JPS60192739A - Rubber composition - Google Patents

Abstract

PURPOSE:A rubber composition exhibiting excellent wet- and ice-skid characteristics, rolling friction characteristics, and breaking characteristics, suitable for a tire tread, containing a specified block copolymer obtained by copolymerizing styrene and butadiene. CONSTITUTION:Styrene and butadiene are copolymerized to obtain initially about 95-100wt% styrene-butadiene copolymer block (A) containing styrene in an amount of 10-80wt% and the butadiene part having an average vinyl-bond content (alpha) of 30-70wt%, and further polymerized with additional monomers fed in to obtain a polybutadiene copolymer block (B) having the aforementioned alpha of 60wt% or less. At least 20wt% block copolymer in which at least 20wt% component A and at least 20wt% component B are contained, the alpha of component A is at least 5wt% higher than that of component B, the glass transition temperature of component A is at least 30 deg.C higher than that of component B, and the total bonded styrene content is 5-40wt%, and of which at least 20wt% is a branched block copolymer coupled with a coupling agent containing 3-4 functionalities is compounded with a natural rubber, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber composition suitable for tire treads, which is made of styrene and butadiene as raw materials and is made of a block copolymer having two different blocks.

Recently, the requirements for automobile running stability and fuel efficiency have become even more stringent. There has been a strong demand for rubber that has high ice skid resistance and low rolling friction resistance. However, it is difficult to satisfy these properties at the same time, and in particular, wet skid properties, ice skid properties, and rolling friction properties are in contradictory relationships. Among conventional polymers, polymers with relatively high glass transition temperatures (Tg) such as emulsion polymerized SBH have good wet skid properties, while polymers with low Tg, such as high cis 1.4-BR, have good ice skid properties. Good rolling friction characteristics. However, ice skid characteristics are characteristics at low temperatures, and rolling friction characteristics are characteristics at temperatures above room temperature. Although this is a necessary condition for good rolling friction characteristics, it is difficult to say that it is a sufficient condition. In other words, when the above properties are expressed as viscoelastic index of vulcanized rubber, wet skid property is -δ near 0℃ (the larger the better), ice skid property is the glass transition temperature (the lower the better), and rolling friction. Characteristics are 50~
It is expressed as tan δ at 70° C. (the smaller the better), and there is a contradiction in satisfying the required characteristics at the same time. Therefore, by blending different types of polymers,
Attempts have been made to reconcile the above contradictory characteristics, but
Even if some improvement has been made, it has not yet reached the point where it satisfies the currently required performance.

In recent years, S mainly obtained using organolithium initiators
Attempts were made to modify DR and BR, and butadiene (hereinafter referred to as BD)
SB with a relatively high vinyl bond content in the
R and I3R have greatly improved the balance of wet skid characteristics and rolling friction characteristics compared to conventional emulsion polymerized 5BR1 natural rubber and high-cis 1.4-BR (
JP-A-54-62248, JP-A-56-110753
(British Patent No. 1166832, etc.). However, the above polymers have poor ice skid properties and cannot satisfy the required performance targeted by the present invention.

The present inventors conducted studies to further improve the wet skid properties and rolling friction properties of styrene-butadiene copolymers obtained using organolithium initiators. By using a block copolymer consisting of two block parts with different amounts of vinyl bonding metal or a branched polymer thereof, the above properties are improved, and the two block parts with different glass transition points are made compatibilized through the vulcanization process. As a result, we obtained an interesting finding that the peak of the dispersion curve at temperature −1 δ obtained by the kinetic measurement method becomes broad (%Kasho 57-109817
No. 57-200439).

The present inventors further investigated this phenomenon in which the peak of the temperature-tan δ dispersion curve becomes broad, and found that by making the difference in glass transition temperature (Tg) of each block part of the polymer a constant value, It was discovered that wet skid characteristics, ice skid characteristics, and rolling friction characteristics can be balanced, leading to the present invention.

That is, the present invention provides a block copolymer obtained by copolymerizing styrene and butadiene, comprising: (1) a styrene content of 10 to 80% by weight, and an average vinyl bond content of the butadiene portion of 30 to 70% by weight; styrene
A butadiene copolymer block is used as a copolymer block prisoner, (11) the average vinyl bond content of the butadiene part is 601
The following polybutadiene block is a copolymer block [F
]), (ii+) each of copolymer block (to) and copolymer block I is contained at least 20 times or more, and (1v) the average vinyl bond content of the butadiene moiety of the copolymer block is , the average vinyl bond content of copolymer block 0 is 5% or more larger (V) The copolymer block has a glass transition temperature higher than copolymer block 0 by (capital) ℃ or more, (■1) The total bound styrene content of the block copolymer is 5 to 40% by weight (ViD the weight of the block copolymer is 3 to 4%).
It is a branched proton copolymer coupled with a functional coupling agent, and (Vii+) in the above block copolymer, the distribution of the vinyl bond content of the butadiene moiety of each copolymer block is at least 10%, and the rubber composition contains at least a weighted amount of the block copolymer.

Compared to the copolymers disclosed in JP-A-57-102912 and JP-A-57-109817, the rubber composition of the present invention contains: (1) a block copolymer having a branched block copolymer; ■There is a difference in the limiting conditions of the block part (4) and 0, and the fracture characteristics are significantly superior.

Furthermore, in JP-A No. 57-200439, by incorporating a carbon-metal bond into a block copolymer,
It has excellent wet skid characteristics, rolling friction characteristics, and breaking characteristics. However, the block copolymer of the present invention
Compared to the block copolymer disclosed in JP-A-57-200439, it has an excellent balance of ice skid properties and wet skid properties. This excellent property can be obtained by having each of the copolymer blocks (A), (Bl) having a vinyl bond content distribution of at least 10%.

Furthermore, by appropriately selecting the bound styrene content in each block part of the block copolymer of JP-A-57-200439 and the vinyl bound metal content in the butadiene part, physical properties close to those of the composition of the present invention can be obtained. However, the balance between ice skid characteristics and wet skid characteristics is not sufficient. Therefore, in the present invention, the physical properties are improved by providing each block with a distribution of vinyl bonds. Although the cause is not necessarily clear, the peak of the temperature - δ dispersion curve after vulcanization of the block copolymer is broadened by expanding the Tg region temperature of the copolymer block polymer [F]). The elastic modulus of the Tg region (E5
This means that the rate of change in the wet skid characteristics measured at room temperature has become more gradual.
It is thought that this worked effectively to improve the ice skid characteristics measured in the -10°C range.

In addition, metals other than Sn, such as Si, Ge, P
In the case of b, the ice skid characteristics, rolling friction characteristics, and fracture characteristics are unsatisfactory.

That is, by providing at least one of the copolymer blocks of the block copolymer with a vinyl bond content distribution, the fracture characteristics are improved (Patent Publication No. 57-102912), and the molecular chain Carbon-metal (
It is known that breaking properties are improved by introducing Sn) bonds (Japanese Patent Application Laid-Open No. 57-200439), but by forming a limited block copolymer as in the present invention, wet The fact that a stone has a good balance of skid properties, ice skid properties, rolling friction properties, and fracture properties is a completely new finding and cannot be easily deduced from the above-mentioned known facts. In addition, JP-A-57-165445 discloses a block copolymer having two block parts with different amounts of combined styrene content, and a part of which becomes a branched polymer through a coupling reaction. , a composition with excellent heat resistance and wear resistance is disclosed. The composition has the desired balance of physical properties, especially wet skid! 1' It is not possible to obtain a balance between the yen property and the ice skid property.

The excellent balance of wet skid properties, ice skid properties, and rolling friction properties obtained by the present invention is achieved by combining two copolymers with different kinomer compositions and glass transition temperatures that differ by more than a certain value. It is obtained by using a block copolymer that has been formed into blocks through a polymerization process, and a portion of which has become a branched copolymer through a coupling reaction.

Simply blending the above copolymer (g) and copolymer (2) does not provide the physical properties targeted by the present invention.

'The block copolymer of the present invention can be obtained by adiabatic or elevated temperature polymerization using an organolithium initiator in the presence of a polar compound such as an ether compound or a tertiary amine compound. First, the copolymer block or copolymer block (b) is polymerized, then the other block is polymerized, and then a coupling agent is added to form a branched/copolymer-containing block. A copolymer is obtained. The amount of vinyl-bonded gold in the butadiene moiety can be controlled by changing the amount of the polar compound in the polymerization system or the polymerization temperature in adiabatic or temperature-programmed polymerization. Moreover, the distribution rlJ of vinyl bonds in the butadiene moieties in each block part of the block copolymer can be controlled by -C by the polymerization temperature rlJ in adiabatic and temperature-programmed polymerization.

As the coupling agent, tri- to tetrafunctional (7) compounds are used, and among these, tin halide compounds are particularly preferred, and it is most preferred that the bond in the molecular chain is a butadienyl-8n bond.

The content of the branched block copolymer is at least 20% by weight, preferably at least 30% by weight. If the weight is less than 20% by weight, the breaking properties and ice skid properties of the rubber composition will be poor, which is not preferable.

The upper limit of the content of the branched block copolymer in the block copolymer of the present invention is not particularly limited, but 8
It is industrially very difficult to obtain a weight coefficient of 0 or more.

When obtaining a block copolymer of Moida()3 R-S B 11→-8n type, a small amount of butadiene may be added before the coupling reaction in order to generate more butadienyl-8n bonds. preferable.

The content of bound styrene is 10 to 8 in the copolymer.
The total bound styrene content in the block copolymer is in the range of 0% by weight, preferably 20 to 80% by weight, more preferably 25 to 75% by weight, and the total bound styrene content in the block copolymer is 5 to 40% by weight, preferably 10 to 75% by weight. It is 40% by weight, more preferably 15 to 35% by weight. The bound styrene content of copolymer block (2) is 10 ffi J! If it is less than 1, the wet skid characteristics will be unsatisfactory. If the bound styrene content of the copolymer block exceeds 80% by weight, the rolling friction properties and breaking properties will be poor, which is not preferable. Copolymer block (■) does not contain bound styrene. If styrene is included, the balance between wet skid characteristics and ice skid characteristics will be poor. If the total bound styrene content of the block copolymer is less than 5% by weight, the fracture properties and ice skid properties will be poor, and if it exceeds 40% by weight, the rolling friction properties and ice skid properties will be poor and unsatisfactory.

In the copolymer block (1) of the block copolymer of the present invention, the polystyrene block consisting of nine or more chains of bonded styrene has a styrene content of 2% of the styrene content of the copolymer block (2).
When the weight is in the range of 35 to 25, preferably 3 to 25, the balance between wet skid characteristics and ice skid characteristics is particularly good.

Furthermore, in the block copolymer of the present invention, if the joint between copolymer block (2) and copolymer block (g) contains a polystyrene block, wet skid properties and ice skid properties are improved.

The above polystyrene block has 9 chains of bonded styrenes.
It means more than one block, and is measured by the following measurement method. Carbon tetrachloride solution (2
01n9/0.4mAICc/,, ) was prepared and '
It was measured using H-NMR (FX-100 manufactured by JEOL (a)), and calculated using the following formula from the peak area of styrene.

In order to obtain the above polystyrene block, the amount of randomizing agent such as ether or tertiary amine must be adjusted depending on the charging ratio of styrene/butadiene during polymerization of the copolymer block, or There are methods such as polymerizing styrene in the latter half of the polymerization of (a) or after the completion of the polymerization, and then polymerizing the copolymer block (2), but the former is preferable from the point of view of industrial production.

The average vinyl bond content of the butadiene moiety is 30 to 70% by weight, preferably 35 to 70% by weight in the copolymer block (4).
70% by weight, and in the case of (co)polymer blocks, it is 60% by weight or less, preferably 55% by weight or more.

The distribution of vinyl bonds in each block is essential for improving wet skid properties, ice skid properties, and fracture properties. 101 or more in the distribution, preferably 1
51 or higher is required.

The distribution of vinyl bonds is usually determined by adiabatic polymerization using the fact that the vinyl bond content of the butadiene moiety varies depending on the polymerization temperature when obtaining a butadiene-based copolymer using a catalyst of an organic lithium compound and a polar compound such as ether. It is obtained by expanding it in a temperature of . 40℃~ as shown in the attached drawing
When adiabatic polymerization is carried out in the range of 80°C, the difference between the vinyl bond content at 40°C and the vinyl bond content at 80°C becomes the vinyl bond distribution IJ.

In addition, the copolymer and block copolymer are copolymer block ff
3), the average vinyl bond content is 5% or more by weight larger than that of 3).

If the vinyl bond content of the copolymer block (4) is less than 30% by weight, it is unfavorable for ensuring the glass transition temperature difference between the copolymer block and the copolymer block (2), and it also deteriorates rolling friction properties and wetness. The balance of skid characteristics becomes unsatisfactory. When the amount of vinyl bonding metal exceeds 70% by weight, the fracture properties become poor. Although the all-vinyl bonded metal content of the block copolymer of the present invention is not particularly limited, preferably 2
It ranges from 5 to 60% by weight. Outside this range, the balance between wet skid characteristics and rolling friction characteristics will be poor.

If the difference in the average vinyl bond content between the copolymer block and the copolymer block color falls outside the scope of the present invention, -
This is not preferable for making the temperature dispersion peak of δ broad, and the balance of various physical properties is also poor.

In the block copolymer of the present invention, copolymer block (4) needs to have a glass transition temperature (Tg) higher than (co)polymer block (2) by 30°C or more, preferably -1t, and <40°C or more. It is. If the difference in Tg is less than 0.degree. C., wet skid characteristics and ice skid characteristics cannot be balanced.

In the block copolymer of the present invention, the copolymer block (support) and the copolymer block (2) are contained in an amount of at least 20% by weight or more, preferably 30% by weight or more. If it is less than the weight ratio, the balance between wet skid 4tlE and ice skid characteristics will be poor and unsatisfactory.

Mooney viscosity of the block copolymer of the present invention < ηX to ML
) is preferably 20-150; if it is less than 20, the rolling friction properties will be poor, and if it exceeds 150°C, the workability will be poor.

The block copolymer of the present invention comprises natural rubber, cis 1,4-
One or more types selected from polyisoprene rubber, polybutadiene rubber, other styrene-butadiene copolymer combs, ethylene-propylene-diene (EPDM) copolymer rubber, butyl rubber, halogenated EPDM, and halogenated butyl rubber. Mixed with rubber and cooled.

The content of the block copolymer in the rubber composition of the present invention must be at least 20% by weight or more, preferably 30% by weight or more. It is not possible to satisfy all of the characteristics, ice skid characteristics, and rolling friction characteristics at the same time.

This is because the rubber composition containing the block copolymer obtained by the present invention has good wet skid properties, ice skid properties, and rolling friction properties, and is also excellent in breaking properties.

It can be suitably used as a rubber material for tire treads. In that case, various commonly used compounding agents, such as carbon black, process oil (aromatic oil, naphthenic oil, paraffin oil, etc.), filler, vulcanization accelerator, vulcanizing agent, etc. can be used as is.

The present invention will be described in more detail below with reference to Examples, but the present invention is not limited by these Examples unless the gist of the invention is exceeded.

Examples 1-10, Comparative Examples 1-15 The samples shown in Table 1 were obtained using the polymerization recipe shown in Table 2.

Cyclohexane was used as a solvent, and n was used as a polymerization initiator.
-Using butyllithium, first create a copolymer block (
Polymerization was carried out under the polymerization conditions of 2). The temperature conditions were adiabatic without heating or cooling. Next, after the polymerization conversion rate reached 95 to 100%, a predetermined amount of monomer was further charged and adiabatic polymerization was carried out under the polymerization conditions of copolymer block (1). After the polymerization was completed, a prescribed coupling agent was added. For sample Exp-19, after polymerizing in the order of copolymer block (1) - copolymer block (2), butadiene 59 was added to perform a coupling reaction. Sample Exp-22 was obtained with the same formulation as Exp-19 except that 5 g of butadiene was not added.

The styrene content and vinyl bond content in the polymer were measured using an infrared spectrophotometer.

The content of nine or more bonded styrene chains in the copolymer block (2) is determined by the IH-
I measured NMR and found it. In addition, the first stage polymerization conversion rate is 80
%, the proportion of nine or more bonded styrene chains in the styrene-butadiene copolymer is 0 for all samples, and the polystyrene blocks are copolymer block ■ and copolymer block (B). It was included in the joint. The polymer of sample E x p -19 was
A polystyrene block was formed in the latter half of the stage.

The content of the branched copolymer was determined by gel permeation chromatography (GPC) method (WATER8 Model 200 GPC, fy Ram: 5TYRAGEL-ICP, 1
0', 10' (4 feet) From FIG. 1, it can be seen that the distribution of vinyl bonds in the copolymer block is 201%, and the distribution of vinyl bonds in the copolymer block [F]) is 19%. Similarly, the distribution of vinyl bonds was determined for other samples as well.

Samples Expl-20 were prepared according to the formulation shown in Table 3. The vulcanization conditions were 145°C,
It was a minute. As a result, the properties of the obtained vulcanizate are shown in Table 4. In addition, the wet skid resistance value (room temperature) and -δ at 0°C measured by the Stanley Noskid resistance meter were used as indicators of wet skid characteristics, and the ice skid resistance value measured by the above-mentioned skid resistance meter ( The tensile strength was used as an index of rolling friction resistance (measured value at -10°C).

Examples 1 to 10 have a better balance of wet skid characteristics, ice skid characteristics, and rolling friction characteristics, and also have better fracture characteristics and wear resistance than Comparative Examples 1 to 15.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between polymerization temperature and microstructure in polymerization of block copolymer sample Exp-1 produced in Examples. Fig. 1 Polymerization temperature ("C)" 2- Wa',:,'? 'Ichi Sonomi - Town; - (spontaneous) Showa fk+ July 1959 318 Patent length 1:) Shiga 'P Tono 10.1, l'10) lj 7h: Jar. 1981! 1bi19-1 No. 50095 2, Name of the invention f; 1゜Com composition 3, Relationship with the case of the person making the amendment Special 5゛11 Former head's name (417) 11 Synthetic Comb stock i (company (other l)
4'+ 1 4, Agent 〒1t17 (2 idiots) Contents of amendment +11 Corrected ``branched bay copolymer'' on page 8, line 8 of Mei Ill. 81 as ``branched block copolymer.'' . (2) Same book, page 22, line 4 “57vRAGlil, -1
0', 106.10' J to rST'/RAGEL
-10', 10', 10', 10' J. Tensile strength was used as an index of physical properties. ” I am corrected. (In table 1 on page 24 of the 41st page, the amount of bound styrene (%) rlJ in block (A) of Exp-11 is corrected to "8". (5) In table 2 on page 25 of the same store, Exp- II and I
Block 2 (Δ1m f, of cattle) 'Tadiene/Snaren (g) l'212 I38'1'230 I2
0J, l-230I20. J rll17 I63J
and t+rlI. +61 Same book, page 28, line 4, 1 Comparative Example-71 is corrected by η1 as 1 Comparative Example-6. (7) Add the following after the same book, page 13, line 9 1'-# ('desired.'). Specific examples of the tin halide compounds include tetrachlortin, methyltrichlorotin, butyltrichlorotin. Soot,
Examples include phenyltrichlorotin, diphenyldichlorotin, triphenylchlortin, and compounds in which chlorine is replaced with bromine or iodine.

Claims (1)

[Scope of Claims] (1) A block copolymer obtained by copolymerizing styrene and butadiene, which (1) has a styrene content of 10 to 80% by weight and an average vinyl bond content in the butadiene moiety! Styrene with a weight rating of 30-70
A butadiene copolymer block is used as a copolymer block prisoner, and (11) the average vinyl bond content of the butadiene part is 60%.
The following polybutadiene blocks are combined into copolymer blocks (6
), (iii) each of the copolymer block and the copolymer block is contained in a weighted amount of % or more, and (1v) the average vinyl bond content of the butadiene moiety of the copolymer block is (V) The copolymer block (2) contains at least 5% by weight of the average vinyl bond content of the polymer block (2).
2) the glass transition temperature is 30°C or more higher, and (vl) the total bound styrene content of the block copolymer is 5 to 40
(VID 20% by weight or more of the above block copolymer is 3 to 3% by weight)
It is a branched block copolymer coupled with a tetrafunctional coupling agent. A rubber composition characterized in that the inside thereof is at least 10% and contains at least 20% by weight of such a block copolymer. (2) In the bonded styrene part of the copolymer block (4) The rubber composition according to claim 1, wherein the content of polystyrene blocks consisting of nine or more chains of styrene is 2 to 35% by weight. (3) In the block copolymer, the copolymer The rubber composition according to claims 1 and 2, wherein the joint between the block block and the copolymer block (1) has a polystyrene block. The rubber composition according to item 2 or 3.