JPH075791B2 - Fuel hose inner tube rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a rubber composition for a fuel hose inner tube for an automobile.

<Prior Art> In a fuel hose used in a fuel circuit of an automobile, the inner tube rubber that comes into contact with the fuel oil is sulfur vulcanized mainly from fuel oil-resistant acrylonitrile-butadiene rubber and / or its hydride. Rubber compositions are widely used.

In the sulfur vulcanization type rubber composition, various combinations of sulfur and a vulcanization accelerator are known, but from the viewpoint of aging resistance and workability, conventionally, in the rubber composition for the fuel hose inner pipe, 1-3 parts by weight of sulfur to 100 parts by weight of raw rubber,
1 to 3 parts by weight of a thiazole-based or sulfenamide-based primary vulcanization accelerator and 0.5 to 2 parts by weight of a dithiocarbamate-based secondary vulcanization accelerator are blended. Especially when a small amount of sulfur is added, tetramethylthiuram disulfide (TMTD) is used as a secondary vulcanization accelerator and sulfur-releasing vulcanizing agent.
Often 2 parts by weight is compounded.

<Problems to be Solved by the Invention> If the vehicle is left out of operation for a long period of time, such as in long-term inventory or overseas transportation, the fuel pump may not operate when the engine is subsequently started.
This is because the components in the rubber composition of the inner tube of the fuel hose are eluted in the fuel oil and react with copper and zinc in the fuel circuit and alloys and compounds containing them, and (1) Insulator is generated in the switch part. (2) Precipitate that blocks the orifice is generated. (3) Precipitate that clogs the filter is generated.

Therefore, among the components in the rubber composition, when investigating and examining paying attention to sulfur and a vulcanization accelerator having a high reactivity with metal, (1) the sulfur content released from sulfur and the sulfur compound is Reacts with copper to form an insulator or precipitate of copper sulfide (2) Among the dithiocarbamate vulcanization accelerators represented by the following formulas (I) and (II), the carbon number of the alkyl group (R) is The dimethyldithiocarbamate-based vulcanization accelerator which is No. 1 reacts with copper and dimethyldithiocarbamate copper (CuMD
C) Generates an insulator and reacts with zinc to form a zinc dimethyldithiocarbamate (ZnMDC) precipitate or a precipitate (In the formula, R is an alkyl group, Me is Na, K, Cu, Zn,
Fe, Se, Te, Cd, and other metals, and n represents the valence of Me) (In the formula, R represents an alkyl group).

These products have low solubilities in fuel oil, and if the concentrations are higher than the solubilities, they may cause problems at the time of starting the engine. In particular, TMTD in which the alkyl group (R) in the above formula (II) is 1 is useful as a vulcanization accelerator and a sulfur-releasing vulcanizing agent in a small amount of sulfur compound, and is usually used in an amount of 1 to 2 parts by weight. Become.

<Means and Actions for Solving Problems> The present inventors have found that among the dithiocarbamate vulcanization accelerators represented by the above formulas (I) and (II), the alkyl group (R)
The dimethyldithiocarbamate vulcanization accelerator having 2 or more carbon atoms has strong reactivity with copper and zinc but has high solubility in fuel oil, and a certain amount of these vulcanization accelerators should be blended. It was found that, by reacting with copper and zinc and the products deposited on these surfaces to dissolve them in fuel oil, a clean metal surface can be always maintained and no precipitate is generated.

That is, the present invention is, firstly, based on 100 parts by weight of a raw rubber mainly composed of an acrylonitrile / butadiene copolymer rubber, a dithiocarbamate vulcanization accelerator represented by the above formula (I) and formula (II). Among them, the rubber composition for a fuel hose inner pipe is provided, which is obtained by blending a total of 1 to 4 parts by weight of a vulcanization accelerator having an alkyl group (R) having 2 to 4 carbon atoms.

The carbon number of the alkyl group (R) of the dithiocarbamate-based vulcanization accelerator is set to 4 or less, because if the number of carbons exceeds 4, the workability of rubber kneading becomes poor and the processing becomes complicated. This is because the manufacturing cost increases.

Among the dithiocarbamate vulcanization accelerators represented by the above formula (I) of the present invention, the alkyl group (R) has 2 to 4 carbon atoms.
Examples of the vulcanization accelerator include zinc diethyldithiocarbamate (ZnEDC) and zinc dibutyldithiocarbamate (ZnEDC).
nBDC), sodium diethyldithiocarbamate (NaED
C), sodium dibutyldithiocarbamate (NaBDC), selenium diethyldithiocarbamate (SeEDC), teryl diethyldithiocarbamate (TeEDC), etc., and among the dithiocarbamate vulcanization accelerators represented by the above formula (II), Examples of the vulcanization accelerator having 2 to 4 carbon atoms in the group (R) include tetraethylthiuram disulfide (TE
DC), tetrabutyl thiuram disulfide (TBTD), etc.

1 to 4 parts by weight is suitable, and more preferably 1.5 parts by weight.
~ 3 parts by weight. If it exceeds 4 parts by weight, the reaction product will not dissolve in the fuel oil, resulting in problems in workability and physical properties. If the amount is less than 1 part by weight, it is not sufficient in consideration of the effects of the sulfur content and other vulcanization accelerators used together.

Secondly, in addition to satisfying the above requirements, the following requirements are required. This is because the amount of sulfur and vulcanization accelerator, which are highly reactive with copper and zinc and difficult to dissolve in fuel oil, is kept to the minimum necessary, and the amount of insulators and precipitates is reduced. That is, the total amount of sulfur and the sulfur content released from the sulfur compound is 1 part by weight or less, and among the dithiocarbamate vulcanization accelerators represented by the above formulas (I) and (II), the alkyl group (R The total amount of the dimethyldithiocarbamate vulcanization accelerator having 1 carbon atom of 1) is 1 part by weight or less.

Examples of the sulfur compound releasing sulfur other than sulfur of the present invention include morpholine disulfide [MS, released sulfur (hereinafter
= 27%], alkylphenol disulfide (trade name Vultac2-5, s = 15.3-29), dipentamethylenethiuram tetrasulfide (DPTT, s = 25), morpholinodithiobenzothiazole (MDB, s = 11.3), TMTD (s = 1
3.3), TETD (s = 10.8), etc. Among the dithiocarbamate vulcanization accelerators represented by the above formulas (I) and (II), zinc dimethyldithiocarbamate is used as the dimethyldithiocarbamate vulcanization accelerator whose alkyl group (R) has 1 carbon atom. (ZnMDC), sodium dimethyldithiocarbamate (NaMDC), potassium dimethyldithiocarbamate (KMDC), copper dimethyldithiocarbamate (CuMD
C), iron dimethyldithiocarbamate (FeMDC), TMTD, etc. The amount of each of these components is appropriately 1 part by weight or less, and if the amount is more than 1 part, an insulator or a precipitate will be formed even if the vulcanization accelerator of the first requirement is compounded. Among other combination agents, mercaptobenzothiazole (MBT) and dibenzothiazyl disulfide (MBTS) are M
Since it is easy to form a metal salt of BT, and stearic acid easily forms zinc stearate and the like, it is preferable to mix as little as possible.

The acrylonitrile-butadiene copolymer rubber referred to in the present invention means acrylonitrile-butadiene rubber having an acrylonitrile content of 20% or more, acrylonitrile-butadiene rubber containing a carboxyl group or an amino group, acrylonitrile-butadiene and acrylic acid alkyl ester or acrylic. Multi-component copolymer rubber such as acid fluoroester,
Highly unsaturated rubber in which 50% or more of the conjugated diene of these copolymer rubbers has been hydrogenated, etc., and the raw rubber mainly composed of these copolymer rubbers means these copolymer rubbers and fluororubbers and epi rubbers. It means a blend with other rubbers such as chlorohydrin rubber and synthetic resins such as polyvinyl chloride and fluorine resin.

It goes without saying that the rubber composition of the present invention also contains commonly used compounding agents such as a reinforcing agent, a filler, a plasticizer, an antioxidant and a vulcanization aid.

<Examples> Hereinafter, more specific description will be given with reference to Examples and Comparative Examples.
The present invention is not limited to these examples unless it exceeds the gist.

Comparative examples 1 and 2 and Examples 1 to 2 having the composition shown in the upper part of Table 1
A rubber composition of 5 was prepared and tested for its effect on metals in fuel oil.

The test method is as follows.

A 2 mm thick rubber sheet molded into the same vulcanized state as the hose product was cut into about 5 mm square and used as a 40 g sample. Put this rubber sample in a test tube and put the fuel oil C specified in JIS K6301.
180 ml was added. Next, the surface was well polished and degreased with a thickness of 2 mm.
20mm square copper plate (Tough pitch copper plate C-1100P specified in JIS H3100) and brass plate (C-360 specified in JIS H3250)
After 4) was weighed, it was suspended in fuel oil so as not to come into contact with the rubber sample, and a cooling pipe was attached to the upper part. This test tube is 60 ℃
It was heated in a constant temperature water bath for 8 hours and allowed to cool at room temperature for 16 hours. After repeating this operation for 6 cycles, (1) the weight change of the copper plate and the brass plate after the test was determined.

(2) The copper plate after the test was sandwiched between two well-polished copper plates which were the same as before the test, and the electrical conductivity was confirmed at a voltage of 12V.

(3) The fuel oil from which the metal plate and the rubber sample were removed was centrifuged and dried, and the weight of the precipitate was measured.

The test results are shown in the lower part of Table 1.

It can be seen that in each of the examples of the present invention, no insulating coating was formed on the copper plate and the amount of precipitate was small.

Further, fuel hoses each having an inner layer of 5.9 mm and an outer diameter of 12.2 mm and having an inner layer reinforced structure, in which the rubber compositions of Comparative Example 1 and Example 1 were used as inner tubes, were prepared. Each of these test hoses (1) 1m,
A test circulation device having a high-pressure circulation pump (2) that operates independently of changes in the copper plate and a test electromagnetic fuel pump (3) that stops operating when an insulator is formed on the copper plate in the circuit as shown in FIG. Each of them was attached separately.

At the same time, test copper plate (5) similar to the above in gasoline (4)
Suspend and hang up by high pressure circulation pump (2) for 5 minutes a day.
By circulating gasoline at ℃, the electrical conductivity of the test copper plate (5) was confirmed every 10 days.

The gas tank (6) is hermetically sealed and the Liebig cooling pipe (7) is attached to the top, and it is installed in a constant temperature water tank (8) at 40 ° C.
The connection with each pump was via a nylon tube (10) provided with a flow rate adjusting cock (9) on the way. When the fuel hose (1) made of the rubber composition of Comparative Example 1 is attached 20
No electricity was supplied on the day, and the test electromagnetic fuel pump (3) tried to operate, but did not operate. 40 when equipped with the fuel hose (1) of Example 1
Even on the first day, the test copper plate (5) was energized, and the test electromagnetic fuel pump (3) also operated without any abnormality.

The hose of the example was not inferior to the hose of the comparative example in other performances required for the fuel hose.

<Effects of the Invention> As described in detail above, the rubber composition of the present invention is used for an inner tube of a fuel hose, and becomes inoperable by forming an insulating coating on a terminal of a fuel pump or the like in a fuel oil circuit. No deposits are formed in other metal orifices, or a large amount of deposits are not formed.

It should be noted that the physical properties and fuel oil resistance required for the fuel hose inner tube material do not deteriorate.

Therefore, the rubber composition of the present invention can be suitably used for a fuel hose inner tube.

[Brief description of drawings]

FIG. 1 is an explanatory view of a fuel circulation device for a fuel hose test. (1) …… Test hose, (2) …… High pressure circulation pump (3) …… Electromagnetic fuel pump for test (4) …… Gasoline, (5) …… Test copper plate (6) …… Gasoline tank, ( 7) …… Liebig cooling pipe (8) …… Constant temperature water tank, (9) …… Flow adjustment cock (10) …… Nylon tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideaki Goto, No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) Inventor Kei Mori, 4145, Yasuda, Mabi-cho, Kibi-gun, Okayama (72) Inventor Seisuke Ueki 867 Nakasho, Kurashiki City, Okayama Prefecture (56) Reference JP-A-50-24344 (JP, A) JP-A-47-6281 (JP, A)

Claims (1)

[Claims] 1. An alkyl group among dithiocarbamate vulcanization accelerators represented by the following formula (I) or (II) based on 100 parts by weight of a raw rubber mainly composed of an acrylonitrile / butadiene copolymer rubber. A total of 1 to 4 parts by weight of a vulcanization accelerator having 2 to 4 carbon atoms (R) is blended, and the total amount of sulfur and sulfur released from the sulfur compound is 1 part by weight or less, and the following formula ( Of the dithiocarbamate vulcanization accelerators represented by I) and (II), the total amount of dimethyldithiocarbamate vulcanization accelerators having an alkyl group (R) having one carbon atom is 1 part by weight or less. Rubber composition for inner tube of fuel hose. (In the formula, R is an alkyl group, Me is Na, K, Cu, Zn,
Metals such as Fe, Se, Te, and Cd, and n represent the valence of Me. ) (In the formula, R represents an alkyl group.)