JP4636025B2 - Fluoro rubber composition - Google Patents

Description

  The present invention relates to a fluororubber composition, a sealing material obtained by vulcanization molding of the composition, and a sealing material for an oxygen sensor.

An oxygen sensor (O ₂ sensor) for detecting oxygen concentration, which is one of the uses of the rubber composition of the present invention, is used for detecting oxygen concentration in exhaust gas from an internal combustion engine of an automobile, for example. Although oxygen sensors for automobiles are usually protected with metal, etc., they are attached to high-temperature exhaust pipes, etc., and the inside of the sensor is exposed to a high-temperature exhaust gas flow that contains a large amount of oxidizing substances. It is necessary to have excellent properties.

  Oxygen sensors for automobiles are often mounted on the lower side of the vehicle body floor, such as those mounted downstream of a catalyst that purifies exhaust gas and those that require detection of catalyst deterioration. In this case, the oxygen sensor for automobiles is subject to external impacts such as vibration impact from the engine and road surface, stone splash, water exposure, etc., so it may have mechanical impact resistance, thermal shock resistance, waterproofness, etc. Required.

  The oxygen sensor for automobiles is usually cylindrical, and in order to introduce the oxygen concentration detection unit of the oxygen sensor to the outside by introducing the oxygen concentration detection unit into the oxygen concentration detection unit of the oxygen sensor, Several lead wires are built in. The lead wire is disposed so as to penetrate through a sealing material called a bush in order to fix the lead wire without coming into contact with each other at a portion taken out from the automobile oxygen sensor.

  This sealing material usually has a cylindrical shape as a basic shape, and in use, after passing through a lead wire through a through hole extending in the height direction of several previously provided columns, pressure is applied in the radial direction. Add caulking. In the present specification, the radial direction means a direction perpendicular to the center line in the height direction of the cylinder from the side surface of the cylinder.

  This sealing material is compressed to some extent by caulking, and it is desirable to have elasticity so that the lead wire can be securely fixed, and sealing properties such as waterproofness and airtightness are exhibited. Similar to the oxygen sensor body, it is also desired to have characteristics such as heat resistance and impact resistance. Therefore, as a sealing material, conventionally, a sealing material obtained by vulcanizing and molding a fluororubber composition made of fluororubber having these characteristics has been often used.

  On the other hand, it is desirable for the sealing material to have a small compression set so as to exhibit excellent sealing characteristics. However, in the conventional fluororubber composition, the compression set of the sealing material can be reduced by increasing the crosslinking density by increasing the amount of the vulcanizing agent added, but the cracking property due to the high compression of the sealing material is Conversely, there was a problem that worsened. Conversely, it is possible to improve the cracking property of the sealing material by reducing the crosslinking density by reducing the amount of the vulcanizing agent, but the compression set of the sealing material will increase, so a high-dimensional balance will be required to satisfy both. Was impossible.

  As a technique for solving these problems, a rubber composition in which the compounding ratio of various additives to be added to fluororubber is defined (for example, see Patent Document 1 and Patent Document 2). However, both were insufficient to satisfy both compression set and crackability.

  Further, a seal comprising a copolymer obtained from a monomer component containing vinylidene fluoride, tetrafluoroethylene and hexafluoropropylene, and comprising a fluorine-containing elastomer having a weight average molecular weight of 400,000 to 700,000 A material is disclosed (for example, see Patent Document 3). However, the compression set of the sealing material is not sufficient, and the processability of the fluororubber and the fluororubber composition has a problem that the fluidity is so poor that the Mooney viscosity cannot be measured, and the process cannot be practically performed. .

  Furthermore, in recent years, with higher performance of engines and equipment and higher awareness of environmental protection, more accurate sensor control is required. Is moving to the upstream side of the exhaust gas flow, but the exhaust gas flow is hotter toward the upstream side.

  Further, as the interior of an automobile engine room becomes denser, it is desired to reduce the size of the engine in order to expand the indoor living space. The downsizing of the engine contributes to reducing the weight and fuel consumption of automobiles, so the demand for development is high, but the temperature inside the engine will rise. Some oxygen sensors are installed at such high temperature sites.

  Therefore, conventionally, cracking under high compression and compression set resistance have tended to deteriorate as the temperature increases, but as a fluororubber used for sealing materials, the use environment is higher than in the past. However, it has been demanded that these characteristics are not impaired.

JP-A-9-188793 JP 2001-192482 A International Publication No. 03/074625 Pamphlet

  The present invention provides a fluororubber composition having high temperature sealability, crackability, and workability, a seal material obtained by vulcanization molding of the composition, and a seal material for an oxygen sensor.

  That is, the present invention is a rubber composition comprising a fluororubber and a vulcanizing agent, and the vulcanizing agent is 0.5 to 1.7 parts by weight with respect to 100 parts by weight of the fluororubber in the composition, And it is related with the rubber composition whose Mooney viscosity (ML1 + 20, 140 degreeC) of the fluororubber in this composition is 70-150.

  It is preferable that the Mooney viscosity (ML1 + 20, 140 ° C.) of the fluororubber is 100 to 150.

  The fluororubber is preferably a fluororubber containing vinylidene fluoride units.

  The fluororubber is preferably a binary fluororubber comprising a vinylidene fluoride unit and a hexafluoropropylene unit.

  When X (parts by weight) is added to 100 parts by weight of fluororubber, 20% + Y when the compression set at 25% compression at 280 ° C. × 72 hours is Y (%). It is preferable to satisfy ≦ 70.

  The vulcanizing agent is preferably a polyhydroxy compound.

  It is preferable to contain 5 to 30 parts by weight of a bituminous coal filler with respect to 100 parts by weight of the fluororubber.

  The present invention also relates to a sealing material obtained by vulcanizing the rubber composition.

  It is preferable to heat-treat at a temperature of 280 ° C. or higher for 1 hour or longer after vulcanization molding.

  The compression set at 25% compression of the P-24 • O-ring at 280 ° C. × 72 hours is defined as Y (%), and the cracking rate at 50% compression of the O-ring at 280 ° C. × 1 hour is defined as Z (%). Sometimes it is preferable to satisfy 10Y + Z ≦ 500.

  Moreover, this invention relates to the sealing material for oxygen sensors which consists of the said sealing material.

  Furthermore, the present invention is an oxygen sensor sealing material obtained by vulcanizing a rubber composition comprising fluororubber and a vulcanizing agent, wherein the Mooney viscosity (ML1 + 20, 140 ° C.) of the fluororubber in the composition is It is related with the sealing material for oxygen sensors which are 70-150.

  The rubber composition of the present invention is a rubber composition comprising a fluororubber and a vulcanizing agent, and the vulcanizing agent is 0.5 to 1.7 parts by weight with respect to 100 parts by weight of the fluororubber in the composition. In addition, since the Mooney viscosity (ML1 + 20, 140 ° C.) of the fluororubber in the composition is 70 to 150, the sealing material obtained by vulcanization molding can be provided with a sealing property and a cracking property at a high temperature. The rubber composition also has good processability. Furthermore, the sealing material made of the rubber composition of the present invention maintains its sealing performance when used for a long time at a high temperature.

The present invention is a rubber composition comprising a fluoro rubber and a vulcanizing agent,
The vulcanizing agent is 0.5 to 1.7 parts by weight with respect to 100 parts by weight of the fluororubber in the composition, and the Mooney viscosity (ML1 + 20, 140 ° C.) of the fluororubber in the composition is 70 to 150. It is related with the rubber composition which is.

  Examples of the fluoro rubber include perfluoro fluoro rubber and non-perfluoro fluoro rubber.

  Perfluoro fluoro rubbers include tetrafluoroethylene (hereinafter referred to as TFE) / perfluoro (alkyl vinyl ether) (hereinafter referred to as PAVE) copolymer, TFE / hexafluoropropylene (hereinafter referred to as HFP) / PAVE. Examples thereof include a system copolymer.

  Examples of the non-perfluorofluororubber include vinylidene fluoride (hereinafter referred to as VdF) -based polymers, TFE / propylene-based copolymers, and the like, each of which is independent or does not impair the effects of the present invention. Any combination can be used within a range.

  Moreover, what was illustrated as the said perfluoro fluororubber or non-perfluoro fluororubber is a main monomer, and what copolymerized the monomer for crosslinking, a modified monomer, etc. can be used suitably. As the crosslinking monomer or the modifying monomer, a known crosslinking monomer such as an iodine atom, bromine atom, or one containing a double bond, a transfer agent, a modified monomer such as a known ethylenically unsaturated compound, or the like can be used. .

  Specific examples of the VdF polymer include a VdF / HFP copolymer, a VdF / TFE / HFP copolymer, a VdF / TFE / propylene copolymer, and a VdF / ethylene / HFP copolymer. VdF / TFE / PAVE copolymer, VdF / PAVE copolymer, VdF / chlorotrifluoroethylene (hereinafter referred to as CTFE) copolymer, and the like. More specifically, it is preferably a fluorine-containing copolymer composed of 25 to 85 mol% of VdF and 75 to 15 mol% of at least one other monomer copolymerizable with VdF, more preferably , A fluorine-containing copolymer comprising 50 to 80 mol% of VdF and 50 to 20 mol% of at least one other monomer copolymerizable with VdF.

  Here, as at least one other monomer copolymerizable with VdF, for example, TFE, CTFE, trifluoroethylene, HFP, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetra Examples thereof include fluorine-containing monomers such as fluoroisobutene, PAVE and vinyl fluoride, and non-fluorine monomers such as ethylene, propylene and alkyl vinyl ether. These can be used alone or in any combination.

  Among the fluororubbers, a fluororubber containing VdF units is preferable from the viewpoints of heat resistance, compression set, workability, and cost. From the viewpoint of good compression set, two of VdF units and HFP units are used. It is more preferable that it is a ternary fluororubber. In the binary fluororubber, the total of VdF units and HFP units is preferably 90 mol% or more, more preferably 95 mol% or more, and particularly preferably 100 mol%.

  The Mooney viscosity (ML1 + 20, 140 ° C.) of the fluororubber in the rubber composition of the present invention is 70 to 150, preferably 80 to 150, more preferably 90 to 150, and 100 to 150. More preferably it is. When the Mooney viscosity of the fluororubber is less than 70, it tends to be impossible to give a good balance of compression set and cracking property under high temperature and high compression conditions to the resulting sealing material. Molding tends to be difficult. In general, products whose Mooney viscosity is adjusted to 60 are commercially available and widely used. However, a fluororubber composition having both sealing properties, cracking properties, and workability under high temperature and high compression conditions. This range is not sufficient for construction and it is necessary to select a Mooney viscosity in the region that is not generally used.

  Here, the Mooney viscosity is a value obtained by measurement using a Mooney viscosity measuring device (manufactured by MV2000E ALPHA TECHNOLOGIES) in accordance with JIS K 6300 (1994). The measurement conditions are values measured using an L-shaped rotor at 140 ° C. with a preheating time of 1 minute and a measurement time of 20 minutes.

  In the present invention, the fluororubber in the rubber composition may be one kind or a combination of two or more, but in the case of two or more, the Mooney viscosity of the combined fluororubbers is the above predetermined value. It only has to be in the range. Specifically, for example, even when a Mooney viscosity of 60 and a fluorine rubber of 160 are blended to reach a Mooney viscosity of 110, the present invention falls within the scope of the present invention.

  The rubber composition of the present invention is obtained by blending a vulcanizing agent with the fluororubber. Moreover, you may use a vulcanization accelerator with a vulcanizing agent.

  The vulcanizing agent and the vulcanization accelerator are used for vulcanizing the fluororubber. Here, vulcanization means that the same or different polymer chains of fluororubber are cross-linked by a vulcanizing agent. By cross-linking in this way, the fluororubber is improved in tensile strength and is good. It can be set as the sealing material of this invention which has elasticity.

  The vulcanization system used in the present invention may be appropriately selected depending on the kind of the cure site or the use of the obtained sealing material when the fluorinated rubber contains a crosslinkable group (cure site). As the vulcanization system, any of a polyol vulcanization system, a peroxide vulcanization system, and a polyamine vulcanization system can be adopted.

  Here, the vulcanized fluoro rubber vulcanized by the polyol vulcanization system has a carbon-oxygen bond at the crosslinking point, has a small compression set, good moldability, and excellent sealing properties. Because of its characteristics, it is suitable for the sealing material of the present invention.

  Since the vulcanized fluororubber vulcanized by the peroxide vulcanization system has a carbon-carbon bond at the crosslinking point, a polyol vulcanization system having a carbon-oxygen bond at the crosslinking point and a carbon-nitrogen double bond. Compared to a polyamine vulcanization system having a bond, it is characterized by excellent chemical resistance and steam resistance.

  Vulcanized fluororubber vulcanized by polyamine vulcanization has a carbon-nitrogen double bond at the cross-linking point and is characterized by excellent dynamic mechanical properties. However, as compared with a vulcanized fluoro rubber obtained by vulcanization using a polyol vulcanization system or a peroxide vulcanization system vulcanizing agent, compression set which is the most important physical property as a sealing material tends to increase.

  Therefore, it is preferable to use a polyol vulcanization system or a peroxide vulcanization system vulcanizing agent as the rubber composition of the present invention. From the viewpoint of excellent sealing properties as described above, a polyol vulcanizing system vulcanizing agent is preferable. It is more preferable to use

  As the vulcanizing agent in the present invention, polyamine-based, polyol-based and peroxide-based vulcanizing agents generally known for fluoro rubbers can be used.

  Examples of the polyamine vulcanizing agent include polyamine compounds such as hexamethylenediamine carbamate, N, N′-dicinnamylidene-1,6-hexamethylenediamine, and 4,4′-bis (aminocyclohexyl) methanecarbamate. Among these, N, N′-dicinnamylidene-1,6-hexamethylenediamine is preferable.

  As the polyol vulcanizing agent, a compound conventionally known as a vulcanizing agent for fluororubber can be used. For example, a polyhydroxy compound, particularly, a polyhydroxy aromatic compound is preferably used from the viewpoint of excellent heat resistance. It is done.

  The polyhydroxy aromatic compound is not particularly limited. For example, 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A), 2,2-bis (4-hydroxyphenyl) perfluoropropane. (Hereinafter referred to as bisphenol AF), resorcin, 1,3-dihydroxybenzene, 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 (hereinafter referred to as bisphenol B), 4,4-bis (4-hydroxyphenyl) valeric acid, 2 , 2-Bis (4-hydroxyphenyl) Tetrafluorodichloropropane, 4,4′-dihydroxydiphenyl sulfone, 4,4′-dihydroxydiphenyl ketone, tri (4-hydroxyphenyl) methane, 3,3 ′, 5,5′-tetrachlorobisphenol A, 3,3 Examples include ', 5,5'-tetrabromobisphenol A. These polyhydroxy aromatic compounds may be an alkali metal salt, an alkaline earth metal salt or the like, but when the copolymer is coagulated using an acid, it is preferable not to use the metal salt.

The peroxide vulcanizing agent may be a compound having a reactive activity with respect to peroxy radicals and polymer radicals. For example, CH ₂ ═CH—, CH ₂ ═CHCH ₂ —, CF ₂ ═CF And a polyfunctional compound having a functional group such as-. Specifically, for example, triallyl cyanurate, triallyl isocyanurate (TAIC), triallyl formal, triallyl trimellitate, N, N′-n-phenylenebismaleimide, dipropargyl terephthalate, diallyl phthalate, tetra Allyl terephthalate amide, triallyl phosphate, bismaleimide, fluorinated triallyl isocyanurate (1,3,5-tris (2,3,3-trifluoro-2-propenyl) -1,3,5-triazine-2, 4,6-trione), tris (diallylamine) -S-triazine, triallyl phosphite, N, N-diallylacrylamide, 1,6-divinyldodecafluorohexane, hexaallylphosphoramide, N, N, N ′, N'-tetraallyltetraphthalamide, N, N, N , N'- tetraallyl malonamide, trivinyl isocyanurate, 2,4,6-vinyl methyl trisiloxane, tri (5-norbornene-2-methylene) cyanurate, triallyl phosphite. Among these, triallyl isocyanurate (TAIC) is preferable from the viewpoint of vulcanizability and physical properties of the vulcanizate.

  Among these vulcanizing agents, a polyhydroxy compound is preferable because the compression set of the obtained sealing material is small, moldability is good, and sealing properties are excellent. Group compounds are more preferred, and bisphenol AF is more preferred.

  As a compounding quantity of a vulcanizing agent, it is 0.5-1.7 weight part with respect to 100 weight part of fluororubber, It is preferable that it is 0.6-1.5 weight part, 0.7-1 More preferably, it is 3 parts by weight. If the vulcanizing agent is less than 0.5 parts by weight, the crosslinking density tends to be low and the compression set tends to be large. If the vulcanizing agent exceeds 1.7 parts by weight, the crosslinking density becomes too high and cracks occur during compression. It tends to be easier.

  In the polyol vulcanization system, a vulcanization accelerator is usually used in combination with the polyol vulcanizing agent. When a vulcanization accelerator is used, the vulcanization reaction can be promoted by promoting the formation of an intramolecular double bond in the dehydrofluorination reaction of the fluororubber main chain.

  As the polyol vulcanization accelerator, a compound having a property that it is difficult to add to the fluororubber main chain is preferable, and an onium compound is generally used. The onium compound is not particularly limited, and examples thereof include ammonium compounds such as quaternary ammonium salts, phosphonium compounds such as quaternary phosphonium salts, oxonium compounds, sulfonium compounds, cyclic amines, and monofunctional amine compounds. Of these, quaternary ammonium salts and quaternary phosphonium salts are preferred.

  The quaternary ammonium salt is not particularly limited. For example, 8-methyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8-methyl-1,8-diazabicyclo [5, 4,0] -7-undecenium iodide, 8-methyl-1,8-diazabicyclo [5,4,0] -7-undecenium hydroxide, 8-methyl-1,8-diazabicyclo [5 , 4,0] -7-Undecenium methyl sulfate, 8-ethyl-1,8-diazabicyclo [5,4,0] -7-undecenium bromide, 8-propyl-1,8-diazabicyclo [5 , 4,0] -7-undecenium bromide, 8-dodecyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8-dodecyl-1,8-diazabicyclo [5 4,0] -7-undecenium hydroxide, 8-eicosyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8-tetracosyl-1,8-diazabicyclo [5, 4,0] -7-undecenium chloride, 8-benzyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride (hereinafter referred to as DBU-B), 8-benzyl-1 , 8-diazabicyclo [5,4,0] -7-undecenium hydroxide, 8-phenethyl-1,8-diazabicyclo [5,4,0] -7-undecenium chloride, 8- (3- Phenylpropyl) -1,8-diazabicyclo [5,4,0] -7-undecenium chloride and the like. Among these, DBU-B is preferable from the viewpoint of vulcanizability and physical properties of the vulcanizate.

  The quaternary phosphonium salt is not particularly limited. For example, tetrabutylphosphonium chloride, benzyltriphenylphosphonium chloride (hereinafter referred to as BTPPC), benzyltrimethylphosphonium chloride, benzyltributylphosphonium chloride, tributylallylphosphonium chloride, tributyl. -2-methoxypropylphosphonium chloride, benzylphenyl (dimethylamino) phosphonium chloride, and the like. Among these, benzyltriphenylphosphonium chloride (BTPPC) is preferable from the viewpoint of vulcanizability and physical properties of the vulcanizate. .

  Further, as a vulcanization accelerator, a quaternary ammonium salt, a solid solution of a quaternary phosphonium salt and bisphenol AF, or a chlorine-free vulcanization accelerator disclosed in JP-A-11-147891 can be used.

  The peroxide vulcanization accelerator may be an organic peroxide that can easily generate a peroxy radical in the presence of heat or a redox system. Specifically, for example, 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, t-butylperoxymaleic acid, t-butylperoxyiso Examples thereof include propyl carbonate. Among these, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane is preferable.

  As a compounding quantity of a vulcanization accelerator, 0.1-2.0 weight part is preferable with respect to 100 weight part of fluororubber, 0.1-1.5 weight part is more preferable, 0.1-0. More preferred is 7 parts by weight. If the blending amount of the vulcanization accelerator is less than 0.1 parts by weight, the vulcanization rate becomes slow, so the productivity tends to deteriorate, and if it exceeds 2.0 parts by weight, the vulcanization rate becomes too fast. Scorch and molding defects tend to occur.

  A filler may be added to the rubber composition of the present invention. As a filler, what is generally used for fluororubbers may be used.

  As fillers, for example, thermal black, furnace black, channel black, bituminous coal filler (mineral black), talc, white carbon, clay, magnesium oxide, calcium oxide, titanium oxide, silicon oxide, aluminum oxide, and other metal oxides, Metal hydroxides such as magnesium hydroxide, aluminum hydroxide, calcium hydroxide, carbonates such as magnesium carbonate, aluminum carbonate, calcium carbonate, barium carbonate, silicates such as magnesium silicate, calcium silicate, sodium silicate, aluminum silicate, Sulfates such as aluminum sulfate, calcium sulfate, barium sulfate, synthetic hydrotalcite, metal sulfides such as molybdenum disulfide, iron sulfide, copper sulfide, diatomaceous earth, asbestos, lithopone (zinc sulfide / barium sulfide) Graphite, carbon black, carbon fluoride, calcium fluoride, etc. coke and the like.

  Although the compounding quantity of a filler changes with kinds of filler, it is preferable that it is normally 0-100 weight part with respect to 100 weight part of fluororubber, and 0-50 weight part is more preferable. When the filler exceeds 100 parts by weight, the hardness increases, the workability deteriorates and the compression set tends to deteriorate.

  In order to achieve both high sealing performance and high cracking performance, it is preferable to use a combination of bituminous coal filler and other fillers. As a compounding quantity of the bituminous coal filler in this case, 5-30 weight part is preferable with respect to 100 weight part of fluororubber, 5-20 weight part is more preferable, and 5-15 weight part is further more preferable. When the blending amount of the bituminous coal filler is less than 5 parts by weight, the compression set tends to deteriorate, and when it exceeds 30 parts by weight, the hardness of the molded product tends to be hard and the sealing property tends to be deteriorated. Even if the hardness is adjusted by the ratio with other fillers, if the bituminous coal filler exceeds 30 parts by weight, the mechanical strength is lowered and the crack is easily broken during compression.

  To the rubber composition of the present invention, a metal oxide or a metal hydroxide may be added as an acid acceptor or a vulcanization acceleration aid.

  Metal oxides are mainly used as acid acceptors, and are used in polyol vulcanization systems and polyamine vulcanization systems to neutralize acidic substances generated during vulcanization.

  Metal hydroxide is mainly used as a vulcanization accelerator, and reacts with the vulcanization accelerator in the polyol vulcanization system to effect the fluorination reaction by activating the dehydrofluorination action and the vulcanization accelerator. It can be promoted.

  Examples of the metal oxide include magnesium oxide, lead oxide, calcium oxide, zinc oxide, iron oxide, titanium oxide, silicon oxide, and aluminum oxide. Among these, as the acid acceptor, magnesium oxide and its surface-treated product are preferable. In addition to this, synthetic hydrotalcite can also be used as the acid acceptor. In addition, zinc oxide is used for improving heat resistance, iron oxide, titanium oxide and silicon oxide are used as a colorant and filler, and aluminum oxide is used as a thermal conductivity imparting agent.

  Examples of the metal hydroxide include calcium hydroxide, magnesium hydroxide, aluminum hydroxide and the like. Among these, calcium hydroxide and its surface-treated product are preferable.

  The addition amount of the metal oxide and the metal hydroxide is preferably 0 to 25 parts by weight and more preferably 0 to 10 parts by weight with respect to 100 parts by weight of the fluororubber. If the metal oxide exceeds 25 parts by weight, scorching tends to occur, and if the metal hydroxide exceeds 25 parts by weight, compression set tends to deteriorate.

  Furthermore, in the rubber composition of the present invention, as long as the effects of the present invention are not impaired, a processing aid, a release agent, a colorant, a conductivity imparting agent, a thermal conductivity imparting agent, a surface non-adhesive agent, You may add compounding agents, such as an adhesion | attachment / adhesive, a softness | flexibility imparting agent, a heat resistance improving agent, and a flame retardant.

  The rubber composition of the present invention comprises a rubber kneading generally used with a fluoro rubber, a vulcanizing agent, and if necessary, a vulcanization accelerator, a filler, a metal oxide, a metal hydroxide, and other compounding agents. It is obtained by kneading using an apparatus. As the rubber kneading apparatus, a roll, a kneader, a Banbury mixer, an internal mixer, a twin screw extruder, or the like can be used.

  Vulcanizing agents, vulcanization accelerators, fillers, metal oxides, metal hydroxides, and other compounding agents must be uniformly dispersed in the rubber. If not uniformly dispersed, the vulcanization rate is reduced, It tends to cause a decrease in mechanical strength / elongation and a deterioration in crackability during compression.

  In particular, when a polyhydroxy compound is used as the vulcanizing agent, the melting point of the vulcanizing agent / vulcanization accelerator is often relatively high, and the vulcanizing agent / vulcanization acceleration is performed in order to disperse the rubber uniformly. After the agent is kneaded while being melted at a high temperature of 120 to 200 ° C. using a closed type kneader such as a kneader, the filler, metal oxide, metal hydroxide, and other compounding agents are relatively less than this. A method of kneading at a low temperature is preferred. There is also a method in which a vulcanizing agent and a vulcanization accelerator are once melted and uniformly dispersed using a solid solution in which a melting point drop is caused.

  Furthermore, after kneading the fluororubber, vulcanizing agent, vulcanization accelerator, filler, metal oxide, metal hydroxide, and other compounding agents, the mixture is allowed to stand at room temperature for 12 hours or more and then kneaded again. Further, dispersibility can be improved.

  The sealing material of the present invention can be obtained by vulcanizing and molding the rubber composition of the present invention using a general rubber molding machine. A compression press, an injection molding machine, an injection molding machine or the like can be used as the rubber molding machine. A rubber composition preformed into a predetermined shape using a roll, an extruder, or a preforming machine is used at 150 to 230 ° C. The primary vulcanization is performed by heating at about 1 to 60 minutes. The method using a compression press is a molding method suitable for fluororubber having a higher Mooney viscosity than other methods, and is suitably used as a method for molding the sealing material of the present invention.

  The sealing material formed by the primary vulcanization is preferably subjected to secondary vulcanization using an air oven. Secondary vulcanization is performed for the purpose of completing the above primary vulcanization reaction, decomposing the remaining vulcanizing agent and vulcanization accelerator without cross-linking reaction, and releasing gas generated during vulcanization. By performing secondary vulcanization, the mechanical properties such as tensile strength and compression set of the sealing material of the present invention can be improved.

  The above secondary vulcanization conditions usually vary depending on the vulcanization system, the polyamine vulcanization system is 180-220 ° C. for about 16-24 hours, the polyol vulcanization system is 210-260 ° C. for about 16-24 hours, and the peroxide vulcanization system. The system is generally performed at 160 to 200 ° C. for about 2 to 24 hours. In the case of the sealing material of the present invention, it is characterized by a sealing property and a cracking property under high temperature and high compression, and secondary vulcanization at a higher temperature is preferable. In the case of the sealing material of the present invention, it is preferable to perform secondary vulcanization at a temperature of 280 ° C. or more for 1 hour or more, and at a temperature of 250 ° C. or more for 3 hours or more, and then at a temperature of 290 ° C. or more for 1 hour or more. It is more preferable to vulcanize. If the secondary vulcanization temperature is low, the compression set becomes insufficient due to the influence of the residual vulcanizing agent and vulcanization accelerator at high temperature, and if the secondary vulcanization temperature is too high, the polymer deteriorates.

  The blending amount of the vulcanizing agent with respect to 100 parts by weight of the fluororubber in the rubber composition of the present invention is X (parts by weight), and the compression set at 25% compression of the P-24 · O-ring at 280 ° C. × 72 hours is Y. (%) Preferably satisfies 20X + Y ≦ 70, more preferably satisfies 20X + Y ≦ 68, and more preferably satisfies 20X + Y ≦ 67. The lower limit of 20X + Y is not particularly limited, but preferably satisfies 1 ≦ 20X + Y, and more preferably satisfies 30 ≦ 20X + Y. If 20X + Y exceeds 70, even if the blending amount of the vulcanizing agent is adjusted, it tends to be difficult to achieve both compression set and crackability.

  Further, 25% compression of a P-24 · O ring obtained by vulcanizing and molding the rubber composition of the present invention is Y (%) at a compression set of 280 ° C. × 72 hours, and 50% compression of the O ring is 280 ° C. X When the cracking rate in 1 hour is Z (%), 10Y + Z ≦ 500 is preferably satisfied, 10Y + Z ≦ 480 is more preferable, and 10Y + Z ≦ 460 is more preferable. Further, the lower limit value of 10Y + Z is not particularly limited, but preferably satisfies 100 ≦ 10Y + Z. If 10Y + Z exceeds 500, it tends to be difficult to achieve both compression set and crackability.

  Since the sealing material of the present invention has sealing properties and cracking properties under high temperature and high compression as described above, it is possible to apply pressure such as caulking for the purpose of ensuring the sealing properties. It can be suitably used for applications that require maintaining sealing properties for a long period of use.

  Furthermore, the present invention is an oxygen sensor sealing material obtained by vulcanizing a rubber composition comprising fluororubber and a vulcanizing agent, wherein the Mooney viscosity (ML1 + 20, 140 ° C.) of the fluororubber in the composition is It is related with the sealing material for oxygen sensors which are 70-150.

  As the fluororubber and the vulcanizing agent, those described above can be preferably used. The Mooney viscosity of the fluororubber, the measuring method of Mooney viscosity, the vulcanization conditions, and the like are the same as described above.

  Although the compounding quantity of a vulcanizing agent is not specifically limited, The said compounding quantity can be employ | adopted.

  The application of the sealing material of the present invention is not particularly limited. For example, an engine body of an automobile engine, a main motion system, a valve system, a lubricant / cooling system, a fuel system, an intake / exhaust system; a drive system transmission system; Chassis steering systems; brake systems; gaskets that require heat resistance, oil resistance, fuel oil resistance, antifreeze for engine cooling, and steam resistance, such as basic electrical components, electrical components for control systems, and electrical components for equipment And sealing materials such as non-contact type and contact type packings (self seal packing, piston ring, split ring type packing, mechanical seal, oil seal, etc.).

  The sealing material used in the engine body of the automobile engine is not particularly limited. For example, a cylinder head gasket, a cylinder head cover gasket, an oil pan packing, a gasket such as a general gasket, an O-ring, a packing, a timing belt cover gasket, etc. For example, a sealing material.

  The seal material used in the main motion system of the automobile engine is not particularly limited, and examples thereof include a shaft seal such as a crankshaft seal and a camshaft seal.

  The seal material used in the valve system of the automobile engine is not particularly limited, and examples thereof include a valve stem oil seal of an engine valve.

  The seal material used in the lubricant / cooling system of the automobile engine is not particularly limited, and examples thereof include an engine oil cooler seal gasket.

  The sealing material used in the engine fuel system for automobiles is not particularly limited. For example, fuel injection such as an oil seal of a fuel pump, a filler seal of a fuel tank, a tank packing, a connector O link of a fuel tube, etc. Examples thereof include an injector cushion ring, an injector seal ring, an injector O-ring, and a carburetor flange gasket.

  The sealing material used for the intake / exhaust system of the automobile engine is not particularly limited. For example, the intake manifold packing of the manifold, the exhaust manifold packing, the throttle body packing of the throttle, the turbine shaft seal of the turbo charge, etc. Can be given.

  The seal material used in the transmission system of an automobile engine is not particularly limited. For example, a transmission-related bearing seal, an oil seal, an O-ring, a packing, an automatic transmission O-ring, packings, etc. can give.

  The sealing material used for the brake system of the engine for automobiles is not particularly limited. For example, oil seals, O-rings, packings, master cylinder piston cups (rubber cups), caliper seals, boots, etc. Etc.

  The sealing material used for the electrical equipment for the automobile engine is not particularly limited, and examples thereof include an O-ring and a packing of a car air conditioner.

  Among these, the sealing material of the present invention is particularly suitable for an oxygen sensor, and further suitable for an automobile oxygen sensor.

  Applications other than those for automobiles are not particularly limited, for example, oil-resistant, chemical-resistant, heat-resistant, steam- or weather-resistant packings, O-rings, and other sealing materials in transportation such as ships and airplanes; Packing, O-rings, sealing materials for food plants, and similar packings, O-rings, sealing materials for food plant equipment (including household products); similar packings, O-rings, sealing materials for nuclear plant equipment; The same packing, O-ring, sealing material and the like can be mentioned.

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

<Mooney viscosity>
The obtained fluororubber was sheeted three times through a kneading roll machine (roll gap: about 1 mm) equipped with two 8-inch rolls, and an L-shaped rotor was used using a Mooney viscosity meter (manufactured by MV2000E ALPHA TECHNOLOGIES). Was measured at 140 ° C. with a preheating time of 1 minute and a measurement time of 20 minutes in accordance with JIS K 6300 (1994).

<Weight average molecular weight (Mw) and number average molecular weight (Mn)>
Apparatus: HLC-8020 (manufactured by Tosoh Corporation)
Column: GPC KF-806M (Showa Column) 2 GPC KF-801 (Showa Column) 1 GPC KF-802 (Showa Column) 1 Detector: RI detector (Tosoh Corp.)
Developing solvent: Tetrahydrofuran Column temperature: 40 ° C
Calibration curve temperature: 35 ° C
Sample concentration: 0.1% by weight
Standard samples: various monodisperse polystyrene ((Mw / Mn) = 1.14 (Max)), TSK
standard POLYSYRENE (manufactured by Tosoh Corporation)

<Composition analysis>
¹⁹ F-NMR (Bruker AC300P type) was used for measurement. However, the TFE-containing polymer was measured using ¹⁹ F-NMR (FX100 type manufactured by JEOL Ltd.).

<Hardness>
It measured based on JISK6253 (1997) using the type A durometer (Brand name: ASKER, Kobunshi Keiki Co., Ltd.) using the vulcanized sheet obtained by the Example and the comparative example.

<Tensile breaking strength and tensile breaking elongation>
Using the vulcanized sheets obtained in Examples and Comparative Examples, using a tensile tester (Tensilon, manufactured by Orientec Co., Ltd.), according to JIS K6251 (1993), under conditions of 500 mm / min, Using Dumbbell No. 4, the tensile strength at break and the tensile elongation at 23 ° C. were measured.

<Compression set>
According to ASTM D1313 (1994), the compression set after the P-24 · O-rings obtained in Examples and Comparative Examples were allowed to stand for 72 hours at a temperature of 280 ° C. and a compression deformation of 25%. It was measured.

<Crack ratio>
The P-24 · O-ring obtained in Examples and Comparative Examples was charged into a compression device and a spacer preheated to 280 ° C., and held for 1 hour under conditions of a compression rate of 50% and 280 ° C., and then the compression device The sample was taken out from the container and visually checked for cracks. A total of 10 O-links were examined, and the cracking rate was determined from the following formula.
Cracking rate (%) = [(number of cracked O-rings) / 10] × 100

Each trade name in the table and specification is as follows.
BIS-AF: Bisphenol AF
P-21: bisphenol AF and BTPPC mixed at a weight ratio of 2: 1, melted at 180 ° C. for 1-2 hours, cooled and pulverized, solid solution N-990: thermal black 325-BA manufactured by Cancarb, Keystone Filler & Mfg Bituminous coal filler MA-150 manufactured by Kyowa Chemical Industry Co., Ltd. Highly active magnesium oxide CALDIC 2000: Calcium hydroxide manufactured by Omi Chemical Industry Co., Ltd.

Production Example 1 (Production of seed polymer)
As a stirrer, a polymerization tank having an internal volume of 1.8 liters having an electromagnetic induction stirrer was charged with 720 g of pure water, 290 g of a 10 wt% ammonium perfluorooctanoate aqueous solution, and 0.6 g of diethyl malonate. After fully replacing with nitrogen gas, the pressure was reduced. This operation was repeated three times, and 20 g of VdF and 51 g of HFP were charged under reduced pressure, and the temperature was raised to 80 ° C. with stirring. Subsequently, 0.02 g of ammonium persulfate (APS) dissolved in 0.6 g of pure water was injected with nitrogen gas to initiate polymerization. The polymerization pressure was set to 2 MPa, and in order to compensate for the pressure drop during the polymerization, a VdF / HFP mixed monomer (78/22 (mol%)) was continuously supplied, and polymerization was performed with stirring. By the end of the polymerization, 215 g of monomer was fed into the tank.

The weight of the obtained emulsion was 1233 g, the polymer concentration was 18.1 wt%, and the number of polymer particles was 1.2 × 10 ¹⁶ particles / water 1 g. After 30 minutes, the stirring was stopped and the monomer was released to stop the polymerization.

Production Example 2 (Production of binary fluororubber (BP-1))
977 g of pure water and 10.2 g of an aqueous dispersion of polymer particles produced in Production Example 1 were charged into a 1.83 liter polymerization tank having the same electromagnetic induction stirrer as in Production Example 1, and the system was filled with nitrogen gas. After sufficient substitution, the pressure was reduced. This operation was repeated three times. Under reduced pressure, 142 g of VdF and 449 g of HFP were charged, and the temperature was raised to 80 ° C. with stirring. Subsequently, 0.08 g of APS dissolved in 1.45 g of diethyl malonate and 15 g of pure water was injected with nitrogen gas to start the polymerization, and the polymerization was continued under the conditions of (a) and (b). Stirring was stopped and the monomer was released to stop the polymerization.
(A) VdF / HFP (78/22 (mol%)) monomer mixture was continuously supplied, and the pressure in the gas phase portion was maintained at 6 MPa. Further, 282 g of monomer was supplied into the tank until the polymerization was completed.
(B) The stirring speed was maintained at 560 rpm.

The weight of the obtained emulsion was 1376 g, and the polymer concentration was 26.4% by weight. Moreover, it was 363 g as fluororubber, the weight average molecular weight Mw measured by GPC was 510,000, the number average molecular weight Mn was 210,000, and Mw / Mn was 2.4. Further, the composition of the polymer measured by ¹⁹ F-NMR was VdF / HFP = 78/22 (mol%).

Production Example 3 (Production of Binary Fluoro Rubber (BP-2))
The fluororubber was polymerized in the same manner as in Production Example 2 except that 1.80 g of diethyl malonate and 0.09 g of APS were used.

The polymerization time was 2.7 hours, the weight of the obtained emulsion was 1380 g, and the polymer concentration was 26.7% by weight. The fluororubber was 368 g, the weight average molecular weight Mw measured by GPC was 460,000, the number average molecular weight Mn was 200,000, and Mw / Mn was 2.3. Further, the composition of the polymer measured by ¹⁹ F-NMR was VdF / HFP = 78/22 (mol%).

Production Example 4 (Production of binary fluororubber (BP-3))
A fluororubber was polymerized in the same manner as in Production Example 2, except that 2.0 g of diethyl malonate and 0.09 g of APS were used.

The polymerization time was 2.9 hours, the weight of the obtained emulsion was 1372 g, and the polymer concentration was 26.4% by weight. The fluororubber was 362 g, the weight average molecular weight Mw measured by GPC was 400,000, the number average molecular weight Mn was 170,000, and Mw / Mn was 2.4. Further, the composition of the polymer measured by ¹⁹ F-NMR was VdF / HFP = 78/22 (mol%).

Production Example 5 (Production of Binary Fluoro Rubber (BP-4))
A fluororubber was polymerized in the same manner as in Production Example 2 except that 2.80 g of diethyl malonate and 0.12 g of APS were used.

The polymerization time was 2.5 hours, the weight of the obtained emulsion was 1364 g, and the polymer concentration was 26.5% by weight. The fluororubber was 361 g, the weight average molecular weight Mw measured by GPC was 290,000, the number average molecular weight Mn was 130,000, and Mw / Mn was 2.2. Further, the composition of the polymer measured by ¹⁹ F-NMR was VdF / HFP = 78/22 (mol%).

Production Example 6 (Production of ternary fluororubber (BP-5))
In a stainless steel autoclave with an internal volume of 48 liters having no ignition source, 29 liters of pure water and 29 g of C ₇ F ₁₅ COONH ₄ as an emulsifier were placed, and the system temperature was sufficiently replaced with nitrogen gas. The temperature was raised to 60 ° C. While stirring at 200 rpm, a mixed gas of VdF, HFP, and TFE was charged so that the internal pressure was 15 kgf / cm ² G at VdF / HFP / TFE = 56/28/16 (mol%).

  Then, a solution prepared by dissolving 24 g of ammonium persulfate in 50 mL of water was injected using nitrogen to initiate the reaction.

Since the pressure decreases with the progress of the polymerization reaction, the mixed gas of VdF, HFP and TFE is VdF / HFP / TFE = 66.5 / 16 / 17.5 (mol%), and the internal pressure is 15 kgf / cm ² G At the same time, isopentane as a chain transfer agent was equally divided into 5 parts with respect to the reaction yield, and a total amount of 2.5 cm ^{3 was} charged. After 326 minutes from the start, the supply was stopped, the autoclave was cooled, the unreacted monomer was released, and a translucent aqueous dispersion having a solid content concentration of 20 to 25% by mass was obtained. The obtained aqueous dispersion was coagulated by a conventional method, and the coagulated polymer was washed and dried to obtain a white solid of a ternary fluoroelastomer having VdF / TFE / HFP = 65/20/15 (mol%). Got.

When the polymerization average molecular weight was measured by the above-mentioned method, it was 550,000. Moreover, the composition of the polymer measured by ¹⁹ F-NMR was VdF / TFE / HFP = 65/20/15 (mol%).

Example 1 (Production of binary fluororubber composition)
While heating the jacket of a pressure type kneader with an internal volume of 3 liters to 140 ° C. with a heater, gradually add 4000 g of the binary fluororubber obtained in Production Example 2, and then BIS-AF
26 g and P-21 26 g were added and kneaded for 12 minutes. Each time kneading for 3 minutes, the rotor was stopped, the pressure lid was released, the top and bottom of the rubber were switched by reverse rotation of the rotor, and pressurization and kneading were repeated. The rubber temperature immediately after completion of kneading was 168 ° C. The rotation speed of the rotor was set to 33 rpm for the front blade and 22 rpm for the rear blade.

  A composition comprising fluororubber, a vulcanizing agent and a vulcanization accelerator (S) is cooled and finally sheeted using a kneading roll machine equipped with two 12 inch diameter rolls after completion of kneading. -1) was taken out.

  Composition (S-1), thermal black (manufactured by N-990 Cancarb), bituminous coal filler (manufactured by 325BA Keystone Filler & Mfg), highly active magnesium oxide (manufactured by MA-150 Kyowa Chemical Industry Co., Ltd.), hydroxylation Calcium (CALDIC 2000, manufactured by Omi Chemical Co., Ltd.) was added so as to have a blending ratio shown in Table 2, and mixed at 25 to 70 ° C. by a normal method using a kneading roll machine equipped with two 8-inch rolls. Kneaded. This was left at room temperature for about 20 hours, kneaded again in the same roll machine, finally sheeted to a thickness of about 2 mm, and the unvulcanized rubber sheet (G-1) was taken out.

Next, the unvulcanized rubber sheet (G-1) was subjected to primary vulcanization with a 100-ton compression press at 170 ° C. for 10 minutes at a gauge pressure of 60 kgf / cm ² to obtain a vulcanized sheet (width: about 140 mm, length). : About 110 mm, thickness: about 2 mm) and a P-24 • O-ring (inner diameter: 23.7 mm, thickness 3.5 mm, exercise O-ring). Further, the obtained vulcanized sheet and P-24 • O-ring were subjected to secondary vulcanization at 260 ° C. for 5 hours and 300 ° C. for 2 hours.

Examples 2 to 4 and Comparative Examples 1 to 3
A vulcanized sheet and a P-24 • O-ring were obtained in the same manner as in Example 1 except that the fluororubbers obtained in Production Examples 2 to 6 were used and the blending conditions shown in Table 2 were used.

  In Table 2, X is the compounding amount (parts by weight) of the vulcanizing agent with respect to 100 parts by weight of the fluororubber, and Y is the compression set at 25% compression of the P-24 • O-ring at 280 ° C. × 72 hours ( Z) is the crack rate (%) at 50% compression of the P-24 • O-ring at 280 ° C. × 1 hour.

Claims (9)

A rubber composition comprising a binary fluororubber comprising a vinylidene fluoride unit and a hexafluoropropylene unit and a vulcanizing agent being a polyhydroxy compound ,
The vulcanizing agent is 0.5 to 1.7 parts by weight with respect to 100 parts by weight of the fluororubber in the composition, and the Mooney viscosity (ML1 + 20, 140 ° C.) of the fluororubber in the composition is 80 to 150. A rubber composition. 2. The rubber composition according to claim 1, wherein the Mooney viscosity (ML1 + 20, 140 ° C.) of the fluororubber is 100 to 150. 3. When X (parts by weight) is added to 100 parts by weight of fluororubber, 20% + Y when the compression set at 25% compression at 280 ° C. × 72 hours is Y (%). The rubber composition according to claim 1 or 2, wherein ≦ 70 is satisfied. The rubber composition according to any one of claims 1 to 3 , comprising 5 to 30 parts by weight of a bituminous coal filler with respect to 100 parts by weight of the fluororubber. Sealing material obtained by vulcanizing the rubber composition according to any one of claims 1-4. 6. The sealing material according to claim 5 , wherein after the vulcanization molding, the heat treatment is performed at a temperature of 280 [deg.] C. or more for 1 hour or more. The compression set at 25% compression of the P-24 • O-ring at 280 ° C. × 72 hours is defined as Y (%), and the cracking rate at 50% compression of the O-ring at 280 ° C. × 1 hour is defined as Z (%). The sealing material according to claim 5 or 6 , wherein 10Y + Z ≦ 500 is sometimes satisfied. Oxygen sensor sealing material made of a sealing material according to any one of claims 5-7. A sealing material for an oxygen sensor obtained by vulcanizing a rubber composition comprising a binary fluororubber comprising a vinylidene fluoride unit and a hexafluoropropylene unit and a vulcanizing agent being a polyhydroxy compound ,
A sealing material for oxygen sensors, wherein the Mooney viscosity (ML1 + 20, 140 ° C.) of the fluororubber in the composition is 80 to 150.