JPH09300924A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the bending of the top of a bead filler, by forming the bead filler by a thermoplastic resin having a predetermined Young's modulus or a thermoplastic elastomer in which a thermoplastic resin component and an elastomer component are blended together. SOLUTION: Both ends 4a of a carcass layer 4 are bent over from the inner side of a tire to the outer side thereof around a bead core 5 so as to surround a bead filler 6. A plurality of belt layers 7 is embedded in the peripheral side of the carcass layer 4 of a tread 1. Also, the bead filler 6 consists of a thermoplastic resin whose Young's modulus is set to 50 to 500MPa or a thermoplastic elastomer composition in which a thermoplastic resin component and an elastomer component are blended together. Then, a ratio A/hF of a cross sectional area A on the cross section of the tire meridian of the bead filler 6 to a height hF in a tire diametral direction from a bead base line L to the peripheral end 6a of the bead filler 6, is set to 0.2mm<=A/hF<= 3.5mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that has both the weight reduction and the road noise problem in an extremely low frequency range.

[0002]

2. Description of the Related Art In recent years, with the weight reduction of vehicles, there has been a strong demand for weight reduction of tires. Conventionally, for example, there is a proposal to reduce the weight of the bead filler by reducing the weight, but when the bead filler is reduced in this way, the rigidity of the sidewall portion, particularly the rigidity in the circumferential direction, is significantly reduced, whereby
Road noise in the extremely low frequency range in the frequency band around 40 Hz becomes worse.

Therefore, as a solution to the above problem, there has been proposed a method in which the bead filler is made thin and elongated to reduce the weight of the bead filler while ensuring circumferential rigidity. However, the elongated bead filler has a problem that the shape of the bead filler is not stable in an unvulcanized state, so that the top portion of the bead filler is easily bent, resulting in uneven rigidity on the circumference.

[0004]

The object of the present invention is to reduce the size and weight of the bead filler without deteriorating the road noise in the extremely low frequency range and avoiding the bending of the top of the bead filler. It is an object of the present invention to provide a pneumatic tire in which the rigidity of the filler can be made uniform on the circumference.

[0005]

Means for Solving the Problems The present invention which achieves the above object, is a pneumatic tire having a bead filler provided on the outer circumference of a bead core arranged at the left and right bead portions, wherein the bead filler has a Young's modulus of 50 to 500 MPa. It is characterized by comprising a thermoplastic resin or a thermoplastic elastomer composition in which a thermoplastic resin component and an elastomer component are blended.

By forming the bead filler from a thermoplastic resin or a thermoplastic elastomer composition having a Young's modulus of 50 to 500 MPa, which is much higher than that of rubber, the same circumference as that of a conventional bead filler made of rubber is obtained. Directional rigidity can be achieved with a smaller cross-sectional area. Therefore, even if the bead filler is reduced in size to reduce the weight, road noise in the extremely low frequency range in the frequency band around 40 Hz does not deteriorate. Moreover, since the top portion of the bead filler is also difficult to bend, the rigidity of the bead filler on the circumference can be made uniform.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The configuration of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an example of the pneumatic tire of the present invention, wherein 1 is a tread portion, 2 is a bead portion, and 3 is a sidewall portion. Left and right sidewall portions 3 are extended outwardly (outer diameter side) in the tire radial direction in connection with the left and right bead portions 2, and a tread portion 1 extending in the tire circumferential direction between the left and right sidewall portions 3. Is provided.

One carcass layer 4 is provided inside the tire. Beat cores 5 are respectively arranged on the left and right bead portions 2, and bead fillers 6 are provided on the outer periphery of the beat cores 5. Both ends 4 a of the carcass layer 4 are folded from the inside of the tire to the outside around the beat core 5 so as to surround the bead filler 6. A plurality of belt layers 7 are embedded on the outer side of the carcass layer of the tread portion 1. CL is a tire center line passing through the tire equator line. In the present invention, in the pneumatic tire having the above-described configuration, the bead filler 6 has a Young's modulus of 50 to 5
It is composed of a thermoplastic resin adjusted to 00 MPa or a thermoplastic elastomer composition in which a thermoplastic resin component and an elastomer component are blended.

As described above, the bead filler 6 is formed by using the thermoplastic resin or the thermoplastic elastomer composition having flexibility in which the Young's modulus is significantly higher than that of the rubber. Equivalent circumferential rigidity can be obtained with a smaller cross-sectional area, and as a result, even if the bead filler 6 is made thin and elongated to make it lighter, road noise in the extremely low frequency range in the frequency band around 40 Hz can be obtained. Is not deteriorated and the top of the bead filler is difficult to bend, so that the rigidity of the bead filler 6 can be made uniform on the circumference.

If the Young's modulus is less than 50 MPa,
The hardness of the bead filler 6 becomes too low, and it becomes difficult to obtain the same circumferential rigidity as that of the conventional bead filler made of rubber with a smaller cross-sectional area. On the contrary, 500MPa
If it exceeds the range, the hardness of the bead filler 6 becomes too high, so that the bead filler 6 is easily broken and causes a tire failure. The bead filler 6 has a ratio A / hF of a sectional area A in the tire meridian section and a tire radial height hF from the bead base line L to the outer peripheral end 6a of the bead filler 6 to 0.2 [mm] ≦ A. /HF≦3.5 [mm] is preferable. If A / hF exceeds 3.5, the weight of the filler will increase and the weight will not be reduced, or the rigidity in the circumferential direction will be insufficient due to insufficient bead filler height hF, and the extremely low frequency range road noise will be deteriorated. . If A / hF is less than 0.2, the lateral rigidity becomes insufficient and the steering stability is significantly reduced.

The tire radial height hF is related to the tire cross-section height SH indicated by the tire radial length between the bead base line L and the toled surface 1A of the tread portion 1 on the tire center line CL. And the ratio hF
/ SH is preferably set to 0.25 ≦ hF / SH ≦ 0.8. If hF / SH is smaller than 0.25, sufficient circumferential rigidity cannot be secured, and extremely low frequency road noise will be deteriorated. On the other hand, when it is larger than 0.8, it causes a tire failure.

In the present invention, the thermoplastic resin used for the bead filler 6 has a Young's modulus of 50 to 500.
The material is not particularly limited as long as it can be set to MPa, and examples thereof include polyamide resins [for example, nylon 6 (N6), nylon 66 (N66), nylon 4
6 (N46), nylon 11 (N11), nylon 12
(N12), nylon 610 (N610), nylon 6
12 (N612), nylon 6/66 copolymer (N6 /
66), nylon 6/66/610 copolymer (N6 / 6
6/610), nylon MXD6 (MXD6), nylon 6T, nylon 6 / 6T copolymer, nylon 66 / P
P copolymer, nylon 66 / PPS copolymer] and N-alkoxyalkylated products thereof, for example, 6-nylon methoxymethylated product, 6-610-nylon methoxymethylated product, 612-nylon methoxymethylated product, Polyester resin [for example, polybutylene terephthalate (PBT), polyethylene terephthalate (P
ET), polyethylene isophthalate (PEI), PE
T / PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester,
Aromatic polyesters such as polyoxyalkylene diimide diacid / polybutylene terephthalate copolymers], polynitrile resins [eg polyacrylonitrile (PA
N), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), (meth) acrylonitrile /
Styrene copolymer, (meth) acrylonitrile / styrene / butadiene copolymer], polymethacrylate resin [eg polymethylmethacrylate (PMMA), polyethylmethacrylate], polyvinyl resin [eg vinyl acetate, poevinyl] Alcohol (PVA), vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PDVC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride /
Methyl acrylate copolymer, vinylidene chloride / acrylonitrile copolymer (ETFE)], cellulose resin [eg cellulose acetate, cellulose acetate butyrate], fluorine resin [eg polyvinylidene fluoride (PVD)
F), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer], imide resin [for example, aromatic polyimide (PI)] and the like can be preferably used.

The above-mentioned thermoplastic elastomer composition can be constituted by mixing an elastomer component with the above-mentioned thermoplastic resin component, which also has a Young's modulus of 50 to 500 MP.
The kind and mixing ratio of the materials are not particularly limited as long as they are blended so as to be a. Examples of the elastomer include diene rubber and hydrogenated products thereof (eg, NR, IR, epoxidized natural rubber, SB
R, BR (high cis BR and low cis BR), NBR, hydrogenated NBR, hydrogenated SBR], olefin rubber [eg ethylene propylene rubber (EPDM, EPM), maleic acid modified ethylene propylene rubber (M-EPM)] ,
IIR, isobutylene and aromatic vinyl or diene monomer copolymer, acrylic rubber (ACM), ionomer], halogen-containing rubber [eg Br-IIR, CI-
IIR, bromide of isobutylene paramethylstyrene copolymer (Br-IPMS), chloroprene rubber (C
R), hydrin rubber (CHR), chlorosulfonated polyethylene rubber (CSM), chlorinated polyethylene rubber (C
M), maleic acid modified chlorinated polyethylene rubber (MC
M)], silicone rubber [eg, methyl vinyl silicone rubber, dimethyl silicone rubber, methylphenyl vinyl silicone rubber], sulfur-containing rubber [eg, polysulfide rubber], fluorine rubber [eg, vinylidene fluoride rubber, fluorine-containing vinyl ether rubber] , Tetrafluoroethylene-propylene rubber, fluorine-containing silicon rubber, fluorine-containing phosphazene rubber], thermoplastic elastomers (for example, styrene elastomer, olefin elastomer, ester elastomer, urethane elastomer, polyamide elastomer), etc. It can be preferably used.

When the specific thermoplastic resin component and the elastomer component have different compatibility, the two components can be made compatible with each other by using an appropriate compatibilizer as the third component. By mixing the compatibilizer with the blend system, the interfacial tension between the thermoplastic resin and the elastomer component decreases, and as a result, the rubber particle diameter forming the dispersion layer becomes fine, so that the properties of both components are reduced. It will be more effectively expressed. As such a compatibilizer, generally, a copolymer having a structure of both or one of a thermoplastic resin and an elastomer component, or an epoxy group, a carbonyl group, a halogen group, which can react with the thermoplastic resin or the elastomer component, The copolymer may have a structure having an amino group, an oxazoline group, a hydroxyl group, or the like. These may be selected according to the type of the thermoplastic resin and the elastomer component to be mixed, and those usually used include styrene / ethylene / butylene block copolymer (SEBS) and its maleic acid-modified product, EPDM, EPM And EPDM / styrene or EPDM / acrylonitrile graft copolymers and their maleic acid-modified products, styrene / maleic acid copolymers, and reactive phenoxines.
The amount of the compatibilizer to be added is not particularly limited, but is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the polymer component (total of the thermoplastic resin and the elastomer component).

The composition ratio of the specific thermoplastic resin component (A) and the elastomer component (B) in the case of blending the thermoplastic resin and the elastomer is not particularly limited and may be appropriately selected depending on the Young's modulus and the cross-sectional area of the bead filler. It may be determined, but a preferable range is a weight ratio of 90/10 to 30/70. In the polymer composition according to the present invention, in addition to the essential polymer component, other polymers such as the above-described compatibilizer polymer may be mixed as long as the necessary properties of the polymer composition for a tire of the present invention are not impaired. it can. The purpose of mixing other polymers is to improve the compatibility between the thermoplastic resin and the elastomer component, to improve the moldability of the material, to improve the heat resistance, to reduce the cost, etc. Examples of the material used include polyethylene (PE) polypropylene (PP), polystyrene (PS), ABS, SBS, polycarbonate (PC).
And the like. The polymer composition according to the present invention further includes a filler (calcium carbonate, titanium oxide, alumina, etc.), a reinforcing agent such as carbon black and white carbon, a softening agent, which is generally added to the polymer composition,
A plasticizer, a processing aid, a pigment, a dye, an antiaging agent and the like may be optionally added as long as the above Young's modulus requirements are not impaired.

Further, the elastomer component can be dynamically vulcanized during mixing with the thermoplastic resin. The vulcanizing agent, vulcanization aid, vulcanization conditions (temperature, time) and the like for dynamically vulcanizing may be appropriately determined according to the composition of the elastomer component to be added, and are not particularly limited. . As the vulcanizing agent, a general rubber vulcanizing agent (crosslinking agent) can be used. Specifically, examples of the ionic vulcanizing agent include powdered sulfur, precipitated sulfur, highly dispersible sulfur, surface-treated sulfur, insoluble sulfur, dimorpholine disulfide, and alkylphenol disulfide. About 4 phr [parts by weight per 100 parts by weight of the rubber component (polymer)] can be used.

As the organic peroxide type vulcanizing agent,
Benzoyl peroxide, t-butyl hydroperoxide, 2,4-bichlorobenzoyl peroxide,
Examples thereof include 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and 2,5-dimethylhexane-2,5-di (peroxylbenzoate).
About 1 to 20 phr can be used.

Further, as the phenol resin type vulcanizing agent, bromide of alkylphenol resin, tin chloride,
A mixed crosslinking system containing a halogen donor such as chloroprene and an alkylphenol resin can be exemplified.
About 20 phr can be used. In addition, zinc white (about 5 phr), magnesium oxide (about 4 phr)
Lisage (about 10 to 20 phr), p-quinone dioxime, p-dibenzoylquinone dioxime, tetrachloro-p-benzoquinone, poly-p-dinitrosobenzene (about 2 to 10 phr), methylene dianiline (0. 2
About 10 to 10 phr).

If necessary, a vulcanization accelerator may be added. Examples of the vulcanization accelerator include general vulcanization accelerators such as aldehyde / ammonia, guanidine, thiazole, sulfenamide, thiuram, dithioate, and thiourea, for example, About 2 phr can be used. Specifically, the aldehyde / ammonia-based vulcanization accelerator is hexamethylenetetramine or the like, the guadinine-based vulcanization accelerator is diphenylguadinine or the like, and the thiazole-based vulcanization accelerator is dibenzothiazyldisulfide ( DM), 2-mercaptobenzothiazole and its Zn salt, cyclohexylamine salt, and the like, and as a sulfenamide-based vulcanization accelerator, cyclohexylbenzothiazylsulfenamide (CBS), N-oxydiethylenebenzothiazyl-2- Sulfenamide, Nt-butyl-2-benzothiazole Sulfenamide, 2- (thymolpolynyldithio) benzothiazole, etc. As thiuram vulcanization accelerators, tetramethylthiuram disulfide (TMTD), tetraethyl Thiuram disulfide, tetrame Le monosulfide (TMTM), dipentamethylenethiuram tetrasulfide and the like, as the dithio acid salt-based vulcanization accelerator,
Zn-dimethyldithiocarbamate, Zn-diethyldithiocarbamate, Zn-di-n-butyldithiocarbamate, Zn-ethylphenyldithiocarbamate, T
e-diethyldithiocarbamate, Cu-dimethyldithiocarbamate, Fe-dimethyldithiocarbamate,
Examples of thiourea-based vulcanization accelerators such as pipecoline pipecolyl dithiocarbamate include ethylene thiourea and diethyl thiourea.

As the vulcanization accelerating aid, general auxiliaries for rubber can be used in combination. For example, zinc white (about 5 phr), stearic acid, oleic acid and their Zn salts (2 to 5). 4 phr) etc. can be used. The method for producing a thermoplastic elastomer composition is as follows: a thermoplastic resin component and an elastomer component (an unvulcanized product in the case of rubber) are used in advance.
Melt kneading with a shaft kneading extruder, etc., continuous phase (matrix)
By dispersing the elastomer component as a dispersed phase (domain) in the thermoplastic resin forming the. When vulcanizing the elastomer component, add a vulcanizing agent under kneading,
The elastomer component may be dynamically vulcanized. The various additives (excluding the vulcanizing agent) to the thermoplastic resin or the elastomer component may be added during the kneading, but it is preferable to mix them before kneading. The kneader used for kneading the thermoplastic resin and the elastomer component is not particularly limited, and a screw extruder, a kneader, a Banbury mixer, a twin-screw kneader or the like can be used. Above all, it is preferable to use a twin-screw kneading extruder for kneading the thermoplastic resin and the elastomer component and for dynamic vulcanization of the elastomer component. Further, two or more kinds of kneaders may be used and the kneading may be performed sequentially. As the conditions for the melt-kneading, the temperature may be at least the temperature at which the thermoplastic resin melts. The shear rate during kneading is preferably from 1,000 to 7,500 Sec ^-1 .
The total kneading time is preferably 30 seconds to 10 minutes, and when a vulcanizing agent is added, the vulcanization time after the addition is preferably 15 seconds to 5 minutes. The polymer composition produced by the above method may be formed into a desired shape by a usual thermoplastic resin molding method such as injection molding or extrusion molding.

The bead filler thus obtained has a structure in which the elastomer component (B) is dispersed as a discontinuous phase in the matrix of the thermoplastic resin (A). By adopting such a structure, it is possible to impart sufficient flexibility to the bead filler and sufficient rigidity due to the effect of the resin layer as a continuous phase, and at the same time, regardless of the amount of the elastomer component, a thermoplastic resin can be used during molding. It is possible to obtain molding processability equivalent to.

Adhesion between these bead fillers and the rubber layer opposite thereto is carried out by applying an adhesive obtained by dissolving a usual rubber-based, phenolic resin-based, acrylic copolymer-based, isocyanate-based polymer and a crosslinking agent in a solvent to the bead filler. Then, a method of adhering by heat and pressure during vulcanization molding, or an adhesive resin such as styrene butadiene styrene copolymer (SBS), ethylene ethyl acrylate (EEA), styrene ethylene butylene block copolymer (SEBS) There is a method in which a multilayer laminate is prepared by coextruding or laminating with a bead filler and adhering it to a rubber layer during vulcanization. Examples of the solvent-based adhesive include a phenol resin-based resin (Chemlock 220, Road Co., Ltd.), a chlorinated rubber-based resin (Chemrock 205, Chemlock 234B), and an isocyanate-based resin (Chemrock 402).

In the above embodiment, the pneumatic tire in which the belt layer is arranged has been described, but the present invention is not limited to this, and any pneumatic tire in which a bead filler is arranged on the outer periphery of the bead core can be used. It goes without saying that it can be preferably used.

[0024]

【Example】

 Preparation of Bead Filler Table 1 shows the material for bead filler used in the present invention.

[0025]

[Table 1] The bead filler was produced by a method in which a bead core was previously inserted in a bead filler molding die and the above material was injection-molded therein. The cross-sectional area of the produced bead filler was 140 mm ² .

For the materials having the above-mentioned material widths and Young's modulus of 40 and 50 MPa, 0.4 phr, 2 phr and 1 phr were dynamically added to the composition of zinc white, zinc stearate and stearic acid in Table 1 respectively. As a vulcanizing system, a rubber component was dispersed in a resin component with a twin-screw kneader, and then continuously added and kneaded and dynamically vulcanized to prepare a thermoplastic elastomer.

As an adhesive between the bead filler and the rubber material, Chemlock 234B (Road Co.) was previously applied to the bead filler. Production of tire Using the bead filler (bead core / bead filler integrated product) produced as described above, a tire was molded and vulcanized in a conventional manner. (Invention tires 1 to 4, comparative tires 1 and 2) As a comparative example, a normal bead filler (made of rubber)
A conventional tire 1 using No. 1 and a tire (conventional tire 2) in which the bead filler (rubber) was thin and elongated were also prepared. The size of the manufactured tire is 205 /
It is 65R15 94S.

Each of these test tires was examined for road noise in the extremely low frequency range, bead filler weight, bending of the top of the bead filler, and durability under the following measurement conditions, and the results shown in Table 2 were obtained. Road noise in extremely low frequency range (R / N) Each test tire was mounted on a JATMA standard rim, air pressure was set to 200 kPa, and it was mounted on a passenger car with a displacement of 3000 cc. Rough road surface (paved road) was 50 km / h speed. A feeling test of 40 Hz road noise on the driver's seat window side when the vehicle was driven was carried out by five panelists, the results were evaluated by a 10-point method, and the average of each value of the five people was taken as the evaluation value. The larger the value, the lower the road noise in the extremely low frequency range. Weight of Bead Filler The weight of the bead filler before molding of each test tire was measured, and the result was compared with the bead filler of Conventional Tire 1 of 100.
It evaluated by the index value. The larger the value, the heavier the weight. Bend at the top of the bead filler Before the tire was molded, it was examined whether or not there was a bend at the top of the bead filler, and the result is shown by ◯ ×. The case where bending is recognized is x, and the case where bending is not recognized is o. Durability Each test tire (excluding conventional tires) was mounted on a JATMA standard rim, and an indoor drum test was performed under the conditions of an air pressure of 180 kPa and a speed of 81 km / h (test conditions based on JISD-4230), and a bead after running 2754 km The state of the filler was examined. O indicates no abnormality, and X indicates that the bead filler was broken.

[0029]

[Table 2]

As is clear from Table 2, Young's modulus is 50
The tire of the present invention in which a bead filler made of a thermoplastic resin or a thermoplastic elastomer composition adjusted to ~ 500 MPa is arranged has the following features:
It can be seen that the road noise in the extremely low frequency range does not deteriorate and there is no bending at the top of the bead filler, so that the bead filler rigidity can be made uniform on the circumference. Also,
It can also be seen that the bead filler does not break.

[0031]

As described above, according to the present invention, in a pneumatic tire in which a bead filler is provided on the outer periphery of the bead cores arranged on the left and right bead portions, the bead filler is a thermoplastic resin or a thermoplastic resin having a Young's modulus of 50 to 500 MPa. Since it is composed of a thermoplastic elastomer composition in which a plastic resin component and an elastomer component are blended, even if the bead filler is made compact and lightweight, the road noise in the extremely low frequency range does not deteriorate, and the bead filler top It is possible to avoid bending and make the bead filler rigidity uniform on the circumference.

[Brief description of drawings]

FIG. 1 is a half sectional view of a tire meridian showing an example of a pneumatic tire of the present invention.

[Explanation of symbols]

1 tread part 2 bead part 3 sidewall part 4 carcass layer 5 bead core 6 bead filler 6a outer peripheral edge 7 belt layer

Claims (3)

[Claims] 1. A pneumatic tire in which a bead filler is provided on the outer circumference of a bead core arranged in the left and right bead portions, wherein the bead filler is a thermoplastic resin having a Young's modulus of 50 to 500 MPa or a thermoplastic resin component and an elastomer component. A pneumatic tire composed of a blended thermoplastic elastomer composition. 2. A ratio A of a cross-sectional area A of the bead filler in a tire meridian section and a tire radial height hF from a bead base line L to an outer peripheral end of the bead filler.
The pneumatic tire according to claim 1, wherein / hF is 0.2 ≦ A / hF ≦ 3.5. 3. The ratio hF / SH between the tire radial height hF and the tire cross-section height SH is 0.25 ≦ hF / SH ≦.
The pneumatic tire according to claim 2, wherein the pneumatic tire has a thickness of 0.8.