JP5251320B2 - Pneumatic run flat tire - Google Patents

Description

  The present invention relates to a pneumatic run-flat tire, and more particularly, to a pneumatic run-flat tire that is improved in run-flat durability while reducing weight.

  In the pneumatic tire for run flat, a side reinforcing layer made of hard rubber having a crescent cross section is inserted in the left and right sidewall portions, and a self-supporting type tire that supports the load by the side reinforcing layer, A pneumatic tire is the same as a normal tire, but there is a core support type in which a core support is mounted on the wheel side and a load is supported from the inner surface of the tire by the core support.

  Among these, in the former self-supporting pneumatic run-flat tire 100, as shown in FIG. 6, the side wall portion is curved inward during the run-flat running, and the tread portion 102 is grounded at both ends and the center portion. Set to a state in which it is warped up. Therefore, the buttress portions 103 on both outer sides of the tread portion 102 are strongly bent, and the inner liner layers in the region surrounded by the circle C in the figure strongly contact each other to generate heat due to friction and eventually break down. There is a phenomenon. 101 is a rim.

  In order to prevent such a destructive phenomenon and improve the run-flat durability, the volume of the side reinforcing layer 104 having a crescent-shaped cross section inserted into the side wall portion may be increased. However, when the volume of the side reinforcing layer 104 is increased, the tire weight increases, and thus there is a problem that fuel efficiency during normal driving is increased.

  On the other hand, in a core-support type pneumatic run flat tire, as a proposal for suppressing heat generation due to friction between the core support and the tire inner surface during run flat running, It has been proposed to form a lubricant layer containing a lubricant on at least one of the child support surfaces (Patent Document 1).

However, the core-supported run-flat tire described in Patent Document 1 suppresses heat generation on the inner surface of the tread. This does not contribute to the improvement of the run-flat durability of a pneumatic run-flat tire having a self-supporting side reinforcing layer where the occurrence location is in the vicinity of the buttress portion.
JP 2004-175222 A

  An object of the present invention is to provide a pneumatic run-flat tire having a side reinforcing layer made of hard rubber having a crescent-shaped cross section in view of the above points, and can greatly improve run-flat durability while reducing the weight. The object is to provide a pneumatic run-flat tire.

  The run flat tire of the present invention that achieves the above-mentioned object is a pneumatic run flat tire in which side reinforcing layers made of hard rubber having a crescent cross section are inserted in the left and right sidewall portions, and an inner liner layer is disposed on the inner surface of the tire. The pneumatic run-flat tire in which a hollow capsule containing a lubricant is blended in at least one of the inner liner layer and the side reinforcing layer.

  According to the pneumatic run-flat tire of the present invention, in the run-flat tire having the side reinforcement layer, since the hollow capsule containing the lubricant is blended in at least one of the inner liner layer and the side reinforcement layer, the inner liner layer And / or weight reduction of a side reinforcement layer can achieve the weight reduction of the whole run flat tire, and can aim at the fuel consumption reduction at the time of normal driving | running | working. In addition, when running on a flat run, when the tire inner surface of the buttress part comes into contact with the rubber and wears away, the lubricant in the hollow capsule oozes out so that friction can be suppressed, thus improving run flat tire durability. Can do it.

  Hereinafter, the pneumatic run flat tire of the present invention will be specifically described.

  In the pneumatic run flat tire 1 according to the present invention shown in FIG. 1, 2 is a tread portion, 3 is a sidewall portion, 4 is a bead portion, and 6 is a bead filler. The buttress part 5 is formed so as to be located on the radially outer side of the sidewall part 3 and to be continuous with the outer side of the end part of the tread part 2. A carcass layer 8 is disposed so as to straddle between the left and right bead cores 7 inserted into the bead portion 4, and a belt layer 9 made of a steel cord and a belt cover layer made of an organic fiber cord on the outer peripheral side of the carcass layer 8. 10 are provided. An inner liner layer 11 for preventing air permeation is provided on the inner surface of the tire. A side reinforcing layer 12 made of hard rubber having a crescent-shaped cross section is inserted inside the sidewall portion 3 so as to be interposed between the carcass layer 8 and the inner liner layer 11.

  As shown in FIG. 2, at least one rubber layer of the inner liner layer 11 and the side reinforcing layer 12 is blended with a number of hollow capsules 13, and a gas is contained in the hollow capsules 13 together with a lubricant. ing. The blending density in the rubber layer of the hollow capsule 13 may be uniform throughout the inner liner layer 11 and / or the side reinforcing layer 12, but is preferably distributed so as to have a higher density especially in a necessary region. It is good to let them.

  In the embodiment of FIG. 3, when the hollow capsule 13 is blended with the side reinforcing layer 12, the blending density in the rubber layer of the hollow capsule 13 is determined by the outer region 14 and the inner region 15 in the tire radial direction of the side reinforcing layer 12. In other words, the blending density of the radially outer region 14 is made higher than the blending density of the radially inner region 15.

  As described above, during the run-flat running, the inner surfaces of the tires in the buttress portion 5 are particularly in contact with each other and wear or generate heat, so that the blending density of the hollow capsules 13 in the radially outer region 14 is increased. In addition, wear and heat generation on the tire inner surface can be effectively suppressed, and run-flat durability can be improved.

  In the embodiment of FIG. 4, similarly, when the hollow capsules 13 are blended in the side reinforcing layer 12, the blending density of the hollow capsules in the tire inner region 16 of the side reinforcing layer 12 is higher than the blending density in the tire outer region 17. It is configured. In this way, by increasing the blending density of the hollow capsules in the entire tire inner region, it is possible to suppress wear and heat generation regardless of where the rubber on the tire inner surface comes into contact.

  In the embodiment of FIG. 5, when the hollow capsule 13 is blended in the inner liner layer 11, the thickness of the inner liner layer 11 is made larger only in the region corresponding to the buttress portion 5 than in the other region, A larger amount of the hollow capsule 12 is arranged.

  As described above, as the region A in which the thickness of the inner liner layer 11 is increased, the intersection point p where a perpendicular is drawn from the end of the belt cover layer 10 to the inner liner layer 11 and the midpoint q of the tire cross-section height H are included. At least the region between the two points p and q is used, and the thickness of the inner liner layer 11 in this region A is preferably 1.2 to 3.5 times the thickness of the inner liner layer on the tire equator. In this way, by increasing the thickness of the inner liner layer at least in the region corresponding to the buttress portion 5, the absolute amount of the hollow capsule is arranged in a larger amount than the portion other than the region A. It can suppress so that the tire inner surface corresponding to the part 5 may not be worn out. When the thickness of the region A exceeds 3.5 times the thickness of the inner liner layer on the tire equator, the mass becomes too large, which is not preferable. The advantageous effect described above is less than 1.2 times. Becomes smaller.

  In the illustrated embodiment described above, the side reinforcing layer 12 is disposed inside the carcass layer 8, but in the present invention, the positional relationship between the carcass layer 8 and the side reinforcing layer 12 is not limited thereto. The side reinforcing layer 12 may be disposed outside the tire of the carcass layer 8. In particular, in a tire in which two or more carcass layers are provided, it is preferably disposed between those carcass layers.

  In the present invention, the hollow capsule has a configuration in which a lubricant is included in the shell together with the expansion gas.

  As the lubricant, naphthenic oil, paraffin oil, aroma oil, or silicone oil is preferably used. Although these can use what is marketed for rubber | gum compounding, it is preferable that it is a nonpolar thing from points, such as compatibility with the rubber | gum which comprises a side reinforcement layer and an inner liner layer.

  The shell of the hollow capsule 10 is not particularly limited, but is preferably made of a thermoplastic resin, and it is preferable that the shell contains a substance that generates gas by being vaporized or expanded by heat. The hollow capsule is blended with an unvulcanized rubber material and then molded into a green tire. Before the green tire is vulcanized, the capsule contains an expandable substance. This is vaporized and expanded by heat during vulcanization to form a space inside. The manufacturing method of a hollow capsule is well-known, and there are also many commercial items. Preferably, the hollow capsule includes a thermoplastic resin particle that includes a lubricant that is vaporized or expanded by heat to generate gas and a non-polar oil. The use ratio of the vaporizable / swellable substance and the lubricant is preferably such that the weight fraction of the lubricant is 1 to 20% by weight based on the total weight of the lubricant and the vaporizable substance.

  As the thermoplastic resin constituting the shell of the hollow capsule, the main monomer is nitrile monomer (I), and this nitrile monomer (I) and unsaturated double bond in the molecule A polymer obtained by polymerizing a monomer (II) having a carboxyl group and a monomer (III) having two or more polymerizable double bonds is preferred.

  More preferably, the thermoplastic resin constituting the shell of the hollow capsule is a copolymerizable monomer for adjusting expansion characteristics in addition to the monomers (I), (II), and (III). Those composed of a polymer obtained by polymerization together with (IV) are preferred.

  The blending ratio of each monomer is preferably 40 to 90% by weight, more preferably 50 to 85% by weight of nitrile monomer (I), and preferably an unsaturated double bond in the molecule. And monomer (II) having a carboxyl group in an amount of 7 to 50% by weight, more preferably 10 to 45% by weight, and preferably a monomer (III) having two or more polymerizable double bonds. It is good to contain 0.05 to 5 weight%, More preferably, it is 0.2 to 3 weight%. Further, the copolymerizable monomer (IV) for adjusting the expansion property to be copolymerized as necessary may contain 0 to 20% by weight, more preferably 0 to 15% by weight.

  The thermally expandable hollow capsule preferably has a volume retention of 50% or more, more preferably 70 to 100, after applying a load of 15 MPa to the expanded body heated and expanded in a state where it is not blended in the rubber layer. % Range. In order to obtain thermally expandable hollow capsules by these polymerizations, the polymerization initiator is an oil-soluble peroxide or an azobis compound and has a half-life of 1 to 25 hours at the reaction temperature. Is preferably used.

  In the present invention, examples of the nitrile monomer (I) that can be used include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile, and the like, and mixtures thereof. Particularly preferred is acrylonitrile and / or methacrylonitrile. The copolymerization ratio of the monomer (I) is preferably 35 to 95% by weight, more preferably 45 to 90% by weight.

  Examples of the monomer (II) having an unsaturated double bond and a carboxyl group in the molecule include acrylic acid (AA), methacrylic acid (MAA), itaconic acid, styrene sulfonic acid or sodium salt, maleic acid, citracone Examples are acids and mixtures thereof. The copolymerization ratio of the monomer (II) is preferably 4 to 60% by weight, more preferably 10 to 50% by weight. If the copolymerization ratio of the monomer (II) is less than 4% by weight, the expandability in the high temperature region may be lowered.

  Examples of the monomer (III) having two or more polymerizable double bonds include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene, allyl methacrylate, triacryl formal, triallyl isocyanate, ethylene glycol di (meta) ) Acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,4-butanediol (meth) acrylate, 1,9-nonanediol di (meth) acrylate, polyethylene glycol having a weight average molecular weight of 200 (PEG # 200) di (meth) acrylate, polyethylene glycol having a weight average molecular weight of 400 (PEG # 400) di (meth) acrylate, 1,6-hexanediol (meth) acrylate, trimethylolpropane tri Methacrylate, and the like and mixtures of these.

  The copolymerizable monomer (IV) may be additionally copolymerized in order to adjust the expansion characteristics. Examples of the copolymerizable monomer (IV) include vinylidene chloride and vinyl acetate. , (Meth) acrylate esters such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, styrene, styrene sulfonic acid or the like Examples thereof include styrene monomers such as sodium salt, α-methylstyrene and chlorostyrene, acrylamide, substituted acrylamide, methacrylamide and substituted methacrylamide. Monomer (IV) is an optional component, and when it is added, the copolymerization ratio is preferably 0.05 to 20% by weight, more preferably 1 to 15% by weight.

  The thermoplastic resin forming the shell of the hollow capsule can be obtained by suspension polymerization by a conventional method. The polymerization initiator is preferably an oil-soluble peroxide or an azobis compound and has a half-life at the reaction temperature of 1 to 25 hours, more preferably 5 to 20 hours. Examples of the polymerization initiator include peroxide compounds such as dialkyl peroxides, dialsyl peroxide, peroxy acid esters, peroxydicarbonates, and azo compounds.

  As the thermally expandable substance encapsulated in the shell of the hollow capsule, one having a property of vaporizing or expanding by heat and having a vapor pressure at 150 ° C. of 1.4 to 3.0 MPa is used. Preferably, the vapor pressure is 1.5 to 2.8 MPa. When the vapor pressure at 150 ° C. is lower than 1.4 MPa, when the average particle diameter before expansion of the hollow capsule is reduced, the expansion ratio cannot be increased, and a resin-coated bubble having a desired size is formed. Can not do it. On the other hand, if the vapor pressure at 150 ° C. is higher than 3.0 MPa, the processing stability is lowered, which is not preferable. Note that the vapor pressure at 150 in the thermally expandable material is a value approximated by the Rankine-Dupre vapor pressure equation.

  Such a heat-expandable substance is not particularly limited as long as it has the above-mentioned vapor pressure. For example, at least one selected from the group consisting of hydrocarbons such as isoalkane and normal alkane is used. Illustrated. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-rutilehexane, 2,2,4-trimethylpentane, etc., and normal alkanes include n-butane, n-bropan, n-hexane, Examples thereof include n-heptane and n-octane. These hydrocarbons may be used alone or in combination. Moreover, even if it is a substance other than the above, if it mixes with these hydrocarbons and the vapor pressure in 150 degreeC will be 1.4-3.0 Mpa, it can be mixed and used.

  Moreover, as a preferable form of the thermally expansible substance, one obtained by dissolving hydrocarbons which are gaseous at normal temperature in hydrocarbons which are liquid at normal temperature is preferable. By using such a mixture of hydrocarbons, a sufficient expansion force can be obtained from the low temperature region to the high temperature region in the vulcanization temperature range (150 to 190 ° C.) of the unvulcanized tire.

  In the present invention, the above-mentioned hollow capsule has an average particle size of about 15 to 50 μm, which is smaller than the conventional one, and a method for producing such a hollow capsule includes a monomer, a polymerization initiator, A dispersion is prepared by dispersing an oily mixture containing a thermally expandable substance or the like as oil droplets in an aqueous dispersion medium. Here, when the thermally expandable substance is a hydrocarbon which is a gas at normal temperature, it is preferably performed in a sufficiently cooled state. Subsequently, this dispersion liquid is heated by a conventionally known method to carry out suspension polymerization, whereby a hollow capsule can be obtained. In particular, in order to obtain hollow capsules having an average particle size of 20 to 30 μm, a continuous high-speed rotation high shear type stirring and dispersing machine is preferably used as described in JP-A-7-96167.

  An inner liner layer and a side reinforcement in which a rubber composition for an inner liner and a rubber composition for a side reinforcing material, each comprising a rubber composition shown in Table 1, were prepared, and the amounts of hollow capsules were as shown in Table 2, respectively. Pneumatic tires (conventional examples) using five types of pneumatic run-flat tires (Examples 1 to 5) having a layer and inner liners and side reinforcing layers not containing hollow capsules were produced.

  As the hollow capsule, one produced as follows was used.

  After mixing 45 g of colloidal silica having a solid content of 40%, 1 g of diethanolamine-adipic acid condensate, 150 g of sodium chloride and 500 g of ion-exchanged water, the pH was adjusted to 3.5 to produce an aqueous dispersion medium. Next, as an oil component, 70 g of acrylonitrile, 70 g of methacrylonitrile, 70 g of methacrylic acid, 3 g of ethylene glycol dimethacrylate and 1 g of azobis (2,4-dimethylylvaleronitrile) are mixed to obtain a monomer mixture in a uniform solution. It was adjusted. To this monomer mixture, 20 g of isopentene, 30 g of 2-methylpentane, and 2.6 g of aroma oil were added, and the mixture was charged into an autoclave, and an aqueous dispersion medium was further charged. After stirring the charged product at 700 rpm for 5 minutes, the inside of the autoclave was purged with nitrogen and reacted at a reaction temperature of 60 ° C. for 8 hours. The reaction pressure was 0.5 MPa and stirring was performed at 350 rpm. The thermal expansibility of the thermally expansible hollow capsule obtained by this reaction was analyzed.

  That is, when the expansion characteristics were analyzed by the method described in JP-A No. 11-2616 using a TMA-7 type manufactured by PerkinElmer, the foaming start temperature was 159 ° C., and the maximum expansion temperature was 210 ° C. there were.

  With respect to the above six types of pneumatic run flat tires, rolling resistance and run flat durability were measured by the following test methods, and the results are shown in Table 2.

  The evaluation was performed using an index with the rolling resistance and run flat durability of the conventional example as 100. The larger the index, the better the performance.

  The evaluation results are as shown in Table 2, and the pneumatic run-flat tire according to the present invention is excellent in rolling resistance due to its light weight and also very excellent in run-flat durability.

(1) Rolling resistance A tire having a tire size of 225 / 45R17 was assembled on a rim (17 × 71 / 2JJ) at an air pressure of 230 kPa, and the rolling resistance value at a load of 4.5 kN was measured using a rolling resistance tester. Evaluation was compared using the reciprocal of the measured value.

(2) Run-flat durability A test tire with a valve core of 0 kPa is attached to the right rear wheel of a 2500cc FR vehicle, and an elliptical circuit is run counterclockwise at 90 km / h under a load condition equivalent to four passengers. The distance traveled until failure occurred was measured and compared.

It is a meridian half sectional view showing a pneumatic run flat tire concerning the present invention. FIG. 2 is a cross-sectional view showing a situation in which hollow capsules are dispersed and arranged in a side reinforcing layer and / or an inner liner layer of the tire of FIG. 1. It is a meridian half sectional view showing other examples of the pneumatic run flat tire concerning the present invention. It is a meridian half cross-sectional view showing still another example of the pneumatic run-flat tire according to the present invention. It is a meridian half cross-sectional view showing still another example of the pneumatic run-flat tire according to the present invention. It is explanatory drawing which shows the condition at the time of run-flat driving | running | working of a pneumatic run-flat tire with sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic run flat tire 2 Tread part 3 Inner liner layer 4 Side wall part 5 Buttress part 6 Bead filler 7 Bead core 8 Carcass layer 9 Belt layer 10 Belt cover layer 11 Inner liner layer 12 Side reinforcement layer 13 Hollow capsule 14 Tire radial direction 15 Tire inner side region 16 Tire inner region 17 Tire outer region 100 Self-supporting pneumatic run-flat tire 101 Rim 102 Tread portion 103 Buttress portion 104 Side reinforcement layer H Tire cross-sectional height

Claims (10)

  In a pneumatic run flat tire in which side reinforcing layers made of hard rubber having a crescent cross section are inserted in the left and right sidewall portions, and an inner liner layer is disposed on the inner surface of the tire, at least one of the inner liner layer and the side reinforcing layer is provided. Pneumatic run-flat tire with hollow capsules containing lubricant. The pneumatic run-flat tire according to claim 1, wherein a shell of the hollow capsule is made of a thermoplastic resin, and a gas is included in the shell together with the lubricant . The pneumatic run-flat tire according to claim 1 or 2, wherein the lubricant is any one of naphthenic oil, paraffin oil, aroma oil, and silicone oil.   The pneumatic run according to any one of claims 1 to 3, wherein a compounding amount of the hollow capsule in the inner liner layer and / or the side reinforcing layer is 0.5 to 25 parts by weight with respect to 100 parts by weight of the rubber component. Flat tire.   In the structure which mix | blended the hollow capsule with the said side reinforcement layer, the compounding density of the said hollow capsule made the radial direction outer side area | region of the said side reinforcement layer higher than the radial direction inner area | region. Pneumatic run flat tire.   The composition according to any one of claims 1 to 4, wherein in the configuration in which hollow capsules are blended in the side reinforcing layer, the density of the hollow capsules is set such that a tire inner region of the side reinforcing layer is higher than a tire outer region. Run flat tire.   In the configuration in which hollow capsules are blended in the inner liner layer, at least the two points from the intersection of the belt cover layer covering the belt layer of the tread portion to the midpoint of the tire cross-section height from the intersection of the perpendicular to the inner liner layer The pneumatic run-flat tire according to any one of claims 1 to 6, wherein the thickness of the inner liner layer in the intermediate region is 1.2 to 3.5 times the thickness of the inner liner layer at the tire equator.   The thermoplastic resin constituting the shell of the hollow capsule is composed of a nitrile monomer (I) as a main component, a monomer (II) having an unsaturated double bond and a carboxyl group in the molecule, two or more The pneumatic run-flat tire according to any one of claims 2 to 7, which is a polymer polymerized from the monomer (III) having a polymerizable double bond.   9. The air according to claim 8, which is a polymer polymerized from a copolymerizable monomer (IV) for adjusting expansion characteristics in addition to the monomers (I), (II) and (III). Run flat tire.   The pneumatic run-flat tire according to any one of claims 1 to 9, wherein a weight fraction of the lubricant in the hollow capsule is 1 to 20% by weight.

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