JP2009051955A - Method for producing masterbatch and rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a masterbatch in which a silica fine particle is uniformly dispersed in a rubber by mixing a rubber latex with water glass, departing from a conventional kneading method in which a bumbury's mixer etc. are used. <P>SOLUTION: This method for producing the masterbatch containing the fine particle silica and the rubber comprises mixing the fine particle silica of ≤100 nm produced from the water glass with a rubber latex of 100 parts by mass, so that the silica component becomes ≥5 parts by mass and ≤70 parts by mass, and then aggregating and solidifying a solid content by adding at least either an acid or a salt, wherein the pH of the water glass is adjusted to 9-11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a masterbatch used for a rubber composition used for molding a rubber product and a rubber composition using the masterbatch.

  Conventionally, when producing a rubber and silica composition, solid rubber and dry silica have been mixed through a rubber kneading step. In natural rubber, the raw material is latex, which is solidified and dried to obtain solid rubber. On the other hand, when using wet silica for silica, fine particles are prepared from water glass, and dried silica is obtained through a filtration step and a drying step. As the silica, fine particle silica having a particle diameter of about 20 to 60 nm is usually used. That is, as a method of compounding silica as a reinforcing agent in rubber, conventionally, a so-called kneading method in which kneading is performed using a Banbury mixer, an open roll, a kneader or the like is employed.

  In this kneading method, solid rubber and silica are separately separated from the latex and water glass, and the process of drying is performed, so that the production efficiency is not good. Moreover, since silica has silanol groups on its surface and exhibits hydrophilicity, it generally has low affinity with rubber that exhibits hydrophobicity. Moreover, since silica has a strong self-aggregation property, it is not easy to uniformly disperse silica in rubber.

  On the other hand, a method for obtaining a composite by mixing latex and water glass in a liquid state has already been reported. Although water glass is mixed with latex, fine particle silica is not generated from water glass, and the silica component tends to aggregate in an amorphous state. Therefore, silica is not present as fine particles simply by mixing latex and water glass, and therefore it is difficult to produce a rubber composition in which silica fine particles are uniformly dispersed in rubber.

  In Patent Document 1, after mixing acrylonitrile-butadiene rubber latex and water glass, this latex is dropped with an acid to solidify the rubber component, thereby silicic acid-NBR in which silicic acid is dispersed in a fine state. A method of manufacturing a composite material is disclosed.

  Patent Document 2 discloses a method for producing a rubber composition by coagulating a compounded latex containing an epoxidized natural rubber and water glass with an acid or a salt. In this production method, it is described that silica is finely and uniformly dispersed without forming an aggregate in the rubber composition.

Patent Document 3 proposes a method for producing a coarse-grain vulcanizable mixture by coprecipitation of a mixture of water glass and rubber latex using an acid. However, generally, the method of mixing water glass with rubber latex cannot eliminate the tendency of the silica component to aggregate in an amorphous state.
JP 2006-2011 JP 2007-2177 A JP 47-1090 A

  An object of the present invention is to provide a method for producing a masterbatch in which silica fine particles are uniformly dispersed in rubber by mixing rubber latex and water glass, instead of the conventional kneading method using a Banbury mixer or the like. Provided is a rubber composition capable of obtaining a rubber product excellent in mechanical strength such as modulus, elongation and hardness using such a master batch.

  In the present invention, 100 parts by mass of rubber latex is mixed with fine particle silica having a particle diameter of 100 nm or less produced from water glass so that the silica component is 5 parts by mass or more and 70 parts by mass or less, and then at least an acid. Or it is a manufacturing method of the masterbatch containing fine particle silica and rubber | gum by adding any of salt and solidifying solid content.

  The water glass whose pH is adjusted to 9 to 11 is suitably used for producing fine particle silica. The particle diameter of the fine particle silica is preferably 30 nm or less. The rubber latex is preferably natural rubber latex or epoxidized natural rubber.

  The present invention relates to a rubber composition using a master batch obtained by the production method.

  In the present invention, instead of the conventional kneading method, an aqueous solution of water glass containing rubber latex and fine particle silica is mixed to produce a compounded latex, which is coagulated to produce a master batch. Therefore, the fine particle silica is uniformly dispersed in the rubber, and the vulcanized rubber composition using the silica is excellent in mechanical strength such as modulus, elongation and hardness.

  Also, the masterbatch of the present invention and the rubber composition using the same mix the rubber latex and water glass aqueous solution at the initial stage of production, so that the energy consumption can be greatly reduced, and the conventional rubber component and silica are separated. Compared to the method of kneading after drying, the cost is greatly reduced.

In the present invention, 100 parts by mass of rubber latex was mixed with fine particle silica having a particle diameter of 100 nm or less produced from water glass so that the silica component (SiO ₂ ) was 5 parts by mass or more and 70 parts by mass or less. Thereafter, at least either an acid or a salt is added to agglomerate and solidify the solid content, thereby producing a masterbatch containing fine particle silica and rubber.

<Rubber latex>
In the present invention, the rubber latex includes natural rubber (NR), epoxidized natural rubber, a copolymer of styrene and butadiene (SBR), a copolymer of styrene, isoprene and butadiene (SBIR), α-methylstyrene, Copolymer of butadiene (MSBR), brominated product of copolymer of p-methylstyrene and isobutylene, copolymer of acrylonitrile and butadiene (NBR), copolymer of acrylonitrile, butadiene and isoprene (NBIR) Copolymer of acrylonitrile and isoprene (NIR), isoprene rubber (IR), copolymer of isobutene and isoprene (IIR), butadiene rubber (BR), chloroprene rubber (CR), ethylene, propylene and diene A copolymer (EPDM) etc. are mentioned. In particular, natural rubber (NR) or epoxidized natural rubber is preferably used.

The epoxidized natural rubber can be produced by treating natural rubber with, for example, hydrogen peroxide and formic acid, or by treating with peracetic acid. This reaction epoxidizes the double bonds present in the natural rubber molecule. The structure of epoxidation can be clarified from proton nuclear magnetic resonance spectrum ( ¹ H-NMR) and infrared absorption spectrum (IR), and from the results of IR and elemental analysis, the content of epoxy group (epoxy group) Conversion rate) can be measured.

  The epoxidation rate is preferably 3 to 70 mol% or more, more preferably 5 to 65 mol%, and still more preferably 7 to 60 mol%. In the present invention, two or more types of epoxidized natural rubber having an epoxidation rate within the above range may be used.

  When the epoxidation rate of the epoxidized natural rubber is less than 5 mol%, the number of sites that interact with the silica component generated from water glass is reduced, and desired properties can be imparted to the rubber composition. There is a risk that the effect of improving the mechanical strength and dynamic mechanical properties of the rubber product formed from the rubber composition may be insufficient. Conversely, when the epoxidation rate of the epoxidized natural rubber exceeds 70 mol%, the rubber composition becomes too sticky, the rubber elasticity is impaired, or the glass transition point is too high. There are fears that durability at low temperatures may be reduced, and that mechanical blending may be difficult due to adhesion to an inner wall of a kneader or the like.

  However, the rubber other than the epoxidized natural rubber has a pyridyl group, carboxyl group, amino group, carbamoyl group or N-hydroxymethylcarbamoyl group in the molecule (so-called pyridine-modified rubber, carboxy-modified rubber, Amino-modified rubber or amide-modified rubber), when the other rubber latex is coagulated with an acid or salt in the presence of water glass, it is a finely powdered rubber that cannot be kneaded. Since the composition may be produced, the amount of the other rubber latex is set within a range in which the rubber composition as a whole can maintain a kneadable state.

  In the present invention, before mixing with water glass, two or more kinds of rubber latex are mixed, or before mixing with one acid latex and water glass with an acid or salt, the compounded latex is mixed. Other rubber latex can also be mix | blended in it.

<Water glass>
The water glass is usually represented by a composition represented by the following formula.
Na ₂ O · nSiO ₂ · mH ₂ O
The coefficient n is a value represented by a molecular ratio of SiO ₂ / Na ₂ O, and is a range specified in (JIS K 1408 _-1966 ), generally called a molar ratio. Although this coefficient n is not specifically limited, Preferably it is 2.1-3.1, More preferably, it is 3.1. When the coefficient n is 3.1, the silica component (in terms of SiO ₂ ) in the water glass increases, so that the efficiency of the composite treatment with rubber is improved.

  In general, the water glass having the coefficient n of 3.1 is commercially available as water glass No. 3. The water glass which can be used for this invention is not limited to this, For example, No. 1-3 water glass prescribed | regulated to JISK1408, and other various grade products can be used.

The amount of water glass, for the silica component which is generated from the water glass, the content of a rubber composition (SiO ₂ equivalent amount) may be set to be in the range described below.

<Formation of fine particle silica>
The aqueous solution of water glass is adjusted so that the pH is preferably in the range of 9-11. When the pH is less than 9, gelation tends to occur, and when the pH exceeds 11, the fine particle silica tends to dissolve. Preferably the pH is adjusted in the range of 9.5 to 10.5.

  Furthermore, the temperature of the aqueous solution of water glass is desirably adjusted to 10 ° C to 70 ° C. If the temperature is less than 10 ° C., the production rate of fine-particle silica is slow, and if the temperature exceeds 70 ° C., the evaporation of water in the aqueous solution becomes violent and the concentration of water glass in the aqueous solution tends to become unstable. The temperature of the aqueous solution is preferably in the range of 15 ° C to 40 ° C.

The concentration of the silica component (SiO ₂ ) contained in the water glass in the aqueous solution is preferably in the range of 1% by mass to 10% by mass. When the concentration is less than 1% by mass, a large amount of water glass aqueous solution is required for complexing with the rubber latex, and when the concentration exceeds 10% by mass, silica aggregation tends to occur. The concentration of the silica component in the aqueous solution is preferably in the range of 1.5 to 4% by mass. However, when water glass that has been desalted is used, the upper limit of the concentration is higher because silica aggregation is less likely to occur.

  The reaction time ranges from 1 hour to 72 hours. If it is less than 1 hour, the production of fine-particle silica is not sufficient, and the reaction is completed in about 72 hours. Preferably, it is performed at room temperature under stirring conditions for 6 to 24 hours.

  The particle diameter of the fine particle silica obtained by the above method is 100 nm or less, preferably 30 nm or less. Here, the size of the particle diameter can be arbitrarily adjusted by adjusting the pH of the aqueous solution, the concentration of the silica component, the reaction temperature, the reaction time, and the like.

<Mixing of fine particle silica and rubber latex>
Next, an aqueous solution containing fine particle silica produced by the above-described method is mixed with rubber latex to obtain a compounded latex. Thereafter, the mixed latex is sufficiently stirred until it becomes a uniform solution. Here, the rubber solid content in the rubber latex is preferably in the range of 10% by mass to 70% by mass.

On the other hand, the aqueous solution containing fine particle silica has a silica component (SiO ₂ equivalent) content of 5 to 70 parts by weight, preferably 5 to 40 parts by weight, more preferably 100 parts by weight of rubber latex. It is 8-35 mass parts. When the content of the silica component (SiO ₂ equivalent amount) is less than 5 parts by mass with respect to 100 parts by mass of the rubber latex, the amount of silica is reduced when used as a master batch. On the other hand, when the content of silica component (SiO ₂ equivalent amount) exceeds 70 parts by mass with respect to 100 parts by mass of rubber latex, it becomes difficult to obtain uniform dispersion in the rubber latex of fine particle silica, and the compounded latex is coagulated. The uniform dispersibility of the fine particle silica in the later rubber composition is lowered.

<Coagulation of compounded latex>
A compounded latex is produced by uniformly mixing an aqueous solution containing the fine particle silica with a rubber latex, and then coagulated to produce a master batch of a rubber composition in which the fine particle silica is uniformly dispersed in the rubber.

  Solidification of the compounded latex includes acid coagulation, salt coagulation, methanol coagulation and the like, but acid coagulation, salt coagulation, or a combination thereof is preferable in order to coagulate the rubber latex and fine particle silica by uniform dispersion. Examples of the acid for coagulation include sulfuric acid, hydrochloric acid, formic acid, and acetic acid. Examples of the salt for coagulating the blended latex include monovalent to trivalent metal salts such as calcium salts such as sodium chloride, magnesium chloride, calcium nitrate, and calcium chloride.

  When the amount of silica is small relative to the rubber latex, the type of metal salt is not limited, but when the amount of silica is large, monovalent and divalent metal salts such as sodium chloride and magnesium chloride are preferred. Here, when a trivalent metal salt is used, the cohesive force between silicas is too strong, and finally it is difficult to be finely dispersed.

<Master batch>
The rubber composition obtained by coagulating the compounded latex is used as a master batch. In the master batch, since the fine particle silica is uniformly dispersed in the rubber composition, the fine particle silica can be evenly dispersed in the final rubber composition obtained when mixed with other rubber components and a rubber compounding agent. it can.

  A feature of the present invention is that a rubber composite in which fine particle silica is dispersed can be obtained by preparing fine particle silica from water glass and mixing it with latex without drying. Instead of directly blending water glass, the pH of the water glass is adjusted to prepare fine particle silica first. Then, by adding acid, salt, etc. to the blended latex obtained by mixing the water glass aqueous solution containing fine silica and rubber latex and coagulating it, a composite masterbatch in which fine silica is surrounded around the spherical rubber is obtained. It is done.

  By kneading the master batch with rubber, fine dispersion of silica can be further improved. The fine particle silica is in a spherical form, and the bonding force between adjacent silica particles is weaker than that of the agglomerated silica, so it is considered that the fine particles are easily separated by the external force of rubber kneading. The rubber composition obtained from the rubber kneading of the masterbatch has the same strength as that obtained by blending conventional dry silica with rubber.

  When conventional dry silica is mixed into the rubber composition, the silica particles are dispersed apart, whereas in the masterbatch of the present invention, the fine particle silica is present in the form of cocoon bunches. This is presumably because the latex is in a spherical form, and the fine particle silica penetrates into the gaps and aggregates, so that the aggregates are not completely loosened even after rubber kneading. As a result, the resulting masterbatch particulate silica is configured in the form of bunches of various sizes.

<Rubber composition using masterbatch>
In the masterbatch of the present invention, known additives can be blended according to the use of the vulcanized product and the required physical properties. Examples of the additive include a vulcanizing agent, a vulcanization accelerator, a vulcanization acceleration aid, a filler, a plasticizer, and an antiaging agent.

  Examples of the vulcanizing agent include organic sulfur-containing compounds such as sulfur, trimethylthiourea, and N, N′-diethylthiourea. These can be used alone or as a mixture of two or more.

  Vulcanization accelerators include, for example, the trade name “Soccinol DM” (MBTS) manufactured by Sumitomo Chemical Co., Ltd., “Soccinol PX” (ZnEPDC) manufactured by the Company, “Soccinol PZ” (ZnMDC) manufactured by the Company, There are “Soccinol EZ” (ZnEDC), “Soccinol BZ” (ZnBDC), “Soccinol MZ” (ZnMBT), “Soccinol TT” (TMTD), etc. These can be used alone or as a mixture of two or more. Examples of the vulcanization acceleration aid include zinc white.

  Examples of the vulcanization acceleration aid include fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and metal oxides such as zinc white.

  Examples of the filler include silica, carbon black, kaolin clay, hard clay, calcium carbonate, barium sulfate, and diatomaceous earth. The blending amount of the filler is determined according to the mechanical strength required for the vulcanized product. If it is a range which does not impair the effect | action and effect of this invention accompanying containing water glass, it can mix | blend suitably. The silica is not particularly limited and can be appropriately selected from those conventionally used as rubber reinforcing agents, for example, dry process silica, wet process silica (hydrous silicic acid), etc., but wet process silica is preferred. is there.

  In the present invention, a silane coupling agent is preferably blended. For example, vinyltrichlorosilane, vinyltriethoxysilane, vinyltris (β-methoxy-ethoxy) silane, β- (3,4-epoxycyclohexyl) -ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycine Sidoxypropylmethyldiethoxysilane, γ-methacryloxypropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, Bis- (3- (triethoxysilyl) propyl) tetrasulfide, bis- (3- (triethoxysilyl) propyl) disulfide, γ-trimethoxysilylpropyldimethylthiocarbamyl tetrasulfide, γ-trimethoxysilylpropyl Examples include benzothiazyl tetrasulfide. The silane coupling agent is preferably 1 to 20 parts by mass when the total amount of fine particle silica contained in the rubber composition and additionally added silica is 100 parts.

  Examples of the plasticizer include paraffinic oil, ester oil, and olefin oil. The blending amount of the plasticizer is determined according to the hardness required for the processed product while preventing the occurrence of bleeding. If it is a range which does not impair the effect | action and effect of this invention accompanying water glass being contained, it can mix | blend suitably.

  Anti-aging agents include, for example, imidazoles such as 2-mercaptobenzimidazole, such as phenyl-α-naphthylamine, N, N′-di-β-naphthyl-p-phenylenediamine, N-phenyl-N′-isopropyl- Examples include amines such as p-phenylenediamine, and phenols such as di-tert-butyl-p-cresol and styrenated phenol.

  In addition to the additives exemplified above, for example, pigments may be blended depending on the use of the product obtained by processing the master batch. In order to vulcanize and mold a rubber composition using the masterbatch of the present invention, an unvulcanized masterbatch is sufficiently masticated and then mixed with a vulcanization accelerator, a vulcanization accelerator, and the like. After kneading and then kneading with a vulcanizing agent, forming into a desired shape, heating and vulcanization may be performed. Synthetic rubber and natural rubber may be mixed in a latex state as described above, but can also be mixed in the mastication step in a solid rubber state.

The present invention will be described below based on examples and comparative examples, but the present invention is not limited to the examples.
Example 1
A master batch was produced according to the following steps.

<Preparation of water glass aqueous solution>
Water glass No. 3 (Na ₂ O.nSiO ₂ .mH ₂ O, n = 3.2) manufactured by Fuji Chemical Co., Ltd. and having a silica component (SiO ₂ equivalent) content equivalent to 28% is used as the water glass. It was. The silica component content (concentration) of the water glass aqueous solution was 2%, adjusted to pH 10, and stirred at 25 ° C. for 24 hours. Thereafter, the silica was taken out and subjected to TEM observation, whereby fine silica particles having a diameter of about 20 nm were obtained. The TEM observation photograph is shown in FIG.

<Adjustment and coagulation of compounded latex>
NR latex (high ammonia type, rubber component 60%) was mixed with the water glass aqueous solution containing fine particle silica to prepare a compounded latex. The rubber latex was mixed so that the silica component was 10 g with respect to 100 g. After sufficiently stirring until the blended latex became uniform, the blended latex was adjusted to pH 7 with sulfuric acid, and solidified by adding aluminum chloride. The obtained solid was filtered to recover the rubber, washed with pure water and dried.

  After drying the solid, a master batch was obtained. This TEM observation photograph is shown in FIG. In FIG. 2, fine silica particles derived from water glass in a black portion are dispersed around a rubber latex in a white portion. It can be seen that the fine-particle silica does not produce large silica aggregates exceeding several μm.

<Rubber composition using masterbatch>
The master batch was kneaded with a roll, and a compounding agent (crosslinking agent, silane coupling agent, etc.) shown in Table 1 was added to obtain a rubber composition. This was vulcanized at 150 ° C. for 10 minutes to produce a vulcanized rubber. A TEM observation photograph of the vulcanized rubber sample is shown in FIG. In FIG. 3, a sample section was cut out and observed with a microtome. Similar observations were made in FIG.

The compounding agents used in Table 1 are as follows.
(Note 1) Natural rubber: Rubber obtained by coagulating NR latex.
(Note 2) Compounded latex: The compounded latex produced based on Example 1 was used.
(Note 3) Silica: Ultrazil VN3 granulated type manufactured by Degussa Co. was used.
(Note 4) Silane coupling agent: Si266 manufactured by Degussa was used.
(Note 5) Stearic acid: Beads stearic acid manufactured by Nippon Oil & Fats Co., Ltd., “Kashiwa” was used.
(Note 6) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Metal Mining Co., Ltd. were used.
(Note 7) Sulfur: 200 mesh 5% oil-filled powder sulfur manufactured by Tsurumi Chemical Co., Ltd. was used.
(Note 8) Vulcanization accelerator 1: “Noxeller NS” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. was used.
(Note 9) Vulcanization accelerator 2: “Soxinol D” manufactured by Sumitomo Chemical Co., Ltd. was used.

<Evaluation of vulcanized rubber sheet>
The following physical properties were evaluated for the vulcanized rubber sheets (thickness 2 mm) obtained in each Example and Comparative Example.
(1) Mechanical strength Based on JIS K 6251 “Tensile test method for vulcanized rubber”, tensile stress at 50%, 100%, 200%, 300% elongation M ₅₀ (MPa), M ₁₀₀ (MPa) M ₁₀₀ (MPa) M ₃₀₀ (MPa) Strength at break T _B (MPa) and elongation at break E _B (%) were measured. For the measurement, a test piece (dumbbell No. 3 type) obtained by hollowing out a vulcanized rubber sheet was used, and the measurement conditions were a temperature of 23 ° C. and a tensile speed of 500 mm / min.
(2) Hardness The durometer hardness (type A) of the vulcanized rubber sheet was measured according to JIS K 6253 “Method for testing the hardness of vulcanized rubber and thermoplastic rubber”.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Since the masterbatch of the present invention and the rubber composition using the same are mixed with a rubber latex and a water glass aqueous solution at the initial stage of production, the energy consumption can be greatly reduced. Excellent mechanical strength.

  Therefore, significant demand can be expected in the tire industry, where energy consumption is reduced and demand for non-petroleum resource products is high.

The TEM photograph of the fine particle silica in the water glass aqueous solution of Example 1 is shown. The TEM photograph of the rubber composition of the masterbatch of Example 1 is shown. The TEM photograph of the vulcanized rubber composition of Example 1 is shown.

Claims (5)

  After mixing 100 mass of rubber latex with fine particle silica having a particle diameter of 100 nm or less produced from water glass so that the silica component is 5 parts by mass or more and 70 parts by mass or less, at least either acid or salt A method for producing a masterbatch containing fine particles of silica and rubber by solidifying the solid content by adding the above.   The manufacturing method of Claim 1 with which fine particle silica is manufactured from the water glass adjusted to pH 9-11.   The production method according to claim 1, wherein the particle diameter of the fine-particle silica is 30 nm or less.   The method according to claim 1, wherein the rubber latex is natural rubber latex or epoxidized natural rubber.   The rubber composition using the masterbatch obtained with the manufacturing method of Claims 1-4.