JPS645061B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pneumatic tire, and more particularly to a pneumatic safety tire that includes an annular elastic reinforcement on the inner surface of the side portion of the tire or on the inner surface extending between the side portion and the shoulder portion. It has been a long-held dream of tire engineers to develop a tire that does not cause any problems when driving even when a pneumatic tire is punctured and its air pressure drops to almost zero. There has been a strong demand for such tires from the viewpoint of safety. As a typical example,
Many safety tires are known in which the side portions, shoulder portions, or both of the tire sides are reinforced.
For example, Japanese Patent Publication No. 45-40483, Japanese Patent Publication No. 50-12921, Japanese Patent Publication No. 49-20802, Japanese Patent Publication No. 49-70303, Japanese Patent Publication No. 49-116702, Japanese Patent Publication No. 50-59902,
No. 50-60905, No. 50-60906, No. 50-
Publication No. 60907, Publication No. 50-78003, Publication No. 50-111704
No. 50-121902, No. 50-138502, No. 51-20301, No. 51-64203, No. 51-64203, No. 51-20301, No. 51-64203, No.
Safety tires such as those described above are disclosed in Publication No. 51-69804 and the like. However, although many tires have been proposed, there are almost no cases of them being put into practical use because the reinforcement rubber does not have sufficient bending or heat resistance. . That is,
When the air pressure is zero, the load on the tire is borne by the side parts, so the rubber that reinforces the side parts needs to have a high compression modulus.Generally, rubber has a high modulus. This has the disadvantage that the bending resistance is extremely reduced and heat generation is more likely to occur. Therefore, in order to meet the performance required of reinforcing rubber, the gauge of the reinforcing rubber must be made extremely thick without making the modulus of the reinforcing rubber too high.As a result, the weight of the tire increases and Not only did the ride comfort deteriorate significantly, but the heat generated was more likely to accumulate, and eventually the rubber was destroyed, making it impossible to drive. In order to improve such drawbacks, the present applicant has reinforced with syndiotactic 1,2-polybutadiene staple fibers as described in Japanese Patent Publication No. 57-50681 (Japanese Patent Application No. 54-26795). However, there was still room for further improvement. That is, since the short fibers are syndiotactic-1,2-polybutadiene, the maximum hysteresis loss associated with the glass transition temperature (30 to 40°C) of the amorphous portion is
Since the heat generation temperature of the tire is within the range of 30℃ to 120℃ under normal usage conditions or when driving with a flat tire, it is difficult to reduce hysteresis loss, which makes it possible to drive even with a flat tire. Dramatic improvements in mileage were limited, and the downside was even greater for fuel-efficient tires, which have been in increasing demand in recent years. In view of the current situation, the inventors of the present invention have conducted intensive research with the aim of providing a pneumatic safety tire that can dramatically improve the distance that can be traveled in the event of a puncture and also improve rolling resistance. ,
An annular reinforcement is made of a rubber composition made by adding a specific amount of carbon black, a specific amount of sulfur and/or a sulfur-containing organic vulcanizing agent, and a specific micro organic short fiber to the rubber normally used for tires. The inventors have discovered that the desired pneumatic safety tire can be obtained by using the same as the above, and have achieved the present invention. That is, the present invention includes a pair of left and right bead portions, a pair of side portions connected to each bead portion, and a tread spanning between both side portions, and further includes a pair of treads on the inner surfaces of both side portions or on the inner surface extending from the side portions to the shoulder portion. In a pneumatic tire equipped with an annular elastic reinforcement, the annular elastic reinforcement has a crescent-shaped cross section and is made of natural rubber, synthetic polyisoprene rubber,
Butyl rubber, halogenated butyl rubber, polybutadiene rubber, styrene-butadiene copolymer rubber,
Contains 10 to 100 parts by weight of carbon black and sulfur and/or sulfur per 100 parts by weight of at least one rubber selected from ethylene-propylene-diene ternary copolymer rubber and acrylonitrile-butadiene copolymer rubber. The organic vulcanizing agent has a sulfur content of 4 to 10 parts by weight and a glass transition temperature of the amorphous portion is lower than 30°C or 120°C.
℃, the melting point of the crystal part is 160℃
3 microorganic short fibers having an average short fiber length of 0.8 to 30 μm, an average short fiber diameter of 0.02 to 0.8 μm, and a ratio of average short fiber length to average short fiber diameter of 8 to 400.
Consisting of a rubber composition containing ~30 parts by weight,
Moreover, the weight of the annular elastic reinforcement is 15% of the tire weight.
~30%, regarding pneumatic safety tires. In the present invention, "having a crescent-shaped cross section" is broadly understood and includes not only regular and irregular crescent-shaped cross-sections, but also arcuate cross-sections. The attached drawing shows a cross section of a pneumatic safety tire as an example of the present invention. In the drawings, 1 is a tire, 2 is a tread portion, 3 is a side portion, 4 is a bead portion, and 5 is an annular elastic reinforcement. In the present invention, the micro organic short fibers used in the reinforcing body have a glass transition temperature of the amorphous portion lower than 30°C or higher than 120°C,
Average short fiber length is 0.8-30μm, average short fiber diameter is 0.02
~0.8 μm, the ratio of the average short fiber length to the average short fiber diameter is 8 to 400, and the melting point of the crystal part is 160°C or higher, such as polyvinylidene chloride, polyvinylidene fluoride, polyvinylidene fluoride, etc. -p-tert-
Butylstyrene, p-chlorostyrene, dichlorostyrene, poly-α-methylstyrene, poly-2
- methylstyrene, poly-2,5-dimethylstyrene, poly-trimethylstyrene, poly-p-phenylstyrene, poly-o-vinylbenzyl alcohol, poly-p-vinylbenzyl alcohol,
Isotactic polypropylene, poly-4-
These short fibers are made of methyl-1-pentene, poly-vinylnaphthalene, poly-oxymethylene, poly-bisphenol A carbonate, 1,4-poly-2,3-dimethylbutadiene, etc. Here, the reason why the glass transition temperature of the amorphous portion is lower than 30℃ or higher than 120℃ is because the heat generation temperature of the tire when running under normal usage conditions is within the range of 30℃ to 120℃. Therefore, short fibers whose amorphous portion has a glass transition temperature within this range usually have a large hysteresis loss. Also, the glass transition temperature of rubber is around -50℃, so if we consider its affinity with rubber, the glass transition temperature should be 30℃.
More preferred are micro short organic fibers that are lower than . In addition, the average short fiber length of the above micro organic short fibers is
The reason why the average short fiber diameter is 0.8 to 30 μm, the average short fiber diameter is 0.02 to 0.8 μm, and the ratio of the average short fiber length to the average short fiber diameter is 8 to 400 is as follows. If the average short fiber length is less than 0.8 μm, the crack growth resistance of the resulting rubber composition will not be sufficiently improved, and if it exceeds 30 μm, workability such as kneading with a Banbury mixer will be significantly reduced, which is not preferred. If the average short fiber diameter is less than 0.02 μm, the micro short fibers will be cut and become too short during kneading or sheeting with rolls, and if it exceeds 0.8 μm, the stress per surface area of the short fibers will increase and the rubber This is not preferable because there is a risk that the adhesive surface with the rubber composition will be destroyed, and as a result, the resulting rubber composition will have a large degree of creep and its bending resistance will decrease. If the ratio of the average short fiber length to the average short fiber diameter is less than 8, the original characteristics of short fiber reinforcement, such as high reinforcing properties, cut resistance, and crack growth resistance, will decrease significantly, and if it exceeds 400, the short fiber This is not preferable because the stress applied during operation is greater than the strength, and the short fibers are likely to be cut. In addition, the melting point of the crystal part of the microorganic short fibers must be 160℃ or higher, which is necessary not only during tire running but also during tire manufacturing, which can reach over 100 degrees. This is because if the short microfibers melt and harden again, their morphology will change and there is a risk that the desired reinforcing effect cannot be expected. Further, it is more preferable that the maximum diameter of the short microorganic fibers is 10 μm or less, and if microorganic short fibers with a diameter exceeding 10 μm are present, they become fracture nuclei and the rubber is likely to be destroyed. Microorganic short fibers are 3 parts per 100 parts by weight of rubber.
~30 parts by weight is blended, but in this case, two or more types of the above-mentioned micro organic short fibers may be blended. If the amount is less than 3 parts by weight, hardly any effect can be expected, which is undesirable, and if it exceeds 30 parts by weight, workability will be significantly reduced, which is not preferred. Furthermore, microorganic short fibers can be produced, for example, in the following manner. Taking isotactic polypropylene as an example, polymerized powdered isotactic polypropylene is swollen and crushed in n-hexane at 60°C to form a slurry, and then
It is ejected from a nozzle at a pressure of ~110 Kg/cm ² to produce micro short fibers. This is again dispersed in n-hexane, mixed with polymer cement, stirred, and then subjected to a normal rubber drying process to form a masterbatch. At this time, the length, diameter, and length/diameter ratio of the microorganic short fibers obtained can be changed by controlling the solvent used for swelling, the temperature at that time, the pressure at the time of jetting from the nozzle, etc. is possible. In addition, microorganic short fibers are used as a masterbatch because it is relatively easy to uniformly disperse short fibers in rubber, but short fibers are directly mixed into rubber together with commonly used compounding agents such as carbon black. It is also possible to do so. Although the case of isotactic polypropylene has been described here, other microorganic short fibers can also be obtained in the same manner by swelling them with a relatively poor solvent and crushing them into a slurry form. Of course, it is also possible to mix a good solvent and a poor solvent and adjust the composition to a suitable composition. In the present invention, it is necessary to mix 10 to 100 parts by weight of carbon black with respect to 100 parts by weight of rubber in the reinforcing body. If the amount is less than 10 parts by weight, the strength at break of the resulting rubber composition will decrease, which is undesirable, and if it exceeds 100 parts by weight, the workability will drop significantly, which is undesirable. In the present invention, the sulfur and/or sulfur-containing organic vulcanizing agent used in the reinforcing body is blended in an amount of 4 to 10 parts by weight, preferably 5 to 8 parts by weight, based on 100 parts by weight of the above mixture. If the amount is less than 4 parts by weight, a sufficient elastic modulus cannot be obtained, which is undesirable, and if it exceeds 10 parts by weight, the breaking strength rapidly decreases and the impact resistance properties deteriorate, which is not preferable.
Here, as the organic vulcanizing agent containing sulfur, 4,
4'-dithiodimorpholine, alkylthiuram disulfide, and alkylphenol disulfide are preferably used. Further, in the present invention, vulcanization accelerators, anti-aging agents, softeners, etc. commonly used in the rubber industry can be appropriately blended into the reinforcing body, if necessary. In addition, in the present invention, the weight of the reinforcing body must be in the range of 15 to 30% of the tire weight, its cross-sectional shape is crescent-shaped, and the maximum thickness position of the reinforcing body is at the maximum width position of the tire. Alternatively, it is more preferable that the crescent shape be located at a position radially outward of the maximum width position of the tire. If the weight of the reinforcing body is less than 15% of the tire weight, the desired reinforcing effect cannot be obtained and the runflat performance in the event of a puncture will be extremely deteriorated, while if it is heavier than 30%, the heat generation property will decrease. Therefore, the runflat running performance is still insufficient. In addition, due to the recent demand for fuel savings from the viewpoint of resource and energy conservation, it has become necessary to remove the spare tire in order to reduce vehicle weight as much as possible. It weighs more than the original 5 tires, and there is no point in removing the spare tire. From this point of view, the weight of the reinforcing body is preferably 15 to 25% of the weight of the tire. Further, the pneumatic safety tire of the present invention may be a tire reinforced with any cord such as steel cord or textile cord. The pneumatic safety tire of the present invention having the above configuration includes a rubber composition having high modulus, high bending resistance, and low hysteresis loss on the inner surface of the side portion or the inner surface extending from the side portion to the shoulder portion. By arranging them in a specific shape, compared to conventional pneumatic safety tires, the distance that can be traveled even if a puncture occurs is dramatically increased, and rolling resistance is also improved, making them extremely useful industrially. It is something. The present invention will be described in detail using Examples and Comparative Examples. Examples 1 to 9, Comparative Examples 1 to 28 40 parts by weight of FEF carbon black, 2 parts by weight of stearic acid, 1 part by weight for 100 parts by weight of blended rubber with 50 parts by weight of synthetic polyisoprene rubber and 50 parts by weight of polybutadiene rubber. part of N-phenyl-
N'-isopropyl-p-phenylenediamine and 37 types of microorganic short fibers shown in Table 1 were each added.
A rubber composition compounded at a ratio of 10 parts by weight was heated to a rubber temperature.
After kneading for 5 minutes at 155°C in a Banbury mixer (50 rpm), 3 parts by weight of zinc white, 0.2 parts by weight of dibenzothiazyl disulfide, and 0.8 parts by weight of N-oxydiethylene-2-benzothiazolyl sulfate were added. Thirty-seven rubber compositions were prepared by blending phenamide and 5 parts by weight of sulfur. Average rebound elasticity and short fiber working history for these rubber compositions;
Furthermore, using 2000g of these rubber compositions, a pneumatic tire with tire size 185HR14 (weight 10.5Kg,
An annular elastic reinforcement body with a crescent-shaped cross section is provided on the inner surface of the side part of a steel belt (as shown in the figure), and the tire is run at a speed of 80 km/hr under a JIS 100% load and an internal pressure of 0 kg/cm ² until the tire breaks. The driving (runflat driving) distance was determined. The results are shown in Table 1. The average rebound elasticity and work history of short fibers were evaluated as follows. (Average impact resilience) Impact resilience was evaluated at 30°C, 60°C, 90°C and 120°C in accordance with BS903 Part 19, and the value is the average value. However, if the materials of the short microfibers are different, the elastic modulus will not necessarily be the same even if the blending amount is the same, so it is difficult to clearly express the effects of the present invention by simply comparing each rubber composition. be. Therefore synthetic polyisoprene rubber 50
2 parts by weight of stearic acid, 1 part by weight of N-phenyl-N'-isopropyl-p-phenylenediamine, and 3 parts by weight of zinc white per 100 parts by weight of a blend rubber of 50 parts by weight of polybutadiene rubber and 50 parts by weight of polybutadiene rubber. , 0.2 parts by weight of dibenzothiazyl disulfide,
0.8 parts by weight of N-oxydiethylene-2-benzothiazolylsulfenamide, 5 parts by weight of sulfur
Several types of rubber compositions containing varying amounts of FEF carbon black were prepared, and
The elastic modulus and rebound resilience were measured at 120°C, and a master curve was created by plotting the elastic modulus on the horizontal axis and the rebound resilience on the vertical axis at each temperature. From these master curves, read the impact resiliency of the rubber composition reinforced only with carbon black, which corresponds to the elastic modulus of the micro short fiber rubber composition to be evaluated. This was taken as the rebound elasticity of the short fiber reinforced rubber composition. The higher the value, the better. (Work history of short fibers) The average length and average diameter of the micro organic short fibers in the raw rubber are measured in advance, and then, after creating a rubber composition as described above, the average length and average diameter of the micro organic short fibers are measured. The diameter was determined, and if these values were 85% or more of the average length and average diameter of the raw rubber, they were marked as ○, and if they did not reach 85%, they were marked as ×. Incidentally, the average diameter and average length of the microorganic short fibers were determined as follows. After extruding raw rubber (or rubber composition) containing microorganic short fibers using a capillary rheometer under the conditions of L/D = 4, 100°C, and 20 sec ^-1 , it is extruded at 4 kg/cm ² in a vulcanization can. , vulcanize at 150°C for 1 hour. Ultrathin sections were cut from this vulcanizate in directions perpendicular and parallel to the extrusion direction, and the diameter and length of the short microfibers were measured using an electron microscope. The average diameter and average length were determined using the following formula. = Σniri/Σni = Σnili/Σni where: Average diameter: Average length ri: Short fiber diameter li: Short fiber length ni: Number of short fibers with diameter ri or length li Σni: 300

【table】

【table】

[Table] As is clear from Table 1, the glass transition temperature is
The pneumatic safety tire of the present invention, which is equipped with an annular elastic reinforcing body made of a rubber composition containing microorganic short fibers having a temperature of 30°C or lower or 120°C or higher and a melting point of 160°C or higher, has a flat tire travel distance, i.e. It can be seen that the runflat mileage is significantly long. Examples 10 to 12, Comparative Examples 29 to 34 Nine types of rubber compositions were prepared in the same manner as in Example 1, by blending isotactic polypropylene in various forms as shown in Table 2 as microorganic staple fibers. The roll workability of these compositions was evaluated by observing the presence or absence of roll bags during kneading with a 10-inch roll.
Furthermore, in the same manner as in Example 1, the average impact resilience, work history of short fibers, and runflat running were evaluated. The results are shown in Table 2.

[Table] * Unable to manufacture tires due to poor roll workability As is clear from Table 2, the pneumatic safety tires of the present invention have good workability and a significantly long runflat mileage. Examples 13 to 15, Comparative Examples 35 to 37 Rubber compositions having the formulations shown in Table 3 were prepared,
Roll workability was evaluated in the same manner as in Example 1. Next, these rubber compositions were used as reinforcing bodies in the same manner as in Example 1, and runflat running and shoulder heat generation temperature were evaluated. The results are shown in Table 3. The reinforcement weight ratio shown in Table 3 refers to the tire size
For 185HR14 tires (weight 9.7Kg), when the internal pressure is 0Kg/ ^cm2 , the distance between the vehicle and the road surface is 97% of the distance between the vehicle and the road surface when the internal pressure is normal (1.7Kg/ ^cm2 ). This is the value obtained by multiplying the weight of the reinforcing body required to achieve this by the tire weight (9.7 kg) and multiplying it by 100. For run-flat running, tires made under the above conditions were tested under a JIS 100% load and an internal pressure of 0.
The vehicle was run under conditions of Kg/cm ² and speed of 80 Km/h, and the distance traveled until the tire broke was determined. In addition, regarding the shoulder heat generation temperature, in order to keep the thickness of the reinforcement body constant, we reinforced it with 2000g/piece of rubber.
The temperature of the shoulder portion of the tire was determined after running for 30 minutes under the conditions of 100% JIS load, 0 kg/cm ² internal pressure, and 80 km/h speed.

[Table] *2. Rolling workability is poor and tires cannot be made.
As is clear from Table 3, the pneumatic safety tire of the present invention has good workability, a significantly long runflat mileage, and a low heat generation temperature in the shoulder portion. Examples 16 to 19, Comparative Examples 38 to 39 Rubber compositions having the formulations shown in Table 4 were prepared,
Runflat running and shoulder heat generation temperature were evaluated in accordance with Example 13. The results are shown in Table 4.

【table】

[Table] As is clear from Table 4, the pneumatic safety tire of the present invention has a significantly long runflat distance and a low shoulder heat generation temperature. Examples 20 to 23, Comparative Examples 40 to 41 The rubber composition of Example 11 was provided as a reinforcing body on the side inner surface of a tire size 185HR14 with varying reinforcement weight, and each tire was evaluated for runflat running. The results are shown in Table 5.

[Table] As is clear from Table 5, the pneumatic safety tire of the present invention has a significantly long runflat distance. Although not shown in the examples, the carbon black blended into the reinforcing body had an iodine adsorption amount of 90ml/
Dibutyl phthalate oil absorption amount is 90ml/100g or less
It has been found that using carbon black with a thickness of g or more is more effective, and that the reinforcing effect is further improved if the maximum thickness position of the reinforcing body is at the tire maximum width position or outside that position in the tire radial direction. Ta.

[Brief explanation of the drawing]

The accompanying drawing is a cross-sectional view of the pneumatic safety tire of the present invention. DESCRIPTION OF SYMBOLS 1... Tire, 2... Tread part, 3... Side part, 4... Bead part, 5... Annular elastic reinforcement body.

Claims (1)

[Scope of Claims] 1. A device comprising a pair of left and right bead portions, a pair of side portions connected to each bead portion, and a tread spanning between both side portions, and further on the inner surface of both side portions or the inner surface extending from the side portion to the shoulder portion. In a pneumatic tire equipped with a pair of annular elastic reinforcing bodies, the annular elastic reinforcing bodies have a crescent-shaped cross section and are made of natural rubber, synthetic polyisoprene rubber, butyl rubber, halogenated butyl rubber, polybutadiene rubber, or styrene-butadiene copolymer. 10 to 100 parts by weight of carbon black, sulfur and/or sulfur per 100 parts by weight of at least one rubber selected from composite rubber, ethylene-propylene-diene ternary copolymer rubber, and acrylonitrile-butadiene copolymer rubber. An organic vulcanizing agent containing sulfur content of 4 to 10
The glass transition temperature of the weight part and the amorphous part is lower than 30°C or higher than 120°C, the melting point of the crystal part is 160°C or higher, the average short fiber length is 0.8 to 30 μm, and the average short fiber length is 0.02 to 0.8 μm. and the ratio of average short fiber length to average short fiber diameter is 8 to
A pneumatic tire comprising a rubber composition containing 3 to 30 parts by weight of microorganic short fibers having a composition of 400, and characterized in that the weight of the annular elastic reinforcing body is 15 to 30% of the tire weight. safety tires. 2 Micro organic short fibers are polyvinylidene chloride,
Poly-vinylidene fluoride, poly-p-tert-butylstyrene, p-chlorostyrene, dichlorostyrene, poly-α-methylstyrene, poly-2-methylstyrene, poly-2,5-dimethylstyrene,
polytrimethylstyrene, poly-p-phenylstyrene, poly-o-vinylbenzyl alcohol,
Poly-p-vinylbenzyl alcohol, isotactic polypropylene, poly-4-methyl-
1-pentene, poly-vinylnaphthalene, poly-
The pneumatic safety tire according to claim 1, which is oxymethylene, poly-bisphenol A carbonate, and 1,4-poly-2,3-dimethylbutadiene. 3. The method according to claim 1 or 2, wherein the organic vulcanizing agent blended into the annular elastic reinforcement is 4,4'-dithiodimorpholine, alkylthiuram disulfide, or alkylphenol disulfide. Pneumatic safety tires. 4. The pneumatic safety tire according to claim 1, 2, or 3, wherein the annular elastic reinforcing body has a crescent-shaped cross section with the maximum thickness at the tire maximum width position. 5. The pneumatic safety according to claim 1, 2, or 3, in which the annular elastic reinforcement has a crescent-shaped cross section with the maximum thickness at a position radially outward from the tire maximum width position. tire.