JP2011153191A - Process of kneading rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of kneading a rubber composition which improves the silica dispersion efficiency of a rubber composition including silica to improve the productivity of the rubber composition by reducing the kneading step and can reduce electricity consumption. <P>SOLUTION: The method includes kneading a rubber composition including silica by an internal kneader having an inner volume of the kneading chamber of 50 liters or more with a fill factor [(the volume of the rubber composition kneaded/the inner volume of the kneading chamber)&times;100] in the silica introduction/kneading step being 50-60%. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for kneading a rubber composition capable of improving the silica dispersion efficiency of a rubber composition containing silica.

Conventionally, when a rubber composition is kneaded using a closed kneader (internal mixer), a method in which a certain amount of compounded chemicals are added and kneaded with respect to the input mass of the rubber raw material is generally used. there were.
By the way, in recent years, silica is frequently used in tire production from the viewpoint of low heat generation.
However, when silica is blended in a large amount, dispersion tends to be difficult, and it is often difficult to obtain a rubber composition having good dispersibility of silica. Thus, in the production of a rubber composition containing silica, a rubber composition containing carbon black in order to sufficiently incorporate and disperse silica in the rubber so as not to impair the physical properties after vulcanization of the rubber composition. It was necessary to provide the silica charging and kneading step many times as compared with the above.

For the above problems, Patent Document 1 discloses (A) a step of mixing a rubber containing a filler with a kneading mixer, and (B) forming a rubber sheet by using a sheeting roll of the kneaded rubber discharged from the kneading mixer. And (C) passing the rubber sheet between a pair of front and rear corrugated rolls having a plurality of grooves in the roll surface rotation direction and having convex and concave surfaces constituting the grooves of each roll facing each other. And a step of making the thickness of the rubber sheet 1/3 or less.
Patent Document 2 describes the rubber raw material (B) before and / or during the kneading in the step of kneading the compounded chemicals (B) into the rubber raw material (A) using a closed mixer. A rubber kneading method is proposed in which at least one compounding amount in the compounding chemicals (B) is controlled based on a value obtained by actually measuring or estimating the viscosity of A).
However, the method of Patent Document 1 introduces new equipment, which is inferior in economic efficiency and increases in power consumption. In addition, the method of Patent Document 2 requires continuous measurement or estimation of the viscosity of the rubber raw material (A), which is complicated and low in productivity and difficult to improve the dispersibility of silica. It was.
Therefore, there is a demand for improvement of a kneading method of a rubber composition containing silica by a new method.

Japanese Patent Laid-Open No. 2002-347023 JP 2005-199503 A

  In view of the above situation, the present invention improves the silica dispersion efficiency of a rubber composition containing silica, improves the productivity of the rubber composition by reducing the kneading step, and enables a reduction in power consumption. It is an object of the present invention to provide a method for kneading a product.

As a result of intensive studies to solve the above problems, the present inventor has improved the silica dispersion efficiency of the rubber composition containing silica by drastically renewing the kneading method of the rubber composition containing silica. Found to get.
The present invention has been completed based on such findings.
That is, the present invention
[1] A method of kneading a rubber composition containing silica with a closed kneader having a volume of 50 liters or more in a kneading chamber, wherein the fill factor {(volume of kneaded rubber composition / kneading chamber) Volume) × 100} is 50 to 60%, a kneading method of a rubber composition,
[2] The method for kneading a rubber composition according to the above [1], wherein the entire amount of silica is kneaded in a single silica kneading step,
[3] The volume filling rate {(total volume of raw materials constituting the rubber composition / volume in the kneading chamber) × 100} in the silica charging and kneading step is 110 to 130%, as described in [1] or [2] above [4] The rubber composition according to any one of [1] to [3], wherein the rubber composition contains 50 parts by mass or more of silica with respect to 100 parts by mass of the rubber component. This is a method for kneading a product.

According to the kneading method of the rubber composition containing silica of the present invention, the efficiency of incorporation and dispersion of silica into the rubber component is improved, the productivity of the rubber composition is improved by reducing the kneading step, and the power consumption is increased. Reduction can be made possible.
In the kneading method of the present invention, even if the fill factor is lowered, the effect of reducing the silica charging and kneading step is great, so that the kneading time can be shortened and the energy consumption can be reduced overall.

It is the schematic which shows an example of the kneading | mixing state in the closed kneading apparatus used in the kneading | mixing method of the rubber composition of this invention, and the apparatus. It is the schematic which shows the relationship between the specific energy (KWH / kg) and silica carbon black uptake | capture rate (%) in the kneading | mixing method of the rubber composition of this invention, and the kneading | mixing method of the rubber composition used as a comparative example. It is the schematic which shows the example of the kneading | mixing time (sec) of the silica addition kneading | mixing process-the load electric power (KW / kg) curve of a kneading machine in the kneading | mixing method of the rubber composition of this invention, and the kneading | mixing method of the rubber composition used as a comparative example. is there.

The method for producing a rubber composition of the present invention is a method of kneading a rubber composition containing silica with a closed kneader having a volume of 50 liters or more in a kneading chamber, wherein the filler factor {(kneaded) The volume of the rubber composition / the volume of the kneading chamber) × 100} is 50 to 60%. If the fill factor (hereinafter sometimes abbreviated as “FF”) is less than 50%, the throughput in one silica charging and kneading step is reduced, and the problem of the present invention cannot be solved. . On the other hand, if the fill factor exceeds 60%, the silica incorporation into the rubber component and the efficiency of dispersion will decrease. Here, “the volume of the rubber composition being kneaded” refers to the volume in a state where raw materials other than all the rubber components are kneaded, incorporated and dispersed in the rubber component of the rubber composition. For example, silica has a large bulk volume (that is, a small bulk specific gravity), but its volume in a state where it is kneaded, incorporated and dispersed in the rubber component is significantly smaller than the bulk volume.
The reason why the volume of the kneading chamber of the hermetic kneader is limited to 50 liters or more is that the effect of the present invention can be enjoyed more greatly as the volume of the kneading chamber increases. From this point of view, there is no upper limit to the volume of the kneading chamber, and it may be the maximum value of the volume of the kneading chamber of a closed kneader currently on the market.

  In the method for producing the rubber composition of the present invention, the entire amount of the silica is preferably kneaded in a single silica charging and kneading step. This is because if the silica charging and kneading step is single, the productivity of the rubber composition is further improved by reducing the kneading step, and the power consumption can be more suitably reduced.

Further, the bulk filling rate {(total volume of raw materials constituting the rubber composition / volume in the kneading chamber) × 100} in the silica charging and kneading step is preferably 110 to 130%. This is because if the bulk filling rate is 110% or more, the processing efficiency in the silica charging and kneading step is improved, and if it is 130% or less, it is easier to input the raw materials into the closed kneader. Here, the “total volume of raw materials constituting the rubber composition” means the bulk of all rubber components, fillers such as silica and other raw materials that are input into the kneading chamber of the closed kneader in the silica charging and kneading step. Refers to the total volume.
The bulk volume in the present invention is measured based on the apparent specific gravity method using a powder tester PT-N type powder characteristic measuring device manufactured by Hosokawa Micron Corporation or a device having an equivalent function.

  The rubber composition produced by the kneading method of the present invention preferably contains 50 parts by mass or more of silica with respect to 100 parts by mass of the rubber component. It is because the effect of this invention can be enjoyed more greatly by including 50 mass parts or more of silica.

  The rubber component of the rubber composition produced by the kneading method of the present invention is not limited, but a diene rubber is preferable. Examples of the diene rubber include natural rubber, synthetic isoprene rubber, butadiene rubber, styrene-butadiene rubber, ethylene-α-olefin-diene terpolymer rubber, chlorobrene rubber, halogenated butyl rubber, and styrene having a halogenated methyl group. A copolymer of styrene and isobutylene is preferably used.

There is no restriction | limiting in particular as a silica used for the rubber composition which concerns on this invention, It can select and use arbitrarily from what is conventionally used as a filler for reinforcement of rubber conventionally.
Any commercially available silica can be used. Among these, wet silica, dry silica, and colloidal silica are preferably used. Among them, wet silica having the most remarkable effect of improving fracture properties and wet grip is used. Is particularly preferred. The BET specific surface area (measured according to ISO 5794/1) of silica is preferably 100 m ² / g or more, more preferably 150 m ² / g or more, particularly preferably 170 m ² / g or more. Examples of such silica include Tosoh Silica Co., Ltd., trade name “Nipsil AQ” (BET specific surface area = 190 m ² / g), “Nipsil KQ”, and Degussa product name “Ultrazil VN3” (BET specific surface area = 175 m ² / g) can be used.

If desired, the rubber composition according to the present invention may contain an inorganic filler other than carbon black and silica in addition to the above-described silica.
Carbon black is not particularly limited, and for example, SRF, GPF, FEF, HAF, N339, IISAF, 1SAF, SAF and the like are used, iodine adsorption amount (IA) is 60 mg / g or more, and dibutyl phthalate oil absorption amount (DBP) Is preferably 80 ml / 100 g or more of carbon black. By using carbon black, the effect of improving grip performance and fracture resistance is increased, but HAF, N339, IISAF, ISAF, and SAF, which are excellent in wear resistance, are particularly preferable.

Examples of inorganic fillers other than silica include alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina, alumina monohydrate such as boehmite and diaspore (Al ₂ O ₃ .H ₂ O), gibbsite, and buyer. Aluminum hydroxide [Al (OH) ₃ ] such as Wright, aluminum carbonate [Al ₂ (CO ₃ ) ₂ ], magnesium hydroxide [Mg (OH) ₂ ], magnesium oxide (MgO), magnesium carbonate (MgCO ₃ ), Talc (3MgO · 4SiO ₂ · H ₂ O), attapulgite (5MgO · 8SiO ₂ · 9H ₂ O), titanium white (TiO ₂ ), titanium black (TiO _2n-1 ), calcium oxide (CaO), calcium hydroxide [ Ca (OH) _2], magnesium aluminum oxide _{(MgO · Al 2 O 3)} , clay _{(Al 2 O 3 · 2SiO 2} ), kaolin (Al ₂ O ₃ · 2S O ₂ · 2H ₂ O), pyrophyllite _{(Al 2 O 3 · 4SiO 2} · H 2 O), bentonite _{(Al 2 O 3 · 4SiO 2} · 2H 2 O), aluminum silicate (Al ₂ SiO _5, Al ₄ / 3SiO ₄ / 5H ₂ O etc.), magnesium silicate (Mg ₂ SiO ₄ , MgSiO ₃ etc.), calcium silicate (Ca ₂ · SiO ₄ etc.), aluminum calcium silicate (Al ₂ O ₃ · CaO · 2SiO etc.) ₂ ), magnesium calcium silicate (CaMgSiO ₄ ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO (OH) ₂ .nH ₂ O], zirconium carbonate [Zr (CO ₃ ) ₂ ], crystalline aluminosilicates containing hydrogen, alkali metals or alkaline earth metals that correct the charge, such as various zeolites, can be used.

  In the rubber composition which concerns on this invention, it is preferable to mix | blend 1-20 mass% of silane coupling agents with respect to the total compounding quantity of a silica and another inorganic filler. The silane coupling agent reacts with the OH group present on the surface of the inorganic filler and the conjugated diene polymer of the rubber component to act as a bonding bridge between the inorganic filler and the rubber to form a reinforcing phase. A silane coupling agent may be used individually by 1 type, and may be used in combination of 2 or more type.

The silane coupling agent used in the present invention includes bis- (3-triethoxysilylpropyl) tetrasulfide, bis- (3-trimethoxynylpropyl) tetrasulfide, bis- (3-methyldimethoxysilylpropyl) tetrasulfide, bis- ( 2-triethoxysilylethyl) tetrasulfide, bis- (3-triethoxysilylpropyl) disulfide, bis- (3-trimethoxysilylpropyl) disulfide, bis- (3-triethoxysilylpropyl) trisulfide, 3-hexanoylthio Propyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxy Lan, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, 2-lauroylthioethyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-aminopropyltrimethoate Silane, 3-aminopropyltriethoxysilane, γ-grindoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, Examples include 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-trimethoxysilylpropylmethacryloyl monosulfide and the like.
In addition, as commercial products, the product name “NXT Low-V Silane” (registered trademark), the product name “NXT Ultra Low-V Silane” (registered trademark), and the product name “NXT Z” (registered trademark) manufactured by Momentive Performance Materials. Etc.) are preferably used.

  In the rubber composition according to the present invention, various chemicals usually used in the rubber industry, for example, a vulcanizing agent, a vulcanization accelerator, a scorch inhibitor and the like are added to the rubber composition as long as the object of the present invention is not impaired. A sulfur-based compounding agent, process oil, anti-aging agent, zinc white, stearic acid and the like can be contained.

Next, a typical closed kneading apparatus used in the present invention will be described. FIG. 1 is a schematic view showing an example of a closed kneading apparatus used in the kneading method of a rubber composition of the present invention and a kneading state in the apparatus.
The closed kneading apparatus shown in FIG. 1 is a tangential one-blade batch type closed kneader and is called an “internal mixer”. The closed kneading apparatus 10 includes a kneader 11, a power unit 21, a hydraulic cylinder 19, and a guide lot 20. This kneader 11 is constituted by a combination of a kneader main body 12 and a floating weight 18. The kneader main body 12 forms a kneading chamber (kneading chamber) 13 in which two cylindrical surfaces formed in a semicircular cross section are combined. Above the kneading chamber 13, an opening 14 formed in a cylindrical surface is provided.
In addition, as the batch type closed kneader, a Banbury type or a pressure kneader is generally used.

A pair of rotors 15a and 15b are provided on the central axis of the semicircular cylindrical surface of the kneading chamber 13. The first rotor 15a has a rotating shaft 16a, and the second rotor 15b has a rotating shaft 16b. Yes. The first rotor 15a and the second rotor 15b are provided with a first blade 17a and a second blade 17b, respectively. The pair of rotors 15a and 15b are rotated by the power unit 21 around the first and second rotary shafts 16a and 16b, and are rotated by the first blade 17a and the second blade 17b. The rubber component and raw materials such as silica are kneaded while being sheared to produce the mixture 1.
The floating weight 18 is provided with an outer peripheral surface 18 a that fits inside the opening 14 of the kneading machine main body 12, and a rubber compound and a rubber compounding material such as carbon black by pressure from the hydraulic cylinder 19 and the guide lot 20. Is pressed and pressed to facilitate mixing.
FIG. 1 shows a closed kneading apparatus having a tangential 1 wing type batch type closed kneading machine, but it has a meshing 1 wing type, a tangential 2 wing type, or a meshing 2 wing type (having two blades). Two rotors are provided) or a tangential three-wing or meshing three-wing (two rotors with three blades) are used as well.

After completion of the silica charging and kneading step according to the present invention, the obtained mixture is cooled and, if desired, left in the aging step {room temperature (about 23 ° C.). }, A vulcanizable rubber composition is obtained by performing a vulcanizing compound kneading step of blending the vulcanizing compound with the obtained mixture.
If desired, a master batch kneading step (also referred to as “X-mill step”) in which the mixture obtained in the silica charging kneading step is kneaded again between the silica charging kneading step and the vulcanizing compound kneading step. May be performed.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.
Examples 1-3, Comparative Examples 1-2 and Reference Example 1
In Examples 1 to 3 and Comparative Examples 1 and 2, using an internal kneading apparatus having a volume of 200 liters in the kneading chamber shown in FIG. 1, an emulsion-polymerized styrene-butadiene copolymer rubber (manufactured by JSR Corporation, Non-oil extended) A rubber composition comprising 100 parts by mass of silica, 75 parts by mass of silica (manufactured by Tosoh Silica Co., Ltd., wet silica) and 15 parts by mass of carbon black ISAF (manufactured by Asahi Carbon Co., Ltd.) as a single silica Kneading was performed with five different fill factors in the charging and kneading step. The fill factor of Example 1 is 50%, the fill factor of Example 2 is 60%, the fill factor of Example 3 is 55%, the fill factor of Comparative Example 1 is 70%, and the fill factor of Comparative Example 2 is 65%. there were. Each of these five types of rubber compositions was first kneaded by adding all the rubber components and then all the silica and carbon black.
In Reference Example 1, 100 parts by mass of an emulsion-polymerized styrene-butadiene copolymer rubber (manufactured by JSR Corporation, non-oil extended) as a rubber component, and 90 parts by mass of carbon black ISAF (manufactured by Asahi Carbon Co., Ltd.) as a filler. The resulting rubber composition was kneaded at a fill factor of 70% in a single carbon black charging and kneading step. In Reference Example 1, all the rubber component was added, and then the entire amount of carbon black was added and kneaded.

  FIG. 2 shows specific energy (KWH / kg) and silica in the rubber composition kneading method of the present invention (Examples 1 and 2) and the comparative rubber composition kneading method (Comparative Example 1 and Reference Example 1). -It is the schematic which shows the relationship with carbon black uptake rate (%). Here, the specific energy (KWH / kg) is a value divided by the total mass of the rubber composition for kneading the electric power applied to the closed kneading apparatus in the silica charging and kneading step, and per unit mass of the rubber composition. Refers to load power. The silica / carbon black incorporation rate (%) represents the rate (%) of silica and carbon black incorporated in the silica charging and kneading step, and the kneading was stopped during the kneading. The amount of silica and carbon black incorporated into the rubber component was quantified and calculated by thermal analysis.

As is apparent from FIG. 2, in the kneading method of the rubber compositions of Examples 1 and 2 within the range of 50 to 60% fill factor, the rubber composition of the reference example having a fill factor of 70% is blended with carbon black alone. A silica uptake rate comparable to that of the method was obtained. Thereby, the silica dispersion efficiency was improved, and the productivity of the rubber composition could be improved by reducing the kneading step. In addition, power consumption can be reduced.
On the other hand, in the kneading method of the rubber composition having a fill factor of 70% in Comparative Example 1, the silica uptake rate was remarkably reduced and the silica dispersion efficiency was low. This makes it difficult to reduce the kneading process, and power consumption cannot be reduced.

FIG. 3 shows the kneading time (sec) of the silica charging kneading step in the rubber composition kneading method of the present invention (Examples 2 and 3) and the comparative rubber composition kneading method (Comparative Example 2) —kneader. It is the schematic which shows the example of a load electric power (KW / kg) curve. Here, the kneading time (sec) starts immediately after the entire amount of silica and carbon black is collectively charged after the entire amount of the rubber component is charged.
As is clear from FIG. 3, in the method of kneading the rubber compositions of Examples 2 and 3 within the range of 50-60% fill factor, the load power at the initial stage of kneading time (sec) Power) and the silica agglomerates are rapidly broken, so that the silica uptake rate is increased as described above.
On the other hand, in the kneading method of the rubber composition with a fill factor of 65% in Comparative Example 2, it took time from the initial kneading time (sec) until the load power increased, and the silica uptake rate was remarkably reduced. The silica dispersion efficiency was low.

  Since the kneading process can be reduced by the kneading method of the rubber composition of the present invention, the productivity of the rubber composition can be improved, and the power consumption can be reduced. Therefore, various rubber compositions for tires, in particular, rubber for tire treads. It is suitably used for the production of the composition, and the productivity of various tires for passenger cars, light cars, light trucks, trucks and buses, and off-the-road can be improved. Moreover, the kneading method of the rubber composition of the present invention is also suitably used for the production of rubber members for various industrial rubber products such as belt conveyors, rubber dams, rubber hoses and the like, and rubber members for daily necessities such as shoe soles.

DESCRIPTION OF SYMBOLS 1 Mixture 10 Sealing-type kneading apparatus 11 Kneading machine 12 Kneading machine main body 13 Kneading chamber 14 Opening part 15a 1st rotor 15b 2nd rotor 16a 1st rotating shaft 16b 2nd rotating shaft 17a 1st blade | wing 17b 2nd Blade 18 floating weight 18a outer peripheral surface 19 hydraulic cylinder 20 guide lot 21 power section

Claims (4)

  A method of kneading a rubber composition containing silica with a closed kneader having a volume of 50 liters or more in a kneading chamber, wherein the fill factor of the silica charging kneading step {(volume of kneaded rubber composition / volume in the kneading chamber) × 100} is 50 to 60%. A method for kneading a rubber composition, wherein:   The method for kneading a rubber composition according to claim 1, wherein the entire amount of the silica is kneaded in a single silica charging and kneading step.   The kneading of the rubber composition according to claim 1 or 2, wherein a bulk filling rate {(total volume of raw materials constituting the rubber composition / volume of kneading chamber) x 100} in the silica charging and kneading step is 110 to 130%. Method.   The method for kneading a rubber composition according to any one of claims 1 to 3, wherein the rubber composition contains 50 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.

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