JPH11116841A - Silica-attached carbon black, its production and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject carbon black showing viscoelastic properties comparable with those of silica, improving poor dispersibility and processability of silica to those comparable with carbon black's and useful as an additive for rubber by surface treatment of carbon black with a specific compound to fuse silica with the carbon black surfaces. SOLUTION: This carbon black, coated with 10 wt.% or less of silica and having the OH group at 0.6/nm<2> or more, is obtained by surface treatment with a silicon-containing compound, with organic groups totally bound to silicon via oxygen, to fuse it with the carbon black surfaces. It is recommended that the silicon-containing compound is an oligomer shown by the formula [(n) is 1 or 2; (m) is 0 or more; and R is a 1-4C alkyl], e.g. tetramethoxysilane condensate of low molecular weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to carbon black to which silica is impregnated, and to its application to rubber compositions.

[0002]

2. Description of the Related Art Tan index is an index of heat generation when a vulcanized rubber composition containing reinforcing particles is repeatedly deformed.
For example, it is known that the tan δ at 50 to 70 ° C. should be reduced to reduce the rolling resistance of the tire tread and reduce fuel consumption. On the other hand, the braking characteristics and the like on a wet road surface are better when tan δ near 0 ° C. is larger. Improve the temperature dependence of tan δ, ie, 50-70
As a method of reducing tan δ at 0 ° C. and increasing tan δ at around 0 ° C., blending silica as a filler has been attempted. For example, JP-A-3-252433 describes that silica and a silane coupling agent are blended in a solution polymerization method SBR. Also, Japanese Patent Laid-Open No. 7-1
Japanese Patent No. 65991 describes that a bifunctional material capable of reacting particularly with silica and rubber is excellent as a silane coupling material.

[0003] This is because particles having silanol groups on the surface, for example, silica particles are kneaded into a diene rubber together with a silane coupling agent such as bis (triethoxysilylpropyl) -tetrasulfane and vulcanized. It is known that particles and rubber are chemically bonded via a coupling agent, whereby the tan δ at around 60 ° C. of the particle-containing vulcanized rubber composition is reduced, and the abrasion resistance is improved. It is considered that the improvement of the physical properties of the material is observed.

[0004] However, when silica is blended as a filler, the temperature dependence of tan δ can be improved, but the silica filler has a strong self-cohesive force and is difficult to disperse in rubber, resulting in poor workability. There is. In addition, an expensive syringe coupling agent is usually added to silica in an amount of 5-1.
There is also a problem that the compound cost increases because it is necessary to add as much as 5%.

[0005] Further, when a silane coupling agent having a sulfur atom as described above is blended without blending a silica filler with carbon black, the particle-containing rubber composition becomes 6%.
There is a case where tan δ around 0 ° C. is considerably reduced.
However, at low temperature (−10 to 0 ° C.), under low strain (0.1 to 1)
Braking characteristic for complex elastic modulus (E ^*) and dynamic elastic modulus (E ') is high in%) there is a drawback to decrease.

[0006] On the other hand, it has been proposed to surface-treat carbon black blended in a rubber composition with silica or silane. For example, JP-A-53-100190 and JP-A-61-291659 describe a method in which an organic compound or organometallic compound of silicon dissolved in a solvent or water is mixed with carbon black and dried. Typically, dimethylpolysiloxane or silicone oil is used as the silicon compound. Also,
JP-A-56-125249 describes a carbon black having a surface coated with a silane coupling agent dissolved in a solvent. JP-A-63-635755 proposes a method of dispersing carbon black in water and neutralizing sodium silicate with sulfuric acid to deposit amorphous silica on the carbon black surface.
However, it is hard to say that any of these methods is suitable for industrialization in terms of process and economy such as removal and recovery of a solvent or neutralization operation. Also, Japanese Patent Application Laid-Open No. Hei 4-233976 proposes that carbon black is chemically modified with a specific organic silicon compound (specifically, a sulfur-containing silane coupling agent having a specific structure). However, this method also has process and economic problems such as an extraction operation and a post-treatment for denaturation. Moreover, in the method of treating these carbon blacks with a surface treatment agent such as silica or silane, it is expected that the surface treatment agent will not adhere sufficiently uniformly to all carbon black surfaces.

[0007]

DISCLOSURE OF THE INVENTION In view of the above problems, the inventors of the present invention have a viscoelastic property comparable to that of silica (temperature dependence of tan δ), and have a low dispersibility and a low processability of carbon black. In order to provide a similarly improved reinforcing particle and a rubber composition containing the same, a method for attaching silica to the surface of carbon black has been studied.

[0008]

As a result, when the silica component is added to the carbon black to improve the braking characteristics when the carbon black is blended with the rubber component, the function of the surface of the carbon black together with the amount of the silica added is improved. It has been found that the amount of groups, especially OH groups, especially silanol groups, has a significant effect. Furthermore, by performing a surface treatment of carbon black using a specific silicon-containing compound, silanol groups can be efficiently and effectively present on the surface of carbon black. The rubber composition containing black was found to exhibit excellent properties, and the present invention was completed.

That is, according to the present invention, the amount of silica
% By weight or less, in silica-impregnated carbon black having OH groups of 0.6 / nm ² or more. Such a carbon black of the present invention has a large number of silanol groups introduced on its surface, and has been attempted by blending particles having a silanol group such as silica particles, a reduction in tan δ of the vulcanized rubber composition at around 60 ° C., Improvement of physical properties such as abrasion resistance can be achieved without blending particles such as silica.

In addition, a low temperature range (-10 to 0) such as when a silane coupling agent having a sulfur atom is blended.
° C), complex elastic modulus (E ^* ) under low strain (0.1-1%)
It is also possible to eliminate the drawback that the braking characteristics are reduced due to high dynamic elastic modulus (E '). Moreover, according to the silica-impregnated carbon black of the present invention, it is possible to improve the difficulty of dispersibility and the difficulty of processing, which are disadvantages of silica, to the same level as carbon black. Therefore, according to the present invention, reinforcing particles having both advantages of silica and carbon black,
That is, the present invention provides reinforcing particles having viscoelastic characteristics (temperature dependence of tan δ) comparable to that of silica, and having hardly dispersible and difficult-to-process silica as improved as carbon black, and a rubber composition comprising the same. It is possible to do.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, carbon black as a raw material to which silica is attached in the present invention is not particularly limited, but when blended with rubber, various types known as usable in the rubber industry, for example, furnace black (A
Classification according to STMD1765), channel black,
Thermal black, acetylene black and the like are preferred. In order to produce such a raw material carbon black, for example, in the case of furnace black, a highly aromatic heavy oil is introduced into a high-temperature gas stream, and the heavy oil can be obtained by incomplete combustion or thermal decomposition.

The amount of silica impregnated in the carbon black impregnated with silica of the present invention is 10% by weight or less, preferably 6% by weight or less, more preferably 5 to 2% by weight. If the amount of silica impregnated exceeds 10% by weight, the dispersion characteristics when compounded with rubber will be significantly deteriorated. Next, the silica-impregnated carbon black of the present invention has an OH group content of at least 0.6 / nm ² , particularly preferably at least 0.8 / nm ² . OH
The measurement of the group was performed and determined by the following method.

2 g of the sample carbon black was precisely weighed in a sample container, and about 100 ml of dilute hydrochloric acid was added thereto, followed by stirring.
Adjust so that it becomes 3.5. Further, 30 g of sodium chloride is added so that the total volume becomes about 150 ml. Thereafter, a 0.100N aqueous sodium hydroxide solution was added, and p
Adjust to H4.0. Metrohm automatic titrator (E
(536 + 655 Dosimat) using an aqueous 0.100 N sodium hydroxide solution, and the titer up to pH 9.0 is read from the recording paper. The amount of OH group is calculated from the titer based on the following formula.

[0014]

## EQU2 ## Titration / 1000 ml × 0.1 N × Avogatro number / (nitrogen specific surface area × collected amount) = O per nm ²
Number of H groups The amount of silanol groups in the OH groups is preferably at least 0.3 / nm ² , particularly preferably 0.6 / nm ^2.
Above.

The amount of the silanol group can be determined by previously measuring the amount of the OH group in the carbon black before the silica is attached by the above method, and subtracting it from the amount of the OH group measured after the silica is attached. . Particularly preferably, the number of OH groups is 5.5 × 10 ¹⁹ / g or more. The number of OH groups per unit g can be calculated from the above titration method and the determined value, and the specific surface area of the carbon black used. Particularly preferably, when the amount of silica impregnated is a wt% and the amount of silanol groups is b / nm ² , these a and b satisfy the following relationships.

[0016]

## EQU3 ## a ≦ 10, b ≧ 0.3, b / a ≦ 0.1 In this range, very excellent properties are exhibited when blended with the rubber component. The carbon black of the present invention described above can be obtained by bringing carbon black into contact with a specific silicon compound and performing a surface treatment. That is, all organic groups come into contact with the silicon compound bonded to silicon via oxygen.

Such silicon compounds typically include silanes and / or polysiloxanes in which all organic groups are bonded to silicon via oxygen, and all organic groups are bonded to silicon via oxygen. Silanes and / or siloxanes are hydrogen, an alkyl group,
A silane to which a vinyl group, a phenyl group or another functional group is bonded, and / or (Si—O) n as a main chain (the main chain may be branched or form a ring);
Refers to a polysiloxane in which hydrogen, an alkyl group, a vinyl group, a phenyl group, or another functional group is bonded via O.

Preferably, a tetraalkoxysilane and / or polyalkoxysiloxane in which a C1-4 alkoxy group is bonded to Si is used. The latter can be easily obtained as the former low condensate. Examples of the latter include those represented by the following general formula (A).

[0019]

(RO) ₃ —Si—O— [Si (OR) _n —O _(3-n) ] _m R (A) where n = 1 or 2, m is an integer of 0 or more, and R are X1-4 alkyl groups which may be different from each other. The alkyl group may be replaced by hydrogen. In particular, R = CH ₃
As an example of-, there is an oligomer which is a low condensate of tetramethoxysilane, and "MKC silicate MS51" manufactured by Mitsubishi Chemical Co., Ltd. contains a small amount of a monomer (that is, tetramethoxysilane) of 1% by weight or less, For this reason, it is preferable because it is excellent in quality stability, is less toxic by monomers, and is safe in use. In the present invention, silane and / or polysiloxane in which all of these organic groups are bonded to silicon via oxygen can be used as it is. Alternatively, a hydrolyzed condensate obtained by further condensing a hydrolyzed product may be used.

Examples of the hydrolytic condensate include “MKC silicate MS51SG1” (manufactured by Mitsubishi Chemical Corporation) obtained by hydrolyzing and condensing the above oligomer of tetramethoxysilane in alcohol. This is preferably used since a large number of silanol groups are generated by hydrolysis. Since these tetraalkoxysilanes and / or polyalkoxypolysiloxanes have a large number of alkoxy groups, they are extremely excellent in adhering to carbon black and generating silanol groups, and the resulting surface-treated carbon black and a rubber composition containing the same are compounded. It is conceivable that the properties of the product are greatly improved.

It is to be noted that a mixture of silane and / or polysiloxane in which all of these organic groups are bonded to silicon via oxygen and other organic components such as a silane coupling agent may be brought into contact with carbon black. Absent. In this case, the other organic components are silanes and / or polysiloxanes 10 in which all organic groups are bonded to silicon via oxygen.
It is 50 parts by weight or less, preferably 20 parts by weight or less based on 0 parts by weight. Examples of the organic component include various resin components and the like in addition to various silane coupling agents, and may be appropriately selected as needed, and may be blended with the silane and / or polysiloxane.

The surface treatment of carbon black with silane and / or polysiloxane in which all organic groups are bonded to silicon via oxygen is performed by bringing these silicon compounds into contact with carbon black. The temperature at the time of contact is preferably 200 ° C. or less. Above 200 ° C. evaporation (gasification) of silanes and / or polysiloxanes in which all organic groups are bonded to silicon via oxygen
Is promoted, and problems such as a decrease in the adhesion yield during spraying occur.

The amount of silane and / or polysiloxane in which all organic groups are bonded to silicon via oxygen is:
The amount of carbon black impregnated with silica is selected so as to fall within the above range, and is generally 0.1 to 50 parts by weight based on 100 parts by weight of carbon black. More preferably, it is 0.2 to 30 parts by weight. If the amount is too small, the effect of improving the temperature dependency of tan δ is small, while if it is too large, the dispersibility during kneading deteriorates and the cost increases.

The contact between the silane and / or polysiloxane in which all of the organic groups are bonded to silicon via oxygen and the carbon black is not particularly limited as long as they can contact each other as described above. However, for example, the contact can be easily made by adding one to the other. In particular, it is preferable that they are brought into contact in the step of granulating carbon black. That is, the silane and / or polysiloxane, in which all organic groups are bonded to silicon via oxygen, is added to the ungranulated carbon black, or granulation is performed while adding the silane and / or polysiloxane. Can be attached to the carbon black surface. The granulation step is preferably wet granulation. Emulsifying and dispersing silane and / or polysiloxane in which all organic groups are bonded to silicon via oxygen in non-granulated carbon black in the same amount of granulated water with nonionic surfactant etc. , An addition method is used. By performing the contact in the "in the presence of water" in this manner, in the subsequent drying step, hydrolysis of the organic group bonded to silicon via oxygen is promoted, and a large number of silanol groups are generated.

After the granulation, a drying step is performed, and it is preferable that the residual moisture in the drying step is 5% by weight or less. The drying step can be performed using a device such as a dryer in the presence of moisture. At this time, it is considered that a part of the organic group bonded to silicon via oxygen is hydrolyzed to generate a silanol group. The carbon black of the present invention is
Although not particularly limited, the nitrogen specific surface area is 20 to 300 m ^2.
/ G and DBP are preferably 50 to 250 cc / 100 g.

According to the production method of the present invention, carbon black to which silica is adhered can be easily produced without requiring complicated operations such as treatment with water glass. Further, according to the carbon black of the present invention, substantially all of the silica component can be uniformly present on the surface of the carbon black as a fine region. Can be obtained.
Also, quality control is easy. Further, according to the present invention, almost all of the charged amount of the silica component, that is, 80%
At least 90% by weight of carbon black can be attached to carbon black, and the yield is very good.

As a method of attaching the silica component to the carbon black, for example, treatment with water glass or colloidal silica can be considered. However, these treatments require complicated operations such as neutralization, and the above-mentioned specific silane, Alternatively, unlike the case where polysiloxane is used, it is difficult to add a large number of silanol groups at the most suitable amount of silica to be impregnated like the carbon black of the present invention.
Although the reason for this is not completely clear, observation by an electron micrograph shows that the adhesion state of the silica component to the carbon black seems to be different, and that the colloidal silica originally has OH groups and the like. The functional groups are significantly less in order than the OH groups that can be generated by the hydrolysis of the silane or polysiloxane described above,
It is considered that the reactivity with carbon black is also poor. Further, silane coupling is a compound in which an organic group such as an alkyl group or a phenyl group is directly bonded to silicon, or a compound in which various organic groups are directly bonded to silicon, which is usually called an organopolysiloxane. Unlike the specific silane or polysiloxane used in the production method of the present invention, the agent does not have a large number of functional groups capable of easily generating an OH group by hydrolysis as a group bonded to silicon. . Therefore, unlike the case of the production method of the present invention, even if it is used for the treatment of carbon black, the silica component cannot be adhered by a simple granulation step, and further, a very large number of silanol groups as a ratio to the amount of adhered silica. It is considered impossible to obtain the carbon black of the present invention to which is added.

As described above, the silica-impregnated carbon black of the present invention obtained by the production method of the present invention has excellent characteristics greatly different from those of the surface-treated carbon black obtained by the prior art. If the silica-impregnated carbon black of the present invention is produced by the production method of the present invention described above, almost the entire amount of the silica component can be present on the surface of the carbon black. In addition, when blended into rubber or the like, it can be made excellent in familiarity with a vehicle.

The amount of the rubber is usually 10 to 200 parts by weight, preferably 20 to 1 part by weight, per 100 parts by weight of the rubber component.
50 parts by weight. The rubber component used in the rubber composition of the present invention is not particularly limited, but is preferably a crosslinkable rubber. More preferably, it is a diene rubber capable of sulfur vulcanization. The rubbers may be used alone or in combination of two or more.

In the rubber composition of the present invention, in addition to the carbon black of the present invention, ordinary carbon black or silica may be used in combination. However, it is desirable that the compounding amount does not exceed 5 times the above silica-impregnated carbon black. The rubber composition of the present invention preferably contains a silane coupling agent. As the silane coupling agent, those conventionally used can be arbitrarily compounded.
Functional ones are preferred. Specific examples include bis (3-traethoxysilylpropyl) -tetrasulfide and mercaptopropyltriethoxysilane.
This is because the silanol groups on the surface of the silica-impregnated carbon black of the present invention react and bond with the alkoxy portion of the silano coupling agent during kneading, and the sulfide portion can react with the rubber-based polymer in the vulcanization reaction. . In this case, by using the carbon black of the present invention, the compounding amount of the silane coupling agent can be smaller than that of ordinary silica compounding. That is, the usual silica compounding requires adding an expensive silane coupling agent in an amount of 5 to 15 parts by weight based on 100 parts by weight of silica. Is used, the amount of the silane coupling agent depends on the amount of silica added to the carbon black of the present invention, but 1 to 10 parts by weight is sufficient. This is thought to be due to the fact that the total amount of silanol groups present on the surface of the carbon black is smaller than the silanol groups on the surface of normal silica particles, and that a sufficient amount of the silane coupling agent to react is sufficient. Means. Therefore, according to the present invention, there is also an advantage that the compound cost is lower than that of the silica-based compound.

The rubber composition containing the carbon black of the present invention is suitably provided for general rubber members such as anti-vibration rubber for tires such as tire tread, undertread and side tread, and belts.

[0032]

The present invention will be described below with reference to examples. (Example 1) "N339" as carbon black
("DIABLACK-N339": Mitsubishi Chemical Corporation)
) Is placed in a laboratory granulator. As a polysiloxane in which all organic groups are bonded to silicon via oxygen, a predetermined amount of an oligomer (trade name: “MKC silicate MS51”), which is a low condensate of tetramethoxysilane, is emulsified with a nonionic surfactant, Add to the above carbon black with water.

The lid of the lab granulator is closed, and high-speed stirring is performed at 60 ° C. for 1 minute. The granules thus obtained were dried with a dryer to obtain silica-impregnated carbon blacks of Examples 1 and 2. Comparative Example 1 Instead of a polysiloxane in which all organic groups are bonded to silicon via oxygen and a nonionic surfactant, colloidal silica (trade name: Snowtex 30:
The same operation as in the example was performed except that Nissan Chemical Industry Co., Ltd.) was used, to obtain a silica-impregnated carbon black of Comparative Example 1. (Comparative Example 2) Also, after heating a 5% by weight water slurry of carbon black to 90 ° C., adding silica diluted with sodium silicate and maintaining the pH at 5 to 10 with dilute sulfuric acid and aqueous sodium hydroxide, carbonized silica. Settled on the surface, then left at pH 6 for 6 hours, filtered, washed with water,
By drying, a silica-impregnated carbon black of Comparative Example 2 was obtained. (Measurement of silica content and colloidal properties of silica-impregnated carbon black) Silica-impregnated carbon black was measured according to the ash content measurement method of JIS K6221.
Ashing was performed at 50 ° C., and the amount of ash was determined. The amount obtained by subtracting the amount of carbon black ash to which no silica was attached from this ash amount was regarded as the silica content. The measurement of the nitrogen specific surface area was performed according to ASTM D3037. The properties of the silica-impregnated carbon blacks of Examples and Comparative Examples are summarized in Table 1.

[Table 1] (Preparation of rubber composition containing silica-impregnated carbon black,
Measurement of Rubber Properties) Each component shown in Table 2 was mixed and kneaded with a Banbury mixer and an open roll mixer according to a conventional method to prepare a rubber composition. These rubber compositions were press-vulcanized at 160 ° C. to prepare vulcanized rubber test pieces. Various tests were performed by the following test methods, and the physical properties were measured. (1) E ^* , tan δ: E ^* , ta which are dynamic viscoelastic properties
nδ is "DVE Rheospectral" manufactured by Rheology Inc.
Was measured under the following conditions.

E ^* : static strain 10%, dynamic strain (amplitude)
2%, frequency 10 Hz, measurement temperature 0 ° C. tan δ: static strain 10%, dynamic strain (amplitude) 2%, frequency 10 Hz, measurement temperature 0 ° C. and 60 ° C. (2) Wear resistance: Lambourn abrasion test The measurement was performed using the following conditions. Test piece: thickness 10mm, outer diameter 44mm, test load 4k
g, 45% slip ratio between grindstone and test piece, measurement temperature 25 ° C

[Table 2] Table 3 shows the measurement results of the rubber properties. As is apparent from Table 3, the silica-impregnated carbon black of the present invention has a higher tan δ in a low temperature range (0 ° C.) and a lower tan δ in a high temperature range, as compared with Comparative Examples. That is, when this rubber composition is used for a tire tread or the like, braking performance on a wet road surface is improved,
In addition, a tire having reduced rolling resistance is obtained. Also, the abrasion resistance is good.

[Table 3]

[0035]

As described above, by using carbon black having a large amount of OH groups, especially silanol groups, and a large amount of silanol groups per silica content on the surface of carbon black, the carbon black is blended with the rubber component. A tread composition having improved braking characteristics and low fuel consumption can be obtained.

Claims (6)

[Claims] 1. A silica-impregnated carbon black having an amount of impregnated silica of 10% by weight or less and OH groups of 0.6 / nm ² or more. 2. A silica-impregnated carbon black having an amount of impregnated silica of 10% by weight or less and an OH group of 5.5 × 10 ¹⁹ / g or more. 3. A silica-impregnated carbon black having a silica-impregnated amount of 10% by weight or less and a silanol group content of 0.3 / nm ² or more. 4. When the amount of silica impregnated is a wt% and the amount of silanol groups is b / nm ² , a ≦ 10, b ≧ 0.3, and b / a ≦ 0.1. A silica-impregnated carbon black characterized by the following. 5. The method according to claim 1, wherein the surface of the carbon black is treated with a silicon-containing compound in which all of the organic groups are bonded to silicon via oxygen to thereby impregnate the silica. 3. The method for producing a silica-impregnated carbon black according to item 1. 6. A method for producing a carbon black-containing rubber composition, comprising blending the silica-impregnated carbon black according to claim 1 with a rubber component.