Tire vulcanization bladder, manufacturing method thereof and rubber composition for bladder

Abstract

A rubber composition for a bladder used for manufacturing a bladder for vulcanizing tire, in which 1 to 5 parts by mass of a polymer having a weight average molecular weight Mw of 1,000,000 or more is blended in 100 parts by mass of a rubber component containing butyl rubber as a main component, and a method for manufacturing a bladder for vulcanization of tires characterized in that the bladder for vulcanization of tires is manufactured by an extrusion molding and an injection molding of a rubber composition for a bladder, in the rubber composition for a bladder, 1 to 5 parts by mass of a polymer having a weight average molecular weight Mw of 1,000,000 or more is blended with 100 parts by mass of a rubber component containing butyl rubber as a main component, and the injection molding of the rubber composition for a bladder is carried out while performing vacuum suction.

Claims

1. A rubber composition for a bladder used for manufacturing a bladder for vulcanizing a tire which comprises: 1 to 5 parts by mass of a styrene-butadiene rubber having a weight average molecular weight Mw of 1,000,000 or more blended in 100 parts by mass of a rubber component containing butyl rubber as a main component.

2. The rubber composition according to claim 1, wherein the styrene-butadiene rubber is a high styrene rubber.

3. A method for manufacturing a bladder for vulcanization of tires which comprises: extrusion molding a rubber composition for a bladder using an extruder to form an extruded rubber composition, followed by injection molding the extruded rubber composition into a bladder mold while performing vacuum suction, wherein the rubber composition for a bladder comprises 1 to 5 parts by mass of a styrene-butadiene rubber having a weight average molecular weight Mw of 1,000,000 or more blended with 100 parts by mass of a rubber component containing butyl rubber as a main component.

4. A tire vulcanizing bladder used for vulcanization molding of a pneumatic tire, which comprises 1 to 5 parts by mass of a styrene-butadiene rubber having a weight average molecular weight Mw of 1,000,000 or more blended in 100 parts by mass of a rubber component containing butyl rubber as a main component, and which has a thermal conductivity of 0.38 W/m.Math.K or more.

5. The tire vulcanizing bladder according to claim 4, wherein the thickness of the bladder is 5 to 15 mm.

6. The tire vulcanizing bladder according to claim 4, wherein the styrene-butadiene rubber is a high styrene rubber.

Description

EXAMPLES

(1) Hereinafter, the present invention will be described in detail with reference to examples.

(2) 1. Production of Rubber Composition for Bladder

(3) In accordance with the compounding recipe shown in Table 1, each compounded material was charged into a Banbury mixer and kneaded to obtain a rubber composition for a bladder.

(4) The specific compounding materials are as follows. IIR: BUTYL 268 manufactured by Exxon Mobil Chemical Company Ultra high molecular weight component: SLR 6430 (linear high polymer type high styrene SBR, Mw: 2 million) manufactured by Dow Chemical Company

(5) CR: 1066 manufactured by Exxon Chemical Company

(6) Carbon black-1: T-NS carbon black

(7) Carbon black-2: DENKA black manufactured by DENKA Co., Ltd. (acetylene black)

(8) Oil: NC 300 SN (aroma process oil) manufactured by JXTG Nippon Oil & Energy Corporation

(9) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd.

(10) Phenolic resin: Tackirol 201 (alkyl phenol formaldehyde resin) manufactured by Sumitomo Chemical Co., Ltd.

(11) Next, the obtained rubber composition for a bladder was extruded into a band shape while sucking a gas component by vacuum using an extruder.

(12) 2. Manufacture of Bladder

(13) Next, the extruded rubber composition was injected toward the bladder mold and vulcanized at 190 C. for 30 minutes to produce a bladder (thickness 7 mm) of 195/65R15 size. At this time of injection of the rubber composition, suction was carried out appropriately by vacuum as shown in Table 1.

(14) In parallel, a vulcanized rubber composition having a size of 100 mm in length50 mm in width10 mm in thickness was prepared by vulcanizing the extruded rubber composition at 190 C. for 30 minutes, thus a test piece for measurement of thermal conductivity was prepared (The sample is homogeneous, the measurement surface is smooth).

(15) 3. Evaluation

(16) Evaluation was made on the following items.

(17) 1) Processability

(18) By measuring ML.sub.1+4 (100 C.) for each rubber composition, the processability as an index of fluidity at the time of injection molding was evaluated. The results are shown in Table 1. The smaller the ML.sub.1+4 number is, the better the workability can be evaluated.

(19) (2) Thermal Conductivity

(20) The thermal conductivity (W/m.Math.K) of each test piece was measured in accordance with JIS-R2616 under the conditions of a measurement temperature of 25 C. and a measurement time of 60 seconds using a thermal conductivity measuring instrument (QTM-500 manufactured by Kyoto Electronics Industry Co.) was measured. The results are shown in Table 1. The larger the numerical value, the easier it is to pass heat, and the shorter the vulcanization time can be.

(21) (3) Bladder Life Test

(22) Tire molding (vulcanization condition: 185 C., 8 minutes) of 195/65R15 size was repeated using each bladder to check the number of use (vulcanization) until the bladder was punctured. Setting Comparative Example 1 to 100, the index was indicated by the following formula. The results are shown in Table 1. The larger the index is, the longer the life of the bladder is.
(Bladder life index)={(number of times of use of each example)/(number of times of use of comparative example 1)}100

(23) TABLE-US-00001 TABLE 1 Compara- Compara- Compara- Compara- tive tive tive tive Example Example Example Example Example Example (Pfr) 1 1 2 2 3 4 Composition IIR (BUTYL 268) 88 90 85 70 88 85 Ultra high molecular 2 0 5 20 2 5 weight component (SLR 6430) CR (Exxon 1066) 10 10 10 10 10 10 Carbon black-1 25 25 25 25 25 25 (T-NS black) Carbon black-2 30 30 30 30 30 30 (DENKA black) Aroma process oil 5 5 5 5 5 5 Zinc oxide 5 5 5 5 5 5 Phenolic resin 8 8 8 8 8 8 (Tackirol) Vacuum during Apply Apply Apply Apply Not Not injection molding apply apply Processability 58 57 60 78 59 60 ML.sub.1+4(100 C.) Thermal conductivity 0.38 0.30 0.39 0.39 0.31 0.32 (W/mK) Bladder life index 111 100 110 63 101 103

(24) As shown in Table 1, in Examples 1 and 2, ML.sub.1+4 was almost the same as Comparative Example 1, while heat conduction and bladder life index were improved. Therefore, thermal conductivity Improvement and improvement of Bladder Life Index, by suppressing bubble growth by strain hardening, were able to be confirmed.

(25) On the other hand, in Comparative Example 2, it is found that ML.sub.1+4 greatly increases due to addition of an excessive high molecular weight component, resulting in deterioration of fluidity. As a result of this deterioration of fluidity, defects which are regarded as rubber flow defects were observed in a part of the bladder, and it was inferred that the defects were starting points which resulted in early crack injuries which resulted in shortening of bladder life.

(26) Comparative Examples 3 and 4 are examples of the same recipe as in Examples 1 and 2 in which vacuum was not applied during injection molding, and it is understood that thermal conductivity and bladder life index are influenced depending on whether or not the inside of the member is degassed.

(27) Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications can be made to the above embodiment within the same and equivalent scope as the present invention.