JP5829056B2 - Method for producing rubber composition - Google Patents

Description

  The present invention relates to a rubber composition, and more particularly, to a method for producing a rubber composition containing silica.

  In order to reduce the heat generation of the rubber composition, it is known to add silica as a reinforcing filler. However, silica easily aggregates due to the influence of silanol groups present on the surface and is inferior in dispersibility, so that it is difficult to sufficiently exhibit its performance. Therefore, in order to improve the dispersibility of silica, a silane coupling agent is used in combination. The silane coupling agent is added to and mixed with the rubber component together with the silica to react with the silanol groups on the silica surface and react with the polymer of the rubber component to link the two together and disperse the silica. To improve.

  By the way, in the mixing process in the rubber composition containing silica, (1) In addition to the rubber component, silica, and silane coupling agent, chemicals such as oil, zinc white, stearic acid, and anti-aging agent are relatively high temperature (150 to 160). (2) generally immediately after that, sulfur and a vulcanization accelerator are mixed (final mixing) at a relatively low temperature (for example, 100 ° C. or less). In that case, it is thought that a characteristic will improve, so that reaction of a silane coupling agent and a silica advances, and it is generally performed to advance reaction by mixing at high temperature. However, the reaction may not be sufficiently advanced by itself.

  Therefore, in the following Patent Document 1, it is disclosed that the reaction of the silane coupling agent is advanced by heat treatment at a high temperature (for example, 100 to 200 ° C.) after non-pro mixing. Patent Document 2 below discloses that the reaction of the silane coupling agent is advanced by heat treatment at 40 to 100 ° C. after final mixing in which sulfur and a vulcanization accelerator are mixed. Although some characteristics are improved by these heat treatments, the balance of workability, reinforcement and low heat build-up is not always sufficient.

  On the other hand, Patent Document 3 below discloses a method for measuring the reaction rate of an added silane coupling agent in a rubber composition containing silica, and the reaction of the silane coupling agent proceeds even at room temperature. It is disclosed. However, this document only discloses that the reaction of the silane coupling agent proceeds at room temperature, and using a rubber mixture in which the reaction rate of the silane coupling agent is improved by aging at room temperature, There is no disclosure regarding the point of preparing a rubber composition by adding a vulcanizing agent or the like, and the point that the balance between processability, reinforcement and low heat build-up is improved. More specifically, Patent Document 3 discloses that the reaction rate of the silane coupling agent in the unvulcanized stage correlates with the low exothermic property. Even if the rate is high, it may not always be sufficient in terms of the balance between workability, reinforcement, and low heat build-up, and it is required to improve the balance of these characteristics.

JP 2005-179436 A JP-A-11-263878 JP 2010-216952 A

  This invention is made | formed in view of the above point, and it aims at improving the balance of workability, reinforcement property, and low heat build-up in the rubber composition containing silica.

  The method for producing a rubber composition according to the first aspect of the present invention is a non-pro rubber mixture in which a reaction rate of the silane coupling agent is 50 to 80% by adding and mixing silica and a silane coupling agent to a rubber component. The non-pro rubber mixture is aged at 15 to 30 ° C. to obtain an aged rubber mixture in which the reaction rate of the silane coupling agent is 90% or more, and a vulcanizing agent and a vulcanization accelerator are added to the aged rubber mixture. Is added and mixed.

In the method for producing a rubber composition according to the second aspect of the present invention, the reaction rate of the silane coupling agent is obtained by adding silica and a silane coupling agent to the rubber component and mixing at a maximum mixing temperature of 120 to 140 ° C. Is obtained by aging the non-pro rubber mixture at 15 to 30 ° C. for 80 to 300 hours to obtain an aged rubber mixture, and the aging rubber mixture is mixed with a vulcanizing agent and a vulcanization accelerator. Add and mix.

  The rubber composition according to the present invention is produced by these methods.

  According to the present invention, the reaction of the silane coupling agent can be allowed to proceed gently by aging the silica-containing non-pro rubber mixture at room temperature, and the balance between workability, reinforcement and low heat build-up can be improved. it can.

  Hereinafter, embodiments of the present invention will be described.

  The manufacturing method of the rubber composition according to the present embodiment includes (1) a non-pro mixing step of obtaining a non-pro rubber mixture by adding and mixing silica and a silane coupling agent to a rubber component, and (2) the non-pro rubber mixture at room temperature. An aging step for obtaining an aging rubber mixture by aging at (15 to 30 ° C.), and (3) a final mixing step (pro-mixing step) for adding a vulcanizing agent and a vulcanization accelerator to the aging rubber mixture and mixing them. Is included. In this way, the silane coupling agent can be allowed to react gently by aging the non-pro rubber mixture for a certain period of time in a normal temperature range of 15 to 30 ° C. And by using a rubber mixture whose reaction rate has been improved by such a mild reaction, by adding and mixing a vulcanizing agent and a vulcanization accelerator in the final mixing step, not only low exothermicity is improved, Processability and reinforcement are also improved. By aging at room temperature in this way, a rubber composition having an excellent balance of the above characteristics can be obtained without performing heat treatment and without using special chemicals.

  In the present embodiment, the rubber component is not particularly limited. For example, natural rubber (NR), epoxidized natural rubber (ENR), styrene butadiene rubber (SBR), polybutadiene rubber (BR), and polyisoprene rubber (IR). And various diene rubbers such as ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR) and butyl rubber (IIR). These rubbers can be used alone or in combination of two or more.

In the present embodiment, the silica is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like, among which wet silica is preferable. . Colloidal properties of the silica is not particularly limited, for example, those which are nitrogen adsorption specific surface area (BET) 80~300m ² / g by BET method is preferably used, more preferably from 100 to 250 m ² / g, further Preferably it is 150-230 m < ² > / g. The BET specific surface area of silica is measured by a single point value of the BET method described in ISO 5794. The blending amount of silica is not particularly limited, and is preferably 5 to 150 parts by mass, more preferably 10 to 120 parts by mass, and further preferably 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. .

In this embodiment, as a silane coupling agent, what contains sulfur in a molecule | numerator is used preferably, and various sulfur containing silane coupling agents mix | blended with a silica in a rubber composition can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) disulfide, bis ( Sulfide silanes such as 3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) disulfide;
3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmethoxysilane, mercaptoethyltriethoxysilane, formula: HS— (CH ₂ ) ₃ —Si ( OC ₂ H ₅ ) _m (O (C ₂ H ₄ O) _k —C ₁₃ H ₂₇ ) “VP Si363” manufactured by Evonik Degussa, represented by _n (where m = average 1, n = average 2, mercaptosilane such as k = average 5);
3-octanoylthio-1-propyltriethoxysilane _{(Formula: CH 3 (CH 2) 6} C (= O) S- (CH 2) 3 -Si (OC 2 H 5) 3), 3- propionylthiocholine trimethoxysilane Protected mercaptosilane such as silane (that is, a silane compound having a thiol ester structure in which a mercapto group is protected with an acyl group) and the like can be mentioned, and these can be used alone or in combination of two or more. it can. It is preferable that the compounding quantity of a silane coupling agent is 2-25 mass parts with respect to 100 mass parts of silica, More preferably, it is 4-15 mass parts.

  In the present embodiment, the vulcanizing agent is not particularly limited, but usually sulfur is used. Examples of sulfur as a vulcanizing agent include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and oil-treated sulfur. These may be used alone or in combination of two or more. Although it does not specifically limit as a compounding quantity of a vulcanizing agent, It is preferable that it is 0.1-10 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 0.5-5 mass parts. is there.

  In the present embodiment, the vulcanization accelerator is not particularly limited. For example, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide ( BBS), N-oxydiethylene-2-benzothiazolylsulfenamide (OBS), N, N-diisopropyl-2-benzothiazolylsulfenamide (DPBS) and other sulfenamides, tetramethylthiuram disulfide (TMTD) ), Thiurams such as tetrabutylthiuram disulfide (TBTD), guanidines such as 1,3-diphenylguanidine (DPG), 1,3-di-O-tolylguanidine (DOTG), dibenzothiazolyl disulfide (MBTS) 2-mercaptobenzothiazole (MBT) How thiazole-based and the like. These can be used alone or in combination of two or more. Although it does not specifically limit as a compounding quantity of a vulcanization accelerator, It is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 0.5-5 mass parts. It is.

  In the rubber composition according to this embodiment, in addition to the above-described components, other reinforcing fillers such as carbon black, softeners such as process oil, plasticizers, anti-aging agents, zinc white, stearic acid, wax Various additives usually used in the rubber industry, such as resins, can be blended.

  In the non-pro mixing step (1), silica, a silane coupling agent, and other additives are added to the rubber component and mixed to obtain a non-pro rubber mixture as an unvulcanized rubber composition. Mixing can be performed using various mixers generally used in the rubber field, for example, a Banbury mixer, a roll, a kneader, etc., preferably using a closed kneader such as a Banbury mixer.

  It is preferable that the other additive added in the non-pro mixing step does not contain a vulcanizing agent and a vulcanization accelerator. That is, in the non-pro rubber mixing step, it is preferable not to include a vulcanizing agent and a vulcanization accelerator in other additives blended in the rubber component. All other additives except the vulcanizing agent and the vulcanization accelerator may be blended in the non-pro rubber mixing stage.

  In general, in the non-pro mixing step, mixing is performed at a relatively high temperature (about 150 to 160 ° C.), but in the present embodiment, mixing is performed at a temperature slightly lower than usual and discharged. That is, the maximum mixing temperature (discharge temperature) when obtaining the non-pro rubber mixture is preferably 120 to 140 ° C., which is lower than usual. By setting the maximum mixing temperature to 140 ° C. or lower, it is possible to prevent the reaction of the silane coupling agent from proceeding excessively at the stage of non-pro mixing discharge, and to ensure the progress effect of the reaction in the subsequent aging process. In addition, workability can be improved by suppressing an increase in the unvulcanized viscosity due to the scorch. In addition, by setting the maximum mixing temperature to 120 ° C. or higher, it is easy to secure a certain degree of reaction rate of the silane coupling agent at the stage of non-pro mixing discharge and sufficiently increase the reaction rate by subsequent normal temperature aging. Become.

  In the non-pro mixing stage according to the present embodiment, a non-pro rubber mixture in which the reaction rate of the silane coupling agent is 50 to 80% is obtained. By setting the reaction rate after non-pro mixing to 50% or more and increasing the reaction rate to some extent, when the reaction rate is further increased by subsequent normal temperature aging, the effect of improving the reinforcing property can be increased. Moreover, the time required for normal temperature aging can be shortened (that is, if the reaction rate in the non-pro mixing stage is too low, it will take too much time for normal temperature aging to be practically used). In addition, by setting the reaction rate after non-pro mixing to 80% or less, it is possible to secure an allowance for improving the reaction rate at room temperature aging, and to exert advantageous effects due to room temperature aging. The reaction rate of the non-pro rubber mixture is more preferably 60 to 80%. Although the reaction rate of the silane coupling agent depends on the type and amount of the silane coupling agent and silica, the influence of the maximum mixing temperature (discharge temperature) in the non-pro mixing process is large, and the mixing temperature is set appropriately. By adjusting, it can adjust in the range of 50 to 80%.

  The reaction rate of the silane coupling agent is measured by the method described in JP 2010-216952 A. That is, in the rubber composition, an extraction treatment is performed using a solvent in which the rubber component does not dissolve in the unvulcanized rubber composition (however, an organic solvent in which a chemical containing an unreacted silane coupling agent dissolves). The unreacted silane coupling agent contained in is extracted, and the content of the reacted silane coupling agent is determined by quantifying the amount of sulfur contained in the rubber composition after extraction, or contained in the extract. The content of unreacted silane coupling agent is determined by quantifying the amount of sulfur produced, and the obtained content of reacted or unreacted silane coupling agent is compared with the blended amount of the silane coupling agent. Thus, the reaction rate of the silane coupling agent can be determined. The amount of sulfur can be quantified using various known sulfur analyzers, for example, ion chromatography (“ICS-1500” manufactured by Nippon Dionex Co., Ltd.), oxygen stream combustion-infrared absorption method (LECO). Japan Co., Ltd. sulfur carbon analyzer “SC-632”).

  In detail, the reaction rate of a silane coupling agent is calculated | required by following formula (A).

Reaction rate (%) = {(S−S ₀ ) / S _r } × (m / m ₀ ) × 100 (A)
In formula, S is a sulfur content (mass%) contained in the rubber composition after extraction. S ₀ is the sulfur content (% by mass) contained in the rubber composition after extraction measured for the rubber composition of the same composition excluding the silane coupling agent. _Sr is the sulfur content (mass%) by the silane coupling agent contained in the rubber composition before extraction calculated from the blending amount of the silane coupling agent. m ₀ is the mass of the rubber composition before extraction, and m is the mass of the rubber composition after extraction.

  The rubber mixture after non-pro mixing (non-pro rubber mixture) is preferably stretched thinly into a sheet using a roll or the like. By making it into a sheet form, in the next aging step, the entire rubber mixture can be quickly brought to a constant temperature, temperature unevenness can be suppressed, and variations in reaction rate can be suppressed.

  In the present embodiment, after the non-pro rubber mixture is obtained in the non-pro mixing step, the aging step (2) is performed before proceeding to the final mixing step. In the aging step, the non-pro rubber mixture is aged at a room temperature of 15 to 30 ° C. for a certain period of time, whereby the reaction of the silane coupling agent is advanced to obtain an aged rubber mixture having a reaction rate of 90% or more. That is, it is preferable that the reaction of the silane coupling agent, which is not sufficient immediately after the non-pro mixing step, is allowed to proceed gently by aging in the normal temperature range, and the reaction rate is increased to 90% or more. By aging in such a normal temperature range, the silane coupling agent can be ideally reacted with the surface of the silica particles, which can contribute to improvement in dispersibility and reinforcement. On the other hand, when heat treatment is performed after non-pro mixing, the reaction rate of the silane coupling agent is improved as shown in the comparative example described later, but the silica particle surface that enhances the silica reinforcement is improved. This is probably because the self-condensation between the silane coupling agents occurs rather than the reaction, and the reinforcing property cannot be improved. The reaction rate of the aging rubber mixture is more preferably 93 to 100%, still more preferably 95 to 99%. The reaction rate in the aged rubber mixture can be measured in the same manner as the reaction rate in the non-pro rubber mixture.

  The aging temperature for aging the non-pro rubber mixture is 15 to 30 ° C as described above, and more preferably 20 to 30 ° C. The aging time for aging the non-pro rubber mixture is not particularly limited as long as the aging time is 90% or more, but is preferably 80 to 300 hours, more preferably 100. ~ 250 hours. Conventionally, the final mixing process is performed immediately after discharge by non-pro mixing, and aging for such a long time is not made from the viewpoint of productivity and is contrary to the technical common sense of those skilled in the art. Met. In this embodiment, contrary to such technical common sense, the above-mentioned excellent effect has been found by aging in a normal temperature range.

  In this embodiment, after aging in a normal temperature range, a final mixing step is performed in which a vulcanizing agent and a vulcanization accelerator are added to and mixed with the aging rubber mixture. As shown in the examples below, by using a rubber mixture whose reaction rate has been improved by a mild reaction by aging in a normal temperature range, and adding and mixing a vulcanizing agent and a vulcanization accelerator in the final mixing step. The balance between workability, reinforcement and low heat build-up can be improved. Mixing in the final mixing step can also be performed using various mixers generally used in the rubber field, for example, a Banbury mixer, a roll, a kneader or the like. The final mixing is preferably carried out at a relatively low temperature (100 ° C. or lower), whereby the increase in Mooney viscosity of the unvulcanized rubber composition due to the progress of crosslinking can be suppressed.

  In the above-described embodiment, the case of one mixing step as the non-pro mixing step has been described, but the non-pro mixing step may be divided into a plurality of times and the aging step may be performed after the plurality of mixing steps. Further, after the non-pro mixing step, a remill step of re-kneading without adding an additive may be performed, and then the aging step may be performed. Further, after the ripening step, an additional non-pro mixing step may be performed, and then the final mixing step may be performed.

  In the present embodiment, the non-pro-rubber mixture and the aged rubber mixture are obtained with the above predetermined reaction rate, but measuring the reaction rate itself is not essential in the method for producing a rubber composition. That is, when determining the production rate of the rubber composition, the reaction rate at each of the above steps is measured, and if the discharge temperature, aging conditions, etc. are determined so that the reaction rate falls within the predetermined range, In the production of the rubber composition, it is not necessary to measure the reaction rate. Of course, the method for producing the rubber composition may include a step for measuring the reaction rate.

  The use of the rubber composition thus obtained is not particularly limited, and tires (eg, parts such as treads, sidewalls, and bead parts), vibration-proof rubbers (eg, engine mounts, strut mounts, body mounts, Suspension bush, etc.), seismic isolation rubber (construction seismic isolation rubber, etc.), and belts such as conveyor belts can be used for various rubber products. Preferably, it is used for a tire, and rubber parts (tread rubber, sidewall rubber, etc.) of various pneumatic tires can be constituted by vulcanization molding at 140 to 200 ° C., for example, according to a conventional method.

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

[First embodiment]
The blending of the rubber composition is as shown in Table 1 below, and the blending was common to the examples and comparative examples.

  Each rubber composition was prepared according to the conditions shown in Table 2 below ("○" is given to the corresponding treatment conditions). Specifically, first, in the non-pro mixing step, the components excluding sulfur and the vulcanization accelerator were mixed with a Banbury mixer and discharged at the discharge temperature shown in Table 2 to obtain a non-pro rubber mixture. The obtained non-pro rubber mixture was formed into a sheet having a thickness of 2 mm using a roll. Next, in Comparative Examples 1, 6, 8, 10, 11, 12, and 14, a rubber composition was prepared by performing a final mixing step immediately after non-pro mixing without performing normal temperature aging and heat treatment. Final mixing was performed by adding sulfur and a vulcanization accelerator to the non-pro rubber mixture and kneading with an open roll at 60 ° C. for 5 minutes. In contrast, in Examples 1 to 3 and Comparative Examples 7, 9, 13, and 15, the sheet-like non-pro rubber mixture was aged at room temperature (25 ° C.) for 168 hours, and then the final mixing step as in Comparative Example 1. The rubber composition was prepared by performing. In Comparative Example 2, the sheet-like non-pro rubber mixture was aged at room temperature (25 ° C.) for 24 hours and then subjected to final mixing in the same manner as in Comparative Example 1. In Comparative Example 3, the sheet-like non-pro rubber mixture was subjected to a heat treatment at 170 ° C. for 3 minutes and then subjected to final mixing in the same manner as in Comparative Example 1, and the technique described in Patent Document 1 was applied. Correspond. In Comparative Example 4, as in Comparative Example 1, a final mixing step was performed immediately after non-pro mixing without performing normal temperature aging and heat treatment, and the final rubber thus obtained was formed into a sheet having a thickness of 2 mm by a roll. And the sheet-like final rubber was aged at room temperature (25 ° C.) for 168 hours to obtain a rubber composition. In Comparative Example 5, a final rubber was formed into a sheet shape in the same manner as in Comparative Example 4, and then the sheet-like final rubber was heat treated at 50 ° C. for 96 hours to prepare a rubber composition. This corresponds to the technique described in 2.

  In the process of preparing the rubber composition, the reaction rate of the silane coupling agent was measured for the rubber composition immediately after non-pro mixing (non-pro rubber mixture). Moreover, about the Example and comparative example which performed normal temperature aging or heat processing about this non-pro rubber mixture, the reaction rate of the silane coupling agent after this process was also measured.

  About each obtained rubber composition, while measuring the Mooney viscosity in an unvulcanized state, 300% modulus was measured about the test sample of the predetermined shape vulcanized at 160 degreeC * 30 minutes. Further, the rubber composition was applied to a cap tread of a tire having a tread having a cap / base structure, and a 205 / 65R159H pneumatic radial tire was produced according to a conventional method, and rolling resistance was evaluated. Each measurement / evaluation method is as follows.

(Reaction rate of silane coupling agent)
According to the method described in JP 2010-216952 A, a sheet-like sample having a thickness of 1 mm or less adjusted to mass m ₀ = 1.00 g is subjected to Soxhlet extraction with acetone for 8 hours, and the rubber composition after extraction is 30 The mass m was measured by vacuum drying at 5 ° C. for 5 hours. Subsequently, the sulfur content S (sulfur concentration: mass%) contained in the rubber composition after extraction was determined by an ion chromatograph “ICS-1500” manufactured by Nippon Dionex Co., Ltd. Also, except for not blending the silane coupling agent in the formulation shown in Table 1 were prepared by the same operation with the same rubber composition, determine the sulfur content S _{0 (wt%)} contained in the rubber composition after extraction, The reaction rate of the silane coupling agent was determined from the above formula (A). Incidentally, the sulfur content S _{r (wt%)} with a silane coupling agent contained in the rubber composition before extraction, which is calculated from the amount of the silane coupling agent is 0.587.

(Mooney viscosity)
Using a Toyo Seiki Co., Ltd. rotorless Mooney measuring machine in accordance with JIS K6300, after preheating the unvulcanized rubber at 100 ° C for 1 minute, the torque value after 4 minutes was measured in Mooney units. Displayed as an index with the value of Example 1 as 100. The smaller the index, the lower the viscosity and the better the workability.

(300% modulus)
A tensile test (dumbbell No. 3 type) was carried out according to JIS K6251 and the modulus value at 300% elongation was displayed as an index with the value of Comparative Example 1 as 100. The larger the value of the 300% modulus, the more effective the silane coupling agent is for silica reinforcement. Therefore, the larger the index, the better the reinforcing property and the more desirable.

(Rolling resistance)
Rolling resistance when running at 23km and 80km / h on a single-axis drum tester for rolling resistance measurement, with a rim of 15x6.5JJ and tires mounted, air pressure of 230kPa and load of 4.4kN It was measured. The results were expressed as an index with the value of Comparative Example 1 as 100. The smaller the index, the smaller the rolling resistance (excellent in low heat generation), and thus the better fuel economy.

  The results are as shown in Table 2. The discharge temperature in the non-pro mixing step was set to 140 ° C., and after non-pro mixing or final mixing, comparison was made by performing normal temperature aging or heat treatment, and compared to Comparative Example 1 in which neither aging nor heat treatment was performed, after non-pro mixing In Example 1 where sufficient room temperature aging was performed, the Mooney viscosity was low, the 300% modulus was high, and the rolling resistance was low. All of these are excellent in characteristics, and it can be seen that the silane coupling agent works ideally by gently reacting with the surface of the silica particles at room temperature. On the other hand, in Comparative Example 2, the room temperature aging was insufficient and almost no improvement effect was observed. In Comparative Example 3 in which heat treatment was performed after non-pro mixing, the 300% modulus was low. This is thought to be because the reaction of the silane coupling agent proceeds by heat treatment, but the self-condensation of the silane coupling agents occurs rather than the reaction with the silica particle surface that enhances the silica reinforcement. It is done. On the other hand, in Comparative Example 4 that was aged at room temperature after final mixing and in Comparative Example 5 that was heat-treated, Mooney viscosity was high, which is considered to be due to scorching. Moreover, in Comparative Examples 4 and 5, the 300% modulus is also lowered, and it is considered that the silane coupling agent is self-condensed.

  When the discharge temperature in the non-pro mixing step is 120 ° C. (Comparative Example 10 and Example 2) and 130 ° C. (Comparative Example 11 and Example 3), the characteristics are obtained by aging at room temperature as in the case of 140 ° C. The effect of the improvement appeared.

  On the other hand, when the discharge temperature is 100 ° C. (Comparative Examples 6 and 7) and 110 ° C. (Comparative Examples 8 and 9), the reaction rate of the silane coupling agent after non-pro mixed discharge is too low. Even after aging, the reaction did not proceed sufficiently and the characteristics were not improved sufficiently. When the discharge temperature is 150 ° C. (Comparative Examples 12 and 13) and 160 ° C. (Comparative Examples 14 and 15), the reaction of the silane coupling agent proceeds at the stage of non-pro mixed discharge. Therefore, not only the effect of the progress of reaction due to normal temperature aging cannot be obtained, but also the discharge temperature is high, scorching occurs, and the Mooney viscosity increases.

[Second Embodiment]
The rubber composition was blended in the same manner as in Example 1 except that 3-octanoylthio-1-propyltriethoxysilane (“NXT” manufactured by GE Silicones) was used as the silane coupling agent. According to the conditions shown in Table 3 below, rubber compositions of Comparative Example 16 and Example 4 were prepared in the same manner as in the first example. Specifically, in Comparative Example 16, a rubber composition was prepared by performing a final mixing step immediately after non-pro mixing without performing normal temperature aging and heat treatment. In Example 4, a rubber composition was prepared by aging a sheet-like non-pro rubber mixture at room temperature (25 ° C.) for 168 hours and then performing a final mixing step. Other preparation methods are the same as those in the first example.

About Comparative Example 16 and Example 4, the reaction rate of the silane coupling agent immediately after non-pro mixing and after normal temperature aging was measured in the same manner as in the first example. In this case, S _r (mass%) = 0.224.

  For each rubber composition, the Mooney viscosity, 300% modulus, and rolling resistance were measured and evaluated in the same manner as in the first example (however, the comparative example 16 was used as a control, and the value was displayed as an index of 100). ).

  The results are as shown in Table 3, and also in the case of using protected mercaptosilane as the silane coupling agent, as in the first example using sulfide silane, an example in which normal temperature aging was performed after non-pro mixing was performed. In No. 4, the Mooney viscosity was low, the 300% modulus was high, and the rolling resistance was low, that is, the balance between workability, reinforcement, and fuel efficiency was excellent.

[Third embodiment]
The rubber composition was blended in the same manner as in the first embodiment except that 3-mercaptopropyltriexisilane (“A-1891” manufactured by Momentive Performance Materials) was used as the silane coupling agent. According to the conditions shown in Table 4 below, rubber compositions of Comparative Example 17 and Example 5 were prepared in the same manner as in the first example. Specifically, in Comparative Example 17, a rubber composition was prepared by performing a final mixing step immediately after non-pro mixing without performing normal temperature aging and heat treatment. In Example 5, a rubber composition was prepared by aging a sheet-like non-pro rubber mixture at room temperature (25 ° C.) for 168 hours and then performing a final mixing step. Other preparation methods are the same as those in the first example.

About the comparative example 17 and Example 5, the reaction rate of the silane coupling agent immediately after non-pro mixing and after normal temperature aging was measured like the 1st example. In this case, S _r (mass%) = 0.343.

  For each rubber composition, the Mooney viscosity, 300% modulus, and rolling resistance were measured and evaluated in the same manner as in the first example (however, the comparative example 17 was used as a control and the value was expressed as an index of 100). ).

  The results are as shown in Table 4, and also in the case of using mercaptosilane as the silane coupling agent, as in Example 1 in which sulfide silane was used, Example 5 in which room temperature aging was performed after non-pro mixing was used. The Mooney viscosity was low, the 300% modulus was high, and the rolling resistance was low. That is, the balance between workability, reinforcement and low fuel consumption was excellent.

  As described above, final mixing is performed using a rubber having a reaction rate of 50 to 80% of the silane coupling agent in the non-pro mixing and discharging stage which is aged at room temperature and the reaction rate after aging is 90% or more. By performing the above, not only the fuel efficiency is improved, but also the workability and the reinforcing property are improved, and a rubber composition having an excellent balance of these characteristics can be obtained.

Claims (4)

  Silica and a silane coupling agent are added to the rubber component and mixed to obtain a non-pro rubber mixture in which the reaction rate of the silane coupling agent is 50 to 80%, and the non-pro rubber mixture is aged at 15 to 30 ° C. A method for producing a rubber composition, comprising obtaining an aged rubber mixture having a reaction rate of a silane coupling agent of 90% or more, and adding and mixing a vulcanizing agent and a vulcanization accelerator to the aged rubber mixture.   The method for producing a rubber composition according to claim 1, wherein the maximum mixing temperature when obtaining the non-pro rubber mixture is 120 to 140 ° C.   The method for producing a rubber composition according to claim 1 or 2, wherein the time for aging the non-pro rubber mixture is 80 to 300 hours.   By adding silica and a silane coupling agent to the rubber component and mixing at a maximum mixing temperature of 120 to 140 ° C., a non-pro rubber mixture in which the reaction rate of the silane coupling agent is 50 to 80% is obtained, and the non-pro rubber mixture is obtained. A method for producing a rubber composition, comprising aging at 15 to 30 ° C. for 80 to 300 hours to obtain an aged rubber mixture, and adding and mixing a vulcanizing agent and a vulcanization accelerator to the aged rubber mixture.