JP2011102451A - Methods for producing agent for reinforcing rubber and rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an agent for reinforcing a rubber, capable of being dried without coagulating fibrillated fiber, and improving the balance of reinforcing properties and low heat build-up by being added to a rubber polymer. <P>SOLUTION: A composite of the fibrillated fiber and a nanofiller is obtained by mixing the nanofiller of an inorganic filler having 2-200 nm of average particle diameter in a weight of 0.1-0.5 time as heavy as the weight of the fiber, with an aqueous dispersion of the fibrillated fiber, and drying the mixed product. The rubber composition is produced by adding and mixing the obtained composite to and with the rubber polymer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber reinforcing agent containing fibrillated fibers, and a method for producing a rubber composition containing the reinforcing agent.

  Conventionally, a technique for reinforcing a rubber composition with fibers is known, and it is also known to blend fibrillated fibers in order to enhance the reinforcing property. Such fibrillated fibers tend to be entangled and agglomerated due to their raised form, and are difficult to disperse uniformly in the rubber composition. Moreover, since it is easy to aggregate in this way, especially in the case of a cellulose, since it has a hydroxyl group (OH), it is easy to aggregate further, Therefore It is marketed as a water suspension body for handleability. Therefore, at the time of manufacturing the rubber composition, it is necessary to disperse the water in the rubber composition while removing water from the fibrillated fibers in a water suspension, and it is not easy to disperse uniformly. Therefore, the actual situation is that the reinforcing properties by the fibrillated fibers are not sufficiently exhibited.

  In Patent Document 1 below, a water-suspended fibrillated fiber is stirred and mixed in water together with latex rubber (so-called wet mixing), and the resulting master batch is used to produce a conventional Banbury mixer, extruder, etc. And mixing with other chemicals (so-called dry mixing) to obtain the final rubber composition. However, this method also has a problem that the rubber polymer is limited to latex rubber.

  Patent Document 2 below discloses blending a rubber composition with a dry product obtained by combining fibrillated fibers and mineral particles (particulate filler) such as carbon black or silica, It is disclosed that an aqueous suspension containing fibrillated fibers and particulate filler is prepared and dried to obtain the dried product. However, in this document, the amount of fibrillated fibers is 0.1 to 100 g, particularly 1 to 10 g, based on 100 g of mineral particles, that is, a large amount of particulate filler is combined with fibrillated fibers. The dried product is obtained (see paragraph 0094). In such a case where a large amount of particulate filler is added, there is a problem that hysteresis loss due to the particulate filler is large and low heat build-up is inferior.

JP 2006-206864 A JP-T-2002-503621

  The present invention has been made in view of the above points. The fibrillated fiber can be dried without agglomeration, and by adding it to the rubber polymer, the balance between reinforcement and low heat generation is improved. An object of the present invention is to provide a rubber reinforcing agent.

  The present inventor can dry a fibrillated fiber without agglomeration by mixing a relatively small amount of nanofiller with a fibrillated water-suspended fiber and drying it. It has been found that the balance between reinforcement and low heat build-up can be improved by adding to the above, and the present invention has been completed.

  That is, in the method for producing a rubber reinforcing agent according to the present invention, nanofillers, which are inorganic fillers having an average particle size of 2 to 200 nm, are added to an aqueous dispersion of fibrillated fibers in an amount of 0.1 to 0.1% of the fiber weight. It is mixed in an amount 0.5 times and dried to obtain a composite of fibrillated fibers and nanofillers.

  Moreover, the manufacturing method of the rubber composition which concerns on this invention adds the rubber reinforcing agent obtained above to a rubber polymer, and mixes it.

  According to the present invention, the fibrillated fiber can be dried without agglomeration, and the balance between reinforcement and low heat build-up can be improved by adding it to the rubber polymer.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  In the present invention, an aqueous dispersion in which fibrillated fibers are dispersed in water is used. As the fibrillated fiber, various short fibers finely pulverized and fibrillated (microfibrillated) by a mechanical shearing force such as a high-pressure homogenizer are used.

  The type of fiber is not particularly limited, and examples thereof include cellulose, polyamide (for example, linear aliphatic polyamide called nylon, aromatic polyamide called aramid, etc.), polyvinyl alcohol, and the like. May be used alone or in combination of two or more.

  Such a fibrillated fiber is generally obtained in the form of a water suspension suspended or dispersed in water by being finely pulverized and fibrillated by mechanical shearing force in water. An aqueous suspension of fibers can be used. Examples of the water suspension include serisch PC-110A, PC-110B, PC-110S, PC-110T, FD-100F, FD-100G, KY-100G, and KY-100S, as microfibrous cellulose. As the fibrous aramid, Tiara KY-400S, KY-400D and the like are commercially available (both are manufactured by Daicel Chemical Industries, Ltd.), and these are preferably used. The form of these commercially available products is in the form of a cotton swab, and such a water suspension in the form of a damp can be used. The ratio of the fibrillated fibers contained in the water suspension is not particularly limited. For example, an aqueous suspension having a fiber ratio of 5 to 95% by weight and a water ratio of 95 to 5% by weight can be used. The third component or impurities may be contained in a small amount.

  The diameter of the fibrillated fiber (that is, fiber diameter) is not particularly limited, but the average fiber diameter is preferably 5 μm or less, more preferably 0.01 to 1 μm. Further, the length of the fibrillated fiber (that is, fiber length) is not particularly limited, but the average fiber length is preferably 10 to 1500 μm. Here, the average fiber diameter is measured by scanning electron microscope observation (SEM). Specifically, 20 fibrillated fibers are randomly extracted from the image data of the microscope, the short diameter is measured, and the phase is measured. The arithmetic average is defined as the average fiber diameter. The average fiber length is measured according to JIS P8121 using a fiber length measuring machine (FS-200) manufactured by KAJANI.

  The aqueous dispersion of fibrillated fibers used in the production method according to the present invention is preferably a dispersion obtained by dispersing fibrillated fibers in water at least 10 times the fiber weight. If this magnification is less than 10 times, that is, if the weight ratio of water to the fibers contained in the dispersion (water / fiber) is less than 10, the viscosity of the dispersion may be high and stirring may be insufficient. The upper limit of this magnification is not particularly limited, but is preferably 100 times or less. More specifically, since the fibrillated fiber is commercially available in the form of a water suspension as described above, the above-mentioned aqueous dispersion can be obtained by adding water to this and stirring to disperse the fiber.

  In the production method according to the present invention, a nanofiller is mixed with the aqueous dispersion of fibrillated fibers thus obtained and dried to obtain a composite of fibrillated fibers and nanofillers. The nanofiller enters between the fibrillated fibers and functions as a baffle plate that suppresses aggregation during drying. Therefore, by mixing the nanofiller, a fibrillated fiber that does not aggregate even when dried can be obtained.

  As the nanofiller, particles of an inorganic filler having an average particle diameter of 2 to 200 nm are used. When the average particle size is less than 2 nm, it is difficult to uniformly disperse in water, and the baffle effect on the fibrillated fibers may be insufficient. On the contrary, when the average particle diameter exceeds 200 nm, it is difficult to enter between the fibrillated fibers, and the baffle effect is reduced, so that the low exothermic property is impaired when blended in the rubber composition. A more preferable average particle diameter is 5 to 50 nm. In addition, the average particle diameter of the nano filler is magnified by 10,000 times with a transmission electron microscope (TEM), and the diameter of 10 randomly extracted particles is measured to obtain an arithmetic average thereof. Desired.

  As the inorganic filler used as the nanofiller, an inorganic filler made of a metal compound such as a metal oxide, hydroxide, carbonate or the like is used, and carbon black is excluded. Silica can also be used as the nanofiller, but as described above, the nanofiller is used for the baffle effect that suppresses the aggregation of the fibrillated fibers. Since the rubber physical properties are affected, it is preferable to use an inorganic filler that does not have such reinforcing properties.

As the inorganic filler, those represented by the following general formula (1) are preferably used.
aM · bSiO _x · cH ₂ O (1)
Wherein M is selected from metals selected from the group consisting of aluminum, magnesium, titanium, zinc and calcium, oxides or hydroxides of these metals, hydrates thereof, or carbonates of these metals. It is at least 1 type, a is an integer of 1-5, b is an integer of 0-10, c is an integer of 0-10, x is an integer of 2-5.

Specifically, clay (Al ₂ O ₃ · 2SiO ₂ , Al ₂ O ₃ · 2SiO ₂ · 2H ₂ O (kaolinite), Al ₂ O ₃ · 4SiO ₂ · H ₂ O (pyrophyllite), Al ₂ O ₃ · 4SiO ₂ · 2H ₂ O (bentonite), montmorillonite, etc.), aluminum silicate (Al ₂ SiO ₅ , Al ₄ · 3SiO ₄ · 5H ₂ O), aluminum calcium silicate (Al ₂ O ₃ · CaO · 2SiO) ₂ ), alumina (Al ₂ O ₃ ), alumina monohydrate (Al ₂ O ₃ .H ₂ O), aluminum hydroxide (Al (OH) ₃ ), aluminum carbonate (Al ₂ (CO ₃ ) ₃ ), magnesium aluminum oxide _{(MgO · Al 2 O 3)} , magnesium hydroxide (Mg _(OH) 2), magnesium oxide (MgO), carbonate magnesium (MgCO _3), magnesium silicate _{(Mg 2 SiO 4, MgSiO 3} ), talc _{(3MgO · 4SiO 2 · H 2} O), attapulgite _{(5MgO · 8SiO 2 · 9H2O)} , titanium oxide _(TiO 2), zinc oxide ( ZnO), calcium oxide (CaO), calcium hydroxide (Ca (OH) ₂ ), calcium carbonate (CaCO ₃ ), calcium silicate (Ca ₂ SiO ₄ ), magnesium calcium silicate (CaMgSiO ₄ ), etc. Any of these may be used alone or in combination of two or more. Among these, layered silicate minerals such as clay, titanium oxide, zinc oxide, calcium carbonate, aluminum hydroxide can be particularly preferably used, and moreover, the above baffle plate effect is more effectively exhibited by the layered structure. Therefore, it is more preferable to use a layered silicate mineral.

  The nanofiller is preferably mixed with an aqueous dispersion of the fibrillated fiber after being made into an aqueous dispersion (also referred to as a slurry solution) dispersed in water. For example, the nanofiller is finely dispersed in water using a high-pressure homogenizer or the like, and the aqueous dispersion of the finely dispersed nanofiller thus obtained is added to the aqueous dispersion of fibrillated fibers and mixed. As a result, a more uniform composite integration of the two can be achieved. The concentration of the nanofiller aqueous dispersion is not particularly limited, but it is preferable to disperse 0.5 to 10 parts by weight of the nanofiller with respect to 100 parts by weight of water.

  The nanofiller is added and mixed in an amount of 0.1 to 0.5 times the fiber weight of the fibrillated fiber. That is, 10 to 50 parts by weight of nanofiller is mixed with 100 parts by weight of fibrillated fiber. Thus, by using a relatively small amount of nanofiller with respect to the fibrillated fiber, it is possible to exhibit the excellent reinforcing properties inherent to the fibrillated fiber while exhibiting the above baffle effect by the nanofiller, and low heat generation The balance with sex can be improved. When the weight ratio of the nanofiller / fibrillated fiber is less than 0.1, the baffle effect by the nanofiller is small, and the dispersibility of the fibrillated fiber becomes insufficient. On the contrary, if the weight ratio of nanofiller / fibrillated fiber exceeds 0.5, the content of nanofiller increases and aggregation of nanofillers occurs, or low exothermic property is impaired.

  In this way, the fibrillated fiber and the nanofiller are mixed, and after sufficiently stirring, the water is removed by filtration or the like to recover the solid content, and then dried to obtain a composite of the fibrillated fiber and the nanofiller. Is obtained. Since water is removed by drying, the fibrillated fibers would normally aggregate and solidify, but the nanofiller that entered between the fibers as described above exerts a baffle plate effect as aggregation suppression, It can be dried without agglomeration. The drying method is not particularly limited, and can be performed using, for example, an oven.

  The dried product of the fibrillated fiber-nanofiller composite obtained above is used as a rubber reinforcing agent to be blended in the rubber composition. That is, a rubber composition is obtained by adding the kneaded composite to a rubber polymer and kneading. For kneading at that time, a Banbury mixer, a roll, a kneader or the like generally used in the preparation of the rubber composition can be used.

  The rubber polymer used as the rubber component is not particularly limited. For example, natural rubber (NR), polyisoprene rubber (IR), styrene butadiene rubber (SBR), polybutadiene rubber (BR), nitrile rubber (NBR), chloroprene. Examples thereof include rubber (CR), ethylene propylene rubber (EPDM), butyl rubber (IIR), halogenated butyl rubber and the like. These may be used alone or in combination of two or more. Among the above, diene rubber is preferably used.

  The compounding quantity of the said composite in a rubber composition is not specifically limited, What is necessary is just to set suitably so that the reinforcement property requested | required according to the use of a rubber composition may be exhibited. Specifically, the blending amount of the fibrillated fiber-nanofiller composite is, for example, 1 to 200 parts by weight, and more preferably 5 to 100 parts by weight with respect to 100 parts by weight of the rubber polymer.

  The rubber composition may contain various additives generally used in the rubber industry, such as softeners, plasticizers, anti-aging agents, zinc white, stearic acid, resins, vulcanizing agents, and vulcanization accelerators. it can. These additives may be added to the rubber polymer together with the composite, or may be added in a step different from the composite, and the order of addition is not particularly limited. Usually, in the first mixing stage, chemicals excluding vulcanizing additives such as vulcanizing agents and vulcanization accelerators are added to the rubber polymer together with the composite and kneaded, and then in the second mixing stage. A rubber composition can be produced by adding and mixing a vulcanizing additive to the kneaded product obtained in the first mixing stage. In addition, carbon black or silica generally blended in a rubber composition as a reinforcing filler can be blended together with the composite.

  The rubber composition according to the present invention is used as rubber members of pneumatic tires such as bead fillers and sidewall rubbers by vulcanization molding according to a conventional method, or for various rubber products such as vibration-proof rubbers and belts. be able to. Preferably, as described above, since the rubber composition can improve the balance between reinforcement and low heat build-up, the rubber composition is used as a rubber member for a pneumatic tire. The balance of fuel efficiency can be improved.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Production Example 1]
As fibrillated water-suspended fibers, “Cerish KY-100G” manufactured by Daicel Chemical Industries, Ltd. (average fiber diameter = 0.1 μm, average fiber length = 500 μm, fine fibrous cellulose = 10% by weight, water = 90% by weight), and 100 parts by weight of this aqueous suspension was dispersed in 410 parts by weight of water to obtain an aqueous dispersion of fibrillated fibers. In addition, “LAPONITE RD” (clay, average particle size = 13 nm) manufactured by ROCKWOOD is used as a nanofiller, and 1 part by weight of the nanofiller is added to 100 parts by weight of water, and then finely submerged in water using a high-pressure homogenizer. By dispersing, an aqueous dispersion of nanofiller was obtained.

  To 510 parts by weight of the aqueous dispersion of fibrillated fibers (10 parts by weight of the fiber), 101 parts by weight of the aqueous dispersion of nanofillers (the nanofiller is added in an amount 0.1 times the weight of the fibrillated fibers). After adding and stirring and mixing with a homomixer, the solid content was recovered by filtering to remove water, and dried in an oven at 120 ° C. for 180 minutes to obtain a dried fibrillated fiber-nanofiller composite. . The obtained dried product was in a soft cotton-like form without being coagulated and solidified.

[Production Example 2]
To 510 parts by weight of an aqueous dispersion of fibrillated fibers (fiber content is 10 parts by weight), 202 parts by weight of an aqueous dispersion of nanofillers (a nanofiller is added in an amount 0.2 times the weight of fibrillated fibers), Others were the same as in Production Example 1 to obtain a dried product of fibrillated fiber-nanofiller composite. The obtained dried product was in a soft cotton-like form without being coagulated and solidified.

[Production Example 3]
To 510 parts by weight of an aqueous dispersion of fibrillated fibers (fiber content is 10 parts by weight), 303 parts by weight of an aqueous dispersion of nanofillers (a nanofiller is added in an amount 0.3 times the weight of fibrillated fibers), Others were the same as in Production Example 1 to obtain a dried product of fibrillated fiber-nanofiller composite. The obtained dried product was in a soft cotton-like form without being coagulated and solidified.

[Production Example 4]
To 510 parts by weight of the aqueous dispersion of fibrillated fibers (10 parts by weight of the fiber), 404 parts by weight of the aqueous dispersion of nanofiller (the nanofiller is added in an amount 0.4 times the weight of the fibrillated fiber), Others were the same as in Production Example 1 to obtain a dried product of fibrillated fiber-nanofiller composite. The obtained dried product was in a soft cotton-like form without being coagulated and solidified.

[Production Example 5]
To 510 parts by weight of an aqueous dispersion of fibrillated fibers (10 parts by weight of fiber), 505 parts by weight of an aqueous dispersion of nanofiller (the nanofiller is added in an amount 0.5 times the weight of the fibrillated fiber), Others were the same as in Production Example 1 to obtain a dried product of fibrillated fiber-nanofiller composite. The obtained dried product was in a soft cotton-like form without being coagulated and solidified.

[Production Example 6] (Comparative Example)
Add 50.5 parts by weight of nanofiller aqueous dispersion (adding 0.05 times the weight of fibrillated fiber) to 510 parts by weight of aqueous dispersion of fibrillated fibers (10 parts by weight of fiber) The others were the same as in Production Example 1 to obtain a dried fibrillated fiber-nanofiller composite.

[Production Example 7] (Comparative Example)
To 510 parts by weight of the aqueous dispersion of fibrillated fibers (fiber content is 10 parts by weight), 808 parts by weight of the aqueous dispersion of nanofiller (the nanofiller is added in an amount 0.8 times the weight of the fibrillated fiber), Others were the same as in Production Example 1 to obtain a dried product of fibrillated fiber-nanofiller composite.

[Production Example 8]
As the nanofiller, “JA-1” (titanium oxide, average particle size = 180 nm) manufactured by Teika Co., Ltd. was used, and 1 part by weight of the nanofiller was added to 100 parts by weight of water. To obtain a nano-filler aqueous dispersion. The same amount of aqueous dispersion of fibrillated fibers as in Production Example 1 (10 parts by weight of fiber) and 404 parts by weight of aqueous dispersion of nanofillers (nanofiller is 0.4 times the weight of fibrillated fibers) Addition), stirring and mixing with a homomixer, filtering to remove water and recovering the solid content, drying in an oven at 120 ° C. for 180 minutes, dried fibrillated fiber-nanofiller composite Got. The obtained dried product was in a soft cotton-like form without being coagulated and solidified.

[Production Example 9]
To 510 parts by weight of an aqueous dispersion of fibrillated fibers (fiber content is 10 parts by weight), 202 parts by weight of an aqueous dispersion of nanofillers (a nanofiller is added in an amount 0.2 times the weight of fibrillated fibers), Others were the same as in Production Example 8 to obtain a dried fibrillated fiber-nanofiller composite. The obtained dried product was in a soft cotton-like form without being coagulated and solidified.

[Production Example 10] (Comparative Example)
“JA-301” (titanium oxide, average particle size = 300 nm) manufactured by Teika Co., Ltd. was used as the nanofiller, and the others were obtained in the same manner as in Production Example 8 to obtain a dried fibrillated fiber-nanofiller composite. It was.

[Preparation of rubber composition]
Using a Banbury mixer, a rubber composition was prepared according to the formulation shown in Table 1 below. Specifically, after adding a reinforcing agent, stearic acid, and zinc oxide to natural rubber, which is a rubber polymer, and kneading to obtain a first mixture (discharge temperature: 150 ° C.), in the second mixing step, A vulcanization accelerator and sulfur were added to one mixture and kneaded to obtain a rubber composition (discharge temperature: 110 ° C.). As a reinforcing agent, in Comparative Example 1, an aqueous suspension of fibrillated fibers (“Cerish KY-100G” manufactured by Daicel Chemical Industries, Ltd.) was added to the rubber polymer as it was, and in Comparative Example 2, the water suspension was added. Along with the suspension, clay (“LAPONITE RD” manufactured by ROCKWOOD, average particle size = 13 nm) was directly added to the rubber polymer. At that time, the aqueous suspension was added so that the blending amount of the solid content (that is, fibrillated fiber) was the amount shown in Table 1. In Comparative Example 6, carbon black was used as a reinforcing agent. Details of each component in Table 1 (excluding those described above) are as follows.

・ Natural rubber: RSS3 ・ Carbon black: “Seast V” manufactured by Tokai Carbon
・ Stearic acid: "Industrial stearic acid" manufactured by Kao Corporation
・ Zinc oxide: “No. 1 Zinc Hana” manufactured by Mitsui Kinzoku Mining
・ Vulcanization accelerator: N-tert-butyl-2-benzothiazolesulfenamide ・ Sulfur: “5% oil-treated powder sulfur” manufactured by Tsurumi Chemical Co., Ltd.

  Each rubber composition obtained was vulcanized at 160 ° C. for 20 minutes to prepare a test piece having a predetermined shape, and the hardness and tan δ were measured and evaluated using the obtained test piece. Each evaluation method is as follows.

Hardness: The hardness measured at 23 ° C. according to JIS K6253 was displayed as an index with the value of Comparative Example 1 being 100. The larger the index, the higher the hardness and the better the reinforcement.

Tan δ: According to JIS K6394, the loss coefficient tan δ was measured under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, a static strain of 10%, and a dynamic strain of 2%, and displayed as an index with the value of Comparative Example 1 being 100. The smaller the index, the smaller the tan δ, and the less the heat is generated.

  The results are as shown in Table 1. Compared to Comparative Example 1 in which the fibrillated water-suspended fiber is blended as it is, and Comparative Example 6 using carbon black as a reinforcing agent, the fibrillation according to the present invention. In Examples 1 to 7 using the fiber-nanofiller composite, the hardness is remarkably high and the reinforcing property is excellent, the tan δ is low and the exothermic property is excellent, and the balance between the reinforcing property and the low exothermic property is achieved. A remarkable improvement effect was observed.

  Such an effect could not be obtained in Comparative Example 2 in which fibrillated water-suspended fibers and clay were added as they were during mixing with the rubber polymer. In Comparative Example 3, although a fibrillated fiber-nanofiller composite was produced, the amount of nanofiller used was too small to obtain an improvement effect. On the other hand, in Comparative Example 4, the amount of nanofiller used was too large and the composite was produced, but the heat generation was inferior. Moreover, in Comparative Example 5, although the composite was produced, the particle size of the nanofiller was too large, and the low exothermic property was inferior.

  According to the present invention, it is possible to produce a rubber composition having an improved balance between reinforcement and low heat generation without deteriorating productivity with conventional equipment such as Banbury mixers and rolls. It can be used for various applications such as anti-vibration rubber and belts.

Claims (5)

  The nano-filler, which is an inorganic filler having an average particle diameter of 2 to 200 nm, is mixed in an aqueous dispersion of fibrillated fibers in an amount of 0.1 to 0.5 times the fiber weight, and dried. A method for producing a rubber reinforcing agent, comprising obtaining a composite of fibrillated fibers and nanofillers.   The method for producing a rubber reinforcing agent according to claim 1, wherein the aqueous dispersion of the fibrillated fibers is obtained by dispersing the fibrillated fibers in water at least 10 times the weight of the fibers.   The method for producing a rubber reinforcing agent according to claim 1 or 2, wherein an aqueous dispersion in which the nano filler is dispersed in water is added to and mixed with the aqueous dispersion of the fibrillated fibers.   The nano filler is at least one inorganic filler selected from the group consisting of layered silicate minerals, titanium oxide, zinc oxide, calcium carbonate, and aluminum hydroxide. The manufacturing method of the reinforcing agent for rubbers of any one of these.   A method for producing a rubber composition, comprising adding a rubber reinforcing agent obtained by the method according to any one of claims 1 to 4 to a rubber polymer and mixing the rubber polymer.