JPH0958208A - Lightweight tubuless tire with good drum durability and airtightness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide good durability with good adhesion of ply-covered rubber to a carcass code by effectively arranging ply-covered rubber suitably mixed with butyl base rubber. SOLUTION: At least part 4' of rubber 4 of ply-covered rubbers 3, 4 has a different composition from the other ply-covered rubbers 3, 4 and contains 40 weight % or less of butyl base rubber or nothing of it. The other ply-covered rubbers 3, 4 contain 50 weight % or more of butyl base rubber. The ply-covered rubber 4' has a step (d) between the outside of a carcass 1 and the wrapping end of the ply at least in a little wider width range than the whole range of the inner surface wrapped by the folded-back ply which is wrapped by the core 6 and the filler 7 of the bead part 6 of a tire. If the ratio of the step (d) to the section height H is in the range of 0.05<=d/H<=0.15, durability level index DW holds the relation DW>=90%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tubeless tire in which the inner liner is eliminated and the weight is reduced. Reduction of harmful exhaust gas in automobile engines and improvement of energy efficiency are strongly demanded for prevention of global warming and promotion of energy saving which is also useful for this. It is desired to reduce the weight of tires in order to reduce rolling resistance.

In this respect, in conventional tubeless radial tires, it is indispensable to attach an air impermeable rubber inner liner to the inner surface of the pneumatic tire in order to prevent air leakage. The liner is, for example, a general radial tire for passenger cars (165SR13).
The size of each tire is about 400 g (about 6% of the weight of the tire), which is an additional structure and conflicts with the demand for weight reduction of the tire.

[0003]

Therefore, it has been attempted to reduce the weight of a tubeless tire by eliminating the inner liner by making the covering rubber applied to the carcass ply have the function of the inner liner, but the following problems still remain. ing.

Usually, butyl rubber such as bromobutyl rubber or chlorobutyl rubber, which has been used for the inner liner and has a small air permeation amount, is used as the carcass ply-covering rubber and the inner liner is abolished. As disclosed in Kaihei 6-156007,
However, it is not so good in terms of air impermeability and also in its adhesiveness with carcass cords. Further, it is possible to eliminate the inner liner by using a rubber composition containing an epoxidized natural rubber as the ply coated rubber.
Although it is disclosed in Japanese Patent Publication No. 55665, it is not suitable for practical use because it has a drawback of being impermeable to air as compared with butyl rubber.

[0005]

Due to the effective arrangement of the ply-coated rubber appropriately blended with butyl rubber, effective air impermeability is achieved even after the inner liner is abolished, and excellent adhesion to the carcass cord is achieved. SUMMARY OF THE INVENTION It is an object of the present invention to provide a lightweight pneumatic tubeless tire that is equipped with high drum durability under high performance.

The air impermeability is obtained by filling a tire under test with an air pressure P of 2.0 kgf / cm ² and leaving it for one month to obtain the difference ΔP between the pressure decreased and the filling pressure.
Air leak rate AP expressed as a percentage of ΔP to P
(%) Was evaluated, and 5% or less was judged to be good.

The drum durability is 200% when the tire is filled with air pressure 1.5 times the standard internal pressure of JATMA standard of the tire.
It is evaluated by the endurance level index DW (%) expressed as a percentage to reach the target distance 10,000km of the mileage until failure in the test in which the vehicle is driven under Load at a traveling speed of 60km / hr until it reaches 10,000km. DW:
90% or more is a level acceptable in the market.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a lightweight tubeless tire formed by applying a ply-covered rubber containing a butyl rubber to a carcass having no inner liner, and at least outside the carcass. One or both or one or both of the winding end edge of the ply on the winding inner surface of the ply double-folding portion wrapped around the core of the bead portion and the filler and the annular region facing the winding end edge, and these. The ply-covered rubber on the entire inner surface of the winding, including the butyl rubber, has a low-blended or unblended rubber composition within 40 mass%. A lightweight rubber that has a high compounding rubber composition of 50 mass% or more and has excellent drum durability and air permeability. A pneumatic pneumatic tubeless tire, in which the carcass cross-section height of the tire radial direction width (D) of the ply winding edge portion or the similar width (E) of the annular region of the ply facing and facing the winding edge edge. All the ratios to the height (H) are 0.15 or more, and the upper edge of the annular region is higher than the winding end edge of the ply in the radial step (d).
And the ratio of this step to the carcass cross-sectional height (H) is within 0.15, and the ply-covered rubber covering the entire outer surface of the carcass including the winding inner surface of the double-folded ply portion is low in butyl rubber. A rubber composition of compounded or non-compounded, and a ply-covered rubber in the entire area of the inside of the carcass is a highly compounded rubber composition of butyl-based rubber that is 100 mass% or more in total with the compounded amount of the above-mentioned butyl-based rubber, and ply coating. A butyl rubber compounded with the rubber is a modified copolymer obtained by halogenating an isoprene-isobutylene copolymer rubber, a halogenated isoprene-isobutylene copolymer rubber, and a copolymer of irimonoolefin and p-alkylstyrene. It is preferable that the rubber is made of one kind or two or more kinds.

The inventors have aimed to reduce the weight of the tire by almost 6% by eliminating the inner liner by blending butyl rubber in the ply-coated rubber. First, natural rubber and butyl rubber are used. (Br-11R or EXXP
RO90-10; all manufactured by Exxon Co., Ltd.) The air leak rate AP
(%) The effect on the endurance level index DW (%) was examined to obtain the results shown in FIGS.

The air leakage rate AP (%) is 50 butyl parts.
If mass% or more, the marketability is maintained at AP 5% or less, while butyl part number 40 mass% or less is required to secure 100% of drum durability level DW; this is 50 mass%.
It became clear that the required DW: 90% could not be achieved in the above cases.

Here, in the case where the drum endurance level DW is lower than 80% (numbers (1), (2) and (3) in FIGS. 1a and 1b)), when the tire failure situation is examined, the carcass hoisting is found. There was a crack between the cord and the coated rubber in the ply coated rubber layer near the edge, especially in the coated rubber.

Therefore, a test was conducted in which a spacer rubber was interposed so that the rolled end of the carcass was separated from the ply.
The cracks became slightly smaller, but they did not stop them.

It is considered that such cracks are caused by over-blending of butyl rubber in that portion, and AP5
% Of the butyl rubber compounding lower limit amount of 50 mass% of the ply-covered rubber, of the carcass outer surface, wrapped around the core of the bead portion of the tire and the filler, and the inner surface of the ply double-folded portion is wound up. When a ply-covered rubber having a mixed amount of butyl rubber in the expanded surface of 10 mm width (represented by step d) exceeding the winding edge is applied, and if the amount of butyl rubber in this portion is 40 mass% or less, DW100 It has been found that% can be combined with AP ≦ 5%.

Next, when the number of butyl portions in this portion was 0 mass%, that is, butyl rubber was not mixed, the width of the expanded surface (step d) was changed and repeated tests were conducted. .15 times or less, AP ≦ 5
It is confirmed that the ply coated rubber with a high butyl content inside the carcass does not change in thickness as measured in the thickness direction of the bead portion, and the rubber gauge of the bead portion is thick.

Regarding d / H, when the butyl number of the ply-covered rubber on the outer surface of the carcass was 40 mass%, a DW of 100% could be secured if d / H ≧ 0.05. Furthermore, the width of the winding edge portion measured in the tire radial direction is D,
Also, D / H or E / H is 0.15 in both cases, where E is the same width of the annular region of the plies facing each other facing the winding edge.
If it is above, it turns out that both AP and DW requirements are fulfilled.

Next, most of the ply coating on at least the outer side of the carcass, including at least one of the winding edge on the winding inner surface of the ply double-folded portion and the annular region facing the winding edge and facing each other. If the compounding amount of butyl rubber per rubber is 40 mass% or less, the required DW value can be obtained. In this case, therefore, the butyl rubber in the ply-coated rubber inside the carcass required to achieve AP ≦ 5%. When the compounding amount was investigated, it was confirmed that a total of 100 mass% or more with the number of butyl parts in the above ply-covered rubber on the outer side of the carcass was required.

In the present invention, the butyl rubber is an isoprene-isobutylene copolymer rubber, a halogenated isoprene-isobutylene copolymer rubber, and a modified copolymerized copolymer obtained by halogenating a copolymer of isomonoolefin and p-alkylstyrene. This is a united rubber, of which isomonoolefin has 4 carbon atoms.
It is preferably from ~ 7, more preferably isobutylene.
The p-alkylstyrene is preferably a straight-chain or branched-chain alkyl group having 1 to 3 carbon atoms, and more preferably p-methylstyrene. The halogen used for modifying the copolymer is preferably bromine or chlorine.

Further, the preferable amount of paraalkylstyrene in the present invention is 1 to 20 mass% in the modified copolymer, and the halogenated amount is 1 to 10 mass%. The modified copolymer (halogenated PMS modified polymer) according to the present invention is described in European Patent Specification No. 8930595.9.
Can be polymerized by the method disclosed in the publication.
That is, isomonoolefin and p-alkylstyrene are copolymerized in a solvent such as methyl chloride in the presence of a Lewis acid catalyst. Here, a preferable Lewis acid is ethylaluminum dichloride or the like, and is used in an amount of 0.001 to 0.2 mass% based on the total amount of the monomers. After completion of the polymerization, a desired modified copolymer can be obtained by radical halogenation using a radical initiator.

In the rubber composition of the ply-coated rubber according to the present invention, as the matrix component other than the above-mentioned butyl rubber, the rubber used in the conventional ply-coated rubber can be used and is not particularly limited. is not.
Further, the rubber composition used in the present invention may be appropriately blended with a commonly used filler anti-aging agent, vulcanizing agent, vulcanization accelerator, and the types and amounts of these may be within the range usually used for tires. It can be adjusted as shown in Table 1.

[0020]

[Table 1] Further, the rubber composition shown in Table 2 for the details of the rubber components in Table 1 was examined.

[0021]

[Table 2] As the carcass cord used in the pneumatic tire according to the present invention, an organic fiber cord such as a polyester cord, a nylon cord, an aromatic polyamide cord or a metal cord such as a steel cord is used.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An example of a pneumatic tubeless tire according to the present invention is shown in FIG. 2 (a) in a cross section of only the right half of the tire equatorial plane, and a cross section of a ply in which the carcass is developed in the tire width direction is shown. Listed in 2 (b).

In the figure, 1 is a carcass, 2 is its ply cord (shown as a single line for simplicity of illustration), 3 and 4 are ply covering rubbers inside and outside the carcass 1, and 5 is a bead. , 6 is a core of the bead portion 5, 7 is a filler, 8 is a tread portion, 9 is a side portion, and 10 is a non-slip groove.

Of the ply-coated rubbers 3 and 4 shown in FIG. 2 (b), at least a part 4'of the rubber 4 has a different rubber composition from the other ply-coated rubbers 3 and 4, and is made of butyl rubber. The compounding amount is low or no compounding, but the remaining ply rubber coatings 3 and 4 have a high compounding rubber composition of 50 mass% or more of the butyl rubber.

The ply covering rubber 4'is a section that is slightly wider than the entire inner surface of the ply double-folded portion wrapped around at least the core 6 and the filler 7 of the tire bead 5 outside the carcass 1. Figure 2 across the width
(A), a step d (about 5 mm) clearly shown in FIGS. 3 and 5 is formed between the winding end and the step d is a ratio to the sectional height H of the carcass 1 and 0.05 ≦ d / H ≦ In the range of 0.15, DW ≧ 90% can be secured, but in addition, as shown in FIG. 4, the radial width D (about 16 mm) at the winding edge 11 is D / with respect to the cross-sectional height H of the carcass 1. The width E of the annular region 12 facing the winding edge 11 is E / H with respect to H so that H ≧ 0.15, and independently or in combination as shown in FIG. It is arranged so that H ≧ 0.15.

Further, as shown in FIG. 6, the ply covering rubber 4'is spread over the entire outside of the carcass 1, and the butyl part of the ply covering rubber 3 inside the carcass 1 is equal to the butyl part of the ply covering rubber 3. It is preferable that the total amount is 100 mass% or more.

FIG. 7 shows a tubeless tire having a conventional structure in which the inner liner 13 is attached to the inner side of the carcass 1 with a gauge of 1 mm and the rubber composition (a) shown in Table 2 is applied to the ply coated rubbers 3 and 4. The inner liner 13 has been abolished, and instead all of the ply coated rubbers 3 and 4 are shown in Table 2.
(B), (c) and (d) of the butyl rubber blended rubber composition and using a comparative tire having the same structure as in FIG. 6, the air impermeability and drum durability of the conventional structure were also used. The results of confirming the effects of the present invention are shown in Table 3 below.
Are shown together.

[0028]

[Table 3] In short, Examples 1 to 6 each have a weight reduction effect of 6% in comparison with the conventional example, together with Comparative Examples 1 to 3, but in Comparative Example 1, deterioration of AP or in Comparative Examples 2 and 3 is remarkable in DW. Contrary to the deterioration, it can be seen that both AP and DW are achieved and suitable for practical use.

[0029]

According to the present invention, it is possible to reduce the weight of a pneumatic tubeless tire by eliminating the inner liner without deteriorating air impermeability and drum durability.

[Brief description of drawings]

FIG. 1 is a graph showing the effect of the number of butyl moieties in a ply-coated rubber on AP and DW.

FIG. 2 is a cross-sectional view of a test tire and a carcass used therein under the development in the width direction.

FIG. 3 is a sectional view of an essential part showing an embodiment.

FIG. 4 is a sectional view of an essential part showing an embodiment.

FIG. 5 is a sectional view of an essential part showing an embodiment.

FIG. 6 is a cross-sectional view of essential parts showing both an example and a comparative example in common.

FIG. 7 is a sectional view of a main part of a tire showing a conventional structure.

[Explanation of symbols]

 1 Carcass 2 Ply cord 3, 4, 4'Ply coated rubber 5 Bead part 6 Core 7 Filler 8 Tread part 9 Side part 10 Non-slip groove 11 Winding edge 12 Annular area 13 Inner liner

Claims (5)

[Claims] 1. A lightweight tubeless tire obtained by applying a ply-covered rubber containing a butyl-based rubber to a carcass whose inner liner has been abolished, and at least outside the carcass, around the core and filler of the bead portion of the tire. One or both of the winding end edge of the ply on the winding inner surface of the ply double-folded portion wrapped around and the facing annular surface facing the winding end edge, or the entire winding inner surface including these. The ply-coated rubber has a low-blended or unblended butyl rubber content of 40 mass% or less, and the ply-coated rubber in the carcass outer residual area and the carcass inner area has a butyl rubber content of 50 mass% or more. It is a lightweight pneumatic tubeless tie with excellent drum durability combined with air permeability. Ya. 2. A carcass cross-section height (H) of a tire radial width (D) at the hoisting edge of the ply or a similar width (E) of the annular region of the ply facing and facing the hoisting edge. The lightweight pneumatic tubeless tire according to claim 1, wherein each ratio is 0.15 or more. 3. The upper edge of the annular region has a higher radial step (d) with respect to the winding edge of the ply and the ratio of this step to the carcass cross-section height (H) is within 0.15. Item 1. A lightweight pneumatic tubeless tire according to item 1 or 2. 4. The ply-covering rubber covering the entire area outside the carcass including the inner surface of the ply double-folded portion is a low or no butyl rubber composition, and the ply-covering rubber inside the carcass comprises: The lightweight pneumatic tubeless tire according to claim 1, which has a high rubber composition of butyl rubber that is 100 mass% or more in total with the compounding amount of the butyl rubber. 5. A butyl rubber blended with a ply-coated rubber is an isoprene-isobutylene copolymer rubber, a halogenated isoprene-isobutylene copolymer rubber, or a halogen-containing copolymer of isomonoolefin and p-alkylstyrene. The lightweight pneumatic tubeless tire according to any one of claims 1 to 4, which is composed of one or two or more of the modified copolymer rubbers obtained by cyclization.