JP5178228B2 - Rubber composition and method for producing the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a rubber composition and a method for producing the same, and more specifically, a reinforcing rubber excellent in durability and rigidity, a tire using the same, and the like, which improves dispersibility of fibers as a filling reinforcing material. The present invention relates to a rubber composition capable of providing a rubber product and a method for producing the same.

  In general, rubber such as tire products is added with a granular inorganic reinforcing material such as carbon black or silica to increase its strength and rigidity. However, such a granular inorganic reinforcing material has a limit in its reinforcing performance because of its shape. Therefore, a technique has been proposed in which short fibers are selected as a rubber reinforcing material to improve hardness, modulus, and the like (see, for example, Patent Document 1). In addition, it has been proposed to use a master batch containing aramid short fibers of 0.5 to 1000 μm for tire rubber (for example, Patent Document 2). Furthermore, a rubber composition in which cellulose fibers are combined with rubber has been proposed (see, for example, Patent Document 3).

Japanese Patent Laid-Open No. 10-7811 JP 2001-164052 A JP 2006-206864 A

By the way, when a fiber such as a cellulose-based fiber is used as a rubber reinforcing material, a composite of hydrophilic cellulose and hydrophobic rubber has a poor dispersibility in the rubber of the reinforcing material and has sufficient durability and rigidity. I can't show it. Also, the adhesiveness or tackiness at the fiber / rubber interface is not sufficient. For this reason, when the rubber is subjected to mechanical stress, separation or peeling of the fiber occurs, and sufficient strength and durability cannot be obtained.
Accordingly, it is an object of the present invention to provide a rubber composition that exhibits sufficient durability and rigidity by enhancing dispersibility and adhesiveness of a reinforcing material composed of cellulosic fibers to a rubber component, and a method for producing the same.

  The present inventor has intensively studied to solve the above problems. As a cellulose-based fiber, cellulose nanofiber having an average fiber diameter of nano-order is used as a rubber reinforcing material, and a silane coupling agent is added to the reinforcing material. By increasing the dispersibility in the rubber component, and further using a sulfide-based silane coupling agent having a polysulfide structure as the coupling agent, the adhesiveness and tackiness at the interface with the rubber component can be increased. The present inventors have found that it can be expected and completed the present invention.

  That is, the rubber composition and the manufacturing method thereof according to the present invention are characterized by the configuration or means described in the following (1) to (7).

(1) in the rubber component, relative to 100 parts by mass of the rubber component of the cellulose nanofiber in the range of 1 to 50, and a sulfide-based silane coupling agent sulfur atoms having a polysulfide structure 2-10, cellulose nanofiber In contrast, a rubber latex and a mixture of the fiber slurry dispersed in water and added with the silane coupling agent are mixed and then dried. And removing the water to obtain a rubber composition.
( 2) The rubber composition according to (1), wherein the cellulose nanofiber has an average fiber diameter in the range of 1 to 1000 nm and an average fiber length in the range of 0.1 to 100 μm.

(3) A slurry of cellulose nanofibers dispersed in water, after adding a silane coupling agent and a rubber latex, the mixture is dried to remove water, (1) The manufacturing method of the rubber composition as described in (2).

(6). In the method for producing a rubber composition according to the above (1) to (5), after mixing a rubber latex and a slurry of the fiber dispersed in water, the mixture is dried to remove water. A process for producing a rubber composition, characterized in that
(7). The method for producing a rubber composition according to (6), wherein the silane coupling agent is added to the slurry.

  In the rubber composition of the present invention, it becomes possible to improve the dispersibility by allowing the cellulose nanofibers that are hydrophilic and the rubber component that is hydrophobic to pass through a silane coupling agent, so that the reinforcing property is improved. . Further, when the silane coupling agent contains sulfur, it is possible to crosslink even the sulfur portion in the coupling agent, so that the adhesion between the fiber and the rubber is improved and the strength can be increased.

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments for carrying out the present invention will be described in detail below. Note that the present invention is not limited to the following embodiments and examples.
The rubber composition according to the present invention contains cellulose nanofibers having an average fiber diameter of nano-order and a silane coupling agent in the rubber component.

The rubber component of the rubber composition according to the present invention is not particularly limited, but examples of those that can be used for tire products include the following rubber components.
The rubber component of the rubber composition is roughly classified and selected from natural rubber and synthetic rubber, and both may be used in combination. The synthetic rubber is not particularly limited and can be appropriately selected from known ones according to the purpose. A diene rubber is preferable, and a styrene-butadiene copolymer (SBR), polyisoprene (IR), polybutadiene (BR) is used. ), Acrylonitrile-butadiene rubber, chloroprene rubber, and butyl rubber.

The cellulose nanofibers blended in the rubber composition according to the present invention preferably have an average fiber diameter in the range of 1 to 1000 nm and an average fiber length in the range of 0.1 to 100 μm. In particular, the average fiber diameter of cellulose nanofibers is more preferably in the range of 1 to 500 nm, and the average fiber length is more preferably in the range of 5 to 50 μm. When the average fiber particle size and the average fiber length are less than the above ranges, the dispersibility decreases, and when the average fiber particle sizes and average fiber lengths exceed the above ranges, the reinforcing performance decreases.
Here, the average fiber diameter and the average fiber length are measured by a pore electrical resistance method (Coulter principle method) by dispersing fibers in an ethylene glycol solution.
Moreover, it is preferable that the said cellulose nanofiber is contained in the range of 1-50 mass parts with respect to 100 mass parts of rubber components, especially the range of 3-20 mass parts. If the amount of fiber is small, the reinforcing effect is not sufficient, and if the amount is large, the processability of rubber becomes worse.

  Examples of the silane coupling agent blended in the rubber composition of the present invention include those known per se, such as bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, Bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercapto Propyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-to Riethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilyl Propyl benzoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilyl Examples thereof include propyl-N, N-dimethylthiocarbamoyl tetrasulfide and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide.

  It is preferable that the said silane coupling agent is contained in the range of 0.05-50 mass% with respect to a cellulose nanofiber, especially 1-20 mass%. When the amount of the silane coupling agent is small, the blending effect is not sufficient. On the other hand, if the amount is excessive, no significant performance improvement is observed and the cost increases.

In the present invention, a sulfide-based silane coupling agent having a polysulfide structure having a sulfur number X of 2 to 10 is particularly preferable among the above-described silane coupling agents.
For example, in a bis-triethoxysilylalkyl polysulfide, the polysulfide has a sulfur number X of 2 to 10, more preferably 3 to 7. The alkyl chain is preferably in the range of 2-4. For example, bis- (3-triethoxysilylpropyl polysulfide is represented by the following general formula (1).

  When such a sulfide-based silane coupling agent having the following polysulfide structure is blended, -OH of the cellulose structure molecule shown in FIG. 1 binds to a silane coupling as shown in FIG. 2, and a sulfur moiety in the coupling agent. However, since it becomes possible to crosslink with the rubber component, the adhesion and adhesion between the fiber and the rubber are improved, and the strength can be increased.

  Next, in order to produce a rubber composition in the present invention, first, the fibers are dispersed in water and then beaten, passed through an orifice, appropriately subjected to mechanical shearing, and dispersed with a high-pressure homogenizer or the like. Slurry. Actually, fibers having various fiber diameters are commercially available, and in the present invention, these are used after being slurried in water. In this case, the concentration of the fiber in the slurry is preferably in the range of 0.1 to 3 parts by mass with respect to 100 parts by mass of water in terms of manufacturing operation. Further, the silane coupling agent of the present invention, in particular, the sulfide-based silane coupling agent is preferably added directly at the time of rubber kneading by the integral blending method after solidifying the slurry, and the coupling agent by kneading shear mixing. A method of reacting the silyl group portion of the silyl group with the —OH group of cellulose and further promoting chemical bonding at the rubber-cellulose interface is desirable.

The method of mixing the slurry of rubber latex, fiber, and silane coupling agent according to the present invention is not particularly limited, and for example, a general method such as a homogenizer, a rotary stirrer, an electromagnetic stirrer, or a propeller stirrer can be used.
In the present invention, water can be removed from the mixed solution by a general method such as oven drying, freeze drying, or spray drying.
Although there is no limitation in particular in solid content concentration of the said liquid mixture in this invention, it is preferable that it is 40 mass% or less, and it is preferable that it exists in the range of 5-15 mass parts. When this solid content concentration exceeds 40 mass%, the viscosity of a liquid mixture will become high too much and the dispersibility of a fiber will fall.

  The rubber composition of the present invention can contain various components usually used in the rubber industry in addition to the above-described compounding components. For example, as various components, fillers (for example, reinforcing fillers such as silica; and inorganic fillers such as calcium carbonate and calcium carbonate); vulcanization accelerators; anti-aging agents; zinc oxide; stearic acid; And additives such as an ozone degradation inhibitor. As vulcanization accelerators, thiazole vulcanization accelerators such as M (2-mercaptobenzothiazole), DM (dibenzothiazyl disulfide) and CZ (N-cyclohexyl-2-benzothiazylsulfenamide); TT And thiuram vulcanization accelerators such as (tetramethylthiuram sulfide); and guanidine vulcanization accelerators such as DPG (diphenylguanidine).

Specifically, the rubber composition can contain 7.0 parts by mass or less of sulfur with respect to 100 parts by mass of the rubber component. In particular, it is the range of 3.0-7.0 mass parts, More preferably, it is the range of 4.0-6.0 mass parts. In the rubber composition, the organic acid cobalt salt can be blended in an amount of 1.0 part by mass or less based on 100 parts by mass of the rubber component. In particular, it is the range of 0.05-1.0 mass part, More preferably, it is the range of 0.3-0.8 mass part. Examples of the cobalt organic acid salt include cobalt naphthenate, cobalt rosinate, or a linear or branched monocarboxylic acid cobalt salt having about 5 to 20 carbon atoms.
Further, it is preferable to add 40 parts by mass or more, more preferably 40 to 100 parts by mass, particularly 50 to 100 parts by mass of carbon black to 100 parts by mass of the rubber component in the rubber composition. Carbon black can be appropriately selected from those usually used in the rubber industry, and examples thereof include SRF, GPF, FER, HAF, ISAF, etc. Among them, GPF and HAF are in terms of balance between physical properties and cost. To preferred.

  In the rubber composition configured as described above, dispersibility in the slurry becomes uniform by blending cellulose nanofibers, and dispersibility in rubber is enhanced by blending the silane coupling agent. In particular, when a silane coupling agent containing a polysulfide structure is blended, dispersibility, affinity to rubber, and adhesion are enhanced, and the reinforcing property can be further improved.

  Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited to these.

200 g of natural rubber latex (solid content concentration: 60% by mass), 300 g of cellulose fiber slurry (“Serish” manufactured by Daicel Chemical Industries, Ltd .: average fiber diameter: 100 nm, average fiber length: 45 μm, solid content concentration: 5% by mass), 1000 g of water, and Polysulfide silanes shown in Table 1 below were mixed in a high-speed mixing homogenizer at 3000 rpm for 5 minutes to obtain a cellulose / natural rubber mixed solution.
This was developed on a vat and dried and solidified in an oven at a temperature of 100 ° C. to obtain a cellulose fiber composite natural rubber (fiber composite rubber).
With respect to 100 parts by mass of the rubber component of the fiber composite rubber, a normal kneading is performed by a laboratory kneader according to the configuration shown in Table 1 below, the resulting mixture is pressure-press vulcanized, and a rubber sheet having a thickness of 2 mm Got.
Evaluation Test A predetermined dumbbell was punched out of the rubber sheet, and a vulcanized rubber tensile test was performed according to ASTM D412 to measure 300% modulus and breaking strength. The measured values are values in Comparative Example 1 set to 100, and the values in each Example are displayed as indexes.

  Note 1 in Table: SERISH KY100G manufactured by Daicel Chemical Industries, Ltd. 2; Furnace Black HAF manufactured by Asahi Carbon Co., Ltd. 3; Noxeller DM manufactured by Ouchi Shinsei Chemical Co., Ltd. NS, Note 5: Si-69 from Degussa.

  The rubber composition of the present invention has high industrial applicability to enhance the dispersibility and adhesiveness of a reinforcing material composed of cellulosic fibers to a rubber component and to exhibit sufficient durability and rigidity.

FIG. 1 is a diagram showing a general cellulose molecular structure. FIG. 2 is a reaction bond relationship diagram of cellulose nanofibers, a silane coupling agent, and rubber.

Claims (3)

In the rubber component, the cellulose nanofiber is in the range of 1-50 with respect to 100 parts by mass of the rubber component , and the sulfide-based silane coupling agent having a polysulfide structure having 2 to 10 sulfur atoms is added to the cellulose nanofiber. In the range of 0.05 to 20% by mass , the rubber latex and the slurry of the fiber added in the water and mixed with the silane coupling agent are mixed, and then the mixture is dried to obtain water. A rubber composition obtained by removing water.   The rubber composition according to claim 1, wherein the cellulose nanofiber has an average fiber diameter in the range of 1 to 1000 nm and an average fiber length in the range of 0.1 to 100 µm. 2. The slurry of cellulose nanofibers dispersed in water, to which a silane coupling agent is added, and a rubber latex are mixed, and then the mixed solution is dried to remove water. Or the manufacturing method of the rubber composition of 2.

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