JP5423114B2 - Manufacturing method of rubber composition, and hydraulic hose having an outer rubber layer formed by the manufacturing method - Google Patents

Description

  The present invention provides a method for producing a rubber composition having oil resistance, cold resistance (low temperature characteristics) and bending fatigue resistance, and oil resistance, cold resistance and bending fatigue resistance in which an outer rubber layer is formed by the manufacturing method. It relates to excellent hydraulic hoses for construction machinery, agricultural machinery and other industrial machinery.

  Hydraulic hoses are mainly used in construction machinery such as power shovels and bulldozers, and hydraulically operated machines such as hydraulic jacks, hydraulic punchers, hydraulic presses, hydraulic benders, and other industrial machines. It plays an important role in transmitting driving force.

  Therefore, this hydraulic hose is required to withstand high pressure and transmit the driving force (pressure) accurately and quickly, and has high oil resistance and low volume expansion due to pressure. In addition, since the hydraulic oil becomes hot during machine operation and is often used in harsh environments where vibrations and bending are always applied, high heat resistance, weather resistance (such as ozone resistance), Flexural fatigue and wear resistance are required. Furthermore, since construction machines, agricultural machines, and other industrial machines are also expected to be used in cold regions, cold resistance (low temperature characteristics) is required in addition to the above characteristics. In particular, regarding cold resistance, evaluation by a low-temperature elastic recovery test (TR test) has recently been regarded as important in place of the conventional scale of low-temperature embrittlement temperature.

  Due to its required characteristics, the hydraulic hose normally operates as shown in FIG. 1 with an inner rubber layer 2 made of rubber (hereinafter also referred to as “inner tube rubber”) filled with hydraulic oil from the inside. Laminate in which a reinforcing layer 3 for withstanding the pressure of oil and an outer rubber layer 4 (hereinafter also referred to as “coating rubber”) for sequentially preventing damage to the reinforcing layer and the inner rubber layer from the outside are laminated. It has a structure. Moreover, providing the said reinforcement layer in multiple layers as needed is also generally performed.

  On the other hand, chloroprene rubber has been generally used for the outer rubber layer of the hydraulic hose from the balance of required properties such as oil resistance, weather resistance, and wear resistance. However, the market has changed due to recent environmental problems. Therefore, it is desired not to use chlorine-based materials, and the need for halogen-free products is increasing.

  As an alternative to this chloroprene rubber, acrylic rubber materials and the like can be mentioned from the viewpoints of the above-mentioned performances, but their use is limited because they are very expensive. Therefore, generally, acrylonitrile-butadiene rubber (NBR) having oil resistance and ethylene-propylene-diene rubber (EPDM) having heat resistance and weather resistance are blended, or further styrene-butadiene rubber (SBR) if necessary. ) And other diene-based materials are blended, and a technique is adopted that exhibits the properties of each rubber in a well-balanced manner.

  This method utilizes the property that the NBR and other diene rubbers such as EPDM and SBR cause phase separation due to differences in physical properties such as polarity strength and vulcanization speed, and are not easily mixed to the molecular level. Is. That is, since these rubber components are present in a phase-separated state, the characteristics of each rubber component are exhibited according to the abundance ratio (blending ratio) in the composition. In addition, about mixing of these rubber | gum, Unexamined-Japanese-Patent No. 62-172043 (patent document 1), Unexamined-Japanese-Patent No. 2001-205745 (patent document 2), Unexamined-Japanese-Patent No. 2001-206987 (patent document 3), etc. However, it does not mention the phase structure of the rubber after mixing.

  Here, the oil resistance of the rubber is exhibited by the blending of NBR, and is particularly correlated with the acrylonitrile content (hereinafter sometimes referred to as “average AN content”) of the entire rubber composition. Therefore, in order to improve the oil resistance of this rubber, it is necessary to increase the average AN content. Usually, the NBR compounding ratio is increased, or a high acrylonitrile content (hereinafter referred to as “AN content”). Or a grade of NBR having). However, as shown in the graph of the rubber composition of the conventional formulation (comparative example) in FIG. 2, the oil resistance improves as the average AN content increases, but the relatively low temperature characteristics (especially evaluated by the TR test) are improved. There is a trade-off between oil resistance and cold resistance. Therefore, when it is intended to achieve the required oil resistance, the desired low temperature characteristics (especially evaluation by the TR test) may not be obtained. In other words, as an alternative to chloroprene rubber, when an NBR / EPDM type or NBR / EPDM / SBR type rubber composition is prepared, the average AN content is sufficient to obtain oil resistance equivalent to that of the chloroprene rubber. As a result, the required low-temperature characteristics may not be achieved, and it is difficult to obtain a hydraulic hose that sufficiently meets market demands.

  Thus, a rubber composition containing at least NBR and EPDM has not been obtained as a rubber composition that has both oil resistance and cold resistance and sufficiently satisfies the demands of the hydraulic hose market and use site. In particular, with conventional NBR-containing EPBR rubber, it is possible to lower the embrittlement temperature by adding a plasticizer (to improve the low-temperature characteristics according to the conventional scale), but oil resistance and low-temperature characteristics by TR test. In addition, it is difficult to supply a rubber composition for a hydraulic hose that can meet the demands of the market and the field by freely adjusting the oil resistance without compromising the low temperature characteristics.

JP 62-172043 A JP 2001-205745 A JP 2001-206987 A

  The present invention has been made in view of the above circumstances. In preparing a rubber composition by mixing acrylonitrile-butadiene rubber (NBR) and ethylene-propylene-diene rubber (EPDM), it is derived from the NBR in the rubber composition. When the oil resistance of the resulting rubber composition is adjusted by changing the acrylonitrile content (average AN content) of the oil, the oil resistance can be freely adjusted according to the required properties of the rubber without impairing the low temperature properties An object of the present invention is to provide a method for producing a rubber composition, and a hydraulic hose having both oil resistance and low-temperature characteristics using the rubber composition prepared by the production method.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have a specific AN content in preparing a rubber composition containing acrylonitrile-butadiene rubber (NBR) and ethylene-propylene-diene rubber (EPDM). By using the NBR, it was found that each rubber component that had undergone phase separation by the conventional method became a single phase uniformly mixed up to the molecular level, and the rubber composition obtained by this method Even if the average AN content is increased in order to improve oil resistance, it is maintained without damaging the cold resistance by the TR test after vulcanization, and the durability in repeated elongation fatigue has phase-separated from the conventional phase. It has been found that it is remarkably superior to the rubber composition. Here, the phase structure of rubber can be determined by the number of loss tangent (tan-δ) peaks obtained by performing viscoelasticity measurement in a predetermined temperature range, for example. That is, when the viscoelasticity measurement is performed in the range of −70 to + 70 ° C. as shown in FIG. 3 and FIG. 4, the tan-δ peak is obtained as two peaks because the conventional formulation is phase-separated into two phases. (Comparative Example), when the mixture is uniformly mixed up to the molecular level to form a single phase, the peak is obtained as a single peak (Example).

  Therefore, as a result of further investigations, the present inventors have used NBR having an acrylonitrile content (AN content) of 26% by mass or less as NBR at a specific blending ratio to adjust the average AN content to a specific range, thereby increasing the viscosity. The tan-δ peak in elasticity measurement is a peak, and a rubber composition having a single-phase structure in which each rubber component is uniformly mixed at the molecular level is obtained, and the low temperature characteristics by the TR test are impaired depending on the required characteristics of the rubber. The present inventors have found that the oil resistance can be freely adjusted without any problems and that it is excellent in repeated elongation fatigue durability, and have completed the present invention.

  Since the rubber composition obtained by the production method of the present invention can freely adjust the oil resistance without damaging the low temperature characteristics by the TR test according to the required characteristics of the rubber, it is a trade-off between oil resistance and low temperature characteristics. Since both required characteristics can be satisfied and the fatigue durability is also excellent, it can be suitably used for the outer rubber of a hydraulic hose.

Therefore, in the present invention, when preparing a rubber composition by mixing acrylonitrile-butadiene rubber (NBR) and ethylene-propylene-diene rubber (EPDM), the content of acrylonitrile derived from the NBR in the rubber composition (average In the method for producing a rubber composition for adjusting the oil resistance of the resulting rubber composition by changing the AN content, an NBR that is unmodified as the NBR and has an acrylonitrile content (AN content) of 26% by mass or less is used. And a rubber composition having a single-phase structure is obtained by adjusting the blending ratio of NBR in the range of 20 to 75 phr and adjusting the average AN content in the range of 5 to 20% by mass. A method for producing a rubber composition, and a hydraulic hose having an outer rubber layer formed of the rubber composition prepared by the production method A.

  As described above, in the method for producing a rubber composition of the present invention, when producing a rubber composition containing NBR and EPDM, a plurality of types of rubber components are blended by using NBR having a specific AN content. Even if it does not cause phase separation, it can be mixed uniformly, solving the trade-off problem of high oil resistance and good low-temperature characteristics, which have been problems until now, and both characteristics according to the required characteristics of rubber. It is possible to produce a rubber composition having a good balance and having excellent fatigue durability. In addition, the rubber composition obtained by the production method of the present invention can be suitably used for applications requiring oil resistance, low temperature characteristics and fatigue durability, and particularly when used as an outer rubber layer of a hydraulic hose. It is possible to provide a product that has a good balance of properties and low-temperature characteristics according to required characteristics.

It is a schematic perspective view which shows one Example of the structure of the hydraulic hose of this invention. It is the graph obtained by plotting the low temperature elastic recovery test result (TR10) of the rubber obtained by the production method of the present invention and the rubber prepared by the conventional method against the average AN content. It is a graph which shows the tan-delta curve obtained from the viscoelasticity measurement of the rubber composition of Example 1, 4 and Comparative Example 1, 4. It is a graph which shows the tan-delta curve obtained from the viscoelasticity measurement of the rubber composition of Examples 3 and 6 and Comparative Examples 3 and 6.

  The method for producing a rubber composition of the present invention comprises the steps of mixing acrylonitrile-butadiene rubber (NBR) and ethylene-propylene-diene rubber (EPDM) to prepare a rubber composition. When the oil resistance of the resulting rubber composition is adjusted by changing the acrylonitrile content (AN content), NBR having a specific AN content is used. In addition, about the mixing means of each component mentioned later, it does not restrict | limit in particular, Kneading machines, such as a well-known roll, an internal mixer, a Banbury rotor, can be used.

  The rubber component includes at least NBR and EPDM. At that time, the blending ratio of NBR in the rubber component is not particularly limited. However, in general, when the outer rubber of the hydraulic hose is used, it is preferably 20 to 75 phr from the viewpoint of oil resistance and the like. More preferably, it is 40-70 phr, More preferably, it is 45-65 phr. If the ratio of NBR is less than 20 phr, the average AN content of the rubber composition is lowered, so that sufficient oil resistance may not be obtained. On the other hand, if it exceeds 75 phr, the amount of EPDM that can be blended is reduced and sufficient. May not be able to obtain good weather resistance.

  The NBR may be appropriately selected from known ones and is not particularly limited, but the acrylonitrile content (AN content) contained in the NBR must be 26% by mass or less. Preferably the thing of 15-26 mass%, More preferably, the range of 20-26 mass% is used. When NBR with an AN content of more than 26% by mass is used, the phase structure with EPDM becomes two-phase, and the low-temperature properties of the low-temperature elastic recovery test (TR test) are impaired, and physical properties such as bending fatigue resistance are degraded. May be incurred.

  Further, the AN content (average AN content) derived from the NBR in the rubber composition as a whole is appropriately adjusted according to the required oil resistance, and is not particularly limited. Is preferably 5 to 20% by mass, and more preferably 13 to 20% by mass. When the average AN content exceeds 20% by mass, there is no particular problem in terms of weather resistance when EPDM is blended, but the rubber elasticity as a rubber composition is lowered, and caulking when a hydraulic hose is obtained. On the other hand, if it is less than 5% by mass, sufficient oil resistance as the outer rubber of the hydraulic hose may not be obtained.

  The blending ratio of the EPDM in the rubber component is not particularly limited, but is usually 25 to 50 phr, preferably 30 to 40 phr, more preferably 30 to 35 phr. If the blending ratio of EPDM is less than 25 phr, the weather resistance may be inferior. On the other hand, if it exceeds 50 phr, the blending amount of NBR will be relatively lowered, resulting in low temperature characteristics, oil resistance, and weather resistance. This is not preferable because it is difficult to establish a balance.

  In the present invention, although not particularly limited, in addition to the NBR and EPDM, a diene rubber other than EPDM can be further blended as the rubber component, and in particular, the compatibility between the NBR and EPDM is improved. In addition, for the purpose of improving the wear resistance of the resulting rubber component, it is preferable to blend styrene-butadiene rubber (SBR). The blending amount of the diene rubber is not particularly limited, and is appropriately set depending on the balance between the EPDM blending amount corresponding to the required weather resistance level and the NBR blending amount corresponding to the required oil resistance level. However, when SBR is blended in the present invention, the blending ratio in the rubber component is 0.1 to 45 phr, preferably 20 to 35 phr.

  Examples of diene rubbers other than SBR include known natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), butyl rubber (IIR), synthetic rubbers such as epoxidized natural rubber, and these natural rubbers. Or the thing by which the molecular chain terminal of synthetic rubber was modified is illustrated.

  In the present invention, although not particularly limited, sulfur is usually used as a vulcanizing agent (crosslinking agent), and the blending ratio thereof is not particularly limited, and is usually 0.5-3. 0.5 phr, preferably 1 to 3.5 phr.

  Here, in the present invention, “phr” means NBR and EPDM, and when other rubbers are blended, the number of blended parts with respect to 100 parts by mass of the total amount of rubber components including other rubbers (however, the above-mentioned NBR, EPDM And the rubber component such as SBR represents the number of blending parts in the rubber component), and the same applies to “phr” for the other blending components thereafter.

  Although it does not restrict | limit especially as a vulcanization accelerator, A thiuram type compound can be used suitably. Specifically, tetramethyl thiuram disulfide (TMTD), tetramethyl thiuram monosulfide (TMTM), tetraethyl thiuram disulfide (TETD), tetrabutyl thiuram disulfide (TBTD), 2-ethylhexyl thiuram disulfide (TOT-N) and the like are known. These vulcanization accelerators can be suitably used, and one or more of these can be used.

  The blending ratio of the thiuram vulcanization accelerator is an effective amount and is not particularly limited, but is usually preferably 0.5 to 2.5 phr, particularly preferably 1 to 2 phr. If the blending amount is less than 0.5 phr, a sufficient effect of improving the vulcanization rate may not be obtained, and the productivity may be deteriorated. On the other hand, if it exceeds 2.5 phr, the vulcanization rate is increased. Since this is likely to occur, there is a risk of causing problems on the processed surface.

  In the rubber composition obtained by the production method of the present invention, an organic acid cobalt can be blended for the purpose of improving the adhesion to a steel cord such as a brass plating wire used for reinforcing a hose. The organic acid cobalt is not particularly limited, and examples thereof include cobalt naphthenate, cobalt stearate, cobalt versatate, and borate of these organic acid cobalt, and use one or more of these. Can do. The blending ratio of the organic acid cobalt is 1 to 5 phr, preferably 1.5 to 3 phr. If the blending amount of the organic acid cobalt is less than 1 phr, sufficient adhesion improvement effect cannot be obtained, and if it exceeds 5 phr, the tackiness (adhesiveness) of the rubber composition becomes strong, so the processability is deteriorated. There is a risk of causing. In addition, the physical properties of the vulcanized rubber may be reduced.

  Furthermore, for the purpose of further improving the adhesiveness, the rubber composition may contain one or both of a phenol resin and resorcin in addition to the organic acid cobalt.

  Additives other than those described above can be blended with the rubber composition obtained by the production method of the present invention, if necessary. For example, vulcanizing agents other than the above, vulcanization accelerators and vulcanization acceleration aids, commonly used carbon, anti-aging agents, plasticizers, petroleum resins, vulcanization retarders, waxes, antioxidants, filling Additives such as agents, foaming agents, oils, lubricants, tackifiers, ultraviolet absorbers, dispersants, compatibilizing agents, homogenizing agents and the like can be appropriately blended.

  When obtaining the rubber composition of the present invention, there is no particular limitation on the blending method of each of the above components, and all the component raw materials may be blended and kneaded at once, and each component may be divided into two or three stages. You may mix | blend and knead | mix. In the kneading, a kneader such as a roll, an internal mixer, a Banbury rotor or the like can be used as described above.

  When a rubber hose having a reinforcing layer is produced using the rubber composition of the present invention, a normal method can be adopted, for example, an inner rubber layer 2 as shown in FIG. 1 and a reinforcement having a steel cord. When manufacturing the hydraulic hose 1 which consists of the layer 3 and the outer surface rubber layer 4, the following method can be illustrated. In this case, the rubber composition of the present invention is used as a rubber for forming the outer rubber layer 4.

  First, an inner rubber layer 2 is formed by extruding a rubber composition for the inner rubber layer (inner tube rubber) 2 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 predetermined number of brass-plated wires are knitted outside the inner rubber layer 2 formed in the inner tube extrusion step, and a reinforcing layer 3 is laminated (knitting step). As the rubber composition to be obtained, the rubber composition obtained by the production method of the present invention described above is extruded to form the outer rubber layer (outer rubber) 4 (outer extrusion process). Furthermore, the outer surface of the outer rubber layer 4 formed in the outer shell extrusion step is coated with a strip-shaped woven fabric (wrapping sheet) made of nylon fibers (mold coating step), and vulcanized under predetermined conditions (vulcanization step). ). After vulcanization, the above-mentioned wrapping sheet is peeled off (mold peeling step), and the mandrel is removed (mandrel extraction step), whereby a hydraulic hose 1 having a reinforcing layer 3 between the inner tube rubber 2 and the outer rubber 4 Become.

  The structure of the hydraulic hose 1 may be a three-layer structure in which the inner tube rubber 2, the reinforcing layer 3 and the outer cover rubber 4 are sequentially laminated from the inside as described above. Although not shown, a four-layer structure in which the above-mentioned reinforcing layers are two layers, or a five-layer structure in which an intermediate layer (intermediate rubber) is arranged between the two reinforcing layers, these structures are hose. What is necessary is just to set suitably according to the required characteristic.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not restrict | limited to the following Example.

[Examples 1-6, Comparative Examples 1-10]
First, the rubber components shown in Table 1 below and an appropriate amount of organic acid cobalt (all raw materials except for the crosslinking agent and vulcanization accelerator) are put into an internal mixer and kneaded until the temperature of the kneaded product reaches 170 ° C. Then, it was cooled to about 40 ° C. or less. Next, appropriate amounts of a crosslinking agent (sulfur) and a vulcanization accelerator were added and kneaded until the temperature of the kneaded product reached 110 ° C. to prepare a rubber composition for a hydraulic hose jacket. Thereafter, the obtained rubber composition was vulcanized and cured under the conditions of 150 ° C. × 60 minutes to produce a rubber sample for a hydraulic hose jacket.

In this case, the details of the rubber components and additives in Table 1 are as follows.
EPDM: “Esplen 505A” manufactured by Sumitomo Chemical Co., Ltd.
NBR (AN20% by mass): “N250S” manufactured by JSR Corporation
NBR (AN 26 mass%): “N240S” manufactured by JSR Corporation
NBR (AN 35% by mass): “N230S” manufactured by JSR Corporation
NBR (AN41 mass%): “N220S” manufactured by JSR Corporation
SBR: “SL556” manufactured by JSR Corporation
Organic acid cobalt: Cobalt naphthenate, sulfenamide vulcanization accelerator manufactured by DIC Corporation: N-tert-butyl-2-benzothiazolylsulfenamide, “Noxeller NS-F” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Thiuram vulcanization accelerator: Tetramethylthiuram disulfide (TMTD), “Noxeller TT” manufactured by Ouchi Shinsei Chemical Co., Ltd.

About the said rubber composition prepared by kneading | mixing and the obtained rubber sample for hydraulic hose jackets, while confirming the phase structure by the following method, the following performance was evaluated. The results are shown in Table 1.
<< Low temperature characteristics (low temperature elastic recovery test) >>
In accordance with JIS K 6261: 2006, the measurement was performed under the conditions using a test piece I shape, an elongation rate of 50%, and IPA-modified alcohol as a refrigerant. In this test, the low temperature characteristics were evaluated by the temperature (TR10) at the time when 10% of the initial length of the test piece was recovered. FIG. 2 shows the results of plotting TR10 against the average AN content of the composition.
<Phase structure>
Using a spectrometer manufactured by Toyo Seiki Co., Ltd., viscoelasticity was measured in the temperature range of -70 to + 70 ° C. In this case, when the obtained loss tangent (tan-δ) peak was a single peak, it was judged as a single phase, and when it was a double peak, it was judged as a two phase. Moreover, the measurement charts of Examples 1 and 4 and Comparative Examples 1 and 4 are shown in FIG. 3, and the measurement charts of Examples 3 and 6 and Comparative Examples 3 and 6 are shown in FIG.
"Oil resistance"
The volume swell ratio after dipping a test piece of width 20 mm × length 40 mm × thickness 2 mm in diesel engine oil “SAE-10W class CD” at 80 ° C. for 72 hours was evaluated according to the following criteria.
○: 59% or less △: 60-79%
X: 80% or more << Repeated elongation fatigue durability (flexural fatigue resistance) >>
A DIN No. 3 dumbbell test piece was prepared, and the test piece was subjected to repeated elongation of 0 to 100% under the conditions of 25 ° C. and a repetition rate of 50 cpm, and the number of times until breakage was measured. In Table 1, it represented with the index | exponent which set the frequency | count of fracture of Example 1 to 100.

  Here, in order to examine the result of Table 1 in detail, the graph obtained by plotting TR10 of an Example and a comparative example with respect to average AN content was shown in FIG. FIG. 3 shows the viscoelasticity measurement results of Examples 1 and 4 and Comparative Examples 1 and 4, and FIG. 4 shows the viscoelasticity measurement results of Examples 3 and 6 and Comparative Examples 3 and 6.

  In FIG. 2, in the comparative example, TR10 tends to increase as the average AN content increases, and it can be confirmed that the low temperature characteristics are impaired when trying to improve the oil resistance of the rubber. On the other hand, in the rubber obtained by the production method of the present invention, TR10 does not substantially change even when the average AN content is increased, and good oil resistance can be obtained without impairing the low temperature characteristics. confirmed. The tendency of this example is clearly different from the tendency shown by the above comparative example, and by using the production method of the present invention, the low temperature characteristics and oil resistance can be freely adjusted according to the required characteristics of rubber. It was confirmed that it was possible.

  FIG. 3 shows a rubber composition (Examples 1 and 4) containing 30.0 phr of NBR having an AN content of 26% by mass or less, and a rubber composition (Comparative Example 1) containing 30.0 phr of NBR exceeding 26% by mass. And 4) are viscoelasticity measurement results. Here, in Comparative Examples 1 and 4 prepared by the conventional manufacturing method, a peak on the high temperature side derived from NBR that appeared near −10 ° C., and a low temperature side derived from EPDM and SBR that appeared near −45 ° C. Two peaks were observed. This result shows that the physical properties of NBR, EPDM, and SBR in the rubber component appear as they are, and each rubber component is present in the composition in a phase-separated state. On the other hand, in Examples 1 and 4, the high temperature side peak derived from NBR shifts to the low temperature side, and the low temperature side peak derived from EPDM and SBR disappears, and the tan-δ peak. Is completely a mountain. Therefore, it was confirmed that by using the production method of the present invention, a rubber composition having a single-phase structure in which each rubber component is uniformly mixed to the molecular level can be obtained.

FIG. 4 shows a rubber composition containing 65.0 phr of NBR having an AN content of 26% by mass or less (Examples 3 and 6) and a rubber composition containing 65.0 phr of NBR exceeding 26% by mass (comparison). It is a viscoelasticity measurement result about Example 3 and 6). As a result, as in FIG. 3, it can be confirmed that the tan-δ peak is completely piled up in the examples, and a rubber composition having a single-phase structure in which each rubber component is uniformly mixed to the molecular level is obtained. It was confirmed that it was obtained.
On the other hand, with respect to bending fatigue resistance, Examples 1 to 6 and Comparative Examples 7 and 8 having a single-phase structure are remarkably superior to Comparative Examples 1 to 6, 9 and 10 that are phase-separated into two phases. From this, it was confirmed that the uniform mixing of each rubber component to the molecular level greatly contributed to the improvement of the bending fatigue resistance.

  As described above, by using the production method of the present invention, a rubber composition having a single-phase structure in which rubber components are uniformly mixed at a molecular level can be prepared. It was confirmed that a rubber composition exhibiting a good balance between low temperature characteristics (TR10) and oil resistance can be obtained without impairing each other, and further excellent in bending fatigue resistance.

  The rubber composition obtained by the method for producing a rubber composition of the present invention is preferably used for a rubber hose jacket rubber from the viewpoint of oil resistance, low temperature characteristics and bending fatigue resistance. The rubber composition is not limited to this, and can be used in any application that requires oil resistance, low temperature characteristics, and bending fatigue resistance.

1 Hydraulic hose 2 Internal rubber layer (inner pipe rubber)
3 Reinforcing layer 4 Outer rubber layer (outer rubber)

Claims (5)

In preparing a rubber composition by mixing acrylonitrile-butadiene rubber (NBR) and ethylene-propylene-diene rubber (EPDM), the NBR-derived acrylonitrile content (average AN content) in the rubber composition was changed. In the method for producing a rubber composition for adjusting the oil resistance of the obtained rubber composition, NBR which is unmodified as the NBR and has an acrylonitrile content (AN content) of 26% by mass or less is used. A rubber composition having a single-phase structure is obtained by adjusting a blending ratio in a range of 20 to 75 phr and adjusting an average AN content in a range of 5 to 20% by mass. Production method.   The method for producing a rubber composition according to claim 1, wherein the blending ratio of the EPDM is in the range of 25 to 50 phr.   The method for producing a rubber composition according to claim 1 or 2, wherein 0.1 to 45 phr of styrene-butadiene rubber (SBR) is mixed with the NBR and EPDM. The production of the rubber composition according to any one of claims 1 to 3, wherein a peak of loss tangent (tan-δ) obtained by measuring viscoelasticity in a temperature range of -70 to + 70 ° C is obtained as a peak. Method.   A hydraulic hose comprising an outer rubber layer formed of a rubber composition prepared by the production method according to any one of claims 1 to 4.

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