipitated resin was collected by filtration, washed twice with acetone, and dried in vacuum to obtain a block of perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin (yield: 94%).

The weight average molecular weight of the obtained fluororesin was 21×10 ⁴ and the molecular weight distribution Mw/Mn was 2.8. Furthermore, the obtained fluororesin was in the form of lumps and had poor powder fluidity. Table 1 shows the evaluation results for the fluororesin.

When the solid ¹⁹ F-NMR measurement of the fluororesin was performed, no peaks showing maxima at -140 to 142 ppm and -143 to 145 ppm were detected. The filtrate in which the resin was precipitated on Zeorola H by the above procedure was dried, the solid was washed with acetone, and after vacuum drying, the obtained oligomer was subjected to solid ^13C -NMR measurement, and a peak was confirmed in the 80 to 100 ppm region. It wasn't done. Furthermore, peaks of carbonyl groups were detected at 139 ppm and 143 ppm.

[Comparative example 2]
Bis(2,3,4,5,6-pentafluorobenzoyl) peroxide: 0.0865 g (0.000205 mol) as initiator, perfluoromonomer as monomer in a glass ampoule with a diameter of 30 mm equipped with a magnetic stirrer. (4-methyl-2-methylene-1,3-dioxolane): 10.0 g (0.0205 mol), Zeorola-H (Nippon Zeon, 1,2,2,3,3,4,4 - Heptafluorocyclopentane): 40.0 g, chloroform (Wako Pure Chemical Industries, Ltd.): 1.111 g (0.00931 mol) as a chain transfer agent, and after repeated nitrogen substitution and depressurization by freeze degassing, the pressure was reduced. (Amount of chain transfer agent: 10% by weight based on the total of monomer and chain transfer agent). Precipitation polymerization was carried out by holding the ampoule upright at 55° C. for 24 hours while stirring with a magnetic stirrer, resulting in a slurry that became cloudy and the resin precipitated in the polymerization solvent. After cooling to room temperature, the ampoule is opened, the liquid containing the generated resin particles is filtered, washed with acetone, and vacuum dried to obtain particulate perfluoro(4-methyl-2-methylene-1,3-dioxolane). ) Resin was obtained (yield: 82%).

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

[Comparative example 3]
A solution of 0.52 g (0.0012 mol) of (CF ₃ CF ₂ CF ₂ COO) ₂ diluted with 52 g of FC-72 as an initiator in a glass ampoule with a volume of 75 mL, and perfluoro(4-methyl) as a monomer. -2-methylene-1,3-dioxolane): 30.0 g (0.12 mol) was added, and after repeated nitrogen substitution and depressurization by freeze degassing, the mixture was sealed under reduced pressure. Radical polymerization was carried out by holding this ampoule at 25° C. for 24 hours. The ampoule was opened, the contents were poured into a beaker containing 600 g of hexane under stirring, and the solid was collected by filtration, washed twice with acetone, and vacuum dried to form a lump of perfluoro(4-methyl-2 -methylene-1,3-dioxolane) resin was obtained (yield 18%). Table 1 shows the evaluation results for the fluororesin. 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 wide.

[Comparative example 4]
In a polymerization glass tube equipped with a stirring bar, 4.8 g (0.020 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) was added as a monomer, and dichloropentafluoropropane (AGC) was added as a solvent. AK-225): 3 mL, ammonium perfluorooctanoate: 0.21 g as an emulsifier, Na ₂ HPO _{4.7H 2} O: 0.24 g as a pH adjuster, (NH ₄ ) ₂ S ₂ O as an initiator. ₈ : 0.15 g, and 50 mL of distilled water degassed with N ₂ as a solvent were charged. The headspace above this solution was purged with N ₂ and then subjected to slight N ₂ pressurization. The contents of this tube were then heated at 75° C. for 5 hours while stirring with a stir bar. The polymer was precipitated by treating the resulting reaction mixture with 80 mL of aqueous HCl (6.3 M). This polymer was washed three times with 200 mL of distilled water and then three 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 above operations from polymerization to drying were separately performed twice more, and the resulting polymers were mixed to obtain a polymer for evaluation. Table 2 shows the evaluation results of the obtained polymer. 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 wide. When the solid ¹⁹ F-NMR measurement of the fluororesin was performed, no peaks showing maxima at -140 to 142 ppm and -143 to 145 ppm were detected.

[Comparative example 5]
In a glass ampoule with a capacity of 75 mL, perfluoro(4-methyl-2-methylene-1,3-dioxolane): 10.0 g (0.041 mol) as a monomer, AK-225: 35 g as a solvent, and 4 as an initiator. , 0.02 g of 4-bis(t-butylcyclohexyl) peroxydicarbonate (Perloyl TCP, manufactured by NOF Corporation) was charged. After repeating nitrogen substitution and depressurization by freezing and degassing, it was melted under reduced pressure. This ampoule was heated at 60° C. for 3 hours while shaking in a thermostatic shaker. The polymer taken out from this ampoule was dried at 100° C. under vacuum (150 mmHg) for 24 hours to obtain a polymer (yield: 76%). The above operations from polymerization to drying were separately performed twice more, and the resulting polymers were mixed to obtain a polymer for evaluation. Table 2 shows the evaluation results of the obtained polymer. The weight average molecular weight of the obtained fluororesin was 12×10 ⁴ , and the molecular weight distribution Mw/Mn was 1.8. When the solid ¹⁹ F-NMR measurement of the fluororesin was performed, no peaks showing maxima at -140 to 142 ppm and -143 to 145 ppm were detected.

[Comparative example 6]
When the fluororesin obtained in Comparative Example 2 was subjected to solid ^19F -NMR measurement, no peaks having maxima at -140 to 142 ppm and -143 to 145 ppm were detected.

[Comparative Example 7]
When the fluororesin obtained in Comparative Example 3 was subjected to solid ^19F -NMR measurement, no peaks having maxima at -140 to 142 ppm and -143 to 145 ppm were detected.

[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 visually observed.

・The organic solvents in which residual resin particles were visually confirmed 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.

Thereafter, the resin particles were cooled to 25°C, filtered through a filter, and rinsed with the solvent to remove the resin particles. The resin particles were washed twice with 10 times the amount of acetone, vacuum dried, and the recovery rate was determined from the dry weight. The recovery rate was over 90% in all cases. Further, 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% based on 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.

As shown in Examples 1 and 2, the fluororesin of the present invention has a lower degree of yellowness in thick-walled melt-molded products (φ10 mm x H17 mm, 24 hours at 280°C in a test tube) compared to Comparative Examples 1 and 3, and thick molded products. Yellowing of the body is also suppressed.

The method for producing a fluororesin of the present invention has a higher yield than the method of Comparative Example 3, and as shown in Examples 1 and 2, it is possible to produce a fluororesin at a yield of 80% or more. Depending on the method, fluororesin can be produced with a yield of 85% or more, or even 90% or more.

The fluororesin obtained by the fluororesin manufacturing method of the present invention has improved yellowness when heated in a test tube at 280°C for 24 hours, and has a narrower molecular weight distribution compared to the method of Comparative Example 3, and the molecular weight distribution Mw/Mn It is possible to produce a fluororesin in which the number is 5 or less, 4 or less depending on the conditions, or even 3 or less.

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

Claims (4)

A fluororesin containing a residue unit represented by the following formula (1) and a terminal group represented by the following formula (2).
(In formula (1), Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ are each independently a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, and a branched chain having 3 to 7 carbon atoms. Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ may be linked to each other to form a ring having 4 to 8 carbon atoms, and the ring may contain an etheric oxygen atom.)
(In formula (2), i is an integer from 3 to 20) The fluororesin according to claim 1, wherein the terminal group represented by formula (2) has a structure represented by formula (3) below.
The fluororesin according to claim 1 or 2, which exhibits maximum peaks in the ranges of -140 to 142 ppm and -143 to 145 ppm in solid ^19F -NMR spectrum analysis. The fluororesin according to any one of claims 1 to 3, wherein the fluororesin is in powder form and has a volume average particle diameter of 1 to 1000 μm.