JPS5944988B2 - Cracks prevention tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crack prevention tape, and more specifically, it is applied to a splice part (joint part) of an inner liner of a tire during the vulcanization process when manufacturing a pneumatic tire.
The present invention relates to a crack prevention tape used to prevent cracks or lights (recesses) from occurring.

Generally, when manufacturing pneumatic tires, before vulcanizing a molded unvulcanized tire, in order to improve the rubber flow during the vulcanization process and to improve the release properties of the bladder after vulcanization. , a release agent is applied over the entire surface of the innermost layer, ie, the inner liner, of the unvulcanized tire.

However, if this mold release agent penetrates into the splice portion of the inner liner, cracks may occur during vulcanization, which may significantly reduce the quality of the tire.

Conventionally, in order to prevent the above-mentioned cracks from occurring, a thin unvulcanized rubber tape with a width of 40mm, for example, is pasted to the splice portion of the inner as a crack-preventing tape.

However, this crack prevention tape made of rubber tape is effective for radial tires where there is little movement of the rubber on the inner surface of the tire during vulcanization, and has the effect of preventing cracks, but it has almost no effect on bias tires. It cannot be used without it.

In the bias tire, in the case of a tube tire, the inner liner layer is generally extremely thin, so cracks are less likely to occur at the splice part.
In the case of tubeless tires, the inner liner generally needs to be thick to prevent air from permeating inside the tire, so if a release agent is applied to the surface and vulcanized, the release agent will seep into the splice area. cracks are likely to occur.

Therefore, as a measure to prevent tubeless tires from cracking,
A measure has been taken in which a crack-preventing tape made of polyethylene film or adhesive tape is applied to the splice portion of the inner liner, a release agent is applied, and then the tape is removed before vulcanization.

Although this measure prevents release agent from being applied to the splice and therefore prevents the release agent from entering the splice, the lack of release agent adhering to the splice may prevent vulcanization. When vulcanizing, the rubber flow at the splice part may deteriorate and light (concavities) may occur. During this time, the mold release agent adhering to the inner surface of the inner liner may adhere to and penetrate the splice portion, which may also cause cracks.

Another method is to apply a thin piece of paper as a crack prevention tape to the splice part and then vulcanize it as is after applying a release agent.

However, in this way, the inner surface of the vulcanized tire is
Since the paper crack prevention tape has no elasticity,
Not only does the paper have the disadvantage of causing cracks that seriously deteriorate its appearance, but the paper crack prevention tape and the inner liner have poor adhesion, so in the case of tubeless tires, paper cracks may occur while driving. The protective tape peels off,
Currently, there are many problems with conventional crack prevention tape, such as small pieces of paper getting into the valve and causing air blockage.

The present invention was made in view of the above-mentioned current situation, and it is an object of the present invention to provide a crack prevention tape that solves the above-mentioned problems all at once.

The feature of this tape is that it has a structure in which a stretchable fabric is coated with rubber, thereby imparting stretchability and vulcanization adhesion to the crack prevention tape.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The crack prevention tape according to the present invention will be described below with reference to the drawings and examples.

As shown in FIG. 1, the present crack prevention tape 3 is constructed by using a fabric 1 made of a stretchable knitted fabric or the like as a base material, and coating this fabric 1 with a rubber 2.

The fabric 1 constituting the crack prevention tape of the present invention is required to have such elasticity as to have elastic recovery against elongation of at least 30 degrees.

A knitted fabric is most suitable as such a fabric, but it can also be applied to a woven fabric as long as the yarn itself is elastic and the woven fabric itself has elasticity.

A knitted fabric is most suitable as the fabric, and various fabrics such as tricot, half tricot, tulle, seven mesh, and pony mesh can be used.

The raw yarn that makes up this knitted fabric can be any of nylon, polyester, polypropylene, rayon, cotton, etc., but it should be relatively thin in thickness from 12 to 70 deniers, and the finished density (per 25.4 mm) will be loops in the weft direction. Number 10-7
The most suitable is one knitted with 0 courses and 10 to 70 wales of loops in the warp direction.

The thickness of the crack prevention tape after coating the fabric 1 with the rubber 2 is 0.05 to 0.30 m.
It is desirable that the m1 width is finished to 10 to 100 mm.

In the above-mentioned knitted fabric, if the thickness of the raw yarn is larger than 70 denier and the finished density is larger than 70 courses or 70 wales, the area between the threads of the knitted fabric becomes smaller, and the adhesion between the rubber on both sides of the coated knitted fabric decreases. In addition to this, the tape becomes thicker and cracks tend to occur at the edges of the tape when the tape is applied, a release agent is applied, and vulcanization is performed.

On the other hand, if the yarn thickness is less than 12 deniers and the finished density is less than 10 courses or 10 wales, the reinforcing effect as an interlining may be lost.

Although it is more desirable that the tape be thinner, it is actually impossible to make the tape thinner than 0.05 mm when the above-mentioned knitted fabric is used as an interlining.

Further, when the thickness is increased, cracks tend to occur along the edges of the tape at the bonded portion between the tape and the inner liner, and when the thickness exceeds 0.30 mm, the rate of occurrence of cracks increases.

Therefore, it is desirable to use a thickness of 0.05 mm or more and 0.30 mm or less, more preferably a thickness of Q, Q5 mm or more and 0.20 u or less.

Next, the rubber composition used for coating needs to be bonded to the inner liner rubber after vulcanization.
Or SBR, BR, IR, IIR.

The main component is synthetic rubber such as EPT, CR, or a blend thereof, and these rubbers may also contain fillers such as carbon and silica, and may further contain sulfur as a vulcanizing agent and a vulcanization accelerator or a vulcanization accelerator. Compositions containing cross-linking agents and anti-aging agents can also be applied.

If the rubber composition to be coated has a high Mooney viscosity, the tape will lose its elasticity and cracks will easily form along the edges of the tape, and conversely, if the Mooney viscosity is too low, it will not be vulcanized during vulcanization. When the rubber composition is crimped onto the vulcanizing bladder, the rubber composition may flow, damaging the appearance or adhering to the vulcanizing bladder.

Therefore, the Mooney viscosity range is ML1+2+, 100
It is desirable to choose a rubber composition with a temperature of 10 to 170 °C.

The width of the tape may be sufficient as long as it can sufficiently cover the splice portion.

Generally, 10m7IL or more is required, and although it varies depending on the thickness of the splice, the lapped length of the bond, or the size of the tire, it is preferably 100mm or less from the viewpoint of workability, and the more preferably used width is 20mm to 40mm. Good range.

EXAMPLES The crack prevention tape of the present invention will be specifically explained below using Examples.

The above Examples ml, 2, 3, and 4 have the above Mooney viscosity (ML) mixed using a Banbury mixer and a roll.
1+2-. 100°C) was 50 for Examples 1 and 2, and 60 for Examples 3 and 4. The rubber compositions were dissolved in toluene to a concentration of 35% and placed on a knitted fabric placed on release paper. It was poured and coated smoothly, and then dried in a dryer (hot air temperature: 80° C., feeding speed: 80 cR/min) to produce a tape with a thickness of 0.15 mm.

When the strength and elongation of these tapes were measured, Example A1 had a cutting strength of 6 kg/width 25 mm in the warp direction, a width of 3 to 7 in the weft direction, and a cutting elongation of 60 kg/width in the warp direction.
It was 110 in the latitude direction.

In Example A2, the cutting strength is 1.5 kg/width 2 in the warp direction.
The cutting elongation was 50 mm in the longitudinal direction and 80 mm in the latitudinal direction.

In Example A3, the cutting strength is 10 kg/width 25 in both the weft and weft directions.
The elongation at 1m or more and 10ky/251m width is:
It was 30 in both the longitudinal and longitudinal directions.

Similarly, in Example A4, the cutting strength was 10ky/in both the weft and weft directions.
The width was 25 m7IL or more, and the elongation at 10 kg/width 25 mm was 40% in the longitudinal direction and 30% in the latitudinal direction.

Furthermore, the tape was cut to a width of 25 mm to make tire sizes of 600-12 4PR, 615-134PR, and 64.
It was attached to the splice part of the inner liner of three types of bias tubeless tires of 0-146PR, and after applying a mold release agent, it was vulcanized.

The results were good, with no cracks occurring at the splice portion of the inner liner or at the surface or edges of the tape.

Furthermore, each of these tires is JIS D4230
As a result of carrying out the first durability test and the high-speed durability test described in , there were no abnormalities such as peeling of the tape.

In Examples A5 and 6, the Mooney viscosity of ML solution J was made to a concentration of 15, and was poured onto the knitted fabric placed on release paper to coat it smoothly, and then dried in a dryer to give a thick Saga is 0.2 in Example-ya 4
In Example 6, a tape of 0.107n7IL was manufactured.

When the strength and elongation of these tapes were measured, the cutting strength of Example 5 was 10 kg/width 25 mm or more in both the weft and weft directions, and the elongation at 10 kg/width 25 mm was 6 mm in the warp direction.
It was 0% and 50% in the latitudinal direction.

In Example A6, the cutting strength was 5 kg/width 25 mm in the warp direction and 4 kg/width 25 mm in the weft direction, and the cutting elongation was 250 mm in the warp direction and 300 mm in the latitudinal direction.

Furthermore, the tape was cut to a width of 25 mm and the tire size was 600-12 4PR1615-134PR,
It was applied to the splice part of the molded inner liner of three types of bias tubeless tires (640-146PR), and a release agent was applied thereto and then vulcanized.

The results were good, with no cracks occurring at the splice portion of the inner liner, the surface or edges of the tape.

Furthermore, in the same manner as Example 1, a durability test and a high-speed durability test were conducted, and no abnormalities such as peeling of the tape were found.

Comparative Example 1 The rubber composition used in Example 1 was made to a thickness of 0.15 m1n.
, a rubber sheet with a width of 25 mm and a 600-12
After molding the 4PR, a release agent was applied to the splice part of the inner liner and then vulcanized.

As a result, cracks occurred along the splice portion of the inner liner.

Comparative Example 2 The CR used in Example 5 was dissolved in toluene and coated on a non-stretchable plain weave fabric whose raw yarn is polyester 50 denier and whose finishing density (in inches) is 50 wefts and 60 warps. Dry it to a thickness of 0.15 mm and a width of 25 mm.
A tape with a diameter of 1.5 mm was manufactured and similarly applied to the splice part of 600-12 4PR and vulcanized.

As a result, the tape could not follow the movement of the inner surface of the tire during vulcanization, and many small racks were generated on the surface of the tape.

As mentioned above, since the crack prevention tape of the present invention is constructed by coating a stretchable fabric with rubber, this crack prevention tape has good vulcanization adhesion as shown in FIG. In addition, because the reinforcing base material has elasticity, it can sufficiently follow changes in bias tires, where the rubber moves a lot during vulcanization, making it more effective than conventional crack prevention tapes that do not have elasticity. A good quality tire with greater crack and light prevention effect can be obtained compared to the previous version.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway plan view of a tape according to an embodiment of the present invention, and Fig. 2 is a partially cutaway perspective view showing the tape applied to the splice portion of the innermost layer of a tire and vulcanized. be. 1... Fabric having elasticity, 2... Rubber.

Claims (1)

[Claims] 1. A crack prevention tape that is applied to the splice part of the innermost layer of an unvulcanized pneumatic tire and is made of a stretchable fabric coated with rubber.