JP2001049028A - Carbon black for compounding in rubber for functional parts and the rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbon black for compounding in rubber for functional parts, which is able to impart a high level of a permanent set in fatigue to a compound rubber and also impart a high heat generation property to the rubber when subjected to UHF vulcanization, and thus, can be well-balanced in the both characteristics, and a rubber composition for functional parts compounded with the carbon black. SOLUTION: The carbon black for compounding in rubber for functional parts has such characteristics that a CTAB specific surface area ranges from 20 to 40 m2/g, an electric resistivity is 0.3 Ω.cm or below when compressed under a pressure of 50 kg/cm2, and a toluene discoloration transmittance (LT) of 95% or over. The rubber composition for functional parts comprises 20 to 200 pts.wt. of the carbon black in 100 pts.wt. of natural rubber, synthetic rubber or a blend thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to door packing materials and window frame sealing materials for automobile interiors, belts,
The present invention relates to carbon black blended in rubber for functional parts such as hoses, and a rubber composition for functional parts blended with this carbon black.

[0002]

2. Description of the Related Art There are various varieties of carbon black for rubber reinforcement depending on their characteristics, and the characteristics of these varieties are the main factors for determining various characteristics of a composition blended with rubber. In the case of compounding with rubber, usually, means for selecting and using carbon black having a variety of characteristics suitable for the purpose of the member is used. For example, as a carbon black compounded in rubber for functional parts, conventionally, SRF
Soft carbon black having a large particle size, such as carbon black and GPF, is useful.

[0003] Rubber members for functional parts such as door packing materials and window frame sealing materials for automobile interiors are required to be used stably for a long period of time, and therefore have high sag resistance and fatigue resistance. It is necessary to have excellent durability. For this reason, studies are being actively conducted to improve the sag resistance and fatigue resistance of these rubber members for functional components by using the colloidal properties of carbon black.

[0004] For example, the present applicant has reported that the mode diameter (Dst) measured by the centrifugal sedimentation method (DCF method) of aggregates is 15 or less.
0 nm or more, the mode diameter (Dst) and its half-value width (ΔDs)
t) (Dst / Dst) is 1.50 or more, and the ratio (B / T) between the coloring power (T) and the blackness (B) is 1.2.
A carbon black for compounding functional parts rubber having a characteristic of 0 or more (Japanese Patent Laid-Open No. 3-14848), a nitrogen adsorption specific surface area (N ₂ SA) of 45 to 65 m ² / g, and a DBP oil absorption (D ₀ ). the ratio of the compression DBP absorption _{(D 1) (D 0 /} D 1) is in the range of 1.10 to 1.20, and the DBP oil absorption amount (D ₀₎ satisfies the property requirements of 60~80ml / 100g A carbon black for compounding functional parts rubber (Japanese Patent Laid-Open No. 8-143784) and the like, which are characterized by this, have been developed and proposed.

However, in recent years, high-frequency (UHF) vulcanization (hereinafter, also referred to as “UHF vulcanization”) has been adopted to improve productivity.
Not only is the sag property small, but also it is necessary to shorten the UHF vulcanization time, that is, to excel in heat generation by high-frequency induction current. The heat generation effect by high frequency is increased by reducing the particle size of the carbon black, but the sag resistance decreases, so that sag resistance and U
It is difficult to achieve both high heat build-up during HF vulcanization.

For the purpose of improving the delay of the vulcanization time in UHF vulcanization, JP-A-6-145554 discloses a DBP oil absorption (DBPA) of 110 to 140 ml / 100.
g, a carbon black having an iodine adsorption amount (IA) of more than 25 mg / g and less than 35 mg / g,
Ratio of nitrogen adsorption specific surface area (N ₂ SA) to IA, N ₂ SA
/ IA is 0.85 to 1.00, the most frequent value (Dst) of the Stokes equivalent diameter by centrifugal sedimentation analysis is larger than the formula, and the coloring power is smaller than the formula. I have. Dst ≧ (DBPA) −7.5 (IA) +405 Coloring power ≦ IA + 20

[0007]

SUMMARY OF THE INVENTION The present inventors have developed a carbon black having a high sag resistance and an excellent exothermic effect in UHF vulcanization from a viewpoint different from the above-mentioned JP-A-6-145554. Research on carbon black, and found that the specific surface area and surface properties of carbon black had a significant effect.

The present invention has been developed on the basis of this finding, and its purpose is to provide a compound rubber with a high level of sag resistance as a rubber member for a functional component and to have a high heat buildup during UHF vulcanization. It is an object of the present invention to provide a carbon black which is high and can achieve both of the characteristics at a high level, and a rubber composition for functional parts which contains the carbon black.

[0009]

The carbon black for compounding a functional component rubber according to the present invention for achieving the above object has a CTAB specific surface area of 20 to 40 m ² / g and a pressure of 50 kg / cm ² when compressed. Is characterized by having an electrical resistivity of 0.3 Ω · cm or less and a toluene coloring transmittance (LT) of 95% or more.

Further, the rubber composition for functional parts of the present invention comprises:
Natural rubber, synthetic rubber, or blended rubber of these 10
0 parts by weight of carbon black having the above characteristics
It is characterized in that it is blended in an amount of 0 to 200 parts by weight.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Among the characteristic requirements of the carbon black of the present invention, the CTAB specific surface area is a characteristic factor which is a prerequisite for a particle size range for maintaining a high level of settability of a compounded rubber, If this value exceeds 40 m ² / g, the deterioration of the settability becomes remarkable. On the other hand, if it is less than 20 m ² / g, even if the surface properties are modified, the heat generation during UHF vulcanization is reduced, making it difficult to shorten the vulcanization time.

The electrical resistivity is an index indicating the conductivity of the carbon black itself, and is a property related to the heat generation during the UHF vulcanization, that is, a property related to the resistance heating property due to the induced current. And the UHF vulcanization time cannot be shortened. Accordingly, the present invention aims to improve the heat generation performance during the UHF vulcanization by setting the value of the electric resistivity when compressed at a pressure of 50 kg / cm ² to 0.3 Ω · cm or less as the electric resistivity. Things.

The toluene coloring transmittance (LT) indicates the degree of the amount of undecomposed hydrocarbon remaining on the surface of the carbon black particles. The smaller the amount of undecomposed hydrocarbon remaining, the more the value of the toluene coloring transmittance (LT) becomes. growing. The remaining undecomposed hydrocarbon is a substance that inhibits the conductivity of carbon black, and the present invention sets the value of toluene coloring transmittance (LT) at 95% to regulate the amount of undecomposed hydrocarbon that inhibits the conductivity. The above is set. As a result, the resistance to heat generation of the unvulcanized rubber composition is increased, and the heat generation performance during UHF vulcanization is improved, that is, the vulcanization time is shortened.

As described above, the carbon black for compounding functional component rubber of the present invention has a CTAB specific surface area, an electric specific resistance,
And by specifying the toluene coloring transmittance (LT), these characteristics can function comprehensively to give a high degree of sag resistance to the compounded rubber and to improve the conductivity of the unvulcanized rubber composition. Is maintained high to improve the conductivity and heat generation, and effectively functions to shorten the UHF vulcanization time.

The values obtained by the following measuring methods are used for the respective characteristics of the carbon black in the above configuration. CTAB specific surface area (m ² / g); ASTM D3765-80
“Standard Test Methods for Carbon Black-CTAB (CET
YL TRIMETHYL AMMONIUM BROMIDE) Surface Area ”. Electrical resistivity (Ω · cm); According to JIS K1469-84“ Acetylene black ”Section 5.6. Toluene color transmittance (%): JIS K6221-82 “Test method for carbon black for rubber” Refer to section 6.2.4.

The carbon black of the present invention is prepared by using a large-diameter cylindrical reactor having a drum-shaped constriction part that gradually converges and opens, and a high-temperature combustion gas containing fuel oil and an appropriate oxidant containing air or oxygen. It is produced by introducing an atomizing gas stream of a feedstock oil into two stages.

High aromatic heavy oils such as creosote oil, FCC oil, ethylene bottom oil and the like are used as the raw material oil. And introduce a sufficient fine particle current. The atomization injection nozzle has, for example, a water-cooled jacket, and has a double-cylinder structure including an outer cylinder nozzle that can expand and contract in the furnace axis direction and an extendable middle cylinder nozzle that is attached to the outer cylinder nozzle. Separately attached to the furnace head. The base oil is introduced in two stages through the outer cylinder nozzle and the center cylinder nozzle together with the atomized air, but the position of the base oil introduction at this time can be changed by advancing / retracting of the outer cylinder nozzle and expansion / contraction of the center axis nozzle. . The carbon black of the present invention uses the above device,
It can be manufactured by controlling the amount of supplied air and fuel oil, the divisional introduction point of the feed oil, the residence time of the carbon black product gas flow in the furnace, and the like.

The rubber composition for functional parts of the present invention is obtained by blending carbon black having the above-mentioned properties in a proportion of 20 to 200 parts by weight with respect to 100 parts by weight of the rubber component. As the rubber component, natural rubber, styrene-butadiene rubber, polybutadiene rubber, isoprene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, ethylene-propylene rubber, other general-purpose synthetic rubbers that can be reinforced by carbon black, or a blend of them is used. Rubber is exemplified.

The rubber composition comprises a carbon black, a vulcanizing agent, a vulcanization accelerator,
It is blended with necessary components such as a vulcanization aid, an antioxidant, a softener, and a plasticizer, and is kneaded and vulcanized to obtain a desired rubber composition for a functional component.

[0020]

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

Examples 1 to 3 and Comparative Examples 1 to 5 (1) Production of carbon black; a wind box provided with a tangential air supply port at the furnace head and a combustion chamber (inner diameter 700 mm , Length 1200mm)
Narrow diameter part coaxially connected to the combustion chamber (inner diameter 400mm, length
200 mm) and a tapered reaction chamber (inner diameter 900 mm, length 9000 mm) that expands continuously from the furnace head, along with the furnace center axis from the furnace head along the furnace axis. The nozzle was inserted, and four combustion burners were set around the nozzle. The feedstock injection nozzle is located at the point where the upstream feedstock introduction point (outlet of the outer cylinder nozzle) converges.
The downstream feedstock introduction points were adjusted so as to be located at the narrow diameter portions.

Using the above-described oil furnace, carbon black was produced using the raw material oil and fuel oil having the properties shown in Table 1 and applying the generation conditions shown in Table 2. The properties of the obtained carbon black were measured, and the results are also shown in Table 2.

[0023]

[Table 1]

[0024]

[Table 2]

(2) Preparation of rubber composition: Each of these carbon black samples was compounded in EPDM rubber at the compounding ratio shown in Table 3. The amount of carbon black was varied so that the hardness (JIS) of the compounded rubber was 70.

[0026]

[Table 3]

(3) Measurement of physical properties of rubber: The compound was vulcanized at a temperature of 150 ° C. for 30 minutes, and the physical properties of each obtained rubber composition were measured according to JIS K6301 “Vulcanized rubber physical test method”. . In addition, the measurement of the exothermic property at the time of UHF vulcanization and the compression set was based on the following.

Evaluation of exothermicity during UHF vulcanization Using an unvulcanized rubber compound as a test piece, QMETER (4342A) manufactured by Yokogawa-Hewlett-Packard Co., Ltd., frequency: 20 MHz, temperature: The dielectric constant (ε) and the loss coefficient (D) were measured at room temperature. The exothermicity during UHF vulcanization can be evaluated using the value of dielectric constant (ε) × loss coefficient (D) as an index. The larger the value, the higher the exothermicity during UHF vulcanization, and the shorter the time, UHF vulcanization can be performed. Measurement of compression set (%) According to JIS K6301 “Vulcanized rubber physical test method”, 7
The measurement was performed at 0 ° C. for 70 hours. In addition, it shows that sag resistance is so high that this value is small.

Rubber properties measured and dielectric constant (ε) ×
Table 4 shows the calculated values of the loss coefficient (D). Also, among the measurement results, a compression set as an index of sag resistance (drag resistance capable of withstanding a permanent strain phenomenon generated when repeated stress is applied) and an index of heat generation characteristics during UHF vulcanization. FIG. 1 is a graph showing the relationship between the dielectric constant (ε) × loss coefficient (D) value.
It was shown to.

[0030]

[Table 4]

From Table 4 and FIG. 1, the rubber compositions of Examples 1 to 3 in which carbon blacks satisfying all the characteristic requirements of the present invention were blended were compared with those of the rubber compositions in which at least one of the characteristic requirements of the present invention was excluded. Compared to the rubber compositions of Examples 1 to 5, compression set, which is an index of sag resistance, is an index of heat generation characteristics during UHF vulcanization (dielectric constant ε
× Loss coefficient D) value is high, and it can be seen that sag resistance and exothermicity during UHF vulcanization are both compatible at a high level.

That is, in Comparative Example 1, the heat generation during the UHF vulcanization was low because of the high electrical resistivity, and in Comparative Example 2, the heat generation during the UHF vulcanization was similarly low because the toluene coloring transmittance (LT) was low. It is lower. Further, Comparative Example 3 having a low CTAB specific surface area and a low LT also shows a decrease in the compression set (dielectric constant ε).
× Loss coefficient D) value is low, and it is recognized that heat generation during UHF vulcanization is inferior. Similarly, in Comparative Examples 4 and 5, the value of (permittivity ε × loss coefficient D) per constant compression set is low, and compatibility between sag resistance and heat generation during UHF vulcanization may be insufficient. I understand.

[0033]

As described above, according to the carbon black for compounding functional component rubber and the rubber composition containing the carbon black of the present invention, the compounded rubber is imparted with a high level of sag resistance and is cured by UHF vulcanization. Excellent heat generation performance at the time,
Both characteristics can be compatible. That is, the rubber member for a functional component has excellent sag resistance and has high heat generation during vulcanization of UHF, so that the vulcanization time can be shortened and productivity can be improved. Therefore, it is extremely useful as a carbon black compounded in rubber for functional parts such as belts and hoses, such as door packing materials and window frame sealing materials for automobile interiors, and as a rubber composition for functional parts.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a permanent compression set and a value of (dielectric constant ε × loss coefficient D) according to an example and a comparative example.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 AC011 AC031 AC061 AC071 AC081 AC091 BB151 DA036 FD016 GJ02 4J037 AA02 CC06 DD07 DD12 EE28 EE48 FF02 FF05 FF11 FF17

Claims (2)

[Claims] (1) a CTAB specific surface area of 20 to 40 m ² / g;
The electrical resistivity when compressed at a pressure of 0 kg / cm ² is 0.3Ω.
cm. A carbon black for compounding functional parts rubber having a characteristic of having a toluene color transmittance (LT) of 95% or more, which is not more than 95 cm. 2. A rubber composition for a functional component, comprising 20 to 200 parts by weight of the carbon black according to claim 1 in 100 parts by weight of a natural rubber, a synthetic rubber, or a blend rubber thereof.