JPS58177703A - Tire - Google Patents

Abstract

PURPOSE:To obtain a tire of excellent running performance further with a less damage trouble during manufacture, by using tread rubber with tear strength 18kg/cm or less at 170 deg.C. CONSTITUTION:If an angle alpha formed by a side wall 3 of a groove 2 and a plane 4 of the grounded part in a tread 1 is smaller than 92 deg., a catch of rubber is generated at mold releasing to cause demold splitting, while if reversely the anglc is larger than 135 deg., drainage is worsened to decrease brake performance and driving stability on a wet surface road, and the angle alpha is formed to a degree above 92 deg. and below 135 deg.. While for a radius of curvature R in the connection part between a groove bottom part 5 and the wall 3 not larger than 2mm., the demold splitting is easily caused, on the contrary for the radius not smaller than 5mm., a curved surface is discontinuously formed to easily generate a groove bottom crack by concentration of stress at running time, and the radius of curvature is set above 2mm. and below 5mm..

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tire that has a tread that has excellent running performance and is less prone to damage during manufacturing.

As a tire that combines the mutually contradictory performance of low rolling resistance (low fuel consumption) and high wet grip, we use conjugated diene-based elastomers, such as butadiene rubber (1, 2-Bit!), which has a large amount of vinyl bonds. ), 5BR (Sol, abbreviated as SBR) made by solution polymerization, and other new synthetic rubbers as the main rubber component have recently come into use. However, the above-mentioned new synthetic rubbers generally have low tensile strength and tear strength, which are further reduced by 4ff at high temperatures, which often results in damage to the tread portion during release from the mold after completion of vulcanization. One way to prevent such damage during demolding (demold splitting) is to apply a mold release agent such as silicone to the surface of the mold or tread. In addition to the problem that the release agent flows into the joints of the tread and sidewalls, causing defects such as open joints, it also requires a great deal of effort to apply the release agent, which is unfavorable in terms of work efficiency.

The inventors have conducted various studies to prevent the above-mentioned demold splitting without impairing the running performance of the tire, and have discovered that the following tire is extremely excellent in practical use. , completed the invention.

That is, the tire according to the present invention is J I 5K63.
The tear strength of the B-type dumbbell piece specified by 011ζ is
Provided with tread rubber of 18 Kp/m or less at 170°C, the angle between the side wall of the tread group part and the plane of the ground contact part is 92 degrees or more and 135 degrees or less), and the connection between the group bottom and the side wall part. It is characterized in that the radius of curvature of the part is 2M or more and 5M or less. Tread rubbers with low tear strength at high temperatures include, for example, conjugated diene-based elastomers produced by solution polymerization, particularly solution-polymerized butadiene rubber, solution-polymerized styrene-butadiene rubber, solution-polymerized in-prene rubber, and solution-polymerized in-prene butadiene rubber. Preferably, the main rubber component is an elastomer composed of one of these or a mixture thereof. These elastomers are capable of achieving both low fuel consumption and high wet grip, which cannot be achieved with other elastomers.

Regarding the shape of the tread part, in Fig. 1,
If the angle α between the side wall 3 of group 2 of tread 1 and the ground plane 4 is smaller than 92 degrees, the rubber will get caught in the rigid type, causing demold splitting; If the angle α is too large, the drainage performance will be poor and the braking performance and steering stability performance on wet road surfaces will be degraded. Therefore, it is preferable that the angle α is 92 degrees or more and 135 degrees or less. Furthermore, if the radius of curvature R of the connection between the group bottom 5 and the side wall 3 is less than 2 fines, demolding is likely to occur, and if it is more than 5I, the curved surface at the group bottom 5 will be discontinuous. Both are unfavorable because groove bottom cracks are more likely to occur due to stress concentration during running. Therefore, it is preferable that the radius of curvature is 2M or more and 5M or less.

Next, in a rib-type and/or block-type tread pattern that bends repeatedly, the ratio W/ It is preferable that L is 0.25 or more. If this is smaller than 0.25, the absorption of deformation energy during deformation of the rubber during mold release will be insufficient, and demold splitting will occur. It becomes uncomfortable. As shown in FIG.
Providing 2 to 5M straight or bent straight or curved sipes is advantageous in terms of dividing and absorbing the deformation energy. The depth (pattern depth) D of group 2 of the tread is preferably 7.5 mm or less in order to prevent the tread rubber from getting caught. moreover,
The shape of the upper end of the protrusion toward the group at the bent portion of the sub and/or block is at least 3/4 of the total depth of the group from the upper end of the group, as shown in FIG.
It is preferable that the depth is maintained at . If the depth at which the top end shape is maintained is too shallow, the movement of the top rubber during demolding will be unstable and demold splitting due to stress concentration will likely occur.

[Examples and comparative examples]

Table 1 shows compounding examples of tread rubber. Table 2 also shows the shape and dimensions of the tread portion in relation to FIGS. 1 to 4. Shown in Table 1.

Tires having the tread shapes shown in Table 2 were manufactured using various rubbers, and the damage state during vulcanization and tire performance were examined. The results are shown in Table 3. The tire type was a steel radial tire with a 1655R13 rib pattern.

In Table 3, the transfer resistance index is an index with the tire of Comparative Example a being 100, and the smaller this index is, the better the tire is. In addition, the wet grip index represents the braking performance on a wet road surface, and is an index with the tire of Comparative Example A set as 100, and the larger this index is, the better the tire is.

1st surface phase bath liquid polymerized butadiene rubber: 30'C) Intrinsic viscosity number [η] in toluene solution is 2.4, vinyl bond content is 80%
Of things.

*22 Bath liquid styrene or butadiene rubber: 3. The intrinsic viscosity number [η] in toluene solution is 3.5.

20% bound styrene, butadiene part with a vinyl bond content of 50%.

[η] is 1.0, bound styrene 20%, vinyl content 5
0% mixture (70:30 mix ratio).

*8 Bath liquid/polymerized imprene rubber: Intrinsic viscosity number [η] in toluene solution at 30°C is 3.0, and the amount of 3.4-bonds is 30.
% stuff.

*4 Bath liquid f combined impregnated butadiene rubber = Intrinsic viscosity number [η] in toluene solution at 30°C is 2.8, 3.4-bond content in isoprene part is 25%, vinyl content in butadiene part is 65% Of things.

*5 Isopropyl-P-phenyl-P-phenylenediamine *6 N-benzothiazyl 5y Using a JISB type dumbbell punched piece, at 170°C.

Measurement was performed using an autograph manufactured by Shimadzu Corporation.

As is clear from the above description, the tire according to the present invention has excellent running performance and is extremely superior in that it causes few damage accidents during manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the tread portion, FIGS. 2 and 3 are sketches of the tread, and FIG. 4 is a perspective view of the group portion. All figures relate to embodiments. 1--tread, 2--group, 3--side wall. Patent applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent attorney Hiroshi Sugawara Figure 2
Figure 3 4Wi

Claims (5)

[Claims] (1) The tear strength of a B-type dumbbell piece specified in JISK6301 is 18 to 4/c at 170°C.
rn or more, the angle between the side wall of the tread group and the ground plane is 92 degrees or more and 135 degrees or less, and the radius of curvature of the connection between the group bottom and the side wall is 2u or more and 5u or less. tire. (2) It has a rib-type and/or block-type tread pattern that repeatedly bends, and the ratio W/L of the lateral bending amount W of the tread group to the bending repetition unit length (pitch) L is 0.25 or more. The tire according to claim 1, wherein the group depth D is 75U or less. (3) The protrusion toward the group side at the bent part of the tread has a length of 3 to 6M and a depth of 2 to 5. The tire according to claim 1 or 2, wherein the siping is provided in a straight or bent straight or curved shape. (4) Claims 1 to 3, wherein the shape of the upper end of the protrusion toward the group at the bent portion of the tread is maintained from the upper end of the group to at least 3/4 of the total depth of the group. Tires listed in any of the preceding sections. (5) The main rubber component of the tread rubber is an elastomer made of one or a mixture of two or more of solution polymerized butadiene rubber, solution polymerized styrene-butadiene rubber, solution polymerized imprene rubber, and solution polymerized isoprene-butadiene rubber. A tire according to any one of claims 1 to 4.