JP2011246514A - Rubber composition and tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition significantly excellent in low loss properties (low heat generation) and abrasion resistance, and a tire excellent in steering stability using the rubber composition.SOLUTION: The rubber composition uses modified natural rubber as a rubber component, wherein the modified natural rubber is obtained through addition of a polar group-containing hydrazide compound after oxidizing natural rubber latex or introducing a polar group into the natural molecule terminal through hydrolysis of phospholipid at the natural rubber molecule terminal and condensation of a polar group-containing carboxylic acid compound, aldehyde, isocyanates, etc. The rubber composition includes an inorganic filler and a specific organosilicon compound as a coupling agent. The organosilicon compound has a cyclic structure including a nitrogen atom and a silicon atom in the molecule, also one or more sulfur atoms, and a site in which one or more groups with low steric hindrance are bonded to one silicon atom.

Description

  The present invention relates to a modified natural rubber and a rubber composition using the same, and more specifically, a rubber composition excellent in low loss and wear resistance, comprising a modified natural rubber having a polar group introduced in the natural rubber and an organosilicon compound. The present invention relates to a product and a tire using the same.

  In recent years, demands for reducing fuel consumption of automobiles are becoming stronger, and tires with low rolling resistance are required. Therefore, a rubber composition excellent in low loss property and low heat generation property is required as a rubber composition used for tire treads and the like. In addition, a rubber composition for a tread is required to have excellent wear resistance and fracture characteristics in addition to low loss. On the other hand, in order to improve the low loss property, wear resistance and fracture characteristics of the rubber composition, it is necessary to improve the affinity between the rubber component and the filler such as carbon black and silica in the rubber composition. It is effective to improve the reinforcing filler and improve the rubber component.

  For example, in order to improve the affinity between the filler and the rubber component in the rubber composition and to improve the reinforcing effect by the filler, synthetic rubber or functional group having improved affinity with the filler by terminal modification Synthetic rubbers and the like have been developed in which the monomers are copolymerized to improve the affinity with the filler.

  On the other hand, with respect to natural rubber, for example, a technique of graft polymerization by adding a vinyl monomer to natural rubber latex (see Patent Documents 1 to 6) is known, and grafted natural rubber obtained by the technique is known. Has been put to practical use in adhesive applications and the like. However, since these grafted natural rubbers are grafted with a large amount (20 to 50% by mass) of a vinyl compound as a monomer, blending with a filler such as carbon black or silica causes a significant increase in viscosity. , Workability will be reduced. In addition, since a large amount of vinyl compound is introduced into the natural rubber molecular chain, the properties of the natural rubber itself are changed, and the excellent physical properties (stress-strain curves in viscoelasticity, tensile tests, etc.) inherent to natural rubber are impaired. End up. Therefore, even if the grafted natural rubber obtained by this technique is used, the affinity with the filler cannot be improved and the reinforcing effect cannot be improved. In addition, it has been proposed to use an epoxidized natural rubber in order to improve the bending crack resistance and strength of the tire (see Patent Document 7).

  On the other hand, a modified natural rubber obtained by adding a polar group-containing monomer to natural rubber latex, graft-polymerizing the polar group-containing monomer to natural rubber molecules in the natural rubber latex, and further coagulating and drying. Technology that improves the rubber composition's affinity by improving the affinity between the rubber component and the filler, and improves the low loss, wear resistance and fracture characteristics of the rubber composition. However, recently, it is required to further improve the low loss property and wear resistance of the rubber composition.

  On the other hand, it is known that silica is used as a filler of a rubber composition as a technique for achieving both performance on a wet surface of a tire and reduction in rolling resistance (for example, Patent Documents 9 to 12). Particles tend to aggregate due to hydrogen bonding of silanol groups, which are surface functional groups, and wettability with rubber molecules is poor, and silica is not well dispersed in rubber. In order to improve this, it is necessary to lengthen the kneading time. Furthermore, if the silica is not sufficiently dispersed in the rubber, the Mooney viscosity of the rubber composition increases and the processability such as extrusion is poor. Further, since the surface of the silica particles is acidic, it adsorbs a basic substance used as a vulcanization accelerator when vulcanizing the rubber composition, and the vulcanization is not sufficiently performed and the elastic modulus does not increase. He also had problems.

  In order to remedy these drawbacks, silane coupling agents have been developed, but the silica dispersion has not yet reached a sufficient level and there is still room for improvement.

JP-A-5-287121 JP-A-6-329702 Japanese Patent Laid-Open No. 9-25468 JP 2000-319339 A JP 2002-138266 A JP 2002-348559 A JP 2007-56205 A International Publication No. 2004/106397 Pamphlet JP-A-6-248116 JP-A-7-70369 JP-A-8-245838 JP-A-3-252431

  An object of the present invention is to provide a rubber composition that is significantly superior in low loss (low heat build-up) and wear resistance as compared with conventional tires, and a tire that is also excellent in handling stability using the rubber composition. There is.

  As a result of intensive studies, the present inventors have found that it is effective to increase the reinforcing layer while improving the dispersibility of the reinforcing filler in order to obtain a rubber composition having excellent low loss and wear resistance. From an idea, a rubber component is a modified natural rubber using an inorganic filler such as silica and a silane coupling agent highly reactive with them, and having a polar group at the molecular terminal highly reactive with the silane coupling agent. It has been found that the above object can be achieved by using a rubber composition.

As described above, the polar group can be introduced into the main chain of the natural rubber molecule by graft polymerization of the polar group-containing monomer to the natural rubber molecule in the natural rubber latex. The presence of a functional group at the terminal can enhance the interaction with the filler. This is because a normal polymer can move freely because it has a free chain at the end even when constrained by reinforcement, crosslinking, or the like. This is also expected from the fact that the terminal modification of the synthetic rubber shows a high modification effect.
However, even when a polar group-containing monomer is graft-polymerized to a natural rubber molecule in the natural rubber latex and the polar group is introduced into the natural rubber molecule, the position where the polar group is introduced is not limited to the molecular end. Further, as a technique for modifying the end of a natural rubber molecule, a technique for introducing a polar group using a metathesis catalyst and a polar group-containing olefin is disclosed in JP 2007-204637, but the catalyst is expensive and the production cost is high. .

In the rubber composition of the present invention, a natural rubber latex is oxidized and then a polar group-containing hydrazide compound is added to produce a modified natural rubber having a polar group added to the end of the molecular chain and used as a rubber component. The oxidation of the natural rubber latex is preferably performed by adding a carbonyl compound and performing oxidation with air or ozone, and then adding 0.01 to 5.0% by mass of the polar group-containing hydrazide compound with respect to the rubber component in the natural rubber latex. .
Proteins and phospholipids are bound to the molecular ends of natural rubber. In the present invention, after the phospholipid is hydrolyzed, a polar group is present at the molecular end by condensing a carboxylic acid compound having a polar group, an aldehyde having a polar group, an isocyanate having a polar group, etc. Natural rubber can also be obtained. The content of the polar group is 0.0005 to 0.2% by mass of the rubber component in the modified natural rubber.

The rubber composition of the present invention uses a modified natural rubber having a polar group introduced at the molecular end as a rubber component and contains a specific organosilicon compound as an inorganic filler and a coupling agent. Is a silicon compound having a cyclic structure containing a nitrogen atom and a silicon atom, having one or more sulfur atoms, and having one or more small steric hindrance groups bonded to the silicon atom. The reaction rate with inorganic fillers such as silica is high, the efficiency of the coupling reaction is increased, the hysteresis of the rubber composition is greatly reduced, and the wear resistance is improved.
The tire of the present invention is a tire using the rubber composition for any of the tire members.

  According to the present invention, a modified natural rubber having a polar group at a molecular end is modified with a conventional polar group-containing monomer by using a rubber component of a rubber composition and an organosilicon compound as a coupling agent. Reinforcement layer because the dispersibility of the filler is higher and the loss is lower and the reactivity with the coupling agent is higher than the rubber composition containing the modified natural rubber in which polar groups are present everywhere in the natural rubber molecule. Thus, a rubber composition having excellent wear resistance can be obtained, and a tire having excellent steering stability can be obtained because of its high elastic modulus.

  Examples of natural rubber latex used as a raw material for the modified natural rubber used in the present invention include field latex, ammonia-treated latex, centrifugal concentrated latex, deproteinized latex treated with a surfactant and an enzyme, and combinations of the above. , Either can be used. In order to reduce side reactions, it is preferable to increase the purity of natural rubber latex.

  The natural rubber latex can be oxidized by a known method. For example, according to JP-A-8-81505, natural rubber latex can be oxidized by air oxidation of natural rubber latex dissolved in an organic solvent at a ratio of 1 to 30% by mass in the presence of a metal-based oxidation catalyst. it can. Here, suitable metal species of the metal-based oxidation catalyst used for promoting air oxidation are cobalt, copper, iron, and the like, and salts and complexes with these chlorides and organic compounds are used. Of these, cobalt catalysts such as cobalt chloride, cobalt acetylacetonate, and cobalt naphthenate are preferable.

  Any organic solvent may be used as long as it does not react with rubber and does not easily oxidize and dissolves rubber. Various hydrocarbon solvents, aromatic hydrocarbon solvents, organic halogens can be used. A system solvent or the like is preferably used. As the hydrocarbon solvent, for example, hexane, gasoline or the like can be used. As the aromatic hydrocarbon solvent, for example, toluene, xylene, benzene and the like can be used. As the organic halogen solvent, for example, chloroform, dichloromethane and the like can be used. Of these, aromatic hydrocarbon-based toluene is preferably used. It is also possible to use a mixed solvent of them and alcohol.

  Further, as described in JP-A-9-136903, oxidation can be carried out by adding a carbonyl compound to natural rubber latex and oxidizing the natural rubber latex. It is appropriate that the carbonyl compound added to the natural rubber latex is added so as to be 20% by volume (V / V%) or less, preferably 0.5 to 10% by volume based on the latex volume regardless of the rubber content. is there. There is no problem even if the concentration of the carbonyl compound exceeds the above range, but not only the reactivity is not increased, but there is a concern that it may be economically disadvantageous. Here, preferable examples of the carbonyl compound include various aldehydes and ketones.

  Examples of aldehydes include formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, n-valeraldehyde, caproaldehyde, heptaldehyde, phenylacetaldehyde, benzaldehyde, tolualdehyde, nitrobenzaldehyde, salicylaldehyde, anisaldehyde, vanillin, piperonal , Methylvaleraldehyde, isocaproaldehyde, paraformaldehyde and the like.

  Examples of ketones include acetone, methyl ethyl ketone, methyl n-propyl ketone, diethyl ketone, isopropyl methyl ketone, benzyl methyl ketone, 2-hexanone, 3-hexanone, isobutyl methyl ketone, acetophenone, propiophenone, n-butyrophenone, and benzophenone. , 3-nitro-4'-methylbenzophenone and the like.

  The above carbonyl compound can be added to natural rubber latex for oxidation, but when air oxidation is performed as an oxidation method, as described in JP-A-9-136903, in order to promote air oxidation It is preferable to perform air oxidation in the presence of a radical generator. As the radical generator, for example, a peroxide radical generator, a redox radical generator, an azo radical generator and the like are preferably used. Examples of peroxide radical generators include benzoyl peroxide, di-t-butyl peroxide, potassium persulfate, ammonium persulfate, hydrogen peroxide, lauroyl peroxide, diisopropyl peroxycarbonate, dicyclohexyl peroxycarbonate, etc. it can.

  Examples of the redox radical generator include cumene hydroxyperoxide and Fe (II) salt, hydrogen peroxide and Fe (II) salt, potassium persulfate or ammonium persulfate and sodium sulfite, sodium perchlorate and sodium sulfite, cerium sulfate ( IV) and alcohols, amines or starches, peroxides such as benzoyl peroxide and lauroyl peroxide, dimethylaniline, tert-butyl hydroperoxide, tetraethylenepentamine and the like.

  As the azo radical generator, for example, azobisisobutyronitrile, methyl azobisisobutyrate, azobiscyclohexanecarbonitrile, azobisisobutylamidine hydrochloride, 4,4'-azobis-4-cyanovaleric acid and the like can be used.

  The radical generator is used by being dissolved or dispersed in natural rubber latex. The amount of radical generator added is suitably 0.01-5% by mass, preferably 0.05-1% by mass, based on the solid content of natural rubber. If the concentration of the radical generator is lower than the above range, the rate of air oxidation is slow and impractical. On the other hand, when the concentration of the radical generator exceeds the above range, molecular chain scission proceeds, and as the molecular weight decreases, the low loss property, wear resistance, and breaking strength of the rubber composition may deteriorate.

  In air oxidation, it is desirable to bring the solution into uniform contact with air. Although the method for making the contact with air uniform is not particularly limited, for example, in addition to shaking in a shake flask, it can be easily performed by stirring, bubbling for blowing air, or the like. Although the temperature which advances air oxidation is normally performed at room temperature-100 degreeC, it is not specifically limited. The reaction is usually completed in about 1 to 5 hours.

  Further, according to the description in JP-A No. 2001-261707, an ozone-containing gas can be blown into natural rubber latex, and natural rubber latex can be oxidized by the oxidizing action of ozone. In this method, the decomposition reaction is accelerated by the addition of hydrogen peroxide.

  The modified natural rubber used in the present invention can be obtained by adding a polar group-containing hydrazide compound after oxidizing natural rubber latex by the above-described method. The polar group-containing hydrazide compound may be added to an oxidized natural rubber latex obtained by oxidizing natural rubber latex, or added to an oxidized natural rubber obtained by coagulating the obtained oxidized natural rubber latex. May be.

  The oxidized natural rubber latex obtained by the above method has a carbonyl group at the end of the natural rubber molecular chain. The polar group-containing hydrazide compound has high reactivity, and thus easily reacts with the oxidized natural rubber latex or the carbonyl group at the end of the rubber molecule in the oxidized natural rubber obtained by coagulating the oxidized natural rubber latex. Therefore, by adding the polar group-containing hydrazide compound to the oxidized natural rubber latex or the oxidized natural rubber, the polar group can be easily introduced at the end of the natural rubber molecule without using an expensive catalyst.

  The polar group-containing hydrazide compound is not particularly limited as long as it is a hydrazide compound having at least one polar group in the molecule. Specific examples of polar groups include amino groups, imino groups, nitrile groups, ammonium groups, imide groups, amide groups, hydrazo groups, azo groups, diazo groups, hydroxyl groups, carboxyl groups, carbonyl groups, and epoxy groups. Preferred examples thereof include an oxycarbonyl group, a nitrogen-containing heterocyclic group, an oxygen-containing heterocyclic group, a tin-containing group and an alkoxysilyl group. These polar group-containing hydrazide compounds can be used alone or in combination of two or more.

  Examples of the amino group-containing hydrazide compound include hydrazide compounds having at least one amino group selected from primary, secondary, and tertiary amino groups in one molecule. These amino group-containing hydrazide compounds can be used alone or in combination of two or more.

  Examples of the primary amino group-containing hydrazide compound include 2-aminoacetohydrazide, 3-aminopropionic hydrazide, 4-aminobutanoic hydrazide, 2-aminobenzohydrazide, 4-aminobenzohydrazide and the like.

  Examples of secondary amino group-containing hydrazide compounds include 2- (methylamino) acetohydrazide, 2- (ethylamino) acetohydrazide, 3- (methylamino) propionic acid hydrazide, and 3- (ethylamino) propionic acid hydrazide. 3- (propylamino) propionic hydrazide, 3- (isopropylamino) propionic hydrazide, 4- (methylamino) butanoic hydrazide, 4- (ethylamino) butanoic hydrazide, 4- (propylamino) butanoic hydrazide 4- (isopropylamino) butanoic hydrazide, 2- (methylamino) benzohydrazide, 2- (ethylamino) benzohydrazide, 2- (propylamino) benzohydrazide, 2- (isopropylamino) benzohydrazide, 4- ( Methylamino) benzo Hydrazide, 4 one (ethylamino) benzohydrazide, 4- (propylamino) benzohydrazide, 4- (isopropylamino) benzohydrazide, and the like.

  Examples of tertiary amino group-containing hydrazide compounds include N, N-disubstituted aminoalkanoic acid hydrazide compounds and N, N-disubstituted aminobenzohydrazide compounds. Examples of these compounds include 2- (dimethylamino) acetohydrazide, 2- (diethylamino) acetohydrazide, 3- (dimethylamino) propionic acid hydrazide, 3- (diethylamino) propionic acid hydrazide, and 3- (dipropylamino). ) Propionic acid hydrazide, 3- (diisopropylamino) propionic acid hydrazide, 4- (dimethylamino) butanoic acid hydrazide, 4- (diethylamino) butanoic acid hydrazide, 4- (dipropylamino) butanoic acid hydrazide, 4- (diisopropylamino) ) Butanoic acid hydrazide, 2- (dimethylamino) benzohydrazide, 2- (diethylamino) benzohydrazide, 2- (dipropylamino) benzohydrazide, 2- (diisopropylamino) benzohydrazide, 4- (dimethylamido) ) Benzohydrazide, 4- (diethylamino) benzohydrazide, 4- (dipropylamino) benzohydrazide, 4- (diisopropylamino) benzohydrazide, and the like.

  Further, it may be a nitrogen-containing heterocyclic group instead of an amino group. Examples of the nitrogen-containing heterocyclic group include pyrrole, histidine, imidazole, triazolidine, triazole, triazine, pyridine, pyrimidine, pyrazine, indole, quinoline. , Purine, phenazine, pteridine, melamine and the like. The heteronitrogen heterocycle may contain other heteroatoms in the ring. Examples of the hydrazide compound having a pyridyl group as the nitrogen-containing heterocyclic group include isonicotino hydrazide and picolino hydrazide. These nitrogen-containing heterocyclic group-containing hydrazide compounds may be used alone or in combination of two or more.

  Examples of the hydrazide compound having a nitrile group include 2-nitroacetohydrazide, 3-nitropropionic hydrazide, 4-nitrobutanoic hydrazide, 2-nitrobenzohydrazide, 4-nitrobenzohydrazide and the like. These nitrile group-containing hydrazide compounds may be used alone or in a combination of two or more.

  Examples of the hydroxyl group-containing hydrazide compound include a hydrazide compound containing at least one hydroxyl group in one molecule. Examples of such hydroxyl group-containing hydrazide compounds include 2-hydroxyacetohydrazide, 3-hydroxypropionic hydrazide, 4-hydroxybutanoic hydrazide, 2-hydroxybenzohydrazide, and 4-hydroxybenzohydrazide. These hydroxyl group-containing hydrazide compounds may be used alone or in a combination of two or more.

  Examples of the hydrazide compound containing a carboxyl group include 3-carboxypropionic acid hydrazide, 4-carboxybutanoic acid hydrazide, phthalic acid monohydrazide, terephthalic acid monohydrazide, and the like. These carboxyl group-containing hydrazide compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the hydrazide compound having an epoxy group include 2- (oxiran-2-yl) acetohydrazide, 3- (oxiran-2-yl) propanoic hydrazide, and 3- (tetrahydro-2H-pyran-4-yl) propanoic hydrazide. Etc. These epoxy group-containing hydrazide compounds may be used alone or in a combination of two or more.

  Examples of the hydrazide compound having a tin-containing group include 3- (tributyltin) propionic acid hydrazide, 3- (trimethyltin) propionic acid hydrazide, 3- (triphenyltin) propionic acid hydrazide, and 3- (trioctyltin) propionic acid hydrazide. 4- (tributyltin) butanoic hydrazide, 4- (trimethyltin) butanoic hydrazide, 4- (triphenyltin) butanoic hydrazide, 4- (trioctyltin) butanoic hydrazide, 2- (tributyltin) benzohydrazide, Tin-containing hydrazides such as 4- (tributyltin) benzohydrazide, 2- (trimethyltin) benzohydrazide, 4- (trimethyltin) benzohydrazide, 2- (trioctyltin) benzohydrazide, 4- (trioctyltin) benzohydrazide Mention may be made of the compound. These tin-containing hydrazide compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  Examples of the hydrazide compound containing an alkoxysilyl group include 2- (trimethoxysilyl) acetohydrazide, 2- (triethoxysilyl) acetohydrazide, 3- (trimethoxysilyl) propionic acid hydrazide, and 3- (triethoxysilyl) propion. Acid hydrazide, 4- (trimethoxysilyl) butanoic hydrazide, 4- (triethoxysilyl) butanoic hydrazide, 2- (trimethoxysilyl) benzohydrazide, 2- (triethoxysilyl) benzohydrazide, 4- (trimethoxy And silyl) benzohydrazide and 4- (triethoxysilyl) benzohydrazide. These alkoxysilyl group-containing hydrazide compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of the method for adding the polar group-containing hydrazide compound include the following three methods.
In the first method, the natural rubber latex subjected to the oxidation reaction is coagulated, pulverized and crushed, and then a polar group-containing hydrazide compound is added. Thereafter, for example, kneading is performed using a mixer, an extruder, a kneader (prebreaker), etc., and a dried modified natural rubber can be obtained.

  In the second method, the natural rubber latex subjected to the oxidation reaction is coagulated, ground and dried, and then a polar group-containing hydrazide compound is added. For example, a step of adding the polar group-containing hydrazide compound solution to the solid oxidized natural rubber after drying by a mixer, an extruder, a kneader, etc. is preferable. Preferably, mixing is performed with a kneader from the viewpoint of improving dispersibility. It is preferable.

  In the third method, the polar group-containing hydrazide compound is added to the natural rubber latex subjected to the oxidation reaction, and water and, if necessary, an emulsifier added, and the mixture is reacted at a predetermined temperature. When the polar group-containing hydrazide compound is added to the oxidized natural rubber latex, an emulsifier is added to the oxidized natural rubber latex in advance, or the polar group-containing hydrazide compound is emulsified and then added to the oxidized natural rubber latex. An organic peroxide can also be added as needed. The emulsifier that can be used is not particularly limited, and examples thereof include nonionic surfactants such as polyoxyethylene lauryl ether. The modified natural rubber can be obtained by coagulating and drying the modified natural rubber latex obtained by adding and reacting the polar group-containing hydrazide compound in this manner.

  In the three methods described above, the coagulant used for coagulating the oxidized natural rubber latex or the modified natural rubber latex is not particularly limited, but is not limited to acids such as formic acid and sulfuric acid, and sodium chloride. Salt. The oxidized natural rubber latex or modified natural rubber latex can be dried using a dryer such as a vacuum dryer, an air dryer or a drum dryer.

（式中、Ｒは、置換基としてアミノ基、イミノ基、ニトリル基、アンモニウム基、イミド基、アミド基、ヒドラゾ基、アゾ基、ジアゾ基、ヒドロキシル基、カルボキシル基、カルボニル基、エポキシ基、オキシカルボニル基、スズ含有基、アルコキシシリル基からなる群から選ばれる極性基を少なくとも１種有する炭素数１〜４のアルキル基、置換基として該極性基を少なくとも１種有するフェニル基、又は含窒素複素環基及び含酸素複素環基からなる群から選ばれる少なくとも１種の極性基である）で表される極性基を有する。
なお、上記一般式（Ａ）中のＲは上述したような極性基含有ヒドラジド化合物のヒドラジド基以外の部分に由来するものである。 The modified natural rubber obtained as described above has the following general formula (A):

(In the formula, R is an amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxy as a substituent. A C1-C4 alkyl group having at least one polar group selected from the group consisting of a carbonyl group, a tin-containing group and an alkoxysilyl group, a phenyl group having at least one polar group as a substituent, or a nitrogen-containing complex A polar group selected from the group consisting of a cyclic group and an oxygen-containing heterocyclic group.
In addition, R in the said general formula (A) originates in parts other than the hydrazide group of a polar group containing hydrazide compound as mentioned above.

  When blending the above modified natural rubber with fillers such as carbon black and silica, in order to improve low-loss characteristics and wear resistance without reducing processability, a small amount of polar groups are evenly distributed in each molecule of natural rubber. Since it is important to be introduced, the addition amount of the polar group-containing hydrazide compound in the modified natural rubber is preferably 0.01 to 5.0% by mass with respect to the rubber component in the natural rubber, and 0.01 to 1 0.0 mass% is more preferable.

Furthermore, in the present invention, a modified natural rubber modified by the following method can also be used.
Normally, proteins and phospholipids are bound to the molecular ends of natural rubber, and it is speculated that proteins and phospholipids at the ends are further bound and associated to form a higher-order branched structure. The phospholipids that form this branch are hydrolyzed.
The hydrolysis of phospholipids can be performed by a known method, and for example, the method described in International Publication WO2004 / 052935 can be applied.

As a method for hydrolyzing phospholipids, natural rubber latex can be treated with an alkali or lipase and / or phospholipase.
Examples of the alkali include sodium hydroxide and potassium hydroxide, and the lipase and phospholipase are not particularly limited, and any of those derived from bacteria, those derived from filamentous fungi, and those derived from yeast may be used. The lipase and phospholipase should be 100 (U / g) or more, preferably 1000 (U / g) or more, more preferably 10,000 (U / g) or more, and still more preferably 100,000 (U / g) or more. good. Examples of such lipases and phospholipases include commercially available lipase M “Amano” 10 (manufactured by Amano Enzyme Co., Ltd.), lipase OF (manufactured by Meika Inc.), phospholipase A1 (manufactured by Sankyo Co., Ltd.) and the like.

The amount of the lipase and / or phospholipase added during the enzyme treatment is 0.005 to 10 parts by weight, particularly 0.01 to 1.0 parts by weight, based on 100 parts by weight of the solid component in the natural rubber latex. A range is preferable. When the amount is within the above range, the phospholipid in the natural rubber latex is appropriately decomposed.
When the added amount (total amount) of the lipase and / or phospholipase is 0.005 to 10 parts by mass, the phospholipid is sufficiently decomposed, the fatty acid contained in the natural rubber is also hardly decomposed, and the rubber is stretched. Tensile strength and wear resistance are improved without lowering crystallinity.

  In adding such an enzyme, other additives such as phosphates such as potassium phosphate, potassium phosphate and sodium phosphate as pH adjusters, and acetates such as potassium acetate and sodium acetate, Furthermore, acids such as sulfuric acid, acetic acid, hydrochloric acid, nitric acid, formic acid, citric acid and succinic acid or salts thereof, or ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate and the like can be used. The enzyme treatment can be carried out without coagulating the natural rubber latex by carrying out the alkaline treatment, preferably at a pH of 8 or more, more preferably 9 or more.

  The enzyme treatment is performed at a temperature of 70 ° C. or less, preferably at a temperature of 60 ° C. or less, more preferably at 50 ° C. or less. If the enzyme treatment temperature is 70 ° C. or lower, natural rubber latex can be stably treated without coagulation. When coagulated, the enzymatic degradation effect decreases.

In addition, it is preferable to use a surfactant in combination with the enzyme treatment of natural rubber latex. As the surfactant, nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants and the like can be used. In particular, nonionic surfactants and anionic surfactants can be used. It is preferable to use an agent or the like.
As the nonionic surfactant, for example, polyoxyalkylene ether, polyoxyalkylene ester, polyhydric alcohol fatty acid ester, sugar fatty acid ester, and alkyl polyglycoside are suitable.
As the anionic surfactant, for example, carboxylic acid type, sulfonic acid type, sulfuric acid ester type, and phosphoric acid ester type are suitable.
Examples of the carboxylic acid surfactant include fatty acid salts, polyvalent carboxylates, rosinates, dimer salts, polymer acid salts, tall oil fatty acid salts, and the like. Examples of the sulfonic acid surfactant include alkylbenzene sulfonate, alkyl sulfonate, alkyl naphthalene sulfonate, naphthalene sulfonate, and diphenyl ether sulfonate. Examples of sulfate surfactants include alkyl sulfates, polyoxyalkylene alkyl sulfates, polyoxyalkylene alkyl phenyl ether sulfates, tristyrenated phenol sulfates, polyoxyalkylene distyrenated phenol sulfates. Etc. Examples of phosphate ester surfactants include alkyl phosphate ester salts and polyoxyalkylene phosphate ester salts.

  The natural rubber latex treated with the enzyme as described above is used for the reaction with the polar group-containing compound as it is, after adjusting the pH or the like, or by concentrating the comb component with a centrifuge or the like.

  In the phospholipid-hydrolyzed natural rubber obtained by the above method, the binding lipid at the end of the natural rubber molecular chain is hydrolyzed to have a hydroxyl group. A polar group can be easily introduced at the end of a natural rubber molecule by condensing the hydroxyl group with a compound having a polar group that reacts with a hydroxyl group.

Specific examples of polar groups include amino groups, imino groups, nitrile groups, ammonium groups, imide groups, amide groups, hydrazo groups, azo groups, diazo groups, hydroxyl groups, carboxyl groups, carbonyl groups, epoxy groups, oxycarbonyl groups. Thiol group, nitrogen-containing heterocyclic group, oxygen-containing heterocyclic group, tin-containing group, alkoxysilyl group and the like can be preferably mentioned.
Examples of the compound having a polar group that reacts with the hydroxyl group include compounds having a carboxyl group, an aldehyde group, a carbonyl group, an alkoxyl group, a hydroxyl group, a isosocyanato group, etc. in addition to the polar group. An acid is preferably used.

  Examples of the compound containing an amino group as a polar group include compounds containing at least one amino group selected from primary, secondary and tertiary amino groups in one molecule. Among these compounds having an amino group, a tertiary amino group-containing compound is particularly preferable. These amino group-containing compounds may be used alone or in a combination of two or more.

Examples of the primary amino group-containing compound include 7-aminoheptanoic acid and β-alanine.
Examples of the secondary amino group-containing compound include 7- (ethylamino) heptanoic acid.
Examples of the tertiary amino group-containing compound include 7- (diethylamino) heptanoic acid.

Further, instead of an amino group, a nitrogen-containing heterocyclic group may be used. Examples of the nitrogen-containing heterocyclic ring include pyrrole, histidine, imidazole, triazolidine, triazole, triazine, pyridine, pyrimidine, pyrazine, indole, quinoline, purine. , Phenazine, pteridine, melamine and the like. The nitrogen-containing heterocycle may contain other heteroatoms in the ring.
For example, a compound having a pyridyl group includes isonicotinic acid.

  Examples of the nitrile group-containing compound include 7-cyanoheptanoic acid. These nitrile group-containing compounds may be used alone or in combination of two or more.

  Examples of the hydroxyl group-containing compound include compounds containing at least one hydroxyl group in one molecule. For example, 6-hydroxyhexanoic acid etc. are mentioned as a hydroxyl group containing carboxylic acid. These hydroxyl group-containing compounds may be used alone or in a combination of two or more.

  Examples of the carboxyl group-containing compound include pimelic acid. These carboxyl group-containing compounds may be used alone or in a combination of two or more.

  Examples of the compound having an epoxy group include 6- (oxiran-2-yl) hexanoic acid. These compounds having an epoxy group may be used alone or in combination of two or more.

  The polar group-containing compound may be added as it is soluble in a solvent, or may be added as a solution. Moreover, it is preferable to emulsify the poorly soluble one.

  In the reaction of carboxylic acid and hydroxyl group, a condensing agent may be used as a reaction accelerator. As the condensing agent, a carbodiimide condensing agent, a triazine condensing agent, a phosphonium condensing agent, a benzotriazole condensing agent, an imidazole condensing agent, or a polar group-containing halogenated carboxylic acid can be used. EDC (1-ethyl-3- (3-dimethylaminopropyl) carbodiimide hydrochloride), DMT-MM (4- (4,4-dimethoxy-1,3,5-triazin-2-yl) -4-methylmorpho Linium chloride), BOP (benzotriazol-1-yl-oxy-tris (dimethylamino) phosphonium hexafluorophosphate), PYBOP (benzotriazol-1-yl-oxy-tripyrrolidinophosphonium hexafluorophosphate), HBTU (O- (benzotriazol-1-yl -N, N, N ', N'- tetramethyluronium hexafluorophosphate), and the like 1,2-benzisothiazolin-3-one.

Further, in order to increase the activity of the condensing agent, HOBT (1-hydroxybenzotriazole), DMAP (4-dimethylaminopyridine), HOSU (N-hydroxysuccinimide), HOAT (1-hydroxy-7-azabenzotriazole) TBTU (o- (benzotriazol-1-yl) -N, N, N ′, N′-tetramethyluronium tetrafluoroborate) or the like may be added. Among these, the combination of EDC and DMAP is desirable because it reacts in a high yield.
As the condensing agent and accelerator, those soluble in a solvent may be added as they are, or may be added as a solution. Those that are hardly soluble are preferably added after emulsification.

  In order to react the polar group-containing compound that reacts with the hydroxyl group with a natural rubber molecule obtained by hydrolyzing phospholipid, the polar group-containing compound and the reaction are promoted in a solution obtained by dissolving the natural rubber in a solvent such as toluene. Therefore, the polar group-containing compound is condensed on the end of the natural rubber molecule by stirring at a predetermined temperature. In addition, in the addition of the polar group-containing compound to the phospholipid-hydrolyzed natural rubber, an emulsifier may be added in advance to the solvent, or the polar group-containing compound may be added to the solvent after emulsification with the emulsifier. The emulsifier that can be used for emulsifying the phospholipid hydrolyzed natural rubber solution and / or the polar group-containing compound is not particularly limited, and examples thereof include nonionic surfactants such as polyoxyethylene lauryl ether.

  In order to improve low loss and wear resistance without degrading the processability of the rubber composition, it is important that the polar group-containing compound is uniformly introduced into each natural rubber molecule. Is preferably carried out with stirring. For example, a reaction component such as a phospholipid-hydrolyzed natural rubber and a polar group-containing compound is charged into a reaction vessel and reacted at 20 to 60 ° C. for 2 to 12 hours. A modified natural rubber in which a polar group-containing compound is condensed and added to is obtained.

  The polar group content of the modified natural rubber is preferably in the range of 0.0005 to 0.2% by mass, and more preferably in the range of 0.005 to 0.1% by mass with respect to the rubber component in the modified natural rubber. . If the content of the polar group of the modified natural rubber is 0.0005 to 0.2% by mass, the physical properties inherent to natural rubber such as viscoelasticity and SS characteristics (stress-strain curve in a tensile tester) can be obtained. It is possible to maintain and improve the low loss property and wear resistance of the rubber composition. Moreover, the processability of the rubber composition is good.

  By re-precipitation and recovery of the modified natural rubber obtained as described above using a poor solvent such as alcohol and water, washing, and drying using a dryer such as a vacuum dryer, air dryer, drum dryer, etc. Thus, a modified natural rubber in a solid state is obtained. The poor solvent for reprecipitation used to recover the modified natural rubber is not particularly limited, and examples thereof include water, alcohols such as ethanol and 2-propanol, acetone, and mixed solvents of these poor solvents. It is done.

  The modified natural rubber has a polystyrene-reduced weight average molecular weight of 200,000 or more as measured by gel permeation chromatography from the viewpoint of ensuring excellent low loss, wear resistance and breaking strength as a rubber composition. And more preferably 400,000 or more.

Next, the organosilicon compound used in the present invention will be described.
The organosilicon compound used in the present invention has a cyclic structure containing a nitrogen atom (N) and a silicon atom (Si) in the molecule and one or more sulfur atoms (S), and has a small steric hindrance. It is characterized by having a site where one or more groups are bonded to a silicon atom (Si). The organosilicon compound of the present invention has a cyclic structure including a nitrogen atom (N) and a silicon atom (Si), and the cyclic structure includes a silicon-oxygen bond (Si-O). It is stable. Therefore, the silicon-oxygen bond (Si—O) is not hydrolyzed to generate an alcohol component, and the volatile organic compound (VOC) gas in use can be reduced.

  The organosilicon compound used in the present invention contains a nitrogen-containing functional group such as an amino group, an imino group, a substituted amino group, or a substituted imino group that has a high affinity with the surface of an inorganic filler such as silica. Unshared electron pairs can participate in the reaction between the organosilicon compound and the inorganic filler, and the speed of the coupling reaction is high. However, when the cyclic structure containing a nitrogen atom (N) and a silicon atom (Si) is a bicyclic structure, since the steric hindrance around the silicon atom (Si) is large, the reactivity with the inorganic filler is low, Coupling efficiency is greatly reduced. Since the organosilicon compound used in the present invention has a site where one or more groups having small steric hindrance are bonded to a silicon atom, the organosilicon compound has high reactivity with an inorganic filler such as silica. Therefore, in place of the conventional silane coupling agent, by adding this organosilicon compound to the inorganic filler-containing rubber composition, the coupling efficiency is improved, and as a result, the hysteresis loss of the rubber composition is greatly increased. It is possible to greatly improve the wear resistance while lowering. In addition, since the organosilicon compound of the present invention has high addition efficiency, a high effect can be obtained even in a small amount, and it contributes to reduction of the blending cost.

In the present invention, the group having a small steric hindrance is preferably a hydrogen atom (—H), a methyl group (—CH ₃ ), and a hydroxyl group (—OH). When a hydrogen atom, a methyl group or a hydroxyl group is bonded to a silicon atom (Si), the reactivity between the organosilicon compound and the inorganic filler is particularly high, and the coupling efficiency can be greatly improved. Moreover, it is preferable that the organosilicon compound of this invention has 1-6 silicon-oxygen bonds (Si-O). When the organosilicon compound has 1 to 6 silicon-oxygen bonds (Si—O), the reactivity with an inorganic filler such as silica is high, and the coupling efficiency is further improved.

  Specifically, the organic silicon compound used in the present invention is preferably a compound represented by the following general formula (I). These organosilicon compounds may be used alone or in combination of two or more.

［式中、Ａは硫黄原子（Ｓ）を含み且つゴム成分と反応する基であり、
Ｒ¹及びＲ²はそれぞれ独立して−Ｍ−Ｃ_ｌＨ_２ｌ−（ここで、Ｍは−Ｏ−又は−ＣＨ_２−で、ｌは０〜１０である）で表わされ、但し、Ｒ^１及びＲ^２の一つ以上は、Ｍが−Ｏ−であり、Ｒ^３は水素原子、メチル基又はヒドロキシル基、Ｒ^４は−Ｃ_ｎＨ_２ｎ＋１であり、ｎは０〜２０である。］

[Wherein A is a group containing a sulfur atom (S) and reacting with a rubber component;
R ¹ and R ² are each independently represented by —M—C ₁ H _{2 1} — (wherein M is —O— or —CH ₂ —, and 1 is 0 to 10), provided that R 1 ^In one or more of ¹ and R ² , M is —O—, R ³ is a hydrogen atom, a methyl group or a hydroxyl group, R ⁴ is —C _n H _{2n + 1} , and n is 0 to 20. ]

In general formula (I), A is a group containing a sulfur atom (S) and reacting with a rubber component. In the organosilicon compound represented by the formula (I), the cyclic structure portion reacts with an inorganic filler such as silica. Therefore, the organosilicon compound further has a group that reacts with the rubber component in the molecule. It will have coupling ability. Here, the group containing a sulfur atom (S) and reacting with the rubber component is a polysulfide group, a thioester group, a thiol group, a dithiocarbonate group, a dithioacetal group, a hemithioacetal group, a vinylthio group, an α-thiocarbonyl group, It preferably contains at least one selected from the group consisting of β-thiocarbonyl group, S—CO—CH ₂ —O moiety, S—CO—CO moiety (thiodiketone group), and S—CH ₂ —Si moiety, It is particularly preferable that at least one of a polysulfide group and a thioester group is included.

In the general formula (I), R ¹ and R ² are each independently represented by —M—C ₁ H _{2 1} —, wherein M is —O— or —CH ₂ , and 1 is 0 to 10 It is. However, in one or more of R ¹ and R ² , M is —O—.
-C _l H _2l -is a single bond or an alkylene group having 1 to 10 carbon atoms, since l is 0 to 10, wherein the alkylene group having 1 to 10 carbon atoms is a methylene group or an ethylene group , Trimethylene group, propylene group and the like. The alkylene group may be linear or branched.

In the general formula (I), R ³ is a hydrogen atom, a methyl group or a hydroxyl group. Since R ³ has small steric hindrance, it greatly contributes to the improvement of the coupling reaction between the rubber component and the inorganic filler.

In the general formula (I), R ⁴ is —C _n H _{2n + 1} , and n is 0 to 20.
-C _n H _{2n + 1} is, for n is 0 to 20, hydrogen or an alkyl group having 1 to 20 carbon atoms. Here, as the alkyl group having 1 to 20 carbon atoms, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, decyl group, undecyl group, dodecyl group, nonadecyl group, And an eicosyl group. The alkyl group may be linear or branched.

[式（ＩＩ）中のＲ^１、Ｒ^２、Ｒ^３及びＲ^４は上記と同義であり、式（ＩＩ）、（ＩＩＩ）及び（ＩＶ）中のＲ^６は下記一般式（Ｖ）又は（ＶＩ） A in the general formula (I) is preferably represented by the following general formula (II), (III) or (IV).

[R ¹ , R ² , R ³ and R ⁴ in the formula (II) have the same meanings as above, and R ⁶ in the formulas (II), (III) and (IV) represents the following general formula (V) or ( VI)

（式中、Ｍ及びｌは上記と同義、ｍは０〜１０であり、Ｘ及びＹはそれぞれ独立して−Ｏ、−ＮＲ^４−又は−ＣＨ_２−で、Ｒ^８は−ＯＲ^４、−ＮＲ^４Ｒ^５又は−Ｒ^４で、Ｒ^９は−ＮＲ^４−、−ＮＲ^４−ＮＲ^４−又は−Ｎ＝Ｎ−であり、但し、Ｒ^４は上記と同義、Ｒ^５はＣｑＨ２ｑ＋１で、ｑは１〜１０である）或いは−Ｍ−Ｃ_ｌＨ_２ｌ−（Ｍ及びｌは上記と同義である）で表わされ、

(Wherein M and l are as defined above, m is 0 to 10, X and Y are each independently —O, —NR ⁴ — or —CH ₂ —, and R ⁸ is —OR ⁴ , — NR ⁴ R ⁵ or —R ⁴ , R ⁹ is —NR ⁴ —, —NR ⁴ —NR ⁴ — or —N═N—, wherein R ⁴ is as defined above, R ⁵ is CqH2q + 1, q 1 to 10 a is) or _{-M-C l H 2l} - is represented by (M and l have the same meanings as mentioned above),

（式中、Ｍ、Ｘ、Ｙ、Ｒ^８、ｌ及びｍは上記と同義、Ｒ^１０は−ＮＲ^４Ｒ^５、−ＮＲ^４−ＮＲ^４Ｒ^５、−Ｎ＝ＮＲ^４である）或いは−Ｃ_ｌＨ_２ｌ−Ｒ^１１（Ｒ^１１は−ＮＲ^４Ｒ^５、−ＮＲ^４−ＮＲ^４Ｒ^５、−Ｎ＝ＮＲ^４又は−Ｍ−Ｃ_ｍＨ_２ｍ＋１或いは炭素数６〜２０の芳香族炭化水素基であり、但し、Ｒ^４、Ｒ^５、Ｍ、ｌ及びｍは上記と同義である）で表わされ、
式（ＩＩ）及び（ＩＩＩ）中のｘは１〜１０であるが、好ましくは２〜４である。 R ⁷ in formula (III) is the following general formula (VII) or (VIII),

(Wherein, M, X, Y, R ⁸ , l and m are as defined above, and R ¹⁰ is —NR ⁴ R ⁵ , —NR ⁴ —NR ⁴ R ⁵ , —N = NR ⁴ ) or —C ₁ H _2l -R ¹¹ (R ¹¹ is -NR ⁴ R ⁵ , -NR ⁴ -NR ⁴ R ⁵ , -N = NR ⁴ or -M-C _m H _{2m + 1} or an aromatic hydrocarbon group having 6 to 20 carbon atoms. Wherein R ⁴ , R ⁵ , M, l and m are as defined above),
X in the formulas (II) and (III) is 1 to 10, preferably 2 to 4.

In the above formulas (V) and (VI), M is —O— or —CH ₂ —, and l and m are 0 to 10. In the formula (V), X and Y are each independently —O—, —NR ⁴ — or —CH ₂ —, and R ⁸ is —OR ⁴ , —NR ⁴ R ⁵ or —R ^4. Where R ⁴ is —C _n H _{2n + 1} and R ⁵ is —C _q H _{2q + 1} . Further, in the above formula (VI), R ⁹ is —NR ⁴ —, —NR ⁴ —NR ⁴ —, or —N═N—, wherein R ⁴ is —C _n H _{2n + 1} .
The -C _n H _{2n + 1,} are as described _above, -C _{m H 2m} -, since m is 0-10, a single bond or an alkylene group having 1 to 10 carbon atoms. Here, examples of the alkylene group having 1 to 10 carbon atoms include a methylene group, an ethylene group, a trimethylene group, and a propylene group, and the alkylene group may be linear or branched.
_Further, -C _{q H 2q + 1,} since q is 0, is hydrogen or an alkyl group having 1 to 10 carbon atoms. Here, examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a decyl group. It may be linear or branched.

R ⁷ in the above formula (III) is represented by the above general formula (VII) or (VIII), or —C ₁ H _2l —R ¹¹ , and particularly preferably represented by —C ₁ H _{2l + 1.} . However, M, X, Y, R ⁸ , R ¹⁰ , l and m are as defined above. Here, R ¹¹ is —NR ⁴ R ⁵ , —NR ⁴ —NR ⁴ R ⁵ , —N═NR ⁴ or —M—C _m H _{2m + 1,} or an aromatic hydrocarbon group having 6 to 20 carbon atoms, R ⁴ , R ⁵ , M, l and m are as defined above.
_{Incidentally,} -C _{l H 2l} - For are as described above, _also, -C _{m H 2m + 1,} since m is 0-10, is hydrogen or an alkyl group having 1 to 10 carbon atoms, carbon atoms Examples of the alkyl group of 1 to 10 include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, and the like. It may be branched. Examples of the aromatic hydrocarbon group having 6 to 20 carbon atoms include aryl groups such as phenyl group, tolyl group, xylyl group, cumenyl group, naphthylene group and tolylene group, and aralkyl groups such as benzyl group and phenethyl group. .

In the compound of the above formula (I), M is preferably —O— (oxygen). In this case, M is -CH ₂ - are highly reactive with an inorganic filler such as silica as compared to compounds wherein.

In the formula (I), R ¹ and R ² are preferably each independently represented by —O—C ₁ H _2l —, R ³ is a hydrogen atom, a methyl group or a hydroxyl group, and the above R ⁶ Is preferably represented by —CH ₂ —C ₁ H _2l —, and R ⁷ is a linear or branched alkyl group represented by —C ₁ H _2l —CH ₃ , or a group having 6 to 20 carbon atoms. An aromatic hydrocarbon group is preferred.

The organosilicon compound used in the present invention is, for example, a compound represented by (C _l H _{21 + 1} O) ₂ R ³ Si-A [wherein l, R ³ and A are as defined above], N An amine compound such as -methyldiethanolamine or N-ethyldiethanolamine is added, and an acid such as p-toluenesulfonic acid or hydrochloric acid or a titanium alkoxide such as titanium tetra-n-butoxide is added as a catalyst, followed by heating. _It can be synthesized by substituting ₁ H _{2l + 1} O- with a divalent group represented by -R ¹ -NR ⁴ -R ^2- .

  Specific examples of the organosilicon compound of the present invention include 3-octanoylthio-propyl (methyl) 1,3-dioxa-6-methylaza-2-silacyclooctane, bis (3- (methyl) 1,3-dioxa- 6-methylaza-2-silacyclooctyl-propyl) disulfide, 3-octanoylthio-propyl (hydroxy) 1,3-dioxa-6-methylaza-2-silacyclooctane, bis (3- (hydroxy) 1,3-dioxa -6-methylaza-2-silacyclooctyl-propyl) disulfide, 3-octanoylthio-propyl (hydro) 1,3-dioxa-6-methylaza-2-silacyclooctane, bis (3- (hydro) 1,3- Dioxa-6-methylaza-2-silacyclooctyl-propyl) disulfide, 3-octanoylthio-propyl (methyl) 1,3-dioxa-6-butylaza-2-silacyclo Octane, bis (3- (methyl) 1,3-dioxa-6-Buchiruaza 2-sila cyclooctyl - propyl) disulfide, and the like.

The rubber composition of the present invention comprises the modified natural rubber, an inorganic filler, and the organosilicon compound. In addition to the modified natural rubber, unmodified natural rubber and various synthetic rubbers can be included as the rubber component.
Although the compounding quantity of a filler is not specifically limited, The range of 5-140 mass parts is preferable with respect to 100 mass parts of said rubber components, and the range of 10-70 mass parts is still more preferable. When the blending amount of the filler is 5 to 140 parts by mass, the hysteresis is lowered and the workability is good.

  The organosilicon compound is blended in an amount of 1 to 20% by weight based on the blending amount of the inorganic filler. When the content of the organosilicon compound is 1 to 20% by mass of the blending amount of the inorganic filler, the effect of reducing the hysteresis loss of the rubber composition and improving the wear resistance is sufficient.

  Examples of the filler used in the rubber composition of the present invention include carbon black and inorganic filler. Examples of the carbon black include GPF, FEF, SRF, HAF, ISAF, and SAF grades.

As the inorganic filler, silica and the following formula (B):
aM _t · bSiO _c · dH ₂ O (B)
[Wherein, M _t represents a metal selected from the group consisting of aluminum, magnesium, titanium, calcium and zirconium, an oxide or hydroxide of these metals, and a hydrate thereof, or a carbonate of these metals. And a, b, c and d are each an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10]. Compounds. These fillers may be used alone or in combination of two or more.

Examples of the inorganic compound of the formula (B) include alumina (Al ₂ O ₃ ) such as γ-alumina and α-alumina; alumina monohydrate such as boehmite and diaspore (Al ₂ O ₃ .H ₂ O); gibbsite Aluminum hydroxide [Al (OH) ₃ ], such as bayerite; aluminum carbonate [Al ₂ (CO ₃ ) ₃ ], magnesium hydroxide [Mg (OH) ₂ ], magnesium oxide (MgO), magnesium carbonate (MgCO ₃ ), Talc (3MgO · 4SiO ₂ · H ₂ O), attapulgite (5MgO · 8SiO ₂ · 9H ₂ O), titanium white (TiO ₂ ), titanium black (TiO _2n-1 ), calcium oxide (CaO), hydroxylated calcium [Ca (OH) _2], magnesium aluminum oxide _{(MgO · Al 2 O 3)} , clay _{(Al 2 O 3 2SiO 2)} , Kaori _{(Al 2 O 3 · 2SiO 2} · 2H 2 O), pyrophyllite _{(Al 2 O 3 · 4SiO 2} · H 2 O), bentonite _{(Al 2 O 3 · 4SiO 2} · 2H 2 O), aluminum silicate ( Al ₂ SiO ₅ , Al ₄ .3SiO ₄ .5H ₂ O, etc., magnesium silicate (Mg ₂ SiO ₄ , MgSiO ₃ etc.), calcium silicate (Ca ₂ SiO ₄ etc.), aluminum calcium silicate (Al ₂ O ₃ · CaO · 2SiO ₂ etc.), magnesium calcium silicate (CaMgSiO ₄ ), calcium carbonate (CaCO ₃ ), zirconium oxide (ZrO ₂ ), zirconium hydroxide [ZrO (OH) ₂ · nH ₂ O], zirconium carbonate [ Zr (CO _{3) 2],} corrected for hydrogen, an alkali metal or alkaline earth charge as various zeolites It can be mentioned crystalline aluminosilicate or the like including a genus.

  Examples of the inorganic filler include silica, aluminum hydroxide, alumina, clay, calcium carbonate and the like. Among these, silica and aluminum hydroxide are preferable, and silica is particularly preferable from the viewpoint of reinforcement. When the inorganic filler is silica, the organosilicon compound has a functional group having a high affinity with a silanol group on the silica surface and / or a functional group having a high affinity with a silicon atom (Si). The effect of improving significantly, reducing the hysteresis loss of a rubber composition, and improving abrasion resistance becomes more remarkable. Silica is not particularly limited, and wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid) and the like can be used. On the other hand, as aluminum hydroxide, Heidilite (registered trademark, manufactured by Showa Denko) Is preferably used.

Silica preferably has a BET surface area of 40 to 350 m ² / g. When the BET surface area of silica is within this range, the particle diameter of silica is appropriate, and wear resistance is improved and hysteresis loss is reduced.

In the rubber composition of the present invention, in addition to the rubber component, inorganic filler and organosilicon compound, compounding agents usually used in the rubber industry, such as anti-aging agents, softeners, stearic acid, zinc white, Vulcanization accelerators, vulcanizing agents, and the like can be appropriately selected and blended within a range that does not impair the object of the present invention. As these compounding agents, commercially available products can be suitably used.
The rubber composition of the present invention is prepared by blending rubber components including modified natural rubber, inorganic fillers and organic silicon compounds with various compounding agents appropriately selected as necessary, kneading, heating, extruding, etc. Can be manufactured.

  The tire of the present invention is characterized by using the rubber composition, and the rubber composition is preferably used for a tread. A tire using the rubber composition as a tread has a significantly reduced rolling resistance and is excellent in fracture characteristics and wear resistance. The tire of the present invention is not particularly limited except that the rubber composition is used for any of the tire members, and can be produced according to a conventional method. Moreover, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

Production Example 1
Production of modified natural rubber A (oxidized natural rubber production process)
The field latex was centrifuged using a latex separator [manufactured by Saito Centrifugal Industries Co., Ltd.] at a rotational speed of 7500 rpm to obtain a concentrated latex having a dry rubber concentration of 60%. 1000 g of this concentrated latex was put into a stainless steel reaction vessel equipped with a stirrer and a temperature control jacket, and 1000 g of water was added. Thereafter, 9.0 g of potassium persulfate and 3.0 g of propionaldehyde were added and reacted with stirring at 60 ° C. for 30 hours to obtain an oxidized natural rubber latex. Next, formic acid was added to adjust the pH to 4.7 to coagulate. This solid was treated 5 times with a creper and crushed through a shredder.
(Modification process)
After determining the dry rubber content of the obtained coagulum, 600 g of the coagulum and an emulsion solution of 3.0 g of isonicotinohydrazide in terms of dry rubber were mixed at 30 rpm at room temperature in a kneader (prebreaker). A modified natural rubber A was obtained by kneading for a minute and uniformly dispersing and drying. Further, when the modified natural rubber A was extracted with petroleum ether and further extracted with a 2: 1 mixed solvent of acetone and methanol, an unreacted hydrazide compound was separated. No hydrazide compound was detected, and therefore the amount of isonicotinohydrazide added to the modified natural rubber A was 0.50% by mass relative to the rubber component in the natural rubber latex. In addition, gel permeation chromatography [GPC: Tosoh HLC-8020, column: Tosoh GMH-XL (two in series), detector: differential refractometer (RI)] modified with a monodisperse polystyrene as a standard When the weight average molecular weight (Mw) of rubber A in terms of polystyrene was determined, Mw was 873,000.

Production Examples 2-3
Production of modified natural rubbers B and C Instead of 3.0 g of isonicotinohydrazide, 3.0 g of 3- (dimethylamino) propionic acid hydrazide was produced in Production Example 2, and 3.3 g of 4-hydroxybenzohydrazide was added in Production Example 3. Otherwise, modified natural rubbers B and C were obtained in the same manner as in Example 1 above. Further, in the same manner as in the modified natural rubber A, the addition amount and the weight average molecular weight (Mw) of the polar group-containing hydrazide compound in the modified natural rubbers B and C were determined. In modified natural rubber B, they were 0.50 mass% and 906000, respectively, and in modified natural rubber C, they were 0.55 mass% and 890000, respectively.

Production Example 4
Preparation of organosilicon compound A In a 500 ml four-necked flask, weigh 60 g of 3-octanoylthio-propyldiethoxymethylsilane, 20 g (1.02 eq) of N-methyldiethanolamine, 0.8 g of titanium tetra-n-butoxide, and 220 ml of toluene. . While stirring with a mechanical stirrer, while flowing dry nitrogen (0.2 l / min), the flask was heated in an oil bath, a Dimroth condenser was attached, and reflux was performed for 11 hours. Thereafter, the solvent was removed by a rotary evaporator at 20 hPa / 40 ° C., and then the remaining volatile components were removed by a rotary pump (10 Pa) and a cold trap (dry ice + ethanol) to obtain 70 g of a yellow transparent liquid organic silicon. Compound A was obtained. It was confirmed that the liquid obtained as a result of analysis by gas chromatography (GC) was composed of 10% raw material and 90% target product. Furthermore, it was analyzed resulting liquid with _{^{1 H-NMR, 1 H-}} NMR (CDCl 3, 700MHz, δ; ppm) = 3.8 (m; 4H), 2.8 (t; 2H), 2 .5 (m; 6H), 2.4 (m; 3H), 1.6 (m; 4H), 1.3 (m; 8H), 0.8 (t; 3H), 0.7 (t; 2H), 0.1 (s; a 3H), represented by formula (I), a is formula (III), in ^{R 4} is -CH _3, ^{R 1} is _{-O-CH 2 CH} 2 - (however, linked to the O side is Si), ^{R 2} is _{-O-CH 2 CH} 2 - (provided that connected to O side is Si), ^{R 3} is _-CH 3, ^{R 6} is _-CH 2 _CH 2 CH ₂ - in, ^{R 7} is _-C 7 _{H 15,} x is 1 compound [i.e., 3'-octanoylthio - propyl - (1-methyl) -1,3-dioxa-6-Mechiruaza 2- It was found that La is cyclooctane.

Production Example 5
Production of organosilicon compound B In a 500 ml four-necked flask, 40 g of bis (3-diethoxymethylsilylpropyl) disulfide, 20 g of N-methyldiethanolamine (1.02 eq), 0.8 g of titanium tetra-n-butoxide, 220 ml of toluene Weigh. While stirring with a mechanical stirrer, while flowing dry nitrogen (0.2 l / min), the flask was heated in an oil bath, a Dimroth condenser was attached, and reflux was performed for 11 hours. Thereafter, the solvent is removed by a rotary evaporator at 20 hPa / 40 ° C., then the remaining volatile components are removed by a rotary pump (10 Pa) and a cold trap (dry ice + ethanol), and 50 g of yellow transparent liquid organosilicon Compound B was obtained. It was confirmed that the liquid obtained as a result of analysis by gas chromatography (GC) was composed of 10% raw material and 90% target product. Moreover, when the obtained liquid was analyzed by ¹ H-NMR,
¹ H-NMR (CDCl ₃ , 700 MHz, δ; ppm) = 3.8 (m; 8H), 2.7 (t; 4H), 2.5 (m; 8H), 2.4 (m; 6H) , 1.8 (m; 4H), 0.7 (t; 4H), 0.1 (s; 6H), represented by formula (I), A is formula (II), R ⁴ Is —CH ₃ , R ¹ is —O—CH ₂ CH ₂ — (where the O side is linked to Si), R ² is —O—CH ₂ CH ₂ — (where the O side is linked to Si), and R ³ is Compound in which —CH ₃ , R ⁶ is —CH ₂ CH ₂ CH ₂ —, and x is 2 [ie, bis (2- (methyl) 1,3-dioxa-6-methylaza-2-silacyclooctyl-propyl) Disulfide].

Examples 1-6 and Comparative Examples 1-6
A rubber composition having a formulation according to Table 1 was prepared by kneading with a Banbury mixer.

In each example and comparative example, the rubber composition was vulcanized at 145 ° C. for 33 minutes, and the loss coefficient (tan δ), storage elastic modulus (G ′), and wear resistance of the vulcanized rubber were determined by the following methods. evaluated. The results are shown in Table 1.

(1) Storage elastic modulus (G ′) and loss factor (tan δ)
Using a spectrometer (dynamic viscoelasticity measuring tester) manufactured by Ueshima Seisakusho, tan δ of vulcanized rubber was measured at a frequency of 52 Hz, an initial strain of 10%, a measurement temperature of 60 ° C., and a dynamic strain of 1%. The index was expressed as 100. The smaller the index value, the lower the tan δ, the lower the loss of the rubber composition, and the higher the storage modulus, the better the steering stability.

(2) Abrasion resistance A rubber composition was vulcanized at 145 ° C. for 33 minutes, vulcanized in accordance with JIS K 6264-2: 2005, using a Lambone-type abrasion tester, at room temperature, with a slip ratio of 25 The test was performed under the condition of%, and the index was displayed with the reciprocal of the wear amount of Comparative Example 1 being 100. The larger the index value, the smaller the wear amount and the better the wear resistance.

1 Modified natural rubbers A to C were produced in Production Examples 1 to 3,
2 Natural rubber D is natural rubber latex solidified as it is 3 Made by Asahi Carbon, # 80
4 Nippon Silica Kogyo Co., Ltd., nip seal AQ,
BET surface area = 220 m ² / g
5 Bis (3-triethoxysilylpropyl) disulfide 6 3-octanoylthio-propyltriethoxysilane 7 Organosilicon compound produced in Production Examples 4 to 5 8 Nouchi 6C manufactured by Ouchi Shinsei Chemical Industry
9 Nouchi 224, manufactured by Ouchi Shinsei Chemical
10 Sanshin Chemical Industry, Sunceller D
11 Sunseller DM, manufactured by Sanshin Chemical Industry
12 Sunseller NS, made by Sanshin Chemical Industry

  From Table 1, the rubber composition containing either one of the modified natural rubber and the organic silicon compound, or only one of them, drastically reduces tan δ, that is, greatly reduces hysteresis loss, thereby reducing heat generation. However, it can be seen that the storage elastic modulus (G ′) is large, the steering stability is improved, and the wear resistance can be greatly improved.

Claims (25)

  A modified natural rubber having a polar group at the end of the molecular chain, a cyclic structure containing a nitrogen atom and a silicon atom in the molecule, one or more sulfur atoms, and at least one silicon atom having a small steric hindrance A rubber composition comprising an organosilicon compound having a portion bonded to the surface.   2. The rubber composition according to claim 1, wherein the modified natural rubber is a modified natural rubber in which a polar group-containing hydrazide compound is added after oxidizing natural rubber latex and a polar group is introduced at a molecular end. .   The rubber composition according to claim 2, wherein the natural rubber latex is oxidized by adding a carbonyl compound to the natural rubber latex and subjecting it to air oxidation.   The rubber composition according to claim 3, wherein the carbonyl compound is an aldehyde and / or a ketone.   The rubber composition according to claim 3 or 4, wherein the air oxidation is performed in the presence of a radical generator.   6. The rubber composition according to claim 5, wherein the radical generator is selected from the group consisting of a peroxide radical generator, a redox radical generator, and an azo radical generator.   The polar group of the polar group-containing hydrazide compound is amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxy group 7. The rubber according to claim 2, wherein the rubber is at least one selected from the group consisting of a carbonyl group, a nitrogen-containing heterocyclic group, an oxygen-containing heterocyclic group, a tin-containing group and an alkoxysilyl group. Composition.   The addition amount of the polar group-containing hydrazide compound in the modified natural rubber is 0.01 to 5.0% by mass with respect to the rubber content in the natural rubber latex. The rubber composition as described. The rubber composition according to any one of claims 1 to 7, comprising a modified natural rubber having a polar group represented by the general formula (A) at the end of the molecular chain of the natural rubber.

[In the formula, R is an amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxy as a substituent. A C1-C4 alkyl group having at least one polar group selected from the group consisting of a carbonyl group, a tin-containing group and an alkoxysilyl group, a phenyl group having at least one polar group as a substituent, or a nitrogen-containing complex It is at least one polar group selected from the group consisting of a cyclic group and an oxygen-containing heterocyclic group. ]   The modified natural rubber is a modified natural rubber obtained by hydrolyzing a phospholipid of a natural rubber molecule and then condensing a polar group-containing compound to introduce a polar group at the end of the natural rubber molecule. Rubber composition.   The rubber composition according to claim 10, wherein the polar group-containing compound is a compound having a group that reacts with a hydroxyl group.   The rubber composition according to claim 11, wherein the group that reacts with a hydroxyl group is a carboxyl group, an aldehyde group, a carbonyl group, an alkoxyl group, a hydroxyl group, and an isocyanato group.   The rubber composition according to claim 12, wherein the group that reacts with a hydroxyl group is a carboxyl group.   The polar group of the polar group-containing compound is amino group, imino group, nitrile group, ammonium group, imide group, amide group, hydrazo group, azo group, diazo group, hydroxyl group, carboxyl group, carbonyl group, epoxy group, oxycarbonyl It is at least one selected from the group consisting of a group, a thiol group, a nitrogen-containing heterocyclic group, an oxygen-containing heterocyclic group, a tin-containing group, and an alkoxysilyl group. Rubber composition.   The rubber composition according to any one of claims 10 to 14, wherein the addition amount of the polar group-containing compound is 0.0005 to 0.20 mass% with respect to the natural rubber component in the natural rubber latex. .   The rubber composition according to any one of claims 1 to 15, wherein 20 parts by mass or more of modified natural rubber is contained in 100 parts by mass of the rubber component of the rubber composition.   The rubber composition according to claim 1, wherein the group having a small steric hindrance in the organosilicon compound is at least one selected from the group consisting of a hydrogen atom, a methyl group and a hydroxyl group. The rubber composition according to claim 1, wherein the organosilicon compound is a compound represented by the following general formula (I).

[Wherein A represents the following general formula (II), formula (III) or formula (IV):

(In Formula (II) and Formula (III), x is 1 to 10)
R ⁶ in formula (II), formula (III), and formula (IV) represents the following general formula (V), formula (VI), or -M-C ₁ H _{2 1-} :

R ⁷ in the formula (III) is represented by the following general formula (VII), formula (VIII), or -C ₁ H ₂₁ -R ¹¹ :

And in common throughout formulas (I)-(VIII), each independently,
R ¹ and R ² are each independently —M—C ₁ H ₂ ¹ — (wherein one or more of R ¹ and R ² is M is —O— in the definitions below),
R ³ is a hydrogen atom, a methyl group or a hydroxyl group,
R ⁴ is -C _n H _{2n + 1} ,
R ⁵ is -C _q H _{2q + 1} ,
R ⁸ is —OR ⁴ , —NR ⁴ R ⁵ or —R ⁴ ,
R ⁹ represents —NR ⁴ —, —NR ⁴ —NR ⁴ —, or —N═N—,
R ¹⁰ represents —NR ⁴ R ⁵ , —NR ⁴ —NR ⁴ R ^5, or —N═NR ⁴ ,
R ¹¹ is —NR ⁴ R ⁵ , —NR ⁴ —NR ⁴ R ⁵ , —N═NR ⁴ or —M—C _m H _{2m + 1,} or an aromatic hydrocarbon group having 6 to 20 carbon atoms is —O— or — CH ₂ -,
l, m, and q are each independently 0 to 10,
n is 0 to 20,
X and Y each independently represent —O—, —NR ⁴ — or —CH ₂ —. In the organosilicon compound, A in the formula (I) is represented by the formula (II), and R ¹ and R ² in the formula are independently —O—C ₁ H _2l —, and R ⁶ is —CH ₂ —C. The rubber composition according to claim 18, wherein the rubber composition is an organosilicon compound represented by ₁ H _2l- (l is independently 0 to 10). In the organosilicon compound, A in formula (I) is represented by formula (III), R ¹ and R ² in the formula are independently —O—C ₁ H _2l —, and R ⁶ is —CH ₂ —C. _l H _2l -, ^{R 7} is _{-C l H 2l -CH 2 -C m} H 2m + 1 (l each independently 0, m is 0-10)
The rubber composition according to claim 18, wherein the rubber composition is an organosilicon compound represented by the formula:   21. A rubber composition, wherein an inorganic filler is further added to the rubber composition according to any one of claims 1 to 20.   The rubber composition according to claim 21, wherein 5 to 140 parts by mass of an inorganic filler is blended with 100 parts by mass of the rubber component, and 1 to 20% by mass of an organic silicon compound is blended with the inorganic filler. object.   The rubber composition according to claim 21 or 22, wherein the inorganic filler is silica or aluminum hydroxide. 24. The rubber composition according to claim 23, wherein the silica has a BET surface area of 40 to 350 m ² / g.   A tire using the rubber composition according to any one of claims 1 to 24.