JP2019049273A - Oil seal - Google Patents

Abstract

To provide an oil seal having hydrolysis resistance properly used under an engine oil environment in which a moisture content is mixed, while having heat resistance and oil resistance comparable to acryl rubber.SOLUTION: An oil seal is composed of a crosslinked body obtained by polyamine-crosslinking of a polymer composed of polyamine-crosslinkable hydrogenation nitryl rubber, and in particular, a content nitryl in the polymer is 20-45 wt.%.SELECTED DRAWING: None

Description

  The present invention relates to an oil seal, and more particularly to an oil seal that has heat resistance and oil resistance comparable to acrylic rubber, but also has hydrolysis resistance that is preferably used even in an engine oil environment mixed with moisture.

  Conventionally, acrylic rubber (ACM) having excellent heat resistance and oil resistance has been widely used as an oil seal.

  On the other hand, the present applicant has disclosed a rubber composition for a fuel seal so far (Patent Documents 1 and 2).

WO2013 / 175877 (fuel seal) WO2013 / 175878 (fuel seal)

  Conventional oil seals have a stable sealing function because acrylic rubber is hydrolyzed into resin and hardened in engine oil mixed with moisture generated by fuel combustion and in poor oil environments that contain a lot of moisture. There is room for further improvement in terms of maintaining

  Since acrylic rubber undergoes hydrolysis in an acid or alkaline environment due to its molecular structure, as a countermeasure, a material change to hydrogenated nitrile rubber (HNBR), which is also excellent in heat resistance and oil resistance, was examined.

  However, it has been found that conventional peroxide-crosslinked HNBR does not have heat resistance comparable to acrylic rubber. There was also room for improvement in the hydrolysis resistance especially in engine oil mixed with moisture.

  Therefore, an object of the present invention is to provide an oil seal having hydrolysis resistance that is suitably used even in an engine oil environment mixed with moisture while having heat resistance and oil resistance comparable to acrylic rubber.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

(Claim 1)
An oil seal comprising a crosslinked product obtained by polyamine crosslinking a polymer comprising a hydrogenated nitrile rubber capable of polyamine crosslinking.
(Claim 2)
2. The oil seal according to claim 1, wherein the nitrile content of the polymer is in the range of 20 to 45% by weight.

  ADVANTAGE OF THE INVENTION According to this invention, the oil seal which has the hydrolysis resistance used suitably also in the engine oil environment into which the water | moisture content mixed while having heat resistance and oil resistance comparable to an acrylic rubber can be provided.

  Below, the form for implementing this invention is demonstrated in detail.

1. Oil Seal The oil seal of the present invention is constituted by a cross-linked product obtained by polyamine cross-linking of a polymer made of hydrogenated nitrile rubber (hereinafter also referred to as HNBR) capable of polyamine cross-linking.

  The crosslinked product according to the present invention exhibits outstanding hydrolysis resistance as compared with acrylic rubber (Comparative Example 2). In addition, even when compared with peroxide-crosslinked HNBR (Comparative Example 1), the resistance to continuous contact with engine oil mixed with moisture for a long time (at least 2000 hours), particularly at high temperatures (at least 150 ° C.). Excellent hydrolyzability. Thereby, it was found that the crosslinked body according to the present invention is suitably used as an oil seal.

  Moreover, the crosslinked body according to the present invention exhibits outstanding heat resistance and oil resistance as compared with peroxide-crosslinked HNBR. It has been demonstrated that this heat resistance and oil resistance are comparable to acrylic rubber and preferably exceed that of acrylic rubber. Therefore, the characteristics required for the oil seal are suitably satisfied with respect to points other than the hydrolysis resistance described above.

2. HNBR (polymer)
The polyamine-crosslinkable HNBR comprises an α, β-ethylenically unsaturated nitrile monomer unit, a diene monomer unit and an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit (3 The original system can be preferably used.

  In addition, polyamine-crosslinkable HNBR includes α, β-ethylenically unsaturated nitrile monomer units, diene monomer units, α, β-ethylenically unsaturated dicarboxylic acid monoester monomer units, and α. , Β-ethylenically unsaturated dicarboxylic acid monoester monomer units other than α, β-ethylenically unsaturated carboxylic acid ester monomer units (quaternary system) can also be preferably used.

  Further, the two types of HNBR described above may be blended and used as a polymer.

  Below, each monomer unit which comprises HNBR is demonstrated.

(1) α, β-ethylenically unsaturated nitrile monomer unit The α, β-ethylenically unsaturated nitrile monomer unit is not particularly limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group. Examples thereof include acrylonitrile, α-halogenoacrylonitrile whose α-position is a chloro group or bromo group, methacrylonitrile whose α-position is an alkyl group, and preferably acrylonitrile or methacrylonitrile is used.

  The content of the α, β-ethylenically unsaturated nitrile monomer unit in the polymer (also referred to as nitrile content or CN content) is preferably 20 to 45% by weight, and more preferably 23 to 45% by weight. Preferably, it is 25 to 45% by weight. Thereby, heat resistance and hydrolysis resistance are further improved, and the characteristics required for the oil seal are suitably satisfied.

(2) Diene monomer units The diene monomer units are 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,4-pentadiene, 1 Derived from a C _{4 to} C ₁₂ conjugated or non-conjugated diene monomer such as 1,4-hexadiene, preferably a conjugated diene monomer, more preferably 1,3-butadiene.

These diene monomer units are, for example, C _{2 to} C ₁₂ α-olefin monomer units such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene. May be used in combination.

  When the diene monomer unit is used without being used in combination with the α-olefin monomer unit, the content of the diene monomer unit in the polymer is not particularly limited, but may be, for example, 20 to 80% by weight. it can.

  When the diene monomer unit is used in combination with the α-olefin monomer unit, the total content of the diene monomer unit and the α-olefin monomer unit in the polymer is not particularly limited. It can be 20 to 80% by weight.

(3) α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit As α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit, maleic acid, fumaric acid, citraconic acid, itaconic acid, etc. C ₁ -C ₁₀ , preferably C ₂ -C ₆ monoalkyl ester, C ₅ -C ₁₂ , preferably C ₆ -C ₁₀ monocycloalkyl ester, C ₆ -C ₁₂ , preferably C ₇ -C ₁₀ mono (alkyl-substituted cycloalkyl) esters and the like, more preferably maleic acid, fumaric acid or monopropyl ester or mono n-butyl ester of citraconic acid, particularly preferably maleic acid mono n-butyl ester Is used.

  Although the content of the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit in the polymer is not particularly limited, it can be, for example, 0.1 to 20% by weight.

(4) Other α, β-ethylenically unsaturated carboxylic acid ester monomer units HNBR is a component other than the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit together with the above-described monomer units. You may have an (alpha), (beta) -ethylenically unsaturated carboxylic acid ester monomer unit.

The α, β-ethylenically unsaturated carboxylic acid ester monomer unit includes a (meth) acrylic acid alkyl ester monomer unit having a C _{1 to} C ₈ alkyl group, and a C _{2 to} C ₈ alkoxyalkyl group. There may be mentioned at least one of (meth) acrylic acid alkoxyalkyl ester monomer unit and diester monomer unit corresponding to the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer.

  When other α, β-ethylenically unsaturated carboxylic acid ester monomer units are used, the content of other α, β-ethylenically unsaturated carboxylic acid ester monomer units in the polymer is not particularly limited. It can be 0.1 to 30% by weight.

(5) Others The iodine value of the polymer is not particularly limited, but can be, for example, 120 or less, 80 or less, 25 or less, and further 15 or less.

  HNBR demonstrated above is also available as a commercial item. Examples of commercially available products include “Zetpol 3610” (CN content 20.5 wt%), “Zetpol 3710” (CN content 23.6 wt%), and “Zetpol 2510” (CN content 35.2 wt%) manufactured by Nippon Zeon. %), “Zetpol 1510” (CN content 43.5 wt%) and the like.

  As the polymer, one type of HNBR may be used alone, or two or more types of HNBR may be used in combination. When two or more HNBRs are used in combination, the nitrile content of the polymer is determined as the nitrile content in a blend composed of two or more HNBRs.

  The blending amount of the polymer in the oil seal (rubber) is not particularly limited. For example, it is preferably 30 to 90% by weight, more preferably 40 to 80% by weight, and most preferably 50 to 70% by weight. preferable.

3. Polyamine Crosslinking The polymer made of HNBR described above can be polyamine crosslinked and is polyamine crosslinked in the oil seal. For polyamine crosslinking, a polyamine compound is used as a crosslinking agent.

  Examples of the polyamine compound include hexamethylenediamine, its carbamate, benzoate or cinnamaldehyde adduct, aliphatic diamine such as diamino-modified siloxane, 4,4'-methylenebiscyclohexylamine or its cinnamaldehyde adduct, bis (4-amino- Alicyclic diamines such as 3-methyldicyclohexyl) methane, 4,4'-methylenedianiline, p, p'-ethylenedianiline, m- or p-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4 '-Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-(m- or p-phenylenediisopropylidene) dianiline, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophen Noxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 4,4′-bis (4-aminophenoxy) biphenol, bis [ 4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis Examples include aromatic diamines such as (4-aminophenoxy) benzene, preferably aromatic diamines, and more preferably p-substituted aromatic diamines.

  The crosslinking agent comprising a polyamine compound can be used, for example, at a ratio of about 0.1 to 15 parts by weight, preferably about 0.2 to 4 parts by weight per 100 parts by weight of the polymer.

  In addition, a crosslinking system composed of a polyamine compound and a crosslinking accelerator composed of a guanidine compound such as 1,3-di-o-tolylguanidine may be used together to constitute a crosslinking system.

4). Plasticizer The oil seal can contain a plasticizer as a compounding agent.

  The plasticizer is not particularly limited, and examples thereof include an aliphatic carboxylic acid diester compound of polyalkylene glycol represented by the following general formula (1).

R ¹ COO (C _n H _2n O) _m COR ² (1)
In [Equation ^{(1), R 1, R} 2 each independently represents an alkyl group or an alkenyl group of _C 1 _{~C 14,} n is an integer of 2 to 4, m is an integer from 2 to 30 . ]

  Such an aliphatic carboxylic acid diester compound of polyalkylene glycol is also available as a commercial product. Examples of commercially available products include polyether ester plasticizer “RS700” (PEG (MW300) di-2-ethylhexanoate) manufactured by Adeka Corporation.

  Although the compounding quantity of a plasticizer is not specifically limited, For example, it is preferable that it is 3-50 weight part per 100 weight part of polymers, It is more preferable that it is 5-30 weight part, It is 10-20 weight part Most preferred.

5. Other compounding agents In addition to the plasticizers described above, for example, compounding agents such as fillers, processing aids, anti-aging agents, lubricants and the like can be appropriately compounded in the oil seal.

6). Method for Producing Oil Seal In one example of a method for producing an oil seal, first, a composition (rubber composition for oil seal) obtained by appropriately adding the above-described compounding agent to the above-described polymer is kneaded using a kneader or the like. . Here, the compounding quantity of each component mentioned above about the oil seal is used for the compounding quantity of each component in the rubber composition for oil seals.

  Next, a cross-linking agent (or a cross-linking system) composed of the polyamine compound described above is added to the composition and kneaded using an open roll. Next, press crosslinking is performed at about 100 to 200 ° C., preferably about 130 to 200 ° C., more preferably about 150 to 200 ° C., for about 30 seconds to 5 hours, preferably about 3 to 10 minutes. Thereafter, if necessary, oven crosslinking (secondary crosslinking) may be performed at about 150 to 200 ° C. for about 0.5 to 24 hours. In this way, the oil seal of the present invention is obtained.

7). Applications The oil seal of the present invention is a seal member (sealing device) for sealing engine oil provided in various engines so as to be in contact with the engine oil, and has an annular structure such as an O-ring. Can have. Further, the oil seal of the present invention can be applied when the oil contains water other than the engine.

  The oil seal of the present invention maintains a good sealing function even in engine oil mixed with water generated by fuel combustion or in a poor oil environment containing a large amount of water.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

Example 1
100 parts by weight of polyamine-crosslinkable hydrogenated nitrile rubber (“Zetpol 3610” manufactured by Nippon Zeon Co., Ltd., 20.5% by weight of CN), silica (“Nipsil E75” manufactured by Tosoh Silica Co., Ltd.), BET specific surface area of 30 to 60 m ² / g: 50 parts by weight of filler, polyoxyethylene alkyl ether phosphate ester (“Phosphanol RL-210” manufactured by Toho Chemical Co., Ltd .; processing aid), 1 part by weight of polyether ester plasticizer (manufactured by ADEKA RS700 ”) and 15 parts by weight of 4,4 ′-(α, α′-dimethylbenzoyl) diphenylamine (anti-aging agent) were kneaded with a kneader to obtain an uncrosslinked dough.

  The obtained uncrosslinked dough was transferred to an open roll, and 2.5 parts by weight of hexamethylenediamine carbamate (crosslinking agent) and 1.6 parts by weight of 1,3-di-o-tolylguanidine (crosslinking accelerator) were added. After kneading, press crosslinking at 170 ° C. for 20 minutes and oven crosslinking (secondary crosslinking) at 170 ° C. for 4 hours were performed to obtain a test piece-like crosslinked product.

(Example 2)
In Example 1, instead of a polyamine-crosslinkable hydrogenated nitrile rubber having a CN content of 20.5% by weight, a polyamine-crosslinkable hydrogenated nitrile rubber having a CN content of 23.6% by weight (manufactured by Nippon Zeon Co., Ltd.) A test piece-like cross-linked product was obtained in the same manner as in Example 1 except that Zetpol 3710 ") was used.

(Example 3)
In Example 1, instead of a polyamine-crosslinkable hydrogenated nitrile rubber having a CN content of 20.5% by weight as a polymer, a polyamine-crosslinkable hydrogenated nitrile rubber having a CN content of 35.2% by weight (manufactured by Nippon Zeon " A test piece-like cross-linked product was obtained in the same manner as in Example 1 except that Zetpol 2510 ") was used.

Example 4
In Example 1, instead of a polyamine-crosslinkable hydrogenated nitrile rubber having a CN content of 20.5% by weight, a polyamine-crosslinkable hydrogenated nitrile rubber having a CN content of 43.5% by weight (manufactured by Nippon Zeon Co., Ltd.) A test piece-like cross-linked product was obtained in the same manner as in Example 1 except that Zetpol 1510 ") was used.

(Comparative Example 1)
Peroxide-crosslinkable hydrogenated nitrile rubber ("Zetpol 2000" manufactured by Nippon Zeon Co., Ltd., CN content 36.2% by weight) 100 parts by weight, FEF carbon ("Seast S0" manufactured by Tokai Carbon Co., Ltd.) 50 parts by weight, zinc oxide 5 Part by weight, 1 part by weight of stearic acid, and 5 parts by weight of a polyether ester plasticizer (“RS700” manufactured by Adeka) were kneaded with a kneader to obtain an uncrosslinked fabric.

  The obtained uncrosslinked dough was transferred to an open roll, and after adding 3 parts by weight of 1,4-bis [1- (tert-butylperoxy) -1-methylethyl] benzene (crosslinking agent) and kneading, 170 ° C., A press-crosslinking for 20 minutes and an oven crosslinking (secondary crosslinking) at 170 ° C. for 4 hours were performed to obtain a test piece-like crosslinked product.

(Comparative Example 2)
100 parts by weight of acrylic rubber (ACM) ("PA-212" manufactured by Unimatec), 60 parts by weight of FEF carbon ("Seast S0" manufactured by Tokai Carbon Co., Ltd.), 1 part by weight of stearic acid, "Strak" manufactured by Schill & Seilacher 2 parts by weight of Toll WB212 ”), 3 parts by weight of sodium stearate (“ NS Soap ”manufactured by Kao Corporation), and 2 parts by weight of 4,4 ′-(α, α′-dimethylbenzoyl) diphenylamine (anti-aging agent) An uncrosslinked fabric was obtained by kneading with a kneader.

  The obtained uncrosslinked dough was transferred to an open roll, kneaded with 2,4,6-trimercapto-s-triazine (sulfur crosslinking agent), press-crosslinked at 180 ° C. for 8 minutes, and 175 Oven crosslinking (secondary crosslinking) at 4 ° C. for 4 hours was performed to obtain a test piece-like crosslinked product.

<Evaluation method>
1. Compression set (CS) (heat resistance evaluation)
Based on JIS K6262, the value after leaving at 150 ° C. for 240 hours with a P14 O-ring was measured. However, in order to maintain consistency with the later-described compression set in oil compression test, the test jig was opened after being cooled to room temperature. The heat resistance was evaluated by setting the limit value of the sealability as the time point when the compression set becomes 80%, and ◯ when it is lower than this and x when it is higher.

2. Compression set in oil (CS) (Evaluation of hydrolysis resistance)
With reference to JIS K6258 and JIS K6262, JIS No. In 3 oils, the values after standing at 150 ° C. for 240 hours and 2000 hours with a P14 O-ring were measured. At the time of opening, the test jig was cooled to room temperature and then opened. The heat resistance was evaluated by setting the limit value of the sealability as the time point when the compression set becomes 80%, and ◯ when it is lower than this and x when it is higher.

  The results are shown in Table 1.

<Evaluation>
From Table 1, the crosslinked bodies of Examples 1 to 4 are comparable to the acrylic rubber (ACM) of Comparative Example 2, have heat resistance exceeding this, and have sufficient hydrolysis resistance that cannot be achieved by ACM. I understand that. Moreover, although the peroxide bridge | crosslinking HNBR shown to the comparative example 1 is excellent in hydrolysis resistance compared with the acrylic rubber (ACM) of the comparative example 2, it turns out that heat resistance is inadequate.

  From the above, the crosslinked bodies of Examples 1 to 4 have hydrolysis resistance suitable for use in engine oil environments mixed with moisture while having heat resistance and oil resistance comparable to acrylic rubber. I understand.

Claims (2)

  An oil seal comprising a crosslinked product obtained by polyamine crosslinking a polymer comprising a hydrogenated nitrile rubber capable of polyamine crosslinking.   The oil seal according to claim 1, wherein the polymer has a nitrile content of 20 to 45 wt%.