JP2019070083A - Fluorine-containing copolymer composition - Google Patents

Abstract

To provide a fluorine-containing copolymer composition that forms crosslinked rubber, having excellent compression set, with at least one of tensile strength and breaking elongation being improved.SOLUTION: [1] A fluorine-containing copolymer composition contains a copolymer having a tetrafluoroethylene-based unit and a propylene-based unit, or a copolymer having a tetrafluoroethylene-based unit and a perfluoro (alkyl vinyl ether)-based unit, and silica. [2] The fluorine-containing copolymer composition described in [1] contains the silica of 20 pts.mass or less relative to the copolymer 100 pts.mass.SELECTED DRAWING: None

Description

  The present invention relates to a fluorine-containing copolymer composition.

  A crosslinked rubber formed by crosslinking a fluorine-containing copolymer is generally excellent in heat resistance, oil resistance and abrasion resistance, and is widely used in the fields of automobile, general machinery, construction, aircraft and the like. In general, crosslinked rubber is required to have good rubber physical properties such as hardness, tensile strength, tensile stress, elongation at break, compression set and the like. In order to reinforce the crosslinked rubber and improve the compression set, generally, about 30 parts by mass of carbon black is contained with respect to 100 parts by mass of the fluorine-containing copolymer (see, for example, Patent Document 1) .

WO 2009/119202

  In the case of a crosslinked rubber containing a large amount of carbon black for the purpose of improving compression set, there is a problem that tensile strength and breaking elongation become insufficient.

  The present invention provides a fluorine-containing copolymer composition having a good compression set and forming a crosslinked rubber in which at least one of tensile strength and breaking elongation is improved.

[1] A fluorine-containing fluorine-containing copolymer comprising a copolymer having a unit based on tetrafluoroethylene and a unit based on propylene, or a copolymer having a unit based on tetrafluoroethylene and a unit based on perfluoro (alkyl vinyl ether) Copolymer composition.
[2] The fluorine-containing copolymer composition according to [1], which contains the silica at a ratio of 20 parts by mass or less with respect to 100 parts by mass of the copolymer.

  According to the fluorine-containing copolymer composition of the present invention, it is possible to form a crosslinked rubber having good compression set and at least one of tensile strength and breaking elongation improved.

The following definitions of terms apply throughout the specification and claims.
The "monomer" means a compound having a polymerizable unsaturated bond. Examples of the polymerizable unsaturated bond include double bonds and triple bonds between carbon atoms.
The “unit based on monomer” is a generic term for an atomic group directly formed by polymerization of one monomer molecule and an atomic group obtained by chemical conversion of a part of the atomic group. . The “unit based on monomer” is also referred to as “monomer unit”.
An "etheric oxygen atom" is an oxygen atom which exists one between carbon-carbon atoms.
"-" Which shows a numerical range means including the numerical value described before and after that as a lower limit and an upper limit.

<Fluorinated copolymer composition>
The composition of the present invention is a copolymer having a unit based on tetrafluoroethylene (hereinafter also referred to as TFE) and a unit based on propylene, or a TFE unit and perfluoro (alkyl vinyl ether) (hereinafter referred to as PAVE). A fluorine-containing copolymer composition comprising a copolymer having a unit based on the above and diatomaceous earth.
The copolymer is obtained by a general radical polymerization method. Examples of the radical polymerization method include living radical polymerization methods such as iodine transfer polymerization method in which radical polymerization is performed in the presence of elemental iodine or an iodine compound.

Examples of the copolymer having a TFE unit and a propylene unit (hereinafter, also referred to as P unit) include the copolymers described in WO 2009/119202 and WO 2017/057512.
Examples of the copolymer having TFE units and PAVE units include the copolymers described in US Pat. No. 4,035,565 and WO 2010/082633.

The following (1)-(2) can be illustrated as a preferable copolymer.
(1) A copolymer having TFE units and P units, wherein the total of TFE units and P units is 65 to 100 mol% with respect to all units (hereinafter referred to as TFE-P copolymer).
(2) A copolymer having TFE units and PAVE units, wherein the total of TFE units and PAVE units is 50 to 100 mol% with respect to all units (hereinafter referred to as TFE-PAVE copolymer).

(1) The following (1-1) and (1-2) can be illustrated as a TFE-P type copolymer.
(1-1) The total of TFE units and P units is 65 to 100 mol%, and the molar ratio of TFE units / P units is 30/70 to 70/30, preferably 45/55 to 65/35, more preferably The copolymer is 50/50 to 60/40. You may contain 0.01-5.0 mass% of iodine atoms.
As other units other than TFE unit and P unit, the unit based on the following other monomers can be illustrated.
As another monomer, fluorinated olefins such as monofluoroethylene, trifluoroethylene, trifluoropropylene, pentafluoropropylene, hexafluoropropylene, hexafluoroisobutylene, dichlorodifluoroethylene, etc .; ethylene, 1-butene, isobutylene etc. Hydrocarbon olefins; alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether) and cyclohexyl vinyl ether; vinyl esters such as vinyl acetate and vinyl propionate; vinyl chloride, vinylidene chloride and trifluorostyrene.
35 mol% or less is preferable with respect to all the units, as for another unit, 33 mol% or less is more preferable, and 31 mol% or less is more preferable.

(1-2) TFE unit, P unit, and one or more units of unit I based on monomer I represented by the following formula (I), wherein the total of TFE unit, P unit and unit I is 98 to 100 moles % Copolymer. You may contain 0.01-5.0 mass% of iodine atoms.
CR ¹ R ² = CR ³ -R ⁴ -CR ⁵ = CR ⁶ R ⁷ (I)
(In formula (I), R ¹ , R ² , R ³ , R ⁵ , R ⁶ and R ⁷ are each independently a hydrogen atom, a fluorine atom or a methyl group, and R ⁴ has 1 carbon atom Or a perfluoroalkylene group of 10 to 10 or a group having an etheric oxygen atom between both ends, one end or a carbon-carbon bond of the perfluoroalkylene group.
As monomer I, CF ₂ CCFO (CF ₂ ) ₃ OCF = CF ₂ , CF ₂ CCFO (CF ₂ ) ₄ OCF CFCF ₂ , CH ₂ CHCH (CF ₂ ) ₆ CH = CH ₂ is exemplified. it can.
0.1-1.5 mol% is preferable, as for content of the unit I with respect to all units, 0.15-0.8 mol% is more preferable, and 0.25-0.6 mol% is more preferable.
The molar ratio of TFE units / P units is preferably 30/70 to 99/1, more preferably 30/70 to 70/30, and still more preferably 40/60 to 60/40.
As units other than TFE unit, P unit, and unit I, units based on the following fluorine-containing monomers or non-fluorinated monomers can be exemplified.
As fluorine-containing monomers, vinyl fluoride, pentafluoropropylene, perfluorocyclobutene, CH ₂ = CHCF ₃ , CH ₂ CHCHCF ₂ CF ₃ , CH ₂ CHCHCF ₂ CF ₂ CF ₃ , CH ₂ CHCHCF ₂ CF ₂ CF ₂ CF ₃ and CH ₂ = CHCF ₂ CF ₂ CF ₂ CF ₂ CF ₃ can be exemplified.
Examples of the non-fluorinated monomer include isobutylene, pentene, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate and vinyl caprylate.
2.0 mol% or less is preferable with respect to all the units, and 1.0 mol% or less is more preferable, and 0.5 mol% or less is especially preferable.

  As commercial products of TFE-P copolymer, “Afrus 100S”, “Afrus 100H”, “Afrus 150P”, “Afrus 150E”, “Afrus 150L”, “Afrus 150C”, “Afrus 150CS”, “Afrus 300S” (Above, manufactured by Asahi Glass Co., Ltd.) and the like.

(2) The following (2-1), (2-2), and (2-3) can be illustrated as a TFE-PAVE type copolymer.
(2-1) The total weight of TFE units and PAVE units is 50 to 100 moles, and the molar ratio of TFE units / PAVE units is 20/80 to 80/20, preferably 50/50 to 80/20. United. You may contain 0.01-5.0 mass% of iodine atoms.
Examples of PAVE include perfluoro (methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether), perfluoro (methoxyethyl vinyl ether), perfluoro (propoxyethyl vinyl ether) and perfluoro (propoxypropyl vinyl ether). it can.
Examples of units other than TFE units and PAVE units include chlorotrifluoroethylene, vinyl fluoride, ethylene, ethylidene norbornene, vinyl crotonate, hexafluoropropylene (HFP), and vinylidene fluoride (VdF).
50 mol% or less is preferable with respect to all the units, and 30 mol% or less is more preferable, and 10 mol% or less is further more preferable.

(2-2) The TFE unit, the PAVE unit, and one or more units of the unit II based on the monomer II represented by the following formula (II), and the total of the TFE unit, the PAVE unit, and the unit II is 50 to 100 moles % Copolymer. You may contain 0.01-5.0 mass% of iodine atoms.
CR ¹¹ R ¹² = CF-Q-R ¹³ -CO-Z (II)
(In formula (II), R ¹¹ and R ¹² are each independently a hydrogen atom or a fluorine atom, Q is a single bond or an etheric oxygen atom, R ¹³ is a fluoroalkylene group or two or more fluoroalkylenes At least one end of the group or a group having an etheric oxygen atom between carbon-carbon bonds, and -Z is -OH, -OR ¹⁴ , -NR ¹⁵ R ¹⁶ , -NR ¹⁷ NR ¹⁸ H, or NR ¹⁹ OR ²⁰ And R ¹⁴ is an alkyl group, and R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ and R ²⁰ each independently represent a hydrogen atom or an alkyl group.)
When R ¹³ is a fluoroalkylene group, the number of carbon atoms is preferably 1 to 6, and more preferably 1 to 4.
When R ¹³ is a fluoroalkylene group having an etheric oxygen atom, the number of carbon atoms is preferably 2 to 10, and more preferably 2 to 6. The etheric oxygen atom is present at one end of the fluoroalkylene group, between carbon-carbon bonds, or both.
When R ¹³ is a fluoroalkylene group having an etheric oxygen atom, a perfluoroalkylene group is preferred.
1-6 are preferable and, as for the carbon atom number of R < ¹⁴ >, 1 or 2 is more preferable.
Each of R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ and R ²⁰ independently is preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and a hydrogen atom or an alkyl group having 1 or 2 carbon atoms Is more preferred.
-Z is ^{-OR 14} is more preferable.
As monomer II,
CF ₂ = CFO (CF ₂ ) ₂ COOCH ₃ ,
CF ₂ = CFO (CF ₂ ) ₃ COOCH ₃ ,
CF ₂ = CFO (CF ₂ ) ₄ COOCH ₃ ,
CF ₂ = CFO (CF ₂ ) ₅ COOCH ₃ ,
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₂ COOCH ₃ ,
CF ₂ = CFOCF ₂ CF (CF ₃ ) O (CF ₂ ) ₃ COOCH ₃ ,
CF ₂ = CFO (CF ₂ ) ₂ O (CF ₂ ) ₂ COOCH ₃ ,
CF ₂ = CFO (CF ₂ ) ₃ O (CF ₂ ) ₂ COOCH ₃ ,
_{CH 2 = CFCF 2 OCF (CF} 3) COOCH 3,
_{CH 2 = CFCF 2 OCF (CF} 3) CF 2 OCF (CF 3) COOCH 3 can be exemplified.
By irradiation with light having a wavelength of 150 to 300 nm, -Q-R ¹³ -CO-Z of unit II causes a reaction in which -CO-Z is eliminated to produce a -Q-R ¹³ radical, resulting in two -Q By the reaction of -R ¹³ · radicals, a cross-linked structure (-QR ¹³ -R ¹³ -Q-) is formed between molecules.
0.01-100 mol% is preferable, as for content of the unit II with respect to all units, 0.1-20 mol% is more preferable, and 0.1-5 mol% is more preferable.
The molar ratio of TFE units / PAVE units is preferably 5/95 to 95/5, more preferably 20/80 to 80/20, and still more preferably 50/50 to 70/30.
As the TFE unit, the PAVE unit and the unit other than the monomer II, the unit (4) described in paragraph [0041] of WO 2015/098773 can be exemplified.
30 mol% or less is preferable with respect to all the units, and, as for another unit, 10 mol% or less is more preferable.
0.1-4 mmol / g is preferable, as for content of group represented by -CO-Z per 1 g of the said copolymer, 0.1-3 mmol / g is more preferable, 0.3-1 mmol / g Is more preferred.

(2-3) a total of 50 to 100 moles of TFE units and PAVE units, and the molar ratio of TFE units / PAVE units is 92/8 to 99/1, more preferably 95/5 to 99/1 Polymer. You may contain 0.01-5.0 mass% of iodine atoms.
As other units other than a TFE unit and a PAVE unit, the unit based on the other monomer of said (2-1) can be illustrated.
10 mol% or less is preferable with respect to all the units, and, as for another unit, 5 mol% or less is more preferable.

  As commercially available products of TFE-PAVE copolymer, Viton GLT, Viton GFLT (above, manufactured by DuPont Elastomers), etc. are exemplified.

  The storage shear elastic modulus G 'of the copolymer is preferably 100 kPa to 600 kPa, more preferably 200 kPa to 500 kPa, and still more preferably 200 kPa to 400 kPa. The larger the storage shear modulus G ', the higher the molecular weight of the polymer and the higher the density of molecular chain entanglement. When the storage shear modulus G 'of the copolymer is in the above range, good rubber physical properties of the crosslinked rubber can be easily obtained. The value of the storage shear modulus G 'is a value measured by the method described later.

  The silica contained in the composition of the present invention may be either hydrophobic silica or hydrophilic silica. Hydrophobic silica is a silica particle the surface of which is hydrophobized using a hydrophobic compound, the surface of which is hydrophobic, with little or no hydrophilic functional group on the surface. Hydrophilic silica is a silica particle which is not hydrophobized using a hydrophobic compound and whose surface is hydrophilic. Usually, many hydroxyl groups are present on the surface of hydrophilic silica particles. By containing at least one of hydrophobic silica and hydrophilic silica in the composition of the present invention, it is possible to improve rubber physical properties such as compression set, tensile strength and elongation at break of a crosslinked rubber formed from the composition. Can.

  Examples of hydrophobic compounds used for hydrophobizing treatment of silica include dimethylsilyl (dimethyldichlorosilane), hexamethyldisilazane (trimethylsilyl), silicone oil (dimethylpolysiloxane), dimethylsiloxane, aminoalkylsilyl, alkylsilyl and methacrylsilyl. Etc. are illustrated.

The specific surface area of the silica is preferably 20 m ² / g or more, more preferably 30 or more and 500 or less m ² / g, and still more preferably 50 or more and 450 or less m ² / g. When the specific surface area of silica is in the above range, the rubber physical properties of the crosslinked rubber can be easily improved.

  The apparent specific gravity of silica is preferably 20 to 300 g / L, more preferably 30 to 250 g / L, and still more preferably 40 to 200 g / L. When the apparent specific gravity of silica is in the above range, the rubber physical properties of the crosslinked rubber can be easily improved.

  5-50 nm is preferable, as for the average primary particle diameter of a silica, 6-45 nm is more preferable, and 7-40 nm is especially preferable. When the average primary particle size is within the above range, the dispersibility of silica in the composition is likely to be enhanced.

Silica is generally classified into wet silica and dry silica based on its production method. From the viewpoint of preventing void defects when molding and processing a crosslinked rubber, dry silica is preferable.
Silica is commercially available, and examples thereof include AEROSIL 50, 200, 300, NAX 50, R 972 V, R 9200, RX 200, R 8 200, RX 300-5, and the like manufactured by Nippon Aerosil. The silica contained in the composition may be used alone or in combination of two or more.

  1-50 mass parts is preferable with respect to 100 mass parts of copolymers, as for content of the silica in the said composition, 5-30 mass parts is more preferable, and 10-20 mass parts is more preferable. When the content is within the above range, the rubber physical properties of the crosslinked rubber can be easily improved.

The composition of the present invention preferably contains a crosslinking agent. When the crosslinking agent is contained, a crosslinked product obtained by crosslinking the copolymers in the composition can be easily obtained. The crosslinked product is usually a crosslinked rubber having rubber elasticity.
Examples of the crosslinking agent include organic peroxides, polyols, amines and triazines. Among these, organic peroxides are preferable in terms of easily obtaining a crosslinked rubber excellent in rubber physical properties.
As the organic peroxide, one having a temperature at which the half life becomes 1 minute is 130 to 220 ° C. is preferable. Specifically, dibenzoyl peroxide, dicumyl peroxide, di (tert-butyl) peroxide, tert-butyl peroxyacetate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxybenzoate, 2,5-dimethyl-2,5- Bis (tert-butylperoxy) hexane, 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexyne-3, α, α′-bis (tert-butylperoxy) -p-diisopropylbenzene, 2, 5-dimethyl-2,5-bis (benzoylperoxy) hexane and the like are exemplified. The crosslinking agent contained in the composition may be one kind alone, or two or more kinds.
0.01-10 mass parts is preferable with respect to 100 mass parts of copolymers, and, as for content of the organic peroxide in the said composition, 0.1-5 mass parts is more preferable. When the content is within the above range, a crosslinked rubber having excellent physical properties is easily obtained.

It is preferable that the composition of the present invention contains a coagent. When the crosslinking assistant is contained, crosslinking between the copolymers in the composition proceeds smoothly, and a crosslinked rubber having excellent physical properties can be obtained.
As a crosslinking coagent, the compound which has a 2 or more unsaturated bond in 1 molecule is illustrated. Specific examples of the crosslinking assistant include triallyl cyanurate, triallyl isocyanurate, bismaleimide, ethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, trimethylolpropane trimethacrylate, divinyl benzene and the like. Be done. Among these, triallyl cyanurate and triallyl isocyanurate are preferable. The crosslinking aid contained in the composition may be used alone or in combination of two or more.
0.1-10 mass parts is preferable with respect to 100 mass parts of a copolymer, and, as for content of the crosslinking adjuvant in the said composition, 0.5-7 mass parts is more preferable. When the content is within the above range, physical properties such as hardness of the crosslinked product of the composition are excellent.

The composition of the present invention may contain other components. Examples of other components include known elastomers, additives and the like which are composed of resins other than the above-mentioned copolymer.
The content of the known elastomer is preferably 0 to 50 parts by mass with respect to 100 parts by mass of the copolymer.

  The composition of the present invention may contain carbon black. Examples of carbon black include furnace black, acetylene black, thermal black, channel black, graphite and the like. Among these, furnace black or thermal black is more preferable in terms of reinforcement. Specifically, HAF-LS, HAF, HAF-HS, FEF, GPF, APF, SRF-L, SRF-LM, SRF-HM, MT and the like are exemplified. The carbon black contained in the composition may be one kind alone, or two or more kinds.

  The content of carbon black in the composition is preferably 1 to 20 parts by mass, and more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the copolymer.

Examples of the additive include fillers, processing aids, dispersion aids, plasticizers, softeners, antiaging agents, adhesion aids and the like.
As fillers other than silica and carbon black, quartz powder, diatomaceous earth, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, mica powder, aluminum sulfate, calcium sulfate And barium sulfate, asbestos, graphite, wollastonite, molybdenum disulfide, carbon fiber, aramid fiber, various whiskers, glass fiber and the like.
Examples of processing aids include sodium stearate, calcium stearate, fatty acid derivatives such as stearic acid amide, natural waxes, synthetic waxes and the like. Examples of the dispersion aid include higher fatty acids and metal amine salts thereof. Examples of the plasticizer include phthalic acid derivatives, adipic acid derivatives and sebacic acid derivatives. Examples of the softener include lubricating oil, process oil, coal tar and castor oil.
As the antiaging agent, phenylenediamine, hindered amine, phosphate, quinoline, cresol, phenol, dithiocarbamate metal salt and the like are exemplified. Examples of adhesion promoters include silane coupling agents and titanate coupling agents. In addition, colorants, ultraviolet light absorbers, flame retardants, oil resistance improvers, foaming agents, anti-scorch agents, tackifiers, lubricants and the like can be added as required.

  The composition of the present invention is a copolymer, a silica, and, if necessary, a crosslinking agent, a crosslinking aid, a processing aid, a filling, by a kneading method using a kneading apparatus such as a roll, a kneader, a Banbury mixer, and an extruder. It can be prepared by mixing with other ingredients such as wood.

  The Mooney viscosity of the composition of the present invention is preferably 10 to 130. When the Mooney viscosity is in the above range, processability, mechanical properties of the crosslinked product, and the like tend to be favorable. The Mooney viscosity of the composition is measured using SMV-201 manufactured by Shimadzu Corporation according to JIS K6300-1: 2013, using an L-shaped rotor having a diameter of 38.1 mm and a thickness of 5.54 mm, and preheating time at 121 ° C. The value is measured by setting the rotor rotation time to 4 minutes for 1 minute.

<Method of producing crosslinked rubber>
By crosslinking (vulcanizing) the composition of the present invention, a crosslinked rubber is obtained. The composition may be formed into a desired shape and then crosslinked, or may be formed after crosslinking. The molding method and the crosslinking method are not particularly limited, and known methods may be applied. Examples of the crosslinking method include hot press crosslinking, steam crosslinking, hot air crosslinking, lead-free crosslinking and the like. The crosslinking treatment may be performed separately for the primary crosslinking and the secondary crosslinking. By crosslinking in two steps, the rubber properties and the like of the crosslinked rubber can be stabilized. As primary crosslinking conditions, a method of heating at 100 to 200 ° C. for several seconds to 24 hours is exemplified. As secondary crosslinking conditions, a method of heating at 100 to 300 ° C. for about 30 minutes to 48 hours is exemplified.

60-99 are preferable, as for the hardness of the crosslinked rubber which consists of said composition, 60-90 are more preferable, and 65-85 are more preferable.
100% or more is preferable, 150% or more of the elongation at break of the crosslinked rubber which consists of said composition is more preferable, and 200% or more is still more preferable. The upper limit is not particularly limited, but is usually 500% or less.
The tensile strength (strength) of the crosslinked rubber comprising the composition is preferably 8 MPa or more, more preferably 10 MPa or more, and still more preferably 15 MPa or more. The upper limit is not particularly limited, but is usually 40 MPa or less.
The 100% tensile stress of the crosslinked rubber comprising the above composition is preferably 3 MPa or more, more preferably 4 MPa or more, and still more preferably 5 MPa or more. The upper limit is not particularly limited, but is usually 15 MPa or less.
50% or less is preferable, as for the compression set of the crosslinked rubber which consists of said composition, 40% or less is more preferable, and 30% or less is more preferable. The lower limit is not particularly limited, but is usually 1% or more.
The specific gravity of the crosslinked rubber comprising the composition is usually in the range of 1.4 to 1.8.
The hardness, breaking elongation, tensile strength, tensile stress, compression set and specific gravity of the above crosslinked rubber are values measured by the method described later.

(Mechanism of action)
Since the fluorine-containing copolymer composition of the present invention contains silica, it has the same good compression set as when a large amount of carbon black is added, and other physical properties which are difficult to realize by the addition of carbon black, That is, at least one of the tensile strength and the breaking elongation forms a crosslinked rubber. It is speculated that the hardness, structural stability, chemical stability, etc. of silica contribute to the improvement of the physical properties of the crosslinked rubber.

  EXAMPLES The present invention will be described in more detail using the following examples, but the present invention is not limited to these examples.

<Measurement method>
[Composition of copolymer]
The composition (molar ratio of each unit) of the copolymer was determined by ¹⁹ F-nuclear magnetic resonance (NMR) analysis, fluorine content analysis, and infrared absorption spectrum analysis.
[Iodine content of copolymer]
The iodine content in the copolymer was quantified by an apparatus combining an ion chromatograph and a sample processing apparatus for automatic sample burner ion chromatograph AQF-100 manufactured by Dia Instruments.
[Storage shear modulus G 'of copolymer]
A value measured at a temperature of 100 ° C., an amplitude of 0.5 degree, and a frequency of 50 times / minute according to ASTM D5289 and D6204 using RPA2000 manufactured by Alpha Technologies, Inc., was defined as a storage shear modulus G ′.

<Evaluation of physical properties of crosslinked rubber>
[100% tensile stress, tensile strength, elongation at break, hardness]
The fluorine-containing copolymer composition is primarily crosslinked by heat pressing at 160 ° C. for 10 minutes, and then heated in an oven at 200 ° C. for 4 hours for secondary crosslinking to obtain a sheet of crosslinked rubber having a thickness of 2 mm. The The obtained crosslinked rubber sheet was punched out using a No. 3 dumbbell to prepare a sample.
100% tensile stress, tensile strength and breaking elongation were measured according to JIS K6251.
The hardness (Shore A) was measured according to JIS K6253.

[Measurement of specific gravity]
The specific gravity of the crosslinked rubber was measured by a method according to JIS K6220-1 using a densitometer manufactured by Shin Koden Co., Ltd.

[Measurement of compression set (CS)]
The fluorine-containing copolymer composition is primarily crosslinked by heat pressing at 160 ° C. for 10 minutes, and then heated in an oven at 200 ° C. for 4 hours for secondary crosslinking to form a crosslinked rubber plate having a thickness of 12.5 mm. Obtained. Using the crosslinked rubber plate, a compression set test was conducted at 200 ° C. for 70 hours according to JIS K6262, and the compression set of the crosslinked rubber was measured.

<Components contained in the fluorine-containing copolymer composition>
Copolymer A: A copolymer having TFE units, C3DVE units and P units, the ratio of TFE units is 56 mol% and the ratio of P units is 43.8% of the total of all units constituting the copolymer A Mole%, the proportion of C3DVE units is 0.2 mol%, G ′ = 330 kPa, and 0.5 mass% of iodine atoms are contained with respect to the total mass of the copolymer.
Copolymer B: A copolymer having TFE units and P units, the ratio of TFE units is 56 mol%, the ratio of P units is 44 mol%, and G ′ with respect to the total of all units constituting the copolymer B. = 280 Pa, containing 0.4% by mass of iodine atom based on the total mass of the copolymer.
Copolymer C: AFRAS 150P (product name, manufactured by Asahi Glass Co., Ltd.), a copolymer having TFE units and P units, the ratio of TFE units is 54 mol% with respect to the total of all units constituting the copolymer C. The proportion of P units is 46 mol%, G ′ = 240 Pa.
Copolymer D: Copolymer having TFE units and perfluoro (methyl vinyl ether) units (PMVE units), the proportion of TFE units is 69 mol% with respect to the total of all units constituting the copolymer D, PMVE units The ratio of G is 31 mol%, G ′ = 540 Pa, and the iodine atom is contained at 0.15 mass% with respect to the total mass of the copolymer.
Hydrophilic silica A: AEROSIL 50 (product name), specific surface area 50 ± 15 m ² / g, apparent specific gravity about 50 g / L, average primary particle diameter 30 nm, manufactured by Nippon Aerosil Co., Ltd.
Hydrophilic silica B: AEROSIL 200 (product name), specific surface area 200 ± 25 m ² / g, apparent specific gravity about 50 g / L, average primary particle diameter 12 nm, manufactured by Nippon Aerosil Co., Ltd.
Hydrophilic silica C: AEROSIL 300 (product name), specific surface area 300 ± 30 m ² / g, apparent specific gravity about 50 g / L, average primary particle diameter 7 nm, manufactured by Nippon Aerosil Co., Ltd.
Hydrophobic silica A: AEROSIL NAX 50 (product name), specific surface area 40 ± 10 m ² / g, apparent specific gravity about 60 g / L, average primary particle diameter 40 nm, manufactured by Nippon Aerosil Co., Ltd.
Hydrophobic silica B: AEROSIL R972V (product name), specific surface area 110 ± 20 m ² / g, apparent specific gravity about 90 g / L, average primary particle diameter 16 nm, manufactured by Nippon Aerosil Co., Ltd.
Hydrophobic silica C: AEROSIL R9200 (product name), specific surface area 170 ± 20 m ² / g, apparent specific gravity about 200 g / L, average primary particle diameter 12 nm, manufactured by Nippon Aerosil Co., Ltd.
Hydrophobic silica D: AEROSIL RX 200 (product name), specific surface area 140 ± 25 m ² / g, apparent specific gravity about 50 g / L, average primary particle diameter 12 nm, manufactured by Nippon Aerosil Co., Ltd.
Hydrophobic silica E: AEROSIL R8200 (product name), specific surface area 160 ± 25 m ² / g, apparent specific gravity about 140 g / L, average primary particle diameter 12 nm, manufactured by Nippon Aerosil Co., Ltd.
Hydrophobic silica F: AEROSIL RX300-5 (product name), specific surface area 300 ± 30 m ² / g, apparent specific gravity about 50 g / L, average primary particle diameter 7 nm, manufactured by Nippon Aerosil Co., Ltd.
Carbon black A: MT-C (product name) manufactured by Asahi Carbon Co., Ltd.
Carbon black B: Siest S (product name) manufactured by Tokai Carbon Co., Ltd.
Crosslinking auxiliary A: triallyl isocyanurate, TAIC WH-60 (product name), manufactured by Nippon Kasei Co., Ltd.
Crosslinking auxiliary agent B: triallyl isocyanurate, TAIC (product name), manufactured by Nippon Kasei Co., Ltd.
Filler: TiO ₂ powder.
Crosslinking agent A: 2,5-dimethyl-2,5-bis (tert-butylperoxy) hexane (abbreviation: Perhexa 25B).
Crosslinking agent B: α, α'-bis (tert-butylperoxy) -p-diisopropylbenzene (abbreviation: Percadox 14).
Processing aids: calcium stearate.

Example, Comparative Example
Each component was uniformly knead | mixed using 2 rolls by the mixing | blending (mass ratio) shown to Tables 1-4, and the fluorine-containing copolymer composition was prepared. About each composition, the test article of crosslinked rubber was produced by the method mentioned above, and the physical property was evaluated. The results are shown in Tables 1 to 4.
In the table, Test Examples 1, 20, 24, and 28 are comparative examples, and the other test examples are examples.

  The crosslinked rubbers of the examples containing silica had good compression set and at least one of tensile strength and breaking elongation was improved.

Claims (2)

  A fluorine-containing copolymer comprising a copolymer having a unit based on tetrafluoroethylene and a unit based on propylene, or a copolymer having a unit based on tetrafluoroethylene and a unit based on perfluoro (alkyl vinyl ether), and silica Composition.   The fluorine-containing copolymer composition according to claim 1, wherein the silica is contained in a ratio of 20 parts by mass or less with respect to 100 parts by mass of the copolymer.