JPH0418439A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition having remarkably improved fatigue resistance by blending a chloroprene rubber with uniformly colloidal carbon black having selective properties. CONSTITUTION:The aimed composition obtained by blending (A) 100 pts.wt. chloroprene rubber with (B) 20-100 pts.wt. carbon black having selective characteristics expressed by formula I to formula III (N2SA is specific surface area of nitrogen adsorption; Dst is stokes mode diameter of carbon black aggregate; Dst is half value width of the above-mentioned stokes mode diameter) and obtained by controlling conditions such as ratio of feed air and fuel oil feed amount and fuel oil combustion in a method introducing atomizing stream of raw material oil into high-temperature combustion gas by fuel oil and an 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 curing agent, curing accelerator, aging agent, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rubber composition with improved fatigue resistance, and more particularly, to a rubber composition comprising chloroprene rubber blended with selected carbon black having uniform colloidal properties. The present invention relates to a fatigue-resistant rubber composition.

[Conventional technology]

Among industrial rubber products, rubber materials used for various vibration isolators, seal members, hoses, belts, 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, Japanese Patent Application Laid-Open No. 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 cementola;
A fatigue resistant rubber composition formed by a wet carbon master bunch process of coagulation is disclosed. However, there is a limit to the degree of improvement in fatigue resistance when compounding carbon flank rubber with fine grids removed, and in the case of chloroprene rubber, the nitrogen adsorption specific surface area of carbon black (N
When the ASA) exceeds 60 m''/g, the fatigue resistance deteriorates significantly even if the fine grids are removed. JP-A-61-29
In the invention of Publication No. 0255, 1 to 20 parts by weight of a metal oxide vulcanizing agent, 5 to 30 parts by weight of silica, 1115 to 50 parts by weight of reinforcing filler such as carbon black, and bismaleimide are added to 100 parts by weight of chloroprene rubber. Although carbon black is blended with 2 to 10 parts by weight to extend the life of the rubber belt, no consideration has been given to the characteristics of carbon black, so the causal relationship between its colloidal properties and the fatigue resistance of the compounded rubber has not been elucidated. On the other hand, Japanese Patent Application Laid-Open No. 62-57438 states that the arithmetic mean diameter (Dn): 2211,! /≦Dn≦3
811μ, aggregate diameter (0st): 60 Ta1l≦
(1st≦130Ilμ, standard deviation S of summer mean diameter distribution
(mμ): [3)≦0.333
) +45.0, aggregate strength: ΔDBP = DB
P-24M40BP (mffi/100g)≦1
oaf/100g, NzSA(m”/g)/IA(
A rubber composition having compounding ease and heat resistance is disclosed in which 20 to 100 parts by weight of carbon blank having colloidal properties (sg/g) ≧1.08 is blended into the rubber component. However, the rubber component targeted by this invention is natural rubber or diene-based synthetic rubber, and chloroprene rubber has not been studied. The anti-vibration rubber composition described in JP-A No. 64-9250 is composed of vulcanizable rubber 1
A reinforced rubber composition in which 00 parts by weight is combined with 5 to 100 parts by weight of polyamide fine short fibers, carbon black and vulcanizable rubber in a specific range of ratios, and the purpose is to improve fracture strength and fatigue properties. However, the characteristics of the blended carbon black have not been studied. 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. However, chloroprene rubber has not been targeted for improvement, and the characteristics of compounded carbon black have not been examined. Furthermore, JP-A-1-14
The invention of No. 6934 discloses a specific butadiene-based polymer,
The subject matter is a vibration-proof rubber composition containing natural rubber and/or high-cis isoprene rubber and carbon black. Therefore, the characteristics of the polymer composition! However, the properties of the blended carbon black are not considered.

[Problem to be solved by the invention]

As described above, in the conventional techniques aimed at improving rubber fatigue properties, there are no examples of improving the fatigue properties of compounded rubber from the colloidal characteristics of carbon black, except for the invention disclosed in JP-A-62-57438. Not found.

Furthermore, as mentioned above, the target rubber component of the invention of JP-A No. 62-57438 is natural rubber or diene-based synthetic rubber, and no study has been conducted on chloroprene rubber. According to the research conducted by the present inventor, it has been confirmed that when using chloroprene rubber, fatigue resistance cannot be effectively improved when the fist is ≦130!1μ as specified in the invention of JP-A-6257438. There is. Therefore, natural rubber or diene-based synthetic rubber and chloroprene rubber differ greatly in the design direction of carbon black properties for improving fatigue resistance.

The object of the present invention is to provide a rubber composition having excellent fatigue resistance, in which the target rubber component is chloroprene rubber, and in this case, carbon black having optimal colloidal properties is blended.

[Means for Solving the Problems] A rubber composition according to the present invention for achieving the above-mentioned object contains 20 to 100 parts by weight of carbon blank having the following selective properties to 100 parts by weight of chloroprene rubber. The structural feature is that

(1) NzSA (m”/g)≦60(2)
D S t (nm)≧130 (3n △ Ds
t/pst≦0, 95, where N2SA is the nitrogen adsorption specific surface area, fist is the Stokes mode diameter of the carbon blank fabrigate, and ΔDst is the half width of the Stokes mode diameter.

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

(1) N, SA ASTM D3037-86'Standard
TestMethod for Carbon Bla
ck-Surface Area by Nitrog
The N25A value of IRB#5 measured using this method is
80.3n+”/g.

(2) t5st, △Dst 20% dry carbon black containing a small amount of surfactant
Carbon black concentration is 50 by mixing with ethanol aqueous solution.
mg/j! Prepare a dispersion liquid and use ultrasonic waves to sufficiently disperse it and use it as a sample. A disk centrifugation device (manufactured by Joyes Lobe1, UK) was installed at 800 rpm.
After adding a spin solution (2% glycerin aqueous solution) for 10 d, the IMl buffer solution (ethanol aqueous solution) was injected. 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. Let the Stokes mode diameter of the maximum frequency in the obtained distribution curve be D S t (nm), and 5 of the maximum frequency
△D is the difference (half width) between two large and small points that give a frequency of 0%.
Let s t (nm). ASTM according to this measurement method
D24 “5 standard Reference
Black C-3 (N-234)'' jest is 80n+m, and ΔDst is 60n-.

Among the carbon blank characteristic items specified in the present invention,
The range of N2SA (ig"/g)≦60 belongs to the soft region and is a prerequisite for imparting fatigue resistance to compounded chloroprene rubber.N2SA of 60va"7
If it exceeds g, no improvement in fatigue resistance can be expected, and heat generation increases, leading to heat aging of the rubber.

D S t (nm)≧130 and △Dst/Dst
The colloidal property of ≦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. When these colloidal property requirements are simultaneously satisfied, good fatigue resistance is imparted to the blended chloroprene rubber.

The effect of improving fatigue resistance becomes greater when Nz5A is smaller and [
) The larger st is, the more remarkable the improvement tendency is.

Carbon blanks with the above characteristics are produced using a wide-diameter cylindrical reactor with a drum-shaped constriction that slowly converges and expands.
It can be produced by a method in which an atomized air stream of feedstock oil is introduced in two stages into high-temperature combustion gas of fuel oil and an appropriate oxidizing agent containing air or oxygen.

Highly aromatic heavy oils such as taleosote oil and ethylene bottom oil are used as feedstock oils, and are injected in a state of sufficient particulate airflow through an atomizing injection nozzle to obtain highly homogeneous mixing with high-temperature combustion gases. Introduce.

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 the desired N2SA is produced by adjusting the ratio of the total amount of supplied air to the total amount of raw fuel oil introduced and the amount of reaction additives in the usual manner. rate is 170% or less, and the flow velocity of combustion gas at the upstream feedstock oil introduction position is 60 m/sec.
As mentioned above, the conventional coarse particle carbon blank production conditions (fuel oil combustion rate of 200% or more, combustion gas flow rate L
ow/sec, hereafter, residence time of reaction product gas in the furnace 90
By setting conditions different from 0 to 1100 milliseconds), the colloidal characteristics specified in the present invention are imparted.

A carbon blank having the above-mentioned selective properties is blended into chloroprene rubber according to a conventional method. The target chloroprene rubber can be either sulfur-modified or non-sulfur-modified. The blending ratio of carbon blank is in the range of 20 to 100 parts by weight per 100 parts by weight of the chloroprene rubber component, and contains vulcanizing agents, vulcanization accelerators, anti-aging agents, vulcanization aids, softeners, plasticizers, etc. The rubber composition of the present invention is obtained by kneading with necessary components.

[For production]

The rubber composition according to the present invention has N! In addition to a low surface area property with an SA of 60-278 or less, carbon black is blended that also has 1) colloidal properties with an st of 130 nm or more and a ΔDst/pst ratio of 0.95 or less, and the selective properties of the carbon black functions effectively to impart excellent fatigue resistance to chloroprene rubber.

In particular, the Stokes mode diameter (Ost) of the aggregate is relatively high, and this Stokes mode diameter (fi
Carbon black having a relatively small distribution width (ΔOs t) with respect to st) and having the above-mentioned colloidal property range, when kneaded with chloroprene rubber, aggregates are well separated from each other to form an extremely uniform dispersed structure. The homogeneous and 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.
Through such effects, a rubber composition with effectively improved fatigue resistance can be obtained.

(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) Production of carbon black A combustion chamber (inner diameter 700 m
5. It has a cylindrical structure lined with refractory bricks with a length of 100,100 mm, an inner diameter of 250 mm, an inner diameter of 250 mm, and a length of 200 mm. In a reactor equipped with a wind box equipped with a tangential air supply port and a quench nozzle that can be repositioned in the downstream region of the rear reaction chamber, a double-tube nozzle structure is installed from the furnace head along the central axis of the furnace. A feedstock oil atomization injection nozzle was inserted, and four combustion burners were coaxially installed around it.The feedstock oil atomization injection nozzle was installed at the feedstock oil introduction point on the upstream side (output hole of the outer cylinder nozzle). The feedstock oil introduction point on the downstream side was adjusted so that it was located at the convergent portion, and the downstream feedstock oil introduction point was located at the narrow diameter portion.

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

Fuel oil has a specific gravity (15/4℃) of 0.903 and a viscosity (C
5T 50"C) 16.1, residual coal content 5.4%, sulfur content 1.8%, flash point 96°C hydrocarbon oil, as feedstock oil, specific gravity (15/4°C) 2 .10, benzene insoluble content 0.03%, correlation coefficient (B!IcI) 140,
A highly aromatic hydrocarbon oil with an initial boiling point of 103°C was used.

Table 1 shows the native conditions applied, and Table 2 shows the properties 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 (Wort) (1) Combustion gas flow rate at the downstream feedstock oil introduction position.

(2) Residence time of generated carbon black-containing gas to water cooling point.

Table 2 Table 3 (wort) Comparative examples All carbon blacks were manufactured by Tokai Carbon■, 1) is "Geast S J, 2) is "Geast SOJ, 3) is [Geast 3HJ], 4) is "Geast 3" It is.

(2) Rubber compounding Next, each carbon black in Table 2 was compounded with chloroprene rubber in the compounding ratio shown in Table 3, and the compound was vulcanized at a temperature of 145°C for 35 minutes to obtain a rubber composition ( Wort) (1)
“Neobrene W” [manufactured by Showa Denko/Dupont ■].

(2) “Accelerator 22-S” [Uro Kagaku Kogyo ■
Made].

(3) "Crack CD" (manufactured by Ouchi Shinko Kagaku Kogyo IJ-).

(3) Fatigue test A rubber fatigue test was performed on each rubber composition obtained,
The results are shown in Table 4.

The fatigue test was conducted using a pre-fabricated Danher shape (length 7 hm).
, Thickness 2-1 Narrow part length 25m+m, Radius 4IIl
The vulcanized specimen of ll) was repeatedly stretched using a Monsanto Fatigue tester at an elongation 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 1 Japanese Standards Association, which is widely used for life analysis, to calculate the mean life (TTF).
The number of failures was calculated.

Table 4 From the results in Table 4, each of the rubber compositions according to Examples shows a high degree of fatigue resistance, but the rubber compositions of Comparative Examples that do not meet any of the requirements of the carbon flank properties of the present invention do not meet the requirements of Examples. It is recognized that the fatigue resistance is significantly inferior compared to the above.

C. Effects of the Invention As described above, the rubber composition provided by the present invention has the selective characteristics of the blended carbon black, especially the uniform colloidal properties, and has improved performance compared to conventional carbon black blends of the equivalent particle size. It has significantly improved fatigue resistance.

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

Applicant: Tokai Carbon Co., Ltd. Agent: Patent Attorney Masaya Takahata

Claims (1)

[Scope of Claims] 1. A rubber composition comprising 20 to 100 parts by weight of carbon black having the following selective properties to 100 parts by weight of chloroprene rubber. (1) N_2SA (m^2/g)≦60 (2) @D@st (nm)≧130 (3) ΔDst/@D@st≦0.95 However, N_2SA is nitrogen adsorption specific surface area, @D@ st is the Stokes mode diameter of carbon black aggregate, Δ
Dst refers to the half width of the Stokes mode diameter.