JP2008038124A - Rubber composition and pneumatic tire produced by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having rolling resistance properties and wet grip performance improved in balanced state while keeping good processability and abrasion resistance. <P>SOLUTION: The rubber composition contains 100 pts.mass of a rubber component containing natural rubber and/or diene rubber and 0.5-80 pts.mass of a polyhydroxy alkanoate containing one or more structural units expressed by general formula (R is a 1-22C hydrocarbon group containing one or more double bonds). The invention further provides a pneumatic tire produced by using the composition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition containing polyhydroxyalkanoate (PHA) and a pneumatic tire using the same.

  Performances required for automobile tires are diverse, such as low fuel consumption, handling stability, wear resistance, and riding comfort performance, and various studies have been conducted to improve these performances. In recent years, in particular, it has been desired to reduce fuel consumption by improving rolling resistance characteristics. However, since the rolling resistance characteristics and the grip performance are in a conflicting relationship, if the hysteresis loss is reduced to reduce rolling resistance, the grip The problem is that the force becomes smaller and the braking performance deteriorates.

  In order to solve this problem, for example, a method of using a silica and a silane coupling agent to reduce heat generation and improve grip performance has been reported. However, it has been found that in tires using a rubber composition containing silica, the rigidity of the rubber decreases with repeated running, resulting in a significant decrease in grip. In addition, since silica particles tend to aggregate due to hydrogen bonding of silanol groups, which are surface functional groups of silica, the silica particles are insufficiently dispersed in the rubber, and the Mooney viscosity of the rubber composition is increased. There is a problem that processability such as extrudability cannot be obtained sufficiently.

  In recent years, from the viewpoint of environmental protection, the use of natural resources has become an issue in tires. For example, a method for improving wet grip performance by using a starch composite has been proposed. However, in this method, a mixing step at a high temperature is necessary to sufficiently disperse the starch composite, which not only complicates the process but also promotes the deterioration of the polymer.

  Patent Document 1 proposes a method of decomposing a vulcanized rubber composition contained in wastes of rubber products including waste tires with microorganisms. According to this method, the used tire can be disassembled, but Patent Document 1 does not consider improvement in characteristics of the tire itself.

On the other hand, from the viewpoint of environmental protection, the development of resins that can be degraded over time by the use of microorganisms, that is, biodegradable resins, is being developed. About polyhydroxyalkanoate (PHA), which is a degradable resin, it is known that various compositions and structures are produced by controlling the type of microorganism, medium composition, culture conditions, etc. Studies have been made on the control of the composition and structure of produced PHA mainly from the viewpoint of improving physical properties. Polymers produced from microorganisms can be used for production of various products by melt processing or the like, as with conventional plastic materials. In addition, the polymer is biodegradable and has the advantage of being decomposed by microorganisms in nature, and does not remain in the natural environment and cause environmental pollution unlike many conventional organic polymer compounds. . However, since PHA has been mainly studied as an alternative to conventional plastics, there has been a problem that it is difficult to use in a rubber composition for tires because of its poor flexibility like rubber.
JP 2004-99738 A

  The present invention provides a pneumatic tire that solves the above problems and uses a specific rubber composition to improve the rolling resistance characteristics and wet grip performance in a well-balanced manner while maintaining good workability and wear resistance. The purpose is to do.

  The present invention relates to the following general formula for 100 parts by mass of a rubber component containing natural rubber and / or diene rubber:

(Wherein R is a hydrocarbon group having 1 to 22 carbon atoms containing one or more double bonds) 0.5 to 0.5 polyhydroxyalkanoate containing one or more structural units represented by The present invention relates to a rubber composition contained within a range of 80 parts by mass.

  In the present invention, the polyhydroxyalkanoate preferably has a weight average molecular weight in the range of 500 to 20,000.

  In the present invention, the rubber component contains at least one functional group selected from an alkoxyl group, an alkoxysilyl group, an epoxy group, a glycidyl group, a carbonyl group, an ester group, a hydroxy group, an amino group, and a silanol group. It is preferable to include a functional group-containing natural rubber and / or a functional group-containing diene rubber.

In the present invention, the rubber component preferably contains epoxidized natural rubber.
Moreover, in this invention, 5-100 mass parts of silica is contained with respect to 100 mass parts of a rubber component, and a silane coupling agent is contained so that it may become 1-20 mass% with respect to content of this silica, respectively. It is preferable to do.

  The present invention further relates to a pneumatic tire using the above rubber composition.

  In the present invention, rolling resistance characteristics and wet grip performance are improved in a well-balanced manner while maintaining good workability and wear resistance by using a rubber composition containing a polyhydroxyalkanoate containing a specific structural unit. It is possible to obtain a used pneumatic tire.

  The rubber composition of the present invention has the following general formula with respect to 100 parts by mass of a rubber component containing natural rubber and / or diene rubber.

(Wherein R is a hydrocarbon group having 1 to 22 carbon atoms including one or more double bonds), polyhydroxyalkanoate (PHA) including one or more structural units represented by 0 Within 5-80 parts by mass.

  Since the hydrocarbon group represented by R in the above general formula contains one or more double bonds, PHA has flexibility and compatibility with natural rubber and / or diene rubber increases. A rubber composition having excellent wear resistance can be obtained.

  In the present invention, the hydrocarbon group represented by R described above has 1 to 22 carbon atoms. If the number of carbon atoms is 1 or more, PHA has a hydrocarbon group, so that an effect of reducing fuel consumption can be obtained. If the number of carbon atoms is 22 or less, an increase in viscosity during production of an unvulcanized rubber composition can be suppressed, and processability Is obtained. The number of carbon atoms is particularly preferably 2 or more, more preferably 3 or more, and particularly preferably 20 or less, and further preferably 18 or less.

The PHA blended in the present invention may contain only one kind of structural units represented by the above general formula, but contains two or more kinds of structural units having different hydrocarbon groups represented by the above R. Also good. Of the hydrocarbon groups represented by R, as a hydrocarbon group containing one double bond, CH ₃ (CH ₂ ) ₅ CH═CHCH ₂ —, CH ₃ (CH ₂ ) ₅ CH═CH (CH ₂ ) _3- , CH ₃ CH ₂ CH = CHCH _2- , CH ₃ (CH ₂ ) ₃ CH = CHCH _2- , CH ₃ (CH ₂ ) ₄ CH = CH-, CH ₃ (CH ₂ ) ₄ CH ═CH (CH ₂ ) ₂ —, CH ₃ (CH ₂ ) ₇ CH═CHCH ₂ —, CH ₃ (CH ₂ ) ₇ CH═CH (CH ₂ ) ₃ —, CH ₃ (CH ₂ ) ₉ CH═CHCH ₂ - such as a hydrocarbon group containing 2 or more double _{bonds, CH 3 (CH 2) 4} CH = CHCH 2 CH = CHCH 2 -, CH 3 (CH 2) 4 CH = CHCH 2 CH = CH (CH 2) _{3 -, CH 3 CH 2 CH} = CHCH 2 CH = CH- and the like, can be exemplified, and these hydrocarbon groups It is preferred that one or more kinds are contained. Among them, PHA represents a hydrocarbon group represented by R in the above general formula as CH ₃ (CH ₂ ) ₅ CH═CHCH ₂ — and CH ₃ (CH ₂ ) ₅ CH═CH (CH ₂ ) ₃ —. In particular, it is particularly preferred in that the flexibility of PHA and the compatibility between PHA and natural rubber and / or diene rubber are good.

  In the present invention, it is preferable that PHA substantially consists of only one or more structural units represented by the above general formula, but the PHA has a different structure represented by R in the above general formula. Other structural units may be included. Examples of such other structural units include those in which the structure corresponding to R in the above general formula is a hydrocarbon group having no double bond. In this case, the number of one or more structural units satisfying the above general formula preferably accounts for 5% or more, further 10% or more, and further 15% or more of the total number of structural units constituting the PHA. In this case, a rubber composition having sufficiently high compatibility between natural rubber and / or diene rubber and PHA and excellent wear resistance can be obtained. Further, when PHA has other structural units that differ only in the structure represented by R in the above general formula, all structural units in which the number of one or more structural units satisfying the above general formula constitutes PHA Carbon of other structural units which occupy 5% or more of the number and satisfy the above general formula within the range of 8 to 18 carbon atoms and / or differ only in the structure represented by R of the above general formula It is preferable that the number is adjusted to be in the range of 4-18. Here, the other structural unit is preferably composed of only those having a carbon number in the range of 4 to 18, but may be in the above range as a weight average of the entire PHA molecular chain.

  In this invention, PHA is mix | blended within the range of 0.5-80 mass parts with respect to 100 mass parts of rubber components containing a natural rubber and / or a diene rubber. When the blending amount is less than 0.5 parts by mass, the effect of improving rolling resistance characteristics and wet grip performance cannot be sufficiently obtained by blending PHA. When the blending amount exceeds 80 parts by mass, the dispersibility of PHA deteriorates and wear resistance is increased. However, other workability that cannot be sufficiently obtained deteriorates. The blending amount of PHA is particularly preferably in the range of 3 to 60 parts by mass, and more preferably in the range of 5 to 50 parts by mass.

  It is preferable that the weight average molecular weight of PHA mix | blended in this invention exists in the range of 500-20,000. If the weight average molecular weight is 500 or more, there is little risk of PHA blooming on the rubber surface. Moreover, if it is 20,000 or less, PHA can be uniformly disperse | distributed in a rubber composition, and there is little risk that a wear-resistant fall will arise. In view of the balance of wear resistance, rolling resistance characteristics, and wet grip performance, the weight average molecular weight is preferably in the range of 500 to 15,000.

  The molecular structure and content of the structural unit in the blended PHA can be evaluated using a gas chromatograph, a nuclear magnetic resonance apparatus (NMR) or the like, and the weight average molecular weight of the PHA can be measured using a gel permeation chromatograph (GPC) or the like. It can be evaluated.

  The PHA blended in the present invention is produced, for example, by using a microorganism that produces PHA. As microorganisms that produce PHA, for example, microorganisms belonging to the genus Pseudomonas are preferably used, and specific examples include Pseudomonas oleovorans and Pseudomonas putida.

  As a carbon source in producing PHA using a microorganism that produces PHA, unsaturated fatty acids and derivatives thereof are preferably used. Specifically, long-chain unsaturated fatty acids having 12 to 26 carbon atoms and derivatives thereof, Examples include triglycerides obtained from long chain unsaturated fatty acids having 12 to 26 carbon atoms and derivatives thereof, vegetable oils, animal oils, fish oils containing long chain fatty acids having 12 to 26 carbon atoms, or derivatives thereof. Among them, long-chain fatty acids such as oleic acid, linoleic acid, linolenic acid, and triglycerides obtained from these fatty acids, palm oil, coconut oil, corn oil, olive oil, rapeseed oil, soybean oil and other vegetable oils, fish oil, whale oil, pork fat, Animal oil such as beef tallow is preferably used.

  As a method for producing PHA, a generally used microorganism culturing method can be adopted, and examples thereof include a method of culturing under a restrictive condition of a nitrogen source. Specifically, the target PHA can be obtained by, for example, a method in which a microorganism is grown in the presence of an arbitrary carbon source and then cultured by supplying the above-described carbon source as a PHA synthesis raw material.

  The obtained PHA can be recovered by a commonly used method. Specifically, after completion of the culture, a method of extracting with a PHA-soluble organic solvent such as chloroform, a method of precipitating and recovering a PHA-insoluble organic solvent such as methanol, a method of extracting by alkali treatment or enzyme treatment, cells A method of extracting PHA after pulverizing cells with a pulverizer or the like, a method of separating and recovering with an ultrafiltration membrane or the like can be employed.

  The rubber component of the present invention includes natural rubber and / or diene rubber. Diene rubbers include styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), and butyl rubber. (IIR), halogenated butyl rubber and the like. These rubbers may be used alone or in combination of two or more.

  The rubber component of the present invention contains a functional group-containing natural group containing at least one functional group selected from an alkoxyl group, an alkoxysilyl group, an epoxy group, a glycidyl group, a carbonyl group, an ester group, a hydroxy group, an amino group, and a silanol group. It is preferable to include rubber and / or a functional group-containing diene rubber. When natural rubber and / or diene rubber contains these functional groups, the effect of improving the compatibility between the rubber component and PHA is obtained. When the rubber component contains epoxidized natural rubber, it is preferable in that the compatibility between the rubber component and PHA is particularly good.

  At least one functional group selected from an alkoxyl group, an alkoxysilyl group, an epoxy group, a glycidyl group, a carbonyl group, an ester group, a hydroxy group, an amino group, and a silanol group is a functional group-containing natural rubber or a functional group-containing diene system. It is preferably contained in the rubber in the range of 1 to 80 mol%. If the content of the functional group is 1 mol% or more, the effect of improving the compatibility between the rubber component and PHA can be obtained satisfactorily, and if it is 80 mol% or less, the viscosity at the production of the unvulcanized rubber composition The rise is suppressed and processability is improved.

  As a method of incorporating natural rubber and / or diene rubber with at least one functional group selected from an alkoxyl group, an alkoxysilyl group, an epoxy group, a glycidyl group, a carbonyl group, an ester group, a hydroxy group, an amino group, and a silanol group For example, a method of introducing a functional group into a polymerization terminal of a styrene-butadiene copolymer polymerized with an organolithium initiator in a hydrocarbon solvent, a natural rubber or a diene rubber by a chlorohydrin method, a direct oxidation And a method of epoxidation by a method such as a hydrogen peroxide method, an alkyl hydroperoxide method, and a peracid method.

  Further, in the present invention, the silica is in the range of 5 to 150 parts by mass and the silane coupling agent is in the range of 1 to 20% by mass with respect to the silica content with respect to 100 parts by mass of the rubber component. It is preferable to contain each so that it may become. When the blending amount of silica is 5 parts by mass or more, heat generation of the tire during running is reduced, and good wet grip performance and wear resistance are obtained. Moreover, when it is 150 mass parts or less, the workability at the time of manufacture of a rubber composition, and workability | operativity become favorable by the viscosity rise at the time of manufacture of an unvulcanized rubber composition being suppressed.

As the silica, those conventionally used for reinforcing rubber can be used. For example, the silica can be appropriately selected from dry silica, wet silica, colloidal silica and the like. In addition, it is preferable to use one having a nitrogen adsorption specific surface area (N ₂ SA) in the range of 100 to 300 m ² / g, and further in the range of 120 to 280 m ² / g. When N ₂ SA of silica is 100 m ² / g or more, it is preferable in terms of a large reinforcing effect on the rubber composition, and when it is 300 m ² / g or less, the dispersibility of the silica in the rubber composition is good, It is preferable at the point which can prevent the exothermic increase of a rubber composition.

  The rubber composition of the present invention preferably further contains a silane coupling agent. When the content of the silane coupling agent is 1% by mass or more with respect to the content of silica, a coupling effect by the blending of the silane coupling agent is sufficiently obtained. Even if the silane coupling agent is added in an amount of more than 20% by mass, the increase in the coupling effect is small for the cost increase, and if the content of the silane coupling agent is excessively high, the reinforcing property and wear resistance are increased. However, the content of the silane coupling agent with respect to the content of silica is preferably 20% by mass or less because it may decrease. The content is particularly preferably in the range of 2 to 15 parts by mass.

  As the silane coupling agent, any silane coupling agent conventionally used in combination with a silica filler can be used. Specifically, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) Tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-methyldiethoxysilylpropyl) tetrasulfide, bis (2-methyldiethoxysilylethyl) Tetrasulfide, bis (4-methyldiethoxysilylbutyl) tetrasulfide, bis (3-methyldimethoxysilylpropyl) tetrasulfide, bis (2-methyldimethoxysilylethyl) tetrasulfide, bis (4-methyldimethoxysilylbutyl) Til) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) Trisulfide, bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, bis (3-methyldiethoxy) Silylpropyl) disulfide, bis (2-methyldiethoxysilylpropyl) disulfide, bis (4-methyldiethoxypropyl) disulfide, bis (3-methyldimethoxysilylpropyl) disulfide, bis (2-methyldimethoxysilylpropyl) disulfide, Bis (4-methyldimethoxysilylbutyl) disulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-aminopropyltriethoxysilane 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycine De trimethoxy silane, .gamma.-glycidoxypropyltrimethoxysilane, .gamma.-glycidoxypropylmethyldiethoxysilane, .gamma.-glycidoxypropyl methyldimethoxysilane, and the like.

  Of these, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, and the like are particularly preferably used in terms of both the coupling effect and the manufacturing cost. These silane coupling agents may be used alone or in combination of two or more.

  The rubber composition of the present invention includes the above rubber component, PHA, silica, silane coupling agent, filler such as carbon black, softener, antioxidant, ozone degradation inhibitor, anti-aging agent, sulfur Other additives such as vulcanizing agents, vulcanization accelerators, vulcanization accelerating aids, peroxides, zinc oxide, stearic acid, and the like can be appropriately blended.

  When carbon black is blended, the blending amount of the carbon black is preferably, for example, 100 parts by mass or less, and more preferably 1 to 80 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount of carbon black is 100 parts by mass or less, there is little risk of deteriorating the dispersibility and workability during preparation of the rubber composition.

The carbon black, the nitrogen adsorption specific surface area, for example in the range of 80~280m ² / g, are preferably used those further in the range of 100 to 200 m ² / g. If the nitrogen adsorption specific surface area is 80 m ² / g or more, good wet grip performance and wear resistance can be obtained when the rubber composition is used in a tire, and if it is 280 m ² / g or less, a rubber composition is obtained. The deterioration of the abrasion resistance of the rubber composition due to the deterioration of the dispersibility of carbon black during the preparation is prevented.

  A silane coupling agent is blended in the rubber composition of the present invention, but other coupling agents such as aluminate coupling agents and titanium coupling agents can be used in combination depending on the application.

  Further, the rubber composition for tires of the present invention may further contain inorganic fillers such as clay, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, titanium oxide alone or in combination. A mixture of more than one species can be used.

  Softeners include petroleum-based softeners such as process oil, lubricating oil, paraffin, liquid paraffin, petroleum asphalt, and petroleum jelly, and fatty oil-based softeners such as soybean oil, palm oil, castor oil, linseed oil, rapeseed oil, and coconut oil. Agents, waxes such as tall oil, sub, beeswax, carnauba wax and lanolin, and fatty acids such as linoleic acid, palmitic acid, stearic acid and lauric acid. The blending amount of the softening agent is preferably 100 parts by mass or less with respect to 100 parts by mass of the rubber component, and in this case, there is a risk of reducing the wet grip performance when the rubber composition is used in a tire. Less is.

  As the vulcanizing agent, an organic peroxide or a sulfur vulcanizing agent can be used. Examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2, 5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne- 3 or 1,3-bis (t-butylperoxypropyl) benzene or the like can be used. Moreover, as a sulfur type vulcanizing agent, sulfur, morpholine disulfide, etc. can be used, for example. Of these, sulfur is preferred.

  Vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerators. Those containing at least one of them can be used.

  Examples of the sulfenamide system include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (Nt-butyl-2-benzothiazylsulfenamide), N, N-dicyclohexyl-2- Examples thereof include sulfenamide compounds such as benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, and N, N-diisopropyl-2-benzothiazolesulfenamide.

  Examples of the thiazole type include MBT (2-mercaptobenzothiazole), MBTS (dibenzothiazyl disulfide), sodium salt of 2-mercaptobenzothiazole, zinc salt, copper salt, cyclohexylamine salt, 2- (2,4-dinitro). Phenyl) mercaptobenzothiazole, 2- (2,6-diethyl-4-morpholinothio) benzothiazole and the like.

  Examples of thiurams include TMTD (tetramethylthiuram disulfide), tetraethylthiuram disulfide, tetramethylthiuram monosulfide, dipentamethylenethiuram disulfide, dipentamethylenethiuram monosulfide, dipentamethylenethiuram tetrasulfide, dipentamethylenethiuram hexasulfide. , Tetrabutyl thiuram disulfide, pentamethylene thiuram tetrasulfide and the like.

  Examples of thiourea compounds include thiourea compounds such as thiacarbamide, diethyl thiourea, dibutyl thiourea, trimethyl thiourea, and diortolyl thiourea.

  Examples of guanidine compounds include guanidine compounds such as diphenyl guanidine, diortolyl guanidine, triphenyl guanidine, orthotolyl biguanide, and diphenyl guanidine phthalate.

  Examples of dithiocarbamate include zinc ethylphenyldithiocarbamate, zinc butylphenyldithiocarbamate, sodium dimethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc diamyldithiocarbamate, zinc dipropyldithiocarbamate And a complex salt of zinc pentamethylenedithiocarbamate and piperidine, zinc hexadecyl (or octadecyl) isopropyldithiocarbamate, and the like.

  Examples of the aldehyde-amine system or aldehyde-ammonia system include acetaldehyde-aniline reaction product, butyraldehyde-aniline condensate, hexamethylenetetramine, acetaldehyde-ammonia reaction product, and the like.

  As the anti-aging agent, amine-based, phenol-based, and imidazole-based compounds, carbamic acid metal salts, waxes, and the like can be appropriately selected and used.

  Furthermore, a plasticizer can be mix | blended with the rubber composition for tires of this invention as needed. Specifically, DMP (dimethyl phthalate), DEP (diethyl phthalate), DHP (diheptyl phthalate), DOP (dioctyl phthalate), DINP (diisononyl phthalate), DIDP (diisodecyl phthalate), BBP (phthalate) Acid butyl benzyl), DLP (dilauryl phthalate), DCHP (dicyclohexyl phthalate), hydrophthalic anhydride ester, DOZ (di-2-ethylhexyl azelate), DBS (dibutyl sebacate), and the like.

  The rubber composition for tires of the present invention includes, for example, an organic acid such as phthalic anhydride, salicylic acid, benzoic acid, a nitroso compound such as N-nitrosodiphenylamine, N-cyclohexylthio as an anti-scorch agent for preventing or retarding scorch. Phthalimide or the like can be used.

  The method for producing a tire using the rubber composition of the present invention is not particularly limited. For example, the rubber composition of the present invention is extruded in accordance with the shape of a tire member applied in an unvulcanized stage, A conventionally used method such as a method of obtaining a tire by pressing with a tire molding machine can be employed.

  The rubber composition of the present invention can be suitably applied to various tires for passenger cars, trucks / buses, heavy machinery and the like. FIG. 1 is a cross-sectional view showing the right half of a pneumatic tire according to the present invention. The tire T has a bead portion 1, a sidewall portion 2, and a tread portion 3. Further, a bead core 4 is embedded in the bead portion 1. Further, a carcass 5 provided from one bead portion 1 to the other bead portion, folded back at both ends to lock the bead core 4, and a belt layer 6 composed of two or more belt plies outside the crown portion of the carcass 5, Is arranged. A bead apex 7 extending in the sidewall direction from the upper end of the bead core 4 is disposed in a region surrounded by the carcass 5 and the folded portion 5a. The rubber composition of the present invention can be suitably used mainly for tread parts, sidewall parts, carcass plies and belt plies of pneumatic tires.

[Example]
EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Synthesis of PHA>
PHA was synthesized by microorganisms using oleic acid as a carbon source. Pseudomonas putida PGA1 was cultured at 30 ° C. for 6 hours using the initial medium shown below, and further cultured for 72 hours while sequentially adding an aqueous oleic acid solution and an aqueous magnesium sulfate solution shown below as feed stock solutions. After completion of the culture, the cells were collected by centrifugation, and the cells were washed with distilled water and methanol. Thereafter, extraction with chloroform yielded the desired PHA. The composition ratio of the monomer unit as a structural unit of the obtained PHA was evaluated by a gas chromatograph (“GC-14A” manufactured by Shimadzu Corporation). The column used is “Rtx-200” manufactured by RESTEK, and the measurement conditions are an initial temperature of 60 ° C., a heating rate of 8 ° C./min, and a final temperature of 300 ° C. for 30 minutes. The results are shown in Table 1.

Further, the molecular structure of the obtained PHA was evaluated with a nuclear magnetic resonance apparatus (“UNITY INOVA-500” (500 MHz) manufactured by Varian). The solvent was deuterated chloroform, the measurement conditions for ¹ H-NMR were a pulse width of 2.9 μsec, the repetition time was 1.95 sec, and the number of integrations was 64 times. The measurement condition for ¹³ C-NMR was a pulse width of 4.0 μsec. The monomer unit of PHA represented by the above general formula was assigned from the NMR spectrum, with a repetition time of 15 sec and a cumulative number of 5000 times. The number of carbon atoms of the assigned monomer unit and the structure represented by R in the above general formula are as follows.
(C: 6) CH ₃ (CH ₂ ) ₂ −
(C: 8) CH ₃ (CH ₂ ) ₄ −
(C: 10) CH ₃ (CH ₂ ) ₆ −
(C: 12) CH ₃ (CH ₂ ) _8- and CH ₃ (CH ₂ ) ₅ CH = CHCH _2-
(C: 14) CH ₃ (CH ₂ ) ₁₀ − and CH ₃ (CH ₂ ) ₅ CH═CH (CH ₂ ) ₃ −
Furthermore, the weight average molecular weight (Mw) of the obtained PHA was evaluated by gel permeation chromatograph (GPC) (“HLC-8020” manufactured by Tosoh Corporation). The column used was “TSKgel GMH _XL ” manufactured by Tosoh Corporation, and the mobile phase was tetrahydrofuran. The weight average molecular weight of the obtained PHA was Mw = 13,000.

(Initial medium)
Total capacity: 3L
(NH ₄ ) ₂ HPO ₄ : 3.66 g / L
Oleic acid: 15 g / L
pH: 6.8
The pH adjustment was performed using 2M NH ₄ OH and 2M NaOH.

(Supply stock solution)
Oleic acid: 15 g / L
MgSO ₄ · H ₂ O: 5 g / L

<Manufacture of rubber composition>
Of the blending components shown in Table 2, the components excluding sulfur and the vulcanization accelerator were kneaded at 130 to 140 ° C. for 5 minutes using a 1.7 liter closed mixer to obtain a master batch. Sulfur and a vulcanization accelerator were added to this master batch and kneaded at 50 ° C. for 5 minutes using an 8-inch open roll to obtain an unvulcanized rubber composition. This was further press vulcanized at 170 ° C. for 20 minutes to obtain rubber compositions of Examples and Comparative Examples. The following characteristics evaluation was performed about the unvulcanized rubber composition and the obtained rubber composition.

<Processability>
With respect to the unvulcanized rubber composition, the Mooney viscosity (ML1 + 4) was measured at 130 ° C. according to the Mooney viscosity measurement method defined in JIS K6300, and the Mooney viscosity index defined by the following equation was calculated. The larger the Mooney viscosity 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 Example or each Comparative Example) × 100
The results are shown in Table 2.

<Abrasion resistance>
About the obtained rubber composition, the amount of lamborn wear was measured with a lambone wear tester under the conditions of a temperature of 20 ° C., a slip rate of 20%, and a test time of 5 minutes. The volume loss was calculated, and the wear index defined by the following equation was calculated. The higher the index, the better the wear resistance.
Abrasion index = (volume loss of comparative example 1) / (volume loss of each example or each comparative example) × 100
The results are shown in Table 2.

<Rolling resistance characteristics>
About the obtained rubber composition, using the viscoelastic spectrometer “VES” (manufactured by Iwamoto Seisakusho Co., Ltd.), the rubber of each example and each comparative example under conditions of a temperature of 70 ° C., an initial strain of 10%, and a dynamic strain of 2%. The tan δ of the composition was measured, and the rolling resistance index defined by the following formula was calculated. The larger the rolling resistance index, the better the rolling resistance characteristics.
Rolling resistance index = (tan δ of Comparative Example 1) / (tan δ of each Example or each Comparative Example) × 100
The results are shown in Table 2.

<Wet grip performance>
About the obtained rubber composition, the wet skid was measured according to the method of ASTM E303-83 using a portable skid tester manufactured by Stanley, and the wet skid index defined by the following formula was calculated. The higher the wet skid index, the better the wet grip performance.
Wet skid index = (measured value of each example or comparative example) / (measured value of comparative example 1) × 100
The results are shown in Table 2.

Note 1: Natural rubber is RSS # 3.
Note 2: The epoxidized natural rubber is “ENR-50” (epoxidation rate: 50 mol%) manufactured by Kumplan Guthrie Berhad (Malaysia).
Note 3: SBR is “SBR1502” (styrene unit amount: 23.5 mass%) manufactured by JSR Corporation.
Note 4: The functional group-containing SBR is a hydroxyl (OH) group-containing styrene butadiene rubber “ASAPRENE E10” (styrene unit amount: 39% by mass) manufactured by Asahi Kasei Corporation.
Note 5: Silica is “Ultrasil VN3” (N ₂ SA: 210 m ² / g) manufactured by Degussa.
Note 6: The silane coupling agent is “Si266” (bis (3-triethoxysilylpropyl) disulfide) (average value of l: 2.2) manufactured by Degussa.
Note 7: Aroma oil is “JOMO Process X140” manufactured by Japan Energy Corporation.
Note 8: The anti-aging agent is “NOCRACK 6C” (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Note 9: Stearic acid is manufactured by NOF Corporation.
Note 10: Zinc oxide is “Zinc Hana 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
Note 11: Sulfur is “powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.
Note 12: Vulcanization accelerator TBBS is “Noxeller NS” (N-tert-butyl-2-benzothiazyl sulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Note 13: The vulcanization accelerator DPG is “Noxeller D” (N, N′-diphenyl guanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

  From the result shown in Table 2, in Examples 1-3 using the rubber composition containing PHA containing a specific structural unit, it has the same compounding components as Examples 1-3 except for not containing PHA. Compared to Comparative Examples 1 to 3 using the rubber composition, the rolling resistance index and the wet skid index are improved while maintaining the Mooney viscosity index and the wear index equal to or higher than those. Therefore, it can be seen that by using the rubber composition of the present invention, it is possible to obtain a pneumatic tire having improved rolling resistance characteristics and wet grip performance while maintaining processability and wear resistance.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  In the present invention, a rubber composition containing a polyhydroxyalkanoate (PHA) containing a specific structural unit is used for, for example, a tread portion, a sidewall portion, a carcass ply, a belt ply or the like of a pneumatic tire. Thus, it is possible to obtain a pneumatic tire in which rolling resistance characteristics and wet grip performance are improved in a well-balanced manner while maintaining good workability and wear resistance.

It is sectional drawing which shows the right half of the pneumatic tire which concerns on this invention.

Explanation of symbols

  T tire, 1 bead part, 2 sidewall part, 3 tread part, 4 bead core, 5 carcass, 5a folded part, 6 belt layer, 7 bead apex.

Claims (6)

For 100 parts by mass of the rubber component containing natural rubber and / or diene rubber, the following general formula:

(In the formula, R is a C1-C22 hydrocarbon group containing one or more double bonds)
The rubber composition which contains the polyhydroxyalkanoate which contains 1 type or 2 types or more of structural units represented by 0.5-80 mass parts.   The rubber composition according to claim 1, wherein the polyhydroxyalkanoate has a weight average molecular weight in the range of 500 to 20,000.   A functional group-containing natural rubber in which the rubber component contains at least one functional group selected from an alkoxyl group, an alkoxysilyl group, an epoxy group, a glycidyl group, a carbonyl group, an ester group, a hydroxy group, an amino group, and a silanol group; 2. The rubber composition according to claim 1, comprising a functional group-containing diene rubber.   The rubber composition according to claim 1, wherein the rubber component comprises an epoxidized natural rubber.   2 to 150 parts by mass of silica, and 1 to 20% by mass of a silane coupling agent with respect to the content of silica, respectively, with respect to 100 parts by mass of the rubber component. The rubber composition as described.   A pneumatic tire using the rubber composition according to claim 1.

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