JPH0471936B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a diene copolymer composition. More specifically, the present invention relates to a composition that has high wet skid resistance, low rolling 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 tire characteristics 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 cracking resistance, etc., but it is necessary to have a good balance of various physical properties. be. Particularly from the viewpoint of saving resources and energy, it is important to have low energy loss and low rolling resistance. Among these physical properties, high wet skid resistance for handling stability and low rolling resistance for fuel efficiency are particularly important properties, but conventional knowledge suggests that these two properties are contradictory. It was recognized. Conventionally, natural rubber, polyisoprene rubber, high cis 1,
4 Polybutadiene rubber, styrene-butadiene rubber, etc. are mainly used, but natural rubber, polyisoprene rubber, and high-cis polybutadiene rubber have low energy loss and low rolling resistance, but have low spill resistance on wet road surfaces. . On the other hand, styrene-butadiene rubber has high wet skidding resistance, but is insufficient as a fuel-saving tire material because it generates a lot of heat, causes large energy loss, and has high rolling resistance. Conventionally, blending technology of various polymers has been developed to compensate for the drawbacks of these polymers.
For example, blends of styrene-butadiene rubber and high-cis polybutadiene are mainly used for relatively small passenger car tires. However, the characteristics of maintaining high wet skid resistance and low rolling resistance were far insufficient compared to the standards required in recent years. The inventors of the present application have carried out basic studies on wet skid resistance and rolling resistance, which were previously thought to be contradictory, while at the same time focusing on kneading processability, roll processability, extrusion resistance, which are required in practical tire manufacturing. We have investigated the structure of polymers with excellent processability and methods for producing such polymers, and have found that polymers with specific structures have both high wet skid resistance and excellent rolling resistance. He discovered that the process showed even better processability and filed a patent application (application number 57-53387 (see Japanese Patent Application Laid-Open No. 58-168611)). The inventors of the present application have conducted intensive studies on methods for improving the tear strength and adhesion, which are problems when molding such polymers into the shape of tire components. The present invention has been achieved by discovering that a combined composition can further improve tear strength and adhesiveness without impairing the characteristics of excellent wet skid resistance, rolling resistance, and processability. Next, the background of the present invention will be described in more detail.
Previous application by the present inventors (Application No. 57-53387)
As described in the specification (see JP-A-58-168611), 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 a 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 rolling 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 a tire from the perspective of tread rubber compounding, it is necessary to reduce the energy loss due to compressive deformation, bending deformation, and shear deformation of the tread rubber, but this is a loss considering the dynamic viscoelastic properties of rubber. Compliance (E″/(E) ² ) and loss modulus (E″)
means to reduce On the other hand, wet/skid resistance is considered to be the frictional resistance generated in response to 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 applied stress, so a torque is generated in the opposite direction to the traveling direction, but the resistance due to this torque is frictional resistance, and the movement It depends on the loss tangent (tan δ = E″/E′) of the viscoelastic properties (Japan Rubber Association Journal 48 No. 11 1970).
Both the hardness performance and the rolling resistance performance depend on the dynamic loss of the rubber (E″, E″/(E ^* ) ² , E″/E′), but an increase in these values will conversely increase the resistance. wet
Skid performance is improved. In short, it is desirable for the dynamic loss characteristic value to be larger in terms of wet skidding resistance, while it is desirable to be smaller in terms of rolling 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 materials. However, as a result of various studies, the inventors focused on the fact that the range of deformation speeds 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, and the frequency is in the range of several tens of hertz, whereas wet skidding 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 regions to which the dynamic loss characteristics contribute are different from each other. Therefore, by making the loss characteristics as low as possible in the low-frequency region that contributes to rolling resistance performance, and increasing the loss characteristics as much as possible in the high-frequency region that contributes to wet skid resistance performance, it is possible to improve both contradictory performances. . From this point of view, the inventor studied the molecular structure, molecular weight distribution, etc. of the polymer, and
Specification of the earlier application (Japanese Patent Application No. 57-53387)
58-168611), it has low rolling resistance and high wet skid resistance,
Furthermore, a branched polymer with excellent processability was invented. An object of the present invention is to provide a polymer composition that has improved tear strength and adhesiveness, which are important when molding a polymer into a tire member, without impairing these excellent characteristics. That's true. 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 mixture of polymers is -50.
℃ or higher, and the polymer mixture consists of three types of polymers (A), (B), and (C), and the polymer (A)
is a linear polymer with an intrinsic viscosity of 1.0 to 4.0, and polymer (B) is a branched polymer in which polymer (A) has a silicon-vinyl aromatic compound bond bonded using silicon tetrachloride as a binder. and the bonding amount of the vinyl aromatic compound in the polymers (A) and (B) is 15 to 35% by weight, and the polymer (A),
The content of 1.2 bonds in the bonded butadiene of (B) is 30 mol% or more and less than 60 mol%, and the polymer (C) is bonded in a linear form with an intrinsic viscosity of 0.1 to less than 0.8 or using silicon tetrachloride as a binder. It is a branched polymer having a silicon-vinyl aromatic compound bond, and the proportion of polymer (C) in the total weight of polymers (A), (B), and (C) is 1% by weight or more10 % by weight or less, and the proportion of polymer (B) in the total weight of polymers (A) and (B) is 70% by weight or more. If the glass transition temperature of the polymer mixture is lower than -50°C, the wet grip performance of tires using the polymer will be lowered and the braking properties will deteriorate. Therefore, in the polymer composition of the present invention, the polymer mixture The glass transition temperature of is limited to -50°C or higher. Furthermore, in the composition of the present invention, the molecular weight of the polymer (A) is within a range such that the intrinsic viscosity of the polymer (A) measured in toluene at 80°C is 1.0 to 4.0 [dl/g]. is preferred. When the intrinsic viscosity of the polymer (A) is less than 1.0, the dynamic loss becomes large and the rolling resistance deteriorates, whereas when the intrinsic viscosity of the polymer (A) exceeds 4.0, the resulting As a result, the molecular weight of the polymer (B) becomes significantly large, and the quantitative properties of the polymer mixture and its composition during extrusion processing deteriorate.
Practically unfavorable. Further, in the composition of the present invention, the polymer (B) is a branched polymer in which the polymer (A) is bonded using silicon tetrachloride as a binder. In the composition of the present invention, the amount of polymer (B) is controlled so that it accounts for 70% by weight or more of the total amount of polymer (A) and polymer (B). If this proportion is less than 70% by weight, the processability of the polymer mixture and its composition will deteriorate, resulting in serious performance deterioration, such as the inability to obtain a smooth rubber sheet during roll processing. As a method for producing the polymer (B), a known living anion polymerization method using an alkali metal compound as a polymerization initiator is effective. In this method, an active polymer corresponding to the polymer (A) is synthesized in advance, and the terminal A method may be adopted in which a part or all of the ends are joined together using a binding agent. That is, a binder, which is silicon tetrachloride, is made to act on an active polymer solution obtained by copolymerizing a vinyl aromatic compound and butadiene using a polymerization initiator. When copolymerizing, due to the difference in reactivity between vinyl aromatic compounds and butadiene, butadiene is preferentially polymerized in the early stage of polymerization, and the end of the polymer becomes a vinyl aromatic compound in the late stage of the reaction. is a known fact. When the binder is allowed to act on a polymer chain having such a polymer end, the resulting polymer chain has a vinyl aromatic compound-silicon end. In this case, the weight ratio of polymer (B) having bonded branches to the total amount of polymers (A) and (B) was measured by gel permeation chromatography (GPC). It can be read from the molecular weight distribution. That is, the relative ratio of the peak height corresponding to the average molecular weight of the polymer (B) having bonded branches to the peak height corresponding to the average molecular weight of the unbranched polymer (A), respectively. can be defined as the weight ratio of the polymer. The polymer (B) of the composition of the present invention is in a bonded form using silicon tetrachloride as a binder. Moreover, as mentioned earlier, the amount of polymer (B) is
Of the total amount of polymer (A) and polymer (B), 70
In order to obtain this preferred ratio, the amount of binder should be 0.175 to 0.25 mole per mole of polymerization active terminals. In the composition of the present invention, the amount of vinyl aromatic compound bound in the polymers (A) and (B) is in the range of 15 to 35% by weight. The higher the styrene content, the better the wet and skid resistance performance, but if it exceeds 35% by weight, the tear strength and abrasion resistance tend to decrease, and from the balance of both, the above range is suitable for the purpose of the present invention. It is compatible. Further, the content of 1,2 bonds in the bound butadiene of polymers (A) and (B) is 30 mol% or more and less than 60 mol%. Wet skid resistance improves as the 1,2 bond content increases, but if it exceeds 60 mol %, the tear strength and abrasion resistance drop significantly, which is not preferable. On the other hand, if the 1,2 bond content is less than 30 mol %, it is not suitable because the wet skid resistance will decrease. Further, in the composition of the present invention, the polymer (C) is a linear or branched polymer having an intrinsic viscosity of 0.1 to less than 0.8. If the intrinsic viscosity is 0.8 or more, the polymer composition will have poor tackiness, and the composition will be unsuitable for the purpose of the present invention, for example, the effect of improving the tear strength of the vulcanizate obtained from the composition will be lost. will be given. On the other hand, if the intrinsic viscosity is less than 0.1, rolling resistance performance deteriorates, or part of the rubber sheet peels off during roll processing, resulting in a decrease in processability, which is undesirable. Also, polymer (A), (B), of polymer (C),
The proportion of (C) in the total weight is 1% by weight or more
Limited to 10% by weight or less. If this proportion is less than 1% by weight, the effect of improving adhesion and tear strength will not be sufficient;
If it exceeds the above, rolling resistance performance deteriorates, which is not preferable. Further, in order to obtain a composition which has extremely excellent rolling resistance performance and has a good effect of improving adhesion and tear strength, this proportion is preferably 1% by weight or more and 5% by weight or less. Similarly, in order to maintain a favorable balance between rolling resistance performance and the effects of improving adhesion and tear strength, the polymer (C) is a branched polymer having a shape bonded using silicon tetrachloride as a binder. In this case, the proportion of branched polymer chains in the polymer (C) is 70% by weight or more, preferably 80% by weight or more. The content of this branched polymer chain is also controlled by the molar ratio of the binder to the active polymer, and the amount of the binder used is 0.175 mol to 0.250 mol, preferably 0.200 mol to 0.250 mol, per 1 mol of the active polymer. Should. Polymers (A), (B), (C) in the composition of the invention
When using a copolymer of a vinyl aromatic compound and butadiene as They include butylstyrene and vinyl group-substituted derivatives of styrene, such as α-methylstyrene, but styrene and p-methylstyrene are preferably selected from the viewpoint of easy availability for implementation on an industrial scale. In addition to the above-mentioned polymer mixture, the composition of the present invention contains compounding agents commonly used in the processing and molding of tire components, such as carbon black, extender oil, anti-aging agent, sulfur, and vulcanization accelerator. It can be used in combination with etc. Further, in the composition of the present invention, it is preferable to mix 0 to 30 parts by weight of natural rubber and/or synthetic isoprene rubber to 100 to 70 parts by weight of the above polymer mixture. If the blending amount of natural rubber and/or synthetic isoprene rubber exceeds 30 parts by weight, it is undesirable because the wet braking performance will deteriorate. In order to maintain a good balance, it is more preferable to contain 5 to 25 parts by weight. EXAMPLES Next, in order to make the present invention more clear, the present invention will be described with reference to examples, but the present invention is not limited thereto. Note that measurements of various physical properties in 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 Measured using a DuPont differential scanning calorimeter (D, S, C) at a heating rate of 20°C/min. The transition temperature was determined from the position of the transition endothermic peak. Roll processability Adjust the temperature of the 6″ roll to 50℃ and adjust the roll gap.
Polymers or mixtures of polymers were wound around the wires with varying lengths of 0.7 mm, 1.0 mm, 1.5 mm, and 2.0 mm, and the condition was observed and scored as follows.

[Table] Analysis of the content of polymers (A) and (B) Using Toyo Soda HLC-802UR, selecting columns 10 ₃ , 10 ₄ , 10 ₆ , and 10 ₇ as distribution columns, and detecting with a refractometer. It was used as a vessel. The molecular weight distribution of the mixture of polymers (A) and (B) 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 polymers (A) and (B) was determined as the weight ratio of each polymer. Wet and 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% and a double amplitude of 0.1.
% at a frequency of 11 Hz while varying the temperature. Tear strength was measured on a type B test piece according to JIS K-6301. Adhesion Measured using a pick-up tack meter manufactured by Toyo Seiki at a temperature of 23° C., a crimping load of 500 g, a crimping time of 10 seconds, and a peeling speed of 10 mm/min. The formulation for obtaining the vulcanizate was as follows. 100 parts of polymer 60 parts of carbon black 20 parts of aromatic oil 5 parts of zinc white 2 parts of stearic acid 2 parts of vulcanization accelerator 16 parts of sulfur Examples 1 to 3 Styrene was produced in hexane using butyllithium as a polymerization initiator in the presence of tetrahydrofuran. In Examples 1 and 2, a separately synthesized linear polymer ( In addition, in Example 3, the solution of C) was mixed with a solution of a polymer (C) containing a branched polymer chain having a silicon-vinyl aromatic compound bond bonded using silicon tetrachloride as a binder at a predetermined ratio. mixed with. The solvent was distilled off from the obtained solution to recover a polymer mixture, and various physical properties were measured as a vulcanized product. In addition, the physical property values of polymer (A) are for a sample taken out from the polymerized polymer in a small amount before being treated with silicon tetrachloride, and the glass transition temperature of the mixture of (A), (B), and (C) is for the untreated sample. Measurements were made on sulfur mixtures. The results are shown in Table 1. As shown in Table 1, the composition of the present invention has high wet skid resistance and low loss modulus (E'') and loss compliance (E''/1E ^* 1 ² ), so it has excellent braking characteristics and rolling resistance. Both properties are excellent, the roll processability is also very good, and the tear strength is high at 20 to 22 (Kg/cm ² ).
Furthermore, since the adhesiveness is as high as 570 to 590 (g/15 mm), the composition of the present invention has high wet skid resistance, low rolling resistance, and excellent processability, as well as meeting the requirements when molding tire components. It was also shown that the polymer composition had improved tear strength and adhesion. Comparative Example 1 Similar physical property measurements were performed on a mixture of polymers (A) and (B) in Examples 1 to 3 without mixing polymer (C). These results are also shown in Table 1, and the composition of Comparative Example 1 has a high wet skid resistance performance and rolling resistance performance.
Although it has an excellent balance of workability, the tear strength is low at 18 (Kg/cm) and the adhesiveness is 450 (g/mm).
As a result, the practical molding processability required when molding tire components is poor, and the improvement effect of the present invention cannot be seen.

【table】

[Table] Next, the rubber compositions obtained according to the formulations of Examples 1 to 3 and Comparative Example 1 were used for toreading,
We manufactured 165SR13 steel radial tires and measured their rolling resistance, wet braking performance, and handling stability. The results are shown in Table 2. Rolling resistance performance The above tires are mounted on a 60 inch drum at a speed of 80 km/h.
The rolling resistance performance was measured by running under conditions of an internal pressure of 2.0 kg ^f /cm ² and a load of 300 kg. The table shows commercially available
Relative values are shown based on SBR1500. The smaller the number, the better the rolling resistance performance. All of the examples of the present invention are recognized to have significantly improved rolling resistance performance compared to SBR1500. Wet brake performance When the above tires are installed on a passenger car with a displacement of 1500 c.c.,
The friction coefficient μ was calculated from the stopping distance from a speed of 60 km/h when one person was riding on a slippery concrete road surface with water sprinkled on it, and
It is shown as a relative value based on the standard. The higher the number, the better the wet braking performance. In all of the embodiments of the present invention, it is recognized that wet braking performance is significantly improved over SBR1500. Steering stability performance When the above tires are installed on a passenger car with a displacement of 1500c.c.
At the JARI general test track, the air pressure was 1.8Kg ^f / ^cm2 , 1
The steering stability performance during driving under the name of the vehicle is shown as a relative value with the standard value of 3.0 for the commercially available SBR1500. Steering stability performance is evaluated based on straight-line stability, steering response, ground contact, and convergence.The overall evaluation of each evaluation is shown, and the higher the value, the better. All of the examples of the present invention are recognized to have improved handling stability performance compared to SBR1500.

【table】

Claims (1)

[Scope of Claims] 1. A composition containing a mixture of a copolymer of a vinyl aromatic compound and butadiene, wherein the glass transition temperature of the mixture of polymers is -50°C or higher; are three types of polymers (A), (B),
(C), and the polymer (A) has an intrinsic viscosity of 1.0 to
4.0, the polymer (B) is a branched polymer in which the polymer (A) has silicon-vinyl aromatic compound bonds bonded using silicon tetrachloride as a binder, and The bonding amount of the vinyl aromatic compound in the polymers (A) and (B) is 15 to 35% by weight, and the 1.2 bond content in the bonded butadiene of the polymers (A) and (B) is 30 mol% or more and 60 mol %, and the polymer (C) is a branched polymer having a linear or silicon-vinyl aromatic compound bond bonded using silicon tetrachloride as a binder with an intrinsic viscosity of 0.1 to less than 0.8, and Polymer (A), (B),
The proportion of the polymer (C) in the total weight of (C) is 1% by weight or more and 10% by weight or less, and the polymer (A),
The proportion of polymer B in the total weight of (B) is 70
% or more by weight. 2. The composition according to claim 1, wherein the proportion of polymer C in the total weight of polymers (A), (B), and (C) is 1% by weight or more and 5% by weight or less. 3. The polymer (C) contains a branched polymer chain having a silicon-vinyl aromatic compound bond bonded using silicon tetrachloride as a binder, and the branched polymer chain in the polymer (C) Proportion is 70% by weight
The composition according to any one of claims 1 to 2, which is the above. 4. The polymer (C) contains a branched polymer chain having a silicon-vinyl aromatic compound bond bonded using silicon tetrachloride as a binder, and the branched polymer chain in the polymer (C) Proportion is 80% by weight
The composition according to any one of claims 1 to 2, which is the above. 5 Mixture of polymers (A), (B), (C) 100-70
5. The composition according to claim 1, which contains from 0 to 30% by weight of natural rubber and/or synthetic isoprene rubber. 6 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 -50°C or higher, and the polymer mixture contains three types of polymers. (A), (B),
(C), and the polymer (A) has an intrinsic viscosity of 1.0 to
4.0, and polymer (B) is a branched polymer in which polymer (A) has silicon-vinyl aromatic compound bonds bonded using silicon tetrachloride as a binder; In addition, the bonding amount of the vinyl aromatic compound in the polymers (A) and (B) is 15 to 35% by weight, and the 1,2 bond content in the bonded butadiene of the polymers (A) and (B) is 30% by mole. or more and less than 60 mol%, and the polymer (C) is a linear or branched polymer having a silicon-vinyl aromatic compound bond bonded using silicon tetrachloride as a binder and having an intrinsic viscosity of 0.1 to less than 0.8. Yes, and also polymer (A),
Polymer (C) in the total weight of (B) and (C)
The proportion of polymer (B) is 1% by weight or more and 10% by weight or less in the total weight of polymers (A) and (B).
A tire comprising a tread made of a composition characterized in that the proportion of is 70% by weight or more.