JP2006183804A - Roller bearing for alkaline environments - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller bearing for alkaline environments which minimizes a deterioration of a seal member, maintaines a preferable sealability for a long period of time, and is excellent in reliability and durability even when the roller bearing is used in an alkaline atmosphere. <P>SOLUTION: The roller bearing for alkaline environments used in an alkaline atmosphere includes an inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and the seal member provided at opening portions at both ends of the inner ring and the outer ring in the axial direction. The seal member has a rubber molded body which makes contact with at least the alkaline atmosphere. The rubber molded body is a molded body of fluororubber composition capable of being vulcanized, which fluororubber composition is composed of a copolymer containing tetrafluoroethylene, propylene, and a bridging monomer consisting of unsaturated hydrocarbon with a carbon number of 2-4 in which hydrogen atoms are partially replaced by fluorine atoms. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rolling bearing for an alkaline environment, and more particularly to a rolling bearing for an alkaline environment used in a chemical plant or the like in an alkaline atmosphere.

In chemical plant equipment such as polymer material production plants and liquid crystal film production equipment, there are treatment tanks in high-concentration alkaline solutions, and rolling bearings used for stirring and transport are relatively short-lived. There is a problem that. Generally, stainless steel and ceramic with high corrosion resistance are used for the inner ring, outer ring, and rolling element of such a bearing. However, wear and lock due to entry of hard foreign matters from the outside are raised as a cause of short life. In order to prevent the intrusion of foreign matter, it is only necessary to provide a seal member at both axial openings of the inner ring and the outer ring. Generally, when acrylonitrile rubber or acrylic rubber used as a bearing seal member is used, a rubber material is used. Since the alkali resistance of the resin is poor, the durability cannot be ensured, for example, it is dissolved or the strength is significantly reduced and broken. On the other hand, fluororubber is an example of rubber having excellent chemical resistance. Conventionally used fluororubbers include binary copolymers of vinylidene fluoride and hexafluoropropylene (VDF-HFP), and terpolymers of which tetrafluoroethylene is added (VDF-HFP-TFE). So-called FKM is common. However, even if these fluororubbers have a high alkali concentration, there is a problem that strength is lowered and sufficient durability cannot be obtained.
On the other hand, a method is known in which durability of a rolling bearing in an alkaline solution is improved by using an alkali-resistant resin material such as polyethylene as the material of the seal member (Patent Document 1).
However, if the sliding contact portion between the seal member and the inner ring or the outer ring is brought into contact for the purpose of improving the sealing performance, the resin has a high elastic modulus, so that the contact portion has a high tightening force and the rotational torque of the bearing increases. There is a problem. There is a method of using a non-contact type seal in order to prevent torque increase, but with this method, intrusion prevention of foreign matters becomes incomplete, resulting in a short life.

Further, even when the above-described fluororubber is used, there is a problem that it is difficult to suppress the deterioration with time of the fluororubber.
When the rubber elastic body used for the sealing member is cured due to deterioration with time, the sealing performance is deteriorated. In addition, the contact pressure at the seal surface is increased, and the rotational torque of the bearing is increased. As a result, frictional heat is generated, and the grease is further deteriorated.
JP 2003-49855 A

  The problem to be solved is that even when a rolling bearing is used in an alkaline atmosphere, there is no rolling bearing for an alkaline environment that has little deterioration of the sealing member, maintains good sealing performance for a long time, and has excellent reliability and durability. That is the point.

The alkaline environment rolling bearing of the present invention is an alkaline environment rolling bearing used in an alkaline atmosphere, and the rolling bearing includes an inner ring and an outer ring, and a plurality of rolling elements interposed between the inner ring and the outer ring, A seal member provided at both axial openings of the inner ring and the outer ring, the seal member having at least a rubber molded body in contact with the alkaline atmosphere, and the rubber molded body includes tetrafluoroethylene, propylene, and A molded article of a vulcanizable fluororubber composition comprising a copolymer comprising a crosslinking monomer comprising an unsaturated hydrocarbon having 2 to 4 carbon atoms in which some of the hydrogen atoms are substituted with fluorine atoms. It is characterized by being. In addition, an alkaline atmosphere means the state which contacts alkaline gas, a solution, and solid regularly or unsteadily.
The crosslinking monomer is trifluoroethylene, 3,3,3-trifluoropropene-1, 1,2,3,3,3-pentafluoropropene, 1,1,3,3,3-pentafluoropropylene And at least one monomer selected from 2,3,3,3-tetrafluoropropene.
The molded product of the fluororubber composition has a rubber hardness of 60 to 90 °. The rubber hardness (degree) is a value measured according to JIS K 6253.
The copolymer includes vinylidene fluoride.
The inner ring, outer ring and rolling element are made of corrosion-resistant steel or ceramic.

  The rolling bearing for alkaline environment of the present invention includes tetrafluoroethylene, propylene, and a crosslinking monomer composed of an unsaturated hydrocarbon having 2 to 4 carbon atoms in which a part of hydrogen atoms are substituted with fluorine atoms. Since the seal member is formed of a vulcanizable fluororubber composition formed of a copolymer, physical properties are hardly deteriorated even when immersed in an alkaline solution, and entry of foreign matters can be effectively prevented. For this reason, durability of the rolling bearing for alkaline environments used in a chemical plant and various manufacturing apparatuses in an alkaline atmosphere can be improved.

The fluororubber composition that can be used in the present invention comprises tetrafluoroethylene, propylene, and a crosslinking monomer comprising an unsaturated hydrocarbon having 2 to 4 carbon atoms in which some of the hydrogen atoms are substituted with fluorine atoms. And a vulcanizable fluororubber composition comprising a copolymer.
Examples of the crosslinking monomer composed of an unsaturated hydrocarbon having 2 to 4 carbon atoms in which a part of hydrogen atoms are substituted with fluorine atoms include trifluoroethylene, 3, 3, 3-trifluoropropene-1, 1, 2, 3, 3, 3-pentafluoropropene, 1, 1, 3, 3, 3-pentafluoropropylene, 2, 3, 3, 3-tetrafluoropropene are mentioned. A preferred crosslinking monomer is 3,3,3-trifluoropropene-1.

  As a fourth component in the copolymer that can be used in the present invention, vinylidene fluoride, chlorotrifluoroethylene, perfluoro (alkyl vinyl) ether, perfluoro (alkoxy vinyl) ether, perfluoro (alkoxyalkyl vinyl) ether, perfluoroalkyl alkenyl ether, A perfluoroalkoxy alkenyl ether etc. can be mix | blended.

The copolymer constituting the fluororubber composition is 45 to 80% by weight, preferably 50 to 78% by weight, more preferably 65 to 78% by weight of tetrafluoroethylene, based on the whole copolymer. Is 10 to 40% by weight, preferably 12 to 30% by weight, more preferably 15 to 25% by weight, and the crosslinking monomer is 0.1 to 15% by weight, preferably 2 to 10% by weight, more preferably 3%. ~ 6% by weight.
When vinylidene fluoride is copolymerized, the vinylidene fluoride is 2 to 20% by weight, preferably 10 to 20% by weight. Above 20% by weight, resistance to alkaline compounds decreases.

This fluororubber production method is disclosed in, for example, International Publication No. WO02 / 092683, and is produced by an emulsion polymerization method or a suspension polymerization method.
In order to vulcanize these fluororubbers, vulcanization accelerators selected from polyhydroxy (polyol) vulcanizing agents, quaternary ammonium salts, fourth phosphonium salts, third sulfonium salts, etc., calcium hydroxide and magnesium oxide Etc., fillers such as carbon black, clay, barium sulfate, calcium carbonate and magnesium silicate, processing aids such as octadecylamine and wax, heat aging inhibitors and pigments can be blended. For example, each blending amount is 0.1 to 20 parts by weight, preferably 0.5 to 3 parts by weight of the vulcanizing agent, and 0.1 to 20 parts by weight of the vulcanization accelerator, preferably 0.5 to 100 parts by weight of the copolymer. 3 parts by weight, acid acceptor 1-30 parts by weight, preferably 1-7 parts by weight, filler 5-100 parts by weight, and processing aid 0.1-20 parts by weight.

In addition to these, a second vulcanizing agent such as an organic peroxide compound may be added in an amount of 0.7 to 7 parts by weight, preferably 1 to 3 parts by weight. Furthermore, fillers and additives that can be blended in general rubber compositions can be used as appropriate within a range that does not impair the resistance to urea compounds and the sealing properties.
As a method for mixing or molding these compositions, a process used for general rubber processing can be adopted. After kneading with an open roll, a Banbury mixer, a kneader, various sealed mixers, etc., press molding (press vulcanization) ), Extrusion molding, injection molding, etc. In order to improve the characteristics, it is preferable to perform secondary vulcanization after molding, and this is performed by sufficiently heating in an oven (for example, 200 ° C. for 24 hours).

  The rubber hardness of the molded body of the fluororubber composition that can be used in the present invention is 60 to 90 °. Preferably it is 70-80 degrees. If it is less than 60 °, it becomes too soft and wear resistance decreases, and if it exceeds 90 °, the rotational torque becomes too large and the temperature of the rolling bearing rises. The rubber hardness (degree) was measured according to JIS K 6253.

  The alkaline environment in which the rolling bearing for an alkaline environment of the present invention can be used is an environment that constantly or unsteadily contacts at least one alkaline substance selected from an alkaline gas, an alkaline solution, and an alkaline solid. Among these, the rolling bearing for alkaline environment of the present invention is an aqueous solution containing sodium hydroxide and an aqueous solution containing potassium hydroxide, which are generally used in chemical plant equipment such as a polymer material production plant and a liquid crystal film production apparatus. It can be particularly suitably used in an environment where it comes into contact.

An example of a rolling bearing for alkaline environment of the present invention is shown in FIG. FIG. 1 is a cross-sectional view of a deep groove ball bearing.
In the deep groove ball bearing 1, an inner ring 2 having an inner ring rolling surface 2a on the outer peripheral surface and an outer ring 3 having an outer ring rolling surface 3a on the inner peripheral surface are arranged concentrically, and the inner ring rolling surface 2a and the outer ring rolling surface 3a. A plurality of rolling elements 4 are arranged between the two. Sealing members 6 that are fixed to the cage 5 that holds the plurality of rolling elements 4, the outer ring 3, and the like are provided in the axial end openings 7 a and 7 b of the inner ring 2 and the outer ring 3, respectively.

The seal member 6 may be a rubber molded body alone or a composite of a rubber molded body and a metal plate, a plastic plate, a ceramic plate, or the like. From the viewpoint of durability and ease of fixing, a composite of a rubber molded body and a metal plate is preferable.
An example of the sealing member 6 made of a composite of a rubber molded body and a metal plate is shown in FIG. The seal member 6 is obtained by fixing a fluororubber molded body 6b to a metal plate 6a such as a steel plate. As the fixing method, either mechanical fixing or chemical fixing may be used. As a preferable fixing method, there can be mentioned a method in which a metal plate is placed in a vulcanizing mold, and molding and vulcanization are performed and fixed at the time of vulcanization of a fluororubber molded article.

The seal member 6 can be mounted by (1) fixing one end 6c of the seal member 6 to the outer ring 3, and forming the labyrinth gap along the V groove on the seal surface of the inner ring 2 at the other end 6d. One end 6c of the member 6 is fixed to the outer ring 3, and the other end 6d is brought into contact with the V groove side surface of the seal surface of the inner ring 2. (3) One end 6c of the seal member 6 is fixed to the outer ring 3, and the other end 6d is the inner ring. 2 is contacted with the side surface of the V-groove of the sealing surface, but a low-torque structure is provided by providing a suction-preventing slit or the like in the contacting lip portion.
In any of the above mounting methods, the surrounding alkaline solution comes into contact with the rubber molded body 6 b constituting the seal member 6. The rubber molded body 6b is formed of the above-described fluororubber molded body at least at a portion in contact with the alkaline solution. For example, the rubber molded body 6b may be a single fluororubber molded body as described above, or a laminated body in which a conventional rubber molded body is laminated on the back surface of the above-described fluororubber molded body at a portion in contact with an alkaline solution.

The rubber composition used in each example and comparative example is shown below.
An unvulcanized rubber composition was obtained by kneading with the composition shown in Table 1 using an open roll at a roll temperature of 50 ° C. Each material used in Table 1 is shown below.
(1) Fluoro rubber 1: manufactured by DuPont Dow Elastomer Co., Ltd .; VTR8802 (with vulcanizing agent)
(2) Fluoro rubber 2: manufactured by DuPont Dow Elastomer; A32J
(3) Magnesium oxide: manufactured by Kyowa Chemical Industry Co., Ltd .;
(4) Calcium hydroxide: manufactured by Omi Chemical Co., Ltd .; Calbit (5) Carbon: manufactured by Engineered Company; N990

実施例１は、長時間の浸漬でも劣化が軽微であり、アルカリ溶液に対して優れた耐性を有していた。
比較例１は、アルカリ溶液に浸漬された場合の物性劣化が著しい。短時間（ 72 時間程度）の浸漬後、200 時間では、試験片の表面に溶解がみられた。 Example 1 and Comparative Example 1
Using the unvulcanized rubber composition, a vulcanized molded product was obtained with a vulcanizing press. The actual temperature of the mold was 170 ° C, and the vulcanization time was vulcanized at 170 ° C for 12 minutes as the primary vulcanization. Subsequently, secondary vulcanization was performed in a thermostatic bath. Secondary vulcanization conditions are 200 ° C for 24 hours.
The obtained vulcanized molded product was punched into the shape of a JIS K 6251 No. 3 test piece to prepare a test piece. The specimen was immersed in a 30% aqueous solution of sodium hydroxide at 80 ° C. for 1000 hours, and the physical properties before and after immersion were measured. The measured physical properties were measured for hardness, tensile strength, tensile elongation, and volume, and evaluated for hardness change, tensile strength change rate, tensile elongation change rate, and volume change rate with respect to the physical property values before immersion. The measurement conditions were the same as JIS K 6253 for hardness, JIS K 6251 for tensile strength and tensile elongation, and JIS K 6258 for the volume before and after immersion. The results are shown in Table 2. In Table 2, * indicates that measurement is impossible.

In Example 1, the deterioration was slight even when immersed for a long time, and it had excellent resistance to the alkaline solution.
In Comparative Example 1, physical property deterioration is significant when immersed in an alkaline solution. After 200 hours of immersion after a short time (about 72 hours), dissolution was observed on the surface of the test piece.

  Since the rolling bearing for alkaline environment of the present invention has excellent alkali resistance, it can be suitably used for a rolling bearing used in an alkaline atmosphere.

It is sectional drawing of the rolling bearing for alkaline environments. It is sectional drawing of the rolling bearing seal member for alkaline environments.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Deep groove ball bearing 2 Inner ring 3 Outer ring 4 Rolling element 5 Cage 6 Seal member

Claims (5)

  A rolling bearing for an alkaline environment used in an alkaline atmosphere, wherein the rolling bearing includes an inner ring and an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and openings in both axial directions of the inner ring and the outer ring. A sealing member provided at the same, and the sealing member has at least a rubber molded body in contact with the alkaline atmosphere, the rubber molded body is tetrafluoroethylene, propylene, and a part of hydrogen atoms are fluorine atoms. Rolling for alkaline environment, characterized by being a molded body of a vulcanizable fluororubber composition comprising a copolymer comprising a substituted monomer comprising a substituted C2-C4 unsaturated hydrocarbon bearing.   The crosslinking monomer is trifluoroethylene, 3,3,3-trifluoropropene-1, 1,2,3,3,3-pentafluoropropene, 1,1,3,3,3-pentafluoropropylene 2. The rolling bearing for alkaline environment according to claim 1, wherein the rolling bearing is at least one monomer selected from 2,3,3,3-tetrafluoropropene.   The rolling bearing for alkaline environment according to claim 1 or 2, wherein the copolymer contains vinylidene fluoride.   4. A rolling bearing for an alkaline environment according to claim 1, wherein the molded product of the fluororubber composition has a rubber hardness of 60 to 90 [deg.].   The rolling bearing for an alkaline environment according to claim 1, wherein the inner ring, the outer ring and the rolling element are made of corrosion-resistant steel or ceramic.

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