JP2023159467A - Rubber molded product - Google Patents

Abstract

To provide a rubber molded product capable of suppressing a metal foreign matter from being bitten into a normal/reverse rotation oil seal or the like, and suitably used as a seal material such as an oil seal.SOLUTION: A rubber molded product contains 10-50 pts.wt. of a filler having an average particle diameter of 0.2-5.0 μm per 100 pts.wt. of rubber, and has an arithmetical average height of a cross section roughness of a vulcanized molded product of 0.1-1.0 μm Sa. The rubber molded product which contains a filler having an average particle diameter of 0.2-5.0 μm and has an arithmetical average height of a cross section roughness of a vulcanized molded product of 0.1-1.0 μm Sa is selected so as to exhibit an excellent effect of suppressing a metal foreign matter from being bitten into a slide surface of a seal and a shaft by reducing a film thickness of a seal slide surface of a normal/reverse rotation oil seal or the like. With this, the rubber molded product is suitably used as a seal material such as an oil seal.SELECTED DRAWING: None

Description

The present invention relates to a rubber molded article. More specifically, the present invention relates to a rubber molded product used as a material for oil seals and the like.

Oil seals are widely used as important mechanical parts in fields such as automobiles and industrial machinery. Among these, dual-rotation oil seals, which are designed to keep fluid sealed even when various parts rotate in both forward and reverse directions, are used as parts for pumps, automobile differentials, agricultural machinery, railway vehicles, etc. It is used in a wide range of fields.

Conventionally used oil seals may cause leakage of the sealed fluid when a member in contact with the oil seal is rotated in the forward rotation direction and then reversed.

The applicant has previously proposed a method using fluororubber as a rubber material, which has excellent oil resistance and fuel oil resistance and is used as a sealing material for O-rings, packing, etc. in a wide range of fields such as automobiles and industrial machinery. A fluororubber composition prepared by adding 1 to 100 parts by weight of wollastonite with an aspect ratio of 8 or more per part and kneading it, and forming a sliding surface by vulcanization molding, for use in railway vehicles. An oil seal for both forward and reverse rotation is proposed (Patent Document 1).

Furthermore, in Patent Document 2, an average amount per 100 parts by weight of fluororubber is used as a molding material for oil seals that has excellent durability such as heat resistance and abrasion resistance, and also satisfies lubricant resistance and sealing properties. A fluororubber composition containing 3 to 60 parts by weight of at least one of diatomaceous earth, wollastonite, talc, graphite, and carbon fiber with a particle size of 6 to 35 μm is proposed.

However, in the market, in oil seals for both forward and reverse rotation, the sliding surface of the shaft may be damaged by metal foreign matter contained in the oil, and in this case, it becomes necessary to replace the shaft. In order to avoid such a phenomenon, it is desirable to suppress damage to the shaft and extend the period of use of the shaft.

Based on the analysis results of recovered products from the market, we found that the cause of damage to the shaft is that metal foreign matter contained in the oil is interposed between the sliding surface of the lip and the shaft. is estimated to occur.

Japanese Patent Application Publication No. 2008-64201 Patent No. 6,435,666

An object of the present invention is to provide a rubber molded product that can be used suitably as a sealing material for oil seals, etc., and can prevent metal foreign matter from getting caught in oil seals for both forward and reverse rotation.

The object of the present invention is to provide a vulcanized molded product containing 10 to 50 parts by weight of a filler with an average particle diameter of 0.2 to 5.0 μm per 100 parts by weight of rubber, and the arithmetic mean height of the cross-sectional roughness to be 0.1 to 1.0. This is achieved by a rubber molded product with μm Sa.

The rubber molded product according to the present invention contains a filler with an average particle diameter of 0.2 to 5.0 μm, and the arithmetic mean height of the cross-sectional roughness of the vulcanized molded product is selected to be 0.1 to 1.0 μm Sa. By reducing the thickness of the oil film on the sliding surfaces of seals such as oil seals for both forward and reverse rotation, it has the excellent effect of suppressing foreign metal objects from getting caught in the sliding surfaces of seals and shafts. . Therefore, it is suitably used as a sealing material such as an oil seal.

The rubber molded product of the present invention contains a filler having an average particle diameter of 0.2 to 5.0 μm per 100 parts by weight of rubber, and the arithmetic mean height of the cross-sectional roughness of the resulting vulcanized molded product is 0.1 to 1.0 μm. It is Sa.

Examples of the rubber include fluororubber, nitrile rubber, acrylic rubber, etc., and fluororubber is used because it has excellent heat resistance, oil resistance, and the like.

As the fluororubber, a copolymer rubber of vinylidene fluoride or tetrafluoroethylene with at least one other fluorine-containing olefin or olefin is used, such as vinylidene fluoride [VdF]-hexafluoropropylene [HFP] copolymer. , vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-perfluoro(methyl vinyl ether) copolymer, vinylidene fluoride -Tetrafluoroethylene-perfluoro(methyl vinyl ether) terpolymer, tetrafluoroethylene-propylene copolymer, tetrafluoroethylene-perfluoro(methyl vinyl ether) copolymer, tetrafluoroethylene-perfluoro(methyl vinyl ether) -Ethylene ternary copolymers, etc., and crosslinkable groups such as bromine- and/or iodine-containing compounds, nitrile groups, glycidyl groups, hydroxyalkyl groups, perfluorophenyl groups, etc. are introduced into these various copolymer rubbers. can also be used.

The fluororubber contains a filler with an average particle size (measured by laser diffraction scattering method) of 0.2 to 5.0 μm, preferably 0.2 to 3.0 μm, in an amount of 10 to 50 parts by weight, preferably 10 to 50 parts by weight, per 100 parts by weight of fluororubber. It is blended in a proportion of 40 parts by weight.

It is thought that the rougher the rubber, the thicker the oil film on the sliding surface, which makes it easier for foreign matter present in the oil to get caught in the sliding surface of the sealing material and the shaft. Therefore, if a filler with an average particle diameter larger than this is used, in both forward and reverse rotation seals, foreign matter present in the oil will be interposed between the sliding surfaces of the lip and shaft, and the foreign matter will be caught in the shaft. This may result in injury.

On the other hand, if a filler with an average particle diameter smaller than this is used, the arithmetic mean height of the cross-sectional roughness, which is the objective of the present invention, cannot be imparted to the vulcanized product, resulting in poor sealing performance. I start putting it away. Here, when the filler is fibrous, the average particle diameter means its average fiber length.

Furthermore, if the filler is used in a smaller proportion than this, it will not be possible to give the vulcanized product the arithmetic mean height of cross-sectional roughness that is the objective of the present invention, resulting in poor sealing performance. On the other hand, if it is used in a proportion greater than this, it tends to become sandy during kneading, making it impossible to knead.

As the filler, diatomaceous earth, polytetrafluoroethylene resin [PTFE], wollastonite, graphite, etc. are used, preferably diatomaceous earth and PTFE.

Various compounding agents required for vulcanization operation, physical properties, functionality, etc. are added to the rubber composition consisting of the above essential components, such as polyol-based or organic peroxide-based compounds used in fluororubber vulcanization. Vulcanizing agents, vulcanization aids such as quaternary onium salts, polyfunctional unsaturated compound co-crosslinking agents, reinforcing agents or fillers such as carbon black, divalent metal oxides or hydroxides, hydrotalcite, etc. After the acid acceptor and other necessary ingredients are mixed, the composition is prepared by any kneading method using open rolls, kneaders, etc., and heated at about 160 to 200°C for about 3 to 30 minutes. By performing primary vulcanization using a press and, if necessary, secondary vulcanization at approximately 150 to 250°C for approximately 0.5 to 24 hours, it is vulcanized and molded into sealing materials such as oil seals.

The resulting vulcanized product is selected so that the arithmetic mean height of the cross-sectional roughness is about 0.1 to 1.0 μm Sa. The maximum height of the cross-sectional roughness is approximately 10 to 20 μm Sz.

Next, the present invention will be explained with reference to examples.

Example 1
VdF-HFP copolymer (Dupont product Viton A500) 100 parts by weight Carbon black (CANCARB product THERMAX N990 LSR) 2
Diatomaceous earth (Central silica product Oplite W3005K; average particle size 2.7μm) 20 〃
Magnesium oxide (Kyowa Chemical Industry Products Star Mag CX-150) 5
Calcium hydroxide (Ohmi Chemical Industry product CALDIC#1000) 5
Bisphenol AF 50% by weight fluororubber diluted product 2.3
(Unimatec product CHEMINOX AF-50)
35% by weight phosphate crosslinking accelerator diluted product (Company product B-35F) 1
The above ingredients were kneaded using an internal kneader and an open roll, and then press vulcanized at 180℃ for 4 minutes using a 2RT-35t press machine and oven vulcanized at 200℃ for 15 hours (secondary vulcanization). A 2 mm thick test piece for roughness measurement and an oil seal were vulcanized and molded.

Example 2
In Example 1, the amount of carbon black was changed to 13.5 parts by weight, and the amount of diatomaceous earth was changed to 14.1 parts by weight.

Example 3
In Example 1, the amount of carbon black was changed to 18 parts by weight, and the same amount (20 parts by weight) of PTFE (AGC product FLUON PTFE L-172JE; average particle size 0.24 μm) was used instead of diatomaceous earth.

Example 4
In Example 3, the amount of carbon black was changed to 30 parts by weight.

Comparative example 1
In Example 1, the same amount (20 parts by weight) of Chuo Kasei Products SILIKA #6B (average particle size 12.6 μm) was used as diatomaceous earth.

Comparative example 2
In Example 1, diatomaceous earth was not used.

Comparative example 3
In Example 1, the same amount (20 parts by weight) of carbon beads (Marilin GC-025 manufactured by Gunei Kagaku Kogyo; average particle diameter 25 μm) was used instead of diatomaceous earth.

Comparative example 4
In Comparative Example 1, the amount of diatomaceous earth was changed to 70 parts by weight.

Roughness was measured using the test pieces obtained in each of the above Examples and Comparative Examples, and shaft durability was evaluated using an oil seal.
Roughness: JIS B0601, ISO 4287 compliant, cutoff: λs 2.5μm, λc 0.8mm
Cut the vulcanized product of the rubber composition using a slicer, etc., and cut the smooth cross section.
Observation using a non-contact method using a laser microscope
Shaft durability test in which the arithmetic mean height was calculated and the maximum height was measured: The oil seal was set in a rotating tester, and alumina with a particle size of 2.0 μm (market
Assuming metal foreign matter in recovered oil) containing turbine oil centered around the rotating shaft
The test oil temperature was 120℃, the rotation speed was 1500rpm, and the normal rotation was 1 hour.
The shaft was operated for 120 hours with 5 minutes of pause and 5 minutes of rest as one cycle.
Measure wear depth
If the shaft wear depth is less than 20μm, it will be evaluated as ○, and if it is more than 20μm, it will be evaluated as ×.

The results obtained in each of the above Examples and Comparative Examples are shown in the following table.
table
Implementation comparison example
Measurement/Evaluation Item 1 2 3 4 1 2 3 4
[Surface roughness of female cut]
Arithmetic mean height (μm Sa) 0.79 0.53 0.68 0.55 1.16 - 2.70 -
Maximum height (μm Sz) 17.6 16.7 13.6 15.2 21.7 - 45.7 -
[Shaft durability]
Shaft wear depth evaluation ○ ○ ○ ○ × - × -
[Sealability]
Pump amount measurement △ ○ ○ ○ 〇 × 〇 -

From the above results, the following can be said.
(1) In each of the examples, by using a fine filler and reducing the roughness of the material surface, it is difficult for foreign matter to get caught in the lip seal sliding surface, and the shaft durability is improved.
(2) If the average particle size of the filler is large, foreign matter is likely to get stuck, making it impossible to ensure the desired shaft durability (Comparative Examples 1 and 3).
(3) If a filler is not added, the oil pumping function will deteriorate and sufficient sealing performance cannot be obtained (Comparative Example 2).
(4) If the blending amount of the filler is too large, the mixture tends to become sandy during kneading, making it impossible to knead (Comparative Example 4).

Claims (6)

A rubber molded product containing 10 to 50 parts by weight of a filler with an average particle diameter of 0.2 to 5.0 μm per 100 parts by weight of rubber, and the arithmetic mean height of the cross-sectional roughness of the vulcanized molded product is 0.1 to 1.0 μm. The rubber molded article according to claim 1, wherein the rubber is fluororubber. The rubber molded article according to claim 1, wherein the filler is diatomaceous earth or polytetrafluoroethylene resin powder. The rubber molded product according to claim 1, wherein the maximum height of cross-sectional roughness of the vulcanized molded product is 10 to 20 μm Sz. A sealing material comprising the rubber molded product according to claim 1. The sealing material according to claim 5, which is used as an oil seal.