JP2012017757A - Rubber composition for inner tube of hose, and hose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for an inner tube of a hose, whose oil resistance and low temperature resistance are both superior and in which deterioration of mechanical property is prevented.SOLUTION: The rubber composition for the inner tube of the hose contains: 100 pts.mass of a rubber composition containing 55 mass% or more of an acrylonitrile-butadiene rubber; and 5 to 20 pts.mass of a titanium oxide.

Description

  The present invention relates to a rubber composition for a hose inner pipe and a hose.

Conventionally, acrylonitrile butadiene rubber (NBR) is generally used for rubber compositions for hose inner pipes used for hoses such as hydraulic hoses and marine hoses.
The rubber composition for hose inner pipes is particularly required to have oil resistance and cold resistance, and these characteristics depend on the amount of bound acrylonitrile (AN amount) of NBR. That is, when the amount of AN increases, the oil resistance improves, while the embrittlement temperature increases and the cold resistance is inferior. On the other hand, when the amount of AN decreases, the cold resistance tends to be excellent while the oil resistance tends to be poor.
Therefore, for example, Patent Document 1 discloses that the applicant of the present application provides “rubber of acrylonitrile-butadiene rubber (NBR), quartz and kaolinite for the purpose of providing a rubber composition having excellent oil resistance and cold resistance. And a cold-resistant rubber composition containing an aggregate ”([Claim 1]).

JP 2007-77270 A

By the way, the invention described in Patent Document 1 contains “aggregates of quartz and kaolinite”, and while improving oil resistance and cold resistance, mechanical properties such as elongation at cutting deteriorate. I found out that there was a case.
In recent years, the level of properties required for rubber compositions for hose inner pipes has increased, and it is also required to achieve both oil resistance and cold resistance at a higher level.
Accordingly, an object of the present invention is to provide a rubber composition for a hose inner tube in which both oil resistance and cold resistance are excellent and deterioration of mechanical properties is suppressed.

As a result of intensive investigations to solve the above problems, the present inventors have found that a rubber composition in which a predetermined amount of titanium oxide is blended with a rubber component mainly composed of acrylonitrile butadiene rubber is oil resistant without deterioration of cold resistance. And the deterioration of mechanical properties was also suppressed, and the present invention was completed.
That is, the present invention provides the following (1) to (4).

  (1) A rubber composition for an inner tube of a hose containing 100 parts by mass of a rubber component containing 55% by mass or more of acrylonitrile butadiene rubber and 5 to 20 parts by mass of titanium oxide.

  (2) The rubber composition for a hose inner tube according to (1), further comprising 90 parts by mass or more of carbon black with respect to 100 parts by mass of the rubber component.

  (3) The rubber composition for an inner tube of a hose according to (1) or (2), wherein the amount of bound acrylonitrile of the acrylonitrile butadiene rubber is 25 to 35% by mass.

  (4) A hose comprising an inner pipe, a reinforcing layer disposed on the outer peripheral side of the inner pipe, and an outer pipe disposed on the outer peripheral side of the reinforcing layer, wherein the inner pipe is the above (1 ) A hose formed using the rubber composition for an inner tube of a hose according to any one of (3) to (3).

According to the present invention, it is possible to provide a rubber composition for an inner tube of a hose which is excellent in both oil resistance and cold resistance and in which deterioration of mechanical properties is suppressed.
Moreover, since the hose using the rubber composition for hose inner pipes of the present invention is excellent in oil resistance and cold resistance, it is suitably used for a hydraulic hose or the like and useful.

It is a perspective view which cuts and shows each layer of a hose.

<Rubber composition for hose inner tube>
The rubber composition for hose inner pipe of the present invention (hereinafter also referred to as “the rubber composition of the present invention”) includes 100 parts by mass of a rubber component containing 55% by mass or more of acrylonitrile butadiene rubber, and 5 to 20 parts by mass of titanium oxide. And a rubber composition for hose inner pipes.
Hereinafter, each component contained in the rubber composition of the present invention will be described.

(Rubber component)
The rubber component contained in the rubber composition of the present invention contains 55% by mass or more of acrylonitrile butadiene rubber (NBR), and may contain 100% by mass of NBR (including only NBR).
From the reason that the oil resistance of the rubber composition of the present invention is more excellent, the NBR content in the rubber component is preferably 80% by mass or more.

  NBR is a copolymer of acrylonitrile (AN) and butadiene. In the present invention, the amount of bound acrylonitrile of NBR (hereinafter referred to as “AN amount”) is 25 to 35% by mass because the balance between oil resistance and cold resistance of the rubber composition of the present invention is improved. It is preferable that it is 28 to 33% by mass.

Examples of the rubber component other than NBR include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), 1,2-butadiene rubber, styrene-butadiene rubber (SBR), chloroprene rubber (CR), Examples thereof include butyl rubber (IIR) and ethylene-propylene-diene rubber (EPDM). These may be used alone or in combination of two or more.
Of these, SBR and BR are preferably used because of low cost and better cold resistance of the rubber composition of the present invention.

(Titanium oxide)
The rubber composition of the present invention contains 5 to 20 parts by mass of titanium oxide with respect to 100 parts by mass of the rubber component. In the present invention, the titanium oxide is not particularly limited as long as it is titanium dioxide (TiO ₂ ).
Thereby, the rubber composition of this invention is excellent in both oil resistance and cold resistance. This is probably because the titanium oxide delayed the crosslinking rate of the rubber component to lower the crosslinking density, and the rubber composition of the present invention was improved in flexibility and improved in cold resistance. At this time, since the titanium oxide is difficult to mix with mineral oil such as gasoline and lubricating oil which are nonpolar oils, the rubber composition of the present invention is oil resistant even if the crosslinking density of the rubber component is reduced. It is thought that the deterioration of the property was prevented.

  Further, the rubber composition of the present invention contains the above-mentioned titanium oxide in the above-mentioned range, thereby comparing with a rubber composition containing other inorganic fillers (for example, aggregates of quartz and kaolinite, calcium carbonate, etc.). Thus, a decrease in mechanical properties such as elongation at break and modulus is suppressed.

  The titanium oxide content is 5 to 15 parts by mass with respect to 100 parts by mass of the rubber component because the increase in the die swell of the rubber composition of the present invention can be suppressed and the deterioration of the extrusion processability can be suppressed. Is preferred.

(Carbon black)
The content of carbon black optionally contained in the rubber composition of the present invention is preferably 90 parts by mass or more with respect to 100 parts by mass of the rubber component. When the content of the carbon black is within this range, a modulus suitable as a rubber composition used for the inner tube of the hose can be obtained.
Moreover, it is preferable that content of the said carbon black is 120 mass parts or less with respect to 100 mass parts of said rubber components. When the carbon black content is in this range, the rubber composition of the present invention has suitable mixing processability and extrusion processability, and the minimum Mooney viscosity is in a preferable range.
Although it does not specifically limit as said carbon black, For example, HAF, FEF, GPF, SRF, FT, MT etc. are mentioned.
HAF (High Ablation Furnace) and FEF (Fast Extracting Furnace) have a relatively small particle size with an average primary particle size of around 40 nm. GPF (General Purpose Furnace), SRF (Semi Reinforming Furnace), FT (Fine Thermal), and MT (Medium Thermal) have a relatively large average particle diameter of about 80 nm.
Furnace is manufactured by a furnace method in which oil and air as raw materials are blown into a fuel furnace and continuously burned incompletely, and carbon black that has passed through a cooler is captured by a bag filter and granulated. . Thermal is produced by a thermal method by pyrolysis of natural gas.
Of these, GPF is preferably used because the modulus and extrusion processability of the rubber composition of the present invention are improved.

(Various additives)
In addition to the components described above, the rubber composition of the present invention includes various additives such as a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, a vulcanization aid, an oil, an antiaging agent, a plasticizer, and a scorch inhibiting agent. Can be blended. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used.

(Production method)
The method for producing the rubber composition of the present invention is not particularly limited, and examples thereof include a method of kneading the above-described components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). It is done.
The rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

<Hose>
Next, the hose of the present invention will be described. The hose of the present invention is a hose comprising an inner tube, a reinforcing layer disposed on the outer peripheral side of the inner tube, and an outer tube disposed on the outer peripheral side of the reinforcing layer, wherein the inner tube is It is a hose formed using the rubber composition of the present invention.

Hereinafter, an example of a preferred embodiment of the hose of the present invention will be described with reference to FIG. FIG. 1 is a perspective view of each hose layer cut away.
As shown in FIG. 1, the hose 1 includes an inner tube 2, a reinforcing layer 3 disposed adjacent to the outer peripheral side of the inner tube 2, and an outer tube 4 disposed adjacent to the outer peripheral side of the reinforcing layer 3. And have.
In the hose 1, the inner tube 2 is formed using the rubber composition of the present invention.
The reinforcing layer 3 may be formed in a blade shape or may be formed in a spiral shape. Although the material which forms the reinforcement layer 3 is not specifically limited, Metal materials, such as fiber materials, such as a polyamide fiber and a polyester fiber, a hard steel wire (for example, a brass plating wire, a zinc plating wire), etc. are illustrated suitably, However, fiber materials are preferred, and polyamide fibers are more preferred.

  The hose of the present invention is not limited to the above-described three-layer structure. For example, the hose has a five-layer structure in which two reinforcing layers are provided and an interlayer rubber layer is provided between the two reinforcing layers. You may have.

  The manufacturing method of the hose of this invention is not specifically limited, A conventionally well-known method can be used. Specifically, for example, after laminating an inner tube, a reinforcing layer, and an outer tube in this order on a mandrel, these layers are subjected to steam vulcanization, oven under conditions of 130 to 190 ° C. and 30 to 180 minutes. Preferable examples include vulcanization (hot air vulcanization) or a method of producing by vulcanization adhesion by hot water vulcanization.

Since the hose of the present invention uses the rubber composition of the present invention for the inner pipe, it is excellent in oil resistance and cold resistance.
The use and application conditions of the hose of the present invention are not particularly limited. However, since the hose of the present invention is excellent in oil resistance and cold resistance, it is suitably used for, for example, a hydraulic hose and a marine hose.

  Hereinafter, the present invention will be specifically described with reference to examples. The present invention is not limited to these.

<Examples 1-3, Comparative Examples 1-5>
The components shown in Table 1 below were blended in the proportions (parts by mass) shown in Table 1 below.
Specifically, first, components other than the vulcanizing agent and the vulcanization accelerator among the components shown in Table 1 below were kneaded for 5 minutes with a 2-liter closed mixer to obtain a master batch. Next, a vulcanizing agent and a vulcanization accelerator were kneaded with the obtained master batch with an open roll to obtain a rubber composition. Next, the obtained rubber composition was vulcanized for 45 minutes under a pressure of 3.0 MPa using a press molding machine at 148 ° C. to obtain a vulcanized sheet having a thickness of 2 mm.

<Unvulcanized physical properties>
[Minimum Mooney viscosity (Vm)]
The minimum Mooney viscosity (Vm) is determined by using a Mooney viscometer (L-shaped rotor) according to “Mooney viscosity test” described in JIS K6300-1: 2001 for the obtained rubber composition, and a preheating time of 1 This is the minimum value of the Mooney viscosity on the Mooney viscosity-time curve when the rotor was rotated at the test temperature of 125 ° C.
[Scorch time (ML 5up)]
The scorch time (ML 5up) represents the time to rise 5M from the lowest Mooney viscosity (Vm), and M represents the Mooney unit.

<Physical properties after vulcanization>
[50% modulus (M ₅₀ ), 100% modulus (M ₁₀₀ )]
A test piece was produced by punching out a JIS No. 3 dumbbell-shaped rubber sheet piece from the obtained vulcanized sheet, and using the produced test piece, a tensile test at a pulling speed of 500 mm / min in accordance with JIS K6251: 2004. Was performed at room temperature, and 50% modulus (M ₅₀ ) [MPa] and 100% modulus (M ₁₀₀ ) [MPa] were measured.
[Tensile strength (T _B ), elongation at break (E _B )]
A test piece was produced by punching out a JIS No. 3 dumbbell-shaped rubber sheet piece from the obtained vulcanized sheet, and using the produced test piece, a tensile test at a pulling speed of 500 mm / min in accordance with JIS K6251: 2004. Was performed at room temperature, and tensile strength (T _B ) [MPa] and elongation at break (E _B ) [%] were measured.
[Hardness (Hs)]
A JIS No. 3 dumbbell-shaped rubber sheet piece was punched out from the obtained vulcanized sheet, and a test piece was prepared. Using the prepared test piece, according to JIS K6253: 2006 “Type A durometer hardness test”, Shore A hardness was measured.

<Oil resistance>
In accordance with JIS K6258: 2003, a test piece was prepared from a vulcanized rubber sheet, immersed in a test oil (IRM901 or IRM903) at 100 ° C. for 72 hours, and the hardness change rate (ΔHs [%]) after immersion, Volume change rate (ΔV [%]) and mass change rate (ΔW [%]) were measured.

<Cold resistance>
In accordance with JIS K6261-2006, a test piece was prepared from a vulcanized rubber sheet, and the temperature at which 50% of the total number of test pieces was destroyed when the test piece was subjected to impact bending under specified conditions was measured. .

<Extrudability>
The obtained rubber composition was measured for die swell (DS [%]) using a circular die in accordance with ASTM D 2230-77, Method B. The measurement conditions were a screw rotation speed of 40 rpm, a head temperature of 80 ° C., a cylinder temperature of 70 ° C., and a hopper temperature of 70 ° C., and die swell (DS [%]) was calculated by the following equation. The smaller the die swell, the better the extrudability.
DS = (W / lρS ₀ −1) × 100 (W, l is the mass and length of the sample, ρ is the specific gravity, and S ₀ is the die area.)

The following components were used as the components in Table 1.
-NBR: Krynac 2865F (AN amount 28% by mass, manufactured by LANXESS)
-SBR: NIPOL 1502 (manufactured by Nippon Zeon)
・ Carbon black: GPF (Diamond Black G, manufactured by Mitsubishi Chemical Corporation)
・ Titanium oxide: Taipei R-820 (Ishihara Sangyo Co., Ltd.)
・ Calcium carbonate: Heavy calcium carbonate (Maruo Calcium)
・ Vulcanization aid: Zinc oxide (Zinc Hana No. 3, manufactured by Shodo Chemical Industry Co., Ltd.)
-Anti-aging agent: Non-flex OD-3 (manufactured by Seiko Chemical Co., Ltd.)
Plasticizer: Dioctyl adipate (manufactured by Jay Plus)
・ Vulcanizing agent: Sulfur (made by Hosoi Chemical Co., Ltd.)
・ Vulcanization accelerator: Tetramethylthiuram monosulfide (Sunceller TS, manufactured by Sanshin Chemical Industry Co., Ltd.)
-Scorch inhibitor: N- (cyclohexylthio) phthalimide (SANTOGARD PVI DS POWDER, manufactured by FLEXSYS)

From the results shown in Table 1 above, Examples 1 to 3 containing titanium oxide have excellent mechanical properties (unvulcanized physical properties, post-vulcanized physical properties) and oil resistance comparable to those of Comparative Example 1. It was found that the embrittlement temperature was lower than those of Comparative Examples 1 to 5, and the cold resistance was excellent.
Furthermore, when Examples 1-3 were seen, it turned out that both oil resistance and cold resistance are equally excellent. Furthermore, it was found that as the compounding amount of titanium oxide decreases, the die swell tends to decrease and the extrudability tends to be good.
Surprisingly, Examples 1 to 3 containing titanium oxide are reduced in 50% modulus (M ₅₀ ) and 100% modulus (M ₁₀₀ ) as in Comparative Examples 3 to 5 containing calcium carbonate. It turned out that it becomes favorable also compared with the comparative example 1.

In contrast, Comparative Examples 1 and 2 not containing titanium oxide and Comparative Examples 3 to 5 containing calcium carbonate instead of titanium oxide all have high embrittlement temperatures and are inferior in cold resistance. I understood.
Further, when Comparative Example 1 and Comparative Example 2 are compared, Comparative Example 2 in which the blending amount of carbon black is 100 parts by mass has a higher embrittlement temperature and lower cold resistance than Comparative Example 1, and the lowest Mooney. It was found that viscosity (Vm) and elongation at break (E _B ) were also degraded.
Further, when Comparative Example 1 and Comparative Examples 3 to 5 are compared, Comparative Examples 3 to 5 containing calcium carbonate have a higher embrittlement temperature and lower cold resistance than Comparative Example 1, and are described above. Thus, 50% modulus (M ₅₀ ) and 100% modulus (M ₁₀₀ ) were also found to be inferior.

1 Hose 2 Inner pipe 3 Reinforcement layer 4 Outer pipe

Claims (4)

100 parts by mass of a rubber component containing 55% by mass or more of acrylonitrile butadiene rubber;
A rubber composition for an inner tube of a hose containing 5 to 20 parts by mass of titanium oxide.   Furthermore, the rubber composition for hose inner pipes of Claim 1 which contains 90 mass parts or more of carbon black with respect to 100 mass parts of said rubber components.   The rubber composition for an inner tube of a hose according to claim 1 or 2, wherein the amount of bound acrylonitrile of the acrylonitrile butadiene rubber is 25 to 35% by mass. A hose comprising an inner tube, a reinforcing layer disposed on the outer peripheral side of the inner tube, and an outer tube disposed on the outer peripheral side of the reinforcing layer,
The hose in which the said inner pipe is formed using the rubber composition for hose inner pipes in any one of Claims 1-3.