JP5631761B2 - Method for producing rubber composition for tire - Google Patents

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 added the additive except for the vulcanizing compound to the diene rubber and mixed the amine antioxidant without adding the amine antioxidant in the first mixing step. It was found that the above-mentioned problems can be solved by suppressing the self-condensation reaction of mercaptosilane by adding in the final mixing step together with the agent, and the present invention has been completed.

That is, in the method for producing a tire rubber composition according to the present invention, an additive containing a filler and a mercaptosilane is added to a diene rubber, and an amine antioxidant, a vulcanizing agent, and a vulcanization accelerator are added. Without mixing in a kneader, the mixture is discharged at the first discharge temperature , and the mixture obtained in the first mixing step is kneaded in the kneader, and the mixture is discharged at the second discharge temperature. and re-kneading step, the mixture obtained in the re-kneading step, an amine-based antioxidant, and a final mixing step of mixing by adding a vulcanizing agent and the vulcanization accelerator, only contains the second exhaust temperature It is within the range of 120 to 140 ° C.

  According to the present invention, the addition of the amine-based anti-aging agent is not the first mixing step, but the final mixing step, so that the processing in the case of using mercaptosilane without impairing the physical properties of the vulcanized rubber. Can improve sex.

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

  The rubber composition for tires according to the embodiment contains a diene rubber, a filler, a mercaptosilane, an amine-based antioxidant, 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 amine-based anti-aging agent include N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (6PPD), N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD). ), N, N′-diphenyl-p-phenylenediamine (DPPD), N, N′-di-2-naphthyl-p-phenylenediamine (DNPD), N- (3-methacryloyloxy-2-hydroxypropyl)- P-phenylenediamine-based anti-aging agents such as N′-phenyl-p-phenylenediamine and N-cyclohexyl-N′-phenyl-p-phenylenediamine; p- (p-toluenesulfonylamide) diphenylamine, 4,4′- Bis (α, α-dimethylbenzyl) diphenylamine (CD), octylated diphenylamine (OD PA), diphenylamine-based antioxidants such as styrenated diphenylamine; various aromatic secondary agents such as naphthylamine-based antioxidants such as N-phenyl-1-naphthylamine (PAN) and N-phenyl-2-naphthylamine (PBN) An amine type anti-aging agent is mentioned. These can be used alone or in combination of two or more. Among these, it is preferable from the point of a weather resistance to use p-phenylenediamine type | system | group antioxidant. Although the compounding quantity of an amine type anti-aging agent is not specifically limited, It is preferable that it is 0.5-10 mass parts with respect to 100 mass parts of diene rubbers, More preferably, it is 1-5 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 is generally used in rubber compositions for tires such as anti-aging agents other than amine-based anti-aging agents, softening agents such as oil, stearic acid, zinc white, and wax. Various additives can be blended.

  The method for producing a rubber composition according to this embodiment includes adding an additive containing a filler and a mercaptosilane to a diene rubber, and kneading without adding an amine antioxidant, a vulcanizing agent, and a vulcanization accelerator. A first mixing step of mixing in a machine, a re-kneading step of kneading the mixture obtained in the first mixing step with a kneader, an amine-based anti-aging agent and a vulcanizing agent in the mixture obtained in the re-kneading step And a final mixing step of adding and mixing the vulcanization accelerator. 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 amine anti-aging agent, 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.

  As described above, this embodiment is characterized in that no amine-based antioxidant is added in the first mixing step. That is, this type of anti-aging agent is usually added in the first mixing step together with other additives such as fillers in order to enhance dispersibility in diene rubber, but in this embodiment, such technical common sense is used. On the contrary, the amine-based antioxidant is not added in the first mixing step, but is added together with the vulcanizing compounding agent in the final mixing step. The reason is as follows. That is, mercaptosilane changes to a structure having mercapto groups at both ends by a self-condensation reaction, and this causes reaction between the polymer and polymer of a diene rubber, resulting in deterioration of processability. Further, mercaptosilane is more acidic than sulfide silane, and when a basic amine-based anti-aging agent coexists, the mixed rubber shifts to basic and promotes a self-condensation reaction. Therefore, in this embodiment, the amine-based anti-aging agent that promotes the self-condensation reaction is added in the final mixing step, thereby suppressing the self-condensation reaction of mercaptosilane. Workability can be improved without impairing other physical properties.

  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.

  The discharge temperature (second discharge temperature) in this re-kneading step can be set to the same temperature as the discharge temperature in the first mixing step, but is preferably set to 120 to 140 ° C. That is, in general, the re-kneading step is set to the same discharge temperature as the first mixing step, but it is more preferable to set the temperature lower than the discharge temperature in the first mixing step. As described above, mercaptosilane causes deterioration of workability due to self-condensation reaction, but by setting the second discharge temperature during re-kneading to 120 to 140 ° C. as described above, the self-condensation reaction of mercaptosilane is further increased. Therefore, processability can be further improved.

  In the re-kneading step, 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 step, and then in the final mixing step, an amine-based antioxidant and a vulcanizing agent. And a vulcanization accelerator are mixed. Specifically, in the final mixing step, the kneader is charged with the mixture obtained in the re-kneading step, and the amine-based anti-aging agent, vulcanizing agent and vulcanization accelerator are added and kneaded. The mixture is discharged from the kneader at a predetermined discharge temperature. 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 amine-based anti-aging agent, the vulcanizing agent, and the vulcanization accelerator are added. For example, the preliminary mixing prior to the first mixing step is performed. In the mixing step, a part of the additive may be added to the diene rubber and mixed. Moreover, you may mix | blend additives other than an amine type anti-aging agent, a vulcanizing agent, and a vulcanization accelerator in the final 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. The following Example 1 and Example 4 are reference 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 excluding sulfur and the vulcanization accelerator were added and mixed, and the mixture was discharged at the first discharge temperature (160 ° C.). 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 are added and mixed to the obtained mixture, and the mixture is discharged at a third discharge temperature (100 ° C.), whereby each rubber composition. I got a thing. However, the amine anti-aging agent was added at each charging step shown in Table 1. The second discharge temperature was 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)
Sulfide silane: bis (3-triethoxysilylpropyl) disulfide, “Si75” manufactured by Evonik Degussa
・ 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.
Amine-based anti-aging agent: “Antigen 6C” manufactured by Sumitomo Chemical Co., Ltd., N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (6PPD)
・ 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 an amine-based anti-aging agent was added in the first step (first mixing step), burns occurred during kneading, the sheet skin state was poor, and the workability was poor. It was. Also in Comparative Example 2 in which the amine-based anti-aging agent was added in the second step (re-kneading step), the sheet skin state was still inferior. On the other hand, when it is Examples 1-3 which added amine type anti-aging agent at the 3rd step (final mixing process), Mooney viscosity is low with respect to the comparative example 1, a sheet | seat skin state is also favorable, and workability. In addition to the excellent dispersibility of the silica, the tearing force was also improved, and the low heat build-up was also improved. In particular, in Examples 2 and 3 in which the discharge temperature in the second step (re-kneading process) was set to 120 to 140 ° C., workability (Mooney viscosity), tearing force, and low heat generation were compared to Example 1. A further improvement effect was observed in all sexes. Also, in the case where the type of mercaptosilane was changed, in comparison examples 4 and 5 in which the amine-based anti-aging agent was added in the first step or the second step, the processability was inferior, whereas the amine-based anti-aging agent was used. As compared with Comparative Example 4, the Mooney viscosity is low, the sheet skin state is good, the workability is excellent, and the tearing force and low heat build-up are also improved. The effect was recognized. In Comparative Example 3 using sulfide silane, tan δ was high, and an excellent low heat generation effect such as mercaptosilane was not obtained.

Claims (2)

Add an additive containing a filler and mercaptosilane to a diene rubber and mix with a kneader without adding an amine anti-aging agent, a vulcanizing agent and a vulcanization accelerator, and mix the mixture at the first discharge temperature. A first mixing step for discharging;
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 an amine anti-aging agent, a vulcanizing agent and a vulcanization accelerator to the mixture obtained in the re-kneading step ;
Unrealized method for producing a rubber composition for a tire, wherein the second discharge temperature is in the range of 120 to 140 ° C. The. The method according to claim 1 tire rubber composition, wherein said first exhaust temperature is 0.99 ° C. or higher.