JP2001114903A - Method for manufacturing rubber composition with dispersed carbon black - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a rubber composition that is improved in dispersion of carbon black saving labors as much as possible in the kneading of a rubber composition containing carbon black. SOLUTION: The method for manufacturing a rubber composition with dispersed carbon black comprises extruding a master batch having at least previously dispersed carbon black in a polymer with the use of a twin screw extruder and subsequently kneading the extruded product with a compounding accelerator such as a vulcanizing accelerator and a vulcanizing agent.

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 in which carbon black is dispersed, and more particularly to a rubber composition in which carbon black is dispersed by using a twin-screw extruder to improve the dispersion of carbon black. The present invention relates to a method for manufacturing a product.

[0002]

2. Description of the Related Art In a rubber composition containing a reinforcing carbon black, the size of the primary particles constituting the carbon black and the size of the structure which is a higher-order structure of the carbon black are caused by the reinforcing property. Is well known. That is, as the particle diameter of the primary particles becomes smaller and the structure becomes larger, the reinforcing property to the rubber becomes larger.

[0003] Today, rubber compositions containing carbon black are used in various fields such as power transmission belts such as V-belts and V-ribbed belts. In particular, carbon black is dispersed in power transmission belts that are repeatedly subjected to compressive force. When the rubber composition was used, large agglomerates of carbon black were generated, and the reinforcing property, abrasion resistance, tensile strength, and hysteresis were not exhibited, causing an early belt life.

For this reason, conventionally, attempts have been made to modify the surface of carbon black, or esters of unsaturated fatty acids having 8 to 24 carbon atoms or 8 to 24 carbon atoms.
It has also been proposed to use carbon black dispersants consisting of esters of 24 unsaturated alcohols.

[0005]

However, in the case of carbon black having a high surface area, no remarkable improvement in the dispersing effect was found in the means for modifying the surface of carbon black. In addition, when a dispersant is used, it is difficult to adjust the charging time and the optimum blending amount, and there is a possibility that the physical properties of the rubber such as modulus are adversely affected.

The present invention has been made in order to solve the above-mentioned problems. In kneading a rubber composition containing carbon black, a rubber composition having a good dispersion of carbon black with minimum effort is required. It is intended to provide a manufacturing method.

[0007]

That is, according to the first aspect of the present invention, a masterbatch in which at least carbon black is dispersed in a polymer is extruded by a twin-screw extruder, and then a vulcanization accelerator is added thereto. A method for producing a rubber composition in which carbon black is dispersed, in which a compounding agent such as a vulcanizing agent is kneaded, wherein a masterbatch in which carbon black is previously dispersed in a polymer is extruded by a twin-screw extruder. Thus, the dispersion of carbon black in the matrix can be improved.

[0008] The invention according to claim 2 of the present application is to prepare a masterbatch in which carbon black is dispersed in a polymer in advance, extrude the masterbatch by a twin-screw extruder, and then use the masterbatch by a closed kneader. The present invention relates to a method for producing a rubber composition in which carbon black is kneaded with a compounding agent such as a vulcanization accelerator and a vulcanizing agent.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polymers used in the present invention include natural rubber, SBR (styrene-butadiene rubber),
Sulfur-modified or non-sulfur-modified chloroprene rubber, acrylonitrile-butadiene rubber, HNBR (hydrogenated nitrile rubber), a mixture of HNBR and a metal salt of an unsaturated carboxylic acid, EPDM (ethylene-propylene-diene monomer), or olefin-based Ester-based and urethane-based thermoplastic elastomers are used.

[0010] Carbon black is, for example, HAF, MA
F, EPC, ISAF, etc., and the amount of addition is 5 to 100 parts by weight per 100 parts by weight of the polymer. In addition, carbon black is not limited to this type.

In the present invention, a master batch is prepared by previously kneading a polymer and carbon black with an open roll, a kneader or the like. In this method, 5 to 100 parts by weight of carbon black is added to 100 parts by weight of a polymer by an open roll and kneaded, and then the kneaded master batch is released once and cooled to 20 to 50 ° C. This is to prevent scorch of the polymer. In addition, 0 to 20 parts by weight of a softening agent can be added together with carbon black. This improves the compatibility between the carbon black and the polymer, and improves the dispersion in the polymer.

Subsequently, the master batch is extruded while being kneaded by a twin-screw extruder. The twin-screw extruder used here is of a type in which a pair of screws are rotated in the same direction, and a kneading unit feeds a rubber material fed from a hopper, and a polymer material sent from the feeding unit. It consists of a compression part and a melting part which thermoplastically plasticizes the kneaded polymer material and sends it towards the die. For this reason, the master batch is basically a mixture of carbon black and a polymer, and it is not preferable to mix a vulcanizing agent and a vulcanization accelerator. The addition of a vulcanizing agent cures the polymer, making kneading and extrusion difficult. By kneading and extruding the master batch with a twin-screw extruder, the dispersion of carbon black in the matrix can be improved.

A rubber composition kneaded with a twin-screw extruder is mixed with 20
Cool to 50 ° C. Next, a predetermined amount of a filler, a softening agent, an antioxidant, a vulcanization accelerator in the obtained rubber composition,
A vulcanizing agent composed of sulfur or organic peroxide is kneaded with a Banbury mixer or an open roll. However, depending on the polymer, it is not necessary to cool the kneaded rubber composition, and it is also possible to perform finish kneading continuously.

Specifically, a rubber composition kneaded by a twin-screw extruder is mixed with a known filler such as a filler other than a vulcanizing agent comprising sulfur or an organic peroxide, a softening agent, an antioxidant, a vulcanization accelerator and the like. Is kneaded using a Banbury mixer and an open roll, and finally a vulcanizing agent is added to perform final kneading.

Examples of the softener include general plasticizers for rubber, for example, phthalates such as dibutyl phthalate (DBP) and dioctyl phthalate (DOP), adipates such as dioctyl adipate (DOA), and dioctyl sebacate (DOS). Etc., phosphates such as tricresyl phosphate, etc., or general petroleum softeners. The softener is added in an amount of 0 to 20 parts by weight, preferably 5 to 100 parts by weight of the polymer.
１６16 parts by weight.

Among the vulcanizing agents, organic peroxides include di-
t-butyl peroxide, dicumyl peroxide,
t-butylcumyl peroxide, 1.1-t-butylperoxy-3.3.5-trimethylcyclohexane,
2.5-di-methyl-2.5-di (t-butylperoxy) hexane, 2.5-di-methyl-2.5-di (t-
Butylperoxy) hexane-3, bis (t-butylperoxydi-isopropyl)) benzene, 2.5-di-methyl-2.5-di (benzoylperoxy) hexane, t-
Butylperoxybenzoate, t-butylperoxy-2
-Ethyl-hexyl carbonate and the like are used. The compounding amount is 0.2 to 10 parts by weight based on 100 parts by weight of the polymer. If the amount is less than 0.2 parts by weight, crosslinking is not sufficiently performed, and if the amount exceeds 10 parts by weight, sufficient elasticity cannot be obtained.

Examples of the vulcanization accelerator include N-cyclohexylbenzothiazylsulfenamide, N, N-diethyl-2-benzothiazylsulfenamide, 2-mercaptobenzothiazole, 2-mercaptothiazoline,
-Mercaptoimidazoline, diphenyl guanidine,
Triphenyl guanidine, thiohydropyridine, Z
n-dimethyl dithiocarbamate, Zn-diethyl
Dithiocarbamate, Zn-diethyldithiocarbamate, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, other aldehydes / ammonia, aldehydes / amines, alkyl / amines, nitrosos, and the like are not particularly limited. .
The addition amount is 1 to 5 parts by weight based on 100 parts by weight of the rubber.

[0018]

The present invention will be described below in detail with reference to examples. Examples 1 to 5 According to the composition shown in Table 1, EP was first opened with an open roll.
A master batch was prepared by roughly kneading so that a predetermined carbon black was added to 100 parts by weight of DM. A small cut of this master batch is used as a twin screw extruder (JSW
(Nippon Steel Works) and kneaded to extrude the rubber composition. Extrusion was performed at a rubber discharge speed of 40 g / min and a screw rotation speed of 100 rpm. The temperature of each cylinder was kept constant at 70 ° C., and only the die head was open.

Subsequently, the rubber composition was charged into a BR Banbury mixer and kneaded at a rotation speed of 40 rpm for 30 seconds. Then, a compound excluding the vulcanizing agent shown in Table 1 was charged and kneaded for 4 minutes. A sulfuric acid was added, and the mixture was kneaded for 30 seconds, followed by finish kneading. The obtained unvulcanized rubber composition was cured at 165 ° C for 30 minutes.
Vulcanized for minutes.

The evaluation of the dispersibility of carbon black in the obtained vulcanized rubber sheet, a dynamic tensile fatigue test and a tensile test were carried out by the following methods. Table 1 shows the results.

1. Evaluation of Dispersibility of Carbon Black The spin-spin relaxation time (T ₂ ) of the sample was measured by using the solid-echo method and the CPMG method of pulse NMR measurement used as a method for evaluating the molecular motion of the rubber compounding system. Next, define the average relaxation time MT ₂ by the following equation using the T ₂ value in each phase of the rubber compound. MT ₂ = Σ
(T _2i × V _i) from the (T _2i:: each phase of T2, V _i of each phase fraction) molecular motion of the polymer chain by adsorption onto the carbon black of the polymer chains are expected to be suppressed, the higher the dispersion of carbon black MT ₂ is reduced. Particularly, in a high temperature region (150 ° C.) where the molecular motion of the polymer chain is active, the effect of restraining the molecular motion of the polymer chain by the carbon black is remarkable, so that the MT ₂ value at 150 ° C. It was used as a sex index.

2. Tensile fatigue test A sample prepared by driving a vulcanized rubber sheet into a No. 4 dumbbell shape was attached to a chuck of a tensile tester, and an atmosphere temperature of 1
A fatigue test was performed at 30 ° C. and a displacement of 75% by repeatedly applying a tensile stress 8 times / minute.

3. Static test The tensile strength of the vulcanized rubber sheet was measured according to JIS K6251.

Comparative Examples 1-3 Polymers of the rubber compound shown in Table 1 and carbon black were roughly kneaded with an open roll to produce a master batch.
Subsequently, the other ingredients were kneaded with the master batch using a Banbury mixer in the same manner as in the example, and the obtained unvulcanized rubber composition was vulcanized at 165 ° C. for 30 minutes. Evaluation of the dispersibility of carbon black in the obtained vulcanized rubber sheet, tensile dynamic fatigue test, and tensile test were performed by the following methods. Table 1 shows the results.

[0025]

[Table 1]

[0026] From this result, with respect to MT _2, Example is smaller than that of Comparative Example, it is shown that the dispersion of the carbon black is good. Further, since the examples have good dispersibility of carbon black, it can be seen that the tensile fatigue properties and the tensile properties are also good.

Examples 6 to 8 and Comparative Examples 4 to 6 According to the formulations shown in Table 2, similar to Example 1, the master batch was roughly kneaded with an open roll so as to add a predetermined amount of carbon black to 100 parts by weight of EPDM. Produced. A small cut of this master batch was put into a twin-screw extruder (manufactured by JSW Japan Steel Works, Ltd.) and kneaded to extrude a rubber composition. Extrusion conditions are the same as in the first embodiment.

Subsequently, the rubber composition was charged into a BR Banbury mixer and kneaded at a rotation speed of 40 rpm for 30 seconds. Then, a compound excluding the vulcanizing agent shown in Table 2 was charged and kneaded for 4 minutes. A sulfuric acid was added, and the mixture was kneaded for 30 seconds, followed by finish kneading. The obtained unvulcanized rubber composition was cured at 165 ° C for 30 minutes.
Vulcanized for minutes. Table 3 shows the results of carbon black dispersibility evaluation, tensile dynamic fatigue test, and tensile test in the obtained vulcanized rubber sheet.

[0029]

[Table 2]

[0030] Consequently, even in embodiments that do not use oil, MT ₂ is smaller than that of Comparative Example shows that dispersibility of carbon black is good, also a better tensile fatigue and tensile properties You can see that.

Example 9 and Comparative Example 7 A master batch was prepared by roughly kneading the CR rubber compound shown in Table 3 by using an open roll so as to add predetermined carbon black to 100 parts by weight of CR in the same manner as in Example 1. Produced. A small cut of this master batch was put into a twin-screw extruder (manufactured by JSW Japan Steel Works, Ltd.) and kneaded to extrude a rubber composition. Extrusion conditions are the same as in the first embodiment.

Subsequently, the rubber composition was charged into a BR Banbury mixer, kneaded at a rotation speed of 40 rpm for 30 seconds, and then a compound excluding the vulcanizing agent shown in Table 3 was charged, kneaded for 2 minutes, and further kneaded. A sulfuric acid was added, and the mixture was kneaded for 30 seconds, followed by finish kneading. The obtained unvulcanized rubber composition was cured at 153 ° C for 20 minutes.
Vulcanized for minutes. Table 3 shows the results of carbon black dispersibility evaluation, tensile dynamic fatigue test, and tensile test in the obtained vulcanized rubber sheet.

[0033]

[Table 3]

From the results, it is found that the MT ₂ of the example is smaller than that of the comparative example, indicating that the dispersibility of the carbon black is good, and that the tensile fatigue property and the static property are also good.

Example 10 and Comparative Example 8 A master batch was prepared by roughly kneading the natural rubber compounds shown in Table 4 by using an open roll in the same manner as in Example 1 so that a predetermined amount of carbon black was added to 100 parts by weight of NR. And a small cut is made into a twin screw extruder (JSW
(Nippon Steel Works) and kneaded to extrude the rubber composition. Extrusion conditions are the same as in the first embodiment.

Subsequently, the rubber composition was charged into a BR Banbury mixer and kneaded at a rotation speed of 40 rpm for 3 minutes.
The composition excluding the vulcanizing agent shown in Table 4 was charged, kneaded for 4 minutes, further added with a vulcanizing agent, kneaded for 30 seconds, and finished kneaded. The obtained unvulcanized rubber composition was vulcanized at 150 ° C. for 20 minutes. Table 4 shows the results of evaluation of carbon black dispersibility, tensile dynamic fatigue test and tensile test in the obtained vulcanized rubber sheet.

[0037]

[Table 4]

From the results, it can be seen that the example is smaller than the comparative example, indicating that the dispersibility of the carbon black is good, and that the tensile fatigue properties and the tensile properties are also good. Thus, from the results of the pulse NMR measurement, the MT ₂ values of the master batches produced by the twin-screw extruder were lower for all the blending systems. It is thought that the dispersibility of the carbon black was improved by the twin-screw extrusion.

Although no remarkable difference was observed in the results of the tensile test, the number of tensile times at break became larger when a twin-screw extruder was used in the tensile fatigue test, and a significant improvement in fatigue characteristics was observed. Was.

[0040]

As described above, in the invention described in the present application, a master batch in which at least carbon black is dispersed in a polymer is extruded by a twin-screw extruder.
In this method, a vulcanization accelerator, a vulcanizing agent and other compounding agents are kneaded, and the method for producing a rubber composition is as follows. A masterbatch in which carbon black is dispersed in a polymer in advance is extruded with a twin-screw extruder. Thus, there is an excellent effect of improving the dispersion of carbon black in the matrix to improve the tensile fatigue properties and tensile properties.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshihiro Yamada 4-1-1-21 Hamazoedori, Nagata-ku, Kobe Mitsusei Belt Co., Ltd. (72) Inventor Toru Noguchi 4-1-1, Hamazodori, Nagata-ku, Kobe-shi F-term (reference) in Mitsuboshi Belting Co., Ltd.

Claims (2)

[Claims] 1. A masterbatch in which at least carbon black is dispersed in a polymer in advance is extruded by a twin-screw extruder, and a compounding agent such as a vulcanization accelerator and a vulcanizing agent is kneaded into the extruded masterbatch. A method for producing a rubber composition in which carbon black is dispersed. 2. A masterbatch in which carbon black is dispersed in a polymer in advance is prepared, and the masterbatch is extruded by a twin-screw extruder. Then, a vulcanization accelerator, a vulcanization accelerator and a vulcanization accelerator are added to the masterbatch by an internal kneader. A method for producing a rubber composition in which carbon black is dispersed, wherein a compounding agent such as a sulfurizing agent is kneaded.