JP6329608B2 - Pneumatic tire and crosslinked rubber composition - Google Patents

Description

  The present invention relates to a pneumatic tire and a crosslinked rubber composition.

  In general, a crosslinked rubber composition used for a tire tread is blended with several kinds of rubber components according to required performance. When different types of rubber components are present, it is known that the fillers are unevenly distributed (filler dispersibility is poor) because the compatibility between the rubber components and the fillers is different.

  The fact that the filler is unevenly distributed means that the filler dispersibility is deteriorated, and it is considered that when the filler dispersibility is deteriorated, the fracture characteristics and the wear resistance are deteriorated. This is because if the dispersibility of the filler is poor, the filler aggregates, and the aggregated filler serves as a starting point of fracture, thereby deteriorating the fracture characteristics and wear resistance.

  Thus, various techniques for improving filler dispersibility in the crosslinked rubber composition have been proposed (Patent Document 1, etc.). However, better filler dispersibility is not necessarily superior in fracture characteristics and wear resistance, and there are exceptions. That is, although the filler dispersibility in the crosslinked rubber composition is excellent, it has been confirmed that when the abrasion resistance of the crosslinked rubber composition or rubber product is measured, an excellent result cannot be obtained.

  Until now, the destruction and friction phenomena of rubber have been observed by various methods to elucidate the mechanism that causes such an exception, but it has not been completely elucidated.

  On the other hand, an X-ray CT (Computed Tomography) imaging technique is known as a technique for analyzing a material constituting a solid sample and a low density region included therein. For example, Patent Document 2 describes an analysis method for visually analyzing a material constituting a friction material and a low-density region existing inside, but a state in which external energy such as extension is added to a sample object It is not described until the analysis of the sample and the analysis of the density of the sample.

JP 2007-2031 A JP 2009-85732 A

  An object of the present invention is to provide a pneumatic tire and a crosslinked rubber composition excellent in wear resistance.

  As a result of intensive studies, the inventors have found that cracks generated inside the crosslinked rubber composition can be reduced by reducing the voids during elongation due to an applied stress of 3.0 MPa and increasing the uniformity of the filler distribution state. It has been found that growth can be suppressed and wear resistance can be further improved, and the present invention has been completed.

That is, the present invention includes a bead core provided in each of the pair of right and left bead portions, a carcass ply extending from the crown portion to both bead portions via both sidewall portions, and a tire diameter larger than the carcass ply. An inner liner disposed on the inner side in the direction, and provided on the outer side in the tire radial direction from the carcass ply, containing two or more rubber components and fillers, and having a void volume at the time of elongation due to an applied stress of 3.0 MPa. And a tread having a filler dispersibility D represented by the following formula (I) of 2.0 or less.
_{D = (A 1 / B 1} ) / (A 0 / B 0) (I)
In formula (I),
A ₁ is the volume fraction of rubber component A in the filler gel,
B ₁ is the volume fraction of rubber component B in the filler gel,
A ₀ is the volume fraction of the blended rubber component A,
B ₀ represents the volume fraction of the blended rubber component B.

Further, the present invention is a crosslinked rubber composition containing two or more kinds of rubber components and fillers, and the volume of voids when stretched by an applied stress of 3.0 MPa is 7.5% or less. It relates to a crosslinked rubber composition having a filler dispersibility D represented by I) of 2.0 or less.
_{D = (A 1 / B 1} ) / (A 0 / B 0) (I)
In formula (I),
A ₁ is the volume fraction of rubber component A in the filler gel,
B ₁ is the volume fraction of rubber component B in the filler gel,
A ₀ is the volume fraction of the blended rubber component A,
B ₀ represents the volume fraction of the blended rubber component B.

  The rubber component is preferably a rubber component including one or more rubber components including a conjugated diene compound.

  It is preferable that the void portion is a region where the density is 0 to 0.1 times that of the crosslinked rubber composition before elongation.

  It is preferable that the volume evaluation method for the void is X-ray CT imaging.

  The decay time of the phosphor for converting X-rays into visible light is preferably 100 ms or less.

The X-ray luminance is preferably 10 ¹⁰ photons / s / mrad ² / mm ² /0.1% bw or more.

  The pneumatic tire of the present invention having a tread having a small amount of voids when stretched by an applied stress of 3.0 MPa and having a highly uniform filler distribution state, and a filler having few voids when stretched by an applied stress of 3.0 MPa According to the crosslinked rubber composition of the present invention having a high distribution state uniformity, it is possible to provide a pneumatic tire and a crosslinked rubber composition excellent in wear resistance.

It is a perspective view which shows roughly an example of the evaluation apparatus which evaluates the density distribution at the time of the expansion | extension of a crosslinked rubber composition. It is a flowchart which shows the process sequence of the evaluation method of the density distribution of the crosslinked rubber composition at the time of expansion | extension.

  The crosslinked rubber composition of the present invention is a crosslinked rubber composition containing two or more kinds of rubber components and fillers, has few voids when stretched by an applied stress of 3.0 MPa, and has high uniformity in filler distribution state. It is a crosslinked rubber composition. In addition, the crosslinked rubber composition in this specification is a rubber composition that has been crosslinked with a vulcanizing agent or an organic peroxide.

Rubber component The two or more rubber components are not particularly limited, and isoprene-based rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), acrylonitrile butadiene rubber. Two or more rubber components used in the conventional rubber industry such as diene rubber such as (NBR) and butyl rubber can be appropriately selected and used. Especially, it is preferable to contain 1 or more types of rubber components containing a conjugated diene type compound, and it is preferable to contain SBR and BR from a viewpoint of the balance of low fuel consumption, abrasion resistance, durability, and wet grip performance. The two or more rubber components in the present invention refer to two rubber components (for example, BR and SBR, NR and SBR, etc.) having different polymer main chain structures, and are different in chemical properties and physical properties. Rubber components having the same main chain structure (such as two types of SBR having different chemical properties) are not applicable.

  SBR is not particularly limited, and examples thereof include emulsion polymerization SBR (E-SBR), solution polymerization SBR (S-SBR), and the like, and may or may not be oil-extended. Further, terminal-modified S-SBR and main chain-modified S-SBR with enhanced interaction force with the filler can also be used. These SBRs may be used alone or in combination of two or more.

The styrene content of SBR is preferably 16% by mass or more, more preferably 20% by mass or more, further preferably 25% by mass or more, and particularly preferably 30% by mass or more from the viewpoint of grip performance. Also, if the styrene content is too high, the styrene group is adjacent, the polymer becomes too hard, the cross-linking tends to be uneven, the blowability at high temperature running may be deteriorated, and the temperature dependency increases, The performance change with respect to the temperature change becomes large, and there is a tendency that the stable grip performance in the running / late period cannot be obtained well, so 60 mass% or less is preferable, 50 mass% or less is more preferable, and 40 mass% is preferable. The following is more preferable. In the present specification, the styrene content of SBR is calculated by ¹ H-NMR measurement.

  The vinyl content of SBR is preferably 10% or more, more preferably 15% or more from the viewpoint of Hs and grip performance of the crosslinked rubber composition. Moreover, from a viewpoint of grip performance, EB (durability), and abrasion resistance, 90% or less is preferable, 80% or less is more preferable, 70% or less is further more preferable, and 60% or less is especially preferable. In addition, in this specification, the vinyl content (1,2-bond butadiene unit amount) of SBR can be measured by an infrared absorption spectrum analysis method.

  SBR has a glass transition temperature (Tg) of preferably −45 ° C. or higher, and more preferably −40 ° C. or higher. The Tg is preferably 10 ° C. or lower, and more preferably 5 ° C. or lower from the viewpoint of preventing embrittlement cracks in the temperate winter season. In the present specification, the glass transition temperature of SBR is a value measured by performing differential scanning calorimetry (DSC) in accordance with JIS K 7121 under the condition of a heating rate of 10 ° C./min.

  The weight average molecular weight (Mw) of SBR is preferably 700,000 or more, more preferably 900,000 or more, and further preferably 1,000,000 or more from the viewpoint of grip performance and blowability. Further, from the viewpoint of blowability, the weight average molecular weight is preferably 2 million or less, and more preferably 1.8 million or less. In addition, in this specification, the weight average molecular weight of SBR is gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE manufactured by Tosoh Corporation). It can be determined by standard polystyrene conversion based on the measured value by HZ-M).

  The content of the SBR in the rubber component is preferably 30% by mass or more, and more preferably 40% by mass or more because sufficient grip performance can be obtained. In addition, the content of SBR is preferably 90% by mass or less, more preferably 85% by mass or less, and further preferably 80% by mass or less from the viewpoints of wear resistance, grip performance, and fuel efficiency.

  Among them, it is preferable that SBR having a styrene content of 16 to 60% by mass is contained in an amount of 40% by mass or more and SBR having a styrene content of 25 to 55% by mass because higher grip performance and blowability can be exhibited. It is more preferable that 50 mass% or more is included.

  The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B, etc., high cis content BR (Hisys BR), manufactured by Nippon Zeon Co., Ltd. BR synthesized using a modified BR such as BR1250H, a BR containing syndiotactic polybutadiene crystals such as VCR412 and VCR617 manufactured by Ube Industries, Ltd., and a rare earth element catalyst such as BUNA-CB25 manufactured by LANXESS (Rare earth BR) or the like can be used. These BR may use 1 type and may use 2 or more types together. Of these, high cis BR and rare earth BR are preferred because they are excellent in workability, wear resistance and fracture characteristics.

  When BR is contained, the content of BR in the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more, and more preferably 20% by mass or more from the viewpoints of wear resistance, grip performance, and fuel efficiency. Is more preferable. The content is preferably 70% by mass or less, and more preferably 60% by mass or less from the viewpoint of wear resistance, grip performance, and low fuel consumption.

  The filler can be arbitrarily selected from those conventionally used in cross-linked rubber compositions, but carbon black and silica are mainly preferred.

  Examples of carbon black include furnace black, acetylene black, thermal black, channel black, graphite, and the like. These carbon blacks may be used alone or in combination of two or more. Among these, furnace black is preferable because it can improve the low temperature characteristics and wear performance in a well-balanced manner.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 70 m ² / g or more, more preferably 90 m ² / g or more, from the viewpoint that sufficient reinforcement and wear resistance can be obtained. Also, N ₂ SA of carbon black is excellent in dispersibility, from the viewpoint that it is difficult to heat generation, preferably 300 meters ² / g or less, more preferably 250m ² / g. In this specification, N ₂ SA of carbon black is measured according to JIS K 6217-2 “Basic characteristics of carbon black for rubber—Part 2: Determination of specific surface area—Nitrogen adsorption method—Single point method” Value.

  In the case of containing carbon black, the content with respect to 100 parts by mass of the rubber component is preferably 3 parts by mass or more, and more preferably 4 parts by mass or more. When the amount is less than 3 parts by mass, sufficient reinforcing properties tend not to be obtained. The carbon black content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 60 parts by mass or less. When it exceeds 200 mass parts, there exists a tendency for workability to deteriorate, the tendency to generate | occur | produce heat easily, and a tendency for abrasion resistance to fall.

  The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 80 m ² / g or more, more preferably 100 m ² / g or more, from the viewpoint of durability and elongation at break. The N ₂ SA of the silica, from the viewpoint of fuel economy and workability, preferably 250 meters ² / g or less, more preferably 220 m ² / g. Note that the N ₂ SA of the silica herein is a value measured in accordance with ASTM D3037-93.

  The content with respect to 100 parts by mass of the rubber component in the case of containing silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more from the viewpoint of durability and elongation at break. Further, the content of silica is 200 parts by mass from the viewpoint of improving dispersibility at the time of kneading, and suppressing reduction of workability due to re-aggregation of silica during heating during rolling and storage after rolling. The following is preferable, and 150 parts by mass or less is more preferable.

  When silica is contained, it is preferable to use a silane coupling agent in combination. As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, Si75, Si266 (bis (3-triethoxysilyl) manufactured by Evonik Degussa Co., Ltd. Propyl) disulfide), sulfides such as Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by the same company, 3-mercaptopropyltrimethoxysilane, NXT-Z100, NXT-Z45, NXT manufactured by Momentive, etc. Mercapto-based (silane coupling agent having a mercapto group), vinyl-based such as vinyltriethoxysilane, amino-based such as 3-aminopropyltriethoxysilane, glycidoxy-based such as γ-glycidoxypropyltriethoxysilane, 3- Nitropropi Nitro-based, such as trimethoxysilane, 3-chloropropyl-chloro system such as trimethoxysilane. These may be used alone or in combination of two or more. Of these, sulfide type and mercapto type are preferable from the viewpoints of strong bonding strength with silica and excellent low heat build-up.

  In the case of containing a silane coupling agent, the content with respect to 100 parts by mass of silica is preferably 2 parts by mass or more, and more preferably 3 parts by mass or more. When content of a silane coupling agent is less than 2 mass parts, there exists a tendency for the silica dispersibility improvement effect not to be fully acquired. Further, the content of the silane coupling agent is preferably 25 parts by mass or less, and more preferably 20 parts by mass or less. When content of a silane coupling agent exceeds 25 mass parts, there exists a tendency for the effect corresponding to cost not to be acquired.

  In addition to the above components, the crosslinked rubber composition of the present invention contains compounding agents generally used in the production of crosslinked rubber compositions, such as resin components, oil, zinc oxide, stearic acid, anti-aging agents, waxes. , A sulfur donor, a vulcanizing agent, a vulcanization accelerator and the like can be appropriately blended.

In the crosslinked rubber composition of the present invention, the volume of the void portion when stretched by an applied stress of 3.0 MPa is 7.5% or less, and the filler dispersibility D represented by the following formula (I) is 2.0 or less. It is characterized by being.
_{D = (A 1 / B 1} ) / (A 0 / B 0) (I)
In formula (I),
A ₁ is the volume fraction of rubber component A in the filler gel,
B ₁ is the volume fraction of rubber component B in the filler gel,
A ₀ is the volume fraction of the blended rubber component A,
B ₀ represents the volume fraction of the blended rubber component B.

  The crosslinked rubber composition having a small void area is excellent in durability against external stresses such as fracture characteristics and wear resistance. In addition, the crosslinked rubber composition containing two or more rubber components and having a highly uniform filler distribution state can be prevented from being broken starting from the interface of the rubber components. The crosslinked rubber composition of the present invention can achieve high wear resistance due to a small volume of voids when stretched by an applied stress of 3.0 MPa and high uniformity of the filler distribution state. The volume of the void when elongated by an applied stress of 3.0 MPa is preferably 7.0% or less.

  In order to realize a state where the volume of the void portion when stretched by an applied stress of 3.0 MPa is 7.5% or less, it is necessary to make the cross-linked state in the rubber composition uniform. Examples of means for homogenizing the cross-linked state include, for example, homogenizing the dispersion state of the vulcanizing agent and / or vulcanization accelerator by increasing the kneading time or increasing the number of kneading. It is done.

  The void portion will be described. First, when the stress applied to the crosslinked rubber composition exceeds a critical value specific to the crosslinked rubber composition, density deviation occurs in the crosslinked rubber composition, and a low density region is generated inside. This low density region has a reversible part and an irreversible part.

  The reversible portion is a low density region that occurs when the applied stress is small (1.5 MPa), and disappears when the stress is released, and the density distribution is a low density region that recovers to its original uniform state. Here, the low density region generated when the applied stress is small is a region having a density of 0.1 to 0.8 times the average density of the crosslinked rubber composition before stretching. By evaluating the distribution of the reversible portion, the rubber test piece can be evaluated with high accuracy.

  The irreversible part is a low-density region that occurs when the applied stress is large (3.0 MPa), and the internal structure (bonding of molecular chains) of the crosslinked rubber composition is partially broken by the stress. Even after the release, the low density region remains without being restored to the original state. Here, among the irreversible portion, the region where the internal structure is extremely destroyed and the region where the density is 0 to 0.1 times the average density of the crosslinked rubber composition before elongation is defined as the void. The rubber test piece can be evaluated with high accuracy by evaluating the distribution of the voids.

  The method for evaluating the volume of the void during elongation by an applied stress of 3.0 MPa is not particularly limited as long as the density distribution of the crosslinked rubber composition during elongation can be evaluated, but X-ray CT imaging was used. An evaluation method is preferred.

  A method for evaluating the density distribution of a crosslinked rubber composition during elongation using X-ray CT imaging will be described with reference to the accompanying drawings. FIG. 1 is a perspective view schematically showing an example of an evaluation apparatus used in the evaluation method. An evaluation apparatus 1 shown in FIG. 1 includes a stress applying unit 2, a photographing unit 3, and an evaluating unit 4.

  The stress applying means 2 applies a stress that elongates the rubber test piece 10 to generate a low density region inside the rubber test piece 10.

  The stress applying means 2 includes a pair of jigs 21 and 22 to which the test piece 10 is fixed, and a driving means 23 for applying a stress to the test piece 10 by relatively moving the jig 21 and the jig 22. It is preferable to have. The driving unit 23 moves the other jig 22 in the axial direction of the test piece 10 while the one jig 21 is fixed. Thereby, the stress which expands the rubber test piece 10 in the axial direction is applied.

  The stress applied to the test piece 10 is detected by a load cell (not shown) or the like. The position and format of the load cell are arbitrary. A predetermined stress is applied to the rubber test piece 10 by the stress applying means 2. The driving means 23 is configured to rotate the test piece 10 and the jigs 21 and 22 around the axis of the rubber test piece 10.

The imaging means 3 irradiates the test piece 10 with X-rays to capture a projected image. The imaging unit 3 includes an X-ray tube 31 that emits X-rays, and a detector 32 that detects X-rays and converts them into electrical signals. While the test piece 10 and the jigs 21 and 22 are rotated around the axis of the test piece 10, the imaging unit 3 takes a plurality of projection images, whereby a projection image of the test piece 10 over the entire circumference can be obtained.

The detector 32 has a phosphor 32a for converting X-rays into visible light. The decay time of the phosphor 32a is preferably 100 ms or less. When the decay time of the phosphor 32a exceeds 100 ms, when a plurality of projection images are continuously photographed while rotating the test piece 10 or the like around the axis of the test piece 10, an afterimage of the projection image previously taken is obtained. There is a risk of affecting a projected image to be taken later. From such a viewpoint, the more desirable decay time of the phosphor 32a is 50 ms or less, and the still more preferred decay time is 10 ms or less.

  The evaluation means 4 evaluates the performance of the crosslinked rubber composition based on the density distribution measured from the projected image. For example, a computer 40 is applied to the evaluation means 4. The computer 40 includes a main body 41, a keyboard 42, and a display device 43. The main body 41 is provided with a storage device such as an arithmetic processing unit (CPU), a ROM, a working memory, and a hard disk. The storage device stores in advance processing procedures (programs) for executing the simulation method of the present embodiment.

  FIG. 2 is a flowchart showing the processing procedure of the evaluation method of the density distribution of the crosslinked rubber composition during elongation using the evaluation apparatus 1. The evaluation method of the density distribution includes steps S1 and S2 in which stress is applied to the test piece 10 to generate a density deviation (low density region) inside the rubber test piece 10, and the rubber test piece 10 is irradiated with X-rays. Thus, it includes photographing steps S3 and S4 for photographing the projected image, and evaluation steps S5 and S6 for evaluating the density distribution of the crosslinked rubber composition based on the density distribution measured from the projected image.

  In step S <b> 1, the rubber test piece 10 is fixed to the jigs 21 and 22.

  Although the shape of the rubber test piece 10 is not particularly limited, a cylindrical shape and a rectangular parallelepiped are preferable, and a cylindrical shape is more preferable because it has symmetry and can easily obtain a highly reproducible measurement result.

  The rubber test piece 10 preferably has a diameter that is 5 times or more the axial length, more preferably 10 times or more, and even more preferably 20 times or more. According to such a test piece 10, when stress is applied to the rubber test piece 10, deformation of the side surface of the rubber test piece 10 is limited. As a result, the volume of the rubber test piece 10 is increased, and a very large stress is applied to the inside. Therefore, a low density region is likely to be generated inside the test piece 10, and the performance evaluation of the elastic material can be performed quickly and easily.

  The rubber test piece 10 is fixed to both jigs while being sandwiched between the jigs 21 and 22. The upper end surface of the rubber test piece 10 is fixed to the lower end surface of the jig 21, and the lower end surface of the test piece 10 is fixed to the upper end surface of the jig 22. The fixing method can be appropriately selected depending on the test environment and the like. For example, fixation by an adhesive or fixation by vulcanization adhesion of an elastic material constituting the test piece 10 can be applied. Moreover, the test piece 10 and the jig | tool 21 and 22 are fixed by providing a corresponding engaging part in an upper end surface, a lower end surface, a lower end surface, and an upper end surface, respectively, and engaging each engaging part. It may be.

  In step S2, as shown in FIG. 1, the driving means 23 causes the jig 21 and the jig 22 to move in the axial direction of the rubber test piece 10, that is, the direction in which the jig 22 moves away from the jig 21, and the rubber The test piece 10 is extended. When the stress exceeds the critical value inherent to the crosslinked rubber composition, density deviation occurs in the rubber test piece 10 and a low density region is generated inside.

  In the present invention, among the low-density regions generated when the applied stress is large, the stress for stretching the rubber test piece 10 when measuring the distribution of voids, which is a region where the internal structure is extremely destroyed, is 3. 0 MPa.

  In step S3, the X-ray tube 31 irradiates the rubber test piece 10 with X-rays. X-rays pass through the rubber test piece 10 and are detected by the detector 32. The detector 32 converts the detected X-ray into an electric signal and outputs it to the computer 40.

The brightness of X-rays irradiated from the X-ray tube 31 to the rubber test piece 10 is greatly related to the S / N ratio of the X-ray scattering data. When the luminance of X-ray is small, the signal intensity tends to be weaker than the statistical error of X-ray, and it may be difficult to obtain data having a sufficiently good S / N ratio even if the measurement time is extended. . From such a viewpoint, the luminance of the X-ray is preferably 10 ¹⁰ photons / s / mrad ² / mm ² /0.1% bw or more.

  In step S4, the electrical signal output from the detector 32 is processed by the computer 40 to obtain a projection image.

  In step S5, the projection image is reconstructed by the computer 40, and a three-dimensional tomographic image of the rubber test piece 10 is acquired. And in process S6, the density distribution of the crosslinked rubber composition at the time of expansion | extension can be evaluated from a tomographic image, and the volume of a space | gap part can be calculated | required.

As described above, the crosslinked rubber composition of the present invention is characterized in that the filler dispersibility D represented by the following formula (I) is 2.0 or less.
_{D = (A 1 / B 1} ) / (A 0 / B 0) (I)
In formula (I),
A ₁ is the volume fraction of rubber component A in the filler gel,
B ₁ is the volume fraction of rubber component B in the filler gel,
A ₀ is the volume fraction of the blended rubber component A,
B ₀ represents the volume fraction of the blended rubber component B.

  The filler dispersibility D is preferably 1.8 or less. Further, the filler dispersibility D is preferably 1.0 or more, and more preferably 1.5 or more.

  In order to realize the state where the filler dispersibility D is 2.0 or less, it is necessary to make the distribution state of the filler in the rubber component uniform. As a means for making the distribution state of the filler uniform, for example, a master batch in which the filler is dispersed in advance in a rubber component in which the filler is difficult to be distributed may be used. For example, in the case of a compounding system in which 90% or more of the rubber component is composed of SBR and BR, the filler tends to be less distributed in BR than in SBR. Good.

  The filler dispersibility D is the ratio of the two kinds of rubber components blended, and the two kinds of fillers in the filler gel obtained from the rubber composition before vulcanization (unvulcanized rubber composition) after kneading all the compounding agents. This is a value obtained by comparing the rubber component ratio, and the closer the value of D is to 1, the closer the ratio of the two rubber components blended and the rubber component ratio in the filler gel are.

  Here, the filler gel is formed by combining a filler such as silica and a rubber component, and a rubber component existing around the filler is included in the filler gel. Therefore, the rubber component in which the filler exists can be analyzed by analyzing the rubber component ratio in the filler gel. From this, the closer the value of filler dispersibility D is to 1, the closer the ratio of the two rubber components blended to the ratio of the rubber component where the filler is present, that is, the better the dispersion depending on the amount of rubber component blended by the filler Indicates that

  The method for analyzing the rubber component ratio in the filler gel is not particularly limited, and examples include analysis by NMR method, Fourier transform infrared spectroscopy, gas chromatography and the like. Of these, Fourier transform infrared spectroscopy or gas chromatography is preferred because it is not easily affected by the carbon black contained therein.

  The cross-linked rubber composition of the present invention can be produced by a general method as long as the cross-linked rubber composition exhibiting the above-described void volume at the time of elongation and filler distribution is obtained. For example, after kneading ingredients other than the vulcanizing agent and vulcanization accelerator among the above-mentioned components in a known kneader used in a general rubber industry such as a Banbury mixer, a kneader, and an open roll, In addition, a vulcanizing agent and a vulcanization accelerator can be added and further kneaded and then vulcanized.

  Before the kneading of the rubber component and the filler, the rubber component can be made uniform because the cross-linked state of the cross-linked rubber composition can be made uniform, and a rubber composition having a small volume at the time of elongation can be easily obtained. A production method including a step of starting kneading of the sulfur donor and the sulfur atom-containing vulcanization accelerator, adding a filler to the obtained kneaded material, and kneading at a kneading temperature of 120 ° C. or higher is preferable.

  The sulfur donor refers to, for example, elemental sulfur or a sulfur compound that releases active sulfur under a temperature and pressure of vulcanization conditions (for example, 150 ° C., 1.5 MPa) or lower. In other words, this sulfur compound generally exhibits a function as a vulcanizing agent, for example, under vulcanization conditions (for example, 150 ° C., 1.5 MPa) or lower temperature and pressure. The released active sulfur forms a part of a pendant structure described later.

  The said sulfur atom containing vulcanization accelerator refers to the vulcanization accelerator containing the sulfur atom couple | bonded with the other molecule | numerator with the single bond. Although sulfur atom-containing vulcanization accelerators may or may not release active sulfur, sulfur atom-containing vulcanization acceleration that does not release active sulfur from the viewpoint of suppressing the progress of the crosslinking reaction during kneading. Agents are preferred.

  Before kneading the rubber component and the filler, by starting the kneading of the rubber component, the sulfur donor and the sulfur atom-containing vulcanization accelerator, the sulfur donor and sulfur atom-containing vulcanization accelerator of the filler Since adsorption can be prevented, the sulfur donor and sulfur atom-containing vulcanization accelerator in the rubber component can be efficiently dispersed. In the production method, a filler is added to a kneaded product obtained by kneading a rubber component, a sulfur donor, and a sulfur atom-containing vulcanization accelerator, and kneaded at a kneading temperature of 120 ° C. or higher. Active sulfur is released from the sulfur donor by a kneading temperature of 120 ° C. or higher and a mechanical shearing force during kneading. The activated sulfur, the sulfur atom-containing vulcanization accelerator and the rubber component react, and the rubber component contains all or part of the sulfur atom-containing vulcanization accelerator (hereinafter referred to as “vulcanization accelerator residue”). That is, a pendant structure in which “-S-vulcanization accelerator residue” is bonded to the rubber component is formed. The mechanism of this reaction is that the released active sulfur reacts with the sulfur atom of the sulfur atom-containing vulcanization accelerator to form a structure in which two or more sulfur atoms are bonded, and the structure part and the double bond of the rubber component It is presumed that the part is reacting. By kneading in a state where the pendant structure is formed, the vulcanization accelerator residue moves together with the rubber component, so that the uniformity of the dispersion state of the vulcanization accelerator residue in the entire rubber composition is improved. Can do. Thereby, in this manufacturing method, the crosslink density at the time of vulcanization can be made uniform. Here, the kneading temperature is an actual measurement temperature of the rubber composition in the kneader, and the surface temperature of the rubber composition can be measured with a non-contact temperature sensor or the like.

  As described above, the characteristics of the production method are that the kneading of the rubber component, the sulfur donor, and the sulfur atom-containing vulcanization accelerator is started before the filler is kneaded, and 120 ° C. or higher after the filler is added. Kneading at a kneading temperature of 1. Any material may be added in any step as long as the above requirements are satisfied. For example, when the kneading process is a two-step process consisting of a process X and a process F, the kneading of the rubber component, the sulfur donor and the sulfur atom-containing vulcanization accelerator is started in the initial stage of the process X, and filling is performed in the middle of the process X. An agent may be added and kneaded at a kneading temperature of 120 ° C. or higher, and the subsequent step F may be performed. Also, for example, when the kneading step is a three-step process consisting of step X, step Y and step F, kneading of the rubber component, sulfur donor and sulfur atom-containing vulcanization accelerator is started in step X, and the subsequent steps The filler may be added at Y and kneaded at a kneading temperature of 120 ° C. or higher, and the subsequent step F may be performed. As another example of the case of three steps, kneading of a rubber component, a sulfur donor, and a sulfur atom-containing vulcanization accelerator is started at the beginning of step X, and a filler is added in the middle of step X to 120 Kneading may be carried out at a kneading temperature of not less than 0 ° C., and the subsequent step Y and step F may be carried out. In the initial stage of step X, the kneading of the rubber component, the sulfur donor and the sulfur atom-containing vulcanization accelerator is started. Further, a filler may be added during the process X, a filler may be further added in the subsequent process Y, and the mixture may be kneaded at a kneading temperature of 120 ° C. or higher, and the subsequent process F may be performed. In addition, you may perform a remill between each process.

  The kneading temperature of the rubber component, the sulfur donor, and the sulfur atom-containing vulcanization accelerator is not particularly limited, but the crosslinking reaction by the sulfur donor and the sulfur atom-containing vulcanization accelerator proceeds. From the viewpoint of suppression, it is preferably less than 160 ° C, more preferably 150 ° C or less.

  Further, the kneading time of the rubber component, the sulfur donor and the sulfur atom-containing vulcanization accelerator before adding the filler to the rubber component is not particularly limited. From the viewpoint of improving dispersibility, for example, 10 More than a second.

  The kneading temperature after adding the filler is preferably 170 ° C. or lower from the viewpoint of suppressing the crosslinking reaction from proceeding excessively.

  The kneading time after the filler is added to the rubber component and the kneading temperature reaches 120 ° C. is not particularly limited, but is, for example, 2 minutes or more from the viewpoint of improving dispersibility. The kneading time referred to here is the time from when the filler is added to the rubber component and the kneading temperature reaches 120 ° C. until when all the steps of the kneading process are completed. When the kneading temperature reaches 120 ° C. by adding a filler, the time from that point to the point when the process F ends.

  As described above, as the sulfur donor, a sulfur compound that releases elemental sulfur and / or active sulfur described above can be used. Examples of the elemental sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.

  If too much elemental sulfur is added as a sulfur donor, the vulcanization reaction may proceed excessively in the kneading step. Therefore, the content with respect to 100 parts by mass of the rubber component when elemental sulfur is used as the sulfur donor is preferably 0.1 parts by mass or less. The elemental sulfur content is preferably 0.05 parts by mass or more from the viewpoint of fracture strength.

Examples of the sulfur compound that functions as a sulfur donor include a polymer polysulfide represented by-(-MS-C-) _n- , or a structure -S _n- (wherein two or more sulfur atoms are single-bonded. and compounds that have n ≧ 2) and release active sulfur. As the compounds, alkylphenol disulfide, morpholine _{disulfide, -S n - (n ≧ 2} ) thiuram vulcanization accelerator having a (tetramethylthiuram disulfide (TMTD), tetraethyl thiuram disulfide (TETD), tetrabutyl thiuram disulfide (TBTD), dipentamethylene thiuram tetrasulfide (DPTT), etc.), vulcanization accelerator 2- (4'-morpholinodithio) benzothiazole (MDB), polysulfide silane coupling agent (for example, Si69 (manufactured by Degussa) Bis (3-triethoxysilylpropyl) tetrasulfide)), sulfide compounds represented by the following formula (1), (2) or (3).

（式中、Ｒ¹は、同一または異なって、置換基を有してもよい炭素数３〜１５の１価の炭化水素基を表す。ｎは、２〜６の整数を表す。）

(In the formula, R ^1, same or different, .n representing a monovalent hydrocarbon group of carbon atoms which may 3-15 have a substituent, represents an integer from 2 to 6.)

R ¹ in formula (1) is a monovalent hydrocarbon group having 3 to 15 carbon atoms which may have a substituent, and the number of carbon atoms is preferably 5 to 12, more preferably 6 to 10. preferable. The monovalent hydrocarbon group for R ¹ may be linear, branched or cyclic, and any of saturated and unsaturated hydrocarbon groups (aliphatic, alicyclic, aromatic hydrocarbon groups, etc.) But you can. Of these, an aromatic hydrocarbon group which may have a substituent is preferable.

Examples of R ¹ include an alkyl group having 3 to 15 carbon atoms, a substituted alkyl group, a cycloalkyl group, a substituted cycloalkyl group, an aralkyl group, and a substituted aralkyl group. Among these, an aralkyl group and a substituted aralkyl group are exemplified. preferable. Here, examples of the alkyl group include a butyl group and an octyl group; examples of the cycloalkyl group include a cyclohexyl group; examples of the aralkyl group include a benzyl group and a phenethyl group; and examples of the substituent include an oxo group (═O). And polar groups such as hydroxy group, carboxyl group, carbonyl group, amino group, acetyl group, amide group and imide group.

  Moreover, n in Formula (1) is an integer of 2-6, and 2-3 are preferable.

（式中、Ｒ²は、同一または異なって、置換基を有してもよい炭素数３〜１５の２価の炭化水素基を表す。ｍは、２〜６の整数を表す。）

(Wherein, R ² are the same or different, .m representing a divalent hydrocarbon group which may having 3 to 15 carbon atoms have a substituent, represents an integer from 2 to 6.)

R ² in the above formula (2) is a divalent hydrocarbon group having 3 to 15 carbon atoms which may have a substituent, and the carbon number is preferably 3 to 10, and preferably 4 to 8 More preferred. The divalent hydrocarbon group for R ² may be linear, branched or cyclic, and any of saturated and unsaturated hydrocarbon groups (aliphatic, alicyclic, aromatic hydrocarbon groups, etc.) But you can. Especially, the aliphatic hydrocarbon group which may have a substituent is preferable, and a linear aliphatic hydrocarbon group is more preferable.

Examples of R ² include an alkylene group having 3 to 15 carbon atoms and a substituted alkylene group. Here, examples of the alkylene group include a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, and a nonylene group, and examples of the substituent include those similar to the substituent for R ¹ .

  Moreover, m in the said Formula (2) is an integer of 2-6, and 2-3 are preferable.

  Specific examples of the sulfide compounds represented by the above formulas (1) and (2) include N, N′-di (γ-butyrolactam) disulfide, N, N′-di (5-methyl-γ-butyrolactam). ) Disulfide, N, N′-di (5-ethyl-γ-butyrolactam) disulfide, N, N′-di (5-isopropyl-γ-butyrolactam) disulfide, N, N′-di (5-methoxy-γ-) Butyrolactam) disulfide, N, N′-di (5-ethoxy-γ-butyrolactam) disulfide, N, N′-di (5-chloro-γ-butyrolactam) disulfide, N, N′-di (5-nitro-γ) -Butyrolactam) disulfide, N, N'-di (5-amino-γ-butyrolactam) disulfide, N, N'-di (δ-valerolactam) disulfide, N, N'-di (δ -Caprolactam) disulfide, N, N'-di (ε-caprolactam) disulfide, N, N'-di (3-methyl-δ-caprolactam) disulfide, N, N'-di (3-ethyl-ε-caprolactam) Disulfide, N, N′-di (3-isopropyl-ε-caprolactam) disulfide, N, N′-di (δ-methoxy-ε-caprolactam) disulfide, N, N′-di (3-ethoxy-ε-caprolactam ) Disulfide, N, N′-di (3-chloro-ε-caprolactam) disulfide, N, N′-di (δ-nitro-ε-caprolactam) disulfide, N, N′-di (3-amino-ε-) Caprolactam) disulfide, N, N'-di (ω-heptalactam) disulfide, N, N'-di (ω-octalactam) disulfide, dithiodi Caprolactam, morpholine disulfide, N-benzyl-N - [(dibenzylamino) disulfanyl] phenylmethanamine (N, N'- dithiobis (dibenzyl amine)), and the like. These sulfide compounds may be used alone or in combination of two or more.

（式中、Ｒ³は、同一または異なって、アルキル基、ベンゾチアゾリル基、アミノ基、モルホリノ基、ジアルキルチオカルバモイル基、または下記式（４）で表される基を表す。ｋは、２〜６の整数を表す。

(In the formula, R ³ is the same or different and represents an alkyl group, a benzothiazolyl group, an amino group, a morpholino group, a dialkylthiocarbamoyl group, or a group represented by the following formula (4). K is 2-6. Represents an integer.

（式中、Ｒ⁴は、同一または異なって、アルキル基、ベンゾチアゾリルスルフィド基、シクロアルキル基または水素原子を表す。）

(In the formula, R ^{4 s} are the same or different and each represents an alkyl group, a benzothiazolyl sulfide group, a cycloalkyl group or a hydrogen atom.)

R ³ in the above formula (3) is the same or different and represents an alkyl group, a benzothiazolyl group, an amino group, a morpholino group, a dialkylthiocarbamoyl group, or a group represented by the above formula (4). An alkyl group having 1 to 10 carbon atoms, a benzothiazolyl group, an amino group, a morpholino group, or a dialkylthiocarbamoyl group (the alkyl groups are the same or different and are alkyl groups having 1 to 10 carbon atoms) are preferable.

  Examples of the alkyl group having 1 to 10 carbon atoms and the alkyl group having 1 to 10 carbon atoms in the dialkylthiocarbamoyl group include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, Examples include iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, 2-ethylhexyl group, octyl group, nonyl group and the like.

More preferably, R ³ in the above formula (3) is the same or different and is a benzothiazolyl group, a morpholino group, or a dialkylthiocarbamoyl group (the alkyl groups are the same or different and are alkyl groups having 1 to 5 carbon atoms). ). More preferably, they are the same or different and are a benzothiazolyl group or a dialkylthiocarbamoyl group (the alkyl group is the same or different and is an alkyl group having 1 to 5 carbon atoms).

  K in the said Formula (3) is an integer of 2-6, and 2-3 are still more preferable.

R ⁴ in formula (4) is the same or different and is an alkyl group, a benzothiazolyl sulfide group, a cycloalkyl group or a hydrogen atom. The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, and the cycloalkyl group is preferably a cycloalkyl group having 5 to 8 carbon atoms.

  Examples of the sulfide compound represented by the above formula (3) include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, 2- (morpholinodithio) benzothiazole, dibenzothiazolyl disulfide, N-cyclohexyl-2. -A benzothiazolylsulfenamide etc. are mentioned, Dibenzothiazolyl disulfide can be used conveniently especially. These may be used alone or in combination of two or more.

  When the sulfur compound that functions as a sulfur donor is used, the content with respect to 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more and 0.2 parts by mass or more because it promotes the formation of a pendant structure. More preferred. In addition, the content of the compound is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and still more preferably 2 parts by mass or less from the viewpoint of suppressing gelation during kneading.

  Vulcanization accelerators that function as sulfur donors include vulcanization accelerators containing sulfur atoms that are bonded to other molecules by single bonds. Therefore, the sulfur atom-containing vulcanization accelerator that functions as a sulfur donor has the functions of both the sulfur donor and the sulfur atom-containing vulcanization accelerator, and the sulfur atom-containing vulcanization accelerator that functions as a sulfur donor. A pendant structure can also be formed by blending a large number of agents alone or using two or more agents in combination. However, if a large amount of sulfur atom-containing vulcanization accelerator that functions as a sulfur donor is blended, the crosslinking reaction may proceed excessively during kneading, and if it is blended in a small amount, the effect of uniformizing the crosslinking density may not be obtained. Therefore, sulfur donors and sulfur atom-containing vulcanization accelerators to be kneaded before adding the filler include sulfur donors (sulfur atom-containing vulcanization accelerators functioning as sulfur donors and / or other sulfur donors). And a sulfur non-releasing sulfur atom-containing vulcanization accelerator.

  The sulfur non-releasing sulfur atom-containing vulcanization accelerator is, for example, a sulfur atom-containing vulcanization accelerator that does not release active sulfur under vulcanization conditions (eg, 150 ° C., 1.5 MPa) or lower temperature and pressure. Refers to an agent. In other words, this sulfur non-releasing sulfur atom-containing vulcanization accelerator exhibits a function as a vulcanizing agent, for example, under vulcanization conditions (for example, 150 ° C., 1.5 MPa) or lower temperature and pressure. Sulfur atom-containing vulcanization accelerator.

The sulfur-releasing of the sulfur-containing vulcanization _{accelerators, -S n - (n ≧ 2} ) no, thiazole vulcanization accelerator (2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazole Zinc salt (ZnMBT), 2-mercaptobenzothiazole cyclohexylamine salt (CMBT), etc.), sulfenamide vulcanization accelerators (N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N- (Tert-butyl) -2-benzothiazolesulfenamide (TBBS), N, N-dicyclohexyl-2-benzothiazolylsulfenamide), vulcanization accelerator tetramethylthiuram monosulfide (TMTM), dithiocarbamine Acid salt vulcanization accelerator (piperidinium pentamethylene dithiocarbamate (PPDC) Zinc dimethyldithiocarbamate (ZnMDC), zinc diethyldithiocarbamate (ZnEDC), zinc dibutyldithiocarbamate (ZnBDC), zinc N-ethyl-N-phenyldithiocarbamate (ZnEPDC), zinc N-pentamethylenedithiocarbamate (ZnPDC), dibutyl And sodium dithiocarbamate (NaBDC), copper dimethyldithiocarbamate (CuMDC), iron dimethyldithiocarbamate (FeMDC), tellurium diethyldithiocarbamate (TeEDC) and the like. Note that di-2-benzothiazolyl disulfide (MBTS), which is a thiazole vulcanization accelerator, has -S _n- (n ≧ 2) and is a vulcanization accelerator that releases sulfur. In general, the compounding amount does not exhibit a function as a vulcanizing agent with respect to natural rubber or butadiene rubber, so that it can be used in the same manner as a sulfur non-releasing sulfur atom-containing vulcanization accelerator.

  The content of the sulfur atom-containing vulcanization accelerator with respect to 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, and more preferably 1.5 parts by mass or more, because the vulcanization reaction proceeds efficiently in the vulcanization process. More preferred. In addition, the content is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less from the viewpoint of scorch properties and suppression of precipitation on the surface.

  In the production method, it is preferable to add a filler to the rubber component and knead at a kneading temperature of 120 ° C. or higher, and then knead an additional sulfur donor. By adding an additional sulfur donor, it is possible to sufficiently advance the crosslinking reaction during vulcanization while suppressing excessive progress of the crosslinking reaction during kneading.

  The additional sulfur donor is added, for example, in Step F after adding a filler to the rubber component and kneading at a kneading temperature of 120 ° C. or higher. The additional sulfur donor may be the same as that kneaded before adding the filler to the rubber component, or may be a different one, such as powdered sulfur, precipitated sulfur, colloidal sulfur, Elemental sulfur such as surface-treated sulfur and insoluble sulfur can be used.

  The content of the additional sulfur donor is not particularly limited, but is preferably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component, because the vulcanization reaction proceeds efficiently in the vulcanization step. More than mass part is more preferable. In addition, the content of the additional sulfur donor is preferably 3.0 parts by mass or less, and more preferably 2.5 parts by mass or less, because it is excellent in wear resistance.

  When adding an additional sulfur donor in the step F, a general vulcanization accelerator may be added. Examples of general vulcanization accelerators include thiuram disulfides and polysulfides that are sulfur atom-containing vulcanization accelerators, guanidine-based, aldehyde-amine-based, and aldehydes that are vulcanization accelerators that do not have sulfur atoms. -Ammonia-based and imidazoline-based vulcanization accelerators are included.

  The content of the vulcanization accelerator added in Step F with respect to 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more. Moreover, the mass ratio of the blending amount of the vulcanization accelerator added in Step F to the blending amount of the sulfur atom-containing vulcanization accelerator kneaded before adding the filler to the rubber component is greater than 0% and 80% or less. Preferably, it is 60% or less. By setting it to 80% or less, a crosslinked rubber composition excellent in scorch properties, fracture characteristics, and abrasion resistance can be obtained.

  Moreover, it is preferable to employ | adopt the manufacturing method which can improve the conventional filler dispersibility from the reason that the crosslinked rubber composition excellent in filler distribution property is obtained. As a manufacturing method which can improve filler dispersibility, the method of mix | blending as a masterbatch which knead | mixed the rubber component with low compatibility with a filler among the rubber components to mix | blend with a filler, etc. are mentioned. Specifically, in the case of a crosslinked rubber composition in which a rubber component containing SBR and BR and silica are blended, SBR is more compatible with silica, so silica is likely to be unevenly distributed in SBR. Are mixed as a master batch obtained by kneading and the uneven distribution in SBR can be suppressed, and a crosslinked rubber composition excellent in silica dispersibility can be obtained.

  The crosslinked rubber composition of the present invention can be used for tire members such as tire treads, undertreads, carcass, sidewalls and beads, as well as anti-vibration rubbers, belts, hoses, and other rubber industrial products. In particular, because of excellent abrasion resistance, a tire having a tread composed of the crosslinked rubber composition of the present invention is preferable.

  A tire using the crosslinked rubber composition of the present invention can be produced by an ordinary method using the uncrosslinked rubber composition. That is, an uncrosslinked rubber composition in which the above-mentioned compounding agent is blended as needed with a diene rubber component is extruded to a shape such as a tread and bonded together with other tire members on a tire molding machine. A tire can be manufactured by forming an unvulcanized tire by molding by a normal method and heating and pressurizing the unvulcanized tire in a vulcanizer.

  It does not specifically limit as a structure of the pneumatic tire of this invention, It can be set as the structure of the conventional pneumatic tire. That is, the pneumatic tire of the present invention can be obtained by using at least one of the tire members constituting the pneumatic tire having the conventional structure as a member using the crosslinked rubber composition of the present invention. Among them, a bead core provided in each of the pair of left and right bead parts, a carcass ply that extends from the crown part to both bead parts through both side wall parts, and is anchored to the bead core, and on the inner side in the tire radial direction than the carcass ply. The inner liner disposed and the outer diameter in the tire radial direction from the carcass ply, and the volume of the void when elongated by an applied stress of 3.0 MPa is 7.5% or less, and is represented by the formula (I) It is preferable to use a pneumatic tire including a tread having a filler dispersibility D of 2.0 or less. The tread here is a portion in contact with the road surface. When the tread is composed of two or more different crosslinked rubber compositions, at least one of the crosslinked rubber compositions is the crosslinked rubber composition of the present invention. Then, it is a tire of the present invention.

  The present invention will be specifically described based on examples, but the present invention is not construed as being limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples are shown together.
SBR1: prepared by the method for producing modified SBR1 described later (S-SBR, styrene content: 26% by mass, vinyl content: 59%, Tg: -25 ° C., Mw: 4 × 10 ⁵ )
SBR2: Nipol 1502 manufactured by Nippon Zeon Co., Ltd. (E-SBR, styrene content: 23.5% by mass, vinyl content: less than 20%, Tg: −54 ° C., Mw: 5 × 10 ⁵ )
BR: BR150B manufactured by Ube Industries, Ltd.
Masterbatch BR: Masterbatch silica kneaded by blending 70 parts by weight of Ultrasil VN3 with 100 parts by weight of BR150B: Ultrasil VN3 manufactured by Evonik (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Evonik
Carbon black: Diamond Black I manufactured by Mitsubishi Chemical Corporation (N ₂ SA: 98 m ² / g, DBP oil absorption: 124 ml / 100 g)
Zinc oxide: 2 types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Beads stearic acid manufactured by NOF Co., Ltd.
Anti-aging agent: Ozonon 6C (N- (1,3-dimethylbutyl) -N-phenyl-p-phenylenediamine, 6PPD) manufactured by Seiko Chemical Co., Ltd.
Oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Elemental sulfur: Tsurumi Chemical Industry Co., Ltd. Sulfur powder Vulcanization accelerator: Ouchi Shinko Chemical Industrial Co., Ltd. Nocceler NS (TBBS, N-t- butyl-2-benzothiazolyl sulfenamide)
Sulfur donor: Renogran CLD80 (caprolactam disulfide) manufactured by Rhein Chemie

Hereinafter, various chemicals used in the manufacturing method of SBR1 are shown together.
Cyclohexane: cyclohexanepyrrolidine manufactured by Kanto Chemical Co., Ltd .: pyrrolidine divinylbenzene manufactured by Kanto Chemical Co., Ltd .: 1.6M n-butyllithium hexane solution of divinylbenzene manufactured by Sigma-Aldrich Co., Ltd .: 1. manufactured by Kanto Chemical Co., Inc. 6M n-butyllithium hexane solution Isopropanol: Isopropanol styrene manufactured by Kanto Chemical Co., Ltd .: Styrene butadiene manufactured by Kanto Chemical Co., Ltd .: 1,3-butadiene tetramethylethylenediamine manufactured by Takachiho Chemical Co., Ltd .: Kanto Chemical Co., Ltd. N, N, N ′, N′-tetramethylethylenediamine modifier: 3- (N, N-dimethylaminopropyl) trimethoxysilane manufactured by AMAX Co., Ltd.

Production method of SBR1 To a 100 ml container sufficiently purged with nitrogen, add 50 ml of cyclohexane, 4.1 ml of pyrrolidine, and 8.9 ml of divinylbenzene, and then add 0.7 ml of 1.6 M n-butyllithium hexane solution at 0 ° C. and stir. did. After 1 hour, isopropanol was added to stop the reaction, and extraction / purification was performed to obtain monomer A. Next, 600 ml of cyclohexane, 12.6 ml of styrene, 71.0 ml of butadiene, 0.06 g of monomer A, and 0.11 ml of tetramethylethylenediamine were added to a 1000 ml pressure-resistant container sufficiently purged with nitrogen, and 1.6 M n- at 40 ° C. 0.2 ml of butyllithium hexane solution was added and stirred. After 3 hours, 0.5 ml of a denaturant was added and stirred. After 1 hour, 3 ml of isopropanol was added to terminate the polymerization. After adding 1 g of 2,6-tert-butyl-p-cresol to the reaction solution, reprecipitation treatment was performed with methanol, followed by heating and drying to obtain SBR1.

Examples 1 to 13 and Comparative Examples 1 to 3
According to the formulation shown in Tables 1 and 2, various chemicals shown in Step X were kneaded for 5.0 minutes at a discharge temperature of 100 ° C. in a 1.7 L Banbury mixer (Step X). Next, the kneaded product of step X and various chemicals shown in step Y were kneaded for 30 seconds at 140 ° C. or higher in a 1.7 L Banbury mixer, and further kneaded for 3 minutes at a discharge temperature of 150 ° C. (step Y). . And the kneaded material of the process Y and the various chemicals shown in the process F were kneaded at about 80 ° C. for 3 minutes using an open roll (process F) to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was extruded into a tread shape by an extruder equipped with a predetermined-shaped die, and bonded together with other tire members to form an unvulcanized tire, under the condition of 170 ° C. A test tire (tire size: 195 / 65R15) was produced by press vulcanization for 12 minutes. The following evaluation was performed about the obtained unvulcanized rubber composition and the tire for a test. The results are shown in Tables 1 and 2.

Volume of void part Each rubber test piece obtained by cutting out a cylindrical rubber test piece having a diameter of 10 mm and a height of 1 mm from the tread part of the test tire is fixed to the jig shown in FIG. 3D created by CT imaging with X-rays (brightness: 10 ¹⁶ photons / s / mrad ² / mm ² /0.1% bw) when stretched by an applied stress of 0 MPa, and reconstruction of the captured images From the tomographic image of the image, the volume ratio of the voids in the rubber test piece during elongation was calculated from the density distribution. X-ray CT imaging is performed at the beam line BL20B2 of the large synchrotron radiation facility SPring-8, the phosphor uses P43 (Gd ₂ O ₂ S: Tb) with an attenuation time of 1 ms, and the CT reconstruction is the Convection Back Projection. By this method, 200 tomographic images having a thickness of 10 μm were stacked. Moreover, the space | gap part was performed as an area | region where the density became 0-0.1, when the average density of the rubber test piece before extending | stretching was set to 1. As shown in FIG.

Filler distribution (D)
0.5 g of each unvulcanized rubber composition was cut into 1 mm square pieces, and the mass was accurately measured (Rg). The mass of a 100 mesh stainless steel basket was precisely weighed (Kg), and the entire amount of the weighed sample was transferred to a stainless steel basket and the mass was measured (Rg + Kg). This was immersed in a bottle with a stopper containing 100 ml of toluene and left at 23 ° C. for 24 hours. Thereafter, the car was pulled up, dried at 23 ° C. for 24 hours, and further dried under reduced pressure for 24 hours so as to become a constant weight at 70 ° C., and toluene insolubles were accurately weighed together with the car (Gg + Kg). Moreover, the rubber component ratio in the obtained toluene insoluble content was determined by gas chromatography (A: B).
Then, the following calculation formula, was calculated volume fraction of the rubber component A in the filler gel (A ₁₎ and the volume fraction of the rubber component B in the filler gel (B _1).
A ₁ = [G- (R × (Filler mass / Rubber composition total mass))] / [R × (Rubber mass / Rubber composition total mass)] × [A / (A + B)]
B ₁ = [G− (R × (Filler mass / Rubber composition total mass))] / [R × (Rubber mass / Rubber composition total mass)] × [B / (A + B)]
Moreover, to calculate the volume fraction of the rubber component A blended (A ₀₎ and compounded volume fraction of the rubber component B a (B _0), was calculated filler distributive D by the following formula (I).
_{D = (A 1 / B 1} ) / (A 0 / B 0) (I)

Wear resistance The same test tire produced as described above is mounted on four wheels of a domestic FF vehicle, and the groove depth of the tire tread portion after a running distance of 8000 km is measured. From the arithmetic mean value, the mileage when the tire groove depth decreases by 1 mm was calculated, and the abrasion resistance index of Comparative Example 1 was set to 100, and the results of each formulation were displayed as an index according to the following formula (wear resistance) index). The larger the wear resistance index, the better the wear resistance.
Abrasion resistance index = (travel distance when 1 mm groove depth decreases) / (travel distance when tire groove of Comparative Example 1 decreases by 1 mm) × 100

Examples 14-16
Various chemicals shown in Step X were kneaded in a 1.7 L Banbury mixer according to the blending contents, discharge temperature and time shown in Table 3 (Step X). Next, the kneaded product of Step X and the various chemicals shown in Step Y were kneaded in a 1.7 L Banbury mixer according to the discharge temperature and time shown in Table 3, and further kneaded at a discharge temperature of 150 ° C. for 3 minutes ( Step Y). And the kneaded material of the process Y and the various chemicals shown in the process F were kneaded according to the discharge temperature and time shown in Table 3 using an open roll (process F) to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was extruded into a tread shape by an extruder equipped with a predetermined-shaped die, and bonded together with other tire members to form an unvulcanized tire, under the condition of 170 ° C. A test tire (tire size: 195 / 65R15) was produced by press vulcanization for 12 minutes. The following evaluation was performed about the obtained tire for a test. The results are shown in Table 3.

  From the results of Tables 1 to 3, the pneumatic tire of the present invention including a tread having a small number of voids when stretched by an applied stress of 3.0 MPa and having a highly uniform filler distribution state, and stretched by an applied stress of 3.0 MPa It can be seen that the crosslinked rubber composition of the present invention having few voids at the time and high uniformity in the filler distribution state is a pneumatic tire and a crosslinked rubber composition having excellent wear resistance.

DESCRIPTION OF SYMBOLS 1 Evaluation apparatus 2 Stress application means 3 Imaging | photography means 4 Evaluation means 10 Rubber test piece

Claims (14)

A bead core provided in each of the pair of left and right bead parts;
A carcass ply that extends from the crown portion to both bead portions via both sidewall portions and is moored to the bead core;
An inner liner disposed inside the tire radial direction from the carcass ply;
It is provided on the outer side in the tire radial direction than the carcass ply, contains two or more rubber components and fillers, and has a volume of voids of 7.5% or less when stretched by an applied stress of 3.0 MPa. A pneumatic tire characterized by comprising a tread having a filler dispersibility D shown by (I) of 2.0 or less,
The pneumatic tire in which the void portion is a region in which the density is 0 to 0.1 times that of the crosslinked rubber composition before elongation.
_{D = (A 1 / B 1} ) / (A 0 / B 0) (I)
In formula (I),
A ₁ is the volume fraction of rubber component A in the filler gel,
B ₁ is the volume fraction of rubber component B in the filler gel,
A ₀ is the volume fraction of the blended rubber component A,
B ₀ represents the volume fraction of the blended rubber component B. A crosslinked rubber composition containing two or more rubber components and a filler;
The volume of the void when elongated by an applied stress of 3.0 MPa is 7.5% or less,
A crosslinked rubber composition having a filler dispersibility D represented by the following formula (I) of 2.0 or less,
The crosslinked rubber composition, wherein the void portion is a region where the density is 0 to 0.1 times that of the crosslinked rubber composition before elongation.
_{D = (A 1 / B 1} ) / (A 0 / B 0) (I)
In formula (I),
A ₁ is the volume fraction of rubber component A in the filler gel,
B ₁ is the volume fraction of rubber component B in the filler gel,
A ₀ is the volume fraction of the blended rubber component A,
B ₀ represents the volume fraction of the blended rubber component B. The crosslinked rubber composition according to claim 2, wherein the volume of the void portion when elongated by an applied stress of 3.0 MPa is 7.3% or less. The crosslinked rubber composition according to claim 2, wherein the volume of the void portion when elongated by an applied stress of 3.0 MPa is 7.0% or less. The crosslinked rubber composition according to claim 2, wherein the volume of the void when elongated by an applied stress of 3.0 MPa is 6.7% or less. The crosslinked rubber composition according to claim 2, wherein the volume of the void when elongated by an applied stress of 3.0 MPa is 6.4% or less. The crosslinked rubber composition according to claim 2, wherein the volume of the void portion when elongated by an applied stress of 3.0 MPa is 6.3% or less. The crosslinked rubber composition according to any one of claims 2 to 7, wherein the filler dispersibility D is 1.7 or less. The crosslinked rubber composition according to any one of claims 2 to 7, wherein the filler dispersibility D is 1.6 or less. The crosslinked rubber composition according to any one of claims 2 to 9, wherein the rubber component is a rubber component containing at least one rubber component containing a conjugated diene compound. The volume of the void portion at the time of elongation due to an applied stress of 3.0 MPa is calculated from the density distribution of the crosslinked rubber composition at the time of elongation using X-ray CT imaging. The crosslinked rubber composition as described in 1. The density distribution of the crosslinked rubber composition at the time of extension using X-ray CT imaging is evaluated by an evaluation apparatus provided with imaging means, and the imaging means detects an X-ray tube that irradiates X-rays and X-rays to detect electrical signals. The crosslinked rubber composition according to claim 11 , further comprising: a detector that converts X-rays into visible light , wherein the detector includes a phosphor for converting X-rays into visible light, and the decay time of the phosphor is 100 ms or less. The X-ray intensity of emitted from the X-ray tube ^{10 10 photons / s / mrad 2} / mm 2 /0.1%bw more than is claim 1 2 crosslinked rubber composition. A bead core provided in each of the pair of left and right bead parts;
A carcass ply that extends from the crown portion to both bead portions via both sidewall portions and is moored to the bead core;
An inner liner disposed inside the tire radial direction from the carcass ply;
A pneumatic tire, comprising: a tread that is provided on the outer side in the tire radial direction than the carcass ply and includes the crosslinked rubber composition according to any one of claims 3 to 13.

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