Fluororesin and Method for Producing the Same

Abstract

To provide a fluororesin which is excellent in melting molding processability, suppresses yellow discoloration after heat-melting and contains an oxolane ring, and a method for producing the same.SOLUTION: There are provided a fluororesin which contains a residue unit represented by the following general formula (3), has a weight average molecular weight Mw of 5×104 to 3×105, and has yellowness of a molded article obtained by heat-melting at 280°C for 24 hours (3 mm thickness) of 3 or less, and a method for producing the same. [Formula 1]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 a bulky ring structure, so they are amorphous 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 of perfluoro-2-methylene-4-methyl-1,3-dioxolane (PFMMD), which is a type of fluororesin containing an oxolane ring. Although polyPFMMD is excellent in heat resistance, according to the studies of the present inventors, it has a high melt viscosity, poor melt moldability, poor defoaming property during heat melting, and significant yellowing after heat melting.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] To lower the melt viscosity and improve the melt formability, reducing the molecular weight of the polymer is effective. According to Non-Patent Document 1, it is possible to reduce the molecular weight by using carbon tetrabromide (CBr 4 ) as a chain transfer agent. However, as a result of investigations by the present inventors, it has been found that a polymer whose molecular weight has been reduced using carbon tetrabromide (CBr 4 ) as the chain transfer agent described in Non-Patent Document 1 has a problem of significant yellowing after heat melting.

[0007] An object of the present invention is to solve the problems in the fluororesin containing the above oxolane ring. Specifically, an object is to provide a fluororesin containing an oxolane ring that is excellent in melt formability and has suppressed yellowing after heat melting, and a method for producing the same.

[0008] Furthermore, when the molecular weight of the polymer is reduced, the glass transition temperature also decreases. When the glass transition temperature decreases, the heat resistance is impaired. Also, as a result of investigations by the present inventors, it has been found that when the molecular weight is reduced using carbon tetrabromide (CBr 4 ) as a chain transfer agent, there is a problem that cracks occur during cooling after heat forming. Also, Non-Patent Document 1 does not mention anything about the melt viscosity, the defoaming property during melting, or the occurrence of cracks. Moreover, the properties of a resin that achieves both the defoaming property during melting and the occurrence of cracks have not been clarified at all. Furthermore, the properties of a resin that satisfies all of the defoaming property during melting, the occurrence of cracks, the heat resistance, and the melt viscosity have not been clarified either. Non-Patent Document 1 also describes polymerization examples using chain transfer agents other than carbon tetrabromide (CBr 4 ), but as a result of investigations by the present inventors, there was no resin that was excellent in melt formability and had suppressed yellowing after heat melting. Also, there was no resin that achieved both the defoaming property and the occurrence of cracks, and there was no resin that satisfied all of the defoaming property during melting, the occurrence of cracks, the heat resistance, and the melt viscosity.

[0009] Also, as a result of investigations by the present inventors, carbon tetrabromide (CBr 4It has also been found that the polymer whose molecular weight has been reduced by the method using

[0010] The present invention further aims to provide a fluororesin containing an oxolane ring, which is excellent in melt molding processability, has suppressed yellowing after heat melting, has a low melt viscosity, is excellent in heat resistance and defoaming property during melting, and has little crack generation during cooling after heat molding.

Means for Solving the Problems

[0011] The present invention is as follows. [1] A fluororesin containing a residue unit represented by the following general formula (1), having a weight average molecular weight Mw in the range of 5×10 4 ~3×10 5 and having a yellowness degree of 6 or less for a heat-melt molded product (3 mm thick) heated at 280 °C for 24 hours.

Chemical formula

[10] The fluororesin according to any one of [1] to [9], wherein the melt viscosity at 250°C at a shear rate of 10 -2 s is 1×10 2 ~5×10 4 Pa·s.

[11] The fluororesin according to any one of [1] to

[10] , which contains a residue unit represented by the following general formula (3). [Chemical formula]

[12] In the presence of a radical polymerization initiator and a chain transfer agent, polymerizing a monomer represented by the following general formula (4) to obtain a fluororesin containing a residue unit represented by the following general formula (5), wherein the chain transfer agent is an organic compound having 1 to 20 carbon atoms containing at least one atom selected from the group consisting of a hydrogen atom and a chlorine atom, and the fluororesin has a weight average molecular weight Mw of 5×10 4 ~3×10 5 and the yellowness of a heat-melt molded product (3 mm thick) heated at 280 °C for 24 hours is 6 or less. A method for producing a fluororesin. [Chemical formula] (In formulas (4) and (5), Rf 5 , Rf 6 , Rf 7 , Rf 8 each independently represents 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, and the perfluoroalkyl group may have an etheric oxygen atom. Also, Rf 5 , Rf 6 , Rf 7 , Rf 8 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.)

[13] The method according to

[12] , wherein the amount of the chain transfer agent is 3 to 50% by weight based on the total of the monomer and the chain transfer agent.

[14] The method according to

[12] or

[13] , wherein the polymerization is carried out in an organic solvent that dissolves the monomer represented by the general formula (4) and precipitates the fluororesin containing the residue unit represented by the general formula (5).

[15] The method according to any one of

[12] to

[14] , wherein the chain transfer agent is an organic compound having 1 to 20 carbon atoms containing a chlorine atom.

[16] The production method according to any one of

[12] to

[15] , wherein the chain transfer agent is an organic compound having 1 to 20 carbon atoms containing a chlorine atom and a hydrogen atom.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a fluororesin containing an oxolane ring, which is excellent in heat resistance and melt molding processability and has suppressed yellowing after heat melting. Further, according to the present invention, it is possible to provide a fluororesin containing an oxolane ring, which is excellent in heat resistance and melt molding processability, has suppressed yellowing after heat melting, has a low melt viscosity, is excellent in defoaming property during melting, and has little crack generation during cooling after heat molding.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0014] The fluororesin of the present invention contains a residue unit represented by the following general formula (1), and the weight average molecular weight Mw is 5 × 10 4 ~3×10 5 and the yellowness of the heat-melted molded product (3 mm thick) of the fluororesin at 280 ° C for 24 hours is 6 or less.

[0015] [Chemical formula]

[0016] (In formula (1), Rf 1 , Rf 2 , Rf 3 , Rf 4 each independently represents 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. 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.) The invention will be described in detail below.

[0017] The present invention is a fluororesin containing a residue unit represented by a specific general formula (1). Since the fluororesin of the present invention has a bulky ring structure contained in the specific general formula (1), it is amorphous and has high transparency and high heat resistance. Also, since it is composed only of carbon, fluorine, and oxygen, it has high electrical properties, chemical resistance, waterproofness, and oil and liquid repellency.

[0018] In the residue unit represented by the general formula (1) in the present invention, Rf 1 , Rf 2 , Rf 3 , Rf 4 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. 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.

[0019] 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. 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. 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. Examples of the linear perfluoroalkyl group which may have an etheric oxygen atom having 1 to 7 carbon atoms include, for example, -CF 2 OCF 3 group, -(CF 2 ) 2 OCF 3 group, -(CF 2 ) 2 OCF 2 CF 3 group, and the like. Examples of the cyclic perfluoroalkyl group which may have an etheric oxygen atom having 3 to 7 carbon atoms include, for example, 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.

[0020] Rf 1 、Rf 2 、Rf 3 、Rf 4 At least one of them is preferably 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 from the viewpoint of exhibiting excellent heat resistance.

[0021] Specific examples of the residue unit represented by the general formula (1) include, for example, the residue unit represented by the following general formula (2).

[0022]

Chemical formula

[0023] Among these, a fluororesin containing a residue unit represented by the following general formula (3) 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.

[0024]

Chemical formula

[0025] The fluororesin of the present invention has a weight average molecular weight Mw of 5×10 4 ~3×10 5 In this range. When the weight average molecular weight Mw is in this range, the melt viscosity at a shear rate of 10 -2 s and 250°C can be 1×10 2 ~3×10 5 Pa·s, and as a result, it has excellent melt molding processability. Furthermore, it also has excellent defoaming properties during melting. Also, when the weight average molecular weight Mw is in this range, it will have less crack generation during heating and cooling. From the viewpoints of excellent melt molding processability and excellent defoaming properties during melting, the fluororesin of the present invention preferably has a weight average molecular weight Mw in the range of 5×10 4 ~2×10 5 In this range. When the weight average molecular weight Mw is in this range, the melt viscosity at a shear rate of 10 -2 s and 250°C can be 1×10 2 ~2×10 4 Pa·s, and as a result, it has excellent melt molding processability and further excellent defoaming properties, so it is preferable. From the viewpoints of excellent melt molding processability and excellent defoaming properties during melting, more preferably, the weight average molecular weight Mw is in the range of 5×10 4 ~1.5×10 5It is in the range of, and from the viewpoint of less crack generation during heating and cooling, it is more preferably 6×10 4 ~1.5×10 5 in the range of.

[0026] The weight average molecular weight Mw of the fluororesin of the present invention can be calculated using gel permeation chromatography (GPC). For example, using a standard polymethyl methacrylate with a known molecular weight as a standard sample and a solvent that can dissolve both the standard sample and the fluororesin as an eluent, and calculating from the elution times of the sample and the standard sample and the molecular weight of the standard sample. As the said solution, what added 1,1,1,3,3,3 - hexafluoro - 2 - propanol (manufactured by Wako Pure Chemical Industries, Ltd.) which is 10 wt% with respect to AsahiCrin AK - 225 (manufactured by Asahi Glass Co., Ltd.) to AK - 225 can be mentioned.

[0027] There is no particular limitation on 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. 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 1.2 to 8, more preferably 1.2 to 5, still more preferably 1.5 to 3, and still more preferably 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.

[0028] The fluororesin of the present invention has a yellowness degree of 6 or less for a heat - melted molded product (3 mm thick) heated at 280°C for 24 hours. The yellowness degree of a heat - melted molded product (3 mm thick) heated at 280°C for 24 hours is preferably 5 or less, more preferably 4 or less, and still more preferably 3 or less. The measurement method of the yellowness degree of a heat - melted molded product (3 mm thick) heated at 280°C for 24 hours is as follows.

[0029] Weigh 2.0 g of fluororesin into a petri dish with an inner diameter of 26.4 mm (only the receiver of the flat petri dish lid and receiver set manufactured by Flat Co., Ltd., with a glass thickness of 1 mm at the bottom), place it in an inert oven (DN411I manufactured by Yamato Scientific), leave it standing at room temperature for 30 minutes under an air flow (20 L / min), then heat it up to 280°C over 30 minutes and heat it at 280°C for 24 h. Then, while maintaining the air flow (20 L / min), keep the oven door closed, turn off the power of the inert oven, let it cool for 12 h, 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 Sciences Corporation). From the measured transmittance data, data at 5 nm intervals in the wavelength range of 380 nm to 780 nm were extracted, and according to the method of JIS Z8701, the tristimulus values X, Y, and Z in the XYZ color system were calculated, and according to the method of JIS K7373, the yellowness index (YI) in the C light source (auxiliary illuminant C) was calculated to obtain the yellowness index (YI) of the fluororesin heat-melt molded product including the petri dish. The yellowness index (YI) of the petri dish alone (only the receiver) was measured, and the yellowness index (YI) of the 3-mm-thick fluororesin heat-melt molded product was obtained by subtracting the yellowness index (YI) of the petri dish alone (only the receiver) from the yellowness index (YI) of the fluororesin molded product including the petri dish. Incidentally, the yellowness index (YI) of the petri dish alone (only the receiver) was 0.21.

[0030] Generally, to lower the melt viscosity, reducing the molecular weight is effective, but there is a problem that the glass transition temperature decreases when the molecular weight is reduced. The fluororesin of the present invention preferably has a glass transition temperature of 125°C or higher and 145°C or lower despite the weight average molecular weight being in the above range. The fluororesin of the present invention preferably has a glass transition temperature of 125°C or higher and 140°C or lower, more preferably 128°C or higher and 140°C or lower, and still more preferably 129°C or higher and 135°C or lower.

[0031] The glass transition temperature of the fluororesin of the present invention can be measured by determining the intermediate glass transition temperature using a differential scanning calorimeter (DSC). As measurement conditions, for example, the sample is placed in an aluminum sample pan, and the first time under a nitrogen stream: -80°C → 200°C → -80°C (heating rate: 10°C / min), the second time: -80°C → 200°C (heating rate: 10°C / min). The glass transition temperature can be calculated by determining the intermediate glass transition temperature according to the description in JIS-K7121 from the chart when heating for the second time. At this time, as the apparatus, one calibrated with a standard substance such as indium or tin can be used.

[0032] The fluororesin of the present invention has a shear rate of 10 -2 s and a melt viscosity at 250°C of 1×10 2 ~3×10 5 Pa·s, which is preferable from the viewpoints of excellent melt molding processability, excellent defoaming property during melting, less crack generation during heating and cooling, and suppression of yellowing after heating and melting. The above melt viscosity is more preferably in the range of 1×10 2 ~5×10 4 Pa·s from the viewpoints of excellent melt molding processability, excellent defoaming property during melting, less crack generation during heating and cooling, and suppression of yellowing after heating and melting. More preferably, it is in the range of 1×10 3 ~5×10 4 Pa·s, and even more preferably in the range of 1×10 3 ~2×10 4 Pa·s. Examples of the method for measuring the melt viscosity include measurement using a commercially available rotational rheometer, and the method described in JIS K 7244-10 can be exemplified.

[0033] The fluororesin of the present invention preferably has an area occupied by bubbles in a heat-melt molded product (3 mm thick, 26.4 mm in diameter) heated at 280°C for 24 hours of 10% or less with respect to the area of the molded product, from the viewpoint of good heat formability. The area occupied by bubbles in a heat-melt molded product (3 mm thick, 26.4 mm in diameter) heated at 280°C for 24 hours is preferably 5% or less with respect to the area of the molded product, and more preferably 0%. Here, the ratio of the area occupied by bubbles in a heat-melt molded product (3 mm thick, 26.4 mm in diameter) heated at 280°C for 24 hours to the area of the molded product can be visually determined when it is obvious visually, and can also be obtained by taking a photograph of the molded product and analyzing it with image analysis software or the like.

[0034] The fluororesin of the present invention preferably has 10 or fewer bubbles in a heat-melt molded product (3 mm thick, 26.4 mm in diameter) heated at 280°C for 24 hours, from the viewpoint of good heat formability. The number of bubbles in a heat-melt molded product (3 mm thick, 26.4 mm in diameter) heated at 280°C for 24 hours is preferably 5 or fewer, and more preferably 0.

[0035] The fluororesin of the present invention preferably has a difference B - A between the weight loss amount A immediately after heating to 300°C at a rate of 10°C / min in air by TG-DTA and the weight loss amount B after holding at 300°C for 30 minutes after heating to 300°C of 1.0% or less, from the viewpoint of having excellent heat resistance. More preferably, the difference B - A is 0.5% or less, and even more preferably 0.3% or less. Here, the weight loss amount A (weight %) immediately after heating to 300°C is obtained by (sample weight immediately after heating to 300°C) / (weighed sample weight) × 100, and the weight loss amount B after holding at 300°C for 30 minutes after heating to 300°C is obtained by (sample weight after holding at 300°C for 30 minutes after heating to 300°C) / (weighed sample weight) × 100.

[0036] 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).

[0037] Next, a method for producing the fluororesin of the present invention will be described.

[0038] The fluororesin of the present invention includes polymerizing a monomer represented by the following general formula (4) in the presence of a radical polymerization initiator and a chain transfer agent to obtain a fluororesin containing a residue unit represented by the following general formula (5), and can be produced by a method using an organic compound having 1 to 20 carbon atoms containing at least one atom selected from the group consisting of a hydrogen atom and a chlorine atom as the chain transfer agent. Thereby, the obtained fluororesin has a weight average molecular weight Mw in the range of 5×10 4 ~3×10 5 and the yellowness of a heat-melt molded product (3 mm thick) heated at 280 °C for 24 hours is 6 or less.

[0039]

Chemical formula

[0040] (In formula (4), Rf 5 , Rf 6 , Rf 7 , Rf 8 each independently represents one kind 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. The perfluoroalkyl group may have an etheric oxygen atom. Also, Rf 5 , Rf 6, Rf 7 , Rf 8 may be connected to each other to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an ether oxygen atom.)

[0041]

Chemical formula

[0042] (In formula (5), Rf 5 , Rf 6 , Rf 7 , Rf 8 each independently represents 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 ether oxygen atom. Also, Rf 5 , Rf 6 , Rf 7 , Rf 8 may be connected to each other to form a ring having 4 to 8 carbon atoms, and the ring may be a ring containing an ether oxygen atom.) Rf in formulas (4) and (5) 5 , Rf 6 , Rf 7 , Rf 8 is synonymous with Rf in formulas (1) and (3) 1 , Rf 2 , Rf 3 , Rf 4 respectively.

[0043] In the method for producing a fluororesin of the present invention, by using an organic compound having 1 to 20 carbon atoms containing at least one atom selected from the group consisting of a hydrogen atom and a chlorine atom as a chain transfer agent, while suppressing yellowing after heat melting, the molecular weight of the fluororesin can be controlled within the above range. Here, the chain transfer agent refers to a substance that has the effect of reducing the molecular weight by being present in the system during radical polymerization of the fluororesin. 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, isopropanol, etc.; chloroform, dichloromethane, carbon tetrachloride, chloromethane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, hexachloroethane, benzyl chloride, pentafluorobenzyl chloride, pentafluorobenzoyl chloride, etc., organic compounds having 1 to 20 carbon atoms containing a chlorine atom. Among them, from the viewpoints of suppressing yellowing after heat melting, controlling the molecular weight of the fluororesin, excellent melt molding processability, excellent defoaming property during melting, less crack generation during heating and cooling, and excellent yield, it is preferably an organic compound having 1 to 20 carbon atoms containing a chlorine atom, and more preferably represented by the general formula (A).

[0044]

Chemical formula

[0045] (In formula (A), m is an integer from 0 to 3, n is an integer from 1 to 3, p is an integer from 0 to 1, q is an integer from 0 to 1, and m + n + p + q = 4. R 1 and R 2 are each independently a hydrocarbon group having 1 to 19 carbon atoms or an oxygen atom, and the oxygen atom may form a double bond with adjacent carbon atoms. R 1 and R 2The total number of carbon atoms is from 1 to 19, and the hydrocarbon group may have one or more atoms selected from an oxygen atom, a fluorine atom, and a chlorine atom, and may not have a hydrogen atom. The hydrocarbon group may be linear, branched, alicyclic, or aromatic, and R 1 and R 2 may be linked to each other to form a ring having 3 to 19 carbon atoms.) Among them, from the viewpoints of suppressing yellowing after heat melting, controlling the molecular weight of the fluororesin, excellent melt molding processability, excellent defoaming property during melting, less crack generation during heating and cooling, and excellent yield, it is more preferable that it is an organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom. Examples of the organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom include chloroform, dichloromethane, chloromethane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, benzyl chloride, pentafluorobenzyl chloride, and the like. Further, in the organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom, from the viewpoints of suppressing yellowing after heat melting, controlling the molecular weight of the fluororesin, excellent melt molding processability, excellent defoaming property during melting, less crack generation during heating and cooling, and excellent yield, it is preferable that the number ratio of the hydrogen atom to the chlorine atom is in the range of hydrogen atom:chlorine atom = 1:9 to 9:1, and more preferably in the range of 1:9 to 5:5. Further, from the viewpoints of suppressing yellowing after heat melting, controlling the molecular weight of the fluororesin, excellent melt molding processability, excellent defoaming property during melting, less crack generation during heating and cooling, and excellent yield, the organic compound having 1 to 20 carbon atoms containing a hydrogen atom and a chlorine atom is preferably represented by the following general formula (B) or (C), and more preferably represented by the general formula (B).

[0046] [Chemical formula]

[0047] (In the formula (B), m and n are each independently an integer of 1 to 3, p is an integer of 0 to 1, q is an integer of 0 to 1, and m + n + p + q is 4. R 1and R 2 are each independently a hydrocarbon group having 1 to 19 carbon atoms, and R 1 p and R 2 q The total number of carbon atoms of is 0 to 19, and the hydrocarbon group may have one or more atoms selected from an oxygen atom, a fluorine atom, and a chlorine atom, and may not have a hydrogen atom. Further, the hydrocarbon group may be linear, branched, alicyclic, or aromatic, and R 1 and R 2 may be linked to each other to form a ring having 3 to 19 carbon atoms.)

[0048]

Chemical formula

[0049] (In formula (C), m, n, u, and v are each independently an integer from 0 to 3, m + u is 1 to 5, n + v is 1 to 5, p, q, r, and s are each independently an integer from 0 to 1, m + n + p + q is 3, r + s + u + v is 3, R 1 , R 2 , R 3 , R 4 , R 5 are each independently a hydrocarbon group having 1 to 18 carbon atoms, and R 1 , R 2 , R 3 , R 4 , R 5 The total number of carbon atoms of is 0 to 18, and the hydrocarbon group may have one or more atoms selected from an oxygen atom, a fluorine atom, and a chlorine atom, and may not have a hydrogen atom. Further, the hydrocarbon group may be linear, branched, alicyclic, or aromatic, and R 1 , R 2 , R 3 , R 4 , R 5 Two or more groups selected from may be linked to each other to form a ring having 3 to 19 carbon atoms, and there may be a plurality of such rings.) Examples of the organic compound having 1 to 20 carbon atoms and containing a chlorine atom represented by the general formula (A) include chloroform, dichloromethane, carbon tetrachloride, chloromethane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, hexachloroethane, benzyl chloride, pentafluorobenzyl chloride, pentafluorobenzoyl chloride and the like. Examples of the organic compound having 1 to 20 carbon atoms and containing a hydrogen atom and a chlorine atom represented by the general formula (B) include chloroform, dichloromethane, chloromethane, dichloroethane, trichloroethane, tetrachloroethane, pentachloroethane, benzyl chloride, pentafluorobenzyl chloride and the like. Examples of the organic compound having 1 to 20 carbon atoms and containing a hydrogen atom and a chlorine atom represented by the general formula (C) include 1,1,1-trichloroethane and the like.

[0050] Furthermore, a fluororesin that achieves both defoaming properties and crack generation during melting, has excellent defoaming properties and heat resistance during melting, has a low melt viscosity, and has little crack generation, and is also excellent in yield can be obtained. Therefore, the amount of the chain transfer agent is preferably 3 to 50% by weight, more preferably 3 to 30% by weight, and even more preferably 4 to 20% by weight based on the total of the monomer and the chain transfer agent.

[0051] In the method for producing the resin of the present invention, from the viewpoint of suppressing yellowing after heat melting, having excellent melt molding processability, having excellent defoaming properties during melting, having little crack generation during heating and cooling, and having excellent yield, as the polymerization solvent, it is preferable to use an organic solvent (hereinafter referred to as "precipitation polymerization solvent") that dissolves the monomer represented by the general formula (4) and precipitates a fluororesin containing the residue unit represented by the general formula (5).

[0052] Whether a certain organic solvent is an organic solvent for precipitating a certain resin can be determined by whether the polarity of the organic solvent is within a specific range. In the present invention, it is preferable to select an organic solvent having a polarity within a specific range as the precipitation polymerization solvent based on the Hansen solubility parameters.

[0053] The Hansen solubility parameter is obtained by dividing the solubility parameter introduced by Hildebrand into three components: the dispersion term δD, the polar term δP, and the hydrogen bonding term δH by Hansen, and representing them in three-dimensional space. The dispersion term δD represents the effect of dispersion forces, the polar term δP represents the effect of dipole-dipole forces, and the hydrogen bonding term δH represents the effect of hydrogen bonding forces. In three-dimensional space, the farther the coordinates of a resin are from the coordinates of an organic solvent, the less soluble the resin is in the organic solvent.

[0054] The definition and calculation method of the Hansen solubility parameter are described in the following literature: Charles M. Hansen, "Hansen Solubility Parameters: A User's Handbook", CRC Press, 2007. For organic solvents whose literature values are unknown, the Hansen solubility parameter can be easily estimated from their chemical structures by using computer software (Hansen Solubility Parameters in Practice (HSPiP)).

[0055] In the present invention, HSPiP 5th Edition is used. For organic solvents registered in the database, their values are used, and for organic solvents not registered, estimated values are used.

[0056] Regarding the Hansen solubility parameter of a resin, it can be determined by checking whether the resin precipitates when a solution of the resin dissolved in a good solvent is added to a number of different organic solvents with known Hansen solubility parameters. Specifically, when the coordinates of the Hansen solubility parameters of all the organic solvents used in the test are shown in three-dimensional space, find a sphere (solubility sphere) such that the coordinates of the organic solvents in which resin A does not precipitate are all enclosed inside the sphere, and the coordinates of the organic solvents that cause resin A to precipitate are outside the sphere. The center coordinates of the solubility sphere are taken as the Hansen solubility parameter of the resin.

[0057] When the coordinates of the Hansen solubility parameter of a certain organic solvent not used in the solubility test are (δD, δP, δH), if the coordinates are included inside the solubility sphere, it is considered that the organic solvent does not precipitate the resin but dissolves it. On the other hand, if the coordinates are outside the solubility sphere, it is considered that the organic solvent precipitates the resin.

[0058] In the present invention, as the Hansen solubility parameter of the resin particles, the value obtained by estimating the Hansen solubility parameter of the compound represented by the following general formula (6) (pentamer of the compound represented by general formula (5)) using HSPiP was used. By this method, for example, the Hansen solubility parameters δD, δP, and δH of the resin particles containing a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit represented by general formula (3) are 11.6, 3.5, and 1.4 (MPa 1 / 2 ) respectively.

[0059]

Chemical formula

[0060] (In formula (6), Rf 9 , Rf 10 , Rf 11 , Rf 12 each independently represents one kind 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. The perfluoroalkyl group may have an etheric oxygen atom. Also, Rf 9 , Rf 10 , Rf 11 , Rf 12 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.).

[0061] And as the precipitation polymerization solvent in the present invention, it is preferable to select an organic solvent having a dissolution index R with the resin calculated by formula (7) from the Hansen solubility parameter of 4 or more. R = 4 × {(δD 1 - δD 2 ) 2 + (δP 1 - δP 2 ) 2 + (δH 1 - δH 2 ) 2} 0.5 ···(7) Here, δD 1 , δP 1 , δH 1 are the dispersion term, polar term, and hydrogen term of the Hansen solubility parameter of the resin particles, respectively, and δD 2 , δP 2 , δH 2 are the dispersion term, polar term, and hydrogen term of the Hansen solubility parameter of the organic solvent, respectively.

[0062] For example, the following organic solvents can be cited as organic solvents having an affinity Ra of 4 or more with a resin containing a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit.

[0063]

Table 1

[0064] Furthermore, as the precipitation polymerization solvent, from the viewpoint of suppressing yellowing after heat melting, having excellent melt molding processability, excellent defoaming property during melting, generating few cracks during heating and cooling, and having excellent yield, an organic solvent containing a fluorine atom and a hydrogen atom in the molecule is preferable. 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.

[0065] 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 preferred. From the viewpoint of suppressing yellowing after heat melting, excellent melt molding processability, excellent defoaming property during melting, less crack generation during heating and cooling, and excellent yield, 1,2,2,3,3,4,4-heptafluorocyclopentane is preferred. As for the ratio of fluorine atoms to hydrogen atoms in the molecule of the precipitation polymerization solvent, from the viewpoint of suppressing yellowing after heat melting, excellent melt molding processability, excellent defoaming property during melting, less crack generation during heating and cooling, and excellent yield, the atomic number ratio of fluorine atoms:hydrogen atoms = 1:9 to 9:1 is preferably satisfied.

[0066] Whether the organic solvent is an organic solvent that precipitates a resin containing a residue unit represented by the general formula (5) can be determined by dropping a solution in which the resin is dissolved in a good solvent into the organic solvent. If the resin precipitates, it can be judged that the organic solvent is an organic solvent that precipitates the resin. The good solvent is a solvent that dissolves the resin, and examples thereof include perfluorocarbons such as perfluorohexane and hexafluorobenzene.

[0067] As the radical polymerization initiator for radical polymerization, for example, bis(perfluorobenzoyl) peroxide (PFBPO), (CF 3 COO) 2 、(CF 3 CF 2 COO) 2 、(C 3 F 7 COO) 2 、(C 4 F 9 COO) 2 、(C 5 F 11 COO) 2 、(C 6 F 13 COO) 2 、(C 7 F 15 COO)2 , (C 8 F 17 COO) 2 and other perfluoro organic peroxides; organic peroxides such as benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-tert-butyl peroxide, tert-butyl cumyl peroxide, dicumyl peroxide, tert-butyl peroxyacetate, perfluoro(di-trt-butyl peroxide), bis(2,3,4,5,6-pentafluorobenzoyl) peroxide, tert-butyl peroxybenzoate, tert-butyl perpivalate; azo initiators such as 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-butyronitrile), 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, 1,1'-azobis(cyclohexane-1-carbonitrile), etc. Among them, from the viewpoint of suppressing yellowing after heat melting, excellent melt molding processability, excellent defoaming property during melting, and less crack generation during heating and cooling, perfluoro organic peroxides are preferred, and bis(perfluorobenzoyl) peroxide (PFBPO) is more preferred. Here, the perfluoro organic peroxide refers to a compound having a structure in which the hydrogen atoms of the organic peroxide are replaced by fluorine atoms.

[0068] In the production method of the present invention, it is preferable that the monomer represented by the general formula (4) is perfluoro(4-methyl-2-methylene-1,3-dioxolane) represented by the general formula (8), and the residue unit represented by the general formula (5) is a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit represented by the general formula (9).

[0069]

Chemical formula

[0070]

Chemical formula

[0071] By manufacturing according to the method of the present invention, the obtained fluororesin is suppressed in yellowing after heat melting, excellent in melt molding processability, excellent in defoaming property during melting, less likely to generate cracks during heating and cooling, has a small change in the weight loss amount when held at 300 ° C for a certain period of time, and is less likely to cause thermal decomposition.

Examples

[0072] Hereinafter, the present invention will be described in more detail based on examples. However, the examples are illustrative of the present invention and the present invention is not intended to be limited to the examples.

[0073] <Physical property measurement method> (1) Weight average molecular weight Mw, 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.) 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 was used. As the standard sample, standard polymethyl methacrylate manufactured by Agilent was used, and the weight average molecular weight Mw and number average molecular weight Mn in terms of polymethyl methacrylate were calculated from the elution times of the sample and the standard sample. The molecular weight distribution Mw / Mn was calculated by dividing the weight average molecular weight Mw by the number average molecular weight Mn.

[0074] (2) Glass transition temperature An aluminum sample pan (52-023P manufactured by Hitachi High-Tech Science Corporation) was weighed with approximately 10 mg of the sample, covered with an aluminum lid (52-023C manufactured by Hitachi High-Tech Science Corporation), and the sample was sealed using an electric sample sealer (die) (manufactured by Hitachi High-Tech Science Corporation) to prepare the sample. Using a DSC device (DSC6220 manufactured by Hitachi High-Tech Science Corporation), under a nitrogen gas flow (500 mL / min), the first time: -80°C → 200°C → -80°C (heating rate: 10°C / min), the second time: -80°C → 200°C (heating rate: 10°C / min), and the temperature was raised according to this program. At this time, from the chart when the temperature was raised the second time, the glass transition temperature was calculated by determining the intermediate glass transition temperature according to the description in JIS-K7121. Also, the DSC device used was calibrated for temperature with indium and tin as standard substances.

[0075] (3) Melt viscosity Using a rotational rheometer MCR-300 manufactured by Anton-Paar, the complex viscosity at 250°C and a frequency of 10 -2 (rad·s -1 ) was measured, and the value of the complex viscosity was expressed as the melt viscosity.

[0076] (4) Weight loss Weighed approximately 10 - 15 mg of the sample onto an aluminum sample pan (SSC000E030 manufactured by Hitachi High-Tech Science Corporation), and using a TG / DTA apparatus (TG / DTA6200AST2 manufactured by Hitachi High-Tech Science Corporation), heated it from 40°C to 300°C at a rate of 10°C / min under an air flow (160 mL / min), and held it at 300°C for 1 hour. The difference B - A between the weight loss A immediately after heating to 300°C at a rate of 10°C / min in air by TG / DTA and the weight loss B after heating to 300°C and holding at 300°C for 30 minutes was determined. Here, the weight loss A (weight %) immediately after heating to 300°C was determined by (sample weight immediately after heating to 300°C) / (weighed sample weight)×100, and the weight loss B after heating to 300°C and holding at 300°C for 30 minutes was determined by (sample weight after heating to 300°C and holding at 300°C for 30 minutes) / (weighed sample weight)×100. At this time, as the air, compressed air from a compressor passed through a dehumidifier (dew point temperature -20°C or lower) was used.

[0077] (5) Defoaming property Weighed 2.0 g of fluororesin onto 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 Corporation, with a glass thickness of 1 mm at the bottom), placed it in an inert oven (DN411I manufactured by Yamato Scientific), left it standing at room temperature for 30 minutes under an air flow (20 L / min), then heated it to 280°C over 30 minutes, and heated it at 280°C for 24 h. Then, while maintaining the air flow (20 L / min), with the oven door closed, turned off the power of the inert oven, allowed it to cool for 12 h, and took 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, compressed air from a compressor passed through a dehumidifier (dew point temperature -20°C or lower) was used.

[0078] Observed the appearance of the fluororesin heat-melt molded product (3 mm thick, 26.4 mm in diameter), counted the number of bubbles, and calculated the ratio of the area occupied by the bubbles to the area of the molded product, and judged according to the following criteria.

[0079] ◎: 0 bubbles ○: There are 1 to 10 bubbles and the area occupied by the bubbles is 10% or less of the area of the molded product. △: There are 11 or more bubbles and the area occupied by the bubbles is 10% or less of the area of the molded product. △’: There are 1 to 10 bubbles and the area occupied by the bubbles is 11% or more of the area of the molded product. ×: There are 11 or more bubbles and the area occupied by the bubbles is 11 - 69% of the area of the molded product. ××: There are 11 or more bubbles and the area occupied by the bubbles is 70% or more of the total area of the molded product. (6) Cracks after heating, melting, and cooling at 280°C Weighed 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), placed it in an inert oven (DN411I manufactured by Yamato Scientific), left it standing at room temperature for 30 minutes under an air flow (20 L / min), then heated it to 280°C over 30 minutes and heated it at 280°C for 24 h. Then, while maintaining the air flow (20 L / min), with the oven door closed, turned off the power of the inert oven, allowed it to cool for 12 h, and took out the sample to obtain a fluororesin heat - melted 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, compressed air passed through a dehumidifier (dew - point temperature of - 20°C or lower) was used.

[0080] Observed the appearance of the fluororesin heat - melted molded product (3 mm thick, 26.4 mm in diameter), counted the number of cracks, and judged according to the following criteria.

[0081] ○: The number of cracks is 3 or less. △: The number of cracks is 4 - 10. ×: The number of cracks is 11 - 49. ××: The number of cracks is 50 or more. (7) Yellowness index (YI) of the 280°C 24 - h heat - melted molded product (3 mm thick) 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.), leave it standing at room temperature for 30 minutes under an air stream (20 L / min), then heat it up to 280°C over 30 minutes and heat it at 280°C for 24 h. Then, while maintaining the air stream (20 L / min), keep the oven door closed, turn off the power of the inert oven, let it cool for 12 h, 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-Technologies Corporation). From the measured transmittance data, the data at 5 nm intervals in the wavelength range of 380 nm to 780 nm were extracted, and according to the method of JIS Z8701, the tristimulus values X, Y, and Z of the XYZ colorimetric system were calculated. 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 by subtracting the yellowness index (YI) of the petri dish alone (only the receiver) from the yellowness index (YI) of the fluororesin molded product including the petri dish, the yellowness index (YI) of the fluororesin heat-melt molded product with a thickness of 3 mm was obtained. Incidentally, the yellowness index (YI) of the petri dish alone (only the receiver) was 0.21.

[0082] Example 1 A solution of 0.0432 g (0.000103 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator dissolved in 0.130 g of hexafluorobenzene was placed in a 30-mm-diameter glass ampoule equipped with a magnetic stir bar. 5.0 g (0.0205 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, 19.87 g of Zeorola-H (manufactured by Nippon Zeon Co., Ltd., 1,2,2,3,3,4,4-heptafluorocyclopentane) as a polymerization solvent, and 0.556 g (0.00465 mol) of chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) as a chain transfer agent were added. After repeating nitrogen substitution 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 turbid and the resin precipitated in the polymerization solvent was obtained. After cooling to room temperature, the ampoule was opened, the liquid containing the generated resin particles was filtered off, washed with acetone, and vacuum dried to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (yield: 82%). The molecular weight distribution Mw / Mn was 2.5. The evaluation results of the fluororesin are shown in Table 2.

[0083] Example 2 A solution of 0.0432 g (0.000103 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator dissolved in 0.130 g of hexafluorobenzene was placed in a 30 mm diameter glass ampoule equipped with a magnetic stir bar. Then, 5.0 g (0.0205 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, 19.87 g of Zeorola-H (manufactured by Nippon Zeon Co., Ltd., 1,2,2,3,3,4,4-heptafluorocyclopentane) as a polymerization solvent, and 1.250 g (0.0105 mol) of chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) as a chain transfer agent were added. After repeating nitrogen substitution and pressure release, it was sealed under reduced pressure (amount of chain transfer agent: 20% 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 the ampoule was upright, precipitation polymerization was carried out by holding at 55 °C for 24 hours, and a slurry in which it became turbid 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 vacuum dried to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (yield: 80%). The molecular weight distribution Mw / Mn was 2.7. The evaluation results of the fluororesin are shown in Table 2.

[0084] Example 3 A solution prepared by dissolving 0.0432 g (0.000103 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator in 0.130 g of hexafluorobenzene was placed in a 30-mm-diameter glass ampoule equipped with a magnetic stir bar. Then, 5.0 g (0.0205 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) was added as a monomer, 19.87 g of Zeorola-H (manufactured by Nippon Zeon Co., Ltd., 1,2,2,3,3,4,4-heptafluorocyclopentane) was added as a polymerization solvent, and 0.435 g (0.00364 mol) of chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) was added as a chain transfer agent. After repeating nitrogen substitution and pressure release, the ampoule was sealed under reduced pressure (amount of chain transfer agent: 8.0 wt% based on the total of the monomer and the chain transfer agent). While stirring the magnetic stir bar with a stirrer in an upright state of this ampoule, precipitation polymerization was carried out by holding at 55 °C for 24 hours, and a slurry in which the solution became turbid and the resin precipitated in the polymerization solvent was obtained. After cooling to room temperature, the ampoule was opened, the liquid containing the generated resin particles was filtered off, washed with acetone, and dried under vacuum to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (yield: 81%). The molecular weight distribution Mw / Mn was 2.4. The evaluation results of the fluororesin are shown in Table 2.

[0085] Example 4 A solution prepared by dissolving 0.0432 g (0.000103 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator in 0.130 g of hexafluorobenzene was placed in a 30-mm-diameter glass ampoule equipped with a magnetic stir bar. Then, 5.0 g (0.0205 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, 19.87 g of Zeorola-H (manufactured by Nippon Zeon Co., Ltd., 1,2,2,3,3,4,4-heptafluorocyclopentane) as a polymerization solvent, and 0.236 g (0.00197 mol) of chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) as a chain transfer agent were added. After repeating nitrogen substitution and pressure release, the ampoule was sealed under reduced pressure (amount of chain transfer agent: 4.5% 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 the ampoule was upright, precipitation polymerization was carried out by holding at 55 °C for 24 hours, and a slurry in which the solution became turbid and the resin precipitated in the polymerization solvent was obtained. After cooling to room temperature, the ampoule was opened, the liquid containing the generated resin particles was filtered off, washed with acetone, and dried under vacuum to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (yield: 83%). The molecular weight distribution Mw / Mn was 2.8. The evaluation results of the fluororesin are shown in Table 2.

[0086] Example 5 A solution prepared by dissolving 0.0432 g (0.000103 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator in 0.130 g of hexafluorobenzene was placed in a 30-mm-diameter glass ampoule equipped with a magnetic stir bar. Then, 5.0 g (0.0205 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, 19.87 g of Zeorola-H (manufactured by Nippon Zeon Co., Ltd., 1,2,2,3,3,4,4-heptafluorocyclopentane) as a polymerization solvent, and 0.155 g (0.00130 mol) of chloroform (manufactured by Wako Pure Chemical Industries, Ltd.) as a chain transfer agent were added. After repeating nitrogen substitution and pressure release, the ampoule was sealed under reduced pressure (amount of chain transfer agent: 3.0 wt% 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 the ampoule was upright, precipitation polymerization was carried out by holding at 55 °C for 24 hours, and a slurry in which the solution became turbid and the resin precipitated in the polymerization solvent was obtained. After cooling to room temperature, the ampoule was opened, the liquid containing the generated resin particles was filtered off, washed with acetone, and dried under vacuum to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (yield: 74%). The molecular weight distribution Mw / Mn was 2.5. The evaluation results of the fluororesin are shown in Table 2.

[0087] Comparative Example 1 The polymerization was carried out in accordance with the polymerization conditions described in Sample 92 and 93 of Table 2 in Non-Patent Document 1. However, the charged amount of the polymerization initiator was set to an amount between Sample 92 and 93. In a 75 mL glass ampoule, 0.017 g (0.0000407 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as the initiator, 5.0 g (0.0205 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as the monomer, and 8.2 g of hexafluorobenzene as the polymerization solvent were added. After repeating nitrogen substitution and pressure release, it was sealed under reduced pressure. This ampoule was placed in a constant temperature bath at 60 °C and held for 24 hours to carry out radical solution polymerization, and a viscous liquid in which the resin was dissolved was obtained. After cooling to room temperature, the ampoule was opened, and the resin solution was diluted with 36 g of hexafluorobenzene to prepare a resin-diluted solution for viscosity adjustment. 1 L of chloroform was added to a beaker equipped with anchor blades, and the above resin-diluted solution was added to the chloroform with stirring to precipitate the resin. By vacuum drying, a perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin was obtained (yield: 66%). The molded product after heating at 280 °C for 24 h had many bubbles, and the coloring was stronger than that of Example 5 by visual observation and weaker than that of Comparative Example 2. The molecular weight distribution Mw / Mn was 1.9. The evaluation results of the fluororesin are shown in Table 2.

[0088] Comparative Example 2 The polymerization was carried out according to the polymerization conditions described in Sample 84 of Table 3 in Non-Patent Document 1. However, there is no description of the polymerization time in Non-Patent Document 1, and in this example, it was set to 24 hours. In a 75 mL glass ampoule, 0.0578 g (0.000137 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as the initiator, 10.0 g (0.0410 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as the monomer, 16.32 g of hexafluorobenzene as the polymerization solvent, and carbon tetrabromide (CBr 4)0.0341 g (0.000286 mol) was placed, nitrogen substitution and pressure release were repeated, and then it was sealed under reduced pressure (amount of chain transfer agent: 0.34 wt% based on the total of monomer and chain transfer agent). This ampoule was placed in a constant temperature bath at 60 °C and held for 24 hours to perform radical solution polymerization, and a viscous liquid in which the resin was dissolved was obtained. After cooling to room temperature, the ampoule was opened, and the resin solution was diluted with 64 g of hexafluorobenzene for viscosity adjustment to prepare a resin diluted solution. 1 L of chloroform was placed in a beaker equipped with anchor blades, and the above-mentioned resin diluted solution was added to the beaker with stirring to precipitate the resin. The precipitated resin was recovered by filtration and then vacuum dried to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin (yield: 54%). The molecular weight distribution Mw / Mn was 3.7. The evaluation results of the fluororesin are shown in Table 2.

[0089] Comparative Example 3 It was carried out according to the polymerization conditions described in Sample 78 of Table 3 in Non-Patent Document 1. However, the polymerization time was not described in Non-Patent Document 1, and it was set to 24 hours in this example. In a 75 mL glass ampoule, 0.0539 g (0.000128 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator, 10.0 g (0.0410 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, 16.32 g of hexafluorobenzene as a polymerization solvent, and carbon tetrabromide (CBr 4)0.1143 g (0.000957 mol) was placed, nitrogen substitution and pressure release were repeated, and then it was sealed under reduced pressure (amount of chain transfer agent: 1.13% by weight based on the total of monomer and chain transfer agent). This ampule was placed in a constant temperature bath at 60 °C and held for 24 hours to conduct radical solution polymerization, and a viscous liquid in which the resin was dissolved was obtained. After cooling to room temperature, the ampule was opened, and the resin solution was diluted with 36 g of hexafluorobenzene for viscosity adjustment to prepare a resin diluted solution. 1 L of chloroform was added to a beaker equipped with anchor blades, and with stirring, the above resin diluted solution was added to the chloroform to precipitate the resin, and by vacuum drying, perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin was obtained (yield: 40%). The molecular weight distribution Mw / Mn was 2.5. The evaluation results of the fluororesin are shown in Table 2.

[0090]

Table 2

[0091] The method for producing a fluororesin of the present invention has a higher yield compared to the method described in Non-Patent Document 1, and as shown in Examples 1 to 5, a fluororesin can be produced at a yield of 70% or more, and depending on the conditions, a fluororesin can be produced at a yield of 75% or more.

Industrial Applicability

[0092] The present invention is useful in fields related to fluororesins.

Claims

1. The weight average molecular weight Mw is 5×10 ４ ~2×10 ５ and the yellowness index of a 3 mm thick molded product obtained by heating and melting at 280° C. for 24 hours is 3 or less. 【Chemistry 1】

2. The fluororesin according to claim 1, having a glass transition temperature of 125°C or higher and 145°C or lower.

3. Shear rate 10 －２ s, the melt viscosity at 250°C is 1×10 ２ ~3×10 ５ The fluororesin according to claim 1 or 2, having a viscosity of Pa·s.

4. The fluororesin according to any one of claims 1 to 3, having a molecular weight distribution Mw / Mn of 1.2 to 8.

5. The fluororesin according to any one of claims 1 to 4, which has 10 or less cracks in a product (3 mm thick, 26.4 mm diameter) melt-molded at 280°C for 24 hours.

6. 6. The fluororesin according to any one of claims 1 to 5, wherein a difference B-A between a weight loss amount A immediately after heating to 300°C at 10°C / min in air in a TG-DTA and a weight loss amount B after heating to 300°C and then holding at 300°C for 30 minutes is 1.0% or less.

7. The fluororesin according to any one of claims 1 to 6, wherein the area of ​​bubbles in a molded product (3 mm thick, 26.4 mm diameter) obtained by heating and melting the resin at 280°C for 24 hours is 10% or less of the area of ​​the molded product.

8. The fluororesin according to any one of claims 1 to 7, in which the number of bubbles in a product (3 mm thick, 26.4 mm diameter) melt-molded at 280°C for 24 hours is 10 or less.

9. Shear rate 10 －２ s, the melt viscosity at 250°C is 1×10 ２ ~5×10 ４ The fluororesin according to any one of claims 1 to 8, having a viscosity of Pa·s.

10. The method includes polymerizing a monomer represented by the following general formula (8) in the presence of a radical polymerization initiator and a chain transfer agent to obtain a fluororesin containing a residue unit represented by the following general formula (9), the polymerization being carried out in an organic solvent that dissolves the monomer represented by the general formula (8) and precipitates a fluororesin containing a residue unit represented by the general formula (9), the chain transfer agent being an organic compound having 1 to 20 carbon atoms and containing at least one atom selected from the group consisting of a hydrogen atom and a chlorine atom, and the fluororesin having a weight average molecular weight Mw of 5×10 ４ ~3×10 ５ and a yellowness index of a 3 mm thick molded product obtained by heating and melting at 280° C. for 24 hours is 3 or less. 【Chemistry 2】 【Chemistry 3】

11. The method according to claim 10, wherein the amount of the chain transfer agent is 3 to 50% by weight based on the total amount of the monomer and the chain transfer agent.

12. The method according to claim 10 or 11, wherein the chain transfer agent is an organic compound having 1 to 20 carbon atoms and containing a chlorine atom.

13. The method according to any one of claims 10 to 12, wherein the chain transfer agent is an organic compound having 1 to 20 carbon atoms and containing a chlorine atom and a hydrogen atom.

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