Molded article and manufacturing method for molded article

Abstract

The invention provides a molded article containing a specific fluororesin and having excellent hydrophilicity. The molded article containing the fluororesin has a melt flow rate of 1.00 g/10 min or lower and a water contact angle of 90° or smaller. The fluororesin contains at least one copolymer selected from the group consisting of a copolymer containing a tetrafluoroethylene unit and a perfluoro(alkylvinylether) unit and a copolymer containing a tetrafluoroethylene unit and a hexafluoropropylene unit.

Claims

1. A molded article comprising a fluororesin, a surface of the molded article having a water contact angle of 90° or smaller, the fluororesin containing at least one copolymer selected from the group consisting of a copolymer containing a tetrafluoroethylene unit and a perfluoro(alkylvinylether) unit and a copolymer containing a tetrafluoroethylene unit and a hexafluoropropylene unit, and the whole of the molded article having a melt flow rate of 0.20 g/10 min or lower, the molded article is obtained by molding the fluororesin to provide an untreated molded article and irradiating the untreated molded article at a temperature of 110° C. to 240° C. in the presence of air.

2. The molded article according to claim 1, wherein the molded article contains 100 to 1000 functional groups on at least a surface thereof per 10.sup.6 carbon atoms in a main chain, and the functional groups include a —OH group, a —COF group, and a —COOH group.

3. The molded article according to claim 1, wherein the molded article is a tube.

4. A method for manufacturing the molded article according to claim 1, the method comprising: molding a fluororesin to provide an untreated molded article; and irradiating the untreated molded article with 40 to 100 kGy of radiation at 110° C. to 240° C. in the presence of air, the fluororesin containing at least one copolymer selected from the group consisting of a copolymer containing a tetrafluoroethylene unit and a perfluoro(alkylvinylether) unit and a copolymer containing a tetrafluoroethylene unit and a hexafluoropropylene unit.

5. The method for manufacturing the molded article according to claim 4, wherein the irradiation causes a melt flow rate increasing rate of 0% or lower.

6. The method for manufacturing the molded article according to claim 4, wherein the radiation is an electron beam.

7. The method for manufacturing the molded article according to claim 4, wherein the irradiation is performed at a temperature lower than a melting point of the fluororesin.

8. The method for manufacturing the molded article according to claim 4, wherein the molded article is a tube.

9. The molded article according to claim 1, wherein the whole of the molded article has a melt flow rate of <0.1 g/10 min.

Description

EXAMPLES

(1) The invention is described hereinbelow with reference to examples and comparative examples. Still, the invention is not intended to be limited to these examples.

(2) The parameters in the examples and comparative examples were determined by the following methods.

(3) MFR

(4) The MFR was defined as the mass (g/10 min) of the polymer that flows out of a nozzle having an inner diameter of 2 mm and a length of 8 mm per 10 minutes at 372° C. and a load of 5 kg using a melt indexer (Yasuda Seiki Seisakusho Ltd.) in conformity with ASTM D3307.

(5) Number of Functional Groups

(6) A sample having a thickness of 0.15 to 0.3 mm was cut out of the surface of the molded article, and the sample was manually pressed to provide a film having a thickness of 0.15 to 0.2 mm. This film was scanned 40 times and analyzed to provide an infrared absorption spectrum using a Fourier transform infrared (FT-IR) spectrometer (trade name: 1760 X, PerkinElmer Co., Ltd.). Then, a difference spectrum was obtained with a base spectrum of a sample which is completely fluorinated and thus contains no functional group. Based on the absorption peaks of the specific functional groups in the difference spectrum, the number N of the functional groups per 1×10.sup.6 carbon atoms in the sample was calculated from the following formula (A):
N=I×K/t  (A) I: absorbance K: correction coefficient t: thickness of film (mm)

(7) For reference, the absorption frequency, molar extinction coefficient, and correction coefficient of the functional groups in the present description are shown in Table 2. The molar extinction coefficient is determined from the FT-IR measurement data of a low molecular weight model compound.

(8) TABLE-US-00002 TABLE 2 Absorption frequency Molar extinction coefficient Functional group (cm.sup.−1) (l/cm/mol) Correction coefficient Model compound —COF 1883 600 388 C.sub.7F.sub.15COF —COOH free 1815 530 439 H(CF.sub.2).sub.6COOH —COOH bonded 1779 530 439 H(CF.sub.2).sub.6COOH —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, —OH 3648 104 2236 C.sub.7H.sub.15CH.sub.2OH —CF.sub.2H 3020 8.8 26485 H(CF.sub.2CF.sub.2).sub.3CH.sub.2OH —CF═CF.sub.2 1795 635 366 CF.sub.2═CF.sub.2
Water Contact Angle

(9) The water contact angle was determined using a water contact angle meter CA-A (Kyowa Interface Science Co., Ltd.).

Example 1

(10) NEOFLON PFA AP-230SH pellets (MFR 2.4 (g/10 min), Daikin Industries, Ltd.) were molded using a tube extruder to provide a tube having an outer diameter of 12 mm and a thickness of 1.1 mm. The resulting tube was cut into a length of 40 cm. This piece was put into an electron beam irradiation container of an electron beam processing system (NHV Corp.), and the inside of the container was filled with the air.

(11) The temperature inside the container was increased up to 80° C. and stabilized at this temperature. Then, 40 kGy of an electron beam was applied at an electron beam accelerating voltage of 3 MeV and an exposure intensity of 20 kGy/5 min. The water contact angle of the resulting tube on the inner surface thereof and the MFR (melt flow rate) of the tube were determined. Further, the number of the functional groups of the resulting tube was determined. The results are shown in the following Table 4.

Examples 2 and 3

(12) A tube was produced in the same manner as in Example 1, except that the temperature and atmosphere inside the container were changed as shown in the following Table 3.

Example 4

(13) NEOFLON PFA AP-230SH pellets (MFR 2.4 (g/10 min), Daikin Industries, Ltd.) were molded using a heat-press molding machine to provide a 120-mm-diameter disc-shaped and 0.3-mm-thick sheet-shaped test piece. The resulting test piece was put into an electron beam irradiation container of an electron beam processing system (NHV Corp.), and the inside of the container was filled with the air. The temperature inside the container was increased up to 150° C. and stabilized at this temperature. Then, 80 kGy in total of an electron beam was applied to the test piece at an electron beam accelerating voltage of 3 MeV and an exposure intensity of 20 kGy/5 min. The water contact angle and MFR of the resulting sheet on the surface thereof, and the number of the functional groups of the sheet were determined. The results are shown in Table 4.

Example 5

(14) The same process as in Example 4 was performed, except that the temperature inside the container was changed as shown in Table 3.

Example 6

(15) The same process as in Example 4 was performed, except that the temperature and atmosphere inside the container were changed as shown in Table 3.

Example 7

(16) NEOFLON PFA AP-230 pellets (MFR 2.2 (g/10 min), Daikin Industries, Ltd.) were molded using a heat-press molding machine to provide a 120-mm-diameter disc-shaped and 0.3-mm-thick sheet-shaped test piece. The resulting test piece was put into an electron beam irradiation container of an electron beam processing system (NHV Corp.), and the inside of the container was filled with the air. The temperature inside the container was increased up to 180° C. and stabilized at this temperature. Then, 40 kGy in total of an electron beam was applied to the test piece at an electron beam accelerating voltage of 3 MeV and an exposure intensity of 20 kGy/5 min. The water contact angle, the MFR (melt flow rate), and the number of the functional groups of the resulting sheet on the surface thereof were determined. The results are shown in Table 4.

Example 8

(17) A tube was produced in the same manner as in Example 1, except that NEOFLON PFA AP-230 pellets (MFR 2.2 (g/10 min), Daikin Industries, Ltd.) were used as the PFA material. The electron beam irradiation was performed under the conditions shown in Table 3. The results are shown in Table 4. In Example 8, the concentration of water in the air present inside the tube was 0.10 g/100 cc upon electron beam irradiation.

Comparative Example 1

(18) A tube was produced in the same manner as in Example 1, except that electron beam irradiation was not performed. The measurement results are shown in Table 4.

Comparative Example 2

(19) A compressed sheet was produced in the same manner as in Example 4, except that electron beam irradiation was not performed. The measurement results are shown in Table 4.

Comparative Example 3 and Comparative Example 4

(20) A compressed sheet was produced in the same manner as in Example 4, and irradiation was performed under the conditions as shown in Table 3. The measurement results are shown in Table 4.

Comparative Example 5

(21) A compressed sheet was produced in the same manner as in Example 7, except that electron beam irradiation was not performed. The measurement results are shown in Table 4.

(22) TABLE-US-00003 TABLE 3 Test piece Electron beam irradiation conditions Thickness Irradiation Exposure Material Form (mm) temperature (° C.) (kGy) Atmosphere Comparative PFA Tube 1.1 Not irradiated Example 1 (AP-230SH) (Outer diameter 12 mm) Example 1 1.1 80 40 Air Example 2 1.1 180 40 Air Example 3 1.1 240 40 Nitrogen + air (1 vol %) Comparative Compressed sheet 0.3 Not irradiated Example 2 Comparative 0.3 25 110 Air Example 3 Comparative 0.3 200 20 Air Example 4 Example 4 0.3 150 80 Air Example 5 0.3 180 80 Air Example 6 0.3 240 80 Nitrogen + air (1 vol %) Comparative PFA Compressed sheet 0.3 Not irradiated Example 5 (AP-230) Example 7 0.3 180 40 Air Example 8 Tube 1.1 180 100 Nitrogen + water (outer diameter 12 mm) (0.03 g/40 cm tube)

(23) TABLE-US-00004 TABLE 4 Water MFR (g/10 min) Number of functional groups (per 1 million C atoms) contact 372° C., 5 kg load OH COF COOH free COOH bond Total angle (die 2 mmØ × 8 mmH) 3636 cm.sup.−1 1880 cm.sup.−1 1815 cm.sup.−1 1779 cm.sup.−1 (per 1 million C atoms) (degrees) Comparative 2.4 0 0 0 0 0 111 Example 1 Example 1 <0.1 0 167 153 290 610 90 Example 2 <0.1 0 203 166 494 863 83 Example 3 <0.1 0 171 157 312 640 87 Comparative 2.1 0 0 0 0 0 110 Example 2 Comparative 85 0 110 15 35 150 102 Example 3 Comparative <0.1 0 88 17 38 143 105 Example 4 Example 4 <0.1 0 180 47 55 282 90 Example 5 <0.1 0 337 87 119 544 86 Example 6 <0.1 0 205 8 92 306 90 Comparative 2.2 13 29 18 0 60 101 Example 5 Example 7 <0.1 1 239 37 60 338 80 Example 8 <0.1 10 0 240 260 510 71

(24) In Comparative Example 3, the irradiation temperature was 25° C., i.e., lower than 80° C., and the exposure was 110 kGy, i.e., higher than 100 kGy. Thus, the resin was deteriorated and the MFR was high, so that the resin unfavorably became brittle and fragile. Similarly, the radiation at an irradiation temperature lower than 80° C. deteriorated the resin, so that the resin material unfavorably became brittle and fragile even though the exposure fell within the range of 40 to 100 kGy. Further, the radiation at an exposure higher than 100 kGy also deteriorated the resin, so that the resin material unfavorably became brittle and fragile even though the irradiation temperature fell within the range of 80° C. to 240° C.