JPH1160984A - Carbon black and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain carbon black and a rubber composition suitable for tire tread simultaneously satisfying improvement in wear resistance and grip and reclamation in fuel cost characteristics. SOLUTION: This carbon black belongs a hard-based region having >=80 (m<2> /g) CTAB(cetyltetraammonium bromide) and >=80 (mL/100 g) compression DBP and satisfies selective characteristic requirements of (1) nitrogen adsorption specific surface area (N2 SA); N2 SA-CTAB<=50, (2) nitrogen content (N; wt.%); 3.0×10<-3> <=N/CTAB<=1.2×10<-2> , (3) oxygen content(0; wt.%); 0/CTAB<=1.3×10<-2> , (4) the weight ratio of nitrogen content and oxygen content O/N; O/N<=3.0, (5) a basic functional group concentration (B; meq/g); 2.0×10<-4> <=B/ CTAB<=1.0×10<-2> and (6) a shell rubber amount (S); 5.0×10<-6> <=S<=5.0×10<-5> . This rubber composition is obtained by compounding 20-100 pts.wt. of the carbon black with 100 pts.wt. of rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon black and a rubber composition, and more particularly to a carbon black and a rubber composition suitable for a tire tread having excellent gripping power and low fuel consumption.

[0002]

2. Description of the Related Art In recent years, with the advancement of high-performance driving performance and resource saving and low fuel consumption of automobiles, a high balance of various characteristics is required also in tire performance.
In particular, research and development of tire treads that simultaneously have multiple characteristics, such as improved grip with the road surface, reduced tire wear, and improved fuel consumption characteristics (tire rolling resistance) during driving, have been actively pursued. I have. In view of these characteristics, carbon black plays a significant role in the components of the tire tread, and development of a new carbon black that improves the above characteristics is an urgent issue.

It is well known that a rubber containing carbon black dramatically increases its mechanical strength. However, the dominant factors for the rubber reinforcing property of this carbon black are two factors such as morphology and surface activity. They are roughly classified into species. Specifically, the following factors are generally known (Carb
on Black, 2nd Edition (1993), Edited by JBDonne
t, RC Bansal, MJ Wang, MARCEL DEKKER, INC., Carbon Black Handbook Chapter 4, Carbon Black Association,
Published in 1961 (Book Publishing Co., Ltd.).

(1) Factors related to morphology Primary particle diameter and its statistical distribution, degree of branch development for aggregates that are aggregates of primary particles, aggregate shape, aggregate diameter and its distribution using centrifugal sedimentation, Typical values include a specific surface area using various adsorbed species corresponding to the particle diameter. (2) Factors related to surface activity Physical adsorption of rubber molecules on the carbon black surface,
It is considered that physicochemical adsorption of rubber molecules on the surface, such as chemical bonding between a chemically reactive functional group present on the surface of the carbon black and rubber molecules and rubber molecule radicals, is essentially important. As the index, active hydrogen,
Oxygen-containing functional groups such as carboxylic acids, quinone-type oxygen, hydroxyl groups, and lactones have been reported. Regarding the surface activity, a quantitative index of the interaction between the carbon black and the rubber has been searched for by using various methods for many years, but it has not been determined yet.

[0005] Conventionally, research and development have been carried out mainly on the relationship between the former form factor and rubber physical properties, and remarkable improvements have been made in abrasion resistance and the like (33rd Rubber Technology Symposium Text, pp. 44-61, 1994, Japan Rubber Association Research Committee). That is, in order to improve the wear resistance, increase the blending amount of carbon black, reduce the primary particle diameter (increase the specific surface area), and develop the structure (increase the DBP oil absorption and the compressed DBP oil absorption). A technique was developed to sharpen the aggregate diameter distribution.

On the other hand, improvement in grip performance of a tire (generally, loss coefficient tan δ at 0 to 20 ° C. at 10 to 100 Hz).
It is known that the grip performance is improved when the value increases, and that the tire fuel efficiency during running is improved (when the loss coefficient tanδ at 60 ° C is reduced, the fuel efficiency during running is improved. ) Also greatly contributes to the improvement effect of carbon black. That is, it is known that increasing the amount of carbon black, reducing the primary particle diameter, and suppressing the degree of structure development are effective in improving the grip force. Also,
It is known that, in order to improve the fuel efficiency characteristics of a tire, it is effective to reduce the amount of carbon black, increase the primary particle diameter, and develop a structure.

As described above, it is possible to independently improve the properties of each rubber. However, simultaneously improving the abrasion resistance, the grip force and the fuel consumption properties can be achieved only by optimizing the form of carbon black. There are limitations. Furthermore, regarding the reduction of the primary particles to fine particles, there is also a problem in rubber processing that the kneadability and dispersibility of carbon black are reduced.
Optimum design has been made for the form of carbon black from both sides of the distribution of the importance of various rubber properties and processability. By the way, even if the improvement of the rubber properties by such a form slightly changes due to a change in manufacturing conditions for form control,
The structure is optimized for carbon black having almost constant surface activity. On the other hand, research and development for improving the rubber properties using carbon black whose surface activity is actively controlled have been energetically advanced in recent years.

Attention has been paid to oxygen-containing functional groups present on the surface as a means of controlling surface activity, and improvement of rubber physical properties by a combination of conventional form control and surface activity has been reported. For example, in Japanese Patent Application Laid-Open No. 7-330958, after increasing the amount of carboxyl groups on the surface by oxidation treatment with ozone more than usual, a carbon black in which the amount of carboxyl groups is controlled by heat treatment in a non-oxidizing atmosphere is adjusted, In the blended system of expanded styrene butadiene rubber (SBR1712), improvement of abrasion resistance and reduction of tan δ (60 ° C.) are achieved. In addition, the present inventors also studied the improvement of surface activity focusing on the amount of oxygen and the amount of hydrogen contained in carbon black separately.As a result, H / O was increased by a synergistic effect with morphological optimization. Succeeded in increasing the surface activity and maintaining a high level of abrasion resistance while maintaining excellent fuel economy (60 ° C
(Reduction of the loss coefficient tanδ)
192509).

[0009]

However, in the prior art which focuses on the oxygen-containing functional group as described above, it is difficult to improve the fuel efficiency when the grip force is increased, and conversely, the fuel efficiency is improved and the grip is improved. There is a problem that the power is reduced, and it has been a problem to control both independently. Accordingly, an object of the present invention is to provide a carbon black and rubber composition suitable for use in tire treads that simultaneously achieves an improvement in grip force and an improvement in fuel efficiency while maintaining a high level of wear resistance.

[0010]

The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, the nitrogen component and the oxygen component contained in carbon black play an important role in bonding with rubber. In addition to finding that two new indices corresponding to the concentration of basic functional groups present on the carbon black surface and the amount of rubber bound to the carbon black surface show a good correlation with rubber properties, their optimal As a result, the improvement of the grip force and the improvement of the fuel economy have been achieved at the same time, and the present invention has been completed.

That is, the carbon black of the present invention has a CT
AB is 80 (m ² / g) or more, compressed DBP is 80 (mL / 100g)
(1) Nitrogen adsorption specific surface area (N ₂ SA); N ₂ SA-CTAB ≦ 50 (2) Nitrogen content (N; wt%); 3.0 × 10 ⁻³ ≤ N
/CTAB≦1.2×10 ⁻² (3) Oxygen content (O; wt%); O / CTAB ≦ 1.3 × 1
0 ^-2 (4) Weight ratio of nitrogen content to oxygen content O / N; O / N ≦
3.0 (5) Basic functional group concentration (B; meq / g); 1.8 × 10 ^-4
≦ B / CTAB ≦ 1.0 × 10 ⁻² (6) Shell rubber amount (S); 5.0 × 10 ⁻⁶ ≦ S ≦ 5.
It has a selective characteristic of 0 × 10 ⁻⁵ . Further, the rubber composition of the present invention is characterized in that 20 to 100 parts by weight of the above-described carbon black of the present invention is blended with 100 parts by weight of rubber.

The present invention relates to a hard carbon black in which CTAB, compressed DBP and N ₂ SA are optimized, and introduces a new nitrogen content index in addition to the oxygen content which has been attracting attention. By doing so, they found that the control range of the surface activity of carbon black on rubber could be expanded, and found that the concentration of basic functional groups on the surface was important as a specific index indicating the surface activity quantitatively. As an index, a new index called the amount of HCl adsorption was introduced.
Furthermore, a new index called the amount of shell rubber is constructed as an index indicating the strength of the interaction of carbon black with rubber, and by simultaneously controlling the amount of oxygen, the amount of nitrogen, the concentration of the basic functional group, and the amount of shell rubber, the resistance to shell rubber is improved. While maintaining abrasion,
It improves fuel economy while at the same time increasing grip.

Hereinafter, the present invention will be described in detail. The first important point in the present invention is that the strength of surface activity can be freely controlled by controlling the amounts of nitrogen and oxygen contained in carbon black, and a specific index of surface activity is found. As a basic functional group concentration. The mechanism for controlling the interaction between rubber and carbon black by nitrogen and oxygen will be described below. Nitrogen and oxygen in carbon black, which essentially play an important role in improving the physical properties of the rubber of the present invention, are nitrogen and oxygen present on the surface of carbon black which directly contact rubber molecules and constitute an interface. Nitrogen and oxygen inside the micropores and inside the carbon black on the carbon black surface where the molecules cannot reach do not contribute to the improvement of the physical properties. Therefore, it is preferable to concentrate nitrogen and oxygen on the surface in order to more remarkably exert the effects of the present invention.

The nitrogen present on the carbon black surface is
It is considered that amines exist on the carbon surface.
That is, a -NH2 group, a = NH group, RN = R '(R and R' are hydrocarbons), and a heterocyclic ring (Chapter 4, Carbon Black, 2nd Edition
(1993), Edited by JBDonnet, RC Bansal, MJ W
ang, MARCEL DEKKER, INC.). As is generally known, nitrogen has a property of easily forming a hydrogen bond with a proton because it has a lone pair of electrons. Therefore, it is presumed that the presence of a large amount of nitrogen on the surface of the carbon black facilitates the chemical adsorption of rubber molecules via hydrogen, and as a result, the interaction between the carbon black surface and the rubber becomes strong.

Since the nature of the chemical adsorption of rubber is the proton adsorption ability of amines which are nitrogen-containing functional groups, that is, basicity, the basic functional group content of carbon black is used as an index directly contributing to the improvement of rubber physical properties. Is an important indicator. As a result of intensive studies in the present invention, utilizing the fact that bases such as amines react with hydrochloric acid to form hydrochloride, the amount of basic functional group is determined from the decrease in hydrochloric acid when carbon black and hydrochloric acid are reacted. Quantitative analysis revealed that the basic functional group concentration had a good correlation with the improvement of rubber reinforcement. By using this index, it is possible to quantitatively indicate the degree of proton adsorption capacity effective for chemisorption of rubber, that is, the basic functional group in nitrogen present in carbon black. It has become possible.

On the other hand, oxygen present on the surface of carbon black is considered to exist in the form of a bond such as an acidic functional group, quinone-type oxygen, or ether oxygen (Carbon Bla, supra).
ck, Chapter 4, or Carbon Black Handbook Chapter 4,
Edited by the Carbon Black Association, published in 1961. In any case, although containing oxygen to some extent, the inclusion of oxygen causes a bias in the electron distribution and generates a permanent dipole moment. Then, the so-called Van der Waals' force is reduced, and the presence of oxygen causes a reduction in the physical adsorption energy of rubber on the surface of carbon black.

Although it has been reported that a carboxyl group or a hydroxyl group is involved in chemical bonding with a diene rubber, the inventors of the present invention have studied and found that the proton donating property of the acidic functional group is retarded in vulcanization. However, no improvement in the physical properties of the rubber due to the acidic functional group was observed, and it was concluded that the vulcanization retardation was rather unfavorable for practical applications. In addition, it has been reported that quinone-type oxygen is involved in bonding with rubber radicals generated during kneading, and that quinone groups play a large role in improving rubber reinforcing properties.

However, even if the present inventors heat-treat carbon black in an argon atmosphere to reduce oxygen, hardly any decrease in rubber physical properties is observed.
It has been found that the heat treatment at 0 to 1100 ° C. increases the elastic modulus. Since oxygen in carbon black was almost completely eliminated by this heat treatment, it was inferred that acidic functional groups, quinone-type oxygen and the like did not essentially play an important role in rubber reinforcing properties. As described above, the present inventors have determined that a smaller amount of oxygen is preferable from the viewpoint of strengthening the interaction with rubber.

As described above, among the characteristics of the tire tread rubber, the grip force and the fuel consumption characteristics are closely related to the temperature dependency of the viscoelasticity of the rubber composition.
That is, the grip force has a strong correlation with the value of the loss coefficient tan δ at 0 ° C. to 20 ° C., and the greater the value, the greater the grip force. In addition, the fuel consumption characteristic during running is 6
It is known that the smaller the value at 0 ° C., the better the fuel efficiency characteristics are. Tanδ generally related to loss
Is the sum of the loss in the rubber matrix, the loss due to friction between carbon blacks, and the contribution of friction at the interface between carbon black and rubber. In particular, in the case of a hard carbon rubber composition having a high specific surface area, the surface area of carbon black is large, so the contribution of the interface between carbon black and rubber is large, and the structure of the interface is dominant in controlling tan δ.

It is presumed that the essential mechanism of the improvement of the fuel consumption characteristics and the increase of the grip force in the present invention lies in the optimization of the adsorption energy of rubber on the surface of carbon black.
That is, when the stress is relatively strong, such as deformation at 0 ° C. to 20 ° C., rubber molecules slide on the carbon surface at the interface, and as a result, frictional heat is generated and tan δ increases.
At 60 ° C., the rubber is softened, so that the stress is relatively small and the rubber molecules do not slide on the carbon surface for the deformation.
The present invention defines an appropriate state of adsorption between carbon black and rubber molecules so that tan δ at 0 ° C. becomes small. The optimized range of the amount of nitrogen and the amount of oxygen for that purpose are as follows: (1) Nitrogen content (N;% by weight); 3.0 × 10 ⁻³ ≦ N
/CTAB≦1.2×10 ⁻ (2) Oxygen content (O; wt%); O / CTAB ≦ 1.3 × 1
0 ^-2 (3) Weight ratio of nitrogen content to oxygen content O / N; O / N ≦
3.0, and the range in which the amount of the basic functional group was optimized was: (4) Basic functional group concentration (B; meq / g); 1.8 × 10 ^-4
It is characterized in that ≦ B / CTAB ≦ 1.0 × 10 ⁻² .

In the present invention, optimization of the adsorption state is defined by the above-described restrictions on the amounts of nitrogen and oxygen, the abundance ratio of nitrogen and oxygen, and the concentration of the basic functional group. N / CTAB
In the case of <3.0 × 10 ⁻³ , the effect of increasing the adsorptive power by nitrogen is too small, and in the case of O / CTAB> 1.3 × 10 ⁻² , the amount of oxygen is too large and the adsorption energy is small. However, the improvement of grip power and fuel consumption characteristics is insufficient. O
Although the lower limit of / CTAB is not clearly defined, the oxygen content is O / CTAB ≧ 1 ×
10 ^-4 is preferred. On the other hand, if N / CTAB> 1.2 × 10 ^-2 , the gripping force is reduced because the adsorption energy is too strong, which is not preferable. On the other hand, when O / N> 3.0, the increase in adsorption power due to nitrogen is canceled out by the effect of oxygen, so that the overall adsorption power is reduced, and the improvement in gripping power and fuel efficiency becomes insufficient. Although the lower limit of O / N is not clearly defined, it is preferable that O / N ≧ 1 × 10 ⁻³ from the viewpoint of economy such as manufacturing cost.

Regarding the basic functional group concentration, B / CTAB <
If it is 1.8 × 10 ⁻⁴ , the concentration of the basic functional group is so small that effective improvement of the rubber properties cannot be achieved. On the other hand, B / CTAB> 1.0
In the case of × 10 ^-2 , the amount of adsorbed rubber is too large, so that the dispersion of carbon black in the rubber is poor, and the kneading processability is undesirably reduced. Even if the conditions of the present invention are satisfied with respect to the amounts of nitrogen and oxygen and the ratio thereof, the physical properties of the rubber are not improved unless the concentration of the basic functional group, which is important for the interaction with the rubber, is appropriate. Even if the group concentration satisfies the conditions of the present invention, if the amount of oxygen is large and the concentration of the acidic functional group is high, the effect of the basic functional group by nitrogen is canceled by the acidic functional group. Simultaneously satisfying the restrictions on the amounts of nitrogen and oxygen and the restrictions on the basic functional group is essential in the present invention.

The various characteristic indices used for defining the carbon black of the present invention are determined by the following measuring methods. (1) CTAB (cetyltetraammonium bromide);
(2) Compressed DBP (24M4DBP); conforms to the method of ASTM D3493 (3) Nitrogen adsorption specific surface area (N ₂ SA); conforms to the method of ASTM D3037 (4) In carbon black Nitrogen and oxygen content; measured by FISONS Instruments EA 1108 Elemental An
alyzer was used.

Nitrogen is measured based on the "dynamic flash burning" method. The carbon black of the test specimen is completely burned by flash burning, and nitrogen is converted into nitrogen oxide. Further, it is reduced to N ₂ gas by the catalyst layer, and finally detected as a N 2 gas concentration by a thermal conductivity detector.・ Oxygen is measured based on the “Unterzaucher Modified” method. Oxygen in carbon black is completely converted to CO by high-temperature pyrolysis under a catalyst, and detected as a CO gas concentration by a thermal conductivity detector. The sample used for the elemental analysis measurement is dried in advance at 110 ° C. for 2 hours or more in order to remove the influence of moisture adsorbed on the carbon black surface, and then subjected to the test.

(5) Method of Measuring Basic Functional Group Concentration (B; meq / g) About 2 g of carbon black previously vacuum-dried at 110 ° C. for 30 minutes or more is precisely weighed and put into a 100 mL Erlenmeyer flask. There 1/1
Inject 50 mL of 00N HCl solution, sufficiently disperse the carbon black, and shake for 2 hours in a sealed state. The solution after shaking is filtered under pressure to separate the carbon black and the reacted HCl solution. Take 10 mL of the HCl solution after the reaction, perform neutralization titration with a 1 / 100N NaOH solution, calculate the amount of HCl adsorbed per 1 g of carbon black from the amount of the dropped NaOH solution, and calculate the basic functional group concentration (B; meq / g).

The second important point in the present invention is that the control of the amounts of nitrogen, oxygen and basic functional groups is a necessary condition for improving the physical properties of the rubber, and the results of intensive studies have been made. And the introduction of a shell rubber amount (S), which is an important index for defining the surface activity of carbon black on rubber. That is, by defining the amount of the shell rubber together with the amounts of nitrogen, oxygen and basic functional group, the inventors succeeded in finding necessary and sufficient conditions for improving the rubber properties for the first time.

(6) The method of measuring the amount of shell rubber (S) is as follows: 50 parts by weight of carbon black with respect to 100 parts by weight of styrene butadiene rubber (SBR # 1500 manufactured by Nippon Synthetic Rubber Co., Ltd.). Is adjusted. The adjustment method is as follows. For kneading, a twin-screw roll kneader (Nishimoto Koki Co., Ltd. E90) is used. First, 10 g of rubber is wound around a roll in front of a twin-screw kneader whose temperature has been previously adjusted to 60 ° C. The used biaxial roll kneader has a roll diameter of 90 mm and a roll gap of about 0.2 m.
m and the roll guide width is about 10 cm. After winding the rubber, 5 g of carbon black previously vacuum-dried at 100 ° C. for 30 minutes or more is precisely weighed, poured into the rubber pool between the biaxial rolls, and sufficiently kneaded to obtain a good dispersion state. . After kneading, the roll gap is adjusted appropriately to take out a sheet-like rubber composition having a thickness of about 3 mm.

The sheet-shaped rubber composition is heat-treated at 120 ° C. in an argon atmosphere for 10 minutes, and then left to cool in the air for 1 hour. 0.5 g of the rubber composition thus adjusted was precisely weighed, cut into a size of about 1 mm square, put into a 200 mL Erlenmeyer flask, poured with 150 mL of orthodichlorobenzene, and treated at 170 ° C. for 20 hours. By doing so, the rubber other than carbon black is sufficiently dissolved in the solvent. When the rubber and carbon black solutions thus obtained are separated using a centrifuge, the carbon black with the rubber adhered to the surface can be separated and extracted from the solution.

Since orthodichlorobenzene is a solvent having a very high solubility in rubber, this extract is carbon black having a trace amount of rubber adhered to the surface. Therefore, it is possible to know from the weight W (g) of this extract how much rubber was fixed on the carbon black surface. Drying conditions are vacuum drying at 120 ° C. for 5 hours or more.
The weight W is precisely weighed. The shell rubber amount (S) is obtained from the weight W by the following equation: S = {(W−0.5 / 3) / (0.5 / 3)} / {N ₂ SA × (24M4DBP) ² }

Shell rubber is a measure of the ability of orthodichlorobenzene to dissolve the rubber, and is a quantification of the ability of rubber to adsorb on the surface of carbon black. In order to take into account the effect of the form, it is divided by N ₂ SA and converted to unit area. And also
Divided by (24M4DBP) ² to account for structure effects. Carbon black with an aggregate structure that has a large number of branched structures is fixed to the carbon black surface as much as non-branched (small DBP) carbon black because rubber is fixed to the branch part. The amount of rubber increases. As a result of the measurement, using the amount corresponding to the branched structure after kneading, 24M4DBP, the effect of the structure derived from the aggregate structure was (24M4DBP) ²
It was found that standardization was possible by dividing by.

Regarding the shell rubber amount (S) defined in this way, in the present invention, 5.0 × 10 ⁻⁶ ≦ S ≦ 5.0.
Satisfying × 10 ^-5 is an essential requirement. Here, nitrogen, oxygen and a basic functional group are other essential requirements. (1) Nitrogen content (N; wt%); 3.0 × 10 ⁻³ ≦ N /
CTAB ≦ 1.2 × 10 ⁻² , (2) Oxygen content (O; wt%); O / CTAB ≦ 1.3 × 1
0 ^-2, (3) the weight ratio of the nitrogen content and the oxygen content O / N; O / N ≦
3.0, (4) Basic functional group concentration (B; meq / g); 1.8 × 10 ^-4
Even if the condition of ≦ B / CTAB ≦ 1.0 × 10 ⁻² is satisfied, if the shell rubber amount (S) is less than 5.0 × 10 ⁻⁶ , the rubber adsorption ability on the surface is insufficient. As a result, the improvement of the grip force and the fuel consumption characteristics becomes insufficient. On the other hand, if the shell rubber amount (S) exceeds 5.0 × 10 ⁻⁵ , the kneading property of carbon black is remarkably reduced, so that sufficient dispersion cannot be obtained by kneading in an actual machine, and the physical properties of rubber are deteriorated. Appropriate.

In the present invention, the third important point is that the improvement of tan δ by controlling the adsorption state of the surface exhibits its characteristics only in synergy with the optimization of the form of carbon black. In other words, in order to express a basically high level of wear resistance, it is essential to form fine particles and to have a high structure. Improved power and fuel economy characteristics are achieved. That is, unless the CTAB satisfies both 80 m ² / g or more and the compressed DBP satisfies both 80 mL / 100 g or more, basically, a high level of wear resistance is not exhibited. Further, when the surface is roughened by activation or the like, the rubber reinforcing property is reduced. Therefore, the condition of N ₂ SA-CTAB ≦ 50 is imposed on N ₂ SA-CTAB which is an index indicating the surface roughness. N ₂ SA-
If the CTAB exceeds 50, the wear resistance is undesirably reduced.

The carbon black in the present invention is preferably provided that it satisfies the conditions defined by the present invention with respect to nitrogen, oxygen, basicity and shell rubber as defined in the present invention.
There is no limitation on the method for producing carbon black. An essential requirement of the present invention is the control of surface activity by controlling nitrogen and oxygen. A method for producing carbon black in which the nitrogen content and the oxygen content are controlled is exemplified below. Regarding the control of the amount of nitrogen, (1) In the oil furnace method, the adjustment of the nitrogen content at the stage of the feedstock oil, specifically, the mixing of a feedstock oil having a high nitrogen content and a nitrogen compound into the feedstock oil. (2) After the raw oil is blown into the reaction furnace in the oil furnace method, a nitrogen compound is blown into the carbon black path or sprayed in an arbitrary step such as a carbon black formation reaction step, a cooling step, a granulation step, or the like. And so on. (3) Introducing a nitrogen functional group on the surface of carbon black by heat-treating carbon black in an ammonia gas atmosphere. In this case, there is no particular limitation on the carbon black before the treatment, but for example,
Furnace black (including oil furnace black and gas furnace black) or channel black can be used.

On the other hand, regarding the control of oxygen, (1) In the oil furnace method, it can be controlled by the position at which the raw oil is blown, the amount of the raw oil blown, and the like. (2) In addition, various methods can be adopted, such as controllable by the drying temperature, the drying time, the oxygen concentration in the atmospheric gas and the like in the drying step.

The carbon black specified in the present invention is blended with at least one kind of rubber among diene rubbers such as isoprene rubber, butadiene rubber, butyl rubber and styrene-butadiene copolymer, and natural rubber according to a conventional method. . That is, a closed kneader such as a Banbury mixer or an open kneader such as a twin-roll kneader can be suitably used. In the rubber composition of the present invention, at the time of tire production, a compounding agent usually used, for example, sulfur, a vulcanization accelerator, a vulcanization accelerator, an antioxidant, etc. are appropriately compounded. be able to. The compounding ratio of carbon black is 20 per 100 parts by weight of rubber.
To 100 parts by weight. If the amount is less than 20 parts by weight,
On the other hand, sufficient abrasion resistance cannot be obtained. On the other hand, if it exceeds 100 parts by weight, the viscosity of the composition becomes too high, so that sufficient kneading cannot be performed, and as a result, the rubber properties are reduced. I will.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to specific examples.

[0037]

EXAMPLES Examples of the improvement of the physical properties of the carbon black and the rubber composition specified in the present invention will be specifically described below in comparison with comparative examples, but the present invention is not limited to these examples. Not. However, the methods for measuring various physical properties of rubber used in the following examples are specifically shown below.

(1) Evaluation of 300% Elastic Modulus The evaluation was carried out in accordance with JIS K6251 “Tensile test method for vulcanized rubber”. In addition, the obtained result was displayed as an index (index) when the result of the standard sample was set to 100. That is, (elastic modulus of test rubber / elastic modulus of standard sample) × 100. An index larger than 100 indicates a higher elastic modulus.

(2) Evaluation of tan δ at 0 ° C. and 60 ° C. The tan δ at 0 ° C. for evaluating the grip force and the tan δ at 60 ° C. for evaluating the fuel consumption characteristics were measured using a viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd. 1) Apparatus; Viscoelastic spectrometer manufactured by Toyo Seiki Co., Ltd. 2) Sample; length 20mm, width 5mm, thickness 2mm 3) Measurement temperature; 0 ° C and 60 ° C 4) Frequency; 10Hz 5) Initial elongation; 10% 6) Strain amplitude: 2% The obtained results are shown as an index when the result of the standard sample is set to 100. That is, (tan δ of test rubber / tan δ of standard sample) × 100. An index larger than 100 indicates that the value of tan δ is larger.

(3) Evaluation of wear characteristics The wear characteristics were evaluated using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho under the conditions of a slip ratio of 60% as follows. 1) Apparatus; single-unit Lambourn abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd. 2) Outer diameter 305mm, grain GC, grain size 80, bonding degree K 3) Sample; outer diameter 49mm, inner diameter 23mm, width 5mm 4) Sand; carborundum 90 mesh 5) Conditions: sample speed 50.8m / min (330rpm), sandfall
15 g / min The obtained results are shown as an index when the result of the standard sample is set to 100. That is, (abrasion amount of standard sample / abrasion amount of test rubber) × 100. An index larger than 100 indicates superior wear resistance.

Examples 1 to 5 and Comparative Examples 1 to 3 In order to examine the effects of nitrogen and oxygen contained in carbon black, carbon black (standard sample) produced in advance by the furnace method was treated with ammonia gas shown below. The carbon black is controlled by controlling the nitrogen and oxygen contents in the carbon black by heat treatment under the following conditions, and the characteristic values of the carbon black and the characteristic values of the carbon black when kneaded with the rubber and the physical properties of the rubber are measured. The results are shown in Table 2. The specific method of ammonia gas treatment and the method of rubber kneading are as follows.

(1) Surface Modification of Carbon Black by Heat Treatment under Ammonia Gas Carbon black, which was previously vacuum-dried at 70 ° C. to 100 ° C. for 1 hour or more, was heated to a predetermined temperature in an ammonia gas atmosphere at 2.5 to 3 Time processed. After the treatment at the predetermined temperature was completed, the resultant was cooled to room temperature in an ammonia gas atmosphere. After vacuum drying at 70 ° C to 100 ° C for 10 hours or more, it was subjected to carbon characteristic value evaluation and rubber test.

(2) Rubber kneading According to the rubber compounding shown in Table 1, using a Banbury type lab plast mill (B75) manufactured by Toyo Seiki Co., Ltd. and a biaxial roll (E90) manufactured by Nishimoto Koki Co., Ltd. The rubber composition was kneaded according to a conventional method.

[Table 1]

[0044]

[Table 2]

Examples 1 to 5 in Table 2 and Comparative Examples 1 and 2
From the results, when the treatment temperature in the ammonia gas atmosphere is low and the amount of introduced nitrogen is small (Comparative Example 1), the activation reaction proceeds because the ammonia gas treatment temperature is too high, and N ₂ SA-CTAB is too large (Comparative Example 1). Contrary to 2), it can be seen that the carbon black of the example defined by the present invention achieves the improvement of the abrasion resistance, the improvement of the fuel economy and the improvement of the grip force at the same time with respect to the untreated standard sample.

Examples 6 to 9 and Comparative Examples 3 and 4 Carbon black having a relatively large particle size (CTAB: 94 m ² / g
Level) was used as a standard sample, and various characteristics of carbon black adjusted by the same heat treatment method in an ammonia gas atmosphere as in Examples 1 to 5 were examined. Table 3 summarizes the measurement results of the characteristic values of the carbon black and the physical properties of the rubber.

[0047]

[Table 3]

As is apparent from Examples 6 to 9 and Comparative Examples 3 and 4 in Table 3, the carbon black satisfying the requirements of the present invention has improved abrasion resistance, improved fuel consumption characteristics, and improved gripping power as compared with the standard sample. It can be seen that the improvement is achieved simultaneously. Here, it should be noted that the heat treatment temperature in ammonia gas is merely a parameter for controlling the surface properties, and the absolute value of the temperature has no significance. Nitrogen, oxygen, basic functional group concentration defined by the present invention,
The amount of the shell rubber is of essential importance, and the optimum temperature varies depending on the reactivity of the surface of the carbon black to be modified with ammonia gas.

Examples 10 and 11, Comparative Example 5 Using carbon black of 135 m ² / g CTAB as a standard sample, heat treatment was performed in an atmosphere of ammonia gas in the same manner as in the above Examples and Comparative Examples to obtain the characteristic values of carbon black and rubber. Physical properties were examined. Table 4 summarizes the measurement results of the characteristic values of the carbon black and the physical properties of the rubber. Also in this case, it is apparent that the carbon black defined by the present invention simultaneously achieves the improvement of the abrasion resistance, the improvement of the fuel consumption characteristics, and the improvement of the grip force with respect to the standard sample.

[0050]

[Table 4]

Examples 12 to 13 Furnace blacks were experimentally produced using a carbon black reactor having a schematic sectional structure as shown in FIG. The insertion position of the feed oil for carbon black with respect to the flow of the combustion flame 2 into the reactor 1 is divided into two positions, and the normal feed oil is blown into the feed oil inlet (front stage) 3 and the feed oil inlet (late stage). In No. 4, the invention was devised so that nitrogen was concentrated on the surface of carbon black by blowing a feedstock oil having a particularly high nitrogen content. As a standard sample to be compared, carbon black produced by injecting ordinary raw material oil into both the first and second stages was prototyped. Table 5 summarizes the results of examining the characteristic values and rubber properties of the standard sample and the two types of prototype carbon blacks whose nitrogen content was adjusted. Obviously, even when nitrogen was introduced into the carbon black surface by the raw material oil, the carbon black defined in the present invention showed a remarkable improvement in rubber physical properties as in the case of heat treatment in ammonia gas.

[0052]

[Table 5]

By using the raw material oil having the nitrogen content adjusted as described above, the same effect as in the case of heat treatment in an ammonia gas atmosphere can be obtained in carbon black in which the nitrogen content and the oxygen content are controlled. It is essential for the improvement of the physical properties that nitrogen, oxygen, basic functional groups present on the surface of carbon black, and the surface activity represented by the amount of shell rubber satisfy the relationship defined in the present invention. However, the method is not limited to the exemplified ammonia gas treatment and the adjusting method such as increasing the amount of the nitrogen component in the feedstock oil used in the production.

[0054]

As described above, the rubber composition using the carbon black defined in the present invention as described above can be applied to a tire tread to provide abrasion resistance, grip power and fuel efficiency which are essentially important in a tire tread. Characteristics can be highly balanced. That is, high grip force and low fuel consumption characteristics can be simultaneously satisfied without impairing wear resistance.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a reactor used for a trial production of carbon black used in Examples 12 and 13.

[Explanation of symbols]

 1 Inside the reactor 2 Combustion flame 3 Feed oil inlet (front) 4 Feed oil inlet (back)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichiro Mukai 2775-17 Ozenji Temple, Aso-ku, Kawasaki City, Kanagawa Prefecture (72) Inventor Yasuhisa Sawa 1-2-11 Katano, Kokurakita-ku, Kitakyushu-shi, Fukuoka Prefecture (72) Inventor Kanai Takayo 3-4-5 Hayama-cho, Kokura-minami-ku, Kitakyushu-shi, Fukuoka (72) Inventor Masaki Kurihara 16-5-107, Yamaguchidai, Tawara-cho, Atsumi-gun, Aichi (72) Inventor Yuji Ota 1 Midorigahama, Tahara-cho, Atsumi-gun, Aichi -2

Claims (2)

[Claims] 1. A compressed DBP having a CTAB of 80 (m ² / g) or more
Belongs to a hard system region of 80 (mL / 100 g) or more, and (1) Nitrogen adsorption specific surface area (N ₂ SA); N ₂ SA-CTAB ≦ 50 (2) Nitrogen content (N; wt%); 3.0 × 10 ⁻³ ≦ N
/CTAB≦1.2×10 ⁻² (3) Oxygen content (O; wt%); O / CTAB ≦ 1.3 × 1
0 ^-2 (4) Weight ratio of nitrogen content to oxygen content O / N; O / N ≦
3.0 (5) Basic functional group concentration (B; meq / g); 1.8 × 10 ^-4
≦ B / CTAB ≦ 1.0 × 10 ⁻² (6) Shell rubber amount (S); 5.0 × 10 ⁻⁶ ≦ S ≦ 5.
Carbon black characterized by satisfying the selective property requirement of 0 × 10 ⁻⁵ . 2. A rubber composition comprising 100 to 100 parts by weight of rubber and 20 to 100 parts by weight of the carbon black according to claim 1.