JPH09164809A - Pneumatic tire for passenger car and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve draining capability at the time of high speed driving with dry performance maintained without changing the width of a groove in a tread surface. SOLUTION: This tire is constituted by disposing a main groove 1 which extends in the circumferential direction of the tire at a tread surface T and forming an external layer which is made up of one type chosen from a group constituted of thermoplastic elastomer composition, water repellent rubber whose contact angle with water is 100 deg.-140 deg., ultrahigh molecular weight polyethylene, and fluoro rubber type thermoplastic elastomer at least. This manufacturing method for tire consists of the following procedures: a film type or sheet type material which is made up of one type chosen from the group above is stuck at a formation point of the main groove which extends at least in the circumferential direction of the tire at the tread surface of a green tire, and the green tire is vulcanized using a metallic mold whose main groove forming protrusion surface is provided with chromium plating at least.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for passenger cars having improved drainage properties at high speed and a method for manufacturing the pneumatic tire.

[0002]

It is generally known that in order to improve the wet performance (drainability) of a pneumatic tire for passenger cars, it is good to increase the groove area of the tread surface. For example, when a plurality of straight-shaped main grooves extending in the tire circumferential direction on the tread surface and a plurality of sub-grooves in the tire width direction that intersect these straight-shaped main grooves are arranged, these main grooves and sub-groove grooves are arranged. Wider width improves drainage.

However, if the groove width of the groove is made too wide in order to increase the groove area of the tread surface, the actual ground contact area is reduced and the tread rigidity is reduced, so that the dry performance such as steering stability is reduced. I will end up. Therefore, there is a limit to widen the groove width. Therefore, it was difficult to improve the drainage property at high speed while balancing the dry performance.

[0004]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a pneumatic tire for passenger cars, which has improved drainage performance at high speed while maintaining dry performance without changing the groove width of the groove on the tread surface, and the same. It is to provide a manufacturing method.

[0005]

The pneumatic tire for passenger cars of the present invention is a pneumatic tire for passenger cars in which a main groove extending in the tire circumferential direction is arranged on a tread surface, and a thermoplastic elastomer is provided at least on the surface of the main groove. The composition is characterized in that an outer layer made of one kind selected from the group consisting of a composition, a water-repellent rubber having a contact angle of water of 100 ° to 140 °, an ultrahigh molecular weight polyethylene, and a fluororubber thermoplastic elastomer is formed.

Further, according to the method for producing a pneumatic tire for a passenger car of the present invention, the contact angle of the thermoplastic elastomer composition and water is 100 ° to 100 ° in the main groove formed at least in the tire circumferential direction on the tread surface of the green tire. A film-like or sheet-like material made of one kind selected from the group consisting of 140 ° water-repellent rubber, ultra-high molecular weight polyethylene, and fluororubber thermoplastic elastomer is attached, and this green tire is used for forming at least the main groove. It is characterized in that it is vulcanized by using a die whose surface is plated with chrome.

Since the above-mentioned thermoplastic elastomer composition, water-repellent rubber, ultra-high molecular weight polyethylene, and fluororubber thermoplastic elastomer each have low friction resistance and are water-repellent, an outer layer made of them is formed on the surface of the main groove. By forming the water, water that has entered the main groove during running on a wet road can be easily discharged from the main groove quickly, so that the drainage performance can be improved. Here, the “surface of the main groove” refers to the entire surface of the main groove including the groove wall surface and the groove bottom surface of the main groove.

[0008]

FIG. 1 is a plan view showing an example of a tread pattern of a pneumatic tire for passenger cars of the present invention. In FIG. 1, on the tread surface T, one wide main groove 1 extending in the tire circumferential direction is arranged on both left and right sides of the tire equatorial line C. Further, a plurality of sub-grooves 3 that intersect the main grooves 1 and extend to the tire width direction ground contact end 2 are arranged at an arbitrary pitch interval over the circumference of the tire. Main grooves 1, 1 for adjusting the rigidity of the tread surface
Narrow grooves 4 and 5 extending in the tire circumferential direction are arranged therebetween, and sipes 6 and 7 are arranged in regions on both outer sides of the main groove 1 so as to face the tire circumferential direction.

It is sufficient that at least one main groove 1 is provided, but in order to balance good dry performance and wet performance, one main groove 1 with a groove width of 10 to 20% of the tread ground contact width W is provided. It is preferable that three pieces are arranged. Main groove 1
If there are two, the groove width is tread contact width W of 12
It is good to be ~ 16%. This tread contact width W is J
ATMA standard rim, air pressure, width under 100% load.

By arranging the main groove 1 and the sub-groove 3 in this way, the drainage property can be improved, but in the present invention, in order to secure the more excellent drainage property during high speed running, it is shown in FIG. Thus, at least on the surface of the main groove 1, the thermoplastic elastomer composition and the contact angle of water 10
The outer layer 9 is formed of one kind selected from the group consisting of 0 ° to 140 ° water-repellent rubber, ultrahigh molecular weight polyethylene, and fluororubber thermoplastic elastomer. It is desirable that the outer layer 9 is also provided on the surface of the sub groove 3.

The thermoplastic elastomer composition has a structure in which a thermoplastic resin and an elastomer component are mixed and the elastomer component is dispersed as a discontinuous phase in the matrix of the thermoplastic resin. Further, a thermoplastic elastomer composition obtained by vulcanizing an elastomer component dispersed as a discontinuous phase during kneading (dynamic vulcanization) and having a stable dispersion structure is preferable.

The thermoplastic resin is not particularly limited, and examples thereof include polyamide resins such as nylon 6 and nylon 66, polyethylene terephthalate (PE).
T), polyester resins such as polybutylene terephthalate (PBT) and polyethylene isophthalate (PEI), polynitrile resins such as polyacrylonitrile (PAN), polymethacrylate resins such as polymethylmethacrylate (PMMA), vinyl acetate ( EVA),
Polyvinyl resin such as polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), fluorine resin such as polyvinyl fluoride (PVF), imide resin such as aromatic polyimide (PI), polyvinylidene chloride (P)
VDC), polyvinyl chloride (PVC) and the like.

The elastomer component is, for example, natural rubber (NR), isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR).
Diene rubber such as ethylene propylene rubber (EPD
M, EPM) and other olefinic rubbers, brominated butyl rubber (Br-IIR), chlorinated butyl rubber (Cl-II)
Rubber such as halogen rubber such as R).

The water-repellent rubber having a water contact angle of 100 ° to 140 ° is obtained by adding phenyltriethoxysilane or polytetrafluoroethylene to the compounding of a usual rubber composition for tire tread. For example, as can be seen from Table 1 below, 1 part by weight of phenyltriethoxysilane was added to No. 1 (contact angle 95 °), which is the compounding content (parts by weight) of a usual rubber composition for tire tread ( No. 2)
Has a water contact angle of 106 °, and 10 parts by weight of polytetrafluoroethylene is added to No. 1 (No.
In 3), the contact angle of water is 107 °.

[0015]

[Table 1] The ultrahigh molecular weight polyethylene has a weight average molecular weight (Mw) of 500,000 or more, preferably 1,000,000 or more, and more preferably 2 to 8,000,000. This weight average molecular weight is a numerical value measured by a viscosity method.

Examples of the fluororubber thermoplastic elastomer include copolymers composed of vinylidene fluoride / hexafluoropropylene copolymer units and tetrafluoroethylene / ethylene copolymer units. Examples of the fluoroelastomer thermoplastic elastomer include Daier TP
E (Daikin Industries) is commercially available.

Next, at least on the surface of the main groove 1, the contact angle between the thermoplastic elastomer composition and water is 100 ° to 140 °.
A method of forming the outer layer made of one kind selected from the group consisting of water-repellent rubber having a temperature of 90 ° C., ultra high molecular weight polyethylene, and fluororubber thermoplastic elastomer will be described. First, a film-like or sheet-like material made of one kind selected from the above group is attached to the tread surface of a green tire. In this case, the entire surface of the tread surface may be attached, or only the formation portion of the main groove 1 may be attached. The thickness of the film-like or sheet-like material may be 100 μm for the thermoplastic elastomer composition, ultra-high molecular weight polyethylene, and fluororubber thermoplastic elastomer, and may be 700 μm for the water-repellent rubber. Thermoplastic elastomer compositions, ultra high molecular weight polyethylene, and fluororubber thermoplastic elastomers have a modulus higher than that of rubber, so that excessive thickness results in poor durability, and when too small, film or sheet form during tire production. Since the material is damaged and the improvement of drainage cannot be expected, it is preferably 30 to 400 μm, preferably 50.
˜150 μm is preferable. When the thickness of the water-repellent rubber is excessive, the buffing process described below takes time, and when the thickness is too small, the film-shaped or sheet-shaped material is used as the main groove 1 during tire production.
Since it cannot be expected to improve drainage because it does not adhere sufficiently to the surface of 500 to 1500 μm, preferably 700 to
1000 μm is preferable.

Then, a green tire having a tread surface of one kind selected from the above-mentioned group is formed into the main groove 1
And a vulcanization is performed by a mold having a projection for forming the above-mentioned inner surface and at least the projection being plated with chrome. The thickness of the chrome plating is preferably 20 to 30 μm. The reason why the vulcanization is performed by using a mold in which at least the projections on the inner surface are plated with chromium is as follows.

That is, in order to improve the wet performance of the tire during high speed running, the key point is how quickly the water is discharged from the main groove 1 to the outside at higher speeds. Therefore, in view of the fact that the surface irregularities of the surface of the main groove 1 when viewed microscopically impede the discharge of water, in order to improve the water discharge efficiency, the surface irregularities of the main groove 1 should be minimized, that is, The surface should be smooth. On the other hand, if the surface of the projection for forming the main groove is plated with chrome, the surface of the projection becomes extremely smooth, so vulcanizing the green tire with this mold will make the surface of the main groove 1 a smooth surface with as few irregularities as possible. Therefore, the drainage performance can be further improved.

After vulcanization, the film-like or sheet-like material appears on the entire tread surface or in a partial area. Therefore, the tires may be mounted on the vehicle as they are, and run-in to wear out unnecessary portions other than the surface of the main groove 1. Alternatively, the surface may be buffed before the tire is shipped.

[0021]

EXAMPLES The following tires having a tire size of 195/60 R15, a tread pattern shown in FIG. 1, and a tire structure in common were prepared (conventional tire 1, invention tire 1).
4), the drainage properties of these tires during high speed running were evaluated. Table 2 shows the results.

Conventional tire 1 No outer layer was formed on the main groove surface. Inventive Tire 1 An outer layer having a thickness of 100 μm was formed on the surface of the main groove with a thermoplastic elastomer composition containing 40% by weight of nylon 11 and 60% by weight of a brominated IIR rubber composition.

Inventive Tire 2 An outer layer of No. 2 water repellent rubber of Table 1 having a thickness of 700 μm was formed on the main groove surface. Inventive Tire 3 An outer layer having a thickness of 100 μm was formed on the surface of the main groove with ultrahigh molecular weight polyethylene having a weight average molecular weight of 2,000,000.

Tire 4 of the Present Invention An outer layer having a thickness of 700 μm is formed on the surface of the main groove with a fluororubber thermoplastic elastomer of Daiel TPE (Daikin Industries). Evaluation method of drainage property during high-speed running: A vehicle speed that gives the maximum lateral acceleration on a test road with a water depth of 10 mm and a turning radius of 100 m is defined as a critical speed. It is evaluated by an index with the critical speed of the conventional tire 1 being 100. Larger numbers are better.
Table 2 As is clear from Table 2, the tires 1 to 4 of the present invention are superior to the conventional tire 1 in drainage property during high speed running.

[0025]

As described above, according to the present invention, the thermoplastic elastomer composition, at least on the surface of the main groove,
Since the outer layer made of one kind selected from the group consisting of water-repellent rubber having a water contact angle of 100 ° to 140 °, ultra-high molecular weight polyethylene, and fluororubber thermoplastic elastomer is formed, the groove width of the groove on the tread surface is reduced. It is possible to improve the drainage property during high speed running without changing it.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a tread pattern of a pneumatic tire for passenger cars of the present invention.

FIG. 2 is a sectional view showing an XX section in FIG.

[Explanation of symbols]

1 main groove 2 tire width direction grounding end 3 sub groove
4, 5 Narrow groove 6, 7 Sipe 9 Outer layer T Tread surface C
Tire equatorial line

Claims (4)

[Claims] 1. A pneumatic tire for passenger cars having a main groove extending in the tire circumferential direction on a tread surface, wherein at least the surface of the main groove has a repellency of a thermoplastic elastomer composition and water having a contact angle of 100 ° to 140 °. A pneumatic tire for passenger cars having an outer layer formed of one type selected from the group consisting of water-based rubber, ultra-high molecular weight polyethylene, and fluororubber thermoplastic elastomer. 2. The thickness of the outer layer is 30 to 400 μm for the thermoplastic elastomer composition, ultrahigh molecular weight polyethylene, and fluororubber thermoplastic elastomer, and 500 to 1500 μm for the water repellent rubber. Item 1. A pneumatic tire for passenger cars according to Item 1. 3. A thermoplastic elastomer composition, a water-repellent rubber having a water contact angle of 100 ° to 140 °, an ultra high molecular weight polyethylene, and a main groove formed in at least a circumferential direction of a tire on a tread surface of a green tire. A film-like or sheet-like material made of one kind selected from the group consisting of fluororubber thermoplastic elastomers is pasted, and this green tire is used at least for the main groove forming projections using a chrome-plated mold. A method for producing a pneumatic tire for a passenger car to be vulcanized. 4. The thickness of the chrome plating is 20 to 30 μm.
The method for producing a pneumatic tire for passenger cars according to claim 3, wherein the pneumatic tire is m.