JP2004034744A - Manufacturing method for studless tire and its tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a studless tire which has enhanced digging-up friction (scraping effect) without reducing sticky friction and has excellent performance on ice and snow. <P>SOLUTION: A tread is formed of diene-based rubber (a) in which short fiber or a plate material (b) of Mohs hardness of 3-7 is dispersed and orientated in an extrusion direction. The tread has complex modulus E1 in a tread thickness direction measured at 25°C, complex modulus Eα in the extrusion direction when tread rubber is formed into a sheet of 2mm with a roll, and complex modulus Eβ when the sheet of 2mm is turned by 90° which satisfy the formula: 60≤(E1-Eβ/Eα-Eβ)×100≤100, and the tread has tread rubber hardness of 45-70° measured at -10°C. <P>COPYRIGHT: (C)2004,JPO

Description

【００４３】
特許請求範囲の短繊維を配合し、トレッド厚さ方向に短繊維を配向させた実施例１および２は、トレッド周方向に短繊維を配向させた比較例１と比べて、氷雪上性能が優れていた。
【００４４】
トレッドに短繊維または板状材料を配合していない比較例２、トレッドゴム硬度が７０度よりも高い比較例４、トレッドにモース硬度が３未満の短繊維を配合した比較例３、特許請求範囲の短繊維を用いているが、トレッドの厚さ方向に短繊維が配向していない比較例１では、氷雪上性能が実施例より劣っていることがわかる。
【００４５】
【発明の効果】
本発明によれば、氷雪路面での粘着摩擦を損なうことなく、掘り起こし摩擦を向上させた、氷雪上性能に優れたスタッドレスタイヤを得ることができる。
【図面の簡単な説明】
【図１】タイヤトレッドの断面図である。
【図２】本発明のトレッドの作製方法を示す説明図である。
【図３】本発明のトレッドの作製方法を示す説明図である。
【符号の説明】
１　タイヤトレッド
２　短繊維または板状材料
３　ゴムシート
４　カレンダーロール
５　カット部分
Ａ　短繊維または板状材料の配向方向
Ｂ　押し出し方向[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention particularly relates to a tire excellent in performance on snow and on ice.
[0002]
[Prior art]
In recent years, studless tires without spikes have become widespread as tires traveling on icy and snowy roads. In this studless tire, in order to improve the performance on ice, it is necessary to increase road digging friction and adhesive friction, and various studies have conventionally been made to increase the friction coefficient of tread rubber on an ice road surface.
[0003]
On the other hand, in order to improve the strength, rigidity, abrasion resistance and the like of a tire, a tread rubber using a short fiber compounded rubber containing short fibers is known. However, when the tread rubber is extruded by a calender roll or an extruder, the compounded short fibers are oriented along the extrusion direction, that is, the circumferential direction of the tire tread. As a result, most of the tread rubber that touches the road surface has short fibers oriented in the tire circumferential direction, so the scratching effect does not function effectively, and most of the tread rubber is used for studless tires that require high digging and friction. Did not.
[0004]
On the other hand, as disclosed in Japanese Patent No. 2,637,887, the short fiber has a diameter of 0.1 to 0.3 mm as disclosed in Japanese Patent No. It is proposed to use thick and short fibers having a low aspect ratio. In this case, in the extrusion process, since the short fibers are less likely to be oriented, the chances of the ends of the short fibers coming into contact with the road surface are increased as compared to the conventional one oriented in the tire circumferential direction, and the scratching effect is improved to some extent. . However, the improvement of the scratching effect is limited only to the loss of the orientation of the short fibers, and the satisfactory performance on ice has not yet been obtained.
[0005]
As described above, at present, there is no tire excellent in performance on ice and snow that simultaneously improves the adhesive friction, the excavation friction, and the scratch friction on ice and snow road surfaces, or is balanced.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing a studless tire and a tread excellent in performance on ice and snow, which has improved dug-up friction (scratching effect) without impairing adhesive friction.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the inventors conceived the materials to be added and the degree of orientation, and accumulated research. As a result, short fibers or plate-like materials having a Mohs' hardness of 3 to 7 are dispersed in the tread rubber, oriented in the thickness direction of the tread rubber, and have a tread rubber hardness of 45 when measured at -10 ° C. The complex elastic modulus E1 in the tread thickness direction of the tread rubber measured at 25 ° C., the complex elastic modulus Eα in the extrusion direction when the composition is sheeted to 2 mm with a roll, and the complex elastic modulus Eα in the 90 ° direction When the complex elastic modulus is Eβ, the following equation 60 ≦ (E1-Eβ / Eα−Eβ) × 100 ≦ 100
The present inventors have found that a great effect can be achieved on the improvement of the scratching effect (digging-up friction) without losing the adhesive friction, and that the performance on ice and snow can be greatly improved, thereby achieving the present invention.
[0008]
That is, the present invention measures at 25 ° C. a tread obtained by dispersing (a) a short fiber or a plate-like material having a Mohs' hardness of 3 to 7 in a diene rubber so as to be oriented in the tread thickness direction. The complex elastic modulus E1 in the thickness direction of the tread, the complex elastic modulus Eα in the extrusion direction when the tread rubber is sheeted to 2 mm with a roll, and the complex elastic modulus Eβ in the 90-degree direction are expressed by the following equation: 60 ≦ (E1−Eβ / Eα−Eβ) × 100 ≦ 100
And a studless tire having a tread having a tread rubber hardness of 45 to 70 degrees when measured at -10C.
[0009]
The short fiber or plate-like material (b) is a short fiber having an average fiber diameter of 1 to 100 μm and an average length of 0.1 to 5 mm or a plate-like material having an average thickness of 1 to 90 μm and an average length of 0.1 to 5 mm. It is preferable that
[0010]
In addition, the present invention provides a step of extruding a rubber composition for tread containing a short fiber or a plate-like material having a Mohs' hardness of 3 to 7 into a sheet shape, and cutting the sheet perpendicularly to the extrusion direction to 90 The complex elastic modulus E1 in the tread thickness direction measured at 25 ° C., the complex elastic modulus Eα in the extrusion direction when the tread rubber is sheeted to 2 mm with a roll, and its 90 ° direction The complex elastic modulus Eβ is expressed by the following formula: 60 ≦ (E1-Eβ / Eα−Eβ) × 100 ≦ 100
And a method for producing a tread having a tread rubber hardness of 45 to 70 degrees when measured at −10 ° C.
And a step of extruding a rubber composition for a tread containing a short fiber or a plate-like material having a Mohs' hardness of 3 to 7 into a tube shape, and forming a sheet by cutting one portion of a side wall of the tubular rubber sheet in the extrusion direction. A step of cutting the sheet parallel to the extrusion direction, rotating the sheet 90 degrees, and superimposing the sheets again. The complex elastic modulus E1 in the thickness direction of the tread measured at 25 ° C. and the tread rubber are rolled by 2 mm. When the sheet is sheeted, the complex elastic modulus Eα in the extrusion direction and the complex elastic modulus Eβ in the 90-degree direction are expressed by the following equation: 60 ≦ (E1−Eβ / Eα−Eβ) × 100 ≦ 100
And a tread having a tread rubber hardness of 45 to 70 degrees when measured at -10C.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The studless tire of the present invention has a tread in which (a) a diene rubber and (b) a specific short fiber or a plate-like material are dispersed so as to be oriented in the tread thickness direction.
[0012]
As the diene rubber (a) in the tread, a commonly used rubber can be used. Specific examples include, for example, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), and the like. These may be used alone or by kneading two or more kinds. Can be
[0013]
The short fiber or plate-like material (b) dispersed in the tread has a Mohs hardness of 3 to 7. If the short fiber or plate-like material (b) has a Mohs hardness of less than 3, it is softer than ice, so the scratching effect (digging and rubbing) is not sufficient. , Dust problems occur. The short fiber or plate-like material (b) preferably has a Mohs hardness of 5 to 7.
[0014]
The average fiber diameter of the short fibers blended in the tread is preferably 1 to 100 μm, more preferably 3 to 50 μm. When the average fiber diameter of the short fibers is smaller than 1 μm, the bending strength is insufficient, and the effect of scratching the road surface (digging and raising friction) tends to be insufficient. On the other hand, if it is larger than 100 μm, the rubber hardness tends to be high, and the adhesive friction tends to decrease.
[0015]
The average thickness of the plate material mixed in the tread is preferably from 1 to 90 μm, more preferably from 3 to 45 μm. When the average thickness of the plate-like material is less than 1 μm, the bending strength is insufficient, and there is a tendency that the effect of scratching the road surface (digging-up friction) cannot be sufficiently expected. On the other hand, if it is larger than 100 μm, the rubber hardness tends to be high, and the adhesive friction tends to decrease.
[0016]
The average length of the short fibers or the plate-like material (b) is preferably from 0.1 to 5 mm, more preferably from 0.1 to 3 mm. If the average length of the short fibers or the plate-like material (b) is shorter than 0.1 mm, the precipitation length on the rubber surface is short, and the scratching effect (digging and friction) on the road surface tends to be insufficient. . On the other hand, when the length is longer than 5 mm, it becomes difficult to disperse and orient the short fibers or the plate-like material (b), and the processability of the rubber tends to decrease.
[0017]
The average aspect ratio of the short fibers or the plate-like material (b) is preferably from 10 to 1,000, particularly preferably from 50 to 500. If the average aspect ratio is less than 100, it is difficult for the short fibers or the plate-like material (b) to be oriented in the diene rubber (a), and there is a tendency that a sufficient effect of scratching the road surface (digging-up friction) cannot be obtained. On the other hand, if the average aspect ratio exceeds 10000, it tends to be a foreign substance in the diene rubber (a) due to its length in the major axis direction, and the mechanical fatigue properties tend to be poor. The aspect ratio refers to a ratio of the average length of the short fibers or the plate-like material (b) to the average fiber diameter (average length ÷ average fiber diameter).
[0018]
As the material of the short fiber or plate-like material (b), glass fiber, carbon fiber, polyester fiber, metal fiber (tungsten, iron, copper, platinum, stainless steel), potassium titanate fiber, aluminum whisker, potassium titanate whisker, Aluminum borate whiskers, titanic acid whiskers, zinc oxide whiskers, and the like are conceivable. Among them, it is preferable to use glass fiber or carbon fiber, since the glass fiber or the carbon fiber is easily broken and oriented in an appropriate length during the rubber kneading process.
[0019]
In the tread, the complex elastic modulus in the tread thickness direction measured at 25 ° C. is El, the complex elastic modulus in the extrusion direction when the tread rubber is sheeted to 2 mm with a roll is Eα, and the complex elasticity in the 90 ° (perpendicular) direction. Assuming that the rate is Eβ, the following equation (E1-Eβ / Eα−Eβ) × 100
Is 60 or more, preferably 80 or more. When the value of the above formula is less than 60, the orientation of the short fiber or the plate-like material (b) in the thickness direction of the tread cannot be obtained, and the friction performance on ice becomes insufficient.
[0020]
In the tread, the tread rubber hardness measured at −10 ° C. is 45 to 70 degrees, and preferably 50 to 65 degrees. When the hardness at −10 ° C. is less than 45 degrees, the rubber at normal temperature becomes too soft, and for example, the steering stability on a dry road surface becomes poor. On the other hand, if it is larger than 70 degrees, the rubber itself becomes too hard, and the ground contact property between the tread rubber surface and the ice and snow road surface is poor, and the ice and snow road performance is poor. Here, the tread rubber hardness refers to the hardness in the tread thickness direction.
[0021]
In the tread, the ratio (E1 / E2) of the complex elastic modulus El in the tread thickness direction measured at 25 ° C. to the complex elastic modulus E2 in the tire circumferential direction of the tread is preferably 1.1 to 4, preferably 1.2. -3.5 is more preferable. When the ratio of E1 / E2 is smaller than 1.1, short fibers or plate-like materials cannot be oriented in the tread thickness direction, and abrasion performance on ice tends to be insufficient. Further, when El / E2 is larger than 4, the material becomes hard, so that a problem of workability tends to occur.
[0022]
The short fiber or plate-like material (b) may be one kind of short fiber or plate-like material, or may be two or more kinds of short fiber or plate-like material. Further, a combination of a short fiber and a plate-like material can be applied.
[0023]
The short fiber or plate material (b) is preferably 2 to 30 parts by weight, more preferably 2 to 20 parts by weight, based on 100 parts by weight of the diene rubber (a). When the blending amount of the short fibers or the plate-like material (b) is less than 2 parts by weight, the amount of the short fibers or the plate-like material formed on the tread surface decreases, and a sufficient road surface scratching effect (digging-up friction) can be obtained. There is no tendency. On the other hand, if it is more than 30 parts by weight, the rubber becomes hard and the rigidity increases, and the processability tends to decrease.
[0024]
In the present invention, the short fiber or plate-like material (b) is compounded in a tread rubber and dispersed so as to be oriented in the tread thickness direction, and the complex elastic modulus in the tread thickness direction measured at 25 ° C. in the tread is measured. E1, the complex elastic modulus Eα in the extrusion direction when sheeting is performed at 2 mm with a roll, and the complex elastic modulus Eβ in the 90-degree direction are expressed by the following equation: 60 ≦ (E1−Eβ / Eα−Eβ) × 100 ≦ 100
Thus, a pneumatic tire is provided which improves excavation friction without impairing adhesive friction, and in particular, has excellent running performance on ice and snow.
[0025]
As a method for producing the tread, a commonly used extrusion method is used. When a tread is formed from a tread rubber sheet obtained by simply extruding, as shown in FIG. 1A, the orientation direction A in the tread of the short fiber or plate material 2 is the circumferential direction of the tread.
[0026]
On the other hand, as shown in FIG. 2, a rubber composition containing the short fibers or the plate-like material 2 is rolled by a calender roll 4, and the obtained rubber sheet 3 is cut perpendicularly to the extrusion direction B. When a tread is formed from a tread rubber sheet obtained by a method in which the tread rubber sheet is rotated by 90 degrees and then overlapped again, as shown in FIG. Is in the tread thickness direction.
[0027]
Alternatively, as shown in FIG. 3 (a), after extruding the rubber composition for a tread containing the short fibers or plate-like material 2 into a tube shape, one portion of a side wall of the tube-like rubber sheet is cut in the extrusion direction. Then, the tubular rubber sheet 3 is formed (cut portion 5). Then, as shown in FIG. 3B, the tread is formed from a tread rubber sheet obtained by cutting the sheet 3 in parallel with the extrusion direction B, rotating the sheet 3 by 90 degrees, and re-stacking the sheets. Also, as shown in FIG. 1B, the orientation direction A of the short fibers or the plate-like material 2 in the tread is the tread thickness direction.
[0028]
In the manufacturing method of extruding the rubber composition for a tread into a tube, the extruded rubber hits a plate on a disk, and in the process of spreading, the short fibers or the plate-like material 2 is circumferentially moved by the pressure and the distance between the disks. By the mechanism of orienting in the direction, the short fibers or plate-like materials are extruded while being oriented in the circumferential direction of the tube, as shown in FIG.
[0029]
In the tread of the studless tire of the present invention, a method for orienting the short fibers or plate-like materials in the tread thickness direction is not limited to the above-described method, and the short fibers or plate-like materials may be oriented in the direction. If so, other methods can be used.
[0030]
【Example】
Next, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.
[0031]
The raw materials used in the examples and comparative examples are summarized below.
[0032]
(material)
Natural rubber: RSS # 3 grade high cis polybutadiene: Ubepol BR150B manufactured by Ube Industries, Ltd.
Carbon black N220: Show black N220 manufactured by Showa Cabot Corporation
Silica: Nipsil VN3 manufactured by Nippon Silica Co., Ltd.
Silane coupling agent: Degussa Si69 (bis (3-triethoxysilylpropyl) trusulsulfide)
Paraffin oil: Diana process oil wax manufactured by Idemitsu Kosan Co., Ltd .: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Anti-aging agent: Nocrack 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Stearic acid: zinc oxide stearate manufactured by NOF Corporation: zinc oxide No. 1 glass fiber manufactured by Mitsui Kinzoku Mining Co., Ltd. 1: Mohs hardness 6, average fiber diameter 33 μm, average length 3 mm
Glass fiber 2: Mohs hardness 6, average fiber diameter 200 μm, average length 0.5 mm
Carbon fiber: Mohs hardness 6.5, average fiber diameter 18 μm, average length 5 mm
Nylon fiber: Mohs hardness 2, average fiber diameter 8 μm, average length 3 mm
Vulcanization accelerator: Noxeller CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Sulfur: powdered sulfur manufactured by Tsurumi Chemical Co., Ltd.
Examples 1 and 2 and Comparative Examples 1-4
(Tire molding method)
According to the compounding ratios in Table 1, Comparative Examples 1 and 2 were obtained by orienting short fibers in the tread circumferential direction by a commonly used extrusion method (FIG. 1A), and Examples 1, 2 and Comparative Examples Samples Nos. 3 and 4 were prepared by orienting short fibers in the tread thickness direction by the method shown in FIG. 2 (FIG. 1 (b)). Using the obtained rubber sheet for a tire tread, various test tires were molded and produced by a usual method. The following tests and evaluations were performed using the obtained tires.
[0034]
(Complex modulus)
The measurement was performed using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho under the conditions of a temperature of 25 ° C., a measurement frequency of 10 Hz, an initial strain of 10% and a dynamic strain of 1%. As the sample, a rubber piece having a thickness of 1.0 mm, a width of 4 mm, and a length of 5 mm was cut out from a tire tread portion and used for measurement. The complex elastic modulus in the tread thickness direction was E1, and the elastic modulus in the tire circumferential direction was E2.
[0035]
Under the above conditions, the complex elastic modulus in the extrusion direction when the tread rubber was sheeted to 2 mm with a roll was Eα, and the complex elastic modulus in the 90 ° (perpendicular) direction was Eβ.
[0036]
(Performance on ice)
A tire of 195 / 65R15 size was prepared and mounted on a 2000 cc domestic FR vehicle, and the braking stop distance on an ice plate from 30 km / h per hour was determined. The evaluation was performed using an index determined by the following equation based on Comparative Example 1. The higher the index, the better the performance on ice.
[0037]
(Brake stop distance of Comparative Example 1) ÷ (Brake stop distance) × 100
Before running the test, the tire surface was run for 200 km each.
[0038]
(Snow performance)
The lap time of the passenger car on the snow course was measured, and evaluated by an index obtained by the following equation based on Comparative Example 1. The higher the index, the better the performance on snow.
[0039]
(Circulation time of Comparative Example 1) ÷ (Circulation time) × 100
Before running the test, the tire surface was run for 200 km each.
[0040]
(Rubber hardness)
According to JIS K6253, a sample was taken out of the tread rubber in the thickness direction using a type A hardness tester and measured in an atmosphere at -10 ° C.
[0041]
Table 1 shows the results.
[0042]
[Table 1]

[0043]
Examples 1 and 2 in which the short fibers according to the claims are blended and the short fibers are oriented in the tread thickness direction have better performance on ice and snow than Comparative Example 1 in which the short fibers are oriented in the tread circumferential direction. I was
[0044]
Claims: Comparative Example 2 in which short fibers or plate-like materials are not blended in the tread, Comparative Example 4 in which tread rubber hardness is higher than 70 degrees, Comparative Example 3 in which treads are blended with short fibers having Mohs hardness of less than 3, Claims However, in Comparative Example 1 where the short fibers are not oriented in the thickness direction of the tread, the performance on ice and snow is inferior to that of the examples.
[0045]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the studless tire excellent in the performance on ice and snow which improved the excavation friction without impairing the adhesive friction on the ice and snow road surface can be obtained.
[Brief description of the drawings]
FIG. 1 is a sectional view of a tire tread.
FIG. 2 is an explanatory view showing a method for producing a tread of the present invention.
FIG. 3 is an explanatory view showing a method for producing a tread of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tire tread 2 Short fiber or plate material 3 Rubber sheet 4 Calender roll 5 Cut part A Orientation direction B of short fiber or plate material Extrusion direction

Claims (4)

In a tread in which (a) a short fiber or a plate-like material having a Mohs' hardness of 3 to 7 is dispersed in (a) a diene rubber so as to be oriented in the tread thickness direction, the tread thickness direction measured at 25 ° C. The complex elastic modulus E1, the complex elastic modulus Eα in the extrusion direction when the tread rubber is sheeted to 2 mm with a roll, and the complex elastic modulus Eβ in the 90-degree direction are expressed by the following equation: 60 ≦ (E1−Eβ / Eα−Eβ) × 100 ≦ 100
And a tread having a tread having a tread rubber hardness of 45 to 70 degrees when measured at -10C. The short fiber or plate material (b) is a short fiber having an average fiber diameter of 1 to 100 μm and an average length of 0.1 to 5 mm or a plate material having an average thickness of 1 to 90 μm and an average length of 0.1 to 5 mm. The studless tire according to claim 1. A step of extruding a rubber composition for tread containing a short fiber or a plate-like material having a Mohs' hardness of 3 to 7 into a sheet shape, cutting the sheet perpendicularly to the extrusion direction, rotating each 90 degrees, and stacking again. A complex elastic modulus E1 in the tread thickness direction measured at 25 ° C., a complex elastic modulus Eα in the extruding direction when the tread rubber is sheeted to 2 mm by a roll, and a complex elastic modulus Eβ in the 90-degree direction, The following formula 60 ≦ (E1-Eβ / Eα−Eβ) × 100 ≦ 100
And a tread rubber having a tread rubber hardness of 45 to 70 degrees when measured at -10C. A step of extruding a rubber composition for a tread containing a short fiber or a plate-like material having a Mohs' hardness of 3 to 7 into a tubular shape, a step of forming a sheet by cutting one portion of a side wall of the tubular rubber sheet in the extrusion direction, and Cutting the sheet in parallel to the extrusion direction, rotating the sheet 90 degrees each time, and superimposing the sheets again. The complex elastic modulus E1 in the tread thickness direction measured at 25 ° C. and the tread rubber are sheeted to 2 mm by a roll. The complex elastic modulus Eα in the extrusion direction and the complex elastic modulus Eβ in the 90-degree direction are calculated by the following equation: 60 ≦ (E1−Eβ / Eα−Eβ) × 100 ≦ 100
And a tread rubber having a tread rubber hardness of 45 to 70 degrees when measured at -10C.

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