JP2012153758A - Production method for rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve processibility when using mercaptosilane, without impairing physical properties of vulcanized rubber.SOLUTION: There is provided a production method for a rubber composition for tire, comprising a first mixing step of adding an additive containing a filler and mercaptosilane to a diene-based rubber, mixing it with a kneader without adding vulcanizing agent nor vulcanization promoter and discharging the mixture at a first discharge temperature, a rekneading step of kneading with a kneader the mixture obtained in the first mixing step and discharging the obtained mixture at a second discharge temperature, and a final mixing step of adding a vulcanizing agent and a vulcanization promoter to the mixture obtained in the rekneading step and mixing, wherein the second discharge temperature is set within a range of 120-140°C.

Description

  The present invention relates to a method for producing a rubber composition used for a pneumatic tire.

  Conventionally, in tire rubber compositions, it is known that the balance between wet performance, which is grip performance on wet road surfaces, and rolling resistance performance can be improved by blending silica as a filler. Silica itself is inferior to carbon black in reinforcing properties and is difficult to uniformly disperse in a rubber composition, and therefore a silane coupling agent is used in combination.

  Examples of the silane coupling agent include sulfide silane and mercaptosilane. Among these, mercaptosilane is advantageous in terms of reducing rolling resistance. However, mercaptosilane may be burned (scorched) during the kneading of the rubber composition or during the extrusion process, and a vulcanized rubber having good physical properties may not be obtained.

  In order to improve the scorch performance of such mercaptosilane, the following Patent Document 1 discloses that an isocyanate compound is blended together with mercaptosilane, and in Patent Document 2 below, a large amount of zinc oxide is blended. It is disclosed. However, methods such as these methods that add other additives or increase the amount of some additives may affect the physical properties of the vulcanized rubber. There is a need to improve scorch performance.

JP 2006-089698 A JP 2007-217465 A

  In view of the above points, an object of the present invention is to improve workability when mercaptosilane is used without impairing physical properties of a vulcanized rubber.

  The present inventor, in the re-kneading step performed as the next step of the first mixing step of adding and mixing the additive excluding the vulcanizing compound to the diene rubber, the discharge temperature discharged from the kneader is lower than usual. It was found that by setting the temperature to a predetermined temperature, the self-condensation reaction of mercaptosilane can be suppressed to solve the above problems, and the present invention has been completed.

  That is, the method for producing a tire rubber composition according to the present invention includes adding an additive containing a filler and a mercaptosilane to a diene rubber, and mixing the mixture with a kneader without adding a vulcanizing agent and a vulcanization accelerator. A first mixing step of discharging the mixture at a first discharge temperature, a re-kneading step of kneading the mixture obtained in the first mixing step with a kneader and discharging the mixture at a second discharge temperature; A final mixing step of adding and mixing a vulcanizing agent and a vulcanization accelerator to the mixture obtained in the re-kneading step, wherein the second discharge temperature is in the range of 120 to 140 ° C. Is.

  According to the present invention, by controlling the discharge temperature in the re-kneading step as described above, the workability when using mercaptosilane can be improved without impairing the physical properties of the vulcanized rubber.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The tire rubber composition according to the embodiment contains a diene rubber, a filler, a mercaptosilane, a vulcanizing agent, and a vulcanization accelerator.

  As the diene rubber used as a rubber component in the rubber composition, various diene rubbers generally used in a rubber composition for tires can be used and are not particularly limited. Specifically, natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), ethylene-propylene- Examples include diene rubber (EPDM), butyl rubber (IIR), and halogenated butyl rubber. These can be used alone or in combination of two or more. The diene rubber is preferably natural rubber, polybutadiene rubber, styrene-butadiene rubber, or a blend of two or more thereof.

  As the filler, for example, various inorganic fillers such as silica, carbon black, titanium oxide, aluminum silicate, clay, and talc can be used, and these can be used alone or in combination of two or more. Among these, silica alone or a combination of silica and carbon black is preferable. Silica is not particularly limited, and examples thereof include wet silica, dry silica, colloidal silica, and precipitated silica. It is particularly preferable to use wet silica containing hydrous silicic acid as a main component. Also, the carbon black is not particularly limited, and various carbon blacks such as SAF, ISAF, HAF, FEF, GPF and the like used as a rubber reinforcing agent can be used.

  Although the compounding quantity of the said filler is not specifically limited, It is preferable that it is 20-200 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 30-150 mass parts. Moreover, as a preferable aspect, when using a silica, it is preferable that the compounding quantity of a silica is 10-150 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 20-100 mass parts. Moreover, when using together silica and carbon black as a filler, it is preferable that both total amount is 20-200 mass parts with respect to 100 mass parts of diene rubber, More preferably, it is 30-150 mass parts.

  The mercaptosilane is blended as a silane coupling agent for dispersing and coupling the filler in the diene rubber, and can react with the alkoxy group capable of reacting with the hydroxyl group on the filler surface and the diene rubber. The coupling agent is not particularly limited as long as it is a coupling agent having a mercapto group (—SH) as a functional group. Specifically, those represented by the following general formula (1) are preferably used.

(R ¹ ) _m (R ² ) _n Si—R ³ —SH (1)
In the formula, R ¹ is an alkoxy group having 1 to 3 carbon atoms, more preferably a methoxy group or an ethoxy group. R ² is an alkyl group, alkenyl group or alkyl polyether group having 1 to 40 carbon atoms, more preferably an alkyl group or alkenyl group having 1 to 4 carbon atoms, or —O— (R ^a —O). _k— R ^b (wherein R ^a is an alkylene group having 1 to 4 carbon atoms, R ^b is preferably an alkyl group having 1 to 16 carbon atoms, and k = 1 to 20). It is an ether group. R ³ is an alkylene group having 1 to 16 carbon atoms, more preferably an alkylene group having 2 to 4 carbon atoms. m = 1 to 3 and m + n = 3. In addition, when there are two or more R ¹ and R ² in one molecule, they may be the same or different.

Specific examples of the mercaptosilane represented by the general formula (1) include, for example, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropyldimethylmethoxy. Silane, mercaptoethyltriethoxysilane, and “VP Si363” manufactured by Evonik Degussa (R ¹ : OC ₂ H ₅ , R ² : O (C ₂ H ₄ O) _k —C ₁₃ H ₂₇ , R ³ :-( CH ₂ ) ₃ −, m = average 1, n = average 2, k = average 5) and the like are preferable, and these can be used alone or in combination of two or more.

  Although the compounding quantity of mercaptosilane is not specifically limited, It is preferable that it is 1-20 mass parts with respect to 100 mass parts of said fillers (preferably 100 mass parts of silica), More preferably, it is 3-15 mass parts. .

  Examples of the vulcanizing agent include sulfur such as powdered sulfur, precipitated sulfur and insoluble sulfur, sulfur compounds such as sulfur chloride, sulfur dichloride, morpholine disulfide and alkylphenol disulfide, and peroxides. Among them, in particular, Sulfur is preferred. Although the compounding quantity of a vulcanizing agent is not specifically limited, It is preferable that it is 0.1-10 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 0.5-5 mass parts.

  The kind of the vulcanization accelerator is not particularly limited and can be used. For example, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N-oxydiethylene-2-benzothiazolylsulfenamide ( Sulfenamide vulcanization accelerators such as OBS), N, N-diisopropyl-2-benzothiazolylsulfenamide (DPBS), N, N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS); Methyl thiuram monosulfide (TMTM), tetramethyl thiuram disulfide (TMTD), tetraethyl thiuram disulfide (TETD), tetrabutyl thiuram disulfide (TBTD), dipentamethylene thiuram tetrasulfide (DPTT), dipentamethylene thiuram hex Thiuram vulcanization accelerators such as sulfide and tetrabenzylthiuram disulfide (TBZTD); 2-mercaptobenzothiazole (MBT), di-2-benzothiazolyl disulfide (MBTS), salt of 2-mercaptobenzothiazole (zinc salt) (ZnMBT), sodium salt (NaMBT), cyclohexylamine salt (CMBT), etc.), thiazole vulcanization accelerators such as 2- (4′-morpholinodithio) benzothiazole; 1,3-diphenylguanidine (DPG), etc. Examples include guanidine vulcanization accelerators; various vulcanization accelerators such as aldehyde-amine vulcanization accelerators such as hexamethylenetetramine (H). Among these, it is preferable to use at least one selected from a sulfenamide vulcanization accelerator, a thiuram vulcanization accelerator, and a thiazole vulcanization accelerator, and particularly preferably a sulfenamide vulcanization accelerator. Is to use. It is preferable that the compounding quantity of a vulcanization accelerator is 0.1-7 mass parts with respect to 100 weight part of diene rubbers, More preferably, it is 0.5-5 mass parts.

  In addition to the above components, the rubber composition according to the embodiment contains various additives commonly used in rubber compositions for tires, such as softeners such as oil, stearic acid, zinc white, anti-aging agent, and wax. can do.

  The manufacturing method of the rubber composition according to the present embodiment is a first method in which an additive containing a filler and a mercaptosilane is added to a diene rubber, and mixed in a kneader without adding a vulcanizing agent and a vulcanization accelerator. A mixing step, a re-kneading step of kneading the mixture obtained in the first mixing step with a kneader, and a final mixing step of adding and mixing a vulcanizing agent and a vulcanization accelerator to the mixture obtained in the re-kneading step It consists of. Here, as the kneader, known various rubber kneaders such as a Banbury mixer which is a closed kneader can be used.

  In the first mixing step, the diene rubber is added to the kneader and the additives other than the vulcanizing agent and the vulcanization accelerator are added and kneaded. When kneading, the temperature rises due to heat generated by shearing, so the mixture is discharged from the kneader at a predetermined first discharge temperature. The first discharge temperature is set to 150 ° C. or higher in order to improve the dispersibility of the additive. Although the upper limit of 1st discharge | emission temperature is not specifically limited, Usually, it is 200 degrees C or less. The first discharge temperature is more preferably 160 to 180 ° C. The mixture discharged from the kneader is usually cooled by leaving it at room temperature. At that time, the cooling effect can be enhanced by stretching the mixture into a sheet.

  In the re-kneading step, the cooled mixture obtained in the first mixing step is put into a kneader and re-kneaded. In the re-kneading process, it is preferable to carry out only kneading without adding an additive. Even in the re-kneading step, the temperature rises due to the kneading, so the mixture is discharged from the kneader at the predetermined second discharge temperature.

  This embodiment is characterized in that the discharge temperature (second discharge temperature) in this re-kneading step is set to 120 to 140 ° C. That is, in general, in the re-kneading process, the discharge temperature is set to be the same as that in the first mixing process, but in the present embodiment, the predetermined temperature is set lower than the discharge temperature in the first mixing process. The reason is as follows. That is, since mercaptosilane changes to a structure having mercapto groups at both ends by a self-condensation reaction, the reaction between the polymer and polymer of a diene rubber causes deterioration of processability. On the other hand, in this embodiment, the self-condensation reaction of mercaptosilane can be suppressed by setting the second discharge temperature at the time of re-kneading to 120 to 140 ° C. as described above. Workability can be improved without impairing the processability.

  In the re-kneading process, the mixture discharged from the kneader is cooled by being allowed to stand at room temperature in the same manner as after the first mixing process, and then, in the final mixing process, the vulcanizing agent and the vulcanization accelerator are added. Mixed. Specifically, in the final mixing step, the kneader is charged with the mixture obtained in the re-kneading step, the vulcanizing agent and the vulcanization accelerator are added, kneaded, and the mixture at a predetermined discharge temperature. Is discharged from the kneader. In the final mixing step, in order to suppress the reaction of the vulcanizing agent and the vulcanization accelerator, the discharge temperature (third discharge temperature) is preferably set lower than the first and second discharge temperatures. 3 The discharge temperature is preferably less than 120 ° C, more preferably set to 90 to 110 ° C.

  In the above embodiment, in the first mixing step, all the additives other than the vulcanizing agent and the vulcanization accelerator are charged. For example, in the premixing step prior to the first mixing step, a diene type is used. A part of the additive may be added to the rubber and mixed. Moreover, you may mix | blend additives other than a vulcanizing agent and a vulcanization accelerator in the last mixing stage.

  The use of the rubber composition thus obtained is not particularly limited, and for various uses such as large tires for passenger cars, trucks and buses, tread parts, sidewall parts, bead parts, tires of pneumatic tires of sizes. It can be applied to each part of the tire such as a cord covering rubber. That is, according to a conventional method, the rubber composition is molded into a predetermined shape by, for example, extrusion, and combined with other parts, and then vulcanized and molded at, for example, 140 to 180 ° C. to produce a pneumatic tire. can do.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Using a Banbury mixer, each rubber composition of Examples and Comparative Examples was prepared according to the formulation (parts by mass) shown in Table 1 below. Specifically, first, in the first mixing step (NP) as the first step, components other than sulfur and the vulcanization accelerator were added and mixed, and the mixture was discharged at the first discharge temperature. The mixture was stretched into a sheet and then allowed to cool at room temperature. Next, in the re-kneading step (remill) as the second step, the cooled mixture is re-kneaded, the mixture is discharged at the second discharge temperature, and the resulting mixture is stretched into a sheet and left at room temperature. And cooled. Thereafter, in the final mixing step (final) as the third step, sulfur and a vulcanization accelerator were added to and mixed with the obtained mixture, and the mixture was discharged at the third discharge temperature to obtain each rubber composition. . The first to third discharge temperatures are as described in Table 1. The details of each component in Table 1 are as follows.

・ SBR1: LANXESS "VSL5025"
・ SBR2: "SBR1502" manufactured by JSR Corporation
Carbon black: N339, “Seast KH” manufactured by Tokai Carbon Co., Ltd.
・ Silica: Tosoh Silica Co., Ltd. “Nip Seal AQ”
Mercaptosilane 1: “VP Si363” manufactured by Evonik Degussa
Mercaptosilane 2: “VP Si263” manufactured by Evonik Degussa (3-mercaptopropyltriethoxysilane, (C ₂ H ₅ O) ₃ Si (CH ₂ ) ₃ —SH)
Silane coupling agent 1: bis (3-triethoxysilylpropyl) tetrasulfide, “Si69” manufactured by Evonik Degussa
Silane coupling agent 2: bis (3-triethoxysilylpropyl) disulfide, “Si75” manufactured by Evonik Degussa
Silane coupling agent 3: 3-octanoylthio-1-propyltriethoxysilane, “NXT” manufactured by Momentive Performance Materials
・ Oil: “Process NC140” manufactured by Japan Energy Co., Ltd.
・ Stearic acid: “Lunac S20” manufactured by Kao Corporation
・ Zinc flower: “Zinc flower 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Anti-aging agent: “Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd.
・ Wax: “Sunnock N” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization accelerator: “Soxinol CZ” manufactured by Sumitomo Chemical Co., Ltd., N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)
・ Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.

  Each rubber composition was evaluated for Mooney viscosity, sheet skin condition, tearing force, and loss tangent tan δ. Each evaluation method is as follows.

Mooney viscosity: an index of processability, and in accordance with JIS K6300, after preheating the unvulcanized rubber at 100 ° C. for 1 minute, the inverse of the value obtained by measuring the torque value after 4 minutes in Mooney units is a comparative example. The value was expressed as an index where the value of 1 was 100. Higher values mean lower Mooney viscosity and better processability.

-Sheet skin state: The unvulcanized rubber discharged in the final mixing step was formed into a sheet shape with an 8-inch roll, and the state of the surface and both ends was observed. The case where the surface and both end portions were in a smooth state was indicated as “◯”, the surface was rough, and the end portion corresponding to at least one of the jagged shape was indicated as “x” as inferior in workability.

・ Tearing force: A sample vulcanized at 150 ° C. for 30 minutes is punched out with a crescent shape defined in JIS K6252, and a test sample is prepared by making a notch of 0.50 ± 0.08 mm in the center of the indentation. About the sample, the tear test was done with the tensile speed of 500 mm / min with the tensile tester by Shimadzu Corporation. The value of Comparative Example 1 is expressed as an index with a value of 100, and the higher the value, the higher the tearing force and the better.

Tan δ: Using a viscoelasticity tester manufactured by Toyo Seiki Co., Ltd. for a sample vulcanized at 150 ° C. for 30 minutes, loss factor tan δ at a frequency of 10 Hz, a static strain of 10%, a dynamic strain of 1%, and a temperature of 60 ° C. The reciprocal of tan δ was expressed as an index with the value of Comparative Example 1 being 100. Larger numbers indicate less heat generation (excellent in low heat generation), and therefore lower rolling resistance of the tire.

  The results are as shown in Table 1, and in Comparative Example 1 in which the discharge temperature in the re-kneading step (remill) is 160 ° C., which is the same as that in the first mixing step, burns are generated during kneading, the sheet skin condition is poor, and the workability It was inferior to. In Comparative Example 2, the discharge temperature in the re-kneading process was too low, and the reaction between silica and mercaptosilane was insufficient. On the other hand, in Comparative Examples 3 to 6 using sulfide silane, the workability including the sheet skin state was good regardless of the discharge temperature of the re-kneading process, but tan δ was high and excellent low like mercaptosilane. No exothermic effect was obtained. In Comparative Examples 7 and 8, a silane coupling agent in which the mercapto group was protected with a substituent was used, and therefore, although it was excellent in workability including the sheet skin state, regardless of the discharge temperature of the re-kneading process. In addition, an excellent low heat generation effect such as mercaptosilane was not obtained.

  On the other hand, when it is Examples 1-3 which used mercaptosilane 1 as a silane coupling agent and set the discharge temperature of the re-kneading process to 120-140 degreeC, Mooney viscosity is low with respect to the comparative example 1. Also, the sheet skin condition is good, the processability is excellent, and the dispersibility of silica is improved. The tearing force is also improved, and the same or better results are obtained for the low heat generation.

  Moreover, also in the case of using mercaptosilane 2, in Comparative Example 9 where the discharge temperature of the re-kneading process is high, the sheet skin state was poor and the processability was poor. On the other hand, when it is Examples 4-5 which set the discharge temperature of the re-kneading process to 120-140 degreeC, compared with Comparative Example 9, Mooney viscosity is low, a sheet | seat skin state is also favorable, and it is excellent in workability. At the same time, an improvement effect was observed in terms of tearing force and low heat build-up.

Claims (2)

A first mixing step of adding an additive containing a filler and a mercaptosilane to a diene rubber, mixing the mixture with a kneader without adding a vulcanizing agent and a vulcanization accelerator, and discharging the mixture at a first discharge temperature When,
A re-kneading step of kneading the mixture obtained in the first mixing step with a kneader and discharging the mixture at a second discharge temperature;
A final mixing step of adding and mixing a vulcanizing agent and a vulcanization accelerator to the mixture obtained in the re-kneading step;
And the second discharge temperature is in a range of 120 to 140 ° C.   The method for producing a tire rubber composition according to claim 1, wherein the first discharge temperature is 150 ° C. or higher.