JPS62189149A - Molding of tire - Google Patents

Abstract

PURPOSE:To permit utilization the titled method for the bonding of the splicing part of the tread of a racing tire or the like by providing the splicing surface of the tire tread having the principal polymer of high styrene rubber with good adhesive property and prominent vulcanizing bonding property. CONSTITUTION:A rubber composite including 30wt% or more of combined styrene in the total sum of polymers is employed. An annular tire tread is formed by connecting one end of a belt type material, consisting of such rubber composite, to the other end of the same. In this case, first, one end of the belt tye material is cut with a cutter heated to 100 deg.-300 deg.C so that an angle between a cutting surface and the surface thereof is 50 deg. or less, while the other end is cut with the same cutter so that an angle between the cutting surface and the bottom surface thereof becomes 50 deg. or less. Then, both ends of the same material are cut so as to cross the widths thereof to form bonding surfaces. Subsequently, the bonding surfaces formed in such manner are bonded with each other within 60min. This bonding may be perfomred as it is without employing rubber cement or the like.

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 splice surfaces (joint surfaces) of tire treads.

[Prior art]

Conventionally, there are roughly two types of methods for splicing a tire tread 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. In other words, ■It is made with a tread mainly made of natural comb (NR) or isoprene rubber (IR), and the splice surface is cut by cutting the strip extruded from an extrusion molding machine crosswise with a cutter on a bias. method of bonding the splice surfaces as they are; and ■ styrene-butadiene copolymer rubber (SBR) or butadiene rubber (B
This is done in accordance with the trend centered on R), and the splice surface is formed by cutting the strip on a bias crosswise with a cutter, then applying highly adhesive rubber cement to the splice surface and letting it dry. This method is followed by lamination.

In the method described in (1) above, the adhesion of the tread rubber itself is good and the lamination work is easy, and the adhesion of the vulcanized splice is sufficiently high and there is no problem, but the rubber used is NR or IR. The disadvantage is that it is limited to.

In addition, in the above method (■), since the tread rubber itself has poor adhesiveness, it is necessary to apply rubber cement (tread splice cement, hereinafter referred to as splice cement), which has excellent adhesiveness and vulcanization adhesion, to both sides of the joint. be.

As this splice cement, in the case of ordinary l-red rubber compounding, a cement having a similar compounding to the tread rubber compounding and containing a large amount of tackifier such as tackifier is effective. However, certain tread rubber formulations, i.e., the bound styrene content of the polymer used,
For tread rubber with a high styrene content exceeding 10% by weight, applying splice cement to both sides of the joint can provide good adhesion to the joint surfaces, but the splice adhesive strength after vulcanization decreases, causing l - There is a problem that the 1/7 splice part peels off.

[Purpose 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.

[Structure of the invention]

Therefore, the present invention provides 30% by weight of the total polymer.
When joining one end (tb end) of the strip made of the rubber composition containing bound styrene to form an annular tire tread, a cutter heated to 100°C to 300°C is used to join one end to the cut surface and the surface. 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. The gist of this invention is a tire molding method characterized by bonding the bonded surfaces together within 60 minutes.

Hereinafter, the configuration of the present invention will be explained in detail.

Rubber compositions containing bound styrene in an amount of 30% by weight or more based on the total amount of polymers used in the present invention (if multiple polymers are used, the total bound styrene content is 30% by weight or more)
0% by weight or less) is, for example, SBR with a bound styrene content of 30% by weight or more mixed with carbon black, oil, and other additives. Tire treads made of such rubber compositions do not adhere to splices after vulcanization, regardless of what kind of rubber cement is used or cemented with the same composition as the rubber composition. The breaking force is significantly lower than the breaking strength 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, one end is bonded with a cut surface using a knife heated to 100°C to 300°C. Both ends of the strip are cut transversely so that the angle between the other end and the bottom surface is 50 degrees or less, respectively, to form a joint surface. Since the above rubber composition has a high bound styrene content, the unvulcanized tread rubber tends to be hard and have poor tack. 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 bloom material is removed, so the tack is at a level sufficient for forming work. I ended up going to Hi-Hi. In this case, the temperature of the cutter is important; it is 100°C or more and less than 300°C, preferably 200-200°C.
It is 50°C. At temperatures below 100'C, it is difficult to easily cut the tread without deforming it;
If this value is exceeded, the rubber will easily decompose and carbonize when it comes into contact with the blade, reducing its adhesion and tack. Cutting may be performed by cutting the end of a slightly longer strip from either the vertical or horizontal direction relative to the upper or lower surface of the strip, or by sequentially cutting the strip that has been wound long beforehand. You can also take it. 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. 5
When cutting and laminating at an angle greater than 0 degrees, the press pressure perpendicular to the bonding surface generated by the mold and bladder during vulcanization, that is, the adhesive pressure, decreases, resulting in a sufficiently high splice. This is because the joint strength cannot be obtained.

Next, in the present invention, the bonding surfaces formed as described above are bonded together within 60 minutes. This lamination is
It can be done as is without using rubber cement or the like. The reason for setting the time to be within 60 minutes is that after 60 minutes after cutting, blooms increase on the surface, the tack decreases, and the adhesion 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. Incidentally, the blending proportions 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 by a normal extrusion method using a roll and a tuber and unvulcanized. A strip was produced. This was then cut under various conditions shown in Table 2 below, molded and vulcanized to produce a racing slick tire with a tire size of 2251515-13.

Various performances of these tires were evaluated.

The results are shown in Table-2. The adhesion strength of the spline was determined based on the state of the splice after running on the circuit and the results of a tensile test using a JI No. 53 dumbbell test piece cut from the tire.

Table 2 L (Blend-1) High styrene SBR*1 137.5 SAF grade carbon black No. 1203 zinc white
5 stearic acid
2 Anti-aging 11-agent *22 Aromatic oil 82.5 Sulfur
2.5 Vulcanization accelerator *3
Note 1.5) *1 Oil-extended product containing 37.5 parts by weight of cold-type emulsion polymerized 5BR1 oil with a bound styrene content of 35% by weight.

*2 N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine.

*3 N-cyclohexyl-2-benzothiazole sulfenamide.

(Left space on this page) Note) (1) Judgment was made based on the following criteria based on the appearance of the splice after running 15 laps on a 4.4km circuit.

Kazuyoshi where the splice part is not visible at all. Good (○).

Items where the splice part is peeled off to a depth of 1 mm or less.
Fairly good (△).

If the splice part is peeled off deeper than 1, it is defective (x) 6 (2) Place a 2mm thick sheet of vulcanized rubber from the trend part parallel to the tread layer of the tire so that the splice part is in the center position. It was cut out and then punched out using a JIS No. 3 dumbbell so that the splice part was located at the center of the row 1 constant part, and the tensile strength of this was measured according to JTS 46301. The measured value is the average value of four samples. Measured values marked with an asterisk (*) on the right shoulder indicate that the fracture occurred at the joint interface, and those without a mark indicate that the fracture cannot be identified as the joint interface, or that the fracture occurs elsewhere.

(3) The tack when laminating unvulcanized treads and 7 ds cut under each condition during molding was judged according to the following criteria.

It will try to peel off again just by pressing lightly. Good (0) if it does not peel off easily.

It is easy to join by just pressing lightly. Items that can be peeled off if pulled strongly - Slightly good (△).

Easy to join without just pressing lightly The one that peels off is defective (x).

(4) The cement used was obtained by blending 30 parts by weight of an alkylphenol resin with the rubber composition of Formulation 2 in Table 3, and then melting the mixture in a rubber volatilizer to a solid content of 10%.

From the above results, when joining splices of SBR tread rubber with a high styrene content, if cement is applied to the joint surface as before, the tank will be good regardless of the cutting method, but the adhesive strength after vulcanization will decrease. Furthermore, even when cutting with a heated blade, if the cutting angle is too large or if the length of time after cutting is too long, the adhesive strength after vulcanization decreases.

On the other hand, this is an example that does not meet the conditions of the present invention, but it can be seen that both the tank and vulcanization adhesion are good, and it 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 tread rubbers with different combinations of bound styrene contents shown in Table 3. The results are shown in Table 4. In addition, S in Table 3
Both BR (styrene 23.5% and 40%) are emulsion polymerized cold type SBR, and other compounding agents are shown in Table 1.
This is the same as shown in .

(Margins below this page) 15 As is clear from these results, the bound styrene content is 3.
With 0% by weight ungrooved SBR type Treso' rubber, good tank and post-vulcanization adhesive strength can be obtained by the conventional method, and there is no improvement even when cutting and molding are carried out under the conditions of the present invention. On the other hand, it can be seen that in tread rubbers with a bound styrene content of 30% by weight or more, good adhesion is achieved only by the method of the present invention.

〔Effect of the invention〕

As explained above, according to the method of the present invention, high styrene SBR (combined styrene content of 30% by weight or more), for which sufficiently strong adhesion could not be obtained with the conventional technique of applying cement, can be used.
)-) The splice portion of the tread rubber mainly composed of tread rubber can be firmly adhered to the same degree of breaking strength as 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 running, and the like.

Claims (1)

[Claims] When joining one end and the other end of a strip made of a rubber composition containing bound styrene in an amount of 30% by weight or more of the total polymer to form an annular tire tread, the heating temperature is 100°C to 30°C.
Using a knife heated to 0°C, cross each end of the strip at one end with an angle between the cut surface and the surface and at the other end with an angle of 50 degrees or less between the cut surface and the bottom surface. A tire molding method characterized by cutting to form a joint surface, and then bonding these joint surfaces together within 60 minutes.