Process for producing fluorinated oligomer having COOH groups at both ends

A fluorinated oligomer having COOH groups at both end and a .rho..sub.50.degree. value of 1,000 to 10,000 is produced by swelling a fluorine rubber crosslinking product in an organic solvent, followed by decomposition in the presence of a base and a peroxide. The obtained fluorinated oligomer is soluble in solvent and thus easy to separate from fillers, etc., and can be effectively used as a chain-elongating agent for epoxy resin, isocyanate resin, oxazoline resin, etc.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a fluorinated oligomer having COOH groups
 at both end, a process for producing the same and a composition comprising
 the same together with epoxy resin, and more particularly to a fluorinated
 oligomer having COOH groups at both ends, obtained by decomposition of
 fluorine rubber crosslinking products, a process for producing the same
 and a composition comprising the same with epoxy resin.
 2. Description of Related Art
 Utilization of ordinary rubber wastes by regeneration has no positive cost
 merits, but utilization of vulcanized fluorine rubber wastes, typical of
 which are flashes generated during the rubber vulcanization-molding, is an
 important task from the viewpoint of cost reduction, because the high raw
 material cost of fluorine rubber.
 So far, the cross-linked, vulcanized fluorine rubber has been regenerated
 by mechanically pulverizing flashes, waste pieces, etc. of the
 crosslinked, vulcanized fluorine rubber, followed by plasticing, or by
 further treatment with nitric acid, potassium permanganate or various
 amines [JP-A 59-217734 and 59-217735; U.S. Pat. No. 3,291,761; DP-A 2 360
 927 and 2 420 993; Kautschuk+Gummel.multidot.Kunststoffe 23. Jahrgang,
 Heft March 1976, page 218 and ibid. 45. Jahrgang, Nr. September 1992, page
 742; Proiz-vo Shin, Rezinotekhn; Asbestotekhn. Izdfii (Moskva) 1979,vol.
 6, page 7]. The regenerated fluorine rubber is mixed with virgin rubber
 (fresh rubber) as a filler and is used as a kind of extender.
 However, the crosslinking structure of the crosslinked, vulcanized fluorine
 rubber must be decomposed to obtain the regenerated fluorine rubber from
 the crosslinked, vulcanized fluorine rubber. Furthermore, the vinylidene
 fluoride structure of vinylidene fluoride copolymer usually used in the
 fluorine rubber is actually hard to decompose under basic conditions or
 the crosslinking structure based on polyhydroxy compound (polyol) is not
 so decomposed even with a strong acid such as nitric acid, etc. as to
 regenerate and isolate the rubber moiety.
 Still furthermore, the crosslinked, vulcanized fluorine rubber contains a
 filler in almost all the cases, and it is desirable to obtain regenerated
 fluorine rubber completely freed from such a filler. It is pointed out
 that the above-mentioned regeneration procedure is not always applicable,
 depending on the crosslinking system used for the formation of
 crosslinked, vulcanized fluorine rubber, and thus is not generally
 applicable.
 On the other hand, U.S. Pat. No. 3,291,761 discloses a process for
 reclaiming revulcanizable polymers by dehydrogenfluoride reaction an
 amine-vulcanized vinylidene fluoride-hexafluoropropene copolymer and
 subjecting the resulting double bonds to oxidative decomposition, using
 KMnO.sub.4. Antipollution countermeasures are indispensable to the process
 with respect to removal of heavy metal Mn.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide an oligomer obtained by
 decomposition of fluorine rubber crosslinking products, the oligomer being
 soluble in solvents and thus easy to separate from fillers, etc. and
 effectively utilizable as a chain-elongating agent for epoxy resin,
 isocyanate resin, oxazoline resin, etc.
 The object of the present invention can be attained by a fluorinated
 oligomer having COOH groups at both ends and a .rho..sub.50.degree. value
 of about 100 to about 10,000. Such a fluorinated oligomer having COOH
 groups at both ends can be produced by swelling fluorine rubber
 crosslinking products in an organic solvent, followed by decomposition in
 the presence of a base and a peroxide.
 DETAILED DESCRIPTION OF THE INVENTION
 Fluorine rubber crosslinking products to be decomposed according to the
 present invention are wastes such as flushes, scraps, molding failures,
 etc. resulting from vulcanization molding using polyol, amine, peroxide,
 or the like. Fluorine rubber to be vulcanization-molded includes, for
 example, copolymers of vinylidene fluoride with other fluorine-containing
 olefin or olefin such as at least one of tetrafluoroethylene,
 hexafluoropropene, chlorotrifluoroethylene, pentafluoropropene,
 perfluoro(alkyl vinyl ether), propylene, etc., typically such vinylidene
 fluoride copolymers as vinylidene fluoride-hexafluoropropene copolymer,
 vinylidene fluoride-hexafluoro-propene-tetrafluoroethylene terpolymer,
 vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene
 fluoride-perfluoro(methyl vinyl ether)-copolymer, vinylidene
 fluoride-tetrafluoroethylene-perfluoro(methyl vinyl ether) terpolymer,
 etc. Besides the above-mentioned copolymers, tetrafluoroethylene
 copolymers such as tetrafluoroethylene-propylene copolymer,
 tetrafluoro-ethylene-perfluoro(methyl vinyl ether) copolymer,
 tetrafluoroethylene-perfluoro(methyl vinyl ether)-ethylene terpolymer,
 etc. can be used. The copolymers can also include copolymers with Br-
 and/or I-containing compounds, or monomers having such a crosslinkable
 group as a nitrile group, a glycidyl group, a hydroxyalkyl group, a
 perfluorophenyl group, etc.
 These fluorine rubber crosslinking products are dipped in an organic
 solvent for thorough swelling of the entirety over one day or more and
 then are subjected to decomposition treatment. Any organic solvent can be
 used for this purpose, so long as it can swell the fluorine rubber
 crosslinking products, and such a solvent includes, for examples, ketones,
 amides (i.e. dimethylformamide, dimethylacetamide, etc.),
 sulfur-containing compounds (i.e. dimethyl sulfoxide, sulfolane, etc.),
 alcohols, lower fatty acids, esters, halogen-containing compounds (i.e.
 trichlorotrifluoroethane, hexafluoroisopropanol, trifluoroethanol,
 trichloroacetic acid, etc.), or the like.
 Decomposition treatment in such a swollen state is carried out in the
 presence of a base and a peroxide. The base includes, for example,
 hydroxides, carbonates or organic acid salts of alkali metals, tertiary
 amines, tertiary phosphines, etc. The peroxide includes, for example,
 H.sub.2 O.sub.2, persulfates, peracetic acid, organic peroxides, organic
 hydroperoxides, etc. H.sub.2 O.sub.2 is most preferable from the
 economical viewpoint. Addition of the base and the peroxide can be carried
 out in the order of the peroxide to the base each all in one run or in
 divided portions.
 For the swelling in an organic solvent, it is preferable to use a phase
 transfer catalyst, typically, a quaternary onium salt such as a quaternary
 ammonium salt or a quaternary phosphonium salt, particularly in case of
 pulverized fluorine rubber crosslinking products as dispersed in a latex
 state, thereby contributing to an increase in the rate of decomposition
 reaction.
 A quaternary ammonium salt or a quaternary phosphonium salt represented by
 the following general formula can be used as a quaternary onium salt:
EQU (R.sub.1 R.sub.2 R.sub.3 R.sub.4 N).sup.+ X.sup.-
EQU (R.sub.1 R.sub.2 R.sub.3 R.sub.4 P).sup.+ X.sup.-
 where R.sub.1 to R.sub.4 are each an alkyl group having 1 to 25 carbon
 atoms, an alkoxy group, an aryl group, an alkylaryl group, an aralkyl
 group or a polyoxyalkylene group, or two or three of which may form a
 heterocyclic structure together with N or P; and X.sup.- is an anion such
 as Cl.sup.-, Br.sup.-, I.sup.-, HSO.sub.4.sup.-, H.sub.2 PO.sub.4.sup.-,
 RCOO.sup.-, ROSO.sub.2.sup.-, RSO.sup.-, ROPO.sub.2 H.sup.-,
 CO.sub.3.sup.--, etc.
 Specifically, the quaternary onium salt includes, for example, quaternary
 ammonium salts such as tetraethylammonium bromide, tetrabutylammonium
 chloride, tetrabutylammonium bromide, tetrabutylammonium iodide,
 n-dodecyltrimethylammonium bromide, cetyldimethylbenzylammonium chloride,
 methylcetyldibenzylammonium bromide, cetyldimethylethylammonium bromide,
 octadecyltrimethyl ammonium bromide, cetylpyridinium chloride,
 cetylpyridinium bromide, cetylpyridinium iodide, cetylpyridinium sulfate,
 1-benzylpyridinium chloride, 1-benzyl-3,5-dimethylpyridinium chloride,
 1-benzyl-4-phenylpyridinium chloride, 1,4-dibenzylpyridinium chloride,
 1-benzyl-4-(pyrrolidinyl)-pyridinium chloride,
 1-benzyl-4-pyridinopyridinium chloride, tetraethylammonium acetate,
 trimethylbenzylammonium benzoate, trimethylbenzylammonium-p-toluene
 sulfonate, trimethylbenzylammonium borate,
 8-benzyl-1,8-diazabicydo[5,4,0]-undec-7-enium chloride,
 1,8-diazabicyclo-[5,4,0]-undecen-7-methylammonium methosulfate,
 5-benzyl-1,5-diazabicyclo[4,3,0]-5-nonenium chloride,
 5-benzyl-1,5-diazabicyclo-[4,3,0]-5-nonenium bromide,
 5-benzyl-1,5-diazabicyclo[4,3,0]-5-nonenium tetrafluoroborate,
 5-benzyl-1,5-diazabicyclo[4,3,0]-5-nonenium hexafluorophosphate, etc., and
 quaternary phosphonium salts such as tetraphenylphosphonium chloride,
 triphenylbenzylphosphonium chloride, triphenylbenzylphosphonium bromide,
 triphenylmethoxymethylphosphonium chloride,
 triphenylmethylcarbonylmethylphosphonium chloride,
 triphenylethoxycarbonylmethylphosphonium chloride,
 trioctylbenzylphosphonium chloride, trioctylmethylphosphonium bromide,
 trioctylethylphosphonium acetate, trioctylethylphosphonium dimethyl
 phosphate, tetraoctylphosphonium chloride, cetyldimethylbenzylphosphonium
 chloride, etc.
 Decomposition temperature is not particularly limited in the decomposition
 treatment. The decomposition treatment is carried out at a temperature of
 usually about 0 to about 100.degree. C., preferably about 10.degree. to
 about 30.degree. C. from the viewpoint of exothermic control. Molecular
 weight and acid value of the decomposition product can be adjusted as
 desired by selecting a proportion of double bonds to be introduced by the
 base.
 For example, in case of vinylidene fluoride-hexafluoropropene copolymer, it
 seems that the decomposition reactions take place according to the
 following reaction mechanism:
 ##STR1##
 The decomposition reaction mixture is phase-separated with strong
 hydrochloric acid, and the coarse filler component is at first filtered
 off as filter cakes through a filter. The washing solution resulting from
 washing of the filter cakes, together with the filtrate, is charged into a
 large amount of water to conduct precipitation, followed by vigorous
 stirring for a long time. Such operations are repeated three times for
 reprecipitation. The resulting oily matters are transferred onto a glass
 dish, etc., spreaded thereon, and dried at about 65.degree. C. for about 3
 days, whereby a fluorinated oligomer having COOH groups at both ends can
 be obtained as a oily viscous liquid.
 The thus obtained fluorinated oligomer having COOH groups at both ends has
 a .rho..sub.50.degree. value of about 100 to about 10,000, preferably
 about 200 to about 2,000, as measured by a Brook field type viscometer,
 and can be used as a chain-elongating agent for epoxy resin, isocyanate
 resin or oxazoline resin, preferably for epoxy resin.
 Any one of glycidyl ether type, glycidyl ester type, glycidyl amine type,
 alicyclic type, etc. can be used for the epoxy resin. For particularly
 preferable glycidyl ether type epoxy resin, any one of bifunctional types
 of aromatic series such as bisphenol A type, bisphenol S type, brominated
 bisphenol Atype, hydrogenated bisphenol F type, bisphenol F type,
 bisphenol AF type, biphenyl type, naphthalene type, fluorene type, etc. or
 of aliphatic series such as ethyleneglycol type, etc. and multifunctional
 types such as phenol novolak type, orthocresol novolak type, DPP novolak
 type, trishydroxyphenylmethane type, tetraphenylolethane type, etc. can be
 used as the epoxy resin.
 The fluorinated oligomer having COOH groups at both ends and the epoxy
 resin can be used in a ratio of the former to the latter of generally 100
 parts by weight: about 10 to about 50 parts by weight, preferably about 10
 to about 20 parts by weight, though depending upon the epoxy equivalent
 weight. A mixture of these two components is heated at about 20.degree. to
 about 40.degree. C. for about 3 to about 60 minutes until appearance of a
 sign of elasticity, then placed into a mold heated to about 50.degree. to
 about 70.degree. C., secured as sandwiched between fluorinated resin films
 by screws, then heated at about 50.degree. to about 150.degree. C. for
 about 0.1 to about 2 hours and postcured at room temperature for about 1
 to about 30 days or at about 50.degree. to about 150.degree. C. for about
 0.1 to about 2 hours.
 The curing products are distinguished not only in vulcanization physical
 properties such as 100% modulus, tensile strength, elongation,
 elongational strain, etc., but also in solvent resistance, particularly
 hydrocarbon resistance.
 The present invention provides an oligomer having COOH groups at both ends
 by decomposition of fluorine rubber crosslinking products, the oligomer is
 soluble in solvents and thus can be easily separated from fillers, etc.
 contained in the crosslinking products, and also can be used as a
 chain-elongating agent for epoxy resin, isocyanate resin, oxazoline resin,
 etc. with effective use for a solvent-resistant sealant, adhesive, coating
 material, etc.
 PREFERRED EMBODIMENTS OF THE INVENTION
 The present invention will be described in detail below, referring to
 Examples.

EXAMPLE 1
 Polyol-crosslinked fluorine rubber crosslinking products (fluorine rubber
 content: 83.3% by weight) obtained by press vulcanizing a mixture
 consisting of 100 parts by weight of vinylidene fluoride-hexafluoropropene
 copolymer (molar ratio=75:25), 10 parts by weight of MT carbon black and
 10.1 parts by weight of other additives (magnesium oxide, calcium
 hydroxide, vulcanizing agent of diol series, etc.) were mechanically
 pulverized.
 450 g of the pulverized fluorine rubber crosslinking products, 13.9 g of
 benzyltriethylammonium chloride and 2550 g of acetone were charged into a
 glass reaction vessel having a capacity of 5,500 ml, provided with a
 dropping funnel, a stainless steel stirring vanes, a thermometer and a gas
 vent pipe, left for standing at about 20.degree. C. for 24 hours, and then
 cooled to 14.degree. C. over a water bath, followed by dropwise addition
 of 288.5 g of 33% H.sub.2 O.sub.2 over 5 minutes and successively an
 aqueous 45% KOH solution (120 g in terms of KOH) over 25 minutes.
 Temperature increase was continued over 60 minutes with gas generation.
 Then, the reaction mixture was kept at about 20.degree. to about
 25.degree. C. for 6 hours and then left for standing at room temperature
 overnight.
 The reaction mixture with no phase separation was acidified to pH2 by 130
 ml of strong hydrochloric acid and passed through a fine metallic filter
 for separation into a rough filler component and a rubber component. The
 filler component remaining solid matters on the filter was washed with 500
 g of acetone. The washing solution resulting from the washing, together
 with the filtrate, was added to a 4-fold volume of water, followed by
 vigorous stirring for 6 hours. The resulting precipitates were repeatedly
 subjected to reprecipitation treatment three times, using an aqueous 50
 wt. % acetone solution. The first purification was carried out by adding
 strong hydrochloric acid to the aqueous 50 wt. % acetone solution, thereby
 acidifying it to pH2, and next purification was carried out by
 transferring the acidified, wet materials onto a glass dish and drying the
 materials in a thinly spread liquid state at about 60.degree. to about
 65.degree. C. under a reduced pressure of 5 mmHg for 70 hours, thereby
 bringing the materials into a constant weight.
 234 g of black viscous liquid (.eta..sub.50.degree. =285 Pa.cndot.s) was
 thereby obtained and was found to be a mixture consisting of 99% by weight
 of oligomer (.eta..sub.50.degree. =250 Pa.cndot.s) and 1% by weight of
 filler, by infrared absorption spectral ratio (I.sub.1760 /I.sub.1450).
 .sup.19 F-NMR(CDCl.sub.3, CFCl.sub.3, .delta.): -115 to 120 ppm (-CF.sub.2
 COOH)
 .sup.1 H-NMR(CDCl.sub.3, TMS, .delta.): 7.6 to 7.8 ppm (--COOH)
 EXAMPLE 2
 In Example 1, after cooling to 14.degree. C. over the water bath, the
 aqueous 45 wt. % KOH solution (60 g in terms of KOH) was dropwise added to
 the mixture, followed by stirring at 20.degree. C. for 6 hours and leaving
 it for standing at room temperature for 18 hours. Then, 288.5 g of 33%
 H.sub.2 O.sub.2 was dropwise added thereto over 5 minutes and then the
 aqueous 45 wt. % KOH solution (69 g in terms of KOH) was dropwise added
 thereto over 20 minutes. Heat generation and gas generation were observed
 upon the dropwise addition of H.sub.2 O.sub.2 and heat generation was
 observed upon the dropwise addition of the aqueous KOH solution.
 Separation and purification were then carried out in the same manner as in
 Example 1.
 283.5 g of black viscous liquid (.eta..sub.50.degree. =8300 Pa.cndot.s) was
 thereby obtained, and was found to be a mixture consisting of 87% by
 weight of oligomer (.eta..sub.50.degree. =3460 Pa.cndot.s) and 13% by
 weight of filler.
 EXAMPLE 3
 In Example 1, a Kapron filter was used in place of the metallic filter,
 whereby 247.5 g of a black viscous liquid (.eta..sub.50.degree. =620
 Pa.cndot.s) was obtained and found to be a mixture consisting of 93% by
 weight of oligomer (.eta..sub.50.degree. =323 Pa.cndot.s) and 7% by weight
 of filler.
 EXAMPLE 4
 In Example 1, after cooling at 14.degree. C. over the water bath, 96.2 g of
 33% H.sub.2 O.sub.2 was dropwise added to the mixture over 2 minutes and
 then an aqueous 40 wt. % KOH solution (40 g in terms of KOH) was dropwise
 added thereto over 10 minutes. Temperature elevation by +8.degree. C. and
 gas generation were observed. Then, dropwise addition of the same amounts
 of H.sub.2 O.sub.2 and aqueous 40 wt. % KOH solution was carried out twice
 after 1.5 hours and after 3 hours.
 391.5 g of a black viscous liquid (.eta..sub.50.degree. =3100 Pa.cndot.s)
 was obtained and found to be a mixture consisting of 81% by weight of
 oligomer (.eta..sub.50.degree. =445 Pa.cndot.s) and 19% by weight of
 filler.
 EXAMPLE 5
 In Example 4, pulverized, polyol-crosslinked fluorine rubber crosslinking
 products (fluorine rubber content: 74.6% by weight) obtained by press
 vulcanizing a mixture consisting of 100 parts by weight of vinylidene
 fluoride-hexafluoropropene copolymer (molar ratio=80:20), 20 parts by
 weight of MT carbon black and 14 parts by weight of other additives
 (magnesium oxide, calcium hydroxide, bisphenol AF,
 benzyltriphenylphosphonium chloride, etc.) were used as the pulverized
 fluorine rubber crosslinking products. The amount of
 benzyltriethylammonium chloride was changed to 12.4 g, and 258.4 g of sum
 total of 33% H.sub.2 O.sub.2 and 107.4 g (in terms of KOH) of sum total of
 the aqueous 40 wt. % KOH solution were dropwise added each in 3 divided
 portions to the mixture.
 373.5 g of a black viscous liquid (.eta..sub.50.degree. =2590 Pa.cndot.s)
 was thereby obtained and found to be a mixture consisting of 67% by weight
 of oligomer (.eta..sub.50.degree. =255 Pa.cndot.s) and 33% by weight of
 filler.
 EXAMPLE 6
 In Example 4, pulverized, polyol-crosslinked fluorine rubber crosslinking
 products (fluorine rubber content: 74.6% by weight) obtained by press
 vulcanizing a mixture consisting of 100 parts by weight of vinylidene
 fluoride-hexafluoropropene copolymer (molar ratio=80:20), 35 parts by
 weight of white filler such as calcium silicate, etc., 10 parts by weight
 of Fe.sub.2 O.sub.3 and 14 parts by weight of other additives (magnesium
 oxide, calcium hydroxide, bisphenol AF, benzyltriphenylphosphonium
 chloride, etc.) were used as the pulverized fluorine rubber crosslinking
 products. The amount of benzyltriethylammonium chloride was changed to
 10.5 g, and 219.9 g of sum total of 33% H.sub.2 O.sub.2 and 90.6 g (in
 terms of KOH) of the aqueous 40 wt. % KOH solution were dropwise added
 each in 3 divided portions to the mixture.
 225 g of a dark brown viscous liquid (.eta..sub.50.degree. =2850
 Pa.cndot.s) was thereby obtained and found to be a mixture consisting of
 87% by weight of oligomer (.eta..sub.50.degree. =1750 Pa.cndot.s) and 13%
 by weight of filler.
 EXAMPLE 7
 In Example 6, the sum total of 33% H.sub.2 0.sub.2 was changed to 435.8 g.
 243 g of a dark brown viscous liquid (.eta..sub.50.degree. =410 Pa.cndot.s)
 was thereby obtained and found to be a mixture consisting of 98% by weight
 of oligomer (.eta..sub.50.degree. =430 Pa.cndot.s) and 2% by weight of
 filler.
 EXAMPLE 8
 In Example 7, the benzyltriethylammonium chloride was not used
 252 g of a dark brown viscous liquid (.eta..sub.50.degree. 340 Pa.cndot.s)
 was thereby obtained and found to be a mixture consisting of 97% by weight
 of oligomer (.eta..sub.50.degree. =325 Pa.cndot.s) and 3% by weight of
 filler.
 As a result of measurements by infrared absorption spectrum, .sup.19 F-NMR
 and .sup.1 H-NMR, it was found that the viscous liquids obtained in the
 foregoing Examples 1 to 7 were all fluorinated oligomers each having COOH
 groups at both ends.
 EXAMPLE 9
 100 parts by weight of each of the fluorinated oligomers each having COOH
 groups at both ends obtained in Examples 1 to 7 were placed into glass or
 ceramic crucibles, respectively, to which a specific amount of epoxy resin
 (Yuka-Shell Epoxy product E-154, epoxy equivalent weight: 179) was added,
 followed by mixing with stirring over 10 minutes. Then, the crucibles were
 placed into a thermostat and heated for about 3 to about 60 minutes until
 appearance of a sign of elasticity. The individual mixtures in that state
 were placed into respective molds heated to about 60.degree. C., and
 secured as sandwiched between fluorinated resin films by screws to prevent
 adhesion and attain flattening. The molds were placed into a thermostat of
 hot air circulation type and heated at 130.degree. C. for one hour. Sheets
 (120 mm.times.60 mm.times.1 mm) were taken out of the molds and further
 heated at 130.degree. C. for one hour.
 From the sheets were cut out test pieces, 2 mm thickness in the direction
 perpendicular to the grain effect direction. Test pieces were subjected to
 measurements of vulcanization physical properties according to JIS K-6301.
 The results are shown in the following Table 1.
 TABLE 1
 Epoxy Gel- 100% Elon-
 resin lation mod- Tensile Elon- gational
 Oli- parts by time ulus strength gation strain
 No. gomer weight) (min.) (MPa) (MPa) (%) (%)
 1 Exam- 15.1 30 6.3 12.4 180 5
 ple 1
 2 Exam- 14.9 30 7.2 10.4 150 5
 ple 1
 3 Exam- 13.1 15 8.2 15.1 145 5
 ple 2
 4 Exam- 14.1 40 7.0 10.8 150 5
 ple 3
 5 Exam- 14.0 40 6.5 12.4 150 5
 ple 3
 6 Exam- 12.2 50 5.9 12.8 150 5
 ple 4
 7 Exam- 9.9 25 11.7 14.3 125 5
 ple 5
 8 Exam- 13.0 25 11.6 16.9 150 5
 ple 6
 9 Exam- 14.7 25 6.6 12.8 170 10
 ple 7
 Remarks)
 Gellation time: the time until the flow ability was lost by stirring was
 visually measured
 Elongational strain: according to JIS K-6262 (100% elongation and recovery
 after 24 hours with its residual strain being measured at 23 .+-.
 2.degree. C.)
 EXAMPLE 10
 In No. 7 of Example 9, the amount of epoxy resin was changed and results as
 shown in the following Table 2 were obtained.
 TABLE 2
 Epoxy resin Gellation 100% Tensile Elongational
 (parts by time modulus strength Elongation strain
 weight) (min.) (MPa) (MPa) (%) (%)
 9.9 25 11.7 14.3 125 5
 8.0 25 9.4 10.0 110 5
 6.0 30 6.1 6.6 120 5
 -- -- -- 8.7 100 2
 EXAMPLE 11
 In Nos. 1 and 2 of Example 9, 15.0 parts by weight of epoxy resin was used,
 and heating temperature and heating time were changed, as shown in the
 following Table 3. Results as shown in the following Table 3 were
 obtained.
 TABLE 3
 Elon-
 100% Tensile Elon- gational
 modulus strength gation strain
 Heating conditions (MPa) (MPa) (%) (%) -.DELTA.w
 130.degree. C. for 7.0 11.2 170 0
 1 hr -130.degree. C. for 1 hr
 130.degree. C. for 1 hr 4.1 5.0 120 5 1.4
 -150.degree. C. for 5 hrs
 130.degree. C. for 1 hr 9.8 60 0 7.2
 -200.degree. C. for 5 hrs
 130.degree. C. for 1 hr 3.5 9.0 210 5
 -room temp. for 34 days
 (as sandwiched between
 fluorinated resin films)
 130.degree. C. for 1 hr 1.4 6.0 300 12
 -room temp. for 34 days
 (in a state freed from the
 fluorinated resin films)
 Remark)
 -.DELTA.w: change in mass by heating
 EXAMPLE 12
 In Example 9, 100 parts by weight of fluorinated oligomer having COOH
 groups at both ends obtained in Example 8 was used, and heating conditions
 were changed as shown in the following Table 4. Results as shown in the
 following Table 4 were obtained.
 TABLE 4
 Epoxy
 resin Gella- 100% Elon- Elonga-
 (parts tion mod- Tensile ga- tional
 by time Heating ulus strength tion strain
 weight) (min.) conditions (MPa) (MPa) (%) (%) -.DELTA.w
 9.3 10 130.degree. C. 2.5 6.4 150 5
 for 1 hr
 -130.degree. C.
 for 1 hr
 130.degree. C.
 for 1 hr
 -150.degree. C.
 for 5 hrs
 130.degree. C.
 for 1 hr
 -200.degree. C.
 for 5 hrs
 9.0 10 130.degree. C. 1.8 4.6 140 5
 for 1 hr
 -130.degree. C.
 for 1 hr
 130.degree. C. 3.2 4.7 145 5 0.2
 for 1 hr
 -150.degree. C.
 for 5 hrs
 130.degree. C. 4.2 6.3 130 0 0.7
 for 1 hr
 -200.degree. C.
 for 5 hrs
 7.1 10 130.degree. C. 1.2 3.5 200 3
 for 1 hr
 -130.degree. C.
 for 1 hr
 130.degree. C. 1.6 4.6 165 5 0.24
 for 1 hr
 -150.degree. C.
 for 5 hrs
 130.degree. C. 2.9 5.8 135 0 0.79
 for 1 hr
 -200.degree. C.
 for 5 hrs
 11.0 5 130.degree. C. 3.2 6.5 145 5
 for 1 hr
 -130.degree. C.
 for 1 hr
 130.degree. C. 3.8 6.8 150 5 0.17
 for 1 hr
 -150.degree. C.
 for 5 hrs
 130.degree. C. 5.6 8.7 135 0 0.65
 for 1 hr
 -200.degree. C.
 for 5 hrs
 15.2 4 130.degree. C. 5.2 8.4 130 5
 for 1 hr
 -130.degree. C.
 for 1 hr
 130.degree. C. 6.4 8.6 130 5 0.13
 for 1 hr
 -150.degree. C.
 for 5 hrs
 130.degree. C. 7.6 8.8 115 0 0.48
 for 1 hr
 -200.degree. C.
 for 5 hrs
 EXAMPLE 13
 In Example 12, Yuka-Shell epoxy product E-152 (epoxy equivalent weight:
 175), E-828 (epoxy equivalent weight: 195) or E-604 (epoxy equivalent
 weight: 120) was used as epoxy resin in addition to the Yuka-Shell epoxy
 product E-154, and results as shown in the following Table 5 were
 obtained.
 TABLE 5
 Epoxy
 resin Gella- 100% Elon- Elonga-
 (parts tion mod- Tensile ga- tional
 by time Heating ulus strength tion strain
 weight) (min.) conditions (MPa) (MPa) (%) (%) -.DELTA.w
 E-154 5 130.degree. C. 2.7 5.2 140 0
 (11.0) for 1 hr
 -130.degree. C.
 for 1 hr
 130.degree. C. 4.1 8.2 120 5 0.57
 for 1 hr
 -150.degree. C.
 for 5 hrs
 130.degree. C. 3.9 7.1 120 5 3.6
 for 1 hr
 -200.degree. C.
 for 5 hrs
 E-152 10 130.degree. C. 2.1 5.8 180 5
 (11.0) for 1 hr
 -130.degree. C.
 for 1 hr
 130.degree. C. 4.0 8.4 135 5 0.62
 for 1 hr
 -150.degree. C.
 for 5 hrs
 130.degree. C. 2.9 7.3 150 5 3.8
 for 1 hr
 -200.degree. C.
 for 5 hrs
 E-828 15 130.degree. C. 2.1 5.0 175 3
 (12.0) for 1 hr
 -130.degree. C.
 for 1 hr
 130.degree. C. 3.3 8.2 160 5 0.60
 for 1 hr
 -150.degree. C.
 for 5 hrs
 130.degree. C. 2.6 7.7 160 5 3.9
 for 1 hr
 -200.degree. C.
 for 5 hrs
 E-604 10 130.degree. C. 2.5 9.8 280 7
 (7.4) for 1 hr
 -130.degree. C.
 for 1 hr
 130.degree. C. 3.2 5.8 130 5 2.5
 for 1 hr
 -150.degree. C.
 for 5 hrs
 130.degree. C. (swollen) 14.0
 for 1 hr
 -200.degree. C.
 for 5 hrs
 EXAMPLE 14
 In Example 12, various epoxy resins were used, and the curing products were
 subjected to n-hexane or ethanol dipping test at room temperature for 7
 days or 30 days to determine percent swelling (unit: %). The results are
 shown in the following Table 6.
 TABLE 6
 Epoxy resin n-Hexane Ethanol
 (Parts by weight) 7 days 30 days 7 days 30 days
 E-154 (7) 0.5 1.0 16 (collapsed)
 E-154 (9) 0.4 0.9 18 10
 E-154 (11) 0.3 0.7 16 10
 E-154 (15) 0.3 0.6 14 10
 E-154 (11) 0.3 0.7 15 15
 E-152 (11) 0.3 0.8 19 17
 E-828 (12) 0.4 0.8 23 13
 E-604 (7.4) 0.3 0.6 20 (collapsed)
 EXAMPLE 15
 In Example 12, various epoxy resins were used and the curing products
 obtained at 130.degree. C. for one hour -130.degree. C. for one hour was
 dipped into water at 100.degree. C. for 3 hours, and changes in the
 vulcanization physical properties before and after the dipping were
 measured. Results as shown in the following Table 7 were obtained.
 TABLE 7
 Epoxy Elonga-
 resin 100% Tensile Elon- tional
 (parts modulus strength gation strain
 by weight) (MPa.) (MPa) (%) (%) -.DELTA.w
 Before dipping
 E-154 (11) 2.7 5.2 140 0
 E-152 (11) 2.1 5.8 180 5
 E-828 (12) 2.1 5.0 175 3
 E-604 (7.4) 2.5 9.8 280 7
 After dipping
 E-154 (11) 0.4 1.7 265 20 1.3
 E-152 (11) 0.3 1.7 475 75 1.3
 E-828 (12) 0.4 1.6 570 135 1.3
 E-604 (7.4) (collapsed)