KR20030094907A - Rubber composition for innerliner of tubeless type radial pneumatic tire for truck and bus - Google Patents

Abstract

PURPOSE: An inner liner rubber composition of a tubeless radial pneumatic tire for a truck and a bus is provided, to improve the air permeation resistance, the fatigue resistance and the crack resistance. CONSTITUTION: The rubber composition comprises 80-90 wt% of a halogenated butyl rubber; and 10-20 wt% of polystyrene-polyisobutylene-polystyrene block copolymer having a weight average molecular weight of 40,000-80,000, a molecular weight distribution (Mw/Mn) of 1.1-1.2 and a three-arm block and containing 25-45 wt% of polystyrene.

Description

Rubber composition for innerliner of tubeless type radial pneumatic tire for truck and bus}

The present invention relates to a rubber composition for a tire inner liner, and more particularly, to a combination of a polystyrene-polyisobutylene-polystyrene block copolymer having a cephale block structure with a halogenated butyl rubber, air permeability, fatigue resistance and crack resistance. The present invention relates to a rubber composition which improves the properties at the same time and improves the dimensional uniformity during rolling and molding of the inner liner rubber.

Recently, in the case of truck and bus tires, the proportion of tubeless tires that do not use tubes is gradually increasing, unlike in the past when tubes are used.

However, it is common to use halogenated butyl rubber in the inner liner of such a tubeless tire to maintain air permeability. However, when butyl rubber is used, dimensional uniformity is not maintained well in the rolling process and the molding process of the inner liner rubber.

On the other hand, recently, block copolymers containing two kinds of rubbers and plastics, which are not mixed with each other, have both rubbery and plastic properties (aka, thermoplastic elastomers). In the case of such thermoplastic elastomers, individual plastics The phase is sandwiched by a continuous rubber phase to form physical crosslinks. Such block copolymers have properties such as crosslinked rubber below the glass transition temperature on plastics and can be processed like plastics above the glass transition temperature, which is very advantageous for reprocessing than rubber.

Therefore, the present inventors have included the above-mentioned thermoplastic elastomer in the inner liner rubber composition and used together with a conventional halogenated butyl rubber, thereby improving air resistance, fatigue resistance and crack resistance simultaneously, and rolling and forming the inner liner rubber. It was found that the process can improve the dimensional uniformity has been completed the present invention.

The present invention can improve the air permeability, fatigue resistance and crack resistance at the same time and improve the dimensional uniformity during the rolling and molding process of the inner liner rubber. The inner liner rubber composition of the radial pneumatic tire for tubeless trucks and buses The purpose is to provide.

The inner liner rubber composition of the radial pneumatic tire for tubeless truck and bus of the present invention for achieving the above object is 80 to 90% by weight of halogenated butyl rubber as raw material rubber; Polystyrene-polyisobutylene-polystyrene block copolymer having a weight average molecular weight of 40,000 to 80,000, a molecular weight distribution (Mw / Mn) of 1.1 to 1.2, a polystyrene content of 25 to 45% by weight, and having a structure of cephale block It is characterized by containing 20% by weight.

Figure 1 shows a schematic diagram of the linear block structure and the cephale block structure in the polystyrene-polyisobutylene-polystyrene block copolymer, the left side is a linear block structure and the right side is a cephaloc block structure.

The present invention will be described in more detail as follows.

The present invention provides a polystyrene-polyisobutylene-polystyrene block copolymer to improve the air permeability, fatigue resistance and crack resistance, which are required properties of the inner liner, and to improve the dimensional uniformity during rolling and molding of the inner liner rubber. The present invention relates to an inner liner rubber composition mixed with halogenated butyl rubber.

In the present invention, the polystyrene-polyisobutylene-polystyrene block copolymer mixed with halogenated butyl rubber has a weight average molecular weight of 40,000 to 80,000, a molecular weight distribution (Mw / Mn) of 1.1 to 1.2, and a polystyrene content of 25 to 45 weight % And has the structure of a cefal block. This is shown in Table 1 when compared with the general block copolymer.

DN-75 DN-76 DN-77 (present invention block copolymer) PS-P (EP) -PS (Kraton G1650) Structure Linear block Linear block Three arm block Linear block Weight average molecular weight (Mw) 84,000 47,400 68,200 64300 Molecular Weight Distribution (Mw / Mn) 1.12 1.12 1.16 1.19 Styrene Content (wt%) 23.9 37.1 35.3 29.0 DN-75: Polystyrene-polyisobutylene-polystyrene block copolymer (linear, molecular weight ↑) DN-76: Polystyrene-polyisobutylene-polystyrene block copolymer (linear, molecular weight ↓) DN-77: Polystyrene Polyisobutylene-polystyrene block copolymer (cephaloc) PS-P (EB) -PS: Obtained by polymerizing polystyrene and polybutadiene and then reducing and saturating the double bond in the polybutadiene moiety.

In the description of Table 1, a schematic diagram of the linear block structure and the cephaloc block structure is shown in FIG. 1. In FIG. 1, the left side is a schematic diagram which shows linear diblock and a triblock copolymer, and the right side is a schematic diagram of the polystyrene-polyisobutylene-polystyrene block copolymer which has a cephale block structure which concerns on this invention.

In the present invention, the polystyrene-polyisobutylene-polystyrene block copolymer having a cephale block structure is included in the halogenated butyl rubber at about 10 to 20% by weight.

Polystyrene-polyisobutylene-polystyrene block copolymer having a cephale block structure has the characteristics of plastic and rubber at the same time, so it can be used together with halogenated butyl rubber to improve the air permeability, fatigue resistance and crack resistance of the inner liner rubber. It is also possible to improve the dimensional uniformity in the rolling process and the molding process of the inner liner rubber.

In addition, halogenated butyl rubber is generally used as a raw material rubber in the inner liner rubber composition, and has excellent air permeability due to the chemical structure of the butyl group.

In addition, of course, the present invention may add other compounding agents in a conventional compounding amount, specifically, 60 parts by weight of carbon black, 6 parts by weight of aromatic oil, 8 parts by weight of processing aid, 5 parts by weight of resin, stearic acid 0.5 parts by weight, 2 parts by weight of vulcanization accelerator, 2 parts by weight of zinc oxide as vulcanizing agent, and 1 part by weight of sulfur may be added.

The inner liner rubber composition according to the present invention is an optimal combination that can simultaneously improve the dimensional uniformity, air permeability, fatigue resistance and crack resistance during processing.

Hereinafter, the effect was demonstrated by carrying out the test comparison of the characteristic of the rubber composition manufactured by the Example and the comparative example with the effect obtained by implementing this invention.

Examples 1-2 and Comparative Examples 1-4

As shown in Table 2, a rubber sheet was prepared by blending the blending agent using a half-barrier mixer. The rubber sheet was quenched in a vulcanization press at 170 ° C. for 15 minutes to prepare test specimens, and then modulus, air permeability, crack growth resistance, and fatigue resistance were measured, and the Mooney viscosity was measured at Monsanto. It measured by the produced MV2000. The results are shown in Table 3 below.

Example Comparative Example One 2 One 2 3 4 Halogenated Butyl Rubber - - 100 - - - 90% Halogenated Butyl Rubber-10% DN-75 - - - 100 - - 90% Halogenated Butyl Rubber-10% DN-76 - - - - 100 - 90% Halogenated Butyl Rubber-10% G1650 - - - - - 100 90% Halogenated Butyl Rubber-10% DN-77 100 - - - - - 80% Halogenated Butyl Rubber-20% DN-77 - 100 - - - - Carbon black 60 60 60 60 60 60 oil 6 6 6 6 6 6 Processing aid 8 8 8 8 8 8 Suzy 5 5 5 5 5 5 Stearic acid 0.5 0.5 0.5 0.5 0.5 0.5 Vulcanization accelerator 2 2 2 2 2 2 Zinc oxide 2 2 2 2 2 2 brimstone One One One One One One

Example Comparative Example One 2 One 2 3 4 Die swell % (Shear rate 3.5 Hz) 32 28 45 36 37 35 Tensile Initial Properties 300% modulus 38 44 35 37 32 39 Elongation at Break (%) 822 823 821 821 891 769 Tensile strength (kgf / ㎠) 93 108 86 90 78 96 Breaking energy (kgf / ㎡) 382 444 353 369 347 369 Tensile (100 ℃ X Note) 300% modulus 42 47 41 42 39 46 Elongation at Break (%) 757 756 750 752 832 653 Tensile strength (kgf / ㎠) 88 101 82 86 75 86 Breaking energy (kgf / ㎡) 333 382 308 323 312 281 Tensile (100 ℃ X Note) 300% modulus 46 50 46 47 43 51 Elongation at Break (%) 692 688 683 694 743 543 Tensile strength (kgf / ㎠) 84 94 78 83 72 81 Breaking energy (kgf / ㎡) 291 323 366 288 267 220 Heat resistance Breakage Energy Retention Per Week 87.3 85.3 86.8 88.3 87.7 77.2 Fatigue Resistance (Kcycle) Room temperature 592 551 455 581 576 572 100 degrees Celsius X 554 514 387 542 538 423 100 degrees Celsius X 508 463 321 498 502 328 Crack growth resistance (㎛ / cycle) Room temperature 3.5 3.7 5.9 3.4 3.6 5.7 100 degrees Celsius X 4.5 4.7 7.8 4.4 4.3 8.1 100 degrees Celsius X 5.4 5.5 9.3 5.3 5.5 10.1 Air permeability index × 10 ^-10 (㎡ / secN) 1.10 0.89 1.42 1.16 0.95 1.58 (1) Fatigue resistance was measured by fatigue to failure tester by measuring 6 samples under 118% strain condition and 50 times remaining rate of 6 samples was obtained. (2) Crack growth resistance was measured in 13mm sample. A crack of 1 mm is applied to the tip of the sample and the number of times until the sample breaks at 118% strain in the fatigue to failure tester is measured. (3) The smaller the air permeability index, the better the air permeability.

From the results in Table 3, first, in the case of using the polystyrene-polyisobutylene-polystyrene block copolymer of the present invention in the die swell showing the dimensional uniformity during processing, The die swell value is bad.

This can be said to be a high dimensional uniformity during processing when using the polystyrene-polyisobutylene-polystyrene block copolymer according to the present invention. In particular, it can be seen that Example 1 and Example 2 using DN-77 having a cephaloc block structure rather than a linear block has the best dimensional uniformity during processing.

Second, in the case of air permeability, Comparative Example 4 having a site where polybutadiene is reduced in the block copolymer has poor air permeability even in comparison with Comparative Example 1. However, when the block copolymer containing isobutylene group is applied, air permeability is improved in common compared with the comparative example 1. In particular, in the case of Example 2 of the present invention containing 20% by weight of polystyrene-polyisobutylene-polystyrene block copolymer it can be seen that the air permeability is improved by about 78%.

Third, in the case of fatigue resistance, when the polystyrene-polyisobutylene-polystyrene block copolymer is included in about 10% by weight, it is improved by about 30% compared to Comparative Example 1, which does not use it. However, when the block copolymer ratio is increased from 10% by weight to 20% by weight, fatigue fatigue may be found to decrease slightly.

Fourth, in the case of crack resistance, Comparative Example 4 having the site where the polybutadiene was reduced in the block copolymer was substantially equivalent to Comparative Example 1 in which the block copolymer was not used, but in the block air containing isobutylene groups. When coalescing is applied, crack resistance improves compared with the comparative example 1 in common.

In conclusion, Example 2 using 100% by weight of 80% halogenated butyl rubber-20% DN-77 block copolymer shows the most optimum physical properties in terms of air permeability and dimensional uniformity during processing.

As described in detail above, the inner liner rubber composition in which a polystyrene-polyisobutylene-polystyrene block copolymer having a cephaloc block structure according to the present invention is mixed with a halogenated butyl rubber has air resistance, fatigue resistance and crack resistance. At the same time, it is possible to improve the dimensional uniformity in the rolling process and the molding process of the inner liner rubber.

Claims (1)

80 to 90% by weight of halogenated butyl rubber as raw material rubber; Polystyrene-polyisobutylene-polystyrene block copolymer having a weight average molecular weight of 40,000 to 80,000, a molecular weight distribution (Mw / Mn) of 1.1 to 1.2, a polystyrene content of 25 to 45% by weight, and having a structure of cephale block An innerliner rubber composition for radial pneumatic tires for tubeless trucks and buses comprising 20% by weight.