Rubber composition and hose

Abstract

To provide a technique that can contribute to make it easier to obtain the desired workability, mechanical properties, insulation properties, and light weight, and to make it easier to suppress changes in the insulation properties.SOLUTION: There is provided a rubber composition obtained by blending at least an ethylene-propylene diene rubber (ethylene content within the range of 51 to 66 mass%), carbon black (iodine adsorption content within the range of 5 to 40 mg / g, nitrogen adsorption specific surface area within the range of 10 to 60 m2 / g, DBP oil absorption content within the range of 110 to 160 g / cm3, ratio indicated by the nitrogen adsorption specific surface area / iodine adsorption content of 1.3 m2 / mg or more, and toluene color transmission of 90% or more), clay (average particle diameter within the range of 1 to 10 μm), and a softener so that the total mass is within the range of 300 to 400 pts.mass. The range of the carbon black content is 70 to 170 pts.mass, the range of clay content is 10 to 60 pts.mass, and the range of softener content is 30 to 100 pts.mass based on 100 pts.mass of the ethylene-propylene diene rubber.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition and a hose made using said rubber composition, and relates to a technique applicable to water hoses such as radiator hoses for automobiles. [Background technology]

[0002] For example, various hoses used in automobiles (for example, water hoses such as radiator hoses) are made of rubber compositions.

[0003] Rubber compositions have been applied that not only have processability (kneadability, moldability, etc.), but also have certain mechanical properties (material strength, etc.) so that desired attachment properties (shape retention) can be obtained at the intended attachment point of the hose (hereinafter simply referred to as the attachment point). One example is compounding a reinforcing filler such as carbon black into the rubber composition, but with the recent trend toward electrification of automobiles, etc., there is an increasing demand for rubber compositions that exhibit various characteristics.

[0004] For example, in cases where electrical and electronic systems (e.g. batteries, inverters, electronic devices, etc.) or metal parts may be present at or near the attachment point of the hose, the hose is required to have high resistance and improved insulation to prevent unintended leakage current.

[0005] However, carbon black, which is blended as a reinforcing filler in a rubber composition, has a higher electrical conductivity than, for example, other blending components such as polymers. Therefore, as the blending ratio of carbon black in a rubber composition increases, the volume resistivity tends to decrease. As a result, it has been difficult to obtain the desired insulation properties in a hose using a rubber composition blended with carbon black.

[0006] Therefore, in the rubber composition of Patent Document 1, in addition to blending carbon black, an inorganic filler (clay in Patent Document 1) is also blended to suppress the blending ratio of the carbon black and to maintain a certain volume resistivity (for example, 10 6 It has been considered to increase the resistance by ensuring a resistance of 0.1% or more (Ω·cm). In addition, for the rubber composition of Patent Document 2, it has been considered to increase the resistance by compounding carbon black having a relatively low toluene coloring transmittance (30 to 50% in Patent Document 2).

[0007] Furthermore, in order to contribute to global environmental measures (such as improving the fuel efficiency of automobiles), there is a demand for hoses to be lightweight by reducing their specific gravity. Therefore, in the rubber composition of Patent Document 3, the use of a reinforcing filler with low specific gravity and high insulating properties (Patent Document 3 uses carbon black and pulverized bituminous coal in combination) has been considered. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 3240884 [Patent Document 2] JP 2004-281293 A [Patent Document 3] Patent No. 7180448 Summary of the Invention [Problem to be solved by the invention]

[0009] In the case of a hose made of a rubber composition simply blended with inorganic fillers or the like (reducing the blending ratio of carbon black) as in Patent Document 1, even if a certain volume resistivity can be maintained in an uncompressed state, the volume resistivity may be likely to decrease when the hose is compressed. In such a case, it is conceivable to increase the blending ratio of the inorganic filler, but this is likely to lead to an increase in the specific gravity of the hose, and there is a risk that the lightness of the hose may decrease.

[0010] In addition, even if carbon black having a relatively low toluene coloring transmittance is used as in Patent Document 2, the volume resistivity is insufficient (for example, 10 6 Ω·cm), which may result in reduced insulation.

[0011] Furthermore, in the case of a rubber composition containing a reinforcing filler having a low specific gravity and high insulating properties as in Patent Document 3, even if a certain volume resistivity can be obtained, as the proportion of the filler increases, the mechanical properties decrease, and there is a risk that the desired attachment property cannot be obtained.

[0012] The present invention has been made in consideration of the above circumstances, and aims to provide a technology that can contribute to making it easier to obtain desired processability, mechanical properties, insulation properties, and light weight, and to making it easier to suppress changes in the insulation properties. [Means for solving the problem]

[0013] The rubber composition and hose according to the present invention can contribute to solving the above-mentioned problems, and one embodiment of the rubber composition is a rubber composition in which at least ethylene propylene diene rubber, carbon black, clay, and softener are blended in a total amount within the range of 300 to 400 parts by mass, and the carbon black is blended in a range of 70 to 170 parts by mass, the clay is blended in a range of 10 to 60 parts by mass, and the softener is blended in a range of 30 to 100 parts by mass, relative to 100 parts by mass of the ethylene propylene diene rubber. The ethylene propylene diene rubber has an ethylene content within the range of 51 to 66% by mass, and the carbon black has an iodine adsorption amount within the range of 5 to 40 mg / g and a nitrogen adsorption specific surface area within the range of 10 to 60 m. 2 / g, DBP oil absorption is 110-160g / cm 3 Within the range, the ratio of the nitrogen adsorption specific surface area to the iodine adsorption amount is 1.3m 2 / mg or more, and a toluene coloring transmittance of 90% or more. The clay has an average particle size in the range of 1 to 10 μm and a volume resistivity of 10 7It is characterized by a resistance of Ω·cm or more.

[0014] One embodiment of the hose has at least one rubber hose layer formed by molding the rubber composition into a tube shape, and the rubber hose layer has a volume resistivity of 10 7 It is characterized by a resistance of Ω·cm or more.

[0015] The hose may further comprise a reinforcing layer laminated on at least one of the inner peripheral surface and the outer peripheral surface of the rubber hose layer.

[0016] The rubber hose layer may have a thickness within a range of 2.0 to 4.5 mm.

[0017] The hose may be any water-based hose selected from the group consisting of a radiator hose, a bypass hose, a heater hose, a reserve tank hose, a drain hose, and a cooling hose for electrical and electronic systems. Effect of the Invention

[0018] According to the present invention, it is possible to easily obtain desired processability, mechanical properties, insulating properties, and light weight, and to contribute to easily suppressing changes in the insulating properties. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a schematic diagram for explaining a method for evaluating the specific volume resistivity of a rubber test piece used in a verification example. [Diagram 2] FIG. 2 is a schematic diagram for explaining a method for evaluating the insulation properties of an evaluation rubber hose used in a verification example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The rubber composition according to the embodiment of the present invention and the hose made using the rubber composition are completely different in structure from the rubber compositions shown in Patent Documents 1-3, for example.

[0021] That is, the rubber composition of this embodiment is one in which at least four components, namely, ethylene propylene diene rubber, carbon black, clay, and softener (hereinafter simply referred to as main components), are blended in a total amount within the range of 300 to 400 parts by mass.

[0022] The main components are blended in a predetermined ratio (parts by mass) (blended as in the Examples described later), and among the main components, ethylene propylene diene rubber, carbon black, and clay are applied in combinations having specific physical properties shown in (A) to (C) below (applied in combinations not disclosed in Patent Documents 1 to 3).

[0023] (A) Ethylene propylene diene rubber: Ethylene content is within the range of 51 to 66% by mass (B) Carbon black: Iodine adsorption capacity is within the range of 5 to 40 mg / g, and nitrogen adsorption specific surface area is 10 to 60 m 2 / g, DBP oil absorption is 110-160g / cm 3 Within the range, the ratio of the nitrogen adsorption specific surface area to the iodine adsorption amount is 1.3m 2 / mg or more, toluene coloring transmittance is 90% or more (C) Clay...average particle size is within the range of 1 to 10 μm.

[0024] Such a rubber composition has desired processability (e.g., kneadability, moldability), mechanical properties (e.g., material strength such as tensile properties), insulation properties (e.g., 10 7 It is easy to obtain a specific volume resistivity of 300 Ω·cm or more, light weight (e.g. low specific gravity), and it is also easy to suppress changes in the insulation properties (e.g. suppressing the decrease in specific volume resistivity when compressed).

[0025] Furthermore, in a hose made using the rubber composition, the various properties required of the hose (for example, corrosion resistance, water leakage resistance, and insulating properties) can be easily obtained.

[0026] The rubber composition and hose of the present embodiment may be made by blending the major components in the respective prescribed proportions (parts by mass) as described above, and the ethylene propylene diene rubber, carbon black, and clay among the major components may have the specific physical properties shown in (A), (B), and (C) above, respectively, and various design modifications are possible.

[0027] In other words, it is possible to appropriately apply common technical knowledge in various fields (such as the hose field) and, as necessary, to appropriately refer to prior art documents and the like to modify the design, and the following embodiment is one example of such a modification.

[0028] Example <Major components of rubber composition> The rubber composition is made by blending at least ethylene propylene diene rubber, carbon black, clay, and a softener as main components. The main components may be blended in a total amount of 300 to 400 parts by mass, and the blending ratio of each of the main components can be appropriately set as described later (for example, ethylene propylene diene rubber is 100 parts by mass, and the other main components can be appropriately set to be within a predetermined range).

[0029] <Ethylene propylene diene rubber> The ethylene propylene diene rubber may be any rubber having the physical properties shown in (A) above. The ethylene propylene diene rubber is not limited to being blended in one type, but may be blended in two or more types (for example, two types may be used in combination in the verification example described later).

[0030] <Carbon black> The carbon black may have the physical properties shown in (B) above. The blending ratio of the carbon black may be set to be within the range of 70 to 170 parts by mass relative to 100 parts by mass of the ethylene propylene diene rubber (in the case of oil-extended ethylene propylene diene rubber, the blending ratio is 100 parts by mass excluding the oil-extended component; the same applies to the blending ratios of other components below).

[0031] <Clay> The clay may be any clay having the physical properties shown in (C) above, and a specific example is calcined clay, etc. The mixing ratio of the clay may be set to be within the range of 10 to 60 parts by mass relative to 100 parts by mass of the ethylene propylene diene rubber.

[0032] <Softener> The softener may be applied in the form of, for example, a water hose for an automobile, and a suitable specific example is process oil such as paraffin oil, but is not particularly limited. The blending ratio of the softener may be set to be within the range of 30 to 100 parts by mass, assuming that the ethylene propylene diene rubber is 100 parts by mass.

[0033] <Ingredients other than the main ingredients> In the rubber composition, various additives may be appropriately blended as components other than the main components (for example, blended according to the various properties of the desired hose). Examples of the additives include vulcanizing agents, vulcanization accelerators, vulcanization aids, etc.

[0034] <Preparation and molding of rubber composition> The rubber composition may be prepared by appropriately blending the main components and other necessary additives, and may be appropriately prepared by kneading using a kneading machine such as a pressure kneader, a Banbury mixer, an intermix mixer, or an open roll.

[0035] As a specific example, when a vulcanizing agent and a vulcanization accelerator are blended as additives to a rubber composition as in the verification example described later, first, components other than the vulcanizing agent and the vulcanization accelerator are blended and kneaded, and then the vulcanizing agent and the vulcanization accelerator are added to the kneaded mixture and further kneaded to prepare the composition.

[0036] The rubber composition thus prepared can be molded into a desired product, such as a hose, using a molding machine (such as an extruder or mandrel) appropriate for the desired product.

[0037] A specific example is a hose having a rubber hose layer formed by molding a rubber composition into a tubular shape, but it is not limited to a single-layer structure having one rubber hose layer, and may be a multi-layer structure in which multiple rubber hose layers are coaxially stacked.

[0038] Also, it may be a structure in which a reinforcing layer, an outer protective layer, etc. are appropriately laminated coaxially, rather than simply having a rubber hose layer. For example, a reinforcing layer may be laminated on at least one of the inner and outer peripheral surfaces of the rubber hose layer (for example, in the case of a multi-layer structure in which two or more rubber hose layers are laminated, the reinforcing layer may be laminated between two adjacent rubber hose layers).

[0039] The reinforcing layer may be formed, for example, by braiding reinforcing yarn or wire into a braid or spiral shape on at least one of the inner and outer circumferential surfaces of the rubber hose layer.

[0040] Specific examples of the hose include, in the case of a water system hose for an automobile, a hose selected from the group including a radiator hose, a bypass hose, a heater hose, a reserve tank hose, a drain hose, a cooling hose for electrical and electronic systems, and the like.

[0041] The thickness dimension of the rubber hose layer (which can be calculated by (hose outer diameter - hose inner diameter) / 2) is not particularly limited, but may be appropriately set within the numerical range applied to automotive water hoses, specifically within the range of 2.0 to 4.5 mm.

[0042] <Verification example> Rubber compositions S1 to S7 and P1 to P8 were prepared by the methods described below, and evaluation samples of each of the rubber compositions S1 to S7 and P1 to P8 were prepared as appropriate and subjected to various evaluations.

[0043] <Preparation of Rubber Composition> Various materials shown in Tables 1 and 2 below were appropriately blended and kneaded to prepare rubber compositions S1 to S7 according to the examples and rubber compositions P1 to P8 according to the comparative examples.

[0044] In the kneading, the materials other than the vulcanizing agent and the vulcanization accelerator were first kneaded for 5 minutes using a Banbury mixer to obtain a kneaded product. Then, the vulcanizing agent and the vulcanization accelerator were added to the kneaded product while cooling the kneaded product using an open roll (cooling water temperature in the open roll was set to about 20°C), and the kneading was continued for 5 minutes.

[0045] [Table 1]

[0046] [Table 2]

[0047] Details of the various materials shown in Tables 1 and 2 are as follows: EPDM-1; ENB content 4%, ethylene content 54.5%, Mooney viscosity (ML 1+4 )70, oil extension rate 0%, ENEOS Corporation "EP27" EPDM-2; ENB content 4.5%, ethylene content 66%, Mooney viscosity (ML 1+4 )69, oil extension rate 75%, ENEOS Corporation "EP98" Carbon black-1; nitrogen adsorption specific surface area 28m 2 / g (SRF grade), iodine adsorption amount 10 mg / g, DBP oil absorption amount 123 g / cm 3 , Toluene colored, transmittance 99%, Asahi Carbon Co., Ltd. "Development Carbon 1" Carbon black-2; nitrogen adsorption specific surface area 28m 2 / g (SRF grade), iodine adsorption amount 9mg / g, DBP oil absorption amount 122g / cm 3 , Toluene coloring, transmittance 99%, Asahi Carbon Co., Ltd. "Development Carbon 2" Carbon black-3: Nitrogen adsorption specific surface area 28 m 2 / g (SRF grade), iodine adsorption amount 11 mg / g, DBP oil absorption amount 125 g / cm 3 , Toluene coloring, transmittance 99%, Asahi Carbon Co., Ltd. "Development Carbon 3" Carbon black-4; nitrogen adsorption specific surface area 53m 2 / g (FEF grade), iodine adsorption amount 40mg / g, DBP oil absorption amount 120g / cm 3 , Toluene colored, transmittance 99%, Tokai Carbon Co., Ltd. "ERB401" Carbon black-5; nitrogen adsorption specific surface area 28m 2 / g (SRF grade), iodine adsorption amount 19 mg / g, DBP oil absorption amount 128 g / cm 3 , Toluene colored, transmittance 45%, Asahi Carbon Co., Ltd. "Asahi #52" Carbon black-6; nitrogen adsorption specific surface area 41m 2 / g (FEF grade), iodine adsorption amount 41mg / g, DBP oil absorption amount 110g / cm 3 , Toluene colored, transmittance 99%, Asahi Carbon Co., Ltd. "Asahi #60UG" Carbon black-7; nitrogen adsorption specific surface area 31m 2 / g (SRF grade), iodine adsorption amount 30mg / g, DBP oil absorption amount 140g / cm 3 , Toluene colored, transmittance 94%, "Seast SVH" manufactured by Tokai Carbon Co., Ltd. Carbon black-8; nitrogen adsorption specific surface area 27m 2 / g (SRF grade), iodine adsorption amount 19 mg / g, DBP oil absorption amount 133 g / cm 3 , Toluene colored transmittance 18%, "Seast SRA" manufactured by Tokai Carbon Co., Ltd. Carbon black-9; nitrogen adsorption specific surface area 19m 2 / g, iodine adsorption amount 16mg / g, DBP oil absorption amount 98g / cm 3 , Toluene colored, transmittance 95%, SPHERON♯6400 manufactured by Co., Ltd. Stearic acid: "Camellia stearate" manufactured by Nippon Oil & Fats Co., Ltd. Zinc oxide: Sakai Chemical Industry Co., Ltd. "Zinc oxide type 2" Oil: Diana Process PW-380 manufactured by Idemitsu Kosan Co., Ltd. Clay: Imerys SA "BURGESS No.30" Vulcanizing agent-1 (sulfur); Tsurumi Chemical Industry Co., Ltd. "Kinkajirushi Micro Powder Sulfur 200Mesh" Vulcanizing agent-2 (4,4'-dithiodimorpholine); LANXESS "Rhenogran DTDM-80" · Vulcanization accelerator 1 (N-cyclohexyl-2-benzothiazolyl sulfenamide); "Noccela CZ-G" manufactured by Ouchi Koh Chemical Co., Ltd. Vulcanization accelerator-2 (Tetramethylthiuram disulfide); "Noccela TT-P" manufactured by Ouchi Kogyo Chemical Co., Ltd. · Vulcanization accelerator-3 (Dipentamethylene thiuram tetrasulfide); "Noccela TRA" manufactured by Ouchi Koh Chemical Co., Ltd. Vulcanization accelerator 4 (zinc dibutyldithiocarbamate); "Percasit ZDBC" manufactured by Nouryon Chemical Industries, Ltd. · Vulcanization accelerator-5 (zinc dialkyldithiophosphate); "Rhenogran ZAT-70" manufactured by Ouchi Shinko Chemical Co., Ltd.

[0048] <Creating sheet-shaped evaluation samples> For rubber compositions S1 to S7 and P1 to P8, they were vulcanized by compression molding using a 2 mm sheet mold with a cavity having a thickness of 2 mm at 160°C for a vulcanization time of (ct90+5) to obtain 2 mm thick vulcanized rubber sheets (hereinafter simply referred to as evaluation rubber sheets).

[0049] <Creating a cylindrical evaluation sample> For rubber compositions S1 to S7 and P1 to P8, a cylindrical test piece making mold having a diameter of 29.0 mm and a height of 12.5 mm was used to perform vulcanization molding at 150°C for a vulcanization time of (Tc90+10) to obtain cylindrical vulcanized rubber test pieces for compression set testing having a diameter of 29.0 mm and a height of 12.5 mm (hereinafter simply referred to as rubber test pieces).

[0050] <Creating a tube-shaped evaluation sample> First, rubber compositions S1 to S7 and P1 to P8 were extrusion molded to obtain tubular unvulcanized molded bodies with an inner diameter of 16 mm and an outer diameter of 24 mm. Then, the unvulcanized molded bodies were vulcanized while a metal mandrel was inserted into the inner circumference side to obtain tubular evaluation samples (hereinafter, simply referred to as evaluation rubber hoses). The vulcanization molding was performed by steam vulcanization using an autoclave at 160°C for a vulcanization time of (tC(90)+5) minutes.

[0051] <Workability> For the rubber compositions S1 to S7 and P1 to P8, the kneading property (so-called rubber kneading cohesiveness, etc.) during preparation was observed to evaluate the processability.

[0052] In addition, in the evaluation and judgment of processability, the kneadability of each of the rubber compositions S1 to S7 and P1 to P8 was compared, and when the kneadability was relatively high, it was marked as "◯", and when the kneadability was relatively low, it was marked as "X".

[0053] <Vulcanization characteristics (measurement of vulcanization speed (unvulcanized test))> For rubber compositions S1 to S7 and P1 to P8, a vulcanization tester (VR-3110) was used in accordance with JIS K6300-2 to draw vulcanization curves for 20 minutes at a measurement temperature of 160°C, an amplitude angle of ±1°, and a vibration frequency of 100 cpm. The vulcanization characteristics were evaluated by determining the tC(10) and tC(90) values ​​from the vulcanization curves.

[0054] In assessing the vulcanization characteristics, tC(90) of less than 5 minutes was rated as "X", since it was deemed that the vulcanization start time was short and that scorching (rubber burning) was likely to occur during molding. tC(90) of 5 minutes or more and less than 8 minutes was rated as "O". tC(90) of 8 minutes or more was rated as "△", since it was deemed that the vulcanization time was long and that productivity was poor.

[0055] <Mooney Scoach Time (Mooney Scoach Exam)> For rubber compositions S1 to S7 and P1 to P8, a Mooney viscometer was used in accordance with JIS K 6300-1 using an L-type rotor. The minimum Mooney viscosity at a measurement temperature of 125°C was determined as Vm, and the time t5 required for the viscosity to rise by 5M from Vm was measured, and this t5 was defined as the Mooney scorch time.

[0056] In the evaluation of the Mooney scorch test, a Mooney scorch time of less than 8 minutes was deemed to be prone to scorching and was marked as "X." A Mooney scorch time of 8 minutes or more but less than 10 minutes was deemed to be likely to limit the storage period of unvulcanized rubber and was marked as "△." A Mooney scorch time of 10 minutes or more was marked as "◯."

[0057] <Tensile properties (tensile test)> For each of the evaluation rubber sheets obtained using the rubber compositions S1 to S7, P1 to P8, a JIS No. 3 dumbbell was used to punch out the rubber sheets. The elongation at break (Eb) and strength at break (Tb) were measured in accordance with JIS K 6251, and the rubber hardness (Hs(A); JIS A) was measured in accordance with JIS K 6253-3 to evaluate the tensile properties.

[0058] In the evaluation of tensile properties, rubber hardness was rated as "△" when the Hs value was 66 or less and 74 or more, and "○" when the Hs value was within the range of 67 to 73. In addition, breaking elongation (EB) was rated as "○" when it was 300% or more, "△" when it was 250% or more and less than 300%, and "×" when it was less than 250%. In addition, breaking strength (TB) was rated as "○" when it was 10 MPa or more, and "△" when it was less than 10 MPa, as it was considered that the strength was low and that it may be difficult to use depending on the hose.

[0059] <Specific gravity> For each of the evaluation rubber sheets obtained using the rubber compositions S1 to S7 and P1 to P8, the density was measured in accordance with JIS-K6268, and evaluation was performed based on the specific gravity calculated from the density.

[0060] In assessing the specific gravity, a value less than 1.21 was marked as "○", a value between 1.21 and 1.25 was marked as "△", and a value greater than 1.25 was marked as "×".

[0061] <Volume resistivity> For each of the rubber test pieces obtained using the rubber compositions S1 to S7 and P1 to P8, the specific volume resistivity in an uncompressed state and in a compressed state (30% compressed state) was measured and evaluated by the method described below.

[0062] The uncompressed volume resistivity was measured in accordance with JIS-K6271-1.

[0063] The volume resistivity in a compressed state was measured by first sandwiching a rubber test piece Sa between two copper plates (length 40 mm × width 70 mm × thickness 1.5 mm) 11, 12 from both ends of the rubber test piece Sa, as shown in FIG. 1, and electrically connecting the copper plates 11, 12 with a conductor 13 and an electrical resistance meter 14.

[0064] Next, for the rubber test piece Sa in the state shown in FIG. 1, the electrical resistance value (hereinafter, R2) when compressed by 30% in the clamping direction (compressed in the direction of the white arrow shown in FIG. 1) and the electrical resistance value (hereinafter, R1) when released from the compressed state to a non-compressed state were measured.

[0065] The specific volume resistivity in the uncompressed state and the electrical resistance values ​​R1 and R2 were then substituted into the following formula (1) to calculate the specific volume resistivity in the compressed state.

[0066] "Volume resistivity in compressed state (30% compressed state)" = "Volume resistivity in uncompressed state" x (R2 / R1) …… (1) In addition, in the evaluation and judgment of the volume resistivity, the volume resistivity in the compressed state calculated by the formula (1) is 10 7 If it is larger than Ω·cm, mark it as "○", and if it is larger than 10 6 Ω cm or more 10 7 Ω·cm or less is marked "△", 10 6 Cases of less than Ω·cm were marked as “×”.

[0067] <Hose moldability (extrusion processability)> For each evaluation rubber hose obtained using rubber compositions S1 to S7 and P1 to P8, the moldability was evaluated by observing the dimensional stability (whether the discharge amount was stable) during extrusion molding (when extrusion molding at a constant speed) and the surface condition of each evaluation rubber hose.

[0068] In the evaluation of moldability, a comparatively good dimensional stability and surface condition was rated as "good," and a comparatively poor dimensional stability and surface condition was rated as "good."

[0069] <Hose insulation> For each of the rubber hoses for evaluation obtained using the rubber compositions S1 to S7 and P1 to P8, the surface resistance was measured by the method (terminal method) described below to evaluate the insulating properties.

[0070] First, as shown in FIG. 2, the tips 32 of two needle-shaped measuring terminals 31 of an electrical resistance meter 3 (only one is shown in FIG. 2) were brought into contact with the outer surface of the evaluation rubber hose Sb placed on the measuring platform 21 of the balance 2, with a gap of 4 cm between them (contacted in an inclined position as described below).

[0071] Moreover, each measuring terminal 31 was held by the clamp 41 of the stand 4 in a position inclined at 20° with respect to the horizontal direction, and a load of 1 N was applied to the evaluation rubber hose Sb.

[0072] Then, the surface resistance at a voltage of 500 V was measured between each of the measuring terminals 31 on the outer circumferential surface of the evaluation rubber hose Sb to evaluate the insulation properties.

[0073] In addition, the insulation property is evaluated based on a surface resistance of 10 7 If it is larger than Ω, mark it as "○", and if it is larger than 10 6 Ω or more 10 7 10 Ω or less is marked "△", 6 Cases where the resistance was less than Ω were marked as "X".

[0074] <Corrosion resistance of hose (SST test (salt spray corrosion test))> For each of the rubber hoses for evaluation obtained using the rubber compositions S1 to S7 and P1 to P8, the corrosion resistance was evaluated by the method described below.

[0075] First, an aluminum round bar was inserted and attached to the inner periphery of the rubber hose for evaluation, and a metal clamp (spring type) was attached (attached so as to clamp) to the outer periphery of the rubber hose for evaluation.Then, an SST test was performed on the rubber hose for evaluation with the round bar and clamp attached, and the changes over time (rust formation state) of the round bar and clamp were observed to evaluate the corrosion resistance.

[0076] In assessing corrosion resistance, a rating of "X" was given if the time from the start of the SST test until rust appeared was within 1,000 hours, and a rating of "O" was given if no rust appeared even after more than 1,000 hours from the start of the SST test.

[0077] <Leak-proof hose> For each of the rubber hoses for evaluation obtained using the rubber compositions S1 to S7 and P1 to P8, the water leakage resistance was evaluated by the method described below.

[0078] First, one end of a pipe with an outer diameter of 17 mm was inserted and attached to the inner periphery of the rubber hose for evaluation, and a metal clamp (spring type) was attached (attached so as to clamp) to the outer periphery of the rubber hose for evaluation.The rubber hose for evaluation with the pipe and clamp attached was then placed in an oven at a specified temperature of 120°C for 168 hours to perform heat aging, after which water was injected from the other end of the pipe to apply water pressure and the pressure value at the time when water leakage occurred was measured to evaluate the leak resistance.

[0079] In assessing leak resistance, a pressure value of less than 0.3 MPa at the time of leakage was marked "X", a value between 0.3 MPa and 0.4 MPa was marked "△", and a value of 0.4 MPa or more was marked "O".

[0080] <Overall Judgment> When all of the evaluation items shown above are "good", the overall judgment is "◎". When one to three of the evaluation items are "△" and the rest are all "good", it is deemed that there is a possibility that the product may be appropriately applied as a hose product, for example, and the overall judgment is "good". When any one of the evaluation items is "bad", it is deemed that there is a possibility that the product may be difficult to apply as a hose product, and the overall judgment is "bad".

[0081] [Table 3]

[0082] [Table 4]

[0083] From the compounding ratios of each rubber composition shown in Tables 1 and 2 and the results shown in Tables 3 and 4, the following can be said.

[0084] First, in rubber compositions S1 to S7, the main components ethylene propylene diene rubber, carbon black, clay, and softener are blended in a total amount within the range of 300 to 400 parts by mass, and when the ethylene propylene diene rubber is taken as 100 parts by mass, the carbon black is blended in a range of 70 to 170 parts by mass, the clay is blended in a range of 10 to 60 parts by mass, and the softener is blended in a range of 30 to 100 parts by mass. Furthermore, the ethylene propylene diene rubber, carbon black, and clay are each in a category having the physical properties shown in (A), (B), and (C) above (hereinafter referred to as the example category).

[0085] In the rubber compositions S1 to S3, all of the evaluation items were marked with "◯" and the overall evaluation was judged to be "◎", which was a good result. In the rubber compositions S4 to S7, even though several (three or less) of the evaluation items were marked with "△", the rest were all marked with "◯" and the overall evaluation was judged to be "◯", which was a satisfactory result.

[0086] On the other hand, in the rubber compositions P1 to P8 which are out of the range of the examples even partially, at least one of the evaluation items was marked with "x", and the overall evaluation was marked with "x".

[0087] Specifically, all of the rubber compositions P1 to P8 were rated as "x" in terms of volume resistivity and corrosion resistance. Furthermore, the rubber composition P2 was rated as "x" in terms of surface resistance, and the rubber composition P8 was rated as "x" in terms of tensile property, elongation at break (EB).

[0088] Therefore, according to the embodiment of the rubber compositions S1 to S7, excellent processability (kneadability, moldability), mechanical properties (material strength such as tensile properties), insulation properties (10 7 It was confirmed that it is possible to obtain a specific volume resistivity of 200 Ω·cm or more), light weight (low specific gravity), and suppress changes in the insulation properties (suppress the reduction in specific volume resistivity in a compressed state), thereby achieving the various properties required of a hose (for example, corrosion resistance, leak resistance, and insulation properties).

[0089] Although the present invention has been described in detail above only with respect to the specific examples, it will be apparent to those skilled in the art that various modifications are possible within the scope of the technical concept of the present invention, and it is natural that such modifications fall within the scope of the claims. [Explanation of symbols]

[0090] Sa: Rubber test piece Sb: Rubber hose for evaluation 2... Balance 3,14…Electrical resistance meter 4…Frame

Claims

1. A rubber composition containing at least ethylene propylene diene rubber, carbon black, clay, and a softener in a total amount within the range of 300 to 400 parts by mass, the carbon black is blended in a range of 70 to 170 parts by mass, the clay is blended in a range of 10 to 60 parts by mass, and the softener is blended in a range of 30 to 100 parts by mass, relative to 100 parts by mass of the ethylene propylene diene rubber; The ethylene propylene diene rubber has an ethylene content in the range of 51 to 66 mass%; The carbon black has an iodine adsorption amount in the range of 5 to 40 mg / g and a nitrogen adsorption specific surface area of ​​10 to 60 m ２ / g, DBP oil absorption is 110 to 160 g / cm ３ In the range of 1.3 m ２ / mg or more, toluene coloring transmittance is 90% or more, The clay has an average particle size in the range of 1 to 10 μm; Volume resistivity is 10 ７ A rubber composition having a modulus of elasticity of Ω·cm or more.

2. The rubber composition according to claim 1 is molded into a tube shape to form at least one rubber hose layer, and the rubber hose layer has a volume resistivity of 10 ７ A hose characterized in that it has a resistance of Ω·cm or more.

3. 3. The hose according to claim 2, wherein a reinforcing layer is laminated on at least one of the inner peripheral surface and the outer peripheral surface of the rubber hose layer.

4. 3. The hose according to claim 2, wherein the thickness of the rubber hose layer is within a range of 2.0 to 4.5 mm.

5. 5. The hose according to claim 2, which is a water-based hose selected from the group consisting of a radiator hose, a bypass hose, a heater hose, a reserve tank hose, a drain hose, and a cooling hose for electric and electronic systems.

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