JP2016060750A - Lignin derivative for rubber reinforcement, lignin resin composition and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lignin derivative for rubber reinforcement capable of adding excellent elastic modulus and tensile property, a rubber composition having good balance of rubber elastic modulus and hysteresis loss property and a lignin resin composition capable of manufacturing the rubber composition.SOLUTION: The lignin derivative for rubber reinforcement can exhibit functions as a reinforcement agent by adding it to a rubber composition and is obtained by a biomass digestion process using an agent containing no sulfur. The biomass digestion process is preferably an alkali digestion process and for example an alkali solution mainly containing sodium hydroxide is used as the agent for this.SELECTED DRAWING: None

Description

  The present invention relates to a lignin derivative for reinforcing rubber, a lignin resin composition, and a rubber composition.

  In recent years, there has been a demand for the development of technology that uses biomass as an alternative to petroleum-derived products and new materials, and technology that converts biomass into chemical products and resin products. In particular, cellulose, hemicellulose, and lignin, which are main components of general plants, are expected to be effectively used because they have a large amount of resources.

  Of these, lignin depends on the species and part of the tree, but for example, it is contained in wood at a ratio of about 30%. Since this lignin has a structure rich in aromatic rings, it can be used as an aromatic resin raw material.

  Currently, industrially obtained lignin includes, for example, lignin obtained by a kraft cooking process, which is the mainstream of pulp production methods. On the other hand, lignin obtained by an alkaline cooking process used for some pulp production, for example, lignin obtained by a soda cooking process using sodium hydroxide, is relatively natural because it contains almost no sulfur in its molecular structure. It is thought that it is close to lignin.

  In addition to this, there are disclosed resin compositions, tires, and the like that are used as resin raw materials by taking out lignin by various methods aiming at use as materials (see, for example, Patent Documents 1 and 2).

  Moreover, since lignin has a highly polar structure rich in phenolic hydroxyl groups and alcoholic hydroxyl groups, it is also considered to be used as a tackifier and an antioxidant for adding rubber compositions. (For example, refer to Patent Document 3).

  Further, lignin is expected to be used as a rubber reinforcing material. The rubber reinforcement has functions to increase the elastic modulus of rubber composition, reduce hysteresis loss, and increase mechanical strength. The rubber component rigidity, low heat generation and mechanical strength are Increases the effect.

  By the way, in Patent Document 1, lignin is dissolved in a black liquor containing sodium hydroxide and sodium sulfide, and lignin is recovered from the black liquor and used as a particulate filler for adding it to a rubber composition. Use is disclosed. However, in this case, since the properties as a filler are not sufficient, the rigidity and mechanical strength of the rubber composition are reduced.

  On the other hand, Patent Document 2 discloses that biomass is treated using cresol and concentrated sulfuric acid, and lignophenol obtained thereby is used as a rubber reinforcing resin. However, since such a rubber-reinforced resin contains a large amount of phenols that are petroleum-derived components, it is difficult to effectively use biomass, and the rigidity of the rubber composition cannot be sufficiently increased.

Special table 2011-520208 gazette JP 2008-285626 A Special table 2012-229330 gazette

  An object of the present invention is to provide a rubber-reinforced lignin derivative capable of imparting excellent elastic modulus and tensile properties, a rubber composition having a good balance between rubber elastic modulus and hysteresis loss, and the rubber composition. It is providing the lignin resin composition which can be manufactured.

Such an object is achieved by the present inventions (1) to (10) below.
(1) A rubber-reinforced lignin derivative, which is obtained by a biomass cooking process using a chemical containing no sulfur.

  (2) The lignin derivative for rubber reinforcement according to the above (1), wherein the biomass cooking process is an alkali cooking process.

  (3) The rubber according to (1) or (2), which is obtained through the step of neutralizing the black liquor obtained by the biomass cooking process with carbon dioxide and the step of dehydrating the treated product after neutralization. Lignin derivative for reinforcement.

  (4) The rubber-reinforced lignin derivative according to any one of the above (1) to (3), wherein the drug is mainly composed of sodium hydroxide.

  (5) The rubber-reinforced lignin derivative according to any one of (1) to (4), wherein 90% by mass or more is soluble in an organic solvent.

(6) soluble in organic solvents,
The number average molecular weight is 300-5000,
The lignin derivative for rubber reinforcement according to any one of (1) to (5), wherein the softening temperature is 200 ° C. or lower.

(7) A lignin resin composition comprising the rubber-reinforced lignin derivative according to any one of (1) to (6).
(8) The lignin resin composition according to (7), further including a phenolic resin.

  (9) The lignin resin composition according to (8), wherein the phenolic resin includes at least one of cashew-modified phenol resin, tall-modified phenol resin, alkyl-modified phenol resin, and cashew resin.

  (10) A rubber composition comprising the lignin resin composition according to any one of (7) to (9).

  According to the present invention, it is possible to impart excellent elastic modulus and tensile properties by using an alkali-digested lignin that has a relatively natural structure and contains almost no sulfur, and is added to the rubber composition. A lignin derivative for rubber reinforcement is obtained.

  Further, according to the present invention, a rubber composition having a good balance between the rubber elastic modulus and the hysteresis loss property, and a lignin resin composition capable of producing the rubber composition are obtained by mixing with a resin. .

  Hereinafter, the rubber-reinforcing lignin derivative, lignin resin composition and rubber composition of the present invention will be described in detail based on preferred embodiments.

  The rubber-reinforcing lignin derivative of the present invention is obtained by a biomass cooking process using a chemical not containing sulfur, and can be mixed with rubber to prepare a rubber composition.

Hereinafter, the lignin derivative for rubber reinforcement of the present invention will be described.
<Lignin derivatives for rubber reinforcement>
First, the lignin derivative for rubber reinforcement will be described. Lignin, together with cellulose and hemicellulose, is a major component that forms the skeleton of plants and is one of the most abundant substances in nature.

  The lignin derivative for rubber reinforcement is a compound having a phenol derivative as a unit structure. Since this unit structure has a chemically and biologically stable carbon-carbon bond or carbon-oxygen-carbon bond, it is less susceptible to chemical degradation and biological degradation. For this reason, the lignin derivative for rubber reinforcement is useful as a resin raw material to be added to the rubber composition.

  In the present specification, the high molecular weight lignin contained in biomass is simply referred to as “lignin”, and the relatively low molecular weight lignin derived from this lignin is referred to as “lignin derivative”. Further, the biomass in the present invention is a plant containing lignin or a processed product of the plant. Examples of plants include broadleaf trees such as beech, birch, oak, coniferous trees such as cedar, pine, and oak, bamboo, Examples include gramineous plants such as rice straw and coconut shells.

  Specific examples of the lignin derivative for reinforcing rubber include a guaiacylpropane structure represented by the following formula (1), a syringylpropane structure represented by the following formula (2), and 4-hydroxyphenyl represented by the following formula (3). Examples include a propane structure. From conifers, mainly guaiacylpropane structures, from broadleaf trees, mainly guaiacylpropane structures and syringylpropane structures, and from herbs, mainly guaiacylpropane structures, syringylpropane structures, and 4-hydroxy Each phenylpropane structure is extracted.

  In addition to the above basic structure, the lignin derivative for reinforcing rubber may be a lignin derivative obtained by introducing a functional group (lignin secondary derivative).

  The functional group possessed by the lignin secondary derivative is not particularly limited, but for example, those in which two or more of the same functional groups can react with each other or those capable of reacting with other functional groups are suitable. Specific examples include an epoxy group, a methylol group, a vinyl group having a carbon-carbon unsaturated bond, an ethynyl group, a maleimide group, a cyanate group, and an isocyanate group. Of these, a lignin derivative having a methylol group introduced (methylolated) is preferably used. Such a lignin secondary derivative is self-cross-linked by a self-condensation reaction between methylol groups, and is more cross-linked to an alkoxymethyl group or a hydroxyl group in the following cross-linking agent. As a result, a cured product having a particularly homogeneous and rigid skeleton and excellent in solvent resistance can be obtained.

  Here, the lignin derivative for rubber reinforcement according to the present invention is obtained by a biomass cooking process using a chemical not containing sulfur. Such a lignin derivative for reinforcing rubber can be imparted with excellent elastic modulus and tensile properties to the rubber composition by being mixed with rubber.

  That is, the rubber composition used for manufacturing the rubber product contains additives for various purposes in addition to the raw rubber. One of these additives is a reinforcing agent. By adding a reinforcing agent, hardness, tensile strength, abrasion resistance, etc. can be provided to the rubber composition. Therefore, the rubber composition excellent in such rubber characteristics can be prepared by mixing the lignin derivative for reinforcing rubber according to the present invention with rubber.

  On the other hand, according to the biomass cooking process using the chemical | medical agent which does not contain sulfur, the lignin derivative for rubber reinforcement which hardly contains sulfur in a molecule | numerator is obtained. Such a lignin derivative for reinforcing rubber is a derivative of an alkali-digested lignin whose structure is relatively close to a natural structure and hardly contains sulfur. For this reason, even when mixed with rubber, the possibility of causing a vulcanization reaction is reduced. Thus, the vulcanization reaction can be started in the addition of the vulcanizing agent separately performed, and the progress of the vulcanization reaction can be strictly controlled according to the addition amount of the vulcanizing agent. As a result, in the rubber composition, the rubber viscosity can be increased during kneading, or overcuring (overcuring) and undercuring (unvulcanized) can be controlled, and a rubber composition having excellent rubber properties is prepared. can do.

  The sulfur content of the rubber-reinforced lignin derivative according to the present invention is preferably less than 0.05% by mass, and more preferably 0.03% by mass or less. As described above, such a lignin derivative for reinforcing rubber hardly causes a vulcanization reaction between the lignin derivative and the rubber even when mixed with the rubber. Can be controlled.

  The rubber-reinforcing lignin derivative according to the present invention is preferably soluble in an organic solvent, and has a polystyrene-equivalent number average molecular weight of 300 to 5000 measured by gel permeation chromatography (GPC) analysis. What is 300-3000 is more preferable. Such a lignin derivative having a number average molecular weight is excellent in reactivity with a resin when it is subjected to, for example, mixing with a resin, and when a resin composition is prepared by mixing with a resin, rubber reinforcing properties are obtained. An excellent resin composition can be obtained.

  Examples of the organic solvent include alcohols such as methanol and ethanol, phenols such as phenol and cresol, ketones such as methyl ethyl ketone and acetone, cyclic ethers such as tetrahydrofuran and dioxane, and acetonitrile. Examples include nitriles, N, N-dimethylformamide, N, N-dimethylacetamide, amides such as n-methylpyrrolidone, and halogenated alkyls such as methylene chloride and chloroform.

  Here, an example of a procedure for measuring the molecular weight by the gel permeation chromatography analysis will be described.

  First, a lignin derivative for rubber reinforcement is dissolved in a solvent to prepare a measurement sample. The solvent used at this time is not particularly limited as long as it can dissolve the lignin derivative, but tetrahydrofuran is preferable from the viewpoint of measurement accuracy of gel permeation chromatography.

  Next, “TSKgelGMMHXL (manufactured by Tosoh)” and “G2000HXL (manufactured by Tosoh)”, which are organic general-purpose columns filled with a styrene polymer filler, are connected in series to the GPC system “HLC-8320GPC (manufactured by Tosoh)”. To do.

  200 μL of the above measurement sample was injected into this GPC system, and at 40 ° C., tetrahydrofuran as an eluent was developed at 1.0 mL / min. Retention time using differential refractive index (RI) and ultraviolet absorbance (UV) Measure. On the other hand, the number average molecular weight of the rubber-reinforced lignin derivative can be calculated from a calibration curve showing the relationship between the retention time and molecular weight of standard polystyrene prepared separately.

  The molecular weight of the standard polystyrene used for preparing the calibration curve is not particularly limited. For example, the number average molecular weight is 427,000, 190,000, 96,400, 37,900, 18,100. Standard polystyrene (manufactured by Tosoh) of 10,200, 5,970, 2,630, 1,050 and 500 can be used.

  Moreover, the softening point of the lignin derivative for rubber reinforcement according to the present invention is preferably 200 ° C. or less, and more preferably 80 to 160 ° C. When the softening point exceeds the above upper limit, depending on the composition of the rubber mixed with the lignin derivative, the heat melting property and fluidity of the lignin derivative for rubber reinforcement are lowered, and the rubber reinforcement characteristics due to poor dispersion in the rubber. There exists a possibility that the moldability of a deterioration or a rubber composition may fall. On the other hand, when the softening point is below the lower limit, the heat melting property and fluidity of the lignin derivative for rubber reinforcement become too high, and it may be hardened by blocking at room temperature to deteriorate the storage stability.

  In addition, the method of measuring a softening point used the ring and ball type softening point tester (Mertec Co., Ltd. ASP-MG2 type | mold) according to JISK2207.

  Moreover, the lignin derivative for rubber reinforcement according to the present invention may have a carboxyl group. When it has the said carboxyl group, it may bridge | crosslink with the crosslinking agent described below, and since a crosslinking density can be improved by a crosslinking point increasing, it is excellent in solvent resistance. Moreover, it may act as a catalyst for the crosslinking agent, can promote the crosslinking reaction of the crosslinking agent with respect to the lignin derivative, and is excellent in solvent resistance and curing rate.

In addition, when the lignin derivative mentioned above has a carboxyl group, the carboxyl group can be confirmed by the presence or absence of absorption of a peak at 172 to 174 ppm when subjected to ¹³ C-NMR analysis.

  Moreover, it is preferable that 90 mass% or more of the lignin derivative for rubber reinforcement according to the present invention is soluble in an organic solvent. Since such a lignin derivative is uniformly reduced in molecular weight, the dispersibility of the lignin derivative can be enhanced when preparing a rubber composition by mixing with rubber. For this reason, a homogeneous rubber composition can be prepared. In addition, the uniformity of the resin composition with the phenolic resin is increased, and excellent rubber reinforcement characteristics are obtained.

  Examples of the organic solvent at this time include lower alcohols such as methanol, and ketones such as acetone and methyl ethyl ketone.

<Method for producing lignin derivative for rubber reinforcement>
Next, the manufacturing method of the lignin derivative for rubber reinforcement mentioned above is demonstrated.

  The manufacturing method of the lignin derivative for rubber reinforcement is not particularly limited as long as it is obtained by a biomass cooking process using a chemical not containing sulfur.

  Several types of biomass cooking processes are known. For example, a kraft cooking process, an alkali cooking process, a sulfite cooking process, and the like are often used. Of these, the alkali cooking process, which is a process using a sulfur-free chemical as a chemical for biomass digestion, is useful as a process for use as a material including the lignin derivative for rubber reinforcement of the present invention. .

  The reason for this is that, in the pulp and paper industry, some alkali cooking processes have been put into practical use, and the mainstream kraft cooking process equipment can be diverted. Generally, lignin is obtained as a black liquor for pulp production from an alkali cooking process, but since this lignin does not contain sulfur, it may be used for materials including rubber reinforcement.

  Conventionally, black liquor containing lignin has been utilized as a fuel, but it is significant from the viewpoint of increasing the added value of biomass to be directed to the production of lignin derivatives for reinforcing rubber with higher added value. In recent years, there is a movement to use chemicals for the three main components contained in wood. Therefore, the total use of the three components is relatively easy, and the production cost of lignin for rubber reinforcement can be reduced and can be obtained stably.

  In addition, as a chemical | medical agent (alkali cooking liquid) which does not contain sulfur, For example, Although sodium hydroxide, potassium hydroxide, calcium hydroxide, the alkali solution containing sodium carbonate etc. are mentioned, Preferably sodium hydroxide is used as a main component. An aqueous solution (soda cooking liquor) is used. When biomass is digested using an aqueous solution containing sodium hydroxide as a main component, generation of harmful substances can be suppressed, so that cooking with less environmental load can be performed.

  Although the density | concentration of an alkali cooking liquid is not specifically limited, It is preferable that it is about 2-25 mass% (aqueous solution), and it is more preferable that it is about 4-15 mass%.

  Examples of the additive added to the alkaline cooking liquid include sodium sulfide, quinone cooking aid, oxygen-based, hydrogen peroxide-based, and polysulfide-based various reducing agents.

  Moreover, it is preferable that the active alkali (vs. chip | tip mass) of an alkali cooking liquid is 5-30%, and the liquid ratio with respect to a chip | tip mass is 1-5 L / kg.

  Moreover, the processing temperature in an alkali cooking process is 140-180 degreeC, and it is preferable that it is processing time 10-400 minutes.

  In addition, the chemical | medical agent which does not contain sulfur means the alkaline solution whose sulfurization degree is less than 5% (preferably 3% or less). The degree of sulfidization is, for example, a numerical value that indicates the sodium sulfide concentration in terms of sodium oxide with respect to the total concentration of sodium hydroxide and sodium sulfide in terms of sodium oxide in the alkaline solution.

  Moreover, you may make it perform various additional processes, such as a refinement | purification process, a modification | reformation process, and a solvent extraction process, with respect to the lignin derivative manufactured by the biomass cooking process as mentioned above.

  For example, the lignin derivative manufactured by the biomass cooking process can be refine | purified by giving a refinement | purification process. This refining process includes, for example, a step of acidifying black liquor (by-product after producing dissolved pulp in the cooking process) obtained by a biomass cooking process, and a step of dehydrating the processed product after acidification. Have. By undergoing such a purification treatment, the lignin derivative contained in the black liquor can be purified to a high purity and recovered in a solid state. For this reason, a solid state lignin derivative can be obtained. The solid lignin derivative recovered in this way can be used as a lignin derivative for rubber reinforcement, that is, a lignin derivative having a function as a reinforcing agent.

  Moreover, a highly purified lignin derivative is useful also in the point which can reinforce a rubber composition uniformly, and can give a uniform rubber elasticity and the outstanding tensile characteristic.

  In the acidifying step, any method capable of acidifying the black liquor, for example, adding an organic acid such as formic acid or acetic acid or an inorganic acid such as hydrochloric acid, nitric acid or sulfuric acid, sulfur dioxide, carbon dioxide, etc. A method of introducing gas or the like is used. Among these, a method of introducing carbon dioxide is preferably used from the viewpoint that the rubber reinforcement property of the lignin derivative after acidification becomes good.

  In the process of dehydrating the processed product, any method capable of removing moisture in the processed product, for example, a method using various devices such as a centrifugal separator, a filter press device, a band filter, a rotary filter, a drum filter, a precipitation tank, etc. Is used. In addition, dehydration in this specification means removing not only the water contained in the processed material but also liquids other than water.

  Moreover, this refinement | purification process can be performed based on the method described in the Japanese translations of PCT publication No. 2008-516100, for example.

  On the other hand, examples of the reforming treatment include a treatment for introducing a functional group into a lignin derivative produced by a biomass cooking process. For example, the process etc. which contact the compound containing the functional group to introduce | transduce with a lignin derivative are mentioned.

  Solvent extraction is a process in which a lignin derivative produced by a biomass cooking process is dissolved in a solvent capable of dissolving the lignin derivative, and then the solvent-soluble component is mainly extracted. Examples of the process for taking out the solvent-soluble component include filtering the solid residue after dissolving the solvent to concentrate and drying the soluble component. The lignin derivative that has undergone such solvent extraction treatment has a low molecular weight and is excellent in heat melting property, so that it can be easily mixed with rubber and can improve rubber reinforcing properties. Further, since the molecular weight and physical properties become uniform, it is useful in that a homogeneous rubber composition can be prepared.

<Lignin resin composition>
Next, the lignin resin composition of the present invention will be described.

  The lignin resin composition of the present invention contains a lignin derivative for rubber reinforcement and a resin. Such a lignin resin composition is capable of preparing a rubber composition having a good balance between rubber elastic modulus and hysteresis loss by being mixed with raw material rubber.

(resin)
The resin mixed with the lignin derivative for reinforcing rubber is not particularly limited, and examples thereof include phenol resins, epoxy resins, furan resins, urea resins, and melamine resins. Of these, phenol resins are preferably used. By mixing the phenolic resin and the lignin derivative for rubber reinforcement, the phenolic resin and the lignin derivative are cross-linked, so that the rubber reinforcing characteristics can be further improved when used as a rubber composition.

  The amount of resin added in the lignin resin composition is preferably 10 parts by mass or more and 1000 parts by mass or less, and 20 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the lignin derivative for rubber reinforcement. Is more preferable. By adding the resin at such a ratio, the phenolic resin and the lignin derivative can be crosslinked without excess or deficiency.

  Examples of the phenolic resin include phenols or those obtained by reacting phenols and a modified compound with aldehydes. Among these, as phenols, for example, cresols such as o-cresol, m-cresol and p-cresol, ethylphenols such as o-ethylphenol, m-ethylphenol and p-ethylphenol, isopropylphenol and butylphenol , Butylphenols such as p-tert-butylphenol, long-chain alkylphenols such as p-tert-amylphenol, p-octylphenol, p-nonylphenol, p-cumylphenol, etc., one or two of these A mixture of seeds or more can be used.

  On the other hand, examples of the modifying compound include compounds having an aromatic structure such as catechol, pyrogallol, bisphenol F, and bisphenol A having two or more hydroxyl groups in the molecule, and polycyclic aromatic structures such as naphthol having a hydroxyl group. , Melamine, terpenes, furan resins such as furfural, plant-derived components such as tung oil, linseed oil, cashew oil, tannin, tall oil, and the like. Since cashew oil has a phenol structure, the phenolic resin includes cashew resin.

  Among these, the phenolic resin preferably contains at least one of cashew-modified phenol resin, tall-modified phenol resin, alkyl-modified phenol resin, and cashew resin. Since such a phenolic resin is excellent in compatibility with the raw rubber, it is considered that it can be uniformly dispersed when mixed with the raw rubber to prepare a homogeneous rubber composition. That is, a rubber composition that is homogeneous and has a large rubber elastic modulus can be obtained.

  As the cashew-modified phenol resin, for example, cashew oil which is a natural product containing cardanol or cardol having an unsaturated double bond in the side chain is used, and this is obtained by condensation or addition reaction with phenols and aldehydes. Can be mentioned. The cashew-modified phenolic resin includes a novolak type and a resol type, both of which are used. However, considering the cost and the like, the novolak type is preferably used.

  The tall-modified phenol resin is a phenol resin modified with tall oil. It is thought that the form in which the double bond of unsaturated fatty acid in tall oil is bonded to the phenol ring of the phenol resin, the form in which tall oil is dispersed and mixed in the phenol resin, or the form in which these are mixed .

  Examples of the alkyl-modified phenol resin include those obtained by reacting aldehydes with phenols having an alkyl group such as bisphenol A or nonylphenol, octylphenol, and dodecylphenol.

  Examples of the cashew resin include cashew oil or a polymer thereof, which is a natural product containing cardanol or cardol having an unsaturated double bond in the side chain, or a polymer reacted with an aldehyde or a saccharide. It is done.

  In addition, when the phenols and the modified compound are reacted, examples of the catalyst include inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, phosphorous acid, oxalic acid, diethyl sulfuric acid, paratoluenesulfonic acid, and organic phosphonic acid. Such organic acids, metal salts such as zinc acetate, and the like can be used alone or in combination of two or more.

  Although the molecular weight of such a phenol-type resin is not specifically limited, It is preferable that it is about 400-5000 in a number average molecular weight, and it is more preferable that it is about 500-3000. By setting the number average molecular weight of the phenolic resin within the above range, the handleability of the phenolic resin is improved. If the average molecular weight of the phenolic resin is below the lower limit, depending on the composition of the phenolic resin, the phenolic resin becomes a highly viscous material, or even when solidified, it tends to solidify depending on the environment. There is a risk of On the other hand, if the average molecular weight of the phenolic resin exceeds the upper limit, depending on the composition of the phenolic resin, the phenolic resin may be difficult to dissolve in the solvent, or the compatibility with the compound may be reduced. .

  In addition, the number average molecular weight of a phenol-type resin can be measured using the method similar to the lignin derivative mentioned above.

  The form of the lignin resin composition obtained using such a resin and a lignin derivative for reinforcing rubber is not particularly limited, and examples thereof include powder, granules, pellets, and varnishes. In addition, from a viewpoint of the handleability at the time of mixing with raw material rubber, it is preferable that the form of a lignin resin composition is a granular form or a pellet form.

  In addition, the rubber composition of the present invention may further contain a filler, a crosslinking agent, and other components as described later.

  Moreover, the solid content concentration in the lignin resin composition is not particularly limited, but is, for example, about 60 to 98% by mass, preferably about 70 to 95% by mass.

<Method for producing lignin resin composition>
Next, the manufacturing method of the lignin resin composition mentioned above is demonstrated.

Although the manufacturing method of a lignin resin composition is not specifically limited, For example, the raw material mentioned above is thrown into a kneader and the method of kneading | mixing is mentioned. If necessary, any raw materials may be premixed and then kneaded. Further, the order of kneading the raw materials described above is not particularly limited, and all the raw materials may be kneaded at the same time, or may be kneaded sequentially in an arbitrary order.
Examples of the kneader include a mixer, a kneader, and a roll.

  Moreover, when kneading | mixing, you may make it heat or use an organic solvent as needed. Examples of the organic solvent include methanol, ethanol, propanol, butanol, methyl cellosolve, acetone, methyl ethyl ketone, methyl isobutyl ketone, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and quinoline. , Cyclopentanone, m-cresol, chloroform and the like, and one or a mixture of two or more of these is used.

<Rubber composition>
Next, the rubber composition of the present invention will be described.

  The rubber composition of the present invention includes at least a raw rubber and the above-described lignin derivative for reinforcing rubber. Alternatively, the rubber composition of the present invention includes at least a raw rubber and the above-described lignin resin composition. Such a rubber composition has a good balance between rubber elastic modulus and hysteresis loss. Such a rubber composition is useful, for example, as a tire rubber composition capable of achieving both good steering stability and reduction in rolling resistance.

(Raw material rubber)
Examples of the raw rubber include various natural rubbers and various synthetic rubbers. Specifically, natural rubber (NR), modified natural rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), ethylene propylene diene rubber (EPDM), acrylonitrile butadiene Examples thereof include rubber (NBR), chloroprene rubber (CR) and the like, and one or more of these can be used in combination. In particular, natural rubber (NR), modified natural rubber, styrene butadiene rubber (SBR), and butadiene rubber (BR) are superior in properties such as trauma resistance, wear resistance, fatigue resistance, and flex crack growth resistance. One or more rubbers selected from among these are preferably used, and at least one of natural rubber and butadiene rubber (BR) is more preferably used from the viewpoint of availability.

  When blending styrene butadiene rubber (SBR) and butadiene rubber (BR), the content of SBR and BR is preferably 50% by mass or less in the rubber composition, more preferably 30% by mass or less. preferable. When the SBR and BR content is less than or equal to the above upper limit, the ratio of petroleum resources in the rubber composition can be kept low, and the burden on the environment can be further reduced.

  Further, the rubber composition of the present invention has at least one functional group selected from the group consisting of alkoxyl groups, alkoxysilyl groups, epoxy groups, glycidyl groups, carbonyl groups, ester groups, hydroxy groups, amino groups, and silanol groups. It may contain at least one of a functional group-containing natural rubber containing a group (modified natural rubber) and a functional group-containing diene rubber. When natural rubber and diene rubber contain these functional groups, these raw rubbers react or interact with the surface of the filler, thereby improving the dispersibility of the filler in the rubber composition.

  In addition, it is preferable that the functional group mentioned above is contained in the ratio of 0.001-80 mol% of raw material rubber, and it is more preferable that it is contained in the ratio of 0.01-50 mol%, and 0.0. More preferably, it is contained at a ratio of 02 to 25 mol%. If the content of the functional group is within the above range, the effect of reacting with or interacting with the surface of the filler can be obtained better, and at the time of producing unvulcanized rubber (rubber composition not containing a vulcanizing agent) The increase in the viscosity is suppressed, and the processability is improved.

  Examples of the method of incorporating the above-described functional group into the raw rubber include, for example, a method of introducing a functional group into the polymerization terminal of a styrene-butadiene copolymer polymerized using an organolithium initiator in a hydrocarbon solvent, Examples thereof include a method of epoxidizing rubber or diene rubber by a method such as a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, or a peracid method.

  In the rubber composition of the present invention, the rubber component is such that at least one of natural rubber, modified natural rubber, styrene butadiene rubber (SBR) and butadiene rubber (BR) accounts for 50 to 100% by mass of the raw rubber. Is preferably set. When the composition of the rubber component is set within the above range, the rubber elastic modulus (storage elastic modulus E ′) can be increased, and the hysteresis loss (loss tangent tan δ near 60 ° C.) can be reduced. . Thereby, for example, it is possible to obtain a rubber composition for tires that can achieve both good steering stability and reduction in rolling resistance.

  From the viewpoint of reducing environmental impact, it is desirable to increase the proportion of natural rubber and modified natural rubber, but other rubber components such as styrene butadiene rubber (SBR) and butadiene rubber (BR) are added to these. By doing so, the wear resistance and flex crack growth resistance of the rubber composition can be further increased, and therefore the rubber component may be selected based on such a viewpoint.

  The addition amount of the raw rubber is not particularly limited, but is preferably 100 parts by mass or more and 10000 parts by mass or less, and 200 parts by mass or more and 5000 parts by mass with respect to 100 parts by mass in total of the lignin derivative for rubber reinforcement and the resin. More preferably, it is more preferably 300 parts by mass or more and 2000 parts by mass or less. By setting the addition amount of the raw rubber within the above range, it is possible to suppress the elongation of the rubber composition from being excessively increased due to the hardness of the rubber composition being sufficiently secured while ensuring the reinforcing effect of the rubber composition.

(filler)
Moreover, the rubber composition of this invention may contain the filler other than the component mentioned above.

  As the filler, those usually used in resin compositions and rubber compositions can be employed. Specific examples include at least one selected from the group consisting of carbon black, silica, alumina, and cellulose fiber. Particularly, at least one selected from silica and carbon black is preferably used. By using these fillers, it is possible to increase the rubber elastic modulus (storage elastic modulus E ′) and reduce the hysteresis loss (loss tangent tan δ near 60 ° C.).

  The content of the filler is preferably 10 to 150 parts by mass with respect to 100 parts by mass of the raw rubber. The rubber elastic modulus of the rubber composition can be increased by setting the filler content to the lower limit value or more. On the other hand, by setting the filler content to the upper limit value or less, the rubber elastic modulus is prevented from excessively increasing, and the processability during the preparation of the rubber composition is improved, and the filling in the rubber composition is performed. It is possible to suppress a decrease in wear resistance, elongation at break and the like due to deterioration of the dispersibility of the agent. Moreover, the increase in the hysteresis loss property of a rubber composition can be suppressed.

  In particular, when silica is blended as a filler, the silica is blended at a ratio of 3 to 150 parts by weight with respect to 100 parts by weight of the raw rubber, and the silane coupling agent is 1 to 20% by weight of the silica content. It is preferable to mix | blend in the ratio. In the rubber composition, the rubber elastic modulus of the rubber composition can be increased by setting the silica content with respect to 100 parts by mass of the raw rubber to the lower limit value or more. On the other hand, by setting the content of silica relative to 100 parts by mass of the raw rubber to be equal to or less than the above upper limit, while suppressing the rubber elastic modulus from rising excessively, while improving the workability at the time of preparing the rubber composition, It is possible to suppress a decrease in abrasion resistance, elongation at break and the like due to deterioration of the dispersibility of the filler in the rubber composition. Moreover, the increase in the hysteresis loss property of a rubber composition can be suppressed.

  In addition, as for content of a silica, it is more preferable that it is a ratio of 5-100 mass parts with respect to 100 mass parts of raw rubber, and it is further more preferable that it is a ratio of 10-80 mass parts.

As silica, those conventionally used for reinforcing rubber can be used, and examples thereof include dry method silica, wet method silica, colloidal silica and the like. In particular, those having a nitrogen adsorption specific surface area (N2SA) of 20 to 600 m ² / g are preferably used, those having 40 to 500 m ² / g are more preferably used, and those having 50 to 450 m ² / g are further used. Preferably used. When N2SA of silica is not less than the lower limit, the reinforcing effect on the rubber composition is increased. On the other hand, when N2SA of silica is not more than the above upper limit value, the dispersibility of silica in the rubber composition becomes good, and for example, a rubber composition excellent in low hysteresis loss can be obtained.

  Moreover, a filler is not limited to what was mentioned above. Examples of the constituent material of the filler include talc, fired clay, unfired clay, mica, silicates such as glass, oxides such as titanium oxide and alumina, magnesium silicate, calcium carbonate, magnesium carbonate, hydro Carbonates such as talcite, oxides such as zinc oxide and magnesium oxide, hydroxides such as aluminum hydroxide, magnesium hydroxide and calcium hydroxide, sulfates such as barium sulfate, calcium sulfate and calcium sulfite Alternatively, borates such as sulfite, zinc borate, barium metaborate, aluminum borate, calcium borate, sodium borate, nitrides such as aluminum nitride, boron nitride, and silicon nitride can be given. And the powder, particle | grains, fiber piece, etc. which were comprised with these materials are used for a filler.

  In addition, organic fillers such as inorganic fillers such as carbon fiber, wood powder, pulp pulverized powder, cloth pulverized powder, thermosetting resin cured powder, aramid fiber, and talc are also included in the lignin resin composition of the present invention. It can be used as a filler contained in a product.

(Crosslinking agent)
Moreover, the rubber composition of this invention may contain the crosslinking agent other than the component mentioned above.

  The cross-linking agent is not particularly limited as long as it can cross-link either one or both of the raw rubber and the rubber-reinforcing lignin derivative, but preferably includes a compound represented by the following formula (4). It is done.

［式（４）中のＺは、メラミン残基、尿素残基、グリコリル残基、イミダゾリジノン残基および芳香環残基のうちのいずれか１種である。また、ｍは２〜１４の整数を表す。また、Ｒは独立して炭素数１〜４のアルキル基または水素原子である。ただし、−ＣＨ_２ＯＲは、メラミン残基の窒素原子、尿素残基の１級アミノ基の窒素原子、グリコリル残基の２級アミノ基の窒素原子、イミダゾリジノン残基の２級アミノ基の窒素原子および芳香環残基の芳香環の炭素原子のいずれかに直接結合している。］

[Z in Formula (4) is any one of a melamine residue, a urea residue, a glycolyl residue, an imidazolidinone residue, and an aromatic ring residue. Moreover, m represents the integer of 2-14. R is independently an alkyl group having 1 to 4 carbon atoms or a hydrogen atom. However, -CH 2 _OR, the nitrogen atom of the melamine residues, the nitrogen atom of the primary amino groups of the urea residues, the nitrogen atom of the secondary amino group of the glycolyl residues, the secondary amino group of the imidazolidinone residues It is directly bonded to either the nitrogen atom or the carbon atom of the aromatic ring residue. ]

  A rubber composition containing such a compound is excellent in mechanical properties after curing, and contributes to improvement in durability and appearance of the cured product. This is because the compound represented by the above formula (4) contained in the cross-linking agent can form a polyfunctional cross-linking point. Therefore, the lignin derivative for rubber reinforcement is cross-linked uniformly and uniformly. This is because a rigid skeleton is formed. The rigid skeleton improves the mechanical properties and durability (boiling resistance, etc.) of the cured product, and also suppresses the occurrence of blisters and cracks, thereby improving the appearance of the cured product.

In addition, as described above, —CH ₂ OR is a nitrogen atom of a melamine residue, a nitrogen atom of a primary amino group of a urea residue, a nitrogen atom of a secondary amino group of a glycolyl residue, or 2 of an imidazolidinone residue. It is directly bonded to either the nitrogen atom of the primary amino group or the carbon atom of the aromatic ring residue, but two or more “—CH ₂ OR” are bonded to the same nitrogen atom or carbon atom. In this case, it is preferable that “R” included in at least one of “—CH ₂ OR” is an alkyl group. Thereby, a lignin derivative (A) can be bridge | crosslinked reliably.

  In this specification, the melamine residue refers to a group having a melamine skeleton represented by the following formula (A).

  In this specification, the urea residue refers to a group having a urea skeleton represented by the following formula (B).

  In this specification, the glycolyl residue refers to a group having a glycolyl skeleton represented by the following formula (C).

  In the present specification, the imidazolidinone residue refers to a group having an imidazolidinone skeleton represented by the following formula (D).

  In this specification, an aromatic ring residue refers to a group having an aromatic ring (benzene ring).

  Moreover, especially as a compound represented by the said Formula (4), the compound represented by either of following formula (5)-(8) is used preferably. These react with the cross-linking reaction points on the aromatic ring contained in the phenol skeleton in the lignin derivative for rubber reinforcement, thereby surely cross-linking the lignin derivative and causing self-crosslinking by self-condensation reaction between functional groups. . As a result, a cured product having a particularly homogeneous and rigid skeleton and excellent in mechanical properties, durability and appearance can be obtained.

［式（５）中、ＸはＣＨ_２ＯＲまたは水素原子であり、Ｒは独立して炭素数１〜４のアルキル基または水素原子である。また、ｎは１〜３の整数を表す。］

Wherein (5), X is _CH 2 OR or a hydrogen atom, R is independently an alkyl group or a hydrogen atom having 1 to 4 carbon atoms. N represents an integer of 1 to 3. ]

［式（６）中、Ｒは独立して炭素数１〜４のアルキル基または水素原子である。］

[In Formula (6), R is a C1-C4 alkyl group or a hydrogen atom independently. ]

［式（７）中、Ｒは独立して炭素数１〜４のアルキル基または水素原子である。］

[In Formula (7), R is a C1-C4 alkyl group or a hydrogen atom independently. ]

［式（８）中、Ｒは独立して炭素数１〜４のアルキル基または水素原子である。］

[In formula (8), R is a C1-C4 alkyl group or a hydrogen atom independently. ]

  As the compound represented by the above formula (5), a compound represented by the following formula (9) or the following formula (10) is particularly preferably used. These react with a crosslinking reaction point on the aromatic ring contained in the phenol skeleton in the lignin derivative to particularly surely crosslink the lignin derivative and cause self-crosslinking by self-condensation reaction between functional groups. As a result, a cured product having a particularly uniform and rigid skeleton and excellent mechanical properties, durability and appearance can be obtained.

［式（９）中、ｎは１〜３の整数を表す。］

[In formula (9), n represents the integer of 1-3. ]

［式（１０）中、ｎは１〜３の整数を表す。］

[In Formula (10), n represents the integer of 1-3. ]

  The cross-linking agent may contain at least one compound of hemisamethylenetetramine, quinuclidine, and pidgin instead of or together with the compound represented by the formula (4). . A cured product containing such a cross-linking agent has excellent mechanical strength and high durability and appearance. This is because hexamethylenetetramine, quinuclidine, and pidgin cross-link the lignin derivative for rubber reinforcement uniformly and densely to form a homogeneous and rigid skeleton.

  The crosslinking agent may contain a crosslinking agent component other than the above compound. Examples of the cross-linking agent component other than the above compound include, for example, orthocresol novolac epoxy resin, bisphenol A type epoxy resin, epoxidized glycerin, epoxidized linseed oil, epoxy resin such as epoxidized soybean oil, hexamethylene diisocyanate, toluene diisocyanate. Isocyanate compounds, compounds that can be cross-linked by electrophilic substitution reaction on aromatic rings of lignin derivatives, aldehydes such as formaldehyde, acetaldehyde, paraformaldehyde, furfural, aldehyde sources such as polyoxymethylene, resol type phenol Examples of the conventional phenol resin such as a resin include a known crosslinking agent and a compound that can be crosslinked by electrophilic substitution reaction on the aromatic ring of the lignin derivative. And it is preferable that the content rate of these crosslinking agent components in a crosslinking agent is 80 mass% or more before crosslinking reaction.

  The addition amount of the crosslinking agent is not particularly limited, but is preferably 5 to 120 parts by mass, and more preferably 10 to 100 parts by mass with respect to 100 parts by mass of the lignin derivative for rubber reinforcement.

(Other ingredients)
The rubber composition of the present invention may contain other components in addition to the components described above.

  Examples of other components include softeners, tackifiers, antioxidants, ozone degradation inhibitors, anti-aging agents, sulfur and other vulcanizing agents, vulcanization accelerators, vulcanization accelerators, peroxides, Examples include zinc oxide and stearic acid.

As the vulcanizing agent, for example, an organic peroxide or a sulfur vulcanizing agent can be used.
Among these, examples of the organic peroxide include benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butyl cumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, and 2,5-dimethyl. -2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) ) Hexin-3,1,3-bis (t-butylperoxypropyl) benzene and the like.

  On the other hand, examples of the sulfur-based vulcanizing agent include sulfur and morpholine disulfide. Of these, sulfur is particularly preferably used.

  Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine, aldehyde-ammonia, imidazoline, and xanthate vulcanization accelerators. An agent etc. are mentioned, and the thing containing at least 1 sort is used among these.

  As the anti-aging agent, for example, amine-based, phenol-based, and imidazole-based compounds, carbamic acid metal salts, waxes, and the like are appropriately selected and used.

  The rubber composition of the present invention can further be appropriately mixed with compounding agents usually used in the rubber industry, such as stearic acid and zinc oxide.

  Moreover, the solid content concentration in the rubber composition is not particularly limited, but is, for example, about 60 to 98% by mass, and preferably about 70 to 95% by mass.

  Such a rubber composition can be applied to all uses of conventional rubber compositions, and specifically, can be applied to uses such as tires, belts, rubber crawlers, anti-vibration rubbers, and shoes.

<Method for producing rubber composition>
Next, the manufacturing method of the rubber composition described above will be described.

  Although the manufacturing method of a rubber composition is not specifically limited, For example, the process of kneading | mixing raw material rubber | gum, the lignin derivative for rubber reinforcement, and another raw material is included. If necessary, any raw materials may be premixed and then kneaded. Further, the order of kneading the raw materials described above is not particularly limited, and all the raw materials may be kneaded at the same time, or may be kneaded sequentially in an arbitrary order.

Examples of the kneader include a mixer, a kneader, and a roll.
Further, when kneading, an organic solvent may be used as necessary. Examples of the organic solvent include methanol, ethanol, propanol, butanol, methyl cellosolve, acetone, methyl ethyl ketone, methyl isobutyl ketone, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and quinoline. , Cyclopentanone, m-cresol, chloroform and the like, and one or a mixture of two or more of these is used.

Here, an example of the manufacturing method of a rubber composition is demonstrated for every process.
First, (1) a rubber-reinforced lignin derivative and a resin are mixed to obtain a mixed resin.

  Next, (2) rubber containing no vulcanization system by kneading raw material rubber, mixed resin and optional components (excluding vulcanizing agent and vulcanization accelerator) with a closed kneader. A composition (unvulcanized rubber composition) is obtained. At this time, kneading conditions (kneading temperature, kneading time, etc.) are appropriately set according to the kneader.

  Next, (3) A vulcanizing agent and a vulcanization accelerator are added to the rubber composition obtained by the above (2) using the kneader including rolls such as an open roll, and kneaded again. A rubber composition containing a vulcanization system is obtained.

<Method of curing rubber composition>
Next, a process for obtaining a cured product of the rubber composition will be described.

  A cured product of the rubber composition can be obtained by molding and curing the rubber composition. The molding method is not particularly limited because it varies depending on the application, but when molding using a mold, the produced rubber composition is molded using a mold equipped with a hydraulic press. . Thereby, the hardened | cured material of the rubber composition shape | molded by the target shape is obtained.

  Moreover, the rubber composition of this invention can be used as a rubber composition for tires as an example. For example, when the rubber composition of the present invention is used as a rubber composition for tire cap treads, it is produced by a usual method. That is, after an unvulcanized rubber composition is extruded into the shape of a tread portion of a tire, it is bonded together by a tire molding machine by a normal method to form an unvulcanized tire. Next, the unvulcanized tire can be heated and pressurized in a vulcanizer to obtain a tire.

  The molding temperature is preferably about 100 to 280 ° C, more preferably about 120 to 250 ° C, and still more preferably about 130 to 230 ° C. If the molding temperature exceeds the upper limit, the rubber may be deteriorated. On the other hand, if the molding temperature is lower than the lower limit, sufficient molding may not be possible.

  As mentioned above, although the lignin derivative for reinforcing rubber, the lignin resin composition and the rubber composition of the present invention have been described, the present invention is not limited thereto. For example, the lignin resin composition and the rubber composition include Arbitrary components may be added respectively.

Next, specific examples of the present invention will be described.
1. Production of Rubber Composition Hereinafter, various raw materials used in Examples and Comparative Examples are listed.

Natural rubber: RSS3 manufactured by Tochi
Curing agent: Hexamethylenetetramine Carbon black: HAF manufactured by Mitsubishi Chemical Corporation
Silica: manufactured by Evonik, Ultrasil VN3 (BET specific surface area: 175 m ² / g)
Silane coupling agent: Si-69, manufactured by Evonik
Zinc oxide: Made by Sakai Chemical Industry Co., Ltd. Stearic acid: Beads stearic acid YR made by NOF Corporation
Sulfur: manufactured by Hosoi Chemical Industry Co., Ltd., fine sulfur vulcanization accelerator: manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., MSA-G
Phenolic resin: Sumitomo Bakelite, PR-50731
Cashew modified novolac type phenolic resin: PR-12686, manufactured by Sumitomo Bakelite Co., Ltd.
Tall-modified novolac type phenolic resin: PR-13349, manufactured by Sumitomo Bakelite Co., Ltd.

Example 1
(1) Kraft cooking process A cooking solution was added to 300 g of cedar chips (absolutely dry amount) and cooked in an autoclave at a temperature of 170 ° C and a pressure of 0.8 MPa for 120 minutes. The cooking liquor is an alkaline solution prepared so that the water content is 92.9% by mass and the sodium hydroxide content is 7.1% by mass. Further, the active alkali (to the mass of the chip) of this cooking liquid was 23%, and the liquid ratio was 3 L / kg. By this cooking, soda pulp (AP) was obtained and black liquor containing a lignin derivative was obtained.

(2) Purification process Next, at 80 ° C., the obtained black liquor (pH 13 to 13.5) was adjusted to pH 9 with carbon dioxide. The adjusted black liquor was dehydrated with a filter press to obtain a cake having a solid content of about 30%. The obtained cake was resuspended by adding twice the amount of water, and adjusted to pH 5 with sulfuric acid. The adjusted suspension was adjusted to 80 ° C., dehydrated with a filter press, and then washed with 80 ° C. water twice the amount of cake to obtain a lignin cake having a solid content of about 70%. Thereby, a lignin derivative for rubber reinforcement was obtained.

  Here, about the obtained lignin derivative for rubber reinforcement, the content rate of sulfur was measured by the flask combustion-titration method. As a result, in any of the rubber-reinforced lignin derivatives obtained in Example 1 and each Example described later, the sulfur content was less than 0.04% by mass.

  In addition, the number average molecular weight and softening point of the obtained rubber-reinforced lignin derivative were measured. The measurement results are shown in Table 1.

(3) Preparation of rubber composition Next, 50 parts by mass of a lignin derivative for reinforcing rubber and 50 parts by mass of a cashew-modified phenol resin were previously melt-mixed in a hot plate at 130 ° C. and pulverized to obtain a mixed resin. It was.

  Next, 100 parts by mass of the obtained mixed resin, 500 parts by mass of a natural rubber compound, 350 parts by mass of carbon black, 10 parts by mass of hexamethylenetetramine as a resin cross-linking agent, 15 parts by mass of sulfur as a vulcanizing agent, 7.5 parts by mass of MSA-G as a sulfur accelerator, 25 parts by mass of zinc oxide as a vulcanization accelerator, and 10 parts by mass of stearic acid as a mold release agent are kneaded at 100 ° C. in a Banbury mixer, and a rubber composition Got.

(Example 2)
A rubber composition was obtained in the same manner as in Example 1 except that the addition of the cashew-modified phenol resin was omitted and the lignin derivative for rubber reinforcement was changed to 100 parts by mass.

(Example 3)
A rubber composition was obtained in the same manner as in Example 1 except that a eucalyptus chip was used instead of a cedar chip and a tall-modified phenol resin was added instead of a cashew-modified phenol resin.

Example 4
A rubber composition was obtained in the same manner as in Example 3 except that a novolac type phenol resin was added instead of the toll-modified phenol resin.

(Example 5)
A rubber composition was obtained in the same manner as in Example 1 except that eucalyptus chips were used instead of cedar chips.

(Example 6)
A rubber composition was obtained in the same manner as in Example 5 except that the addition amount of the lignin derivative for rubber reinforcement and the addition amount of the cashew-modified phenol resin were changed as shown in Table 1, respectively.

(Example 7)
A rubber composition was obtained in the same manner as in Example 5 except that the addition amount of the lignin derivative for rubber reinforcement and the addition amount of the cashew-modified phenol resin were changed as shown in Table 1, respectively.

(Example 8)
A rubber composition was obtained in the same manner as in Example 5 except that the addition of the cashew-modified phenol resin was omitted and the lignin derivative for rubber reinforcement was changed to 100 parts by mass.

Example 9
A rubber composition was obtained in the same manner as in Example 5 except that silica was further added as a filler and the addition amount of carbon black was changed as shown in Table 1.

(Example 10)
A rubber composition was obtained in the same manner as in Example 5 except that the purification process was omitted in the production of the rubber-reinforced lignin derivative and a rubber-reinforced lignin derivative extracted directly from the black liquor was used.

(Example 11)
A rubber composition was obtained in the same manner as in Example 8 except that hexamethylenetetramine was not used.

(Comparative Example 1)
(1) Biomass decomposition process 300 g of cedar chips (absolutely dry amount) and 1600 g of pure water were introduced into a rotary autoclave having a capacity of 2.4 L. Then, while the contents were stirred at a rotation speed of 300 rpm, the cedar chips were decomposed by processing at a processing temperature of 300 ° C. and a processing pressure of 9 MPa for 180 minutes.

Subsequently, the decomposition product was filtered and washed with pure water to separate a water-insoluble portion. This water-insoluble part was immersed in acetone and then filtered to recover the acetone-soluble part.
Subsequently, acetone was distilled off from the acetone soluble part to obtain a lignin derivative.

(2) Purification process Next, in the same manner as in Example 1, the lignin derivative obtained in (1) was purified.

(3) Production of rubber composition Next, a rubber composition was obtained in the same manner as in Example 6.

(Comparative Example 2)
A rubber composition was obtained in the same manner as in Comparative Example 1 except that the addition of the cashew-modified phenol resin was omitted and the lignin derivative was changed to 100 parts by mass.

(Comparative Example 3)
A rubber composition was obtained in the same manner as in Comparative Example 1 except that the addition of the lignin derivative for rubber reinforcement, the addition of the cashew-modified phenol resin, and the addition of the resin crosslinking agent were omitted.

(Comparative Example 4)
A rubber composition was obtained in the same manner as in Comparative Example 1 except that the addition of the lignin derivative for rubber reinforcement and the addition of the cashew-modified phenol resin were omitted, and 100 parts by mass of the novolac type phenol resin was added.

(Comparative Example 5)
A rubber composition was obtained in the same manner as in Comparative Example 1, except that the addition of the lignin derivative for rubber reinforcement was omitted and 100 parts by mass of the cashew-modified phenol resin was added.

2. Evaluation of Rubber Composition First, the rubber compositions obtained in each Example and each Comparative Example were vulcanized at 160 ° C. for 20 minutes using a hydraulic press to prepare a vulcanized rubber sheet having a thickness of 2 mm.

2.1 Measurement of Tensile Stress at Cutting and Tensile Elongation at Cutting Next, the rubber sheet was subjected to the tensile stress at the time of cutting and the tensile at the time of cutting using a strograph manufactured by Toyo Seiki Co., Ltd. Elongation was measured. The tensile speed at the time of measurement was 50 mm / min. Moreover, the shape of the test piece was a dumbbell type, the distance between grips was 60 mm, the width was 5 mm, and the measurement temperature was 25 ° C.

  Subsequently, the relative value of the measurement result about the rubber sheet obtained by each Example and each comparative example when the measurement result about the rubber sheet obtained by the comparative example 3 was set to 100 was calculated | required. The calculation results are shown in Table 1.

2.2 Measurement of storage elastic modulus E ′ and loss tangent tan δ Next, the rubber sheet was subjected to storage elastic modulus E at 30 ° C. under dynamic conditions using a dynamic viscoelasticity measuring device manufactured by TA Instruments. 'And the reciprocal of the loss tangent tan δ at 60 ° C were measured.

  The length of the test piece was 22 mm, the width was 10 mm, the heating rate was 5 ° C./min, the strain was 2%, and the measurement frequency was 1 Hz.

  Subsequently, the relative value of the measurement result about the rubber sheet obtained by each Example and each comparative example when the measurement result about the rubber sheet obtained by the comparative example 3 was set to 100 was calculated | required. The calculation results are shown in Table 1.

  Note that a large value of the reciprocal of the loss tangent tan δ means that the loss tangent tan δ of the viscoelastic property is small, and consequently that the thermal energy generated by repeated deformation can be suppressed, that is, the hysteresis loss property is small. Therefore, for example, when the rubber composition obtained in each example and each comparative example is applied to a rubber composition for a tire, a tire having a small rolling resistance can be obtained.

  As can be seen from Table 1, the cured product of the rubber composition obtained in each example has a storage elastic modulus E ′ that is a measure of hardness compared to the cured product of the rubber composition obtained in each comparative example. Is big. In addition, the cured product of the rubber composition obtained in each example has a larger tensile stress at cutting and tensile elongation at cutting than the cured product of the rubber composition obtained in Comparative Examples 4 and 5. Therefore, according to this invention, it became clear that the rubber composition which has the outstanding elasticity modulus and the tensile characteristic can be implement | achieved.

  Further, by adding the resin together with the lignin derivative, the reciprocal of the loss tangent tan δ at 60 ° C. can be increased and the hysteresis loss of the cured product of the rubber composition can be reduced as compared with the case where no resin is added. It was recognized that

  Therefore, according to the present invention, the rubber composition having a small hysteresis loss property related to the reciprocal of tan δ at 60 ° C. and a large rubber elastic modulus related to the storage elastic modulus E ′ at 30 ° C., that is, the rubber elastic modulus It was revealed that a rubber composition having a good balance between the hysteresis loss and the hysteresis loss can be realized.

  Therefore, it became clear that the lignin derivative for rubber reinforcement according to the present invention can function as a reinforcing agent.

Claims (10)

  A lignin derivative for rubber reinforcement, which is obtained by a biomass cooking process using a chemical containing no sulfur.   The lignin derivative for rubber reinforcement according to claim 1, wherein the biomass cooking process is an alkali cooking process.   The rubber-reinforced lignin derivative according to claim 1 or 2, which is obtained through a step of neutralizing black liquor obtained by the biomass cooking process with carbon dioxide and a step of dehydrating the treated product after neutralization.   The lignin derivative for rubber reinforcement according to any one of claims 1 to 3, wherein the chemical is mainly composed of sodium hydroxide.   The rubber-reinforced lignin derivative according to any one of claims 1 to 4, wherein 90% by mass or more is soluble in an organic solvent. Soluble in organic solvents,
The number average molecular weight is 300-5000,
The lignin derivative for rubber reinforcement according to any one of claims 1 to 5, which has a softening temperature of 200 ° C or lower.   A lignin resin composition comprising the lignin derivative for rubber reinforcement according to any one of claims 1 to 6.   Furthermore, the lignin resin composition of Claim 7 containing a phenol-type resin.   The lignin resin composition according to claim 8, wherein the phenolic resin includes at least one of cashew-modified phenol resin, tall-modified phenol resin, alkyl-modified phenol resin, and cashew resin.   A rubber composition comprising the lignin resin composition according to any one of claims 7 to 9.