JPH0348025B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a tire molding method that improves the adhesion of the splice surface (joint surface) of a tire tread. [Prior Art] Conventionally, there are roughly two types of methods for tire tread splicing when one end and the other end of a belt-shaped article made of a rubber composition are joined to form an annular tire tread. That is, it is carried out using a tread mainly made of natural rubber (NR) or isoprene rubber (IR), in which a strip extruded from an extrusion molding machine is cut crosswise on a bias with a cutter to form a splice surface. A method of bonding splice surfaces as they are, and styrene
This is done using a tread made mainly of butadiene copolymer rubber (SBR) or butadiene rubber (BR), and the splice surface formed by cutting the extruded strip on a bias crosswise with a cutter has excellent adhesion. This method involves applying rubber cement, drying it, and then laminating it. In the above method, the adhesiveness of the tored rubber itself is good and the lamination work is easy, and the adhesive strength of the splice part after vulcanization is sufficiently high and there is no problem, but the disadvantage is that the rubber used is limited to NR or IR. There is. In addition, in the above method, since the adhesion of the treaded rubber itself is poor, it is necessary to apply rubber cement (treaded splice cement, hereinafter referred to as splice cement), which has excellent adhesiveness and vulcanization adhesion, to both sides of the joint. be. In the case of a conventional tored rubber compound, a cement having a similar formulation to the tored rubber compound and containing a large amount of tackifier such as tackifier is effective as the splice cement. However, in certain treaded rubber formulations, i.e. high styrene treaded rubbers where the bound styrene content exceeds 30% by weight of the polymer used, splice cement applied to both sides of the joint may provide good adhesion to the joint surfaces. Although it can be done, the splice adhesive strength after vulcanization decreases,
There is a problem with the tread splice part peeling off while driving. [Object of the Invention] An object of the present invention is to provide a tire molding method capable of imparting good tackiness and excellent vulcanization adhesion to the splice surface of a tire tread whose main polymer is high styrene rubber. [Configuration of the Invention] Therefore, the present invention provides that 30 out of the total polymer
When joining one end and the other end of a strip made of a rubber composition containing bound styrene in a weight percent or more to form an annular tire tread, one end is bonded to the cut surface and the surface using a knife heated to 100°C to 300°C. At the other end, the angle between the cut surface and the bottom surface is 50 degrees or less, and both ends of the strip are cut transversely to form a joint surface, and then these joint surfaces are The gist of this is a tire molding method characterized by bonding the tires together within 60 minutes. Hereinafter, the configuration of the present invention will be explained in detail. 30% by weight of the total polymer in the present invention
Rubber compositions containing the above bound styrene (if multiple polymers are used, the total bound styrene content is 30% by weight or more), for example, carbon black in SBR with a bound styrene content of 30% by weight or more. , oil, and other ingredients. Tire treads made of such rubber compositions have excellent splice adhesive strength after vulcanization, regardless of what kind of rubber cement is used or cemented with the same composition as the rubber composition. The breaking strength is significantly lower than that of the non-splice part. In the present invention, when joining one end and the other end of a strip made of such a rubber composition to form an annular tire tread, first, a blade heated to 100°C to 300°C is used to join one end to the cut surface and the other end. At the other end, the angle between the cut surface and the bottom surface is 50 degrees or less, and both ends of the strip are cut transversely to form a joint surface. Since the above-mentioned rubber composition has a high content of bound styrene, the unvulcanized tread rubber tends to be hard and have poor tackiness. Therefore, by cutting this with a heated knife to form a fresh splice surface, the surface rubber is softened by the heat of the knife, and at the same time, the blooming material is removed, so the tack is at a level sufficient for forming work. It will improve to. in this case,
The temperature of the cutlery is important, 100℃ or higher and lower than 300℃,
Preferably it is 200-250°C. At temperatures below 100°C, it is difficult to easily cut the tread without deforming it, and at temperatures above 300°C, the rubber easily decomposes and carbonizes on contact with the blade, conversely reducing its adhesion and tack. I end up. To cut, cut the slightly longer end of the strip vertically against the top and bottom surfaces of the strip.
You can go from either side, and
It is also possible to sequentially cut off a long strip that has been wound up in advance. The angle between the cut surface and the surface and the angle between the cut surface and the bottom surface must each be 50 degrees or less. When cutting and laminating at an angle greater than 50 degrees, the press pressure perpendicular to the laminating surface, that is, the adhesion pressure generated by the mold and bladder during vulcanization, decreases and is not sufficiently high. This is because adhesive strength at the splice portion cannot be obtained. Next, in the present invention, the bonding surfaces formed as described above are bonded together within 60 minutes.
This lamination may be performed as is without using rubber cement or the like. The reason why the time limit is within 60 minutes is because after 60 minutes after cutting, blooms increase on the surface and the tack decreases, as well as the adhesive strength of the splice after vulcanization also decreases to a normal low level. For this reason, it is preferable that the bonding be performed as soon as possible within 60 minutes after cutting. After laminating in this manner, a product can be obtained by vulcanization. Examples and comparative examples are shown below. It should be noted that the blending ratios are expressed in parts by weight unless otherwise specified. Examples, Comparative Examples (1) Examples 1 to 3, Comparative Examples 1 to 4 A rubber composition consisting of formulation 1 shown in Table 1 below was extruded using a normal extrusion method using a roll or a tuber to form an unvulcanized product. A strip was produced. Then,
This was cut under various conditions shown in Table 2 below, molded and vulcanized to produce racing slick tires with tire sizes of 225/515-13. Various performances of these tires were evaluated. Table this result.
Shown in 2. The adhesive strength of the splice portion was determined from the condition of the splice portion after running on the circuit and the results of a tensile test using a JIS No. 3 dumbbell test piece cut from the tire. Table-1 (Composition-1) High styrene SBR*1 137.5 SAF grade carbon black 120 No. 3 zinc white 5 Stearic acid 2 Anti-aging agent*2 2 Aromatic oil 82.5 Sulfur 2.5 Vulcanization accelerator*3 1.5 (Note) *1 Cold type emulsion polymerized SBR with bound styrene content of 35% by weight, oil-extended product with 37.5 parts by weight of oil. *2 N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine. *3 N-cyclohexyl-2-benzothiazole sulfenamide.

[Table] From the above results, when joining splices of SBR tored rubber with a high styrene content, if cement is applied to the joint surface as before, the tack will be good regardless of the cutting method, or the adhesive force after vulcanization will decrease. thing,
Furthermore, even when cutting with a heated blade, if the cutting angle is too large or if the time after cutting is left for a long time, the adhesive strength after vulcanization decreases. On the other hand, in an example that satisfies the conditions of the present invention, tack,
It can be seen that both the vulcanization adhesion is good and the product is excellent in practicality. (2) Examples 4 to 5, Comparative Examples 5 to 10 The same tests as in Examples 1 to 3 were conducted using various tread rubbers with different bound styrene contents shown in Table 3. The results are shown in Table 4. In addition, SBR in Table 3 (styrene 23.5%, 40%)
Both are emulsion polymerized cold type SBR, and the other ingredients are the same as those shown in Table 1.

【table】

〔Effect of the invention〕

As explained above, according to the method of the present invention, a splice part of a treaded rubber mainly made of high styrene SBR (bonded styrene content of 30% by weight or more), for which sufficiently strong adhesion could not be obtained using the conventional technique of applying cement, can be achieved. can be bonded as strongly as the breaking strength of the non-splice portion. Therefore, the present invention can be effectively used for joining splices of treads of high grip tires that use a large amount of high styrene SBR, racing tires intended for circuit driving, and the like.

Claims (1)

[Claims] 1. When joining one end and the other end of a strip made of a rubber composition containing bound styrene in an amount of 30% or more by weight of the total polymer to form an annular tire tread, use a knife heated to 100°C to 300°C, At one end, the angle between the cut surface and the surface is 50 degrees or less, and at the other end, the angle between the cut surface and the bottom surface is each 50 degrees or less, and both ends of the strip are cut transversely to form a joint surface. , and then bonding these bonded surfaces together within 60 minutes.