COPOLYMER, MOLDED BODY, EXTRUDED BODY, AND TRANSFER MOLDED BODY

Abstract

There is provided a copolymer containing tetrafluoroethylene unit and perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of perfluoro(propyl vinyl ether) unit of 4.9 to 7.0% by mass with respect to the whole of the monomer units, a melt flow rate at 372 C. of 0.5 to 1.5 g/10 min, and the number of functional groups of 20 or less per 10.sup.6 main-chain carbon atoms.

Claims

1. A copolymer, comprising tetrafluoroethylene unit and perfluoro(propyl vinyl ether) unit, wherein the copolymer has a content of perfluoro(propyl vinyl ether) unit of 4.9 to 7.0% by mass with respect to the whole of the monomer units, a melt flow rate at 372 C. of 0.5 to 1.5 g/10 min, and the total number of CFCF.sub.2, CF.sub.2H, COF, COOH, COOCH.sub.3, CONH.sub.2 and CH.sub.2OH of 20 or less per 10.sup.6 main-chain carbon atoms.

2. The copolymer according to claim 1, wherein the copolymer has a melt flow rate at 372 C. of 0.7 to 1.3 g/10 min.

3. An extrusion formed article, comprising the copolymer according to claim 1.

4. A transfer molded article, comprising the copolymer according to claim 1.

5. A coated electric wire, comprising a coating layer comprising the copolymer according to claim 1.

6. A formed article, comprising the copolymer according to claim 1, wherein the formed article is a sheet or a pipe.

Description

EXAMPLES

[0136] The embodiments of the present disclosure will now be described by Examples as follows, but the present disclosure is not limited only to these Examples.

[0137] Each numerical value in the Examples was measured by the following methods.

[0138] (Content of Monomer Unit)

[0139] The content of each monomer unit was measured by an NMR analyzer (for example, manufactured by Bruker BioSpin GmbH, AVANCE 300, high-temperature probe).

[0140] (Melt Flow Rate (MFR))

[0141] The polymer was made to flow out from a nozzle having an inner diameter of 2.1 mm and a length of 8 mm at 372 C. under a load of 5 kg by using a Melt Indexer G-01 (manufactured by Toyo Seiki Seisaku-sho, Ltd.) according to ASTM D1238, and the mass (g/10 min) of the polymer flowing out per 10 min was determined.

[0142] (Number of Functional Groups)

[0143] Pellets of the copolymer was formed by cold press into a film of 0.25 to 0.30 mm in thickness. The film was 40 times scanned and analyzed by a Fourier transform infrared spectrometer [FT-IR (Spectrum One, manufactured by PerkinElmer, Inc.)] to obtain an infrared absorption spectrum, and a difference spectrum against a base spectrum that is completely fluorinated and has no functional groups is obtained. From an absorption peak of a specific functional group observed on this difference spectrum, the number N of the functional group per 110.sup.6 carbon atoms in the sample was calculated according to the following formula (A).

N=IK/t(A) [0144] I: absorbance [0145] K: correction factor [0146] t: thickness of film (mm)

[0147] For reference, the absorption frequency, the molar absorption coefficient and the correction factor for the functional groups in the present disclosure are shown in Table 2. The molar absorption coefficients are those determined from FT-IR measurement data of low molecular model compounds.

TABLE-US-00002 TABLE 2 Molar Absorption Extinction Functional Frequency Coefficient Correction Group (cm.sup.1) (l/cm/mol) Factor Model Compound COF 1883 600 388 C.sub.7F.sub.15COF COOH 1815 530 439 H(CF.sub.2).sub.6COOH free COOH 1779 530 439 H(CF.sub.2).sub.6COOH bonded COOCH.sub.3 1795 680 342 C.sub.7F.sub.15COOCH.sub.3 CONH.sub.2 3436 506 460 C.sub.7H.sub.15CONH.sub.2 CH.sub.2OH.sub.2, 3648 104 2236 C.sub.7H.sub.15CH.sub.2OH OH CF.sub.2H 3020 8.8 26485 H(CF.sub.2CF.sub.2).sub.3CH.sub.2OH CFCF.sub.2 1795 635 366 CF.sub.2CF.sub.2

[0148] (Melting Point)

[0149] The polymer was heated, as a first temperature raising step, at a temperature-increasing rate of 10 C./min from 200 C. to 350 C., then cooled at a cooling rate of 10 C./min from 350 C. to 200 C., and then again heated, as second temperature raising step, at a temperature-increasing rate of 10 C./min from 200 C. to 350 C. by using a differential scanning calorimeter (trade name: X-DSC7000, manufactured by Hitachi High-Tech Science Corporation); and the melting point was determined from a melting curve peak observed in the second temperature raising step.

Example 1

[0150] 26.6 L of pure water was charged in a 174 L-volume autoclave; nitrogen replacement was sufficiently carried out; thereafter, 30.4 kg of perfluorocyclobutane and 1.76 kg of perfluoro(propyl vinyl ether) (PPVE) were charged; and the temperature in the system was held at 35 C. and the stirring speed was held at 200 rpm. Then, tetrafluoroethylene (TFE) was introduced under pressure up to 0.58 MPa, and thereafter 0.010 kg of a 50% methanol solution of di-n-propyl peroxydicarbonate was charged to initiate polymerization. Since the pressure in the system decreased along with the progress of the polymerization, TFE was continuously supplied to make the pressure constant, and 0.058 kg of PPVE was added for every 1 kg of TFE supplied and the polymerization was continued for 6 hours. TFE was released to return the pressure in the autoclave to the atmospheric pressure, and thereafter, an obtained reaction product was washed with water and dried to thereby obtain 15 kg of a powder.

[0151] The obtained powder was melt extruded at 360 C. by a screw extruder (trade name: PCM46, manufactured by Ikegai Corp) to thereby obtain pellets of a TFE/PPVE copolymer. The PPVE content of the obtained pellets was measured by the method described above. The results are shown in Table 3.

[0152] The obtained pellets were put in a vacuum vibration-type reactor VVD-30 (manufactured by OKAWARA MFG. CO., LTD.), and heated to 210 C. After vacuumizing, F2 gas diluted to 20% by volume with N.sub.2 gas was introduced to the atmospheric pressure. 0.5 hour after the F.sub.2 gas introduction, vacuumizing was once carried out and F.sub.2 gas was again introduced. Further, 0.5 hour thereafter, vacuumizing was again carried out and F.sub.2 gas was again introduced. Thereafter, while the above operation of the F.sub.2 gas introduction and the vacuumizing was carried out once every 1 hour, the reaction was carried out at a temperature of 210 C. for 10 hours. After the reaction was finished, the reactor interior was replaced sufficiently by N.sub.2 gas to finish the fluorination reaction. By using the fluorinated pellets, the above physical properties were measured by the methods described above. The results are shown in Table 3.

Example 2

[0153] Fluorinated pellets were obtained as in Example 1, except for changing the charged amount of PPVE to 2.12 kg, adding 0.068 kg of PPVE for every 1 kg of TFE supplied, and changing the polymerization time to 7 hours. The results are shown in Table 3.

Example 3

[0154] 51.8 L of pure water was charged in a 174 L-volume autoclave; nitrogen replacement was sufficiently carried out; thereafter, 40.9 kg of perfluorocyclobutane, 3.01 kg of perfluoro(propyl vinyl ether) (PPVE), and 0.92 kg of methanol were charged; and the temperature in the system was held at 35 C. and the stirring speed was held at 200 rpm. Then, tetrafluoroethylene (TFE) was introduced under pressure up to 0.64 MPa, and thereafter 0.013 kg of a 50% methanol solution of di-n-propyl peroxydicarbonate was charged to initiate polymerization. Since the pressure in the system decreased along with the progress of the polymerization, TFE was continuously supplied to make the pressure constant, and 0.063 kg of PPVE was additionally charged for every 1 kg of TFE supplied. The polymerization was finished at the time when the amount of TFE additionally charged reached 40.9 kg. Unreacted TFE was released to return the pressure in the autoclave to the atmospheric pressure, and thereafter, an obtained reaction product was washed with water and dried to thereby obtain 43.5 kg of a powder.

[0155] By using the obtained powder, the fluorination reaction was carried out as in Example 1 to thereby obtain fluorinated pellets. The results are shown in Table 3.

Comparative Example 1

[0156] 26.6 L of pure water was charged in a 174 L-volume autoclave; nitrogen replacement was sufficiently carried out; thereafter, 30.4 kg of perfluorocyclobutane, 1.32 kg of perfluoro(propyl vinyl ether) (PPVE), and 0.06 kg of methanol were charged; and the temperature in the system was held at 35 C. and the stirring speed was held at 200 rpm. Then, tetrafluoroethylene (TFE) was introduced under pressure up to 0.58 MPa, and thereafter 0.010 kg of a 50% methanol solution of di-n-propyl peroxydicarbonate was charged to initiate polymerization. Since the pressure in the system decreased along with the progress of the polymerization, TFE was continuously supplied to maintain make the pressure constant, and 0.046 kg of PPVE was added for every 1 kg of TFE supplied and the polymerization was continued for 5.5 hours. TFE was released to return the pressure in the autoclave to the atmospheric pressure, and thereafter, an obtained reaction product was washed with water and dried to thereby obtain 15 kg of a powder.

[0157] The obtained powder was melt extruded at 360 C. by a screw extruder (trade name: PCM46, manufactured by Ikegai Corp) to thereby obtain pellets of a TFE/PPVE copolymer. The PPVE content of the obtained pellets was measured by the method described above. The results are shown in Table 3.

[0158] The obtained pellets were put in a vacuum vibration-type reactor VVD-30 (manufactured by OKAWARA MFG. CO., LTD.), and heated to 210 C. After vacuumizing, F2 gas diluted to 20% by volume with N.sub.2 gas was introduced to the atmospheric pressure. 0.5 hour after the F.sub.2 gas introduction, vacuumizing was once carried out and F2 gas was again introduced. Further, 0.5 hour thereafter, vacuumizing was again carried out and F.sub.2 gas was again introduced. Thereafter, while the above operation of the F2 gas introduction and the vacuumizing was carried out once every 1 hour, the reaction was carried out at a temperature of 210 C. for 10 hours. After the reaction was finished, the reactor interior was replaced sufficiently by N.sub.2 gas to finish the fluorination reaction. By using the fluorinated pellets, the above physical properties were measured by the methods described above. The results are shown in Table 3.

Comparative Example 2

[0159] Fluorinated pellets were obtained as in Comparative Example 1, except for changing the charged amount of PPVE to 1.72 kg, changing the charged amount of methanol to 0.08 kg, adding 0.057 kg of PPVE for every 1 kg of TFE supplied, and changing the polymerization time to 6.5 hours. The results are shown in Table 3.

Comparative Example 3

[0160] Fluorinated pellets were obtained as in Comparative Example 1, except for changing the charged amount of PPVE to 2.12 kg, changing the charged amount of methanol to 0.03 kg, adding 0.068 kg of PPVE for every 1 kg of TFE supplied, and changing the polymerization time to 7 hours. The results are shown in Table 3.

Comparative Example 4

[0161] Non-fluorinated pellets were obtained as in Example 1, except for changing the charged amount of PPVE to 2.08 kg, adding 0.067 kg of PPVE for every 1 kg of TFE supplied, and changing the polymerization time to 7 hours. The results are shown in Table 3.

Comparative Example 5

[0162] 51.8 L of pure water was charged in a 174 L-volume autoclave; nitrogen replacement was sufficiently carried out; thereafter, 40.9 kg of perfluorocyclobutane and 3.33 kg of perfluoro(propyl vinyl ether) (PPVE) were charged; and the temperature in the system was held at 35 C. and the stirring speed was held at 200 rpm. Then, tetrafluoroethylene (TFE) was introduced under pressure up to 0.64 MPa, and thereafter 0.004 kg of a 50% methanol solution of di-n-propyl peroxydicarbonate was charged to initiate polymerization. Since the pressure in the system decreased along with the progress of the polymerization, TFE was continuously supplied to make the pressure constant, and 0.068 kg of PPVE was additionally charged for every 1 kg of TFE supplied. The polymerization was finished at the time when the amount of TFE additionally charged reached 40.9 kg. Unreacted TFE was released return the pressure in the autoclave to the atmospheric pressure, and thereafter, an obtained reaction product was washed with water and dried to thereby obtain 41.0 kg of a powder.

[0163] By using the obtained powder, the fluorination reaction was carried out as in Example 1 to thereby obtain fluorinated pellets. The results are shown in Table 3.

TABLE-US-00003 TABLE 3 Number of PPVE functional Melting content MFR groups point (% by mass) (g/10 min) (groups/C10.sup.6) ( C.) Example 1 5.5 0.7 <6 301 Example 2 6.4 1.3 <6 298 Example 3 5.9 0.9 <6 301 Comparative 4.4 1.3 <6 302 Example 1 Comparative 5.4 2.3 <6 301 Example 2 Comparative 6.4 2.2 <6 298 Example 3 Comparative 6.3 1.1 58 299 Example 4 Comparative 6.4 0.2 <6 298 Example 5

[0164] The description <6 in Table 3 means that the number of functional groups is less than 6.

[0165] Then, by using the obtained pellets, the following properties were evaluated. The results are shown in Table 4.

[0166] (Haze Value)

[0167] By using the pellets and a heat press molding machine, a sheet of approximately 1.0 mm in thickness was prepared. The sheet was immersed in a quartz cell filled with pure water, and the haze value was measured according to JIS K 7136 using a haze meter (trade name: NDH 7000SP, manufactured by NIPPON DENSHOKU INDUSTRIES CO., LTD.).

[0168] (Compression Set Rate (CS))

[0169] The measurement of the compression set rate was carried out according to a method described in ASTM D395 or JIS K6262:2013.

[0170] Approximately 2 g of the pellets was charged in a metal mold (inner diameter: 13 mm, height: 38 mm), and in that state, melted by hot plate press at 370 C. for 30 min, thereafter, water-cooled under a pressure of 0.2 MPa (resin pressure) to thereby prepare a formed article of approximately 8 mm in height. Thereafter, the obtained molded article was cut to prepare a test piece of 13 mm in outer diameter and 6 mm in height. The prepared test piece was compressed to a compression deformation rate of 50% (that is, the test piece of 6 mm in height was compressed to a height of 3 mm) at a normal temperature by using a compression device.

[0171] Then, the compressed test piece being fixed on the compression device was allowed to stand still in an electric furnace at 65 C. for 72 hours. The compression device was taken out from the electric furnace, and cooled to room temperature; thereafter, the test piece was dismounted. The collected test piece was allowed to stand at room temperature for 30 min, and the height of the collected test piece was measured and the compression set rate was determined by the following formula.

Compression set rate (%)=(t.sub.0t.sub.2)/(t.sub.0t.sub.1)100 [0172] t.sub.0: an original height of the test piece (mm) [0173] t.sub.1: the height of a spacer (mm) [0174] t.sub.2: the height of the test piece dismounted from the compression device (mm)

[0175] In the above test, t.sub.0 was 6 mm and t.sub.1 was 3 mm.

[0176] (Tensile Strength (TS) at 150 C.)

[0177] The tensile strength at 150 C. was measured according to ASTM D638.

[0178] A formed article having high tensile strength at 150 C. has excellent pressure resistance.

[0179] (Sheet Formability)

[0180] A 14 mm extruder (manufactured by Imoto machinery Co., LTD.) and a T die were used to form pellets to prepare a sheet. The extrusion conditions were as follows. [0181] a) Take-up speed: 0.1 m/min [0182] b) Roll temperature: 120 C. [0183] c) Film width: 70 mm [0184] d) Thickness: 1.00 mm [0185] e) Extrusion condition: [0186] Cylinder screw diameter=14 mm, a single-screw extruder of L/D=20 [0187] Set temperature of the extruder: barrel section C-1 (330 C.), barrel section C-2 (350 C.), barrel section C-3 (370 C.), T die section (380 C.)

[0188] The extrusion forming of the copolymer was continued until it became possible to stably extrude the copolymer from the forming machine. Then, the copolymer was extrusion-formed to prepare a sheet of 3 m or longer in length (70 mm in width) so as to be 1.00 mm in thickness. The portion of the film at 2 to 3 m from the edge of the obtained sheet was cut to prepare a test piece (1 m in length, 70 mm in length) to measure a variation in thickness. The thickness was measured at a total of three points, i.e., the central point in the width direction of the edge of the prepared sheet and two points 25 mm away from the central point in the width direction. Moreover, the thickness was measured at a total of nine points, i.e., three central points located at an interval of 25 cm from the central point in the width direction of one end of the sheet toward the other end and two points 25 mm away from each central point in the width direction. Concerning the total 12 measured values, the case where the number of measured values outside the range of 1.00 mm 10% being 1 or less was regarded as good, and the case where the number of measured values outside the range of 1.00 mm 10% being 2 or more was regarded as poor.

[0189] (Pipe Formability)

[0190] A pipe 10.0 mm in outer diameter and 1.0 mm in wall thickness was obtained by a 30-mm extruder (manufactured by Tanabe Plastics Machinery Co., Ltd.). The extrusion conditions were as follows. [0191] a) Die inner diameter: 25 mm [0192] b) Mandrel outer diameter: 13 mm [0193] c) Sizing die inner diameter: 10.5 mm [0194] d) Take-over speed: 0.4 m/min [0195] e) Outer diameter: 10.0 mm [0196] f) Wall thickness: 1.0 mm [0197] g) Extrusion condition [0198] Cylinder screw diameter=30 mm, a single screw extruder of L/D=22 [0199] Set temperature of the extruder: barrel section C-1 (350 C.), barrel section C-2 (370 C.), barrel section C-3 (380 C.), head section H-1 (390 C.), die section D-1 (390 C.), die section D-2 (390 C.)

[0200] The obtained pipe was observed and evaluated according to the following criteria. The appearance of the pipe was visually checked. [0201] Good: good appearance [0202] Poor: poor appearance, e.g., the cross section is not circular by being flat or having uneven thickness

[0203] (Test of Own Weight Deformation in Melting)

[0204] A formed article of 13 mm in diameter and approximately 6.5 mm in height was prepared by using the pellets and a heat press molding machine. The obtained formed article was cut to prepare a test piece of 6.3 mm in height. The prepared test piece was put in a SUS-made laboratory disk, and heated in an electric furnace at 330 C. for 30 min, and thereafter, the test piece together with the laboratory disk was water cooled. There was measured by slide calibers, the diameter of the surface (bottom surface) of the test piece taken out which surface had contacted with the laboratory disk, and the bottom surface area increase rate was calculated by the following formula.

[0205] Bottom surface area increase rate (%)={the bottom area of the test piece after the heating (mm.sup.2)the bottom area of the test piece before the heating (mm.sup.2)}/the bottom area of the test piece before the heating (mm.sup.2)100

[0206] It is meant that the lower the bottom surface area increase rate, the more hardly the formed article deforms by its own weight in melting. The copolymer giving formed articles low in the bottom surface area increase rate is excellent in that even in the case of preparing thick sheets and large pipes by forming the copolymer by extrusion forming, the formed articles in a molten state hardly deform and there can be obtained the formed articles having the desired shapes after being cooled and solidified.

[0207] (Abrasion Test)

[0208] By using the pellets and a heat press molding machine, a sheet-shape test piece of approximately 0.2 mm in thickness was prepared, and a test piece having 10 cm10 cm was cut out therefrom. The prepared test piece was fixed on a test bench of a Taber abrasion tester (No. 101 Taber type abrasion tester with an option, manufactured by YASUDA SEIKI SEISAKUSHO, LTD.) and the abrasion test was carried out under the conditions of at a load of 500 g, using an abrasion wheel CS-10 (rotationally polished in 20 rotations with an abrasive paper #240) and at a rotation rate of 60 rpm by using the Taber abrasion tester. The weight of the test piece after 1,000 rotations was measured, and the same test piece was further subjected to the test of 10,000 rotations and thereafter, the weight thereof was measured. The abrasion loss was determined by the following formula.

Abrasion loss (mg)=M1M2 [0209] M1: the weight of the test piece after the 1,000 rotations (mg) [0210] M2: the weight of the test piece after the 10,000 rotations (mg)

[0211] (Carbon Dioxide Permeability Coefficient)

[0212] By using the pellets and a heat press molding machine, a sheet-shape test piece of approximately 0.1 mm in thickness was prepared. By using the obtained test piece, carbon dioxide permeability was measured with a differential pressure type gas permeation meter (L100-5000 gas permeability meter, manufactured by Systech Illinois) according to the method described in JIS K7126-1:2006. The carbon dioxide permeability value at a permeation area of 50.24 cm.sup.2 at a test temperature of 70 C. at a test humidity of 0% RH was obtained. The obtained carbon dioxide permeability and the test piece thickness were used to calculate the carbon dioxide permeability coefficient from the following equation.

Carbon dioxide permeability coefficient (cm.sup.3.Math.mm/(m.sup.2.Math.24 h.Math.atm))=GTRd [0213] GTR: carbon dioxide permeability (cm.sup.3/(m.sup.2.Math.24 h.Math.atm)) [0214] d: test piece thickness (mm)

[0215] (Air Permeability Coefficient)

[0216] By using the pellets and a heat press molding machine, a sheet-shape test piece of approximately 0.1 mm in thickness. Using the obtained test piece, air permeability was measured with a differential pressure type gas permeation meter (L100-5000 gas permeability meter, manufactured by Systech Illinois) according to the method described in JIS K7126-1:2006. The air permeability value at a permeation area of 50.24 cm.sup.2 at a test temperature of 70 C. at a test humidity of 0% RH was obtained. The obtained air permeability and the test piece thickness were used to calculate the air permeability coefficient from the following equation.

Air permeability coefficient (cm.sup.3.Math.mm/(m.sup.2.Math.24 h.Math.atm))=GTRd [0217] GTR: air permeability (cm.sup.3/(m.sup.2.Math.24 h.Math.atm)) [0218] d: test piece thickness (mm)

[0219] (Ethyl Acetate Permeability)

[0220] By using the pellets and a heat press molding machine, a sheet-shape test piece of approximately 0.1 mm in thickness was prepared. 10 g of ethyl acetate was put in a test cup (permeation area: 12.56 cm.sup.2), and the test cup was covered with the sheet-shape test piece; and a PTFE gasket was pinched and fastened to hermetically close the test cup. The sheet-shape test piece was brought into contact with ethyl acetate, and held at a temperature of 60 C. for 45 days, and thereafter, the test cup was taken out and allowed to stand at room temperature for 1 hour, thereafter, the amount of the mass lost was measured. Ethyl acetate permeability (g.Math.cm/m.sup.2) was determined by the following formula.

Ethyl acetate (g.Math.cm/m.sup.2)=the amount of the mass lost (g)the thickness of the sheet-shape test piece (cm)/the permeation area (m.sup.2)

[0221] (Rate of Deflection at 110 C. Under Load)

[0222] By using pellets and a heat press molding machine, a sheet-shape test piece of approximately 4.2 mm in thickness was prepared, and a test piece having 8010 mm was cut out therefrom and heated in an electric furnace at 100 C. for 20 hours. Except that the obtained test piece was used, a test was carried out according to the method described in JIS K-K 7191-1 with a heat distortion tester (manufactured by YASUDA SEIKI SEISAKUSHO, LTD.) under the condition of a test temperature of 30 to 150 C., a temperature-increasing rate of 120 C./hour, a bending stress of 1.8 MPa, and a flatwise method. The rate of deflection under load was determined by the following formula. A sheet, the rate of deflection at 110 C. under load of which is small, has excellent rigidity at a high temperature of 110 C.

Rate of deflection under load (%)=a2/a1100 [0223] a1: test piece thickness before the test (mm) [0224] a2: amount of deflection at 110 C. (mm)

[0225] (Creep Resistance Evaluation)

[0226] Creep resistance was measured according to the method described in ASTM D395 or JIS K6262:2013. By using the pellets and a heat press molding machine, a formed article of 13 mm in outer diameter and 8 mm in height was prepared. The obtained formed article was cut to prepare a test piece of 13 mm in outer diameter and 6 mm in height. The prepared test piece was compressed to a compression deformation rate of 25% at normal temperature by using a compression device. The compressed test piece being fixed on the compression device was allowed to stand still in an electric furnace at 80 C. for 72 hours. The compression device was taken out from the electric furnace, and cooled to room temperature; thereafter, the test piece was dismounted. The collected test piece was allowed to stand at room temperature for 30 min, and the height of the collected test piece was measured and the extent of recovery was determined by the following formula.

Extent of recovery (%)=(t.sub.2t.sub.1)/t.sub.3100 [0227] t.sub.1: the height of the spacer (mm) [0228] t.sub.2: the height of the test piece dismounted from the compression device (mm) [0229] t.sub.3: the height after compressive deformation (mm)

[0230] In the above test, t.sub.1 was 4.5 mm and t.sub.3 was 1.5 mm.

[0231] (Hydrogen Peroxide Solution Immersion Test)

[0232] 25 g of pellets was immersed in 50 g of a 3% by weight aqueous hydrogen peroxide solution, heated at 90 C. for 20 hours in an electric furnace, further heated at 121 C. for 1 hour in a sterilizer, and then cooled to room temperature. The pellets were taken out from the aqueous solution, TISAB solution (10) (manufactured by KANTO CHEMICAL CO., INC.) was added to the remaining aqueous solution, and the fluorine ion concentration in the obtained aqueous solution was measured with a fluorine ion meter. From the obtained measured value, the fluorine ion concentration (the amount of fluorine ions dissolving out) per pellet weight was calculated according to the following formula:

Amount of fluorine ions dissolving out (mass ppm)=measured value (mass ppm)amount of aqueous solution (g)/pellet weight (g)

[0233] (Extrusion Pressure)

[0234] The extrusion pressure was measured by using a twin capillary rheometer RHEOGRAPH 25 (manufactured by Goettfert Inc.). There was defined as the extrusion pressure, a pressure value obtained by subjecting, to the Bagley correction, a pressure value in the cylinder after extrusion was carried out by using a main die of 1 mm in inner diameter and 16 in L/D and a sub-die of 1 mm in diameter and lower than 1 in L/D and at a measurement temperature of 390 C., a preheating time after charge of the pellets of 10 min and a shear rate of 20 sec-1 for 10 min. A copolymer low in the extrusion pressure is excellent in formability such as extrudability and injection moldability.

[0235] (Dielectric Loss Tangent)

[0236] By melt forming the pellets, a cylindrical test piece of 2 mm in diameter was prepared. The prepared test piece was set in a cavity resonator for 6 GHz, manufactured by Kanto Electronic Application and Development Inc., and the dielectric loss tangent was measured by a network analyzer, manufactured by Agilent Technologies Inc. By analyzing the measurement result by analysis software CPMA, manufactured by Kanto Electronic Application and Development Inc., on PC connected to the network analyzer, the dielectric loss tangent (tan ) at 20 C. at 6 GHz was determined.

TABLE-US-00004 TABLE 4 Hydro- gen peroxide solution Creep immer- Test Rate resist- sion of CO.sub.2 Air of ance test of defor- permea- permea- Ethyl deflec- evalu- Amount Com- ma- bility bility acetate tion ation fluorine Ex- pres- tion co- co- per- at Extent ions tru- sion 150 C. Sheet Pipe by Abra- efficient efficient mea- 110 C. of dissolv- sion value tensile for- for- own sion cm.sup.3-mm/ cm.sup.3-mm/ bility under recov- ing out pres- Dielec- Haze rate strength ma- ma- weight loss (m.sup.2 .Math. (m.sup.2 .Math. (g .Math. load ery (ppm by) sure tric (%) (%) (MPa) bility bility (%) (mg) 24 h .Math. atm) 24 h .Math. atm) cm/m.sup.2) (%) (%) mass (kPa) tangent Example 1 3.8 77 20.5 Good Good 15.5 8.2 2245 593 7.2 85% 26% 2.3 275 0.00042 Example 2 3.7 77 20.5 Good Good 28.8 9.2 2262 599 6.9 86% 21% 2.7 179 0.00043 Example 3 3.7 77 20.5 Good Good 20.0 8.3 2257 596 7.1 86% 24% 2.5 231 0.00043 Compara- 6.7 77 20.0 28.8 10.1 1945 510 7.2 78% 32% 1.9 179 0.00040 tive Example 1 Compara- 6.4 78 19.5 49.4 11.3 1995 527 6.9 79% 24% 2.3 120 0.00041 tive Example 2 Compara- 4.7 78 20.0 47.4 10.7 2165 573 6.8 84% 20% 2.7 124 0.00043 tive Example 3 Compara- 3.4 78 20.5 24.4 8.5 2474 651 8.7 86% 19% 11.0 201 0.00057 tive Example 4 Compara- 1.5 77 21.0 4.0 6.6 2598 699 7.4 94% 25% 2.7 656 0.00044 tive Example 5