JP2005126555A - Rubber composition for tire sidewall reinforcing layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition for a tire sidewall reinforcing layer for use in the sidewall of a run-flat tire that maintains its rigidity when subjected to puncture, suppresses its heat generation and enables its long-distance travel through mitigating rubber breakage even if subjected to repeated flexural deformation. <P>SOLUTION: This rubber composition for the tire sidewall reinforcing layer comprises (a) 100 pts. wt. of a diene rubber component, (b) 20-120 pts. wt. of a filler and (c) 5-70 pts. wt. of polypropylene powder ≤500μm in mean particle size, wherein the total compounding amount of the components(b) and (c) is ≤125 pts. wt. The run-flat tire using this composition is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition for a tire sidewall reinforcing layer.

  In recent years, run-flat tires have been developed that enable safe driving even when tires are punctured. In run-flat tires, rubber with high modulus of elasticity is used, and a thick reinforcing rubber layer is placed on the sidewalls to maintain tire rigidity during tire punctures and when subjected to repeated bending deformation This also reduces rubber breakage and enables long-distance travel (see, for example, Patent Document 1). However, in order to ensure run-flat running performance with rubber having a low elastic modulus, it is necessary to increase the thickness of the reinforcing rubber layer, resulting in an increase in tire weight and an increase in heat generation. Further, in order to increase the elastic modulus of the tire, a method of adding an excessive amount of carbon black is known, but the heat generation of the tire increases, the tensile elongation at break decreases, and the durability of the tire decreases. .

JP 2001-213999 A

  The present invention provides a sidewall portion of a run-flat tire that maintains tire rigidity during tire puncture, suppresses heat generation, reduces rubber damage even when repeatedly subjected to bending deformation, and enables long-distance running. An object of the present invention is to provide a rubber composition for reinforcement used in the above.

  The present invention relates to (a) 100 parts by weight of a rubber component composed of a diene rubber, (b) 20 to 120 parts by weight of a filler, and (c) 5 to 70 parts by weight of propylene powder having an average particle size of 500 μm or less. The rubber composition for a tire sidewall reinforcing layer, which is a rubber composition for a tire sidewall reinforcing layer, wherein the total amount of the filler (b) and the propylene powder (c) is 125 parts by weight or less.

  The rubber composition preferably has a maximum temperature during kneading within a range of 120 to 170 ° C.

  The present invention also relates to a run flat tire using a rubber composition for a tire sidewall reinforcing layer.

  According to the present invention, by blending a specific amount of propylene powder, the rubber composition for a tire sidewall reinforcing layer can be increased in elasticity, and the run flat performance of a run flat tire having a sidewall molded from the composition can be improved. Can be improved.

  The rubber composition for a tire sidewall reinforcing layer of the present invention comprises a rubber component (a), a filler (b) and a propylene powder (c).

  The rubber component (a) is made of a diene rubber. Examples of the diene rubber include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), butadiene rubber containing syndiotactic crystals (see JP-A-7-97481), 1,4-added isoprene. Examples thereof include rubber (IR) and acrylonitrile butadiene rubber (NBR). These can be used alone or in combination.

  When natural rubber and butadiene rubber are mixed and used, the content of butadiene rubber is preferably 10 to 70% by weight, more preferably 20 to 50% by weight in the rubber component. If the content is less than 10% by weight, the proportion of natural rubber increases, and the effect of reversion due to vulcanization of natural rubber appears. As a result, heat generation increases and the durability tends to be adversely affected. If it exceeds 100%, the processability deteriorates and the strength tends to decrease as a rubber physical property.

  Examples of the filler (b) include carbon black and silica.

  The blending amount of the filler (b) is 20 to 120 parts by weight, preferably 30 to 100 parts by weight, more preferably 40 to 80 parts by weight with respect to 100 parts by weight of the rubber component. When the blending amount is less than 20 parts by weight, the result is that the rubber is remarkably inferior. On the other hand, if it exceeds 120 parts by weight, the heat generation becomes high and the durability deteriorates.

Nitrogen adsorption specific surface area of carbon black is preferably 20~120m ² / g, more preferably 30~80m ² / g. When the nitrogen adsorption specific surface area is less than 20 m ² / g, the reinforcing property of the rubber tends to deteriorate. Moreover, when it exceeds 120 m < ² > / g, the heat_generation | fever of rubber | gum will become high and there exists a tendency which is not preferable in terms of durability.

  The average particle size of the propylene powder (c) is 500 μm or less, preferably 10 to 100 μm, more preferably 10 to 50 μm. When the average particle diameter exceeds 500 μm, the propylene powder remains as a foreign substance in the rubber and the durability is lowered.

  The amount of the propylene powder (c) is 5 to 70 parts by weight, preferably 10 to 60 parts by weight, and more preferably 30 to 50 parts by weight with respect to 100 parts by weight of the rubber component. If the blending amount is less than 5 parts by weight, the effect of improving the elastic modulus and the effect of reducing the exothermic property cannot be obtained. Moreover, when it exceeds 70 weight part, the intensity | strength of rubber | gum will fall and workability will also fall.

  In the rubber composition of the present invention, the total amount of the filler (b) and the propylene powder (c) is 125 parts by weight or less, preferably 40 to 110 parts by weight, more preferably 50 to 100 parts by weight. When the total amount exceeds 125 parts by weight, the workability tends to be deteriorated, the heat generation is disadvantageous, and the durability is deteriorated. Moreover, if it is less than 40 weight part, there exists a tendency for reinforcement property to deteriorate.

  Furthermore, in the rubber composition of the present invention, in addition to the rubber component (a), the filler (b), and the propylene powder (c), if necessary, a softener such as mineral oil, an anti-aging agent, Additives commonly used in the rubber industry such as vulcanizing agents, vulcanization accelerators, and vulcanization accelerating aids can be appropriately blended.

  The rubber composition of the present invention contains a rubber component (a), a filler (b), a propylene powder (c) and other compounding agents as required, in a normal processing apparatus such as a roll, a Banbury mixer, a kneader, etc. It is obtained by kneading using The maximum temperature at the time of kneading is preferably 120 to 170 ° C. and not more than the melting point of the polypropylene powder (c). More preferably, it is 125-165 degreeC, More preferably, it is 130-160 degreeC. If the maximum temperature during kneading is less than 120 ° C., kneading is often insufficient and the dispersion state is lowered, which is not preferable. On the other hand, if the maximum temperature exceeds 170 ° C., the melting point of the polypropylene powder is around 170 ° C., so that the polypropylene powder is melted, the layers are changed, the rubber is not collected, and the sheet processability is lowered.

  The rubber composition of the present invention is used as a tire sidewall portion reinforcing layer of a run flat tire.

  Specifically, the side wall portion reinforcing layer can be used for the reinforcing rubber layer 8 in the side wall portion of the run-flat tire 1 as shown in FIG. The reinforcing rubber layer 8 is disposed on the sidewall portion 2 and used to increase the rigidity of the tire. Specifically, the reinforcing rubber layer 8 is arranged in contact with the inside of the tire carcass ply 3 from the bead portion 7 to the shoulder portion, and a crescent-shaped reinforcing rubber layer 8 that gradually decreases in thickness in both end directions. Examples thereof include a reinforcing rubber layer disposed between the bead portion and the tread portion between the carcass ply main body portion and the folded portion, and two reinforcing rubber layers disposed between the plurality of carcass plies or the reinforcing plies.

  The thickness of the reinforcing rubber layer 8 is preferably 5 to 25 mm, more preferably 10 to 15 mm. If the thickness of the reinforced rubber layer is less than 5 mm, there is a tendency that the durability as a run-flat tire cannot be satisfied. If the thickness exceeds 25 mm, the tire rigidity increases, and riding comfort and driving stability deteriorate. There is a tendency that heat generation becomes large and it is not preferable in terms of durability.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not restrict | limited only to these.

  Table 1 summarizes the raw materials used in the examples and comparative examples.

Examples 1-3 and Comparative Examples 1-3
According to the contents of Table 1, the raw materials excluding sulfur and the vulcanization accelerator were kneaded using 1.7 L Banbury manufactured by Kobe Steel. Next, a rubber composition was prepared by adding sulfur and a vulcanization accelerator to the obtained kneaded material and kneading the mixture with a biaxial roller at 160 ° C. for 30 minutes. The following test was done about the obtained rubber composition. The results are shown in Table 2.

(hardness)
The prepared rubber composition was measured with a JIS-A hardness meter in an atmosphere at 25 ° C. It shows that hardness is so high that a numerical value is large.

(Viscoelasticity measurement)
Using a VES-F-3 manufactured by Iwamoto Seisakusho, E * (complex elastic modulus) and tan δ (loss tangent) at 60 ° C. were measured at a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%. The larger this E * value, the higher the rigidity and the better. Also, the smaller the tan δ value, the less heat is generated and the better.

(Tensile test)
From the prepared rubber composition, a tensile test was carried out using a No. 3 dumbbell according to JIS-K6251, and the breaking strength and breaking elongation were measured. The larger the value, the better the strength of the rubber.

(Run flat running test)
A tire of 225 / 60ZR16 size was produced by a conventional method, and the tire was mounted on a 2500 cc class vehicle, and the vehicle was driven at a constant speed of zero internal pressure and a speed of 90 km / h, and the distance traveled until the tire was damaged was measured. . The larger the value, the better the run-flat running performance.

  In Example 1, compared with Comparative Example 1, the hardness and E * were higher, the breaking strength and breaking elongation were increased, and the run-flat travelable distance was improved. Further, the tan δ value was equivalent to that of Comparative Example 1, and heat generation could be suppressed.

  In Example 3, the hardness and E * were significantly improved, and the run-flat travelable distance could be improved.

  In Comparative Example 2 in which only a small amount of propylene powder was blended and in Comparative Example 3 in which a large amount of propylene powder was blended, the run-flat travelable distance could not be improved.

It is sectional drawing of a run flat tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Side wall part 3 Carcass ply 4 Belt layer 5 Tread part 6 Bead core 7 Bead part 8 Reinforcement rubber layer 9 Bead apex

Claims (3)

(A) Tire side containing (b) 20 to 120 parts by weight of a filler and (c) 5 to 70 parts by weight of propylene powder having an average particle size of 500 μm or less with respect to 100 parts by weight of a rubber component composed of a diene rubber. A rubber composition for a tire side wall reinforcing layer, which is a rubber composition for a wall side reinforcing layer, wherein the total amount of filler (b) and propylene powder (c) is 125 parts by weight or less. The rubber composition for a tire sidewall reinforcing layer according to claim 1, wherein the maximum temperature during kneading is in the range of 120 to 170 ° C. A run flat tire using the rubber composition for a tire sidewall reinforcing layer according to claim 1.

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