JP2007246930A - Transparent elastomer composition and method for producing the same - Google Patents

Abstract

Disclosed is an elastomer molded product in which fluororesin fine particles are uniformly finely dispersed in an elastomer and excellent in mechanical strength, abrasion resistance, transparency, and the like.
A transparent elastomer composition obtained by co-coagulation of an emulsion of fluororesin fine particles having an average particle diameter of 20 to 150 nm and an emulsion of elastomer particles, wherein the fluororesin fine particles are uniformly finely dispersed in the elastomer.
[Selection figure] None

Description

  The present invention relates to a transparent composition of an elastomer and fluororesin fine particles, for example, a transparent elastomer composition in which a fluoroelastomer is finely dispersed in a fluorine-containing elastomer as a matrix. This elastomer composition can provide a molded article having improved mechanical strength, and is useful as a base elastomer for various molded articles. Further, by selecting an additive to be added to the composition, an elastomer molded product having further excellent mechanical strength and transparency can be provided.

  The addition of a fluororesin to a fluoroelastomer has heretofore been known and aims to improve the mechanical strength as a clean filler and to use the low friction characteristics of the fluororesin. Further, as a mixing method, in addition to a dry blend method using a normal rubber kneading roll, a method for increasing dispersibility using a solvent has been proposed.

  For example, in Japanese Patent Application Laid-Open No. 55-155101, a fluororubber excellent in wear resistance is obtained by blending a low molecular weight product of polytetrafluoroethylene (PTFE). Japanese Patent Laid-Open No. 63-178149 describes a method of adding and mixing PTFE powder into a fluororubber solution in order to improve the gas barrier property and mechanical strength of rubber. The publication proposes blending a large amount of fluororesin of 30 to 150 parts by weight with 100 parts by weight of rubber together with an organic solvent to lower the friction coefficient and improve the mechanical properties.

  As an example of blending a fluororesin in order to obtain cleanness, WO97 / 08239 pamphlet is composed of 5 to 50 parts by weight of fluororesin powder having an average particle size of 0.2 to 50 μm in 100 parts by weight of fluororubber. It is described that the product is excellent as a sealant for an etching apparatus, and the WO95 / 02634 pamphlet contains 2 to 50 parts by weight of a fluororesin fine powder with respect to 100 parts by weight of a rubber component. It is described that the product is a clean composition suitable for semiconductor wet processes.

  However, these prior arts are all added to and mixed with rubber (elastomer) as a matrix, and even if the dispersibility is enhanced by using a solvent, the smaller the particle size, the more difficult it is to uniformly disperse. It becomes. This is because, for example, when fluororesin fine particles are dispersed in a transparent elastomer, the fluororesin particles should be transparent if they are uniformly dispersed. An elastomer composition has not been obtained.

  If the fluororesin fine particles are not uniformly dispersed, the strength of the molded product obtained by vulcanization molding is small, and the purpose of adding the fluororesin is not sufficiently achieved.

  An object of the present invention is to provide an elastomer composition in which fine fluororesin particles are uniformly dispersed in a transparent elastomer and the effect of adding a fluororesin can be maximized.

  That is, the present invention relates to a transparent elastomer composition in which fluororesin fine particles are finely dispersed in a transparent elastomer.

  The transparent elastomer constituting the matrix is preferably a fluorine-containing elastomer, and the fluororesin fine particles are preferably fine particles having an average particle diameter of 20 to 150 nm.

  The present invention also relates to an elastomer composition comprising a crosslinking agent, optionally a crosslinking accelerator, and a filler.

  The elastomer composition of the present invention can be obtained, for example, by co-coagulation after mixing an emulsion of transparent elastomer particles and an emulsion of fluororesin fine particles.

  The present invention also relates to an elastomer molded product obtained by vulcanization molding of the elastomer composition, and further to a transparent elastomer molded product.

  In the present invention, the term “transparent” means that the haze value described later is 50% or less.

  ADVANTAGE OF THE INVENTION According to this invention, the composition which can give the elastomer molded article excellent in mechanical strength, abrasion resistance, transparency, etc. can be provided.

  The present invention achieves uniform dispersion of fluororesin fine particles, which has been difficult in the past, by a method of co-coagulation after mixing an emulsion of transparent elastomer particles and an emulsion of fluororesin fine particles.

  Whether or not the fluororesin fine particles are uniformly finely dispersed is clear when observed with a transmission electron microscope (TEM) (see FIG. 1 described later), and the transparency of the transparent elastomer as a matrix is fluororesin. It can be judged by whether or not the fine particles are maintained after mixing. That is, the blend obtained by the dry blending method in which the fluororesin fine particles having the same particle size are once coagulated and dried and then mixed by a mixing method using a solvent or a solvent is clouded. This is presumably because the fluororesin fine particles are secondary aggregated or localized and dispersed (see FIG. 2 described later).

  The elastomer composition before cross-linking of the present invention has a transparency having a haze value of 50% or less, preferably 40% or less, particularly 30% or less.

  The elastomer for a matrix used in the present invention may be a transparent elastomer that can form an emulsion in the form of particles and has an affinity for a fluororesin. From this point, a fluorine-containing elastomer is preferable.

  As the fluorine-containing elastomer, for example, the formula (1):

（式中、ｍ／ｎ＝９５〜５０／５〜５０（モル％。以下同様）、Ｒ_fは炭素数１〜８のパーフルオロアルキル基）で示される２元共重合体エラストマー（テトラフルオロエチレン（ＴＦＥ）／パーフルオロ（アルキルビニルエーテル）（ＰＡＶＥ）系エラストマー）、
式（２）：

(Wherein, m / n = 95 to 50/5 to 50 (mol%; hereinafter the same), R _f is a C 1-8 perfluoroalkyl group) and a binary copolymer elastomer (tetrafluoroethylene) (TFE) / perfluoro (alkyl vinyl ether) (PAVE) elastomer),
Formula (2):

（式中、ｌ／ｍ／ｎ＝９５〜３５／０〜３０／５〜３５、Ｒ_fは炭素数１〜８のパーフルオロアルキル基）で示される３元共重合体エラストマー（ＴＦＥ／ヘキサフルオロプロピレン（ＨＦＰ）／ＰＡＶＥ系エラストマー）など、
式（３）：

(Wherein l / m / n = 95 to 35/0 to 30/5 to 35, R _f is a C 1-8 perfluoroalkyl group) terpolymer copolymer elastomer (TFE / hexafluoro) Propylene (HFP) / PAVE elastomer), etc.
Formula (3):

（式中、ｍ／ｎ＝８５〜６０／１５〜４０）で示される２元共重合体エラストマー、
式（４）：

(Wherein, m / n = 85-60 / 15-40), a binary copolymer elastomer,
Formula (4):

（式中、ｌ／ｍ／ｎ＝８５〜２０／０〜４０／１５〜４０）で示される３元共重合体エラストマー、
式（５）：

(Wherein, 1 / m / n = 85 to 20/0 to 40/15 to 40)
Formula (5):

（式中、ｌ／ｍ／ｎ＝９５〜４５／０〜１０／５〜４５、Ｚ¹、Ｚ²およびＺ³はそれぞれ独立してフッ素原子または水素原子、Ｒ_fは炭素数１〜８のパーフルオロアルキル基）で示される３元共重合体エラストマー、または

(Wherein, l / m / n = 95 to 45/0 to 10/5 to 45, Z ¹ , Z ² and Z ³ are each independently a fluorine atom or a hydrogen atom, and R _f has 1 to 8 carbon atoms. A terpolymer elastomer represented by a perfluoroalkyl group), or

（ｌ／ｍ／ｎ＝１〜８０／０〜８０／１０〜５０、Ｒ_fは前記と同じ）などがあげられる。

(L / m / n = 1 to 80/0 to 80/10 to 50, R _f is the same as described above).

  More specifically, TFE / PAVE copolymer elastomer, vinylidene fluoride (VdF) / hexafluoropropylene (HFP) copolymer elastomer, VdF / HFP / TFE copolymer elastomer, VdF / TFE / PAVE copolymer Examples thereof include elastomers, and these elastomers may be further copolymerized with a monomer containing a small amount of a crosslinkable reactive group. Examples of the crosslinkable reactive group include an iodine atom, a bromine atom, a nitrile group, a carboxyl group, an unsaturated double bond, and a hydroxyl group.

  These fluorine-containing elastomers can be produced by an ordinary emulsion polymerization method, and the resulting emulsion, which is a polymerization reaction product, can be used as it is or in a co-coagulation described later with the concentration adjusted appropriately. Alternatively, it may be once dried and then re-emulsified and dispersed.

  Examples of the elastomer other than the fluorine-containing elastomer include hydrogenated nitrile butadiene rubber, acrylic rubber, and silicone rubber.

  The average particle diameter of the elastomer particles in the emulsion is not particularly limited, and is, for example, 10 to 800 nm, preferably 20 to 500 nm. However, if it is smaller than 10 nm, it is difficult to coagulate, and if it is larger than 800 nm, the emulsion becomes unstable and co-coagulation is difficult to be performed.

The fluororesin fine particles to be finely dispersed in the elastomer are not particularly limited. For example, (1) polytetrafluoroethylene (PTFE);
(2) TFE / CF ₂ = CF—O—R _f ¹ (FVE) copolymer (wherein the composition range exhibits non-elastomeric properties. For example, CF ₂ = CF—O—R _f ¹ is 15 mol% or less. R _f ¹ is a linear or branched fluoro- or perfluoroalkyl group, or a fluoro- or perfluorooxyalkyl group optionally having one or more ether type oxygen atoms)), for example TFE / PAVE copolymer (PFA);
(3) TFE / CF ₂ = CF-R _f ¹ copolymer (however, composition range showing non-elastomeric properties, for example, CF ₂ = CF-R _f ¹ is 15 mol% or less. R _f ¹ is the same as above. ), For example, TFE / HFP copolymer (FEP);
(4) ethylene / TFE (30 to 60/70 to 40. mol%, the same applies hereinafter) copolymer;
(5) polychlorotrifluoroethylene (PCTFE);
(6) ethylene / chlorotrifluoroethylene (CTFE) (30-60 / 70-40) copolymer;
(7) polyvinylidene fluoride (PVdF);
(8) Vinylidene fluoride (VdF) / TFE (70-99 / 30-1) copolymer;
(9) VdF / TFE / CTFE (50 to 99/30 to 0/20 to 1) copolymer;
(10) VdF / TFE / HFP (60 to 99/30 to 0/10 to 1) copolymer;
(11) ethylene / TFE / HFP (6-60 / 40-81 / 1-30) copolymer;
(12) Fine particles such as 3,3,3-trifluoropropylene-1,2-trifluoromethyl-3,3,3-trifluoropropylene-1 / PAVE (40-60 / 60-40) copolymer can give. Among these, when imparting low friction to a molded article, the above (1) is preferable, and the above (2) and (3) are particularly preferable from the viewpoint of improving the compatibility of the perfluoroelastomer component.

  The PTFE of (1) includes not only a TFE homopolymer but also modified PTFE obtained by copolymerizing a small amount of a comonomer within a range not giving melt fluidity. Examples of the comonomer include HFP, CTFE, perfluorovinyl ether, trifluoroethylene, perfluoroalkylethylene, and the like. When perfluorovinyl ether is used as a comonomer, it is up to 2% by weight, preferably 0.001. The copolymerization is in an amount of ˜1% by weight, more preferably 0.01 to 1% by weight.

  These fluororesins can be produced by an ordinary emulsion polymerization method, and the emulsion, which is a polymerization reaction product, can be used as it is or in a co-coagulation described later with the concentration adjusted appropriately. Alternatively, it may be once dried and then re-emulsified and dispersed.

  The average particle diameter of the fluororesin fine particles in the emulsion is less than 150 nm, preferably 20 to 150 nm, more preferably 20 to 100 nm. When the average particle size is too small, the productivity is remarkably lowered, and when it is 200 nm or more, a uniform dispersion cannot be obtained.

  The mixing ratio of the elastomer and the fluororesin may be appropriately selected depending on the characteristics desired to be given to the molded product, but the fluororesin is 1 part by weight or more, preferably 5 parts by weight from the viewpoint of obtaining a reinforcing effect with respect to 100 parts by weight of the elastomer. It is desirable that the amount is 150 parts by weight or less, preferably 100 parts by weight or less, more preferably 50 parts by weight or less from the viewpoint that rubber processing of the resulting crosslinked product is easy.

  The combination of elastomer and fluororesin should be selected according to the intended function, taking into account whether the coagulation properties of each elastomer are close and whether there is an affinity as a polymer. .

Preferred combinations include, for example, (a) TFE / PAVE elastomer and TFE / PAVE resin (PFA);
(B) TFE / PAVE elastomer and TFE / HFP resin (FEP);
(C) VdF / HFP elastomer and PVdF resin;
(D) VdF / HFP / TFE elastomer and PVdF resin;
(E) TFE / propylene elastomer and ethylene / TFE resin (ETFE)
However, it is not limited to these.

  The elastomer composition of the present invention can be produced by mixing and co-coagulating the emulsion of elastomer particles and the emulsion of fluororesin fine particles. Co-coagulation can be carried out according to a known coagulation method. For example, a method in which a mixed liquid in which an emulsion of elastomer particles and a fluororesin fine particle emulsion are mixed is dropped into the coagulating liquid, or a method in which the coagulating liquid is dropped into the emulsion mixed liquid.

  The concentration of the mixed emulsion may be appropriately determined depending on productivity and the like, and is not particularly limited, but is usually 5 to 50% by weight, preferably 10 to 30% by weight. In coagulation, it is also possible to dilute 2 to 10 times with pure water.

  Specific examples of the co-coagulation method include a salting-out method, an acid coagulation method, a freeze coagulation method, and a method of coagulating by applying a mechanical shearing force.

  As the coagulant, for example, acids such as nitric acid, hydrochloric acid and sulfuric acid; metal salts such as aluminum nitrate and aluminum sulfate can be used. Of these, the acid is easy to operate because it keeps the polymer clean. Are preferably metal salts.

  The coagulated product obtained by co-coagulation can be used as a basic material for molding by washing as necessary and drying in a hot air oven or a vacuum dryer.

  When the elastomer composition of the present invention is used as a basic material, the obtained molded product can be provided with excellent mechanical strength, wear resistance, transparency, moldability and the like.

  A crosslinkable elastomer composition can be obtained by blending the elastomer composition of the present invention with a crosslinking agent and further a crosslinking accelerator.

  As the crosslinking system, a crosslinking system usually employed for elastomers can be applied, and examples thereof include an oxazole crosslinking system, an imidazole crosslinking system, a thiazole crosslinking system, a triazine crosslinking system, a peroxide crosslinking system, a polyol crosslinking system, and a polyamine crosslinking system. . In addition, crosslinking with radiation, electron beam, ultraviolet rays or the like is also possible.

  Examples of the crosslinking agent used in the oxazole crosslinking system, imidazole crosslinking system, and thiazole crosslinking system include, for example, formula (I):

（式中、Ｒ¹は−ＳＯ₂−、−Ｏ−、−ＣＯ−、炭素数１〜６のアルキレン基、炭素数１〜１０のパーフルオロアルキレン基または結合手であり、Ｒ²およびＲ³は一方が−ＮＨ₂であり他方が−ＮＨ₂、−ＯＨまたは−ＳＨである）で示されるビスアミノ（チオ）フェノール系架橋剤あるいはテトラアミン系架橋剤、式（II）：

(Wherein R ¹ is —SO ₂ —, —O—, —CO—, an alkylene group having 1 to 6 carbon atoms, a perfluoroalkylene group having 1 to 10 carbon atoms, or a bond, and R ² and R ³ Bisamino (thio) phenol-based cross-linking agent or tetraamine-based cross-linking agent represented by the formula (II): one is —NH ₂ and the other is —NH ₂ , —OH or —SH.

（式中、Ｒ¹は前記と同じ、Ｒ⁴は

(Wherein R ¹ is the same as above, R ⁴ is

）で示されるビスアミドラゾン系架橋剤、式（III）または（IV）：

) Bisamidrazone crosslinking agent represented by formula (III) or (IV):

（式中、Ｒ_f ²は炭素数１〜１０のパーフルオロアルキレン基）、

(Wherein R _f ² is a perfluoroalkylene group having 1 to 10 carbon atoms),

（式中、ｎは１〜１０の整数）で示されるビスアミドキシム系架橋剤などがあげられる。

(Wherein n is an integer of 1 to 10), and the like.

  Moreover, you may use a crosslinking accelerator together as needed.

  The blending amount is 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, and 0.1 to 10 parts by weight, preferably 0.2 to 0.2 parts by weight, based on 100 parts by weight of the elastomer. ~ 5 parts by weight.

  Examples of the crosslinking agent used in the peroxide crosslinking system include 1,1-bis (t-butylperoxy) -3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, Di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α, α-bis (t-butylperoxy) -p-diisopropylbenzene, 2,5-dimethyl-2,5-di ( t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) -hexyne-3, benzoyl peroxide, t-butylperoxybenzene, 2,5-dimethyl-2, 5-di (benzoylperoxy) hexane, t-butylperoxymaleic acid, t-butylperoxyisopropyl carbonate, etc. Can be illustrated.

  In the case of a peroxide crosslinking system, it is desirable to use a crosslinking accelerator. Examples of the crosslinking accelerator include triallyl cyanurate, triallyl isocyanurate, triallyl formal, triallyl trimellitate, N, N'-m-phenylenebismaleimide, dipropanegyl terephthalate, diallyl phthalate, tetraallyl terephthalate amide And triallyl phosphate.

  The amount of the crosslinking agent is 0.05 to 10 parts by weight, preferably 1.0 to 5 parts by weight, and 0.1 to 10 parts by weight, preferably 0 to 0.1 parts by weight, based on 100 parts by weight of the elastomer. .5 to 5 parts by weight.

  In the case of the peroxide cross-linking system, it is not necessary to use inorganic fillers for cross-linking, and color development is not caused by cross-linking. Can be provided.

  The transparent crosslinked elastomer molded article obtained by the present invention has a transparency having a haze value of 50% or less, preferably 40% or less, particularly 30% or less.

  As the crosslinking agent used in the polyol crosslinking system, a commonly used polyhydroxy aromatic compound can be used. For example, 2,2-bis (4-hydroxyphenyl) propane (so-called bisphenol A), 2,2-bis (4 -Hydroxyphenyl) perfluoropropane (so-called bisphenol AF), resorcin, 1,3,5-trihydroxybenzene, 1,7-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 4,4 ' -Dihydroxydiphenyl, 4,4'-dihydroxystilbene, 2,6-dihydroxyanthracene, hydroquinone, catechol, 2,2-bis (4-hydroxyphenyl) butane (so-called bisphenol B), 4,4-bis (4-hydroxy Phenyl) valeric acid, 2,2 Bis (4-hydroxyphenyl) tetrafluorochloropropane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ketone, tri (4-hydroxyphenyl) methane, 3,3 ', 5,5'-tetrachloro Examples thereof include bisphenol A, 3,3 ′, 5,5′-tetrabromobisphenol A, and alkali metal salts or alkaline earth metal salts thereof.

  In the polyol crosslinking system, it is preferable to use a crosslinking accelerator in combination. Examples of the crosslinking accelerator include ammonium compounds, phosphonium compounds, oxonium compounds, sulfonium compounds and the like, and quaternary ammonium salts and quaternary phosphonium salts are particularly preferable.

  The blending amount is 0.5 to 5 parts by weight of the crosslinking agent with respect to 100 parts by weight of the elastomer, and the crosslinking accelerator is 5 to 400 parts by weight, preferably 10 to 100 parts by weight with respect to 100 parts by weight of the crosslinking agent. .

Moreover, a polyamine compound is mention | raise | lifted as a crosslinking agent used by a polyamine crosslinking system. The polyamine compound is a primary amine or a secondary amine that binds two or more basic nitrogen atoms in the molecule, and in many cases, these are converted into salts to adjust the reactivity to be mild. use. As specific examples, alkylenediamines such as ethylenediamine carbamate, hexamethylenediamine carbamate, and 4,4'-diaminocyclohexylmethane carbamate are used relatively frequently. Schiff salts such as N, N′-dicinnamylidene-1,6-hexamethylenediamine can also be used. It can be preferably used by using together with other basic compounds of polyamine aromatic compounds having poor basicity. Other basic compounds include, for example, diphenylguanidine, di-O-triguanidine, diphenylthiourea, 2-mercaptoimidazoline, etc., and —NH ₂ and / or in a molecule used as a crosslinking accelerator for synthetic rubber. Examples thereof include a compound having —NH— or a divalent metal hydroxide.

  A compounding quantity is 0.1-10 weight part with respect to 100 weight part of elastomers, Preferably it is 0.5-5 weight part.

  Examples of other additives include fillers (excluding the fluororesin) and pigments.

  Examples of the filler include carbon black (in particular, inorganic fillers such as graphitized carbon black, silicon oxide, titanium oxide, and alumina; organic fillers such as polyimide. The blending amount is 100 weights with respect to 100 parts by weight of the elastomer. Part or less, preferably 1 to 50 parts by weight.

  Additives such as the cross-linking agent, cross-linking accelerator and filler may be added at the time of co-coagulation if possible, but may be mixed after producing a composition of elastomer and fluororesin fine particles. . The mixing method may be a kneading method using a conventionally known roll.

  The crosslinkable elastomer composition in which the fluororesin fine particles thus obtained are finely dispersed can be kneaded and crosslinked to produce a crosslinked molded product. As a kneading method, a usual method such as roll kneading or kneader kneading can be adopted, and a molding method such as a usual compression molding method, injection molding method, extrusion molding method or transfer molding method can be adopted. The molding conditions may be the same as the conventional conditions.

  The resulting cross-linked molded article maintains the transparency of the matrix elastomer when no filler is included. Although the transparency may be slightly lowered, the visible light transmittance of 20% or more of the elastomer alone is still maintained.

  Regardless of the presence or absence of a filler, the crosslinked molded product of the present invention is excellent in mechanical strength, post-processability, plasma resistance, and gas barrier properties. Further, finely dispersed fluororesin fine particles are unlikely to fall off from the matrix elastomer, so that there is little possibility of generating particles even when used as, for example, a sealing material for a semiconductor manufacturing apparatus.

  The elastomer composition of the present invention is suitable as a molded article shown in the following Tables 1, 2 and 3 utilizing its excellent characteristics.

Specifically, it can be used by being incorporated in the following semiconductor manufacturing apparatus.
(1) Etching device Dry etching device Plasma etching device Reactive ion etching device Reactive ion beam etching device Sputter etching device Ion beam etching device Wet etching device Ashing device (2) Cleaning device Dry etching cleaning device UV / O ₃ cleaning device Ion Beam cleaning equipment Laser beam cleaning equipment Plasma cleaning equipment Gas etching cleaning equipment Extraction cleaning equipment Soxhlet extraction cleaning equipment High-temperature high-pressure extraction cleaning equipment Microwave extraction cleaning equipment Supercritical extraction cleaning equipment (3) Exposure equipment Stepper Coater / Developer (4) Polishing equipment CMP apparatus (5) Film forming apparatus CVD apparatus Sputtering apparatus (6) Diffusion / ion implantation apparatus Oxidation diffusion apparatus Ion implantation apparatus

  Next, the present invention will be described with reference to synthesis examples and examples, but the present invention is not limited to such synthesis examples and examples.

Synthesis Example 1 (Production of emulsion of fluorine-containing elastomer particles)
In a stainless steel autoclave with an internal volume of 47 liters and no ignition source, 30 liters of pure water and 300 g of C ₇ F ₁₅ COONH ₄ as an emulsifier, and 2.7 g of disodium hydrogen phosphate as a pH adjuster After thoroughly degassing the system with nitrogen gas, the temperature was raised to 50 ° C. while stirring at 200 rpm, and a mixed gas of tetrafluoroethylene (TFE) and perfluoro (methyl vinyl ether) (PMVE) (TFE / PMVE = 24/76 molar ratio) was charged so that the internal pressure was 1.18 MPa. Next, 100 ml of an aqueous solution of ammonium persulfate (APS) having a concentration of 55.8 mg / ml was injected under nitrogen pressure to initiate the reaction.

When the internal pressure dropped to 1.08 MPa as the polymerization proceeded, 62.3 g of the diiodine compound [I (CF ₂ ) ₄ I] was injected under nitrogen pressure. Next, 60 g of TFE was self-pressurized and 60 g of PMVE was press-fitted with a plunger pump so that the pressure was 1.18 MPa. Thereafter, as the reaction proceeds, TFE and PMVE are similarly injected, and the pressure is increased and decreased between 1.08 to 1.18 MPa, and the total amount of TFE and PMVE is 6.5 kg, 7.8 kg, and 9. When 1 kg and 10.4 kg were reached, CF ₂ = CFOCF ₂ CF ₂ CH ₂ I, which is an iodine compound, was injected under a pressure of 25.6 g nitrogen. Thereafter, 20 ml of an aqueous solution of 52.5 mg / ml APS was injected under nitrogen pressure every 12 hours from the start of polymerization.

  33 hours after the start of the polymerization reaction, when the total amount of TFE and PMVE reached 13 kg, the autoclave was cooled, unreacted monomers were released, and fluorine-containing elastomer particles having a solid content concentration of 27.5% by weight ( An emulsion (A-1) having an average particle size of 70 nm was obtained.

A part of this emulsion was taken out and coagulated with nitric acid, and the precipitate was washed and dried to obtain elastomer particles. This elastomer has a Mooney viscosity ML _{1 + 10} (100 ° C.) of 42, a composition ratio in ¹⁹ F-NMR analysis is TFE / PMVE = 62/38 (mol%), and a glass transition temperature Tg measured by DSC. (Median) was −3 ° C.

Synthesis Example 2 (Production of emulsion of fluororesin fine particles)
In a 6 liter stainless steel autoclave with no ignition source, 3 liters of pure water and 30 g of C ₃ F ₇ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ as an emulsifier as a pH adjuster After charging 0.27 g of disodium hydrogen phosphate and 12 hydrate, the system was thoroughly purged with nitrogen gas and deaerated, the temperature was raised to 80 ° C. while stirring at 600 rpm, and tetrafluoroethylene (TFE) and A mixed gas of perfluoro (methyl vinyl ether) (PMVE) (TFE / PMVE = 88/12 molar ratio) was charged so that the internal pressure was 0.20 MPa. Subsequently, 4 ml of a 2.5 mg / ml aqueous solution of ammonium persulfate (APS) was injected under nitrogen pressure to initiate the reaction.

  When the internal pressure dropped to 0.15 MPa as the polymerization proceeded, a mixed gas of TFE / PMVE (TFE / PMVE = 95/5 molar ratio) was injected with nitrogen gas so that the internal pressure was 0.20 MPa. Thereafter, the TFE / PMVE mixed gas (95/5 molar ratio) was injected in the same manner as the reaction proceeded, and the pressure was increased and decreased between 0.15 and 0.20 MPa.

  4.5 hours after the start of the polymerization reaction, when the total charged amount of TFE and PMVE reaches 331 g, the autoclave is cooled, unreacted monomers are released, and the fluororesin fine particles having a solid content concentration of 9.7% by weight An emulsion (B-1) (average particle size: 44 nm) was obtained. The average particle diameter was measured with LPA-3000, 3100 manufactured by Otsuka Electronics Co., Ltd. by mixing 120 mg of emulsion with 4.4 g of dimethyl sulfoxide.

A part of this emulsion was taken out and coagulated with nitric acid, and the precipitate was washed and dried to obtain a white fluororesin fine powder. The melt flow rate MFR of this fluororesin cannot be measured under the condition of holding at 372 ° C. for 5 minutes, the composition ratio in ¹⁹ F-NMR analysis is TFE / PMVE = 94.5 / 5.5 (mol%), The melting point measured by DSC was 290 ° C.

Synthesis Example 3 (Production of emulsion of fluororesin fine particles)
In a 6 liter stainless steel autoclave with no ignition source, 3 liters of pure water and 30 g of C ₃ F ₇ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ as an emulsifier as a pH adjuster After charging 0.27 g of disodium hydrogen phosphate and 12 hydrate, the system was thoroughly purged with nitrogen gas and deaerated, the temperature was raised to 80 ° C. while stirring at 600 rpm, and tetrafluoroethylene (TFE) and A mixed gas of perfluoro (methyl vinyl ether) (PMVE) (TFE / PMVE = 88/12 molar ratio) was charged so that the internal pressure was 0.20 MPa. Subsequently, 4 ml of a 2.5 mg / ml aqueous solution of ammonium persulfate (APS) was injected under nitrogen pressure to initiate the reaction.

When the internal pressure dropped to 0.15 MPa as the polymerization proceeded, 2.92 g of the diiodine compound [I (CF ₂ ) ₄ I] was injected under nitrogen pressure. Next, a mixed gas of TFE / PMVE (TFE / PMVE = 95/5 molar ratio) was injected with nitrogen gas so that the internal pressure became 0.20 MPa. Thereafter, the TFE / PMVE mixed gas (95/5 molar ratio) was injected in the same manner as the reaction proceeded, and the pressure was increased and decreased between 0.15 and 0.20 MPa.

  9.9 hours after the start of the polymerization reaction, when the total amount of TFE and PMVE reached 327 g, the autoclave was cooled, unreacted monomers were released, and the fluororesin fine particles having a solid content concentration of 9.4% by weight An emulsion (B-2) (average particle size: 44 nm) was obtained.

A part of this emulsion was taken out and coagulated with nitric acid, and the precipitate was washed and dried to obtain a white fluororesin fine powder. The melt flow rate MFR of this fluororesin is 21.1 g / 10 minutes under the condition of keeping at 372 ° C. for 5 minutes, and the composition ratio in ¹⁹ F-NMR analysis is TFE / PMVE = 94.9 / 5.1 (mol%) The melting point measured by DSC was 280.7 ° C.

Synthesis Example 4 (Production of emulsion of fluorine-containing elastomer particles)
In a stainless steel autoclave with an internal volume of 3 liters that has no ignition source, 1 liter of pure water and 10 g of C ₃ F ₇ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) COONH ₄ as an emulsifier as a pH adjuster After charging 0.09 g of disodium hydrogen phosphate and 12 hydrate, the system was thoroughly purged with nitrogen gas and degassed, the temperature was raised to 53 ° C. while stirring at 600 rpm, and tetrafluoroethylene (TFE) and A mixed gas of perfluoro (methyl vinyl ether) (PMVE) (TFE / PMVE = 25/75 molar ratio) was charged so that the internal pressure was 0.78 MPa. Subsequently, 20 ml of a 264 mg / ml aqueous solution of ammonium persulfate (APS) was injected under nitrogen pressure to initiate the reaction.

When the internal pressure decreased to 0.69 MPa due to the progress of polymerization, CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ CN (CNVE) was injected under 2.2 g nitrogen pressure. Subsequently, 4.7 g of TFE and 5.3 g of PMVE were injected under their own pressure so that the pressure became 0.78 MPa. Thereafter, TFE and PMVE are injected in the same manner as the reaction proceeds, and the pressure is increased and decreased repeatedly between 0.69 and 0.78 MPa. When the total amount of TFE and PMVE reaches 70 g, CNVE is set to 2. Injected with 2 g nitrogen pressure.

  Six hours after the start of the polymerization reaction, when the total amount of TFE and PMVE reached 130 g, the autoclave was cooled, unreacted monomers were released, and the fluorine-containing elastomer particles having a solid content concentration of 11.3 wt% 1160 g of emulsion (A-2) was obtained.

  100 g of this emulsion was diluted with 300 g of water and slowly added to 280 g of a 3.5 wt% aqueous hydrochloric acid solution with stirring. After the addition, the mixture was further stirred for 5 minutes, and the resulting coagulated product was filtered off. The obtained elastomer particles were further washed with 200 g of HCFC-141b and filtered. Washing with HCFC-141b and filtration were repeated 4 times, followed by vacuum drying at 60 ° C. for 72 hours to obtain 11.2 g of a fluorine-containing elastomer.

When the composition ratio of this fluorine-containing elastomer was determined by ¹⁹ F-NMR analysis, it was TFE / PMVE / CNVE = 60.4 / 38.9 / 0.7 (mol%).

Example 1
1236 g of the fluorine-containing elastomer particle emulsion (A-1) obtained in Synthesis Example 1 and 619 g of the fluororesin fine particle emulsion (B-1) obtained in Synthesis Example 2 were mixed (solid content ratio: fluorine-containing elastomer / Fluororesin = 85/15 weight ratio), and co-coagulated by dropping into 411 g of a stirring 9% nitric acid aqueous solution over 10 minutes. The obtained co-coagulated product was washed with water and dried to obtain an elastomer composition in which fluororesin fine particles were finely dispersed in the fluorine-containing elastomer.

  When this elastomer composition was measured by DTA, absorption considered to be based on a fluororesin was observed at 272.6 ° C. Moreover, this composition was transparent (haze value: 12%).

(Measurement of haze value)
A test sample having a thickness of 0.7 mm is prepared while applying pressure as necessary at the melting temperature (60 to 150 ° C.) of the test elastomer composition. This test sample is measured with a DC haze meter (manufactured by Toyo Seiki Co., Ltd., a measuring device corresponding to JIS K7105 and ASTM D 1003).

  In addition, the haze value of the crosslinked molded product mentioned later uses the sheet | seat of thickness 2mm produced by bridge-molding the elastomer composition as a test sample.

  A photograph of this elastomer composition taken at a magnification of 20000 times by a replica method using a transmission electron microscope (TEM) is shown in FIG. In FIG. 1, it can be seen that the granular convex portions are fluororesin fine particles, and a large number of fluororesin fine particles (average particle diameter is about 40 nm) are uniformly and finely dispersed. The difference in the finely dispersed state is clear when compared with a TEM photograph (FIG. 2) of the composition obtained in Comparative Example 3 described later.

Example 2
Co-coagulation was carried out in the same manner as in Example 1 except that the amount of the fluororesin fine particle emulsion (B-1) was changed to 412 g to obtain an elastomer composition (solid content ratio: fluorine-containing elastomer / fluororesin). = 90/10, weight ratio). This composition was transparent (haze value: 12%).

Example 3
Co-coagulation was carried out in the same manner as in Example 1 except that the amount of the fluororesin fine particle emulsion (B-1) was changed to 206 g to obtain an elastomer composition (solid content ratio: fluorine-containing elastomer / fluororesin = 95/5, weight ratio). This composition was transparent (haze value: 11%).

Example 4
An elastomer was co-coagulated as in Example 1 except that 638 g of the fluororesin fine particle emulsion (B-2) obtained in Synthesis Example 3 was mixed instead of the fluororesin fine particle emulsion (B-1). A composition was obtained (solid content ratio: fluorine-containing elastomer / fluororesin = 85/15, weight ratio). This composition was transparent (haze value: 12%).

Example 5
100 parts by weight of the elastomer composition produced in Example 1 is 1 part by weight of 2,5-dimethyl-2,5-di (t-butylperoxy) hexane as a crosslinking agent and 1 part by weight of triallyl isocyanurate as a crosslinking accelerator. And kneaded with an open roll to obtain a crosslinkable elastomer composition.

  The vulcanizability of this crosslinkable elastomer composition was examined by the method described later. The results are shown in Table 4.

  Further, the crosslinkable elastomer composition was press-crosslinked at 150 ° C. for 30 minutes and then oven-crosslinked at 180 ° C. for 4 hours to obtain a crosslinked product. The physical properties of this crosslinked product were measured. Further, an O-ring (P-24) was produced under the same crosslinking conditions, and compression set was measured. Furthermore, the haze value of the crosslinked elastomer sheet (thickness 2 mm) was measured. The results are shown in Table 4.

(Vulcanizability)
For each vulcanizing composition, a vulcanization curve is determined at a temperature shown in Table 4 using a JSR type curlastometer type II, and the minimum torque, maximum torque, induction time and optimum vulcanization time are determined.

(Normal physical properties)
According to JIS K6301, 100% modulus, tensile strength, tensile elongation and hardness (JIS A hardness) in a normal state (25 ° C.) are measured.

(Compression set)
The compression set after 70 hours at 200 ° C. is measured according to JIS K6301.

Examples 6-10
A crosslinkable elastomer composition having the composition shown in Table 4 was produced in the same manner as in Example 5 to examine the vulcanizability, and a crosslinked product was produced under the same crosslinking conditions as in Example 5 to obtain normal properties and compression set. The haze value was examined. The results are shown in Table 4.

  In addition, the filler mixed in Examples 6 to 8 is silicon oxide (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.).

Comparative Examples 1-2
A crosslinkable elastomer composition was produced in the same manner as in Example 5 except that the fluororesin fine powder was not mixed (haze value: 10%). While examining the vulcanizability of this composition, a crosslinked product was produced under the same crosslinking conditions as in Example 5, and the normal state properties and compression set were examined. The results are shown in Table 4.

Comparative Example 3
Nitric acid was added to the emulsion (A-1) of the fluorine-containing elastomer particles obtained in Synthesis Example 1 for coagulation, and the precipitate was washed and dried to obtain elastomer particles. On the other hand, nitric acid was added to the fluororesin fine particle emulsion (B-1) obtained in Synthesis Example 2 for coagulation, and the precipitate was washed and dried to obtain a white fluororesin powder. 15 parts by weight of the fluororesin powder was dry blended with 85 parts by weight of the elastomer particles to obtain a white opaque composition (haze value: 82%). A TEM photograph (magnified 20000 times) of this composition is shown in FIG. As is clear from FIG. 2, the elastomer portion (flat portions on both sides in FIG. 2) and the portion where the fluororesin fine particles are aggregated (the portion where the surface of the central portion in FIG. 2 is rough) are clearly separated. Yes.

  A crosslinkable elastomer composition was produced in the same manner as in Example 5 except that this composition was used, and the vulcanizability was examined. A crosslinked product was produced under the same crosslinking conditions as in Example 5 to obtain normal properties, compression The permanent set and haze value were examined. The results are shown in Table 4.

Example 11
300 g of the fluorinated elastomer particles (A-2) obtained in Synthesis Example 4 and 619 g of the fluororesin fine particles (B-1) obtained in Synthesis Example 2 are fluorinated elastomer / fluorine resin = 85/15 (weight ratio). The mixture was added dropwise to 981 g of a 9% nitric acid aqueous solution that had been mixed and stirred for 20 minutes for co-coagulation. The obtained co-coagulated product was washed with water and dried to obtain a transparent elastomer composition (haze value: 18%) in which fluororesin fine particles were finely dispersed in the fluorine-containing elastomer.

Example 12
With respect to 100 parts by weight of the elastomer composition produced in Example 11, 2,2-bis-[(3-amino-4-phenylamino) phenyl] hexafluoropropane (Journal of Polymer Science, 1.45 parts by weight (synthesized by the method described in Polymer Chemistry, Vol. 20, 2381-2393 (1982)) were kneaded with an open roll to prepare a crosslinkable elastomer composition. When the vulcanizability of this crosslinkable elastomer composition was examined by the above method, it was as follows.

Vulcanizability (170 ° C)
Minimum torque: 0.45kg
Maximum torque: 2.90kg
Induction time: 4.4 minutes Optimal vulcanization time: 8.7 minutes

  Further, this crosslinkable elastomer composition was press-crosslinked at 170 ° C. for 15 minutes and then oven-crosslinked at 204 ° C. for 18 hours and then at 288 ° C. for 18 hours to produce a crosslinked product. For the obtained crosslinked product, the normal physical properties were measured in the same manner as described above, and an O-ring (P-24) was prepared under the same conditions as described above, and the compression set was measured. The results are as follows.

Normal state physical properties 100% modulus: 2.9 MPa
Tensile strength: 19.4 MPa
Elongation: 252%
Hardness (JIS A): 74

Compression set (200 ° C, 70 hours, 25% compression)
Compression set: 15%

It is a transmission electron micrograph (20000 times) of the elastomer composition obtained in Example 1 of the present invention. It is a transmission electron micrograph (20000 times) of the elastomer composition obtained by the comparative example 3 in this invention.

Claims (5)

A transparent fluorine-containing elastomer composition in which fluorine resin fine particles having an average particle diameter of 20 to 100 nm are finely dispersed in a fluorine-containing elastomer. The composition of claim 1 comprising a crosslinking agent. The composition according to claim 1 or 2, which does not contain a filler. The composition according to claim 1, which has a haze value of 50% or less. The method for producing a transparent elastomer composition according to claim 1, wherein the emulsion of fluorine-containing elastomer particles and the emulsion of fluororesin fine particles having an average particle diameter of 20 to 100 nm are mixed and then co-coagulated.

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