JPS594634A - Branched copolymeric composition and tire prepared using said composition in tread - Google Patents

Abstract

PURPOSE:A composition, prepared by incorporating copolymers of a sepcific vinyl aromatic compound and butadiene, and having improved tear strength and tackiness without deteriorating the high wet skid resistance, low rolling resistance and processability, and useful for treads in tires. CONSTITUTION:A branched copolymeric composition prepared by incorporating two types of copolymers (A) and (B) of a vinyl aromatic compound and butadinene within (30/70)-(95/5) weight ratio range between the copolymers (A) and (B). Preferably, the glass transition temperature of the resultant composition is -60 deg.C or above, and the intrinsic viscosity is 1.3-4.0dl/g. The copolymers (A) and (B) are copolymers of the vinyl aromatic compound and butadiene containing 70wt% or more high polymer chain modified with a trifunctional or tetrafunctional binder. The copolymer (A) has 1.7-6.0dl/g intrinsic viscosity, and the copolymer (B) has 0.8-1.7dl/g intrinsic viscosity. The addition of 1- 10pts.wt. linear butadiene polymer having 0.1-0.8dl/g intrinsic viscosity, etc. to 100pts.wt. resultant composition further improves the tear strength and tackiness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to branched polymer compositions. More specifically, it relates to a composition containing a branched polymer mixture that has high wet skid resistance, low transfer resistance (excellent workability), and high tear strength and adhesiveness, which are problematic in practical processing.

In recent years, there has been an increasing demand for fuel efficiency in automobiles, and the characteristics of tires have a particularly important influence on fuel efficiency, and their improvement is strongly desired.

The properties required for tires include wear resistance, wet skid resistance, low heat generation, bending resistance, chipping resistance, group cranking resistance, etc., but it is necessary to have a good balance of various physical properties. . In particular, from the perspective of resource and energy conservation, it is important that energy loss and relocation resistance be small.

Among these physical properties, high wet skid resistance for handling stability and low rolling resistance for fuel efficiency are particularly important properties, but from conventional knowledge, these two properties are recognized as contradictory properties. It had been.

Traditionally, natural rubber, polyisoprene rubber, high-cis 1°4 polybutadiene rubber, styrene-butadiene rubber, etc. have been mainly used as rubber for tires, especially rubber for treads. Although it has low energy loss and low transfer resistance, it also has low skid resistance on wet road surfaces.

On the other hand, styrene-butadiene rubber has high wet skid resistance, but is insufficient as a fuel-saving tire material because it generates a lot of heat, causes large energy loss, and has high transfer resistance.

Conventionally, blending technologies of various polymers have been developed to compensate for the shortcomings and shortcomings of these polymers.For example, blends of styrene-butadiene rubber and high-cis polybutadiene are mainly used for relatively small passenger car tires. It is used.

However, maintaining high wet and skid resistance,
Regarding the characteristic of maintaining low transfer resistance, it was extremely inadequate compared to the level required in recent years.

The inventors of the present application have proceeded with basic studies on wet/skid resistance and transfer resistance, which were previously considered to be contradictory, while at the same time focusing on cross-wire workability, roll workability, and other properties required for tire manufacturing. We investigated the structure of a polymer with excellent processability such as extrusion processability, and the manufacturing method of such a polymer, and found that a branched polymer with a specific structure has both high wet and skid resistance and excellent transfer resistance. In addition, they discovered that it showed even better workability and filed a patent application (application number 57-53387).

The inventors of the present application have conducted intensive studies on methods for improving the tear strength and adhesiveness, which are problems when molding such branched polymers into the shape of tire members. If a polymer composition is made of a composite of The present invention was achieved by discovering that the composition has excellent characteristics.

Next, the background of the present invention will be described in more detail.

As described in the specification of the previous application filed by the present inventors (Application No. 57-53387), the rolling resistance performance and wet skid resistance performance of a tire can be recognized from the viewpoint of viscoelasticity as follows.

First, the rolling resistance of a tire is caused by energy loss that accompanies repeated deformation of the tire while the vehicle is running. In other words, while the tire is running, deformation when it touches the ground and recovery when it leaves the ground are repeated, and at this time a phase difference occurs in the relationship between stress and strain, resulting in hysteresis loss, or energy loss. , improving transfer resistance is nothing less than reducing such energy loss.

It is known that such energy loss is affected not only by the structure of the tire carcass and breaker, the sidewall rubber composition, but also by the tread rubber composition. Therefore, in order to reduce the rolling resistance of tires from the perspective of tread rubber compounding, it is necessary to reduce energy loss due to compressive deformation, bending deformation, and shear deformation of the tread rubber. This means reducing loss compliance (E'/(E)2) and loss modulus (El).

On the other hand, wet/skid resistance is considered to be the frictional resistance generated against the stress received from the road surface when the tire slides on an uneven road surface.

In other words, a viscoelastic body such as a tire exhibits deformation recovery with a time delay in response to the stress it receives, so a torque is generated in the opposite direction to the direction of travel, but the resistance due to this torque is frictional resistance, and the Loss tangent (tan δ-E
(Journal of Japan Rubber Association 43 Na)
1l 1970).

Therefore, both wet skid resistance and rolling resistance performance are improved by increasing the dynamic loss characteristic (E''·E''/E') of the rubber by 2°. In short, it is desirable for the dynamic loss characteristic value to be large in terms of wet/skid resistance, while it is desirable to be small in terms of transfer resistance.

Therefore, it has been conventionally recognized that these two performances are contradictory, and it has been thought that satisfactory results cannot be obtained using the same raw material. However, as a result of various studies, the inventors focused on the fact that the range of deformation rate to which the material is subjected differs between wet/skid resistance and rolling resistance. In other words, rolling resistance performance is the deformation speed that corresponds to the rotational speed of the tire, and the frequency is in the range of several tens of hertz at normal running speeds, whereas wet/skid resistance performance is the deformation speed that corresponds to the rotational speed of the tire, whereas wet skid resistance performance is the deformation speed that corresponds to the rotational speed of the tire. This is a very high frequency region, and the deformation frequency region to which the dynamic loss characteristics contribute is different from each other. Therefore, in the low frequency range that contributes to transfer resistance performance, the loss characteristics are made as low as possible, and wet resistance and
In the high frequency region that contributes to skid performance, both contradictory performances can be improved by making the loss characteristics as high as possible.

From this point of view, the inventor studied the molecular structure and molecular weight distribution of polymers and filed an earlier application (Japanese Patent Application No. 57-53387).
It has low transfer resistance and wet resistance as shown in the specifications of
A branched polymer that not only has high threading performance but also has excellent processability has been invented.

The purpose of the present invention is to provide a branched polymer composition that has improved tear strength and adhesion, which are important when molding a polymer into a tire member, without impairing these excellent characteristics. It is to be.

The composition of the present invention is a composition containing a mixture of a copolymer of a vinyl aromatic compound and butadiene, wherein the glass transition temperature of the polymer mixture is 160°C or higher, and The polymer consists of (II'), and the polymer (A+, (Bl) are each trifunctional or
A copolymer of a vinyl aromatic compound and butadiene containing a polymer chain modified with a tetrafunctional binder of 70 folds or more, and the intrinsic viscosity of the polymer is t, 7 (dn/p) or more. e, o (dl/P), and the intrinsic viscosity of the polymer is 0.8 (dl/f'J or more, 1.7 Cd#/P).
) A polymer composition characterized in that the weight ratio in the polymer mixture with Bl is 30/70 to 9515.

More preferably, the glass transition temperature of the mixture to and within the polymer is 150°C or higher, and the average intrinsic viscosity of this mixture is 1.5 (dl/P) to 4,0 (dl/P).
'/P).

When the glass transition temperature of the polymer mixture becomes low, the wet and skid resistance performance of tires using compositions containing the polymer mixture decreases, resulting in deterioration of braking properties. The polymer (A)
The glass transition temperature of the mixture (B) is limited to -60°C or higher, preferably -150°C or higher.

In the polymer composition of the present invention, polymer (A), GB
) are each a copolymer of a vinyl aromatic compound and butadiene, but as long as the aforementioned glass transition temperature range of the mixture is met, the polymers N), ("l
The glass transition temperatures of the two may be the same or different.

The glass transition temperature of polymers (Al, (Bl) is determined by setting the content of the vinyl aromatic compound bonded to each polymer and the amount of 1.2 bonds in the bonded butadiene to predetermined values.Generally The higher the content of the vinyl aromatic compound and the amount of the 1.2 alloy, the higher the glass transition temperature tends to be, and from the standpoint of wet and skid resistance, it is considered that the higher the content, the better. On the other hand, if the vinyl aromatic compound content exceeds 35% by weight, the tear strength and abrasion resistance of the rubber tend to decrease. The strength tends to decrease.In view of the balance of these properties, in the composition of the present invention, the polymer (A),
(The amount of vinyl aromatic compound bonded in Bl is 1
5 to 35% by weight, and 1.
It is preferable that the amount of 2-bond metal is 30 molti or more and less than 60 molti.

In addition, in the present invention, in order to obtain a polymer composition with excellent processability, # is added to each of the polymer (A) and the polymer strength).
The polymer chains modified with a trifunctional or tetrafunctional binder are controlled to account for at least 70% by weight of the polymer chains of the polymer. In this case, a polymer chain modified with a trifunctional or tetrafunctional binder means that there is a polymer chain that is bonded by chemical bonds in three or four directions from atoms or atomic groups in the polymer chain. It means a polymer chain having a shape like that.

As a method for producing a polymer containing such a modified branched polymer chain, a well-known glueing anionic polymerization method using an alkali metal compound as a polymerization initiator is effective. A method may be adopted in which the active polymer terminals are bonded together by the action of an agent.

Within and in each of the polymers contained in the polymer compositions of the present invention, at least 70% by weight of the polymer chains are polymer chains having attached branches as explained above, and the remaining polymer chains are The molecular chain is a polymer chain without branches.

In this case, the weight ratio of the polymer chains having bonded branches in the polymer is determined from the molecular weight distribution measured by gel permeability chromatography (GPC).
I can read it. In other words, the relative ratio between the height of the peak corresponding to the average molecular weight of polymer chains with combined branches and the height of the peak corresponding to the average molecular weight of polymer chains without branches is the weight ratio of each polymer chain. It is defined as

In the polymer ^), (B), the bonded polymer chains can have a shape modified by a trifunctional or tetrafunctional binder, or a mixture thereof. .

The higher the proportion of the modified polymer chains, the better the roll processability, and is controlled to be at least 70% by weight, preferably 80% by weight or more.

If the proportion of modified polymer chains is 70% by weight or more,
The wrapping stability of the rubber sheet during roll processing is good and the processing operation is easy, and if this ratio is 80% by weight or more, a good sheet with a smooth surface can be obtained.

In order to obtain such a preferable ratio of modified polymer chains, the molar ratio of the binder used to the active polymer terminal should be controlled during polymer production; for example, a tetrafunctional binder may be used. If so, the amount should be 0.175 to 0.250 mol per mol of active polymer terminal.

In the polymer composition of the present invention, the molecular weight within the polymer is
The intrinsic viscosity of the polymer (B) is limited to 1.7 (dl/P) or more and less than 6.0 (dl/P) when measured in toluene at 30°C. Intrinsic viscosity is 0
．． 8 (dl/f) or more and less than 1.7 (dl/F). If the molecular weight of the polymer (A) or (Bl) is lower than the above range, the dynamic loss will be large and the transfer resistance performance will deteriorate. On the other hand, if the intrinsic viscosity within the polymer exceeds 6.0 (#/P), processing operations using normal processing machines become difficult, such as poor quantitative extrusion properties during extrusion processing.

In addition, when the intrinsic viscosity of the polymer (B) exceeds 1.7 [:dl/P], the effect of improving tear strength and adhesion, which are important when molding the polymer composition as a tire component, can be improved. becomes scarce.

The mixing ratio of polymer (A) and polymer (B) that provides a composition with a good balance of transfer resistance performance, processability, tear strength, and adhesiveness is 30/70 to 9 by weight.
The range is 515. If the amount of polymer (B) exceeds this ratio, the transfer resistance performance deteriorates, which is not preferable.

In addition, the intrinsic viscosity of the mixture of (B) and (B) in the polymer is determined by the intrinsic viscosity and composition ratio of each of the polymers (B) and (B). From the point of view of good balance, polymer (A
l, the intrinsic viscosity measured for the mixture of (B) is 1
．． ! It is preferably in the range of 3 (dl/P) to 4.0 (dl/P), and more preferably in the range of 1.5 (d6/P) to z, 5
It is particularly preferable that the range is 1.

In order to further improve tear strength and adhesiveness, the polymer composition of the present invention has an intrinsic viscosity of 0.1 [dl/y] or more per 100 parts of the polymer (A) and the mixture within the polymer.
．． 8 (dA'/y) and may contain 1 to 10 parts of a butadiene polymer or a copolymer of a vinyl aromatic compound and butadiene (C1) having a flocculent or branched structure.

If the intrinsic viscosity of the polymer (C) is 0.8 or more, or if the content of the polymer (C) is less than 1 part, the effect of improving tear strength and adhesiveness will be small; If the intrinsic viscosity of the polymer (C1) is less than 0.1, or if the content of the polymer (q) exceeds 10 parts, the transfer resistance performance will deteriorate. It is preferable to use within the viscosity and content ranges.

In the polymer 1 composition of the present invention, polymer (A), (
”) or the I vinyl aromatic compound which is the raw material monomer of (C), styrene, benzene nucleus-substituted derivatives of styrene, such as m-methylstyrene, P-methylstyrene, P-tert-butylstyrene, or Vinyl-substituted derivatives of styrene, such as α-methylstyrene, are selected, but from the viewpoint of ease of availability for implementation on an industrial scale, one or two of styrene, P-methylstyrene, and α-methylstyrene are selected. Mixtures of more than one species are preferably selected.

In addition to the above-mentioned polymer mixture, the composition of the present invention is mixed with compounding agents used for processing and molding ordinary tire parts, such as carbon black, extender oil, anti-aging agent, sulfur, and vulcanization accelerator. and can be used.

The composition of the present invention also contains a polymer mixture as described above.
It is preferable to mix 0 to 70 parts by weight of natural rubber and/or synthetic in-prene rubber in an amount of 0 to 30 parts by weight. If the amount of natural rubber and/or synthetic impregnated rubber exceeds 30 parts by weight, it is undesirable because wet braking performance will deteriorate, and better processability and
In order to maintain a good balance between transfer resistance performance and wet braking performance, it is more preferable to contain 5 to 25 parts by weight.

Next, in order to make the present invention clearer, the present invention will be described with reference to examples, but the present invention is not limited thereto in any way.

Measurements of various physical properties in the weir examples and comparative examples were carried out under the following conditions.

Intrinsic viscosity [η] Measured using an Ostwald solution viscosity meter at 30° C. in toluene solvent.

Glass transition point 2 using a DuPont differential scanning calorimeter (D, S, C)
Measurement was performed at a heating rate of 0° C./min, and the transition temperature was determined from the position of the transition endothermic peak.

The roll processability was adjusted to 610°C at a temperature of 50°C, and the roll gap was adjusted to 0.
7 mfn, 1.0 m, n, 1.5-m, 2
．． A polymer or a mixture of polymers was wound around the film, and the condition was observed and evaluated as follows.

Measurement of the ratio of modified polymer chains depending on the polymer chain (-) Using HLC-802UR manufactured by Toyo Soda, 103.10', 10', and 107 columns were selected as distribution columns, and a refractometer was used. It was used as a detector.

The molecular weight distribution of the polymer was measured at 40°C using tetrahydrofuran (THF) as a developing solvent. The relative ratio of the peak heights corresponding to the average molecular weights of the modified and unmodified polymer chains was determined as the weight ratio of each polymer chain.

Wet skid resistance performance A 6.5 mm thick vulcanized rubber sheet was measured using a portable skid resistance tester manufactured by Stanley. An asphalt surface sprayed with water at a temperature of 20° C. was selected as the contact road surface.

Dynamic Loss Value Using a dynamic solid viscoelasticity meter manufactured by Toyo Baldwin Co., Ltd., the vulcanized sheet was measured at an initial elongation of 0.6%, both amplitudes o and i*, and a frequency of 11 Hz while varying the temperature.

Tear strength was measured on type B test pieces according to JISK-6301.

Pressing load was 5ooy at a temperature of 23°C using a pick-up tack meter made by Toyo Seiki.

The measurement was carried out under conditions of a pressure bonding time of 10 seconds and a peeling speed of 10 mm/min.

The formulation for obtaining the vulcanizate was as follows.

Polymer 100 parts Aroma oil 20 parts Stearic acid 2 parts Sulfur 1.6 parts Carbon black 60 parts Zinc white 5 parts Vulcanization accelerator 2 parts Examples 1 to 3 Using n-butyllithium as a polymerization initiator, tetrahydrofuran and A polymer IAI having branches bonded by applying silicon tetrachloride to an active polymer solution obtained by copolymerizing styrene and butadiene in the coexistence of hexane,
(Bl was synthesized respectively. The obtained polymer solutions were mixed so that the mixing ratio of one polymer (B) in the polymer became a predetermined weight ratio, and the polymer mixture was recovered by methanol reprecipitation method.

Table 1 shows the physical properties of polymers (A), (Bl) and (A)/(Bl mixtures).

The compositions of Examples 1 to 3, which are the compositions of the present invention, have high wet skid resistance performance of 60 to 82, low dynamic loss value BiI (E'/IE*12), and poor roll processability. Excellent, and the tear strength at 150℃ is also 20-23 (
Vn) and high tackiness of 570 (9715 m1n) or more.

Comparative Example 1 Comparative Example 1 is an example not based on the present invention, in which the polymer chain modified with a binder is as low as 51°C, and the glass transition temperature is also as low as -57°C. This is an example.

In this case, the dynamic loss is also E'=22.7 (immediate/12)
In addition, the wet skid resistance performance is insufficient, and the rubber sheet has no stickiness during roll processing, making it difficult to process. This polymer was found to be unsuitable for the purposes of the present invention.

Comparative Example 2 Comparative Example 2 has a high proportion of polymer chains modified with a binder at 85 chains, but is an example that does not contain the polymer (B) according to the present invention. Comparative Example 20 polymer has excellent wet skid resistance performance, dynamic loss value, and roll processability, but tear strength and adhesiveness are insufficient, and the object of the present invention has not been achieved.

Example 4 A branched polymer (A+, (Bl) synthesized in the same manner as in Examples 1 to 3 had an intrinsic viscosity of 0°46 (dN/P3) and a styrene content of 25
A linear styrene-butadiene copolymer (C) in which the vinyl content of the butadiene moiety is 4Qwt% is
Parts by weight were mixed and various physical properties were measured. The results are shown in Table 2.

As shown in Table 2, the composition of Example 4, which is a composition of the present invention, has excellent wet skid resistance performance, low dynamic loss value, extremely good roll processability, and tear strength. It was found that this compound has high adhesiveness and is suitable for practical processing.

Next, the rubber compositions obtained according to the formulations of Examples 1 to 4 and Comparative Examples 1 to 2 were used for a tread, and 165
5R13 steel radial tires were manufactured and their rolling resistance, wet braking performance, and steering stability performance were measured.

The results are shown in Table 3.

Transfer resistance performance The above tires are mounted on a 60 inch drum at a speed of F3 Q K
m/h, internal pressure 2.01'f'/n2, and load 300 to measure transfer resistance performance.

The table shows relative values based on commercially available SBR1500. The smaller the value, the better the transfer resistance performance.

In all of the examples of the present invention, it is recognized that the transfer resistance performance is significantly improved over SBR1500.

Wet brake performance The above tire was installed on a passenger car with a displacement of 1500 cc, and the friction coefficient μ was calculated from the stopping distance from a speed of 5Q km/in when one person was riding on a slippery concrete road surface with water sprinkled on it. Relative values are shown based on SBR1500.

The higher the number, the better the wet braking performance.

In all of the embodiments of the present invention, it is recognized that the wet braking performance is significantly improved over the SBR1500.

Stability performance The above tire was installed on a passenger car with a displacement of 1500 (!L) and the air pressure was 1.8KIF'/
(111") The steering stability performance when driving with one person on board is expressed as a relative value, with the commercially available SBR1500 as the standard value of 3.0. The steering stability performance includes straight-line stability, steering response, ground contact, and convergence. The overall evaluation of each evaluation is shown, and the higher the value, the better.

In all of the examples of the present invention, it is recognized that the handling stability performance is improved over 5BIL and 1500.

Claims (9)

[Claims] (1) A composition containing a mixture of a copolymer of a vinyl aromatic compound and butadiene, wherein the glass transition temperature of the polymer mixture is 160°C or higher, and the polymer mixture is a copolymer ( A). Polymers (A) and (B) are composed of a vinyl aromatic compound containing at least 70% by weight of polymer chains modified with a trifunctional or tetrafunctional binder, and butadiene. The intrinsic viscosity of the copolymer (c) is 1.7 (dl/P) or more and less than 6.0 (d6/$'), and the intrinsic viscosity in the direction of the polymer is 0.8 ( dl/P) or more 1
．． 7 (dl/?), and the polymer direction and polymer (B)
The weight ratio in the polymer mixture with is 30/70 to 9
A branched polymer composition characterized in that: 515. (2) The bonding amount of the vinyl aromatic compound in the polymer (A) (Bl) is 15 to 35% by weight, and the polymer G
The composition according to claim 1, wherein the amount of 1.2 bonded gold in the bound butadiene of AI, (B) is 30 molti or more and less than 60 molti. (3) Polymer direction and intrinsic viscosity of 0.1 (dl/P) or more and 0.8 (dl/P) per 100 parts of the mixture of polymer (B).
F) and contains 1 to 10 parts of a butadiene polymer having a linear or branched structure or a copolymer of butadiene and a vinyl aromatic compound ρ).
) or (2). (4) Claims (1) to (3) wherein the polymer direction and the glass transition temperature of the mixture of polymer (B) are 150°C or higher.
Compositions as described in Section. (5) The average intrinsic viscosity of the mixture of polymer (A) and polymer (B) is 1.3 (dl/P) to 4.0 (dl/P).
/y) The composition according to any one of claims (1) to (4). (6) The average intrinsic viscosity of the mixture of the polymer (Al and the polymer) is 1.5 (dl/F) to 2.5 (dl/f), according to claims (1) to (4). The composition according to any one of the above. (7) Claims (1) to (6) wherein at least one of the polymers (A) and (Bl) contains 80 weight or more of a polymer chain modified with a trifunctional or tetrafunctional binder. ) The composition according to any one of the above items. (8) The composition according to claims (1) to (7), wherein the vinyl aromatic compound is one or a mixture of two or more of styrene, P-methylstyrene, and α-methylstyrene. (9) Add 0 to 3% of natural rubber and/or synthetic impregnated rubber to the polymer, based on 100 to 70% by weight of the mixture of (B).
The composition according to claims (1) to (1) containing 0% by weight of mackerel. a [polymer (Al, (Bl, (C1 mixture 1)
The composition according to any one of claims (3) to (7), which contains natural rubber and/or synthetic isoprene rubber in an amount of 0 to 30% by weight based on 0 to 70% by weight. Ql) A tire using the composition according to any one of claims (1) to (1) as a tread.