JP2010164063A - Rubber composition for hose jacket - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a halogen-free rubber composition for a hose jacket compatibly maintaining good vulcanization speed and adhesion properties, having sufficient oil resistance, weather resistance and wear resistance, and suitably used as jacket material for hydraulic hose. <P>SOLUTION: The rubber composition for hose jacket contains ethylene-propylene-diene rubber (EPDM) and acrylonitrile-butadiene rubber (NBR) containing nitrile of 40 mass% or less as rubber component. The content of EPDM is 25-40 phr and the content of NBR to whole rubber component is 10-20 mass% in nitrile content. The rubber composition also contains a thiuram vulcanization accelerator, and an organic acid cobalt of 1-5 phr. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition for a hose jacket that is preferably used as a jacket for a hydraulic hose of a building machine, an agricultural machine, or other industrial machines. The present invention also relates to a rubber composition for hose jackets having a good vulcanization rate.

  Hydraulic hoses are used in hydraulic machines such as construction machines such as excavators and bulldozers, agricultural machines such as tillers and tractors, and other industrial equipment such as hydraulic jacks, hydraulic punchers, hydraulic presses and hydraulic benders. The driving force is transmitted by the pressure of hydraulic oil filled in the inside.

  Therefore, this hydraulic hose is required to endure high pressure and transmit the driving force (pressure) accurately and quickly, and has high oil resistance and low volume expansion due to pressure. Also, since the hydraulic oil is often used during the operation of the machine due to the high temperature of the machine and in the harsh environment where vibration and bending are always applied outdoors, high heat resistance, weather resistance, abrasion resistance, etc. Desired.

  Such a hydraulic hose has a rubber inner rubber layer (hereinafter also referred to as “inner tube rubber”) filled with hydraulic oil, a reinforcing layer to withstand the pressure of the hydraulic oil, and prevents external damage. In general, a structure in which outer surface rubber layers (hereinafter referred to as “coating rubber”) are sequentially laminated from the inner side is provided, and a plurality of reinforcing layers are often provided.

  Conventionally, chloroprene rubber has been used for the outer rubber layer of such a hydraulic hose from the balance of oil resistance, weather resistance, and wear resistance. However, halogen-free rubber that replaces this chloroprene rubber is used due to environmental problems. It has been demanded.

  The rubber for the hose is also an important factor for the adhesiveness with the steel cord used for the reinforcing layer, in particular, the commonly used brass plating wire. The adhesiveness of the rubber composition is improved by blending organic acid cobalt with No. 12138 (Patent Document 1) or JP-A-56-162648 (Patent Document 2) to promote the copper sulfide formation reaction. It has been proposed. However, when the organic acid cobalt is blended, vulcanization delay is caused and adjustment of the vulcanization time may be difficult, and restrictions on the production conditions increase, and the handling in production tends to be inferior.

  Furthermore, Japanese Patent Application Laid-Open No. 58-72436 (Patent Document 3) and Japanese Patent Application Laid-Open No. 59-162648 (Patent Document 4) contain a phenol resin or a maleic anhydride-modified polymer and a functional group on brass plating. It has been proposed to improve the adhesion of the rubber composition by forming hydrogen bonds with it. However, in the method using the phenol resin, rubber hardness may increase and fatigue may be reduced. In the method using the modified polymer, an unvulcanized or vulcanized rubber may be used depending on the functional group of the modified polymer. The surface tackiness may increase excessively and adversely affect workability and the appearance of rubber products.

Japanese Patent Laid-Open No. 55-12138 JP-A-56-162648 JP 58-72436 A JP 59-162648 A

  The present invention has been made in view of the above circumstances, has both vulcanization speed and adhesiveness, has sufficient oil resistance, weather resistance, and wear resistance, and is suitable as a covering material for hydraulic hoses. An object of the present invention is to provide a rubber composition for a hose jacket used in the above.

  As a result of intensive studies to solve the above problems, the present inventor has found that a rubber component containing ethylene-propylene-diene rubber (EPDM) and acrylonitrile-butadiene rubber (NBR) having a specific nitrile content in a specific ratio. In addition, by blending a thiuram vulcanization accelerator and a specific amount of organic acid cobalt, it is possible to achieve both good vulcanization speed and adhesion, and good oil resistance, weather resistance, and abrasion resistance. The present invention has been completed.

Therefore, the present invention contains ethylene-propylene-diene rubber (EPDM) as a rubber component and acrylonitrile-butadiene rubber (NBR) having a nitrile content of 40% by mass or less, and the content ratio of the EPDM is 25 to 40 phr, and the NBR The hose is characterized in that the nitrile content of the rubber component is 10 to 20% by mass and contains a thiuram vulcanization accelerator and 1 to 5 phr of organic acid cobalt. Outer rubber composition, and
In the hose comprising an inner tube rubber layer forming the inner surface of the hose, an outer rubber layer forming the outer surface of the hose, and a reinforcing layer provided between the inner tube rubber layer and the outer rubber layer, the outer surface There is provided a hose characterized in that a rubber layer is formed of the rubber composition for a hose jacket according to the present invention.

  In addition, as a result of further studies, the present inventor can improve the adhesion more reliably and well by adding a predetermined amount of phenol resin or resorcin, and also uses a sulfenamide vulcanization accelerator in combination. Thus, the vulcanization speed can be increased more reliably and satisfactorily, and further, by blending other diene rubber such as styrene-butadiene rubber (SBR) as a part of the rubber component, this can be achieved with the EPDM and NBR phases. It has been found that it can act as a container and can further improve the wear resistance of rubber.

Accordingly, the present invention provides the following (1) to (5) as preferred embodiments.
(1) The rubber composition for a hose jacket of the present invention containing 0.5 to 5 phr of a phenol resin, and the hose of the present invention having an outer rubber layer formed of the rubber composition for a hose jacket.
(2) The rubber composition for a hose jacket of the present invention containing resorcin from 0.3 to 3 phr, and the hose of the present invention in which an outer rubber layer is formed from the rubber composition for a hose jacket.
(3) A rubber composition for a hose jacket according to the present invention, which further contains a sulfenamide vulcanization accelerator together with a thiuram vulcanization accelerator, and an outer rubber layer formed from the rubber composition for a hose jacket The above-described hose of the present invention.
(4) The rubber composition for a hose jacket according to the present invention, which further contains another diene rubber together with the EPDM as a rubber component, and the present invention in which an outer rubber layer is formed from the rubber composition for a hose jacket Hose.
(5) The rubber composition for hose jacket of the present invention, wherein the diene rubber is styrene-butadiene rubber (SBR), and the hose of the present invention in which an outer rubber layer is formed from the rubber composition for hose jacket. .

  The rubber composition for hose jacket of the present invention can achieve halogen-free considering the environment, has excellent adhesion to brass plating wire, and has good oil resistance, weather resistance, and wear resistance The outer rubber layer can be formed with good workability without causing a decrease in the vulcanization speed.

  As described above, the rubber composition for hose jackets of the present invention contains, as a rubber component, ethylene-propylene-diene rubber (EPDM) and acrylonitrile-butadiene rubber (NBR) having a specific nitrile content at a specific ratio, and It contains a thiuram vulcanization accelerator and a specific amount of organic acid cobalt.

  The blending ratio of the EPDM is 25 to 40 phr, preferably 30 to 40 phr, more preferably 35 to 40 phr. If the blending ratio of EPDM is less than 25 phr, the weather resistance will be inferior. On the other hand, if it exceeds 40 phr, the oil resistance and wear resistance will be reduced, and the smoothness of the extruded rubber surface will be reduced in workability. Thus, it may be difficult to ensure good dimensional accuracy.

  As the NBR, those having a nitrile content (AN content) of 40% by mass or less are used, particularly those having 10 to 40% by mass, preferably 20 to 40% by mass, more preferably 20 to 35% by mass. It is done. Here, if the AN content exceeds 40% by mass, the difference in polarity with other polymers becomes larger. As a result, the balance of the distribution of the compounded chemicals is lost, and the adhesiveness to the wire and the co-crosslinking property between different polymers, etc. Decreases. In addition, since the high nitrile-containing NBR has low low temperature resistance, the low temperature resistance of the jacket rubber applied is also lowered.

  The blending ratio of the NBR is such that the nitrile content (AN content) in the rubber component in the rubber composition is 10 to 20% by mass, preferably the nitrile content is 10 to 15% by mass, more preferably 12-13% by mass. In this case, if the blending ratio of NBR is less than 10% by mass in terms of the nitrile content in the rubber component, the oil resistance is poor and the object of the present invention cannot be achieved, while if it exceeds 20% by mass. It is not preferable because it is inferior in low temperature resistance.

  In the present invention, although not particularly limited, in addition to the above EPDM and NBR, a diene rubber other than EPDM can be further blended as a rubber component, and in particular, the compatibility between the above EPDM and NBR is improved. For the purpose of improving the abrasion resistance of the resulting rubber composition, it is preferable to blend styrene-butadiene rubber (SBR). The blending amount of the diene rubber is not particularly limited and is an appropriate amount, but in the case of SBR, it is preferably 10 to 40 phr, particularly preferably 20 to 30 phr. In this case, if the blending ratio of SBR is less than 10 phr, a sufficient effect due to blending may not be obtained. On the other hand, if it exceeds 40 phr, a blending composition that sufficiently exhibits the combined characteristics of EPDM and NBR is constituted. May be difficult, and it may be difficult to achieve both long-term weather resistance and oil resistance.

  Examples of the diene rubber other than SBR include natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), syndiotactic-1,2-polybutadiene and the like.

  The thiuram vulcanization accelerator is not particularly limited, and a known thiuram vulcanization accelerator can be used. Specifically, tetramethylthiuram disulfide (TMTD), tetramethylthiuram monosulfide (TMTM), tetraethyl Examples include thiuram disulfide (TETD) and tetrabutyl thiuram disulfide (TBTD), and one or more of these can be used.

  The mixing ratio of the thiuram vulcanization accelerator is an effective amount and is not particularly limited, but is usually preferably 0.1 to 5 phr, and more preferably 1 to 3 phr. When the blending ratio of the thiuram vulcanization accelerator is less than 0.1 phr, the vulcanization speed may be slow and the rubber composition may be inferior in workability. Conversely, if the blending ratio exceeds 5 phr, the vulcanization speed is excessive. May be partially cross-linked by heat generated during scouring and processing of the compounded rubber, which may impair the appearance and durability of the product.

  Although not particularly limited, it is preferable to use a sulfenamide vulcanization accelerator in combination with the thiuram vulcanization accelerator in order to increase the vulcanization rate more effectively. In this case, as the sulfenamide vulcanization accelerator, N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, Nt-butyl-2-benzo Known materials such as thiazole sulfenamide can be used.

  The mixing ratio of the sulfenamide vulcanization accelerator is not particularly limited, but is preferably 0.1 to 1 phr, particularly preferably 0.3 to 0.6 phr. In some cases, the effect of the amide vulcanization accelerator blending may not be sufficiently obtained. On the other hand, if it exceeds 1 phr, the vulcanization rate will increase excessively, resulting in burns and reduced adhesion to the brass plating wire. There is.

  Although not particularly limited, in the present invention, sulfur is usually used as a vulcanizing agent, and the blending ratio thereof is not particularly limited, and is usually 0.5 to 3 phr, particularly 1 to 3. It can be 2.5 phr.

  Next, the organic acid cobalt is not particularly limited, and examples thereof include cobalt naphthenate, cobalt stearate, cobalt versatate, cobalt dodecanoate, and the like, and one or more of these can be used. The organic acid cobalt effectively improves the adhesion with the steel cord used for the reinforcing layer of the hose, particularly the brass plating wire, and the blending ratio is 1 to 5 phr, preferably 2 to 4 phr. . If the blending amount of the organic acid cobalt is less than 1 phr, it is not possible to obtain a sufficient adhesive improvement effect. Conversely, if it exceeds 5 phr, it is excessively added, which may cause a decrease in adhesiveness with the brass plating wire. Absent.

  In the present invention, for the purpose of further improving the adhesiveness, in addition to the organic acid cobalt, either or both of a phenol resin and resorcin can be used in combination.

  As the phenol resin, either modified or unmodified may be used. Specifically, alkylphenol resin, cashew-modified phenol resin, oil-modified phenol resin and the like are exemplified, and one or more of these can be used. . The blending ratio of the phenol resin is not particularly limited, but is preferably 0.5 to 5 phr, and particularly preferably 0.5 to 2 phr. If the blending ratio is less than 0.5 phr, sufficient blending effect may not be obtained. On the other hand, if the blending ratio exceeds 5 phr, further improvement in adhesion cannot be expected, and the rubber hardness increases and durability decreases. There is a possibility.

  The blending ratio of the resorcin is not particularly limited, but is preferably 0.1 to 3 phr, particularly preferably 0.3 to 1 phr, and if it is less than 0.1 phr, a sufficient effect by blending can be obtained. On the other hand, even if it exceeds 3 phr, no further improvement in adhesion can be expected, and there is a possibility that durability will be lowered due to an increase in rubber hardness.

  An appropriate amount of additives other than those described above can be added to the rubber composition of the present invention as required. For example, vulcanizing agents other than the above, vulcanization accelerators and vulcanization acceleration aids, commonly used carbon, anti-aging agents, plasticizers, petroleum resins, waxes, antioxidants, fillers, oils, lubricants In addition, additives such as ultraviolet absorbers, dispersants, compatibilizers, homogenizers, and the like can be appropriately blended.

  As a method for producing a rubber hose by forming an outer rubber layer (coating rubber) using the rubber composition of the present invention, a normal method can be adopted, for example, an inner tube rubber layer, a steel cord When manufacturing a hydraulic hose comprising a reinforcing layer and an outer rubber layer, the following manufacturing method can be exemplified.

  First, an inner rubber layer (inner tube rubber) is formed by extruding a rubber composition for the inner tube rubber layer on the outer side of a core (mandrel) having a diameter approximately equal to the inner diameter of the hose to cover the mandrel. (Inner tube extrusion process). Next, a reinforcing layer is formed by braiding a predetermined number of brass plating wires on the outer side of the inner rubber layer formed in the inner tube extrusion step (knitting step), and the outer cover rubber of the present invention is formed on the outer side of the reinforcing layer. The composition is extruded to form an outer rubber layer (outer rubber) (outer extrusion process). Further, the outer surface of the outer rubber layer formed in the jacket extrusion process is coated with an appropriate resin (resin mold coating process), and vulcanized under predetermined conditions (vulcanization process). After vulcanization, the coating resin is peeled off (resin mold peeling step), and the mandrel is removed (mandrel extraction step) to produce a hydraulic hose having a reinforcing layer between the inner tube rubber and the jacket rubber.

  The structure of the hydraulic hose may be a three-layer structure in which the inner tube rubber, the reinforcing layer, and the jacket rubber are sequentially laminated from the inside as described above. It is also possible to adopt a five-layer structure in which an intermediate layer (intermediate rubber) is disposed between the two reinforcing layers, and these structures may be appropriately set according to the required characteristics of the hose.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not restrict | limited to the following Example. In addition, in the following example, a part and% show a mass part and mass%.

[Examples 1 to 20, Comparative Examples 1 to 13]
The rubber composition was kneaded with the formulation shown in Table 1 and Table 2 below to obtain a rubber composition for a hose jacket. In this case, in the kneading operation, first, each compounding agent excluding the vulcanizing agent is added to the raw rubber and kneaded with a Banbury mixer or a kneader (non-pro kneading), taken out from the kneader and sufficiently cooled, and then vulcanized. The remaining compounding agent containing the agent was added and returned to the kneader again to knead (professional kneading).

In this case, the detail of each compounding component in Table 1 and Table 2 is as follows.
EPDM: “EP35” manufactured by JSR Corporation
SBR: “Toughden 2000R” manufactured by Asahi Kasei Chemicals
NBR (AN% 35%): “N230S” manufactured by JSR Corporation
NBR (AN% 40%): “N220S” manufactured by JSR Corporation
NBR (AN% 48%): “N215SL” manufactured by JSR Corporation
Organic acid cobalt: Cobalt naphthenate (manufactured by DIC Corporation)
Phenol resin: “Sumilite Resin PR-12687” manufactured by Sumitomo Bakelite Co., Ltd.
Resorcin: Resorcinsulfenamide-based vulcanization accelerator manufactured by Mitsui Chemicals, Inc .: “Noxeller CZ-G” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Thiuram vulcanization accelerator: “Noxeller TOT-N” manufactured by Ouchi Shinsei Chemical Co., Ltd.

  Each rubber composition prepared by kneading is vulcanized and cured in accordance with the die vulcanization test A method defined in JIS K 6300, and vulcanization speed is measured using a character meter manufactured by A & D Co., Ltd. (T90) was measured. Also, taking T90 (min) as 1 vest and taking the time to reach 1.5 vest at a temperature of 150 ° C., vulcanizing each rubber composition under a pressure condition of 6.5 MPa, separately for hose jacket Rubber samples were prepared and the following properties and performance were evaluated. The results are shown in Tables 1 and 2.

[hardness]
In accordance with JIS K 6253, the hardness was measured using a durometer hardness test type A technique. “CL-150” manufactured by Kobunshi Keiki Co., Ltd. was used for the measurement.
[Weatherability]
It was measured under the conditions of 50 ° C., 50 pphm, 0-20% elongation, and 50 hours according to “5. Dynamic ozone degradation test tension method” of JIS K 6259. For measurement, “Ozone Weather Meter” manufactured by Suga Test Instruments Co., Ltd. was used.
[Oil resistance]
In accordance with JIS K 6258, a soaking test was performed under conditions of oil used: grease (naphthene + paraffin) at 80 ° C. for 72 hours, and the volume change rate (ΔV) was measured. For the measurement, “TEST TUBE AGING TESTER” manufactured by Toyo Seiki Seisakusho was used.
[Low temperature resistance]
In accordance with “4. Low-temperature impact embrittlement test” of JIS K 6261, the impact embrittlement temperature was measured using “BRITLENSESS TEMP. TESTER” manufactured by Toyo Seiki Seisakusho Co., Ltd.
[Abrasion resistance]
In accordance with JIS K 6264 "6. Akron Wear Test" B method, the wear volume was measured using "Aklon Wear Tester" manufactured by Shimadzu Corporation.
[Adhesiveness]
After seven brass plating wires are arranged in parallel in contact with each other and attached to an unvulcanized rubber composition sheet and vulcanized, the five wires excluding the two ends are peeled one by one, and the wires are removed. The area with rubber was determined as a percentage with 100% of the state where the rubber was attached to all the surfaces of the wire that were in contact with the rubber, and the average value of the five was used as the measurement result.

  As shown in Table 1 and Table 2, the rubber composition for hose jackets of the present invention has a good vulcanization speed and adhesiveness, as well as sufficient oil resistance, weather resistance, low temperature resistance, and wear resistance. Therefore, it was confirmed that it has excellent performance as a jacket material for a hydraulic hose.

Claims (8)

  The rubber component contains ethylene-propylene-diene rubber (EPDM) and acrylonitrile-butadiene rubber (NBR) having a nitrile content of 40% by mass or less, the EPDM content is 25 to 40 phr, and the NBR content is the rubber component. A hose jacket rubber composition characterized in that the nitrile content in the whole is 10 to 20% by mass, contains a thiuram vulcanization accelerator, and contains 1 to 5 phr of organic acid cobalt.   The rubber composition for hose jackets according to claim 1, containing 0.5 to 5 phr of phenol resin.   The rubber composition for a hose jacket according to claim 1 or 2, which contains resorcin in an amount of 0.3 to 3 phr.   The rubber composition for a hose jacket according to any one of claims 1 to 3, further comprising a sulfenamide vulcanization accelerator together with a thiuram vulcanization accelerator.   The rubber composition for a hose jacket according to any one of claims 1 to 4, further comprising another diene rubber as the rubber component together with the EPDM.   The rubber composition for a hose jacket according to any one of claims 1 to 5, wherein the diene rubber is styrene-butadiene rubber (SBR).   In the hose comprising an inner tube rubber layer forming the inner surface of the hose, an outer rubber layer forming the outer surface of the hose, and a reinforcing layer provided between the inner tube rubber layer and the outer rubber layer, the outer surface A hose comprising a rubber layer formed of the rubber composition for a hose jacket according to any one of claims 1 to 6.   The hose according to claim 7, which is a hydraulic hose filled with hydraulic oil of a hydraulic drive device.