JP2010083992A - Nitrile rubber composition and fuel cap gasket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitrile rubber composition having good adhesiveness to a coated layer of diamond-like carbon formed on the surface of a molded product even when not less than a predetermined amount of a plasticizer is incorporated and a fuel cap gasket on the surface of which the coated layer of diamond-like carbon is formed. <P>SOLUTION: The nitrile rubber composition is used in molding a molded product to be used by directly forming a coated layer composed of diamond-like carbon on the surface and comprises 30-50 pts.mass adipic ester based plasticizer having a molecular weight of 250 or more based on 100 pts.mass nitrile rubber. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nitrile rubber composition and a fuel cap gasket comprising the nitrile rubber composition.

  Conventionally, a fuel cap gasket used as a seal material for a fuel cap attached to an opening of a fuel tank of an automobile is made of a nitrile rubber (NBR: acrylonitrile-butadiene rubber) composition. In addition, the fuel cap gasket is chlorinated on the surface of the molded body in order to improve slidability and prevent sticking to the opening of the fuel tank. However, since chlorination is performed in a wet process, there is a problem in terms of working environment.

  Therefore, as an alternative to chlorination, a method of forming a diamond-like carbon (DLC) coating layer on the surface of a material made of a nitrile rubber material as described in Patent Documents 1 and 2 can be considered.

However, the nitrile rubber composition described in Patent Document 1 ensures the adhesion of the diamond-like carbon coating layer to the surface of the molded body by limiting the amount of compounding agent such as a plasticizer to a small amount. It is what. Therefore, this nitrile rubber composition cannot be used for a gasket for a fuel cap that needs to contain many plasticizers in order to suppress swelling due to the influence of fuel oil such as gasoline.
Japanese Patent Laid-Open No. 10-130428 JP-A-9-249873

  Therefore, even if a plasticizer of a predetermined amount or more is blended, a nitrile rubber composition having good adhesion of the diamond-like carbon coating layer formed on the surface of the molded body, and a diamond-like carbon coating layer formed on the surface It is an object of the present invention to provide an improved fuel cap gasket.

In order to solve the above-mentioned problems, the nitrile rubber composition of the present invention is a nitrile rubber composition used for molding a molded body used by directly forming a coating layer made of diamond-like carbon (DLC) on the surface. There,
25 to 55 parts by mass of a plasticizer having a molecular weight (M.W.) of 200 or more is blended with 100 parts by mass of nitrile rubber.

  In order to solve the above problems, the fuel cap gasket of the present invention is obtained by vulcanizing a molded body made of the nitrile rubber composition, and a coating layer made of diamond-like carbon is directly formed on the surface of the molded body. A fuel cap gasket characterized by having

  The aspect of each element in the present invention is exemplified below.

1. Nitrile rubber-based rubber The nitrile rubber-based rubber is not particularly limited, but nitrile rubber (NBR: acrylonitrile-butadiene rubber), polymer alloy of nitrile rubber and vinyl chloride resin (PVC) (NBR + PVC), hydrogenated nitrile rubber, etc. Can be illustrated.

2. Plasticizer The plasticizer compounded to improve the processability of the nitrile rubber composition and suppress the influence of fuel oil such as gasoline (swelling by osmosis or atrophy by extraction) is not particularly limited. An ester plasticizer such as an adipate ester plasticizer and a phthalate ester plasticizer is preferable because of its good compatibility with rubber, and an adipate ester plasticizer is more preferable from the viewpoint of safety. .
When the molecular weight of the plasticizer is less than 200 and the blending amount is increased, the plasticizer moves to the surface of the molded body of the nitrile rubber composition, so that the adhesion of the diamond-like carbon coating layer to the surface becomes worse. Preferably, it is 250 or more. The upper limit of the molecular weight is not particularly limited, but is preferably 3000 or less.
When the blending amount with respect to 100 parts by mass of the nitrile rubber-based rubber is less than 25 parts by mass, fuel oil such as gasoline penetrates into the nitrile rubber composition, so that the swelling becomes large. On the other hand, when the blending amount is increased, the plasticizer is extracted from the nitrile rubber composition as the fuel oil such as gasoline penetrates, so that the swelling is suppressed. Therefore, it is preferable that the compounding quantity with respect to 100 mass parts of nitrile rubber-type rubbers is 30-50 mass parts.

2-1. Adipate ester plasticizer The adipate ester plasticizer is not particularly limited, but diethyl adipate (MW: 202), dipropyl adipate (MW: 230), diisopropyl adipate (M W .: 230), dibutyl adipate (MW: 258), diisobutyl adipate (MW: 258), di-tert-butyl adipate (MW: 258), dipentyl adipate ( MW): 286), di-tert-pentyl adipate (MW: 286), dihexyl adipate (MW: 314), bis (2-ethylbutyl) adipate (MW: 314) ) Etc. can be illustrated.

3. Vulcanization The vulcanizing agent used for vulcanizing the nitrile rubber composition is not particularly limited, and examples thereof include sulfur and peroxide. Moreover, although it does not specifically limit, you may use together a vulcanization accelerator, a vulcanization acceleration adjuvant, etc.

4). Diamond-like carbon A method for forming a diamond-like carbon coating layer on the surface of the molded body is not particularly limited, and examples thereof include a method described in Patent Document 2 (Japanese Patent Laid-Open No. 9-249873).

5). Other compounding agents The nitrile rubber composition can be compounded with other compounding agents such as carbon black, a filler, an anti-aging agent, etc., in order to ensure performance as a gasket for a fuel cap.

6). Molded body The usage of the molded body is not particularly limited, but it can be exemplified by the use of a sealing material in contact with fuel oil such as gasoline during use, etc. Examples thereof include fuel rubber parts such as a gasket for a fuel cap.

  According to the present invention, a nitrile rubber composition having good adhesion of the diamond-like carbon coating layer formed on the surface of the molded body even when a predetermined amount or more of the plasticizer is blended, and the surface of the diamond-like carbon on the surface. A fuel cap gasket in which a coating layer is formed can be provided.

A nitrile rubber composition used for forming a molded article used by directly forming a coating layer made of diamond-like carbon on the surface,
A nitrile rubber composition comprising 30 to 50 parts by mass of an adipate ester plasticizer having a molecular weight of 250 or more per 100 parts by mass of a nitrile rubber series rubber.

  A fuel cap gasket 10 of this embodiment shown in FIG. 1 is obtained by vulcanizing a nitrile rubber composition molded into a ring shape so that it can be fitted to the fuel cap 1, and a coating layer made of diamond-like carbon on the surface thereof. It is what has.

  Therefore, four types of examples in which the type and blending amount of the plasticizer in the nitrile rubber (NBR) composition were changed, and three types in which the blending amount of the plasticizer was reduced or the plasticizer was changed to a low molecular weight one. The evaluation results for the performance of the examples (adhesion, slidability, fuel oil swelling) are shown in Table 1 below. The unit of each raw material component in the blending column is hpr (parts per undred parts of rubber), which is a ratio of parts by mass to 100 parts by mass of nitrile rubber. Table 1 also shows the measured values of slidability and fuel oil swelling of the conventional chlorinated surface (prior art).

  As a raw material component used in Examples or Comparative Examples, a polymer alloy (NBR + PVC) of nitrile rubber (NBR) and vinyl chloride resin (PVC) is used as a nitrile rubber-based rubber, MAF is used as a carbon black, filler Calcium carbonate is used as (filler), three types of adipic acid ester plasticizers having a molecular weight of 314, 258 or 174 are used as plasticizers, and amine heat-resistant anti-aging agents are used as heat-resistant anti-aging agents, An amine ozone aging inhibitor was used as the ozone aging inhibitor, and sulfur and peroxide were used as the vulcanizing agent.

The sample of each Example and the comparative example was created as follows.
Molding and vulcanization were performed at 170 ° C. for 10 minutes so that the kneaded materials were used as test pieces for each evaluation. However, about the thing of the peroxide vulcanization | cure, after that, the secondary vulcanization | cure was performed on the conditions for 60 minutes at 120 degreeC further in the thermostat.
A diamond-like carbon (DLC) coating layer was formed on the surface of the test piece vulcanized as described above.

  The performance of each of the examples and comparative examples of the present invention was evaluated as follows.

(1) Adhesion Ethanol is added to a test piece (initial stage) before dipping in fuel oil or the like and test fuel oil C (comprising 50% by volume of isooctane and 50% by volume of toluene) specified in JIS K6258. Evaluation was performed in accordance with JIS K5600-5-6 (cross-cut method) using a test piece that was immersed in 65% by volume of CE20 for 72 hours at 65 ° C and then vacuum-dried at 60 ° C for 24 hours.
The case where peeling did not occur in the DLC coating layer was evaluated as ◯, and the case where peeling occurred in the DLC coating layer was evaluated as x.

(2) Sliding property After the DLC coating layer face up and the test piece is fixed on a smooth horizontal surface, the contact surface with the test piece is washed with IPA (isopropyl alcohol). Is placed on the test piece. Then, the glass dish was pulled in the horizontal direction at a speed of 200 mm per minute, the load at that time was measured, and the friction coefficient was calculated and evaluated.
The case where the friction coefficient is less than or equal to the conventional friction coefficient (static friction coefficient: 0.60, dynamic friction coefficient: 0.51) was evaluated as ◯, and the case where the friction coefficient exceeded the conventional friction coefficient was evaluated as x.

(3) Swelling of fuel oil Based on JIS K6258, the test fuel oil C was used and tested at 40 ° C. under immersion conditions for 48 hours to determine the volume change rate. Moreover, it replaced with the test fuel oil C on the same immersion conditions, also tested about CE20 which added 20 volume% of ethanol to the test fuel oil C, and calculated | required and evaluated the volume change rate.
A sample having a volume change rate of 0 to 20% when immersed in test fuel oil C was evaluated as ◯, and a sample having a volume change rate outside the above range was evaluated as x. Moreover, it was set as (circle) about the thing whose volume change rate when immersed in CE20 is 0-35%, and the thing whose volume change rate is outside the said range was evaluated as x.

From the above results, this example in which 30 to 50 phr of adipic acid ester plasticizer having a molecular weight of 314 or 258 is blended is compared with the blending of adipic acid ester plasticizer having a molecular weight of 174 (blending 50 hpr). Unlike Example 3, the DLC coating layer was not peeled off, and the adhesion of the DLC coating layer to the molded article was good.
Further, in this example, the DLC coating layer was provided on the surface of the molded body, so that the slidability was improved as compared with the conventional one.
Further, in this example, Comparative Example 1 in which the blending amount of the adipate ester plasticizer having a molecular weight of 258 is small (20 phr) and Comparative Example 2 in which the blending amount of the adipate ester plasticizer having a molecular weight of 174 is small (20 phr) The influence (swelling) by the fuel oil was small, and it could be used for a gasket for a fuel cap. In particular, Examples 2 and 4 in which the blending amount of the plasticizer was large (50 phr) were less affected by the fuel oil (swelling) than the conventional examples.

  In addition, this invention is not limited to the said Example, In the range which does not deviate from the meaning of invention, it can change suitably and can be actualized.

It is sectional drawing (the state with which the fuel cap was mounted | worn) of the gasket for fuel caps of a present Example.

Explanation of symbols

1 Fuel cap 10 Gas cap gasket

Claims (3)

A nitrile rubber composition used for forming a molded article used by directly forming a coating layer made of diamond-like carbon on the surface,
A nitrile rubber composition comprising 25 to 55 parts by mass of a plasticizer having a molecular weight of 200 or more per 100 parts by mass of a nitrile rubber-based rubber.   The nitrile rubber composition according to claim 1, wherein the plasticizer is an adipate ester plasticizer.   A fuel cap gasket comprising: a molded body comprising the nitrile rubber composition according to claim 1 or 2; and a coating layer comprising diamond-like carbon is directly formed on a surface of the molded body. .

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