JPH0418438A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition having improved fatigue resistance by blending a natural rubber or diene based synthetic rubber with uniformly colloidal carbon black hand selective characteristics. CONSTITUTION:The aimed composition obtained by blending (A) 100 pts.wt. natural rubber or diene based synthetic rubber with (B) 20-100 pts.wt. carbon black having selective characteristics expressed by formula I to formula IV (N2SA is a specific surface area of nitrogen adsorption; DBP is DBP oil absorption amount; Dst is stokes mode diameter of carbon black aggregate; Dst is half value width of the above-mentioned stokes mode diameter) and obtained by a method introducing atomizing stream of raw material oil into high- temperature combustion gas by fuel oil and a oxidizing agent containing air or oxygen at two stages using a wide-diameter cylindrical reaction furnace having gradually converging, opening and spreading drum-like squeezing part, and kneading the blend with other necessary components.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a rubber composition with improved fatigue resistance, and more particularly, the present invention relates to a rubber composition having improved fatigue resistance. This invention relates to a fatigue-resistant rubber composition containing black.

[Conventional technology]

Among industrial rubber products, rubber materials used for various vibration isolators, seal members, hoses, healds, etc. are required to have excellent fatigue resistance against harsh usage environments. Therefore, many attempts have been made to improve the fatigue resistance of this type of rubber products, and many proposals have been made for improvements mainly in terms of component composition.

For example, JP-A-60-108444 discloses mixing an organic suspension containing carbon black, which has been passed through a sieve to remove the grid, with rubber latex or rubber cement.
A fatigue resistant rubber composition formed by a wet carbon master hatch process is disclosed. Japanese Patent Publication No. 61-2902
In the invention of Publication No. 55, 1 to 20 parts by weight of a metal oxide vulcanizing agent and 5 to 5 parts by weight of silica are added to 100 parts by weight of chloroprene rubber.
30 parts by weight of reinforcing filler such as carbon black 1
By blending 5 to 50 parts by weight of bismaleimide and 2 to IO parts by weight, the life of the rubber belt is extended. The anti-vibration rubber composition described in JP-A No. 64-9250 is a reinforced rubber composition in which 100 parts by weight of vulcanizable rubber is combined with 5 to 100 parts by weight of polyamide fine short fibers, carbon black and vulcanized. It is a blend of available rubbers in a specific range of ratios, and is intended to improve fracture strength and fatigue properties. JP-A-64-20245 discloses a method for producing a rubber composition comprising natural rubber and/or polyisoprene rubber, polybutadiene rubber, and carbon black that has excellent fatigue resistance. Furthermore, JP-A-1-146934 proposes a vibration-proof rubber composition containing a specific butadiene polymer, natural rubber and/or high-cis isoprene rubber, and carbon black.

However, in the above invention technology, the characteristics of carbon black based on the causal relationship between blended carbon black and rubber fatigue have not been investigated, so there is a limit to the degree of improvement in fatigue resistance.

On the other hand, in Japanese Patent Application Laid-open No. 62-57438, the arithmetic mean diameter (On) determined by an electron microscope: 22 mμ≦On
≦38-μ, aggregate diameter (Ilist): 60Ilμ≦f
ist≦130mμ, standard deviation of arithmetic mean diameter distribution S(m
μ): (S)≦0゜333×Cfist) +4
5.0, aggregate strength: ΔDBP = DBP-24M40
BP (ml/loog)610m17100g
, NASA (II”/g) / IA (#g/g)
A rubber composition with fatigue resistance and heat generation resistance has been shown in which 20 to 100 parts of carbon black with a characteristic of ≧1.08 is blended with the rubber component, and the colloidal properties of carbon black have been elucidated. being done.

[Problem to be solved by the invention]

However, with the colloidal properties of carbon black specified in the invention of JP-A No. 62-57438, although the effect of improving fatigue resistance is recognized, there are many disadvantages in which other rubber properties are forced to be sacrificed. . For example, fi
Since the st is limited to less than 130 nm, it is relatively difficult to suppress heat generation, and this property limitation increases the static-dynamic ratio when compounded into anti-vibration rubber for automobile engine mounts. This leads to side effects such as decreased sound absorption.

As a result of extensive research into the characteristics of carbon black that can improve the fatigue resistance of compounded rubber without such side effects, the inventor found that the Stokes mode diameter (ht) of carbon black fabric is in the range of 13 on- or more. It has been clarified that, even in the case of low heat, fatigue resistance can be effectively improved by changing the design of other characteristics without degrading reliability performance such as heat generation.

The present invention was developed based on this knowledge, and its purpose is to improve fatigue resistance and heat generation resistance by blending carbon black with an optimal property range for target rubber components such as natural rubber or diene-based synthetic rubber. Our goal is to provide a rubber composition that has excellent properties such as:

[Means to solve the problem]

To achieve the above object, the rubber composition according to the present invention contains 20 parts by weight of carbon black having the following selective properties per 100 parts by weight of natural rubber or diene synthetic rubber.
100 parts by weight is considered as a structural vf characteristic.

(1) Nz SA≦60m2/g (2) DB P≦100ml/100g (3) 1
30nm≦DSL≧220nm (4) △Ds t/[
)s t≦0.95, where N2SA is the nitrogen adsorption specific surface area, DBP is the DBP oil absorption, Dst is the Stokes mode diameter of the carpon blank fabrigate, and ΔDsL is the half width of the Stokes mode diameter.

Each characteristic of carbon black applied to the present invention is determined by the following measurement method.

(1) N2SA ASTM D 3037-86 “5 standard
TestMethod for Carbon Bl
ack-5surface Area by Nitro
genAdsorptron"Method B.The N2SA value of IRB#5 measured by this method is
80.3m” 7g.

(2) DBP JIS K 6221 (1975) rTesting method for carbon black for rubber" Section 6.1.2, according to oil absorption method A.

(3) Dst, ΔDst 20% dry carbon black containing a small amount of surfactant
Mix with ethanol aqueous solution to carbon black concentration 5 (
lsg/j! Prepare a dispersion liquid and use ultrasonic waves to sufficiently disperse it and use it as a sample. Disk centrifugation device (manufactured by Joyes Lab 1, UK) at 8000 rpm
Set the rotation speed to +i, add 10 d of spin liquid (2% aqueous glycerin solution), and then inject 1 d of buffer solution (aqueous ethanol solution). Next, after adding 0.5 d of sample with a syringe, centrifugal sedimentation is started, and at the same time, a recorder is operated to optically create a distribution curve of the Stokes equivalent diameter of the aggregate. The Stokes mode diameter of the maximum frequency in the obtained distribution curve is () s t (nm), and the difference (half width) between the two large and small points where a frequency of 50% of the maximum frequency is obtained is ΔD
Let s t (++m). AS by this measurement method
TM D24 °“5 standard Refer
nce Black C-3 (N-234)'' [)s
t is 80n, and ΔDst is 60mm.

Among the carbon black characteristic items specified in the present invention, N
2 SA≦60+”/g and DBP≦100at/1
The range of 00g belongs to the soft characteristic range and is a prerequisite for imparting fatigue resistance to compounded rubber.

If this requirement is not met, no improvement in the fatigue resistance of compounded rubber can be expected; however, the condition where N2SA is less than 60 m''/g is an important characteristic factor for suppressing the heat build-up of rubber. Become.

130r+m≦[)st≦220nm and △Ds t
The colloidal property of /Qst≦0.95 is characterized by the Stokes mode diameter of the carbon black aggregate being located at a high level and being relatively small in the distribution with respect to the Stokes mode diameter, and meeting the above prerequisites. In addition, when these colloidal property requirements are satisfied at the same time, it becomes possible to impart good fatigue resistance to the compounded rubber without impairing other properties. When the fist is less than 130 nm, the fatigue resistance of the rubber is effectively improved, but at the same time it causes an increase in heat generation and a significant decrease in sound absorption properties in vibration damping applications. Moreover, if pst exceeds 220 nm, fatigue resistance will rapidly deteriorate, which is not preferable. Furthermore, ΔDst/
[) If the st ratio exceeds 0.95, homogeneous dispersion of the rubber components cannot be ensured, and improvement in fatigue resistance will not proceed smoothly.

Carbon Brass, which has the above characteristics, uses a wide-diameter cylindrical reactor with a drum-shaped constriction that slowly converges and expands, and performs high-temperature combustion using fuel oil and an appropriate oxidizing agent containing air or oxygen. It can be produced by a method of introducing an atomized stream of raw material oil into gas in two stages.

Highly aromatic heavy oil such as creosote oil or ethylene bottom oil is used as the feedstock oil, and a sufficient fine particle airflow is generated through the atomization injection nozzle to obtain a highly homogeneous mixture with the high temperature combustion gas. will be introduced.

The atomization injection nozzle is, for example, a double-tube structure having a water-cooled jacket and consisting of an outer cylinder nozzle that can move forward and backward in the direction of the furnace axis and a telescopic central cylinder nozzle that is inserted into the outer cylinder nozzle. It is attached to the reactor head separately. The feedstock oil is introduced in two stages along with atomizing air through the outer tube nozzle and the center tube nozzle, but the feedstock oil introduction position can be changed as appropriate by advancing and retracting the outer tube nozzle and expanding and contracting the center tube nozzle. .

Using the above device, carbon black with a desired Nz5A is produced by adjusting the ratio of the total amount of air supplied to the total amount of raw fuel oil introduced and the amount of reaction additives in the usual manner. 170% or less, and the flow velocity of combustion gas at the upstream feedstock oil introduction position is 6 (1 m/sec,
As described above, conventional coarse particle carbon black generation conditions (fuel oil combustion rate of 200% or more, combustion gas flow rate of 10
m/sec, hereafter, residence time of reaction product gas in the furnace 900
By setting conditions different from 1100 milliseconds), the colloidal properties specified in the present invention are imparted.

Carbon black having the above-mentioned selective properties is blended into natural rubber or diene-based synthetic rubber such as styrene-butadiene copolymer according to conventional methods. The blending ratio of carbon black is 20 to 1 part by weight per 100 parts by weight of the rubber component.
The rubber composition of the present invention is obtained by kneading the rubber composition with necessary components such as a vulcanizing agent, a vulcanization accelerator, an anti-aging agent, a vulcanization aid, a softener, and a plasticizer.

[For production]

When natural rubber or diene-based synthetic rubber is blended, the basic characteristics of carbon black to improve fatigue resistance are to increase Nt SA and increase DBP and PS.
t is designed to be low. However, N2SA is 6
If the Dst exceeds 0m"/g or if the Dst is below 130rv, the fatigue resistance of the compounded rubber will improve, but at the same time there will be side effects such as an increase in heat generation and a deterioration in sound absorption, and the overall rubber performance will deteriorate. The rubber composition according to the present invention contains carbon black that has specific colloidal properties related to NASA, DBP, and j5st, and the selective properties of the carbon black are natural rubber or diene-based. It functions effectively to impart excellent fatigue resistance to synthetic rubber without reducing other properties.

In particular, the Stokes mode diameter (Dst) of the aggregate is relatively high, and this Stokes mode diameter ([)
Carbon black having a distribution width (ΔOs t) smaller than st) by about 9 times and having colloidal properties within the above-mentioned range, when kneaded into a rubber component, aggregates are well separated from each other to form an extremely uniform dispersed structure.

The homogeneously dispersed compound structure not only has fewer defects, but also has the effect of equalizing the load on the rubber polymer molecular chains during fatigue, and through this effect, the fatigue resistance performance is effectively improved. It is converted into a rubber composition.

〔Example〕

Examples of the present invention will be described below in comparison with comparative examples.

Examples 1 to 3, Comparative Examples 1 to 4 (1) Manufacture of carbon black A combustion chamber (inner diameter 700 I
IIl, length 1000m+*) and inner diameter 250a+s,
It has a cylindrical structure lined with refractory bricks and is connected to a tapered reaction zone (length 9000 mm) that expands through a narrow diameter part with a length of 2001+a+, and is equipped with a tangential air supply port at the furnace head. In a reactor equipped with a door box and a quench nozzle that can be repositioned in the downstream region of the rear reaction chamber, a feedstock oil atomization injection nozzle with a double-tube nozzle structure runs from the head of the reactor along the central axis of the reactor. was inserted, and four combustion burners were installed coaxially around it. The raw material oil atomization injection nozzle was adjusted so that the upstream raw material oil introduction point (the jet hole of the outer cylinder nozzle) was located at the convergence region, and the downstream raw material oil introduction point was located at the narrow diameter region.

Carbon black meeting the property requirements of the present invention was produced using the above reactor.

Fuel oil has a specific gravity (15/4°C) of 0.903 and a viscosity (
CST 50°C) 16.1, residual coal content 5.4%, sulfur content 1.8%, and a flash point of 96°C. As feedstock oil, specific gravity (15/4°C) 2. 10, a benzene insoluble content of 0.03%, a correlation coefficient (BMCI) of 140, and a highly aromatic hydrocarbon oil having an initial boiling point of 103°C.

Table 1 shows the generation conditions applied, and Table 2 shows the characteristics of the carbon black obtained. In addition, Comparative Examples 1 to 4 in Table 2
The graph shows a conventional type of carbon black that falls outside the characteristic range of the present invention.

Table 1 (Table note) (1) Combustion gas flow velocity at the downstream feed oil introduction position.

Table 2 (2) Rubber composition Next, each carbon black in Table 2 was blended with natural rubber according to the blending ratio shown in Table 3.
A rubber composition was obtained by vulcanization for a minute.

Table 3 (wort) Comparative carbon blacks are all manufactured by Tokai Carbon■, 1) is [GEST SJ, 2) is [GEST S
OJ, 3) is ``Geest 3) IJ, 4) is ``Geest 3j.

(wort) (1) “Kikata Process x 140” [manufactured by Kyodo Oil ■].

(3) Rubber performance evaluation A rubber fatigue test and a heat generation test were conducted for each rubber composition obtained.

The fatigue test was conducted using a pre-fabricated Danher shape (length 78+
+n, thickness ;)mm, length of narrow part 25nua, width 4
A vulcanized specimen of mm) was repeatedly stretched using a Monsanto Fatigue tester at a stretching rate of 0 to 100%, a tensile cycle of 100 cycles/min, and at room temperature, and the number of times until breakage was reduced to 1. Each sample is measured 24 times, and the results are plotted on Weibull probability paper [Japanese Standards Association], which is widely used for life analysis, to calculate the mean life (MTTF: yaanti+Ie o
f failure) was calculated.

The heat generation test was performed according to ASTM D623-78, with a diameter of 0.
．． A 7 inch, 1.0 inch high cylindrical vulcanized test piece was set in an automatic Guntrich flexometer tester (manufactured by Ueshima Seisakusho), with a vibration frequency of 1800 rpm, a stroke of 0.225 inch, and a load of 311 b. , test temperature 5
The range of temperature rise (HB U (He
At Build Up)).

The measurement results obtained are shown in Table 4. In addition, Figure 1 shows the results of Table 4 in terms of mean service life (MTTF) and increase in heat generation (HBU).
), and Figure 2 shows the relationship between the N2SA of the blended carbon black and the mean life (MTTF).

Table 4 From the results shown in Table 4 and Figure 1, the rubber compositions of the Examples have better fatigue resistance per constant heat generation than those of the Comparative Examples. It is recognized that fatigue resistance is relatively high. Therefore, it is clear that in the present invention, fatigue resistance is improved while suppressing heat generation to a low level.

〔Effect of the invention〕

As described above, according to the present invention, a rubber composition is provided which has excellent fatigue resistance without deteriorating dynamic performance due to the unique function due to the selective characteristics of the blended carbon black.

Therefore, it is useful as a rubber composition for use in various industrial rubber products that require fatigue resistance.

Figure 1 Figure 2

[Brief explanation of the drawings] Fig. 1 is a correlation graph of heat generation increase width (HBU) and mean life (MTTF) of rubber compositions according to Examples and Comparative Examples.
Figure 2 shows the N2SA and mean life (MTT) of compounded carbon black in rubber compositions according to Examples and Comparative Examples.
F) is a correlation graph. N of blended carbon black! SA (I/g) June 21, 1990

Claims (1)

[Claims] 1. 20 parts by weight of carbon black having the following selective properties per 100 parts by weight of natural rubber or diene-based synthetic rubber.
A rubber composition characterized in that it contains 100 parts by weight. (1) N_2SA≦60m^2/g (2) DBP≦100ml/100g (3) 130nm≦@D@st≦220nm (4) ΔD
st/@D@st≦0.95 However, N_2SA is nitrogen adsorption specific surface area, DBP is DBP
The oil absorption amount, @D@st, is the Stokes mode diameter of the carbon black aggregate, and ΔDst is the half width of the Stokes mode diameter.