JP4415665B2 - Tetrafluoroethylene copolymer - Google Patents

Description

  The present invention relates to a tetrafluoroethylene copolymer.

  A copolymer of tetrafluoroethylene and perfluoro (alkyl vinyl ether) (hereinafter referred to as PFA) is excellent in heat resistance and chemical resistance, and is used for pipes, tubes, valves, etc. used in the chemical and semiconductor industries. Widely used as wafer baskets, chemical containers, lining materials, etc.

  As PFA, a copolymer of tetrafluoroethylene (hereinafter referred to as TFE) and perfluoro (propyl vinyl ether) (hereinafter referred to as PPVE) (hereinafter referred to as TFE / PPVE copolymer) is commercially available. . The member formed from the TFE / PPVE copolymer has a low elastic modulus and a low yield strength and is easily deformed. For this reason, when the member is used under high stress or pressure, it is necessary to increase its thickness in order to improve durability, which is a restriction on member design. Moreover, it is economically disadvantageous to use a large amount of expensive TFE / PPVE copolymer. Since TFE / PPVE copolymer members are prone to cracking under high stress, development of PFA excellent in stress cracking resistance is required.

  Patent Document 1 describes a copolymer of TFE and perfluoro (ethyl vinyl ether). The copolymer is excellent in bending fatigue resistance, but there is no description about the elastic modulus and yield strength characteristics. Patent Document 2 describes a copolymer of TFE and perfluoro (alkyl vinyl ether) having a specific perfluorocycloalkyl group, but the copolymer cannot be melt-molded.

  The present inventors obtained a fluororesin having a high elastic modulus by heat-treating a fluororesin obtained by copolymerizing TFE, PPVE and a monomer having a crosslinkable functional group at a high temperature in an oxygen atmosphere (patent) See reference 3.) However, this manufacturing method has a long heat treatment time and low productivity. Moreover, when the crosslinkable functional group remains, the chemical resistance of the fluororesin is not sufficient.

JP 7-126329 A Japanese Patent Publication No. 60-7646 Japanese Patent No. 3210000

  An object of the present invention is to provide a copolymer of TFE and a specific perfluorovinyl ether which is excellent in melt moldability and chemical resistance, has a high elastic modulus and yield strength, and is excellent in stress crack resistance.

The present invention relates to a polymer unit (A) based on tetrafluoroethylene and CF ₂ ═CFOR ^f1 R ^f2 (wherein R ^f1 may contain a polyfluoroalkylene group, and R ^f2 may contain an etheric oxygen atom) Or a polymer unit (B) based on a monomer represented by the following formula: (A) / (B) in a molar ratio of 99.7 / 0.3. A tetrafluoroethylene copolymer is provided which has a capacity flow rate of 0.1 to 1000 mm ³ / sec.

  The tetrafluoroethylene copolymer of the present invention has high elastic modulus and yield strength, and is excellent in stress crack resistance. Moreover, it is excellent in melt moldability, chemical resistance, and heat resistance.

In the present invention, R ^f1 in CF ₂ ═CFOR ^f1 R ^f2 is a polyfluoroalkylene group. Preferably, 1 to 10 carbon atoms, having no ring structure, a perfluoroalkylene group. R ^f1 is a difluoromethylene group, perfluoro dimethylene group, perfluoro trimethylene group are preferable. When R ^f1 is present, CF ₂ = CFOR ^f1 R ^f2 has good copolymerizability with TFE.

R ^f2 is a polyfluorocycloalkyl group based on a 4-membered ring or a 5-membered ring , which may contain an etheric oxygen atom. Preferably, it is a perfluorocycloalkyl group based on a 4-membered ring or 5-membered ring which may contain an etheric oxygen atom.

The ring is preferably a ring having 1 or 2 etheric oxygen atoms, more preferably an oxolane ring or a 1,3 dioxolane ring. A substituent such as a polyfluoroalkyl group or a polyfluoroalkoxy group may be bonded to the ring carbon atom. As the substituent, a perfluoroalkyl group having 4 or less carbon atoms and a perfluoroalkoxy group having 4 or less carbon atoms are preferable, and a trifluoromethyl group is more preferable. R ^f2 is more preferably a perfluorocycloalkyl group having an oxygen atom in the ring. Specific examples of R ^f2 include the following structures.

The monomer represented by CF ₂ = CFOR ^f1 R ^f2 is 1 selected from the group consisting of a monomer represented by the formula (1), a monomer represented by the formula (2), and a monomer represented by the formula (3). It is preferable that it is a seed or more. Furthermore, the monomer represented by the formula (1) is more preferably perfluorotetrahydrofurfuryl vinyl ether. Hereinafter, the monomer represented by the formula (1) is also referred to as PTFVE.

  The monomer represented by the formula (1) can be produced by various methods. For example, fluorination of tetrahydrofurfuryl alcohol or esterification with perfluorocarboxylic acid halide as necessary, followed by formation thereof The product can be synthesized by adding hexafluoropropene oxide (HFPO) to a product obtained by liquid-phase pyrolysis of a product or perfluoroester, and further subjecting it to gas-phase pyrolysis.

In the present invention, the polymer units (B) based on the monomer represented by TFE-based polymer units (A) / CF ₂ = CFOR ^f1 R ^f2 are 99.7 / 0.3 to 90/10 in molar ratio. When the ratio of (B) is less than 0.3, the copolymer is brittle with a molecular weight that allows melt molding, and when it is more than 10, the elastic modulus of the copolymer is low. Within this range, the elastic modulus and yield strength are high and the stress crack resistance is excellent. Preferably (A) / (B) is 99.5 / 0.5 to 95.0 / 5.0 in molar ratio, more preferably 99.0 / 1.0 to 97.0 / 3.0. is there.

The volume flow rate (hereinafter referred to as Q value) of the TFE copolymer of the present invention is 0.1 to 1000 mm ³ / sec. The Q value is an index representing the melt fluidity of the fluorinated copolymer and is a measure of the molecular weight. A large Q value indicates a low molecular weight, and a small Q value indicates a high molecular weight. The Q value in the present invention is an extrusion speed when a TFE copolymer is extruded into an orifice having a diameter of 2.1 mm and a length of 8 mm under a load of 7 kg at a temperature of 380 ° C. using a flow tester manufactured by Shimadzu Corporation. . If the Q value is too small, the melt fluidity is insufficient, and the surface of the molded product is not uniform and smooth. If it is too large, the mechanical strength of the TFE copolymer is low. Within this range, the melt moldability is excellent. Q values of the TFE copolymer of the present invention is preferably from 1 to 500 mm ³ / sec, 2~200mm ³ / sec is more preferable.

In the present invention, in addition to TFE and CF ₂ ═CFOR ^f1 R ^f2 , other monomers copolymerizable with TFE may be used in combination. The structure of the other monomer is not particularly limited. Specific examples include hydrocarbon olefins such as ethylene; vinyl fluoride, vinylidene fluoride, trifluoroethylene, CH ₂ ═CX (CF ₂ ) _n Y (where, X and Y are each independently hydrogen or a fluorine atom, n is an integer of 2 to 8.) A fluoroolefin having a hydrogen atom in an unsaturated group such as; an unsaturated group such as hexafluoropropylene or chlorotrifluoroethylene Fluoroolefin having no hydrogen atom (except TFE); perfluoro (alkyl vinyl ether) such as perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), PPVE, perfluoro (butyl vinyl ether);
Vinyl esters such as vinyl acetate; vinyl ethers such as alkyl vinyl ether, glycidyl vinyl ether, hydroxybutyl vinyl ether, methylvinyloxybutyl carbonate, and the like.

  The other monomer is particularly preferably at least one selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, and perfluoro (alkyl vinyl ether). The obtained TFE copolymer is excellent in heat resistance and chemical resistance. The content of the polymerized units (C) based on other monomers is preferably (C) / ((A) + (B) + (C)) in a molar ratio of 0.001 to 0.1, preferably 0.002 0.08 is more preferable.

  The method for producing the TFE copolymer of the present invention is not particularly limited, and a polymerization method using a generally used radical polymerization initiator is employed. Polymerization methods include bulk polymerization, solution polymerization using organic solvents such as fluorinated hydrocarbons, chlorinated hydrocarbons, fluorinated chlorohydrocarbons, alcohols and hydrocarbons, aqueous media, and suspensions using organic solvents as necessary. Examples thereof include suspension polymerization, emulsion polymerization using an aqueous medium and an emulsifier.

The radical polymerization initiator is preferably an initiator having a half-life of 10 hours and a temperature of 0 to 100 ° C, more preferably an initiator having a temperature of 20 to 90 ° C. Specific examples include azo compounds such as azobisisobutyronitrile, non-fluorine diacyl peroxides such as isobutyryl peroxide, octanoyl peroxide, benzoyl peroxide, lauroyl peroxide, and diisopropyl peroxydicarbonate. Peroxyesters such as oxydicarbonate, tert-butyl peroxypivalate, tert-butyl peroxyisobutyrate, tert-butyl peroxyacetate, (Z (CF ₂ ) _p COO) ₂ (where Z is hydrogen Inorganic peroxidation such as fluorine-containing diacyl peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, etc. Thing etc. are mentioned.

  The radical polymerization conditions are not particularly limited, and the polymerization temperature is preferably 0 to 100 ° C, more preferably 20 to 90 ° C. The polymerization pressure is preferably from 0.1 to 10 MPa, more preferably from 0.5 to 3 MPa. The polymerization time is preferably 1 to 30 hours.

In the present invention, the TFE copolymer is preferably a TFE copolymer that has been subjected to a fluorination treatment and has substantially no unstable terminal group. Here, having substantially no unstable terminal group means having no more than 10 unstable terminal groups such as —COF, —CH ₂ OH, and —CO ₂ H per million carbon atoms. . More preferably, it is 5 or less. When the number of unstable end groups is small, the heat resistance and chemical resistance of the TFE copolymer are further improved. As a method for the fluorination treatment, a method in which the TFE copolymer is brought into contact with fluorine gas at a temperature of 200 ° C. or higher is preferable. The fluorine gas is also preferably diluted with an inert gas such as nitrogen gas. By the fluorination treatment, the unstable end group is converted to stable —CF ₃ .

  Applications of the TFE copolymer of the present invention include chemical tubes, fittings, tanks, valves, wafer baskets, piping and tank inner linings for semiconductor manufacturing equipment and chemical plants, copy rolls for OA equipment, lithium batteries, fuel cells, etc. The packing etc. are mentioned.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited to these. The composition, tensile strength, tensile elongation, tensile modulus, tensile yield strength, and MIT bending life of the TFE copolymer were measured by the methods described below.

[Composition of TFE Copolymer] According to the description of Asahi Glass Research Report 1990, 40 (1), 75, the TFE copolymer was determined by ¹⁹ F-NMR measurement in a hot melt state.

  [Tensile Strength, Tensile Elongation, Tensile Elastic Modulus, Tensile Yield Strength] Measured according to ASTM D3159 using a test piece at a tensile speed of 50 mm / sec.

  [MIT bending life] In accordance with ASTM D2176, a sample bending test was performed using a bending tester (MITO-D, manufactured by Toyo Seiki Co., Ltd.) under conditions of a load of 1.25 kg, a bending angle of ± 135 degrees, and room temperature. It was. The number of bendings until the sample breaks is the MIT bending life. The MIT bending life is an index of the stress crack resistance of the TFE copolymer, and the longer the MIT bending life, the better the stress crack resistance. The sample was prepared by punching a film having a thickness of 0.220 to 0.236 mm obtained by compression-molding a TFE copolymer at 340 ° C. into a strip shape having a width of 12.5 mm.

(Reference Example 1)
(Esterification reaction)
20 g of 2-tetrahydrofurfuryl alcohol and 21.8 g of triethylamine are placed in a flask and stirred in an ice bath, and 71.5 g of FCOCF (CF ₃ ) OCF ₂ CF ₂ CF ₃ is kept at an internal temperature of 10 ° C. or lower. The solution was added dropwise over 1 hour. After completion of the dropwise addition, the mixture was stirred at room temperature for 2 hours, 50 mL of water was added at an internal temperature of 15 ° C. or lower, the obtained crude liquid was separated, washed with water, dried over magnesium sulfate, filtered, and distilled under reduced pressure. To obtain 66.3 g of an ester compound of the formula (II).

(Fluorine reaction)
To a 500 mL nickel autoclave, 313 g of trichlorotrifluoroethane (R-113) was added and stirred, and kept at 25 ° C. After blowing nitrogen gas for 1 hour, fluorine gas diluted to 20% with nitrogen gas was blown for 1 hour at a flow rate of 8.08 L / h. Next, while blowing fluorine gas at the same flow rate, a solution prepared by dissolving 5.01 g of the compound (II) obtained by esterification in 100 g of R-113 was injected over 4.7 hours. Further, 9 mL of an R-113 solution having a benzene concentration of 0.01 g / mL was injected while raising the temperature from 25 ° C. to 40 ° C. while blowing fluorine gas at the same flow rate, and stirring was continued for 0.4 hours. Next, 6 mL of the above benzene solution was injected while maintaining the pressure in the reactor at 40 ° C., stirring was continued for 0.4 hours, and the same operation was repeated three times. The total amount of benzene injected was 0.33 g, and the total amount of R-113 injected was 33 mL.

(Perfluoroester thermal decomposition reaction)
2.1 g of compound (III) obtained by fluorination was charged into a flask together with 0.02 g of NaF powder and heated at 140 ° C. while stirring. A reflux condenser whose temperature was adjusted to −10 ° C. was installed at the top of the flask. After cooling, 2.0 g of a liquid sample was collected, and this was precision distilled to obtain 0.8 g of compound (IV).

(Perfluorotetrahydrofurfuryl vinyl ether synthesis reaction)
After charging 16.5 g of dehydrated and dried CsF in an autoclave, the inside of the reactor was degassed, and after adding 662 g (2.7 mol) of compound (IV) and 139 g of tetraglyme, the reactor was cooled to −20 ° C. Then, 450 g (2.7 mol) of hexafluoropropylene oxide (HFPO) was continuously supplied so that the internal pressure of the reactor was kept at a slightly reduced pressure, to carry out the reaction. After completion of the reaction, 1010 g was recovered with a separatory funnel, washed with tetraglyme, then dropped into an aqueous solution in which 330 g of KOH was dissolved, and water was distilled off after neutralization. The obtained white solid was dried under reduced pressure, a metal trap cooled to liquid nitrogen temperature was connected while maintaining the reduced pressure state, and the temperature in the dryer was raised to 270 ° C. While collecting the gas generated by the decomposition reaction in the metal trap, the reaction was continued until the gas generation was completed to obtain 700 g of Compound (I) (PTFVE: monomer represented by the formula (1)).

(Reference Example 2)
A monomer represented by the formula (2) in the same manner as in the reaction procedure of Reference Example 1, except that 2,2-dimethyl-4-methylol-1,3-dioxolane is used instead of 2-tetrahydrofurfuryl alcohol. Got.

(Reference Example 3)
A monomer represented by the formula (3) in the same manner as in the reaction procedure of Reference Example 1, except that 2,4-dimethyl-2-methylol-1,3-dioxolane is used instead of 2-tetrahydrofurfuryl alcohol. Got.

[Example 1]
Charge 590 g of ion-exchange water, 353 g of CHFCClCF ₂ CF ₂ Cl, 54.8 g of PTFVE, and 16.4 g of methanol into a 1.2 liter pressure vessel equipped with a stirrer, and pressurize TFE at an internal temperature of 50 ° C. Was charged to 1.21 MPa. Subsequently, ₃ mL of a 0.1% solution of (CF ₃ CF ₂ CF ₂ COO) ₂ (solvent: CHFCClCF ₂ CF ₂ Cl) (hereinafter referred to as initiator solution) was charged, and polymerization was started at 50 ° C. During the polymerization, the initiator solution was charged intermittently, and a total of 20.2 mL was charged. As the polymerization progressed, the pressure decreased, so TFE was continuously charged to keep the pressure constant. When the amount of TFE added later became 145 g, the internal temperature was cooled to room temperature, unreacted TFE was discharged, and the pressure vessel was opened. The contents of the pressure vessel were filtered through a glass filter to obtain a slurry-like TFE copolymer. The obtained slurry was dried at 120 ° C. for 8 hours to obtain 155 g of a white TFE copolymer. The obtained TFE copolymer had a molar ratio of polymerized units based on TFE / polymerized units based on PTFVE of 98.3 / 1.7 and a Q value of 1.7 mm ³ / sec. The tensile strength was 32.6 MPa, the tensile elongation was 310%, the yield strength was 14.0 MPa, the tensile modulus was 154 MPa, and the MIT bending life was 1,230,000 times.

[Example 2]
The pressure vessel of Example 1 was charged with 590 g of ion-exchanged water, 353 g of CHFCClCF ₂ CF ₂ Cl, 11.0 g of PTFVE, 33.9 g of PPVE, and 17.6 g of methanol, and at an internal temperature of 50 ° C., TFE Was charged until the pressure reached 1.21 MPa. Next, 3 mL of the same initiator solution used in Example 1 was charged, and polymerization was started at 50 ° C. During the polymerization, the initiator solution was charged intermittently for a total of 16.7 mL. As the polymerization progressed, the pressure decreased, so TFE was continuously charged to keep the pressure constant. When the amount of TFE added later became 145 g, the internal temperature was cooled to room temperature, unreacted TFE was discharged, and the pressure vessel was opened. The contents of the pressure vessel were filtered through a glass filter to obtain a slurry-like TFE copolymer. The obtained slurry was dried at 120 ° C. for 8 hours to obtain 153 g of a white TFE copolymer. The composition of the obtained TFE copolymer was such that the polymer unit based on TFE / polymer unit based on PTFVE / polymer unit based on PPVE had a molar ratio of 98.4 / 0.4 / 1.2, and the Q value was 2 It was 2 mm ³ / sec. The tensile strength was 36.9 MPa, the tensile elongation was 360%, the yield strength was 13.6 MPa, the tensile modulus was 146 MPa, and the MIT bending life was 880,000 times.

[Comparative Example 1]
150 g of TFE copolymer was obtained in the same manner as in Example 1 except that 42.4 g of PPVE, 18.9 g of methanol, and a total of 12.9 ml of the initiator solution were charged instead of PTFVE. As for the composition of the obtained TFE copolymer, the polymer unit based on TFE / polymer unit based on PPVE was 98.5 / 1.5 in a molar ratio, and the Q value was 2.3. The tensile strength was 33.1 MPa, the tensile elongation was 340%, the yield strength was 13.3 MPa, the tensile modulus was 141 MPa, and the MIT bending life was 780,000 times.

[Example 3]
157 g of a TFE copolymer is obtained in the same manner as in Example 1 except that 70.7 g of the monomer represented by the formula (2) is charged instead of PTFVE. The composition of the obtained TFE copolymer is such that the polymer unit based on the TFE-based polymer unit / the monomer represented by the formula (2) has a molar ratio of 98.3 / 1.7, and the Q value is 2.0 mm ^3. / Sec. The tensile strength is 33.0 MPa, the tensile elongation is 320%, the yield strength is 13.9 MPa, the tensile elastic modulus is 155 MPa, and the MIT bending life is 1.15 million times.

[Example 4]
156 g of TFE copolymer is obtained in the same manner as in Example 1 except that 70.7 g of the monomer represented by the formula (3) is charged instead of PTFVE. The composition of the obtained TFE copolymer is such that the polymer unit based on TFE / the polymer unit based on the monomer represented by formula (3) is 98.4 / 1.6 in terms of molar ratio, and the Q value is 2.3 mm ^3. / Sec. The tensile strength is 33.5 MPa, the tensile elongation is 300%, the yield strength is 14.0 MPa, the tensile elastic modulus is 152 MPa, and the MIT bending life is 1.08 million times.

The tetrafluoroethylene copolymer of the present invention is useful as a molding material for various members in the chemical industry and the semiconductor industry.

Claims (4)

Polymer unit (A) based on tetrafluoroethylene and CF ₂ ═CFOR ^f1 R ^f2 (where R ^f1 is a polyfluoroalkylene group, R ^f2 may contain an etheric oxygen atom, a 4-membered ring or a 5-membered ring A polymer unit (B) based on the monomer represented by (A) / (B) in a molar ratio of 99.7 / 0.3 to 90/10. The tetrafluoroethylene copolymer is characterized in that the volume flow rate is 0.1 to 1000 mm ³ / sec. The tetrafluoroethylene copolymer according to claim 1, wherein the monomer represented by CF ₂ ═CFOR ^f1 R ^f2 is a monomer represented by any one of formulas (1) to (3).

The tetrafluoroethylene copolymer according to claim 1, wherein the monomer represented by CF ₂ ═CFOR ^f1 R ^f2 is a monomer represented by the formula (1).

  Furthermore, it contains polymerized units (C) based on other monomers, and (C) / ((A) + (B) + (C)) is in a molar ratio of 0.001 to 0.1. The tetrafluoroethylene copolymer according to 2.