JPH0230882B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to tires, particularly bicycle and motorcycle tires, and relates to a composite rubber sheet formed by mixing fibrillated aromatic polyamide short fibers into rubber in a laminate forming the ground-contacting side of the tire. interposed in at least one layer in the circumferential direction,
This is intended to strengthen the tire's ground contact area and ensure strong adhesive strength of the laminate. Conventionally, as a means of preventing this type of damage that occurs at the tread part of a tire, a synthetic fiber canvas having high tensile strength is placed as a breaker (reinforcing layer) between the tread part of the tire and the carcass. The use of canvas made of aromatic polyamide fibers with excellent high tensile strength (trade name: Kevlar manufactured by DuPont or Cornex manufactured by Daijin) was certainly effective in terms of toughness, but this The use of canvas significantly inhibits the adhesion between the tire tread and the carcass, resulting in peeling between the tire tread and the tire tread during or after the tire is running, resulting in a significant shortening of the tire's lifespan. . This invention was developed with the main purpose of preventing the occurrence of delamination between the layers constituting the ground contact side of a tire and ensuring sufficient toughness. The composite rubber sheet mixed therein is interposed in at least one layer between the carcass located on the inside of the tire and the back surface of the tread in the laminated carcass constituting the tire's ground-contacting part, and is different from conventional tires. The purpose of the present invention is to provide a tire of this type in which the ground contact side portion of the tire is reinforced in various ways, and which can achieve remarkable effects in strengthening the ground contact side portion and preventing peeling of this portion. A practical example will be explained using the drawings. Figure 1 is a cross-sectional view of a bicycle tire according to the present invention, in which 1 and 1 are made of ordinary bead wire or twisted organic or inorganic fibers such as aromatic polyamide fibers, glass fibers, or carbon fibers. A bead made of rope, which is surrounded by a two-ply sudare carcass 3 made of a bias-like sudare cloth coated with adhesive treated rubber on organic or inorganic fiber cords at both ears of the tire, and is embedded in the bead rubber 2 respectively. There is. This sagging carcass 3 is folded back in the tire width direction to form a 3-ply laminated body at the ground contact side portion of the tire. Further, on the surface of this laminated sagging carcass 3, thin sidewall rubber 4 and thick tread rubber 5 whose surfaces are patterned on the ground contact side of the tire are integrally laminated and adhered in accordance with the usual manner. The above structure is similar to that of a normal tire, but the feature of the present invention is that a composite rubber sheet 8 in which fibrillated short fibers 6 made of aromatic polyamide with a small diameter are mixed in rubber is placed on the ground contact side of the tire. It has a configuration in which it is arranged as a part of the constituent layer of the part. This composite rubber sheet 8 is usually mixed with fine fibrillated aromatic polyamide short fibers, more specifically Kevlar pulp manufactured by DuPont, in a proportion of 10 to 250 parts by weight based on 7100 parts by weight of rubber. It is something. This Kepler pulp has a diameter
It is an aggregate of thin fibrillated short fibers with a diameter of 1.5 d and a length of 0.5 to 8.0 mm, exhibiting a curled or branched shape, and randomly mixed into the rubber in an intertwined state. Here, if the short fiber group 6 mixed in the rubber 7 is less than 10 parts by weight, no reinforcing effect can be expected, and if it is more than 250 parts by weight, the properties of the rubber will deteriorate. The composite rubber sheet 8 is obtained by kneading rubber and short fibers using a roll or banbury, and molding the kneaded product into a sheet using a calender or an extruder. The composite rubber sheet 8 having the above structure is buried in the circumferential direction directly between the back surface of the tread 5 and the laminated carcass (FIG. 1), or this composite rubber sheet 8 is buried between the laminated carcass 3 directly. Alternatively, the composite rubber sheet 8 is embedded circumferentially both on the back side of the tread 5 and between the laminated carcass 3 (FIG. 3). In the embodiments of the present invention illustrated in FIGS. 1 to 3 above, there are eight layers of composite rubber sheets of rubber and short fibers made of aromatic polyamide fibrillated between the laminates on the ground contact side of the tire. Due to the presence of this short fiber, with at least one layer of embedded intervening
The toughness of the installation part can be ensured, and when solid debris with sharp points penetrates the tread part of the tire and attempts to damage it, the short fibers of the rubber sheet will strongly resist this and break through the canvas breaker. Demonstrates reinforcing function equal to or greater than that of Also, from Figure 1,
The tire illustrated in the figure has a tread portion 5 and a carcass 3.
It does not reduce the adhesive force with the tread portion, and is highly effective in suppressing the phenomenon of peeling of the tread portion during or after the tire is running. Furthermore, by disposing two layers of composite rubber sheets as illustrated in FIG. 3, the puncture resistance effect becomes even more remarkable. Next, various experimental results will be disclosed below in order to help better understand the various effects possessed by the tire according to the present invention. Experimental Example 1 First, in the composite rubber sheet used in carrying out this invention, the types of short fibers mixed in the rubber, including fibrillated aromatic polyamide short fibers, were determined. We determined the difference in puncture resistance that occurs when the tires are changed. The various short fibers selected as samples were (1) short fiber Kevlar pulp made of fibrillated aromatic polyamide manufactured by DuPont (trade name): average length 2 mm, thickness 1.5 d, (2) aromatic fiber manufactured by Teijin Company. Polyamide short fiber Cornex (trade name): average length 6mm, thickness 10d, (3) Cotton: average length 1.5mm, oval cross section, major axis 16μ, minor axis 8μ, (4) Polyester staple fiber: length Average length: 0.5 mm, thickness: 1.5 d (5) 6-Nylon staple fiber: Average length: 0.5 mm, thickness: 3 d. Rubber 100 consisting of the composition shown in Table 1 below
50 parts by weight of the above five types of short fibers are added to the parts by weight, kneaded with a roll, molded into a composite rubber sheet with a thickness of 0.5 mm using a calender, and then molded with a calendar. Two types of sheets were made in the perpendicular direction and the direction perpendicular to the molding direction, and these two types of sheets were mixed with a 3-ply 6-nylon bias sag with rubber and a 0.3 mm natural material having the composition shown in Table 2 below. A composite rubber sheet was interposed between the rubber sheet and vulcanization was performed at 150°C for 30 minutes to obtain a laminated sheet. Sample 12 made by cutting these laminated sheets
The puncture resistance was evaluated using the following methods. The impact crack testing machine used in this test was made of a 2 kg steel material with a protrusion 14 having acute-angled teeth 13 protruding from above a rubber substrate 11, as shown in FIG. 4. The weight 15 is attached to a pair of left and right frames 16, 16.
It has a structure that allows it to fall naturally while being guided between the cut specimens 12 and 12. The cracks occurring on the cut specimen 12 were observed, and the distance between the specimen 12 and the vertical plumb 15 was measured, and the results shown in Table 3 below were obtained. Ta. For the samples 12 to be placed on the folded rubber substrate 11, it is necessary that the weave of the bias sagging layer constituting the sample be placed in the same direction. Differences in the direction of the weave of the bias sdale layer cause differences in its toughness, which makes experimentation under a single situation an important requirement.

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[Table] From the above results, the short fibers of the aromatic polyamide used in this invention are fibrillated, and the arrangement of the short fibers in the rubber is different from that of other aromatic polyamide short fibers (cornex). Since it is random, there is no anisotropy in the composite sheet. Therefore, even if the composite sheet extruded from the calender in the extrusion direction is wrapped and molded so as to match the circumferential direction of the tire, the puncture resistance will not be deteriorated and the tire molding operation will be easy. On the other hand, in a composite sheet in which Teijin Co., Ltd.'s Cornex, which is also a short fiber made of aromatic polyamide but is not fibrillated, is mixed into rubber, the short fibers are clearly arranged in the parallel and perpendicular directions. If a composite sheet extruded from a calendar, which has anisotropy in the grains and is parallel to the grains, is wrapped and molded in the circumferential direction of a tire, the puncture resistance of the obtained tire will be in the grain parallel direction. In this case, the result is much inferior to that in the direction perpendicular to the grain, and this leads to weakening of the tire itself. Furthermore, from this experimental example, in this invention,
It has also been significantly demonstrated that it has better puncture resistance than other staple fibers. Experimental Example 2 Next, regarding the composite rubber sheet used when carrying out this invention, the puncture resistance changes depending on the amount of fibrillated aromatic polyamide short fibers mixed into the rubber. In order to confirm that
By varying the amount added to 100 parts by weight,
The mixture was kneaded with a roll, and then extruded with a calender into several types of composite rubber sheets with a thickness of 0.5 mm, and these sheets were mixed into a 3-ply 6-nylon rubber-attached bias slide as shown in Table 2 above. interposed between the 0.3mm thick natural rubber sheet
A laminated sheet was obtained by vulcanization and integration at 150°C for 30 minutes. These laminated sheets were cut, and the resulting samples were evaluated for puncture resistance using the impact crack tester shown in Example 1 above. The results are shown in Table 4 below. As a comparative example, a canvas made of aromatic polyamide fiber (Kevlar manufactured by Dupont) was used as the canvas disclosed herein, and the canvas was 1500D/1×1500D/1/60 fibers/5cm×60 fibers/5cm. This canvas was immersed in a resorcinol-formalin-latex liquid (RFL liquid) and reacted for 2 minutes at 200°C or lower, and then this treated canvas was laminated between the sudare and the natural rubber sheet. .

[Table] From the above experiments, it was confirmed that as the amount of fibrillated aromatic polyamide staple fibers added increases, the toughness approaches that of Kevlar canvas, which has excellent toughness. Experimental Example 3 Next, a peel durability test was conducted to compare the adhesive strength between the composite rubber sheet used in carrying out the present invention, the Kevlar canvas, and the tread. The tire shown in FIG. 1, in which a composite rubber sheet made of a composite of fibrillated aromatic polyamide staple fibers and rubber is embedded in the circumferential direction between the tire tread and the carcass, and aromatic polyamide fibers. A tire using canvas fabric as a tire breaker (reinforcing material) was molded by a known method. The short fibers are Kevlar pulp manufactured by DuPont, and the rubber compound into which they are mixed is shown in Table 1 above. It was pasted in the circumferential direction. In addition, the rubber compounds of the tire tread and side worm are shown in Table 2 above,
Furthermore, the sudare carcass used was one in which 6-nylon sudare with rubber was laminated on the bias. The experimental tire thus obtained had a diameter of
The adhesion between the tread and the composite sheet was measured before and after running using a 26" x 1 3/8" wide tire, and the results are shown in Table 5 below. Tire running test conditions are mileage 6300km, load
The adhesion test was carried out under conditions of 70 kg and an internal pressure of 2.0 kg/ ^cm2 , and the tread of the tire was cut to a width of 2.5 cm.
The test was performed using a peel tester (Autograph manufactured by Shimadzu Corporation) at a tensile speed of 50 mm/min.

[Table] From the above results, it is understood that as the amount of short fibers mixed increases, the adhesive force with the tire tread decreases. This fact is completely opposite to the above-mentioned Experimental Example 2, where increasing the amount of short fibers increases the toughness. Therefore, from the above Experimental Examples 2 and 3, a compromise and overall desirable mixing ratio of rubber and short fibers that can improve the toughness of the tire and suppress the peeling phenomenon in the tire tread region is as follows, per 100 parts by weight of rubber.
It is considered that a composite rubber sheet in which the short fibers are selected in approximately the same amount or less is preferable in terms of both toughness and peeling resistance. The following points were comprehensively clarified from the results of the above experiments. A composite rubber sheet in which short fibers of fibrillated aromatic polyamide are mixed into rubber has poor orientation of short fibers in the calender extrusion direction (parallel to the grain) and in the right angle direction (perpendicular to the grain). Since it is not attached, there is no anisotropy in puncture resistance.
Therefore, for example, even if sheets extruded by a calender are laminated as they are, aligned in the circumferential direction of a tire, there is no significant difference in their toughness, making the tire molding process extremely easy. Become. In addition, fibrillated aromatic polyamide short fibers have better puncture resistance and are more durable than other short fibers. Furthermore, if a composite rubber sheet is used in which fibrillated aromatic polyamide staple fibers are mixed into the rubber, it will have better adhesion to the toledo than a canvas made of aromatic polyamide fibers.
In this respect, the running life of the tire could be significantly extended.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a tire embodying the present invention, Figs. 2 and 3 are enlarged cross-sectional views of a part of a tire showing other embodiments, and Fig. 4 is a cross-sectional view for confirming puncture resistance. 1 is a schematic explanatory diagram of an impact crack tester used for. In the figure, 1 is a bead, 3 is a sagging carcass, 5 is a tread, 6 is a fibrillated aromatic polyamide short fiber, 7 is rubber, and 8 is a composite rubber sheet.

Claims (1)

[Scope of Claims] 1. In a tire in which a tread is attached to the ground-contact side surface of a carcass that covers the entire width of the tire while surrounding beads arranged on a pair of ears of the tire, the ground-contact side of the tire Of the laminated carcass constituting the parts, a composite rubber sheet made of at least one layer of fibrillated aromatic polyamide short fibers mixed in rubber is interposed between the carcass and the tread located on the inner surface of the tire. Motorcycle tires. 2. The motorcycle tire according to claim 1, wherein the composite rubber sheet is interposed between the rear surface of the tire tread and the carcass. 3. The motorcycle tire according to claim 1, wherein the composite rubber sheet is interposed between a laminated carcass of the tire. 4. The two-wheeled vehicle tire according to claim 1, wherein the composite rubber sheet is interposed on the back surface of the tread and between the laminated carcass.