JP3614196B2 - Pneumatic tire and manufacturing method thereof - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a pneumatic tire and a method for manufacturing a pneumatic tire.
[0002]
[Prior art]
For tires, various rubber-kneaded fabrics are cut, stacked, or joined together, and the raw tires (raw tires) before vulcanization that have been made into tire shapes are attached to the vulcanizer, and the inside is a bladder, etc. It is manufactured by molding and vulcanizing for a certain period of time under high internal pressure and high temperature. At this time, if the air between the raw tire and the tire mold is not released to the outside, the tire surface becomes bare and becomes a defective product, which is particularly noticeable in high performance tires with complex irregularities that have increased in recent years. For this reason, the air is generally discharged outside by the following method.
a. Provide a vent hole that leads to the outside of the mold.
b. Sectional type split mold or small segment, however, a. B. In this case, since a thin rubber sticks out between the molds, an operation for trimming the rubber is performed. In particular, protrusion that is difficult to trim such as flash becomes a problem as work that requires more man-hours.
On the other hand, in the vulcanization method using a normal mold, the mold is easily soiled, and it requires a lot of labor and cost to clean the mold.
[0003]
As a means for suppressing the protrusion of rubber, one of the objectives is to make the sectional mold or the small segment of the tread pattern part, but it is not always perfect. It is difficult, and man-hours are required more than before.
Further, as a means for preventing the protrusion, the following rubberization which is difficult to flow can be considered, but each has a problem.
a. Hardening by increasing the filling amount of carbon black etc .:
There is difficulty in kneading work, and it is extremely difficult to put into practical use in consideration of the blending amount considered from the required performance of the tire, and the practicality is poor.
b. How to speed up vulcanization:
From the fact that rubber bulge is the flow of rubber at the start of vulcanization, in order to increase the vulcanization speed of the rubber material in contact with the mold, it is conceivable to select the amount of sulfur and the type of vulcanization accelerator and increase the amount. However, it is extremely difficult to put it to practical use because the effect cannot be obtained as expected, and so-called burn phenomenon is likely to occur during kneading, extrusion, or rolling.
c. Use of rubber curing agents:
It is conceivable to use a curing agent as a composition to harden the unvulcanized rubber and prevent mold breakage, but it is extremely practical due to the occurrence of curing in the kneading and subsequent processing steps and from the viewpoint of tire performance. Have difficulty.
d. Cross-linking agent surface application:
Although the rubber surface can be cured by applying a crosslinking agent to the surface before vulcanization, there are problems such as an increase in process and material costs.
e. Use of electron irradiation as a pre-curing means:
For example, Japanese Patent Publication No. 56-11605 proposes the use of a carbon-carbon bond reaction between rubber molecules by electron irradiation as one of the pre-vulcanization means as one of the means for suppressing the occurrence of the vent spew and flash. .
However, although it is extremely effective in suppressing the protrusion of rubber such as spew and flash by electron irradiation treatment, in addition to safety problems such as expensive equipment and difficulty in preventing X-rays In addition, there is a problem that the rubber performance is deteriorated due to the electron irradiation beam (particularly, the wear resistance is reduced by 5 to 10%), which can be put into practical use, but requires a large space.
[0004]
[Problems to be solved by the invention]
In view of these problems of the prior art, the object of the present invention is to (a. Between sectional mold molds, b. Small segmental molds in the tread portion, c. It is to provide a pneumatic tire in which the protrusion (flash and vent spew) of rubber generated at a small diameter is suppressed, and a method for producing the same.
[0005]
[Means for Solving the Problems]
As a result of repeated studies to solve the above problems, the present inventor has developed a method of heating and crosslinking only the outer surface of the unvulcanized rubber compounded body after extrusion processing, raw processing, etc. of the rubber compounded kneaded dough. As a result, the present inventors have completed the pneumatic tire of the present invention and the manufacturing method thereof.
[0006]
The present invention has the following configurations 1 and 2 .
(1) After the raw build tire unvulcanized combining rubber kneading dough surface precured, a pneumatic tire made by molding vulcanization, the unvulcanized that combines rubber kneading dough The raw tire is irradiated with far infrared rays or infrared rays from a heat source of 500 ° C. to 6000 ° C., and the output and focus of the heat source or light source are adjusted so that the outer surface temperature becomes 250 ° C. to 350 ° C., and the irradiation time is less than 3 seconds. A method for producing a pneumatic tire, characterized in that the outer surface is pre-vulcanized and then molded and vulcanized.
(2) a tread material an unvulcanized rubber material of the rubber kneading dough tread member is extruded formed by surface precured A pneumatic tire using the tread portion, a tread member for a rubber kneading The unvulcanized rubber compounding material obtained by extruding the dough is irradiated with far infrared rays or infrared rays from a heat source of 500 ° C. to 6000 ° C., and the output and focus of the heat source or light source are adjusted so that the outer surface temperature becomes 250 ° C. to 350 ° C. A method for producing a pneumatic tire, comprising molding and vulcanizing a surface-heat treated raw tread material obtained by performing preliminary vulcanization of the outer surface with an irradiation time of less than 3 seconds in a tread portion.
[0007]
The unvulcanized green tire according to the present invention is a kneaded dough after kneading work in which predetermined compounding agents and fillers are uniformly dispersed in raw rubber using various kneaders, and a tire before vulcanization. A tread material or the like is cut, overlapped, or joined to various shapes to form a tire that is close to the tire shape. Specific examples include raw processed products of tires before vulcanization such as radial tires and bias tires.
[0008]
The pneumatic tire according to the present invention can be obtained by heating the outer surface of an unvulcanized green tire and performing preliminary vulcanization for crosslinking only the outer surface, followed by predetermined molding vulcanization. As the heating method, an infrared heater is shown. Usually, a heat source that generates infrared rays or far infrared rays such as a heater using a lamp such as a halogen lamp, a ceramic heater, or a nichrome wire heater is set at a distance of 0.1 to 100 cm to the outer surface of the unvulcanized rubber compound. Heat. Normally, (in the case of halogen heater, color temperature) heat source temperature was between 500 to 6000 ° C., the irradiation time at temperature is 250 to 350 ° C. of the outer surface of the unvulcanized rubber body that processes in less than 3 seconds. For tire tread producing member, especially, the surface temperature of a good than the processing time of 3 seconds at 250 ° C. to 350 ° C.. In the treatment for 3 seconds or more, foaming may occur and the appearance may be deteriorated. In the present invention, the vulcanization for crosslinking the outer surface of the unvulcanized tire tread raw member of the unvulcanized raw tire may be performed by vulcanizing only the outer surface thickness of 1.0 mm or less by the above heating method. it can. Crosslinking (vulcanization) of the outer surface exceeding 1.0 mm in thickness makes it difficult to obtain the required shape during vulcanization due to significant surface hardening. In addition, there is a risk of generating a so-called bear.
[0009]
The rubber compounding composition of the raw tire according to the present invention has various compositions depending on the part constituting the tire such as tread and carcass, but synthetic rubber, natural rubber, carbon black, zinc white, stearic acid, anti-aging agent, It is composed of softening agents such as vulcanization accelerators, sulfur, aroma oil, spindle oil, etc., and is capable of thermal crosslinking.
Particularly in the case of blending tread tires, for example, the raw rubber is 85 parts by weight of carbon black, 20 parts by weight of oil, 3 parts by weight of ZnO, 1.5 parts by weight of sulfur and 1 part of vulcanization accelerator with respect to 100 parts by weight of SBR. .2 parts by weight, mixing of 1.0 part by weight of anti-aging agent is shown.
Raw tires were made close to the tire shape by cutting, stacking, or joining various shapes to unvulcanized tread materials, uncured carcass materials, etc., obtained by these various formulations. Is.
[0010]
[Action]
An unvulcanized raw tire that has been surface-treated only on the outer surface by the method of the present invention (preliminarily vulcanized) is less than the flow of rubber inside the unvulcanized raw tire at the start of vulcanization when the main vulcanization is performed as a tire. Since the flow of the outer surface is suppressed, the protrusion of rubber such as flasher and benspu after vulcanization is remarkably suppressed. Therefore, the appearance of the vulcanized tire found from the vulcanizer becomes good.
[0011]
【Example】
Hereinafter, the present invention will be described with reference to examples.
The composition of the rubber kneaded dough used in the examples and comparative examples is as follows.
Rubber-kneaded fabric formulated for tire tread:
SBR 100 parts by weight Carbon black 85 parts by weight Process oil 20 parts by weight Zinc white 3 parts by weight Sulfur 1.5 parts by weight Vulcanization accelerator 1.2 parts by weight Anti-aging agent 1.0 part by weight Slab sheet:
The rubber kneaded dough was sheeted to a thickness of 2 mm, and a slab sheet vulcanized under vulcanization conditions of 165 ° C., 20 kgf / cm ² and 10 min was produced.
The breaking strength (Tb) and breaking elongation (Eb) were measured by punching out a test sheet with a JIS No. 3 dumbbell and using the test method of JIS K6301.
[0012]
Example 1
An unvulcanized raw tread material (width 300 mm, thickness 10 mm) obtained by extruding rubber kneaded dough blended for tire treads at a tracing speed of 30 m / min with a surface temperature of 300 ° C., A rubber surface treatment process was performed by irradiating with a halogen heater (heater zone: width 0.2 m, length 1 m) having a heat source temperature of about 3000 ° C. (irradiation time 2 seconds) (see FIG. 1). Only about 100 μm of the surface layer of the raw tread material was vulcanized, and the inside remained unvulcanized raw tread.
[0013]
Example 2
Halogen heaters (six halogen lamps) are used while rotating raw tires (raw tires) before vulcanization that have been made into tire shapes by cutting, stacking, and joining various rubber-kneaded fabrics. The rubber surface treatment was performed by irradiating at a heat source temperature of 3000 ° C. and vulcanizing the surface under conditions of a surface temperature of 300 ° C. and an irradiation time of 2.5 seconds (see FIG. 2).
This surface-treated raw tire was vulcanized (conditions: 165 ° C., 10 min) by a conventional method. The protrusions were significantly reduced from those without surface treatment.
[0014]
A raw tread material was produced in accordance with Example 1, and it was examined how the surface temperature, irradiation time, and the size of the hole in the mold affect the spew generation during vulcanization. The results are shown in FIGS.
Raw tread surface treatment conditions:
The raw tire tread rubber produced according to Example 1 was surface treated by irradiating with a halogen heater at a predetermined surface treatment temperature (175 ° C., 200 ° C., 300 ° C.) and a predetermined irradiation time (1 to 4 seconds). Tire tread rubber was obtained.
This surface-treated raw tire tread rubber was vulcanized at 165 ° C., 20 Kgf / cm ² , 10 min using a mold having holes with predetermined diameters (0.2, 0.3, 0.4 mmψ). Thereafter, the length of the rubber (spy) that entered the hole of the mold was measured.
In addition, it shows that the crosslinking effect by surface treatment is so good that the length is short.
3 shows the case where the surface treatment temperature is 175 ° C., FIG. 4 shows the case where the surface treatment temperature is 200 ° C., and FIG. 5 shows the case where the surface treatment temperature is 300 ° C.
As a result, the surface treatment temperature was 300 ° C. and the irradiation time was 2 seconds. However, those treated for 3 seconds at 300 ° C. had a problem in appearance due to the generation of bubbles on the surface.
[0015]
Previous mentioned predetermined methods fabricated thickness 2mm slab sheet halogen heater [70 volts (60 Hz)] from a distance 4cm far rubber surface with predetermined irradiation time (20 seconds, 40 seconds, 60 seconds) was irradiated Surface treatment was applied. This was vulcanized at 165 ° C., 20 kgf / cm ² , 10 min, and then the breaking strength (Tb) and breaking elongation (Eb) were measured by a predetermined method. The result is shown in FIG.
[0016]
Comparative Example 1
The slab sheet of the slab sheet the same way an electron irradiation treatment (accelerating voltage 200 KV, current 10 mA), was subjected to a surface treatment of a predetermined dose (20~400Mrad). This was vulcanized at 165 ° C., 20 kgf / cm ² , 10 min, and then the breaking strength (Tb) and breaking elongation (Eb) were measured by a predetermined method. The result is shown in FIG. As the irradiation dose increases, the physical properties decrease significantly. Further, when the irradiation amount was 40 Mrad or more, fine cracks were generated when the rubber was pulled.
[0017]
【The invention's effect】
Since the pneumatic tire according to the present invention suppresses the protrusion of rubber such as burrs, flashes, spews, etc. during mold molding vulcanization, finishing work and correction work such as burring removal of the product tire after vulcanization are reduced, A product tire excellent in appearance and quality is obtained, and the productivity of the tire is improved. Furthermore, since the dirt on the mold is remarkably reduced, the cleaning work of the mold is also reduced.
In addition, there is less decrease in the breaking strength, breaking elongation, etc. of rubber after vulcanization compared to the conventionally known electron irradiation treatment methods, and the preliminary vulcanization of raw tires in the production method of the present invention is easily handled. Since the device can be manufactured and is compact, it can be easily attached to an existing production line, and an expensive device such as a conventional electron beam processing method is not required, and there is no need for an X-ray protection device or the like. There are advantages such as good things.
[Brief description of the drawings]
FIG. 1 is a schematic view of surface treatment of an extruded unvulcanized tread rubber material.
FIG. 2 is a schematic view of surface treatment of a raw rubber tire.
FIG. 3 is a graph showing the relationship between the halogen heater irradiation time and spew [surface treatment temperature (175 ° C.)].
FIG. 4 is a graph showing the relationship between the halogen heater irradiation time and spew [surface treatment temperature (200 ° C.)].
FIG. 5 is a diagram showing the relationship between the halogen heater irradiation time and spew [surface treatment temperature (300 ° C.)].
FIG. 6 is a diagram showing the relationship between halogen heater irradiation time, tread rubber breaking strength, and breaking elongation.
FIG. 7 is a diagram showing the relationship between the irradiation dose of electron irradiation rays and the breaking strength and breaking elongation of tread rubber.
[Brief description of symbols]
1, Halogen heater 2, Extruder 3, Raw tread material 4, Calendar roll 5, Raw tire

Claims (2)

After the raw build tire unvulcanized combining rubber kneading dough surface precured, a pneumatic tire made by molding vulcanization, the unvulcanized raw structure that combines rubber kneading dough The tire is irradiated with far-infrared rays or infrared rays from a heat source of 500 ° C. to 6000 ° C., and the output and focus of the heat source or light source are adjusted so that the outer surface temperature becomes 250 ° C. to 350 ° C. A method for producing a pneumatic tire, characterized by performing preliminary vulcanization and molding vulcanization. The tread material comprising an unvulcanized rubber material which is extruded a rubber kneading dough tread member and the surface precured A pneumatic tire using the tread portion, extruding a rubber kneading dough tread member Irradiate processed unvulcanized rubber compounding material with far-infrared rays or infrared rays from a heat source of 500 ° C. to 6000 ° C. and adjust the output and focus of the heat source or light source so that the outer surface temperature becomes 250 ° C. to 350 ° C. A method for producing a pneumatic tire, characterized in that a surface-heat treated raw tread material obtained by pre-curing the outer surface in less than 3 seconds is molded and vulcanized using a tread portion.

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