JP2001323071A - Method for producing carbon master batch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon master batch capable of obtaining a rubber composition with improved tanδ balance, elongation properties and abrasion resistance without making a division blending. SOLUTION: This method for producing a carbon master batch is characterized by comprising the following process: either one of two kinds of rubber latex differing in glass transition temperature from each other is preliminarily crosslinked with a crosslinking agent, and then the resultant latex thus preliminarily crosslinked, the other kind of latex, carbon black and a flexibilizer are blended together, the resultant blend is coagulated, dehydrated and then dried, thus obtaining a carbon black-containing rubber composition.

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 carbon masterbatch containing carbon black and a softening agent, and more particularly to a raw rubber preliminarily crosslinked (gelled) and another raw material having a different glass transition temperature Tg. By mixing rubber in one stage, tan δ balance, tan
The present invention relates to a method for producing a carbon masterbatch capable of obtaining a rubber composition having improved δ temperature dependence, elongation characteristics and wear characteristics.

[0002]

2. Description of the Related Art It has been proposed to improve the balance of tan δ of a tire tread rubber in order to reduce the fuel consumption of automobiles. Many suggestions have been made.

For example, Japanese Patent Application Laid-Open No. 10-226736 discloses a carbon filler gel in which a master batch in which rubber A is mixed with a predetermined amount of carbon and oil is prepared in advance, and then rubber A and rubber B having different Tg are mixed. A method for producing a control rubber is described. According to this method,
Although the tan δ balance is improved while maintaining the abrasion resistance, there is a problem in the process of manufacturing the masterbatch and the work process of mixing rubbers having different Tg with a mixer, and also because the masterbatch has a high carbon concentration. It was very hard and there was a problem of workability in the mixer process.

Japanese Patent Application Laid-Open No. H11-80438 discloses a method of preparing a rubber composition by a latex blending method, in which a latex obtained by pre-crosslinking a rubber latex (gel rubber latex) and an uncrosslinked latex of the same kind of rubber are mixed. A method of stirring, salting out and drying is described. In this way, elongation properties and modulus are improved,
There is a problem that it is difficult to obtain a rubber composition having a balance between abrasion resistance and tan δ.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention solves the above-mentioned problems of the prior art and provides a carbon masterbatch capable of obtaining a rubber composition having improved tan δ balance, elongation characteristics and abrasion resistance. The purpose is to develop a manufacturing method.

[0006]

According to the present invention, any one of two types of rubber latexes having different glass transition temperatures is preliminarily cross-linked by using a cross-linking agent,
Then, the pre-crosslinked latex, another type of latex, carbon black and a softening agent are mixed, and a mixture containing these is coagulated, dehydrated and dried to produce a carbon black-containing rubber composition. A method for manufacturing a masterbatch is provided.

According to the present invention, raw rubber A and raw rubber B
Of two types of rubber latex having a glass transition temperature of TgA ≧ TgB + 10 ° C. (where, TgA: glass transition temperature of raw rubber A, TgB: glass transition temperature of raw rubber B) And then mixing the pre-crosslinked rubber A latex, rubber B latex, carbon black and softener, coagulating, dehydrating and drying the mixture to obtain a carbon black-containing rubber composition. And a method for producing a carbon master batch.

According to the present invention, further, the glass transition temperature of the raw rubber A and the raw rubber B is TgA ≧ TgB + 10 ° C. (where TgA: glass transition temperature of the raw rubber A, Tg
(B: glass transition temperature of raw material rubber B) Of the two types of rubber latexes, the rubber B latex is pre-cross-linked using a cross-linking agent, and then the pre-cross-linked rubber B latex, rubber A latex, carbon black And a softening agent, and coagulating, dehydrating and drying the mixture containing them to produce a carbon black-containing rubber composition.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventor has improved tan δ balance by one-stage mixing without using split mixing, for example, as disclosed in JP-A-10-226736.
Further studies have been conducted to produce a carbon masterbatch having improved abrasion resistance. At least one of two types of rubber latex having different glass transition temperatures is crosslinked (gelled) in advance, and then the other is prepared. It has been found that a desired carbon masterbatch can be produced by mixing a rubber latex, a predetermined amount of carbon black and a softener, coagulating, dehydrating and drying the mixture.

The raw rubbers A and B used in the present invention have glass transition temperatures TgA (° C.) and TgB (° C.)
May be different, but it is more preferable if the above relational expression is satisfied, and it is more preferable if TgA ≧ TgB + 20 ° C.

The rubber that can be used as the raw material rubber A in the present invention is not particularly limited as long as it satisfies the glass transition temperature TgA, but a conjugated diene polymer is particularly preferred. Examples of such conjugated diene-based polymers include one or more polymers or copolymers of conjugated dienes such as butadiene, isoprene, pentadiene, and chloroprene, at least one conjugated diene and at least one copolymerizable therewith. One kind of monomer, for example, aromatic vinyl compounds such as styrene, vinyltoluene and α-methylstyrene, unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile, acrylic acid, methacrylic acid, maleic acid, maleic anhydride and the like. Copolymers with unsaturated carboxylic acid esters such as unsaturated carboxylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, and methoxyethyl acrylate are exemplified. Particularly preferred polymers are block copolymers having a polymer block mainly composed of a conjugated diene and a polymer block mainly composed of an aromatic vinyl compound. The boundaries between each block of the block copolymer may be clear or unclear. The proportion of each block is from 0 to 100% by weight of a conjugated diene, from 0 to 100% by weight of an aromatic vinyl diene, preferably from 20 to 80% by weight of a conjugated diene and from 2 to 4% by weight of an aromatic vinyl diene.
0 to 80% by weight.

On the other hand, there is no particular problem for the raw material rubber B as long as it satisfies the above glass transition temperature TgB, but it is preferable to use a diene raw material rubber which has been subjected to emulsion polymerization or solution polymerization.
For example, polybutadiene, styrene-butadiene copolymer, styrene-isoprene-butadiene copolymer, polyisoprene, natural rubber and the like can be mentioned. Further, according to the present invention, the average weight average molecular weight Mw (A) of the raw rubber A
Is 100,000 to 1.2 million, the average weight average molecular weight Mw (B) of the raw rubber B is 200,000 or more, and 0.1 ≦
It is preferable that the relation of Mw (A) / Mw (B) ≦ 6.0 is satisfied.

In the present invention, one of the two types of rubber latex is preliminarily cross-linked by adding a cross-linking agent in advance and at a predetermined temperature and time. Examples of the crosslinking agent include peroxide, sulfur, a sulfur-based compound, and a two-component system of a peroxide and a reducing agent. Examples of the peroxide include t-butyl hydroperoxide (t-BuOOH), benzoyl peroxide, dicumyl peroxide, potassium persulfate, and ammonium persulfate. Examples of the sulfur-based compound (sulfur donor crosslinking agent) include dipentamethylenethiuram tetrasulfide (TRA), tetramethylthiuram disulfide (TMTD), and 2- (4-morpholinodithio) benzothiazole (MDB). Examples of the reducing agent include organic reducing agents such as amine compounds and alcohol compounds, and inorganic reducing agents such as ferrous salts and sodium bisulfite. If necessary, a crosslinking aid such as triallyl isocyanurate, triallyl cyanurate, N, N'-m-phenylenebismaleimide can be used in combination. Peroxides such as potassium sulfate are preferred, and potassium or ammonium persulfate is particularly preferred. In the present invention, the preliminary crosslinking is usually performed at room temperature to 180 ° C.
C., preferably in the range of 40 to 80.degree. C., at normal pressure or under pressure, in a closed system or a non-closed system.
The concentration of the crosslinking agent is usually preferably about 0.01 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the solid content of the latex.

According to the present invention, the latex of the raw rubber A and the latex of the raw rubber B to be mixed have a solid content weight ratio of A
/ B is preferably 20/80 to 80/20, and more preferably the rubber latex to be pre-crosslinked is 20 to 50 parts by weight. When the rubber to be pre-crosslinked is A, if the compounding ratio of the rubber A is less than 20, the effect of uneven distribution of carbon black is small, and the desired effects such as high grip property and abrasion resistance are small.
On the other hand, if it exceeds 80, the uneven distribution of carbon is too large, and the reinforcing effect itself is weakened, and the strength characteristics deteriorate. On the other hand, when the rubber latex to be pre-crosslinked is B, if the compounding ratio of rubber A is less than 20, the uneven distribution of carbon black is too large, the reinforcing effect is reduced, and the strength characteristics are significantly deteriorated. On the other hand, if it exceeds 80, the effect of uneven distribution of carbon is small, and the glass transition temperature of A, which is a matrix side rubber, is greatly affected, so that the temperature dependence of tan δ is increased, and it is difficult to obtain stable characteristics.

There is no particular limitation on the method of compounding the latex obtained by preliminarily crosslinking one of the two rubber latexes having different glass transition temperatures with a crosslinking agent, the other rubber latex and carbon black. Generally, a mixture of rubber latex and carbon black and a softening agent uniformly dispersed therein is mixed and stirred, then coagulated with an acid such as dilute sulfuric acid and a polymer flocculant, and then dehydrated and dried to obtain the carbon of the present invention. A black-containing rubber composition can be produced.

As the carbon black used in the present invention, in the case of a tire tread, preferably,
Nitrogen adsorption specific surface area (N ₂ SA) (ASTM D 303
7 is 70 m ² / g or more, more preferably 80 to 160 m ² / g, and the DBP oil absorption (JIS K)
Measured according to 6221) is preferably 80 ml / 10
0 g or more, more preferably 100 to 130 ml / 100 g
Use The carbon black may be an organic or inorganic surface treatment for increasing the bonding with rubber or a material obtained by attaching a small amount of metal oxide such as silica to the surface. The rubber composition of the present invention, that is, the compounding amount of carbon black compounded in the carbon-containing rubber composition is 40 to 100 parts by weight, preferably 50 to 100 parts by weight based on 100 parts by weight of the final rubber polymer. . If the compounding amount of this carbon black is too small, the reinforcing property decreases,
If the desired physical properties cannot be obtained, and if the amount is too large, it is not preferable because the production of the carbon black master batch becomes difficult.

As the softening agent, those generally used for rubber compounding, such as aromatic process oil and paraffin oil, are compounded in an amount of 70 parts by weight or less, preferably 10 to 55 parts by weight, per 100 parts by weight of the raw rubber.

The carbon masterbatch produced by the method according to the present invention can be blended with other raw rubber by a general method and used, for example, as a rubber composition for a tire tread. In order to obtain the desired effect, it is preferable that 50 parts by weight or more per 100 parts by weight of the total amount of the raw rubber is derived from the carbon masterbatch produced by the method according to the present invention.

The carbon masterbatch produced by the method according to the present invention and the rubber composition containing the same may optionally contain various additives commonly used for tires in addition to the above-mentioned essential components. And the compounding amount thereof can be a general amount. Such optional additives include, for example, vulcanizing agents, vulcanization accelerators, anti-aging agents,
Fillers, plasticizers and the like can be mentioned.

[0020]

EXAMPLES Hereinafter, the contents and effects of the present invention will be described more specifically with reference to Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

Examples 1-8, Standard Example 1 and Comparative Examples 1-2 Masterbatches 1 used in Examples 1-8 and Comparative Example 2
No. 9 was produced based on the composition (parts by weight) shown in Table I. The components are as follows.

Raw rubber A latex: styrene content 4
7.4%, vinyl content 12.7%, glass transition temperature-
Styrene butadiene copolymer rubber latex having a weight average molecular weight of 1.2 million at 20.7 ° C Raw rubber B latex: styrene content 25.3%, vinyl content 15.4%, glass transition temperature -50.7 ° C,
Styrene butadiene copolymer rubber latex having a weight average molecular weight of 620,000 Carbon black: N ₂ SA (m ² / g) of 112, D
ISAF grade carbon black with BP oil absorption (ml / 100g) of 112 Softener: Aromatic process oil

[0023]

[Table 1]

The latex of the raw rubber A was pre-crosslinked by the following method. That is, 1 part by weight of potassium persulfate was previously dissolved in a small amount of water with respect to 100 parts by weight of the solid content of the latex of the raw material rubber A, and this was charged into the latex. Heat for an hour,
A pre-crosslinked latex was made. The latex of the raw rubber A used in the master batch 4 was prepared by adding 1 part by weight of t-butyl hydroperoxide (t-BuCOOH, 69 wt%) to 100 parts by weight of the solid content of the latex.
After sealing, the mixture was heated at 160 ° C. for 6 hours with stirring to prepare a pre-crosslinked latex. The rubber compositions used in Examples 1 to 8 were prepared by the following method. The latex of the raw rubber B, the carbon black, and the softening agent were sequentially mixed with the latex of the pre-crosslinked rubber A in the weight ratio shown in Table I,
Dilute sulfuric acid was added while stirring with a high-speed stirrer to adjust the pH to 4.2.
Then, a commercially available polymer flocculant was added to obtain a particulate aggregate. After washing the aggregates with water, the remaining water was squeezed out with a roller and dried with warm air at 50 ° C. for 8 hours.
8 was obtained. The master batch 6 was prepared by the same method as described above except that the amount of potassium persulfate, which is a crosslinking agent for pre-crosslinking the rubber A latex, was changed to 2 parts by weight based on the rubber solid content. It uses latex. Next, the master batches 1 to 8 and the following additional components were kneaded together in the amount (parts by weight) shown in Table II for 3 to 5 minutes in a 1.8-liter closed mixer.
Released when 5 ° C was reached. The amounts are shown in Table II.

Zinc oxide: Zinc flower No. 3 Stearic acid: Industrial stearic acid Antioxidant 6C: N-phenyl-N '-(1,3-dimethylbutyl) -p-phenylenediamine Wax: Industrial paraffin wax

[0026]

[Table 2]

Next, as a final step, the following vulcanization accelerator and sulfur were kneaded with an 8-inch open roll to obtain a rubber composition. Powdered sulfur: 5% oil-treated powdered sulfur Vulcanization accelerator CZ: N-cyclohexyl-2-benzothiazylsulfenamide Vulcanization accelerator DPG: Diphenylguanidine

The rubber composition used in Standard Example 1 was prepared by mixing rubber A and rubber B with the following components (parts by weight) of carbon black, a softening agent, a vulcanization accelerator and sulfur, as shown in Table II. With 1.8 liter closed mixer
The mixture was kneaded for ４4 minutes and released when the temperature reached 165 ± 5 ° C., and the above vulcanization accelerator and sulfur were kneaded with an 8-inch open roll.

In the rubber composition used in Comparative Example 1, in the first step, the rubber B was blended (in parts by weight) as shown in Table II with carbon black, a softener, and a vulcanization accelerator and the above-mentioned additional components excluding sulfur. With a 1.8 liter closed mixer
Knead for 4 minutes, release when it reaches 150 ± 5 ° C, then in the second step knead with rubber A in a 1.8 liter closed mixer for 3-5 minutes, release when it reaches 165 ± 5 ° C Then, as a final step, a vulcanization accelerator and sulfur were obtained by kneading an 8-inch open roll.

The rubber composition used in Comparative Example 2 was prepared by preliminarily cross-linking the latex of rubber A by the above-mentioned method. Carbon black and a softening agent were sequentially mixed in the weight ratios shown in Table I, and a master batch 9 was obtained in the same manner as in the example. Then, this was mixed with a vulcanization accelerator and the above-mentioned additional components excluding sulfur to 1.8. Knead for 3-4 minutes with a closed liter mixer, release when it reaches 150 ± 5 ° C,
Next, as a final step, a vulcanization accelerator and sulfur were kneaded with an 8-inch open roll.

The sample composition was press-vulcanized in a 15 × 15 × 0.2 cm mold at 160 ° C. for 20 minutes to prepare a target test piece, and the vulcanization properties were evaluated. The results are shown in Table II.

The method for testing the vulcanizate properties of the compositions obtained in each of the examples is as follows. 1) Breaking strength, 300% deformation stress: JIS K 625
1 (Dumbbell-shaped No. 3 type) 2) tan δ: Measured at 20 Hz, initial elongation 10% and dynamic strain 2% using a viscoelastic device rheograph solid manufactured by Toyo Seiki Seisakusho (sample width 5 mm, 3) Abrasion resistance: Measured with a Lambourn-type abrasion tester, the loss of abrasion is determined by the following method, and the result is displayed as an index. Abrasion resistance (index) = [(with reference specimen) Weight loss / (weight loss in each test piece)] × 100 However, the reference test piece was calculated as a standard example in Table II.

As shown in the results of Table II, Examples 1 to 8 have improved breaking strength and deformation stress as compared with the comparative example, and have greatly improved tan δ balance and abrasion resistance index as compared with the standard example. As a result, it is possible to achieve both improved grip performance and reduced rolling resistance when used as a tire, and a longer life.

Examples 9 to 16 and Comparative Examples 3 to 4 Masterbatches 10 to 18 used in Examples 9 to 16 and Comparative Example 4 were produced based on the formulations (parts by weight) shown in Table III. The ingredients are the same as those used in masterbatches 1 to 9, and the additives are represented in the same manner as above except that the rubber latex to be pre-crosslinked is a latex of rubber B.
The rubber composition was obtained by mixing with the compounding amount (parts by weight) of IV. Incidentally, the latex of the raw rubber B used in the master batch 13 is based on 100 parts by weight of the latex solid content.
t-butyl hydroperoxide (t-BuCOOH, 6
9 wt%), and the mixture was sealed and heated at 160 ° C. for 6 hours with stirring to prepare a pre-crosslinked latex.

[0035]

[Table 3]

[0036]

[Table 4]

The rubber composition used in Comparative Example 3 was blended (in parts by weight) as shown in Table IV. In the first step, rubber A was prepared by removing carbon black, a softener, and further excluding a vulcanization accelerator and sulfur. The mixture was kneaded with a 1.8 liter closed mixer for 3 to 4 minutes together with the added components, and released when the temperature reached 150 ± 5 ° C. Next, in the second step, the mixture was kneaded with a rubber B in a 1.8 liter closed mixer for 3 to 5 minutes, and released when the temperature reached 165 ± 5 ° C. Further, as a final step, a vulcanization accelerator and sulfur were added at 8 inches. Was kneaded with an open roll to obtain a rubber composition.

The rubber composition used in Comparative Example 4 was prepared by preliminarily cross-linking rubber B latex by the above method at the compounding amount (parts by weight) shown in Table IV. , Carbon black and a softening agent were sequentially mixed at the weight ratio shown in Table II, and a master batch 18 was obtained in the same manner as in the example. Next, this is kneaded with a 1.8-liter closed mixer for 3 to 4 minutes together with the vulcanization accelerator and the above-mentioned additive components except sulfur, and when it reaches 150 ± 5 ° C., it is released. A vulcanization accelerator and sulfur were obtained by kneading an 8-inch open roll.

The sample composition was press-vulcanized in a 15 × 15 × 0.2 cm mold at 160 ° C. for 20 minutes to prepare a target test piece, and the vulcanization properties were evaluated. The results are shown in Table IV.

The method for testing the vulcanizate properties of the compositions obtained in each example is as follows. 1) Breaking strength, 300% deformation stress: JIS K 625
1 (Dumbbell-shaped No. 3 type) 2) tan δ: Measured at 20 Hz, initial elongation 10% and dynamic strain 2% using a viscoelastic device rheograph solid manufactured by Toyo Seiki Seisakusho (sample width 5 mm, 3) Abrasion resistance: Measured with a Lambourn type abrasion tester, and the wear loss is indicated by an index using the following method. Abrasion resistance (index) = [(weight loss on reference test piece) / (Weight loss in each test piece)] × 100 However, the reference test piece was calculated in Table I as a standard example.

As shown in the results of Table IV, Examples 9 to 16
Has improved rupture strength and deformation stress as compared with the comparative example, and has a smaller temperature dependency of tan δ and improved abrasion resistance as compared with the standard example. Life extension is achieved.

[0042]

According to the present invention, tan δ balance, ta
A rubber composition having excellent nδ temperature dependency, elongation characteristics and wear characteristics can be obtained, and the productivity is greatly improved and these characteristics are further improved as compared with the conventional method.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/30 C08K 3/30 5/00 5/00 5/14 5/14 C08L 21/02 C08L 21 / 02 // C09C 1/48 C09C 1/48 B29K 19:00 B29K 19:00 507: 04 507: 04 F term (reference) 4F070 AA04 AA06 AA07 AA08 AC04 AC20 AC56 AE01 AE02 AE08 DA38 DA39 DB01 DC05 FB03 FB04 4F201 AA45 AB03 AB07 AB18 BA09 BC01 BC03 BC12 BC37 BK01 BK06 BK12 BN22 BN44 BN50 BQ50 4J002 AC01X AC03W AC03X AC06W AC06X AC07W AC08W AC08X AC09W AE053 BP01W DA036 DG037 EK007 FD016 FD023 FD37 AE01

Claims (9)

[Claims] 1. A latex of one of two types of rubber latex having a different glass transition temperature is pre-cross-linked using a cross-linking agent, and then the pre-cross-linked latex, another type of latex, carbon black and A method for producing a carbon masterbatch, comprising mixing a softener, coagulating, dehydrating, and drying a mixture containing the same to produce a carbon black-containing rubber composition. 2. Two kinds of glass transition temperatures of the raw rubber A and the raw rubber B having a relationship of TgA ≧ TgB + 10 ° C. (however, TgA: glass transition temperature of the raw rubber A, TgB: glass transition temperature of the raw rubber B). The rubber A latex of the rubber latex is pre-cross-linked using a cross-linking agent, and then the pre-cross-linked rubber A latex, rubber B latex, carbon black and softener are mixed, and a mixture containing these is coagulated. A method for producing a carbon masterbatch, comprising producing a carbon black-containing rubber composition by dehydration and drying. 3. Two kinds of glass transition temperatures of the raw rubber A and the raw rubber B having a relationship of TgA ≧ TgB + 10 ° C. (where TgA: glass transition temperature of the raw rubber A, TgB: glass transition temperature of the raw rubber B). The rubber B latex of the rubber latex is pre-cross-linked using a cross-linking agent, and then the pre-cross-linked rubber B latex, rubber A latex, carbon black and softener are mixed, and the mixture containing these is coagulated. A method for producing a carbon masterbatch, comprising producing a carbon black-containing rubber composition by dehydration and drying. 4. The mixed solid weight ratio A / B of the latex of the raw rubber A and the latex of the raw rubber B is 80/20.
The production method according to any one of claims 1 to 3, wherein the production method is 20/80. 5. The compounding amount of the crosslinking agent used in the pre-crosslinking treatment of the rubber latex is 0.01 to 2 with respect to 100 parts by weight of the solid content of the raw rubber latex to be pre-crosslinked.
The production method according to any one of claims 1 to 4, wherein the amount is 0 parts by weight. 6. The method according to claim 1, wherein the crosslinking agent used for pre-crosslinking the latex is a peroxide.
The production method according to the paragraph. 7. The method according to claim 1, wherein the crosslinking agent used for pre-crosslinking the latex is potassium persulfate or ammonium persulfate. 8. The carbon black having a nitrogen surface area (N
8. The process according to claim 1, wherein ₂ SA) is 50 to 200 m ² / g) and the DBP oil absorption is 60 to 140 ml / 100 g. 9. A rubber composition for tires, wherein at least 50 parts by weight of 100 parts by weight of raw rubber are derived from a carbon masterbatch produced by the production method according to any one of claims 1 to 8.