JP2013166899A - Soft furnace carbon black and rubber composition compounded therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide soft furnace carbon black achieving improvement in break of ribbon, bite-into properties of ribbon and retention of extruded profile, while keeping various characteristics described in prior inventions, when compounded into rubber; and a rubber composition compounded therewith.SOLUTION: A soft furnace black has following characteristics: 35-50 m/g N2SA; 100-130 mL/100 g DBPA; 80% or more toluene tinting transmittance, the modal Stokes diameter (Dmode) of aggregate size obtained by centrifugal settling method satisfies a relation expressed by formula (1): Dmode≤{(DBPA)-(IA)}+78 [in formula, (IA) is adsorption amount of iodine], being in a range of 100-200 nm, and an aggregate size distribution index (X) expressed by formula (a) is in a range of 0.68-0.72 (in formula, ΔD-50 expresses a half value of width in the aggregate size distribution).

Description

  The present invention relates to a soft furnace carbon black and a rubber composition containing the same.

Carbon black is categorized according to the main application characteristics of rubber compounding, that is, processability and reinforcement. The main soft carbon blacks are semi-reinforcing furnace carbon black (SRF) and general-purpose furnace carbon. There are black (GPF), good extrudability furnace carbon black (FEF), and the like.
The above-mentioned expression “soft type” is derived from giving a soft rubber composition at the time of rubber compounding, good workability at the time of rubber compounding, low exothermic property of the compound, and large amount compounding is possible. And is widely used as a filling reinforcing agent for rubber members such as tire carcass, tube, belt, sheet material, weather strip and the like.
On the other hand, there are “hard” carbon blacks, that is, carbon blacks that give a hard rubber composition when blended with rubber, and the main hard carbon blacks are super wear-resistant furnace carbon black (SAF), quasi-super wear resistance Furnace Carbon Black (ISAF) and High Wear Resistance Furnace Carbon Black (HAF) are used for tire tread rubber compounds and various belts.

By the way, as basic characteristics of carbon black, specific surface area evaluated by iodine adsorption amount (IA), nitrogen adsorption specific surface area (N2SA), etc., and connection of carbon black particles evaluated by dibutyl phthalate oil absorption amount (DBPA), etc. Although it is well known that there is a higher-order structure (structure), it has been widely recognized that the evaluation of imparting properties of carbon black to rubber is impossible only with the above two properties. It is difficult to control the rubber characteristics only by the characteristics.
In view of such a situation, the present inventor conducted centrifugal sedimentation analysis on furnace carbon black having characteristics of iodine adsorption amount (IA) of 15 to 25 mg / g and dibutyl phthalate oil absorption (DBPA) of 100 to 150 mL / 100 g. A soft furnace carbon in which the most frequent value of the Stokes equivalent diameter (Dst: corresponding to JIS notation “Dmode” in the definition of the present invention) is larger than the calculated value of the following formula 1 and the coloring power is smaller than the following formula 2. Black was proposed (see Patent Document 1).
Formula 1 Dst ≧ (DBPA) −7.5 × (IA) +350
Formula 2 Coloring power ≦ (IA) +25

This carbon black has the effect of improving the properties such as rebound resilience and compression set, as well as improving the poor dispersion when a large amount of carbon black is blended with rubber and the deterioration of the extrusion characteristics of the rubber compound. However, since the range of iodine adsorption is on the lower side than that of conventional carbon black, the reinforcing property, particularly the tensile property, tends to be lowered.

In order to remedy this drawback, the inventor has an iodine adsorption amount (IA) of 35 to 50 mg / g, a dibutyl phthalate oil absorption (DBPA) in the range of more than 120 mL / 100 g and less than 140 mL / 100 g, and ΔDBPA (DBPA-24M4DBPA) is in the range of more than 40 mL / 100 g and less than 50 mL / 100 g, and the most frequent value (Dst) of the Stokes equivalent diameter of the carbon black aggregate by centrifugal sedimentation analysis.
Dst ≧ {(DBPA) ² − (IA) ² } ^1/2 +80 (1)
A soft furnace carbon black having a surface area larger than that of the carbon black disclosed in Patent Document 1 is proposed (see Patent Document 2). According to this carbon black, the dispersibility in the rubber composition can be remarkably improved, and excellent rebound resilience and compression set characteristics can be imparted to the rubber composition.
However, these high-structure carbon blacks have a problem in that the extrusion characteristics are lowered due to the increase in Mooney viscosity of the compounded rubber, and the breaking elongation characteristics of the vulcanized rubber are lowered.
Therefore, there is an urgent need for a carbon black capable of further improving the extrusion characteristics of the rubber compound while maintaining the characteristics achieved by the prior inventions according to the above Patent Documents 1 and 2. It was.

JP-A-2-11664 JP-A-3-227375

  The present invention is a soft furnace carbon black capable of preventing ribbon breakage and improving the bite of the ribbon while maintaining the various properties (dispersibility, reinforcement) of the invention of the prior application when blended with rubber, and It aims at providing the rubber composition which mix | blended this.

（式中、ΔＤ−５０は、アグリゲートサイズ分布の半値幅を表す。）
２） 天然ゴム及び／又は合成ゴムに、１）記載のソフト系ファーネスカーボンブラックを配合したことを特徴とするゴム組成物。 The above problems are solved by the following inventions 1) to 2).
1) In a soft furnace carbon black having basic characteristics such as a nitrogen adsorption specific surface area (N2SA) of 35 to 50 m ² / g, a dibutyl phthalate oil absorption (DBPA) of 100 to 130 mL / 100 g, and a toluene color permeability of 80% or more. The most frequent Stokes diameter (Dmode) of the aggregate size obtained by the centrifugal sedimentation method satisfies the relationship represented by the following formula (1) and is in the range of 100 to 200 nm [(IA) in the formula is iodine adsorption) amount〕,
Dmode ≦ {(DBPA) ² − (IA) ² } ^1/2 +78 (1)
A soft furnace carbon black having an aggregate size distribution index (X) represented by the following formula (a) in the range of 0.68 to 0.72.

(In the formula, ΔD-50 represents the full width at half maximum of the aggregate size distribution.)
2) A rubber composition comprising the natural furnace and / or synthetic rubber and the soft furnace carbon black described in 1).

  According to the present invention, the extrusion characteristics, which are the advantages of the conventional FEF, can be further improved without deteriorating the physical properties of the rubber. In addition, it is possible to provide a soft furnace carbon black capable of preventing ribbon breakage and improving ribbon biteability while maintaining the reinforcing property, and a rubber composition containing the same.

The longitudinal cross-sectional view which shows an example of the manufacturing furnace suitable for manufacture of the carbon black of this invention. FIG. 2 is a partially enlarged vertical cross-sectional view of the top portion of FIG. 1.

（式中、ΔＤ−５０は、アグリゲートサイズ分布の半値幅を表す。）
上記カーボンブラックをゴムに配合した場合、従来のＦＥＦと比べて、ゴム物性を維持しつつ、リボン切れの防止やリボンの食い込み性の向上、押出形状の保持性の向上を実現できる。 Hereinafter, the present invention will be described in detail.
As a result of diligent research, the present inventor performed centrifugal separation in a furnace carbon black having nitrogen adsorption specific surface area (N2SA), dibutyl phthalate absorption (DBPA), and toluene-colored permeability as defined in the invention of 1) above. The most frequent Stokes diameter (Dmode) of the aggregate size obtained by the sedimentation method satisfies the relationship represented by the following formula (1) and is in the range of 100 to 200 nm [(IA) in the formula is the iodine adsorption amount] ,
Dmode ≦ {(DBPA) ² − (IA) ² } ^1/2 +78 (1)
And the soft furnace carbon black in which the aggregate size distribution index (X) represented by the following formula (a) is in the range of 0.68 to 0.72 was found. A preferable range of the Dmode is 100 to 180 nm.

(In the formula, ΔD-50 represents the full width at half maximum of the aggregate size distribution.)
When the carbon black is blended with rubber, it is possible to realize prevention of ribbon breakage, improvement of ribbon biting property, and improvement of extrusion shape retention, while maintaining rubber properties as compared with conventional FEF.

Carbon black satisfying the requirements of the nitrogen adsorption specific surface area (N2SA), dibutyl phthalate oil absorption (DBPA), and toluene coloring permeability, which are the premise of the invention of 1), is known. If the nitrogen adsorption specific surface area (N2SA) is less than 35 m ² / g, the viscosity of the rubber compound will be excessively lowered, making it difficult to maintain the shape during extrusion, and if it exceeds 50 m ² / g, the viscosity will be excessively increased. It becomes difficult. Further, when the dibutyl phthalate oil absorption (DBPA) is less than 100 mL / 100 g, shrinkage after extrusion increases, and when it exceeds 130 mL / 100 g, the compression set resistance is lowered. Further, when the toluene coloring transmittance is less than 80%, it becomes difficult to avoid the contamination of the rubber compound, so that it is preferably 85% or more, more preferably 90% or more.

Furthermore, the ratio (Y) of the nitrogen adsorption specific surface area (N2SA) and iodine adsorption amount (IA) represented by the following formula (b) is 0.9 to 1.1, and the nitrogen represented by the following formula (c) It is preferable that the ratio (Z) of the adsorption specific surface area (N2SA) and the CTAB adsorption specific surface area (CTAB) is 0.9 to 1.1 because the physical properties can be improved more effectively.

In the present invention, the aggregate size distribution index (X) is used as an index representing the surface properties of carbon black. When this (X) exceeds 0.72, the strength of the unvulcanized rubber fabric is low. Since it becomes weak, it becomes difficult to improve the extrusion characteristics, and when it is less than 0.68, the viscosity of the unvulcanized rubber fabric rapidly increases, and it becomes difficult to maintain processability.
Further, when the (Y) (Z) is within the specified range, the rubber physical properties are further improved.

  Examples of the rubber to which the carbon black of the present invention can be applied include natural rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber, ethylene-propylene-diene copolymer rubber, butyl rubber, halogenated butyl rubber, acrylonitrile-butadiene rubber, and the like. It is done. You may apply to the blend rubber which combined these rubbers arbitrarily.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these Examples.

Examples 1-6, Comparative Examples 1-5
[Production example]
The FEF of the present invention was produced using an oil furnace having the structure shown in Fig. 1 and Fig. 2 [Japanese Patent Laid-Open No. 7-316460 (see applicant Asahi Carbon Co., Ltd.). It was controlled by changing the oil introduction amount, the feedstock oil introduction temperature, the combustion chamber introduction air amount, the reaction chamber introduction air amount, and the distance to the quenching position, where a to h in FIG. The distance to the quenching position was changed by selecting any one of a to h and installing a quench water injection spray device The properties of the feedstock are as shown in Table 1.

Tables 2 and 3 show the carbon black production conditions of Examples and Comparative Examples.

Tables 4 and 5 show the physicochemical properties of the carbon blacks obtained under the production conditions shown in Tables 2 and 3. Moreover, the physicochemical characteristic of general FEF (Asahi # 60G: Asahi Carbon Co., Ltd.) is also shown as a control example.

[Measurement of each characteristic]
The physicochemical properties of each carbon black were measured as follows.
(1) DBP oil absorption (DBPA)
Measured by the method described in JIS K6217-4: 2008. Absorbed DBP volume per 100 g (mL / 100 g) was shown.
(2) Nitrogen adsorption specific surface area (N2SA)
Measured by the method described in JIS K6217-2: 2001. The amount of adsorbed nitrogen per unit weight (m ² / g) was shown.
(3) Iodine adsorption amount (IA)
Measured by the method described in JIS K6217-1: 2008. The amount of iodine adsorbed per unit weight (mg / g) was shown.
(4) CTAB adsorption specific surface area (CTAB)
Measured by the method described in JIS K6217-3: 2001. The amount of adsorbed CTAB per unit weight (m ² / g) was shown.
(5) Toluene coloring transmittance Measured by the method described in JIS K6218-4: 2011. The degree to which toluene is colored by the substance extracted from the surface of carbon black is shown by the transmittance (%) with the blank value of toluene being 100.
(6) ΔD-50 / Dmode (X)
The ratio (X) of the mode value Stokes diameter (Dmode) of the aggregate size and the half-value width (ΔD-50) of the aggregate size distribution measured by the method described in JIS K6217-6: 2008 is expressed by the above formula (a). Calculated by

＊１ 商品名：三井エプタロイ ＰＸ−０４９ＰＥ〔三井化学社製〕
＊２ 商品名：ＰＷ−３８０ 〔出光興産社製〕
＊３ 商品名：ノクセラーＭ 〔大内新興化学工業社製〕
＊４ 商品名：ノクセラーＴＴ 〔大内新興化学工業社製〕
＊５ 商品名：ノクセラーＴＲＡ 〔大内新興化学工業社製〕
＊６ 商品名：ノクセラーＢＺ 〔大内新興化学工業社製〕
[Rubber compounding characteristics]
Carbon black shown in Tables 4 and 5 was blended with EPDM (ethylene-propylene-diene rubber) in the proportions shown in Table 6 to obtain rubber compositions, and various properties were measured.
The results are shown in Tables 7 and 8.

* 1 Product name: Mitsui Eptalloy PX-049PE (Mitsui Chemicals)
* 2 Product name: PW-380 [made by Idemitsu Kosan Co., Ltd.]
* 3 Product name: Noxeller M [Ouchi Shinsei Chemical Co., Ltd.]
* 4 Product name: Noxeller TT [Ouchi Shinsei Chemical Co., Ltd.]
* 5 Product name: Noxeller TRA [manufactured by Ouchi Shinsei Chemical Co., Ltd.]
* 6 Product name: Noxeller BZ [Ouchi Shinsei Chemical Co., Ltd.]

※１ 試験片加硫条件：１５０℃×１５分
※２ 試験片加硫条件：１５０℃×２０分

* 1 Specimen vulcanization condition: 150 ° C x 15 minutes * 2 Specimen vulcanization condition: 150 ° C x 20 minutes

Each characteristic in Table 7 and Table 8 was measured by the following method.
Stress relaxation: Method described in JIS K6263: 2004 Mooney viscosity (ML1 + 4 '): Method described in JIS K6300-1: 2001-Damping rate for 0.5 seconds: Method described in JIS K6263-Up to 80% attenuation Time: Method described in JIS K6263 Vm: Method described in JIS K6300-1: 2001 Scorch time (t5) Method described in JIS K6300-1: 2001 Extrusion characteristics: ASTM D2230-96: (2007 ) Method described
(The extrusion operation was performed at a screw rotation number of 20 rpm. The extrusion speed is shown in the table.
It was as follows. )
• Die swell: Calculated from the results of the above extrusion test. • Ribbon breakage / ribbon bite property: The rubber ribbon entering the extruder was visually evaluated during the above extrusion test. [If the rubber is too hard, it will bounce at the biting roll, and if it is too soft, tearing will occur at the biting roll. ]
Green hardness @ 25 ° C .: Method described in JIS K6253: 2006 Hardness: Method described in JIS K6253: 2006 100% modulus: Method described in JIS K6251: 2010 Tensile strength: JIS K6251: 2010 method (measured using dumbbell-shaped No. 1 test piece)
・ Elongation: Method similar to tensile strength ・ Rebound resilience: Method described in JIS K6255: 1996 (measured using a Rupke type measuring device)
Dispersibility: Method described in ASTM D2663-08 Method B

From the results of Tables 7 and 8, the effect of the carbon black of the present invention will be described.
Since many physical properties of carbon black have a correlation with DBPA, it is necessary to compare those having similar DBPA. That is, by comparing Examples 1 and 2 and Examples 3 to 5 as a group, the following can be understood.
(I) About shape retention of extruded shape As the aggregate size distribution index (X) decreases, the stress relaxation time (time to 80% attenuation) tends to increase. The stress relaxation time means the ease of deformation after eliminating the stress applied to the rubber composition, and the longer the stress relaxation time, the harder it is to be deformed. The resulting composition is easy to maintain its shape. Similarly, since the die swell decreases as (X) decreases, the smaller the (X), the smaller the shrinkage after extrusion and the better the shape retention. However, excessive shape retention becomes a factor that the hardness (green hardness) of the unvulcanized rubber becomes too hard, which may adversely affect the subsequent work. Conversely, excessive reduction of the stress relaxation time makes it difficult to maintain the shape, which may also have an adverse effect on the work. The carbon black of the example in which (X) is within the specified range exhibits an appropriate stress relaxation time, and can impart a well-balanced shape retention to the rubber composition.
In addition, since the stress relaxation time tends to be long even if the value of (X) is the same by satisfying the formula (1), the production of carbon black under easier conditions in the management of (X). It can be performed.

(Ii) About ribbon breakage and ribbon bite Originally, DBPA greatly affects the viscosity and hardness of unvulcanized rubber, but Mooney viscosity tends to increase with a decrease in (X). In addition, the unvulcanized dough becomes harder as (X) decreases. The hardness of the unvulcanized fabric (green hardness) indicates the strength of the rubber composition, and the higher the strength, the less likely the ribbon breaks and the better the bite. In other words, a smaller (X) is effective for preventing ribbon breakage and improving bite-in, but if it is excessive, the rubber becomes too hard and bagging may occur, so that (X) as in the present invention. Must be adjusted to an appropriate range.

(Iii) Vulcanized physical properties With the decrease in (X), tensile strength and elongation tend to increase.

(Iv) Dispersibility Dispersibility improves with an increase in Dmode. Further, when the expression (1) regarding Dmode is satisfied, the same level of dispersibility can be obtained with a lower Dmode. However, an excessive increase in Dmode tends to adversely affect the reinforcing effect and the like, but within the range specified by the present invention, an optimal balance can be achieved that combines the maintenance of reinforcing properties and the improvement of dispersibility.

(V) Summary From the above (i) to (iv), it has been found that by reducing (X), not only the extrusion characteristics are improved but also the reinforcing properties are improved. However, since the viscosity of the blend also tends to increase, there is a concern that the processability of the rubber is lowered if (X) is made too small. On the other hand, according to the present invention, it is possible to provide carbon black with a good balance of various characteristics.
In Comparative Example 1, although the ribbon bite is good, the Dmode is too small, so the dispersibility is bad. In Comparative Example 2, the ribbon bite is good, but the Dmode is too large, so that the reinforcing property (100% The modulus, tensile strength, elongation, etc.) were poor.

DESCRIPTION OF SYMBOLS 1 Raw material oil spray nozzle 2 Flammable fluid introduction chamber 3 Oxygen-containing gas introduction pipe 4 Oxygen-containing gas introduction cylinder 5 Current plate 7 Fuel oil spraying device 8 Converging chamber 9 Burner tile 10 Raw material oil spraying device 11 Raw material oil introduction chamber 12 Reaction Chamber 13 Reaction chamber continuation and quenching chamber 14 Condensation zone member 15 Oxygen-containing gas introduction pipe a Installation position of quench water injection spray device b Installation position of quench water injection spray device c Installation position of quench water injection spray device d Rapid cooling water Installation position of press-fitting spray device e Installation position of quench water injection spray device f Installation position of quench water injection spray device g Installation location of quench water injection spray device h Installation position of quench water injection spray device

Claims (2)

In soft furnace carbon black having basic characteristics of nitrogen adsorption specific surface area (N2SA) of 35 to 50 m ² / g, dibutyl phthalate oil absorption (DBPA) of 100 to 130 mL / 100 g, and toluene coloring permeability of 80% or more, The most frequent Stokes diameter (Dmode) of the aggregate size obtained by the sedimentation method satisfies the relationship represented by the following formula (1) and is in the range of 100 to 200 nm [(IA) in the formula is iodine adsorption amount] ,
Dmode ≦ {(DBPA) ² − (IA) ² } ^1/2 +78 (1)
A soft furnace carbon black having an aggregate size distribution index (X) represented by the following formula (a) in the range of 0.68 to 0.72.

(In the formula, ΔD-50 represents the full width at half maximum of the aggregate size distribution.)   A rubber composition comprising the soft furnace carbon black according to claim 1 blended with natural rubber and / or synthetic rubber.

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