JP2007332325A - Rubber composition and air spring using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition capable of improving resistance to fatigue of the reduced diameter air spring and an air spring using it. <P>SOLUTION: The air spring is composed of an inner surface rubber layer 2, an outer surface rubber layer 4 and a reinforcing layer 3 intervening between the both layers 2 and 4, which consists of a reinforcing cord and a topping rubber topping on the reinforcing cord wherein the topping rubber composition has a main component of an isoprene rubber composed of 100 pts.wt. of the rubber component containing a butadiene rubber and 6-13 pts.wt. of an aromatic amine antiaging agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition excellent in fatigue resistance and an air spring using the same.

In recent years, the specifications of the air spring have been reduced in installation space in conjunction with the movement of lighter and lower floor bus trucks as shown in Patent Document 1, and in order to cope with this, the air spring Is becoming smaller and slimmer.
JP 2006-112500 A

  Specifically, an air spring having a small diameter is required. However, such a reduction in the diameter of the air spring leads to an increase in the pressure per unit area of the air spring, and if the expansion and contraction are repeated with such a large pressure load, the conventional air spring is durable. There has been a problem that the performance is reduced.

  Then, in this invention, it aims at providing the rubber composition which can improve fatigue resistance, and an air spring using the same.

  In order to solve the above-mentioned problems, the rubber composition according to the present invention is composed of isoprene-based rubber as a main component, 100 parts by weight of a rubber component containing butadiene rubber, and 6 to 13 parts by weight of an aromatic amine-based antioxidant. It is characterized by blending parts by weight.

  The rubber composition is excellent in fatigue resistance after vulcanization, and an air spring excellent in durability can be obtained by using it as a rubber composition for an air spring having a reduced diameter.

  The present inventor usually uses an aromatic amine-based aging agent in which the amount of the aromatic amine-based anti-aging agent added to prevent rubber aging is about 1 part by weight with respect to 100 parts by weight of the rubber component. It has been found that the fatigue resistance of a vulcanized rubber can be improved by adding an inhibitor excessively to a rubber component, and the present invention has been completed.

  The blending amount of the aromatic amine-based antioxidant is preferably 6 to 13 parts by weight, more preferably 7 to 12 parts by weight, with respect to 100 parts by weight of the rubber component. If the blending amount of the aromatic amine anti-aging agent is less than the above range, the effect of improving fatigue resistance is reduced, and if it exceeds the above range, the strength of the vulcanized rubber may be reduced.

  Here, it is important to use a blend rubber of isoprene-based rubber and butadiene rubber as a rubber component for blending the aromatic amine-based antioxidant. When 100% isoprene-based rubber is used as the rubber component, no improvement in fatigue resistance is observed even if the blending amount of the aromatic amine-based antioxidant is increased. Although the reason is unknown, it is thought to be due to a synergistic effect of the aromatic amine-based antiaging agent, isoprene-based rubber and butadiene rubber.

  As a quantitative relationship between the isoprene-based rubber and the butadiene rubber in the rubber component, it is necessary to have the isoprene-based rubber as a main component. Furthermore, from the viewpoint that the fatigue resistance can be improved more effectively, the rubber component preferably contains 65 parts by weight to 85 parts by weight of isoprene-based rubber and 35 parts by weight to 15 parts by weight of butadiene rubber. More preferred are those containing 70 to 80 parts by weight of isoprene-based rubber and 30 to 20 parts by weight of butadiene rubber.

  As the isoprene-based rubber, natural rubber can be used in addition to isoprene rubber, and these can be used alone or in combination. However, it is preferable to use isoprene rubber from the viewpoint that it does not contain impurities that may affect fatigue resistance.

  The rubber composition described above is excellent in fatigue resistance, and an air spring using the rubber composition exhibits excellent durability even if it has a small diameter.

  The specific structure of the air spring includes an inner rubber layer and an outer rubber layer, and a reinforcing layer interposed between the two layers. The reinforcing layer includes a reinforcing cord and a topping rubber that covers the reinforcing cord. It is made up of. The rubber composition according to the present invention may be used for any of the inner rubber layer, outer rubber layer, and topping rubber, but the deterioration of the air spring subjected to the durability test first appears as a crack in the reinforcing layer. It is preferable to use as a topping rubber.

  That is, by using the rubber composition according to the present invention for the topping rubber, the occurrence of cracks in the reinforcing layer is suppressed, and the inner rubber layer and the outer rubber layer are mainly ozone resistant and heat resistant, such as chloroprene rubber. By using a rubber composition containing a rubber component having excellent properties, it is possible to effectively improve the durability of the entire air spring.

  Examples of the aromatic amine-based antioxidant used in the present invention include amine-ketone antioxidants such as a reaction product of diphenylamine and acetone, a reaction product of diphenylamine and methyl ethyl ketone, and N- (1,3-dimethylbutyl). ) -N'-phenyl-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine and other p-phenylenediamine antioxidants and alkyls Examples thereof include diarylamine antioxidants such as diphenylamine and phenyl-α-naphthylamine. These can be used alone or in combination of two or more. Of these, N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine and a reaction product of diphenylamine and acetone are preferably used in combination.

  As an anti-aging agent, in addition to the above-mentioned aromatic amine-based anti-aging agent, it is also possible to use other types of anti-aging agents such as quinoline-based anti-aging agents for the purpose of improving other characteristics such as heat resistance. is there.

  The type of butadiene rubber is not particularly limited, but if high cis butadiene rubber with a cis 1,4 bond content of 90% or more is used, the processability and fatigue resistance of the vulcanized rubber will be improved. It is preferable that the cis 1,4 bond content is 95% or more.

  The rubber composition according to the present invention can be used as a rubber composition for an air spring for a bus truck and an air spring for a railway vehicle, and can also be used for a rubber product that requires fatigue resistance such as a hose joint for construction. It can be suitably used as a composition.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further in detail, unless this invention exceeds the summary, it is not limited to these Examples.

[Preparation of rubber composition]
In this example, as shown in Table 1, as rubber compositions, nine types (samples 1 to 9) were prepared by changing the constitution of the rubber component and the type and amount of the aromatic amine-based anti-aging agent. Evaluation was performed.

  As the rubber component, isoprene rubber (IR) or natural rubber (NR) is used as the isoprene-based rubber, and high cis type BR (manufactured by LANXESS: trade name “BUNA CB22”, cis 1, butadiene rubber (BR)). A 4-bond content of 98%) was used.

  N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine (6C) and a reaction product of diphenylamine and acetone (BN) are used as aromatic amine anti-aging agents, respectively. Or used together.

  The nine types of samples listed in Table 1 commonly contain carbon black, process oil, sulfur, vulcanization accelerator, zinc oxide, and stearic acid as components other than the rubber component and aromatic amine-based antioxidant. After blending and kneading, vulcanization was conducted for an evaluation test.

[Evaluation test]
(1) Normal properties of vulcanized rubber Each sample listed in Table 1 is vulcanized and measured for hardness (based on JIS K6253), 300% modulus, tensile strength and elongation (all based on JIS K6251). did. The results are shown in Table 1.
(2) Fatigue resistance test of vulcanized rubber Each sample described in Table 1 was vulcanized, and a dematcher extension fatigue test (based on JIS K6270) was performed as a fatigue resistance test. The results are shown in Table 1.

[Evaluation results]
Regarding the fatigue resistance of each sample, as shown in Table 1, a rubber component appropriately blended with IR and BR is used, and this is compounded with an aromatic amine anti-aging agent less than the appropriate range. It can be seen that the fatigue resistance is hardly improved in the case of (Samples 4 to 6).

  In addition, even when an aromatic amine anti-aging agent is used in an appropriate range, if the blend ratio of IR and BR is not appropriate as a rubber component (Sample 1, Sample 4), fatigue resistance is also maintained. Sex does not improve.

  However, in the rubber composition (sample 2 and sample 3) according to the present invention, in which an appropriate blend of IR and BR is used as a rubber component and an appropriate amount of an aromatic amine-based antioxidant is blended. It can be seen that the fatigue resistance is remarkably improved as compared with other samples, and the normal physical properties of the vulcanized rubber are also at a sufficient level.

  In this example, two types of rubber compositions that have been conventionally used for air springs are added as Sample 8 and Sample 9. It can be seen that the rubber compositions (Sample 2 and Sample 3) according to the present invention have sufficiently improved fatigue resistance as compared with Sample 8 and Sample 9.

[Product durability test]
Of the samples listed in Table 1, an air spring was actually manufactured using the rubber composition (Sample 3) according to the present invention having the best fatigue resistance, and the durability as a product was evaluated. I did it. As a comparative product, Sample 8, which is a conventional rubber composition, was used. The test contents are described below.
(1) Production of Air Spring As shown in FIG. 1, a substantially cylindrical one was produced as the air spring according to the present invention. As shown in FIG. 2, the air spring 1 includes an inner rubber layer 2, a reinforcing layer 3 disposed on the outer peripheral side of the inner rubber layer 2, and an outer rubber layer 4 disposed on the outer peripheral side of the reinforcing layer 3. I have.

  The reinforcing layer 3 includes a reinforcing cord and a topping rubber that covers the reinforcing cord. In this example, the rubber composition (sample 3) according to the present invention is used as the topping rubber, and the rubber composition constituting the inner rubber layer 2 and the outer rubber layer 3 is excellent in ozone resistance and heat resistance. Further, by using a rubber composition mainly composed of chloroprene rubber, the fatigue resistance of the entire air spring is effectively improved.

  Examples of fibers used for the reinforcing cord include organic fibers such as rayon, nylon, aramid, carbon, and polyester, and inorganic and metal fibers such as glass and steel. In this embodiment, the nylon cord is used as the reinforcing cord. Is used.

  In order to form a reinforcing layer, a plurality of layers are alternately arranged on the outer circumference of the unvulcanized inner rubber layer so that the cord direction intersects the axis of the air spring with a rubber-coated cord coated with a topping rubber. Wrap around. In this embodiment, the reinforcing layer 3 has a two-layer structure in which two rubber-coated cords are wound.

After winding the rubber-coated cord, an unvulcanized outer rubber layer is formed on the outer periphery of the cord and vulcanized to obtain an air spring. The air spring obtained as described above was an invention. In addition, the air spring produced using the sample 8 only for the rubber composition in the same procedure as the product of the invention was used as a conventional product.
(2) Product durability test A product durability test was conducted using the air springs of the invention product and the conventional product obtained in (1) above. Specifically, as shown in FIG. 3, the upper end and the lower end of the air spring 1 are fixed to the upper plate 5 and the piston 6, respectively. The top plate 5 is fixed to a tester (not shown), and the piston 6 is attached to the arm of the tester.

  The lower end of the air spring 1 is folded back inward so as to push the piston 6 upward. The arm is configured to move up and down at a constant cycle, whereby the air spring 1 is extended and contracted at a constant stroke.

  As specific test conditions, the set height was 268 mm, the arm stroke was ± 80 mm, the internal pressure of the air spring was 0.63 MPa, and the frequency was 2 Hz.

  As a result of the above test, the inventive product could be used up to 2.5 million times without generating air leakage, whereas the conventional product leaked air after 400,000 times. Thereby, it was confirmed that the air spring produced using the rubber composition according to the present invention exhibits excellent durability.

It is a figure which shows the air spring which concerns on this invention, A left half shows sectional drawing and a right half shows an external view. Partial sectional view of the air spring of FIG. Sectional drawing which shows the attachment state of the air spring of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air spring 2 Inner surface rubber layer 3 Reinforcement layer 4 Outer surface rubber layer 5 Top plate 6 Piston

Claims (5)

A rubber composition comprising 6 to 13 parts by weight of an aromatic amine-based anti-aging agent in 100 parts by weight of a rubber component containing isoprene-based rubber as a main component and containing butadiene rubber. The rubber composition according to claim 1, wherein the rubber component comprises 65 parts by weight to 85 parts by weight of isoprene-based rubber and 35 parts by weight to 15 parts by weight of butadiene rubber. The rubber composition according to claim 1 or 2, wherein the isoprene-based rubber is isoprene rubber and / or natural rubber. The air spring formed using the rubber composition in any one of Claims 1-3. An inner rubber layer and an outer rubber layer, and a reinforcing layer interposed between the two layers, the reinforcing layer comprising a reinforcing cord and a topping rubber for topping the reinforcing cord, and the rubber composition as the topping rubber The air spring according to claim 4, wherein an object is used.

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