JP3013696B2 - Rubber composition for sliding members - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition for a sliding member. In particular, it is suitable as a molding material for a vehicle stabilizer bush or the like. Here, the stabilizer bush will be mainly described as an example, but the present invention is not limited to this.

In the following description, the blending unit is a weight unit unless otherwise specified, and “phr” means the blending number of the auxiliary material with respect to 100 parts of the rubber polymer.

[0003]

2. Description of the Related Art As a stabilizer bush, for example, there is a stabilizer bush shown in FIGS.
Reference).

[0004] That is, the bush 10 has a cylindrical structure including an inner peripheral surface 14 for holding the stabilizer bar 12 and an outer peripheral surface 18 having a flat surface 18 a formed in the axial direction for mounting the suspension bar or the vehicle body metal plate 16. It is formed of a total body of rubber.

The bush is attached by holding the stabilizer bar 12 through the inner peripheral surface 14 of the bush, holding the outer peripheral surface 18 by using a clamp 20, and fixing the clamp 20 to a fixing tool such as a bolt and a nut. It is fixed at 22. Here, the stabilizer bar 12 is slidably held on the inner peripheral surface 14 of the bush, that is, rotatably held when receiving a twisting action.

When the stabilizer bar 12 slides, the distance between the stabilizer bar 12 and the inner peripheral surface 14 of the bush is increased.
The slip stick phenomenon occurs and abnormal noise is likely to occur.
As a countermeasure against this, it is customary to mix a higher fatty acid amide (Japanese Patent Application Laid-Open No. 62-277474 / 2774).
No. 78, J, etc.). It is presumed that the blending of the higher fatty acid amide causes the amide to bloom on the inner peripheral surface 14 of the bush, which is the bar sliding surface, to reduce the sliding resistance of the sliding surface.

[0007]

However, it has been difficult to maintain the effect of preventing abnormal noise, that is, the effect of reducing sliding resistance, for a long time.

This is the inner peripheral surface of the bush (bar sliding surface) 14
It is presumed that the higher fatty acid amide that has bloomed is scraped off by hard foreign matter such as sand that has entered between the bar 12 and the inner peripheral surface 14 of the bush along with muddy water and the like.

In view of the above, an object of the present invention is to provide a rubber composition for a sliding member capable of maintaining a sliding resistance reducing effect for a long period of time.

[0010]

The present invention solves the above-mentioned problems,
The problem is solved by the following configuration.

Higher fatty acid amide self-lubricates vulcanized rubber
In a sulfur-vulcanized rubber composition compounded to impart property, a vulcanized rubber immersion test (JIS K6301 compliant, test oil: 100% toluene, test temperature: 23 ± 2)
° C, test time: 24 hours)
Is a high cross-linking density type formulation in which the rubber composition is 230% or less.

[0012]

[Detailed description of means]

(1) A prerequisite is that the rubber composition of the present invention is a composition containing a higher fatty acid amide in order to impart self-lubricating properties to the vulcanized rubber.

Here, as the higher fatty acid amide, those having 12 to 22 carbon atoms are usually used, and saturated / unsaturated fatty acid amides such as stearic acid amide, palmitic acid amide, oleic acid amide, erucyl acid amide and the like are used. It is possible.

The blending amount of the higher fatty acid amide is 5 to 2
0 phr. If it is less than 5 phr, it is difficult to maintain the sliding resistance reducing effect for a long time, and if it exceeds 20 phr, the physical properties of the rubber may be adversely affected.

(2) The rubber polymer (raw rubber) of the rubber composition used in the present invention is not particularly limited, and natural rubber (NR), butadiene rubber (BR) isoprene rubber (IR), styrene butadiene rubber ( SBR), chloroprene rubber (CR), nitrile rubber (NBR), ethylene propylene diene rubber (EPDM), butyl rubber (I
IR) and blended polymers thereof can be used. Among these, natural rubber (NR), butadiene rubber (BR), and blended polymers thereof are particularly desirable.

The rubber composition is obtained by adding various auxiliary materials such as a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, a processing aid, an antioxidant, and a tackifier to the rubber polymer and the higher fatty acid amide. It is appropriately blended and prepared.

[0017] As the vulcanizing agent, for example, sulfur, di-sul <br/> Fi de, etc. can suitably be used in accordance with the rubber species, the amount thereof blended is usually 0.1 to 10 phr.

Examples of the vulcanization accelerator combined with the vulcanizing agent include sulfenamides, thiazoles, thiurams, and the like.
One or more kinds are usually selected from dithiocarbamates, xanthates and the like. The amount of the vulcanization accelerator is usually 0.1 to 10 phr.

As the vulcanization aid, zinc oxide is usually used, and its compounding amount is usually 3 to 15 phr.

As the processing aid, fatty acids such as stearic acid and fatty oils and fats are used. Usually, carbon black, silica, or the like is suitably used as the reinforcing agent. As the softener, paraffin, naphthenate down system can be used aromatic process oils.

(3) In the present invention, the above composition is subjected to a vulcanized rubber immersion test (JIS K6301; test oil: toluene 100%; test temperature: 23 ± 2 ° C .; test time: 24 hours). Volume change rate (ΔV) is 23
A high crosslinking density type of 0% or less is a characteristic constituent feature.

If ΔV exceeds 230%, the amount of bloom of the higher fatty acid amide is small, and it is difficult to achieve the effect of the present invention (the effect of reducing the sliding resistance for a long time). The lower limit of ΔV varies depending on the required performance (for example, vibration isolation) of the sliding member. For example, in the case of a stabilizer bush, ΔV = 100% or more.

In order to obtain a rubber vulcanizate having these physical properties, the rubber polymer is a blend polymer having an equivalent ratio of NR / BR, the vulcanizing agent is sulfur, and the vulcanization accelerator is CZ (cyclohexyl benzothiazyl sulfene). Amide), sulfur / CZ
= 2 / 1.5 to 2/5 (preferably 2 / 2.0 to 2 /
3.5). Note that a vulcanized rubber having a relatively high crosslinking density can be obtained even when the BR ratio is increased with the above blend polymer.

[0024]

The rubber composition for a sliding member of the present invention is characterized in that, as described above, the higher fatty acid amide self-hydrates the vulcanized rubber.
In the rubber composition of the sulfur vulcanization system formulated to impart lubricity, the volume rate of change in the immersion test of vulcanized rubber ([Delta] V) is by a high crosslink density type formulation comprising 230% or less, described later As shown in the test example, the sliding resistance is greatly reduced, and the effect of reducing the sliding resistance of a certain value or more can be maintained for a long period of time.

Therefore, when the stabilizer bush is formed from the rubber composition of the present invention, the effect of preventing abnormal noise can be maintained for a long period of time.

[0026]

[Test example]

(1) Since the higher fatty acid amide and the vulcanization accelerator were varied in the formulation of the following composition, they were used for sliding resistance test (50 × 25 × 8 mm) and immersion test (20 × 50 × 2).
mm) of each test piece (former: 160 ° C x 15)
Min, the latter: 160 ° C. × 10 minutes). However, in Example 2, a blend polymer of NR / BR = 30/70 was used.

Rubber Composition Basic Formulation NR 50 (or 30) parts BR 50 (or 70) parts Stearic acid 1 part Zinc white 5 parts FEF carbon 92 parts Process oil 30 parts Antioxidant 3 parts Oleic acid amide Variable sulfur 2 Part Accelerator CZ variable (2) In the sliding test, a metal plate (made of iron) of the same shape was sandwiched with test pieces, and the metal plate was pulled out in a compressed state so that the compression ratio became 10%. The slidability was evaluated under the following load.

(3) The immersion test (swelling amount ΔV) is based on JIS
In accordance with K6301, the test was performed under the conditions of a test piece: toluene 100%, a test temperature: 23 ± 2 ° C, and a test time: 24 hours.

(4) The amount of bloom was measured for each test piece according to the following procedure.

The weight (initial weight) of the same test piece as used in the sliding test is measured.

After wiping the surface of the test piece with an organic solvent (aromatic hydrocarbon type), the test piece is left to dry at room temperature for one week.

The weight of the dried test piece is measured, and the difference between the dried weight and the initial weight is defined as the bloom amount.

(5) Test Results From the test results shown in FIG. 3 and Table 1, the rubber composition of the present invention shows an increase in the blooming amount of the lubricant due to an increase in the crosslink density, and a significant decrease in the sliding resistance. It can be seen that the effect of reducing the sliding resistance can be maintained for a long period of time by reducing the value.

It can be seen that when the BR blend ratio of the NR / BR blend polymer is increased, the crosslinking density is increased without increasing the amount of the crosslinking accelerator (see Example 2 and Comparative Example 2).

Further, when the blending amount of the lubricant (fatty acid amide) is the same, the relationship between the swelling amount (volume change rate ΔV), which is an indirect index of the crosslink density, and the amount of the lubricant bloom has a linear relationship from FIG. I understand.

Therefore, an increase in the crosslink density results in a relatively small amount of the lubricant in order to obtain the same slidability.

[0037]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a perspective view of a stabilizer bush as an example of a sliding member to which the rubber composition of the present invention is applied.

FIG. 2 is a sectional view of a use mode of the stabilizer bush of FIG. 1;

FIG. 3 is a graph showing the relationship between the number of pull-outs and the pull-out force in the sliding test results.

FIG. 4 Amount of lubricant bloom and swelling (volume change: ΔV)
FIG.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-277447 (JP, A) JP-A-5-255519 (JP, A) JP-A-59-113043 (JP, A) JP-A-4- 277378 (JP, A) JP-A-6-100731 (JP, A) JP-A-6-207051 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 21/00 C08K 5 / 20 C08L 7/00 C08L 9/00

Claims (4)

(57) [Claims] 1. Self-lubricating higher fatty acid amide to vulcanized rubber
In a sulfur vulcanized rubber composition compounded for imparting properties , a vulcanized rubber immersion test (JIS K6301 compliant, test oil: 100% toluene, test temperature: 23 ± 2 ° C, test time: 24 hours ) Is 230%
A rubber composition for a sliding member, wherein the rubber composition is a high crosslinking density type formulation as follows. 2. The rubber polymer according to claim 1, wherein the rubber polymer of the vulcanized rubber is natural rubber (NR), butadiene rubber (B
R), and a sliding member for a rubber composition characterized by being <br/> selected from any of those blend polymer. 3. Higher fatty acid amide self-lubricates vulcanized rubber
In a sliding member made of a sulfur- vulcanized vulcanized rubber compounded for imparting property, a vulcanized rubber immersion test (JISK6301 compliant, test oil: 100% toluene, test temperature: 23 ± 2) ° C, test time: 24 hours) with a volume change rate (ΔV) of 230
% Of a high cross-linking density type or less sliding member. 4. The rubber polymer according to claim 3, wherein the rubber polymer of the vulcanized rubber is natural rubber (NR), butadiene rubber (B
R), and a sliding member characterized by being <br/> selected from any of those blend polymer.