Surface-treating agent for carbon black

Abstract: A surface-treating agent for carbon black comprising an amino-containing low molecular weight diene polymer which comprises a trunk chain of a low molecular weight diene polymer having a molecular weight of 1,000 to 100,000 and having side chains containing amino group in an amount of 0.25 to 20% by mole per the diene unit of the trunk chain at least at a portion except for the ends of the trunk chain. The carbon black surface-treated with the surface-treating agent of the present invention is blended with matrix polymer such as diene rubber, the obtained rubber composition which is superior in processability, mechanical properties and low fuel consumption and is useful, for example, for tyres can be provided.

Description: The present invention relates to a surface-treating agent for carbon black. Carbon black is employed widely as a filler for reinforcing plastics and rubbers. In recent years, high qualities such as high abrasion resistance are required for rubbers, and thus carbon black having a large specific surface area and high reinforcing ability has been used. Carbon blacks having a large specific surface area are, however, difficult to bond with a rubber component in a rubber composition, and the carbon black particles tend to aggregate with each other. As a result, it is not easy to disperse uniformly the carbon black into the rubber component, and in ordinary processing conditions, the desired reinforcing effect cannot be obtained. Also, if it is attempted to disperse uniformly, large mixing energy is required, which lowers productivity. Particularly in the field of tyres, low fuel consumption (low loss tangent) is required. If carbon black having a large specific surface area is blended to improve the mechanical strength of as tyre, the loss tangent (tan δ) becomes large and fuel consumption is increased. For improving the dispersibility of carbon black having a large specific surface area into a rubber component, a method for modifying the surface of the carbon black particles has been proposed and has been partly practised. For example, in JP-B-5643/1970, JP-B-24462/1983, JP-B-30417/1968 and USP 3282719, it is proposed that the aggregation force between the carbon black particles is reduced by addition of oily materials or high molecular weight materials. According to the proposals, however, there is less effect for carbon black having a large specific surface and improvement of mechanical properties and low fuel consumption of a tyre cannot be satisfied at the same time. Also, in JP-A-250042/1987, JP-A-250073/1987, JP-A-152165/1989 and JP-A-284564/1989, the surface of the carbon black particles is treated with an amine compound which is an antioxidant for rubber, and dispersibility of the carbon black is improved, and mechanical properties of the resultant rubber are also improved to some extent. The affinity to the matrix polymer is, however, insufficient and, further, low fuel consumption required in the field of a tyre is also insufficient. According to the descriptions of JP-A-152165/1989 and JP-A-284564/1989, carbon black particles are surface-treated with a saturated high molecular weight compound containing a functional group which has affinity to the polar groups on the surface of carbon black, and it is attempted to improve the affinity to the matrix polymer through the saturated high molecular chain portion. However, this technology utilises the chemical affinity of the saturated high molecular portion to the matrix polymer and there is no chemical bonding with the matrix polymer such as rubber. Therefore, bonding strength with the matrix polymer is often insufficient and, particularly in the field of tyres it is not sufficient to improve low fuel consumption (to decrease the loss tangent). Further, there is proposed to bond chemically a high molecular weight compound with the matrix polymer such as rubber in JP-A-100730.1994. However, the compound has a functional group at one end of the molecular chain, and thus sufficient effect cannot be obtained. It is an object of the present invention to overcome the above deficiencies. As a result of the inventors' investigation of the above-mentioned prior art they have discovered that the following properties are necessary for a surface-treating agent for carbon black, which is superior in reinforcing ability, dispersibility and processability and has strong bonding strength to the matrix polymer such as rubber. 1. Having a functional group which has interaction with an acidic functional group on the surface of carbon black particles and can bond with the carbon black particles. 2. Increasing the number of the functional groups in order to obtain strong interaction to carbon black. 3. Having a reactive portion which produces strong bonding with the matrix polymer such as diene rubber. 4. The reactive portion of (3) being not reactive during the process such as kneading step from the viewpoint of processability. 5. The whole molecular weight being relatively low from the viewpoint of reactivity with carbon black. According to the present invention a surface-treating agent for carbon black is characterised by comprising an amino-containing low molecular weight diene polymer which comprises a trunk chain of a low molecular weight diene polymer having a molecular weight of 1,000 to 100,000 and having side chains containing amino group in an amount of 0.25 to 20% by mole per the diene unit of the trunk chain at least at a portion except for the ends of the trunk chain. Hereinafter, said amino-containing low molecular weight diene polymer will be referred to as "low molecular weight diene polymer". Another aspect of the present invention relates to a carbon black characterised by being bonded with the low molecular weight diene polymer by a hydrogen bond. Hereinafter, said carbon black may be referred to as "surface-treated carbon black". Yet another aspect provides a rubber composition obtained by blending the surface-treating agent, a rubber component containing a diene rubber and a carbon black. In the surface-treating agent for carbon black of the present invention, the amino group portion of the amino-containing low molecular weight diene polymer is bonded by and through a hydrogen bond with the carbon black having on its surface functional groups such as hydroxyl group, carboxyl group, carbonyl group and/or a quinone group. Namely, in the present invention, the surface-treatment of carbon black means to bond the low molecular weight diene polymer of the surface-treating agent with the carbon black through the hydrogen bond. Therefore, the aggregation force of the particles of the surface-treated carbon black according to the present invention becomes weaker than that of the carbon black before the surface treatment. The surface-treated carbon black shows good dispersibility in the matrix polymer which has affinity to the low molecular weight diene polymer bonded on the surface of carbon black particles through the hydrogen bond. Also, the low molecular weight diene polymer bonded with the carbon black can be bonded with the matrix polymer at its carbon-carbon double bond portion. Namely, the carbon black can be bonded with the matrix polymer via the low molecular weight diene polymer. The matrix polymer may be a polymer which can be bonded with the carbon-carbon double bond portion of the low molecular weight diene polymer. As the matrix polymer, there are, for example, styrene-butadiene block copolymer, 1,2-polybutadiene, trans-polyisoprene, various diene rubbers, butyl rubber, halogenated butyl rubber and EPDM as well as various kinds of thermoplastic resins, thermosetting resins containing a vulcanisable group. Among them, the diene rubbers having a carbon-carbon double bond, which is used particularly in the field of tyres, are suitable from the viewpoints that the diene rubbers have affinity to the low molecular weight diene polymer chain of the surface-treating agent and both can be bonded chemically with each other at their carbon-carbon double bond portions. As the diene rubbers, there are, for example, natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR). The diene rubbers may be used alone, or in optional admixture of two or more. It is effective to use the carbon black surface-treated with the surface-treating agent of the present invention in the field of tyres. Hitherto, if the conventional carbon black is added particularly to a rubber composition for a tyre which comprises a diene rubber as rubber component, as mentioned above, improvement of mechanical properties of a tyre is recognised but fuel consumption is increased. To the contrary, if the carbon black surface-treated with the surface-treating agent of the present invention is employed, a tyre superior in both mechanical properties and low fuel consumption can be obtained, although the reason for this is not clear. The reason why the low molecular weight diene polymer having a carbon-carbon double bond is selectively employed as the constituent of the surface-treating agent for carbon black of the present invention is that the low molecular weight diene polymer is less reactive during process steps such as the mixing step with the matrix polymer and good processability can be ensured. For the means to bond chemically the matrix polymer with the low molecular weight diene polymer, there may be employed, for example, a method of vulcanisation using sulfur or a phenolic resin type vulcanising agent in the case where the matrix polymer is a thermoplastic resin, a method of vulcanisation by using sulfur in the case where the matrix polymer is diene rubber, or the like. Particularly in the field of tyres wherein the matrix polymer is the diene rubber, since crosslinking between the unsaturated groups both in the surface-treating agent of the present invention and in the diene rubber is produced at the time when the diene rubber is vulcanised with sulfur, strong bonding can be obtained without adding any particular reaction step. The low molecular weight diene polymer of the amino-containing low molecular weight diene polymer which constitutes the surface-treating agent for carbon black of the present invention is a polymer which has a low molecular weight and is prepared from a diene monomer, for example, a conjugated diene such as butadiene, isoprene or 1,3-pentadiene alone or in optional admixture of two or more, said polymer may contain a copolymer component such as styrene or acrylonitrile. For the low molecular weight diene polymer, there are, for example, liquid polyisoprene, liquid isoprene-styrene copolymer, liquid polybutadiene, liquid isoprene-butadiene copolymer, liquid styrene-butadiene copolymer, liquid acrylonitrile-butadiene copolymer, and the like. Among them, liquid polyisoprene and liquid polybutadiene are preferable from the viewpoint of good affinity to the diene rubber and, further, liquid polyisoprene is further preferable from the viewpoint that excellent strength is obtained. The molecular weight of the low molecular weight diene copolymer is 1,000 to 100,000, because when the molecular weight is too low, improvement of mechanical properties and low fuel consumption of an obtained tyre cannot be satisfied at the same time, and when the molecular weight is too high, the viscosity becomes high, which results in the reaction with carbon black becoming difficult, and then the workability for the surface-treatment of the carbon black becomes lowered. The molecular weight is preferably 3,000 to 80,000 from the viewpoint of suitable viscosity and good handling workability. The molecular weight is further preferably 5,000 to 50,000 from the viewpoint that mechanical properties and low fuel consumption of a tyre are both excellent. In the present invention, by introducing an amino group into the low molecular weight diene polymer, the introduced amino group is bonded through the hydrogen bond with the acidic functional group such as hydroxyl group, carboxyl group, carbonyl group and/or quinone group on the carbon black surface. The amino-containing low molecular weight diene polymer of the present invention contains the amino group in an amount of 0.25 to 20% by mole per diene unit in the trunk chain, because the larger number of the functional group is preferably for the hydrogen bond with the carbon black, the chemical bonding between the low molecular weight diene polymer and the matrix polymer such as diene rubber is not prevented (for example, vulcanisation property is not decreased), and the processability during the kneading with the matrix polymer is not lowered. The content of amino group of the low molecular weight diene polymer is preferably 0.5 to 15% by mole from the viewpoint that decrease of processability caused by increase of the viscosity is prevented, further preferably 1 to 10% by mole from the viewpoint that scorch time becomes long to some extent. With respect to the structure of the amino-containing low molecular weight diene polymer, there are assumed, for example, a case wherein a hydrogen atom on a carbon atom which constitutes the trunk chain and/or side chain of the low molecular eight diene polymer is directly substituted by an amino group, a chase wherein an amino group is bonded through an alkylene group having 1 to 6 carbon atoms, and a case wherein an amino group is bonded through sulfur atom and/or oxygen atom and an alkylene group having 1 to 6 carbons. The method of introducing the amino group into the low molecular weight diene polymer is not particularly limited, and may be a method which is usually employed. For example, a compound containing amino group may be bonded with the low molecular weight diene polymer, or an amino group may be introduced by reacting ammonia or the like. For example, firstly a solution obtained by dissolving the low molecular weight diene polymer into an organic solvent such as xylene or toluene is mixed with a primary amine such as cysteamine or aminothiophenol, a secondary amine such as ethyl thiourea or a tertiary amine such as diethyl thiourea alone or in optional admixture of two or more. The mixture is agitated to 60°l to 160°C for 30 to 120 minutes in an atmosphere of inert gas such as nitrogen or argon to conduct addition-reaction of the low molecular weight diene polymer with the amine. Then, after cooling to room temperature by natural cooling or the like, the solution obtained by the reaction is poured into water, neutralised with an acid such a hydrochloric acid or sodium hydrogencarbonate, and then washed with water again. Further, the organic solvent is removed by heating and drying under vacuum to obtain the desired compound. According to another method of introducing an amino group into the low molecular weight diene polymer thionyl chloride is added to a solution obtained by dissolving the low molecular weight diene .polymer having hydroxyl group into an organic solvent such as xylene or toluene, and the obtained mixture is refluxed at 80° to 140°C for 30 to 120 minutes. Then, after cooling to room temperature by natural cooling or the like, the mixture is poured into water and washed with water several times. Then, ammonium gas generated from aqueous ammonia is passed through the organic phase obtained by separating from the washed mixture by means of a separating funnel to react the low molecular weight diene polymer with ammonium. After the reaction the mixture is poured into water and washed with the above-mentioned acid and water in this order. Subsequently, the organic solvent is removed by heating and drying under vacuum to obtain a desired compound. The carbon black used in the present invention may be a carbon black which as the functional group such as hydroxyl group, carboxyl group, carbonyl group and/or quinone group. The functional group is chemically bonded with an amino group of the amino-containing low molecular weight diene polymer of the surface-treating agent. As the carbon black, there may be employed furnace black, channel black, acetylene black, thermal black or lamp black alone or in optional admixture of two or more. According to the present invention, a carbon black having a relatively high specific surface area can be employed. The BET specific surface area of the carbon black may be 20 to 200m 2 /g, and preferably 100 to 200m 2 /g from the viewpoint that dispersibility of the surface-treated carbon black in the matrix polymer is good, further preferably 130 to 200m 2 /g from the viewpoint that mechanical properties of the rubber moulded article which contains the surface-treated carbon black are improved. Examples of carbon black having a BET specific surface area of 20 to 200m 2 /g are, for instance, GPF, FEF, HAF, ISAF, SAF, examples of 100 to 200m 2 /g are, for instance ISAF, SAF, and examples of 130 to 200m 2 /g are, for instance, SAF, and the like. The iodine adsorption number of the carbon black may be 30 to 160mg/g, and preferably 80 to 160mg/g from the viewpoint that the effect of the surface-treating agent is high, and further preferably 110 to 160mg/g from the viewpoint of improvement of mechanical properties of the rubber composition which contains the surface-treated carbon black. Examples of carbon black having an iodine adsorption number of 30 to 160mg/g are, for instance, FEF, HAF, ISAF, SAF, examples of 80 to 160mg/g are, for instance, ISAF, SAF, and examples of 110 to 160mg/g are, for instance, SF, and the like. As a method of surface-treating the carbon black with the surface-treating agent of the present invention, for example, the carbon black is added to a solution obtained by dissolving the surface-treating agent in xylene or toluene. The solution is subjected to agitation and mixing, and the resulting precipitate is dried by removing the organic solvent under vacuum to obtain the surface-treated carbon black. Also, in order to obtain a rubber without previous surface-treatment of the carbon black, composition, the carbon black and the surface-treating agent are blended separately with the rubber component and then the surface-treatment of the carbon black is carried out during mixing. The rubber composition of the present invention contains the rubber component containing the diene rubber. The kind of diene rubber is not particularly limited, and the effects of the present invention can be obtained with all kinds of diene rubber. As diene rubber, the diene rubber used generally for a rubber composition for tyres such as the above-mentioned NR, BR, IR, SBR, NBR can be used alone or in admixture of two or more. In addition, the usual additives for rubbers, for example, vulcanising agent such as sulfur, accelerator, antioxidant, softening agent, zinc oxide and/or stearic acid may be added to the rubber composition of the present invention in an amount where the effects of the present invention are not decreased. The rubber composition of the present invention may be prepared and vulcanised in the usual manner. When the rubber composition of the present invention is used as a rubber composition for a tyre tread or sidewall, a tyre superior in both low fuel consumption and abrasion resistance is the result. Hereinafter, the present invention is explained on the basis of Examples. It should be noted that the present invention is not limited thereto. Preparation Example 1 (Preparation of the surface-treating agent) 100g of LIR-30 (liquid polyisoprene, molecular weight: 29,000) available from KURARAY CO LTD as the low molecular weight diene polymer was dissolved in xylene to obtain a 10% by weight solution. 11g of cysteamine was admixed with the solution and addition reaction was conducted by agitating the obtained mixture in an atmosphere of nitrogen at 130°C for 2 hours. After cooling to room temperature by natural cooling, the mixture was poured into water, neutralised with formic acid and washed with water again. The organic phase and the water phase were separated by means of a separating funnel and the organic solvent was removed to obtain Surface-Treating Agent 1 of the present invention. The content of amino group of Surface-Treating Agent 1 is 2% by mole per the diene unit. As the method of determining the content of amino group, there was employed a method in which the content was calculated from an intensity ratio of H of NH 2 and H of CH 3 of polyisoprene in 1 H-NMR. An infrared ray analysis and differential thermal analysis were conducted with respect to the obtained surface-treating agent. According to the infrared spectra, absorption of amino group was observed at 1600 cm -1 . In the differential thermal analysis, though a peak of the melting point could be observed at around 98°C in the case of cysteamine alone, the peak at around 98°C disappeared with respect to the surface-treating agent of the present invention. Therefore, it was recognised that an amino group was introduced to the low molecular weight diene polymer. Preparation Example 2 (Preparation of the surface-treating agent) Surface-Treating Agent 2 of the present invention was prepared in the same manner as in Preparation Example 1 except that the amount of cysteamine was 87.8g. The content of amino group of Surface-Treating Agent 2 was 15% by mole per the diene unit. The measurement of the amino content was conducted in the same manner as in Preparation Example 1. Measurements by infrared ray analysis and differential thermal analysis of the obtained surface-treating agent were conducted. According to the infrared spectra, the absorption of amino group was observed at 1600 cm -1 , and it was recognised that an amino group was introduced to the low molecular weight diene polymer. Preparation Example 3 (Preparation of the surface-treating agent) 100g of the LIR 506 (liquid hydroxylated polyisoprene, molecular weight: 25,000, number of functional group: 5.9 OH/molecule) available from KURARAY CO LTD was dissolved in xylene to obtain a 10% by weight solution. 2.8g thionyl chloride was admixed with the solution and the obtained mixture was refluxed at 130°C for 2 hours. Then, after cooling to room temperature by natural cooling, the mixture was poured into water and washed with water twice. The organic phased was collected, and ammonia generated from aqueous ammonia (28%) was introduced into the organic phase to react at 130°C for 2 hours. Them, the mixture was poured into water, neutralised with sodium hydrogencarbonate and washed with water. The water phase and the organic phase were separated by means of a separating funnel. The organic solvent was removed from the separated organic phase by drying under vacuum to obtain Surface-Treating Agent 3 of the present invention. The content of amino group of Surface-Treating Agent 3 was about 6% by mole per diene unit. The measurement of the amino content was conducted in the same manner as in preparation Example 1. The measurements by infrared ray analysis and differential thermal analysis of the obtained surface-treating agent were conducted. According to the infrared spectra, an absorption of amino group was observed at 1600 cm -1 , and it was recognised that an amino group was introduced to the low molecular weight diene polymer. Preparation Example 5 (Preparation of the surface-treating agent) Surface-Treating Agent 5 was prepared in the same manner as in Preparation Example 2 except that LBR:Poly-bd R45M (liquid polybutadiene, molecular weight: 3,000) available from IDEMITSU SEKIYU KAGAKU KABUSHIKI KAISHA was used as the low molecular weight diene polymer. The content of amino group of the surface-treating agent 5 was 2% by mole per the diene unit. The measurement of the amino content was conducted in the same manner as in preparation Example 1. The measurements by infrared ray analysis and differential thermal analysis of the obtained surface-treating agent were conducted. According to the infrared spectra , an absorption of amino group was observed at 160 cm -1 , and it was recognised that an amino group was introduced to the low molecular weight diene polymer. The low molecular weight diene polymers and the amines used for the preparation of Surface-Treating Agents 1 to 5 and the contents of amino group of Surface-Treating Agents 1 to 5 are shown in Table 1. Comparative Preparation Example 1 (Preparation of the comparative surface-treating agent) A living polymer was prepared by polymerising isoprene monomer in n-hexane in the presence of n-butyllithium as an initiator. Carbon dioxide gas was introduced to the polymer in an amount of 10 times by mole of the polymerisable end to obtain Polyisoprene (I) containing COOLi at one end of the molecular chain. Polyisoprene (I) containing COOLi at one end of the molecular chain was washed with hydrochloric acid to obtain Polyisoprene (II) containing COOH at one end. Then, Polyisoprene (II) containing COOH at one end was dissolved in toluene and reacted with hydrazin in an amount of 100 times by mole of the end COOH to obtain polyisoprene (Comparative Surface-Treating Agent) containing NH 2 at one end of the molecular chain. The conversion of COOH to NH 2 was recognised by infrared ray analysis. Experimental Example 1 (Preparation of the surface-treated carbon black) Surface-Treated Carbon Blacks 1 to 5 were prepared by using Surface-Treating Agents 1 to 5 obtained in the Preparation Examples 1 to 5 and N110 (SAF class: BET specific surface area of 163m 2 /g, iodine adsorption number of 140mg/g) available from MITSUBISHI CHEMICAL CORPORATION as the carbon black. After dissolving each of Surface-Treating Agents 1 to 5 in xylene, N110 was dipped into the solution and, then, allowed to stand at room temperature for a day, and dried under vacuum to obtain Surface-Treated Carbon Blacks 1 to 5. (Preparation of the rubber composition) Subsequently, 80 parts by weight of natural rubber and Surface-Treated Carbon Blacks 1 to 5 were mixed in the mixing ratio shown in Table 2 and kneaded together with other additives except for sulfur at 100°C for 4 minutes by means of a BR type Banbury mixer to obtain Rubber Compositions 1 to 5 of the present invention. The obtained Rubber Compositions 1 to 5 were transferred to open rolls, and press vulcanisation was carried out at 150°C for 30 minutes to obtain Vulcanised Rubber Compositions 1 to 5. At the time of the mixing, as the other additives, 2 parts by weight of stearic acid, 3 parts by weight of zinc oxide, 1.5 parts by weight of sulfur and 1 part by weight of NOCCELER NS ((N-t-butyl-2)-benzothiazolylsufeneamide) available from OUCHI SINKO KAGAKU KOGYO KABUSHIKI KAISHA as accelerator were blended in all of the Rubber Compositions. Then, the following tests were carried out to evaluate processability, mechanical properties and low fuel consumption with respect to Vulcanised Rubber Compositions 1 to 5 which were obtained by vulcanising Rubber Compositions 1 to 5 of the present invention. Testing methods (i) Mooney test: Mooney viscosity (ML(1+4)) and scorch time (minute) were measured at 130°C. The results are shown in Table 2. The smaller the Mooney viscosity is, the better the processability is, and the shorter the scorch time is, the more difficult the handling of the non-vulcanised rubber is. (ii) Tensile test: Tensile stress (M300) (Pa) at the time of 300% elongation, tensile strength (Tb) and elongation at break (Eb) (%) were measured according to JIS K 6301. The results are shown in Table 2. (iii) Hardness test: Hardness was measured according to JIS K 6301. The results are shown in Table 2. (iv) Viscoelasticity test: Viscoelasticity (E*) (MPa) and loss tangent (tan δ) were measured by using Visco Elasticity Spectrometer VES available from KABUSHIKI KAISHA IWAMOTO SEISAKUSHO under measuring conditions of a temperature of 70°C, initial stress of 10% and dynamic stress of 2%. The results are shown in Table 2. The smaller the loss tangent is, the lower the fuel consumption is. (v) Abrasion test: Abrasion loss was measured by using a Lambourn abrasion tester under measuring conditions of a temperature of 23°C, slip ratio of 20% and testing time of 5 minutes. The results were represented as an index on the assumption that the abrasion loss of Comparative Rubber Composition 1 described below was 100. The results are shown in Table 2 for abrasion property. The larger the index is, the better the abrasions resistance is. (vi) Degree of swelling with toluene: Volume change before and after swelling was measured by dipping the vulcanised rubber compositions into toluene of 40°C for 48 hours, and the degree of swelling with toluene was calculated according to the following equation: Degree of swelling with toluene (%) = (Volume after swelling/Volume before swelling) x 100 The results are shown in Table 2. The lower the degree of swelling with toluene is, the higher the crosslinking density is. (Preparation of the comparative rubber composition) 80 parts by weight of natural rubber and the same additives as used for the above-mentioned Rubber Compositions of the present invention were mixed in the mixing ratio shown in Table 2. The mixture without sulfur was kneaded at 100°C for 4 minutes by means of a BR type Banbury mixer to obtain Comparative Rubber Composition. After transferring into open rolls, Comparative Rubber Composition was vulcanised with addition of sulfur at 150°C for 30 minutes to obtain Vulcanised Comparative Rubber Compositions 1 to 5. Then, with respect to Vulcanised Comparative Rubber Compositions 1 to 5, the same evaluations were conducted as for the above-mentioned rubber compositions. The results are shown in Table 2. Experimental Example 2 (Preparation of the surface-treated carbon black and the rubber composition) By using the surface-treating agent 1 obtained in Preparation Example 1 and, as the carbon black, N110 (SAF class: BET specific surface area of 163m 2 /g, iodine adsorption number of 140mg/g), N220 (ISDAF class: BET specific surface area of 121m 2 /g, iodine adsorption number of llmg/g), N330 (HAF class: BET specific surface area of 82m 2 /g, iodine adsorption number of 83mg/g) and N550 (FEF class: BET specific surface area of 43m 2 /g, iodine adsorption number of 42mg/g) available from MITSUBISHI CHEMICAL CORPORATION, Surface-Treated Carbon Blacks 1 and 6 to 8 were obtained in the same manner as in Experimental Example 1 and, further, Rubber Compositions 1 and 6 to 8 and Vulcanised Rubber Compositions 1 and 6 to 8 were obtained in the same manner as in Experimental Example 1. Them, the same evaluations were conducted as in Experimental Example 1. The results are shown in Table 3. (Preparation of the comparative rubber composition. According to the mixture and the mixing ratio shown in Table 3, Vulcanised Comparative Rubber Compositions 2 and 6 to 8 were obtained in the same manner as in Experimental Example 1. Then, the same evaluations were conducted as in Experimental Example 1. The results are shown in Table 3. As is seen from Tables 2 and 3, each of the vulcanised rubber compositions which are prepared by using the rubber compositions comprising the carbon black surface-treated with the surface-treating agent fro carbon black of the present invention, has superior processability, mechanical properties and provides in a tyre low fuel consumption compared to the comparative vulcanised rubber compositions. When the other components or additives described in the specification of the present invention are used instead of the components and additives used in Examples, substantially the same results can be obtained. When the carbon black surface-treated with the surface-treating agent of the present invention is blended with the matrix polymer such as diene rubber, the rubber composition which is superior in processability, mechanical properties and low fuel consumption and is useful, for example, for tyres can be provided.

Claims: A surface-treating agent for carbon black characterised by an amino-containing low molecular weight diene polymer which comprises a trunk chain of a low molecular weight diene polymer having a molecular weight of 1,000 to 100,000 and having side chains containing amino group in amount of 0.25 to 20% by mole per the diene unit of the trunk chain at least at a portion except for the ends of the trunk chain. A carbon black characterised by being bonded with the amino-containing low molecular weight diene polymer of claim 1 through hydrogen bond. A rubber composition characterised by being obtained by blending a rubber component containing a diene rubber and the carbon black of claim 2. A rubber composition characterised by being obtained by blending the surface-treating agent of claim 1, a rubber component containing a diene rubber and a carbon black.

Inventors: MINAGAWA YASUHISA, MURAOKA KIYOSHIGE, MINAGAWA, YASUHISA, MURAOKA, KIYOSHIGE
Applicants: SUMITOMO RUBBER IND, SUMITOMO RUBBER INDUSTRIES LIMITED
Application year: 1997
Main classification: C09C1
IPC codes: C08G83, C08C19, C08K9, B60C1, C09C1, C09C3