JP2918495B2 - Method for producing rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rubber composition having an excellent balance of tan δ of a vulcanized product, and more particularly to a method for producing a rubber composition for a pneumatic tire.

[0002]

2. Description of the Related Art It has been proposed to improve the balance of tan δ of tire tread rubber to reduce the fuel consumption of automobiles. Specifically, it has been proposed to mix and mix components and use a terminal modified rubber. I have.

For example, Japanese Patent Publication No. 5-1298 discloses that
A rubber composition is described in which a vulcanizate containing a conjugated diene-based polymer having an aromatic tertiary amino group at a terminal portion of the conjugated diene-based polymer has further improved rebound resilience and tensile strength. On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 55-10434 discloses a raw material rubber comprising an amorphous 1,2-polybutadiene and a natural rubber and / or a polyisoprene rubber (or a conjugated diene rubber may be partially contained). When compounding carbon black to produce a rubber composition for a tire tread,
First, a raw rubber component containing at least 25% by weight of 1,2-polybutadiene and carbon black are mixed at a specific ratio, and then the remaining raw rubber components are added and mixed to improve fuel economy and safety. Have been.

Further, Japanese Patent Application Laid-Open No. 2-129241 proposes to improve the tensile strength and abrasion resistance of a vulcanized product by blending a terminal-modified conjugated diene polymer with carbon black in an organic solvent. .

[0005]

However, the above-mentioned techniques such as the split mixing method of the blending components and the use of the terminal-modified rubber have a problem that, for example, the effect is weak in a high blending system of oil and carbon black. There is a need for improvement. Accordingly, the present invention provides a
An object of the present invention is to provide a method for producing a rubber composition having an excellent balance of nδ.

[0006]

According to the present invention, a terminal-modified and / or coupled diene rubber 20 is provided.
100 to 100 parts by weight of a raw rubber consisting of 50 to 90 parts by weight of a raw rubber mixture (A) containing from 80 to 80% by weight and 50 to 10 parts by weight of a raw rubber (B) made of at least one type of diene-based rubber which is not terminal-modified. Parts, reinforcing agent 50-120
Parts by weight and a softening agent in an amount of 20 to 80 parts by weight to produce a rubber composition, the average glass transition temperature TgA (° C.) of the raw rubber (A) and the average glass transition temperature TgB (° C.) of the raw rubber (B) ) And TgA + 20> T
gB> TgA-20, and after mixing the raw rubber (A) and 80% by weight or more of the total amount of the reinforcing agent at a temperature of 135 ° C. or more, adding and mixing the raw rubber (B) and the remaining reinforcing agent and softener. A method for producing a rubber composition for a pneumatic tire is provided.

According to the present invention, there is also provided a diene-based raw rubber (A ') having a weight average molecular weight Mw (A') in the range of 100,000 to 1.2 million, and a weight average molecular weight Mw of 400,000 or more.
When a rubber composition is produced by mixing a diene raw material rubber (B ′) having (B ′), the weight average molecular weight has the following relationship: 0.08 ≦ Mw (A ′) / Mw (B ') <1 ... (III) Average glass transition temperature TgA' (° C) of raw rubber (A ')
And the average glass transition temperature TgB 'of the raw rubber (B')
(° C.) and the following relationship: TgA ′ + 20> TgB ′> TgA′-20 (I ′) 20 to 90 parts by weight of diene-based raw rubber (A ′) and reinforcing agent 5
0 to 120 parts by weight are first mixed, and then 2 to 80 to 10 parts by weight of the diene raw material rubber (B ') and 100 parts by weight of the total amount of the diene raw rubbers (A') and (B ').
There is provided a method for producing a rubber composition, which comprises adding 0 to 80 parts by weight of a softening agent.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION
δ is almost independent of the rubber-adsorbed phase near the filler such as carbon black, and found to be due to the matrix phase. To improve the balance of tan δ by separating the carbon black surface and the matrix phase as much as possible. Is a successful one. for that reason,
According to the first aspect of the present invention, by preliminarily mixing a terminal modified diene rubber (for example, SBR) having high reactivity with the surface of a reinforcing agent such as carbon black and a reinforcing agent such as carbon black, carbon By covering the surface with a terminal-modified diene rubber and then adding and mixing a diene rubber having low reactivity (for example, emulsion polymerization SBR), a rubber composition having an improved balance of tan δ of the vulcanized product can be obtained.

In a second embodiment of the present invention, two types of diene-based raw rubber satisfying the above-mentioned specific relation (III) are used, and the diene-based raw rubber (A ') and the reinforcing agent are mixed. By mixing the diene-based raw rubber (B ′) and a softener, a rubber composition having an improved balance of tan δ of the vulcanized product can be obtained. Note that Mw (A ') / Mw (B')
If the ratio is less than 0.08, the reinforcing property of the reinforcing agent is reduced, so that the fracture properties and abrasion resistance are reduced. Therefore, if the ratio is more than 1, the effect of the reinforcing agent on the matrix phase and the balance of tan δ are undesirably reduced. It is not preferable because it lowers.

According to a first embodiment of the present invention, diene rubbers synthesized by solution polymerization and terminal-modified and / or coupled (for example, polybutadiene rubber (BR), styrene-butadiene copolymer rubber ( SB
R), styrene-isoprene-butadiene copolymer rubber (SIBR)) in an amount of 20 to 80% by weight, preferably 50 to 80% by weight.
50 to 90 parts by weight, preferably 50 to 80 parts by weight, of a raw rubber mixture (A) containing 80% by weight and a non-terminal-modified diene rubber (B) (for example, emulsion-polymerized or solution-polymerized BR, SBR, SIBR) ) 50 to 120 parts by weight, preferably 50 to 120 parts by weight, of a reinforcing agent (for example, carbon black, silica, etc.) per 100 parts by weight of the raw rubber, comprising 50 to 10 parts by weight, preferably 50 to 20 parts by weight. And 20 to 80 parts by weight of a softener (eg, an aromatic process oil, a naphthene-based process oil, etc.),
In producing a rubber composition preferably containing 35 to 70 parts by weight, the average glass transition temperature TgA (° C.) of the raw rubber (A) and the average glass transition temperature TgB (° C.) of the raw rubber (B) are determined. Has the following relationship: TgA + 20>TgB> TgA-20, preferably 20
>TgA> −45 and TgA + 20>TgB> Tg
A-10, and 80% by weight or more, preferably 85 to 100% by weight of the total amount of the raw rubber (A) and the reinforcing agent is firstly heated at a temperature of 135 ° C or more, preferably 130 to 150 ° C.
For example, a desired rubber composition is obtained by mixing with a closed mixer such as a Banbury mixer and then mixing the raw rubber (B) with the remaining reinforcing agent and softening agent, preferably at a temperature of 135 ° C. or more. Can be.

The terminal-modified diene rubber used in the first embodiment of the present invention can be prepared by a conventional method as described in JP-A-64-60604, by synthesizing rubber-terminated rubber molecules such as solution-polymerized SBR and BR. Alkali metal (eg Li)
And alkaline earth metals (eg, Mg) in the molecule -CO-
Compounds having an N <or -CS-N <bond (for example, amides such as N, N-diethylformamide, N, N-dimethylacetamide, N, N-dimethylbenzamide, N, N'-dimethylurea, N, N U.S. Pat. The compound described in 1,
3-dimethyl-2-imidazolidinone, 1,3-dimethylethylenethiourea and the like and the compounds described in JP-A-61-268702, etc.). At this time, the effect is higher as the modification rate of the synthetic terminal is higher, and usually, the one having a modification rate of 20% or more is used.

The coupled diene rubber used in the first embodiment of the present invention may be prepared by a conventional method, for example, a solution-polymerized diene rubber (SBR, BR, etc.).
At least 20%, preferably 30 to 50% of the remaining terminal alkali metal or alkaline earth metal of the diene rubber terminal-modified by the method described above is tin halide, for example. Alternatively, it can be obtained by reacting with a silicon halide according to a conventional method.

As described above, according to the first embodiment of the present invention, in the first step, a specific diene-based raw rubber (A) and, for example, carbon black are first mixed at a temperature of 135 ° C. or higher to obtain carbon black particles. Terminally modified SBR around
Thus, a desired vulcanizate can be obtained because a rubber adsorbing phase such as that described above is provided and the raw material rubber (B) serving as a matrix phase is blended therein. If the mixing temperature is lower than 135 ° C., the reaction between the reinforcing particles and the terminal-modified (and / or coupled) diene rubber (A) is insufficient, and the desired effect cannot be obtained.

According to the second aspect of the present invention, the weight average molecular weight Mw (A ') of the diene raw rubber (A') having a molecular weight range of 100,000 to 1.2 million, preferably 120,000 to 900,000.
And a molecular weight range of 400,000 or more, preferably 500,000 to 1
Weight-average molecular weight M of 500,000 diene raw rubber (B ')
w (B ′) has the following relationship: 0.08 ≦ Mw (A ′) / Mw (B ′) <1 (III), preferably 0.1 ≦ Mw (A ′) / Mw (B ′) ≦ 0.
8 Average glass transition temperature TgA '(° C) of raw rubber (A')
And the average glass transition temperature TgB 'of the raw rubber (B')
(° C.) TgA ′ + 20> TgB ′> TgA′-20... (I ′) Preferably, TgA ′ + 20> TgA′−10 20> TgA ′> − 45... (II ′) Raw rubber (A) 20 to 90 parts by weight, preferably 50 to 80 parts by weight, and a reinforcing agent (for example, carbon black,
Silica, etc.) 50 to 120 parts by weight, preferably 60 to 1 part by weight
And then 80 to 10 parts by weight, preferably 50 to 20 parts by weight of diene raw material rubber (B ').
20 to 80 parts by weight, preferably 35 to 70 parts by weight, based on 100 parts by weight of the total amount of the diene raw material rubbers (A ') and (B'),
By adding a naphthenic process oil or the like, a rubber composition in which the tan δ of the vulcanized product is balanced can be produced. As the raw rubber, a raw rubber dissolved in an organic solvent or a raw rubber formed into an aqueous emulsion can be used.

The rubber composition of the present invention contains the polymer component
In addition to reinforcing agents and softeners, various additives commonly used in other rubber compositions for automobile tires, such as sulfur, vulcanization accelerators, antioxidants, other fillers, plasticizers, etc. The composition can be vulcanized in a conventional manner. The amount of these additives may be a general amount. For example, the amount of sulfur is preferably 0.5 parts by weight or more, more preferably 1.0 to 2.5 parts by weight, per 100 parts by weight of the rubber component. Vulcanization conditions are also in a general range. These additives are generally blended after completion of the first and second steps, but are not limited thereto.

[0016]

EXAMPLES The present invention will be further described with reference to the following examples, but it goes without saying that the scope of the present invention is not limited to these examples.

Examples 1 and 2 and Comparative Examples 1 to 4 Examples 1 and Comparative Examples 1 and 2 were prepared using SBR-1 (glass transition temperature -30 ° C, bound styrene content 20%, vinyl bound content 6).
5%, terminal-modified / coupling-treated solution-polymerized styrene-butadiene copolymer having a weight average molecular weight of 350,000) and SB
R-2 (glass transition temperature -21 ° C, bound styrene amount 4
5%, a vinyl bond content of a butadiene portion of 12%, and a 50% oil-extended emulsion-polymerized styrene-butadiene copolymer having a weight-average molecular weight of 1.2 million) as a raw material rubber. Was evaluated for vulcanization properties. The results are also shown in Table I.

The vulcanization properties (tan δ) were measured as follows. Initial distortion = 10%, dynamic distortion = 2%, frequency = 20 using Toyo Seiki Seisakusho's rheograph solid.
The viscoelasticity was measured in Hz (sample width 5 mm, temperature 0 ° C and 40 ° C).
℃)

In the vulcanization properties, the higher the tan δ at 0 ° C., the greater the frictional force on a wet road surface (the higher the grip power of the tire). The lower the tan δ at 40 ° C., the smaller the energy loss in constant energy deformation (the tire Rolling resistance is small). In the present invention, tan δ (0
° C) / tan δ (40 ° C) ((a) / (b) in the table)
The larger the value, the better the balance of tan δ (that is, the higher the grip force of the tire and the lower the rolling resistance).

In Comparative Example 1 (standard example), the rubber composition in both steps was the same, and in Example 1, oil-extended emulsion polymerization SBR was all introduced in the second step. The tan δ at 40 ° C. is reduced by about 10%, and tan δ
This shows that the temperature gradient of the tire is large, and that fuel economy can be achieved while maintaining the grip force of the tire. Comparative example 2
Is obtained by charging 30 parts by weight of the modified solution polymerized SBR in the second step. In contrast to Example 1, the tan δ temperature gradient is deteriorated.

In Example 2 and Comparative Examples 3 and 4, SBR-1 was used.
(Glass transition temperature -30 ° C, bound styrene content 20%,
70 parts by weight of a terminal-modified / coupling-treated solution-polymerized styrene-butadiene copolymer having a vinyl bond content of 65% and a weight average molecular weight of 350,000, and SBR-2 (glass transition temperature-
This is an example in which 30 parts by weight of a 50% oil-extended emulsion-polymerized styrene-butadiene copolymer having a bound styrene content of 33%, a vinyl bond content of a butadiene portion of 13%, and a weight average molecular weight of 720,000 were used as a raw rubber at 36 ° C. In these examples, as in the above examples, Example 2 according to the present invention exhibited an effect of improving tan δ as compared with Comparative Example 3 (Standard Example) and Comparative Example 4.

[0022]

[Table 1]

Examples 3 to 4 and Comparative Examples 5 to 8 Comparative Example 5 (standard example) and Comparative Example 6 correspond to the SBR-17
Example in which 0 parts by weight and 30 parts by weight of BR-1 (solution-polymerized butadiene polymer having a cis bond amount of 30%, a vinyl bond amount of 13%, and a weight average molecular weight of 300,000) are used as shown in Table II. It is. The difference in Tg between these raw rubbers is 60
° C, which did not satisfy the conditions of the present invention, and the effect of improving tan δ was not recognized even when the unmodified oil-extended emulsion polymerization SBR was added in the second step.

In Examples 3 and 4, Comparative Example 7 (standard example) and Comparative Example 8, SBR-4 (glass transition temperature -25 ° C,
Bound styrene content 15%, butadiene vinyl content 8
60% by weight of a 0%, terminal-modified / coupling-treated solution-polymerized styrene-butadiene polymer having a weight average molecular weight of 350,000) and 40 parts by weight of the above SBR-2 were blended as shown in Table II as a raw rubber. It is an example.

In Comparative Example 7 (standard example), all raw rubbers were charged in the first step, and in Comparative Example 8 (standard example), the rubber compositions in the first and second steps were the same. Things. Looking at the effect of the differences in mixing these,
As shown in II, in the method in which the raw material rubber is additionally added in the second step, the effect of lowering the tan δ at 40 ° C. is produced, but the tan δ at 0 ° C. is also reduced, and no improvement in the tan δ temperature gradient is observed.

On the other hand, in Examples 3 and 4 of the present invention, as shown in Table II, it is apparent that tan δ at 40 ° C. is reduced and the temperature gradient of tan δ is improved.

[0027]

[Table 2]

Table III shows SBR-1 (glass transition temperature-
30 ° C., bound styrene content 20%, butadiene vinyl bond content 65%, weight-average molecular weight 350,000, terminal-modified / coupling-treated solution-polymerized styrene-butadiene copolymer)
And SBR-2 (a glass transition temperature of -21 ° C., an amount of bound styrene of 45%, an amount of a vinyl bond in a butadiene portion of 12%, and an emulsion-polymerized styrene-butadiene polymer having a weight average molecular weight of 1.2 million) and an SBR-5 (glass transition point). Temperature -36 ° C,
35% bonded styrene, 1 vinyl bonded in butadiene moiety
4%, an emulsion-polymerized styrene-butadiene polymer having a weight average molecular weight of 820,000). Comparative Example 9 was obtained by adding all the compounding agents except the vulcanization system in the first step.
In contrast to the present invention, 0 and 11 indicate that the modified solution polymerized SBR is
This is an example of a case where the process is added in the process. As shown in Table III, Example 5 which is the present invention is different from Comparative Example 9 in that tan at 0 ° C.
δ increases, tan δ at 40 ° C. decreases, and tan
The δ gradient is also large, indicating that low fuel consumption can be achieved while maintaining the grip force of the tire. Conversely, the tan δ at 0 ° C. was lower than that of Comparative Example 9 with respect to Comparative Example 10 in which the modified solution-polymerized SBR was added in the second step.
The tan δ at 0 ° C. has increased and tends to worsen. The same applies to Example 6 and Comparative Example 11.

[0029]

[Table 3]

The components shown in Tables I to III are as follows. SBR-1: Solution-polymerized styrene-butadiene copolymer SBR-2 having a glass transition temperature of -30 ° C., an amount of bound styrene of 20%, an amount of vinyl bond of 65%, and a weight average molecular weight of 350,000 combined with terminal modification and coupling treatment. : Glass transition temperature -21 ° C, bound styrene content 45%, vinyl bound content 12%, weight average molecular weight 120
50% oil-extended emulsion-polymerized styrene-butadiene polymer SBR-3: 50% oil-extended emulsion-polymerized styrene having a glass transition temperature of -36 ° C, a bound styrene amount of 33%, a vinyl bond amount of 13% and a weight average molecular weight of 720,000 -Butadiene polymer SBR-4: Solution-polymerized styrene-butadiene copolymer having a glass transition temperature of -25 ° C, a bound styrene content of 15%, a vinyl bond content of 80%, and a weight-average molecular weight of 350,000, which are combined with terminal modification and coupling treatment. Merged SBR-5: 50% oil-extended emulsion-polymerized styrene-butadiene polymer having a glass transition temperature of -36 ° C, a bound styrene content of 35%, a vinyl bond content of 14% and a weight average molecular weight of 820,000 BR-1: a glass transition temperature -90 ° C, cis bond amount 30
%, A vinyl bond amount of 13%, and a solution-polymerized butadiene polymer having a weight average molecular weight of 300,000 carbon black-1: a nitrogen adsorption specific surface area of 117 m ² /
g, DBP oil absorption 112 ml / 100 g carbon black-2: nitrogen adsorption specific surface area 150 m ² /
g, DBP oil absorption 127 ml / 100 g Zinc oxide: Zinc flower No. 3 Stearic acid: Industrial stearic acid Antioxidant 6C: N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine Aroma oil: Aromatic process oil Powdered sulfur: 5% oil-treated powdered sulfur Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazylsulfenamide Vulcanization accelerator DPG: diphenylguanidine Note) The vinyl bond amount here is butadiene Part vinyl bonding
It is about quantity.

[0031]

As described above, according to the present invention,
The balance of tan δ has been improved and the conventional end-modified SBR
Can reduce the fuel consumption of general-purpose HPT tire treads, for which the use effect was not sufficient,
By using BR, a tan δ reduction effect comparable to solution polymerization can be obtained.

Continuation of the front page (56) References JP-A-6-270603 (JP, A) JP-A-6-32941 (JP, A) JP-A-7-109384 (JP, A) JP-A-5-279162 (JP) JP-A-7-292162 (JP, A) JP-A-6-65418 (JP, A) JP-A-7-18125 (JP, A) JP-A-61-162536 (JP, A) 6-299002 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C08L 7/00-21/02

Claims (8)

(57) [Claims] 1. A rubber composition comprising 50 to 90 parts by weight of a raw rubber mixture (A) containing 20 to 80% by weight of a terminal-modified and / or coupled diene-based rubber and at least one type of diene-based rubber which is not terminal-modified. Raw rubber (B) 5
In producing a rubber composition by mixing 50 to 120 parts by weight of a reinforcing agent and 20 to 80 parts by weight of a softening agent with respect to 100 parts by weight of a raw rubber composed of 0 to 10 parts by weight, an average of the raw rubber (A) is used. The glass transition temperature TgA (° C.) and the average glass transition temperature TgB (° C.) of the raw rubber (B) have the following relationship: TgA + 20>TgB> TgA-20 (I) and reinforcing with the raw rubber (A) A method for producing a rubber composition, comprising mixing 80% by weight or more of the total amount of agents at a temperature of 135 ° C. or more, and then adding and mixing the raw rubber (B) and the remaining reinforcing agent and softener. 2. The average glass transition temperature T of the raw rubber (A)
The method for producing a rubber composition according to claim 1, wherein gA (° C) is in the following range. 20>TgA> -45 ... (II) 3. The raw rubber (A) wherein the terminal-modified diene rubber is an alkali metal or alkaline earth metal at the synthetic end of rubber molecules of the solution-polymerized diene raw rubber.
0% or more in the molecule is -CO-N <or -CS-N <
The method for producing a rubber composition according to claim 1 or 2, which is a styrene-butadiene copolymer rubber and / or a polybutadiene rubber obtained by reacting with a compound having a bond. 4. The diene-based rubber to which the raw rubber (A) is coupled has at least 20% of the alkali metal or alkaline-earth metal at the synthetic end of the rubber molecule of the solution-polymerized raw diene rubber as a tin halide. The method for producing a rubber composition according to any one of claims 1 to 3, wherein the rubber composition is a styrene-butadiene copolymer rubber and / or a polybutadiene rubber obtained by reacting with a silicon halide. 5. The raw rubber (B) wherein the raw rubber (A) comprises a solution-polymerized styrene-butadiene copolymer rubber.
Is a styrene-butadiene copolymer rubber synthesized by emulsion polymerization. The method for producing a rubber composition according to any one of claims 1 to 4, wherein 6. A diene raw rubber (A ′) having a weight average molecular weight Mw (A ′) in the range of 100,000 to 1.2 million,
When a rubber composition is produced by mixing with a diene raw material rubber (B ') having a weight average molecular weight Mw (B') of 400,000 or more, the weight average molecular weight has the following relationship: 0.08≤Mw (A ′) / Mw (B ′) <1 (III) Average glass transition temperature TgA ′ (° C.) of raw rubber (A ′)
And the average glass transition temperature TgB 'of the raw rubber (B')
(° C.) and the following relationship: TgA ′ + 20> TgB ′> TgA′-20 (I ′) 20 to 90 parts by weight of diene-based raw rubber (A ′) and reinforcing agent 5
0 to 120 parts by weight are first mixed, and then 2 to 80 to 10 parts by weight of the diene raw material rubber (B ') and 100 parts by weight of the total amount of the diene raw rubbers (A') and (B ').
A method for producing a rubber composition, comprising adding 0 to 80 parts by weight of a softening agent. 7. The method for producing a rubber composition according to claim 6, wherein the average glass transition temperature TgA ′ (° C.) of the raw rubber (A ′) is in the following range. 20> TgA '>-45 ... (II') 8. A rubber composition for a tire, obtainable by the method according to any one of claims 1 to 7.