Modified nanocellulose, rubber composition, rubber, and rubber reinforcing agent

Abstract

To provide a modified nanocellulose capable of enhancing the strength of rubber.SOLUTION: The present invention provides a modified nanocellulose, comprising nanocellulose and a modifying group introduced into the nanocellulose, the modifying group having a carbon-carbon unsaturated bond and a carboxyl group.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to modified nanocellulose, a rubber composition, rubber, and a rubber reinforcing agent.

Background Art

[0002] In recent years, as a lightweight and high-strength material, rubber with a reinforcing material added to increase its strength has been widely used, and research on using plant fibers as a resin reinforcing material has been underway. Plant fibers are not artificially synthesized but are used after loosening plant-derived fibers. Since plant fibers hardly remain as ash during combustion, problems such as ash treatment in incinerators and landfill treatment do not occur. For this reason, research on using plant fibers as a resin reinforcing material has been underway, and in particular, the use of nanocellulose obtained by defibrating plant fibers to the nanolevel has been studied.

[0003] As a type of nanocellulose, nanocellulose derived from an oxide obtained by oxidizing raw cellulose with hypochlorous acid or its salt is known. For example, Patent Document 1 describes a method for producing nanocellulose having a step of oxidizing a cellulose-based raw material using hypochlorous acid or its salt having an available chlorine concentration of 14 to 43% by mass to produce oxidized cellulose, and a step of defibrating the oxidized cellulose to make it nanosized. Further, Patent Document 2 describes a method for producing nanocellulose having a step of subjecting a cellulose-based raw material to an oxidation reaction while adjusting the pH to a range of 5.0 to 14.0 using hypochlorous acid or its salt having an available chlorine concentration of 6% by mass to 14% by mass, and defibrating the oxidized cellulose to make it nanosized.

[0004] Cellulosic fibers may be used as a reinforcing material to enhance the strength of rubber. However, when cellulosic fibers are used as a rubber reinforcing material, in the case of a composite of hydrophilic cellulose and hydrophobic rubber, there is a problem that the affinity and dispersibility of the reinforcing material for rubber are poor and sufficient rubber properties cannot be exhibited. Therefore, Patent Document 3 describes that by modifying the hydrogen atoms of some hydroxyl groups in cellulose constituting the cellulose fiber with a specific substituent having an unsaturated bond, the modified cellulose fiber can be well dispersed in a highly hydrophobic rubber component, and a crosslinked structure can be formed between the rubber component and the cellulose fiber by sulfur.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a modified nanocellulose capable of improving the strength of rubber.

Means for Solving the Problems

[0007] As a result of intensive studies by the present inventors, it has been found that nanocellulose modified with a modifying group having a carbon-carbon unsaturated bond and a carboxy group can improve the strength of rubber.

[0008] The present invention includes the following embodiments. [1] Nanocellulose, and A modifying group introduced into the nanocellulose, and A modified nanocellulose comprising: wherein the modifying group has a carbon-carbon unsaturated bond and a carboxy group; Modified nanocellulose. [2] The modified nanocellulose according to [1], wherein the nanocellulose is mechanically defibrated nanocellulose without chemical defibration. [3] The modified nanocellulose according to [1], wherein the nanocellulose is chemically defibrated nanocellulose (excluding oxidized nanocellulose oxidized with hypochlorous acid or its salt and substantially free of N-oxyl compounds). [4] Forming a first rubber from a first rubber composition comprising the modified nanocellulose and a rubber component, and When forming a second rubber from a second rubber composition comprising the nanocellulose and the rubber component, (1) the maximum elongation of the first rubber is 60% or more based on the maximum elongation of the second rubber, and (2) the maximum stress of the first rubber is 1.1 times or more based on the maximum stress of the second rubber, or the 300% modulus of the first rubber is 1.05 times or more based on the 300% modulus of the second rubber. The modified nanocellulose according to any one of [1] to [3]. [5] The modified nanocellulose according to any one of [1] to [4], wherein the modifying group is introduced into the nanocellulose via a covalent bond. [6] The modifying group has a partial structure, wherein the partial structure is represented by formula (A1) to formula (A6) and salts thereof:

Chemical formula

Chemical formula

Chemical formula

[10] The modified nanocellulose according to any one of [1] to [9], and a rubber component, and A rubber composition containing the same.

[11] A rubber formed from the rubber composition according to

[10] .

[12] A rubber reinforcing agent containing the modified nanocellulose according to any one of [1] to [9].

[13] A method for producing the rubber composition according to

[10] , comprising: a step of mixing the modified nanocellulose according to any one of [1] to [9] and a rubber component to obtain a mixture; a dispersion step of obtaining a rubber composition by passing the mixture through an open roll to make it thinner; A production method comprising the above steps.

[14] A method for producing the modified nanocellulose according to any one of [1] to [9], comprising: a step of reacting nanocellulose with a dicarboxylic acid compound having a carbon-carbon unsaturated bond and / or its acid anhydride; A production method comprising the above steps. [Advantages of the Invention]

[0009] The present invention can provide a modified nanocellulose capable of improving the strength of rubber. [Brief Description of the Drawings]

[0010]

Fig. 1A

Fig. 1B

Fig. 2A

Fig. 2B

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be specifically described, but the present invention is not limited thereto, and various modifications are possible without departing from the gist thereof.

[0012] <Modified nanocellulose> One embodiment of the present invention relates to modified nanocellulose containing nanocellulose and a modifying group introduced into the nanocellulose, wherein the modifying group has a carbon-carbon unsaturated bond (hereinafter also simply referred to as "unsaturated bond") and a carboxy group.

[0013] The modified nanocellulose according to the present embodiment can improve the strength of rubber. For example, it is assumed that a crosslinked structure is formed between the modified nanocellulose and the rubber component by the unsaturated bond contained in the modifying group, but the present invention is not limited by the above reason.

[0014] In addition, the modified nanocellulose according to the present embodiment can maintain or improve the elongation of rubber as compared with unmodified nanocellulose. For example, it is assumed that the carboxy groups contained in the modifying groups improve the dispersibility of the modified nanocellulose in the rubber component, thereby suppressing the formation of aggregates of the modified nanocellulose that cause cracks. However, the present invention is not limited by the above reasons at all.

[0015] When the modified nanocellulose forms rubber together with the rubber component, it preferably has the following properties.

[0016] [Properties] Forming the first rubber from a first rubber composition containing the modified nanocellulose and the rubber component, and When forming the second rubber from a second rubber composition containing nanocellulose and the rubber component, (1) The maximum elongation of the first rubber is 60% or more, preferably 60 to 140%, more preferably 80 to 140%, still more preferably 80 to 110% based on the maximum elongation of the second rubber, and (2) The maximum stress of the first rubber is 1.1 times or more, preferably 1.1 to 2.4 times, more preferably 1.1 to 1.9 times based on the maximum stress of the second rubber, or the 300% modulus of the first rubber is 1.05 times or more, preferably 1.05 to 1.85 times, more preferably 1.05 to 1.45 times based on the 300% modulus of the second rubber.

[0017] The second rubber in the above [Properties] is used as a comparison control for the first rubber and is the same as the first rubber except that nanocellulose (unmodified nanocellulose) before introducing the modifying group is used.

[0018] The methods for forming the first rubber and the second rubber are as follows. Mix 5 phr of modified or unmodified nanocellulose (in the case of modified nanocellulose, 5 phr in the state before modification) with 100 phr (solid content) of a rubber component (natural rubber), treat with a homomixer, perform dispersion treatment with a planetary stirrer to obtain a rubber composition. Cast the rubber composition into a plastic vat and dry it to obtain a cast-dried product. Knead the cast-dried product in a batch melt kneader, add 2 phr of a crosslinking agent (dicumyl peroxide), and knead for another 10 minutes to obtain a kneaded product. Put the kneaded product into a mold with a thickness of 1 mm, sandwich the top and bottom with SUS plates, and treat with a hot press to obtain a sheet-like rubber. For more detailed conditions, it is as described in Example 1-1 below.

[0019] The measuring methods for the maximum elongation, maximum stress, and 300% modulus of the sheet-like rubber are as described in the examples below.

[0020] [Nanocellulose] "Nanocellulose" in this specification means nanocellulose (unmodified nanocellulose) before introducing a modifying group.

[0021] Nanocellulose can be obtained, for example, by defibrating a cellulose-based raw material and nanosizing it.

[0022] The cellulose-based raw material is not particularly limited as long as it is a material mainly composed of cellulose, and examples include pulp, natural cellulose, and fine cellulose obtained by depolymerizing cellulose by mechanical treatment. The cellulose-based raw material preferably has an I-type crystal structure. As the cellulose-based raw material, commercially available products such as crystalline cellulose made from pulp can be used as they are. In addition, unused biomass containing a large amount of cellulose components such as okara and soybean hulls may be used as the raw material. Also, for the purpose of facilitating the penetration of the oxidizing agent used into the raw material pulp, the cellulose-based raw material may be treated with an alkali at an appropriate concentration in advance. Incidentally, the main component of plants is cellulose, and what is formed by bundling cellulose molecules is called cellulose microfibril. The cellulose in cellulose-based raw materials is also contained in the form of cellulose microfibrils.

[0023] Examples of the fibrillation method include mechanical fibrillation, chemical fibrillation, and combinations thereof.

[0024] Mechanical fibrillation means performing fibrillation by physical treatment using a mechanical device or the like. Examples of the mechanical fibrillation method include the high-pressure homogenizer method, the microfluidizer method (opposing jet collision method), the grinder method, the ball mill pulverization method, the bead mill pulverization method, the freeze pulverization method, and the twin-screw kneading method.

[0025] Chemical fibrillation means performing fibrillation by chemical treatment (including biological treatment). Note that chemical fibrillation includes not only performing fibrillation by the chemical treatment itself but also making fibrillation easier by chemical treatment. Examples of the chemical fibrillation method include the oxidation method, the phosphoric acid esterification method, the phosphorous acid esterification method, the carboxymethylation method, the xanthation method, the sulfonation method, the enzymatic hydrolysis method, the acid hydrolysis method, and the ionic liquid selective dissolution method.

[0026] When combining mechanical fibrillation and chemical fibrillation, it is preferable to perform chemical fibrillation first and then mechanical fibrillation. By performing chemical fibrillation first, mechanical fibrillation tends to be possible with low energy.

[0027] In one aspect, it is preferable that the nanocellulose is nanocellulose mechanically fibrillated without chemical fibrillation.

[0028] In one aspect, it is preferable that the nanocellulose is chemically fibrillated nanocellulose. In this aspect, it is preferable to further mechanically fibrillate the chemically fibrillated nanocellulose. In addition, from the chemically fibrillated nanocellulose in this aspect, oxidized nanocellulose oxidized with hypochlorous acid or its salt and substantially free of N-oxyl compounds may be excluded.

[0029] Examples of the oxidized nanocellulose oxidized with hypochlorous acid or its salt and substantially free of N-oxyl compounds include the oxidized nanocellulose described in International Publication No. 2022 / 009979 and International Publication No. 2022 / 009980. Examples of hypochlorous acid or its salt include aqueous hypochlorous acid, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, and ammonium hypochlorite. Examples of the N-oxyl compound include 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). "Substantially free of N-oxyl compounds" means that no N-oxyl compound is used in the production of oxidized cellulose, that the oxidized cellulose contains no N-oxyl compound at all, or that the content of the N-oxyl compound is 2.0 mass ppm or less, preferably 1.0 mass ppm or less, based on the total amount of the oxidized cellulose. Also, when the content of the N-oxyl compound is preferably 2.0 mass ppm or less, more preferably 1.0 mass ppm or less, as an increase from the cellulose-based raw material, it is considered "substantially free of N-oxyl compounds".

[0030] [Modifier group] The modified nanocellulose according to this embodiment has a modifier group introduced into the nanocellulose, and the modifier group has an unsaturated bond and a carboxyl group.

[0031] The unsaturated bond of the modifier group is preferably a double bond or a triple bond, more preferably an ethylenic double bond. The number of unsaturated bonds is not particularly limited, and at least one is sufficient.

[0032] The carboxyl group of the modifying group may be in the H form (-COOH) or in the salt form. The type of salt is not particularly limited, and examples thereof include alkali metal salts such as lithium salt, sodium salt, and potassium salt; alkaline earth metal salts such as calcium salt and barium salt; other metal salts such as magnesium salt and aluminum salt; ammonium salt, and organic amine salt.

[0033] The introduction position of the modifying group is not particularly limited, but it is preferable that the modifying group is introduced via the hydroxyl group of nanocellulose.

[0034] The bonding form between the modifying group and nanocellulose is preferably a covalent bond, more preferably an ester bond. The ester bond is preferably composed of oxygen (O) derived from the hydroxyl group of nanocellulose and a carbonyl group (CO) derived from the modifying group-introducing compound. Here, the "modifying group-introducing compound" is a compound that reacts with nanocellulose in order to introduce the modifying group into nanocellulose.

[0035] (Structure of the modifying group) The modifying group is preferably represented by the following formula (1). -CO-R 1 ···(1) [In the formula, R 1 is an alkenyl group having 2 to 30 carbon atoms substituted with a carboxyl group.]

[0036] In formula (1), the number of carbon atoms of the alkenyl group is preferably 2 to 20, more preferably 2 to 10, and still more preferably 2 to 6.

[0037] In the present specification, the "alkenyl group" may be linear, branched, or cyclic.

[0038] The modifying group preferably has at least one partial structure selected from the group consisting of the following formula (A1) to formula (A6) and salts thereof.

Chemical formula

[0039] The modifying group preferably has the overall structure of at least one selected from the group consisting of the following formulas (B1) to (B6) and salts thereof. [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [Chemical formula] [In the formula, n 1 ~n 4 is an integer from 0 to 10, R b1 and R b2 are alkenyl groups, The wavy line represents the bond to the nanocellulose.]

[0040] R a1 、R a2 、R b1 and R b2 The number of carbon atoms of the alkenyl group of R is preferably 2 to 28, more preferably 2 to 18, still more preferably 2 to 8. Particularly preferably, it is 2 to 4.

[0041] (Modifier-introducing compound) The modifier-introducing compound is preferably an unsaturated bond-containing dicarboxylic acid compound and / or its acid anhydride (hereinafter, these are collectively simply referred to as "dicarboxylic acid"). That is, the modifier is preferably a group derived from a dicarboxylic acid. Specifically, the modifier is preferably the residue of the dicarboxylic acid bonded to the nanocellulose as a result of the reaction between the dicarboxylic acid and the nanocellulose.

[0042] Examples of the dicarboxylic acid include maleic acid, fumaric acid, itaconic acid, and succinic acid substituted with an alkenyl group, and their acid anhydrides.

[0043] The number of carbon atoms of the dicarboxylic acid is preferably 4 to 32, more preferably 4 to 22, still more preferably 4 to 12. Particularly preferably, it is 4 to 8.

[0044] The degree of substitution (DS) by the modifier-introducing compound is preferably 0.01 to 2.0, more preferably 0.05 to 1.0, still more preferably 0.05 to 0.50 from the viewpoint of sufficient introduction of the modifier and improvement of the rubber strength. The degree of substitution (DS) can be measured by the method described in the examples.

[0045] [Method for introducing modifier] The method for introducing the modifier into the nanocellulose is not particularly limited, and the nanocellulose and the modifier-introducing compound may be reacted. Also, the cellulose and the modifier-introducing compound may be reacted, and then fibrillation treatment may be performed. The reaction conditions may be appropriately determined according to the type of the modifier-introducing compound used.

[0046] The concentration of nanocellulose in the reaction system for the introduction reaction of the modifying group is not particularly limited, but from the viewpoint of the production efficiency of the modified nanocellulose, it is preferably 1.5 to 2.2% by mass, more preferably 1.8 to 2.2% by mass, and still more preferably 2.0 to 2.2% by mass.

[0047] <Rubber composition> One embodiment of the present invention relates to a rubber composition containing the above-described modified nanocellulose and a rubber component.

[0048] Since the rubber composition according to this embodiment contains modified nanocellulose, the strength of the rubber formed from the rubber composition can be improved.

[0049] The amount of the modified nanocellulose is preferably 0.1 to 50 parts by mass, more preferably 0.1 to 30 parts by mass, still more preferably 0.1 to 15 parts by mass, and even more preferably 0.5 to 15 parts by mass with respect to 100 parts by weight of the rubber component (solid content).

[0050] (Rubber component) Examples of the rubber component in this embodiment include a natural rubber component and a synthetic rubber component.

[0051] Examples of the natural rubber component include natural rubber polymers not subjected to chemical modification; chemically modified natural rubber polymers such as chlorinated natural rubber polymers, chlorosulfonated natural rubber polymers, and epoxidized natural rubber polymers; hydrogenated natural rubber polymers; and protein-free natural rubber polymers.

[0052] Examples of the synthetic rubber component include diene rubber polymers such as butadiene rubber (BR) polymer, styrene-butadiene copolymer rubber (SBR) polymer, isoprene rubber (IR) polymer, acrylonitrile-butadiene rubber (NBR) polymer, chloroprene rubber (CR) polymer, styrene-isoprene copolymer rubber polymer, styrene-isoprene-butadiene copolymer rubber polymer, and isoprene-butadiene copolymer rubber polymer; non-diene rubber polymers such as butyl rubber (IIR) polymer, ethylene-propylene rubber (EPM, EPDM) polymer, acrylic rubber (ACM) polymer, epichlorohydrin rubber (CO, ECO) polymer, fluororubber (FKM) polymer, silicone rubber (Q) polymer, urethane rubber (U) polymer, and chlorosulfonated polyethylene (CSM) polymer, etc.

[0053] These rubber components may be used alone or in combination of two or more.

[0054] The form of the rubber component may be solid, a dispersion (latex) in which the rubber component is dispersed in a dispersion medium, or a solution dissolved in a solvent. Examples of the dispersion medium and the solvent include water and organic solvents. The amount of the dispersion medium and the solvent may each be 10 to 1000 parts by mass with respect to 100 parts by weight of the rubber component.

[0055] The rubber component may be uncrosslinked or partially crosslinked.

[0056] (Other Components) The rubber composition according to this embodiment may contain other components. Examples of the other components include crosslinking agents described in the <Rubber> section below.

[0057] <Method for Producing Rubber Composition> The rubber composition according to the present embodiment can be produced by appropriately mixing the above-mentioned modified nanocellulose and a rubber component. Further, the rubber composition according to the present embodiment may be produced by mixing the above-mentioned modified nanocellulose and a rubber component by a known method. The method for producing a rubber composition containing modified nanocellulose is not particularly limited, but for example, it can be produced by a method using an open roll. Specifically, reference can be made to Japanese Patent Application Laid-Open No. 2015-98576 and the like.

[0058] One embodiment of the present invention relates to a method for producing a rubber composition, including a step of mixing the above-mentioned modified nanocellulose and a rubber component to obtain a mixture, and a dispersion step of thinning the mixture with an open roll to obtain a rubber composition.

[0059] <Rubber> One embodiment of the present invention relates to a rubber formed from the above-mentioned rubber composition. The rubber according to the present embodiment can also be expressed as a crosslinked product of the rubber composition.

[0060] The rubber of the present embodiment can be obtained, for example, by heating the rubber composition and / or reacting the rubber composition with a crosslinking agent.

[0061] Examples of the crosslinking agent include sulfur, metal oxides, resin crosslinking agents, organic peroxides, and triazine derivatives. These can be used alone or in combination of two or more.

[0062] Examples of sulfur include powdered sulfur, fine powdered sulfur, precipitated sulfur, colloidal sulfur, sulfur chloride, and the like.

[0063] Examples of the metal oxide include magnesium oxide, calcium oxide, zinc oxide, copper oxide, and the like.

[0064] Examples of the resin crosslinking agent include alkylphenol formaldehyde resins such as alkylphenol formaldehyde resin, thermosetting phenolic resin, phenol dialcohol resin, bisphenol resin, and thermosetting bromomethylalkylated phenolic resin.

[0065] Examples of the organic peroxide include alkyl peroxide, aryl peroxide, acyl peroxide, ketone peroxide, peroxyketal, peroxycarbonate, peroxyester, hydroperoxide, etc. Specifically, dicumyl peroxide can be preferably used as the organic peroxide.

[0066] Examples of the triazine derivative include 2,4,6-trimercapto-s-triazine, 2-methylamino-4,6-dimercapto-s-triazine, 2-(n-butylamino)-4,6-dimercapto-s-triazine, 2-octylamino-4,6-dimercapto-s-triazine, 2-propylamino-4,6-dimercapto-s-triazine, 2-diallylamino-4,6-dimercapto-s-triazine, 2-dimethylamino-4,6-dimercapto-s-triazine, 2-dibutylamino-4,6-dimercapto-s-triazine, 2-di(iso-butylamino)-4,6-dimercapto-s-triazine, 2-dipropylamino-4,6-dimercapto-s-triazine, 2-di(2-ethylhexyl)amino-4,6-dimercapto-s-triazine, 2-dioleylamino-4,6-dimercapto-s-triazine, 2-laurylamino-4,6-dimercapto-s-triazine or 2-anilino-4,6-dimercapto-s-triazine, or sodium salts or disodium salts thereof.

[0067] The addition amount of the crosslinking agent may be adjusted as appropriate. It is usually 0.01 to 15 parts by mass, preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component.

[0068] The temperature during crosslinking may be adjusted as appropriate, and it is usually sufficient if it is in the range of 20 to 200°C.

[0069] <Additive for rubber> One embodiment of the present invention relates to an additive for rubber containing the above-mentioned modified nanocellulose.

[0070] The function of the additive for rubber in this embodiment includes, but is not limited to, the reinforcement of rubber.

[0071] The additive for rubber may be in a liquid state or a solid state. The additive for rubber may be a dried product of modified nanocellulose or a dispersion of modified nanocellulose.

[0072] When the additive for rubber is a dispersion, the additive for rubber contains a dispersion medium capable of dispersing modified nanocellulose. There is no particular limitation on the dispersion medium, and it can be appropriately selected according to the purpose. Specific examples of the dispersion medium include water, alcohols, ethers, ketones, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. These may be used alone or in combination of two or more as the dispersion medium.

[0073] Among the above-mentioned dispersion media, examples of alcohols include methanol, ethanol, isopropanol, isobutanol, sec-butyl alcohol, tert-butyl alcohol, methyl cellosolve, ethylene glycol, and glycerin. Examples of ethers include ethylene glycol dimethyl ether, 1,4-dioxane, and tetrahydrofuran. Examples of ketones include acetone and methyl ethyl ketone.

[0074] When the additive for rubber is a dispersion, the concentration of the modified nanocellulose in the dispersion may usually be in the range of 0.01 to 99% by mass. From the viewpoints of easy availability and handleability, the above concentration is preferably 0.5 to 50% by mass, more preferably 1 to 30% by mass, and still more preferably 1 to 20% by mass.

Examples

[0075] Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples, but the technical scope of the present invention is not limited thereto. In addition, various values in the examples may be used as the preferable lower limit value or upper limit value in the embodiments of the present invention. Also, two values of the same kind in the examples may be appropriately combined to form a preferable numerical range.

[0076] <Measurement of the amount of carboxy groups> To 60 ml of an aqueous dispersion of oxidized cellulose with the concentration of oxidized cellulose adjusted to 0.5% by mass, an aqueous 0.1 M hydrochloric acid solution was added to adjust the pH to 2.5, and then an aqueous 0.05 N sodium hydroxide solution was added dropwise. The electric conductivity was measured until the pH reached 11.0. From the amount of sodium hydroxide (a) consumed in the neutralization stage of the weak acid where the change in electric conductivity was gentle, the amount of carboxy groups (mmol / g) was calculated using the following formula. Amount of carboxy groups = a (ml) × 0.05 / mass of oxidized cellulose (g)

[0077] [Production Example 1: Production method of oxidized cellulose] 500 g of an aqueous sodium hypochlorite solution with a pH of 12.7 and an available chlorine concentration of 12.5 mass% was placed in a glass container with a jacket, and while stirring at 200 rpm using a three-blade retreating impeller of a stirrer (Three One Motor, BL600) manufactured by Shinto Kagaku Co., Ltd., it was heated to 35°C. Then, 47 g of powdered pulp (KC Flock W-100GK) from Nippon Paper Industries Co., Ltd. was added as a cellulose-based raw material. After supplying the cellulose-based raw material, while maintaining the temperature at 35°C, it was stirred until the pH dropped to 10.5. Then, while adding a 25 mass% aqueous sodium hydroxide solution to maintain the pH during the reaction at 10.5, stirring was carried out under the same conditions for a total of 520 minutes after the cellulose-based raw material was introduced. After the reaction was completed, an aqueous hydrogen peroxide solution was added to deactivate the remaining sodium hypochlorite, and then hydrochloric acid was added to convert the carboxyl groups of the oxidized cellulose from the salt form (-COO-Na) to the proton form (-COO-H), obtaining an aqueous dispersion with a pH of 2.5. The aqueous dispersion was subjected to solid-liquid separation by pressure filtration at 0.2 MPa and then washed with an aqueous hydrochloric acid solution with a pH of 2.5. Sodium hydroxide was added to the obtained proton-form oxidized cellulose to return the carboxylic acid groups from the proton form (-COO-H) to the salt form (-COO-Na), obtaining an aqueous dispersion of oxidized cellulose in the salt form with a pH of 7.4. When the amount of carboxyl groups was measured, it was 0.78 mmol / g. Also, the nitrogen component derived from the N-oxyl compound in the oxidized cellulose was measured as the amount of nitrogen using a trace total nitrogen analyzer (TN-2100H manufactured by Mitsubishi Chemical Analytech Co., Ltd.), and as a result of calculating the increase from the raw material pulp, it was 1 ppm or less.

[0078] [Example 1] To the aqueous dispersion of Na-type cellulose oxide (solid content: 7.5%) obtained in Production Example 1, treatment was performed at 10,000 rpm and a liquid volume of 440 g for 33 minutes using a homomixer (Robomix, manufactured by Primix) to defibrate the cellulose oxide into nanocellulose, thereby obtaining an aqueous nanocellulose dispersion. 1N hydrochloric acid aqueous solution was added to the obtained aqueous dispersion and adjusted to a pH of 2.0 to 2.1, and then washed twice with pure water using a tabletop multi-tube centrifuge (H-40α, manufactured by Kokusan). Thereafter, after washing (substituting) four times with acetone in the same manner, acetone-substituted H-type nanocellulose was obtained by concentration by suction filtration using a vacuum pump. JEFFAMINE M-2005 (manufactured by Yaba Kogyo Co., Ltd.) equivalent to the acid value was added to the H-type nanocellulose and stirred. Toluene was added thereto and adjusted to a solid content concentration of 5%. After removing the residue by filtration through a filter cloth, acetone was distilled off from the evaporator to obtain an organic ammonium salt type nanocellulose toluene dispersion. To 1 part by mass of the organic ammonium salt type nanocellulose, 20 parts by mass of maleic anhydride and 42 parts by mass of toluene were added, and the mixture was stirred at 90 °C for 1.5 hours. Methanol was added to the reaction solution and stirred to stop the reaction. Then, it was washed (substituted) seven times with methanol using a tabletop multi-tube centrifuge (H-40α, manufactured by Kokusan) to obtain maleic acid-modified H-type nanocellulose.

[0079] [Example 2] Itaconic acid-modified H-type nanocellulose was obtained in the same manner except that maleic anhydride in Example 1 was changed to itaconic anhydride and the number of parts by mass of toluene was changed to 71 parts by mass.

[0080] [Example 3] Mechanically defibrated CNF (BiNFis, standard product, manufactured by Sugino Machine) was washed (substituted) five times with acetone using a tabletop multi-tube centrifuge (H-40α, manufactured by Kokusan), and then washed (substituted) five times with toluene to obtain toluene-substituted mechanically defibrated nanocellulose. To 1 part by mass of toluene-substituted mechanically defibrated nanocellulose, 20 parts by mass of maleic anhydride and 39 parts by mass of toluene were added, and the mixture was stirred at 90 °C for 1.0 hour. Methanol was added to the reaction solution and stirred to stop the reaction. Then, it was washed (substituted) 7 times with methanol using a tabletop multi-tube centrifuge (manufactured by KOKUSAN, H-40α) to obtain maleic anhydride-modified H-type nanocellulose by mechanical defibration.

[0081] <Measurement of degree of substitution> To 100 ml of a modified nanocellulose aqueous dispersion in which the concentration of the modified nanocellulose obtained from the examples was adjusted to 0.1% by mass, an aqueous 0.1 M hydrochloric acid solution was added to adjust the pH to 2.7. Then, an aqueous 0.05 N sodium hydroxide solution was added dropwise, and the electrical conductivity was measured until the pH reached 11.0. From the amount of sodium hydroxide (a) consumed in the neutralization stage of the weak acid where the change in electrical conductivity was gentle, the amount of carboxyl groups (mmol / g) was calculated using the following formula. Amount of carboxyl groups = a (ml) × 0.05 / mass of modified nanocellulose (g)

[0082] The degree of substitution (DS) was calculated using the following formula from the amount of carboxyl groups of the modified nanocellulose and the amount of carboxyl groups of the raw material nanocellulose (unmodified nanocellulose).

[0083]

Equation

[0084] The degree of substitution (DS) of the maleic anhydride-modified H-type nanocellulose of Example 1 was calculated to be 0.17. The degree of substitution (DS) of the itaconic acid-modified H-type nanocellulose of Example 2 was calculated to be 0.29. The degree of substitution (DS) of the mechanically defibrated maleic anhydride-modified H-type nanocellulose of Example 3 was calculated to be 0.24.

[0085] [Pretreatment for compounding with rubber] An aqueous sodium hydroxide solution with a concentration of 0.05 N was added to the modified nanocellulose so that the amount of carboxyl groups in the modified nanocellulose obtained from the example was the same molar number as the equivalent amount, and a modified Na-type nanocellulose aqueous dispersion was obtained.

[0086] Hereinafter, phr (parts per hundred rubber) means the mass parts of a predetermined substance with respect to 100 mass parts of the rubber component.

[0087] [Example 1-1] 100 phr of natural rubber latex as a solid content (manufactured by Revertex, URACOL, concentration 61 mass%. Hereinafter, this natural rubber is referred to as "NR"), and 5.86 phr as a solid content (5 phr as CNF), a maleic acid-modified Na-type nanocellulose aqueous dispersion (solid content 2.49 mass%) obtained by performing a pretreatment for rubber compounding after being prepared by the method of Example 1 were mixed, treated with a homomixer (manufactured by Primix, Robomix) at 3,000 rpm for 1 minute, and subjected to dispersion treatment with a planetary stirrer (manufactured by THINKY, Awatori Ren-taro ARE310) at Mix 2000 rpm for 1 minute and Defoam 2200 rpm for 1 minute to obtain a rubber composition. The above rubber composition was cast into a plastic vat and dried at 50°C for 3 days. This cast and dried product was kneaded for 5 minutes at 70°C and 60 rpm with a batch type melt kneader (manufactured by Toyo Seiki Seisakusho, Laboplastmill 10S100, mixer R60, Banbury type blade), 2 phr of a crosslinking agent (Parkmill D manufactured by NOF Corporation (also described as "DCP")) was added, and further kneaded for 10 minutes to obtain a kneaded product. This kneaded product was placed in a mold with a thickness of 1 mm, sandwiched between SUS plates, and subjected to a crosslinking reaction and molding by treatment at 165°C, 20 MPa, and 20 minutes with a hot press machine to obtain a sheet-like rubber containing 5 phr as nanocellulose. According to the <Strength Evaluation> described later, a strength test of the obtained sheet-like rubber was conducted.

[0088] [Example 2-1] 100 phr of NR latex as solids and an itaconic acid-modified Na-type nanocellulose aqueous dispersion (1.51% by mass solids) obtained by subjecting, after preparation by the method of Example 2, a pretreatment for rubber compounding to 6.46 phr (5 phr as CNF) as solids were mixed. Thereafter, the same treatments and tests as in Example 1-1 were carried out.

[0089] [Example 3-1] 100 phr of NR latex as solids and a mechanically defibrated maleic acid-modified Na-type nanocellulose aqueous dispersion (1.0% by mass solids) obtained by subjecting, after preparation by the method of Example 3, a pretreatment for rubber compounding to 5 phr as CNF were mixed. Thereafter, the same treatments and tests as in Example 1-1 were carried out.

[0090] [Examples 1-2, 2-2 and 3-2] Rubbers containing 2 phr of CNF were obtained by diluting the respective cast-dried products (CNF: 5 phr) obtained in Examples 1-1, 2-1 and 3-1. That is, the respective cast-dried products (CNF: 5 phr) obtained in Examples 1-1, 2-1 and 3-1 and a cast-dried product of a rubber monomer obtained by drying only the same kind of rubber latex were mixed, and kneading and hot pressing were carried out in the same manner as in Examples 1-1, 2-1 and 3-1 to obtain a sheet-like rubber containing 2 phr of CNF. A test of the strength of the obtained sheet-like rubber was carried out according to <Strength Evaluation> described later.

[0091] [Comparative Example 1-1] A liquid having an oxidized cellulose concentration of 7.5% by mass was obtained by diluting an aqueous dispersion of oxidized cellulose obtained in Production Example 1 with water and treating it at 10,000 rpm for 15 minutes using a homomixer (Primix Corporation, Robomix) to obtain a 7.5% by mass CNF aqueous dispersion. A 5 phr CNF aqueous dispersion as CNF and 100 phr of NR latex as solids were mixed, and dispersion treatment was carried out using a planetary stirrer (Thinky Corporation, Awatori Renkatarou ARE310) at Mix 2000 rpm for 1 minute and Defoam 2200 rpm for 1 minute to obtain a rubber composition. The above rubber composition was cast into a plastic bat and dried at 50°C for 3 days to obtain a cast-dried product. Thereafter, the same kneading, hot pressing, and strength evaluation as in Example 1-1 were carried out.

[0092] [Comparative Example 1-2] To the cast-dried product obtained in Comparative Example 1-1, a cast-dried product of a single rubber obtained by drying only NR latex was mixed, and kneading and hot pressing were carried out in the same manner as in Comparative Example 1-1 to obtain a sheet-like rubber containing 2 phr of CNF. According to the <Strength Evaluation> described below, a strength test of the obtained sheet-like rubber was conducted.

[0093] [Comparative Example 2-1] A cast-dried product was obtained in the same manner as in Comparative Example 1-1, except that the CNF in Comparative Example 1-1 was changed to mechanically defibrated unmodified CNF (BiNFis, manufactured by Sugino Machine Limited, standard product). Thereafter, the same kneading, hot pressing, and strength evaluation as in Example 1-1 were carried out.

[0094] [Comparative Example 2-2] To the cast-dried product obtained in Comparative Example 2-1, a cast-dried product of a single rubber obtained by drying only NR latex was mixed, and kneading and hot pressing were carried out in the same manner as in Comparative Example 2-1 to obtain a sheet-like rubber containing 2 phr of CNF. According to the <Strength Evaluation> described below, a strength test of the obtained sheet-like rubber was conducted.

[0095] [Comparative Example 3] A single rubber was kneaded and its strength was evaluated. That is, NR latex was cast on a plastic bat and dried at 50°C for 3 days. Thereafter, the same kneading, hot pressing, and strength evaluation as in Example 1-1 were carried out.

[0096] <Strength Evaluation> The strength evaluation was carried out by the following tensile test. Dumbbell-shaped test pieces with a total length of 75 mm and a width between the gauge lines of 2 mm were cut out from the sheet-like rubbers obtained in the examples and comparative examples (thickness: 1.1 - 1.4 mm). Using a tensile testing machine (manufactured by INSTRON, INSTRON 5566A), a tensile test was conducted on this test piece at 23 ± 2 °C, with a gauge length of 20 mm and a tensile speed of 500 mm / min in accordance with JIS K6251. By the tensile test, 50% modulus (σ50 (MPa)), 100% modulus (σ100 (MPa)), 300% modulus (σ300 (MPa)), tensile strength (TS (MPa)), elongation at break (Eb (%)), elastic modulus (MPa), and toughness (J) were measured. The results are shown in Table 1 and FIGS. 1 and 2.

[0097] As can be understood from FIGS. 1A and 2A, the nanocellulose oxidized with hypochlorous acid, by being modified, improved the strength of the rubber while maintaining or improving the elongation of the rubber as compared with the unmodified one. As can be understood from FIGS. 1B and 2B, the mechanically defibrated nanocellulose also, by being modified, improved the strength of the rubber while maintaining or improving the elongation of the rubber as compared with the unmodified one.

[0098]

Table 1

Claims

1. Nanocellulose and, a modifying group introduced into the nanocellulose, a modified nanocellulose comprising: wherein the modifying group has a carbon-carbon unsaturated bond and a carboxy group, modified nanocellulose.

2. The nanocellulose is nanocellulose mechanically defibrated without chemical defibration, The modified nanocellulose according to Claim 1.

3. The nanocellulose is chemically defibrated nanocellulose (excluding nanocellulose oxidized with hypochlorous acid or its salt and substantially free of N-oxyl compounds), The modified nanocellulose according to Claim 1.

4. forming a first rubber from a first rubber composition comprising the modified nanocellulose and a rubber component, and when forming a second rubber from a second rubber composition comprising the nanocellulose and the rubber component, (1) the maximum elongation of the first rubber is 60% or more based on the maximum elongation of the second rubber, and (2) the maximum stress of the first rubber is 1.1 times or more based on the maximum stress of the second rubber, or the 300% modulus of the first rubber is 1.05 times or more based on the 300% modulus of the second rubber, The modified nanocellulose according to Claim 1.

5. The modifying group is introduced into the nanocellulose via a covalent bond, The modified nanocellulose according to any one of Claims 1 to 4.

6. The modifying group has a partial structure, the partial structure is represented by Formula (A1) to Formula (A6) and salts thereof: 【Chemical 1】 [Chemical 2] [Chemical 3] [Chemical Formula 4] 【Chemical Formula 5】 [Chemical Formula 6] [wherein, R ａ１ and R ａ２ are alkenyl groups, the wavy line represents a bond to the remainder of the modifying group] and is at least one selected from the group consisting of: The modified nanocellulose according to any one of Claims 1 to 4.

7. The modifying group is represented by Formula (B1) to Formula (B6) and salts thereof: 【Chemical Formula 7】 【Chemical 8】 【Chemical Formula 9】 【Chemical 10】 【Chemical 11】 【Chemical Formula 12】 [wherein, n １ ~n ４ is an integer from 0 to 10, R ｂ１ and R ｂ２ are alkenyl groups, the wavy line represents a bond to the nanocellulose] and is at least one selected from the group consisting of: The modified nanocellulose according to any one of Claims 1 to 4.

8. The modifying group is derived from a dicarboxylic acid compound having a carbon-carbon unsaturated bond and / or its acid anhydride, The modified nanocellulose according to any one of Claims 1 to 4.

9. The dicarboxylic acid compound is at least one selected from the group consisting of maleic acid, fumaric acid, itaconic acid, and succinic acid substituted with an alkenyl group, The modified nanocellulose according to Claim 8.

10. The modified nanocellulose according to any one of claims 1 to 4, and a rubber component, A rubber composition comprising the same.

11. A rubber formed from the rubber composition according to claim 10.

12. A rubber reinforcing agent comprising the modified nanocellulose according to any one of claims 1 to 4.

13. A method for producing the rubber composition according to claim 10, comprising: a step of mixing the modified nanocellulose according to any one of claims 1 to 4 and a rubber component to obtain a mixture; a dispersion step of obtaining a rubber composition by passing the mixture through an open roll to thin it; A production method comprising the same.

14. A method for producing the modified nanocellulose according to any one of claims 1 to 4, comprising: a step of reacting nanocellulose with a dicarboxylic acid compound having a carbon-carbon unsaturated bond and / or an acid anhydride thereof; A production method comprising the same.

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