JP6183422B2 - Method for producing rubber composition for tire - Google Patents

Description

The present invention relates to a method for producing a rubber composition for tires containing an anti-aging agent made from natural resources.

  It is essential to use an anti-aging agent for rubber products such as pneumatic tires. However, since anti-aging agents represented by amine-based anti-aging agents are produced using fossil resources as raw materials, a large amount of heat and carbon dioxide are discharged, so there is a concern about the influence on the global environment.

  For this reason, Patent Documents 1 and 2 propose synthesizing an anti-aging agent using a non-fossil resource (natural resource) as a raw material. However, both of these production methods increase the production cost because they purify compounds synthesized from natural resources, and are insufficient in antioxidant activity compared to amine-based antioxidants made from fossil resources. Because of this, the current situation is not yet widespread.

  On the other hand, in the fields of foods, beverages, etc., it is known that melanoidin, which is a brown compound produced by Maillard reaction, has an antioxidant action (see, for example, Patent Document 3). However, although it is known that Maillard reaction products are involved in the preparation of various foods and beverages, a technique for using melanoidin as an industrially useful anti-aging agent has not yet been established.

JP 2010-17176 A JP 2012-153655 A Japanese Patent No. 3855293

An object of the present invention is to produce a rubber composition for tires containing an anti-aging agent using natural resources as a raw material by a method excellent in industrial productivity.

The method for producing a tire rubber composition of the present invention that achieves the above object comprises a step of heating a mixture of sugar and amino acid to synthesize melanoidin, and a step of mixing the obtained melanoidin and sulfur or a crosslinking agent into a rubber component. It is characterized by including.

In the method for producing a rubber composition for a tire according to the present invention, a mixture of sugar and amino acid, which are natural resources, is heated to synthesize melanoidin, and the resulting melanoidin and sulfur or a crosslinking agent are mixed with the rubber component. A rubber composition having excellent anti-aging performance can be produced. Further, it can be produced only by heating as compared with biosynthesizing a structure having a complicated chemical structure. That is, since the number of steps required to obtain melanoidin from a mixture of sugar and amino acid is small and the heat energy required for the conversion is small, it is a production method with excellent industrial productivity. Further synthesized melanoidins as compared to amine-based antioxidant which fossil resources as raw materials, antioxidant is at least equivalent, the natural resources to suppress the production cost while the raw material, and a good anti-aging property tire A rubber composition can be obtained.

  The mixture of sugar and amino acid can be heated at 50-100 ° C. As the sugar, a monosaccharide composed of aldose and / or ketose can be used. Furthermore, an α-amino acid can be used as the amino acid, and it is preferable to use at least one selected from glycine, alanine, phenylalanine, arginine, lysine, asparagine, histidine, methionine, and tryptophan.

1A is a GC-MS spectrum chart of the chemical structure portion of pyrazine in the melanoidin synthesized in Example 1 of the present application, and FIG. 1B is a standard spectrum chart of GC-MS of pyrazine. FIG. 2A is a GC-MS spectrum chart of the chemical structure portion of pyrrolopyrazine in melanoidin synthesized in Example 1 of the present application, and FIG. 2B is a standard spectrum chart of GC-MS of pyrrolopyrazine. is there.

In the method for producing a rubber composition for tires of the present invention (hereinafter referred to as “rubber composition”) , melanoidin is used as an anti-aging agent. Melanoidine is a brown substance produced by the so-called Maillard reaction that heats sugar and amino compounds. The Maillard reaction is a reaction composed of a large number of elementary reactions. For this reason, the Maillard reaction was discovered in 1912, but the full picture has not been fully elucidated.

  The method for producing a rubber composition of the present invention comprises a step of heating a mixture of sugar and amino acid to synthesize melanoidin, and a step of mixing the obtained melanoidin with a rubber component. Monosaccharides can be used as the saccharide used as the raw material for melanoidin, and aldose and / or ketose can be used. By synthesizing melanoidin using these monosaccharides, melanoidin can be synthesized in a short time.

  Examples of aldoses include glyceraldehyde, erythrose, threose, ribose, arabinose, xylose, lyxose, allose, altrose, glucose, mannose, gulose, idose, galactose, talose and the like. Of these, xylose, glucose, arabinose, glyceraldehyde, and erythrose are preferable.

  Examples of ketoses include dihydroxyacetone, erythrulose, xylulose, ribulose, psicose, fructose, sorbose, tagatose, sedheptulose, coliose and the like. Of these, dihydroxyacetone, erythrulose, xylulose, and fructose are preferable.

  In the present invention, α-amino acids can be used as amino acids. A nitrogen atom can be efficiently introduced into melanoidin by synthesizing melanoidin using α-amino acid. Examples of α-amino acids include alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. be able to. Among these, at least one selected from glycine, alanine, phenylalanine, arginine, lysine, asparagine, histidine, methionine, and tryptophan is preferably used.

  Melanoidine is synthesized by heating the sugar and amino acid mixture described above. The method for heating the mixture of sugar and amino acid is not particularly limited. For example, a solution in which sugar and amino acid are dissolved in a solvent can be heated. Examples of the solvent include water, alcohol, THF (tetrahydrofuran), DMSO (dimethyl sulfoxide), DMF (N, N-dimethylformamide), acetone and the like. Of these, water and alcohol are preferred. Although the usage-amount of a solvent is not restrict | limited in particular, Preferably it is 0.1-20 mass times with respect to the mass of the mixture of sugar and an amino acid, More preferably, it is good in it being 0.5-10 mass times. By making the amount of the solvent used within such a range, melanoidin can be efficiently synthesized.

  In the present invention, the ratio of sugar and amino acid is not particularly limited, but the mass ratio of sugar and amino acid is preferably [sugar] / [amino acid] = 1/4 to 4/1, more preferably 1. / 3 to 3/1, more preferably 2/3 to 3/2. By setting the mass ratio of [sugar] / [amino acid] within such a range, melanoidin can be synthesized efficiently.

  The temperature for heating the mixture of sugar and amino acid is not particularly limited, but can be preferably 50 to 250 ° C, more preferably 80 to 230 ° C. By heating the mixture of sugar and amino acid in such a temperature range, the amount of by-products other than melanoidin can be suppressed.

  The apparatus for heating the mixture of sugar and amino acid is not limited, and may be either batch type or continuous type.

The characteristics of melanoidin obtained by heating a mixture of sugar and amino acid preferably satisfy at least one of the following characteristics (1) to (5).
(1) The nitrogen atom in melanoidin is 3 to 30% by mass (2) When melanoidin is heated in a nitrogen atmosphere at 600 ° C. for 1 hour, 5% by mass or more of carbide remains (3) Melanoidin is pyrazine, It contains at least one compound selected from pyrrolopyrrole and pyrrolopyrazine. (4) The antioxidant power measured by DPPH method of melanoidin is 10000 trolox (mg / 100 g) or more. (5) Melanoidine is water-soluble. There is

  The melanoidin obtained by the production method of the present invention preferably has a nitrogen atom content of 3 to 30% by mass, more preferably 3 to 25% by mass, and even more preferably 5 to 25% by mass. By setting the nitrogen atom content in such a range, an anti-aging agent having a high effect is obtained. In the present specification, the content of nitrogen atoms in melanoidin is determined by a method of measuring nitrogen oxides generated when complete combustion is performed using an elemental analyzer.

  In the melanoidin obtained by the production method of the present invention, the remaining carbide when heated in a nitrogen atmosphere at 600 ° C. for 1 hour is preferably 5 mass% or more, more preferably 10 to 30 mass%. By setting the amount of carbide when heated to 600 ° C. within such a range, an anti-aging agent having a high effect is obtained. In this specification, the measurement of heating melanoidin in a nitrogen atmosphere at 600 ° C. for 1 hour is obtained by a method of measuring the weight after heating using thermogravimetric analysis in a nitrogen atmosphere.

  The melanoidin preferably contains a structure of at least one compound selected from pyrazine, pyrrolopyrrole, and pyrrolopyrazine. By containing a structure selected from pyrazine, pyrrolopyrrole, and pyrrolopyrazine in the structure of melanoidin, it becomes an anti-aging agent having a high effect. The chemical structure of melanoidin can be measured by GC-MS.

  Melanoidin has an antioxidant power measured by the DPPH method of preferably 10,000 trolox (mg / 100 g) or more, more preferably 50,000 to 500,000 trolox (mg / 100 g). The fact that melanoidin has an antioxidant power within such a range means that it has an antioxidant power equal to or higher than that of an anti-aging agent synthesized from fossil resources. In this specification, the antioxidant power based on the DPPH method is measured, for example, as described in Komazawa Women's Junior College Research Bulletin No. 37, pp. 17-22, (2004). It shall be quantified and converted into a quantity to be measured.

  The melanoidin obtained by the production method of the present invention is preferably water-soluble. Since melanoidin is water-soluble, after entering the inside of the rubber composition, there is little migration and the anti-aging performance can be maintained for a long time.

  The manufacturing method of the rubber composition of this invention includes the process of mixing the obtained melanoidin with a rubber component. Examples of rubber components include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, halogenated butyl rubber, styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, solution polymerization random styrene-butadiene-isoprene copolymer. Examples thereof include rubber, emulsion polymerization random styrene-butadiene-isoprene copolymer rubber, emulsion polymerization styrene-acrylonitrile-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, and styrene-butadiene-styrene block copolymer. Of these, natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, and halogenated butyl rubber are preferable. These rubber components can be used alone or in combination.

  The blending amount of melanoidin is preferably 0.01 to 20 parts by mass, more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the rubber component. By setting the blending amount of melanoidin within such a range, the anti-aging performance of the rubber composition can be improved efficiently.

  The rubber composition can include a reinforcing filler. Examples of reinforcing fillers include carbon black, silica, clay, aluminum hydroxide, calcium carbonate, mica, talc, aluminum hydroxide, aluminum oxide, titanium oxide, barium sulfate, and other inorganic fillers, cellulose, lecithin, lignin, An organic filler such as a dendrimer can be exemplified. Among these, it is preferable to blend at least one selected from carbon black and silica. These reinforcing fillers can be blended singly or in combination.

  In addition, the rubber composition may be vulcanized or crosslinked, vulcanization accelerator, silane coupling agent, process oil, softener, processing aid, plasticizer, liquid polymer, thermosetting resin, Various compounding agents generally used in rubber compositions such as plastic resins can be blended. The compounding amounts of these compounding agents can be the conventional general compounding amounts as long as they do not contradict the purpose of the present invention.

  In the rubber composition production method, the compounding agent excluding the vulcanizing compound, the rubber component and melanoidin are kneaded using a rubber kneader such as a Banbury mixer, kneader, open roll, etc., cooled and then vulcanized compounded. An unvulcanized rubber composition is prepared by mixing the agent. The obtained unvulcanized rubber composition is extruded according to the shape of a rubber product such as a pneumatic tire or its member, and vulcanized by vulcanization molding in a vulcanizer. Manufactured.

  The rubber composition obtained by the production method of the present invention can be suitably used as a member constituting an ordinary rubber product, particularly a pneumatic tire or a conveyor belt.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  In the following examples and comparative examples, the chemical structure, nitrogen content, post-heating weight, and antioxidant power of melanoidin and other anti-aging agents were measured by the following methods.

Analysis of Chemical Structure The chemical structure of melanoidin was analyzed by the following method using GC-MS.
Gas chromatograph mass spectrometer: Hewlett Packard, manufactured by JEOL Column: DB-5, manufactured by Agilent Technologies
Injection temperature: 280 ° C
Initial temperature: held at 50 ° C. for 3 minutes Temperature rising rate: 10 ° C./minute Achieving temperature: 320 ° C., held at 320 ° C. for 15 minutes

Measurement of Nitrogen Content About melanoidin and other antioxidants, elemental analysis was performed using an elemental analyzer (PerkinElmer fully automatic elemental analyzer (CHNS / O)) to measure the content of nitrogen atoms.

Mass% after heating
About melanoidin and other anti-aging agents, the mass% after heating was measured by the following method. Melanoidin and other anti-aging agents were weighed, applied to a thermal analyzer (calorimeter measuring device manufactured by TA instrument), and mass% after heating at 600 ° C. (held for 1 hour) was measured under the following conditions.
Nitrogen flow rate: 50 ml / min Initial temperature: 50 ° C. × 3 min hold Temperature increase rate: 10 ° C./min Achieving temperature and hold time: 600 ° C., 600 ° C. × 1 hr hold

Antioxidant power Antioxidant power of melanoidin and other anti-aging agents was measured using the DPPH (stable radical) method under the following conditions.
The stable radical 1,1-Diphenyl-2-picrylhydrazyl (DPPH) is manufactured by Tokyo Chemical Industry Co., Ltd., and 6-Hydroxy-2,5,7,8-tetramethylchloro-2-carboxylic acid (Trolox) is manufactured by Tokyo Chemical Industry Co., Ltd. It was.
To 200 μL of the sample solution, 800 μL of 0.1 M Tris-HCl buffer (pH 7.4) and 1 mL of 0.2 mM DPPH solution adjusted with 50% ethanol were sequentially converted and reacted at room temperature in the dark for 30 minutes. Thereafter, the absorbance (As) at 517 nm was measured. Using the absorbance at the time of adding 50% ethanol instead of the sample solution as a control (Ac), the inhibition rate (%) of the sample was obtained by the following formula. In addition, the concentration of the sample solution which gives 50% inhibition and IC _50. Trolox used as a standard substance was determined for IC ₅₀ in the same manner.
Inhibition rate (%) = (Ac−As) / Ac × 100
The oxidation resistance was indexed based on Troll in terms of 100 g.

Examples 1-3
<Step of synthesizing melanoidin>
Melanoidins 1 to 3 shown in Table 1 were produced by the following synthesis method.
25 parts by mass of the sugar shown in Table 1 and 25 parts by mass of amino acid were dissolved in 50 parts by mass of water to prepare a mixed solution. Melanoidins 1 to 3 were synthesized by stirring the mixed solution at 100 ° C. for 24 hours. The obtained melanoidins 1 to 3 were pulverized to a particle size of several μm or less in a mortar and analyzed using GC-MS. As a result, melanoidins 1 to 3 all had a chemical structure of pyrazine and pyrrolopyrazine. Was recognized. 1 (a) and 2 (a) are charts obtained by measuring melanoidin 1 by GC-MS, which are in good agreement with the standard charts of pyrazine and pyrrolopyrazine shown in FIGS. 1 (b) and 2 (b). ing. Melanoidins 1 to 3 were all water-soluble. Further, the nitrogen content of melanoidins 1 to 3 and the weight after heating were measured, and the results are shown in Table 1. Further, when the antioxidant power of melanoidins 1 to 3 was measured by DPPH (stable radical method), the antioxidant power of melanoidins 1, 2 and 3 was 89000 Trolox (mg / 100 g), 58000 Trolox (mg / 100 g) and 74000 Trolox ( mg / 100 g).

<Process for mixing rubber component and melanoidin>
For the rubber composition in which the compounding agents shown in Table 2 are used as a common compounding agent and the above-described melanoidins 1 to 3 are blended, components other than sulfur and a vulcanization accelerator are mixed for 6 minutes using a 1.7-liter closed Banbury mixer. The mixture was discharged from the mixer at 150 ° C. and cooled to room temperature. Thereafter, the rubber composition (Examples 1 to 3) is prepared by mixing again for 3 minutes using a 1.7 liter closed Banbury mixer, and after release, mixing sulfur and a vulcanization accelerator with an open roll. did. The obtained rubber composition was vulcanized at 160 ° C. for 30 minutes using a predetermined mold to prepare a vulcanized rubber test piece of 15 cm × 15 cm × 2 mm. Using the obtained vulcanized rubber test piece, the change in tensile properties (100% tensile stress) due to the presence or absence of heat aging treatment was measured, and the anti-aging performance was evaluated.

Aging prevention performance (change rate of tensile stress with and without heat aging treatment)
Using the obtained vulcanized rubber test piece, in accordance with JIS K6251, a dumbbell JIS No. 3 type test piece was prepared and left in the measurement environment and the test piece subjected to heat aging treatment (80 ° C., 168 hours). A prepared test piece was prepared. Using the obtained test piece, a tensile test was performed at a tensile speed of 500 mm / min at room temperature (20 ° C.), and a 100% tensile stress at 100% elongation was measured. From the obtained results, 100% tensile stress of a test piece not subjected to heat aging treatment is T0, and 100% tensile stress of a test piece subjected to heat aging treatment (80 ° C., 168 hours) is T1, and heat aging treatment is performed. Table 1 shows the calculated change rate of tensile stress Δ = (T1−T0) / T0 × 100 [%]. The smaller the change rate Δ of this tensile stress, the better the anti-aging performance.

Comparative Examples 1-5
The rubber composition of Comparative Example 1 does not use an anti-aging agent, and the rubber compositions of Comparative Examples 2 to 5 are the same as in Examples 1 to 3 except that the anti-aging agent described in Table 1 is blended. A rubber composition was prepared and its anti-aging performance was evaluated.

The compounds described in Table 1 are as follows.
-Melanoidins 1-3: those synthesized as described above-xylose: D (+)-xylose-glucose manufactured by Kishida Chemical Co., Ltd .: anhydrous crystalline grape sugar manufactured by Showa Sangyo Co., Ltd.- arginine: L-arginine-glycine manufactured by Tokyo Chemical Industry Co., Ltd .: Showa Denko Glycine-6PPD: N-phenyl-N ′-(1,3-dimethylbutyl) -1,4-phenylenediamine, Santoflex 6PPD manufactured by Solutia Euro
-Vitamin C: DSM Vitamin C (ascorbic acid)
-MB: Mercaptobenzimidazole, Nocrack MB manufactured by Ouchi Shinsei Chemical Co., Ltd.

The raw materials listed in Table 2 are as follows.
-Natural rubber: TSR
-Carbon black: Niteron # 10S made by Nikka Chemicals
-Melanoidin or anti-aging agent; those listed in Table 1-Oil: Extract No. 4 S manufactured by Showa Shell Sekiyu KK
-Zinc oxide: 3 types of Zinc Oxide manufactured by Shodo Chemical Industry Co., Ltd.-Stearic acid: Stearic acid manufactured by NOF Corporation-Sulfur: Sulfur treatment sulfur produced by Karuizawa Refinery-Vulcanization accelerator: Sunseller CM-PO (CZ manufactured by Sanshin Chemical Co., Ltd.) )

  As can be seen from Table 1, the rubber compositions of Examples 1 to 3 obtained by the production method of the present invention were compared with Comparative Example 2 in which an anti-aging agent (6PPD and MB) synthesized from fossil resources was blended. It was confirmed that the rubber composition of No. 4 and the rubber compositions of Comparative Examples 3 and 5 blended with natural resources (vitamin C and xylose) had the same or better anti-aging performance.

  The melanoidin used in the present invention can be produced from a natural product by a very simple method, and has radical scavenging ability as is apparent from an oxidation resistance test. Since melanoidin preferentially reacts with radicals generated by the aging of rubber, it is considered that the change in physical properties can be reduced because the change in sulfur crosslinking is suppressed.

Claims (5)

A method for producing a rubber composition for a tire , comprising a step of synthesizing melanoidin by heating a mixture of sugar and amino acid, and a step of mixing the obtained melanoidin and sulfur or a crosslinking agent into a rubber component. The method for producing a rubber composition for a tire according to claim 1, wherein the mixture of sugar and amino acid is heated at 50 to 250 ° C. The method for producing a tire rubber composition according to claim 1 or 2, wherein a monosaccharide consisting of aldose and / or ketose is used as the sugar. The method for producing a tire rubber composition according to any one of claims 1 to 3, wherein an α-amino acid is used as the amino acid. The tire rubber composition according to any one of claims 1 to 4, wherein at least one selected from glycine, alanine, phenylalanine, arginine, lysine, asparagine, histidine, methionine, and tryptophan is used as the amino acid. Manufacturing method.

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