JP2008189898A - Acrylonitrile/butadiene rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an NBR composition which is improved simultaneously together in oil resistance, ozone resistance and cold temperature resistance. <P>SOLUTION: The acrylonitrile/butadiene rubber composition is characterized in that an NBR is blended with an ethylene/vinyl acetate polymer (EVA) having a high vinyl acetate content and/or an ethylene/ethyl acrylate copolymer (EEA) and moreover is added with a mixed plasticizer containing three kinds of plasticizers: 1. an adipic acid-based diester, 2. a sebacic acid-based polyester, and 3. a polyoxyalkylene mono(di)fatty acid ester. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an acrylonitrile butadiene rubber composition, and more particularly to an acrylonitrile butadiene rubber composition having improved ozone resistance and cold resistance without impairing oil resistance.

  Acrylonitrile butadiene rubber (NBR) is known as a rubber having excellent oil resistance. In particular, those having a high nitrile content are superior, but those having a high nitrile content are also known to be inferior in ozone resistance and cold resistance (Non-patent Document 1 ["Troubles and Countermeasures for Rubber / Plastic Materials" p55 2005: Yoshito Otake: Nikkan Kogyo Shimbun]; Non-Patent Document 2 ["Encyclopedia of Rubber", Michio Okuyama et al .: Asakura Shoten]).

  Methods for improving the ozone resistance of NBR include methods of blending NBR with polyvinyl chloride (PVC) and methods of blending polymers such as ethylene vinyl acetate polymer (EVA). However, there is a problem that the cold resistance and the compression set are lowered while improving the properties.

  On the other hand, it is known to add a plasticizer to improve cold resistance. As a plasticizer for improving cold resistance and heat resistance for butadiene rubber such as NBR, as a glycol component, a molecular weight of 200 to 5000 is used. There is a report that an ester containing polyoxyalkylene glycol and an ester containing a dicarboxylic acid having 2 to 10 carbon atoms as a fatty acid is suitable (Patent Document 1 [JP-A-62-253643)], on the other hand. However, there is a problem that cold resistance is reduced due to volatilization or extraction of the plasticizer in use (Non-Patent Document 1), and in addition, many polymer plasticizers such as those described above have problems with cold resistance ( Non-Patent Document 3 [Rubber Industry Handbook, 4th Edition; edited by Japan Rubber Association: (Japan) Rubber Association]).

Furthermore, if the polymer content is increased to obtain ozone resistance, there is a problem that cold resistance cannot be improved even if a plasticizer is added. Using these plasticizers solves these problems. It was difficult to do.
JP-A-62-253643 Troubles and countermeasures for rubber and plastic materials (p55, 2005: written by Yoshito Otake: Nikkan Kogyo Shimbun) Rubber encyclopedia (Michio Okuyama et al .: Asakura Shoten) Rubber Industry Handbook (4th edition; Japan Rubber Association: (Japan) Rubber Association)

  An object of the present invention is to provide an NBR composition having improved oil resistance, ozone resistance and cold resistance at the same time.

  The present invention blends NBR with a high vinyl acetate content ethylene vinyl acetate polymer (EVA) and / or an ethylene-ethyl acrylate copolymer (EEA); 1. adipic acid diester, 2. Sebacic acid-based polyester and It is characterized by an NBR rubber composition containing a mixed plasticizer containing three kinds of polyoxyalkylene mono (di) fatty acid esters.

  In the NBR composition according to the present invention, an ethylene vinyl polymer and / or an ethylene-ethyl acrylate copolymer is blended to improve cold resistance, and a special plasticizer, that is, an adipic acid system having poor compatibility with each other. By adding a plasticizer that can mix diester and sebacic acid polyester with polyoxyalkylene mono (di) fatty acid ester, oil resistance and ozone resistance (dynamic ozone resistance) are improved, and cold resistance is further improved. And the compression set are improved.

  According to the present invention, as described above, NBR is blended with ethylene vinyl acetate polymer (EVA) and / or ethylene-ethyl acrylate copolymer (EEA) having a high vinyl acetate content, and 1. adipic acid diester, 2. Sebacic acid-based polyester and A rubber composition comprising a mixed plasticizer containing three types of polyoxyalkylene mono (di) fatty acid esters is characterized.

  The NBR is preferably a high nitrile, ultrahigh nitrile NBR, water-added NBR, or carboxylated NBR with good oil resistance. Of course, it can also be applied to NBR with a small amount of nitrile such as medium-high nitrile, but in order to be NBR with good oil resistance, cold resistance and ozone resistance, the above-mentioned high nitrile or water added, carboxylated nitrile It is desirable to apply to NBR with good oil resistance such as

  The polymers blended according to the present invention are high vinyl acetate content ethylene vinyl acetate polymers (EVA) and / or ethylene-ethyl acrylate copolymers (EEA) as described above. This EVA and / or EEA is added in order to improve ozone resistance.

  The vinyl acetate content of this EVA is preferably 40 to 90% by weight. If the amount is less than 40% by weight, the effect of improving the ozone resistance may be small. On the other hand, if it exceeds 90% by weight, the properties as a thermoplastic resin appear strongly, so that blending with NBR becomes difficult.

  The EVA and / or EEA is preferably mixed in an amount of 20 to 60 wt% (NBR: 80 to 40 wt%), more preferably 35 to 40 wt% with respect to NBR. If it is less than 20% by weight, the effect of improving ozone resistance is small, while if it exceeds 60% by weight, cold resistance is deteriorated.

  Such a mixture of NBR and EVA and / or EEA, that is, a plasticizer added to the NBR rubber mixture is added in order to improve cold resistance.

  In the present invention, the plasticizer is 1. 1. adipic acid diester, 2. Sebacic acid-based polyester and It is a mixed plasticizer containing three types of polyoxyalkylene mono (di) fatty acid esters.

1. Adipic acid diester Adipic acid diester is added to improve cold resistance.For example, dimethyl adipate, diethyl adipate, divinyl adipate, diisopropyl adipate, diisobutyl adipate, diethylhexyl adipate, diisononyl adipate, One or more of dioctyl acid and diisodecyl adipate can be used.

2. Sebacic acid-based polyester A sebacic acid-based polyester is added together with an adipic acid-based diester to improve cold resistance. As such a sebacic acid-based polyester, an ester polymer of sebacic acid and glycol can be used. Specific examples include dibutyl sebacate (DBS), dioctyl sebacate (DOS), and diethyl sebacate (DES). ), Dinonyl sebacate (DNS), dimethyl sebacate (DMS), dicapryl sebacate (DCS), ditridecyl sebacate (DTDS), di-2-ethylhexyl sebacate, and polyoxydiethylene sebacate. Can be mentioned.

3. Polyoxyalkylene mono (di) fatty acid ester Polyoxyalkylene mono (di) fatty acid ester itself has the effect of improving cold resistance, but as mentioned above, it is a poorly compatible adipic acid diester and sebacic acid polyester. Added to improve compatibility.

  Examples of polyoxyalkylene glycols of such polyoxyalkylene mono (di) fatty acid esters include polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol, polyoxypentamethylene glycol, polyoxyhexamethylene glycol, and ethylene oxide Alternatively, propylene oxide or a random or block copolymer of both may be used. These polyoxyalkylene glycols preferably have a molecular weight of 200 to 5,000, particularly 500 to 2,000 because they are excellent in both cold resistance and heat resistance.

  In the present invention, since polyoxyalkylene glycol alone has a strong polarity, there is a problem in compatibility with rubber, and esterification was performed with a fatty acid component to improve this.

  Among the fatty acid components used in the present invention, examples of unsaturated fatty acids having 14 to 22 carbon atoms include myristoleic acid, palmitoleic acid, oleic acid, erucic acid, linoleic acid, and linolenic acid. Examples of the saturated fatty acid having 2 to 24 carbon atoms include acetic acid, butyric acid, caproic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid.

  Examples of the dicarboxylic acid having 2 to 10 carbon atoms include oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid and the like, and examples of the polymer acid include unsaturated fatty acids having 14 to 22 carbon atoms described above. Examples of the dimer or higher are listed.

  The mixing ratio (weight ratio) of the above-mentioned mixed plasticizer according to the present invention is preferably adipic acid diester: sebacic acid polyester = 1: 0.2 to 1.0. This is because if the sebacic acid polyester is less than 0.2, the cold resistance deteriorates, and if it exceeds 1.0, the compatibility between the plasticizers deteriorates.

  On the other hand, the polyoxyalkylene mono (di) fatty acid ester is preferably 0.5 to 2.0 (weight ratio) with respect to the above-mentioned mixture 1.0 of the adipic acid diester and sebacic acid polyester. If it is less than 0.5, the effect of improving the compatibility of the aforementioned adipic acid-based diester and sebacic acid-based polyester is small. On the other hand, if it exceeds 2.0, bleeding from the rubber increases and the rubber surface becomes sticky. This is because a malfunction occurs.

  As described above. 1. adipic acid diester, 2. Sebacic acid-based polyester and The mixed plasticizer containing three kinds of polyoxyalkylene mono (di) fatty acid ester is preferably added in a proportion of 10 to 50 parts by weight with respect to 100 parts by weight of NBR and EVA. If the amount is less than 10 parts by weight, the effect of improving the cold resistance is small without impairing the oil resistance. On the other hand, if the amount exceeds 50 parts by weight, there is a problem that the bleed from the rubber increases and the rubber surface becomes sticky. Because.

  In the present invention, other additives usually added to the NBR composition can be effectively added. Obviously, for example, reinforcing materials such as carbon black, anti-aging agents, processing aids, vulcanizing agents, vulcanization accelerators and the like can be added.

[Example]
In the examples of the present invention, the following materials were used.
High nitrile NBR (manufactured by Bayer, Pervenin NT3965: trade name)
EVA (manufactured by Bayer, Revaprene 800HV: trade name; vinyl acetate content 80%)
Sebacic acid polyester (Dainippon Ink Chemical Co., Ltd., Polycizer P202: trade name)
Polyalkylene fatty acid ester (manufactured by Toray Fine Chemical Co., Ltd., Thiocol TP759: trade name)
Adipic acid diester (Adeka Sizer RS107: trade name)
The rubber composition is kneaded with additives such as anti-aging agent, zinc oxide, vulcanization accelerator, sulfur (or peroxide vulcanization), and the mixing ratio and mixing ratio of each additive. The method was determined in accordance with, for example, the description of “Rubber Industry Handbook 4th Edition” (Japan Rubber Association).

  The components excluding sulfur at the kneading ratio shown in Table 1 were kneaded with a kneader and then vulcanized to prepare test pieces. In this example, the results when the mixing ratio of adipic acid diester and sebacic acid-based polyester is changed with respect to adipic acid diester 1 are shown.

[Evaluation methods]
The obtained vulcanized rubber composition was evaluated according to the following method. The results are shown in Table 1. Each physical property data was evaluated as follows (the same applies to Example 2 and Example 3).
<Oil resistance>
An oil resistance test was conducted in accordance with JIS K6258 (new JIS).
<Cold resistance>
A cold resistance test was performed in accordance with JIS K6261 (new JIS), and the results were compared with the Gemann T2 value.
<Ozone resistance>
An ozone resistance test was conducted according to JIS K6259 (new JIS).
<Volatilization loss>
The test piece prepared in the example was placed in an oven at 160 ° C. and heated for 80 minutes. By evaporating the plasticizer over time, the weight loss ratio (% by weight) relative to the test sample was measured.

  From the results of Example 1, it can be seen that the mixing ratio of adipic acid diester and sebacic acid-based polyester is 0.2 to 1.0 parts by weight with respect to 1.0 adipic acid diester.

  Test pieces were prepared and evaluated in the same manner as in Example 1 at the kneading ratios shown in Table 2. The results are shown in Table 2. This Example 2 is a test result when the mixing ratio of the fatty acid ester is changed with respect to the mixture 1 of the adipic acid diester and the sebacic acid-based polyester.

  It can be seen that the polyalkylene fatty acid ester is suitably 0.5 to 2.0 parts by weight based on 1.0 mixture of sebacic acid polyester and adipic acid diester.

  Test pieces were prepared and evaluated in the same manner as in Example 1 at the kneading ratio shown in Table 3. The results are shown in Table 3. The result at the time of changing the ratio of a mixed plasticizer with respect to a polymer (NBR + EVA) is shown.

  It turns out that it is suitable that it is 10-50 weight part of 3 types of mixed plasticizers (Sebacic acid type polyester + adipic acid diester + polyalkylene fatty acid ester) with respect to 100 weight part of polymers (NBR + EVA).

  In the NBR composition according to the present invention, an ethylene vinyl polymer is blended in order to improve cold resistance, and a special plasticizer, that is, an adipic acid-based diester and a sebacic acid-based polyester, which are poorly compatible with each other, are mixed with a polyoxyalkylene monoester. (Di) By adding a plasticizer that can be mixed with each other by fatty acid ester, it is possible to further improve cold resistance and compression set while improving oil resistance and ozone resistance (dynamic ozone resistance). it can.

Claims (7)

A mixture of ethylene vinyl acetate polymer (EVA) and / or ethylene-ethyl acrylate copolymer (EEA) with a high vinyl acetate content on acrylonitrile butadiene rubber; 1. adipic acid diester, 2. Sebacic acid-based polyester and An acrylonitrile butadiene rubber composition comprising a mixed plasticizer containing three kinds of polyoxyalkylene mono (di) fatty acid esters. The ethylene vinyl acetate polymer (EVA) and / or ethylene-ethyl acrylate copolymer (EEA) having a high vinyl acetate content is mixed in an amount of 20 to 60% by weight based on the acrylonitrile butadiene rubber. Item 2. The acrylonitrile butadiene rubber composition according to Item 1. The acrylonitrile butadiene rubber composition according to claim 1 or 2, wherein the acrylonitrile butadiene rubber is a high nitrile, an ultra high nitrile, a water-added or carboxylated acrylonitrile butadiene rubber. 4. The acrylonitrile butadiene rubber composition according to claim 1, wherein the ethylene vinyl acetate polymer has a vinyl acetate content of 40 to 90% by weight. 5. The mixing ratio (weight ratio) of the adipic acid-based diester and the sebacic acid-based polyester is 0.2 to 1.0 with respect to the adipic acid-based diester 1. 5. Acrylonitrile butadiene rubber composition. The said polyoxyalkylene mono (di) fatty acid ester is 0.5-2.0 (weight ratio) with respect to the mixture 1 of the said adipic acid type diester and sebacic acid type polyester, The any one of Claim 1 to 5 Acrylonitrile butadiene rubber composition. A mixture of ethylene vinyl acetate polymer (EVA) and / or ethylene-ethyl acrylate copolymer (EEA) having a high vinyl acetate content to the acrylonitrile butadiene rubber; 1. adipic acid diester, 2. Sebacic acid-based polyester and The mixture with a mixed plasticizer containing three kinds of polyoxyalkylene mono (di) fatty acid esters is added in an amount of 10 to 50 parts by weight with respect to 100 parts by weight of the mixture. An acrylonitrile butadiene rubber composition.