JP6378131B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire having a specific sidewall.

By blending microfibrillated plant fibers such as cellulose fibers into the rubber composition as a filler, the rubber composition can be reinforced and the modulus (complex modulus) can be improved. However, since the microfibrillated plant fiber has a strong self-aggregating power and poor compatibility with the rubber component, the dispersibility during rubber kneading is low. Therefore, even if it mix | blends, a fracture | rupture characteristic and low-fuel-consumption property may deteriorate, and the method of improving the dispersibility of microfibrillated plant fiber is calculated | required.

In addition, the cellulose fiber aggregates when dried from the aqueous dispersion, and there is a problem that the cellulose fiber is not dispersed at the nano level when mixed with rubber. For this reason, it was difficult to improve the breaking strength and reduce the rolling resistance. In order to disperse cellulose fibers in rubber, a treatment method has been proposed in which cellulose fibers are once dispersed in water, and then rubber latex is added thereto, stirred, and then dried. (For example, refer to Patent Document 1).

In addition, for the purpose of improving the dispersibility of cellulose fibers in rubber, attempts have been made to use compatibilizers, modify cellulose fibers, or use defibrating resins.

For example, Patent Document 2 discloses a method for improving the compatibility between rubber and microfibril cellulose by chemically modifying microfibril cellulose.
In Patent Document 3, a cellulose fiber is modified to introduce a vinyl group, and a cross-linking relationship is generated between the cellulose fiber and the rubber component via the vinyl group, thereby improving the affinity between the two. A method for improving the dispersibility of cellulose fibers therein is disclosed.

JP2013-204010A JP 2009-084564 A JP 2010-254925 A

As described above, various studies have been conducted on methods for improving the dispersibility of cellulose fibers in rubber. However, for example, the technique of Patent Document 1 is effective for dispersing cellulose fibers, but has a problem that the type of rubber used is limited to latex. Further, the methods of Patent Documents 2 and 3 have room for improvement in that there is no advantage in using cellulose fibers in place of conventional fillers such as carbon black in terms of reinforcement and cost.

Thus, there has been room for further improvement in order to improve the dispersibility of cellulose fibers in rubber, to obtain a rubber composition having excellent breaking characteristics and low energy loss.

The present invention solves the above problems and uses a modified cellulose fiber-containing rubber composition that achieves both excellent rigidity and breaking characteristics and low energy loss by improving the dispersibility of cellulose fibers in rubber. Another object of the present invention is to provide a pneumatic tire having a sidewall having excellent balance in handling stability, rolling resistance characteristics and durability, and also having excellent resistance to flex crack growth.

The present invention relates to a modified cellulose fiber (A) esterified by adding a cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group to cellulose fiber, a dispersion having a softening point of 135 ° C. or less It is related with the pneumatic tire which has a side wall produced using the modified | denatured cellulose fiber containing rubber composition containing the polymer (B) for rubber | gum, and a rubber component (C).

The cyclic polybasic acid anhydride (a) is preferably at least one selected from the group consisting of an acid anhydride group-containing petroleum resin and an acid anhydride group-containing coal resin.

The dispersing polymer (B) is preferably at least one selected from the group consisting of petroleum resins and coal resins.

The rubber component (C) is preferably at least one selected from the group consisting of natural rubber, modified natural rubber, synthetic rubber, and modified synthetic rubber.

The content of the modified cellulose fiber (A) is preferably 0.01 to 30 parts by mass with respect to 100 parts by mass of the rubber component (C).

The modified cellulose fiber-containing rubber composition is obtained by kneading the modified cellulose fiber (A) and the dispersing polymer (B) to obtain a kneaded product, and then kneading the kneaded product and the rubber component (C). Is preferably obtained.

According to the present invention, a modified cellulose fiber (A) esterified by adding a cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group to a cellulose fiber, the softening point is 135 ° C. or less. Since it is a pneumatic tire having a sidewall produced using a modified cellulose fiber-containing rubber composition containing the polymer (B) for dispersion and the rubber component (C), in the modified cellulose fiber-containing rubber composition, The dispersibility of cellulose fibers in rubber is improved, and both excellent rigidity and breaking characteristics and low energy loss are compatible, so that the handling stability, rolling resistance characteristics and durability are excellently balanced, and bending resistance is further improved. A pneumatic tire having a sidewall having excellent crack growth properties. Furthermore, normally, when cellulose fibers are blended with the rubber composition, the cellulose fibers are arranged in the extrusion direction (tire circumferential direction), so that the rigidity in the extrusion direction is improved, but the direction orthogonal to the extrusion direction (tire radial direction) However, according to the present invention, not only the rigidity in the tire circumferential direction but also the rigidity in the tire radial direction can be improved, and a sidewall having excellent driving stability can be obtained. A pneumatic tire having the same can be obtained. This is considered to be due to the good dispersibility of cellulose fibers in rubber.

In the present specification, the tire circumferential direction and the tire radial direction are specifically the directions described in FIG. 1 of JP-A-2009-202865.

The pneumatic tire of the present invention is a modified cellulose fiber (A) esterified by adding a cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group to a cellulose fiber, and has a softening point of 135 ° C. It has the side wall produced using the modified | denatured cellulose fiber containing rubber composition containing the polymer (B) for dispersion | distribution which is the following, and a rubber component (C).

First, a modified cellulose fiber-containing rubber composition for producing a sidewall will be described.
The modified cellulose fiber-containing rubber composition in the present invention is a modified cellulose fiber (A) esterified by adding a cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group to the cellulose fiber, softening It contains a dispersing polymer (B) having a point of 135 ° C. or lower, and a rubber component (C).

The modified cellulose fiber (A) used in the present invention is a cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group (hereinafter simply referred to as “cyclic polybasic acid anhydride (a)”, “ It is obtained by adding acid anhydride (a) ") to cellulose fibers.

Cellulose fibers that can be used to obtain the modified cellulose fiber (A) are not particularly limited, but for example, plant-derived fibers contained in wood, bamboo, hemp, jute, kenaf, cotton, beet, etc., the plant Examples thereof include pulp obtained from the fibers derived from the cellulose, cellulose fibers subjected to mercerization, regenerated cellulose fibers such as rayon, cellophane, and lyocell, and acid anhydride-modified cellulose. Among these, preferable examples of the cellulose fiber material include wood, and examples thereof include sitka spruce, cedar, cypress, eucalyptus, and acacia. And the pulp and paper obtained by using these as raw materials, or the thing which disentangled waste paper is used suitably as a cellulose fiber. A cellulose fiber may be used individually by 1 type, and may use 2 or more types chosen from these.

Examples of the pulp include chemical pulp (kraft pulp (KP), sulfite pulp (SP)), semi-chemical obtained by pulping the plant raw material chemically or mechanically, or a combination of both. Pulp (SCP), Chemi-Grand Pulp (CGP), Chemi-Mechanical Pulp (CMP), Groundwood Pulp (GP), Refiner Mechanical Pulp (RMP), Thermomechanical Pulp (TMP), Chemi-thermomechanical Pulp (CTMP), etc. .

The cellulose fiber has desired characteristics without significantly affecting the reactivity and degree of substitution with a cyclic polybasic acid anhydride (a) having a hydrophobic group having 15 or more carbon atoms, compatibility with rubber, and the like. As long as it does not interfere with obtaining a rubber composition, a hydroxyl group partially substituted with a functional group such as esterification of a hydroxyl group or a carboxyl group may be used. In addition, water contained in the cellulose fiber is previously substituted with a solvent such as toluene or N-methylpyrrolidone so as not to inhibit the reaction with the cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group. It is preferable to keep it.

The cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group used in the present invention has a hydrophobic group in the main chain and / or side chain of the cyclic polybasic acid anhydride, Although it will not specifically limit if a number is 15 or more, 20 or more are preferable. When the number of carbon atoms is less than 15, the compatibility of the modified cellulose fiber (A) with the rubber cannot be improved, and as a result, the rubber composition has excellent rigidity and breaking characteristics and low energy loss. It cannot be made compatible. Further, the upper limit of the carbon number in the cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group is not particularly limited. For example, 1500 is preferable, 200 is more preferable, and 30 is more preferable. preferable. When the carbon number exceeds 1500, it is difficult to knead the resulting modified cellulose fiber (A) with the dispersing polymer (B) and the rubber component (C), and the dispersion of the modified cellulose fiber (A) becomes insufficient. In the rubber composition, there is a possibility that both excellent rigidity and breaking characteristics and low energy loss cannot be achieved.

The cyclic polybasic acid anhydride (a) has a hydrophobic group in the main chain and / or side chain of the cyclic polybasic acid anhydride.

The cyclic polybasic acid anhydride may be a polybasic acid anhydride in which dehydration condensation occurs in the same molecule of the polybasic acid or between two or more polybasic acids to form a cyclic structure. There is no particular limitation. Of these, polybasic acid anhydrides in which dehydration condensation occurs in the same molecule of the polybasic acid and a cyclic structure is formed are preferred.

Examples of the polybasic acid include tribasic acids such as aconitic acid and trimellitic acid; dibasic acids such as succinic acid, itaconic acid, maleic acid, fumaric acid and citraconic acid. Of these, dibasic acids are preferable, dicarboxylic acids such as succinic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid are more preferable, and succinic acid and maleic acid are still more preferable.

Examples of the cyclic polybasic acid anhydride include cyclic carboxylic acid anhydrides having 4 to 10 carbon atoms (preferably 4 to 6) such as succinic anhydride, maleic anhydride, citraconic anhydride, and itaconic anhydride. Can be mentioned. Among these, succinic anhydride and maleic anhydride are preferably used from the viewpoint of poor homopolymerization of the polybasic acid anhydride itself and ease of reaction with the hydrophobic group.

Although it does not specifically limit as long as it has hydrophobicity as a hydrophobic group which the said cyclic polybasic acid anhydride (a) has, For example, a hydrocarbon group, petroleum-type resin, coal-type resin etc. are mentioned.
The hydrocarbon group may be linear or branched, but is preferably linear from the viewpoint of hydrophobicity of the cyclic polybasic acid anhydride (a).
The hydrocarbon group preferably has 11 or more carbon atoms, more preferably 15 or more carbon atoms. The number of carbon atoms of the hydrocarbon group is preferably 1500 or less, more preferably 200 or less, and even more preferably 30 or less. When the number of carbon atoms of the hydrocarbon group is within the above range, the cyclic polybasic acid anhydride (a) can be imparted with appropriate hydrophobicity, and thus the effects of the present invention can be obtained more suitably.

Examples of the hydrocarbon group include an alkyl group, an alkenyl group, and an alkynyl group. Among these, an alkenyl group is more preferable because it can impart moderate hydrophobicity to the cyclic polybasic acid anhydride (a).

Examples of the alkenyl group include dodecenyl group, hexadecenyl group, and octadecenyl group. Among these, a hexadecenyl group and an octadecenyl group are preferable because moderate hydrophobicity can be imparted to the cyclic polybasic acid anhydride (a).

On the other hand, the case where the hydrophobic group of the cyclic polybasic acid anhydride (a) is a petroleum resin means the case where the cyclic polybasic acid anhydride (a) is an acid anhydride group-containing petroleum resin. Moreover, the case where the hydrophobic group which cyclic polybasic acid anhydride (a) has is a coal-based resin means the case where cyclic polybasic acid anhydride (a) is an acid anhydride group-containing coal-based resin. The petroleum resin, acid anhydride group-containing petroleum resin, coal resin, and acid anhydride group containing coal resin will be described later.

Examples of the cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group include dodecenyl succinic anhydride, hexadecenyl succinic anhydride, octadecenyl succinic anhydride, and the like. And cyclic carboxylic acid anhydrides having 15 or more carbon groups; acid anhydride group-containing petroleum resins; acid anhydride group-containing coal resins, and the like.
In addition, as a kind of C15 or more cyclic polybasic acid anhydride (a) which has a hydrophobic group to be used, according to the kind of rubber component (C) used for the modified cellulose fiber containing rubber composition in this invention. The cyclic polybasic acid anhydride (a) is at least one selected from the group consisting of acid anhydride group-containing petroleum resins and acid anhydride group-containing coal resins. Is also a preferred embodiment of the present invention, and more preferably an acid anhydride group-containing petroleum resin.

The acid anhydride group-containing petroleum resin is a petroleum resin having an acid anhydride ring obtained by grafting a cyclic polybasic acid anhydride onto a petroleum resin and having 15 or more carbon atoms, and is known in the art. Obtained by grafting reaction. The acid anhydride group-containing coal-based resin is a coal-based resin having an acid anhydride ring obtained by grafting a cyclic polybasic acid anhydride to the coal-based resin and having 15 or more carbon atoms, Similarly, it can be obtained by a known graft reaction.
For example, a petroleum-based resin or coal-based resin and a cyclic polybasic acid anhydride (for example, maleic anhydride) can be grafted using an organic peroxide and purified. In the graft reaction, an organic solvent that does not react with the cyclic polybasic acid anhydride may be used. From the change of the acid value after the reaction purification with respect to the petroleum-based resin or the coal-based resin before the reaction, it can be confirmed that it is an acid anhydride group-containing petroleum-based resin or an acid anhydride group-containing coal-based resin.

Examples of the petroleum resins include C5 petroleum resins, C9 petroleum resins, C5C9 petroleum resins, dicyclopentadiene resins, and hydrides thereof. Use one or more of these in combination. Can do. Among these, C5C9 petroleum resin is particularly preferable.

Examples of the coal-based resin include coumarone resin, coumarone indene resin, hydrides thereof, and the like, and these can be used alone or in combination.

The cyclic polybasic acid anhydride used to obtain the acid anhydride group-containing petroleum resin or acid anhydride group-containing coal resin has an acid anhydride ring by grafting to the petroleum resin or coal resin. There is no particular limitation as long as petroleum-based resin or coal-based resin is obtained. In order to advance the graft reaction, any carbon-carbon unsaturated bond may be used. For example, maleic anhydride, citraconic anhydride, itaconic anhydride Examples thereof include carbon-carbon unsaturated bond-containing cyclic carboxylic acid anhydrides having 4 to 10 carbon atoms (preferably 4 to 6 carbon atoms) such as acids. Among these, maleic anhydride is preferably used from the viewpoint of graft reactivity with petroleum-based resins and coal-based resins.

Furthermore, examples of the organic peroxide include t-butyl peroxide, t-butyl peroxypivalate, dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanate. , T-butylperoxy-2-ethylhexanate, dibenzoyl peroxide, t-butylperoxylaurate, dicumyl peroxide, di-t-hexyl peroxide, etc., among which dialkyl peroxide Dicumyl peroxide is preferably used. Examples of the organic solvent include saturated aliphatic hydrocarbons such as hexane, heptane, and octane, saturated alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, and methylcycloheptane. Aromatic hydrocarbons that do not contain ethylenic double bonds such as toluene, xylene, ethylbenzene, alkylene glycol alkyl ether alkylates such as ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, diethylene glycol Dialkylene glycol alkyl ether alkylates such as monoethyl ether acetate and diethylene glycol monobutyl ether acetate, ethyl acetate, Alkyl alkylates such as propyl acid, butyl acetate, ethyl propionate, propyl propionate, and butyl propionate can be used. Among them, alkyl alkylates, alkylene glycol alkyl ether alkylates, dialkylene glycol alkyl ether alkylates Preferably used.

The molecular weight of the acid anhydride group-containing petroleum resin and the acid anhydride group-containing coal resin is not particularly limited, but is preferably 400 to 20000, more preferably 500 to 2000 in terms of polystyrene-converted weight average molecular weight measured by gel permeation chromatography. 9,000, more preferably 600-6000. When the weight average molecular weight is less than 400, the compatibility of the modified cellulose fiber (A) with the rubber cannot be improved, and as a result, the rubber composition has excellent rigidity and breaking characteristics and low energy loss. May not be compatible. If the weight average molecular weight exceeds 20000, the viscosity of the resin usually increases, so that it is difficult to knead the resulting modified cellulose fiber (A) with the dispersing polymer (B) or rubber component (C). Dispersion of the cellulose fiber (A) becomes insufficient, and there is a possibility that excellent rigidity and breaking characteristics and low energy loss cannot be made compatible in the rubber composition.

The modified cellulose fiber (A) is obtained by adding a cyclic polybasic acid anhydride (a) having a hydrophobic group having 15 or more carbon atoms to the cellulose fiber and esterifying it (modification reaction). The method for the esterification reaction is not particularly limited, and can be performed by a method that is usually performed as a method for performing the esterification reaction. For example, it can be performed by any of the following methods. The obtained modified cellulose fiber (A) can be usually used for the production of a modified cellulose fiber-containing rubber composition by removing the solvent and catalyst by washing such as filtration and washing with water.
(I) A cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group is added sequentially or collectively in a dispersion in which cellulose fibers previously substituted with a solvent are dispersed, and reacted.
(II) The cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a melted hydrophobic group and the cellulose fiber are mixed and reacted.

The addition rate of the acid anhydride (a) to the cellulose fiber is preferably 5 to 150% by mass, more preferably 10 to 100% by mass in consideration of addition efficiency and rubber affinity.
In addition, the addition rate with respect to the cellulose fiber of an acid anhydride (a) can be calculated by the calculation method performed in the Example mentioned later.

The polymer for dispersion (B) used in the present invention has a softening point of 135 ° C. or less in a ring and ball test based on JIS K2207. When the softening point exceeds 135 ° C., it is difficult to knead the modified cellulose fiber (A) into the rubber component (C) that becomes the matrix when preparing the modified cellulose fiber-containing rubber composition, and the dispersion becomes insufficient. In the composition, it is impossible to achieve both excellent rigidity and breaking characteristics and low energy loss. Moreover, when a softening point is less than 40 degreeC, the softening point of rubber composition itself falls, and there exists a possibility that the rigidity and the fracture | rupture characteristic which were excellent in the rubber composition, and low energy loss cannot be made compatible. The softening point of the dispersing polymer (B) is preferably 120 ° C. or lower, and more preferably 110 ° C. or lower. On the other hand, the softening point is preferably 40 ° C. or higher, more preferably 60 ° C. or higher, and still more preferably 80 ° C. or higher from the viewpoint of dispersibility.

The molecular weight of the polymer for dispersion (B) is not particularly limited, but is preferably from 400 to 20000, more preferably from 500 to 9000, still more preferably from 600 to 6000 in terms of polystyrene-converted weight average molecular weight measured by gel permeation chromatography. is there. If the weight average molecular weight is less than 400, it may cause plasticization of the rubber composition or generation of bubbles during the molding process. As a result, the rubber composition has both excellent rigidity and breaking characteristics and low energy loss. You may not be able to. If the weight average molecular weight exceeds 20000, the viscosity of the resin usually increases, so that depending on the composition of the dispersing polymer (B), kneading with the modified cellulose fiber (A) and the rubber component (C) is difficult. Further, the dispersion of the modified cellulose fiber (A) becomes insufficient, and there is a possibility that excellent rigidity and breaking characteristics and low energy loss cannot be made compatible in the rubber composition.

The dispersing polymer (B) is not particularly limited as long as it has the softening point, and examples thereof include petroleum resins, coal resins, terpene resins, rosin resins, and the like. It is preferably at least one selected from the group consisting of petroleum-based resins and coal-based resins. When the modified cellulose fiber (A) and the rubber are mixed, by using a specific resin that is at least one selected from the group consisting of petroleum-based resins and coal-based resins as a dispersing polymer, The dispersibility of the cellulose fiber can be further improved, and as a result, it is possible to more suitably achieve both excellent rigidity and breaking property and low energy loss in the rubber composition. Particularly preferred are petroleum resins.

Examples of the petroleum resins include C5 petroleum resins, C9 petroleum resins, C5C9 petroleum resins, dicyclopentadiene resins, hydrides thereof, and cyclic polybasic acid anhydrides (for example, anhydrous maleic anhydride). Examples include modified products obtained by (grafting) addition of (acid). Among these, C9 petroleum resin is preferable.

Examples of the coal-based resin include coumarone resins, coumarone indene resins, and hydrides thereof, and modified products obtained by adding (grafting) cyclic polybasic acid anhydrides (for example, maleic anhydride) to these. It is done.

Examples of the terpene resins include α-pinene resins, β-pinene resins, terpene phenol resins, aromatic modified terpene resins, hydrides thereof, and modified products obtained by adding maleic anhydride thereto.

Examples of the rosin resin include gum rosin, wood rosin, tall rosin, hydrogenated rosin, disproportionated rosin, maleic acid modified rosin, fumaric acid modified rosin, (meth) acrylic acid modified rosin, alcohol And esterified rosin condensed with phenol and phenol-modified rosin.

Among these, as the polymer for dispersion (B), a petroleum resin is particularly preferable, and the modified cellulose fiber-containing rubber composition in the present invention contains an acid anhydride group as the modified cellulose fiber (A) from the viewpoint of compatibility. Most preferably, the modified cellulose fiber modified with a petroleum resin contains a petroleum resin as the dispersing polymer (B).

The rubber component (C) used in the present invention is not particularly limited, and general rubbers used in the rubber industry can be used. For example, natural rubber (NR), modified natural rubber, and isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR) and other diene rubbers, halogenated butyl rubber (X-IIR) ) And synthetic rubber such as butyl rubber such as butyl rubber (IIR). The synthetic rubber may be a modified synthetic rubber. Examples of the modified natural rubber include epoxidized natural rubber (ENR) and hydrogenated natural rubber. These rubber components may be used alone or in combination of two or more.
In other words, the rubber component (C) is at least one selected from the group consisting of natural rubber, modified natural rubber, synthetic rubber, and modified synthetic rubber. It is.

The rubber component (C) preferably contains natural rubber and butadiene rubber (BR) from the viewpoint that good flex crack growth resistance can be obtained.

It does not specifically limit as said natural rubber, For example, what is common in tire industry, such as SIR20, RSS # 3, TSR20, can be used.

The content of natural rubber in 100% by mass of the rubber component (C) is preferably 5% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more. If it is less than 5% by mass, excellent fuel efficiency may not be obtained. Moreover, this content becomes like this. Preferably it is 80 mass% or less, More preferably, it is 60 mass% or less, More preferably, it is 50 mass% or less. If it exceeds 80% by mass, the flex crack growth resistance may be reduced.

Although it does not specifically limit as BR, Although what is common in a tire industry can be used, for example, butadiene rubber with high cis content such as BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., and BR150B , Modified butadiene rubber such as BR1250H manufactured by Nippon Zeon Co., Ltd., butadiene rubber containing syndiotactic polybutadiene crystals such as VCR412 and VCR617 manufactured by Ube Industries, Ltd., and rare earth such as BUNA-CB25 manufactured by LANXESS Co., Ltd. Butadiene rubber synthesized using elemental catalysts can be used. These BR may use 1 type and may use 2 or more types together.
The cis content of BR is preferably 70% by mass or more, more preferably 90% by mass or more, and still more preferably 97% by mass or more.
In the present invention, the cis content of BR (cis 1,4 bond content) can be measured by infrared absorption spectrum analysis.

The molecular weight distribution (Mw / Mn) of BR is preferably 1.5 or more, more preferably 2.0 or more. If it is less than 1.5, workability may be deteriorated. The Mw / Mn of BR is preferably 5.0 or less, more preferably 4.0 or less. If it exceeds 5.0, the flex crack growth resistance tends to deteriorate.
In the present invention, the number average molecular weight (Mn) and the weight average molecular weight (Mw) are values converted from standard polystyrene using gel permeation chromatography (GPC).

The Mooney viscosity (ML _{1 + 4} (100 ° C.)) of BR is preferably 10 or more, more preferably 30 or more. If it is less than 10, the dispersibility of the filler tends to decrease. The Mooney viscosity is preferably 120 or less, more preferably 80 or less. If it exceeds 120, there is a concern about the occurrence of rubber burn (discoloration) during extrusion processing.
In the present invention, the Mooney viscosity of BR is measured according to ISO 289 and JIS K6300.

The content of BR in 100% by mass of the rubber component (C) is preferably 30% by mass or more, more preferably 40% by mass or more, and still more preferably, from the viewpoint of exhibiting necessary low fuel consumption and bending crack growth resistance. Is 50 mass% or more. Further, the content is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less, from the viewpoint of workability.

It is preferable that content of the said modified cellulose fiber (A) in the modified cellulose fiber containing rubber composition in this invention is 0.01-30 mass parts with respect to 100 mass parts of said rubber components (C). The effect of the present invention when the content of the modified cellulose fiber (A) in the modified cellulose fiber-containing rubber composition in the present invention is less than 0.01 parts by mass with respect to 100 parts by mass of the rubber component (C). May not be fully utilized. On the other hand, when blended in excess of 30 parts by mass with respect to 100 parts by mass of the rubber component (C), the dispersibility of the modified cellulose fiber (A) in the rubber composition is extremely reduced, and the rubber composition is excellent. There is a possibility that it is impossible to achieve both high rigidity and fracture characteristics and low energy loss. In the modified cellulose fiber-containing rubber composition of the present invention, the content of the modified cellulose fiber (A) is more preferably 0.05 parts by mass or more with respect to 100 parts by mass of the rubber component (C). More preferred is part by mass or more. On the other hand, 20 mass parts or less are more preferable, 15 mass parts or less are still more preferable, and 10 mass parts or less are the most preferable.

In the modified cellulose fiber-containing rubber composition of the present invention, the content of the dispersing polymer (B) is preferably 0.01 to 30 parts by mass with respect to 100 parts by mass of the rubber component (C). . When the content of the dispersing polymer (B) in the modified cellulose fiber-containing rubber composition in the present invention is less than 0.01 parts by mass with respect to 100 parts by mass of the rubber component (C), There is a possibility that the effect cannot be fully exhibited. On the other hand, when the amount exceeds 30 parts by mass with respect to 100 parts by mass of the rubber component (C), the proportion of the dispersing polymer (B) in the rubber composition becomes excessively large, and the rubber composition is excellent. There is a possibility that it is impossible to achieve both high rigidity and fracture characteristics and low energy loss. The content of the dispersing polymer (B) in the modified cellulose fiber-containing rubber composition in the present invention is more preferably 0.05 parts by mass or more with respect to 100 parts by mass of the rubber component (C). 1 part by mass or more is more preferable, and 3 parts by mass or more is particularly preferable. On the other hand, 20 mass parts or less are more preferable, 15 mass parts or less are still more preferable, and 10 mass parts or less are the most preferable.

In the modified cellulose fiber-containing rubber composition of the present invention, the content of the dispersing polymer (B) with respect to the modified cellulose fiber (A) is the same as that of the modified cellulose fiber (A) and the dispersing polymer (B). It is preferable that it is 30-70 mass% with respect to 100 mass% of total contents. When the content ratio of the dispersing polymer (B) to the modified cellulose fiber (A) is within such a range, the dispersibility of the cellulose fiber in the rubber can be further improved. As a result, in the rubber composition It becomes possible to achieve both excellent rigidity and breaking characteristics and low energy loss more appropriately. The content of the dispersing polymer (B) with respect to the modified cellulose fiber (A) is 35 to 65% by mass with respect to 100% by mass of the total content of the modified cellulose fiber (A) and the dispersing polymer (B). It is more preferable that it is 40-60 mass%.

The modified cellulose fiber-containing rubber composition in the present invention contains, for example, a modified cellulose fiber (A), a polymer for dispersion (B), a rubber component (C), and other compounding agents described later as required. It can be obtained by kneading by a conventionally known method and conditions using a rubber kneader or the like. In particular, before kneading with the rubber component (C) or other compounding agent, the modified cellulose fiber (A) is previously prepared. It is preferable to knead the dispersion polymer (B) and knead the resulting kneaded product (resin composition) with the rubber component (C) and other compounding agents. Thus, the modified cellulose fiber (A) can be further refined by kneading the modified cellulose fiber (A) and the dispersing polymer (B) in advance to prepare a resin composition. In addition, the dispersibility of cellulose fibers in rubber is further improved, and it is possible to achieve both high rigidity and low breaking characteristics and low energy loss in the rubber composition. In addition, the rigidity in the tire radial direction can be made particularly excellent, and the workability can be further improved. That is, the modified cellulose fiber-containing rubber composition of the present invention kneads the modified cellulose fiber (A) and the dispersing polymer (B) to obtain a kneaded product (resin composition), and then the kneaded product and the rubber It is also one of the preferred embodiments of the present invention that it is obtained by kneading the component (C).
The modified cellulose fiber (A), the dispersing polymer (B), and a method for producing a modified cellulose fiber-containing rubber composition containing a rubber component (C), the modified cellulose fiber (A), It is obtained by adding a cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group to a cellulose fiber and esterifying, and the polymer for dispersion (B) has a softening point of 135 ° C. or less. And the production method includes a step of kneading the modified cellulose fiber (A), the dispersing polymer (B) and the rubber component (C), and a method for producing a modified cellulose fiber-containing rubber composition Is also one aspect of the present invention. Further, the production method comprises a step of kneading the modified cellulose fiber (A) and the dispersing polymer (B) to obtain a kneaded product, and the obtained kneaded product and the rubber component (C). It is also one preferred embodiment of the present invention to include a step of kneading to obtain a modified cellulose fiber-containing rubber composition.

As described above, the modified cellulose fiber-containing rubber composition of the present invention is obtained by kneading the modified cellulose fiber (A) and the dispersing polymer (B) to obtain a kneaded product (resin composition). The kneaded product and the rubber component (C) are preferably obtained by kneading, but the above-mentioned amount is 100% by mass with respect to 100% by mass of the modified cellulose fiber (A) contained in the modified cellulose fiber-containing rubber composition in the present invention. The ratio of the modified cellulose fiber (A) derived from the resin composition is more preferably 40% by mass or more, further preferably 60% by mass or more, and particularly preferably 80% by mass or more. Moreover, an upper limit is not specifically limited, 100 mass% may be sufficient. On the other hand, the proportion of the dispersing polymer (B) derived from the resin composition is 40% by mass or more with respect to 100% by mass of the dispersing polymer (B) contained in the modified cellulose fiber-containing rubber composition in the present invention. More preferably, 60 mass% or more is further more preferable, and 80 mass% or more is particularly preferable. Moreover, an upper limit is not specifically limited, 100 mass% may be sufficient.

As described above, when the modified cellulose fiber (A) and the dispersing polymer (B) are previously kneaded, the step of kneading the modified cellulose fiber (A) and the dispersing polymer (B) is performed by modifying cellulose. The kneading method is not particularly limited as long as the fiber (A) and the dispersing polymer (B) are kneaded. For example, the modified cellulose fiber (A) may be used in a kneader. It is preferably a step in which the modified cellulose fiber (A) is refined by dispersing in the dispersing polymer (B) and stirring and mixing while receiving a strong shearing force. Examples of the kneader that can be used in the kneading step include a two-roll mill, a three-roll mill, a single-screw extrusion kneader, a twin-screw extrusion kneader, a Banbury mixer, and a pressure kneader. Although it can be used individually by 1 type or in combination of 2 or more types, it is not limited to these. In order to promote the refinement of the modified cellulose fiber (A), it is preferable to use a biaxial extrusion kneader, a Banbury mixer, or a pressure kneader.
The kneading conditions such as kneading temperature and kneading time in the kneading step of the modified cellulose fiber (A) and the dispersing polymer (B) are sufficient for the modified cellulose fiber (A) and the dispersing polymer (B). What is necessary is just to set suitably so that a kneaded and modified cellulose fiber (A) can be refined | miniaturized.

Further, in the kneading step of the modified cellulose fiber (A) and the dispersing polymer (B), in addition to the modified cellulose fiber (A) and the dispersing polymer (B), the fineness of the modified cellulose fiber (A) As long as it does not inhibit the conversion, a part of other compounding agents that can be blended in the modified cellulose fiber-containing rubber composition in the present invention, a lubricant such as stearic acid, an antioxidant and the like may be blended. In 100% by mass of the kneaded product (resin composition) obtained by the process, the total content of the modified cellulose fiber (A) and the dispersing polymer (B) is preferably 80% by mass or more, more preferably 90% by mass or more. Preferably, 93 mass% or more is more preferable, and 95 mass% or more is especially preferable. On the other hand, the upper limit is not particularly limited, and may be 100% by mass.

By blending the lubricant within a range that does not affect the effect of the present invention, the kneaded product of the modified cellulose fiber (A) and the dispersing polymer (B) is easily peeled off from the kneader or the mold, Formability and workability may be improved. The lubricant is not particularly limited, and examples thereof include hydrocarbon lubricants such as paraffin wax and polyethylene wax, fatty acid lubricants such as stearic acid, behenic acid, and 12-hydroxystearic acid, stearic acid amide, oleic acid amide, and Elca. Aliphatic amide-based lubricants such as acid amides can be used. For example, the total of the above resin composition when a lubricant is blended in the resin composition, such as a resin composition comprising a modified cellulose fiber (A), a dispersing polymer (B), a lubricant, and other compounding agents. 1 mass% or more is preferable and, as for the lubricant compounding ratio with respect to this resin composition when it is set as 100 mass%, 3 mass% or more is more preferable. On the other hand, 20 mass% or less is preferable, 10 mass% or less is more preferable, and 7 mass% or less is especially preferable.

By blending the antioxidant within a range that does not affect the effect of the present invention, thermal deterioration of the modified cellulose fiber is alleviated in the kneading step of the modified cellulose fiber (A) and the dispersing polymer (B). May be. The antioxidant is not particularly limited. For example, phenol-based oxidation such as Adeka Stab AO series (manufactured by ADEKA) such as AO-20, AO-30, AO-40, AO-50, AO-60, etc. An inhibitor or the like can be used. For example, the resin composition described above when an antioxidant is blended in the resin composition, such as a resin composition comprising the modified cellulose fiber (A), the dispersing polymer (B), the antioxidant, and other compounding agents. 0.1 mass% or more is preferable and, as for the antioxidant compounding rate with respect to this resin composition when the sum total of a thing is 100 mass%, 0.5 mass% or more is more preferable. On the other hand, 10 mass% or less is preferable and 3 mass% or less is more preferable.

In addition, as long as the effect of the present invention is not impaired, the modified cellulose fiber-containing rubber composition in the present invention includes the modified cellulose fiber (A), the dispersing polymer (B), and the rubber component (C). Other components may be included. For example, a resin having a softening point higher than 135 ° C. that does not correspond to the polymer for dispersion (B) may be mixed with the polymer for dispersion (B). When such a resin is used by mixing with the dispersing polymer (B), the blending amount is preferably 50% by mass or less based on the total amount of the resin and the dispersing polymer (B). .

In the modified cellulose fiber-containing rubber composition in the present invention, in addition to the modified cellulose fiber (A), the dispersing polymer (B), and the rubber component (C), if necessary, other conventionally used in the rubber industry Compounding agents, for example, reinforcing agents such as carbon black and silica, oil, anti-aging agent, zinc oxide, stearic acid, silane coupling agent, curing resin, wax, vulcanizing agent, vulcanization accelerator, etc. it can.

Carbon black that can be blended in the modified cellulose fiber-containing rubber composition in the present invention is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF. These carbon blacks may be used alone or in combination of two or more.

The carbon black has a nitrogen adsorption specific surface area (N ₂ SA) of preferably 20 m ² / g or more, more preferably 30 m ² / g or more. The N ₂ SA is preferably 200 m ² / g or less, more preferably 150 m ² / g or less, and still more preferably 100 m ² / g or less. When it is less than 20 m ² / g, there is a tendency that a sufficient reinforcing effect cannot be obtained, and when it exceeds 200 m ² / g, there is a tendency that fuel efficiency is lowered.

The content of the carbon black is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component (C). The content is preferably 150 parts by mass or less, more preferably 100 parts by mass or less. Within the above range, good fuel economy and flex crack growth resistance can be obtained.

The modified cellulose fiber-containing rubber composition in the present invention may contain a white filler. As the white filler, those generally used in the rubber industry, for example, mica such as silica, calcium carbonate, sericite, aluminum hydroxide, magnesium oxide, magnesium hydroxide, clay, talc, alumina, oxidation Titanium or the like can be used, and silica is preferable from the viewpoint of low fuel consumption.

Examples of the silica include, but are not limited to, dry method silica (anhydrous silicic acid), wet method silica (hydrous silicic acid), and the like, and wet method silica is preferable because it has many silanol groups.

The nitrogen adsorption specific surface area (N ₂ SA) of the silica is preferably 40 m ² / g or more, and more preferably 50 m ² / g or more. If it is less than 40 m < ² > / g, there exists a tendency for the fracture strength after vulcanization to fall. The _N 2 SA of the silica is preferably 300 meters ² / g or less, more preferably 250m ² / g. When it exceeds 300 m ² / g, there is a tendency that low heat build-up and rubber processability are lowered.
In the present invention, the nitrogen adsorption specific surface area of silica is a value measured by the BET method in accordance with ASTM D3037-93.

Content of the said white filler (especially silica) becomes like this. Preferably it is 10 mass parts or more with respect to 100 mass parts of rubber components (C), More preferably, it is 20 mass parts or more. Moreover, this content becomes like this. Preferably it is 120 mass parts or less, More preferably, it is 100 mass parts or less. Within the above range, good fuel economy and flex crack growth resistance can be obtained.

When the modified cellulose fiber-containing rubber composition in the present invention contains silica, it is preferable to further mix a silane coupling agent. The silane coupling agent is not particularly limited, and sulfide systems such as bis (3-triethoxysilylpropyl) disulfide and bis (3-triethoxysilylpropyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyl Mercapto type such as triethoxysilane, vinyl type such as vinyltriethoxysilane, amino type such as 3-aminopropyltriethoxysilane, glycidoxy type of γ-glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxysilane, etc. And chloro-based silane coupling agents such as 3-nitropropyltrimethoxysilane. These silane coupling agents may be used individually by 1 type, and may be used in combination of 2 or more type.

The content of the silane coupling agent is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, and further preferably 2.5 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 0.5 parts by mass, it may be difficult to disperse silica well. Moreover, this content becomes like this. Preferably it is 20 mass parts or less, More preferably, it is 15 mass parts or less, More preferably, it is 10 mass parts or less. Even if it exceeds 20 parts by mass, the effect of improving the dispersion of silica cannot be obtained, and the cost tends to increase unnecessarily. In addition, the scorch time is shortened, and the workability during kneading and extrusion tends to decrease.

The modified cellulose fiber-containing rubber composition in the present invention preferably contains oil as a plasticizer. Thereby, the hardness can be adjusted to an appropriate low level and good workability can be obtained. The oil is not particularly limited, and conventionally known oils such as paraffinic process oil, aroma based process oil, process oil such as naphthenic process oil, vegetable oil and fat, and mixtures thereof can be used.

The content of the oil is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component (C). Moreover, this content becomes like this. Preferably it is 15 mass parts or less, More preferably, it is 10 mass parts or less. Within the above range, good processability is imparted, and excellent fuel economy and flex crack growth resistance are also obtained.

Anti-aging agents that can be blended in the modified cellulose fiber-containing rubber composition of the present invention include diphenylamine (p- (p-toluenesulfonylamide) -diphenylamine, octylated diphenylamine, etc.), p-phenylenediamine (N -(1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine (6PPD), N-phenyl-N'-isopropyl-p-phenylenediamine (IPPD), N, N'-di-2-naphthyl -P-phenylenediamine, etc.).

Examples of the vulcanization accelerator that can be added to the modified cellulose fiber-containing rubber composition in the present invention include thiazoles such as 2-mercaptobenzothiazole, dibenzothiazyl disulfide, and N-cyclohexyl-2-benzothiazylsulfenamide. Vulcanization accelerators; thiuram vulcanization accelerators such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide; N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl-2-benzothiazolesulfenamide , Sulfenamide vulcanization acceleration such as N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N, N′-diisopropyl-2-benzothiazole sulfenamide Agent: Diphenylgua Examples include guanidine vulcanization accelerators such as gin, diortolylguanidine, and orthotolylbiguanidine, and the amount used is 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component (C). Preferably, it is 0.2-3 mass parts more preferably.

In the modified cellulose fiber-containing rubber composition of the present invention, sulfur can be suitably blended as a vulcanizing agent. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The sulfur content is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more with respect to 100 parts by mass of the rubber component (C). If it is less than 1 part by mass, the effect may be small. Moreover, this content becomes like this. Preferably it is 6 mass parts or less, More preferably, it is 4 mass parts or less. If it exceeds 6 parts by mass, the effect of suppressing the curing deterioration may not be sufficiently obtained.

The modified cellulose fiber-containing rubber composition in the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a rubber kneader such as a Banbury mixer, a kneader, or an open roll, and then vulcanizing.

The pneumatic tire of the present invention has a sidewall produced using the above-described modified cellulose fiber-containing rubber composition of the present invention.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition. That is, the modified cellulose fiber-containing rubber composition in the present invention is extruded in accordance with the shape of the sidewall at an unvulcanized stage, molded by a normal method on a tire molding machine, and together with other tire members After bonding and forming an unvulcanized tire, the tire can be manufactured by heating and pressing in a vulcanizer.

The pneumatic tire of the present invention is preferably used as a tire for passenger cars, a tire for trucks and buses, a tire for motorcycles, a tire for competition, and the like, and particularly preferably used as a tire for passenger cars.

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

The physical property measurement methods used in some of these examples are as follows.
(1) Confirmation of the progress of the denaturation reaction The progress of the denaturation reaction was observed using a Fourier transform infrared spectroscopic analyzer “Spectrum one” manufactured by Perkin Elmer. Specifically, since the peak intensity derived from the stretching vibration of the carbonyl carbon and oxygen of the ester bond generated at 1650 to 1750 cm ⁻¹ increases with the progress of the modification reaction, it was qualitatively confirmed.
(2) Measurement of Addition Rate of Acid Anhydride to Cellulose Fiber The addition rate was calculated from the change in mass before and after modification of the cellulose fiber as shown in the following formula (I). A sample for evaluating the addition rate was washed with a sufficient amount of solvent and subjected to measurement. As the washing solvent, a good solvent of acid anhydride was appropriately selected and used.
Wp = (W−Ws) × 100 / Ws (I)
Wp: addition rate of acid anhydride to cellulose fiber (% by mass)
W: Dry mass (g) of modified cellulose fiber (modified cellulose fiber)
Ws: dry mass of cellulose fiber before modification (g)
(3) Measurement of solid content An infrared moisture meter (manufactured by Kett Scientific Laboratory: "FD-620") was used for measurement of solid content.
(4) Measurement of acid value The acid value of the acid anhydride was measured using the following procedure.
0.5 g of acid anhydride was weighed and dissolved in 50 ml of tetrahydrofuran, and 10 drops of 1% ethanol solution of phenolphthalein was added to obtain an acid anhydride solution. While stirring the obtained acid anhydride solution, an ethanol solution of 0.5 N potassium hydroxide was added dropwise to color the system. The end point is the point at which the color does not change for 30 seconds without dropping the potassium hydroxide solution, and the acid value (mg KOH / g) is calculated from the mass of the potassium hydroxide solution added up to the end point using the following formula (II) Was calculated.
Acid value = Wk × 56.1 (II)
Wk: Mass of 0.5 N potassium hydroxide solution added to the end point (g)

[Production of Modified Cellulose Fiber (A-1)]
250.00 g of softwood bleached kraft pulp containing water (hereinafter referred to as NBKP) and 200.00 g of N-methylpyrrolidone and 200.00 g of N-methylpyrrolidone in a container with a volume of 2000 ml, and removing the water to replace the solvent NBKP was obtained. The system was heated to 70 ° C., and 39.75 g of hexadecenyl succinic anhydride as an acid anhydride (a) and 8.53 g of potassium carbonate as an esterification catalyst were added and reacted for 2 hours. The reaction product was washed successively with ethanol, acetic acid, and water, and the solvent was replaced with ethanol, followed by drying to obtain modified cellulose fiber A-1. Ethanol was used as a cleaning solvent for the sample for evaluating the addition rate. In the modified cellulose fiber A-1, the addition ratio of the acid anhydride (a) to the cellulose fiber was 59.6% by mass.

[Synthesis of acid anhydride group-containing petroleum resin (a-1)]
1200.00 g of PetroTac 70 (manufactured by Tosoh Corporation, C5C9 petroleum resin: weight average molecular weight 1300, softening point 70 ° C., bromine number 45 Br ₂ g / 100 g) was charged into a separable flask having a capacity of 3000 ml, and the temperature reached 160 ° C. Heated to a molten state. After maintaining the system at 160 ° C. and performing nitrogen substitution, maleic anhydride (221.00 g) and t-butyl peroxide (6.00 g) were added in 12 portions over 3 hours. Two hours after the completion of the charging, the inside of the system was brought to 180 ° C., and kept under reduced pressure for 2 hours to carry out a purification operation for distilling off unreacted maleic anhydride, whereby an acid value of 98, a softening point of 96 ° C. and a weight average molecular weight of 5800 An acid anhydride group-containing petroleum resin a-1 was obtained.

[Production of Modified Cellulose Fiber (A-2)]
NBKP (250.00 g, solid content: 50.00 g) and N-methylpyrrolidone (200.00 g) containing water were charged into a container with a volume of 2000 ml, and water was distilled off to obtain a solvent-substituted NBKP. The inside of the system was 75 ° C., 50.00 g of acid anhydride group-containing petroleum resin a-1 was weighed as an acid anhydride (a), and potassium carbonate was added together with 8.53 g as an esterification catalyst to react for 3 hours. . The reaction product was washed successively with acetic acid, water and ethanol and dried to obtain modified cellulose fiber A-2. Tetrahydrofuran was used as a washing solvent for the sample for evaluating the addition rate. In the modified cellulose fiber A-2, the addition ratio of the acid anhydride group-containing petroleum resin a-1 to the cellulose fiber was 36% by mass.

[Production of Modified Cellulose Fiber-Containing Resin Composition]
(Production Example 1)
Quinton R100 (manufactured by Nippon Zeon Co., Ltd., C5 petroleum resin: weight average molecular weight 2250, softening point 96 ° C.), modified cellulose fiber A-1, and stearic acid (Nissan Corporation) as a lubricant ) Manufactured bead stearic acid Tsubaki), AO-60 (manufactured by ADEKA Co., Ltd., phenolic antioxidant) was used as an antioxidant, and according to the ratio shown in Table 1 below, a twin-screw kneader (Co., Ltd.) It was put into “KZW” manufactured by Technobel, screw diameter: 15 mm, L / D: 45), and melt-kneaded to obtain a modified cellulose fiber-containing resin composition X-1.

(Production Example 2)
Modified Cellulose Fiber Containing in the same manner as in Production Example 1 except that Petol LX (manufactured by Tosoh Corporation, C9 petroleum resin: weight average molecular weight 1400, softening point 98 ° C.) was used as the dispersing polymer (B). Resin composition X-2 was obtained.

(Production Example 3)
Petol LX (manufactured by Tosoh Corporation, C9 petroleum resin: weight average molecular weight 1400, softening point 98 ° C.) and acid anhydride group-containing petroleum resin a-1 (acid value 98, softening point) 96 ° C., weight average molecular weight 5800), modified cellulose fiber A-2, stearic acid (bead stearic acid Tsubaki manufactured by NOF Corporation) as a lubricant, AO-60 (manufactured by ADEKA Corporation, phenolic) as an antioxidant Using an antioxidant), in accordance with the ratio shown in Table 1 described later, charged into a twin-screw kneader ("KZW" manufactured by Technobel, screw diameter: 15 mm, L / D: 45), melt-kneaded A modified cellulose fiber-containing resin composition X-3 was obtained.

(Production Example 4)
A modified cellulose fiber-containing resin composition X-4 was obtained in the same manner as in Production Example 1 except that the dispersing polymer (B) was not used and blended in the proportions shown in Table 1 described later.

(Production Example 5)
The resin composition consisting only of Quinton R100 was designated as resin composition X-5.

(Production Example 6)
A resin composition consisting only of Petol LX was designated as Resin Composition X-6.

The composition of the resin compositions X-1 to X-6 is shown in Table 1 below.

In Table 1, “inside, cellulose content” in the examples using the modified cellulose fibers indicates the cellulose fiber content in the modified cellulose fibers, and is expressed as a content (mass%) with respect to 100 mass% of the resin composition. “Inner modifier component” indicates the amount derived from the cyclic polybasic acid anhydride (a) in the modified cellulose fiber, and is expressed as a content (mass%) with respect to 100 mass% of the resin composition.

The product names and abbreviations in Table 1 are as follows.
Quinton R100: manufactured by Nippon Zeon Co., Ltd., C5 petroleum resin, weight average molecular weight 2250, softening point 96 ° C.
Petcoal LX: manufactured by Tosoh Corporation, C9 petroleum resin, weight average molecular weight 1400, softening point 98 ° C.
Stearic acid: beads manufactured by NOF Corporation Tsubaki stearic acid AO-60: manufactured by ADEKA Corporation, phenolic antioxidant

<Sidewall>
Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
X-1 to X-6: Resin compositions X-1 to X-6 obtained in Production Examples 1 to 6
Natural rubber: TSR20
Butadiene rubber: BR150B manufactured by Ube Industries, Ltd. (cis content: 97% by mass, ML _{1 + 4} (100 ° C.): 40)
Carbon black: Show Black N550 (N ₂ SA: 42 m ² / g) manufactured by Cabot Japan
Anti-aging agent: NOCRACK 6C (N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine) (6PPD) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Oil: Diana Process AH-24 manufactured by Idemitsu Kosan Co., Ltd.
Zinc oxide: 2 types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Beads Tsubaki Sulfurate manufactured by NOF Co., Ltd .: Seimi Sulfur manufactured by Nippon Kiboshi Kogyo Co., Ltd. (oil content: 10%)
Vulcanization accelerator: Noxeller NS (Nt-butyl-2-benzothiazolesulfenamide [TBBS]) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

(Examples 1-5, Comparative Examples 1-5)
According to the blending content shown in Table 2, chemicals other than sulfur and a vulcanization accelerator were kneaded using a 1.7 L Banbury mixer manufactured by Kobe Steel Co., Ltd. to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the kneaded product obtained, and kneaded using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized to obtain a vulcanized rubber composition.

Further, the obtained unvulcanized rubber composition is molded into a sidewall shape, and is bonded together with other tire members on a tire molding machine to form an unvulcanized tire and vulcanize to obtain a test tire (size 195 / 65R15).
The following evaluation was performed about the obtained unvulcanized rubber composition, the vulcanized rubber composition, and the test tire. The results are shown in Table 2.

(Viscoelasticity test)
A test piece was cut out from the sidewall of the test tire and using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.) under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%. The complex elastic modulus E * a (MPa) in the tire circumferential direction of the test piece and the complex elastic modulus E * b (MPa) in the tire radial direction (radial direction) were measured and expressed as an index by the following formula (elastic modulus) index). The larger the elastic modulus index, the better the elastic modulus, and the higher the rigidity, the better the steering stability.
(Elastic modulus a index) = (E * a of each formulation) / (E * a of Comparative Example 1) × 100
(Elastic modulus b index) = (E * b of each formulation) / (E * b of Comparative Example 1) × 100

(Tensile test)
In accordance with JIS K6251 “How to determine tensile properties of vulcanized rubber and thermoplastic rubber”, a tensile test was conducted using a No. 3 dumbbell-shaped test piece made of vulcanized rubber composition. The elongation (tensile elongation; EB [%]) and the tensile strength at break (tensile breaking strength: TB [MPa]) were measured and expressed as an index according to the following formula (breaking strength index). The larger the breaking strength index, the better the breaking strength and the better the durability.
(Breaking Strength Index) = (EB × TB of each formulation) / (EB × TB of Comparative Example 1) × 100

(Low fuel consumption)
Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.), the loss tangent (tan δ) of the vulcanized rubber composition was measured under conditions of a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%. Measured and indexed by the following formula (low fuel consumption index). The higher the fuel efficiency index, the lower the rolling resistance and the better the fuel efficiency (low fuel efficiency).
(Low fuel consumption index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Tire performance balance index)
Based on each index, a balance index was determined by the following formula. The larger the index, the better the balance between handling stability, fuel efficiency and durability.
(Balance index) = (elastic modulus a index × breaking strength index × low fuel consumption index) / 10000

(Processability: Measurement of Mooney viscosity)
About the obtained unvulcanized rubber composition, according to the measuring method of Mooney viscosity based on JIS K6300, Mooney viscosity was measured at 130 degreeC, and the index was displayed with the following formula (Mooney viscosity index). The larger the index, the lower the Mooney viscosity and the better the processability.
(Mooney viscosity index) = (ML _{1 + 4} of Comparative Example 1) / (ML _{1 + 4 of} each formulation) × 100

(Flexible crack growth test)
Using a vulcanized rubber sheet (vulcanized rubber composition), a sample was prepared based on JIS K6260 “Vulcanized Rubber and Thermoplastic Rubber-Dematcher Bending Crack Test Method”, a bending crack growth test was performed, and 70% elongation was achieved. After the rubber sheet was bent 1,000,000 times, the length of the cracks generated was measured. The reciprocal of the measured value (length) of Comparative Example 1 was taken as 100, and displayed as an index. The larger the index is, the more the crack growth is suppressed and the resistance to flex crack growth is excellent.

In Table 2, the amount of modified cellulose fibers (parts by mass) represents the content (parts by mass) of modified cellulose fibers with respect to 100 parts by mass of the rubber component in the rubber composition.

From Table 2, modified cellulose fiber (A) esterified by adding a cyclic polybasic acid anhydride (a) having 15 or more carbon atoms having a hydrophobic group to cellulose fiber, dispersion having a softening point of 135 ° C. or less In Examples 1 to 5 using the modified cellulose fiber-containing rubber composition containing the polymer (B) for rubber and the rubber component (C), the dispersibility of the cellulose fibers in the rubber is improved. Improvement in breaking strength, fuel efficiency, workability, and flex crack growth resistance are improved as compared with Comparative Example 2 that contains the modified cellulose fiber (A) but does not contain the dispersing polymer (B). The results were equivalent, and in particular, the balance performance of the elastic modulus, breaking strength and fuel efficiency was improved. That is, it was confirmed that both excellent rigidity and fracture characteristics and low energy loss (rolling resistance characteristics) can be achieved, and sufficient resistance to bending crack growth is ensured. From this, the pneumatic tire having a sidewall produced using such a modified cellulose fiber-containing rubber composition has a good balance in handling stability, rolling resistance characteristics and durability, and further has a flex crack growth resistance. It turns out that it is excellent. Furthermore, by making the rubber composition as described above, the dispersibility of the cellulose fibers in the rubber becomes good, and not only the rigidity in the tire circumferential direction but also the rigidity in the tire radial direction is excellent. It is confirmed that a pneumatic tire having a sidewall with excellent steering stability can be obtained.
Although it may be possible to enhance the reinforcing property by blending a large amount of carbon black instead of blending cellulose fibers, from the result of Comparative Example 5, when blending a large amount of carbon black, it is possible to improve rigidity. On the other hand, it can be seen that the rigidity, fracture characteristics, and rolling resistance characteristics cannot be improved in a well-balanced manner, and the processability is poor.

Claims (6)

Carbon atoms of 15 or more cyclic polybasic acid anhydride having a hydrophobic group in the cellulose fibers (a) adding to esterified modified cellulose fibers (A), Ri der softening point of 40 ° C. or higher 135 ° C. or less, Modified cellulose fiber-containing rubber composition containing at least one polymer for dispersion (B) selected from the group consisting of petroleum resins, coal resins, terpene resins, and rosin resins , and a rubber component (C) A pneumatic tire having a sidewall produced using The pneumatic tire according to claim 1, wherein the cyclic polybasic acid anhydride (a) is at least one selected from the group consisting of an acid anhydride group-containing petroleum resin and an acid anhydride group-containing coal resin. The pneumatic tire according to claim 1 or 2, wherein the dispersing polymer (B) is at least one selected from the group consisting of petroleum resins and coal resins. The pneumatic tire according to any one of claims 1 to 3, wherein the rubber component (C) is at least one selected from the group consisting of natural rubber, modified natural rubber, and synthetic rubber. The pneumatic tire according to any one of claims 1 to 4, wherein a content of the modified cellulose fiber (A) is 0.01 to 30 parts by mass with respect to 100 parts by mass of the rubber component (C). A method for producing the pneumatic tire according to claim 1,
The production method, the modified cellulose fibers (A) and the the dispersion polymer (B) and kneaded Ru obtain a kneaded product step, and the resulting kneaded product and the rubber component (C) and kneading And the manufacturing method of a pneumatic tire including the process of obtaining the said modified cellulose fiber containing rubber composition .