JPH0531724A - Method for molding and vulcanizing rubber product - Google Patents

Abstract

PURPOSE:To mold and vulcanize a rubber product such as a tire with good workability without generating molding inferiority by using vulcanizing bladder excellent in mechanical properties, physical properties such as hot water resistance and chemical properties and having good durability and releasability. CONSTITUTION:In the molding and vulcanization of a rubber product using a vulcanizing bladder, the vulcanizing bladder is formed so as to have a multilayered structure composed of a plurality of layers and has a layer (A) composed of a rubber composition based on org. rubber on the innermost side thereof and a layer (B) composed of a rubber composition whose release stress with the rubber product is 0.5kg/cm or less on the outermost side thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding vulcanization method using an improved vulcanization bladder suitable for molding vulcanization of rubber products, particularly tires.

[0002]

2. Description of the Related Art Conventionally, a pneumatic tire is an unmolded tire in which a vulcanization bladder placed inside the unmolded tire in a molding press pushes the unmolded tire outward toward a mold. It is manufactured by pressing against the surface of the mold and molding and curing. By this method an unmolded tire is molded and vulcanized to an external mold that determines the tire tread pattern and sidewall structure.

As a composition of a vulcanizing bladder used for molding and vulcanizing rubber products such as tires, organic rubber, particularly butyl rubber, has been conventionally used. However,
The vulcanization bladder made of organic rubber has poor releasability and lubricity from the inner surface of the tire, and the vulcanization bladder tends to bend when the vulcanization bladder is taken in and out, resulting in defective products when molding the tire with the mold. There was a problem to do. Further, there is a problem that the surface of the vulcanization bladder becomes worn and becomes rough, and the bladder surface adheres to the inner surface of the tire after the tire is cured and during the vulcanization bladder contraction process of the tire curing cycle. Further, since air bubbles are trapped between the vulcanization bladder and the tire surface, heat transfer becomes insufficient and there is a problem of promoting tire vulcanization defects.

When a tire is vulcanized and molded using a vulcanization bladder, in order to solve the above problems and to improve the mold releasability and lubricity from the inner surface of the tire, a silicone emulsion or the like is used. There has been a conventional need for a release agent consisting of However, applying the release agent to the inner surface of the tire not only has disadvantages such as an increase in the number of steps and an increase in intermediate inventory from the viewpoint of the manufacturing process, but also this release agent has an adverse effect during tire molding vulcanization. It often caused the occurrence of defective products.

As a method for solving such a problem, conventionally, a method of modifying a releasable lubricant has been disclosed (Japanese Patent Laid-Open No. 57-111).
393, Japanese Unexamined Patent Publication No. 57-111394, Japanese Unexamined Patent Publication No. 57-1
19992, Japanese Unexamined Patent Publication No. 61-175009, Japanese Unexamined Patent Publication No. 62-
No. 275711, Japanese Patent Laid-Open No. 63-147610), a method of modifying the organic rubber surface of a vulcanizing bladder with a cured silicone film (Japanese Laid-Open Patent Publication Nos. 59-106948 and 61-21501).
5, JP-A-61-100417), a method of using a rubber mixture composition containing an organic rubber and polyorganosiloxane as a rubber composition of a bladder for tire vulcanization (JP-A-61-100417).
61-72505, Japanese Patent Application No. 61-271734, Japanese Unexamined Patent Publication No.
61-175009, Japanese Unexamined Patent Publication No. 63-125311, Japanese Unexamined Patent Publication No. 61-195810, Japanese Unexamined Patent Publication No. 61-100416), methods of using a silicone rubber composition alone, etc. have been proposed. It was

[0006]

However, in the use of the vulcanized bladder improved by the methods listed above, etc.,
As explained below, it has not been possible to provide a method for molding and vulcanizing tires that sufficiently satisfies the needs of the industry. For example, the above-mentioned method of modifying the releasable lubricant cannot obtain a sufficient releasing effect, and the above-mentioned method of modifying the organic rubber surface with a silicone film separates the bladder surface from the tire inner surface. The moldability was improved, and although the tire could be vulcanized without using a release agent, the durability of the surface of the bladder was extremely deteriorated, which was not practical. Similarly, even in the method using the above silicone rubber composition, a tire can be molded without using a release agent,
Silicone rubber has a problem that the life as a bladder is extremely short due to its low hydrolysis resistance, which is a drawback of silicone rubber. Further, in the method using a rubber mixture composition containing the above-mentioned organic rubber and polyorganosiloxane, the hydrolysis resistance and mechanical properties, which are the drawbacks of silicone rubber, can be compensated for by mixing the organic rubber, but on the other hand, the releasability of the bladder is improved. It has a problem that it is difficult to satisfy the bladder life at the same time, and is not practical. In view of the problems of the conventional molding and vulcanizing method of a tire using the vulcanizing bladder as described above,
The object of the present invention is to use a vulcanization bladder having excellent mechanical properties, physical properties such as hot water resistance and chemical properties, and good durability and mold releasability without using a mold release agent. A method for molding and vulcanizing a rubber product such as a tire, which has good workability and does not cause defective molding.

[0007]

The object of the present invention has been achieved by the method for molding and vulcanizing a rubber product having the following characteristics according to the present invention. The characteristic is that, when a rubber product is molded and vulcanized by using a vulcanization bladder, the vulcanization bladder is formed as a multi-layer structure composed of a plurality of layers, and (A) an organic rubber is mainly formed on the innermost side thereof. It has a layer composed of a rubber composition as a component, and the peeling stress from the rubber product is 0.5 kg / cm on the outermost side (B).
That is, it has a layer made of the following rubber composition. Here, the innermost side means a rubber product such as a mold or a tire from the outside,
Among the molding presses arranged in the order of the vulcanization bladder, it means the layer of the vulcanization bladder farthest from the rubber product, and the outermost means the layer of the vulcanization bladder closest to the rubber product.

The average thickness of the entire multilayer structure of the vulcanization bladder used in the present invention must be at least 2.0 mm or more, preferably 2.5 mm to 50 mm, more preferably 3.0 mm to 45 mm. If the average thickness of the vulcanization bladder is less than 2.0 mm, the rubber product cannot be vulcanized sufficiently and uniformly during vulcanization molding of the rubber product. The thickness of the rubber composition layer containing an organic rubber as a main component, which is disposed on the innermost side of the vulcanization bladder used in the present invention, needs to be at least 0.02 mm or more, preferably 0.05 mm or more, and further It is preferably 0.1 mm or more. When the innermost organic rubber layer has a thickness of 0.02 mm or less, the vulcanized bladder has a significantly shortened life during use, and the mechanical strength of the rubber composition layer is insufficient, so that the rubber composition layer is easily broken. is there.

The organic rubber used as the main component of the rubber composition layer disposed in the innermost layer of the vulcanization bladder used in the present invention includes butyl rubber, halogenated butyl rubber,
Saturated rubbers such as ethylene propylene rubber, fluororubber and acrylic rubber, and diene rubbers such as natural rubber, butadiene rubber, isoprene rubber, chloroprene rubber, styrene butadiene rubber and acrylonitrile butadiene rubber can be used. Saturated rubber is preferable, and butyl rubber is particularly preferable. This is because it has good mechanical properties at high temperatures and excellent heat resistance and heat aging resistance.

A reinforcing material and other additives described below can be added to the above-mentioned organic rubber composition constituting the innermost rubber composition layer. For example, a reinforcing agent can be added to the organic rubber composition in order to impart mechanical properties sufficient to withstand use as a vulcanization bladder.
Examples of the reinforcing agent include carbon black, white carbon, silicic anhydride, hydrous silicic acid, synthetic silicic acid, activated calcium carbonate, talc, inorganic reinforcing agents such as alumina, and high styrene resin, coumarone indene resin, phenol resin, lignin. , Selected from organic reinforcing agents such as modified melamine resin and petroleum resin. Carbon black is particularly desirable. In the organic rubber composition, in addition to the above-mentioned reinforcing agent, an antioxidant, a heat resistance improver which are generally used,
All rubber chemicals such as vulcanizing agents and vulcanization accelerators can be added depending on the purpose.

The rubber composition layer disposed on the outermost side of the vulcanization bladder used in the present invention has a peeling stress of 0.
It is necessary to use a rubber composition of 5 kg / cm or less. This is because when a rubber composition having a peeling stress from the rubber product of 0.5 kg / cm or less is used, the mold release property is excellent and it becomes unnecessary to apply the mold release agent to the inner surface of the rubber product. Preferably the peel stress
A rubber composition of 0.2 kg / cm or less, more preferably 0.1 kg / cm or less is used. As such a rubber composition, a silicone rubber composition, a mixed rubber composition of silicone and an organic rubber,
At least one composition selected from the fluororubber composition and the mixed rubber composition of fluororubber and organic rubber is used. From the viewpoint of economy, it is particularly preferable to use a silicone rubber composition or a mixed rubber composition of silicone and organic rubber.

As a rubber composition containing silicone and organic rubber to be used in the rubber composition of the outermost layer constituting the vulcanization bladder of the present invention, the present inventors have disclosed in Japanese Patent Laid-Open No. 61-72505.
Japanese Patent Application No. 61-271734, Japanese Unexamined Patent Publication No. 61-17500
No. 9, Japanese Unexamined Patent Publication No. 63-125311, Japanese Unexamined Patent Publication No. 61-195
All of the rubber compositions proposed in No. 810 and Japanese Patent Laid-Open No. 61-100416 can be used. Examples of the silicone rubber composition that can be used for the rubber composition of the outermost layer of the vulcanization bladder used in the present invention include dimethyl silicone polymer, methylphenyl silicone polymer, methylvinyl silicone polymer, methylphenylvinyl silicone polymer and the like. Use at least one selected from the above.

A reinforcing agent may be added to the outermost rubber composition, for example, the silicone rubber composition, in order to impart mechanical properties sufficient to withstand use as a vulcanization bladder. Examples of the reinforcing agent include carbon black, white carbon, silicic anhydride, hydrous silicic acid, synthetic silicic acid, activated calcium carbonate, talc, inorganic reinforcing agents such as alumina, and high styrene resin, coumarone indene resin, phenol resin, lignin. , Selected from organic reinforcing agents such as modified melanin resin and petroleum resin. It is particularly preferable to use a silica-based reinforcing agent such as white carbon, silicic acid anhydride, hydrous silicic acid, or synthetic silicic acid. For the rubber composition of the outermost layer, for example, for silicone rubber such as an antioxidant, a heat resistance improver, a vulcanizing agent and a vulcanization accelerator which are generally used in addition to the above-mentioned reinforcing agent in the silicone rubber composition. All chemicals can be added depending on the purpose.

[0014]

In the present invention, the peeling stress between the rubber composition layer containing (A) an organic rubber as a main component and (B) a rubber product is 0.5 kg /
By using a vulcanization bladder in combination with a rubber composition layer of cm or less, a rubber composition having a small peel stress, for example, a rubber containing an organic rubber as a main component while taking advantage of excellent releasability of a silicone composition. By blocking vapor with the composition layer, deterioration of the silicone composition due to vapor, which is a drawback, can be prevented and the durability of the vulcanization bladder can be improved. Therefore, according to the method of the present invention using such a vulcanization bladder, the incidence of defective molding is significantly reduced,
It is possible to efficiently perform molding and vulcanization of rubber products.

[0015]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. Example 1 Using the rubber composition shown in Table 1, a vulcanized bladder (Example product 1) having a multi-layer structure consisting of two layers of an inner layer and an outer layer was produced. That is, a rubber composition having the components and component ratios shown in Formula 1 of Table 1 and also having the mechanical properties and hot water resistance shown in Formula 1 was used in the inner layer of the vulcanization bladder, and similarly the formulation of Table 1 was used. The rubber composition shown in FIG. 2 was used as the outer layer of the vulcanization bladder, and the vulcanization bladder was formed into an inner layer of 0.1 mm and an outer layer of 4.5 mm according to the layer thickness shown in Table 2. A bladder (Example product 1) was produced.
Using the obtained vulcanization bladder of Example product 1, a pneumatic tire was molded and vulcanized in accordance with a usual method, and the releasability and durability of the vulcanization bladder (Example product 1) were evaluated. Regarding the releasability, the quality is evaluated by a two-stage evaluation, and the good is ◯ and the bad is ×.
Are shown in Table 2, respectively. The durability is shown by the percentage of the number of possible vulcanizations of the example product 1 with respect to the number of vulcanizations of the comparative example product 1. Peeling stress is 15 cm in length and 1 in width
A strip-shaped test piece of cm was used and measured according to JIS K 6301-1975 peeling test. Example 2 A vulcanized bladder (Example product 2) was produced in the same manner as in Example product 1 except that the thickness of the inner layer of the vulcanization bladder of Example product 1 was 1.0 mm. Using the obtained Example product 2, the tire was molded and vulcanized in the same manner as in Example 1, and the evaluation results are also shown in Table 2.

[0016]

[Table 1]

[0017]

[Table 2]

Comparative Example 1 Using a rubber composition having the components and the component ratios shown in Formula 1 of Table 1 and also having the mechanical properties and hot water resistance shown in Formula 1, vulcanization with a thickness of 4.5 mm was performed. A bladder (Comparative example product 1) was produced. Therefore, Comparative Example product 1 is not formed as a multi-layer structure including an outer layer composed of a rubber composition layer having a peeling stress from the tire inner liner rubber of 0.5 kg / cm or less. Using the obtained comparative example product 1, a tire was molded and vulcanized in the same manner as in Example 1, and the evaluation results are shown in Table 2. Comparative Example 2 A vulcanization bladder having a thickness of 4.5 mm (comparative) was prepared by using the rubber composition having the mechanical properties and hot water resistance shown in Formulation 2 and the components and component ratios shown in Formulation 2 in Table 1. Example product 2) was produced. Therefore, the comparative example product 2 is not formed as a multi-layer structure including an inner layer made of a rubber composition containing an organic rubber as a main component. Using the obtained comparative example product 2, the tire was molded and vulcanized in the same manner as in Example 1, and the evaluation results are shown in Table 2.

The products 1 and 2 of the example have a better releasability and durability comparable to that of the product 1 of the comparative example. on the other hand,
Although the comparative example product 2 has a good releasability, the durability is far inferior to that of the comparative product 1 and is not practical. Comparative example product 2 is
It shows that a vulcanized bladder simply using a silicone rubber composition is not practical in terms of durability.

[0020]

As described above, the method for molding and vulcanizing a rubber product of the present invention is formed as a multi-layer structure composed of a plurality of layers, and is formed on the innermost side with a rubber composition containing an organic rubber as a main component. A vulcanization bladder is used, which has a layer that blocks vapor and a layer that has a high releasability on the outermost side, ensuring both releasability and durability. The tire vulcanization bladder used in the present invention has excellent releasability and excellent mechanical strength, heat resistance, saturated steam resistance, and durability due to the above-mentioned constitution. The vulcanization method is as follows: (1) Molded vulcanization of rubber products is possible without using a mold release agent. (2) Therefore, defective products are hardly generated and the yield is remarkably improved. (3) Vulcanization bladder It has effects such as a long life, and thus, molding and vulcanization of rubber products such as tires can be efficiently performed at low cost.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area B29K 83:00 105: 24 B29L 30:00

Claims (4)

[Claims] 1. When a rubber product is molded and vulcanized by using a vulcanization bladder, the vulcanization bladder is formed as a multi-layer structure composed of a plurality of layers, and (A) an organic rubber is mainly formed on the innermost side thereof. A layer composed of a rubber composition as a component, (B)
A method of molding and vulcanizing a rubber product, comprising a layer made of a rubber composition having a peeling stress from the rubber product of 0.5 kg / cm or less on the outermost side. 2. The thickness of the rubber composition layer containing organic rubber as a main component, which is disposed on the innermost side of the vulcanization bladder, has a thickness of 0.02 mm.
The method for molding and vulcanizing a rubber product according to claim 1, wherein the method is as described above. 3. The method for molding and vulcanizing a rubber product according to claim 1, wherein the average thickness of the entire multilayer structure of the vulcanization bladder is 2.0 mm or more. 4. The method of molding and vulcanizing a rubber product according to claim 1, wherein the organic rubber used for the innermost rubber composition layer of the vulcanization bladder is butyl rubber.