JPH10180766A - Tire bladderless vulcanization method, resin film used in this method, and tire manufactured by this method - Google Patents

Abstract

(57) [Problem] To provide a bladderless vulcanization method in which a heat medium does not possibly enter a tire from a member joint portion on an inner surface of the tire. SOLUTION: In a tire bladderless vulcanization method, a resin film having a yield value of 4 kgf / cm or less is previously coated on a member joint portion on an inner surface of an unvulcanized tire or on the entire inner surface of the tire, and then vulcanized. Is characterized by preventing the heat medium from entering the inside of the tire by the above, preferably as a resin film, particularly a cross-linking exhibiting good heat resistance rupture under the action of a vulcanizing heat medium such as hot water or steam Use a type of polyolefin film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire bladderless vulcanization method, a tire manufactured by the method, and a resin film used for the tire.

[0002]

2. Description of the Related Art In ordinary tire vulcanization, a rubber bag called a bladder is inserted into the inner surface of an unvulcanized tire placed in a vulcanizer, and steam or hot water is introduced as a heating medium into the bladder. Heated and vulcanized.

[0003] However, the conventional tire vulcanization method using a bladder not only requires a large number of man-hours when preparing the bladder and setting it in a vulcanizer, but also requires a large amount of energy loss and takes a long time for vulcanization. There are many obstacles to improving efficiency and reducing costs.

Therefore, recently, in order to solve such a drawback of bladder vulcanization, as shown in, for example, JP-A-6-71652, this bladder is omitted and a heating medium is directly provided on the inner surface of an unvulcanized tire. There have been proposed various attempts to vulcanize tires by introducing the same.

[0005]

As described above, in bladderless vulcanization of tires, since the heat medium for vulcanization is directly introduced into the inner surface of the unvulcanized tire, the joint portion of the member of the unvulcanized tire is incomplete. In this case, the heat medium penetrates into the inside of the tire through this portion, which may cause poor adhesion or deterioration of the member, and the tire obtained after vulcanization is defective.

[0006] Therefore, an object of the present invention is to provide a method for curing a tire by bladderless vulcanization, in which even if there is an incomplete member joint portion on the inner surface of the tire, the heat medium penetrates into the inside of the tire through this portion. It is an object of the present invention to provide a bladderless vulcanization method which does not cause a good product.

[0007]

In order to achieve the above-mentioned object, the present invention relates to a method of vulcanizing a tire without a bladder, wherein a yield value of 4% is previously applied to a member joint on the inner surface of an unvulcanized tire or to the entire inner surface of the tire. A resin film having a heat-resistant rupture resistance to a heat medium of not more than Kgf / cm and 170 ° C. or more is coated, and then vulcanized to prevent the heat medium from entering the tire. .
Note that the yield value refers to a material having a uniform thickness and a shape conforming to JIS.
A value obtained by performing a tensile test using a sample having the shape of a dumbbell-shaped No. 1 tensile test piece specified in K6251 and calculating the product of the yield point stress and the thickness at that time (the same applies hereinafter).

In a preferred embodiment of the present invention, the resin film has a heat-resistant rupture property against a heat medium of 170 ° C. or more, and has a yield value of 0.8 kgf / cm or less, more preferably The use of a crosslinked resin film of 0.5 kgf / cm or less and elongation at break of 80% or more, more preferably 150% or more. In addition, the yield value of the tensile test piece means the higher one of the values measured in the vertical direction and the horizontal direction of the film.

The heating medium on the inner surface side of the tire is usually a heating medium made of hot water or steam, or a mixed heating medium of steam and inert gas (hereinafter referred to as steam / inert gas).
Inert gas mixed heating medium) is used. In so-called hot water vulcanization using hot water as a heat medium, the temperature is usually 170 ° C.
Pressurized hot water of about 190 ° C. is often used as a heat source and a pressure source. In contrast, in so-called steam vulcanization using steam as a heat medium, high-pressure steam of about 190 ° C. to 210 ° C. is often used as a heat source and a pressure source.

In recent years, a gas vulcanization method using a steam / inert gas mixed heating medium has attracted attention from the viewpoint of energy saving, and its use has been expanding. In this type of gas vulcanization method, a steam / inert gas mixed heat medium of about 170 ° C. to 200 ° C. is often used.

In the tire bladderless vulcanizing method according to the present invention, all of these heating media can be employed. Therefore, the resin film coated on the inner surface of the unvulcanized tire is subjected to the action of the respective heating media. Must be capable of exhibiting heat rupture resistance. The yield value of these resin films is preferably 4 kgf / cm or less, and the thickness thereof is preferably in the range of 20 to 250 μm. If the thickness is less than 20 μm, there is a tendency for breakage to occur immediately upon contact with minute projections, and if the thickness is more than 250 μm, the paste moldability, heat conductivity becomes poor, and the cost increases. This is because there is a tendency. In the present invention, a more preferable film thickness is 30 to 100.
μm. This is because the safety and economy of molding can be reliably ensured, which is preferable.

As a resin film capable of exhibiting heat-resistant rupture properties under the action of a hot water heating medium of about 170 to 190 ° C. or a steam / inert gas mixed heating medium, nylon 6, polyethylene terephthalate (PET), a crosslinked type (silane crosslinked or (Electron beam cross-linking) polyolefin film or a film containing polyolefin as a main component. Of these, nylon 6 is easily hydrolyzed at a high temperature, so it is desirable to apply it to hot water vulcanization at a relatively low temperature. The polyolefin referred to here is a combination of polypropylene, polyethylene (low density, medium density, high density type, including linear type in polymerization form, and also includes type polymerized with a single-site catalyst) and ethylene-vinyl acetate. Polymer, ethylene-acrylic acid copolymer,
Refers to an ethylene-acrylate copolymer or the like.

On the other hand, as the resin film capable of exhibiting heat rupture resistance under the action of a steam heating medium at 190 ° C. or higher or a steam / inert gas mixed heating medium, the above-mentioned PE
T, a film made of various types of cross-linked polyethylene or a cross-linked type ethylene-vinyl acetate copolymer can be mentioned as a particularly suitable film.

One method of coating these resin films on the inner surface of the unvulcanized tire is to apply the resin film to a member joint on the inner surface of the unvulcanized tire formed according to a conventional method or to the entire inner surface of the unvulcanized tire. It is to paste by hand. Since this bonding is a manual operation, it takes time and effort, but if the yield value is 4 kgf / cm or less, it can be appropriately selected and used from a thin and flexible film to a relatively thick and hard film.

However, considering the efficiency of the attaching step, attaching on a tire building drum, that is,
At the beginning of unvulcanized tire molding, a resin film is first wound on a molding drum, an inner liner and a carcass ply are pasted on it, and a bead is inserted to create a cylindrical first case. More preferably, the belt and the tread are inflated to the diameter of.

However, the resin film used in this method needs to have an elongation rate and flexibility enough to be able to expand following the shape change when the cylindrical first case is inflated in a toroidal shape. is there. Therefore, the thickness is 2
A resin film having a value of 0 μm or more, a yield value of 0.8 kgf / cm or less, and a breaking elongation of 80% or more is used. However, in this case, the expansion ratio of the first case differs depending on the tire size, the type of the molding machine, and the like. Therefore, considering the safety in molding, the above yield value is 0.5 kgf / cm or less, and the breaking elongation is 1 kg.
More than 50% is more preferable.

The thickness of the resin film is usually achieved by a single resin film having a predetermined thickness, but if necessary, a plurality of the resin films are laminated to obtain a desired thickness. You may do it. In this case, the film to be laminated may be a film composed of the same resin or a film composed of different resins.When laminating films composed of different resins, usually, hot water introduced into the tire at the time of vulcanization or A resin film having good heat resistance and rupture resistance is arranged at a portion which directly contacts the steam. According to the method of laminating the films, even if there is a pinhole in the film, the invasion of the heat medium is completely prevented because the adjacent film seals the pinhole.

Generally, a resin film having a higher heat-resistant rupture property has a higher yield value and is harder, so that it cannot be practically used for a method of attaching it on a forming drum. Therefore, as a result of diligent research, a crosslinked polyolefin film,
For example, it has been found that a crosslinked type polyethylene film or a crosslinked type ethylene-vinyl acetate copolymer film satisfies the above-mentioned required properties and can be suitably used for this method. The bladder-less vulcanizing method for a tire according to the present invention may be applied to any type of tire, such as a tire for a passenger car, a heavy-duty tire mounted on a truck or a bus, or a large tire for a construction vehicle, regardless of a bias or a radial structure. However, the present invention can be applied to tires of all sizes. It is not necessary to peel off the resin film remaining on the inner surface of the tire after vulcanization, but it is preferable to peel and remove this resin film after vulcanization from an aesthetic sense.

As described above, the present invention employs a method of coating a thin heat-resistant resin film on the inner surface of an unvulcanized tire and then vulcanizing the tire in bladderless vulcanization of the tire. Even when there is an incomplete member joint portion on the inner surface, a heat medium such as hot water or steam enters the inside of the tire without causing a defect, and a tire of improved quality can be obtained.

[0020]

DETAILED DESCRIPTION OF THE INVENTION AND

Next, embodiments of the bladderless vulcanizing method according to the present invention will be described in more detail with reference to Examples and Comparative Examples. All test tire sizes are 175 / 70R13
It is.

In practicing the present invention, the following four types of molding / vulcanization systems were employed. Method 1: After forming an unvulcanized tire by a tire forming machine in accordance with a standard method, a band-shaped resin film is applied only to the inner liner joint portion on the inner surface of the tire and covered.
Warm water (170 ° C.) is introduced into the inside and vulcanized. Method 2: Similarly, after forming an unvulcanized tire, a resin film is stuck and coated on the entire inner surface of the tire, and hot water (170 ° C.) is introduced into the inside to vulcanize the tire.

Method 3: Similarly, after forming an unvulcanized tire, a resin film is stuck on the entire inner surface of the tire to cover it, and steam (190 ° C.) is introduced into the inside to cure the tire. Method 4: After winding a resin film on a tire forming drum, an inner liner and other tire members are pasted thereon according to a standard method to form an uncured tire, and then steam (190 ° C.) is introduced into the inside. Vulcanize.

[0023]

[Table 1]

[0024]

[Table 2]

Tables 1 and 2 show the types and characteristics of the resin films used in the examples and comparative examples, and the adaptability to the above-mentioned four methods (paste moldability at the time of molding, heat-resistant rupture resistance to a heat medium). It is a thing.

The yield value, elongation at break, elongation at break, heat moldability (hot water and steam) of each resin film shown in Tables 1 and 2 were evaluated by the following methods.

Yield value (kgf / cm): uniform thickness, J
It is a value indicated by the product of the yield point stress and the original thickness measured on a sample having the shape of a dumbbell-shaped No. 1 tensile test piece specified in IS K6251. If the yield stress is not clear,
The stress at 80% elongation was substituted. In addition, the yield value of the said test piece was measured about each of the length direction and the horizontal direction of the said film. Elongation at break (%): Elongation at break at the above tensile test.

Adhesive moldability: Process adaptability evaluated using the flexibility of the film and the adhesion to the unvulcanized tire inner rubber as indices. ○ indicates good, and × indicates bad.

Heat resistant rupture resistance: After bladderless vulcanization was carried out by the above four molding / vulcanization methods (methods 1 to 4), the condition of the test film on the inner surface of each tire was observed, and if the resin film was not broken, （(Good), x (not good) if broken.

As is clear from Table 1, the crosslinked polyethylene and the resin film composed of the crosslinked ethylene-vinyl acetate copolymer both have good heat-resistant rupture properties and a relatively high yield value. Except for the high-density polyethylene film of the cross-linking type (Examples 1 to 3), despite being a thin film having a thickness of 30 to 120 μm, it is excellently adhered to all the bladderless vulcanization conditions of the above methods 1 to 4. It can exhibit sticking moldability.

Table 2 shows an example in which a film made of a thermoplastic resin is used in place of the above-mentioned crosslinked type resin film. Method 10 (methods 1 to
An unvulcanized tire was prepared by coating the resin film on the inner surface according to 4) and vulcanized.

As is evident from Table 2, it is recognized that the nylon 6 film (Example 11) can exhibit sufficient bonding moldability and heat rupture resistance only for bladderless vulcanization using 170 ° C. hot water as a heat medium. Can be However, 190
In steam vulcanization at ° C., it was found that the nylon 6 film was hydrolyzed and broken by the action of steam, and was not usable. Therefore, it can be said that this type of film is suitable for use under relatively mild hot water vulcanization conditions, for example, when vulcanizing large vehicle tires.

On the other hand, a PET film (Example 1)
2) Except for being inferior in the paste moldability to the method 4, the bladderless vulcanization using warm water and steam as a heat medium (methods 1 to 3) can exhibit sufficient paste moldability and heat rupture resistance.

On the other hand, films made of polypropylene, polyvinylidene chloride, high-density polyethylene, low-density polyethylene, ethylene-vinyl acetate copolymer and polyvinyl alcohol (Comparative Examples 1 to 6) were all 170
It lacked the heat-resistant rupture resistance to hot water at a temperature of not less than ° C and steam heat medium, and was therefore unsuitable as a protective film for bladderless vulcanization. Further, the nylon 6 film having a thickness of 200 μm (Comparative Example 7) and the PET film having a thickness of 100 μm (Comparative Example 8) both have a high yield value of 4 kgf / cm or more, and thus have poor bonding moldability and cannot withstand use. Was something.

[0035]

As described above, according to the present invention, when the tire is bladderless vulcanized, the inner surface of the tire is protected by using a specific resin film, so that the joint time can be reduced without impairing the effect of shortening the vulcanization time. Troubles due to defects can be efficiently prevented. In addition, a safe tire having the same quality as a tire obtained by ordinary bladder vulcanization can be obtained.

 ──────────────────────────────────────────────────の Continuation of the front page (72) Inventor Hideyoshi Ouchi 1-8-30 Tenmabashi, Kita-ku, Osaka City Mitsubishi Chemical Corporation Osaka Branch

Claims (5)

[Claims] 1. A method for vulcanizing a tire without a bladder, wherein a yield value is 4 kgf / cm or less and a heat medium of 170 ° C. or more is applied in advance to a member joint portion on the inner surface of an unvulcanized tire or the entire inner surface of the tire. A bladderless vulcanizing method for a tire, comprising coating a resin film having heat-resistant rupture properties and then vulcanizing to prevent a heat medium from entering a tire. 2. A bladderless vulcanizing method for a tire according to claim 1, wherein the resin film is a crosslinked resin film having a thickness of 20 μm or more, a yield value of 0.8 kgf / cm or less, and a breaking elongation of 80% or more. . 3. The tire bladderless vulcanization method according to claim 1, wherein the resin film is a crosslinked polyolefin film or a film containing polyolefin as a main component. 4. A resin film used in the tire bladderless vulcanization method according to claim 1, 2 or 3. 5. A tire produced by the method for vulcanizing a tire according to claim 1, 2 or 3.