JP6316716B2 - Rubber composition and method for producing the same - Google Patents

Description

  The present invention relates to a rubber composition and a method for producing the same, and also relates to a pneumatic tire using the rubber composition.

  In general, diene rubber is used as a rubber component in a rubber composition, and a filler such as carbon black or silica is blended therein. In order to improve the physical properties of such a rubber composition, it is desirable to improve the compatibility or dispersibility of the filler with respect to the rubber component, and a technique for modifying a diene rubber to improve the dispersibility is known. For example, Patent Document 1 discloses a modified natural rubber obtained by adding a polar group-containing hydrazide compound to natural rubber, and Patent Document 2 includes reacting an organic acid with a diene rubber and then containing a saccharide or the like. A modified diene rubber obtained by reacting an oxygen cyclic compound is disclosed.

  Patent Document 3 discloses a modified diene rubber obtained by oxidative cleavage of a diene rubber with an oxidizing agent and then rebonded by aldol condensation by changing the acid basicity of the latex containing the decomposed diene rubber. It is disclosed that it is used for a rubber composition for a tire. In this case, the effect of improving the dispersibility of the filler can be expected by the functional group introduced into the main chain of the modified diene rubber. However, improvement of physical properties by further improving the dispersibility is desired.

JP 2009-108204 A JP 2014-040514 A JP 2013-163759 A

  An object of this invention is to provide the rubber composition which can improve the dispersibility of a filler, and can improve a physical property in view of the above point, and its manufacturing method.

The rubber composition according to the present invention comprises 100 parts by mass of a rubber component containing a modified diene rubber obtained by reacting a reducing sugar with an aldehyde group and / or keto group at the molecular terminal generated by oxidative cleavage of a diene rubber. On the other hand, it contains 5 to 150 parts by mass of a filler containing silica .

  The pneumatic tire according to the present invention is formed using the rubber composition.

Method for producing a rubber composition according to the present invention generates a decomposed diene rubber having a decomposition to an aldehyde group at the molecular terminal and / or keto groups by oxidizing cleave diene rubber, and the degradation of the diene A modified diene rubber is produced by reacting a reducing sugar with an aldehyde group and / or keto group at the molecular end of the rubber based on aldol condensation, and the resulting modified diene rubber is mixed with a filler containing silica. .

  According to the present invention, the modified diene rubber obtained by reacting a reducing sugar by aldol condensation has a large number of hydroxyl groups derived from the reducing sugar at the molecular terminal, and therefore has high compatibility with fillers such as silica. The dispersibility of the rubber composition can be improved, and the physical properties of the rubber composition such as low heat generation performance can be improved.

  In the rubber composition according to this embodiment, a modified diene rubber obtained by reacting a reducing sugar with an aldehyde group and / or keto group at the molecular end generated by oxidative cleavage of a diene rubber is used as the rubber component. . Modified diene rubber having a large number of hydroxyl groups at the molecular terminals by the reaction of the aldehyde group or keto group of the reducing sugar with the terminal of the aldehyde group (—CHO) or keto group (> C═O) generated by oxidative cleavage Is obtained. By introducing many hydroxyl groups with high affinity with fillers such as silica at the end of the molecular chain, the dispersibility of the filler is improved and the low heat generation performance contributing to the fuel efficiency of the tire is improved. Can do. It has also been found that the low-temperature performance that contributes to the on-ice performance of winter tires is improved.

  The modified diene rubber is decomposed by oxidative cleavage of the diene rubber, and is produced by reacting a reducing sugar with an aldehyde group and / or keto group at the molecular end of the decomposed diene rubber by aldol condensation. More specifically, a perhalogen acid is added to a diene rubber latex and the diene rubber is decomposed by oxidative cleavage, and the latex containing the decomposed diene rubber is changed from acidic to basic and a reducing sugar is added. Thus, a modified diene rubber can be obtained by reacting a reducing sugar with the aldehyde group and / or keto group at the molecular end of the decomposed diene rubber by aldol condensation and coagulating the obtained latex.

  Examples of the diene rubber to be modified include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), Examples include butyl rubber (IIR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber. Among these, it is preferable to use at least one selected from the group consisting of natural rubber, synthetic isoprene rubber, styrene butadiene rubber, and butadiene rubber. The weight average molecular weight (Mw) of the diene rubber is not particularly limited, and may be, for example, 80,000 to 3,000,000, 100,000 to 3,000,000, or 200,000 to 3,000,000.

  As the diene rubber to be modified, it is preferable to use a water-based emulsion, that is, a latex, which is micellar in water, which is a protic solvent. Although the density | concentration (rubber solid content density | concentration) of diene type rubber latex is not specifically limited, It is preferable that it is 5-70 mass%, More preferably, it is 10-50 mass%.

  In order to oxidatively cleave the carbon-carbon double bond of the diene rubber, an oxidant can be used. For example, the oxidant can be oxidatively cleaved by adding an oxidant to the diene rubber latex and stirring. Examples of the oxidizing agent include manganese compounds such as potassium permanganate and manganese oxide, chromium compounds such as chromic acid and chromium trioxide, peroxides such as hydrogen peroxide, perhalogen acids such as periodic acid, ozone, Examples thereof include oxygens such as oxygen. Among these, it is preferable to use a perhalogen acid, and it is more preferable to use a periodic acid. In the oxidative cleavage, a metal-based oxidation catalyst such as a salt or complex of a metal such as cobalt, copper or iron with a chloride or an organic compound may be used in combination. When perhalogen acid is used, the amount used is not particularly limited as long as it can be oxidatively cleaved. For example, 0.1 to 5 parts by mass, or 0.3 to 3 parts by mass with respect to 100 parts by mass of diene rubber in latex Part may be sufficient and 0.5-1.5 mass part may be sufficient. Thus, the physical property improvement effect can be enhanced by reducing the amount of perhalogen acid and performing oxidative cleavage under mild oxidation conditions. If the reaction system cannot be made acidic by reducing the amount of perhalogen acid, an acid such as formic acid may be added to adjust the reaction system to be acidic.

  The diene rubber is decomposed by oxidative cleavage, and a diene rubber having an aldehyde group (—CHO) or a keto group (> C═O) at the terminal is obtained. As one embodiment, the decomposed diene rubber has a structure represented by the following formula (1) at the molecular end.

式中、Ｒ¹は、水素原子、メチル基又はクロロ基である。分解したジエン系ゴムは、その分子鎖の少なくとも一方の末端に上記式（１）で表される構造を持つ。

In the formula, R ¹ is a hydrogen atom, a methyl group or a chloro group. The decomposed diene rubber has a structure represented by the above formula (1) at at least one end of its molecular chain.

  The molecular weight of the decomposed diene rubber decreases due to the oxidative cleavage. The weight average molecular weight (Mw) after decomposition is not particularly limited, and may be, for example, 40,000 to 2,500,000, 80,000 to 2,400,000, or 100,000 to 2,300,000.

  When the diene rubber is decomposed as described above, the latex containing the decomposed diene rubber (hereinafter referred to as depolymerized latex) is basic (that is, alkaline) when acidic, and is basic when basic. The acid basicity is changed so as to be acidic, and a reducing sugar is added to the depolymerized latex. By changing the acid basicity in this way, a coupling reaction (aldol condensation reaction) that is a reverse reaction to cleavage proceeds preferentially. When the diene rubber fragments are recombined with each other, a modified diene rubber containing at least one linking group among the linking groups represented by the following formulas (2) to (5) is generated.

ここで、Ｒ¹が水素原子である末端構造を持つゴム断片同士が結合する場合、式（４）及び／又は式（５）で表される連結基となり、Ｒ¹が水素原子である末端構造を持つゴム断片とＲ¹がメチル基である末端構造を持つゴム断片が結合する場合、式（２）及び／又は式（３）で表される連結基となる。

Here, when rubber fragments having a terminal structure in which R ¹ is a hydrogen atom are bonded to each other, a linking group represented by formula (4) and / or formula (5) is formed, and a terminal structure in which R ¹ is a hydrogen atom. When a rubber fragment having a terminal structure in which R ¹ is a methyl group is bonded to a rubber fragment having R ¹ , a linking group represented by formula (2) and / or formula (3) is obtained.

  In this embodiment, acid basicity is changed as described above, and a reducing sugar is added. Since reducing sugar has an aldehyde group or keto group, an aldol condensation reaction occurs not only between diene rubber fragments but also between diene rubber fragments and reducing sugar. That is, the aldehyde group or keto group of the reducing sugar causes an aldol condensation reaction on the aldehyde group and / or keto group at the molecular end of the decomposed diene rubber. Therefore, a modified diene rubber having an aldol condensate of reducing sugar at the molecular end can be obtained. At that time, by adding excessive reducing sugar, the reaction between the rubber fragment and the reducing sugar can be promoted rather than recombination between the rubber fragments, and the addition of the reducing sugar to the molecular end can be promoted. it can. The addition amount of reducing sugar is not specifically limited, For example, 0.1-40 mass parts may be sufficient with respect to 100 mass parts of decomposed diene rubber, and 0.5-20 mass parts may be sufficient.

  In addition, due to the presence of an oxidizing agent in the reaction system, the carbon-carbon bond portion in the reducing sugar molecule of the reducing sugar aldol condensate bonded to the molecular end is likely to be cleaved. Therefore, in the resulting modified diene rubber, the end group produced by the aldol condensation of reducing sugar is not only the one in which the reducing sugar is bonded to the diene rubber fragment by aldol condensation, but the reducing sugar is cleaved after the bonding. Also usually included. However, those having a structure in which such a reducing sugar is cleaved may or may not be included. Moreover, the terminal group produced by the aldol condensation of the reducing sugar may be introduced only at one end of the modified diene rubber or may be introduced at both ends. The obtained modified diene rubber usually contains not only the terminal group derived from the reducing sugar but also the linking groups represented by the above formulas (2) to (5). It does not have to be included. In addition, the content rate of a coupling group is not specifically limited, For example, 0.001-25 mol% may be sufficient as the sum total of the coupling group of Formula (2)-(5), and 0.1-15 mol% may be sufficient. Here, the content of the linking group is the ratio of the number of moles of the linking group to the number of moles of all the constituent units constituting the modified diene rubber, and is measured by the method described in Patent Document 3.

  The reducing sugar may be aldose or ketose. For example, glucose, allose, altrose, mannose, gulose, idose, galactose, talose, ribose, arabinose, xylose, lyxose, erythrose, threose, glyceraldehyde, fructose, psicose Monosaccharides such as sorbose, tagatose, cedoheptulose, coriose, xylulose, ribulose, erythrulose, and disaccharides such as maltose, lactose, cellobiose, lactulose, etc., which should be used alone or in combination of two or more Can do. In addition, although it can use without distinguishing even if it is D body or L body, D body which is easy to acquire is used normally.

  The adjustment of the pH when changing the acid basicity can be performed by adding an acid or a base to the depolymerized latex, and is not particularly limited. Examples of the acid include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. Examples of the base include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate and the like.

  As described above, a latex containing a modified diene rubber (hereinafter referred to as a modified rubber latex) can be obtained. Thus, a modified diene rubber can be obtained by coagulating and drying the obtained modified rubber latex. The coagulation method is not particularly limited, and may be coagulated using formic acid, or may be coagulated using a hydrophilic organic solvent such as methanol.

  Preferably, it is solidified using a mixed solvent of an organic solvent and water. For example, by using a mixed solvent having an organic solvent / water mass ratio of organic solvent / water = 2/1 to 4/1, a halogen content derived from perhalogen acid (specifically, for example, perhalogen) The modified diene rubber can be coagulated while the acid salt) remains in the mixed solvent. In addition, in the case of a mixed solvent in which an organic solvent and water are mixed, a component that is easily soluble in an organic solvent such as protein or lipid, and a component that is easily soluble in water such as an inorganic substance (for example, a perhalogenate) are both in the solvent. Both of these components can be removed from the modified diene rubber. Therefore, a high-purity modified diene rubber from which impurities are removed can be obtained.

  Here, various organic solvents miscible with water can be used as the organic solvent, for example, methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, allyl alcohol, ethylene glycol, propylene glycol. , Alcohols such as diethylene glycol; ketones such as acetone and methyl ethyl ketone; aldehydes such as formaldehyde, acetaldehyde and propionaldehyde; cyclic ethers such as tetrahydrofuran and 1,4-dioxane; acetonitrile and the like, and any one or two of these These can be used in combination. Among these, water-miscible alcohol is preferable, and more preferably at least one selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, tert-butyl alcohol, ethylene glycol, propylene glycol, and diethylene glycol. is there.

  The method for drying the solid rubber (that is, the modified diene rubber) obtained as the solidified product after solidification is not particularly limited, and for example, a normal dryer such as a vacuum dryer or a hot air dryer is used. be able to. Note that the solidified product may be washed with water before drying.

  From the above, the modified diene rubber according to this embodiment is obtained. The weight average molecular weight (Mw) of the modified diene rubber is not particularly limited, and may be, for example, 80,000 to 3,000,000, 100,000 to 3,000,000, or 200,000 to 3,000,000. The modified diene rubber according to a preferred embodiment is a modified isoprene rubber having a terminal group generated by aldol condensation of a reducing sugar. The modified isoprene rubber is a case where natural rubber and / or synthetic isoprene rubber is used as a modification object, and is a concept including modified natural rubber. Further, the modified diene rubber according to a preferred embodiment is a modified styrene butadiene rubber having a terminal group generated by aldol condensation of a reducing sugar. The modified styrene butadiene rubber is a case where styrene butadiene rubber is used as a modification target.

  In the rubber composition according to this embodiment, the rubber component may be the above-mentioned modified diene rubber alone or a blend of the modified diene rubber and another rubber. Other rubbers are not particularly limited. For example, natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), nitrile rubber (NBR), butyl rubber (IIR), Various diene rubbers such as halogenated butyl rubber are exemplified. These can be used alone or in combination of two or more. The content of the modified diene rubber in the rubber component is not particularly limited, but is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, and still more preferably 50 parts by mass in 100 parts by mass of the rubber component. More than a part.

  In the rubber composition according to the present embodiment, as the filler, for example, various inorganic fillers such as silica, carbon black, titanium oxide, aluminum silicate, clay, and talc can be used. It can be used in combination of more than one species. Among these, silica and / or carbon black is preferably used, and more preferably, silica is the main component, that is, the proportion of silica in the filler is more than 50% by mass.

The silica is not particularly limited, and wet silica (hydrous silicic acid) is preferable. Colloidal properties of the silica is not particularly limited, it is preferable that the nitrogen adsorption specific surface area (BET) is 150 to 250 ² / g by BET method, and more preferably 180~230m ² / g. The BET of silica is measured according to the BET method described in ISO 5794.

  The carbon black is not particularly limited, and various grades of furnace carbon black such as SAF, ISAF, HAF, and FEF, which are used as rubber reinforcing agents, can be used.

  The blending amount of the filler is 5 to 150 parts by mass, preferably 20 to 120 parts by mass, and more preferably 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. Moreover, it is preferable that the compounding quantity of a silica is 5-80 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 30-80 mass parts.

  In the rubber composition according to this embodiment, when silica is blended as a filler, a silane coupling agent such as sulfide silane or mercaptosilane may be blended in order to further improve the dispersibility of silica. Although the compounding quantity of a silane coupling agent is not specifically limited, It is preferable that it is 2-20 mass% with respect to a silica compounding quantity.

  The rubber composition according to the present embodiment is generally used in rubber compositions such as oil, zinc white, stearic acid, anti-aging agent, wax, vulcanizing agent, and vulcanization accelerator in addition to the above components. Various additives can be blended. Examples of the vulcanizing agent include sulfur components such as powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. Although not particularly limited, the blending amount is 100 parts by mass of the rubber component. It is preferable that it is 0.1-10 mass parts, More preferably, it is 0.5-5 mass parts. Moreover, 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 rubber components, More preferably, it is 0.5-5 mass parts.

  The rubber composition according to the present embodiment can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. That is, in the first mixing stage, to the rubber component containing the modified diene rubber, together with the filler, other additives excluding the vulcanizing agent and the vulcanization accelerator are added and mixed. A rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator in the final mixing stage.

  The rubber composition thus obtained can be used for various rubber members for tires, vibration-proof rubbers, conveyor belts and the like. Preferably, it is used for tires, for various uses such as passenger car, large tires for trucks and buses, tread parts, side wall parts, bead parts, tire cord covering rubber, etc. Can be applied. That is, according to a conventional method, the rubber composition is molded into a predetermined shape by, for example, extrusion, and combined with other parts, and then vulcanized and molded at, for example, 140 to 180 ° C. to produce a pneumatic tire. can do. Among these, it is particularly preferable to use as a tire tread formulation.

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

[Synthesis Example 1: Synthesis of modified NR1- and modified NR1 +]
The natural rubber latex was oxidatively cleaved by a method according to Synthesis Example 1 of Patent Document 3 above. Specifically, natural rubber latex (“LA-NR” manufactured by Quay Kasei Co., Ltd., DRC = 60 mass%, Mw = 2.96 million) is adjusted to DRC = 30 mass%, and sodium lauryl sulfate (manufactured by Nacalai Tesque) is used. After adding to a concentration of 1% by mass, 0.7 g of periodic acid (H ₅ IO ₆ ) is added to 100 g of polymer mass in natural rubber latex, and formic acid is added to adjust the pH to 5. The mixture was stirred at 23 ° C. for 3 hours to oxidatively cleave natural rubber. Mw of the obtained depolymerized natural rubber was 2.28 million. The obtained depolymerized latex (pH 5) was adjusted to pH 12 with potassium hydroxide and then divided into two equal parts and immediately used for the next reaction.

  For the modified NR1-, the depolymerized latex divided into two equal parts as described above was allowed to react at room temperature for 18 hours. Thereafter, the modified rubber latex is poured into a mixed solution of ethanol / water = 2/1 (mass ratio) 5 times the volume of the obtained modified rubber latex, and the pH is adjusted to 5 or less with formic acid to coagulate the rubber component. Then, the obtained coagulated product is washed with water and then vacuum-dried at 40 ° C. for 48 hours using a vacuum drying oven, whereby modified natural products having a linking group represented by the above formulas (2) to (5) Rubber NR1- (Mw = 2.56 million) was obtained.

  For the modified NR1 +, 5.0 g of D-glucose (“D-glucose” manufactured by Wako Pure Chemical Industries, Ltd.) per 100 g of rubber was added to the depolymerized latex divided into two equal parts as described above, and reacted at room temperature for 18 hours. . Thereafter, in the same manner as the modified NR1-, it was coagulated and dried to obtain a modified natural rubber NR1 + (Mw = 25.3 million) having a terminal group generated by aldol condensation of glucose.

  Here, Mw is a value in terms of polystyrene measured by gel permeation chromatography (GPC), and is based on the method described in Patent Document 3.

[Synthesis Example 2: Synthesis of modified NR2 +]
After the depolymerized latex obtained in the same manner as in Synthesis Example 1 was adjusted to pH 12 with potassium hydroxide, 5.0 g of D-fructose (“D-fructose” manufactured by Wako Pure Chemical Industries, Ltd.) per 100 g of rubber was immediately added. The mixture was added and allowed to react at room temperature for 18 hours. Thereafter, in the same manner as in Synthesis Example 1, coagulation and drying were performed to obtain a modified natural rubber NR2 + (Mw = 26,220,000) having end groups generated by fructose aldol condensation.

[Synthesis Example 3: Synthesis of modified NR3 +]
The depolymerized latex obtained in the same manner as in Synthesis Example 1 was adjusted to pH 12 with potassium hydroxide, and then immediately 9.6 g of maltose (“D (+)-maltose monohydrate manufactured by Wako Pure Chemical Industries, Ltd.) per 100 g of rubber content. ”) Was added and allowed to react at room temperature for 18 hours. Thereafter, in the same manner as in Synthesis Example 1, it was coagulated and dried to obtain a modified natural rubber NR3 + (Mw = 25,110,000) having end groups generated by aldol condensation of maltose.

[Synthesis Example 4: Synthesis of Modified SBR1- and Modified SBR1 +]
Oxidative cleavage of styrene butadiene rubber latex was performed by a method according to Synthesis Example 5 of Patent Document 3 above. Specifically, styrene butadiene rubber latex (“SBR Latex LX110” manufactured by Nippon Zeon Co., Ltd., DRC = 50 mass%, Mw = 670,000) was adjusted to DRC = 30 mass%, and the polymer in the styrene butadiene rubber latex Periodic acid (H ₅ IO ₆ ) 0.7 g was added to 100 g of mass, and formic acid was further added to adjust the pH to 5, followed by stirring at 23 ° C. for 3 hours to oxidatively cleave the styrene butadiene rubber. Mw of the obtained depolymerized styrene butadiene rubber was 380,000. The obtained depolymerized latex (pH 5) was adjusted to pH 12 with potassium hydroxide and then divided into two equal parts and immediately used for the next reaction.

  For the modified SBR1-, the depolymerized latex divided into two equal parts as described above was allowed to react at room temperature for 18 hours. Thereafter, the modified rubber latex is poured into a mixed solution of ethanol / water = 2/1 (mass ratio) 5 times the volume of the obtained modified rubber latex, and the pH is adjusted to 5 or less with formic acid to coagulate the rubber component. Next, the obtained coagulated product is washed with water, and then vacuum-dried at 40 ° C. for 48 hours using a vacuum drying oven, whereby modified styrene having a linking group represented by the above formulas (4) and (5). Butadiene rubber SBR1- (Mw = 540,000) was obtained.

  Regarding the modified SBR1 +, 5.0 g of D-glucose per 100 g of rubber was added to the depolymerized latex divided into two equal parts as described above, and reacted at room temperature for 18 hours. Thereafter, in the same manner as the modified SBR1-, it was coagulated and dried to obtain a modified styrene butadiene rubber SBR1 + (Mw = 510,000) having an end group generated by aldol condensation of glucose.

[Synthesis Example 5: Synthesis of modified SBR2 +]
The depolymerized latex obtained in the same manner as in Synthesis Example 4 was adjusted to pH 12 with potassium hydroxide, and immediately 5.0 g of D-fructose was added per 100 g of rubber and reacted at room temperature for 18 hours. Thereafter, in the same manner as in Synthesis Example 4, coagulation and drying were performed to obtain a modified styrene butadiene rubber SBR2 + (Mw = 560,000) having end groups generated by fructose aldol condensation.

[Synthesis Example 6: Synthesis of modified SBR3 +]
The depolymerized latex obtained in the same manner as in Synthesis Example 4 was adjusted to pH 12 with potassium hydroxide, and immediately after that, 9.6 g of maltose was added per 100 g of rubber and reacted at room temperature for 18 hours. Thereafter, in the same manner as in Synthesis Example 4, coagulation and drying were performed to obtain a modified styrene butadiene rubber SBR3 + (Mw = 530,000) having a terminal group generated by aldol condensation of maltose.

[Examples 1 to 3 and Comparative Examples 1 to 6]
Using a Banbury mixer, according to the composition (parts by mass) shown in Table 1 below, first, in the first mixing stage, other compounding agents excluding sulfur and vulcanization accelerator are added to the rubber component, and then kneaded. In the final mixing stage, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded to prepare a rubber composition.

The details of each component in Table 1 are as follows.
STR20: commercially available unmodified natural rubber STR20
・ Silica: “Nip seal AQ” manufactured by Tosoh Silica Co., Ltd. (BET = 200 m ² / g)
・ Carbon black: “Seast KH” manufactured by Tokai Carbon Co., Ltd.
Silane coupling agent: “Si75” manufactured by Evonik Degussa
・ Oil: “Process N140” manufactured by JX Nippon Oil & Energy
・ Zinc flower: "Zinc flower No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Wax: Nippon Seiwa Co., Ltd. “OZOACE0355”
Anti-aging agent: “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Sulfur: “Powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
・ Vulcanization accelerator CZ: “Soccinol CZ” manufactured by Sumitomo Chemical Co., Ltd.
・ Vulcanization accelerator D: “Noxeller D” manufactured by Ouchi Shinsei Chemical Co., Ltd.

  About the obtained rubber composition, the test sample was produced by vulcanization-molding using a hot press at 150 degreeC for 20 minute (s), and rolling resistance performance and low temperature performance were evaluated using the obtained test sample. Each evaluation method is as follows.

[Rolling resistance performance]
Using a fully automatic viscoelasticity analyzer manufactured by Ueshima Seisakusho, measurement was performed at a frequency of 10 Hz, an initial strain of 10%, a measurement temperature range of −40 ° C. to 100 ° C., a measurement temperature step of 2 ° C., and a dynamic strain of 0.5%. The tan δ value was used as an index of rolling resistance. It was displayed as an index with the value of Comparative Example 1 being 100. The smaller the index, the less heat is generated, the lower the rolling resistance when used in a tire, and the better fuel economy.

[Low temperature performance]
Using a fully automatic viscoelasticity analyzer manufactured by Ueshima Seisakusho, measurement is performed at a frequency of 10 Hz, an initial strain of 10%, a measurement temperature range of −40 ° C. to 100 ° C., a measurement temperature step of 2 ° C., and a dynamic strain of 0.5%. The value of the complex elastic modulus E ^* was used as an index of low temperature performance. It was displayed as an index with the value of Comparative Example 1 being 100. It shows that it is excellent in the low-temperature performance when it uses for a tire, so that an index | exponent is small.

  The results are as shown in Table 1. Compared to Comparative Example 1 using unmodified natural rubber, Comparative Example 2 using modified natural rubber NR1- in which natural rubber is re-bonded as it is after oxidative cleavage does not provide an effect of improving rolling resistance performance, and is low in temperature. The performance was getting worse. On the other hand, in Examples 1 to 3 using modified natural rubber NR1 +, NR2 + or NR3 + reacted by adding glucose, fructose or maltose after oxidative cleavage of natural rubber, the rolling resistance performance and Both low-temperature performance has been greatly improved. In addition, in the case where glucose was added during kneading of the rubber composition as in Comparative Examples 3 to 6, the excellent improvement effect as in Examples 1 to 3 in which reducing sugar was added and reacted at the time of modification could not be obtained. Therefore, the advantageous effect by reaction was recognized by Examples 1-3.

[Examples 4 to 6 and Comparative Example 7]
Using a Banbury mixer, according to the formulation (parts by weight) shown in Table 2 below, first, in the first mixing stage, other compounding agents excluding sulfur and vulcanization accelerator are added and kneaded, and then kneaded. In the final mixing stage, sulfur and a vulcanization accelerator were added to the obtained kneaded product and kneaded to prepare a rubber composition. Details of each component in Table 2 are the same as those in Table 1.

  About the obtained rubber composition, the test sample was produced by vulcanization-molding using a hot press at 160 degreeC for 20 minutes, and rolling resistance performance and low-temperature performance were evaluated using the obtained test sample. Each evaluation method is as described above, but here, it is expressed as an index with the value of Comparative Example 7 as 100.

  The results are as shown in Table 2. In contrast to Comparative Example 7 using modified styrene butadiene rubber SBR1- in which styrene butadiene rubber was recombined after oxidative cleavage, modified styrene butadiene rubber SBR1 + reacted by adding glucose, fructose or maltose after oxidative cleavage of styrene butadiene rubber. In Examples 4 to 6 using SBR2 + or SBR2 +, both the rolling resistance performance and the low-temperature performance were significantly improved.

Claims (7)

A filler 5 containing silica with respect to 100 parts by mass of a rubber component containing a modified diene rubber obtained by reacting a reducing sugar with an aldehyde group and / or keto group at the molecular end produced by oxidative cleavage of a diene rubber by aldol condensation A rubber composition containing -150 parts by mass.   The rubber composition according to claim 1, wherein the modified diene rubber is a modified isoprene rubber having a terminal group generated by aldol condensation of a reducing sugar.   The rubber composition according to claim 1, wherein the modified diene rubber is a modified styrene butadiene rubber having a terminal group generated by aldol condensation of a reducing sugar.   The rubber composition according to any one of claims 1 to 3, wherein the filler contains 5 to 80 parts by mass of silica.   The pneumatic tire which uses the rubber composition of any one of Claims 1-4. The diene rubber is decomposed by oxidative cleavage to produce a decomposed diene rubber having an aldehyde group and / or keto group at the molecular end, and the aldehyde group and / or keto at the molecular end of the decomposed diene rubber. A method for producing a rubber composition, characterized by reacting a reducing sugar with a group by aldol condensation to produce a modified diene rubber, and mixing the resulting modified diene rubber with a filler containing silica . Diene rubber latex is decomposed by adding perhalogen acid to oxidative cleavage of the diene rubber, and the latex containing the decomposed diene rubber is changed from acidic to basic and decomposed by adding reducing sugar. 7. A modified diene rubber is produced by reacting a reducing sugar with an aldehyde group and / or keto group at the molecular end of a diene rubber subjected to aldol condensation, and coagulating the latex reacted by the aldol condensation. Of producing a rubber composition.