JP5224315B2 - Radiation-crosslinked fluorine-containing copolymer - Google Patents

Description

  The present invention relates to a radiation-crosslinked fluorine-containing copolymer. More specifically, the present invention relates to a radiation-crosslinked fluorine-containing copolymer that is suitably used in a radiation irradiation environment such as a nuclear facility or space.

  The fluorine-containing copolymer is a fluorine-containing monomer such as vinylidene fluoride, tetrafluoroethylene, hexafluoropropene, chlorotrifluoroethylene, perfluoro (propyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (methyl vinyl ether). ) Etc., and has various properties from the elastomer region to the resin region, but since all are fluorine-containing copolymers, thermal stability at high temperatures and extremely low temperatures It has excellent toughness and flexibility, as well as excellent chemical resistance, chemical stability, non-adhesiveness, low friction properties, and excellent electrical properties. have. For this reason, fluorine-containing copolymers are used in various fields such as semiconductors, automobiles, architecture, electricity / electronics, and foods.

  Among them, polytetrafluoroethylene [PTFE], tetrafluoroethylene-perfluoro (propyl vinyl ether) copolymer [PFA], tetrafluoroethylene-hexafluoropropene copolymer [FEP] were bonded to the main chain carbon atom. Since it is a perfluoro copolymer in which all hydrogen atoms are substituted with fluorine atoms, it is particularly excellent in chemical resistance and heat resistance, and also in weather resistance and electrical insulation, so it can be used in various fields. Is planned.

  However, since these fluorine-containing resins are crystalline resins having low rubber characteristics, they have a property of easily developing a creep phenomenon even at a temperature as low as room temperature, and there is a demand for imparting rubber characteristics. In addition, these fluorine-containing resins are extremely sensitive to radiation and are typical radiation-decomposable polymers, so that they are difficult to use in a radiation environment such as a nuclear facility.

Therefore, by providing radiation resistance and rubber properties, it can be used in a radiation environment such as nuclear facilities and outer space, and can be used for sealing materials and packing materials. Various proposals have been made for the purpose.
Japanese Patent No. 3,317,452 Japanese Patent No. 3,337,785 Japanese Patent No. 3,563,928 JP-A-9-278907 JP 2002-327068 A JP-A-6-136218 JP-A-6-136004 JP-A-9-316265

  However, in the perfluoropolymer, there is a problem that the crosslinking reaction does not proceed and the decomposition reaction takes place preferentially unless irradiation is performed at a temperature near the crystal melting point. Further, the temperature range in which the crosslinking reaction proceeds is narrow and has a problem that it is difficult to control.

PTFE, a kind of perfluoropolymer, cannot be melt-molded, so it is difficult to obtain a processed product with a complicated shape. It requires post-processing. On the other hand, with PFA, FEP, etc., which can be melt-formed, it is possible to form a molded product having a complicated structure, but it is still necessary to irradiate near the crystalline melting point. At that time, there is a problem that the control of the irradiation condition is complicated, for example, an auxiliary substrate for holding the shape of the processed product is required.
JP 2001-254839 A JP 2003-49950 A

The present applicants first used a tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer having a crystal melting heat ΔH of 10 J / g or less as a fluorine-containing copolymer that can be radiation-crosslinked under mild conditions. ( Patent No. 4,883,756 ). However, when the molded article made of such a radiation-crosslinked fluorine-containing copolymer is used for a sliding part component such as an electric wire insulator or a bearing in the field of transportation equipment such as an aircraft or an automobile, the mechanical properties or Further improvements in compression set resistance were required.

  An object of the present invention is to provide a radiation-crosslinked fluorine-containing copolymer that is capable of radiation crosslinking under milder conditions and has good mechanical properties or compression set resistance properties even under high temperature conditions of 100 ° C. or higher. It is to provide.

The object of the present invention is to provide a general formula per 100 parts by weight of tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer having a heat of crystal fusion ΔH of 10 J / g or less.
CF ₂ = CFO-Rf-OCF = CF ₂
(Wherein Rf is a fluoroalkylene group having 1 to 15 carbon atoms and may contain an etheric oxygen atom) 0.1 to 10 parts by weight of a fluorine-containing divinyl polyether compound represented by This is achieved by a radiation-crosslinked fluorine-containing copolymer that has been irradiated with a fluorine-containing copolymer composition.

The radiation-crosslinkable fluorine-containing copolymer used in the present invention is not only capable of being crosslinked by irradiation under mild conditions such as 100 ° C. or less among various perfluoropolymers, but also fluorine-containing divinyl polyether. Compound CF ₂ = CFO-Rf-OCF = CF ₂ improves the moldability by adding a predetermined amount, and further improves the mechanical properties or compression set resistance properties of the molded product at higher temperatures such as 100 ° C or higher. It is possible to achieve improvement and is suitable for use as a molded article used in a radiation irradiation environment such as a nuclear facility or outer space.

  In addition, it is also used for medical instruments that can be sterilized by radiation, and also uses its rubber properties, electrical insulation properties, etc., and molded products such as liquid crystal, seal parts in the field of semiconductor manufacturing equipment, and roller parts for conveyance , Fuel cell electrolyte membrane substrates in the energy field (for example, fluorine-containing polymer ion exchange membranes), electric cables and other wire insulators or harnesses in aircraft, automobile and other transportation equipment fields, and POF and other engines It can be used for various applications such as parts for sliding parts such as cables and bearings.

Tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer as a fluorine-containing copolymer that is cross-linked by irradiation, as perfluoro (alkyl vinyl ether) [FAVE] copolymerized with tetrafluoroethylene [TFE] Perfluoro (methyl vinyl ether) [FMVE], perfluoro (ethyl vinyl ether) [FEVE], perfluoro (propyl vinyl ether) [FPVE] is generally used,
CF ₂ = CFO [CF ₂ CF (CF ₃ ) O] _n CF ₃ (n: 2 to 6)
Perfluoro (alkoxyalkyl vinyl ether) represented by

  Preferable fluorine-containing copolymers include TFE-FMVE copolymers, and those having an FMVE content of 38 to 56% by weight, preferably 42 to 52% by weight, are used.

As these fluorine-containing copolymers, those having a heat of crystal fusion ΔH of 10 J / g or less, preferably 8 J / g or less, particularly preferably non-detectable are used. When a material having a ΔH higher than this is used, radiation crosslinking is not realized at an irradiation temperature of 100 ° C. or less, and a radiation-decomposable fluorine-containing copolymer is obtained. As for such a fluorinated copolymer, the disclosure of its copolymer composition and the like is found in the following Patent Document 11, but it shows a specific radiation crosslinking property, its radiation crosslinking property and crystal melting heat amount ΔH. There is no teaching or suggestion about this relationship.
JP 2003-246823 A

  Further, the molecular weight of the obtained fluorine-containing copolymer is not particularly limited, but MFR (melt flow rate; 260 ° C.) as an index of molecular weight is about 0.01 to 100 g / 10 min, preferably about 0.1 to 70 g / 10 min. It is desirable that The MFR can be changed by a molecular weight regulator such as isopropanol.

The copolymerization reaction for obtaining the fluorinated copolymer is also carried out by a solution polymerization method, a suspension polymerization method or the like, but an aqueous emulsion polymerization method is preferred from the viewpoint of the polymerization rate and the uniformity of composition distribution. As the emulsifier used in this polymerization method, fluorinated carboxylates such as ammonium perfluorooctanoate and ammonium perfluoroheptanoate are generally used. From the viewpoint of easy removal of the residual emulsifier,
CF ₃ (CF ₂ ) ₂ O (CF (CF ₃ ) CF ₂ O] _n CF (CF ₃ ) COONH ₄
(n: 1 or 2)
Is preferred. These emulsifiers are used as an aqueous solution having a concentration of about 0.1 to 30% by weight, preferably about 1 to 20% by weight. If the amount (concentration) of the emulsifier is less than this, not only the monomer and the produced copolymer cannot be uniformly dispersed in the aqueous medium, but also a non-uniform composition distribution. On the other hand, if the amount of emulsifier used is larger than this, it is economically disadvantageous.

In the aqueous emulsion polymerization method, a water-soluble inorganic peroxide such as ammonium persulfate, potassium persulfate or sodium persulfate or a redox system in combination with a reducing agent such as sodium bisulfite or sodium sulfite may be used as a polymerization initiator. it can. Further, in order to adjust the pH in the polymerization system, Na ₂ HPO ₄ , NaH ₂ PO ₄ , K ₂ HPO ₄ , KH ₂ PO _{4 and the} like can be used, but preferably ammonia water (concentration of about 10 to 30). % By weight) is used.

  The copolymerization reaction by this polymerization method is generally carried out under conditions of a pressure of about 0 to 5 MPa · G, preferably about 0.3 to 2 MPa · G, a temperature of about 0 to 100 ° C, preferably about 20 to 80 ° C.

After completion of the reaction, the aqueous emulsion is coagulated in an aqueous salt solution such as CaCl ₂ , NaCl, or potassium alum, or in an alcohol solvent such as methanol or ethanol, or a ketone solvent such as acetone, methyl ethyl ketone, or methyl isobutyl ketone. The aqueous emulsion is added dropwise. In order to further reduce the amount of impurities contained in the fluorinated copolymer, freeze coagulation, coagulation using a water-soluble organic solvent, coagulation using a cationic surfactant, etc. It can also be applied.

  Moreover, the solution polymerization method and suspension polymerization method which can reduce the impurity content derived from a polymerization raw material more easily can also be employ | adopted. In the case of the solution polymerization method, an organic solvent such as chlorofluorocarbon, hydrochlorocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, hydrocarbon, perfluoro compound, alcohol or the like is used as a polymerization solvent, and in the case of suspension polymerization method, What added water to these organic solvents can be used as a polymerization solvent.

  As the polymerization initiator used in the solution polymerization method, for example, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, azo-based ones, and the like can be used, but considering the heat resistance of the resulting copolymer, It is desirable to use a fluorine-based, preferably perfluoro-based radical initiator. The amount of radical initiator used is not generally determined depending on the polymerization conditions such as the polymerization solvent used and the polymerization temperature, but is generally about 0.5 to 20 mol%, preferably about 1 to 10%, based on the amount of monomer used. An amount corresponding to mol% can be added at the time of charging, and if the polymerization reaction does not proceed smoothly due to polymerization conditions, monomer composition ratio, etc., a radical initiator may be added again during the polymerization.

  The copolymerization reaction by these polymerization methods is generally carried out under conditions of a pressure of about 0.2 to 3 MPa, preferably about 0.3 to 2 MPa, a temperature of about 0 to 80 ° C, preferably about 10 to 50 ° C. In the copolymerization reaction, it is preferable to add a monomer mixture having a composition ratio substantially the same as that in the initial charge, as in the case of the aqueous emulsion polymerization method. After completion of the reaction, a predetermined fluorine-containing copolymer can be obtained by removing the organic solvent from the polymerization reaction mixture under reduced pressure, separating the aqueous layer by vacuum filtration, centrifugation and the like, and drying under reduced pressure.

  Regardless of which polymerization method is used, other copolymerizable monomers that improve normal physical property values and compression set values within the range that does not impair the radiation crosslinkability required for the fluorine-containing copolymer of the present invention, For example, you may copolymerize the fluorine-containing divinyl polyether mix | blended in the composition used by this invention.

Similarly, other copolymerizable monomers that improve normal physical property values and compression set values include cyano group-containing fluorine-based monomers such as compounds represented by the following general formula:
CF ₂ = CFRfCN
Rf: may contain an etheric oxygen atom, the following compounds are exemplified by from fluoroalkylene group C ₁ -C _15.
CF ₂ = CFO (CF ₂ ) _n OCF (CF ₃ ) CN (n = 2-6)
CF ₂ = CFO (CF ₂ ) _n CN (n = 2〜12)
CF ₂ = CFO (CF ₂ CF (CF ₃ ) 0) _m (CF ₂ ) _n CN (n = 1 to 4, m = 1 to 5)
CF ₂ = CFO (CF ₂ CF (CF ₃ ) 0) _m CF ₂ CF (CF ₃ ) CN (n = 0 to 4)

  Similarly, a fluorinated monomer containing an iodine atom and / or a bromine atom may be copolymerized in order to improve the normal state physical property value and compression set characteristic. Instead of or in addition to the introduction of iodine atoms and / or bromine atoms into the copolymer side chain by such a fluorinated monomer, iodine atoms and / or bromine atoms may be contained at the copolymer ends. .

  When the fluorine-containing copolymer side chain contains an iodine atom and / or a bromine atom, for example, perfluoro (2-bromoethyl vinyl ether), 3,3,4,4, -tetrafluoro-4-bromo-1-butene , 2-bromo-1,1-difluoroethylene, bromotrifluoroethylene, perfluoro (2-iodoethyl vinyl ether), iodotrifluoroethylene and the like.

Further, when an iodine atom and / or a bromine atom is contained at the end of the fluorine-containing copolymer, the general formula X ₁ C _n H _2n X ₂ (X ₁ : F, Br, IX ₂ : Br, I, n: 1) ~ 12) are used, and from the viewpoint of balance of reactivity and handling, n: 1 to 6 1-bromoperfluoroethane, 1-bromoperfluoroethane, 1- Bromoperfluorobutane, 1-bromoperfluoropentane, 1-bromoperfluorohexane, 1-iodoperfluoroethane, 1-iodoperfluoroepropane, 1-iodoperfluorobutane, 1-iodoperfluoropentane, 1- A copolymer containing iodine atoms and / or bromine atoms derived from iodoperfluorohexane or the like is preferably used.

Further, by setting X ₁ and X ₂ to Br and / or I, a crosslinking point can be introduced at the end of the fluorine-containing copolymer. Examples of such compounds include 1-bromo-2-iodotetrafluoroethane, 1-bromo-3-iodoperfluoropropane, 1-bromo-4-iodoperfluorobutane, 2-bromo-3-iodoperfluorobutane, Monobromomonoiodoperfluoropentane, monobromomonoiodoperfluoro-n-hexane, 1,2-dibromoperfluoroethane, 1,3-dibromoperfluoropropane, 1,4-dibromoperfluorobutane, 1,5- Dibromoperfluoropentane, 1,6-dibromoperfluorohexane, 1,2-diiodoperfluoroethane, 1,3-diiodoperfluoropropane, 1,4-diiodoperfluorobutane, 1,5-diiodo Perfluoropentane, 1,6-diiodoperfluorohexane, etc. are used.

As the fluorine-containing divinyl polyether compound represented by the general formula CF ₂ = CFO-Rf-OCF = CF ₂ blended in the fluorine-containing copolymer composition, Rf is a fluoroalkylene group having 1 to 15 carbon atoms. Some are used, which may contain an etheric oxygen atom. More specifically, the following compounds are exemplified.
CF ₂ = CFO (CF ₂ ) ₂ OCF = CF ₂
CF ₂ = CFO (CF ₂ ) ₃ OCF = CF ₂
CF ₂ = CFO (CF ₂ ) ₂ OCF (CF ₃ ) CF ₂ OCF = CF ₂
CF ₂ = CFO (CF ₂ ) ₃ OCF (CF ₃ ) CF ₂ OCF = CF ₂
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ OCF (CF ₃ ) CF ₂ OCF = CF ₂
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₃ OCF (CF ₃ ) CF ₂ OCF = CF ₂
JP 2004-175916 A

  These fluorine-containing divinyl polyether compounds are used in a proportion of 0.1 to 10 parts by weight, preferably 0.2 to 8 parts by weight, per 100 parts by weight of the fluorine-containing copolymer. If the fluorine-containing divinyl polyether compound is used in a larger or smaller proportion, the balance of mechanical properties such as tensile strength at break, tensile elongation and compression set is lost, which is not preferable. In addition, if it is used at a higher ratio, the moldability is also impaired.

  In order to improve the radiation crosslinkability, normal physical property values, and compression set characteristics of the fluorinated copolymer, a compound having a plurality of double bonds other than the above fluorinated divinyl polyether compound is added as a crosslinking aid. Also good. More specifically, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, polyethylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate Acrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, 3-chloro-2-hydroxypropane methacrylate, oligoester acrylate, triallyl isocyanurate monomer, triallyl cyanurate, triallyl trimellitate, Examples include diallyl phthalate, diallyl chlorendeate, and divinyl benzene. These crosslinking aids are used in an amount of about 20 parts by weight or less, specifically about 0.1 to 20 parts by weight, preferably 1 to 15 parts by weight, per 100 parts by weight of the fluorinated copolymer.

(n：0〜5)
で表されるビス(ビニルフェニル)アルカンまたはビス(ビニルアルキルフェニル)アルカンを配合させても良い。より具体的には、p,p-ビス(ビニルフェニル)メタン、m,m-ビス(ビニルフェニル)メタン、p,p-ビス(ビニルフェニル)エタン、m,m-ビス(ビニルフェニル)エタン等が挙げられる。これらのビス(ビニルフェニル)アルカンは、含フッ素共重合体100重量部当り約20重量部以下、具体的には約0.1〜20重量部、好ましくは0.5〜15重量部の割合で用いられる。 Similarly, in order to improve the radiation crosslinkability, normal physical properties, and compression set resistance properties, as a divinyl group-containing compound, a general formula

(n: 0 to 5)
A bis (vinylphenyl) alkane or a bis (vinylalkylphenyl) alkane represented by More specifically, p, p-bis (vinylphenyl) methane, m, m-bis (vinylphenyl) methane, p, p-bis (vinylphenyl) ethane, m, m-bis (vinylphenyl) ethane, etc. Is mentioned. These bis (vinylphenyl) alkanes are used in an amount of about 20 parts by weight or less, specifically about 0.1 to 20 parts by weight, preferably 0.5 to 15 parts by weight per 100 parts by weight of the fluorinated copolymer.

  Preparation of the fluorinated copolymer composition is carried out by blending the fluorinated copolymer with a fluorinated divinyl polyether compound, followed by mixing and kneading in a mixing roll, kneader, Banbury mixer, etc. It is obtained as a product.

  The crosslinkable fluorine-containing copolymer composition obtained by blending the fluorine-containing divinyl polyether compound can be used for compression molding, extrusion molding, calendar molding, blow molding, injection molding, etc. according to the melt viscosity value at the molding temperature. Depending on the molding method, it can be processed into various molded articles such as films, sheets, tubes, hoses, O-rings and the like.

The molded product thus obtained is modified by radiation. As the radiation quality, a radiation quality having a penetrating power is useful, and among the radiation, γ-rays, X-rays or electron beams are suitable for the present invention. When an electron beam is used as the radiation, it is desirable that the transmission power is 1 × 10 ⁶ electron volt or more, preferably 2 × 10 ⁶ electron volt or more, which has good transmission power and can be modified to the inside of the processed product.

  The irradiation environment is not particularly limited, but is preferably in the absence of oxygen, and more preferably in a vacuum (a simple method such as a vacuum pack) or nitrogen, helium, argon or the like. It is desirable to be in an active gas atmosphere. The radiation dose is preferably 10 to 2000 kGy, and if the dose is less than this, sufficient crosslinking reaction does not proceed. On the other hand, if the dose is more than this, problems such as foaming of the molded product will occur.

  The fluorine-containing copolymer used in the present invention can be irradiated with radiation at 100 ° C. or higher, for example, about 120 to 200 ° C., but radiation crosslinking at 100 ° C. or lower, preferably 60 to 0 ° C. The feature is that it is possible. On the other hand, in other perfluoropolymers such as PTFE, PFA, and FEP, irradiation with radiation at 25 ° C gives priority to the decomposition reaction, and the low molecular weight proceeds. The tensile strength at break and elongation cannot be measured.

  In addition, after the irradiation, a post-treatment step can be performed in which the molded product is held in a gas atmosphere capable of annealing or radical-stopping reaction, which is held in an oven at about 200 ° C. or lower, preferably about 50 to 180 ° C. . Examples of the gas capable of reacting with radical termination include hydrocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, hydrogen, and the like, and preferably hydrogen, methane, propane, butane, chlorofluorocarbon, and the like are used.

  Next, the present invention will be described with reference to examples.

Reference example 1
Degassing the 10L SUS316 autoclave equipped with a stirrer to vacuum,
Ion exchange water 4500g
CF ₃ (CF ₂ ) ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ 230g
Sodium bisulfite 0.13g
After repeatedly depressurizing and nitrogen replacement, and sufficiently removing oxygen in the autoclave,
ICF ₂ CF ₂ Br 7.5g
25% ammonia water 38g
And then as a copolymerization monomer tetrafluoroethylene [TFE] 175 g (61 mol%)
Perfluoro (methyl vinyl ether) [FMVE] 185g (39mol%)
When each was charged and heated to 60 ° C, the internal pressure of the autoclave became 0.85 MPa · G. Thereafter, 6.7 g of ammonium peroxodisulfate as an initiator was introduced as an about 3% by weight aqueous solution with a metering pump to initiate the polymerization reaction.

  When the internal pressure of the autoclave decreased to 0.75 MPa · G as the polymerization reaction proceeded, the operation of adding until the internal pressure reached 0.85 MPa · G was repeated until the TFE addition amount reached 775 g. At that time, FMVE was also uniformly added at a composition ratio of TFE / FMVE = weight ratio 49/51 according to the amount of TFE added. After completion of the addition, aging was performed until the internal pressure did not decrease to complete the polymerization reaction.

  Thereafter, the unreacted monomer in the autoclave is released, the emulsion is taken out, and the recovered emulsion is coagulated with 1% by weight ethanol solution of stearyltrimethylammonium chloride, separated, washed with ion exchange water and dried. 1750 g of fluorinated copolymer A was obtained.

Reference example 2
In Reference Example 1, the emulsifier was changed to 100 g of ammonium perfluorooctanoate, 4 g of isopropanol was used instead of ICF ₂ CF ₂ Br, and the initial charge amount of the copolymerization monomer was TFE 180 g (75 mol%), It changed to 160 g (25 mol%) of fluoro (propyl vinyl ether) [FPVE], and the uniform addition composition ratio was performed by TFE / FPVE = weight ratio 97/3, and the fluorine-containing copolymer B 2,900g was obtained.

With respect to these fluorine-containing copolymers, the following items were measured or evaluated.
Copolymer composition ratio: According to infrared absorption spectrum
MFR (Melt Flow Rate): Using a melt indexer manufactured by Toyo Seiki Seisakusho, put the fluorine-containing copolymer into a cylinder with an inner diameter of 9.5 mm, and an orifice with an inner diameter of 2.095 mm and a length of 8.00 mm under a piston load of 200 kg and 5 kg Extrusion amount when extruded through glass transition temperature (Tg), crystal melting point (Tm), crystal fusion heat (ΔH): Seiko Instruments DSC6220 type, temperature program from -50 ℃ to 350 ℃ The glass transition temperature when the sample is heated at a heating rate of 10 ° C / min, cooled to 30 ° C at a cooling rate of 10 ° C / min, and then heated again to 350 ° C at a heating rate of 10 ° C / min. (Tg) was measured, and the endothermic peak vertex was Tm, and the endothermic heat amount of the endothermic peak was ΔH. Tensile strength and elongation: In accordance with JIS K-6250, using a crosslinked sheet prepared to a thickness of 2 mm, A dumbbell-shaped No. 6 test piece compliant with JIS K-6251 is punched out at a tensile speed of 200 mm / min. Measures strength at break at 100 ° C and elongation at break as indicators of decomposability and crosslinkability by radiation irradiation Compression set: In accordance with JIS K-6262, 25% compression is applied in the height direction of the test piece, Measure compression set values at 50 ° C, 100 ° C or 175 ° C

The results obtained in each of the above reference examples are shown in the following Table 1.
Table 1
Reference example
Measurement and evaluation items 1 2
Copolymer composition
TFE (wt%) 53 97
FMVE (wt%) 47 −
FPVE (wt%) − 3
MFR (g / 10min) 72 0
Glass transition temperature Tg (℃) -5 100
Crystal melting point Tm (℃) Not detected 312
Heat of crystal melting ΔH (J / g) Not detected 22
Tensile strength at break (MPa) 0.1 23
Tensile elongation at break (%) 140 460
Compression set
50 ℃ (%) 97 99
100 ℃ (%) 97 100
175 ℃ (%) 100 100

Examples 1-4, Comparative Examples 1-2
A fluorine-containing copolymer in which a predetermined amount of CF ₂ = CFO (CF ₂ ) ₂ OCF (CF ₃ ) CF ₂ OCF = CF ₂ [3PO-DV] is blended with the fluorine-containing copolymer A obtained in Reference Example 1. The composition is kneaded and molded, and roll processability (evaluated as ◯ for those with good winding properties and X as poor for winding properties), moldability (○ for those with a smooth molded product surface, molded with release) After evaluating the product that did not remain in its original form, it was evaluated as x), and then a prescribed amount of radiation (using ⁶⁰ Coγ rays) was applied in a vacuum atmosphere at 30 ° C, followed by annealing at 175 ° C for 10 hours. The obtained radiation-crosslinked fluorine-containing copolymer was measured for tensile break strength at 50 ° C. and 100 ° C., tensile elongation at break, and compression set at 50 ° C., 100 ° C., and 175 ° C.

The evaluation and measurement results obtained in the above Examples and Comparative Examples are shown in the following Table 2 together with the 3PO-DV blending amount and the irradiation dose with respect to 100 parts by weight of the fluorinated copolymer.
Table 2
Example Comparative Example
1 2 3 4 1 2
3PO-DV content (parts by weight) 2 4 5 5 0 20
Roll processability ○ ○ ○ ○ − ○
Formability ○ ○ ○ ○ − ×
Irradiation dose (kGy) 280 440 280 760 120-
Tensile strength at break
50 ℃ (MPa) 10 11 11 10 10-
100 ° C (MPa) 1.6 2.2 2.1 3.2 0.2-
Tensile elongation (%)
50 ℃ (MPa) 140 90 130 90 200-
100 ° C (MPa) 260 150 220 130 190-
Compression set (%)
50 ° C (MPa) 38 27 36 26 66-
100 ° C (MPa) 40 28 36 28 76-
175 ° C (MPa) 40 36 42 35 100-

Comparative Example 3
In Example 1, when the same amount of the fluorinated copolymer B obtained in Reference Example 2 was used instead of the fluorinated copolymer A, both roll processability and moldability were x.

Claims (7)

General formula per 100 parts by weight of tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer having a heat of crystal fusion ΔH of 10 J / g or less
CF ₂ = CFO-Rf-OCF = CF ₂
(Wherein Rf is a fluoroalkylene group having 1 to 15 carbon atoms and may contain an etheric oxygen atom) 0.1 to 10 parts by weight of a fluorine-containing divinyl polyether compound represented by A radiation-crosslinked fluorine-containing copolymer obtained by irradiating a fluorine-containing copolymer composition with radiation.   The radiation-crosslinked fluorine-containing copolymer according to claim 1, which has been irradiated with radiation under an irradiation condition of 100 ° C or lower.   The radiation-crosslinked fluorine-containing copolymer according to claim 2, which has been irradiated with ionizing radiation of 10 kGy or more. Perfluoro (alkyl vinyl ether) as perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether) or general formula
CF ₂ = CFO [CF ₂ CF (CF ₃ ) O] _n CF ₃
The radiation-crosslinked fluorine-containing copolymer according to claim 1, wherein a copolymer obtained by copolymerizing perfluoro (alkoxyalkyl vinyl ether) represented by the formula (where n is an integer of 1 to 6) is used.   The radiation-crosslinked fluorine-containing copolymer according to claim 1, wherein the radiation-crosslinked fluorine-containing copolymer was annealed after being irradiated in a 200 ° C or lower oven. A radiation-crosslinked fluorine-containing copolymer molded article comprising the radiation-crosslinked fluorine-containing copolymer according to any one of claims 1 to 5. The radiation-crosslinked fluorine-containing copolymer molded article according to claim 6, wherein the radiation-crosslinked fluorine-containing copolymer molded article is a film, a sheet, a tube, or a hose.