阅读说明：本技术 氟橡胶组合物、其制造方法以及氟橡胶交联成型品 (Fluororubber composition, process for producing the same, and fluororubber crosslinked molded article ) 是由 村上英幸 阿部俊介 于 2018-06-28 设计创作，主要内容包括：一种氟橡胶组合物,其为碳纳米管母料与氟橡胶原料的混炼混合物,所述碳纳米管母料中每100重量份氟橡胶聚合物配合了4～20重量份的不包含单层碳纳米管的纤维状碳纳米结构体即多层碳纳米管,所述氟橡胶原料至少含有氟橡胶聚合物以及增强性填充剂,所述氟橡胶组合物按照在混炼混合物中多层碳纳米管为0.5～6重量％的方式进行配合。在制造此氟橡胶组合物之时,使用辊或者捏合机进行混炼。此氟橡胶组合物可获得发挥耐磨耗性、耐起泡性的氟橡胶交联成型品。(A fluororubber composition which is a kneaded mixture of a carbon nanotube master batch and a fluororubber raw material, wherein 4 to 20 parts by weight of multilayered carbon nanotubes, which are fibrous carbon nanostructures not containing single-walled carbon nanotubes, are blended per 100 parts by weight of a fluororubber polymer in the carbon nanotube master batch, the fluororubber raw material contains at least a fluororubber polymer and a reinforcing filler, and the fluororubber composition is blended so that the multilayered carbon nanotubes are 0.5 to 6% by weight in the kneaded mixture. In the production of the fluororubber composition, kneading is carried out using a roll or a kneader. The fluororubber composition can give a fluororubber crosslinked molded article exhibiting wear resistance and blister resistance.)

1. A fluororubber composition which is a kneaded mixture of a carbon nanotube master batch and a fluororubber raw material, wherein 4 to 20 parts by weight of multilayered carbon nanotubes are blended per 100 parts by weight of a fluororubber polymer in the carbon nanotube master batch, the multilayered carbon nanotubes are fibrous carbon nanostructures not containing single-layered carbon nanotubes, and the fluororubber raw material contains at least a fluororubber polymer and a reinforcing filler,

the fluororubber composition is compounded so that the amount of the multilayered carbon nanotube in the kneaded mixture is 0.5 to 6 wt%.

2. The fluororubber composition according to claim 1, wherein the fluororubber polymer is a polyol-crosslinkable fluororubber polymer or a peroxide-crosslinkable fluororubber polymer.

3. The fluororubber composition according to claim 1, wherein the reinforcing filler is used in a proportion of 3 to 50 parts by weight per 100 parts by weight of the fluororubber polymer in the fluororubber raw material.

4. A process for producing a fluororubber composition, characterized by kneading the components using a roll or a kneader,

the fluororubber composition is a kneaded mixture of a carbon nanotube master batch and a fluororubber raw material, wherein 4 to 20 parts by weight of multi-layered carbon nanotubes are blended per 100 parts by weight of a fluororubber polymer in the carbon nanotube master batch, the multi-layered carbon nanotubes are fibrous carbon nanostructures not including single-layered carbon nanotubes, the fluororubber raw material contains at least a fluororubber polymer and a reinforcing filler, and the fluororubber composition is blended so that the multi-layered carbon nanotubes are 0.5 to 6% by weight in the kneaded mixture.

5. The method for producing a fluororubber composition according to claim 4, wherein an open roll having a pair of rolls with a roll interval of 0.7 to 1.5mm is used.

6. The method for producing a fluororubber composition according to claim 4, wherein a fluororubber raw material prepared into a billet in advance using a kneader is used as the fluororubber raw material.

7. The method for producing a fluororubber composition according to claim 4, 5 or 6, wherein the kneading is performed at a temperature of 60 to 100 ℃ using a roll or at a temperature of 100 to 200 ℃ using a kneader.

8. A fluororubber crosslinked molded article obtained by crosslinking the fluororubber composition according to claim 1, 2 or 3.

9. The fluororubber crosslinked molded article according to claim 8, which is a shaft sealing material.

10. A carbon nanotube master batch, wherein 4 to 20 parts by weight of a multilayered carbon nanotube, which is a fibrous carbon nanostructure not containing a single-layer carbon nanotube, is blended per 100 parts by weight of a fluororubber polymer.

Technical Field

The present invention relates to a fluororubber composition, a method for producing the same, and a fluororubber crosslinked molded product. More specifically, the present invention relates to a fluororubber composition capable of obtaining a fluororubber crosslinked molded product exhibiting abrasion resistance and blistering resistance (blistering resistance), a method for producing the same, and a fluororubber crosslinked molded product.

Background

Fluororubber compositions are excellent in oil resistance and fuel resistance, and are used as sealing materials for oil seals, O-rings, and packing (packing) in a wide range of fields such as automobiles and industrial machines. In recent years, as the use of the composition has been expanded, there are concerns that: the use under a particularly high load environment causes blistering in the vicinity of the seal and/or abnormal wear of the sliding surface.

In terms of the necessary functions of the sealed product, it is preferable to blend a filler having high reinforcement properties, but there are the following problems: even when a conventional filler is blended, sufficient reinforcing properties cannot be obtained, and good sealing properties (product functions) cannot be obtained.

The following techniques have been disclosed: a dynamic seal product and/or a static seal product for an oilfield device is produced using a carbon fiber composite material obtained by mixing a1 st composite elastomer (obtained by blending carbon nanotubes in natural rubber or the like) and a 2 nd composite elastomer (obtained by blending carbon black in natural rubber or the like) (patent document 1).

Patent document 1 clearly shows that 60 parts by mass or more and 100 parts by mass or less of carbon nanotubes are blended with 100 parts by mass of the 1 st elastic body. Thus, the amount of carbon nanotubes mixed in the 1 st composite elastomer was 37.5 mass% or more. When the 1 st elastomer is a fluororubber polymer, if it exceeds 20 parts by mass per 100 parts by mass of the fluororubber polymer, the following problems arise: the roll kneading property was poor, and the surface of the billet became dry and rough, and was not a normal rubber surface. In patent document 1, since no experiment was conducted on the fluororubber polymer, this serious problem was not noticed.

Patent document 1 discloses that the value of tensile strength and/or elongation at break is increased if carbon nanotubes are blended in natural rubber. However, in the case where the fluororubber is blended with the carbon nanotubes as exemplified above, it is unclear whether or not the values of the tensile strength and/or the elongation at break become large.

Patent document 2 describes the following technique: the carbon nanotubes are blended with an elastomer such as hydrogenated nitrile rubber or fluororubber to obtain a foaming resistance effect. However, patent document 2 describes, in comparative example 3 in which a hydrogenated nitrile rubber is used: when a multilayered fibrous carbon nanostructure containing no single-walled carbon nanotubes is used as the carbon nanotubes, the "blister resistance" effect cannot be obtained.

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a fluororubber composition capable of obtaining a fluororubber crosslinked molded article exhibiting wear resistance and/or blister resistance, a method for producing the same, and a fluororubber crosslinked molded article.

Means for solving the problems

The object 1 of the present invention is achieved by a fluororubber composition which is a kneaded mixture of a carbon nanotube master batch and a fluororubber raw material, wherein 4 to 20 parts by weight of multilayered carbon nanotubes are blended per 100 parts by weight of a fluororubber polymer in the carbon nanotube master batch, the multilayered carbon nanotubes are fibrous carbon nanostructures not including single-walled carbon nanotubes, the fluororubber raw material contains at least a fluororubber polymer and a reinforcing filler, and the fluororubber composition is blended so that the multilayered carbon nanotubes are 0.5 to 6% by weight in the kneaded mixture.

The 2 nd object of the present invention is achieved by a method for producing a fluororubber composition, wherein the fluororubber composition is produced by kneading with a roll or a kneader.

The 3 rd object of the present invention is achieved by a fluororubber crosslinked molded article obtained by crosslinking and molding the fluororubber composition.

ADVANTAGEOUS EFFECTS OF INVENTION

The fluororubber composition of the present invention achieves the following effects: a fluororubber crosslinked molded product exhibiting wear resistance and/or blister resistance can be obtained.

The obtained fluororubber crosslinked molded article can be effectively used as a shaft sealing material or the like.

The carbon nanotube master batch used as a component of the fluororubber molded article of the present invention is excellent in kneading properties, and a fluororubber crosslinked molded article excellent in foaming resistance can be obtained even when a multi-wall carbon nanotube (a fibrous carbon nanostructure not containing a single-wall carbon nanotube) is used as a carbon nanotube.

Detailed Description

1. Carbon nanotube master batch

The carbon nanotube master batch used in the present invention is obtained by mixing and kneading 4 to 20 parts by weight of a multilayered carbon nanotube per 100 parts by weight of a fluororubber polymer.

< carbon nanotube >

The carbon nanotubes used in the present invention are: the carbon hexagonal mesh surface (graphene sheet surface) of graphite is wound to form a cylindrical multilayered carbon nanotube.

In the present invention, a fibrous carbon nanostructure containing no single-walled carbon nanotube is used as the multilayered carbon nanotube. The multilayered carbon nanotube is obtained by layering a plurality of cylinders of hexagonal carbon networks in a carbon nanotube, and may be, for example, a multilayered carbon nanotube obtained by spirally winding a graphene sheet.

The average diameter of the multilayered carbon nanotube is preferably in the range of about 0.5 to 250 nm. As for the average diameter, it can be measured by observation with an electron microscope. In addition, the specific surface area of the multi-layered carbon nanotube is preferably about 250 to 300m²(ii) a range of/g. As a commercially available product of the multilayered carbon nanotube used in the present invention, a product "NC 7000" manufactured by Nanocyl corporation (Belgium) and the like can be used.

As the fluororubber polymer blended in the carbon nanotube master batch, a polyol-crosslinkable fluororubber polymer or a peroxide-crosslinkable fluororubber polymer is preferably used. Further, a polyol-crosslinkable fluororubber polymer and a peroxide-crosslinkable fluororubber polymer may be used in combination.

< polyol-crosslinkable fluororubber Polymer

As the polyol-crosslinkable fluororubber polymer, 1 or 2 or more kinds of homopolymers or copolymers of a fluoroolefin can be used.

Examples of the fluorine-containing olefin include vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, vinyl fluoride, perfluoroacrylic acid ester, perfluoroalkyl acrylate, perfluoromethyl vinyl ether, perfluoropropyl vinyl ether, and the like. These fluorine-containing olefins may be used in 1 kind or 2 or more kinds may be used in combination.

In the present invention, as the polyol-crosslinkable fluororubber polymer, a vinylidene fluoride-hexafluoropropylene 2-membered copolymer, a vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene 3-membered copolymer, and the like are preferably used. These polymers are obtained by solution polymerization, suspension polymerization or emulsion polymerization, and are commercially available (for example, DuPont products "Viton A-500", "Viton B-600", etc.).

< peroxide crosslinkable fluororubber Polymer

As the fluororubber polymer which can be peroxide-crosslinked, a peroxide-crosslinked 3-membered copolymer of a fluoroolefin or the like can be used. Examples of the fluoroolefin include compounds listed in a polyol-crosslinkable fluororubber polymer.

In the present invention, preferable examples of the fluororubber polymer crosslinkable with peroxide include, for example, a peroxide-crosslinkable vinylidene fluoride-hexafluoropropylene-perfluoroalkyl vinyl ether 3-membered copolymer, that is, fluororubber and the like. These polymers are obtained by solution polymerization, suspension polymerization or emulsion polymerization, and are commercially available (e.g., DuPont "GBL-600S", "GLT-600S", Daikin Industries, Ltd. "DAIEL-G801", etc.).

< mixing ratio of carbon nanotube to fluororubber Polymer >

The carbon nanotube master batch is obtained by mixing and kneading 4 to 20 parts by weight of a multilayered carbon nanotube per 100 parts by weight of a fluororubber polymer. When the amount is less than 4 parts by weight, the reinforcing performance of the multilayered carbon nanotube cannot be exhibited, and when the amount is more than 20 parts by weight, the kneading property is deteriorated.

< mixing >

The mixing technique is not particularly limited, and mixing can be performed using a roll mixing device or a kneader mixing device. When a roll kneading apparatus is used as the kneading technique, an open roll (open roll) is preferably used, the open roll preferably includes 2 rolls in a pair, and the roll interval is preferably set to a distance of about 0.7 to 1.5 mm.

The carbon nanotube master batch obtained by the kneading is subjected to mastication of the fluororubber (kneading), and the molecular chain of the fluororubber is appropriately cut to generate radicals. The radicals generated by the mastication are in a state of being easily connected to the multilayered carbon nanotube.

2. Method for producing fluororubber kneaded mixture

< 1 st kneading step >

In the 1 st mixing step, 4 to 20 parts by weight of the multilayered carbon nanotube is mixed with 100 parts by weight of the fluororubber polymer, and the mixture is mixed using an open roll or a kneader to prepare a carbon nanotube master batch.

The mixing technique is not particularly limited, and mixing can be performed using a roll mixing device or a kneader mixing device. When a roll kneading apparatus is used as the kneading technique, it is preferable to use open rolls, and the open rolls preferably include 2 rolls in a pair, and the roll interval is preferably set at an interval of about 0.7 to 1.5 mm.

The temperature of the fluororubber polymer in the kneading is, for example, about 60 to 100 ℃ and preferably about 80 to 100 ℃ when a roll kneading apparatus is used, and about 100 to 220 ℃ and preferably about 150 to 200 ℃ when a kneader kneading apparatus is used.

< 2 nd kneading Process

Next, in the 2 nd kneading step, a fluororubber raw material containing at least a fluororubber polymer and a reinforcing filler is blended into the carbon nanotube master batch so that the multilayered carbon nanotube is 0.5 to 6 wt% in the kneaded mixture, and the mixture is kneaded to prepare a fluororubber composition. The fluororubber polymer may be the same as or different from the fluororubber polymer used in the 1 st kneading step.

The fluororubber polymer is preferably selected from polyol-crosslinkable fluororubber polymers and peroxide-crosslinkable fluororubber polymers. The polyol-crosslinkable fluororubber polymer or the peroxide-crosslinkable fluororubber polymer may be the same polymer as the polyol-crosslinkable fluororubber polymer or the peroxide-crosslinkable fluororubber polymer used in the 1 st kneading step, or may be different from the polyol-crosslinkable fluororubber polymer or the peroxide-crosslinkable fluororubber polymer.

In a preferred embodiment of the present invention, the fluororubber crosslinked material is produced by performing two-stage kneading of the 1 st and 2 nd kneads and then crosslinking the kneaded materials. In the 1 st kneading, roll kneading or kneader kneading is used to prepare a carbon nanotube master batch containing a fluororubber polymer. This master batch was introduced into the 2 nd kneading apparatus as a roll kneading apparatus. In the 2 nd kneading apparatus, the master batch and the fluororubber raw material were kneaded and mixed to produce a fluororubber composition.

When the master batch and the fluororubber material are kneaded by the 2 nd kneading apparatus, the kneading technique is not particularly limited, but kneading may be performed by a kneader kneading apparatus and/or a roll kneading apparatus. Specifically, the following embodiments can be exemplified.

In the 2 nd mixing step, a kneader mixing device can be used as an example. In this case, the master batch may be simultaneously charged with the fluororubber raw material and kneaded, or the fluororubber raw material may be previously kneaded by a kneader, and the master batch may be charged into the mixture and kneaded.

In another embodiment of the 2 nd kneading step, a roll kneading apparatus may be used. At this time, a roll kneading apparatus having a pair of 2 rolls was used. The master batch was wound around the 1 st roll of a roll kneading apparatus, and a fluororubber raw material was put into the master batch, whereby the fluororubber composition was produced.

In addition, in the other embodiment of the 2 nd mixing step, a kneader mixing device and a roll mixing device may be used in combination. In this embodiment, a raw material of the fluororubber is kneaded by a kneader in advance to prepare a green body in advance. Thereafter, the billet is wound around a roll, and the master batch is charged into the roll, whereby a sufficiently kneaded fluororubber composition is produced.

The reinforcing filler contained in the fluororubber raw material may be selected from at least one of wollastonite, carbon black, silica, clay, talc, and the like. The reinforcing filler is used in a proportion of about 3 to 50 parts by weight, preferably about 10 to 30 parts by weight, based on 100 parts by weight of the fluororubber polymer used in the 2 nd kneading step.

The compounding agent contained in the fluororubber raw material other than the reinforcing filler may be added with, for example, other fillers described above such as calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, aluminum silicate, magnesium silicate, calcium silicate, potassium titanate, titanium oxide, barium sulfate, aluminum borate, glass fiber, aramid fiber, diatomaceous earth, and the like; processing aids such as waxes, metal soaps, and carnauba wax (carnauba wax); acid acceptors such as calcium hydroxide, magnesium oxide, zinc oxide, and hydrotalcite; an anti-aging agent; a compounding agent such as a thermoplastic resin. Among them, magnesium oxide is preferable in view of obtaining a low elastic modulus (regenerative elastic modulus), a low friction coefficient, and a low adhesion of the crosslinked fluororubber.

In the 2 nd mixing step of the present invention, mixing is performed as follows using a mixing device such as a roll or a kneader.

In the case of using rolls as the kneading apparatus, the carbon nanotube master batch obtained in the 1 st kneading step (apparatus) was wound around the 1 st roll of the 2 nd kneading apparatus including a pair of 2 rolls. A fluororubber raw material containing at least a fluororubber polymer and a reinforcing filler is put into a block (bulk) of the kneaded product wound around the 1 st roll.

Subsequently, kneading was performed between the 1 st roll and the 2 nd roll. The temperature of the fluororubber polymer in the roll kneading is, for example, about 60 to 100 ℃ and preferably about 80 to 100 ℃. In this way, the fluororubber polymer containing carbon nanotubes is kneaded with the fluororubber material at a relatively high temperature, whereby the fluororubber polymer is likely to enter the gaps between the carbon nanotubes.

Further, the roll interval between the 1 st roll and the 2 nd roll is preferably set to a range of about 0.7 to 1.5 mm. In kneading, the mixture may be fed to an open roll and subjected to thin passing 1 to a plurality of times, for example, 1 to about 10 times. By this thin pass, a high shear force is applied to the fluororubber polymer, and the aggregated carbon nanotubes are well dispersed in the fluororubber polymer.

The step of dispersing the carbon nanotubes in the fluororubber by the shearing force is not limited to the open roll method, and an internal kneading method or a multi-axis extrusion kneading method may be used. When kneading and mixing are carried out using a kneader, the temperature is about 100 to 200 ℃, preferably about 140 to 180 ℃.

< crosslinking step >

In the 2 nd kneading step, a crosslinking agent may be mixed with the separated composite material before, during or after mixing of the fluororubber raw material and the carbon nanotube master batch, and a fluororubber crosslinked molded product may be produced by crosslinking molding.

The polyol-based crosslinking agent used for the polyol-crosslinkable fluororubber polymer is preferably bisphenol.

Specific examples thereof include polyhydroxy aromatic compounds such as 2, 2-bis (4-hydroxyphenyl) propane [ bisphenol a ], 2-bis (4-hydroxyphenyl) perfluoropropane [ bisphenol AF ], bis (4-hydroxyphenyl) sulfone [ bisphenol S ], bisphenol a bis (diphenylphosphate), 4' -dihydroxybiphenyl (4,4' -dihydroxydiphenyl), 4' -dihydroxydiphenylmethane and 2, 2-bis (4-hydroxyphenyl) butane, and bisphenol a and bisphenol AF are preferably used. They may also be in the form of alkali metal salts or alkaline earth metal salts. The content of the polyol-based crosslinking agent is preferably in the range of about 0.4 to 20 parts by weight based on 100 parts by weight of the fluororubber polymer.

Further, as the polyol-based crosslinking agent, a commercially available master batch containing the raw rubber and the crosslinking agent may be used. These crosslinking agents may be used in 1 kind or 2 or more kinds may be used in combination.

In the production of the crosslinked fluororubber, a crosslinking accelerator may be used, and as the crosslinking accelerator, for example, a quaternary phosphonium salt may be used.

Specific examples of the quaternary phosphonium salt include tetraphenylphosphonium chloride, triphenylbenzylphosphonium bromide, triphenylmethoxymethylphosphonium chloride, triphenylmethylcarbonylmethylphosphonium chloride, triphenylethoxycarbonylmethylphosphonium chloride, trioctylbenzylphosphonium chloride, trioctylmethylphosphonium bromide, trioctylethylphosphonium acetate, tetraoctylphosphonium chloride, and hexadecyldimethylbenzylphosphonium chloride. The content of the polyol-based crosslinking accelerator is preferably in the range of about 0.3 to 20 parts by weight based on 100 parts by weight of the fluororubber polymer.

As the crosslinking accelerator, a commercially available master batch containing the raw rubber and the crosslinking accelerator may also be used. These crosslinking agents may be used in 1 kind or in combination of 2 or more kinds.

As the crosslinking accelerator, a quaternary ammonium salt may be used alone, or may be used in combination with the quaternary phosphonium salt. Examples of the quaternary ammonium salt include 5-benzyl-1, 5-diazabicyclo [4.3.0] -5-nonenylium tetrafluoroborate and 5-benzyl-1, 5-diazabicyclo [4.3.0] -5-nonenylium hexafluorophosphate.

These tetrafluoroborates and hexafluorophosphates have melting points of about 80 ℃ or 100 ℃ respectively, and are easily melted when heated and kneaded (about 100 ℃) by a roll, a kneader, a banbury mixer (banbury), or the like, and thus have excellent dispersibility.

As the quaternary ammonium salt, a commercially available master batch containing the raw material fluororubber and the quaternary ammonium salt may be used. These crosslinking accelerators may be used in 1 kind or in combination of 2 or more kinds.

Examples of the organic peroxide-based crosslinking agent corresponding to the fluororubber polymer capable of peroxide crosslinking include 2, 5-dimethylhexane-2, 5-dihydroperoxide, 2, 5-dimethyl-2, 5-di (benzoylperoxy) hexane, t-butylperoxide, dicumyl peroxide (dicumyl peroxide), t-butylcumyl peroxide, 1-di (t-butylperoxy) -3,3, 5-trimethylcyclohexane, 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane, 2, 5-dimethyl-2, 5-di (t-butylperoxy) -3-hexyne, 1, 3-di (t-butylperoxyisopropyl) benzene, t-butylperoxybenzoate, t-butylperoxyisopropyl carbonate, di-n-butyl peroxy-2, 5-di (t-butylperoxy-isopropyl carbonate, di-n-butyl peroxy-2, 5-, N-butyl 4, 4-di (t-butylperoxy) valerate, and the like. As such, commercially available products (e.g., Perhexa 25B-40, Japanese oil and fat products) can be used. The content of the organic peroxide-based crosslinking agent is preferably in the range of about 0.3 to 5 parts by weight relative to 100 parts by weight of the fluororubber polymer.

Further, as the peroxide crosslinking agent, a commercially available master batch containing the raw rubber and the crosslinking agent may be used. These crosslinking agents may be used in 1 kind or 2 or more kinds may be used in combination.

As the crosslinking accelerator (co-agent) usable in the peroxide-based crosslinking system, triallylisocyanurate and the like are used. In addition, when a metal oxide typified by zinc oxide, a fatty acid typified by stearic acid, or a silica-based reinforcing agent is blended, triethanolamine and/or diethylene glycol are exemplified. The content of the crosslinking accelerator is preferably in the range of about 0.1 to 10 parts by weight relative to 100 parts by weight of the fluororubber polymer.

Next, the fluororubber composition, which is the kneaded mixture produced by the kneading in the above-described 2 nd kneading step, is crosslinked, whereby a crosslinked fluororubber product is produced. That is, the fluororubber composition produced as described above is vulcanized by, for example, pressurization and heating, and thereby a crosslinked molded product is molded.

Specifically, the fluororubber composition produced as described above is heated (primarily vulcanized) at a temperature of usually about 140 to 230 ℃ for about 1 to 120 minutes by using an injection molding machine, a compression molding machine, a vulcanization press, an oven, or the like, whereby a fluororubber crosslinked molded product can be obtained.

The primary vulcanization is a step of crosslinking to such an extent that the shape can be maintained in order to form a certain shape (preliminary molding), and in terms of complicated shapes, molding by a mold is preferable, and primary vulcanization may be performed by an oven heated by air or the like.

In the present invention, secondary vulcanization may be carried out as needed. When the secondary vulcanization is performed, a usual method can be employed, but it is preferable to perform the heat treatment at a temperature ranging from about 200 to 300 ℃ for about 1 to 20 hours.

3. Shaft sealing material

By using the obtained crosslinked fluororubber, a sealing material such as a rotary sliding sealing material can be produced. In the fields of automobiles, industrial machines, and the like, shaft sealing materials are widely used as sealing materials between shafts and housings.