JP2006045515A - Fluorine-containing copolymer film and use thereof - Google Patents

Abstract

Disclosed is a fluorine-containing copolymer film having excellent transparency and appearance.
A repeating unit based on ethylene, tables in repeating units based on tetrafluoroethylene, repeating units based on hexafluoropropylene and CF 2 ₌ CFOR ^{f (R} f represents a fluoroalkyl group having 1 to 10 carbon atoms.) A fluorine-containing copolymer comprising a repeating unit based on a fluoroalkyl vinyl ether, wherein the repeating unit is in a characteristic composition range, and a capacity flow rate at 297 ° C. is 0.1 to ³⁰ mm ³ / sec, is molded at 320 ° C. or less. A fluorine-containing copolymer film formed at a temperature.
[Selection figure] None

Description

  The present invention relates to a fluorine-containing copolymer film excellent in appearance and its use.

  Films made of fluororesin films and fluororesin composites are lightweight, and have excellent weather resistance, mechanical strength, etc., so pools, gymnasiums, tennis courts, soccer fields, warehouses, gathering halls, exhibition halls, garden houses, agriculture It is used as a covering material for a house for example (see, for example, Patent Document 1 and Patent Document 2). However, the film made of a composite material of glass fiber and fluororesin disclosed in Patent Document 2 has insufficient transparency. Therefore, when the film is used as a covering material for a roof of a structure, the solar light transmittance of the roof is lowered. Therefore, the growth of the plant inside the structure is insufficient. From the above, the film made of the composite material cannot be applied as a covering material for structures such as horticultural facilities and sports facilities where lawns grow. In addition, there was a problem that the feeling of opening was not enough inside the building. Here, a building in which a film material such as a film is used for a roof or an outer wall is called a film structure. A film that is fixed to a framework such as iron or wood and forms the roof or outer wall of the structure is called a film for a membrane structure.

  An ethylene / tetrafluoroethylene copolymer (hereinafter referred to as ETFE) film is excellent in sunlight transmittance. Therefore, the ETFE film is suitably used as a film for a membrane structure such as an agricultural house, a horticultural house, a sports facility cultivated by a lawn, or an exhibition hall. A plurality of films for a membrane structure, which are superposed, are sandwiched between iron frames to form a panel shape. Air is sent between the films of the panel. It has been proposed that the panel is inflated to obtain a roof (see Non-Patent Document 1). Such a film for a membrane structure is required to have mechanical strength such as tensile strength and tear strength in addition to weather resistance and transparency. In addition, the film for membrane structure is exposed to direct sunlight in summer (see Non-Patent Document 2). Therefore, the film for membrane structure is required to maintain excellent mechanical strength even at a high temperature of about 60 ° C.

  As ETFE excellent in mechanical strength, 40 to 60 mol% of ethylene, 30 to 55 mol% of tetrafluoroethylene (hereinafter referred to as TFE), and 1.5 to 10 mol of hexafluoropropylene (hereinafter referred to as HFP). % And a quaternary copolymer system ETFE in which 0.05 to 2.5 mol% of a comonomer as a fourth component is copolymerized has been proposed. The quaternary copolymer system ETFE is superior in mechanical strength as compared to a ternary copolymer system ETFE that does not copolymerize the comonomer of the fourth component (see Patent Document 3).

  However, such a quaternary copolymer system ETFE has lower thermal stability than a perfluoro-type fluorine-containing copolymer such as a tetrafluoroethylene / hexafluoropropylene copolymer. The quaternary copolymer system ETFE may have a defect called fish eye (hereinafter referred to as FE) during molding. When FE occurs, the appearance of the film is impaired. In addition, the film could be broken starting from the FE.

Japanese Patent Laid-Open No. 3-188132 Japanese Unexamined Patent Publication No. 63-222852 JP-A-57-38807 International Conference on Building Environment Systems and Technology 2nd. S. Tanno et al. , 1997 Architectural Institute of Japan

  The present invention aims to provide a fluorine-containing copolymer film that is required to be developed on the basis of the above-described background, excellent in transparency, low in FE, excellent in appearance, and excellent in mechanical strength. And

The present invention relates to a repeating unit based on ethylene, a repeating unit based on TFE, a repeating unit based on HFP, and a fluoroalkyl represented by CF ₂ ═CFOR ^f (R ^f represents a fluoroalkyl group having 1 to 10 carbon atoms). It consists of repeating units based on vinyl ether, the molar ratio of repeating units based on ethylene / repeating units based on TFE is 10/90 to 60/40, and the content of repeating units based on HFP is 0. Fluorine-containing copolymer having a content of 1 to 20 mol%, the fluoroalkyl vinyl ether content of 0.1 to 10 mol% based on all repeating units, and a volumetric flow rate at 297 ° C of 0.1 to 30 mm ³ / sec Provided is a fluorine-containing copolymer film characterized in that the coalescence is molded at a molding temperature of 320 ° C. or lower. Provide.

  Moreover, this invention provides the film for agricultural houses and the film for membrane structures which consist of a film of this fluorine-containing copolymer.

  The film of the fluorine-containing copolymer of the present invention has little FE and is excellent in transparency and appearance. Moreover, it is excellent also in mechanical strength, such as tear strength and tensile breaking strength.

The fluorine-containing copolymer in the present invention is a repeating unit based on ethylene, a repeating unit based on TFE, a repeating unit based on HFP, and CF ₂ = CFOR ^f (R ^f represents a C 1-10 fluoroalkyl group.) It consists of the repeating unit based on the fluoroalkyl vinyl ether represented by these. Moreover, the molar ratio of the repeating unit based on ethylene / the repeating unit based on TFE is 10/90 to 60/40. The molar ratio is preferably 35/65 to 50/50, and more preferably 45/55 to 50/50. When the molar ratio is within this range, the fluorine-containing copolymer film is excellent in heat resistance, chemical resistance, and weather resistance.

  Content of the repeating unit based on HFP is 0.1-20 mol% with respect to all the repeating units. The content is preferably 0.2 to 15 mol%, more preferably 0.3 to 1.5 mol%. If the content is less than this range, the mechanical strength, particularly Elmendorf tear strength, is low, and if it is more than this range, the heat resistance and mechanical strength are low. When the content is within this range, the fluorine-containing copolymer film is excellent in mechanical strength and heat resistance.

The content of a fluoroalkyl vinyl ether (hereinafter referred to as FAV) represented by CF ₂ = CFOR ^f (R ^f represents a fluoroalkyl group having 1 to 10 carbon atoms) is 0.1 with respect to all repeating units. -10 mol%. The content is preferably 0.2 to 5 mol%, more preferably 0.3 to 1.5 mol%, and most preferably 0.4 to 1.0. When the content of the repeating unit based on FAV is less than this range, the transparency is low, and when it is large, the heat resistance and mechanical strength are low. When the content is within this range, the fluorine-containing copolymer film is excellent in transparency, mechanical strength, and heat resistance.

As ^{R f} is the CF ₂ = CFOR ^f, linear, branched, may be any of circular, it may also contain an etheric oxygen atom. R ^f is preferably linear. ^Rf has 1 to 10 carbon atoms, preferably 1 to 7, and more preferably 2 to 5. R ^f is preferably a polyfluoroalkyl group, more preferably a perfluoroalkyl group. That is, as FAV, perfluoro (alkyl vinyl ether) is more preferable. As specific examples of FAV, CF ₂ = CFOCF ₃ , CF ₂ = CFO (CF ₂ ) ₂ F (hereinafter referred to as PEVE), CF ₂ = CFO (CF ₂ ) ₃ F (hereinafter referred to as PPVE), CF. ₂ = CFO (CF ₂ ) ₄ F (hereinafter referred to as PBVE), CF ₂ = CFOCF ₂ CF (CF ₃ ) ₂ , CF ₂ = CFO (CF ₂ ) ₆ F, CF ₂ = CFOCF ₂ CF (CF ₃ ) O _{(CF 2) 3} F, and the like. As FAV, PEVE, PPVE, and PBVE are more preferable, and PPVE is most preferable.

The volume flow rate at 297 ° C. of the fluorinated copolymer in the present invention is 0.1 to ³⁰ mm ³ / sec. Volume flow rate is preferably 1.0~20mm ³ / sec, 5.0~15mm ³ / sec is more preferable. When the volume flow rate is smaller than this range, melt fracture occurs and the appearance is remarkably impaired. In addition, productivity increases because the load during extrusion increases. When the capacity flow rate is larger than this range, the viscosity of the fluorine-containing copolymer melted at the time of molding becomes low, so that it becomes difficult to wind up as a film.

  Examples of the method for producing a fluorinated copolymer in the present invention include suspension polymerization, solution polymerization, emulsion polymerization, bulk polymerization and the like. In particular, radical polymerization is preferable, and solution polymerization in which ethylene, TFE, HFP, and FAV are copolymerized in the presence of a radical polymerization initiator, a chain transfer agent, and a polymerization medium is more preferable.

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, peroxydicarbonates such as diisopropylperoxydicarbonate, peroxyesters such as tert-butylperoxypivalate, tert-butylperoxyisobutyrate, and tert-butylperoxyacetate. , Diacyl peroxides such as isobutyryl peroxide, octanoyl peroxide, benzoyl peroxide, lauroyl peroxide, (Z (CF ₂ ) _p COO) ₂ (where Z is a hydrogen atom, a fluorine atom or a chlorine atom, and p is 1 Inorganic peroxides such as fluorine-containing diacyl peroxide, potassium persulfate, sodium persulfate, ammonium persulfate, and the like.

  Examples of the polymerization medium include organic solvents such as fluorocarbon, chlorocarbon, fluorochlorocarbon, fluoroether, alcohol, and ether, and an aqueous medium. Examples of chain transfer agents include alcohols such as methanol and ethanol, chlorofluorohydrocarbons such as 1,3-dichloro-1,1,2,2,3-pentafluoropropane, and 1,1-dichloro-1-fluoroethane. Examples thereof include hydrocarbons such as carbon, pentane, hexane, and cyclohexane. The 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, more preferably 2 to 10 hours.

  The film of the fluorine-containing copolymer of the present invention is formed at a molding temperature of 320 ° C. or less. Usually, it is preferable to melt the fluorine-containing copolymer with an extruder to form pellets, and then to form a film. When forming the film, the fluorine-containing copolymer is preferably pelletized in advance. At the time of molding, the pelletized fluorine-containing copolymer can be supplied smoothly. Furthermore, since generation | occurrence | production of the bubble in a film can be suppressed, it is preferable. The temperature at which the fluorinated copolymer is molded into pellets is preferably 320 ° C. or less, more preferably 280 to 315 ° C., and most preferably 301 to 315 ° C. As a method for forming the film, the following method is preferably exemplified. The fluorine-containing copolymer pellets are melted in an extruder and discharged from a T-die. The film discharged and molded from the T-die is wound up by a roll. As extrusion conditions, the temperature of the screw and the T die (hereinafter also referred to as the molding temperature) is 320 ° C. or less. 280-315 degreeC is preferable and 305-315 degreeC is more preferable. When the molding temperature is within this range, the film is less likely to generate FE. As the extruder, a single-screw or twin-screw extruder is preferable.

Size and number of F-E contained in the film of the fluorocopolymer of the present invention are those of less than 0.05 mm ² or more 0.1 mm ² is at 50 / ^{m 2} or less, 0.1 mm ² or more Is preferably 15 pieces / m ² or less. And a 0.05 mm ² or more 0.1mm less than ² things 30 / ^{m 2} or less, and more preferably 0.1mm ² or more of is 10 pieces / ^{m 2} or less. When the size and number of FE are in this range, the fluorocopolymer film has excellent appearance, excellent transparency, and excellent mechanical strength.

  In the film of the fluorine-containing copolymer of the present invention, the Elmendorf tear strength is preferably 70 N or more, and more preferably 75 N or more. The larger the Elmendorf tear strength of the film, the better. Usually, the Elmendorf tear strength of the film is 100 N or less. The tensile strength at break of the film is preferably 50 MPa or more, more preferably 55 MPa or more, and most preferably 60 MPa or more. The larger the tensile breaking strength of the film, the better. Usually, the tensile breaking strength of the film is 100 MPa or less. When the Elmendorf tear strength and the tensile break strength are in this range, the fluorine-containing copolymer film is not easily torn or torn even when subjected to the following external force. Examples of the external force include an external force generated by a collision of flying objects, an external force caused by a strong wind, and an external force generated by snow accumulation on the film. The haze in the film is preferably 15% or less, more preferably 10% or less, and most preferably 8% or less. The lower limit of the haze of the film is preferably as low as possible. Usually, the haze of the film is 0.5% or more. When the haze is in the above range, the film is excellent in transparency. Therefore, it does not inhibit the growth of plants in an agricultural house or membrane structure using the film. In addition, it is possible to produce an open feeling as if you are outdoors.

  The reason why FE is remarkably small in the film of the fluorine-containing copolymer of the present invention is not necessarily clear, but is considered as follows. It is considered that the fluorine-containing copolymer thermally decomposed during molding is contained in the film as a residue. Since the residue is contained in the film, it is considered that FE occurs. Therefore, in order to reduce FE, it is important that the fluorinated copolymer in the present invention is molded at a temperature at which it is not thermally decomposed. In the fluorine-containing copolymer, it has been found that the molding temperature is suitably 320 ° C. or lower. In particular, a range of 280 to 315 ° C is preferable, and a range of 305 to 310 ° C is more preferable. Therefore, it is considered that by molding in this temperature range, a film with less FE and excellent appearance was obtained.

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In addition, the physical-property value described in the Example was measured by the method shown below.
[Composition of fluorinated copolymer] The composition was determined by molten fluorine NMR and fluorine content analysis.
[Melting point (° C)] Using a scanning differential thermal analyzer (DSC220CU, manufactured by Seiko Instruments Inc.), the melting point was determined from the endothermic peak when heated to 300 ° C at 10 ° C / min in a nitrogen atmosphere.
[Capacity flow rate (mm ³ / sec)] Extrusion speed when extruding a fluorine-containing copolymer from an orifice having a diameter of 2.1 mm and a length of 8 mm under a load of 7 kg under a temperature of 297 ° C. using a flow tester manufactured by Shimadzu Corporation It shows with.

[Haze (%)] A 200 μm-thick film obtained by extrusion molding was measured using SM-5 manufactured by Suga Test Instruments Co., Ltd. in accordance with the method described in JIS K7105.
[Elmendorf Tear Strength (N)] A rectangular test piece described in JISK7128-2 was cut out from a 200 μm-thick film obtained by extrusion molding to prepare a sample. The measurement was performed using an Elmendorf tear tester (manufactured by Toyo Seiki Seisakusho).
[Tensile breaking strength (MPa)] A 5B type test piece described in JIS K7162 was cut out from a 200 μm thick film obtained by extrusion molding to prepare a sample. Both ends of the sample were set on a chuck portion of a tensile tester (Orientec Co., Ltd.), a tensile test was performed at a speed of 200 mm / min, and the tensile strength at break was measured.

[Measurement of size and number of FE] Using a film having a thickness of 200 μm obtained by extrusion, a place corresponding to an area of 0.25 m ² from the surface was arbitrarily selected, and F contained in the place The number of -E was counted visually. The number was multiplied by 4, and the number of FE per 1 m ² was calculated. The unit is expressed in units / m ² . The size of the F-E, in accordance contaminants measured Chart (issued Bureau of Engraving and Printing), and the sample reference, 0.1mm ² or more, 0.05 mm ² or more 0.1mm less than ^2, 0.03 mm ² The above was classified into three of less than 0.05 mm ² . In the evaluation of the film of the present invention, the range of less than 0.05 mm ² was not defined because it did not affect the appearance of the film.

[Example 1]
The polymerization tank with a stirrer having an internal volume of 94 liters was deaerated. In the polymerization tank, 70.6 kg of 1-hydrotridecafluorohexane, 1,3-dichloro-1,1,2,2,3-pentafluoropropane (manufactured by Asahi Glass Co., Ltd., hereinafter referred to as AK225cb), 20. 4 kg, PPVE 1.89 kg and HFP 2.25 kg were charged. The temperature in the polymerization tank was raised to 66 ° C., and a mixed gas of TFE / ethylene = 76/24 (molar ratio) was injected until the pressure reached 1.5 MPa-G. In the polymerization tank, 65 mL of a 1% by mass AK225cb solution of tert-butylperoxypivalate was charged as a polymerization initiator to initiate polymerization. A monomer mixed gas of TFE / ethylene = 50/50 (molar ratio) was continuously charged so that the pressure became constant during the polymerization. 7.3 hours after the start of polymerization, when 7.1 kg of the monomer mixed gas was charged, the temperature inside the polymerization tank was lowered to room temperature, and unreacted monomers were purged until the pressure became normal pressure.

The obtained slurry of fluorinated copolymer 1 was put into a 200 L granulation tank charged with 75 kg of water. Next, the slurry and water in the granulation tank were heated to 105 ° C. while being stirred. In the granulation tank, the solvent was granulated while being distilled off. The obtained granulated product was dried at 150 ° C. for 5 hours, whereby 7.4 kg of the fluorinated copolymer granulated product 1 was obtained.
The composition of the fluorinated copolymer 1 is as follows: polymerized units based on TFE / polymerized units based on ethylene / polymerized units based on HFP / polymerized units based on PPVE = 50.6 / 48.2 / 0.7 / 0.7 (mol) Ratio). The melting point was 267 ° C., and the volume flow rate was 5.8 mm ³ / sec.

The fluorinated copolymer granulated product 1 was pelletized with a single-screw extruder at 305 ° C. to obtain pellets 1. Next, the pellet 1 was formed into a film having a thickness of 200 μm at a forming temperature of 310 ° C. using a single screw extruder. Size and number of F-E of the obtained film, of less than 0.05 mm ² or more 0.1 mm ² is 28 / ^m is ^2, 0.1 mm ² or more of six / ^{m 2} met It was. The haze was 7.6%, the Elmendorf tear strength was 82 N, and the tensile break strength was 68 MPa.

[Comparative Example 1]
The fluorine-containing copolymer granulated product 1 was pelletized by a single screw extruder at a temperature of 330 ° C. to obtain pellets 2. The pellet 2 was formed into a film having a thickness of 200 μm at a molding temperature of 330 ° C. using a single screw extruder. Size and number of F-E of the obtained film, of less than 0.05 mm ² or more 0.1 mm ² is 237 / ^m is ^2, 0.1 mm ² or more of 38 pieces / ^{m 2} met It was. The haze was 8.1%, the Elmendorf tear strength was 81 N, and the tensile break strength was 65 MPa.

The fluorine-containing copolymer film of the present invention is suitable for agricultural house films and membrane structure films. Moreover, since it is excellent in transparency, it can also be applied to solar cell protective films, release films, carrier films, and the like.

Claims (9)

A fluoroalkyl represented by a repeating unit based on ethylene, a repeating unit based on tetrafluoroethylene, a repeating unit based on hexafluoropropylene, and CF ₂ = CFOR ^f (R ^f represents a C 1-10 fluoroalkyl group). It consists of repeating units based on vinyl ether, the molar ratio of repeating units based on ethylene / repeating units based on tetrafluoroethylene is 10/90 to 60/40, and the content of repeating units based on hexafluoropropylene is all repeating units. The content of the fluoroalkyl vinyl ether is 0.1 to 10 mol% based on all repeating units, and the volume flow rate at 297 ° C. is 0.1 to 30 mm ³ / sec. The fluorine-containing copolymer is formed at a molding temperature of 320 ° C or lower. A fluorine-containing copolymer film characterized by being formed. The fluorine-containing copolymer film according to claim 1, wherein R ^f is a perfluoroalkyl group. The fluorine-containing copolymer film according to claim 1 or 2, wherein the fluoroalkyl vinyl ether is CF ₂ = CFO (CF ₂ ) ₃ F. The fisheye contained in the film has a size and number of 0.05 mm ² or more and less than 0.1 mm ² of 50 / m ² or less, and 0.1 mm ² or more of 15 / m ² or less. The fluorine-containing copolymer film according to claim 1, 2 or 3.   The film of the fluorine-containing copolymer according to any one of claims 1 to 4, wherein the Elmendorf tear strength is 70 N or more.   The film of the fluorine-containing copolymer according to any one of claims 1 to 5, wherein the haze is 15% or less.   The film of a fluorinated copolymer according to any one of claims 1 to 6, which has a tensile strength at break of 50 MPa or more.   The film for agricultural houses which consists of a film of the fluorine-containing copolymer as described in any one of Claims 1-7. The film for film structures which consists of a film of the fluorine-containing copolymer as described in any one of Claims 1-8.