JPH11325332A - Oil-resistant hose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfy oil resistance, heat resistance and sealability concurrently. SOLUTION: In a hose 1 formed into a four-layer structure comprising an inner layer 2, an intermediate layer 3, a fiber-reinforced layer 4 and an outer layer 5, the inner layer 2 is formed out of hydrogenated nitrile rubber, and the intermediate layer 3 and the outer layer 5 are formed out of acrylic rubber containing a carboxyl group. A content of acrylonitrile in the hydrogenated nitrile rubber is made to be 30 wt.% or more, and its iodine number is made 30 (g/100 g) or less. A thickness (t) of the inner layer 2 is made to be 0.075 T<=t<=0.3 T with respect to the whole thickness of the hose 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oil-resistant hose used for various hydraulic piping systems such as automobiles, and more particularly, to a hose having a laminated structure of two or more layers for improving oil resistance, heat resistance and sealability. Regarding improvement.

[0002]

2. Description of the Related Art An oil-resistant hose of this kind is disclosed in Japanese Patent Application Laid-Open No. 7-24951,
JP-B-6-58156 and JP-A-6-9951
No. 5 is known.

[0003] JP-A No. 7-24951 discloses that the inner layer is a vulcanized hydrogenated nitrile rubber compound, the intermediate layer is a copolymerized rubber compound of a vulcanized unsaturated nitrile and a conjugated diene,
Although the outer layer is formed of a vulcanized ozone-resistant rubber compound, the conjugated diene used for the intermediate layer is particularly useful in an environment where the internal fluid temperature or the external atmosphere temperature rises to about 140 ° C. The heat resistance of the system rubber is not sufficient, and the life of the hose may be shortened due to the deterioration of the intermediate layer, or the sealing property may be deteriorated due to the "set" of the intermediate layer.

On the other hand, in the hose described in Japanese Patent Publication No. 6-58156, a hose having a laminated structure of two or more layers, for example, using hydrogenated NBR as an acrylonitrile copolymer rubber as a material of the inner layer is used. However, heat resistance is not always sufficient, and particularly when heat resistance and pressure resistance are required at the same time, there is a possibility that the sealing property may be deteriorated due to thermal deterioration as described above.

In the hose disclosed in JP-A-6-99515, the hose itself is formed of an acrylic elastomer obtained by copolymerizing a monoalkyl maleate as a carboxyl group monomer. On the other hand, it swells and deteriorates with respect to a specific oil, and still has a problem in durability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a hose capable of simultaneously satisfying oil resistance, heat resistance, and sealing properties. Specifically, swelling and deterioration by oil,
An object of the present invention is to provide a hose that does not have a risk of oil permeation or the like, does not have a decrease in strength due to thermal deterioration, and has no fear of oil leakage from a mechanical fastening portion.

[0007]

According to the first aspect of the present invention, in an oil-resistant hose having a laminated structure of at least two layers, an inner layer is formed of a compound of a hydrogenated nitrile rubber, The outer outer layer is formed of a compound of an acrylic rubber containing a carboxyl group, and the inner and outer layers are vulcanized and integrated.

Here, as described above, as long as it has a laminated structure of at least two layers, an intermediate layer may be interposed between the inner layer and the outer layer to form a three-layer structure.

According to a second aspect of the present invention, a fiber reinforcing layer is interposed between the inner layer and the outer layer according to the first aspect of the present invention, and the inner layer, the fiber reinforcing layer, and the outer layer are vulcanized. It is characterized by being molded and integrated.

Here, the fiber reinforcing layer is interposed between the inner layer and the outer layer together with the intermediate layer, and the whole hose has a substantially four-layer structure of an inner layer, an intermediate layer, a fiber reinforcing layer and an outer layer. May be.

The invention described in claim 3 is the first or second invention.
Wherein the acrylonitrile content of the hydrogenated nitrile rubber of the inner layer is 30% by weight or more.

A fourth aspect of the present invention is characterized in that the iodine value of the hydrogenated nitrile rubber in the inner layer according to any one of the first to third aspects is 30 (g / 100 g) or less.

According to a fifth aspect of the present invention, the hydrogenated nitrile rubber in the inner layer according to any one of the first to fourth aspects is a compound containing at least an organic peroxide vulcanizing agent. Features.

According to a sixth aspect of the present invention, the thickness (t) of the inner layer in the first aspect of the invention is 0.075T ≦ t ≦ 0 with respect to the total thickness (T) of the hose. .3T.

In order to study the material of the inner layer, generally, oil resistance to various hydraulic oils (volume change rate = swelling degree)
The acrylonitrile content of the hydrogenated nitrile rubber compound used as the inner layer of the oil-resistant hose is increased as the acrylonitrile content (AN content) increases. The content is preferably 30% by weight or more, and particularly preferably, the content of acrylonitrile is 40% by weight or more for a hydraulic oil containing a phosphoric acid ester-based additive and having an aniline point of 60 to 90.

Although the low-temperature property (maintenance of rubber elasticity) generally decreases by increasing the acrylonitrile content, the low-temperature property can be ensured by reducing the iodine value (increase the hydrogenation rate). The iodine value is usually from the viewpoint of oil resistance and heat aging resistance (deterioration of physical properties).
It is preferably 30 (g / 100 g) or less as in the invention described in (1), and 10 (g / 100 g) in consideration of low-temperature properties.
The following is desirable.

The heat aging resistance can be further improved by using an organic peroxide as a vulcanizing agent as in the fifth aspect of the present invention. Organic peroxides include dicumyl peroxide, 1,1-di (t-butylperoxy) -3,3,5-trimethylsiloxane, di (t-butylperoxy) diisopropylbenzene, 5-dimethyl-2,5-di (t-butylperoxy) hexane, 2.5
There are -dimethyl-2,6-di (t-butylperoxy) hexane-3 and the like, but it is desirable to use one having a high temperature required to obtain a half-life.

On the other hand, for the outer layer, the carboxyl group-containing acrylic rubber is most excellent in terms of heat aging resistance and compression set, and the invention according to claim 1 is also intended to improve the heat resistance and sealing property of the oil-resistant hose. Use a carboxyl group-containing acrylic rubber. Examples of the carboxyl group-containing acrylic rubber include (a) an acrylic rubber obtained by copolymerizing a carboxyl group-containing monomer, (a) an acrylic rubber obtained by copolymerizing a carboxyl group-containing monomer and ethylene, and (a) and (b) ), And various vulcanizing agents can be used.
For example, a polyamine compound is used.

The elementary yarn of the fiber reinforcing layer interposed between the inner layer and the outer layer according to the second aspect of the present invention may be any of various yarns such as aramid yarn, polyester yarn, nylon yarn, vinylon yarn and rayon yarn. Although it is possible to use those, the aramid yarn and the polyester yarn are particularly suitable in terms of the pressure resistance (maintaining the burst pressure after heat aging) required for the oil-resistant hose of the present invention.

In the invention according to claim 6, the thickness of the inner layer (t) is set to 0.075T ≦ t ≦ 0.3T with respect to the total thickness (T) of the hose. 0.
If it is thinner than 075T, the oil may reach the outer layer and swell the outer rubber if the oil penetrates the inner rubber. It is feared that the sealability may be reduced.

[0021]

According to the first aspect of the present invention, as the acrylic rubber constituting the outer layer, heat set resistance (compression set after heat aging) and low temperature set (compressive set after storage at low temperature). The use of a carboxyl group-containing acrylic rubber excellent in) makes it possible to form a hose with a laminated integrated structure that has good adhesion to the hydrogenated nitrile rubber as the inner layer, and has oil resistance (swelling, deterioration, oil ), Heat resistance (such as a decrease in strength due to thermal degradation), and sealability (oil leakage from the fastening portion).

According to the second aspect of the present invention, the fiber reinforced layer is interposed between the inner layer and the outer layer to be integrated, so that even when hydraulic pressure is applied to the hose, the hose according to the first aspect of the present invention can be used. This has the effect of maintaining the same oil resistance, heat resistance and sealing properties as the invention.

According to the third aspect of the invention, by setting the acrylonitrile content of the hydrogenated nitrile rubber in the inner layer to 30% by weight or more, the oil resistance is further improved.

According to the fourth aspect of the present invention, the iodine value of the hydrogenated nitrile rubber in the inner layer is set to 30 (g / 100 g) or less, so that the hydrogenation rate is increased by the lower iodine value. As a result, there is an effect that the heat resistance is further improved by suppressing the deterioration of the physical properties.

According to the fifth aspect of the present invention, by compressing at least an organic peroxide vulcanizing agent into the hydrogenated nitrile rubber of the inner layer, the compression set after heat aging is improved, and as a result, heat resistance is improved. This has the effect of further improving the settability.

According to the sixth aspect of the present invention, the thickness (t) of the inner layer is set to 0.075T ≦ the total thickness (T) of the hose.
By setting t ≦ 0.3T, even if oil penetrates into the inner layer, it is possible to prevent the outer layer from swelling and to prevent the inner layer from being deteriorated in sealing performance due to “set”.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view showing a preferred embodiment of the present invention, and shows an example in which the present invention is applied to a cooling piping hose for hydraulic oil for an automatic transmission of an automobile.

Generally, oil heated to a maximum of about 140 ° C. flows through a cooling piping system hose for hydraulic oil for an automatic transmission, and the hydraulic pressure reaches a maximum of 1.2 MPa. Further, since the hose is routed in the engine room, the outer surface of the hose is also exposed to high temperatures. Therefore, the hose has 15
Burst pressure after thermal aging at 0 ° C for 1,000 hours is 5.4MP
a or higher, and high performance with a sealing property (oil leakage pressure) of 0.98 MPa or more at a low temperature after thermal aging is required.
At the same time, a hydraulic oil containing a phosphate ester-based additive and having an aniline point of 60 to 90 may be used as the hydraulic oil for an automatic transmission at the same time. Then, as shown in FIG. 1, the hose 1 is divided into an inner layer 2, an intermediate layer 3, and a fiber reinforcing layer 4 in this order from the inside.
These were vulcanized and integrally formed as a total of four layers of the outer layer 5 and the outer layer 5.

Table 1 shows more concrete examples 1 to 4 together with comparative examples.

In the first embodiment, the inner diameter of the hose 1 is 7.5 m
m, the outer diameter was set to 15.0 mm, and the thickness (wall thickness) t of the inner layer 2 was set to 0.5 mm. The rubber material for the inner layer 2 was the one of Formulation Example 1 in Table 2. Specifically, the rubber material of the inner layer 2 is mainly composed of hydrogenated nitrile rubber,
The one having an acrylonitrile content of 44% by weight and an iodine value of 10 (g / 100 g) was used. In addition,
3.2% by weight of dicumyl peroxide as vulcanizing agent
Mixed. Further, it is also possible to use those of Formulation Examples 2 to 4 in which the content of acrylonitrile and the iodine value are changed instead of that of Formulation Example 1.

On the other hand, the rubber material of the intermediate layer 3 was the one of Formulation Example 5 in Table 3. Specifically, the rubber material of the intermediate layer 3 used was a carboxyl group-containing acrylic rubber as a main component and an amine compound added as a vulcanizing agent in an amount of 0.5% by weight. Further, as the rubber material of the outer layer 5, the same rubber composition as that of the intermediate layer 3 was used.

The carboxyl group-containing acrylic rubber of Formulation Example 5, which is the material of the intermediate layer 3 and the outer layer 5, has a particularly high heat resistance as compared with those of Comparative Formulation Examples containing no carboxyl group (Formulation Examples 6 to 9). Excellent in terms of aging and compression set.

The samples for measuring physical properties shown in Tables 2 and 3 were obtained by press vulcanization at 160 ° C. for 30 minutes and then at 175 ° C. for 5 minutes.
An oven vulcanized one was used. The oil used for the oil resistance test was a hydraulic oil for an automatic transmission containing a phosphate ester-based additive and having an aniline point of 60 to 90. For other test methods, see JIS K6301
It was carried out in accordance with.

As shown in Table 1, as the fiber reinforcing layer 4,
Twisted 1,000 denier aramid yarn was braided with 24 hits.

In Example 2, as the fiber reinforcing layer 4, one obtained by twisting a single 1,500 denier polyester yarn and knitting it with 24 beats was used.
Other hose dimensions and rubber materials were the same as those in Example 1.

In Example 3, the rubber material for the inner layer 2 was that of Formulation Example 2 in Table 2, and the other dimensions of the hose and the fiber reinforcing layer 4 were the same as those of Example 1. As apparent from Table 2, the rubber material of Formulation Example 2 had an iodine value of 10 (g / 100) as compared with that of Formulation Example 1.
g) to 25 (g / 100 g).

In the fourth embodiment, the thickness t of the inner layer 2 is set to 1.2 m
m, and the other conditions were the same as in Example 1.

In the comparative example, as apparent from Table 1, the composition of ninth embodiment was used as the intermediate layer 3 and the outer layer 5, and the other conditions were the same as those of the first embodiment. Specifically, the rubber material of Formulation Example 9 has a vinyl group-containing acrylic rubber as a main component and an organic peroxide added as a vulcanizing agent at 1.5% by weight as is clear from Table 3.

As shown in Table 1, the hoses of Examples 1 to 4 and Comparative Example were evaluated from the viewpoints of adhesion, pressure resistance, and low-temperature sealability.

Regarding the adhesion, a hose having a length of 25 mm was used.
Then, a peel test was performed between the layers. A sample with good adhesion and partial material breakage was marked with “〇”, and a sample with poor adhesion and completely separated between any layers was marked with “△”. "
And

With regard to pressure resistance, a 300 mm long hose containing the same phosphate ester-based additive as described above and a hydraulic oil for an automatic transmission having an aniline point of 60 to 90 was sealed, and heated to 150 ° C. in an oven. After heat aging for 1,000 hours, the hose was heated to a surface temperature of 140 ° C. and pressurized to measure a burst pressure.

The low-temperature sealability was measured by assembling a pipe with a bulge and a leaf spring type clamp into a hose having a length of 300 mm, sealing the same working oil as described above, and placing it in an oven for 150 hours.
After heat aging at a specified temperature for a specified time, the oil was pressurized with hydraulic oil in a low temperature tank at -10 ° C, and the heat aging time at which oil leakage occurred at a pressure of 0.98 MPa was recorded.

As is apparent from Table 1, the hoses of Examples 1 to 4 according to the present invention were made of a hydrogenated nitrile rubber forming the inner layer 2 and an acrylic rubber forming the intermediate layer 3 and the outer layer 5. Good adhesiveness between the two, satisfying the required performance of pressure resistance (burst pressure) after heat aging, and even in the low-temperature sealability after heat aging, the heat aging time, which leads to oil leakage, compared to the comparative example And can maintain necessary and sufficient sealing properties for a long time.

In particular, in Examples 1 and 2, as is clear from Tables 1 and 2, the acrylonitrile content of the hydrogenated nitrile rubber forming the inner layer 2 was set to 40% by weight or more. Iodine value of 10 (g / 100g)
In addition, since the thickness (wall thickness) t of the inner layer 2 is set to 0.075T ≦ t ≦ 0.3T with respect to the entire thickness T of the hose, the oil leaks compared to the third and fourth embodiments. It can be seen that the generated heat aging time is long and the sealing performance is further improved.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of an oil-resistant hose showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Oil resistant hose 2 ... Inner layer 3 ... Middle layer 4 ... Fiber reinforcement layer 5 ... Outer layer

Continued on the front page (72) Inventor Takashi Suzuki Kinugawa Rubber Industries, Ltd. 330, Naganuma-cho, Inage-ku, Chiba-shi, Chiba (72) Inventor Tatsumi Onishi 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co. (72) Inventor Tomohito Ota 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Inside Nissan Motor Co., Ltd.

Claims (6)

[Claims] 1. An oil-resistant hose having a laminated structure of at least two layers, wherein an inner layer is formed of a compound of a hydrogenated nitrile rubber, and an outer layer outside the inner layer is a compound of an acrylic rubber containing a carboxyl group. An oil-resistant hose made of a material, wherein the inner and outer layers are vulcanized and integrated. 2. A fiber reinforced layer is interposed between an inner layer and an outer layer, and the inner layer, the fiber reinforced layer and the outer layer are integrally formed by vulcanization molding. Oil resistant hose as described. 3. The oil-resistant hose according to claim 1, wherein the acrylonitrile content of the hydrogenated nitrile rubber in the inner layer is 30% by weight or more. 4. The oil-resistant hose according to claim 1, wherein the iodine value of the hydrogenated nitrile rubber in the inner layer is 30 (g / 100 g) or less. 5. The oil-resistant hose according to claim 1, wherein the hydrogenated nitrile rubber in the inner layer is a compound containing at least an organic peroxide vulcanizing agent. 6. The thickness (t) of the inner layer is equal to the total thickness (T) of the hose.
The oil-resistant hose according to any one of claims 1 to 5, wherein 0.075T?