Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
  • C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L27/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers
  • C08L27/02—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L27/12—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Compositions of derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
  • C08L27/18—Homopolymers or copolymers or tetrafluoroethene

Definitions

• the present invention relates to a solid composition for producing a stretched membrane, and a stretched membrane using the solid composition.
• Fluorine-containing polymers such as tetrafluoroethylene copolymers are used in various industrial fields because of their excellent heat resistance, chemical resistance, flame retardancy, weather resistance, and the like.
• Patent Document 1 describes a method in which modified tetrafluoroethylene polymerized using a specific fluorine-containing surfactant is powdered, paste-extruded, and then stretched to obtain a stretched membrane.
• An object of the present invention is to provide a solid composition for producing a stretched membrane, which can improve the uniformity of the stretched membrane, and a stretched membrane using the same.
• a composition comprising a first polymer which is a crystalline fluorine-containing polymer having a melting point below 20°C or an amorphous fluorine-containing polymer having a glass transition temperature below 20°C, and a second polymer which contains units based on tetrafluoroethylene and is different from the first polymer, the content of the first polymer is 0.01 to 4.0% by mass with respect to the total mass of the first polymer and the second polymer,
• a solid composition for producing a stretched membrane wherein the total content of a compound represented by the following formula (S1) and a compound represented by the following formula (S2) is 100 mass ppb or less.
• each M independently represents a hydrogen atom, Na, K, or NH4
• n1 represents an integer of 3 to 13, or 15 or 17
• n2 represents an integer of 4 to 10, or 12.
• the solid composition according to [1] comprising primary particles containing the first polymer and the second polymer.
• the solid composition according to [2], wherein the aspect ratio of the primary particles is 1.5 or less.
• the first polymer contains units based on perfluoro(alkyl vinyl ether), [4] The solid composition according to any one of [1] to [3], wherein the content of units based on perfluoro(alkyl vinyl ether) is 0.1 to 3.0 mol % relative to the total of all units of the first polymer and all units of the second polymer. [5] The solid composition according to any one of [1] to [4], wherein the first polymer is water-insoluble. [6] A stretched film formed from the solid composition according to any one of [1] to [5] above.
• stretched membranes with excellent uniformity can be obtained.
• unit refers collectively to an atomic group derived from one molecule of the monomer that is formed directly by polymerizing the monomer, and an atomic group obtained by chemically converting a part of the atomic group.
• unit based on a monomer will also be simply referred to as a "unit.”
• a numerical range expressed using “to” means a range that includes the numerical values written before and after "to” as the upper and lower limits. In the numerical ranges described in stages in this specification, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages.
• the “average particle size of primary particles in an aqueous dispersion” is the average particle size (hydrodynamic diameter) determined by cumulant analysis from the autocorrelation function obtained by dynamic light scattering.
• the “average primary particle diameter of aggregated particles” is the arithmetic mean value of the radii of approximate circles obtained by image analysis of an observed image of a scanning electron microscope (SEM image).
• the “aspect ratio of a particle” is the ratio (a/b) of the major axis a of the particle to the longest diameter b among the diameters perpendicular to the major axis a.
• crystalline fluorine-containing polymer refers to a polymer containing fluorine atoms, in which a significant crystalline peak is detected within a diffraction angle (2 ⁇ ) range of 10 to 50° in an X-ray diffraction (XRD) pattern obtained using CuK ⁇ rays (wavelength: 1.5418 ⁇ ) as X-rays.
• XRD X-ray diffraction
• the content (mass % or mol %) of each unit relative to all units contained in the polymer is determined by analyzing the polymer by solid-state nuclear magnetic resonance spectroscopy (NMR), and usually, the content of each unit calculated from the amount of each monomer charged substantially coincides with the actual content of each unit.
• the solid composition for producing a stretched film of this embodiment contains a first polymer and a second polymer different from the first polymer.
• the content of the first polymer is 0.01 to 4.0% by mass relative to the total mass of the first polymer and the second polymer.
• the solid composition is preferably a powder composition.
• the first polymer is a crystalline fluorine-containing polymer having a melting point below 20° C. or an amorphous fluorine-containing polymer having a glass transition temperature (hereinafter also referred to as "Tg") below 20° C.
• Tg glass transition temperature
• the Tg of the first polymer is preferably lower than the polymerization temperature of the second polymer.
• the Tg of the first polymer is preferably 10° C. or less, more preferably 5° C. or less, even more preferably 3° C. or less, and particularly preferably 0° C. or less.
• the Tg of the first polymer is preferably not less than ⁇ 50° C., more preferably not less than ⁇ 45° C., and even more preferably not less than ⁇ 40° C.
• the Tg of the first polymer is not less than the lower limit, the thermal stability of the stretched film is improved.
• a method for adjusting the Tg of the first polymer within the above range for example, a method of adjusting the type and amount of the monomer used in producing the first polymer can be mentioned.
• the first polymer has units based on a fluorine-containing monomer that contains a fluorine atom.
• fluorine-containing monomer constituting the first polymer
• examples of the fluorine-containing monomer constituting the first polymer include tetrafluoroethylene (hereinafter also referred to as "TFE”), perfluoro(alkyl vinyl ether) (hereinafter also referred to as “PAVE”), hexafluoropropylene (hereinafter also referred to as "HFP”), vinylidene fluoride (hereinafter also referred to as "VdF”), CH 2 ⁇ CF-CF 2 -O-Rf-COOH, CH 2 ⁇ CF-CF 2 -O-Rf-SO 3 H, CF 2 ⁇ CF-CF 2 -O-Rf-COOH, CF 2 ⁇ CF-CF 2 -O-Rf-SO 3 H, CH 2 ⁇ CF-O-Rf-COOH, CH 2 ⁇ CF-O-
• the fluorine-containing monomer may have a functional group that contributes to water solubility as a substituent.
• the functional group that contributes to water solubility include a hydroxyl group and an ionic functional group.
• the ionic functional group may be either a cationic functional group or an anionic functional group.
• the ionic functional group include anionic functional groups such as a carboxylic acid group (-COO - ), a sulfonic acid group (-SO 3 - ), a sulfate group (-SO 4 2- ), a phosphonic acid group (-PO 3 2- ), a sulfonimide group (-N - (SO 2 )), and a phosphate group (-PO 4 3- ).
• the functional group that contributes to water solubility is preferably a monovalent group.
• the first polymer may have one or more functional groups that contribute to water solubility.
• the first polymer may also have functional groups that contribute to water solubility on a side chain or at a terminal.
• the first polymer preferably contains units based on TFE (hereinafter also referred to as "TFE units").
• TFE units units based on TFE
• the content of TFE unit in the total unit of first polymer is preferably 30 mol% or more, more preferably 40 mol% or more, and even more preferably 50 mol% or more, because the content of TFE unit is more, the more contributes to heat resistance.
• the upper limit of the content of TFE unit can be adjusted according to the type of unit other than TFE unit, so as to obtain desired Tg.For example, it is preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less.
• the first polymer is preferably water-insoluble in view of the ease of removing the first polymer from water.
• water-insoluble means that the solubility in 1000 g of water at 25°C is less than 100 mg.
• the content of the functional group that contributes to water solubility is preferably 0 to 20 mol %, more preferably 0.000001 to 15 mol %, and even more preferably 0.0001 to 10 mol %, based on all units constituting the first polymer.
• PAVE perfluoro(methyl vinyl ether) (hereinafter also referred to as “PMVE”), perfluoro(ethyl vinyl ether) (hereinafter also referred to as “PEVE”), and perfluoro(propyl vinyl ether) (hereinafter also referred to as “PPVE”).
• PMVE perfluoro(methyl vinyl ether)
• PEVE perfluoro(ethyl vinyl ether)
• PPVE perfluoro(propyl vinyl ether)
• PMVE and PPVE are preferred, with PMVE being more preferred, as they allow for more efficient production of the second polymer.
• the first polymer may contain units based on monomers other than TFE and PAVE, but it is preferable that the first polymer is substantially free of units based on other monomers, in order to more efficiently produce the second polymer.
• substantially free of units derived from other monomers means that the content of units derived from other monomers is 0.01 mol % or less, more preferably 0 mol %, based on the total units of the first polymer.
• the other monomers are preferably HFP and propylene.
• the content of the units based on HFP relative to all units of the first polymer is preferably 0 to 10 mol %, more preferably 0 to 5 mol %, and even more preferably 0 to 1 mol %.
• the second polymer is a fluoropolymer containing TFE units.
• the second polymer does not contain the first polymer.
• the second polymer is preferably a non-melt-processable fluoropolymer.
• the monomers constituting the second polymer include at least TFE, and may further include a monomer other than TFE.
• the second polymer contains at least TFE units and may further contain monomer units other than TFE units.
• the monomer other than TFE may be a fluorine-containing monomer or a fluorine-free monomer that does not contain a fluorine atom.
• fluorine-containing monomer examples include chlorotrifluoroethylene (hereinafter also referred to as "CTFE"), vinylidene fluoride (hereinafter also referred to as "VdF”), FAE, PAVE, hexafluoropropylene, perfluoro(2,2-dimethyl-1,3-dioxole), and perfluoro(4-methoxy-1,3-dioxole).
• the content of TFE units contained in the second polymer is preferably 99.0 to 100.0 mol%, more preferably 99.5 to 100.0 mol%, and even more preferably 99.9 to 100.0 mol%, based on the total units of the second polymer.
• the solid composition includes a first polymer and a second polymer.
• the content of the first polymer is 0.01 to 4.0% by mass, preferably 0.1 to 3.5% by mass, and more preferably 0.3 to 3.0% by mass, based on the total mass of the first polymer and the second polymer.
• the content of the first polymer is at least the lower limit of the above range, the emulsion stability of the second polymer is improved, and when it is at most the upper limit, the heat resistance of the second polymer can be maintained.
• the content of the first polymer relative to the total mass of the solid composition is preferably 0.1 to 4 mass %, more preferably 0.2 to 4 mass %, and even more preferably 0.3 to 3 mass %.
• the content of the second polymer relative to the total mass of the solid composition is preferably from 96 to 99.9 mass %, more preferably from 96 to 99.8 mass %, and even more preferably from 97 to 99.7 mass %.
• the total content of the first polymer and the second polymer relative to the total mass of the solid composition is preferably 99.0 to 100 mass%, more preferably 99.5 to 100 mass%, and even more preferably 99.8 to 100 mass%.
• the content of TFE units relative to the total of all units of the first polymer and all units of the second polymer is preferably 90 to 99.8 mol%, more preferably 93 to 99.5 mol%, and even more preferably 95 to 99.0 mol%.
• the content of TFE units is at least the lower limit of the above range, heat resistance is improved, and when it is at most the upper limit, stability of the aqueous dispersion during production is improved.
• each M independently represents a hydrogen atom, Na, K, or NH4
• n1 represents an integer of 3 to 13, 15, or 17
• n2 represents an integer of 4 to 10, or 12.
• the polymerization temperature is preferably from 20 to 150°C, more preferably from 50 to 100°C.
• the polymerization pressure is preferably 0 to 3 MPa, more preferably 1.0 to 2.0 MPa.
• the polymerization time is preferably 1 to 120 minutes, more preferably 10 to 60 minutes.
• ammonium ions originate from the polymerization initiator (particularly ammonium persulfate) and may be contained in reaction solution A.
• reaction solution A By subjecting reaction solution A to ion exchange treatment using a cation exchange resin to produce aqueous dispersion B, the ammonium ions in aqueous dispersion C after dilution can be reduced.
• the content of ammonium ions relative to the total mass of aqueous dispersion C is preferably 20 ppm by mass or less, more preferably 10 ppm by mass or less.
• the lower limit is not particularly limited and may be 0 ppm by mass.
• a first monomer is polymerized in a first aqueous medium in the presence of compound (1) to produce a first polymer.
• This polymerization is preferably carried out in the presence of compound (1) and a polymerization initiator, and the same polymerization initiator as in the polymerization step (1) of the first polymer can be used as the polymerization initiator.
• a first post-polymerization dispersion is obtained, which is a dispersion containing the first polymer and the first aqueous medium.
• Compound (1) is a compound represented by the following formula (2).
• CX 1 X 2 CX 3 -L-Z...(2)
• X1 and X2 each independently represent a hydrogen atom or an alkyl group
• X3 is a hydrogen atom, a fluorine atom, or an alkyl group
• L is a single bond or a divalent linking group
• M 1 is a hydrogen atom, a metal atom, N(R M11 ) 4 or P(R M12 ) 4 , and when a plurality of M 1 are present, the plurality of M 1 may be the same or different from each other
• R M11 and R M12 each independently represent a hydrogen atom or a substituent, any two R M11 's may be
• X 1 and X 2 each independently represent a hydrogen atom or an alkyl group.
• the alkyl group may be linear, branched, or cyclic.
• the alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 3 carbon atoms, and even more preferably 1 carbon atom. From the viewpoint of increasing the number of particles of the first polymer, it is preferable that X 1 and X 2 are both hydrogen atoms.
• X3 is a hydrogen atom, a fluorine atom, or an alkyl group. Specific examples and preferred embodiments of the alkyl group are the same as the specific examples and preferred embodiments of the alkyl group in X1 and X2 .
• X3 is preferably a fluorine atom or a hydrogen atom, more preferably a hydrogen atom, from the viewpoint of increasing the number of particles of the first polymer.
• L is a single bond or a divalent linking group.
• the divalent linking group include an alkylene group, a carbonyl group, an ether bond, a thioether bond, a sulfonyl group, -NH-, -SiH 2 -, a phenylene group, -CF 2 -, and a group combining two or more of these.
• the group combining two or more of these include an ester bond, a thioester bond, an amide bond, a sulfonamide bond, a combination of an alkylene group and an ether bond, a combination of an alkylene group and an ester bond, and a combination of an alkylene group and an amide bond.
• the alkylene group may be linear, branched, or cyclic, preferably linear or branched, and more preferably branched.
• the alkylene group may have 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms.
• L include a single bond, an alkylene group, an ether bond, an ester bond, * C -CO-NH-R-* Z , and the like, with a single bond, an alkylene group having 1 to 6 carbon atoms, and * C -CO-NH-R-* Z being preferred, and a single bond, an alkylene group having 1 to 2 carbon atoms, and * C -CO-NH-R-* Z being more preferred.
• * C is the bonding site to the carbon atom in formula (2)
• * Z is the bonding site to Z in formula (2)
• R is an alkylene group having 1 to 6 carbon atoms.
• Z is —SO 3 M 1 , —OSO 3 M 1 , —P( ⁇ O)(OM 1 ) 2 , —OP( ⁇ O)(OM 1 ) 2 or —COOM 1 .
• Z from the viewpoint of stabilizing the dispersion and increasing the number of particles of the first polymer, --SO.sub.3M.sub.1 and --COOM.sub.1 are preferred, --SO.sub.3Na and --COONa are more preferred, and --SO.sub.3Na is even more preferred.
• M 1 is a hydrogen atom, a metal atom, N(R M11 ) 4 or P(R M12 ) 4 , and R M11 and R M12 are each independently a hydrogen atom or a substituent.
• the metal atom represented by M1 is preferably a metal atom of Group 1, more preferably Li, Na, or K.
• the substituents represented by R 1 M11 and R 1 M12 are preferably monovalent organic groups, more preferably monovalent hydrocarbon groups, and even more preferably alkyl groups or aromatic hydrocarbon groups.
• the substituent preferably has 1 to 10 carbon atoms.
• the alkyl group may be linear, branched, or cyclic.
• the aromatic hydrocarbon group may be either monocyclic or polycyclic, and is preferably a phenyl group.
• the molecular weight of compound (1) is, for example, 70 to 500, and from the viewpoint of dispersion stability, 70 to 450 is preferred, and 100 to 300 is more preferred.
• compound (1) examples include vinyl sulfonic acid, vinyl phosphonic acid, (meth)acrylic acid, allyl sulfonic acid, allyl phosphonic acid, butenoic acid, crotonic acid, vinyl acetic acid, 2-sulfoethyl methacrylic acid, 4-vinyl benzene sulfonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, N-tigloylglycine, 6-acrylamidohexanoic acid, 1,1-difluoro-2-methyl-2-[(1-oxo-2-propen-1-yl)amino]-1-propanesulfonic acid, 3-methyl-3-[(2-methyl-1-oxo-2-propen-1-yl)amino]-2-butanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2,3-dimethyl-3-[(1-oxo-2-propen-1-yl)
• Preferred examples of compound (1) include vinyl compounds having a sulfonic acid group, phosphonic acid group, or carboxy group; allyl compounds having a sulfonic acid group, phosphonic acid group, or carboxy group; (meth)acrylic acid; (meth)acrylamides having a sulfonic acid group, phosphonic acid group, or carboxy group; and metal salts thereof.
• Preferred examples include vinyl sulfonic acid, sodium vinyl sulfonate, allyl sulfonic acid, sodium allyl sulfonate, 2-acrylamido-2-methyl-1-propanesulfonic acid, sodium 2-acrylamido-2-methyl-1-propanesulfonate, 2-methacrylamido-2-methyl-1-propanesulfonic acid, and sodium 2-methacrylamido-2-methyl-1-propanesulfonate.
• the term "(meth)acrylic acid” encompasses both acrylic acid and methacrylic acid
• (meth)acrylamide” encompasses both acrylamide and methacrylamide.
• the content of compound (1) is preferably 1.0 to 1000 ppm by mass, and in terms of better effects of the present invention, is more preferably 1.0 to 800 ppm by mass, still more preferably 3.0 to 500 ppm by mass, and particularly preferably 5.0 to 300 ppm by mass, relative to the entire first aqueous dispersion.
• the concept of the "first aqueous dispersion" before the initiation of polymerization of the first monomer includes compound (1) and an aqueous medium, but does not include the first monomer and polymerization initiator used in the polymerization of the first polymer.
• the "first aqueous dispersion" refers to a mixture of components excluding the first monomer and the polymerization initiator.
• the content of the first aqueous medium is preferably 20 to 90% by volume, and more preferably 40 to 80% by volume, relative to the volume of the reactor.
• the first monomer used in the present production method includes at least one selected from the group consisting of tetrafluoroethylene (hereinafter also referred to as "TFE”) and hexafluoropropylene (hereinafter also referred to as "HFP").
• the first monomer may include a monomer other than TFE and HFP, and preferably includes a monomer other than TFE and HFP.
• Examples of the monomer other than TFE and HFP include perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE”), propylene, vinylidene fluoride (hereinafter also referred to as "VdF”), CH 2 ⁇ CF-CF 2 -O-Rf-COOH, CH 2 ⁇ CF-CF 2 -O-Rf-SO 3 H, CF 2 ⁇ CF-CF 2 -O-Rf-COOH, CF 2 ⁇ CF-CF 2 -O-Rf-SO 3 H, CH 2 ⁇ CF-O-Rf-COOH, CH 2 ⁇ CF-O-Rf-SO 3 H, CF 2 ⁇ CF-O-Rf-COOH, and CF 2 ⁇ CF-O-Rf-SO 3 H (Rf represents a perfluoroalkyl group having 1 to 10 carbon atoms, and the perfluoroalkyl group may have an etheric oxygen atom between carbon atoms).
• PAVE per
• Emulsifiers containing fluorine atoms and emulsifiers not containing fluorine atoms may be polymeric emulsifiers.
• polymeric emulsifiers include polymers having hydrophilic groups in their side chains.
• polymeric emulsifiers include polymers containing units based on compounds having a site capable of reacting in polymerization and a hydrophilic group. Also included are polymers that do not originally have hydrophilic groups but have been post-treated, such as by hydrolysis, with polymers containing units based on compounds having groups that can become hydrophilic groups.
• the method for producing a solid composition according to this embodiment allows efficient production of a second polymer without the use of an emulsifier. It is believed that during polymerization of the second monomer, the first polymer adsorbs the second monomer at the hydrophobic portion and incorporates it into the first polymer, thereby solubilizing the second monomer. As a result, it is believed that the second monomer is polymerized within or near the first polymer. Furthermore, it is believed that the first polymer contributes to dispersion stabilization in an aqueous medium. When primary particles of the first polymer are present in aqueous dispersion C, it is presumed that the second monomer polymerizes within or near the primary particles of the first polymer, thereby producing primary particles containing the first polymer and the second polymer.
• aqueous dispersion C contains a reducing agent
• the amount of reducing agent used is preferably 1 to 2000 ppm per 100 parts by mass of the second monomer supplied.
• the amount of the second monomer supplied is preferably 1 to 50 parts by mass, more preferably 1 to 40 parts by mass, and even more preferably 1 to 30 parts by mass, per 100 parts by mass of the aqueous medium contained in aqueous dispersion C.
• water-soluble redox catalysts include combinations of oxidizing agents such as bromic acid or its salts, chloric acid or its salts, persulfuric acid or its salts, permanganic acid or its salts, and hydrogen peroxide with reducing agents such as sulfurous acid or its salts, hydrogen sulfite or its salts, thiosulfuric acid or its salts, organic acids, and inorganic salts. Potassium persulfate and ammonium persulfate are preferred as persulfates. Sodium sulfite is preferred as sulfites.
• Inorganic salts include combinations of sulfate anions, sulfite anions, and chloride anions with metal ions.
• the content of TFE units relative to the total of all units of the first polymer and all units of the second polymer is preferably 90 to 99.8 mol%, more preferably 93 to 99.5 mol%, and even more preferably 95 to 99.0 mol%.
• the content of the compound represented by formula (S1) and the content of the compound represented by formula (S2) are each preferably 100 ppb by mass or less, more preferably 50 ppb by mass or less, even more preferably 25 ppb by mass or less, and particularly preferably 0 ppb by mass, relative to the total mass of the first polymer and the second polymer.
• the rolling step can be carried out using a known method. For example, a string-like extrusion bead is sandwiched between a pair of rotating rollers and rolled to obtain a rolled body.
• the shape of the rolled body can be appropriately designed so that a stretched membrane of the desired shape can be obtained when stretched in the subsequent stretching step.
• the stretching step can be carried out using a known biaxial stretching method.
• the solid composition for producing a stretched membrane of this embodiment has a highly uniform stretched state when stretched, and can improve the uniformity of the stretched membrane.
• the reason why the uniformity of the stretched film is improved is not clear, but it is thought that the first polymer fills the grain boundaries, thereby making the entire film uniform.
• a in formula (A2) means a calculated by the above formula (A1).
• XCm ACm/a ⁇ 1/ ⁇ 2 (A2)
• XCm content of compounds with carbon number (n1+1) in the extract (ng/g)
• ACm peak area of the compound in the extract having the carbon number (n1+1)
• ⁇ 1 density of methanol
• ⁇ 2 density of extract
• the quantitation limit in this measurement is 1 ng/g.
• Aqueous dispersion D was diluted to a solids concentration of 0.2% by mass, and the sample dispersion was dropped onto a substrate and dried. Pt was then vapor-deposited onto the sample, and a scanning electron microscope (SEM, JEOL Ltd., JSM-IT700HR InTouchScope) was used to randomly select fields of view at a magnification of 20,000x so that particles did not overlap, and four or more observation images were saved. For 800 or more elliptical particles from the observation images, the brightness was adjusted using the image analysis software "MultiImage Tool," and the particles and substrate were subjected to binarized image processing. The approximate circular radius of each particle was measured and used as the particle diameter. The arithmetic mean value of these particle diameters was considered to be the average primary particle diameter of the dry powder.
• SSG Standard specific gravity
• ASTM D4895-04 The standard specific gravity (SSG) was measured in accordance with ASTM D4895-04. Specifically, 12.0 g of sample was weighed and compression molded in a cylindrical mold with an inner diameter of 28.6 mm to obtain a pellet sample. This was placed in a 290 ° C oven and heated at 120 ° C / hour. After holding at 380 ° C for 30 minutes, the temperature was lowered at 60 ° C / hour and held at 294 ° C for 24 minutes. The sample was held in a desiccator at 23 ° C for 12 hours, and then the specific gravity value of the sample relative to water at 23 ° C was measured, and this was taken as the standard specific gravity. The smaller the SSG value, the larger the molecular weight.
• TII Thermal Instability Index
• Extrusion pressure (hereinafter also referred to as EP) 100 g of the dried powder, left at room temperature for at least 2 hours, was placed in a 500 mL glass bottle, and 21.7 g of lubricating oil (Isopar H (registered trademark), manufactured by Exxon Corporation) was added and mixed for 3 minutes to obtain a mixture.
• lubricating oil Isopar H (registered trademark), manufactured by Exxon Corporation
• the resulting mixture was then left in a 25°C thermostatic chamber for 2 hours, and then extruded at 25°C under the conditions of a reduction ratio (ratio of the cross-sectional area of the die inlet to the cross-sectional area of the die outlet) of 100 and an extrusion rate of 51 cm/min through an orifice with a diameter of 2.5 cm, a land length of 1.1 cm, and an entrance angle of 30° to obtain an extrusion bead (string-like material).
• the pressure required for extrusion at this time was measured and recorded as the extrusion pressure (unit: MPa).
• the sample was clamped and fixed between movable jaws having a gauge length of 5.0 cm, and tensile stress was applied by driving the movable jaws at a speed of 300 mm/min at room temperature (24°C).
• Stress relaxation time Both ends of the stretched bead B were connected to fixtures to form a taut bead sample with a total length of 8 inches (20 cm). The oven was maintained at 390°C, and the fixture and bead sample were inserted into the oven through a (covered) slit in the side of the oven. The time required from the time of insertion into the oven until the bead sample broke was measured as the stress relaxation time (unit: seconds). A longer stress relaxation time indicates better heat resistance, and higher molecular weight and crystallinity after stretching.
• the solids concentration (content of the first polymer) of aqueous dispersion B1, the average particle size of primary particles in aqueous dispersion B1, and the number of particles in aqueous dispersion B1 were determined using the methods described above. The results are shown in Table 6 (the same applies hereinafter).
• Example 1 Preparation of second polymer P2-1 A 100L stainless steel autoclave equipped with a baffle and a stirrer was charged with 1500g of paraffin wax, 47.6kg of aqueous dispersion B1, and 11.4L of deionized water. After nitrogen replacement, the autoclave was decompressed and heated to 70°C, stirring was started, and the pressure was increased to 1.86MPa with TFE. 1L of deionized water containing 3.36g of DSAP (disuccinic acid peroxide) was added to initiate the polymerization reaction. Furthermore, polymerization was allowed to proceed while adding TFE to maintain the internal pressure of the autoclave at 1.86MPa, and a second polymer P2-1 (PTFE) was synthesized.
• DSAP disuccinic acid peroxide
• PTFE a homopolymer of TFE, exhibits non-melt moldability. That is, TFE, which is a second monomer, was polymerized in aqueous dispersion C1, which was prepared by adding deionized water to aqueous dispersion B1. The polymerization reaction was terminated when the amount of TFE added after the start of polymerization reached 13.1 kg, and the TFE in the autoclave was released into the atmosphere. The polymerization time was 150 minutes. The resulting reaction solution was cooled, and the supernatant paraffin wax was removed to obtain an aqueous dispersion D1.
• the resulting aqueous dispersion D1 was diluted with deionized water to a solids concentration of 10% by mass, the temperature was adjusted to 16°C, the mixture was stirred to cause aggregation, and the mixture was filtered to obtain a wet powder.
• the moisture content of the wet powder was 38.1% by mass.
• the moisture content of the wet powder is shown in Table 8 (the same applies below).
• the obtained wet powder was dried to a solids concentration of 99% by mass or more to obtain a dry powder. Specifically, the wet powder was dried at 195°C for 7.1 hours.
• the content of the first polymer P1-1 relative to the total mass of the first polymer and the second polymer was 1.89% by mass.
• the results are shown in Table 8 (the same applies hereinafter).
• the composition of the dry powder was calculated using NMR, and the content of PAVE units relative to the total of TFE units and PAVE units (PMVE units in this example) was 0.6 (mol%). The results are shown in Table 8 (the same applies hereinafter).
• the production conditions in the step of polymerizing the second monomer (TFE) in the aqueous dispersion C1 are shown in Table 7 (the same applies hereinafter). Specifically, the contents of the aqueous medium and the first polymer in the aqueous dispersion C before the start of polymerization of the second monomer are shown in the table. The content of paraffin wax and the amount of the second monomer (TFE) used per 100 parts by mass of the aqueous medium in aqueous dispersion C are shown in the table above. The amount of polymerization initiator used per 100 parts by mass of the second monomer used is shown in the table above. The aqueous dispersion C1 does not contain any of an emulsifier, fluoride ions, sulfate ions, and ammonium ions.
• the particle diameter of the primary particles in aqueous dispersion B and the particle diameter of the primary particles in aqueous dispersion C are the same.
• Table 8 shows the measurement results of the aspect ratio of the primary particles in aqueous dispersion D1. As shown in Table 8, in aqueous dispersion D1, the contents of compound (S1) and compound (S2) relative to the total mass of the primary particles were both below the detection limit, and the total content thereof was in the range of 100 mass ppb or less.
• the standard specific gravity (SSG) and thermal instability index (TII) of the dry powder obtained in this example were measured by the methods described above.
• the mixture (composition for stretching) obtained in this example by adding a lubricating oil to the dry powder was measured for extrusion pressure (EP) by the method described above.
• stretched beads were formed from the mixture (composition for stretching), and the breaking strength was measured to evaluate the stretchability during biaxial stretching.
• Polymerization was allowed to proceed while adding TFE to maintain the internal pressure of the autoclave at 1.40 MPa.
• the polymerization reaction was terminated when the amount of TFE added after the start of polymerization reached 120 g, and the autoclave was cooled, after which the TFE in the autoclave was released into the atmosphere.
• the polymerization time was 84 minutes. Nitrogen was pressurized up to 0.2 MPa, and the temperature was raised to 90°C. After heating the autoclave for 3 hours, it was cooled, and reaction liquid A2 was extracted.
• the first polymer P1-2 in reaction liquid A2 was water-insoluble.
• the reaction solution A2 was freeze-coagulated and then filtered to obtain a first polymer P1-2.
• the first polymer P1-2 had a TFE unit/PMVE unit ratio of 50/50 (molar ratio).
• the Tg was -5°C.
• the polymer had no melting point. This production was carried out twice.
• reaction solution A2 was passed through an ion exchange resin to remove impurities, yielding aqueous dispersion B2 of first polymer P1-2.
• Example 2 Preparation of second polymer P2-2
• the second monomer, TFE was polymerized in aqueous dispersion C2, which was prepared by adding deionized water to aqueous dispersion B2.
• a 100 L stainless steel autoclave equipped with a baffle and a stirrer was charged with 1,500 g of paraffin wax, 47.6 kg of aqueous dispersion B2, and 9.9 L of deionized water.
• the autoclave was purged with nitrogen, then reduced in pressure, heated to 70°C, and then stirred and pressurized to 1.76 MPa with TFE.
• 1 L of deionized water containing 2.80 g of DSAP was added to initiate the polymerization reaction.
• the polymerization was allowed to proceed while adding TFE so as to maintain the internal pressure of the autoclave at 1.76 MPa, thereby synthesizing a second polymer P2-2 (PTFE).
• TFE polymer P2-2
• 1 L of deionized water containing 1.07 g of ammonium sulfite was added over 6 minutes, and the temperature inside the autoclave was then increased to 90° C. at a rate of 15° C. per hour.
• the polymerization reaction was terminated when the amount of TFE added after the start of polymerization reached 14.8 kg, and the TFE in the autoclave was released into the atmosphere.
• the polymerization time was 193 minutes.
• reaction solution A3 was passed through an ion exchange resin to remove impurities, yielding aqueous dispersion B3 of first polymer P1-3.
• Example 3 Preparation of second polymer P2-3
• the second monomer, TFE was polymerized in aqueous dispersion C3, which was prepared by adding deionized water to aqueous dispersion B3.
• a 100 L stainless steel autoclave equipped with a baffle and a stirrer was charged with 1500 g of paraffin wax, 47.6 kg of aqueous dispersion B3, and 11.4 L of deionized water.
• the autoclave was purged with nitrogen, then reduced in pressure and heated to 70°C. Stirring was initiated, and the autoclave was pressurized to 1.86 MPa with TFE.
• 1 L of deionized water containing 3.36 g of DSAP was added to initiate the polymerization reaction.
• the polymerization was allowed to proceed while TFE was added to maintain the internal pressure of the autoclave at 1.86 MPa.
• the polymerization reaction was terminated when the amount of TFE added after the start of polymerization reached 13.1 kg, and the TFE in the autoclave was released into the atmosphere.
• the polymerization time was 188 minutes.
• the resulting reaction solution was cooled, and the supernatant paraffin wax was removed to obtain aqueous dispersion D3.
• a wet powder was obtained from the resulting aqueous dispersion D3, and this was dried to obtain a dry powder.
• Example 4 Production of PTFE
• This example is a comparative example in which PTFE was synthesized using an emulsifier that was a water-soluble fluorine-containing polymer, without using the first polymer.
• a 100 L stainless steel autoclave equipped with a baffle and a stirrer was charged with 9 g of polymer P4 (polymerization unit -CF 2 CF(OCF 2 CF 2 COONH 4 )-) (molecular weight Mn 4500, soluble in water, a powder that did not melt even when heated up to 220°C, had no melting point or Tg, and was thermally decomposed when heated at 220°C or above) obtained in Example 1 of JP-A-11-181009 [0025] to [0027], 1500 g of paraffin wax, and 60 L of deionized water.
• the autoclave was then purged with nitrogen, reduced pressure, and heated to 75°C. After stirring, the pressure was increased to 1.86 MPa with TFE. 1 L of deionized water in which 5.60 g of DSAP had been dissolved was added to initiate the polymerization reaction. The polymerization was allowed to proceed while adding TFE so as to maintain the internal pressure of the autoclave at 1.86 MPa. The polymerization reaction was terminated when the amount of TFE added after the start of polymerization reached 8.8 kg, and the TFE in the autoclave was released into the atmosphere. The polymerization time was 102 minutes. The resulting reaction solution was cooled, and the supernatant paraffin wax was removed to obtain aqueous dispersion D4.
• Example 2 In the same manner as in Example 1, a wet powder was obtained from the resulting aqueous dispersion D4, and this was dried to obtain a dry powder.
• the polymer P4 used as an emulsifier was designated as "P1,” and the PTFE produced by polymerizing TFE in the presence of the polymer P4 was designated as "P2,” and "P1/(P1+P2)" was calculated.
• the reaction solution A5 was freeze-coagulated and then filtered to obtain a first polymer P1-5.
• the first polymer P1-5 had a TFE unit/PMVE unit ratio of 55/45 (molar ratio).
• the Tg was -3°C.
• the polymer had no melting point. This production was carried out twice.
• Example 5 Preparation of second polymer P2-5
• This example is a comparative example in which a large amount of the first polymer is used.
• a 100 L stainless steel autoclave equipped with a baffle and a stirrer was charged with 1,500 g of paraffin wax, 47.6 kg of aqueous dispersion B5, and 11.4 L of deionized water.
• the autoclave was purged with nitrogen, then reduced in pressure, heated to 70°C, and then stirred and pressurized to 1.86 MPa with TFE.
• 1 L of deionized water containing 3.36 g of DSAP was added to initiate the polymerization reaction.
• the polymerization was allowed to proceed while adding TFE so as to maintain the internal pressure of the autoclave at 1.86 MPa, thereby synthesizing a second polymer P2-5 (PTFE).
• the polymerization reaction was terminated when the amount of TFE added after the start of polymerization reached 13.1 kg, and the TFE in the autoclave was released into the atmosphere.
• the polymerization time was 150 minutes.
• the resulting reaction solution was cooled, and the supernatant paraffin wax was removed to obtain aqueous dispersion D5.
• a wet powder was obtained from the obtained aqueous dispersion D5, and this was dried to obtain a dry powder.
• the first polymer P1-6 in the reaction liquid A6 is water-insoluble, and the reaction liquid A6 is an aqueous dispersion in which particles of the first polymer P1-6 are dispersed in an aqueous medium.
• the reaction liquid A6 was freeze-coagulated and then filtered.
• the resulting first polymer P1-6 was analyzed by NMR, and the ratio of TFE units to PMVE units was 63/37 (molar ratio).
• the Tg was ⁇ 6° C. and the polymer had no melting point.
• the reaction solution A6 was passed through an ion exchange resin to remove impurities in the same manner as in Production Example 1, except that the reaction solution A6 was diluted 5 times, thereby obtaining an aqueous dispersion B6 of the first polymer P1-6.
• Example 6 Preparation of second polymer P2-6 A 100L stainless steel autoclave equipped with a baffle and a stirrer was charged with 1500g of paraffin wax, 33.7kg of aqueous dispersion B6 containing 1.1% by mass of the first polymer P1-6, and 24.9L of deionized water. After the autoclave was purged with nitrogen, the pressure was reduced and the temperature was raised to 65°C. Stirring was started, and the pressure was increased to 1.76MPa with TFE. 1L of deionized water containing 2.8g of DSAP (disuccinic acid peroxide) was added to initiate the polymerization reaction.
• DSAP disuccinic acid peroxide
• a second polymer P2-6 (PTFE) was synthesized.
• PTFE a homopolymer of TFE, exhibits non-melt moldability.
• the amount of TFE added after the start of polymerization reached 15.8 kg, the polymerization reaction was terminated, and the TFE in the autoclave was released into the atmosphere.
• the resulting reaction liquid was cooled, and the supernatant paraffin wax was removed to obtain an aqueous dispersion D6.
• a wet powder was obtained from the resulting aqueous dispersion D6, and this was dried to obtain a dry powder.
• the dry powders obtained in Examples 1 to 3 and 6 have good stretchability when biaxially stretched, and stretched films with excellent uniformity can be obtained.
• the dry powder of Example 5 in which the content of the first polymer relative to the total mass of the first polymer and the second polymer was more than 4.0% by mass, broke during stretching.

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