JP5875840B2 - Reaction evaluation method of silane coupling agent in silica compounding - Google Patents

Description

  The present invention relates to a method for evaluating the reaction of a silane coupling agent in silica compounding, and more particularly, to a method for evaluating the reaction mode of a silane coupling agent with respect to silica in a silica compounded rubber composition.

  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. In order to improve the dispersibility and reinforcing property of silica, it is necessary to increase the reaction amount of the silane coupling agent. Therefore, it is required to know the reaction amount of the silane coupling agent in the mixed rubber composition, and the following Patent Document 1 discloses a technique for determining the reaction rate of the silane coupling agent. It is found that the correlation is high.

  By the way, the reaction of the silane coupling agent includes not only a condensation reaction in which the silane coupling agent is bonded to the silanol group of silica (hereinafter referred to as a bonding reaction) but also a self-condensation reaction in which the silane coupling agents react with each other. It is considered. Even if the reaction rate of the silane coupling agent is high, if the self-condensation reaction is large, it cannot be said that the silane coupling agent is effectively reacted with the silica surface, and it is difficult to improve the dispersibility and reinforcement of the silica. However, the reaction rate of the silane coupling agent determined by the following Patent Document 1 includes both the above-mentioned bonding reaction and self-condensation reaction, and cannot be distinguished.

On the other hand, in Patent Document 2 below, from the attribution of the spectrum of silica in a rubber composition obtained by solid high-resolution ²⁹ Si-NMR measurement, the reaction between silica and a silane coupling agent is around −85 to −95 ppm. The peak area of the Q2 structure having a peak, the Q3 structure having a peak in the vicinity of −96 to −105 ppm, and the Q4 structure having a peak in the vicinity of −106 to −115 ppm are respectively represented by S _Q2 , S _Q3, and S _Q4 , and the reaction amount = From [S _Q4 / (S _Q2 + S _Q3 )] × 100, a method for determining the reaction amount of silica and a silane coupling agent is disclosed. In this method, it is possible to make a relative comparison of the reaction amounts, but it is impossible to determine what percentage of the blended silane coupling agent has reacted. Further, this document does not disclose that the above-mentioned NMR spectrum assignment is used as an index of the amount of silica self-condensation reaction.

In addition, the attribution of the spectrum of the silica by solid-state high-resolution ²⁹ Si-NMR measurement is disclosed in the following Non-Patent Document 1 in addition to the above-mentioned Patent Document 2, and is known per se.

JP 2010-216952 A JP 2006-337342 A

Udo Goerl et al., “Investigations Into The Silica / Silane Reaction System”, Rubber Chemistry And Technology, Vol.70, p.608-623, 1997

  An object of this invention is to provide the method of evaluating the reaction form which considered the influence of the self-condensation reaction about the silane coupling agent added in silica compounding in view of said point.

The method for evaluating the reaction of a silane coupling agent according to the present invention is to obtain a reaction rate of a silane coupling agent with respect to an unvulcanized rubber composition in which silica and a sulfur-containing silane coupling agent are mixed with a rubber component, and to obtain residual silanol. The amount of the silane coupling agent is determined, and the reaction form of the silane coupling agent is evaluated based on the reaction rate of the silane coupling agent and the residual amount of silanol. The reaction rate is determined by extracting the unreacted silane coupling agent contained in the rubber composition by performing an extraction treatment with an unvulcanized rubber composition using a solvent that does not dissolve the rubber component. The content of the reacted silane coupling agent is determined by quantifying the amount of sulfur contained in the rubber composition after extraction, or the unreacted silane cup is quantified by determining the amount of sulfur contained in the extract. The content of the ring agent can be obtained, and the obtained content of the reacted or unreacted silane coupling agent can be obtained by comparing with the blending amount of the silane coupling agent. The residual amount of silanol was obtained by obtaining a spectrum of silica in the rubber composition by high-resolution solid-state ²⁹ Si-NMR measurement, and having a Q2 structure having a peak in the vicinity of −85 to −95 ppm from the assignment of the spectrum, −96 The silanol residual amount B = (S _Q2 + S _Q3 ), where the peak areas of the Q3 structure having a peak around ˜−105 ppm and the peak area of the Q4 structure having a peak around −106 to −115 ppm are S _Q2 , S _Q3 and S _Q4 , respectively. / S _Q4 .

  In the reaction evaluation method, the reaction rate A of the silane coupling agent is obtained from the following formula (1), and the effective reaction index C of the silane coupling agent C = A / B from the reaction rate A and the residual silanol amount B. Is preferably obtained.

Reaction rate A (%) = {(S−S ₀ ) / S _r } × (m / m ₀ ) × 100 (1)
In the formula, S is the sulfur content (% by mass) contained in the rubber composition after extraction, and S ₀ is the rubber composition after extraction measured for the rubber composition of the same composition except for the silane coupling agent. sulfur contained in the object is (wt%), S _r is sulfur with a silane coupling agent contained in the rubber composition before extraction, which is calculated from the amount of the silane coupling agent (wt%) It is. M ₀ is the mass of the rubber composition before extraction, and m is the mass of the rubber composition after extraction.

  The method for producing a rubber composition according to the present invention is obtained by adding silica and a sulfur-containing silane coupling agent to a rubber component, mixing them without adding a vulcanization accelerator and a vulcanizing agent, and measuring by the above reaction evaluation method. A rubber composition having a reaction rate A of the silane coupling agent of 75% or more and an effective reaction index C of 75 to 115 was prepared, and a vulcanization accelerator and a vulcanization were added to the obtained rubber composition. A rubber composition containing a vulcanizing agent is prepared by adding and mixing the agent.

  According to this invention, while obtaining the reaction rate of the silane coupling agent in a rubber composition, the residual amount of silanol is calculated | required. When this value is large, the residual amount of silanol means that there is little reaction between the silanol group of silica and the silane coupling agent, that is, there are many self-condensation reactions. Even if the silane coupling agent reacts, if there are many such self-condensation reactions, it cannot contribute to the improvement of the dispersibility and reinforcement of the silica, and the characteristics are not improved. Therefore, by obtaining the silanol residual amount together with the reaction rate of the silane coupling agent, it is possible to evaluate the reaction form taking into account the self-condensation reaction, that is, the silane coupling agent contributing to the improvement of dispersibility and reinforcing properties. It can be evaluated whether an effective response is obtained.

Silica - is an explanatory diagram showing a spectrum of a high-resolution solid-state ^{29 Si-NMR} of the silica in the rubber seeking reaction amount of the silane coupling agent. It is a spectrum figure of the solid high resolution ²⁹ Si-NMR of Example 3 and Comparative Example 5.

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

  In this embodiment, an unvulcanized rubber composition in which silica and a sulfur-containing silane coupling agent are mixed in a rubber component is used as a test object, and the reaction rate of the silane coupling agent is determined for the rubber composition, and the silanol remaining The amount is obtained, and the reaction form of the silane coupling agent is evaluated based on the obtained reaction rate and the remaining amount of silanol.

  First, the rubber composition as a test object will be described.

  In general, a method for producing a silica-containing rubber composition includes 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 a vulcanizing agent and a vulcanization accelerator in the non-pro rubber mixture. Final mixing step (pro-mixing step). In this embodiment, the non-pro rubber mixture is used as an unvulcanized rubber composition as a test object.

  The rubber component is not particularly limited. For example, natural rubber (NR), epoxidized natural rubber (ENR), styrene butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), ethylene propylene diene. Examples include various diene rubbers such as 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.

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 these, 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. .

The silane coupling agent is not particularly limited as long as it contains sulfur in the molecule, and various sulfur-containing silane coupling agents blended with silica in the rubber composition can be used. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylsilyl) 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) i (O} (C 2 H 4 O) k -C 13 H 27) Evonik Degussa represented by _j "VP Si363" (where, i = average 1, j = 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.

  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 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 said rubber components, More preferably, it is 0.5-5 mass parts.

  The vulcanization accelerator is not particularly limited. For example, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (BBS), N -Sulfenamides such as oxydiethylene-2-benzothiazolylsulfenamide (OBS), N, N-diisopropyl-2-benzothiazolylsulfenamide (DPBS), tetramethylthiuram disulfide (TMTD), tetrabutyl Thiuram series such as thiuram disulfide (TBTD), guanidine series such as 1,3-diphenylguanidine (DPG), 1,3-di-O-tolylguanidine (DOTG), dibenzothiazolyl disulfide (MBTS), 2-mercapto Thiazoles such as benzothiazole (MBT) 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, as other components, other reinforcing fillers such as carbon black, softeners such as process oil, plasticizers, anti-aging agents, zinc white, stearic acid, wax, resins, etc. Various additives used in the rubber industry can be blended.

  In the non-pro mixing step, a non-pro rubber mixture as an unvulcanized rubber composition is obtained by adding and mixing silica, a silane coupling agent, and other additives to the rubber component. 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. By this mixing, the rubber composition is heated, whereby the liquid silane coupling agent reacts with silanol groups on the silica surface to become a solid.

  It is preferable that the other additive added in the non-pro mixing step does not contain a vulcanizing agent and a vulcanization accelerator. If a vulcanizing agent or a vulcanization accelerator is blended at this stage, sulfur and the vulcanization accelerator are combined with the rubber component due to heat during mixing, and the rubber composition is also extracted after the extraction when measuring the reaction rate described later. This is because it is difficult to determine only the sulfur content of the silane coupling agent because the sulfur content derived from these remains in the product. In addition, you may mix | blend all the additives other than a vulcanizing agent and a vulcanization accelerator in a non-pro rubber mixing stage.

  Next, a method for obtaining the reaction rate of the silane coupling agent will be described.

The reaction rate of the silane coupling agent can be measured by the method described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2010-216952). That is,
(A1) Extracting the unreacted silane coupling agent contained in the rubber composition by subjecting the unvulcanized rubber composition to extraction using a solvent in which the rubber component does not dissolve,
(A2) The content of the reacted silane coupling agent is determined by quantifying the amount of sulfur contained in the rubber composition after extraction, or the amount of sulfur contained in the extract is unreacted Find the silane coupling agent content,
(A3) The reaction rate of the silane coupling agent is obtained by comparing the obtained content of the reacted or unreacted silane coupling agent with the blending amount of the silane coupling agent.

  When the extraction treatment (a1) is performed, it is preferable that the unvulcanized rubber composition is made into a sheet of 1 mm or less, for example, so that the silane coupling agent can be easily extracted. As the extraction solvent, the rubber component polymer does not dissolve, but various organic solvents in which chemicals including unreacted silane coupling agent dissolve, such as acetone, methyl ethyl ketone, methanol, ethanol, 1-propanol, 2-propanol, acetonitrile Etc. can be used. By the extraction treatment, the unreacted silane coupling agent and the reacted silane coupling agent can be separated. In addition, as an extraction processing method, it is preferable to use Soxhlet extraction.

  The amount of sulfur in the above (a2) can be determined using various known sulfur analyzers, such as ion chromatography (“ICS-1500” manufactured by Nippon Dionex Co., Ltd.), oxygen stream combustion— An infrared absorption method (LECO Japan Co., Ltd. sulfur carbon analyzer "SC-632") etc. are mentioned. At that time, the amount of sulfur contained in the rubber composition after extraction may be quantified, or the amount of sulfur contained in the extract may be quantified, but the former is preferable from the viewpoint of measurement accuracy.

  In said (a3), the reaction rate A of a silane coupling agent can be calculated | required by following formula (1).

Reaction rate A (%) = {(S−S ₀ ) / S _r } × (m / m ₀ ) × 100 (1)

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 (preferably a rubber composition dried by vacuum drying after extraction).

  Next, a method for determining the residual amount of silanol will be described.

The residual amount of silanol can be obtained from the attribution of the spectrum obtained by obtaining a spectrum of silica in the unvulcanized rubber composition by solid high-resolution ²⁹ Si-NMR measurement. At that time, the rubber composition as a measurement target may be the above-mentioned unvulcanized rubber composition itself, or may be in a bound rubber state. Here, the thing of a bound rubber state is a silica which melt | dissolves the said unvulcanized rubber composition with solvents, such as toluene, and has the bound rubber obtained by this in a surface layer part.

The measurement itself of high-resolution solid-state ²⁹ Si-NMR (CP / MAS) is, for example, the above-mentioned Patent Document 2 (Japanese Patent Laid-Open No. 2006-337342) and Non-Patent Document 1 (Rubber Chemistry And Technology, Vol. 70, p. 608). -623) can be used.

By performing solid high resolution ²⁹ Si-NMR measurement on the unvulcanized rubber composition, a silica spectrum as shown in FIG. 1 is obtained. The attribution of each spectrum is as described in Patent Document 2 and Non-Patent Document 1, and a Q2 structure (two OH groups are bonded to Si atoms) has a peak near −85 to −95 ppm. The Q3 structure (one OH group is bonded to Si atom) has a peak in the vicinity of -96 to -105 ppm, and the Q4 structure (OH group in Si atom has a peak in the vicinity of -106 to -115 ppm). Are not connected). Then, peak areas (integrated intensities) S _Q2 , S _Q3, and S _Q4 are obtained for each of the structures of Q2, Q3, and Q4, and the silanol residual amount B is calculated by the following formula (2).

Silanol remaining amount B = (S _Q2 + S _Q3 ) / S _Q4 (2)

The more reaction between the silica and the silane coupling agent, the less silanol groups on the silica surface, that is, the fewer Q2 and Q3 structures and the larger the Q4 structure. Therefore, the ratio of the sum _(S Q2 _{+ S Q3)} of the peak area of Q2 and Q3 structures to the peak area _{S Q4} of Q4 structure, the amount of silanol groups present on the silica surface, i.e. be an index indicating the silanol remaining amount B, the The larger the value, the larger the remaining amount of silanol groups, and the smaller the value, the smaller the remaining amount of silanol groups.

  Next, a method for evaluating the reaction mode of the silane coupling agent based on the reaction rate A and silanol remaining amount B of the silane coupling agent determined above will be described.

  As described above, the reaction of the silane coupling agent includes not only a binding reaction with a silanol group of silica but also a self-condensation reaction in which the silane coupling agents react with each other. It is included and cannot be distinguished. Therefore, the reaction form is evaluated with reference to the residual amount B of silanol. A large amount of residual silanol B means that the above-mentioned bonding reaction is small and indicates that there are many self-condensation reactions. That is, the silanol residual amount B is an index indicating the relative magnitude of self-condensation. Even if the reaction rate A is the same, if the value of the residual amount B of silanol is large, it means that there are many self-condensation reactions and there are few said coupling reactions effective in improving the dispersibility and reinforcing properties of silica. On the other hand, if the reaction rate A is high and the value of the residual amount of silanol B is small, it means that there are many bonding reactions effective for improving the dispersibility and reinforcement of silica. Therefore, by obtaining the silanol residual amount B together with the reaction rate A, it is possible to evaluate the reaction form taking into account the self-condensation reaction, and an effective reaction of the silane coupling agent that contributes to the improvement of dispersibility and reinforcement is obtained. Can be evaluated.

  A specific evaluation method is to calculate the effective reaction index C of the silane coupling agent from the reaction rate A and the silanol residual amount B by the following formula (3).

  Effective reaction index C = (reaction rate A [%]) / (silanol remaining amount B) (3)

  The larger the value of the effective reaction index C, the less the self-condensation reaction and the more the coupling reaction, that is, the less the self-condensation of the silane coupling agent and the more effective reaction with the silica surface. . Conversely, a small value of the effective reaction index C means that the reaction amount of the silane coupling agent itself is small (that is, the reaction rate A is low) or the reaction amount itself is large but the self-condensation reaction is large. , Indicating that it does not react effectively with the silica surface.

  Therefore, the reaction form of silica can be evaluated based on whether the effective reaction index C is equal to or greater than a predetermined value. As the predetermined value, the value of the effective reaction index C is preferably 75 or more, and an effective amount of reaction with the silica surface can be secured to enhance the effect of improving the dispersibility and reinforcement of silica. More preferably, it is 80 or more. The upper limit of the effective reaction index C is not particularly limited from the viewpoint of the physical properties of the rubber composition, but is preferably 115 or less in that an increase in Mooney viscosity at the unvulcanized stage can be suppressed.

  When evaluating the reaction form of the silane coupling agent, it is preferable to evaluate based on whether the reaction rate A is not less than a predetermined value together with the effective reaction index C. If both the effective reaction index C and the reaction rate A are each equal to or higher than a predetermined value, it can be evaluated that the reaction form has few self-condensation reactions and a large amount of effective reaction with the silica surface. And excellent results in improving the reinforcing property. As the predetermined value, the reaction rate A is preferably 75% or more, more preferably 80% or more, and further preferably 90% or more.

  Instead of evaluating with the effective reaction index C in this way, the reaction form of the silane coupling agent may be evaluated based on the respective values of the reaction rate A of the silane coupling agent and the residual amount B of silanol. That is, the reaction form may be evaluated based on whether the reaction rate A is equal to or greater than a predetermined value and whether the residual amount of silanol B is equal to or less than a predetermined value. In this case, the higher the value of the reaction rate A and the lower the residual silanol amount B, the less the self-condensation of the silane coupling agent, indicating that the silica surface is effectively reacted. Therefore, if the reaction rate A is a predetermined value or more and the silanol residual amount B is a predetermined value or less, it can be evaluated that the reaction form has a large effective reaction amount with the silica surface. As a predetermined value in this case, the reaction rate A is preferably 75% or more, more preferably 80% or more, and further preferably 90% or more. The silanol residual amount B is preferably 1.25 or less, and more preferably 1.00 or less. The lower limit of the silanol residual amount B is not particularly limited, but is usually 0.70 or more.

  Next, the manufacturing method of the rubber composition which concerns on this embodiment is demonstrated.

  As the production method, silica and a sulfur-containing silane coupling agent are added to a rubber component, and they are mixed without adding a vulcanization accelerator and a vulcanizing agent. The reaction rate A of the silane coupling agent is 75%. A rubber composition (non-pro rubber mixture) having an effective reaction index C of 75 to 115 is prepared as described above, and then a vulcanization accelerator and a vulcanizing agent are added to the obtained rubber composition and mixed ( By performing final mixing, a rubber composition containing a vulcanizing agent can be prepared.

  A specific method for obtaining such a non-pro rubber mixture having a reaction rate A and an effective reaction index C is not particularly limited, but silica and a silane coupling agent are added to the rubber component, and the maximum mixing temperature is 120 to 150. After obtaining a non-pro rubber mixture by mixing at a temperature of 0 ° C., the non-pro rubber mixture is preferably aged at room temperature (15 to 30 ° C.).

  Thus, by setting the maximum mixing temperature at the time of non-pro mixing slightly lower than usual, it is possible to suppress the self-condensation reaction of the silane coupling agent that increases in progress by discharging at a high temperature at the time of non-pro mixing. The maximum mixing temperature is more preferably 120 to 140 ° C.

  Further, by aging the non-pro-rubber mixture obtained in this way for a certain period of time in the normal temperature range, the coupling reaction between the silica and the silane coupling agent is advantageously advanced, and the reaction rate A and the effective reaction index C are determined. It is possible to improve the reinforcing property and the low heat generation property. The aging temperature is more preferably 20 to 30 ° C. The aging time for aging the non-pro rubber mixture is preferably 80 to 300 hours, more preferably 100 to 250 hours.

  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 aged rubber mixture. 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 this example, the non-pro rubber mixture (especially after aging) as described above is obtained with the above predetermined reaction rate A and effective reaction index C. However, measuring these characteristics itself is a method for producing a rubber composition. Not required. That is, when determining the production process of the rubber composition, the reaction rate A and the effective reaction index C in the non-pro rubber mixture are measured, and the discharge temperature and the aging conditions are determined so that they are within the predetermined range. In this case, it is not necessary to measure the reaction rate in the actual production of the rubber composition. 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.

  In preparing the rubber composition, 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, 3, 4, 5, 6 and 8, a rubber composition was prepared by performing a final mixing step immediately after non-pro mixing without aging at room temperature. 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 2, 7 and 9, the sheet-like non-pro rubber mixture was aged at room temperature (25 ° C.) for 168 hours, and then the final mixing step was performed in the same manner as in Comparative Example 1. Thus, a rubber composition was prepared.

  In the process of preparing the rubber composition, the reaction rate of the silane coupling agent with respect to the non-pro rubber mixture before final mixing (in the case of non-normal temperature aging, immediately after non-pro mixing, in the case of normal temperature aging, immediately after normal temperature aging) A, residual amount B of silanol, and effective reaction index C were determined.

  For each rubber composition after final mixing, the Mooney viscosity in an unvulcanized state was measured, and a 300% modulus was measured for a test sample having a predetermined shape vulcanized at 160 ° C. for 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 A of silane coupling agent)
A sheet-like sample with a thickness of 1 mm or less adjusted to mass m ₀ = 1.00 g was subjected to Soxhlet extraction with acetone for 8 hours, and the rubber composition after extraction was vacuum-dried at 30 ° C. for 5 hours to measure mass m. . 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 A of the silane coupling agent was determined from the above formula (1). 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.

(Silanol remaining amount B)
After immersing the non-pro rubber mixture in toluene and allowing it to stand at room temperature for 24 hours, the rubber polymer is eluted by further replacing the toluene and immersing for 24 hours, and then vacuum-dried at 50 ° C. for 2 hours to produce silica in a bound rubber state. Got. Using this as a measurement sample, solid high-resolution ²⁹ Si-NMR measurement was performed. Specifically, an AVANCE400 manufactured by Bruker is used as the NMR apparatus, the measurement mode is ²⁹ Si-NMR, CP-MAS method (cross polarization-magic angle rotation method), magic angle rotation speed: 4000 Hz, contact time: 5 msec, The spectrum of silica was obtained by setting the number of integrations: 2048 times and the delay time: 5 sec. Then, the peak areas S _Q2 , S _Q3 , and S _Q4 of the Q2, Q3, and Q4 structures are calculated from the spectrum by performing deconvolution with standard software Topspin manufactured by Bruker, and the above formula (2) Thus, the residual amount B of silanol was determined.

(Effective response index C)
From the reaction rate A and silanol residual amount B of the silane coupling agent determined above, the effective reaction index C was calculated by the above formula (3).

(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 5 taken 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 conducted according to JIS K6251 and the modulus value at 300% elongation was displayed as an index with the value of Comparative Example 5 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 5 being 100. The smaller the index, the smaller the rolling resistance (excellent in low heat generation), and thus the better fuel economy.

FIG. 2 is a spectrum diagram of silica in Example 3 and Comparative Example 5 by solid-state high-resolution ²⁹ Si-NMR measurement. As shown in the figure, in comparison with Comparative Example 5 which was not aged at room temperature, in Example 3 which was aged at room temperature, the peak of Q2 structure at −85 to −95 ppm and the peak of Q3 structure at −96 to −105 ppm were lowered. That is, the ratio of silanol groups remaining on the silica surface was lowered, and the value of the remaining amount B of silanol was small.

  As shown in Table 2, the higher the reaction rate A of the silane coupling agent, the more generally each physical property value tended to be favorable. For example, as in Comparative Examples 6 to 9, the reaction rate A was high. However, when the effective reaction index C was low, the Mooney viscosity was high and the performance was poor. On the other hand, in Examples 1 to 3, where the reaction rate A is 75% or more and the effective reaction index C is 75 or more, and both the reaction rate A and the effective reaction index C are high, the Mooney viscosity is low and the 300% modulus is high. The rolling resistance was low, and all of them were excellent in characteristics. Thus, by considering not only the reaction rate A but also the effective reaction index C, the reaction form of the silane coupling agent can be more accurately evaluated.

  Moreover, by aging at room temperature after non-pro mixing, the reaction rate A was increased, the value of the remaining amount of silanol B was effectively reduced, and the effective reaction index C was increased. This is considered to be because the silane coupling agent works ideally by gently reacting with the surface of the silica particles at room temperature, that is, the binding reaction proceeds while suppressing the self-condensation reaction. In this respect, as for physical property data, as is clear from the presence or absence of normal temperature aging at each discharge temperature, the reaction rate A and the effective reaction index C are increased by normal temperature aging, and the physical property values are also good. . In addition, when the discharge temperature is high (Comparative Examples 6 to 9), the reaction of the silane coupling agent has advanced considerably at the stage of non-pro mixed discharge, so the effect cost due to room temperature aging to suppress the self-condensation reaction is small, Mooney viscosity also increased.

[Second Embodiment]
In the composition of the rubber composition, the compounding amount of the silane coupling agent (“Si69” manufactured by Degussa) was changed from 6 parts by mass to 12 parts by mass in the first embodiment, and the others were the same as in the first example. . According to the conditions shown in Table 3 below, in Comparative Examples 10, 12, 13, 14, and 15, rubber compositions were prepared by performing a final mixing step immediately after non-pro mixing without aging at room temperature. In Examples 4 to 6 and Comparative Examples 11 and 16, the above-mentioned sheet-like non-pro rubber mixture was aged at room temperature (25 ° C.) for 168 hours, and then a final mixing step was performed to prepare a rubber composition. Other preparation methods are the same as those in the first example.

  For each example and comparative example, the reaction rate A, residual silanol amount B, and effective reaction index C of the silane coupling agent were determined for the non-pro-rubber mixture before final mixing, as in the first example. For each rubber composition after final mixing, the Mooney viscosity, 300% modulus and rolling resistance were measured and evaluated in the same manner as in Example 1 (however, the value was set to 100 using Comparative Example 13 as a control). (Expressed as an index).

  The results are as shown in Table 3. As in the first example, in Examples 4 to 6 where both the reaction rate A and the effective reaction index C are high, the 300% modulus is high while suppressing the increase in Mooney viscosity. The rolling resistance was low and the characteristics were excellent. In Comparative Example 16, since the reaction rate A was high and the effective reaction index C was also high, the 300% modulus and the rolling resistance were excellent, but the effective reaction index C was too high and in the unvulcanized stage. The Mooney viscosity was high and the processability was poor.

[Third embodiment]
The rubber composition was compounded in the same manner as in the first example except that 6 parts by mass of 3-octanoylthio-1-propyltriethoxysilane (“NXT” manufactured by GE Silicones) was used as the silane coupling agent. According to the conditions shown in Table 4 below, rubber compositions of Comparative Example 17 and Example 7 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 aging at room temperature. In Example 7, the sheet-like non-pro rubber mixture was aged at room temperature (25 ° C.) for 168 hours, and then a final mixing step was performed to prepare a rubber composition. Other preparation methods are the same as those in the first example.

For Comparative Example 17 and Example 7, the reaction rate A, residual silanol amount B, and effective reaction index C of the silane coupling agent were determined in the same manner as in Example 1 for the non-pro rubber mixture before final mixing. In this case, S _r (mass%) = 0.224.

  Further, the Mooney viscosity, 300% modulus, and rolling resistance of each rubber composition after final mixing were measured and evaluated in the same manner as in the first example (however, the value was set to 100 using Comparative Example 17 as a control). (Expressed as an index).

  The results are as shown in Table 4, and also in the case of using protected mercaptosilane as the silane coupling agent, as in the first example using sulfide silane, the examples were subjected to normal temperature aging after non-pro mixing. In No. 7, the reaction rate A was high, the silanol residual amount B was low, and the effective reaction index C was high. Further, the Mooney viscosity was decreased, the 300% modulus was increased, and the rolling resistance was decreased, that is, the balance between workability, reinforcement, and fuel efficiency was excellent.

[Fourth embodiment]
The rubber composition was blended in the same manner as in the first example except that 6 parts by mass of 3-mercaptopropyltrioxysilane (“A-1891” manufactured by Momentive Performance Materials) was used as the silane coupling agent. According to the conditions shown in Table 5 below, rubber compositions of Comparative Example 18 and Example 8 were prepared in the same manner as in the first example. Specifically, in Comparative Example 18, a rubber composition was prepared by performing a final mixing step immediately after non-pro mixing without aging at room temperature. In Example 8, after a sheet-like non-pro rubber mixture was aged at room temperature (25 ° C.) for 168 hours, a final mixing step was performed to prepare a rubber composition. Other preparation methods are the same as those in the first example.

For Comparative Example 18 and Example 8, the reaction rate A of the silane coupling agent, the residual amount of silanol B, and the effective reaction index C were determined in the same manner as in Example 1 for the non-pro rubber mixture before final mixing. In this case, S _r (mass%) = 0.343.

  Further, the Mooney viscosity, 300% modulus, and rolling resistance of each rubber composition after final mixing were measured and evaluated in the same manner as in the first example (however, the value was set to 100 using Comparative Example 18 as a control). (Expressed as an index).

  The results are as shown in Table 5, and in the case of using mercaptosilane as the silane coupling agent, as in Example 1 using sulfide silane, Example 8 in which room temperature aging was performed after non-pro mixing was used. The reaction rate A was high, the silanol residual amount B was low, and the effective reaction index C was high. Further, the Mooney viscosity was decreased, the 300% modulus was increased, and the rolling resistance was decreased, that is, the balance between workability, reinforcement, and fuel efficiency was excellent.

  As described above, according to the present embodiment, not only the reaction rate A of the silane coupling agent but also the effective reaction index C as an index representing the relative magnitude of the self-condensation reaction is added. The reaction form can be more accurately evaluated. Therefore, it is easy to develop a rubber composition that controls the amount of self-condensation reaction and reduces this amount, and a silica-containing rubber composition having excellent characteristics can be obtained.

  Further, as in the above examples, when the reaction rate A of the silane coupling agent is 75% or more and the effective reaction index C is 75 to 115, the Mooney viscosity is low, the 300% modulus is high, and the rolling resistance is low. Therefore, a rubber composition excellent in the balance between processability, reinforcement, and fuel efficiency can be obtained.

Claims (2)

An unvulcanized rubber composition in which silica and a sulfur-containing silane coupling agent are mixed with a rubber component is subjected to an extraction treatment using a solvent in which the rubber component does not dissolve, whereby an unvulcanized rubber composition contained in the rubber composition. The content of the reacted silane coupling agent is obtained by extracting the silane coupling agent of the reaction and quantifying the amount of sulfur contained in the rubber composition after extraction, or the amount of sulfur contained in the extract By determining the content of the unreacted silane coupling agent, the content of the obtained reacted or unreacted silane coupling agent is compared with the blending amount of the silane coupling agent. Find the reaction rate of the ring agent,
A silica spectrum in the rubber composition was obtained by high-resolution solid-state ²⁹ Si-NMR measurement. From the assignment of the spectrum, a Q2 structure having a peak in the vicinity of −85 to −95 ppm and a peak in the vicinity of −96 to −105 ppm were obtained. The remaining area of silanol B = (S _Q2 + S _Q3 ) / S _Q4 is obtained by setting the peak areas of the Q3 structure and the Q4 structure having a peak in the vicinity of −106 to −115 ppm as S _Q2 , S _Q3 and S _Q4 , respectively.
A reaction evaluation method for a silane coupling agent, wherein a reaction form of the silane coupling agent is evaluated based on a reaction rate of the silane coupling agent and a residual amount of silanol. The reaction rate A of the silane coupling agent is obtained from the following formula (1), and the effective reaction index C = A / B of the silane coupling agent is obtained from the reaction rate A and the residual amount B of silanol. The reaction evaluation method of the silane coupling agent according to claim 1.
Reaction rate A (%) = {(S−S ₀ ) / S _r } × (m / m ₀ ) × 100 (1)
(In the formula, S is the sulfur content (% by mass) contained in the rubber composition after extraction, and S ₀ is the rubber after extraction measured for the rubber composition of the same composition excluding the silane coupling agent. sulfur contained in the composition are (% by weight), S _r is sulfur with a silane coupling agent contained in the rubber composition before extraction, which is calculated from the amount of the silane coupling agent (wt% M ₀ is the mass of the rubber composition before extraction, and m is the mass of the rubber composition after extraction.)