JPS61103948A - Rubber composition - Google Patents

Abstract

PURPOSE:To provide the titled composition having low rolling resistance and heat-generation, and high breakage strength, by compounding a rubber composed mainly of an isoprene-butadiene random copolymer containing cis-1,4-bond with carbon black and a vulcanizing agent. CONSTITUTION:An isoprene-butadiene random copolymer containing >=90% cis-1,4 bond, or a mixture of said copolymer and one or more other diene rubbers is used as a stock rubber, and is compounded with carbon black and a vulcanizing agent. The isoprene-butadiene random copolymer is the one having an isoprene-content of 40-95(wt)%, and its amount in the stock rubber is >=20%. The other diene rubber is natural rubber, polyisoprene rubber or polybutadiene rubber (having a cis-bond content of >=90%) and its amount in the stock rubber is >=20%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J The present invention has low rolling resistance and heat generation, and has good breaking strength. The present invention relates to a rubber composition suitable for tire treads and tire sidewalls, and specifically relates to a rubber composition containing as a raw rubber a random copolymer of isoprene-butadiene copolymer whose bonding mode is cis.

[Prior Art] In recent years, reducing fuel consumption has become an important issue in the automobile industry, and low rolling resistance is one of the properties required of tires for the purpose of reducing fuel consumption. Conventionally, in order to reduce the rolling resistance of tire treads, natural rubber, polybutadiene rubber, solution-polymerized styrene-butadiene copolymer, or blends thereof, which have low rolling resistance and excellent heat generation properties, have been used as tread rubber. A rubber composition consisting of

[Problems to be Solved by the Invention] Although the use of these rubbers or rubber compositions improves rolling resistance and heat generation, they cannot be used in traffic or bus tires or in relatively harsh conditions. As a tire for a passenger car, etc., the performance in terms of mechanical strength such as breakage resistance and abrasion resistance has not yet been sufficient.

That is, tires using natural rubber have problems with wear resistance, and in particular, parts of the tire tread wear selectively, resulting in so-called uneven wear that shortens the life of the tire. . Also, in tires that use polyphtadiene rubber.

Repeated compressive fatigue in the tread portion causes mechanical anisotropy, which causes the rubber to peel off from the tread surface, leading to failure. So-called chipping
ng). In a tire made of a rubber composition containing a solution-polymerized styrene-butadiene copolymer,
Due to the low breaking strength, when the tire is removed from the mold during the vulcanization process during tire manufacturing, the pattern of the tread may be damaged by the mold, so-called mold chipping. While driving, stones become lodged in the recesses of the tread pattern, causing trouble such as stone entrapment, which damages the tread.

1. Rubbers or rubber compositions conventionally used as having good heat generation properties and rolling resistance do not have sufficient fatigue fracture properties such as fracture strength and wear resistance, and are suitable for use in large vehicle tires and severe Strict provisions (.

The tire material used in this case was not fully satisfactory.

[Means for Solving the Problems] The present invention solves the above conventional problems and provides a rubber composition that has improved fracture resistance and abrasion resistance, as well as improved heat generation and rolling resistance. It is intended for that purpose.

In a rubber composition containing a raw rubber, carbon black, and a vulcanizing agent, an imprene-butadiene random copolymer alone in which the raw rubber contains 90% or more of cis-1,4 bonds,
Alternatively, a rubber composition characterized in that it is a mixture of the copolymer and one or more other diene rubbers.

The main points are as follows.

The present invention will be explained in detail below.

In the rubber composition of the present invention, the random copolymer of isoprene and butadiene used as the raw material rubber is one in which both isoprene bonds and butadiene bonds are 90% or more of cis-type 1.4 bonds ( (hereinafter referred to as "high cis type"), if the cis 1,4 bond is less than 90%, bonds other than cis type bonds, such as vinyl bonds, will significantly increase the glass transition point of the rubber composition. As a result, the viscous behavior of the rubber becomes noticeable, the heat generation property decreases, the rolling resistance increases, and the breaking properties decrease, etc., and it is unsuitable for use in the present invention. It is portrait.

In addition, in the present invention, the imprene-butadiene lantum co-1i combination contains 40 to 95 units of imprene monomer.
It is preferable from the viewpoint of breaking strength that the content is preferably 50 to 90 weight %, more preferably 65 to 80 weight %.

If the imprene content is less than 40% by weight, sufficient fracture strength may not be obtained, and the composition may have poor fracture resistance such as stone bite and chipping, and may not be able to exhibit excellent effects as a rubber composition for tire treads.

The inprene-butadiene random copolymer used in the present invention is preferably a combination of a lanthanum series rare earth element compound (hereinafter referred to as "rLa compound"), an organoaluminium compound, a Lewis base, and, if necessary, a Lewis acid. It can be produced by polymerizing imprene and butadiene in the presence of a catalyst consisting of:

Here, as the La compound, metal halides, carbonate salts, flucorates, thioalcolades, amides, etc. of 1M metal numbers 57 to 7L are used. Also, as an organoaluminum compound.

General formula ALAiL+ R2R3 (where R1, R2,
R3 each represents hydrogen or a hydrocarbon residue having 1 to 8 carbon atoms; R+, R2, and R3 may be the same;
In addition, those indicated by ) are used, which may be different.

Lewis bases are preferably used to complex La compounds, such as acenaracetone, ketone alcohols, and the like.

As a Lewis acid, the general formula A fLx , R3-n (
or halogen, R is a hydrocarbon residue, and is n-1, 1, 5, 2 or 3. ) or other metal halides are used.

In addition, in the presence of the above catalyst, isoprene and butadiene are usually used in a molar ratio of 5 x 102 to 5 x 1O, particularly 103 to 10'.
It is preferable that A L R+ R2Rz
/La compound has a molar ratio of 5 to 500, especially lO to 3
It is preferable to set it as 00, and furthermore, Lewis base/L
The molar ratio of compound a is preferably 0.5 or more, particularly 1 to 20.

In addition, when using a Lewis acid, the halide/
The La compound has a molar ratio of 1.0 to 10. Preferably 1
．． 5-5.

In addition, the above-mentioned La compound catalyst can be used in a state dissolved in a solvent or supported on silica, magnesia, magnesia chloride, etc. during the polymerization of isoprene-butadiene.

During polymerization, bulk polymerization may be performed with or without a solvent. The polymerization temperature is usually -30 to 150°C.
, preferably from 10 to 80°C, and the single polymerization pressure can be arbitrarily selected depending on the conditions.
f. The rubber composition of the present invention includes the above-mentioned isoprene rubber.
The above-mentioned isoprene-butadiene random copolymer alone or this copolymer and one other! ! A mixture with the above-mentioned diene rubber is used as the raw material rubber. In the present invention, it is desirable that the inprene-butadiene random copolymer is contained in the raw material rubber in an amount of 20% by weight or more. Copolymer content is 20
If the amount is less than % by weight, the effect of improving heat generation properties and breaking strength of the resulting rubber composition may be small.

Other diene rubbers that can be used in combination with the isoprene-butadiene random copolymer include natural rubber, polyimprene rubber, polybutadiene rubber, or a rubber composition that is a blend of two or more of these rubbers. In particular, it is preferable to use natural rubber, polyisoprene rubber, a blend rubber composition of natural rubber and polyisoprene rubber, and polybutadiene rubber.The mixing ratio of these rubbers is preferably 20% by weight or more in the raw rubber. preferable.

In addition, when using a mixture of imprene-butadiene random copolymer with polyisoprene rubber or polybutadiene rubber, the polyisoprene rubber or polybutadiene rubber contains a large number of cis bonds, preferably 90% or more. is suitable. Such high-cis type polyimprene rubber or polybutadiene rubber is easily compatible with the high-cis type imprene-butadiene random copolymer constituting the rubber composition of the present invention, so that a uniform composition can be obtained. As a result, a rubber composition with significantly improved breaking strength can be obtained. When polyimprene rubber and polybutadiene rubber are low cis type with a cis bond content of less than 90%, desired compatibility cannot be obtained, and the fracture properties of the resulting rubber composition are likely to deteriorate. Furthermore, rubber compositions containing these low-cis type polymers have an increased glass transition point and increased viscous behavior, resulting in poor heat generation properties.
In some cases, the problem of increased rolling resistance may occur.

The rubber composition of the present invention is formed by blending the raw rubber as described above, carbon black, a vulcanizing agent, and other additives as necessary, but the blending method and blending ratio of these are different from that of conventional rubber compositions. As the other additives, it is possible to use various compounding agents commonly used in rubber compositions for tires. Specifically, reinforcing agents, softening agents,
Fillers, vulcanization accelerators, anti-aging agents, etc. are included, and are appropriately selected and used depending on the purpose.

The rubber composition of the present invention can be suitably used in a wide range of applications, such as carcass rubber and belt rubber, in addition to outer cover members such as tire treads, sidewalls, and rubber chafers.

[Function] By using an inprene-butadiene random copolymer containing 90% or more of cis-1,4 bonds as the raw rubber, heat generation properties and rolling resistance are improved, and wear resistance, fracture resistance, etc. A rubber composition with significantly improved mechanical strength can be obtained.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Example 1, Comparative Examples 1 to 4 (1) Production of high-cis type inprene-butadiene random copolymer First, the method for polymerizing the inprene-butadiene random copolymer used in this example will be explained.

2500 g of cyclohexane and 350 g of isoprene in a 51 autoclave under nitrogen atmosphere.

150 g of 1.3-butadiene was charged and the temperature was adjusted to 60°C.

In a separate container, 2-ethylhexane-brewed neodymium/acetylacetone/triisobutylaluminum/diethylaluminum chloride were added and mixed in a molar ratio of 1:2:40:4, and the mixture was heated at 50°C in the presence of a small amount of isoprene.
A catalyst was prepared by aging for 0 minutes.

This aged catalyst is used as isoprey and butadiene mono “F-1”.
, 1 mole of neodymium per 2X10'7
1. .

After confirming that the polymerization conversion rate was 100%, 4 g of 2,6-di-tert-butylcatechol was added to 5 mA of methanol and the polymerization reaction was carried out at 60°C for 7 hours. The reaction was terminated by adding the solution.

The obtained polymer cement was poured into methanol in a conventional manner to recover the polymer, and then the polymer was dried in a vacuum dryer at 60° C. to obtain 480 g of polymer. The Mooney viscosity (ML) of this polymer was 50.

4. The composition and microstructure of the obtained polymer (hereinafter referred to as "Polymer A") were determined by NMR (JEOL Ltd. JE
OL GX-400). The results are shown in Table 1.

Table 1 (Unit: % by weight) ■ Production of tire tread A rubber composition was prepared using the polymer shown in Table 2 according to the formulation shown in Table 3. Then, a tire tread was manufactured using the obtained composition under vulcanization conditions of 145°C x 2
0m1n), steel radial tires (165sP13
), tire performance was evaluated according to the evaluation method described below.

The results are shown in Table 4.

No. 2 Mugi Zero 1: Polybutadiene (BROI manufactured by Nippon Gosei Rubber Co., Ltd.) Book 2: Polyisoprene (IR2200 manufactured by Nippon Gosei Rubber Co., Ltd.) t3: Isoprene-butadiene copolymer (organolithium in an inert *organic solvent) Polymer polymerized using an initiator)! 4=Block copolymer Table 3 (1i parts) ■Evaluation method 1.15 Rolling resistance is determined by drum inertia method (internal pressure 2 kg/kg, load 3
00Kg) and expressed as an index. index 100
=2.7Kg, and the lower the index, the better the performance.

The wear resistance was measured by measuring the groove depth of the tires mounted on a taxi and traveling in the field after a mileage of 50,000 km, and expressed as an index. The index 100 corresponds to 3.5 mm, and the higher the index, the better the performance.

Note that the groove depth of the new tire was 8 mm.

Emperor Tadasu Rock-bite fracture resistance was measured in the above field test.

The presence or absence of pattern destruction due to stone bite was observed.

Regarding mold chipping, three identical tires were manufactured and the presence or absence of pattern damage caused by the mold was observed.

Table 4 (Tire Performance) From Table 4, it is recognized that tires with good performance can be manufactured using the rubber composition of the present invention.

Examples 2 to 4 Tires were manufactured using rubber compositions prepared in the same manner as in Example 1, except that the polymer having the composition shown in Table 5 was used, and tire performance was evaluated in the same manner.

The results are shown in Table 6.

Table 5 (weight%) S: Same as in Table 2.

Attack 6D S manufactured by Asahi Kasei Corporation. Iprene”1204th
Table 6 (Tire Performance) From Table 6, it is recognized that tires with good performance can be manufactured using the rubber composition of the present invention. In particular, when the content of the high-cis isoprene-butadiene random copolymer in the raw material rubber is 20% by weight or more, an extremely good rubber composition can be obtained.

[Effects] As detailed above, the rubber composition of the present invention has [isoprene containing 90% or more of cis-1,4 bonds as the raw rubber]
It uses a butadiene random copolymer alone or a mixture of the copolymer and one or more other diene rubbers, and has improved heat generation properties and rolling resistance, as well as fracture resistance and abrasion resistance. Mechanical properties such as these are significantly improved.

Therefore, the rubber composition of the present invention is suitable for tires for large vehicles and tires used under severe conditions, and is suitable for use in tire treads, side rolls, outer cover members such as rubber chafers, and other tire rubber, belt rubber, etc. suitable for a wide range of applications).

Claims (6)

[Claims] (1) In a rubber composition containing raw rubber, carbon black, and a vulcanizing agent, the raw rubber contains 90% of cis-1.4 bonds.
A rubber composition comprising the above-contained imprene-butadiene random copolymer alone, or a mixture of the copolymer and one or more other diene rubbers. (2) The rubber composition according to claim 1, wherein the isoprene-butadiene random copolymer contains 40 to 95% by weight of isoprene. (3) The rubber composition according to claim 1 or 2, wherein the raw rubber contains 20% by weight or more of the isoprene-butadiene random copolymer. (4) Any one of claims 1 to 3, characterized in that the diene rubber other than the isoprene-butadiene random copolymer is selected from natural rubber, polyisoprene rubber, or polybutadiene rubber. Rubber composition according to item 1. (5) The rubber composition according to claim 4, wherein the polyisoprene rubber and polybutadiene rubber contain 90% or more of cis-type bonds. (6) Claim 4 or 5, characterized in that the raw rubber contains 20% by weight or more of a diene rubber other than the isoprene-butadiene random copolymer.
The rubber composition described in .