JPH0967469A - Production of rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable ofspecifying the relationship of the average glass transition temperature of plural material rubbers, and improving balance of tanδ, reducing a fuel cost of general-purpose/HPT-based tire tread, having as much tanδ reducing effect using an inexpensive polymer SBR as that by melt polymerization. SOLUTION: In blending 100 pts.wt. of a raw material rubber comprising (A) 50-90 pts.wt. of a raw material rubber mixture containing 20-80wt.% of a diene-based rubber having a modified and/or coupled diene and (B) 50-10 pts.wt. of a raw material rubber composed of at least one diene-based rubber having an unmodified end with (C) 50-120 pts. wt. of a reinforcing agent and (D) 20-80 pts.wt. of a softener, the average glass transition temperature TgA ( deg.C) of the component A and that TgB ( deg.C) of the component B have the relationship of the formula. The component A is mixed with >=80wt.% of the component C at >=135 deg.C and the mixture and then blended with the component B, the rest of the component C and the component D.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a rubber composition having an excellent tan δ balance 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 in order to reduce fuel consumption of automobiles. Specifically, split mixing of compounding components and use of terminal modified rubber have been proposed. There is.

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

Further, JP-A-2-129241 proposes to blend a terminal-modified conjugated diene polymer with carbon black in an organic solvent to improve the tensile strength and abrasion resistance of a vulcanized product. .

[0005]

However, the above-mentioned techniques such as the divided mixing method of the compounding components and the use of the terminal modified rubber have the problems that the effect is thin in a high compounding system of oil and carbon black, and still remain. The improvement is required. Accordingly, the present invention is directed to the vulcanizate ta
It is an object 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 used.
100 to 50 parts by weight of a raw material rubber mixture (A) containing 50 to 90 parts by weight and 50 to 10 parts by weight of a raw material rubber (B) composed of at least one diene rubber which is not end-modified. Reinforcing agent 50 to 120
When the rubber composition is produced by mixing 20 parts by weight of the softening agent and 20 parts by weight of the softening agent, the average glass transition temperature TgA (° C) of the raw material rubber (A) and the average glass transition temperature TgB (° C of the raw material rubber (B) are measured. ) Has the following relationship, and TgA + 20> T
gB> TgA-20, and mixing 80% by weight or more of the raw material rubber (A) and the total amount of the reinforcing agent at a temperature of 135 ° C. or higher, and then adding and mixing the raw material rubber (B) and the remaining reinforcing agent and softening agent. A method for producing a rubber composition for a pneumatic tire is provided.

According to the present invention, a diene raw material 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 are also used.
When the rubber composition is produced by mixing with the diene raw 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.) has the following relationship: TgA ′ + 20> TgB ′> TgA′-20 (I ′) 20 to 90 parts by weight of diene raw rubber (A ′) and reinforcing agent 5
0 to 120 parts by weight are mixed first, and then 2 to 80 parts by weight of the diene-based raw material rubber (B ') and 100 parts by weight of the total amount of the diene-based raw material rubbers (A') and (B ').
Provided is 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
To find that δ is almost unrelated to the rubber adsorption phase near the filler such as carbon black and to be due to the matrix phase, and improve the tan δ balance 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, carbon is obtained 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. By covering the surface with a terminal-modified diene-based rubber and then adding and mixing a diene-based rubber having low reactivity (for example, emulsion polymerization SBR), a rubber composition having an improved tan δ balance of the vulcanized product can be obtained.

In the second embodiment of the present invention, two kinds of diene raw rubbers satisfying the above-mentioned specific relation (III) are used, the diene raw rubber (A ') and the reinforcing agent are mixed, and then, A rubber composition having an improved tan δ balance of the vulcanized product can be obtained by mixing the diene-based raw material rubber (B ′) and the softening agent therein. Note that Mw (A ') / Mw (B')
If the ratio is less than 0.08, the reinforcing property by the reinforcing agent is deteriorated, and the fracture properties and wear resistance are deteriorated, which is not preferable. On the contrary, if the ratio exceeds 1, the effect of the reinforcing agent on the matrix phase and the balance of tan δ are balanced. It is not preferable because it decreases.

According to the first aspect of the present invention, a diene rubber synthesized by solution polymerization and end-modified and / or coupled (for example, polybutadiene rubber (BR), styrene-butadiene copolymer rubber ( SB
R) and styrene-isoprene-butadiene copolymer rubber (SIBR)) in an amount of 20 to 80% by weight, preferably 50 to 50% 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 diene rubber (B) not end-modified (for example, emulsion-polymerized or solution-polymerized BR, SBR, SIBR ) 50 to 10 parts by weight, preferably 50 to 20 parts by weight of the raw material rubber, and 50 to 120 parts by weight, preferably 60 to 100 parts by weight of a reinforcing agent (for example, carbon black, silica, etc.) per 100 parts by weight of the raw material rubber. And 20 to 80 parts by weight of a softening agent (eg, aromatic process oil, naphthenic process oil, etc.),
Preferably, in producing a rubber composition 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 Has the following relationship: TgA + 20>TgB> TgA-20, preferably 20
>TgA> -45 and TgA + 20>TgB> Tg
A-10, and further 80% by weight or more, preferably 85 to 100% by weight of the total amount of the raw material rubber (A) and the reinforcing agent, 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 type mixer such as a Banbury mixer, and then mixing the raw rubber (B) and the remaining reinforcing agent and softening agent at a temperature of preferably 135 ° C. or higher. You can

The terminal-modified diene rubber used in the first embodiment of the present invention is a synthetic terminal of rubber molecules such as solution-polymerized SBR and BR according to a conventional method as described in JP-A-64-60604. Alkali metal (eg Li)
Or alkaline earth metal (eg Mg) in the molecule -CO-
Compounds having N <or -CS-N <bond (for example, amides such as N, N-diethylformamide, N, N-dimethylacetamide, N, N-dimethylbenzamide, N, N'-dimethylurea, N, N Urea such as'-dimethylethyleneurea, lactams such as ε-caprolactam, N-methyl-ε-caprolactam, N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone. JP-A-61-103904 The compound described in 1,
3-dimethyl-2-imidazolidinone, 1,3-dimethylethylene thiourea and the like, such as the compounds described in JP-A-61-268702 and the like) can be obtained. At this time, the higher the modification rate of the synthetic terminal, the more effective it is. Usually, the modification rate of 20% or more is used.

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

As described above, according to the first aspect of the present invention, in the first step, the specific diene raw rubber (A) and carbon black, for example, are first mixed at a temperature of 135 ° C. or higher to form carbon black particles. Terminal modified SBR around
A rubber-adsorbed phase such as that described above is provided, and the raw material rubber (B) serving as the matrix phase is mixed therein, so that a desired vulcanized product can be obtained. If the mixing temperature is less than 135 ° C., the reaction between the reinforcing agent particles and the terminal-modified (and / or coupled) diene rubber (A) is insufficient and the desired effect cannot be obtained.

According to the second embodiment 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 1,200,000, 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 Raw material rubber (A ') average glass transition temperature TgA' (° C)
And the average glass transition temperature TgB 'of the raw rubber (B')
(C) has the following relationship: TgA '+ 20>TgB'>TgA'-20 ... (I ') Preferably TgA' + 20>TgA'-1020> TgA '>-45 ... (II') Diene system 20 to 90 parts by weight, preferably 50 to 80 parts by weight of the raw material rubber (A) and a reinforcing agent (for example, carbon black,
50 to 120 parts by weight, preferably 60 to 1
00 parts by weight is first contacted, and then 80 to 10 parts by weight of the diene raw rubber (B '), preferably 50 to 20 parts.
20 to 80 parts by weight, preferably 35 to 70 parts by weight, of a softening agent (for example, aromatic process oil, based on 100 parts by weight of the total amount of parts by weight and the diene raw rubbers (A ') and (B')).
A rubber composition in which the tan δ of the vulcanized product is balanced is manufactured by adding a naphthenic process oil or the like). As the raw material rubber, a raw material rubber dissolved in an organic solvent or a raw material rubber in an aqueous emulsion can be used.

The rubber composition of the present invention contains the above polymer component,
In addition to the reinforcing agent and the softening agent, blending various additives generally blended in other rubber compositions for automobile tires such as sulfur, vulcanization accelerator, antioxidant, other fillers, plasticizers, etc. And such formulations can be vulcanized by conventional methods. The amount of these additives may be a general amount. For example, the content 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 added after the completion of the first step and the second step, but the present invention is not limited thereto.

[0016]

EXAMPLES The present invention will be further described below with reference to 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 2 are SBR-1 (glass transition temperature -30 ° C., bound styrene amount 20%, vinyl bond amount 6).
5%, end-modified / coupling solution-polymerized styrene-butadiene copolymer having a weight average molecular weight of 350,000) and SB
R-2 (glass transition temperature -21 ° C, amount of bound styrene 4
5%, vinyl bond amount 12%, 50% oil-extended emulsion-polymerized styrene-butadiene copolymer having a weight average molecular weight of 1.2 million)
And were used as raw rubbers, and as shown in Table I, other components were blended and vulcanized physical properties were evaluated. The results are also shown in Table I.

The vulcanized physical properties (tan δ) were measured as follows. Using Toyo Seiki Seisakusho's Rheological solid, initial strain = 10%, dynamic strain = 2%, frequency = 20
Viscoelasticity was measured in Hz (sample width 5 mm, temperature 0 ° C and 40
℃)

Regarding the vulcanization properties, the higher the tan δ at 0 ° C., the greater the frictional force on the wet road surface (higher the grip force of the tire), and 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
℃) / tan δ (40 ℃) ((a) / (b) in the table
Value), the larger the value, the better the balance of tan δ (that is, the higher the grip force of the tire and the smaller the rolling resistance).

In Comparative Example 1 (standard example), the rubber compositions in both steps were made the same, and in Example 1, all the oil-extended emulsion-polymerized SBR was added in the second step. Tan δ at 40 ° C is reduced by about 10%, and tan δ
It shows that the temperature gradient is large and the fuel consumption can be reduced while maintaining the grip of the tire. Comparative example 2
Indicates that 30 parts by weight of the modified solution-polymerized SBR was added in the second step, and in contrast to Example 1, the temperature gradient of tan δ deteriorates.

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

[0022]

[Table 1]

Examples 3 to 4 and Comparative Examples 5 to 8 Comparative Example 5 (standard example) and Comparative Example 6 are the same as 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 content of 30%, a vinyl bond content of 13% and a weight average molecular weight of 300,000) were used as shown in Table II. Is. The difference in Tg of these raw rubbers is 60
C., which does not satisfy the conditions of the present invention, and the effect of improving tan δ was not observed even when the non-modified oil-extended emulsion-polymerized SBR was added in the second step.

Examples 3 to 4 and Comparative Example 7 (standard example) and Comparative Example 8 are SBR-4 (glass transition temperature -25 ° C.,
60% by weight of a terminally modified / coupling solution-polymerized styrene-butadiene polymer having a bound styrene content of 15%, a vinyl bond content of 80% and a weight average molecular weight of 350,000 and the SBR-
In this example, 240 parts by weight was used as a raw rubber and compounded as shown in Table II.

In Comparative Example 7 (standard example), all the raw material rubbers were added in the first step, and in Comparative Example 8 (standard example), the rubber compositions in the first and second steps were the same. It is a thing. To see the effect of the difference in the mixing method,
As shown in II, the method of additionally adding the raw material rubber in the second step has the effect of lowering the tan δ at 40 ° C., but the tan δ at 0 ° C. also lowers, and no improvement in the temperature gradient of tan δ is observed.

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

[0027]

[Table 2]

Table III shows SBR-1 (glass transition temperature-
30 ° C, bound styrene amount 20%, vinyl bond amount 65%,
Terminal-modified / coupling solution-polymerized styrene-butadiene copolymer having a weight average molecular weight of 350,000) and SBR-2
(Glass transition temperature -21 ° C, amount of bound styrene 45%,
Emulsion-polymerized styrene-butadiene polymer having a vinyl bond amount of 12% and a weight average molecular weight of 1,200,000 and SBR-5 (glass transition temperature -36 ° C, bound styrene amount of 35%, vinyl bond amount of 14%, weight average molecular weight of 820,000). Is an emulsion-polymerized styrene-butadiene polymer). Comparative Example 9 is one in which all compounding agents other than the vulcanizing system were added in the first step,
Contrary to the present invention, Comparative Examples 10 and 11 were modified solution polymerization SB.
This is an example when R is added in the second step. As shown in Table III, Example 5 of the present invention was compared with Comparative Example 9 at 0 ° C.
Tan δ of tan δ is increased and tan δ at 40 ° C. is decreased, and the tan δ gradient is large, which shows that fuel economy can be achieved while maintaining the grip force of the tire. Also,
On the contrary, in comparison with Comparative Example 10 in which the modified solution-polymerized SBR was added in the second step, tan δ at 0 ° C. was lower and tan δ at 40 ° C. was higher than that of Comparative Example 9. . The same applies to Example 6 and Comparative Example 11.

[0029]

[Table 3]

The blending components shown in Tables I to III are as follows. SBR-1: Glass transition temperature -30 ° C, bound styrene content 20%, vinyl bond content 65%, weight average molecular weight 350,000 solution-modified styrene-butadiene copolymer SBR-2 combined with terminal modification and coupling treatment : Glass transition temperature -21 ° C, bound styrene amount 45%, vinyl bond amount 12%, weight average molecular weight 120
50% oil-extended emulsion-polymerized styrene-butadiene polymer SBR-3: glass transition temperature -36 ° C, bound styrene amount 33%, vinyl bond amount 13%, weight-average molecular weight 720,000 50% oil-extended emulsion polymerized styrene -Butadiene polymer SBR-4: Glass transition temperature -25 ° C, bound styrene amount 15%, vinyl bond amount 80%, weight average molecular weight 350,000 solution-modified styrene-butadiene copolymerization using terminal modification and coupling treatment in combination. Combined SBR-5: Glass transition temperature -36 ° C, bound styrene amount 35%, vinyl bond amount 14%, 50% oil-extended emulsion-polymerized styrene-butadiene polymer BR-1: glass transition temperature -90 ° C, cis bond amount 30
%, Vinyl bond amount 13%, weight average molecular weight 300,000 solution-polymerized butadiene polymer carbon black-1: nitrogen adsorption specific surface area 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 white No. 3 Stearic acid: Industrial stearic acid Anti-aging agent 6C: N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine Aroma oil: Aromatic process oil Sulfur powder: Sulfur powder treated with 5% oil Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazylsulfenamide Vulcanization accelerator DPG: Diphenylguanidine

[0031]

As described above, according to the present invention,
Improved tan δ balance, conventional end-modified SBR
It was possible to reduce the fuel consumption of general-purpose HPT-type tire treads that were not sufficiently used in the
BR can be used to obtain a tan δ reduction effect similar to solution polymerization.

Claims (8)

[Claims] 1. From 50 to 90 parts by weight of a raw rubber mixture (A) containing 20 to 80% by weight of a diene rubber end-modified and / or coupled, and at least one diene rubber not end-modified. Raw material rubber (B) 5
When a rubber composition is manufactured by mixing 50 to 120 parts by weight of a reinforcing agent and 20 to 80 parts by weight of a softening agent to 100 parts by weight of a raw material rubber composed of 0 to 10 parts by weight, the average of the raw material rubber (A) is 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 the raw rubber (A) and reinforcement A method for producing a rubber composition, which comprises mixing 80% by weight or more of the total amount of the agent at a temperature of 135 ° C. or more and then adding and mixing the raw rubber (B) and the remaining reinforcing agent and softening agent. 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 end-modified diene rubber of the raw rubber (A) is a solution-polymerized diene-based rubber having a synthetic molecule end of a rubber molecule of the diene-based rubber.
0% or more is -CO-N <or -CS-N <in the molecule.
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 coupled diene rubber of the raw rubber (A) is a tin halide containing 20% or more of the alkali metal or alkaline earth metal at the synthetic end of the rubber molecule of the raw diene rubber solution-polymerized. Alternatively, the method for producing the rubber composition according to any one of claims 1 to 3, which is a styrene-butadiene copolymer rubber and / or a polybutadiene rubber obtained by reacting with silicon halide. 5. The raw material rubber (A) comprises a solution-polymerized styrene-butadiene copolymer rubber, and the raw material rubber (B) is used.
5. The method for producing a rubber composition according to claim 1, wherein the rubber composition is a styrene-butadiene copolymer rubber synthesized by emulsion polymerization. 6. A diene raw material rubber (A ′) having a weight average molecular weight Mw (A ′) in the range of 100,000 to 1,200,000,
When a rubber composition is produced by mixing with a diene raw 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.) has the following relationship: TgA ′ + 20> TgB ′> TgA′-20 (I ′) 20 to 90 parts by weight of diene raw rubber (A ′) and reinforcing agent 5
0 to 120 parts by weight are mixed first, and then 2 to 80 parts by weight of the diene-based raw material rubber (B ') and 100 parts by weight of the total amount of the diene-based raw material rubbers (A') and (B ').
A method for producing a rubber composition, which comprises 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 raw material rubber (A ′) has an average glass transition temperature TgA ′ (° C.) in the following range. 20> TgA '>-45 ... (II') 8. A rubber composition for a tire, which is obtained by the method according to any one of claims 1 to 7.