JP2868872B2 - Pneumatic tire having a foamed rubber layer on the tread - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention uses a foamed rubber layer exhibiting excellent wet grip performance and the like as a tread in summer and spring and autumn (hereinafter, simply referred to as summer) to improve steering performance and performance. The present invention relates to a pneumatic tire having significantly improved ice and snow performance, such as driveability, braking performance, and maneuverability, on a snowy and snowy road surface in winter without impairing heat generation durability performance.

(Prior Art) Conventional pneumatic tires require a chain attached to a tire or a spike in order to ensure driveability, braking performance and maneuverability (hereinafter simply referred to as ice and snow performance) when traveling on ice and snow. He uses a lot of spiked tires with pins in the tread surface.

However, due to wear of chains and spike pins and wear of roads, fine powder of these wears is scattered, causing dust pollution and spike pins causing damage to roads, which is a major social problem. In order to deal with these, recently, so-called studless tires without using spike pins have been proposed, and tread patterns of the tires,
Tread rubber quality has been studied. However, it has not yet been able to exhibit the same ice and snow performance as spiked tires.

On the other hand, in each of JP-A-62-283001, JP-A-63-235921 and JP-A-63-90403, the performance on ice and snow is improved by using a foamed rubber for a tread portion of a pneumatic tire. Is being planned.

However, the use of spiked tires has been legally regulated, and it has become necessary to further improve the performance on ice and snow.

Therefore, an object of the present invention is to increase the tan δ value (−5 ° C. to 0 ° C.) of the rubber composition of the foamed rubber layer of the tread, not only to have the effect of absorbing water on ice by the foamed rubber, but also to increase the surface An object of the present invention is to provide a pneumatic tire using a rubber composition for a tread, which can improve skid performance on ice even by hysteresis loss of foamed rubber having large micro deformation.

(Means for solving the problem) In order to improve the wet skid resistance of the tire,
It is widely known that it is good to use a rubber composition having a large tan δ value of 0 ° C. for a tread rubber. Conventionally, 0 ° C
Glass transition temperature (Tg) to increase the tanδ value of
Although high synthetic rubbers, mainly styrene-butadiene rubbers, have been used, the use of rubbers with a high Tg results in rapid hardening of the rubber at low temperatures, resulting in poor skid resistance on icy and snowy roads.
In other words, improvement of wet skid resistance (tan δ at 0 ° C)
Enlarging the value) and improving the skid resistance on icy and snowy roads (making it soft at low temperatures) can be said to be a trade-off phenomenon.

Accordingly, the present inventors have conducted intensive studies to develop a technology capable of increasing the tan δ value at 0 ° C. without changing the Tg of the polymer. As a result, a specific amount of a specific alkylamine or polyoxyethylene ether was added. As a result, it has been found that the above-mentioned problems can be solved, and the present invention has been completed.

That is, the present invention relates to a pneumatic tire including a tire case and a tread covering a crown portion of the case, wherein the tread has a volume of at least 10% or more of the total volume of the tread on the front side thereof. With layers,
The rubber component containing at least 50 parts by weight of at least one selected from the group consisting of natural rubber, polybutadiene rubber, and a styrene-butadiene copolymer rubber having a glass transition temperature of −45 ° C. or lower, N ₂ SA, Highly reinforcing carbon black having characteristics of 90 to 180 m ² / g, and rubber component 100
For parts by weight, the following general formula: (R ₁ and R ₂ are alkyl groups, x, y, and z are integers from 1 to 30,
Preferably, x and y are each an integer of 1 to 10 and z is an integer of 6 to 20).
Parts, made of foamed rubber containing a foaming rubber is related to a pneumatic tire characterized by having a closed cell range expansion ratio (V _S) of 5-50%.

Here, as the foamed rubber layer, at least one selected from the group consisting of natural rubber, polybutadiene rubber, and styrene-butadiene copolymer rubber having a glass transition temperature (Tg) of -45 ° C. or less is blended in an amount of 50 parts by weight or more. The reason is that when 50 parts by weight or more of a styrene-butadiene rubber having a Tg of -45 ° C or more is used, the rubber is rapidly cured at a low temperature, and the skid resistance of an icy road is deteriorated.

The compounding amount of the compound of the above formula (I) and / or (II) is defined as 0.1 to 50 parts by weight with respect to 100 parts by weight of the rubber component, when the compounding amount is less than 0.1 part by weight. This is because the desired desired effect cannot be obtained. On the other hand, if it exceeds 50 parts by weight, not only the effect commensurate with the increased amount cannot be obtained, but also the physical properties after vulcanization are adversely affected, resulting in undesired results.

The high reinforcing carbon black is preferably added in an amount of 40 to 80 parts by weight based on 100 parts by weight of the rubber component. If the N ₂ SA value of such carbon black is less than 90 m ² / g, abrasion resistance is significantly reduced, while if it exceeds 180 m ² / g, the viscosity of unvulcanized rubber becomes too high and foams during processing. Therefore, it is inappropriate in any case.

Further, as a foaming agent, for example, azodicarbonamide, dinitrosopentamethylene-tetraamine, azobisisobutyronitrile, benzenesulfonylhydrazide, oxybis-benzenesulfonylhydrazide,
For example, resin microcapsules of a high-boiling hydrocarbon compound are used.

The foaming rate V _S of the foamed rubber using such a foaming agent is represented by the following equation: V _S = {(ρ ₀ −ρ _g ) / (ρ ₁ −ρ _g ) −1} × 100 (%) (1) Where ρ ₁ is the density of the foamed rubber (g / cm ³ ), ρ ₀ is the density of the rubber solid phase of the foamed rubber (g / cm ³ ), and ρ _g is the density of the gas inside the foamed rubber bubbles. (G / cm ³ ). The foamed rubber is composed of a rubber solid phase part and a cavity (closed cell) formed by the rubber solid phase part, that is, a gas part in the air bubble. The density ρ _{g of the} gas part is extremely small, almost close to zero,
In addition, since the density ρ ₁ of the rubber solid phase portion is extremely small, the above equation (1) is substantially equal to the following equation: V _S = (ρ ₀ / ρ ₁ -1) × 100 (%) (2) Be equivalent.

In the present invention, foaming rate V _S is desirably a range of 5-50%, preferably 5-30%. It was a preferable range of expansion ratio V _S is 5 to 50 percent, is less than 5%, can not be obtained flexibility of the foamed rubber at a low temperature, and if it exceeds 50%, abrasion resistance is lowered This is because the wear resistance on ice and snow road surfaces and dry road surfaces is practically insufficient.

Further, the foamed rubber used for the tread of the pneumatic tire of the present invention can be obtained by adding a foaming agent to the above-mentioned rubber compound and heating and pressurizing according to a usual tire manufacturing method.

In addition, in addition to the compounding agent in the present invention, compounding agents commonly used in the rubber industry, for example, fillers, softeners,
Antioxidants, vulcanization accelerators, vulcanization accelerators, vulcanizing agents and the like can of course be appropriately compounded within the usual range of compounding amounts as required.

(Action) The compound of the above formula (1) and / or (2) used in the present invention may be a compound between rubber molecules and rubber molecules, between rubber molecules and filler particles (particularly carbon black particles), or between filler particles and filler particles. This has the effect of increasing the interaction such as that described above, thereby making it possible to obtain a rubber composition having a large tan δ value even at high temperatures.

(Examples) Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Reference Examples 1 to 4, Comparative Example 1 Raw materials shown in Table 1 below were blended (parts by weight) using a Banbury mixer, and vulcanized. For the obtained vulcanizate, using a rheometrics viscoelasticity tester,
The tan δ value at 0 ° C. was measured under the condition of a dynamic strain of 1%. The results obtained are shown in the lower part of Table 1.

Next, eight types of tires having a tire size of 165SR13 were constructed using the rubber compositions of Reference Examples 2 and 4 and Comparative Example 1 as tread rubbers, and for each tire, the tread grip on ice and snow road surfaces (skid-resistant skid performance, ice-resistant Skid performance) and tread surface gripping force on wet road surface (wed skid resistance) were evaluated by the following method by an actual vehicle test, and the obtained results are also shown in Table 1.

Treading surface grasping force on ice and snow roads The braking performance was measured by applying a brake while traveling at speeds of 20, 30, and 40 km / H, and the stopping distance was measured. The higher the value, the better the result.

Tread grasping force on wet road surface On wet asphalt road surface, speed 40km / H, 70km
/ H and 100km / H at each speed, sudden braking was applied, and the mileage to complete stop was calculated.
As an index. The higher the value, the better the result.

From the results in Table 1, the rubber composition shown as a reference example was
All were tan δ (0 ° C.) compared to the rubber composition of Comparative Example 1.
It can be seen that the value of is large. In addition, in the tire performance, the tire of the reference example is compared with the tire of the comparative example,
It can be seen that both skid resistance and wet resistance on ice and snow are greatly improved.

Examples 1 to 3 and Comparative Examples 2 to 3 Raw materials shown in Table 2 below were blended (parts by weight) using a Banbury mixer and vulcanized to obtain vulcanized rubber samples. The tan δ value of this vulcanized rubber sample at −3 ° C. was measured. The measurement of the tan δ value was performed at −3 ° C. under the conditions of a dynamic strain of 1% and a frequency of 15 Hz using a viscoelasticity meter manufactured by Rheometrics.

Next, three types of tires having a tire size of 165SR13, in which the rubber compositions of Example 3 and Comparative Examples 2 and 3 were used as tread rubbers, were manufactured. For each tire, the foaming ratio V _S (%) and braking performance on ice were determined as follows. Measured according to the method. The results obtained are shown in Table 2.

Foaming ratio V _S of the expansion ratio V _S foamed rubber is cut out block-like sample from the foam rubber layer of the tread of test tires was measured density ρ ₁ (g / cm ³⁾ of the block-like sample, whereas non-foamed The density ρ ₀ of the tread of the rubber (solid rubber) was measured, and the above formula (2)
Was determined using

On-ice braking performance Four test tires were mounted on a 1500cc passenger car,
The braking distance was measured on ice at an outside temperature of -3 ° C. The index was indicated as an index with the comparative tire set as 100. The larger the value, the better the braking.

From Table 2, it can be seen that Nymeen L-207 or Nonion P-2
It can be seen that the tan δ value at −3 ° C. of the rubber composition containing 10 was significantly improved.

In addition, it can be seen that the use of a foamed rubber containing a specific amount of these compounds in a tread significantly improves the braking performance on ice compared to a conventional foamed rubber tread tire.

(Effects of the Invention) As described above, the skid resistance on ice is improved not only by the effect of absorbing water on ice by foamed rubber but also by the hysteresis loss of foamed rubber whose surface has a microscopic deformation larger than that of normal rubber. In the pneumatic tire of the present invention using the rubber composition capable of forming a tread, the driving performance, braking performance, maneuverability, etc., on a snowy and snowy road surface in winter can be achieved without impairing the steering performance and heat generation durability in summer. The effect is obtained that the performance is remarkably improved.

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C08K 13/02 C08K 13/02 C08L 9/00 C08L 9/00 9/06 9/06 // (C08K 13/02 3:04 5:06 5:17) B29K 7:00 9:00 9:06 105: 04 (56) References JP-A-58-198548 (JP, A) JP-A-61-78870 (JP, A) JP-A-61-261359 (JP, A) JP-A-60-124467 (JP, A) JP-A-58-142937 (JP, A) JP-B-33-1389 (JP, B1) JP-B-44-31801 (JP, B1) ( 58) Field surveyed (Int.Cl. ⁶ , DB name) C08L 7/00-21/02 C08K 3/00-13/08

Claims (1)

(57) [Claims] 1. A pneumatic tire having a tire case and a tread covering a crown portion of the case, wherein the tread has at least a total volume of the tread on its front side.
A foamed rubber layer having a volume of 10% or more, wherein the foamed rubber layer is composed of natural rubber, polybutadiene rubber and glass transition temperature −
A rubber component containing 50 parts by weight or more of at least one selected from the group consisting of styrene butadiene copolymer rubbers having a temperature of 45 ° C. or less, N ₂ SA having a characteristic of 90 to 180 m ² / g, a high reinforcing carbon black, And the following general formula with respect to 100 parts by weight of the rubber component: Wherein R ₁ and R ₂ are an alkyl group, and x, y and z each represent an integer of 1 to 30. 0.1 to 50 parts by weight of a compound represented by the following formula: a pneumatic tire characterized by having a closed cell foam rate (V _S) 5~50% range.