JPH05230286A - Rubber composition and its production - Google Patents

Abstract

PURPOSE:To provide a rubber compsn. which has a high abrasion resistance, a high breaking strength, and a low rolling resistance. CONSTITUTION:A rubber compsn. is provided which contains at least 10 pts. rubber compsn. which is prepd. by mixing a filler having functional groups on the surface with a soln. of a polymer and removing the solvent from the resulting mixture. The polymer is obtd. by the addition reaction of -SiCln groups (wherein n is 1-3) to the molecular ends of an anionic polymer which is obtd. by polymerizing a conjugated diene or a combination of a conjugated diene with an arom. vinyl compd. in the presence of an organolithium polymn. initiator in an org. solvent. The addition reaction is conducted by adding carbon tetrachloride or a compd. having an -SiClm group (wherein m is 2 or 3) to a soln. of the anionic polymer, i.e., a soln. resulting from the polymn. The filler is carbon black or silica. The functional group is -OH or -COOH.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition mainly used for a tire tread, which is reinforced by a filler such as carbon black or silica, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, there has been a social need for reducing fuel consumption of vehicles.
With the increase in tire wear than ever before, there is an increasing demand for tire treads to further reduce rolling resistance, wear resistance, and maintain and improve wet and dry skid resistance at the same time.

In order to improve the above properties, from the viewpoint that it is important to improve the dispersion of the filler in the polymer, the polymer and the filler are preliminarily mixed in a latex state or a solution state, It has been practiced to give this solid content a usual kneading together with fresh rubber, carbon black or the like depending on the case. This is a method generally called wet master-batch, which is an attempt to improve dispersion of carbon black in rubber and improve impact resilience,
Some have been put to practical use. However, in such a method, the polymer and the filler are simply mixed with each other to a high degree, and there is no particular chemical bond between the two, so that abrasion, etc.
The effect of improving the physical properties including the destructive physical properties was insufficient.

On the other hand, by modifying the end of the polymer with a specific functional group, the interaction between the polymer and the filler during kneading is improved, thereby improving the dispersion of the filler and improving the physical properties. Many proposals have been made to measure it (for example, Japanese Patent Publication No. 1-49362). However, there is a limit to such a method, and a method for improving the overall rubber physical properties including further improvement in rolling resistance and improvement in fracture properties is desired.

[0005]

[Means and Actions for Solving Problems] The present inventor has conducted diligent research in view of the above circumstances, and as a result, a conjugated diene or a conjugated diene and an aroma using an organolithium polymerization initiator in an organic solvent was obtained. Group vinyl compound is anionically polymerized, and in this polymer solution, silicon tetrachloride or --SiCl is added.
By introducing a compound containing an m group (m = 2 or 3), a terminal-SiCln group (n = 1 to 3) -containing polymer is obtained, and a filler having a functional group on the surface is further added to this solution. , A so-called wet master-batch, the rubber composition obtained by kneading and mixing a usual rubber chemical, a vulcanizing agent and the like, and by vulcanizing this, excellent in abrasion resistance, breaking strength, and The inventors have found that a rubber composition having extremely low rolling resistance is obtained, and completed the present invention.

That is, the first aspect of the present invention relates to a rubber composition, which is a polymer obtained by polymerizing a conjugated diene or a conjugated diene and an aromatic vinyl compound and adding a --SiCln group to the end of the polymer. A rubber composition containing 10 parts or more of a rubber composition obtained by adding a filler having a functional group on the surface to a coalescing solution, stirring and mixing, and desolvating,
The anionic polymer was obtained by using an organolithium-based polymerization initiator in an organic solvent, and the addition of --SiCln group was caused by adding silicon tetrachloride or --SiC to the polymer solution.
A rubber composition obtained by adding a compound containing an lm group (m = 2 or 3), further comprising a filler added to this polymer solution and mixed by stirring. The filler having a functional group on the surface is carbon black or silica, or a mixture thereof, and in particular, the rubber composition in which the functional group on the surface is -OH group or -COOH group.

A second aspect of the present invention relates to a method for producing the rubber composition, comprising: a) anionic polymerization of a conjugated diene or a conjugated diene and an aromatic vinyl compound in an organic solvent using an organolithium polymerization initiator, b) A compound containing a silicon tetrachloride or -SiClm group (m = 2 or 3) is added to this polymer solution and reacted with the anionic polymer to give a polymer containing a terminal -SiCln (n = 1 to 3) group. C) Next, a method for producing a rubber composition obtained by adding a filler having a functional group on the surface to this polymer solution, stirring and mixing, and removing the solvent, wherein the filling having a functional group on the surface is obtained. Examples of agents and functional groups on the surface thereof are as described above.

That is, according to the present invention, by preliminarily modifying a polymer in a solution and introducing an interaction by a novel chemical bond between functional groups on the surface of the filler, the conventional masterbatch or the mere terminal modification can be performed. This is a dramatic improvement in physical properties that could not be obtained even by the modification method.
The organolithium polymerization initiator used in the present invention may be any one that can be used for ordinary living anionic polymerization, for example, n-BuLi, sec-BuL.
i, tert-BuLi, or any other known material.
Further, if necessary, tetrahydrofuran, ether, tertiary amine or the like may be used as a small amount of a microstructure modifier. The organic solvent used in the present invention may be any of n-hexane, cyclohexane, benzene, toluene and the like, which are also used in ordinary anionic living polymerization.

The base monomer component of the polymer used in the present invention is 1.3-butadiene, isoprene, styrene, .alpha.-methylstyrene, etc., which can be polymerized by using the above-mentioned organolithium polymerization initiator. It may be of any type, including all of these random copolymers, block copolymers, and taper-shaped copolymers. or,
Examples of the aromatic vinyl compound include styrene, vinyltoluene, α-methylstyrene and the like.

At the end of the living polymer, --SiCln
As a method for introducing the (n = 1 to 3) group, silicon tetrachloride, dichlorodiphenoxysilane, methyltrichlorosilane, ethoxydichlorosilane, methoxytrichlorosilane and the like are used. As shown in Formula 1, the reaction formula for introducing a -SiCln group to the end of the living polymer is as follows. First, silicon tetrachloride or -Si is added to the active end of the polymer.
One of the Clm groups reacts with chlorine, resulting in a polymer having a terminal -SiCln group with one less chlorine.

[0011]

[Formula 1]

At this time, if the molar ratio of silicon tetrachloride or --SiClm group to the living end of the polymer is small,
Multiple moles of polymer are added to 1 mole of silicon, causing so-called coupling and leaving no --SiCln group that should react with the filler. Silicon or -S
It is preferable to use an iClm group-containing compound and add it to the system at once in a single shot.

Next, the filler used in the present invention has a functional group capable of reacting with the --SiCln group added to the end of the polymer, such as a hydroxyl group (--OH) or a carboxyl group (--COOH). It is not particularly limited as long as it is a silica, and carbon black such as silica rich in -OH groups, a certain amount of -OH groups and -COOH groups confirmed on the particle surface, channel black, furnace black and the like. , And mixtures thereof are preferably used. Surface-treated calcium carbonate, clay, etc. are also included in this category.

In the reaction of these fillers with the above-mentioned --SiCln group-terminated polymer, if water (H ₂ O) is present in the system, the --SiCln group will react with this water. Since there is a fear that the structure will be activated and change into a structure that does not react with the functional groups on the surface of the filler, it is of course necessary to keep the polymerization system in an inert atmosphere. It is desirable to dry thoroughly. From this point of view, the carbon black immediately after production has a low water content and is active on the surface, and thus is suitable for this application. The method of introducing the filler into the polymer solution is not particularly limited, either as a powder or in the form of a slurry dispersed in the solution, as long as water and the like are mixed.

Regarding the reaction between these fillers and the above-mentioned polymer having a --SiCln group terminal, for example, Formula 2 can be considered. In order to carry out this reaction efficiently, the temperature of the system should be as high as possible and stirring should be carried out. It is desirable to do enough.

[0016]

[Formula 2]

After the reaction for a certain period of time, before removing the solvent, if necessary, other rubber components, fillers,
At this stage, add rubber chemicals such as resins, anti-aging agents, processing aids, stabilizers, cross-linking agents (sulfur, peroxide, etc.), vulcanization accelerators, etc. to be added during normal rubber kneading, and disperse them evenly. It is also possible.

Next, regarding the method for removing the solvent from the rubber composition, any method such as reprecipitation in alcohol, steam stripping, air drying, drum dryer, or vacuum drying may be used. The solid rubber composition thus obtained may be vulcanized and used as it is if it already contains a vulcanizing agent and the like, but generally at this stage, other rubber chemicals, crosslinking agents and the like are used. Kneading with a kneading machine further strengthens the interaction between the rubber and the filler, and further enhances the dispersion of the filler, rubber chemicals, etc., and also results in various wear resistance, rolling resistance, etc. It is also preferable for maximizing the physical properties.

The composition of the terminal-SiCln group polymer and the filler obtained by the wet master batch of the present invention sufficiently exerts its effect if the final product site contains 10 parts or more. In this case, other 90 parts or less may be added with the same or different kind of rubber or filler at the time of kneading.
Of course, it is also possible to obtain the total amount of rubber and filler with the wet master-batch of the invention.

[0020]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. The "parts" in the examples are by weight unless otherwise specified. Example In a dry nitrogen gas atmosphere, an autoclave having an internal volume of 10 liters was charged with 2000 g of cyclohexane, 240 g of 1.3-butadiene, 2.4 mmol of n-butyllithium and 14.4 mmol of tetrahydrofuran, and the mixture was stirred. Polymerization was carried out at 50 ° C. for 4 hours. At this point, the conversion of polymerization was almost 100%, the molecular weight of the obtained polymer was 150,000, and the microstructure was 29% in cis structure, 44% in trans structure and 27% in vinyl structure.

This polymer was transferred to 6 liters of autoclave (A to F) in equal portions while keeping an inert atmosphere, and 3 of these (A, B and C) were made of silicon tetrachloride. 0.8 mmol of each was added and stirred at 50 ° C. for 3 hours, and it was confirmed from the GPC data of the obtained polymer that the coupling of the polymer was slightly suppressed.

Next, 20 g of each non-granulated HAF carbon previously vacuum-dried at 120 ° C. for 24 hours was dispersed in 250 g of each cyclohexane, and the dispersion was strengthened by ultrasonication for 1 hour, and then transferred to B, C and D described above. Then, strong stirring was performed at 70 ° C. for 10 hours. Next, after reprecipitating all of A to F in ethanol, the obtained solid substance was sufficiently vacuum dried.

These solids were kneaded with the compounding recipe shown in Table 1 by a kneader manufactured by Brabender Co., and then at 145 ° C. for 20 minutes.
It was vulcanized for a minute to obtain a physical property measurement sample having a predetermined shape. Table 1 also shows typical physical property values. Regarding electric resistance, the larger the resistance and the smaller the Δtan δ value, the better the dispersion of the filler, and therefore the dispersibility of carbon black and the like can be known. On the other hand, the tan δ value serves as an index of rolling resistance,
The lower this value, the lower the rolling resistance.

[0024]

[Table 1]

[0025]

[Effect] As can be seen from Table 1, the examples according to the present invention have excellent dispersibility of carbon black, the tan δ value which is an index of rolling resistance is the lowest, and further, the Tb value (tensile strength). ), The wear index is clearly superior to that of the comparative example, indicating that the present invention is a method that is extremely suitable for achieving both low rolling resistance and high wear resistance.

Claims (6)

[Claims] 1. A surface of a polymer solution containing a conjugated diene or an anionic polymer obtained by polymerizing a conjugated diene and an aromatic vinyl compound with a --SiCln group (n = 1 to 3) added to the end of the polymer solution. Add a filler having a group, stir and mix,
A rubber composition containing 10 parts or more of a rubber composition obtained by desolvation, wherein the anionic polymer is obtained by using an organic lithium-based polymerization initiator in an organic solvent,
The addition of the SiCln group was obtained by adding a compound containing silicon tetrachloride or -SiClm group (m = 2 or 3) to this polymer solution, and further, a filler was added to this polymer solution. A rubber composition which is mixed by stirring. 2. The rubber composition according to claim 1, wherein the filler having a functional group on the surface is carbon black, silica or a mixture thereof. 3. The surface functional group is --OH group or --C.
The rubber composition according to claim 1, which is an OOH group. 4. A) anionic polymerization of a conjugated diene or a conjugated diene and an aromatic vinyl compound in an organic solvent using an organolithium polymerization initiator, and b) in this polymer solution, silicon tetrachloride or other-
A compound containing a SiClm bond (m = 2 or 3) was added and reacted with the anionic polymer to produce a terminal-SiCln.
(N = 1 to 3) group-containing polymer is obtained, and c) a filler having a functional group on the surface is then added to this polymer solution, and the mixture is stirred and mixed, and the solvent is removed to obtain a rubber composition. .. 5. The method for producing a rubber composition according to claim 4, wherein the filler having a functional group on the surface is carbon black, silica or a mixture thereof. 6. The functional group on the surface is --OH group or --C.
The method for producing a rubber composition according to claim 4, which is an OOH group.